Patent Description:
Tissue papers are those used both domestically and in public spaces for hygienic and sanitary use. A tissue paper product is characterized by different key properties, namely bulk, strength, absorption, softness and even visual appearance. The consumer of this type of product seeks a positive balance in terms of the overallity of these different properties. In addition, the current consumer also intends to purchase environmentally conscious products produced through raw materials and processes that lead, for example, to lower chemical and water consumptions.

The document <CIT> discloses a tissue paper for kitchen applications produced with unbleached pulp of a coniferous wood, with improved whiteness. This is achieved through the use of ultraviolet light absorption compounds and an antioxidant compound.

<CIT> discloses a tissue paper produced using unbleached sulfate pulp. This solution only allows improvements in softness and tensile strength, without any mention of bulk characteristics and absorption capacity.

<CIT> relates to an ecologic and environmentally friendly toilet paper making process which uses unbleached pulp and additionally includes fermentation processes. The characteristics of the paper produced are softness, fineness, durability and a natural fiber fragrance.

<CIT> discloses soft, durable wet pressed tissue products obtained by the use of long fibers having relatively low-coarseness such as Southern softwood fibers, more particularly low-coarseness Southern softwood fibers.

<CIT> refers to absorbent diaper products that are obtained through southern pine fibers with certain values of fiber length and coarseness.

<CIT> discloses a process for obtaining pulps with absorption characteristics for use in absorbent materials, such as diapers and incontinence products. The process includes a cold alkaline treatment.

<CIT> presents a method for making sanitary paper products from recycled newspapers, modifying newspapers fibers to produce soft tissue products by washing the pulp to reduce the proportion of fines in the pulp and by treating the pulp with a surfactant system as it is introduced into the papermachine.

<CIT> concerns a creped tissue paper which incorporates a binding inhibitor, a cationic starch and a carboxymethyl cellulose.

<CIT> describes a method for producing a sanitary product that includes cellulosic fibers and a vegetable oil, mineral and its derivatives.

<CIT> discloses tissue products consisting of cross-linked cellulosic fibers through cross-linking agents from the imidazolidinone group.

<CIT> describes a sanitary paper with excellent touch and that generates little paper dust, consisting of long fibers of size <NUM> mesh.

<CIT> describes pulp for household thin paper constituted by a mixture of softwood and hardwood material, in particular cedar wood.

<CIT> refers to a process for producing a cellulosic product which comprises a microfibrillar polysaccharide and thermoplastic microspheres.

Therefore, there is a need for tissue paper products with a globally improved consumer-appreciated paper properties such as bulk, absorbency, capillarity, strength, softness and consumer-friendly visual appearance of the use of an environmentally sustainable product, produced using existing processes in the industrial pulp and paper production units and with the raw materials commonly used therein, with lower environmental impact and production costs as, for example, on the consumption of chemical additives and water. Such a problem is solved by the invention described herein.

The tissue paper sheets disclosed in this document comprising an unbleached Eucalyptus globulus Kraft fibers pulp unexpectedly enables a range of improved consumer-appreciated paper properties, such as bulk, absorbency, capillarity, strength, softness and consumer-identifying visual appearance of the use of an environmentally sustainable and friendly product.

Additionally, these products are advantageously produced using processes already in place at pulp and paper mills, and the raw materials commonly used therein, with a lower impact on the environment and production costs as regards, for example, to the consumption of chemical additives and water.

An example of the most commonly used industrial processes for pulp production is the kraft process, or sulfate process, in which wood chips are treated at a temperature of around <NUM>-<NUM> with the white liquor, consisting essentially of sodium hydroxide (NaOH) and sodium sulfide (Na<NUM>S). Normal values for the alkali load, the amount of active alkali, in kg Na<NUM>O, required to ensure a correct delignification, range between <NUM> and <NUM> Na<NUM>O per cooking procedure.

The present invention is defined in the current claim <NUM>.

