WO2013125968A1

WO2013125968A1 - A process for retaining calcium carbonate filler in lightweight creped (tissue) paper without negatively affecting the quality of the paper

Info

Publication number: WO2013125968A1
Application number: PCT/PT2013/000011
Authority: WO
Inventors: Victor Manuel CORREIA DA SILVA
Original assignee: Fapajal - Fábrica De Papel Do Tojal, S.A.
Priority date: 2012-02-20
Filing date: 2013-02-19
Publication date: 2013-08-29
Also published as: EP2825700A1; WO2013125968A4; PT106170A

Abstract

The current invention involves a new process for fixing non- cellulosic fillers onto tissue paper between 14 gsm and 50 gsm, either for paper produced from a cellulosic furnish of virgin fibers or for paper produced from a cellulosic furnish of recycled fibers derived from recycled papers. The process consists essentially of introducing in a cellulosic fibrous solution a non-cellulosic filler of calcium carbonate (CaC03) or other, then applying, in sequence, two chemical agents, a micro-particle added before the pressure screen and a polymer in the fibrous solution after the pressure screen. The process did not affect the quality of the paper sheet nor the paper making equipment.

Description

DESCRIPTION

A PROCESS FOR RETAINING CALCIUM CARBONATE FILLER IN

LIGHTWEIGHT CREPED (TISSUE) PAPER WITHOUT NEGATIVELY

AFFECTING THE QUALITY OF THE PAPER

I) BACKGROUND AND TECHNICAL PROBLEM TO BE SOLVED

This invention relates to a new process for retaining calcium carbonate filler in lightweight creped (tissue) paper with a basis weight of between 14 gsm and 50 gsm, for paper produced with virgin fiber cellulosic solution, as well as with recycled fiber cellulosic solution (recycled paper) . The lower the basis weight, the more difficult it is to achieve the retention. The results were observed for paper between 16 gsm and 19 gsm.

The present invention aims to retain calcium carbonate filler in lightweight paper sheets (lightweight creped tissue between 14 gsm and 50 gsm), in order to:

Significantly lower the cost of producing lightweight creped (tissue) paper, replacing virgin pulp or pulp from recycled fibers by calcium carbonate filler, which is cheaper than the fiber raw material, without negatively affecting the properties of the paper or the equipment that produces the paper, and still maintaining the stability of the elements necessary for the proper functioning of the process . Linked to this, the invention maximizes the retention of solids, including cellulosic fiber, on the sheet, while minimizing the solids in the water, which increases the total retention of material on the paper sheet. Improve the properties of the paper, such as softness and whiteness, by the introduction of calcium carbonate .

For several years, the printing and writing pape industry has used materials of relatively lower cost - first kaolin and later carbonate - to replace the much more expensive raw virgin pulp, with the aim of not merely reducing costs but also of achieving certain properties which are important in printing and writing paper. In that industry, the incorporation of calcium carbonate filler currently accounts for about 25% of the weight of the sheet of paper.

The lightweight creped (tissue) paper industry has also been experimenting with using calcium carbonate filler. Some factories have also made trials with, or regularly use, starch, but starch does not replace cellulosic virgin fiber, although it may in some cases reduce the cost of the energy required for paper production.

As for the introduction of fillers, in recent years there has been increasing pressure to achieve a reliable method. From June 2009 to June 2010, with the disproportionate increase in the price of virgin pulp (Figure 1) which corresponds to about 75% of the variable cost of lightweight creped (tissue) paper, and the consequent devastating reduction in margins, these experiments have multiplied. Note that the PIX Price in Figure 1 refers to the price published every Tuesday at 12:00 GMT, by FOEX Indexes Ltd, an independent company specializing in the research and publication of prices and indexes for pulp, paper, recovered paper and biomass of plant origin, which are the basis for the contracts of those raw materials, including long fiber pulp (NBSK or softwood) and short fiber pulp (BHKP or hardwood), denominated in U.S. dollars or in Euros.

Currently, with the increase in pulp prices since the beginning of 2011, experiments in producing lightweight creped (tissue) paper have accelerated.

The trials replacing cellulosic fiber with calcium carbonate filler often result in a poor retention on the sheet or a loss in the quality of the paper, including strength, which is essential to be able to efficiently convert the paper.

