GB2469181A

GB2469181A - Treatment of a natural cellulosic fibre with an anhydride

Info

Publication number: GB2469181A
Application number: GB1004816A
Authority: GB
Inventors: Brian Chandler; Peter Cotterill Oliver; Chris Dowdall
Original assignee: ACETYLATED FIBRES Ltd
Current assignee: ACETYLATED FIBRES Ltd
Priority date: 2009-03-31
Filing date: 2010-03-23
Publication date: 2010-10-06
Also published as: WO2010112896A1; GB201004816D0

Abstract

A natural fibre comprising a modifying group derived from the reaction of an aliphatic/aromatic anhydride with the cellulose of the natural fibre. The natural fibre may be selected from seed, leaf, bast, skin, fruit and stalk fibres, more preferably selected from fique, sisal, banana, agave, wheat, rice, barley, bamboo, grass, coir, cotton, flax, hemp, ramie, jute and kenaf fibres or mixtures thereof. Most preferably, the fibre is derived from recycled paper. The anhydride may be itaconic, succinic, but preferably maleic anhydride. The treatment renders the natural fibres relatively hydrophobic and improves various structural and chemical properties. These fibres are useful for reinforcing composite materials, e.g. thermosetting resins such as bulk moulding compounds (BMC) and sheet moulding compounds (SMC). As such, the treated fibres are an environmentally friendly alternative to glass fibres.

Description

HYDROPHOBISED FIBRES AND THEIR USES

Field of the Invention

The present invention relates to the production of treated natural fibres in order to render then relatively hydrophibic and to improve various structural and chemical properties thereof. The invention is also concerned with the uses of such fibres and a process for the production thereof.

Background of the Invention

Ecological awareness has resulted in a renewed interest in natural materials and issues such as recyclability and environmental safety are becoming increasingly important for the introduction of new composite materials and products.

Environmental legislation as well as consumer demand are all increasing the pressure on manufacturers of materials and end-products to consider the environmental impact of their products at all stages of their life cycle, including recycling and ultimate disposal. These environmental issues have recently generated considerable interest in the development of composite materials based on renewable resources such as natural fibres as environmentally friendly and low-cost alternatives for glass fibres and the use of plastics based on renewable resources for the development of bio-composites. Currently a large number of interesting applications are emerging and especially the transport industry is looking seriously into the use of eco-composites as a way to serve the environment and at the same time save weight and cost.

The traditional methods used to achieve the acetylation of natural products, such as wood, uses autoclaves and has proved too slow and costly to be commercially viable.

Straw has long been recognised as advantageous in the production of load bearing bricks from friable clay matrices; daub and wattle allowed large wall areas to be constructed. In more recent times, the inclusion of fibrous slag in iron was found to impart ductility to the purified metal and the incorporation of reinforcing bars of metal into concrete castings has allowed load bearing structures to be constructed, enhancing the science of civil engineering.

All natural fibres rot over a period of time; a process which is influenced largely by exposure to water, both by direct liquid contact and from moisture in the atmosphere. Not only does this exposure encourage biological degradation of the fibres, but absorption of water into the fibres initially causes swelling and dimensional instability. Partial modification of stalk fibres retains the original fibre structure whilst reacting with the free" hydroxyl groups which are susceptible in the natural state, to biological attack. The modification of these free hydroxyl groups effectively prevents this and increases both molecular weight and volume of the fibre. This is very close to the volume expansion of untreated fibre in water; partial modification thus stabilises the fibre against water induced dimensional changes.

Wood fibres are extensively used in the paper and board industries but are adversely affected by water and moisture. Many techniques have been developed over the last century to minimise this problem.

There are major disadvantages to the current, almost universal, use of glass fibre as reinforcement in composites. Untreated natural fibres however, have not proved to be a viable alternative thus the objective was to develop a process for the modification of natural fibre such that it could be used as a replacement for glass fibre.

There are some significant disadvantages for glass fibre producers and for glass fibres being used as a reinforcement material in composites. With a current glass fibre usage growth rate of 5% per annum (10% in W Europe), there could soon be supply problems. Western Europe, for example, is currently manufacturing well below its requirements and in 1997 imported some 100,000 tonnes of glass fibre (accounting for 17 to 18 % of total demand).and currently ten years later a very high proportion of glass used in Europe comes from China. Furthermore, glass fibre, being synthetic, is environmentally unfriendly. It is a non-renewable resource and furthermore in some applications will allow wicking of moisture resulting in degradation of the composite.

Untreated organic (natural) fibres have been extensively explored as a potential alternative to glass fibre. Their disadvantages in use however have precluded any significant adoption. Untreated organic fibres lack the necessary long-term physical properties, particularly strength and dimensional stability and are subject to rapid bio-deterioration.

Vegetable fibres are generally comprised mainly of cellulose: examples include cotton, jute, flax, ramie, sisal, and hemp.

Therefore, the present invention seeks to provide a natural fibre and products derived from said fibre, which overcome the above mentioned problems.

Therefore, the present invention also seeks to provide a process for the production of such fibres.

Summary of the Invention

According to a first aspect of the present invention, there is provided a natural fibre comprising a modifying group derived from the reaction of an aliphatic or aromatic anhydride with the cellulose of the natural fibre.

Preferably, the natural fibre comprises between 5 and 40 wt % of a modifying group derived from the reaction of an aliphatic or aromatic anhydride with the cellulose of the natural fibre, more preferably between 10 and 30 wt %, more preferably between 13 and 25 wt %, more preferably between 15 and 23 wt %. In a particularly preferred embodiment, there is provided a natural fibre comprising between 16 and 20 wt % of a modifying group derived from the reaction of an aliphatic or aromatic anhydride with the cellulose of the natural fibre, for example about 16, 17,18, l9or2Owt%.

The weight % of the modifying group is measured relative to the untreated natural fibre(s) containing less than 5 wt % water, preferably between 1 and 4 wt % water, preferably less than 2 wt % water.