The described cellulose pulp may be used for the production of tissue paper products comprising unbleached Eucalyptus globulus fibers.

The unbleached Eucalyptus globulus Kraft pulp comprises fibers having a length of not less than <NUM>, a width of not less than <NUM> and a coarseness of not less than <NUM>/<NUM>. The unbleached Eucalyptus globulus pulp presents a viscosity of not less than <NUM>/g and a carboxyl content of not less than <NUM>%.

The present disclosure includes tissue paper sheets incorporating at least <NUM>% (w/w) of an unbleached Eucalyptus globulus Kraft pulp, and short and long cellulose bleached fiber pulps. The paper sheets have globally improved paper properties compared to tissue paper sheets that incorporate only bleached pulps into their composition. The paper sheets have bulk values from <NUM> to <NUM><NUM>/g and a tensile index from <NUM> to <NUM> kN. m/kg, an absorption capacity from <NUM> to <NUM> gH<NUM>O/gpaper, an air permeability from <NUM> to <NUM> /m<NUM>/s, and a softness from <NUM> to <NUM> HF.

The tissue paper sheets disclosed have a tear index greater than <NUM> mN. m<NUM>/g, more preferably from <NUM> to <NUM> mN. m<NUM>/g, a burst index greater than <NUM> kPa. m<NUM>/g, preferably from <NUM> to <NUM> kPa. m<NUM>/g, a capillarity of not less than <NUM>/<NUM>, and an opacity greater than <NUM>%, preferably greater than <NUM>%.

The invention disclosed herein thus includes the use of tissue papers sheets, incorporating the unbleached Eucalyptus globulus Kraft pulp, for the production of household and sanitary products, such as toilet paper, napkins, kitchen paper rolls and tissues.

In the production process of tissue products, the described pulp can be used in different forms, such as in the form of dried pulp bales and in the form of a slush, the later feed to the industrial process through pipeline systems.

The biometric analysis of the fibers was performed in a Fiber Tester equipment (Lorentzen & Wettre), which is an instrument for advanced fiber analysis. The equipment measures, by 2D image analysis, a wide variety of properties such as length, width, fines content, coarseness, among others. Coarseness is defined as the weight per unit length of fiber expressed in milligrams per <NUM> meters. For that, <NUM> (dry basis) of pulp was dispersed in <NUM> of distilled water. Subsequently, all the suspensions were positioned for analysis by the equipment using available software. For each pulp three measurements were made, the final value of each parameter resulting from the arithmetic mean of the values obtained at the three measurements.

Extractable compounds are hydrophobic (lipophilic) components present in wood and extracted by organic solvents.

The extractable compounds content was determined using ethanol/toluene in quantities enough for samples analysis preparation, as it requires a pulp pre-extraction. The extraction was carried out during approximately <NUM> hours (<NUM> extraction cycles) of <NUM> (dry basis) of pulp in a <NUM> capacity Soxhlet extraction apparatus, using <NUM> of a <NUM>:<NUM> (v/v) ethanol/toluene solution. The insoluble residue was filtered and washed with hot absolute ethanol, for removing any remaining toluene, and dried at room temperature, contrary to what is indicated at the standard TAPPI T <NUM> om-<NUM>, since washing with water, as described, could lead to the loss of pentosans and other polysaccharides of low molecular weight. The obtained extract was dried at a rotary evaporator equipment and the extractable content was determined gravimetrically.

Pentosans content was determined according to the Tappi Test Method T <NUM>-<NUM>. This method is based on the action of hydrochloric acid on the pulp hemicelluloses, hydrolyzing them and, consequently, converting the xylose and other pentoses to furfural, which is collected with the distillate and, reacting with orcinol, forms a colored complex making therefore possible the content quantification by spectrophotometry.