Tissue paper has properties which make it difficult to retain fillers in the sheet, including:

> Low basis weight, typically 15gsm to 25 gsm. Although lightweight creped (tissue) paper can be up to 50 gsm, it is with lower basis weights that the difficulty in retention becomes more apparent.

> Creping of the paper

> Paper is formed in paper machines with a concave C- shaped, forming section, referred to as Crescent Former, which since the 1990s has been the most commonly used in tissue paper factories

> Physical properties of the paper (resistance, elongation, etc) . The difficulty in retaining fillers in the sheet results in the filler being lost into the water during the drainage phase of the papermaking process, instead of being retained in the dry paper sheet.

II. STATE OF THE ART

Below are some known attempts to replace cellulosic fiber by calcium carbonate filler:

Patent No. KR20000005241

Use of calcium carbonate filler (kaolin), together with a starch, in an agueous dispersion;

Introduction of the agueous solution of filler, together with the starch, into the fibrous solution used for papermaking;

Introduction of a chemical cationic retention agent (flocculant) into that fibrous solution, after the fan pump of the paper machine;

Further continuation of the normal manufacturing process of tissue paper.

The patent does not appear to aim to retain carbonate in the paper sheet, nor to reduce costs. It refers only to the properties of the tissue paper that may be affected by the use of carbonate together with starch, without apparently indicating whether these are a result of the invention or not.

Patent No. KR20000005242

Use of calcium carbonate filler, which may be of various materials including kaolin, carbonate, aluminum silica, calcium sulfate, starch and others, in an agueous dispersion, together with a chemical anionic polyelectrolyte polymer agent, also in an aqueous dispersion. The use of kaolin is mentioned; Introduction of the aqueous solution of filler, together with the polymer, into the fibrous solution used for papermaking;

> Introduction of a chemical agent for cationic or anionic retention into that fibrous solution, after the Mixing Pump of the paper machine;

Further continuation of the normal manufacturing process of tissue paper. > The patent does not indicate there were satisfactory results in terms of retention or economic benefits. It refers only to factors that may potentially affect tissue paper quality, without apparently indicating whether or not these are a result of the invention. It mentions the environmental benefit of reducing the consumption of forest products.

Other attempts at retention on lightweight creped (tissue) paper sheet

1. Calcium carbonate filler + retention agent, introduced together

^ Use of calcium carbonate filler with a chemical retention agent, mixed into the filler solution itself;

Introduction of the filler thus composed into the fibrous cellulosic solution;

Further continuation of the normal manufacturing process of tissue paper;

□ A retention of 50% of the added carbonate was achieved, and little or nothing onto dry paper; the remainder was found in the white waters, which was not considered economically viable.

2. Introduction of carbonate with the subsequent introduction of a retention agent

Use of calcium carbonate filler, typically carbonate, in an aqueous dispersion;

> Introduction of the aqueous solution into the fibrous solution used for papermaking;

>· Introduction in the same fibrous solution of a chemical agent for cationic or anionic retention into that fibrous solution, after the fan pump of the paper machine;

The results in terms of carbonate retention are unknown, but the lack of publicity, and industry rumors, suggest that the retention was not satisfactory, nor were there positive financial results .

III. INDUSTRIAL RESULT OF FAPAJAL' S INVENTION In May 2011 Fapajal - Fabrica de Papel do Tojal S.A. ("Fapajal") carried out a brief industrial experiment in which it succeeded in retaining between 4% and 6% of calcium carbonate on to the dry paper sheet.

Subsequently a lengthier industrial experiment with the manufacture of virgin fiber paper was carried out, from 23 to 30 November 2011, in continuous production. The retention in the sheet was confirmed. Later, the retention of additional calcium carbonate filler in the fibrous solution of recycled paper was also achieved.

The process of retaining the calcium carbonate filler works on various types of lightweight creped (tissue) paper, both paper produced from virgin pulp and paper produced from recycled pulp. Fapajal manages to retain calcium carbonate filler in both paper produced from virgin fiber and recycled fiber. Note that the recycled fiber solution already contains carbonate, so in this case the interest lies in retaining additional fresh carbonate.

The validation trials focused on virgin fiber paper. Subsequently, Fapajal also succeeded in using carbonate filler in the production of recycled fiber paper, with excellent levels of retention in the sheet.