The natural fibre is preferably selected from the group consisting of seed fibres, leaf fibres, bast fibres, skin fibres, fruit fibres, stalk fibres and mixtures thereof.

Preferably, the natural fibre is selected from the group consisting of fique, sisal, banana, agave, wheat, rice, barley, bamboo, grass, coir, cofton, flax, hemp, ramie, jute, kenaf and mixtures thereof. More preferably the natural fibre is selected from coir, flax, hemp, jute and kenaf, most preferably flax, hemp, jute and mixtures thereof.

In a particularly preferred embodiment, the fibre is derived from recycled paper.

Preferably, the aliphatic anhydride is a 03-06 anhydride, more preferably a C4 anhydride. Preferably the aliphatic anhydride is a C3-C6 olefinic aliphatic anhydride.

The aliphatic anhydride is preferably selected from the group consisting of maleic anhydride, acetic anhydride, itaconic anhydride, succinic anhydride, glutaric anhydride, adipic anhydride, citraconic anhydride and mixtures thereof.

Preferably, the aromatic anhydride is a C6-C12 anhydride, more preferably a C6 anhydride. The aromatic anhydride is preferably phthalic anhydride.

The anhydride is preferably an aliphatic anhydride, and is selected from the group consisting of maleic anhydride, itaconic anhydride and succinic anhydride and mixtures thereof. In one embodiment, preferably the anhydride is not acetic anhydride. Maleic anhydride is especially preferred because of its reactivity, structural benefits and relatively low cost. It should be understood that the use of all the above anhydrides (particularly maleic anhydride), and all preferred features relating thereto, apply to all aspects and embodiments of the present invention.

In this regard, when maleic anhydride is used to modify the fibre, it is postulated that at least one hydroxyl group of a cellulose molecule forms a residue with a maleic group, i.e., HO2CCH=CHCO, to form an ester, i.e., HO2CCH=CHC(O)-O-cellulose. This is a particularly advantageous process in the case of maleic anhydride as the reaction does not have any acidic byproducts. In contrast, the analogous process with acetic anhydride produces significant amounts of acetic acid byproduct which is difficult to remove and has a pungent smell.

The modification of the natural fibre which takes place is a process which improves the physical properties of natural fibres and, largely by virtue of changing the hydrophilic nature of organic fibres to a hydrophobic nature, thereby reducing biodegradation to negligible levels.

The production of fibre containing a modifying group (preferably 16 to 20 wt %) is measured in terms of weight gain of the treated fibres as compared to untreated fibres when they are dried to the same average level (water concentration).

Preferably, the weight increase is measured for fibres (untreated and treated) having the same average water concentration of between 0.5 and 3 wt % water, preferably about 2 wt %.

The level of the modifying group in the fibre is also important. If one reacts the anhydride to a level resulting in a weight gain of less than 16 wt %, then hydrophobicity is not as improved as much as it could be, and the reduction in biodegradation is not maximised. On the other hand, if one reacts the anhydride to a level resulting in a weight gain of greater than about 20 wt %, the structural integrity of the natural fibre may be reduced -the fibre can break and/or become curled or bent. The anhydride modifying group (preferably an aliphatic anhydride, most preferably an olefinic aliphatic anhydride) is preferably present in the range of 16-20 wt %, preferably 17-19 wt %, more preferably 17.5-18.5 wt %, most preferably about 18 wt %. Within these ranges, the natural fibre is substantially resistant to rot and/or natural degradation. It is also substantially water resistant. Preferably, it is also relatively straight (less than about 10 0 variation of bend from the longitudinal axis) and unfractured.

The fibres of the present invention are preferably from about 5 pm to about 100 pm in diameter. Preferably, the fibres of the present invention are from about 500 pm to cm in length. Preferably, the fibres of the present invention are preferably from about 5 pm to about 20 pm in diameter. Preferably, the fibres of the present invention are from about 1000pm to 5 cm in length.

The fibres of the present invention are preferably have an average diameter of from about 5 pm to about 100 pm in diameter. Preferably, the fibres of the present invention are from about 500 pm to 10 cm on average in length. Preferably, the fibres of the present invention are preferably from about 5 pm to about 20 pm on average in diameter. Preferably, the fibres of the present invention are from about 1000pm to 5 cm on average in length.

Treated natural fibre according to the present invention can be supplied in a variety of formats namely; continuous roving, chopped strand mat, chopped roving to specific lengths, woven roving mat and reinforced needle punch felt construction.

By water resistant, it is meant that the fibre is effectively hydrophobic. Preferably, the treated fibre absorbs less than 20 wt % water over 24 hours at 25 °C, preferably less than 10 wt % water, more preferably less than 5 wt % water over 24 hours at 25 00.

According to a second aspect of the present invention, there is provided an article of manufacture comprising a fibre according to the first aspect of the invention.

Preferably, the article of manufacture is used in the construction of structural articles used in the manufacture of buildings; furniture; vehicles, including trains, automobiles, aircraft, spacecraft, boat hulls; railway sleepers and hydrophobic absorbents. In particular, the fibres of the first aspect of the invention may be used to produce composite materials, especially those used in the building construction industry. Such composite materials preferably further comprise a resin and optionally a filler.

Preferably, the article of manufacture comprises between 5 and 95 wt % of the fibres of the first aspect of the invention, more preferably less than 80 wt %, more preferably between 10 and 50 wt %, more preferably between 10 and 40 wt %, for example about 15, 20, 25, 30 or 35 wt % thereof.

Fibre reinforced composite materials are known for use in a variety of applications, including the manufacture of reinforced articles where structural strength is important. Such applications particularly include roofing and construction materials, including partitions, walls, pipe lagging, bricks, breeze blocks, paving slabs, automobile body parts and train body parts.

Preferably, the resin is a thermosetting or thermoplastic resin. Preferably, the resin is present in the range of between 5 and 95 wt % of the composite material, more preferably less than 80 wt %, more preferably between 10 and 50 wt %, more preferably between 10 and 40 wt %, for example about 15, 20, 25, 30 or 35 wt % thereof, most preferably about 22 wt % of the composite.

