PT104702A - AQUEOUS COATING FORMULATIONS FOR APPLICATION IN THE SURFACE TREATMENT OF CELLULOSIC SUBSTRATES - Google Patents

Abstract

The present invention relates to the application of novel coating formulations containing quitanos (and their derivatives) and bacterial cells for the improvement of the final properties of cellulosic materials, such as paper and textile materials. The method involves the preparation of homogeneous mixtures of bacterial and bacterial cells and the surface treatment of the cell substitutes with these mixtures. SURFACE TREATMENTS DESCRIBED BETWEEN SUBSTANTIALLY IMPROVE THE SURFACE, MECHANICAL, OPTICAL, BARRIER, ANTIMICROBIAL PROPERTIES AND FITNESS FOR THE PRINTING OF CELLULOSIC SUBSTRATES.

Description

AQUOSIVE COATING FORMULATIONS FOR APPLICATION IN THE SURFACE TREATMENT OF CELLULOSIC SUBSTRATES "

FIELD OF THE INVENTION The present invention relates to the application of novel coating formulations containing chitosan (and its derivatives) and bacterial cellulose for the improvement of the final properties of cellulosic based materials such as paper and textile materials.

BACKGROUND OF THE INVENTION Chitosan is an aminopolysaccharide prepared by deacetylation of chitin, obtained from marine organisms such as shrimp, crab, lobster, squid stilettos and insect exo-skeletons, among others. The degree of deacetylation of chitosan refers to the percentage of free amine groups obtained by deacetylation of chitin and is generally greater than 50%. The molecular weight of chitosan depends on its origin and the processing conditions. Chitosan exhibits odd physicochemical properties, such as its biocompatibility, antimicrobial activity, biodegradability and excellent film-forming properties, which have attracted scientific and industrial interest in various fields such as biotechnology, pharmacology, biomedicine, wastewater treatment, cosmetics, food science and paper and packaging technology, among others. The incorporation of chitosan into paper materials as a surface coating (and as a bulk additive) has already been reported in a number of scientific papers and patents (eg JP 1014396, JP 2006159431). Chitosan can be applied alone, or combined with paper-specific additives such as starch or inorganic fillers. Papers coated with chitosan exhibit better mechanical, gas barrier, antimicrobial and printability properties. Bacterial cellulose, produced by some bacteria, in particular of the genus Acetobacter, is obtained in the form of a hydrated gel (-95% water). Bacterial cellulose has unique properties, such as high mechanical strength, high crystallinity, and a high purity nanofibrillar network and has been exploited in several applications, particularly in the production of paper materials. Various patents disclose the production of papers or derivatives containing bacterial cellulose as a bulk additive (JP 10273891; JP 8049188; JP 7238488; KR 20030065916), or as a surface treatment (combined with calendering) (NZ 224401 / EP0289993; WO 9311182; US5637197). The fibrous materials coated with bacterial cellulose have good properties of gloss, smoothness, penetration and maintenance of the printing inks and surface resistance. However, bacterial cellulose suspensions tend to undergo segregation of phases when subjected to shear stresses, such as those occurring in the paper press (ie press). The water rich fraction is transferred preferentially to the paper substrate, while the major fraction of the bacterial cellulose remains in the suspension. Some dispersing agents, in particular carboxymethylcellulose and starch, have been used to reduce this effect. For this reason, it is important to develop novel processes that allow the deposition of bacterial cellulose layer (s) on cellulosic substrates in the presence of strong shear stresses. Chitosan and bacterial cellulose have very similar chemical structures and, consequently, also have high compatibility. The combination of these two polysaccharides can be exploited in the optimization of dispersion processes and application (in the presence of shear stresses) of bacterial cellulose on different cellulosic substrates, but also in the production of cellulosic base materials, preferably with improved properties, resulting from the addition bacterial cellulose and chitosan. These novel coated materials combine the functional and physico-chemical properties of chitosan, such as the excellent film-forming properties, and the unique mechanical properties of bacterial cellulose, resulting from its three-dimensional nanofibrillar structure.

DETAILED DESCRIPTION The present invention comprises the surface coating of various cellulosic substrates, including printing and office papers, paperboard, textile substrates, among others, with mixtures of bacterial chitosan cellulose. The term bacterial cellulose, as used herein, refers to bacterial cellulose produced by bacteria of the genera Glucanacetobacter, Rhizobium, Sarcin, Agrobacterium, among others, and may exhibit different degrees of polymerization and crystallinity. The term chitosan includes samples of chitin and chitosan from different sources and with different degrees of deacetylation and molecular weights, as well as chemically and / or physically modified chitosan derivatives, including water soluble and amphiphilic derivatives. The process of this invention involves the preparation of homogeneous mixtures of bacterial chitosan cellulose and the surface treatment of cellulosic substrates with these mixtures.

