WO2023193104A1 - Extruded starch and process of producing paper - Google Patents

Abstract

A process of making paper includes providing a stock having fibrous material, extruded starch and optionally an inorganic filler. The stock is pressed to a minimum solids content before drying. The extruded starch may a) be cationic, b) be chemically or enzymatically modified c) be not cross linked, d) have a solubility in the range of 40-99%, e) have a molecular weight of over 300,000 Da, f) have a weight fraction over 30,000,000 Da of 0.05 or less and/or g) have an RVA viscosity of 15,000 cP or less. Feed starch is extruded with water. Optionally, one or more of a polyol, a humectant or a plasticizer, may be added. Optionally, chemical reagents or enzymes are used during extrusion to modify the starch. Optionally, the extrusion is performed substantially without a crosslinker. The extrusion may be done in a twin-screw extruder, optionally with one or more high shear sections.

Description

EXTRUDED STARCH AND PROCESS OF PRODUCING PAPER

RELATED APPLICATIONS

[0001] This application claims priority to, and the benefit of, US provisional patent application number 63/329,114, Production of Paper and Board, filed on April 8, 2022 and US provisional patent application number 63/351 ,149, Extruded Starch and Process of Producing Paper, filed on June 10, 2022, both of which are incorporated herein by reference.

FIELD

[0002] The present disclosure relates to paper (including tissue, towel, card and board) and papermaking processes, to materials derived from starch, and to the use of materials derived from starch in producing paper, for example as a dry strength agent.

BACKGROUND

[0003] The following paragraphs are not an admission that anything discussed therein is prior art, or part of the knowledge of persons skilled in the art.

[0004] Paper is frequently made in a substantially continuous process on a papermaking machine. Many modern papermaking machines are derived from older machines, for example the Fourdrinier machine developed in the early 1800s. A typical Fourdrinier papermaking machine has at least a forming section, a press section and a drying section. Paper stock is made by combining fibers (alternatively called fiber stock), and other materials such as fillers, optionally with refining or other physical or chemical treatments, and transferred to a head tank (alternatively called a head box or a stuff box) of the papermaking machine. The stock is transferred from the head tank to the headbox of a paper machine and from there onto a wire (typically a moving fabric loop) in the forming section. Water drains from the stock, often aided by suction, through the wire to produce a coherent sheet, optionally called a web. The sheet passes into the press section where more water is removed by pressing the sheet against felts that absorb water. The pressed sheet then passes to the dryer section where it is dried thermally, for example by passing over a series of steam-heated cylinders. In some examples, these sections are followed by one or more of: a size press, a calendaring section and a coating section. A reel section at the end of the machine winds the paper onto rolls for storage, transport or further processing. Alternative machines, for example a cylinder mold machine or a tissue machine, implement similar steps using different arrangements or designs of the machine sections. Paper can be formed in a variety of thicknesses (i.e. 0.07 - 0.18 mm) or weights (i.e. 15 - 300 g/m² or 30-300 g/m²), optionally ranging from lightweight or tissue paper, through ordinary multi-purpose or printing paper (optionally in a range of 60-120 g/m²), to card (optionally 135 g/m² or more) or board (optionally 250 g/m² or more), in single or multiple layers, and with a variety of surface characteristics or other attributes.

[0005] In some examples, starch is added to the paper stock, for example as a dry strength agent. In a conventional process, native granules of starch are cooked in water to form a dissolved starch solution at the papermaking site just before use. Starch granules are most typically dissolved by a jet-cooking process, in which an aqueous starch slurry is contacted with steam at a temperature of about 120 - 130 °C and dissolution takes place in a tube with a process time of about 1-2 minutes. After the starch has been dissolved, it is common to dilute it below 1% solids content before dosing into the papermaking stock to ensure homogeneous mixing with the -paper stock. The dissolved starch is used soon after it is produced to avoid microbial spoilage or retrogradation.

[0006] In other examples, a pre-gelatinized starch slurry or dry cold water-soluble starch is mixed with water and added to the papermaking stock. Cold water-soluble starch can be made, for example, by a process described in US Patent 5,037,929. Alternatively, STA-LOK(TM) 280 from Tate & Lyle contains pre-processed cationic waxy corn starch provided as a 30% solids slurry. In other examples, a dispersion of regenerated starch particles can be used, for example as described in European publication No. 1 ,176,254.

INTRODUCTION

[0007] The following introduction is intended to introduce the reader to the present disclosure, but not to define any invention. One or more inventions may reside in a combination or sub-combination of the features described below, or in other parts of the specification. The inventors do not waive or disclaim their rights to any invention or inventions disclosed in the specification merely by not describing such other invention or inventions in the claims.

[0008] This specification describes a method of making paper. The method includes providing a paper stock, optionally called a stock for brevity, which includes fibrous material such as a fiber stock, water, optionally one or more inorganic fillers, and an extruded starch. Optionally, the paper stock may have one or more additives or auxiliaries. The paper stock is formed into a web. The web is pressed to at least a minimum solids content and dried. The minimum solids content, in wt%, is 46 + (x-10)*0.3, wherein x is the ash content of the dried paper. The extruded starch optionally has one or more attributes. In some examples, the extruded starch is cationic. In some examples, the starch is chemically or enzymatically modified in the extruder, for example the starch may be acid thinned. In some examples, the extruded starch is not cross linked. In some examples, the extruded starch has a solubility, for example as determined by the amount of Rapidly Soluble Starch (RSS), in the range of 40-99%, or 40-93%, or 40-92%, or less than 92%. In some examples, the extruded starch has a molecular weight of over 300,000 Da. In some examples, the extruded starch has a weight fraction over 30,000,000 Da of 0.05 or less. In some examples, the extruded starch at 20 %S (solids content) has an RVA viscosity of 15,000 cP or less.

[0009] This specification also describes a composition including extruded starch. In some examples, the extruded starch is cationic. In some examples, the extruded starch is not cross linked. In some examples, the extruded starch has a solubility in the range of 40- 99% or 40-93%. In some examples, the extruded starch has a molecular weight of 300,000 Da or more, 500,000 Da or more, 2,000,000 Da or more or 4,000,000 Da or more. In some examples, the extruded starch has a weight fraction over 30,000,000 Da of 0.05 or less. In some examples, the extruded starch at 20 %S (solids content) has an RVA viscosity of 15,000 cP or less or 5,000 cP or less.

[0010] This specification also describes a method of making a composition including extruded starch. Feed starch, or a material containing starch, is extruded with water. Optionally, one or more of a processing aid, a polyol, a humectant or a plasticizer (i.e. glycerol), may be added during or after the extrusion. Optionally, the starch is acid- thinned or enzymatically modified during the extrusion. The extrusion may be done in a twin-screw extruder, optionally with one or more mixing and/or high shear sections. Optionally, the feed starch may be cationic or the starch may be cationized in the extruder. [0011] In at least some examples, the extruded starch and/or the method of making paper using extruded starch result in final papers with higher dry strength compared to papers made using conventional starch.

BRIEF DESCRIPTION OF THE FIGURES

[0012] FIG. 1 graphically depicts dependence of Short Span Compression Test (SOT) results on cationic charge level for select pressed sheets comprising starch samples blank, 1 , 15, and 16 at 5 kg/t and 10 kg/t. [0013] FIG. 2 - graphically depicts dependence of Short Span Compression Test (SCT) results on molecular weight for select pressed sheets comprising starch samples 1 , 10 - 11 at 5 kg/t and 10 kg/t.

[0014] FIG. 3 - graphically depicts dependence of Short Span Compression Test (SCT) results on cross-linking for select pressed sheets comprising starch samples 1 , 3, 12, 13 at 5 kg/t and 10 kg/t.

[0015] FIG. 4 - graphically depicts dependence of Burst Test results on crosslinking for select pressed sheets comprising starch samples 1 , 3, 12, 13 at 5 kg/t and 10 kg/t.

[0016] FIG. 5 - graphically depicts dependence of Short Span Compression Test (SCT) results on dry solids content (low DC, high DC) for select pressed sheets comprising starch samples 1 , 17, 18 at 5 and 10 kg/t.

DETAILED DESCRIPTION

[0017] As used in the specification and claims, the singular forms "a", "an" and "the" include plural references unless the context dictates otherwise.

[0018] In a method of making paper, starch is added to stock, for example upstream of the wet end or in the wet end, optionally before, together or after fillers or additives have been added. In some examples, starch is added to the fibrous material before any other additives or fillers are added. Starch may be added to thick or thin stock. The addition of starch increases the strength of the final product paper. The starch may be, for example, regenerated starch particles. The starch is regenerated in the sense that the crystalline structure of native starch granules is broken down and a new particle structure is created. The starch particles each contain multiple starch molecules, which may be optionally crosslinked together. For example, starch particles may be produced as described for example EP Publication No. 1 ,176,254, which is incorporated herein by reference. In other examples, the starch is a thermo-mechanically processed starch, wherein the crystalline structure of the native starch granules is broken down but new supramolecular structures are not necessarily produced, or distinct starch molecules may exist in combination with supramolecular starch structures. Starch particles and other forms of thermo-mechanically processed starch may be produced in an extruder, and the term "extruded starch" may be used to refer to them herein for brevity. However, other processes may be used to produce similar materials. For example, some high shear static mixers that produce similar amounts of mechanical energy may be used. On the contrary, some extruders produce low amounts of mechanical energy and rely more on heat to essentially cook starch, which does not produce similar materials. Extruders that produce high amounts of mechanical energy include, for example, twin screw co-rotating extruders.

[0019] Extruded starch, as described above, is not entirely soluble in some examples. However, the insoluble structures may be very small, for example in the range of 10-1000 nm, or 50-500 nm, and can behave mechanically like a solution even though they might be more accurately described as a dispersion. In some examples, a mixture of extruded starch in water can contain some dissolved starch molecules and some dispersed large starch molecules, supramolecular structures or particles. The terms "dispersion" or "solution" may be used herein to describe mixtures of the extruded starch in water, but neither word is used according to a strict technical definition.