The preferred resins for this invention are synthetic or natural thermosethng resins.

The thermosetting resin is preferably selected from the group consisting of polyester resins, furan resins, phenolic resins, epoxy resins, vinyl ester resins and mixtures thereof. Preferably, the resin is a thermoset polyester or vinyl ester.

Furan resins are defined for the purpose of this application as liquid resins that contain at least 10% w/w of compounds whose molecular structure incorporates the furan ring, with zero, one or two double bonds; and which can be cured by heat or the addition of an acid catalyst, to form a thermoset solid. The furan resin preferably contains some furfuryl alcohol, or reaction products of furfuryl alcohol, e.g. those described in US 5,545,825.

Where a thermoplastic resin is used, it is preferably polyethylene, polypropylene or polystyrene or mixtures thereof.

A catalyst may be incorporated into the composite resin formulation to initiate cure of the resin. Any desired catalyst can be used. The catalyst can be selected from the group of peroxide or acid catalysts. Suitable catalysts will be evident to the skilled person.

Typical acid catalysts include phosphoric acid, alkane sulphonic acids, such as methane sulphonic acid, hydrochloric acid and sulphuric acid, or blends thereof. In most instances, the acid catalyst is added in amounts sufficient to reduce the initial pH of the liquid resin mixture below 4, preferably between 1.5 and 3.0.

Exemplary peroxide catalysts that may be used with the invention include diacyl peroxides, for example benzoyl peroxide; peroxyesters, for exampJe t-butyl-peroxy- 2-ethylhexanoate; dialkyl peroxides such as dicumyl peroxide; hydroperoxides such as cumene hydroperoxide; perketals such as 1, 1-di-(t-butyl-peroxy) cyclohexane; and peroxydicarbonates such as di (2-ethylhexyl) peroxydicarbonate.

Preferably, the filler is selected from the group consisting of cement, clay, gypsum, calcium carbonate, silicates, aggregate and mixtures thereof. Where present, the filler is preferably present in the range of between 20 and 90 wt % of the composite material, more preferably between 40 and 80 wt %, more preferably between 60 and 75 wt % of the composite.

In a preferred embodiment, the article of manufacture may be a rigid or flexible board or panel comprising at least one resin-impregnated layer which contains a fibre according to the first aspect of the present invention. Preferably, the layer is non-woven, for example being a tufted or flocked product or, most preferably, a needled fibrous product. A preferred example is a resin-impregnated needled felt.

Such resin-impregnated fibrous products may be moulded to produce a board, panel, strut, reinforcement, beam, lintel or joist, which find utility in the building construction industry, for example to produce walls and roofing sections for buildings, and structural sections for vehicles.

In a preferred embodiment, the structural items produced according to the present invention (particularly boards and panels) have a flexural strength (determined in accordance with ASTM D790 method) in excess of 50 MPa, preferably in the range of 60-75 MPa. Such structural items are preferably thermoplastic resin impregnated treated fibre products, particularly polyethylene or polypropylene based products.

In a preferred embodiment, the structural items produced according to the present invention (particularly boards and panels) have a flexural modulus (determined in accordance with ASTM D790 method) in excess of 3000 MPa, preferably greater than 5000 MPa, preferably in the range of 5000-6500 MPa. Such structural items are preferably thermoplastic or thermoset resin impregnated treated fibre products, particularly furan-, polyethylene-or polypropylene-based products.

In a preferred embodiment, the structural items produced according to the present invention (particularly bulk moulding compounds) have a break strength (determined in accordance with ASTM D638 method) of greater than 1000 MPa, preferably greater than 3000 MPa, preferably in the range of 3000 MPa-4500 MPa.

The fibrous layers generally are preferably 1 to 30 mm, more preferably 1 to 10 mm, e.g. 1 to 5 mm thick before consolidation into a final structural product. The fibrous layers preferably have a basis weight of from 100-2000 gsm, preferably 250-1000 gsm.

The fibrous layers may be cut into appropriate shapes prior to consolidation into a structural product (i.e., board or panel), or may be cut into appropriate shapes after consolidation into a board or panel. They may also be drilled to provide fixation or anchoring means. The presence of the resin and the fibres maintain the integrity of the structural product, enabling them to be cut or drilled to the desired shape without significantly compromising the strength thereof.

Treated fibres preferably make up between 10 and 60 wt % of a structural product, such as a board or panel, preferably between 15 and 30 wt %.

To increase the stability of the fibrous layers it may be desirable to be laminated to a stablilishing scrim such as a non-woven glass fibre tissue or glass/synthetic or natural fibre tissue. Alternatively, hessian scrim may be used. The stabilising scrim may be adhered to one surface of the fibrous layer, or sandwiched between two such sheets. Alternatively, or additionally, the fibrous layers (preferably needle felt) can be stabilised using a light impregnation or resin or adhesive.

Fibrous layers incorporating the fibres of the present invention may have the fibres organised substantially unidirectionally, cross-directionally, or randomly, or mixtures thereof.

Although it is envisaged that any of the treated fibres of the present invention may be used to provide boards and panels, in a particularly preferred embodiment, the treated fibres used in the production of the board or panel are derived from waste paper (such as newsprint, domestic or commercial waste paper, and the like). This is particularly the case in the construction of building materials such as walls, roofs and floors.

In a further preferred embodiment, the article of manufacture may be a rigid or flexible foam comprising a fibre according to the first aspect of the present invention. Such foam products may be used to provide impact resistant and/or insulating material for use in construction materials. For example, the foam may be used as a cavity wall insulating foam. In particular, where partitions or stud walls contain a cavity or sandwich structure, the foam may be injected or placed in the cavity or space between the wall structures. The foam may be provided in a liquid form, suitable for injection into the cavity or wall space. Alternatively, the foam may be provided pre-moulded and the walls may be constructed around the foam. The foams of the present invention are particularly useful where additional support or strength is required, i.e., where the cavity wall is thin or insubstantial.