About <NUM>-<NUM> (dry basis) of unbleached pulp pre-extracted in ethanol/toluene (<NUM>:<NUM>), together with <NUM> of NaCl and <NUM> of HCL <NUM> N, was inserted into a distillation flask. In a hopper, <NUM> of <NUM> N HCl was added and the acid distillation was started into a volumetric flask placed in an ice bath.

Finally, <NUM> of the distillate was pipetted, <NUM> of the orcinol ferric chloride reagent was added, and the mixture was kept in a thermostatic bath for <NUM> hour. Absolute ethanol was added and the volumetric flask was placed again in the thermostatic bath for another hour. The solution absorbance at <NUM> was then read, and measurements comparisons were carried out using a <NUM> blank of <NUM> N HCl.

The pentosans content was obtained with the aid of the calibration curve and equations presented below: <MAT> <MAT> where w is the dry weight (g) of the sample.

The content of carboxyl groups was determined according to the TAPPI T <NUM> om-<NUM> standard method. About <NUM> ± <NUM> of disintegrated pulp was first weighed and <NUM> of a diluted hydrochloric acid solution (approximately <NUM>) was added during <NUM> hours, ensuring that all existing carboxylic groups are in their protonated form. Subsequently, the pulp was filtered and washed with distilled water until the pH of the filtrate equaled the pH of the distilled water. To the pulp it was added <NUM> of an aqueous sodium bicarbonate-sodium chloride solution, the resulting mixture stirred for about <NUM> hours, filtered, and the filtrate twice titrated (<NUM> in each titration) with a standard solution of hydrochloric acid (<NUM>) using methyl red as indicator. At the first color change the solution was boiled for <NUM> minute to release CO<NUM>. Titration is resumed ending only when the solution changes to pink. The blank was prepared by titrating <NUM> of sodium bicarbonate-sodium chloride solution with <NUM> HCl. The content of carboxyl groups was determined with the following equation: <MAT> where a is the volume, in mL, of hydrochloric acid (<NUM>,<NUM>) spent during titration, b is the volume, in mL, of hydrochloric acid (<NUM>,<NUM>) consumed during the blank titration, Cw is the mass, in g, of the water in the pulp after filtration, and w is the weight, in g, of the dry pulp.

The viscosity was determined according to the SCAN-test standards SCAN-CM <NUM>:<NUM>, which consists on the determination of the viscosity of pulps by solubilization in a dilute copper-ethylenediamine (CED) solution.

The pulp sample was reduced to small fragments in the amount indicated at the table provided by the method (Table <NUM>, Annex C. ) - <NUM> of pulp were weighed. Each sample was placed into a glass vial along with <NUM> of distilled water and some copper wires. The vials were then placed on a shaker for as long as necessary to ensure that the pulp was completely disintegrated. The procedure continued with adding <NUM> of <NUM> CED solution, expelling all existing air and stirring until the sample is completely dissolved. Finally, the temperature of the viscometer bath and the sample's were adjusted to <NUM> ± <NUM> and, with the aid of a syringe, a portion of the solution was aspirated and allowed to flow unobstructed. The time it takes to travel the distance between the two viscometer marks was measured to within ± <NUM>. At least <NUM> readings were taken for each sample.

With the flow time of each sample, tn, it is possible to calculate its relative viscosity, ηrel, through the relationship shown in the equation: <MAT> where h represents the viscometer constant, obtained from the equipment calibration. From the table provided by the aforementioned standard, it is possible to read the value resulting from multiplying the viscosity value with the pulp concentration, [η]C.

Biometric and chemical measurements and comparisons were carried out for an unbleached Eucalyptus globulus pulp (UBP), for a bleached short cellulose fiber pulp (SF), and for a bleached long cellulose fiber pulp (LF).

Tissue paper sheets with a weight of <NUM>/m<NUM>, and not subjected to any pressing procedure, were prepared following an adaptation of the standard method ISO <NUM>-<NUM>:<NUM>. Additionally, <NUM>/m<NUM> tissue paper sheets were prepared according to the same ISO.