[0020] In some examples, an extruded starch contains 99% or less or 93% or less or 92% or less of rapidly soluble starch (RSS). Rapidly soluble starch is starch, whether truly dissolved or not, that behaves to some extent as if in solution when mixed in room temperature water. RSS is measured by adding 4 g of dry extruded starch to 200 ml deionized water; stirring for 2 minutes at 600 RPM; centrifuging at 3000 RPM for 15 minutes; removing 100 ml of the supernatant through decanting or pipette; oven drying the supernatant at 110°C; and measuring the dry mass remaining, which is representative of the mass of starch in the supernatant. The dry mass is divided by 2 g and converted to a percentage to determine the RSS. In examples described further below, an RSS of 92% was achieved in a twin-screw extruder without chemical or enzymatic modification of the starch. In another example, starch with an RSS of 97% was chemically modified with an acid in the extruder. The amount of acid used was less than the amount of acid used to produce acid thinned starch outside of an extruder. It is expected that enzymatic treatments in the extruder may alternatively or additionally be used to produce starch with an RSS up to 97% or 99%. Cross-linked starch produced in an extruder tends to have much lower RSS. However, an RSS of optionally 40 or more can be achieved with cross-linking.

[0021] As described further below, the addition of extruded starch to the stock results in the finished paper having increased strength or other mechanical properties relative to paper made with conventional cooked starch. Further increases in mechanical or other properties are provided by selecting extruded starch that has one or more optional properties. For example, the extruded starch is optionally not cross linked. The extruded starch optionally has an RSS in the range of 40-97% or 40-93%. The extruded starch optionally has a molecular weight of over 300,000 Da or more, 500,000 Da or more, 2,000,000 Da or more, 4,000,000 Da or more, or 5,000,000 Da or more. The extruded starch optionally has a weight fraction over 30,000,000 Da of 0.05 or less. The extruded starch at 20 % solids content optionally has an RVA viscosity of 15,000 cP or less or 10,000 cP or less or 5,000 cP or less. The extruded starch is optionally cationic. Cationicity is optionally measured as the percent nitrogen bound to starch excluding protein nitrogen, which may be in the range of about 0.1 -1.6% or 0.1 -0.8%.

[0022] Further improvements in mechanical properties can also be achieved with operation of other steps in the papermaking process. As the papermaking process continues, a web or sheet formed from the stock is pressed. In a Fourdrinier-type papermaking machine the web is transferred from the forming section to a distinct press section. In other papermaking machines, web formation and pressing may be at least partially integrated, or other arrangements of analogous machinery may be used. The web contains fibrous material, the extruded starch, optionally one or more types of inorganic fillers, and optionally one or more other additives. Typically, the pressed web is dried further in a thermal drying process.

[0023] The inventors have determined that pressing, or otherwise dewatering, the web to at least a minimum solids content increases the strength or other mechanical properties of the final paper, particularly when extruded starch is present in the web. The minimum solids content may vary with the amount of inorganic filler that is also present in the web. In some examples, the - stock is pressed to a minimum solids content defined by formula (I)

D(x) = 46 + (x-10)*0.3 (I)

[0024] where D(x) is the minimum solids content in wt%, and (x) is the ash content in wt% of the finished paper. The minimum solids content refers to the solids content of the pressed sheet, and may be determined using the oven drying method of ISO 638:2008. The ash content x may be measured according to ISO 1762:2019. The ash content of the finished paper is related to the amount of inorganic filter added to the stock.

[0025] In some examples, extruded starch is made by adding one or more starch- containing feed materials, for example native starch or flour, to an extruder. Water is also added to the extruder. Optionally, a processing aid, a polyol, humectant or plasticizer (for example glycerol) may be added to the extruder. When added to the extruder, the processing aid, polyol, humectant, or plasticizer may be added upstream or downstream of a mechanical processing area where most of the mechanical work is done to the feed material. In other options, the processing aid, polyol, humectant, or plasticizer, if any, may be added to the extrudate after extrusion. The one or more starch containing feed materials preferably make up 80% or more of the solids (i.e. all materials other than water) added to the extruder.

[0026] Starches can be processed using mechanical energy. Mechanical energy can be delivered to the starch using high shear mixers, single screw extruders under some conditions, or twin screw extruders which may have co-rotating or contra-rotating screws. Preferred extruders have twin co-rotating screws. The extruder may have several, i.e. 5 or more, or 7 or more, barrels. The extruder preferably includes one or more mixing and/or high shear sections. A mixing and/or high shear section may have a reverse kneading element, or forward and reverse kneading elements. The extruder or other high shear mixer may apply a specific mechanical energy of 100 Wh or more, or 150 Wh or more, or in the range of 175-300 Wh, per kg of starch-containing feed material. The extruder preferably operates at a temperature less than 180 degrees °C to reduce or avoid the presence of short chain molecules (DP < 6) in the extrusion product. The maximum barrel temperature (temperature in the hottest barrel) in the extruder may be less than 180 degrees, or 160 degrees °C or less, or in the range of 120 to 160 degrees C. The extruder may be as described in US patent 9,011 ,741 , Process for Producing Biopolymer Nanoparticles, which is incorporated by reference.

[0027] The feed material contains starch. The feed material may be a single type of native starch alone, or flour, or any combination of starches of different types or a combination of starch and flour. In some examples, the starch is not substantially acid thinned but a small amount of acid may be added as a processing aid. Optionally, a weak acid (pKa of 1 or more), if any, may be added at less than 1 wt%, or less than 0.5 wt%, on a solids basis relative to the feed material. Optionally, a strong acid, if any, may be added at less than 0.7 wy%, less than 0.5 wt%, or less than 0.0001 wt% on a solids basis relative to the feed material. Optionally, one or more enzymes, if any, may be added at less than 10% solids relative to the feed material. The product may have a molecular weight of at least 300,000, at least 500,000, at least 2 million, at least 3 million, at least 4 million or at least 5 million Da. In some examples, the extrusion product has polydispersity index (Mw/Mn) of less than 2. The extrusion product is primarily, i.e. 80% or more by weight when dry, made up of one or more of starch, proteins or other materials found in native starch or flour, or their derivatives.

[0028] Some examples of extruded starch made as described above were compared to a commercially available pre-gelatinized starch. Novel extruded starch products were made according to the process described above using three feed materials. Maximum barrel temperatures were in the range of 120 to 160 degrees C. SME was in the range of 175-300 Wh/kg of starch-containing feed material. In sample A, the feed material was dent corn starch. In sample B, the feed material was corn flour. In sample C, the feed material was waxy corn starch. The extruder was as described in US patent 9,011 ,741 . The feed material was introduced into the extruder with glycerol (5 parts glycerol, 95 parts starch or flour, by weight) and water but without a crosslinker or acid.

[0029] Samples of PCF 1000 by Bunge, a commercially available pre-gelatinized corn flour, were tested for comparison. This product is made by processing corn flour in a single screw extruder. Although an extruder may be involved in making pre-gelatinized starch, single screw extruders are typically configured to provide low specific mechanical energy (SME) and to provide a thermal process rather than a mechanical one. The extruder is used to provide a plug flow process to cook the starch rather than to mechanically process the starch. SME in a single screw extruder is typically much less than 100 Wh/kg. In at least some cases, commercially available pre-gelatinized starch is also processed at very high temperatures, for example 180 degrees C or more. At high temperatures, increased amounts of short chain molecules can be created.

[0030] The various samples were tested by gel permeation chromatography (GPC) in dimethyl sulfoxide (DMSO) to determine their molecular weight and molecular weight distribution. The gel-permeation chromatography was performed on a Malvern Viscotek GPCmax equipped with a Malvern Viscotek TDA (triple detector assembly). The Viscotek TDA was outfitted with refractive index (Rl), intrinsic viscosity, and light scattering (LALLS, RALLS) detectors. For separation, a Polyanalytik (London, ON, Canada) PAA-206M size exclusion chromatography column was used, measuring 8 x 300mm, packed with a polyhydroxymethacrylate-based gel possessing an estimated exclusion limit of 2 x 107 g/mol. Pullulan 50K (Part no. PATD-PUL50K, Mw:46,001 g/mol, PDI: 1.069) was used for calibration, and confirmation was achieved with PolyCALTM Dextran Std-T73K (Mw:71 ,747 g/mol, Mn=53,956 g/mol); both of which were obtained from Polyanalytik (London, ON, Canada). All samples were analyzed under the following experimental conditions: flow rate, 0.6ml/min; column temperature, 70 °C; mobile phase, DMSO (>99.9%) from Anachemia (Montreal, QC, Canada) with 0.05 M LiBr (99+%) from Sigma-Aldrich (Oakville, ON, Canada); sample concentration 2 - 3 mg/ml; injection volume 100 pl; number of replicate experiments was 4. Samples were diluted and filtered through a 0.2 micron filter before entering the GPC column. Results are given in Table 1 below. "% recovery" means the percentage of solids in the sample that passed through the 0.2 micron filter.

Table 1 : Results of GPC Analysis of Various Starch Samples

[0031] Molecular weight (MW) plots for all of the samples showed a peak molecular weight (Peak MW) in the range of 4*10⁶-6*10⁶. However, the PCF 1000 sample had a lower peak in this range and comparatively larger distribution in the range of 1*10⁶-2*10⁶. The PCF 1000 distribution plot also had a tail extending up to 4*10⁷ and a molecular weight fraction (WF/dLogMW where WF stands for weight fraction and dLogMW stands for an interval of the logarithm of the molecular weight Mw) of 0.1 at 3*10⁷ Da. In comparison, samples A, B and C had a molecular weight fraction of 0.025 or less at 3*10⁷. In comparison, commercially available acid thinned starches typically have MW’s less than 2*10⁶.