IV. DESCRIPTION OF THE INVENTION

The Retention of Calcium Carbonate Filler

in Lightweight Creped (tissue) Paper

The retention of calcium carbonate filler in the tissue paper sheet is achieved via a combination of:

Location where the calcium carbonate filler is introduced into the furnish

Type of chemical agents that are added, including two agents for retention and drainage, in order to obtain a retention of calcium carbonate filler on the dry paper sheet, so that the filler is not lost into the water removed during the production of the paper sheet Location where the chemical agents are added

^ ^0rder in which the chemical agents are added.

Fapajal' s manufacturing process is typical of the lightweight creped (tissue) paper industry, as shown in Figure 2. Pulp Preparation from Virgin Fiber

For paper produced from virgin pulp, the pulp received from pulp mills in bales of either short fiber (hardwood) pulp or long fiber (softwood) pulp is placed on conveyors, in various combinations suited to each type of paper, and is disintegrated by a specific equipment called "pulper", in order to separate the pulp fibers and make it suitable for the production of paper. This process is carried out with water (which may be recycled from the paper machine) , typically diluted to a consistency of 5-6%. The disintegration time is about 20 minutes, which is time necessary to separate the cellulosic fibers.

This aqueous fiber is stored in a storage tank and stocked.

For this invention, there is no restriction on the type of virgin pulp used: it may be based on either short or long fiber.

The pulp is pumped out of the storage tank and goes through a cyclonic high consistency (5-6%) cleaning process, in order to remove impurities via the difference in density between the fibers and the contaminants.

The cellulosic fiber then undergoes mechanical defibrillation called refining. This process consists of passing the pulp through a system of specially prepared disks, after which the pulp no longer has a linear but a webbed look, the aim being the creation of connection points between the fibers so that the final paper will have certain mechanical properties, that is, resistance to mechanical traction with measurable values specific to each type of paper.

During the process of refining, the aqueous solution of cellulosic fibers is subjected to the regulation of its consistency, typically around 4.5%, in order to obtain a constant degree of refining.

After the refining process, the pulp is again stored as stock for the production process.

The rejected materials removed in the cleaning process are sent to the Residual Industrial Waters Treatment Plant rWTP") .

Preparing Pulp from Old Paper

Recycled paper is made from secondary fiber, that is, by processing old papers, recovering cellulosic fibers and eliminating a large percentage of existing contaminants.

Below is a detailed description of the process of preparing pulp for recycled paper: The bales of old paper are disintegrated with water, in a specific equipment for disintegrating fiber ("pulper"), which has different characteristics to the pulper for virgin pulp. This process is carried out at a concentration of 14%, and is therefore called high consistency disintegration.

> Since the disintegrated pulp usually contains a large amount of contaminants like plastics, staples, metals, etc., it is subjected to a screening process in which all contaminants larger than 3mm are removed. The pulp is then temporarily stocked.

> Next, the recycled fiber pulp goes through a cyclonic cleaning process, in order to separate contaminants e.g. sand and small size metals, via a difference in density; during this process the pulp has a consistency of 4-5%.

The recycled pulp then undergoes a cleaning process through screening for small size contaminants (> 0.2 mm) .

During this phase, the recycled fiber pulp, already free from solid contaminants, requires cleaning of colloidal contaminants such as secondary carbonates and inks. To this end the pulp is subjected to a cleaning process by flotation, with the aid of surface active chemicals introduced into the pulper. The colloidal particles are swept to the surface through air bubbles, and extracted with the help of foam vacuums. The pulp in this phase is typically diluted at 1%.

> Still at this concentration of 1%, the pulp is then subjected to a process of low consistency cyclonic cleaning, so as to eliminate, via a difference in density, small particles which weigh more than the fibers .

> Free from contaminants, the pulp is then subjected to a washing procedure which consists of thickening the pulp, through draining in specific equipment, typically to a consistency of 14%.

The pulp is stored and undergoes refining (though usually less) as described for the production of virgin fiber pulp.

The waste from the process is treated by the TP mentioned above.

Note that the recycled fiber slurry might not go through all the filtering stages mentioned above, depending upon the degree of whiteness and desired quality of the paper to be produced.