Chitosan solutions are prepared by dissolving chitosan powder samples in aqueous acidic solutions (eg with acetic acid) or in water (if a water-soluble derivative is used). The concentration of chitosan in solution ranges from 0.01 to 50% (chitosan mass / solution weight). Thereafter, bacterial cellulose in different proportions ranging from 0.01 to 10% (bacterial cellulose weight / chitosan weight) is added and dispersed in the solutions using a mechanical homogenizer, being filtered and degasified to remove trapped air.

Other additives, including fillers and pigments (eg calcium carbonate and titanium dioxide), surface sizing agents (eg alkenylsuccinic anhydrides-ASA, alkyl ketene dimers-AKD), wet and dry strength additives ( eg urea-formaldehyde resins and cationic starch), paints and optical brighteners, may be added at this stage to mixtures of bacterial chitosan-cellulose. The application of bacterial chitosan-cellulose blends on the surface of cellulosic substrates can be carried out using technologies already established in the respective industries, such as, in the case of the paper industry, coating equipment with different modes of application (press, metered size-press and film press).

For example, paper materials coated with bacterial chitosan-cellulose have better mechanical, surface, barrier, optical and high printability properties than those recorded for untreated control samples, and even better than those registered for papers commercial printers. In addition, these novel materials exhibit considerably higher properties than materials treated with chitosan solutions alone. The deposition of bacterial chitosan-cellulose blends on the paper surface forms a three-dimensional network of bacterial cellulose nanofibrils embedded in a chitosan film that coats homogeneously and aggregates the plant fibers as well as the inorganic fillers, resulting in a completely new surface morphology ( Figure 1) and consequently in improved or even new properties.

For example, these novel coated papers show unexpected improvements in some surface properties with particular relevance to their suitability for printing such as reduction of vessel detachment and contact / mixing between intercolour bleed colors.

Brief Description of Images

Figure 1 - a) and b) Scanning electron microscopy images -SEM- (at different magnifications) of the paper surface coated with mixtures of bacterial cellulose water soluble chitosan 5 (WSCH-BC) derivative, showing uniform distribution of the WSCH-BC layer on the paper surface containing mineral fillers.

References

Seong, H. S., Whang, H. S. and Ko, S. W., J. Appl. Polym. Sci., 2000, 76, 2009-2015.

Surface coating composition paper, Japanese Patent No. 1014396 (A)

Coating paper type printer paper, Japanese Patent No. 2006159431, 2006

Production of paper containing bacterial cellulose. Japanese Patent No. 10273891

High dynamic strength sheet containing bacterial cellulose, Japanese Patent No. 8049188

Production of compound material of fibber and bacterial cellulose and composite material produced by the process, Japanese Patent No. 7238488 (A)

Korean traditional paper containing bacterial cellulose and method of manufacturing the same, Korea Patent No. 20030065916 (a), 2003

Bacterial cellulose as surface treatment for fibrous web, NZ224401, EP0289993 (A2), May 3, 1988 6

Conditioned bacterial cellulose, International Patent No. WO 93/11182, June 10, 1993

Process of coating a substrate with reticulated bacterial cellulose aggregates, US5637197, June 10, 1997.

Example 1 Method for coating paper sheets with mixtures of chitosan (or a water-soluble chitosan derivative) -cellulose bacterial Chitosan (CH) is a commercial sample having a degree of deacetylation (DDA) of 97% and a mean molecular weight This chitosan was also modified with glycidyltrimethylammonium chloride (GTMAC) to produce a water-soluble derivative following a procedure described [Seong et al]: 5.0 g of chitosan (CH) were dissolved in 250 ml of 1% aqueous acetic acid solution; GTMAC, in a GTMAC mole ratio / nh2 chitosan groups of 4/1, was then added with stirring. This mixture was maintained at 65 ° C for 24 h under N 2. The resulting water soluble chitosan derivative (WSCH) was precipitated and washed with ethanol. The degree of substitution of the amine groups was close to 30%. The bacterial cellulose (BC) used was in the defibrated and wet form (95% humidity).

Form A3 paper sheets (bleached kraft pulp with 100% Eucalyptus globulus, 75g / m2 grammage and a mean thickness of 100prn, produced with AKD bonding and using precipitated calcium carbonate as filler) without any treatment of were used as substrates and as control (CS) sheets. (i) 1% (chitosan / volume solution) solutions of chitosan or water-soluble chitosan were prepared by dissolving them in a 1% (v / v) aqueous solution of acetic acid or in water respectively. Then bacterial cellulose (8 wt.% Bacterial cellulose / chitosan weight) was added and dispersed in the solutions using a mechanical homogenizer for 45 minutes at 20500 rpm, then filtered and degasified to remove trapped air. ii) Application of the bacterial chitosan-cellulose blends (and also the unfilled CH and WSCH solutions) on the surface of the sheets of paper was done with a coating machine. A layer was applied to one side of the sheet of paper. Coating speed was set at 20 m / min and the distance between the cylinders was adjusted to -80 micrometer (precision ± 1 micrometer). The coated papers obtained were dried for 2 minutes at 100 ° C in the drying zone of the coating machine, after the deposition of each layer. Table 1 shows some important final properties of papers coated with mixtures of bacterial chitosan-cellulose (CH-BC and WSCH-BC), chitosan coated papers (CH and WSCH) and control (CS) samples.