[0032] Viscosity of the samples was tested using a Rapid Visco Analyzer (RVA, Perten Instruments) with the following operating procedure. The sample and the analytical solution were dispensed into a new canister at a concentration of 20 % solids, i.e. 7.0 g of dry product was added to the canister and the analyte was added up to a total mass of 35.0 g. The sample weight was determined by correcting for sample moisture content to give a constant dry weight. A new paddle was placed into the canister. The sample was prehomogenized to ensure any sample lumps adhering to the inside of the canister were transferred down into the water and then immediately inserted into the RVA machine to start the measurement. The analyte solution consisted of 16.0 g of sodium carbonate (Na₂CO₃) or 18.7 g of sodium carbonate mono-hydrate (Na₂CO₃ • H2O) added and dissolved into 2 kg of demineralized water with 0.4 ml of Acticide GA biocide (Thor Chemicals). The RVA is designed to measure the viscosity profile of a sample undergoing a thermal cycle. The thermal cycle allows the solubilization of the product and is accompanied by an increase in the sample viscosity. The viscosity behavior as a function of temperature is characteristic of the material and is measured as a function of the temperature program. The following program was used:

[0033] The output of the RVA is a viscosity-time curve. The RVA result for the final viscosity is recorded for each sample. The output result depends upon many factors including starch type, amylose content, molecular weight and molecular weight distribution. Results produced using the sample preparation and RVA analysis protocol described above are given in Table 2 below. cP stands for Centipoise, a measurement unit for viscosity.

Table 2: RVA Analysis of Various Starch Samples

[0034] Viscosity of starch dispersions is affected by the botanical origin of the starch as well as by molecular weight and other factors. Dent starch, for example, retrogrades in water more than waxy corn starch. Starch retrogradation, which is the combination of recrystallization and hydrogen bonding or gelation, is usually accompanied by a series of physical changes such as increased viscosity and turbidity of the retrograded starch solution. More particularly, for non-waxy starch, retrogradation results in the transformation of a starch paste into a firm gel consisting of a 3-dimensional network. Retrogradation likely caused the much higher viscosity for sample A relative to sample C. Extruded starch made with waxy corn starch had a materially lower viscosity than extruded starch made with other feed stocks.

[0035] To compare samples of similar botanical origin, the PCF 1000 and Sample B are both made from corn flour. As illustrated in Table 2, Sample B has a much lower viscosity than PCF 1000 despite their similar feed material. The inventors believe that the reduced viscosity of Sample B is a result of sample B being an extruded starch product as described herein rather than a conventional pre-gelatinized starch. Without intending to be limited or bound by theory, one or both of the narrower MW distribution (higher peak, above 1.5 WF/dLogM, in a molecule weight distribution plot) of Sample B relative to PCF 1000 (peak at about 1.3 WF/dLogM) and the high molecular weight tail of PCF 1000, i.e. the relative lack of molecular weights greater than 3*10⁷ Da in Sample B, may be factors.

[0036] Very high molecular weight starches will attach to a fiber surface, but are more likely to desorb over time due to their bulkiness. Very low molecular weight starches are unable to bridge fibers and do not provide strength. A preferred molecular weight (meaning, unless specified otherwise, the weight averaged molecular weight, alternatively called Mw, which is typically near the peak of a WF I dLog MW to Log MW graph), may be 2,000,000 Da or more or 4,000,000 Da or more; optionally up to 12,000,000 Da, up to 10,000,000 Da or up to 8,000,000 Da. Jet-cookers tend to produce starch with very high molecular weights, for example in the range of 27,000,000 Da to 390,000,000 Da for starch produced at 140C-110C, at least some of which may desorb from pulp fibers during the paper making process and not contribute to paper strength. Acid hydrolyzed and oxidized starches produced without an extruder (as compared to the use of small amounts of acid or enzyme used as a processing aid in making extruded starch) can have lower molecular weights, but random chain scission tends to produce a large fraction of very low molecular weight starch that does not contribute to paper strength. Extrusion preferentially breaks down starch molecules above a critical molecular weight, which is inversely related to the shear stress (i.e. specific mechanical energy or SME) applied by the extruder, with minimal further degredation of starch molecules below the critical molecular weight. For example, the cationic starch used in Examples 1 C below has a Mw of about 4,000,000 Da, 0% weight fraction below 1 ,000,000 Da, about 10% weight fraction above 10,000,000 Da, and 0% weight fraction above about 25,000,000 Da. Other extruded starches may have a weight fraction below 1 ,000,000 Da in the range of 0-8% or 0-1%, or a weight fraction below 100,000 Da in the range of 0-8% or 0-1%. In contrast, acid hydrolysis, oxidative and enzymatic treatments break down starch molecules randomly leading to the creation of some starch molecules having very low molecular weight. Starch that does not adhere to the fibers does not increase paper strength and also increases the biological oxygen demand (BOD) of wastewater produced by the paper making process.

[0037] Typically, the extruded starch is added to the stock upstream of a papermaking machine. Alternatively, the extruded starch may be added to the stock in the papermaking machine, but upstream of the press section or analogous section or device. The - stock may comprise a mixture of fibrous material, extruded starch, optionally one or more inorganic fillers, optionally a paper auxiliary or other additives, and water.

[0038] In some examples, the stock is prepared by adding the extruded starch to an aqueous suspension of the fibrous material. Preparation of the stock may include multiple steps in which the solids content of the stock is varied. For example, a thick stock may comprise the fibrous material at a concentration between about 0.5-40 g/L, 10-40 g/L or 20-40 g/L. A dilute - stock may comprise the fibrous material at a concentration between about 0.5 g/L and about 15 g/L. In some examples the extruded starch is added to a thick - stock, but alternatively extruded starch may be added to a dilute - stock. For example, the paper stock may be prepared by adding the extruded starch to a thick stock having a fibrous material concentration of about 20 to about 40 g/L The thick stock be diluted before being transferred to the wet end to a fibrous material concentration of about 0.5 to about 15 g/L. In some examples the extruded starch is added to aqueous suspension of the fibrous material before any filler or additives are added.

[0039] The stock may comprise the extruded starch at a concentration between about 0.05 wt% and about 5 wt% solid content. The stock - may comprise an inorganic filler (described below as x) of about 0 wt% to about 40 wt.% expressed as ash content. The stock may optionally comprise one or more other additives (also called paper auxiliaries).

[0040] The fibrous material in the stock may comprise virgin fiber, recovered fiber, softwood fiber, hardwood fiber, non-wood fiber, or a combination thereof. The fibrous material may comprise dried market pulp, machine broke, recycled fiber, or a combination thereof. Any softwood or hardwood fiber generally used in the papermaking industry may be used for the fibrous material. For example, the fibrous material may comprise mechanical pulp, bleached and unbleached chemical pulp, and/or fibrous materials from any annual plants (also known as non-wood fibrous material). [0041] If the fibrous material comprises bleached and/or unbleached chemical pulps, the fibrous material may have a pulp drainability of 20 to 30 SR. Pulp drainability can be measured according to standard ISO 5267-1 :1999 in SR units standing for Schopper Riegler units. The fibrous material may have a drainability of about 30 SR, which may be achieved by refining during the pulp preparation process. The fibrous material may have a drainability equal or less than 30SR.

[0042] The extruded starch may be added to the stock as a powder or as a dispersion or mixture. The extruded starch preferably has a cationic charge but may have an anionic charge, a zwitterionic charge, or a neutral charge. The extruded starch may include one or more chemical or enzymatic modifications. In some examples, cationic starch is used. The extruded starch may include a corn starch, a wheat starch, a rice starch, a pea starch, a potato starch, a tapioca starch, a barley starch, and all varieties or cultivars respectively, for example waxy corn starch, or a combination thereof. The extruded starch may comprise a mixture of a starch and a biopolymer, wherein the starch is optionally present at a wt% of at least 50% or 80%, and the biopolymer is optionally another polysaccharide such as a cellulose or gum, a protein such as soy protein or gelatin or whey protein, or a combination thereof.

[0043] The extruded starch may be dried after leaving the extruder to form a dried starch extrudate. The dried starch extrudate may be crushed and/or ground to form an extruded starch powder. The crushing and/or grinding of the dried starch extrudate may comprise crushing with a hammermill and/or grinding via a cryogenic grinding process.

[0044] Optionally, an extruded starch powder is added to water to form a dispersion of extruded starch. The dispersion of extruded starch may have a solids content of about 0.1 wt% to about 50 wt%, or about 1 wt% to about 10 wt%.

[0045] The amount of inorganic filler (ash content) that is added to the stock may be adjusted considering any inorganic filler (ash content) that may be already present, for example because of the use of waste paper and/or coated broke as a source for fibrous material. The inorganic filler may be an inorganic pigment, for example metal oxides, carbonates, silicates, or a combination thereof. The inorganic filler may comprise calcium carbonate, talc, kaolin, bentonite, satin white, calcium sulfate, barium sulfate, titanium dioxide, ground lime, chalk, marble (GCC), precipitated calcium carbonate (PCC), or a combination thereof.

[0046] Optionally, inorganic filler may be added to the stock after the extruded starch has been added. The filler may be added during a stage at which the stock is in a form of thick stock (e.g., at a fibrous concentration of 0.5-40 g/L, 10-40 g/L, or 20 to 40 g/L). The filler may be added during a stage at which the stock is in a form of thin stock (e.g., at a fibrous concentration of 5 to 15 g/L). The filler may be added during both stages, when the stock is thick stock as well as thin stock, where the ratio of thick stock addition to thin stock addition is between about 5/1 to about 1/5.

[0047] The filler content (x) of Formula (I) expressed as paper ash content may be between about 0 wt.% to about 40 wt.%, or between about 0 wt.% to about 20 wt.% based on the total dry weight of the final paper.

[0048] A paper auxiliary may comprise a sizing agent, a wet strength agent, a retention aid, a drainage aid, a dry strength enhancer, an optical brightener, a defoamer, a biocide, a paper dye, or a combination thereof. The paper auxiliary may be added to the stock when the stock has a fibrous material concentration of about 5 g/L to about 15 g/L.