Usually, the recycled fiber paste has a concentration of 3% recycled fiber to 97% water when it reaches the paper machine. Since the old paper, which is the raw material for the recycled fiber, already included over 20% calcium carbonate filler, the recycled fiber slurry already contains 3% to 5% fillers.

The Paper Machine

After the process of preparing pulp from virgin fiber or recycled fiber, the cellulosic pulp or recycled fiber pulp is ready to be made into paper.

Figure 3 shows a diagram of Fapajal's Paper Machine 3, which produces lightweight creped (tissue) paper. Its main components are common to tissue paper machines in general. In that diagram:

The "machine chest" is a storage tank for cellulosic pulp made from virgin or recycled fiber (a mixture of water with the fiber that comes from the pulp preparation area) , located near and in front of the paper machine.

> The "level box" is a relatively small tank located at a certain height, where the level of pulp is kept constant, so as not to allow changes in pressure and consequent changes in the basis weight of the paper sheet. From this level box, the pulp descends by gravity to the fan pump, and the quantity is regulated by the basis weight valve.

> The "fan-pump" is a pump placed at a level below the paper machine, which recirculates water from the white water tank n°l and the head box, and homogenizes the pulp, so that the concentration of fiber to water is 0.02%.

The "pressure screen" is a sieve located between the fan-pump and the headbox of the paper machine, through which the pulp passes. It removes any impurities from the fiber and water mixture. The rejects are taken to the white water tank 2.

The "headbox" receives the pulp solution from the pressure screen, and evenly distributes it onto the felt/wire forming roll, via a jet flowing at a given speed which combining with the speed of the forming roll, produces a specific fiber alignment.

The "forming roll" receives the aqueous pulp solution and by gravity drains a large amount of the water, creating an agglomeration of webbed fibers, called wet paper web. The water that is drained from the fiber goes to the white water tank 1.

The "suction press" is a suction roll where, through vacuum pumps, water is drained until there is 75 to 80% water in the paper web. The drained water goes to white water tank 2.

> The "Yankee dryer", is a large cylinder upon which the paper sheet is dried. Its inside is heated by steam. In fast machines the Yankee dryer is also covered, on top, by a drying box, which circulates air heated via a gas burner, through ventilation. The paper web adheres to the Yankee dryer via a physiochemical process, and after evaporation becomes a dry paper sheet with a moisture content of 5-6%. At the end of the Yankee dryer the creping blade crepes the dry paper sheet.

The "pope reel" is a device that winds the sheet of paper to form a large reel of finished tissue paper (dried to 5% or 6%) with the desired diameter.

"White water tank 1" receives water from the forming roll and most of this large volume of water recirculates to the fan pump.

> "White water tank 2" receives rejected water from the suction press, from the cleaning showers of the forming roll and the waste of the pressure screen.

> The surplus water from white water tank 1 goes to white water tank 2 for further treatment in the fiber recovery equipment.

The "fiber recovery equipament", part of the water treatment, is a device which receives surplus water from white water tank 2 and through a physical- chemical process with flotation separates the water, on one hand, from the fiber with accompanying filler, on the other, that might have been lost in the process of forming and draining the paper sheet. The fiber and the filler return to the process, being reintroduced into o the machine chest. The cleaned water returns to the machine, where it is used to clean equipment.

> The "rewinder" or "slitter rewinder" is not technically part of the paper machine, but the vast majority of paper machines have this equipment at their end, so that the tissue paper can be shaped to the size necessary to its later cutting and folding, to be converted into a consumer product. Introduction of the Calcium Carbonate Filler

The raw material of the non-cellulosic filler can be calcium carbonate, kaolin, carbonate, carbon dioxide, talc, aluminum silicate, calcium silicate, activated carbon, calcium sulfate, and others. Due to its low cost and its properties, natural calcium carbonate (GCC) and precipitated calcium carbonate (PCC) are the preferred raw materials .

In the present invention a calcium carbonate filler consisting of a viscous aqueous solution of calcium carbonate CaC03 was used. The carbonate can be provided by various suppliers - the one we used was supplied by Omya AG and had a density of 1.8 and a CaC03 concentration of 72%, which is typical when applied to the printing and writing paper industry.

