Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
  • C08J5/045—Reinforcing macromolecular compounds with loose or coherent fibrous material with vegetable or animal fibrous material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/02—Cellulose; Modified cellulose
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L61/00—Compositions of condensation polymers of aldehydes or ketones; Compositions of derivatives of such polymers
  • C08L61/20—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
  • C08L61/26—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with heterocyclic compounds
  • C08L61/28—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with heterocyclic compounds with melamine

Definitions

• the invention relates to a composition based on a thermosetting resin and cellulose fibres.
• a composition is known from EP-A-200.409, which describes how certain types of cellulose fibres of bacterial origin can be isolated and used for all kinds of applications, for example as reinforcement in thermosetting resins.
• EP-A-200.409 describes how certain types of cellulose fibres of bacterial origin can be isolated and used for all kinds of applications, for example as reinforcement in thermosetting resins.
• EP-A-200.409 is that the reinforcement of the thermosetting resin by the cellulose fibres is not optimum.
• the cellulose fibres consist of microfibrils with a length/diameter ratio (aspect ratio) of at least 50, a length of at least 0.5 ⁇ m and a crystallinity of at least 60%, which comprise large crystalline zones.
• the microfibrils have a length/diameter ratio of between 75 and 3000 and a length of between 1 ⁇ m and 200 ⁇ m, more preferably a ratio of between 100 and 1000 and a length of between 5 and 100 ⁇ m.
• the microfibrils may be of any suitable origin, for example animal, vegetable or synthetic; preferably they are of an animal or a vegetable origin.
• microfibrils examples include shellfish such as tunicata and plants such as flax, hemp, sisal, wood, valonia, ramie, cotton or jute.
• Microfibrils with a diameter of 10-20 nm with a high crystallinity can be isolated from the aforementioned tunicata shellfish.
• the microfibrils consist of one or more large crystalline zones and have an overall crystallinity of at least 80%.
• Cellulose microfibrils are described in EP-A- 120.471, but there the microfibrils are used to prepare a gel for use in foodstuffs or cosmetics.
• cellulose microfibrils as fibrous reinforcing material has also been described by C. Klason in 'Cellulose in Polymeric Compositions', Composite Systems from Natural and Synthetic Polymers, edited by L. Salmen, Elsevier Science Publishers BV, Amsterdam, 1986, p. 65 ff.
• the said article only mentions the combination of cellulose microfibrils with thermoplastics.
• the article mentions prehydrolized cellulose (bleached pine sulphate) with a length/diameter ratio of more than 100, but with a submicron length.
• the article characterises microfibrils as a promising material but does not present a solution to the problems involved in the production and processing of such fibrils, such as gelling or breaking of fibres.
• cellulose microfibrils as fibrous reinforcing material is also mentioned in WO-A-8912107, but the described cellulose is of microbial origin and consists of a gel-like mass of intertwined, curled, branched ribbons of poorly crystalline microbial cellulose fibrils because a agent is added to the nutrient bath, which agent interferes with the crystallization of the cellulose.
• thermosetting compositions are also described in EP-A- 260.183, but this patent publication does not mention the use of cellulose microfibrils.
• the composition according to the present invention can be obtained by subjecting a cellulose source to a treatment comprising of removing the non-crystalline material, dispersing the crystalline material to obtain microfibrils and suspending the microfibrils to prevent coagulation.
• X-ray diffraction and electron microscopy data have shown that the cellulose fibrils obtained according to the invention are long straight fibrils, containing almost perfect crystalline zones, the zones having a width of approximately 15 n and lengths of several hundred nanometers.
• Powder diffraction data show that the crystallinity of bacterial cellulose is much lower than the crystallinity of the cellulose fibrils made according to the present invention.
• the invention hence also relates to a process for the preparation of a composition containing a thermosetting resin and cellulose microfibrils wherein a) a material containing cellulose fibres and optionally residual material is decomposed to fibrils and the residual material is removed; b) the fibrils are dispersed in a solvent and stabilised; c) the solvent is optionally entirely or partially removed; d) the fibrils are combined with the thermosetting resin to obtain a compound.