[0049] The extruded starch may be added at about 0.5 kg to about 50 kg, for example about 0.6 kg to about 20 kg, of at least one type of extruded starch per metric ton of dry fibrous material. The extruded starch may be added in an amount of about 0.05 wt% to about 5 wt.%, based on the dry weight of fibrous material. The time during which the extruded starch may act on the stock from addition to sheet formation may be between about 0.5 seconds to about 2 hours, or any range of time between about 0.5 second and about 2 hours. Preferably, the time may be in the range of about 2 seconds to about 20 seconds.

[0050] The process may comprise stock treatment in the wet end of the papermaking process (e.g., thick stock and thin stock). The stock treatment with extruded starch may start early in the papermaking process, during pulp preparation, where dried market pulp, machine broke, or recycled fiber materials like OCC may be reslushed before passing other units such as a deflaker and/or refiner. The extruded starch may thus be slushed together with dried fiber materials in the pulper, or may be added to the deflaker and/or refiner units instead. Addition of the extruded starch may be in the form of a dry powder, or in the form of a liquid dispersion.

[0051] The solids content of the web after leaving the press section may be up to, or more than 55 wt.%, depending on the design and operation of the forming section, the design and operation of the press section, the web speed, the type of felts used and their age and the composition of the stock and temperature. The solids content may increase with the pressure exerted in the press as the paper web passes through. The pressure, and hence the solid content of the paper web may be varied within relatively wide limits in different paper machines.

[0052] After leaving the press section, the paper web may be transferred to the drying section of the paper machine. For graphical or packaging paper grades, the paper web may be transferred to a cascade of drying cylinders where the solids content of the paper web can increase from each cylinder to the next. For tissue and hygiene papers, the paper sheet may be transferred to a Yankee cylinder where final drying and creping of the paper sheet can take place. The final dry content of the finished papers may be about 95 wt%.

[0053] The cationic extruded starch can be used as a dry strength agent, for example to improve one or more mechanical performance properties of paper such as tensile strength, burst strength, short-span compression strength and Scott bond strength. The cationic extruded starch can also be used to permit an increase in production speed without breaks in the paper that shut down the line. Alternatively, the cationic extruded starch can be used to maintain strength at a suitable level while other changes are made that may reduce cost or energy consumption but typically reduce strength. For example, reducing the paper basis weight; using shorter fibers; using lower performing mechanically treated, recycled, or non-woody fibers; reducing the level of fiber refining; and, increasing ash content, may all be desirable changes but typically reduce paper strength. Cationic extruded starch can be added to counter (i.e. reduce or eliminate) the loss in strength caused by one or several of these changes.

[0054] To gain a better understanding of the invention described herein, the following examples are set forth. It should be understood that these examples are for illustrative purposes only. Therefore, they should not limit the scope of this invention in anyway. In these examples, the inventors have demonstrated an increase in paper strength relative to paper made with conventional starch and/or solid content below D(x) for final papers having a range of weights. In Examples 1 B a weight of 100 g/m² was selected for consistency between the samples. However, starch similar to Starch sample 1 but made on a commercial scale twin-screw extruder using the same starting material (cationic waxy corn starch) and specific mechanical energy (SME) was subsequently tested in commercial scale tissue, Fourdrinier and linerboard papermaking machines to produce final papers having weights of 16-205 g/m², some of these tests being described in Example 1C. It is expected that similar results for Starch sample 1 and the other samples described below would be produced in papers of other weights, for example but without limitation in the range of 12-240 g/m². The samples described below are not numbered consecutively since other samples were produced but not tested according to the protocol described below.

EXAMPLES

Example 1A - PREPARATION AND CHARACTERIZATION Of EXTRUDED STARCH PRODUCTS AND REFERENCE SAMPLES

Starch sample 1

[0055] 100 parts by weight of a cationic waxy corn starch (Sta-Lok® 180) with a nitrogen content of 0.35% and a moisture content of 11 to 13%, available from Tate & Lyle, was fed into a Buhler twin-screw extruder at a rate of 300 kg/h with a screw speed of 600 RPM. 15 parts by weight of water was added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45-45-40- 130- 130- 130- 135- 135- 135-135-135°C. During extrusion, the specific mechanical energy imparted to the starch was equal to 175 Wh/kg. The bulk density of the extrudate was adjusted by the addition of 3-4 parts of water in barrel 12. The extrudate exited through two twenty-nine-hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7%.

Starch sample 3

[0056] 100 parts by weight of a cationic waxy corn starch (Sta-Lok® 180) with a nitrogen content of 0.35% and a moisture content of 11 to 13%, available from Tate & Lyle, was fed into a Buhler twin-screw extruder at a rate of 300 kg/h with a screw speed of 650 RPM. 12 parts by weight of water, 1 part by weight of an aqueous 10 % sodium hydroxide solution, and 4 parts by weight of an aqueous 10% sodium trimetaphosphate solution were added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45-45-40-130-130-130-135-135-135-135-135°C. During extrusion, the specific mechanical energy imparted to the starch was equal to 244 Wh/kg. The extrudate exited through two twenty-nine-hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7%.

Starch sample 4 [0057] 100 parts by weight of a wet cationic waxy corn starch (Interbond™ C) with a nitrogen content of 0.27% and a moisture content of 11 to 13%, available from Tate & Lyle, was fed into a Buhler twin-screw extruder at a rate of 300 kg/h with a screw speed of 600 RPM. 12 parts by weight of water was added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45-45-40-130-130-130- 135-135-135-135-135°C . During extrusion, the specific mechanical energy imparted to the starch was equal to 214 Wh/kg. The bulk density of the extrudate was adjusted by the addition of 3-4 parts of water in barrel 12. The extrudate exited through two twenty-nine- hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7%.

Starch sample 5

[0058] 100 parts by weight of a cationic potato starch (SolBond PC 80) with a nitrogen content of 0.64% and a moisture content of 11 to 13%, available from Solam, was fed into a Buhler twin-screw extruder at a rate of 300 kg/h with a screw speed of 600 RPM. 6 parts by weight of water and 4.5 parts by weight of glycerol was added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45- 45-40- 130- 130- 130- 135- 135- 135-135- 135°C. During extrusion, the specific mechanical energy imparted to the starch was equal to 206 Wh/kg. The extrudate exited through two twenty-nine-hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7%.

Starch sample 10

[0059] 100 parts by weight of a cationic waxy corn starch (Sta-Lok® 180) with a nitrogen content of 0.35% and a moisture content of 11 to 13%, available from Tate & Lyle, was fed into a Buhler twin-screw extruder at a rate of 200 kg/h with a screw speed of 550 RPM. 6 parts by weight of water and 0.6 parts by weight of aqueous 10% phosphoric acid solution was added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45-45-40- 130- 130- 130-135- 135- 135-135-135°C. During extrusion, the specific mechanical energy imparted to the starch was equal to 239 Wh/kg. The extrudate exited through two twenty-nine-hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7%. Starch sample 11

[0060] 100 parts by weight of a cationic waxy corn starch (Sta-Lok® 180) with a nitrogen content of 0.35% and a moisture content of 11 to 13%, available from Tate & Lyle, was fed into a Buhler twin-screw extruder at a rate of 200 kg/h with a screw speed of 550 RPM. 24 parts by weight of water was added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45-45-40- 130- 130- 130- 135- 135- 135-135-135°C. During extrusion the specific mechanical energy imparted to the starch was equal to 180 Wh/kg. The extrudate exited through two twenty-nine-hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7%.

Starch sample 12

[0061] 100 parts by weight of a cationic waxy corn starch (Sta-Lok® 180) with a nitrogen content of 0.35% and a moisture content of 11 to 13%, available from Tate & Lyle, was fed into a Buhler twin screw extruder at a rate of 200 kg/h with a screw speed of 550 RPM. 12 parts by weight of water, 4 parts by weight of an aqueous 10 % sodium hydroxide solution, and 1 .5 parts by weight of an aqueous 5% sodium trimetaphosphate solution were added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45-45-40-130-130-130-135-135-135-135-135°C. During extrusion, the specific mechanical energy imparted to the starch was equal to 261 Wh/kg. The extrudate exited through two twenty-nine-hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7%.

Starch sample 13

[0062] 100 parts by weight of a cationic waxy corn starch (Sta-Lok® 180) with a nitrogen content of 0.35% and a moisture content of 11 to 13%, available from Tate & Lyle, was fed into a Buhler twin screw extruder at a rate of 200 kg/h with a screw speed of 550 RPM. 12 parts by weight of water, 4 parts by weight of an aqueous 10 % sodium hydroxide solution, and 1 part by weight of an aqueous 5% sodium trimetaphosphate solution were added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45-45-40-130-130-130-135-135-135-135-135°C. During extrusion, the specific mechanical energy imparted to the starch was equal to 269 Wh/kg. The extrudate exited through two twenty-nine-hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7% Starch sample 15

[0063] 100 parts by weight of a cationic waxy corn starch (Cato® 235) with a nitrogen content of 0.25% and a moisture content of 11 to 13%, available from Ingredion, was fed into a Buhler twin-screw extruder at a rate of 200 kg/h with a screw speed of 350 RPM. 18 parts of water was added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45-45-40-130-130-130-135-135-135- 135-135°C. During extrusion the specific mechanical energy imparted to the starch was equal to 139 Wh/kg. The bulk density of the extrudate was adjusted by the addition of 1.5 parts by weight of water in barrel 12. The extrudate exited through two twenty-nine-hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7%.

Starch sample 16

[0064] 100 parts by weight of a cationic waxy corn starch (OptiPRO® 650) with a nitrogen content of 0.65% and a moisture content of 11 to 13%, available from Ingredion, was fed into a Buhler twin-screw extruder at a rate of 200 kg/h with a screw speed of 350 RPM. 15 parts by weight of water was added in the first barrel of the extruder. The extruder had 12 barrels with an adjusted temperature profile of 45-45-45-40- 130- 130- 130- 135- 135- 135-135-135°C . During extrusion, the specific mechanical energy imparted to the starch was equal to 180 Wh/kg. The bulk density of the extrudate was adjusted by the addition of 1 .5 parts of water in barrel 12. The extrudate exited through two twenty-nine-hole dies with each hole having a 2mm diameter, and was cut by a die-face cutter box at 3000 RPM. The shredded extrudate was further dried during air suction conveying, where it then entered a hammermill with a 3 mm sieve. After grinding, the extruded starch powder had a residual water content of 7%. Reference Starch Samples

Starch sample 17

[0065] Starch sample 17 was a waxy corn starch (Sta-Lok® 180) with a nitrogen of 0.35% and a moisture content of 11 to 13%, available from Tate & Lyle. Sample 17 was a granular starch used as a feed starch for the extrusion process in the preparation of Samples 1 , 3, 11 , 12, and 13.

