Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
  • D21J3/00—Manufacture of articles by pressing wet fibre pulp, or papier-mâché, between moulds

Definitions

• the ⁇ present invention relates to moulded cellulosic articles, such as package products, e.g. troughs and trays for food and feed, and toys, ornaments, fancy goods, golf pegs and plantation pots, manufactured from an aqueous fibre suspension comprising cellulase enzyme-treated microfibrillar sulphate pulp (eMFC), and optionally carboxymethylcellulose
• eMFC cellulase enzyme-treated microfibrillar sulphate pulp
• One of the essential driving forces in the development work concerning utilization of wood fibre based pulp, as main raw material for e.g. package products is to maximize the strength properties of the material without increasing the weight thereof. This is important for an efficient utilization of raw material as well as for utilization of transports.
• the strength properties of such package products depend among other things on the number of bonds between individual fibres, the strength and shape of the fibres, the density distribution in the thickness direction and distribution of the orientation of the fibres in different directions, as well as how the fibre matrix has contracted during the drying process.
• the present invention provides an aqueous fibre suspension that can be used for production of moulded cellulosic articles.
• the fibre suspension of the invention is based on cellulase enzyme-treated microfibrillar sulphate pulp (eMFC) and carboxymethylcellulose (CMC).
• microfibrillar cellulose is here intended to describe wood fibres that have been disintegrated to small fragments with a large proportion of the microfibrilles of the fibre wall uncovered. In addition, a large amount of very fine material is formed. The fragments and the fines can thus, if they are applied in the right way, contribute to the creation of a closed surface structure with reduced surface porosity and a smoother board surface. Furthermore, the uncovered microfibrilles on the fines contribute to strengthen the fibre-fibre bonds that are developed during the drying process of the fibre suspension.
• MFC microfibrillar cellulose
• This technique has been tried in the so-called the Recell project at the Institute for Fibre and Polymer Technology (Ohlsson et al. 2000).
• the MFC is in this case produced with the aid of a bead beater.
• the result from the project indicates that mechanically produced MFC pulp has a high specific surface that gives a strong binding capacity in the paper structure, high water retention, good stability in water dispersions and is an insoluble adhesive in colloidal form that does not give the environmental drawbacks as soluble alternatives such as starch-based preparations.
• the cellulose fibres can also be disintegrated to microfibrillar cellulose by enzyme treatment, especially treatment with cellulases.
• This type of microfibrillar cellulose is herein designated eMFC.
• Enzymes have a totally different effect on the fibres than a beater, and therefore there are essential differences between the resulting two types of microfibrillar cellulose.
• the method of producing eMFC by enzyme treatment is an essential part of the manufacturing process of the new type of fibre suspension according to the present invention.
• the present invention comprises a special fibre suspension that is suitable for a number of different moulded cellulosic articles.
• the suspension comprises fibres from sulphate pulp that have been subjected to a special enzyme treatment and optionally subsequently been dispersed and stabilized with carboxymethylcellulose (CMC).
• CMC carboxymethylcellulose
• the aqueous fibre suspension of the invention is produced by treatment of sulphate pulp with the enzymes endoglucanase and cellobiohydrolase followed by addition of carboxymethylcellulose (CMC).
• CMC carboxymethylcellulose
• the enzyme treated hard or soft wood fibres give a combination of properties regarding surface charge, flexibility, particle size and particle size distribution that substantially differ from conventional sulphate pulp.
• the enzyme treated fibres of the invention result in microfibrillar cellulose (eMFC).
• the eMFC designates cellulose fibres that have been disintegrated by enzymatic treatment to small fragments with a large proportion of the microfibrilles of the cell wall uncovered. Furthermore, a large amount of very fine material is formed. The fragments and the fines contribute to reduction of the surface porosity and creation of a smoother surface. The uncovered microfibrilles contribute to strengthening the fibre-fibre bonds that develop during the drying process. Microfibrilles, and in particular well-dispersed disintegrated microfibrilles, have a marked effect on the creation of strong interfibrillar bonds (Mitikka-Eklund et al.1999).
• the present invention is directed to a moulded cellulosic article obtainable by drying and optionally pressing an aqueous fibre suspension comprising cellulase enzyme- treated microfibrillar sulphate pulp (eMFC) in a casting mould to obtain the article.
• the fibre suspension additionally comprises carboxymethylcellulose (CMC).
• the cellulase enzyme is endoglucanase and/or cellobiohydrolase
• the CMC has an average molecular weight of more than 50 000