Although it is envisaged that any of the treated fibres of the present invention may be used to provide foams according to the present invention, in a particularly preferred embodiment, the treated fibres used in the production of the foam derived from waste paper (such as newsprint, cardboard, domestic or commercial waste paper, and the like). This is particularly the case in the construction of building materials such as walls, roofs and floors.

Where foam formulation is provided in liquid form (i.e., prior to foaming, hardening or curing), a wide range of blowing agents may be used in order to produce the foam. In certain embodiments it is preferred that the blowing agent includes one or more HFCs as blowing agents, more preferably one or more C1-C4 HFCs, and/or one or more hydrocarbons, more preferably 04 -C6 hydrocarbons. For example, with respect to HFCs, the present blowing agent compositions may include one or more of difluoromethane (HFC-32), fluoroethane (HFC-161), difluoroethane (HFC- 152), trifluoroethane (HFC-1 43), tetrafluoroethane (HFC-1 34), pentafluoroethane (H FC-125), pentafluoropropane (H FC-245), hexafluoropropane (H FC-236), heptafluoropropane (H FC-227ea), pentafluorobutane (H FC-365), hexafluorobutane (HFC-356) and all isomers of all such HFC's. Alternatively, CO2 may be used as the blowing agent.

Accordingly, the present invention provides foamable compositions containing one or more foam-forming components and fibres according to the first aspect of the present invention. As used herein, the term "foam foaming agent" is used to refer to a component, or a combination of components, which are capable of forming a foam structure, preferably a generally cellular foam structure. The foamable compositions of the present invention preferably include such component(s) and optionally a blowing agent compound. In the case where the foam-forming components are self foaming (because of the generation of gas via reaction) there is no need for a separate blowing agent.

Examples of thermosethng compositions include polyurethane and polyisocyanurate and phenolic foam compositions. This reaction and foaming process may be enhanced through the use of various additives such as catalysts and surfactant materials that serve to control and adjust cell size and to stabilize the foam structure during formation.

In certain other embodiments of the present invention, the one or more components capable of foaming comprise thermoplastic materials, particularly thermoplastic polymers and/or resins. Examples of thermoplastic foam components include polyolefins, such as for example monovinyl aromatic compounds of the formula Ar-OH =CH2 wherein Ar is an aromatic hydrocarbon radical of the benzene series such as polystyrene. Other examples of suitable polyolefin resins in accordance with the invention include the various ethylene resins including the ethylene homopolymers such as polyethylene and ethylene copolymers, polypropylene (PP) and polyethyleneterepthalate (PET). In certain embodiments, the thermoplastic foamable composition is an extrudable composition.

The methods generally comprise providing a foam forming composition, to which is added a quantity of fibres. The composition can then be reacted under the conditions effective to form a foam or cellular structure, as is well known in the art.

Any of the methods well known in the art, such as those described in "Polyurethanes Chemistry and Technology," Volumes I and II, Saunders and Frisch, 1962, John Wiley and Sons, New York, NY may be used or adapted for use in accordance with the foam embodiments of the present invention. In general, such preferred methods comprise preparing polyurethane or polyisocyanurate foams by combining an isocyanate, a polyol or mixture of polyols, an optionally one or more materials selected from the group consisting of blowing agents or a mixture of blowing agents, catalysts, surfactants, flame retardants, colorants, and other additives.

Accordingly, polyurethane or polyisocyanurate foams are readily prepared by bringing together the foam components either by hand mix for small preparations and, preferably, machine mix techniques to form blocks, slabs, laminates, pour-in-place panels and other items. Optionally, other ingredients such as fire retardants, colorants, auxiliary blowing agents, and even other polyols can be added as one or more additional streams to the mixture or reaction site.

The foams of the present invention preferably comprise between 2 and 40 wt % of treated fibres according to the present invention, more preferably between 10 and wt % thereof.

The Applicants have found that one advantage of the foams according to the present invention, and particularly thermoset foams, such as polyurethane, is the ability to achieve a combination of improved structural integrity and exceptional thermal performance. The foams in accordance with the present invention may also provide one or more of improved dimensional stability, compressive strength, water resistance, excellent lamination and/or adhesive properties.

In a particularly preferred embodiment, the board or panels of the present invention may be used in combination with the foam of the present invention in order to provide an insulated wall for a building.

The composite materials of the present invention, particularly the foam materials, preferably include a fire resistant or flame retardant material.

One means of improving the fire resistance of the composites of the present invention involves coating a moulded composite article with a finish that imparts fire resistance. To obtain such a finish, a coating containing the ingredient that imparts fire resistance is applied by spraying, roll coating, brushing or other means onto the surface of the already moulded composite product. An alternative means of imparting fire resistance is by addition of a flame retardant additive to the composite matrix resin or foam premix before it is cured to form the composite or foam. Such flame retardant additive compounds include melamines and polyvinyl chloride. The flame retardant may be added in an amount sufficient to provide effective flame suppression. Typically, the amount of the flame retardant additive ranges from about 1% by weight to about 40% by weight, for example about 1% to about 5% of the composite or foam material.

While the articles of manufacture of the present invention comprise a treated natural fibre as set out above, the invention does not exclude the additional presence of other types of fibre reinforcing material. Such optional fibrous materials may include glass, carbon, natural fibres, polymers, other fibreizable materials known in the art, or mixtures thereof. Examples of fibrous carrier materials that can be used either alone or in combination with glass or carbon fibres include thermoplastics, polyaramids such as KEVLAR�.

Where moulding of the composite materials of the present invention takes place, they may then be moulded using any one of several moulding means known in the art. The composites can be moulded using compression moulding, injection-compression moulding, vacuum moulding and/or injection moulding.

The composite materials are preferably heated in the mould or prior to entering the mould. In order to cure the composite materials, they may be heated in the range of 25-300°C, preferably 60°C-200°C.