Starch sample 18

[0066] Starch sample 18 was a cold-water soluble starch (Sta-Lok® 280) that had been prepared from a cationic waxy corn starch with a nitrogen content of 0.35% and is available from Tate & Lyle. The starch sample was included in the testing program to show the difference between an extrusion process and existing processes for the gelatinization of starch.

Fibraffin K

[0067] Fibraffin K a commercially available cationic potato starch from Siidstarke GmbH that is commonly used for dry strength applications in the paper industry, was used. The Fibraffin K was supplied as starch granules and was cooked as a starch suspension in a jet-cooker or by heating under atmospheric conditions.

[0068] See Table 3 for the composition and physical properties of the starch samples.

Table 3: Composition and physical properties of prepared starch samples

Table 3 Notes: NA: not available

(*) Viscosity (Brookfield, 100 RPM, 25% solids, 25°C, suspensions prepared with 0.8% solution of sodium carbonate (Na₂CO₃).

(**) Rapidly Soluble Starch: (4 g of dry starch added to 200 ml deionized water; stirred for 2 minutes at 600 RPM; centrifuged at 3000 RPM for 15 minutes; decanted or pipetted 100 ml of supernatant into a dish, oven dried at 110°C to determine soluble starch)

(***) In case of Sample 17 (Reference), a suspension of starch granules at 25% solid content was prepared using a 0.8% solution of Na₂CO₃ (sodium carbonate) The suspension was cooked at 90°C on a hot plate for 30 minutes, resulting in a gel that could not be analyzed for measuring viscosity and molecular weight. (****) Amount of cross linker dosed in the extrusion process had influence on the level of rapid starch solubility RSS (for identical feed starches). Higher cross linking resulted in lower level of RSS.

Example 1B - HAND SHEET PREPARATION AND TESTING

Preparation of Stock

[0069] The raw material (- stock) for production of hand sheets was obtained by beating paper sheets in a pulper. The paper sheets were packaging raw papers of the specification "Testliner 2" with a basis weight of 100 g/m². The pulping process was achieved by dissolving the paper sheets with tap water to a solid content at about 3.5%, and by subsequent mechanical processing in the pulper. At the end of the pulping process, the paper pulp had a drainability around 43° SR. Pulp drainability was measured according to standard ISO 5267-1 :1999 in SR units, standing for Schopper Riegler units.

Preparation of Starch Dispersions

[0070] A dispersion of extruded starch powder with 10% solid content was prepared using starch samples 1 , 3, 4, 5, 10, 11 , 12, 13, 15, and 16 in a glass beaker by mixing 50 g extruded starch powder with 450 g of tap water (at a temperature around 20°C) using a propeller mixer (ER10) for 30 minutes at 1000 RPM. Immediately before treating the stock, the dispersion of extruded starch powder went through a 2-step dilution process. 50 ml of the 10% solid content dispersion was transferred to a separate glass beaker. The separated dispersion was then diluted to 1% solid content by addition of 450 g of tap water. The dilution procedure was repeated by mixing 50 ml of the diluted dispersion (at 1% solid content) with 450 g of tap water again, thus obtaining a highly diluted dispersion with a solid content of 0.1%. The highly diluted dispersion of extruded starch powder was then ready to use for addition to the stock.

[0071] In the case of the reference samples, sample 17 and Fibraffin K, a 1% solid content reference starch suspension was prepared in a glass beaker by mixing 5 g of the starch powder with 495 g of tap water (at a temperature around 20°C) using a propeller mixer (ER10) for 15 minutes at 500 RPM. After that, the glass beaker containing the reference starch suspension was transferred into a heated water bath, with a temperature kept between 92°C and 95°C. The beaker was kept in the water bath for 30 minutes with continued stirring at 500 RPM. Immediately before treating the stock, 50 ml of the cooked reference starch solution (with 1% solid content) was diluted with 450 g of tap water, thus obtaining a starch solution with a 0.1% solid content. The highly diluted reference starch solution was then ready to use for addition to the stock.

[0072] In the case of sample 18 (starch dispersion with 30% solid content), a reference starch dispersion with 10% solid content was prepared in a glass beaker by mixing 166.7 g of the original 30% solid content reference starch dispersion with 332.3 g of tap water (at a temperature around 20°C) using a propeller mixer (ER10) for 30 minutes at 1000 RPM. Immediately before treating the stock, the starch dispersion went through a 2- step dilution process. 50 ml of the 10% solid content starch dispersion was transferred to a separate glass beaker. The separated dispersion was then diluted to 1% solid content by addition of 450 g of tap water. The dilution procedure was repeated by mixing 50 ml of the diluted reference starch dispersion (at 1% solid content) with 450 g of tap water again, thus obtaining a highly diluted reference starch dispersion with a solid content of 0.1%. The highly diluted reference starch dispersion was then ready to use for addition to the stock. Stock Treatment

[0073] Separate glass beakers each containing 500 g of pulp suspension at 3.5% solid content were prepared for the treatment with each starch sample including the extruded starch and reference starch. Two different starch addition amounts were used. The lower starch addition amount was 5 g of dry starch per kg of dry pulp corresponding to 87.5 g of starch dispersion or starch solution at 0.1% solid content. The higher starch addition amount was 10 g of dry starch per kg of dry pulp corresponding to 175 g of starch suspension or starch solution at 0.1% starch content.

[0074] After addition of the starch (either a dispersion of extruded starch powder or a reference starch solution/dispersion) to the stock at their respective addition amounts, the components were mixed using a propeller mixer for 30 minutes at 100 RPM. No retention aid was added.

Hand Sheet Making

[0075] Immediately before hand sheet making, a part of the - stock treated with the respective type of starch and the respective addition amount was taken from the glass beakers and further diluted to a solid content of 0.25% (See Table 4, Trials No. 3 to 54). The hand sheets were manufactured using a Rapid Kothen hand sheet former (ISO 5269- 2:2004). The amount of pulp slurry added to the hand sheet former was adjusted to result into hand sheets of 100 g/m² basis weight. The diameter of the hand sheet was 200 mm. Blank Reference [0076] In order to generate a blank reference for the abovementioned cases with starch treatment, additional hand sheets were made without any starch addition (See T able 4, Trial N.o 1 and 2). For the blank reference, a solution of cationic polyacrylamide (Percol® 292 supplied by Solenis) was added as a retention aid to the pulp suspension. The amount added was 0.5 g (polymer solution, as received) per kg (dry pulp). This treatment kept the retention of solids in the blank sheet at the same level as it was observed for sheets with starch treatment. After the addition of the retention aid, the pulp suspension went through the processes of dilution and hand sheet making described above.

Pressing and Drying

[0077] After leaving the Rapid Kothen hand sheet former, the wet hand sheets (starch-treated samples and blank samples) were treated with a hydraulic press to achieve higher dry contents. Therefore, the sheets were sandwiched between two sheets of blotting paper and pressed in a hydraulic press at 6 bar for 30 seconds. After a first pressing step, the dry content was typically found to be in the range between 42% and 44%. For trial points where higher dry contents were targeted, the pressing process was repeated after removing the wet blotting paper from the pressed hand sheet and replacing it with a new pair of dry blotting paper sheets. After the second pressing step, the dry content was typically found in the range between 47% and 48%. After pressing, the hand sheets were dried for 6 minutes at 93°C using a standard light weight dryer for hand sheets. After drying, the hand sheets were kept under controlled environmental conditions in a climate room at 23°C and 50% relative humidity for at least 12 hours.

[0078] The mechanical properties of the hand sheets were characterized by the following standard methods:

Short Span Compression Test

[0079] For measurement of short span compression strengths (SCT), the dry hand sheets were cut into strips with 15 mm width and 125 mm length. 6 strips were taken from each hand sheet. SCT was tested according to standard ISO 9895:2008. 18 strips from 3 hand sheets were used to determine the statistical average for one data point.

Burst Strength

[0080] Burst strength was measured according to standard ISO 2759:2014. Single hand sheets were cut into four pieces. 12 pieces from 3 hand sheets were used to determine the statistical average for one data point.

[0081] Basis Weight - According to standard ISO 536:2019. [0082] Ash content - According to standard ISO 1762:2019.

Results

[0083] Testing results for 54 trial points are summarized in Table 4, including starch-treated samples at two addition levels (5g/kg and 10 g/kg), hand sheets pressed at two levels of dry content (see Trial No. 3 -54), and blank referenced for two levels of dry content. The minimum solids content D(x) (according to formula (1)) was found to be around 45.3%, as there was only a small variation in ash content between different trial numbers. As shown in Table 4, Trial numbers 3, 4, 7, 8, 11 , 12, 15, 16, 19, 20, 23, 24, 27, 28, 31 , 32, 35, 36, 39, and 40, corresponded to a level of solids content at or above D(x) = 45.3%; and Trial numbers 5, 6, 9, 10, 13, 14, 17, 18, 21 , 22, 25, 26, 29, 30, 33, 34, 37, 38, 41 , and 42 corresponded to a level of dry content below D(x) = 45.3%. Trial numbers 23, 24, 25, 26, 47,48, 49, 50, 51 , 52, 53, and 54 did not use an extruded starch.