• the suspension has a viscosity in the range of 100 to 3000 mPas (Brookfield, 100 r.p.m. sp 4 ).
• the sulphate pulp is a bleached sulphate pulp.
• the dry weight of the suspension is in the range of 2 to 15 %.
• the suspension additionally comprises inorganic coating pigments and/or fillers.
• the cellulosic article according to the invention is selected from the group consisting of package products, such as troughs and trays for food and feed, or is selected from the group consisting of toys, ornaments, fancy goods, golf pegs and plantation pots.
• Figure 1 is a diagram that shows the fibre shortening during enzyme treatment and post treatment, for different enzyme treatment durations (1-6 hours).
• the enzyme dosage was 10 g/kg for all test points except for B06 (15 g/kg).
• Figures 2 shows the fibres before and after 1 and 6.5 hour's enzyme treatment. Specifically, Figure 2a shows a light microscopy image of bleached kraft pulp fibres before the enzyme treatment; Figure 2b shows a light microscopy image of bleached kraft pulp fibres after 1 hour enzyme treatment; and Figure 2c shows a light microscopy image of bleached kraft pulp fibres after 6%-hours enzyme treatment.
• Figure 3 illustrates a test bar for testing of stress strain properties and its dimensions.
• Figure 4 is a diagram that shows the tensile stress plotted against the strain at break for the test plates prepared of different types of eMFC fiber suspensions.
• Sample 1 was made of properly dispersed eMFC with the addition of 10% CMC ;
• Sample 3 was the same without addition of CMC;
• Sample 2 was made of the same eMFC pulp, but with an inappropriate dispersion and mixing.
• Figure 5 shows one of the trays made of eMFC . used as test specimen.
• Figure 6 is a diagram that shows the fibre length of the prepared pulps and the density of the trays.
• Figure 7 is a diagram that shows the Young's modulus and the tensile stiffness for test specimens made of the different trays.
• Figure 8 is a diagram that shows strain at break and work at break index for test specimens made of the different trays.
• Figure 9 is a diagram that shows absorption rate characterized with the EMCO test for the different trays.
• the enzyme used was Ecostone L900 from Rohm Enzyme Finland Oy and it consists essentially of two cellulases, namely cellobiohydrolase and endoglucanase.
• ECF bleached softwood sulphate pulp having a dry content of 34% was withdrawn from the press filter of Korsnas board machine PM5.
• the CMC quality was FF10 from Noviant AB having an average molecular weight of 66 000.
• Figures 2a-c show the fibres before and after 1 and 6.5 hours enzyme treatment, respectively.
• the breakdown of the fibres becomes evident, both as fibre shortening and the release of microfibrilles.
• the fibre suspension was subjected to an intense mixing after the enzyme treatment in order to mechanically fragment the fibres that had been weakened by the enzyme treatment. In industrial scale a careful refining could carry this out.
• the eMFC mixture is shown in the following to give unique possibilities of being used as renewable raw material for moulded package products such as e.g. troughs and trays for food and feed, and moreover for toys, ornaments, fancy goods, golf pegs and plantation pots.
• the properties of the material were characterized in tensional load ( Figure 4) and were matched against the properties of some common thermoplastics in Table 1.
• the test bars (Samples) 1 and 3 were relatively rigid and in that respect comparable to several of the thermoplastics. This concerns especially Sample 1 that has been dispersed with CMC. Sample 2, wherein the eMFC pulp had not been mixed completely, did not seem to be of interest for applications wherein the mechanical properties are important. However, the Samples 1 and 3 are rather brittle, and neither the stress at break, approx. 4 MPa, nor the strain at break, 0.1-0.3%, were particularly high compared to the plastics used as references. This is likely a consequence of that the materials are non-homogenous (built-up of fibres) and therefore sensitive to defects. Probably the impact strength is also rather low.
• Figure 8 shows strain at break and work at break for the trays. All the trays made of eMFC pulp were rather brittle. The CMC and the mixing time did not reduce the brittleness. This indicates that the material is not suitable for applications where the impact resistance is important if the brittleness is not compensated by an increased thickness.
• Figure 9 shows that the water absorption time and the wetting resistance are significantly influenced by the enzyme treatment as well as the mixing time. The dynamic water absorption was characterized by an ultrasonic technique (Emtec EST 4.0). A fast declination of the l R -value (i.e. the transmittance) indicates rapid absorption. At short contact times it is the amount and characteristics, (e.g.

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Cited By (16)

Citations (2)

• 2002
  • 2002-12-18 SE SE0203742A patent/SE526681C2/sv not_active IP Right Cessation
• 2003
  • 2003-12-18 EP EP03781247A patent/EP1585861A1/en not_active Withdrawn
  • 2003-12-18 AU AU2003288866A patent/AU2003288866A1/en not_active Abandoned
  • 2003-12-18 WO PCT/SE2003/002030 patent/WO2004055268A1/en not_active Application Discontinuation

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