The pulps described above, SF, LF and UBP were used. The prepared formulations are described in Table <NUM>. Reference formulations (REF <NUM> and REF <NUM>) consist on formulations used in the production of tissue paper sheets. The other formulations were based on the replacement of short fibers content by unbleached pulp (UBP <NUM> to UBP <NUM>).

The same formulations were tested with refined pulps having a Schopper degree of <NUM>/<NUM> °SR (measured by the Schopper-Riegler method, which provide a measure of the rate at which a dilute suspension of pulp may be dewatered). For that, the dried pulps were disintegrated individually, the pH was adjusted to <NUM>-<NUM>, and finally refined in a PFI refiner according to the standard ISO <NUM>-<NUM>. The Schopper degree, °SR, was again confirmed after preparation of the formations indicated in Table <NUM>, standard ISO <NUM>-<NUM>:<NUM>.

The prepared sheets were stored according to the standard ISO <NUM>:<NUM> for further analysis.

The <NUM>/m<NUM> sheets were analyzed as indicated in Table <NUM>.

The softness was analyzed on an Emtec TSA - Tissue Softness Analyzer. This device combines data from the three parameters that have the greatest influence on the human feel to the touch: fibers softness, smoothness and sheet stiffness. The calculation method used by the device is an algorithm that calculates the hand feel (HF).

The water absorption of the tissue papers was determined according to the standard ISO <NUM>-<NUM>:<NUM>, by the immersion absorption method. Approximately <NUM> of paper was placed in a basket of certain dimensions, contrary to what is mentioned at the standard, which indicates the use of <NUM> of paper.

The prepared <NUM>/m<NUM> sheets were analyzed as indicated in Table <NUM>.

Additionally, a Scott Test was carried out and the Gurley's air resistance was measured.

Mechanical strength properties of pulp furnishes ultimately contribute to the strength characteristics of the out coming material, as paper sheets are subjected to considerable stresses during processing and use. The Scott Test is related to the internal fibers bonding strength of the paper when subjected to delamination. It allows the determination of the energy (or force) required to delaminate a sheet of paper in the z-direction. In this method (TAPPI T <NUM> standard) the paper sheet is delaminated under the action of a pendulum of controlled mass and velocity. The internal strength of the fibers is affected by the paper sheets formation (bonding between layers) and also by the process of pulp refining.

The Gurley's air resistance is a structural property that quantifies the time required for a certain volume of air (<NUM>) to pass through a given area of paper under constant pressure, ISO <NUM>-<NUM>:<NUM> standard. It is an indirect measure of the porosity of the fibrous matrix.

Both tests were performed under the same atmospheric conditions used for sample conditioning and sample preparation (T = <NUM> ± <NUM> and Relative Humidity (RH) = <NUM>% ± <NUM>%, according to the ISO <NUM>:<NUM> standard.

The biometric properties of the pulps, SF, LF and UBP, were analyzed, with and without refining, and the results are depicted in Table <NUM>.

Observing the results obtained, it is verified that the fiber length values are within the expected. The fibers UBP have larger width values than the other short fibers. The fibers UBP also present higher values than the other short fibers with regard to coarseness.

Comparing unrefined pulps and after refining pulps, it is verified that the biometric properties of the fibers did not change significantly.

The results of the chemical characterization of the pulps under study are shown in Table <NUM>.

A good degree of cellulose polymerization is maintained for the fibers of the UBP pulp, as inferred by its higher viscosity value than that of SF. The pulp UBP also has a higher percentage of carboxyl content than the other pulps.

The pentosans content (measured by the xylan content, the majority of hemicelluloses in short fiber pulps) is within the typical range for this type of short fiber Eucalyptus globulus pulp.

The paper sheets produced for the reference formulations REF <NUM> and REF <NUM> and with fibres of unbleached Eucalyptus globulus pulp UBP <NUM>, UBP <NUM>, UBP <NUM> and UBP <NUM> were analyzed and major results are depicted in Table <NUM>.