Analysis and Conclusions

[0084] The trials led to results where the solids content after pressing was either below (-1.3% to -3%) the minimum solids content defined by “D(x)” or above (1 .4% to 2.6%) the minimum solids content defined by “D(x)”. It was considered that being 1 .3% to 3% below, or being 1.4% to 2.6% above the minimum solids content of 45.3% was a significant deviation. Blank trials (Trial No. 1 and 2) did not show what was considered a significant response in strength parameters (SCT and burst) when the solids content increased from “below” to “above” the minimum solids content defined by “D(x)” for the tested samples.

[0085] Trial with the cooked starch reference samples (see Table 4, Trial No. 23 - 26 and Trial No. 47 - 50) showed some increase of the strength parameters upon increasing starch addition levels from 5 g/kg dry pulp to 10 g/kg dry pulp. However, these trials did not show what was considered a significant response in strength parameters (SCT and burst) when the solids content increased from “below” to “above” the minimum solids content defined by “D(x)” for the tested samples.

[0086] For Trials including the extruded starch-treated samples, (see Table 4, Trial No. 3 - 22 and Trial No. 27 - 46), what was considered a significant response in strength parameters (SCT and burst) was observed when the solids content increased from “below” to “above” the minimum solids content defined by “D(x)” for the tested samples, for both the lower (5 g/kg) and higher (10 g/kg) starch-addition levels. According to Table 4, the strength increase was on average between 6% and 8%. This response was considered to be significantly higher than what was expected in view of using cooked granular starch with the reference samples (see Table 4, Trial No. 23 - 26 and Trial No. 47 - 50). [0087] The cationic corn starch granules (sample 17) that had been prepared by cooking for T rials No 47 - 50 were also used as a base starch for treatment in the extruder (sample 1), and further used to run Trials No, 3-6. When it came to the application of starch as a dry strength additive in papermaking, it was concluded based on the testing results that processing starch in an extruder resulted in what was considered a significant increase in paper strength compared to processing starch using traditional cooking methods.

[0088] Further, it was found that an industrially gelatinized starch prepared from cationic corn starch with the same cationic charge density (See Table 4, Sample 18, Trial No. 51 - 54) does not show similar paper strength gains upon increase of solids content from “below” to “above” the minimum solids content defined by “D(x)” for the tested samples compared to the hand sheets prepared using the extruded starch-treated samples. From these results, it was considered that processing starch to make it cold water soluble (e.g., gelatinization process) may not be the step in the extruding process that affects the dry strength performance of extruded starch in paper.

[0089] It was observed that trials with the hand sheets that included extruded starch sample 1 showed better strength performance than the reference cooked granular starches and reference pre-cooked starches based on same starch type and cationicity. See Fig. 5. . It was also observed that the strength performance difference between hand sheets that included extruded starch sample 1 (no cross-linking) and sample 12 (cross linking) was not considered to be significant. See Fig. 3 and 4. Further, for all trials, strength performance appeared to level off when going from 5kg/t to 10kg/t. On the basis of these results, it was considered that performance of paper products comprising extruded starch may not rely strongly on (i) cationicity, as product with highest charge showed slightly lower strength performance, see Fig 1 ; (ii) maximizing molecular weight (MW), as product with highest MW showed lower performance, see Fig. 2; and (iii) cross linking variations, as it appeared that crosslinking did not result in what was considered a significant increase in strength performance.

[0090] It was observed that trials with the hand sheets that included extruded starch samples 1 and 12 showed what was considered a significant increase in strength performance going from low dry content (<44%) to high dry content (>46%) for both levels of starch addition (5kg/t and 10kg/t). What was considered a very small increase in strength performance was observed for reference starches - cooked granular starch (sample 17) and cold water soluble starch (sample 18). See Fig. 5. Table 4 - Composition and mechanical properties of prepared hand sheets

Example 1C - MACHINE PRODUCED PAPER

Paper sample 1 [0091] Tissue at a basis weight of 15.5-16.5 g/m² (GSM) was made with 100% RCP

(recovered paper) fiber with extruded cationic starch addition varying from 2, 4, 6, kg/T. As cationic starch addition increased, the zeta potential increased from -12.4 mV to 2.4 mV, and the cationic demand decreased from 78 uEq/L to 3 Eq/L. Retention increased from 75.2% to 88.9%. The cationic starch was effective at neutralizing the charge on the fiber surface. The improved retention also aids in reducing the BOD of the wet-end system.

Paper sample 2

[0092] In one example, a standard waxy corn starch (Interstarch) was modified and extruded to yield a nitrogen content of 0.35% by weight, a molecular weight of 4 X 10^A6 Dalton, and an RSS value of 92%. This cationic extruded starch was added to a machine producing tissue paper from virgin fiber with a composition of 40% soft wood kraft fiber pulp (long fiber), 40% kraft hard wood fiber pulp (short fiber) and 20% bleached chemi- thermomechanical pulp (BCTMP fiber).

[0093] The machine was producing tissue paper at 17.5 g/m2 and at a speed of 1650 m/min. The tissue machine is a twin layer head box. A twin layer head box is a system where there are two head boxes simultaneously adding the pulp slurry onto the wire. In this example, one of the head boxes applies predominately the long fiber and a second head box applies predominately the short fiber.

[0094] Additionally, a cationic polyacrylamide (cPAM) and a polyethyleneimine polymer (PEI) were being added to the system comprising what is referred to in the art of paper making as the retention system or also the retention aid system.

[0095] The extruded starch was only added to the long fiber system. It was added before entering the long fiber machine chest and therefore added before the refiners, the refiner chest and the head tank. Ten (10) kilograms of extruded starch was added to each ton of dry long fiber pulp in the long fiber line resulting in an overall total of five (5) kg of extruded starch added for each ton of finished tissue paper. The extruded starch was added for a period of 23 hours.

[0096] No inorganic filler is added. The solids content, also referred to as dryness, immediately after the pressing section, was measured to be between 44% and 46% solids content during the addition of the extruded starch. The ash content was essentially 0%. The pressing solids exceeded the minimum pressing solids D = 46 + (0 - 10)*0.3 = 43%.

[0097] The tensile strength of the tissue paper was measured a number of times for a period of time before the addition of the extruded starch and for a period of time during the addition of the extruded starch. The tensile strength of the tissue paper is measured in both the machine direction (the direction of the moving wire) and in the cross-machine direction (perpendicular to the direction of the wire). The tensile strength measurements were averaged for the period before the addition of the extruded starch and the period during the addition of the extruded starch.

[0098] Average tensile strength of tissue paper without the extruded starch measured in machine direction was 129 N/m (Newtons per meter)

[0099] Average tensile strength of tissue paper without the extruded starch measured in the cross-machine direction was 65 N/m.

[00100] Average tensile strength of tissue paper made with the extruded starch measured in machine direction was 159 N/m (Newtons per meter)

[00101] Average tensile strength of tissue paper made with the extruded starch measured in the cross-machine direction was 86 N/m.

[00102] The addition of the extruded starch resulted in an increase in the tensile strength of 23% in the machine direction and an increase of 32% in the cross-machine direction.

[00103] The propensity to dusting of the tissue paper was also tested during the period where extruded starch was added and compared to the period where the extruded starch was not added. Dusting is the measurement of fines and fibers that can be removed from the tissue paper. Increasing the bonding of fines and fibers into the tissue matrix results in less dusting that will be experienced in the manufacturing process and in the end use of the tissue. The dusting propensity is evaluated by measuring the fines and fibers that are removed and collected from a 81cm² sample of tissue while experiencing a constant flow of air for a fixed period of time. The 81cm² tissue sample is weighted and placed into the dust collector chamber. The sample is then subjected to a constant flow of air through the chamber. The air flow exiting the chamber is filtered which removes the loose fines and fibers from the air. The collected fines and fibers are weighted and reported as the amount of fines and fibers that are removed as a percentage of the original tissue paper.

[00104] Average % of dust from the tissue paper produced without the extruded starch was measured at 1.3%.

[00105] Average % of dust from the tissue paper produced with the extruded starch was measured at 1.1%

[00106] Softness of tissue paper is a desirable feature for the end users of tissue paper. Those skilled in the art of paper making understand that typically an inverse relationship exists between tissue strength and softness; namely increasing the tensile strength of a tissue paper results in a reduction in the softness of the tissue paper. The softness is measured by a Tissue Softness Analyzer manufactured by Emtec Electronic GmbH. The Tissue Softness Analyser measures micro-surface variations, macro-surface variations and stiffness. These parameters have been evaluated extensively in panel test by humans to develop an algorithm that correlates these features to the human perception of softness and create a quantitative value as an indicator of softness, also referred to as “hand feel”. The higher the “hand feel” value the softer the tissue is considered.

[00107] Average softness measurement of the tissue paper produced without the extruded starch was measured at 74.

[00108] Average softness measurement of the tissue paper produced with the extruded starch was measured at 75.

[00109] Unexpectedly, the application of the extruded starch demonstrated a significant improvement in tensile strength without manifesting any loss in the softness of the tissue.

Paper sample 3

[00110] In another example, a standard waxy starch (Interstarch) was modified and extruded to yield a nitrogen content of 0.35% by weight, a molecular weight of 4 X 10^A6 Dalton, and an RSS value of 92%. This cationic extruded starch was added to a machine producing hand towel paper utilizing 70% hardwood fiber and a 30% softwood fiber then alternatively with a composition 60-70% hardwood fiber, 30% softwood fiber and up to 10% BCTMP. The BCTMP fiber is a shorter lower cost fiber but results in a lowertensile strength end product.

[00111] The machine was producing the hand towel at 18 g/m² on a machine with a twin layer head box.

[00112] Additionally, a cationic polyacrylamide (cPAM) and a polyethyleneimine polymer (PEI) were being added as part of the retention system as well as a wet strength additive.

[00113] The extruded starch was added to the long fiber system at a total addition of 5 kg extruded starch per ton of finished hand towel. It was added before entering the long fiber machine chest and therefore added before the refiners, the refiner chest and the head tank.

[00114] No inorganic filler is added. The solids content of the web, also referred to as web dryness, immediately after the pressing section during the addition of the extruded starch, was measured to be between 44% and 46% solids content. The ash content measured was essentially 0%. The pressing solids exceeded the minimum pressing solids D = 46 + (0 - 10)*0.3 = 43%.