The construction of conventional external and internal walls, ceiling walls and roof systems requires a variety of materials, some of which are relatively heavy. The installation of these materials can also be complex and require varying degrees of precision. Thus, installation of these materials is often labour-intensive, which can result in higher costs being associated with the construction of these types of buildings. Thus, in one embodiment, the present invention provides a pre-manufactured structural building panel system whereby the structural panels can be constructed inexpensively and efficiently off-site for subsequent installation at the construction site. The individual structural panels may made of a pair of structural panels at least partially sandwiching a foam insulation according to the present invention. Alternatively or additionally, the panels themselves can be formed from a composite material containing fibres according to the first aspect of the invention.

A plurality of adjacent pre-manufactured structural building panels can be positioned together to form an interior or exterior wall member of a building. The exterior wall members of a building according to the present invention can include vertical sidewalls, a horizontal roof and ceiling wall, or a slanted roof having a predetermined pitch. As such, the entire exterior and/or of a building can be comprised of building panels according to the invention.

A further use of the treated fibres according to the present invention is to clean up hydrophobic water-immiscible liquid spillage. For example oil spillage in water is a serious health, safety and environmental risk. Also, oil or lubricant spillage around machinery is particularly inconvenient. According to an aspect of the present invention there is provided, for use as an absorbent of hydrophobic water-immiscible liquids, fibres which have been treated according to the first aspect of the present invention. In this aspect of the present invention, the fibres may be presented as an un-consolidated fibres which may be spread on the target liquid.

The fibres may then be swept or vacuumed up to remove them. Alternatively, the treated fibres may be formed into a mat or sheet which can be spread onto the spillage, or put down in anticipation of a spillage. In this aspect of the invention, the treated fibres are preferably those derived from recycled paper (although all treated fibres of the present invention are suitable). This provides an economic use of waste paper. According to this aspect of the invention there is also provided a method of absorbing hydrophobic water-immiscible liquids comprising treating the liquid with the treated fibres.

Examples of hydrophobic water-immiscible liquids which may be absorbed by the modified fibres are crude and refined oil, solvents such as white spirit, toluene benzene and pesticide residues.

The treated fibres are capable of absorbing up to 50 times their own weight of hydrophobic water-immiscible liquids from a spillage thereon in water and will retain up to 30 times their own weight when removed from water and allowed to drain. There is the additional advantage that the treated fibres form a discrete mass of hydrophobic water-immiscible liquid and fibres which floats on clean water whereas untreated fibres forms a mass of hydrophobic water-immiscible liquid and fibres which floats on an emulsified hydrophobic liquid/water mixture. In other words, use of untreated material causes oil to be "dragged" into the water whereas the treated fibres leave the water "clean". This has considerable implications for the clean-up of hydrophobic water-immiscible spillages in inland waterways or in areas where environmental protection is important. The treated fibres have the further advantage, over untreated fibres, in that it is less biodegradable and therefore less likely to deteriorate during storage.

The process for producing fibres according to the present invention is preferably as follows. The untreated fibres used in the present invention are preferably dried prior to treatment. Preferably, the untreated fibres have a water content of less than 4%, preferably about 2% or less by weight.

The natural fibres are subjected to a reaction with the anhydride. In a preferred embodiment, this is a maleation reaction.

The process is preferably carried out in the liquid phase. For example, the reaction may be carried out by immersing the untreated fibres in a mixture of anhydride and a suitable catalyst. Such suitable catalysts include acid catalysts, for instance sulphuric acid, organically substituted sulphuric acids, e.g. benzene sulphonic acid, bisulphates e.g. sodium bisulphate, sulphuryl chloride, and the like, most preferably sulphuric acid. The catalyst is preferably present in an amount of less than 2% by weight of the reagent solution, preferably less than 1 wt %.

The reaction is preferably carried out in the presence of an organic solvent, preferably a hydrocarbon solvent, more preferably a C2-C12 hydrocarbon solvent.

As the above solvents, there may be mentioned, for example, hydrocarbon solvents such as benzene and toluene; ether type solvents such as diethyl ether, tetrahydrofuran, diphenyl ether, anisole and dimethoxybenzene; halogenated hydrocarbon solvents such as methylene chloride, chloroform and chlorobenzene; ketone type solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ester type solvents such as ethyl acetate and butyl acetate; These may be used singly or two or more of them may be used in admixture. The most preferred solvents include benzene, toluene, ether and acetone, most preferably toluene or acetone or a mixture thereof.

Where maleic anhydride is the reagent for the fibre modification, the preferred solvent is a ketone, preferably acetone, which may be used in combination with other hydrocarbon solvents such as toluene or benzene.

The level of modification of untreated fibres (for example, the level of maleation) may be controlled by using a proportional quantity of reagent to weight of untreated fibre. This way, a level of modification of any amount, particularly 16-20 % weight increase, can be achieved reliably and without having to use batch methodology.

If a sufficient quantity of anhydride, and if desired of solvent or diluent, is already present with the cellulose, it will only be necessary to add a suitable catalyst, while if further reagents are necessary, for example further anhydride, such reagent or reagents may be added together with the catalyst.

In a preferred process, the treatment can be carried out in a reaction pressure vessel by submerging the natural fibres in a reagent solution or gas containing the anhydride and any catalysts or solvents required to carry out the reaction.

The fibre may be vacuum impregnated with the reagent solution or gas in order to speed up the introduction of reagents to the fibre.

In a preferred process, the reaction of the anhydride with the cellulose of the fibre is carried out in the presence of an inert gas, such as nitrogen or argon, preferably nitrogen. Preferably, oxygen is substantially excluded from the reaction environs.

Preferably the reaction vessel contains less than 1 % vol. oxygen, preferably less than 0.1 % vol. oxygen. Preferably nitrogen in present in greater than 90% vol., preferably greater than 95 % vol. of the reaction environs.

The pressure in the pressure vessel may be in the range of 2 to 20 bar for a period of 3 to 300 minutes, more preferably 2-10 bar for a period of 5 to 20 minutes.