The results show that with the incorporation of unbleached Eucalyptus globulus pulp (UBP) a bulk increase is obtained compared to REF <NUM> and REF <NUM>. In addition, the increase of the UBP content also led to a significant increase in the tensile index, with UBP <NUM> and UBP <NUM> showing an up to <NUM>% increase compared to REF <NUM>.

Concerning air permeability, the increase in UBP resulted in a higher permeability compared to the references, which suggests a more porous structure.

In terms of capillarity, there is a slight decrease in the capillary rise with the incorporation of UBP fibers.

For the absorption capacity a higher incorporation of UBP led to an improvement of the water absorption capacity.

The presented softness results, with the incorporation of Eucalyptus globulus unbleached pulp, revealed a very slight softness variation (within the measurement error) comparing to the references.

<NUM>/m<NUM> paper sheets produced through the formulations with unrefined UBP incorporation were analyzed and the results are shown in Table <NUM>.

The obtained results are in agreement with the studies for the paper sheets of <NUM>/m<NUM>.

The replacement of short fiber by UBP also allowed obtaining higher values of tensile, tear and burst indexes values than the references (REF <NUM> and REF <NUM>). Scott Test results values showed a decrease with the incorporation of UBP in comparison with REF <NUM> (<NUM>:<NUM>:<NUM>) but, on the other hand, an increase over REF <NUM> (<NUM>:<NUM>:<NUM>).

Paper sheets were produced with the refined pulps with a °SR of <NUM>, considering the reference formulations REF <NUM> and REF <NUM> and with unbleached Eucalyptus Globulus kraft pulp fibers UBP <NUM>, UBP <NUM>, UBP <NUM> and UBP <NUM>. The main results from the analysis of their paper properties are shown in Table <NUM>.

Analyzing the paper properties of the paper sheets produced with the refined pulps, it was found that, even with refining, the bulk increases with the incorporation of refined UBP. Additionally, and as previously noted, the absorption capacity also increases with the incorporation of refined UBP.

Regarding the tensile index, there was also an increase for UBP <NUM> and UBP <NUM>, compared to REF <NUM>.

For softness there is an increase with the incorporation of refined UBP, when comparing to the reference samples, particularly REF <NUM> (up to <NUM> HF points).

<NUM>/m<NUM> paper sheets were produced with <NUM>°SR refined pulps and the main results of the analysis of their paper properties are shown in Table <NUM>.

Analyzing the results from Figure <NUM>, it can be seen that the incorporation of refined UBP led to an increase in the tensile index, tear, opacity, in the Scott test results (internal bonding) and an increase in bulk.

Regarding capillarity, with the incorporation of refined UBP the values of this parameter decreased.

The incorporation of unbleached pulp, refined or not, allows an increased bulk, increased physical and mechanical properties and increased absorption capacity. In terms of softness, there is an increase of this property up to <NUM> HF points with refined pulp.

Based on the results obtained, it can be concluded that replacing bleached pulp with unbleached Eucalyptus globulus pulp has a numerous of advantages.

In terms of key tissue properties, the use of unbleached Eucalyptus globulus pulp enables the development of consumer-appreciated properties such as bulk, strength, absorption, softness and even visual perception, the later which can be coupled with sustainability and environmental concerns.

In addition, being unbleached pulp, less chemicals (bleaching agents are less or no longer needed) and less water (bleaching process is a step where a significant water consumption is observed) are used for its production.

Claim 1:
Tissue paper sheets comprising at least <NUM>% (w/w) of an unbleached Eucalyptus globulus Kraft fibers pulp and having a bulk from <NUM> to <NUM><NUM>/g, a tensile index from <NUM> to <NUM> kN.m/kg, an absorption capacity from <NUM> to <NUM> gH2O/gpaper, an air permeability from <NUM> to <NUM>/m<NUM>/s and a softness from <NUM> to <NUM> HF.