[00115] The tensile strength of the 18 g/m² hand towel was measured for a period of 1 year before the addition of the extruded starch (referred to as the “control”) and then a number of times during the addition of the extruded starch (referred to as the “trial”). The tensile strength of the hand towel is measured in both the machine direction (the direction of the moving wire) and in the cross-machine direction (perpendicular to the direction of the wire).

[00116] For the hand towel made with 70% hardwood fiber and a 30% softwood fiber furnish tensile strengths were:

Tensile (N/m)(MD) Tensile(N/m)(CD)

The trial: 204 147 Control : 184 121

For the hand towel made with 60% hardwood fiber, 30% softwood fiber and 10% BCTMP the tensile strengths were:

Tensile (N/m)(MD) Tensile(N/m)(CD)

The trial: 178 141

Control : 162 107

[00117] The addition of the extruded starch resulted in an increase in the tensile strength in both the machine direction and cross-machine direction. Additionally, these results indicate that using 5 kg/ton of the extruded starch in the lower cost furnish composition utilizing 10% BCTMP could maintain the tensile strength properties of the tissue made without BCTMP.

Paper sample 4

[00118] In another example, a standard waxy starch (Interstarch) was modified and extruded to yield a nitrogen content of 0.35% by weight, a molecular weight of 4 X 10^A6 Dalton, and an RSS value of 92%. This cationic extruded starch was added to a machine producing tissue paper from 100% deinked pulp (DIP) slurry. Deinked pulp is made from fiber that has been collected from various sources after its primary use has expired. The fiber often contains various levels of inorganic mineral pigments often referred to as filler. The amount of pigment that is carried through the deinking process can be controlled to a certain extent. Maintaining the filler in the DIP typically results in lower strength properties achievable as the fillers do not contribute to the strength of the sheet. On the other hand, removal of the filler reduces the overall waste paper yield through the deinking process.

[00119] The machine was producing tissue paper at 15.6 g/m² and at a speed of 1400 meters per minute. The tissue machine is referred to as a gap former. In this system, a head box delivers the pulp slurry in between two moving wires (top wire and bottom wire) which carries the pulp slurry while “draining” or “dewatering” the slurry. After the forming section, the formed mat is transferred into the pressing station for further mechanical dewatering.

[00120] In this example, there are no chemicals used as a retention aid system to enhance the retention.

[00121] In this example, the ash content was 2.5 % and the basis weight 15.6 g/m² for a 3-month period just preceding the period when the extruded starch was added. The ash was carried through from the deinking pulp. The extruded starch was added to the system at the outlet of the mixing chest. The amount of the extruded starch was adjusted to 2.7 kg/ton of finished tissue. The extruded starch was added for a period of 32 hours.

[00122] The addition of the extruded starch resulted in an increase in the retention of the ash content of the tissue paper from 2.5% to 3.3%. This represents a yield increase. Additionally, the basis weight of the tissue paper made during the addition of the extruded starch was 15.3 g/m². Those skilled in the art of paper making would expect an increase of ash content to result in a loss of tensile strength of the tissue paper. As well, the reduction of the basis weight from 15.6 g/m2 to 15.3 g/m2 would be expected to result in a lower tensile strength.

[00123] The measured solids content immediately after pressing section was measured to be between 45% and 47% solids content. This pressing solids exceeds the minimum pressing solids in the papermaking process described in this present disclosure. Minimum pressing solids D = 46 + (3.3-10)*0.3 = 43.4%.

[00124] The tensile strength of the tissue paper was measured for a 3-month period of time before the addition of the extruded starch and for the period of time during the addition of the extruded. The tensile strength of the tissue paper is measured in both the machine direction (the direction of the moving wire) and in the cross-machine direction (perpendicular to the direction of the wire). The tensile strength measurements were averaged for the 3-month period before the addition of the extruded starch and the period during the addition of the extruded starch.

[00125] Average tensile strength of tissue paper without the extruded starch measured in machine direction was 178 N/m (Newtons per meter).

[00126] Average tensile strength of tissue paper without the extruded starch measured in the cross-machine direction was 89 N/m.

[00127] Average tensile strength of tissue paper made with the extruded starch measured in machine direction was 189 N/m (Newtons per meter).

[00128] Average tensile strength of tissue paper made with the extruded starch measured in the cross-machine direction was 83 N/m.

[00129] Unexpectantly, the resultant increased ash content and lower basis weight during the period of the addition of 2.7 kg/ton of the extruded starch did not result in a loss of overall tensile strength of the tissue.

[00130] Additionally, the softness of the tissue improved during the period of the addition of the 2.7 kg/ton of extruded starch. The softness during the addition of the extruded starch was 55.6% compared to the softness of 51.4% during the three month average of this grade before the addition of the extruded starch.

Paper sample 5

[00131] In another example a liner board was produced with a base ply made from 100% recycled OCC (Old Corrugated Container) furnish and a white top ply made from 100% virgin hardwood pulp and added precipitated calcium carbonate (PCC) filler. This liner board is used to make corrugated boxes.

[00132] The paper machine produces a liner board grade of 175 g/m² total board basis weight. The machine uses 10 kg/ton of cationic starch in the top ply. Both the base ply and top ply layers utilize a cationic polyacrylamide polymer together with a bentonite mineral as the retention system.

[00133] An extruded cationic waxy corn starch as described for paper samples 2-4, with a nitrogen content of 0.35% by weight and a molecular weight of 4 X 10⁶ Dalton and an RSS value of 92%, was added at 4 kg/ton of finished liner board to the base ply only at the inlet of the mixing chest for a period of time (referred to as trial). No adjustments were made to the top ply (print ply) or base ply weight ratios. Addition of the extruded starch led to a decrease in the required amount of retention aid required.

[00134] The ash content measured during the period of the addition of the extruded starch was 15.5%. The measured solids content immediately after pressing section was measured to be between 48% and 49% solids content. This pressing solids exceeds the minimum pressing solids in the papermaking process described in this present disclosure. Minimum pressing solids D = 46 + (15.5 - 10)*0.3 = 47.7%.

[00135] The key tests utilized to assess liner board strength are Short span Compression Test (SCT), Burst test and Scott Bond test.

[00136] The SCT is performed by cutting 15 mm wide strips of the produced liner board and holding the sample between two clamps (typically 0.7 mm apart). A compressive force is applied to the sample. The maximum compressive strength is recorded in kilonewtons per meter. The basis weight is divided out and the resultant units are Newton meters per gram (Nm/g).

[00137] The burst pressure is another indicator used to determine the strength of liner board and the resultant corrugated board. It is used as an indication of the performance of packaging containers to withstand stresses during transportation. It is defined as the maximum pressure that the liner board surface, in a perpendicular direction, can withstand before it ruptures. The burst strength is expressed in kilopascal meter squared per gram (kPam²/g).

[00138] The Scott bond test is a measure of the energy required to delaminate a liner board specimen very quickly. The force is applied with a pendulum of a known mass and velocity. The pendulum apparatus provides a rotational tensile stress and therefore minimal shear stress resulting in a rupture that occurs in the z-direction. While the specimen is ruptured in the z-direction, the energy that is absorbed due to elongation and stretching of the fiber matrix is recorded. A stronger fiber network results in higher amounts of energy absorbed during the rupturing of the specimen. The Scott Bond is measured in joules per square meter (J/m²). Results are shown below:

Ash content (%) SCT (Nm/g) Burst (kPam²/g) Scott Bond (J/m²) The trial: 15.5 19.4 2.81 263

Control : 13.4 18.7 2.58 216

[00139] This demonstrates that despite a 15.6% increase in the ash content during the trial period, which is deleterious to the strength of liner board, the extruded cationic starch resulted in increased strength as measured by SCT (3.4% increase), Burst (8.9% increase) and Scott Bond (21.8% increase).

[00140] Previous attempts to increase strength on this machine, as measured by SCT, Burst and Scott Bond, were conducted by adding 3 Kg/t of cationic jet cooked starch to the base ply resulted in no impact on strength.

Paper sample 6

[00141] In another example, a standard waxy starch (Interstarch) was modified and extruded to yield a nitrogen content of 0.35% by weight, a molecular weight of 4 X 10^A6 Dalton, and an RSS value of 92%. This cationic extruded starch was added to a machine producing paper used for graphic printing. The pulp slurry consisted of 75% short fiber, 23% long fiber and 2% BCTMP pulp. Additionally, ground calcium carbonate (GCC) “filler” is added to the pulp slurry so that the ash content of the final paper is 31%. Additionally, an anionic polyacrylamide emulsion is added as the retention system. Additionally, 8 kg/ton of the cationic starch described above is also added. The furnish is added from the headbox to a fourdrinier wire. The total basis weight of the finished paper is 120 g/m². The paper is produced at 680 m/min.

[00142] In this example, 4.3 kg of extruded starch were added for every ton of finished paper. The extruded starch was added to the outlet of the short fiber chest. Paper strength was tested before the addition of the extruded starch, during the addition of the extruded starch and after the addition of the extruded starch. Strength testing indicated that the Scott bond of the paper made during the addition of 4.3 kg/ton of extruded starch were 35% higherthan during the periods made before and afterthe addition of the extruded starch. Additionally, the tensile strength of the paper made during the period of the addition of the extruded starch was 15% higher than the paper made without the addition of the extruded starch.

[00143] Previous attempts to increase the strength of this paper by adding conventional cooked starch did not result in additional strength.

Paper sample 7

[00144] Tissue at a weight of 16.8 g/m² was made with 100% DIP furnish. The target strength was a machine direction (MD) tensile strength of 130-172 N/m and a cross direction (CD) tensile strength of 65-68 N/m. With the addition of 2 kg/T extruded cationic waxy corn starch, MD tensile strength was 158 N/m and CD tensile strength was 80 N/m. With the addition of 2 kg/T extruded cationic Solbond™ PC 50 potato starch, MD tensile strength was 154 N/m and CD tensile strength was 75 N/m. With the addition of 2.4 kg/T extruded cationic Raisamyl™80051 wheat starch, MD tensile strength was 153 N/m and CD tensile strength was 77 N/m. The corn, potato and wheat starches all produced or exceeded target strength at acceptable addition level.