The viscous aqueous solution of carbonate and water is kept in a stainless steel chest dimensioned according to the amount of intended paper production. The solution is kept in a serviceable condition by an agitator placed at the bottom of the tank, which prevents the solution from sedimenting to the bottom.

The calcium carbonate, in the aqueous form described, is injected either into the intake (before) the fan-pump (Option I in the diagram in Figure 3) or into the level box (Option II in the diagram in Figure 3) , so that it is well distributed on to the sheet.

The flow rate of the calcium carbonate solution is measured by a flow meter, and the amount pumped varies depending on the amount of carbonate desired, measured as a percentage of dry paper sheet. This calculation is made according to the following formulas:

V(m I min) * G(gsm) * L(m) * 60

P{Kg/h) =

1000

P - Production of the machine

V - Speed of the machine

G - Basis weight of the paper

L - Width of the machine

(Kg/h) - Kilograms per hour

(m/min) - Meters per minute

(gsm) - Grams per square meter

(m) - Meters

D - Dosage (Flow)

P - Production of the machine

% - Percentage of non-cellusic filler to be incorporated into the paper

d - Density of the CaC03 commercial solution (d=1.8)

C - Concentration of calcium concentration in the commercial solution (C=0.72)

GaC03 - Calcium carbonate

The calcium carbonate filler may be introduced in various different concentrations per ton of dry paper. This invention applies to the incorporation of between 2% and 10% of the basis weight in grams per meter of the virgin fiber paper sheet, for papers between 15 gsm and 25 gsm.

Recycled Paper

The carbonate CaC03 solution is applied in the same way, and at the same location (the intake of the fan-pump or the level box) as in the case of virgin fiber paper.

For recycled paper between 15 and 50 grams per m2, the invention also applies to incorporations of between 2% and 10% fresh carbonate filler, in addition to the non- cellulosic particles that already exist in the fibrous solution .

Chemical Retention Agents

In the case of both virgin fiber paper and recycled fiber paper, the retention of the calcium carbonate filler is achieved by adding two chemical agents to the fibrous solution that already incorporates the calcium carbonate filler :

Silica-based micro-particle. Other micro-particles may be suitable for the purpose, either based on silica or on other coagulants. In this case, the product applied in aqueous solution has the trade name Ultrapositek ®

8693.

The product is applied to the fibrous solution that already contains calcium carbonate filler, via an automatic dispenser, with a dosage of 1.5 to 5 kg per ton of dry paper produced. It was found that 2 to 3.5 kg per ton of dry paper is suitable for typical tissue paper manufactured products.

The product is applied in its normal state, without being diluted.

> Cationic polymer with a modified polyacrylamide (polyelectrolyte) chain. Other cationic polyacrylamide polymers (flocculants) may be used. In the case of the validation trail of the invention, the product with the trade name Core Shell ® N74553 was used.

The product is applied in a ratio of 300 to 700g of product per ton of dry paper produced. In the validation trial, the product was applied in the ratio of 500 to 600g of product per ton of paper produced, depending on the type of paper.

The chemical product is prepared by a first dilution of 0.3 to 0.5%, which extends its molecular chain. The prepared product can now be introduced as is, but the homogenization is improved if it is subjected to a second aqueous dilution of between 10 and 40% of the product prepared in the first dilution.

Location and Sequence of

Introduction of the Chemical Agents

An important aspect of the invention concerns the location where each chemical agent is introduced, and therefore the sequence of the introduction in the manufacturing process. The calcium carbonate filler is introduced into the cellulosic fibrous solution in the intake (before) of the fan-pump, or inside the level box.

The chemical agents are introduced after the introduction of the calcium carbonate filler into the fibrous solution.

The silica-based microparticle is applied after the fan-pump and before the pressure screen; therefore, after the introduction of the cellulosic filler and before the polymer.

> The polymer is injected after the pressure screen; therefore, after the introduction of the cellulosic filler and the micro particle.

The introduction of the two particles at these specific locations is what leads to the retention of the calcium carbonate in the sheet, and is an important aspect of the invention and of the process of retaining calcium carbonate filler to the paper sheet. The micro particle, or another with a different active agent, which may or may not be diluted, must be introduced before the polymer for maximum retention of the calcium carbonate filler on the paper sheet, and in order to minimize its loss in the water eliminated from the process during the drying stage.