Table 1

Samples CS CH CH-BC WSCH WSCH-BC

Gain in weight (%) - 2, 0 2.1 2, 0 2.1 Bendtsen air permeability (μιη / Pa.s) 9, 6 8, 6 7.2 8.4 7.5 Bendtsen roughness ml / min) 331 268 230 229 201 tensile index (Nm / g) 88.4 95.8 96.6 95.1 96.2 Wax test 13A 16A 16-18A 16A 16-18A Vessel detachment glasses / m2) 8689 2635 1453 4324 1832 Opacity (%) 92.1 92.1 92.2 92.2 92.2 Whiteness (ISO) 94.4 96.1 96.1 96.0 95.8 Gamut area 7224 7627 7873 7718 8113 Mixture between printed colors 89.6 75.9 66.6 84.4 75.4

The water-soluble chitosan derivative (WSCH) was prepared by reaction of chitosan with glycidyltetramethyl ammonium chloride (GTMAC), followed by the addition of water-soluble chitosan derivative (HSCH). an established procedure, [Seong et al] and described above, using the same commercial chitosan. Bacterial cellulose, (BC) was used in the defibrated and wet form (95% moisture).

Form A3 sheets of paper (kraft pulp bleached with 100% Eucalyptus globulus, 75g / m2 grammage and 9 average thickness of 100pm, produced with AKD bonding and using precipitated calcium carbonate as a filler), without any treatment were used as substrates (CS control sheets). i) Aqueous solutions of the 1.5% water-soluble chitosan derivative (chitosan weight / volume of solution) were prepared by dissolving the powder in water. Then, bacterial cellulose (10 wt% bacterial cellulose / chitosan weight) was added and dispersed in the solution using a mechanical homogenizer for 45 minutes at 20 500 rpm, then filtered and degasified to remove trapped air. ii) Application of bacterial water-soluble chitosan (and also unfilled WSCH solutions) chitosan blends to the surface of the sheets of paper was done in a coating machine. The coating speed was set at 20 m / min and the distance of the cylinders was adjusted to -80 millimeters (accuracy ± 1 mm). The coated papers obtained were then dried for 2 minutes at 100 ° C in the drying zone of the coating machine after the deposition of each layer. Table 2 shows some important final properties of papers coated with mixtures of the soluble bacterial chitosan cellulose derivative (WSCH-BC), papers coated with the water soluble chitosan derivative (WSCH) and the control (CS) samples. 10

Table 2

Samples CS WSCH WSCH-BC Weight gain (%) - 1.2 2, 2 Bendtsen permeability (μιη / Pa.s; in air) 9.6 4.6 1, 19 Bendtsen 331 Roughness (mL / min) 259 209 Traction index (Nm / g) 88.495.86 96.6 Opacity (%) 92.91.99.92.2 Whiteness (ISO) 94.4 95.6 95.7 Gamut area 7224 8017 8920 Blending between printed colors 89.6 63, 0 34, 8

Lisbon, June 29, 2010 11

Claims (13)

Aqueous coating formulations characterized by containing chitosan and bacterial cellulose for application in surface treatment. The formulations according to claim 1, characterized in that they are used in the surface treatment of cellulosic substrates. The formulations according to any one of claims 1-2, characterized in that the chitosan substrate comprises samples of different origins, with different degrees of deacetylation (DDA) and molecular weights (MW). The formulations according to claim 2 characterized in that the chitosan substrate is a water soluble derivative or an amphiphilic derivative. The formulations according to any one of claims 1-4 characterized in that the concentration of chitosan in solution varies between 0.01-50% (weight of chitosan / weight of aqueous solution). The formulations according to any one of claims 1-5 characterized in that the bacterial cellulose is produced by all producing bacteria, including those of the genera Glucanacetobacter, Rhizobium, Sarcina, Agrobacterium or mixtures thereof. 1 The formulations according to claim 6 characterized in that the bacterial cellulose is previously subjected to chemical modification, such as hydrolysis, oxidation or derivatization, in order to reduce its degree of polymerization and viscosity or to modify its functionalities. The formulations according to any one of claims 1-7, characterized in that the bacterial cellulose content ranges from 0.01-10% (weight of bacterial cellulose / weight of quisotane solution). The formulations according to any one of claims 1-8 characterized in that the dispersion of bacterial cellulose in the chitosan solution is prepared by mechanical means, such as a mechanical homogenizer. The formulations according to any one of claims 1-9 characterized in that the bacterial chitosan-cellulose mixtures include other additives such as fillers, pigments, surface sizing agents, wet and dry strength agents, paints and optical brighteners . The formulations according to any one of claims 1-10, characterized in that the cellulosic substrates are paper and paper-derived materials of different qualities and textile properties or substrates. The formulations according to any one of claims 1-11, characterized in that they are applied through surface coating equipment, namely film application press and film application pressure. A material comprising a cellulosic substrate and a layer of a bacterial chitosan cellulose blend as described in claims 1 to 10.