The reagent solution may have a temperature of 10°C to 120°C preferably 15°C to 50°C, more preferably between 18°C and 25°C.

Particularly good results are obtained where the modifying reagent, e.g., the anhydride, is vaporised prior or during the reaction with the cellulose of the fibre.

This may be achieved for the mass of the reagent solution, or locally by using microwaves or ultrasound energy.

The treated fibres may be separated from the treatment mixture by any means, such a filtration, cyclonic separation, evaporation and mixtures thereof, preferably by cyclonic separation.

Any excess reagent fluid may be removed from the vessel after the reaction has been carried out.

In a particularly preferred process, the treatment of the fibres is carried out in the presence of ultrasonic energy, for example, in the vicinity of a working ultrasonic probe or of an ultrasonic energy transducer, such as a wrap-around ultrasonic energy transducer. The ultrasonic energy may be applied continuously or in a discontinuous manner, such as by pulsed application. Any suitable source of ultrasonic irradiation may be used. An ultrasonic probe may, for example, be inserted into a reaction vessel. Such a vessel may be a continuous flow reaction vessel or a batch mixing vessel. The ultrasonic emitter may be contained in the vessel, or the vessel may be housed in an ultrasonic bath or it may have an ultrasound transducer fixed to the external walls of the vessel. The amplitude and frequency of the ultrasound waves affects the rate of nucleation and crystal growth.

The frequency of the ultrasound waves may for example be from 16 kHz to 1 MHz, preferably from 10-500 kHz, more preferably from 10-100 kHz such as at 10, at 20, 40, 60, 80, or 100 kHz or at any frequency thereinbetween, such as, 30 kHz or 50 kHz. The use of ultrasound has the advantage of reducing damage to the fibres which may occur when excessive heat is required to drive the reaction. Thus, the present invention may be carried out at ambient temperatures.

The ultrasonic irradiation is employed at an amplitude that is appropriate for the formation of crystals of the desired size, for a pre-determined application. For laboratory probe systems with an emitting face of, for example 80 cm2, the amplitude selected may be from about 1-30 pm, typically from 3-20 pm, preferably from 5-10 pm, for examp'e, 6pm. The probes preferably have a power requirement of from 0.1-50 KW.

The reaction mixture may be cooled so as to prevent an excessive rise in temperature when the reaction takes place.

The treatment may be carried out for a period of 3 to 300 minutes, such as a period of 5 to 20 minutes. The treatment can be carried out rapidly and is preferably completed in about 5-30 minutes, preferably 5-15 minutes.

The treated fibres may be removed from the solution after treatment has taken place, optionally washed, and dried. The fibres may be dried by any conventional means, such as a drying oven. In a preferred embodiment, the fibres are dried with microwaves or infrared. Drying is preferably carried out in a drying tunnel on a conveyor.

Drying of the treated fibres or product is carried out until there is less than 4 wt % residual solvent in the treated fibres, preferably less than 1%.

The treatment process of the present invention is preferably a continuous process.

Where a felt of fibres is modified in accordance with the invention, preferably the felt of untreated fibres is passed from a roll of felt into a bath, preferably around festoons, to be treated with the modifying reagent solution. The felt may then be removed from the bath when the requisite weight gain has been achieved and onto another roll. Optional drying steps may be carried out during or after the rolling of the felt onto the second roll. Preferably, the felt is vacuum impregnated with the reagent solution.

The treatment may be carried out continuously by forming a fibrous layer or layers, such as a needle felt. This may be passed through a reaction bath via a conveyor system, thereby producing a length of treated felt. A conveyor can then be used to remove the layer(s) from the bath and excess solvent/unused reagents may be removed, preferably by rolling (preferably with squeeze rollers). The resultant felt may then be dried and optionally rolled into a bale.

Any unused reagent components, and solvents or diluents may be recycled into the process. Such ingredients are replenished with appropriate amounts of reagents.

The relative amounts of reagents may be monitored by conventional methods such as spectroscopy.

Preferably, a constant level of reagents is present in the reagent composition.

Thus, they may be replenished continuously, thereby allowing for a continuous process to be operated.

The untreated fibres may also be treated with ultrasound, preferably in a solvent or water, in order to clean them and to remove unwanted material (such as bark husk and/or shives) prior to treatment with the anhydride. A detergent may also be used in this cleaning process.

The following is a preferred process for the production of fibres of the present invention. A roll of felt containing untreated fibres used in the present invention, preferably needle felt, is used in an impregnation process, preferably a vacuum impregnation process. Preferably, the felt is dried to less than 4 wt % water prior to impregnation. The needle felt may be impregnated with a solution of the anhydride reagent, optionally containing solvent(s) and catalyst(s). The needle felt may then be rolled up on itself. This roll can then be placed in a container, such as a plastic or glass container. The roll may then be subjected to micro-wave energy, for example, in a micro-wave oven. Alternatively, RF or lR radiation may be used to effect the reaction. Preferably the reaction with the anhydride is carried out under an inert gas, such as nitrogen. Preferably, the felt is also dried in a nitrogen atmosphere. The production of a roll of felt in this way is particularly useful for the production of the felts used in the production of resin-impregnated structural panels and parts for trains, planes and automobiles.

Detailed Description of the Invention

General The term "comprising" encompasses "including" as well as "consisting" e.g. a composition "comprising" X may consist exclusively of X or may include something additional e.g. X + Y. The term "about" in relation to a numerical value x means, for example, x+10%.

The word "substantially" does not exclude "completely" e.g. a composition which is "substantially free" from Y may be completely free from Y. Where necessary, the word "substantially" may be omitted from the definition of the invention.

For the purposes of the present invention, a fibre is an elongate body the length dimension of which is greater that the transverse dimensions of width and thickness. Accordingly, the term "fibre" includes monofilament and multifilament, staple and other forms of chopped, cut or discontinuous fibre and the like having regular or irregular cross-section. The term "fibre" includes a plurality of any of the foregoing or a combination thereof.