The above mentioned Figure 3 shows not only the location of the introduction of the calcium carbonate filler, but also the locations, and the sequence, of the introduction of the chemical agents.

In industrial manufacturing, The stability of the properties of the equipment and of the paper produced was proved in industrial production, up to an incorporation of 6% carbonate in the case of virgin pulp paper, and of up to 6% carbonate, in addition to that which already exists in the fibrous recycled solution, in the case of recycled fiber paper.

The loss of carbonate is minimized by the process of recovering the fibers together with the filler, thereby maximizing the yield of the carbonate introduced.

V. VALIDATION OF THE INVENTION

During the invention's industrial trial period, between 23 and 30 November 2011, both the water and the paper were tested.

These tests were made on paper produced by Paper Machine 3 ("PM3"), and observed by technicians of an independent company, who are not Fapajal employees.

The validation trials focused on paper produced from virgin fiber, because the financial benefit is much greater in these types of products, due to the significantly higher price of virgin pulp as a raw material, as compared to old papers .

The trials were carried out on 6 production orders shown in Figure 4 :

Wet Strength Papers (identified as "RHN", which is an internal reference of Fapajal' s) for the production of rolls and hand towels, and kitchen rolls. These papers contain resin, to make them resistant to moisture, so that they do not dissolve when they become moist.

> Toilet Papers, (identified as "CRHN" which is an internal reference of Fapajal's). These papers must dissolve in water so that they do not block domestic pipes, and therefore they do not contain resin.

Figure 4 shows the date of production, the paper grade produced, the Production Order number, and internal Fapajal reference to identify each customer' s production, the percentage of carbonate filler added, and the percentage of different types of virgin pulp raw material that each product contained: long-fibre pulp (from pine and other softwood species) , mixed fiber pulp (sourced from acacia, poplar, birch and other species of both softwood and hardwood) and short-fiber pulp (eucalyptus and other hardwood species) .

Tests were carried out to the paper and the waters, in order to measure:

a) the retention of calcium carbonate on the sheet b) the retention of the carbonate fillers in the white waters, which should be the least possible

c) the quality of the tissue paper produced with added carbonate filler

d) the changes and stability of the process which may have resulted from the addition of calcium carbonate filler. a) Retention of the Calcium Carbonate in the Paper Sheet

For each production order, a range of tests is regularly undertaken on the dry paper, in order to measure its physical and mechanical properties, both near the paper machine during the production and/or in the company's laboratory. In addition to these, further tests were undertaken to determine the retention of fillers in the paper - by incineration and by titration. The summary of these tests is in Figure 5 (a) and (b) .

In order to measure the retention of calcium carbonate in the paper sheet it is extremely important to measure the amount of non-cellulosic filler in the sheet. Fapajal's laboratory uses the method of incineration, based on ISO 2147, to measure the fillers in the paper.

Usually, the non-cellulosic fillers (dust, etc.) in virgin pulp paper are between 0.3% and 0.5% of the dry paper.

The tests show that the filler in the paper with added calcium carbonate ranged from 2.5% to 5.1%, with an average of 3.8%, for the six production orders (see Figure 5 (b) ) . The difference between these and the usual values is a result of the carbonate filler.

The technicians who accompanied Fapajal during the period measured, by titration, calcium carbonate fillers in the dry paper of up to 8.1%, depending on the date and time of the test. Most of the technicians' observations, as disclosed to Fapajal, were between 3.6% and 5.2%. b) Total Retention

The retention of particles and fiber on the paper sheet is calculated by the following formula:

Retention = (headbox consistency in percent - white waters consistency in percent) / headbox consistency in percent X 100.

Thus, the retention is obtained by the difference that exists in the pulp that enters the headbox of the paper machine and what is left behind in the white waters of the pit. Typically, in a good tissue paper machine the result of the analyses undertaken during production show figures for total retention between 70% and 75%, with slightly lower values for fiber retention.

Figure 6 (a) and (b) shows the results of the control tests commonly done to the waters, throughout the production process of lightweight creped (tissue) paper machines, by Fapajal's laboratory technicians. It shows the target value for each characteristic, as well as the average for the period 1 to 22 November (before the industrial trial), and the average for the trial period of 23 to 30 November. (Where no target figure is given, the values are simple observations, with no specific target) .