• the residual material can be removed by rinsing with a sodium hydroxide solution and/or bleach.
• the dispersing is preferably carried out in a homogeniser.
• a homogeniser is an apparatus that is used to homogenise compositions with the aid of high pressures.
• An example of such a homogeniser is the Gaulin Laboratory Homogeniser, from APV Gaulin International S.A. at Hilversum, the Netherlands.
• the suspension of the microfibrils and hence the stabilisation can be effected via the addition of an acid.
• the acid may be for example H 2 S0 4 or HC1.
• the microfibrils are mixed with a thermosetting resin, by dispersing them in a diluted solution of the resin, for example in water.
• the advantage of said process according to the present invention is that the microfibrils are more homogeneously distributed throughout the composition and that less fibre breakage will occur than in the case of a mixing method involving for example compounding in an extruder.
• a disadvantage of said process according to the invention is that the amount of fibres in the product to be obtained is relatively small.
• An additional disadvantage is that all the solvent has to be evaporated. The solvent can be removed through filtration, evaporation and/or freeze drying.
• the microfibrils are mixed with the resin by first processing the fibres to obtain a flat body, for example a plate or a fleece, and then impregnating this flat body with a thin liquid resin, either in the molten state or in solution. If only a small amount of resin can be applied in one impregnation treatment, the treatment can be repeated once or several times.
• the fibres and the resin are mixed in a ratio between 5:1 and 1:5, preferably around 1:1, in a diluted solution, which is then evaporated by means of spray drying. The result of this treatment is a powder consisting of thermosetting resin and cellulose fibres in the aforementioned ratio.
• the product obtained according to the first or second embodiment described above can be ground to obtain a powder consisting at least of microfibrils and an uncured resin. It may be necessary to first dry the product completely or partially before grinding it.
• the obtained powder has the advantages that it can easily be stored, transported and processed.
• the thermosetting resin can be chosen from all possible resins that can be used in compounds. Examples are unsaturated polyesters, epoxy resins, acrylate resins, urethanes, aminoplastics and vinyl-ester resins. Preferably, the resin is chosen from the group consisting of unsaturated polyesters, aminoplastics and epoxy resins.
• the aminoplastic is preferably a melamine-formaldehyde, a urea formaldehyde or a phenol formaldehyde or a mixture thereof.
• the resin may also contain all possible additives, such as co-reacting monomers or solvents.
• the resin may contain initiators and/or catalysts, in an amount known to a person skilled in the art. It is possible to modify the surface of the fibres to realise a better adhesion between the fibres and the resin material. This can be done for example by treating the fiber with isocyanates or via other methods known to a person skilled in the art.
• a fibre-reinforced resin composition according to the invention can also be defined as a compound.
• a compound can be obtained in the form of a so-called sheet moulding compound (SMC), a dough moulding compound (DMC) , a bulk moulding compound (BMC), a melamine-fo ⁇ aldehyde compound (MFC), the described powdery composition or any other form of fibre-reinforced resin composition.
• SMC sheet moulding compound
• DMC dough moulding compound
• BMC bulk moulding compound
• MFC melamine-fo ⁇ aldehyde compound
• Compounds normally known in the art comprise glass fibers as reinforcing material.
• composition can be thickened according to a method known to a person skilled in the art.
• the compound may further contain the usual additives, for example pigments, fillers such as calcium carbonate, aluminium trihydroxide or cellulose, initiators, accelerators, inhibitors, mould-release agents, other reinforcing agents, etc.
• additives for example pigments, fillers such as calcium carbonate, aluminium trihydroxide or cellulose, initiators, accelerators, inhibitors, mould-release agents, other reinforcing agents, etc.
• fibrous reinforcing agents may be chosen from the group comprising for example cellulose fibres, glass fibres, carbon fibres, mineral fibres such as rock wool, aramide fibres, metal fibres, other natural fibres, for example of cotton, jute, sisal, flax or wood, synthetic fibres such as polyethylene fibres or polyester fibres, other microfibres such as microcarbon fibres, or combinations hereof.
• the other fibres may be used in any way in which fibrous reinforcement is usually added to a resin, for example as loose fibres, as long, short or endless fibres, as a mat, " a fleece, a woven, knitted or braided fabric or otherwise, randomly arranged or specially oriented.