The cross-sections of fibres useful herein may vary widely. They may be circular, flat or oblong in cross-section. It is preferred that the fibres be of substantially circular, flat or oblong cross-section, most preferably circular.

The term "fibres" or "fibre" as used in the present invention is intended to mean individual fibres or small groups of fibres, rather than large groups of consolidated or adhered fibres, such as those found in bulk materials, such as wood. For example, the untreated fibres used in the present invention, where present in consolidated bunches of fibres, preferably do not exceed 200 fibres in any one group, more preferably less than 100 fibres, for example, less than 50, 25 or 10 fibres. Preferably, natural untreated fibres used in the present invention are either individual (separate fibres) or are in groups of 2, 3, 4, 5, 6, 7, 8 9 or 10 fibres.

The term "untreated fibres" means any fibres which have not been subjected to the treatment set out in the first aspect of the present invention. However, the term "untreated fibres" is intended to cover natural fibres which have been subjected to cleaning and removal of in excess of 50 wt % of non-fibrous material, preferably greater than 80 wt % of non-fibrous material, preferably greater than 90 wt % of non-fibrous material, preferably greater than 95 wt % of non-fibrous material.

As used herein, the term "treated fibre" is intended to mean a fibre which has been treated according to the first aspect of the invention. More specifically, the treatment is with a reagent solution or gas in order to achieve a reaction between the cellulose in the natural fibre and the reagent which results in the formation of a reaction product (a residue) between the reagent and the cellulose. This is carried out until a weight gain of preferably between 16 and 20 wt % is obtained in the fibre.

Examples of the Present Invention In all of the following examples, the fibres were treated with maleic anhydride.

The physical properties and advantages of treated natural fibre according to the present invention compared to glass fibre are as follows.

Treated natural fibre according to the present invention has a specific gravity (SG) of between 1.05 and 1.1 compared to 2.54 for "E" glass. The stiffness of the glass fibre is about 20% to 25% greater than that for the modified natural fibre, but when expressed as specific stiffness (stiffness/SG) treated natural fibre is significantly superior to glass fibre.

Comparison of Glass and Natural Fibre Properties Glass Fibre Natural Fibre Density g/cm3 2.54 1.10 Tensile Modulus -MPa 70,000 55,000 Specific Tensile Modulus -MPa 27,500 50,000 Tensile Strength -MPa 3,000 1,200 Specific Tensile Strength -MPa 1,180 1,100 Significant weight reduction is gained where treated natural fibre according to the present invention is used as a replacement for glass fibre. This leads to competitive cost advantages -at the indicated price parity with glass on a weight basis, the effective volume cost of modified fibres is approximately half that of glass fibre. This volume cost reduction is particularly significant in large size mouldings, especially in the transport sector where weight considerations are important.

The bulky nature of modified fibre makes it especially suited to closed mould techniques for the production of products. Either premixed compound, pre-impregnated fibres or dry fibre with resin added in mould' can be used. Compared to glass, modified natural fibres are not generally abrasive and do not require special "sizing" to ensure good adhesion to the matrices. Modified fibres are useful reinforcements for thermoplastics, preferably where the processing temperature does not exceed 200°C.

Evaluation of Bio-deterioration and the Effects of Water Testing carried out shows that biological deterioration on the fibres when exposed to treated water is negligible and that when composites of untreated and treated fibres according to the present invention are exposed to cold and hot water, the latter displays significantly better strength retention properties.

Evaluation of Chopped Fibres in Thermoplastic Resins Chopped fibres (1 to 10 cm long) have been evaluated in polyethylene and other low melt thermoplastics at fibre levels of between 10 per cent and 30 per cent of the compound weight. Investigation showed the following:-Physical Properties of modified Jute-Reinforced Thermoplastic Resins Flexural Strength Flexural Modulus (MPa) (M Pa) ____________________ Polypropylene 44 1,300 PP + 40% weight treated jute 69 5,350 PP + 50% weight treated jute 67 6,280 Evaluation of Chopped Fibres in BMC & SMC (Thermosetting Resin Chopped fibres have also been evaluated in bulk moulding compound (BMC) and sheet moulding compound (SMC) with comparable results.

Polyester, epoxy and phenolic resin matrices are all suitable with no fibre "pull-ouV from cured specimens observed at fracture faces.

In BMC, a type of moulding material in which liquid thermosetting resin is compounded with mineral fillers and reinforcing fibres used for a wide range of industrial components and machine covers, comparable fibre volume gives the foJiowing fiexurai (bending) strength, when short fibre length is used (1 to 5 cm).

Glass Fibre Treated Jute Break Strength 42-45 MPa 40-45 MPa Flexural Modulus (Stiffness) 3300 -3800 MPa 3300 -4000 MPa For larger mouldings, such as building panels for roof and wall cladding where fire resistance is important, phenolic resins are preferred and stiffness required giving resistance to bending under wind and snow loading. Using long fibres the stiffness comparison is: Modulus in bend Modulus in tension modified Jute Unidirectional 10000 MPa 5000 MPa Modified Jute Cross Directional 6500 MPa 5000 MPa Glass Random Directional 6000 MPa 6000 MPa Physical properties of composites depend to a large extent on fibre orientation and volume fraction. Bulk moulding compound made from epoxy resin, hot moulded, with 25 per cent volume of chopped fibre and 25 per cent volume of clay filler, resulted in very similar flexural properties, for both glass and maleated natural fibres.

A detailed investigation of both modified jute and modified flax in epoxy resin sheet moulding compound, varying the fibre volume between 15 per cent and 40 per cent, shows that both breaking strength and flexural modulus increase with the fibre volume whilst the SG reduces.

Glass fibre based SMC and BMC typically have SG in excess of 1.5 up to 2.0, dependent upon the formulation and particulate filler selection. Corresponding modified natural fibre composites have SG between 1.2 and 1.35. Significantly, where glass is the reinforcing fibre, the SG increases as more glass is used whereas in the case of maleated natural fibre, the SG reduces as the fibre content increases.