The dates of the industrial trial for the retention of calcium carbonate filler are highlighted, in order to facilitate the comparison between the periods before and after the introduction of calcium carbonate filler.

The aforementioned Figure 6 (a) indicates that during the industrial trial the average retention in the paper sheet was significantly higher than the average for the previous period. This finding suggests that the addition of the two retention agents even improved the retention of the fiber, and this would have a secondary, but significant, consequence, which is an improvement to the quality of the white waters and a reduction of waste.

The measurement of retention in Figure 6 (a) was confirmed by the technicians from the independent company who observed the process, in a report submitted after the industrial trial. In this report, they reported an average total retention of 80%, which a top value of 85%. c) Paper Quality The results of the tests made to validate the invention, and the absence of complaints by clients who received the paper in a "blind" test, confirm our statement that the quality of the paper was not affected by the retention of calcium carbonate filler in the paper sheet. In the case of two properties - whiteness and softness - there even appears to have been an improvement .

Whiteness . Figure 5 (b) shows an increase in this figure, because it was regularly above normal levels for each type of paper. This increase, if it is later confirmed in further tests, can be attributed to the whiteness of carbonate being superior to the whiteness of fiber.

Tensile Strength. This property is one of the most important in tissue paper, because it affects the speed and efficiency of the machines that transform the paper into the final consumer product. Figure 5 (b) shows the target tensile index and wet strength tensile index by production order, and the values achieved. We can infer from this figure that there was no significant loss in the tensile strength of the paper produced with calcium carbonate filler.

One alternative could be to increase the tensile strength by greater refining of the cellulosic paste, which would increase the cost of production. It is important to note that it was not necessary to increase refining of the cellulosic paste, beyond what is usual, during the industrial trial.

Creping. There was no change to the guaranteed stretch of the products.

Thickness . This property was also not negatively affected by the introduction of calcium carbonate filler. The values were close to the target ones during the industrial trial.

Softness . This property, which is qualitative by nature, is difficult to measure. However, in a qualitative "blind" test, when the testers, who were not paper experts, were asked which paper sheet was the softest, they more often chose the paper with calcium carbonate over the paper without the filler. d) Stability of the Process

The tests described below confirm our statement that retaining the carbon carbonate in the sheet of lightweight creped (tissue) paper does not affect the stability of the tissue paper manufacturing process. pH Factor

This figure should be between 7.5 and 8.5 in the white waters of the pit (see Figure 6 (a)), and was not affected by the amount of calcium carbonate filler.

The report of the independent technicians shows the pH in the white waters of the pit, as well as in the various water chests of the paper machine, the headbox, and the filtered waters. The report indicates there was no correlation between the introduction of calcium carbonate filler and variations in pH.

Other Tests to the Waters

The other white water tests, including for hardness, conductivity, anionic charge, negative zeta potential, turbidity, temperature, alcalinity, etc., were carried out during the manufacturing process with calcium carbonate filler by Fapajal (see Figure 6 (a) and (b) ) and/or by the independent technicians, summarized in their report.

There was no observation of any negative effects as a result of adding calcium carbonate fillers.

VI. FINANCIAL BENEFIT

The benefit of introducing calcium carbonate filler to lightweight creped (tissue) paper lies in the economic benefit of the process, which is more important than the potential improvement to the physical properties of the paper.

The greatest economic rewards result from the use of a cheaper raw material, instead of virgin fiber pulp. The improvements to the quality of the paper - whiteness, softness - have already been noted.

Replacing virgin pulp with calcium carbonate filler

Considering:

Price Virgin Pulp = €420/ton

Incorporation of pulp = 1.07

Virgin pulp per ton of paper = €449.40

Price aqueous solution of calcium carbonate CaC03 = €80/ton Garbonate concentration in the aqueous solution = 28%

Price dry calcium carbonate = €lll/ton

Incorporation of polymer kg / ton = 0.6

Price Polymer = €4.46 Incorporation of Micro particle kg / ton = 3

Price Micro particle = €0.75

Energy used in the pumps kW/ton = 1.5

Price Energy 6 / kW = €0.082

Economic results:

Saving in fiber replacement = €22.47

Added cost of calcium carbonate, chemicals and energy = €10.70

[Saving per ton of paper produced = €11

This benefit is amplified by the savings due to the retention of virgin fiber, evident over an extended production.