• the composition preferably consists of 99-20 vol.% (relative to the overall composition) thermosetting resin, 1-80 vol.% (relative to the overall composition) fibrous reinforcement, consisting of 5-100 vol.% microfibrils, and 0-75 vol.% filler. - More preferably, the composition contains 0.5-60 vol.% (relative to the composition) microfibrils; most preferably 1-50 vol.%.
• the compound according to the invention can be processed according to any method for processing compounds known to a person skilled in the art.
• compounds are processed by allowing them to cure in a particular shap under pressure, at an elevated temperature.
• the tensile strength was determined using a Zwick series type 1400 apparatus using a specimen with a width of 20 mm, a bending length of 90 mm, a free stretching length of 40 mm and a strain measurement length of 20 mm at 1% ⁇ in.
• the bending test was carried out according to ASTM D790M.
• the impact resistance was determined according to ISO standard 179, 'Plastics - Determination of Charpy impact strength of rigid materials' using unnotched bars of 10x4x80 mm; the distance between the supports was 40 mm.
• the shells were disintegrated in water with the aid of a Waring blender, after which the suspension obtained was diluted to a concentration of 1% (w/v) and was homogenised in a GAULIN 15 M BTA laboratory homogeniser. The result was a dispersion of microfibrillated cellulose.
• the mixture was filtered using a glass filter with a Dl porosity to separate coagulated cellulose.
• microfibrils and the suspension were then collected through filtration using a glass filter with a D4 porosity and were then rinsed with diluted sodium hydroxide and distilled water.
• the microfibrils were dispersed in water once again and were subjected to a treatment in an ultrasone bath for 2 minutes using a Bronson B12 Sonifier. The result was an 0.7% (w/v) suspension of cellulose microfibrils in water.
• the microfibrils had diameters of between 10 and 20 nm and lengths of different ⁇ m. The length/diameter ratio was above 100 on average.
• microfibrils comprise large monocrystalline zones or whiskers, as appeared from e.g. dark-field electron microscopy. This showed that the straight microfibrils consisted of single crystalline zones with lengths of at least several dozen nm. The crystalline domains were probably longer but they were not observable with this method because they lay slightly out of the plane (and hence outside Bragg refraction conditions). This was confirmed by means of X-ray diffraction. The elements will be called MFC.
• a 55% melamine-formaldehyde solution was prepared by dissolving 611 g of spray-dried melamine- formaldehyde powder in 500 ml of distilled water at 80°C. --- The feltlike sheet was impregnated with the MF solution by immersing it in a bath. The impregnated sheet was freeze-dried to obtain a compound.
• a number of compounds of example II were stacked and compressed at 140°C and 50 bar for 40 minutes, after which they were cooled.
• Test specimens were sawn from the plate thus obtained. Under an electron microscope the compressed compound was found to have a very compact structure.
• Example II The procedure of example I was repeated without the homogenisation step using the Gaulin Homogeniser.
• the MFC obtained was processed to a compound according to the process of example II and the compound was processed according to example III.
• Example V The processes of examples I, II and III were repeated but without the H 2 S0 4 and the ultrasonic treatments. The composites were hence compressed immediately after the treatment with the Gaulin Homogeniser.
• compositions containing about 40 vol.% microfibrils have better mechanical properties than compositions with much smaller or much larger microfibril contents (compare example Illb with Ilia and IIIc) .
• example Illb The results of example Illb according to the invention were compared with the results of some measurements of an SMC based on 25% glass fibres and unsaturated polyesters and an MFC (melamine-formaldehyde compound) based on MF and 30% glass fibres and a BMC based on 15% untreated cellulose (flax).
• the flexural modulus of the compound according to the invention is about 50% higher than that of SMC, while the flexural strength is about 50% higher than that of MFC. All of the measured mechanical properties are better than those of the compound containing flax.
• cellulose fibres present an advantage in terms of weight with respect to glass fibres.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Reinforced Plastic Materials (AREA)

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Cited By (15)

Citations (3)

• 1991
  • 1991-11-18 NL NL9101920A patent/NL9101920A/xx not_active Application Discontinuation
• 1992
  • 1992-11-17 WO PCT/NL1992/000206 patent/WO1993010172A1/en active Application Filing

Patent Citations (3)

Non-Patent Citations (1)

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