Where only fibre and resin are used, the SG of composites using maleated natural fibre is lower than that of the resin alone, i.e. between 1.05 and 1.15 depending on resin and fibre ratio.

Evaluation of (Unidirectional) Fibre in Phenolic Resin Modified natural fibre with phenolic resin, where the fibres are used as continuous roving and orientated in a single direction, yield high strength moulding (see, Table x below). At a resin to fibre ratio of 1:2, flexural strength of 120 MPa and modulus of 15,000 MPa along the fibre direction is achieved. Untreated natural fibres give the same physical properties, however after immersion in water for 24 hours the untreated fibre samples showed significant loss in modulus.

Composite Initial After 24 h @ 20°C After 24h @ 80°C Flexural Modulus (MPa) Treated Fibre 14,800 14,300 11,400 Untreated Fibre 14,100 10,250 8,800

Brief Description of the Drawings

Figure 1 shows an electron micrograph of a fibre treated according to the present invention (-18 wt% increase by maleation). It can be seen that the fibres are relatively straight.

Figure 2 shows an electron micrograph of a fibre treated according to the present invention (--18 wt% increase by maleation). This shows that the fibres are structurally in tact, i.e., not fractured.

Figure 3 shows an electron micrograph of a fibre treated with amounts of maleic anhydride in excess of> 20 wt%. It can be seen that the fibres are bent.

Figure 4 shows an electron micrograph of a fibre treated with amounts of maleic anhydride in excess of> 20 wt%. It can be seen that the fibres are fractured.

Figure 5 shows an apparatus for carrying out a continuous process for treating a needle felt according to the process of the present invention.

Claims

Claims 1. A natural fibre comprising a modifying group derived from the reaction of an aliphatic or aromatic anhydride with the cellulose of the natural fibre.
2. A fibre according to claim 1, wherein the natural fibre comprises between 5 and 40 wt % of the modifying group.
3. A fibre according to claim 1 or claim 2, wherein the natural fibre comprises between 16 and 20 wt % of the modifying group, for example about 16, 17, 18, 19 or 20 wt %.
4. A fibre according to any preceding claim, wherein the fibre is selected from the group consisting of seed fibres, leaf fibres, bast fibres, skin fibres, fruit fibres, stalk fibres and mixtures thereof, preferably selected from the group consisting of fique, sisal, banana, agave, wheat, rice, barley, bamboo, grass, coir, cotton, flax, hemp, ramie, jute, kenaf and mixtures thereof.
5. A fibre according to any of claims 1, 2 or 3, wherein the fibre is derived from recycled paper.
6. A fibre according to any preceding claim, wherein the anhydride and is selected from the group consisting of maleic anhydride, itaconic anhydride and succinic anhydride and mixtures thereof.
7. A fibre according to claim 6, wherein anhydride is maleic anhydride.
8. A fibre according to any preceding claim, wherein the fibre is fibres of the present invention are on average 5 pm to 100 pm in diameter.
9. A fibre according to any preceding claim, wherein the fibres are on average 500pm to 10cm in length.
10. A natural fibre according to any preceding claim comprising at least one HO2CCH=CHC(O)2-modifying group bonded to the cellulose of the fibre.
11. An article of manufacture comprising a fibre according to any preceding claim.
12. An article of manufacture according to claim 11, wherein the article of manufacture is a structural article used in the manufacture of buildings; furniture; vehicles, including trains, automobiles, aircraft, spacecraft, boat hulls; railway sleepers and hydrophobic absorbents.
13. An article of manufacture according to claim 11 or claim 12, wherein the article of manufacture is a composite material comprising a resin or plastic and optionally a filler.
14. An article of manufacture according to any of claims 11 to 13, containing between 5 and 95 wt % of the treated fibres and between 5 and 95 wt % of the resin.
15. An article of manufacture according to any of claims 11 to 14, wherein the resin is selected from the group consisting of polyester resins, furan resins, phenolic resins, epoxy resins, vinyl ester resins and mixtures thereof.
16. An article of manufacture according to any of claims 11 to 15, wherein the article is a board, panel, strut, reinforcement, beam, lintel, brick, breeze block, paving slab, joist or needle felt.
17. An article of manufacture according to any of claims 11 or 12, wherein the article is a foam, preferably a polyurethane, polyisocyanurate or phenolic foam.
18. An absorbent article comprising a fibre according to any of claims 1 to 10, for absorbing hydrophobic liquids.
19. A process for the production of a fibre according to any of claims 1 to 10, comprising: (a) immersing a natural fibre having a residual water content of less than 4% in a reaction container, preferably a reagent bath, comprising an aliphatic or aromatic anhydride and a catalyst; (b) reacting the an aliphatic or aromatic anhydride with the cellulose of the natural fibre until a predefined fibre weight gain is obtained; (c) removing the fibre from the reaction container; and (d) drying the fibre.
20. A process according to claim 19, wherein the predefined weight gain is 16 to 20 wt %
21. A process according to claim 19 or claim 20, wherein the reagent bath comprises maleic anhydride, and optionally a solvent selected from the group consisting of hydrocarbons, ketones and mixtures thereof.
22. A process according to claim 19 or claim 20 or claim 21, wherein the reagent bath comprises less than 1 wt % acetic anhydride, preferably no acetic anhydride.
23. A process according to any of claims 19-22, wherein the natural fibre of step (a) is provided in the form of a needle felt.
24. A process according to any of claims 19-23, wherein the fibres of step (a) are vacuum impregnated with the anhydride and the catalyst.
25. A process for producing an article of manufacture according to any of claims 11 to 16, wherein the article is formed by impregnating a layer containing a fibre according to any of claims 1 to 10 with a resin and optionally a filler, placing the article in a mould, applying pressure to the mould and optionally heat, and removing the article from the mould.
26. A process for producing a foam according to claim 17, comprising providing a foam-forming composition, adding a fibre according to any of claims 1 to 10 and foaming the foam-forming composition.