Note that the calculation was made at a time when the price of virgin fiber was low (November 2011). Obviously, the higher the price of virgin fiber, which is notoriously volatile, the greater the savings of replacing that raw material, responsible for a very high percentage of the variable cost of paper, with calcium carbonate.

Replacing recycled pulp with calcium carbonate

In the case of paper made from recycled cellulosic paste, the saving per ton of paper produced is currently between €4.00 and €5.00, considering the price for old papers of €250/ton and an incorporation of 1.35, which is a normal figure for deinked papers.

VII. CONCLUSIONS

The summary below contains the conclusions of from Fapajal and the independent technicians who verified the productions. The conclusions refer in all cases to the situation after the introduction of calcium carbonate filler CaC03.

• Calcium carbonate retained on the sheet: 2 to 5%, with an average of 3%

• Total retention of 72% to 89%, which is above the normal values for the paper machine

• The retention of carbonate alone was difficult to measure, but there are indications that it was between 60% and 70% There was no increase in the turbidity of the filtered water after production

There was a small improvement in the whiteness of the paper, of 3%, without continued quantification

Paper resistance was unchanged, remaining between the low and average target values for each type of paper

There was no need to increase the refining of the virgin pulp cellulosic paste to maintain resistance

The creping factor was unchanged, remaining at 20% to 22%

There was no apparent negative effect to the felt or wire of the paper machine

There were no breaks in the paper that could be related to the trial

There was no apparent negative impact on the working of the Yankee dryer of the paper machine

The paper apparently became softer after the addition of calcium carbonate filler (qualitative touch test by non-experts) .

Lisbon, 19 February 2013

Claims

1. Process of retaining non-cellulosic fillers in lightweight creped (tissue) paper between 14 gsm and 50 gsm, with no negative effect on the paper sheet characteristics. The process consists of introducing in a cellulosic fibrous slurry a solution of calcium carbonate (CaC03) or other non-cellulosic matter, in a dilution of 72% filler to 28% water, and applying, in sequence, a micro-particle and a polymer which constitute the chemical agents of the process and which are added after the carbonate filler, in the following steps:

a) Introduce the carbonate calcium filler in the cellulosic fibrous solution in the intake of the fan-pump or in the level box of the paper machine; b) Apply the micro-particle in the fibrous solution with the calcium carbonate solution already incorporated, before the pressure screen and, therefore, before the polymer;

c) Inject the polymer in the fibrous solution after the pressure screen.

2. Process as in claim n° 1, characterized by the fact that the calcium carbonate filler can be in natural form ("GCC") or precipitated form ("PCC"), and also be constituted by kaolin, carbonate, talc, carbon dioxide, aluminium silicate, calcium silicate, activated carbon, calcium sulphate and the like.

3. Process as in claim n° 1, characterized by the silicate- based micro-particulate being applied in the proportion of 1.5 Kg to 5 Kg per ton of dry paper produced.

4. Process as in to claims n° 1 and n° 3, characterized by the micro-particle being applied as is, without dilution.

5. Process as in claims n° 1 and n° 4, characterized by the polymer being a cataonic retention agent, through the utilization of a product with a modified polyacrylamide cataonic chain, applied in the proportion fo 300g to 700g per ton of paper produced.

6. Process as in claims n° 1 and n° 5, characterized by application of the polymer using one aqueous dilution only, of 0.3% to 0.5%, in order to extend its molecular chain .

7. Process as in claims n° 1 and n° 6, characterized by application of the polymer using an additional second aqueous dilution of between 10% and 40% of the product prepared in the first dilution.

8. Process as in claims n° 1 and n° 7, characterized by the percentage of fibres and calcium carbonate filler lost in the white waters being recuperated by fibre recovery equipment and re-introduced in the machine chest where it returns to the papermaking process.

9. Process according to claim n° 1, characterized by the carbonate filler comprising from 2% to 10% of the weight of the dry paper sheet made from virgin pulp, in papers from 15 gsm to 25 gsm; with similar incorporation, in addition to the filler already in the fibrous solution, in the case of recycled papers from 15 gsm to 50 gsm.

Lisbon, 19 February 2013