[00145] The embodiments described herein are intended to be examples only. Alterations, modifications, and/or variations can be effected to the particular embodiments by those of skill in the art. The scope of the claims should not be limited by the particular embodiments set forth herein, but should be construed in a manner consistent with the specification as a whole.

[00146] The aspects, embodiments, and/or examples of the present disclosure being thus described, it should be recognized that said aspects, embodiments, and/or examples may be varied in ways that do not depart from the spirit and scope of the present disclosure, and that said variations are intended to be included within the scope of the following claims.

[00147] All publications, patents and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication patent, or patent application was specifically and individually indicated to be incorporated by reference.

Claims

WHAT IS CLAIMED IS:

1 . A process of making paper comprising the steps of, providing a stock, the stock comprising fibrous material, extruded starch, water and optionally one or more inorganic fillers; forming a paper web from the stock; pressing the paper web; and, drying the paper web, wherein the pressed paper web has solids content in wt% that is at least as much as a minimum solids content D(x) defined by formula (I):

D(x) = 46 + (x-10)*0.3 (I) wherein x is the ash content of the dry paper.

2. The process of claim 1 wherein the ash content is determined according to ISO 1762:2019.

3. The process of claim 1 or 2 wherein the paper has a weight in the range of 12-240 g/m².

4. The process of any of claims 1 to 3 comprising adding extruded starch to an aqueous suspension of the fibrous material.

5. The process of any of claims 1 to 4 wherein the stock has a concentration of fibrous material in the range of 0.5 g/L to 15 g/L before draining the stock.

6. The process of claim 5 comprising providing a thick stock at an initial concentration of fibrous material in the range of 0.5 g/L to 40 g/L, 10-40 g/L or 20-40 g/L and diluting the thick stock to concentration in the range of 0.5 g/L to 15 g/L.

7. The process of claim 6 wherein the thick stock has a concentration of inorganic filler in the range of 0 to 20 g/L.

8. The process of any of claims 1 to 7 wherein the extruded starch is present in the stock in a range of 0.05 to 5 wt%, or 0.06 to 2 wt%, relative to the weight of dry fibrous material.

9. The process of any of claims 1 to 8 wherein the extruded starch is not crosslinked.

10. The process of any of claims 1 to 8 wherein the extruded starch is crosslinked.

11 . The process of any of claims 1 to 10 wherein the extruded starch is cationic.

12. The process of any of claims 1 to 11 , wherein the fibrous material comprises softwood fiber, hardwood fiber, non-wood fiber, or a combination thereof.

13. The process of any of claims 1 to 12, wherein the fibrous material comprises waste paper, market pulp, machine broke, recycled fiber, or a combination thereof.

14. The process of any of claims 1 to 13, wherein the inorganic filler comprises one or more pigments selected from the group consisting of metal oxides, silicates, carbonates, calcium carbonate, ground lime, chalk, marble (GCC), precipitated calcium carbonate (PCC), talc, kaolin, bentonite, satin white, calcium sulfate, barium sulfate and titanium dioxide.

15. The process of any of the previous claims wherein at least a portion of the inorganic filler is provided as part of recycled fibrous material.

16. The process of any one of the previous claims, wherein the stock comprises one or more paper auxiliaries, optionally selected from the group consisting of: a sizing agent, a wet strength agent, a retention aid, a drainage aid, a dry strength enhancer, an optical brightener, a defoamer, a biocide, a paper dye, or a combination thereof.

17. The process of any one of the previous claims, wherein the paper has an ash content in the range of about 0 wt.% to about 40 wt.%.

18. The process of any one of the previous claims, wherein the extruded starch has one or more of the following attributes: the extruded starch is cationic; the extruded starch is not cross linked; the extruded starch has a solubility in the range of 40-99 % or 40-93 %; the extruded starch has a molecular weight of over 300,000 Da or over 500,000 Da or over 2,000,000 Da or 4,000,000 Da or more; the extruded starch has a molecular weight of 12,000,000 Da or less or 10,000,000 Da or less, or 8,000,000 Da or less; the extruded starch has a weight fraction (WF/ dLog M) at 30,000,000 Da of 0.05 or less; the extruded starch has a cumulative weight fraction with a molecular weight of 1 ,000,000 Da or less, or 100,000 Da or less, in the range of 0-8% or 0-1 %; the extruded starch has an RVA viscosity of 15,000 cP or less or 5,000 cP or less; and, the extruded starch is chemically or enzymatically modified during extrusion.

19. A method of making a starch-containing product comprising the steps of, treating starch-containing material in an extruder, or in another high shear and/or high specific mechanical energy environment, preferably using a twin screw extruder, optionally with one or more mixing and/or high shear sections, essentially without a crosslinker.

20. The method of claim 19 wherein the starch-containing material is chemically or enzymatically modified in the extruder or other high-shear environment, for example the starch is acid thinned and/or made cationic.

21 . The method of claim 19 or 20 wherein the resulting product has a molecular weight (Mw) of 300,000 Da or more or 500,000 Da or more or 2,000,000 Da or more or 4,000,000 Da or more or 5,000,000 Da or more, optionally up to a maximum of 12,000,000 Da.

22. The method of any of claims 19 to 21 wherein the resulting product has essentially no fraction with molecular weight greater than 3*10⁷ Da.

23. The method of any of claims 19 to 22 wherein the starch -containing material comprises native starch or flour.

24. The method of any of claims 19 to 23 wherein the starch-containing material comprises corn starch, for example waxy corn starch.

25. The method of any of claims 19 to 24 wherein the starch-containing material comprises a cereal starch (e.g. corn, wheat or barley starches), a root or tuber starch (e.g. potato or tapioca starches), or a legume starch (e.g. pea or lentil starches), or a combination of them.

26. The method of claims 19 to 25 wherein the resulting product has an RVA viscosity of 15,000 cP or less or 5,000 cP or less at 20 % solids.

27. The method of any of claims 19 to 26 wherein the extrusion or other treatment is performed at an SME of 100 Wh/kg of starch-containing material or more or 150 Wh/kg of starch containing material or more.

28. The method of any of claims 19 to 27 wherein the extrusion or other treatment is performed at a maximum barrel temperature of 180 degrees C or less or 160 degrees C or less.

29. The method of any of claims 19 to 28 wherein a humectant, a plasticizer or a polyol is added to the extruder.

30. A starch-containing product having a molecular weight (Mw) of over 300,000 Da with one or more of: a) RVA viscosity of 15,000 cP or less at 20% solids, b) substantially no weight fraction over 30,000,000 Da (i.e. WF/dLogMW of 0.05 or less at 3*10⁷ Da), c) a solubility in the range of 40-99%, d) a cumulative weight fraction with a molecular weight of 1 ,000,000 Da or less or 100,000 Da or less in the range of 0-8% or 0-1%, and e) Mw of 12,000,000 Da or less.

31 . The product of claim 30 having a molecular weight (Mw) of 4,000,000 Da or more.

32. The product of claim 30 or 31 having RVA viscosity of 15,000 cP or less or 10,000 cP or less at 20% solids.

33. The product of any of claims 30 to 32, further comprising one or more of: a humectant, a plasticizer, and a polyol, for example glycerol.

34. The product of any of claims 30 to 33 made up primarily, i.e. 80% or more by dry weight, of one or more of starch, proteins or other materials found in native starch or flour, or their derivatives, optionally waxy corn starch.

35. The product of any of claims 30 to 34 having a solubility (RSS) in the range of 40- 93% or 40-92%.

36. The product of any of claims 30 to 35 being cationic, for example having a bound nitrogen content excluding protein nitrogen in the range of about 0.1-1 .6% or 0.1-0.8%.

37. A process for production of paper, card and board, the process comprising draining paper stock comprising a mixture of paper fibers, inorganic fillers, water and at least one type of extruded starch, with sheet formation in the wire section further removal of water from the wet paper sheet by pressing the sheet in a press section and a final step of water removal by thermal treatment in a drying section to form a product, wherein: the paper stock having a fibrous concentration in the range from 0.5 g/L to 40 g/L and an inorganic filler concentration in the range between 0 and 20 g/L, contains at least one type of starch dispersion obtained from an extruded starch, wherein before the paper making process, e.g., the first dewatering step, starts the paper stock containing the starch dispersion is diluted to a fibrous concentration in the range from 0.5 g/L to 15 g/L, wherein the diluted paper stock is then drained to form a sheet and the sheet is pressed in the press section to a solids content D(x) wt % or greater and D(x) computes according to

D(x) = 46 + (x - 10) ■ 0.3 where x is the numerical value of inorganic filler content of the product (in wt %) and D(x) is the minimal solids content (in wt %) to which the sheet is pressed, wherein the extruded starch that provides the starch dispersion is obtained in a process where a feed starch is mixed with an aqueous liquid and where mechanical and thermal energy is applied by shear and/or additional heating in an extruder.

38. A process according claim 37 where the extruded starch is added to the thick stock or to the thin stock of the paper machine wet end system.

SUBSTITUTE SHEET (RULE 26)

39. A process according to claim 37 or 38 where the aqueous liquid is water or alcohol or a mixture of both.

40. A process according to any of claims 37-39 where the feed starch can be any kind of cationic starch, crosslinked cationic starch, anionic starch, crosslinked anionic starch, nonionic starch crosslinked nonionic starch, amphoteric starch, crosslinked amphoteric starch all of them with or without other chemical modifications such as carboxylation, oxidation, hydrolysis, etherification, esterification and the like.

41 . A process according to any of claims 37-40 where besides water an additional plasticizer is added in the step of mixing the feed starch and the aqueous liquid to obtain a mixture.

42. A process according to any of claims 37-41 where reactants carrying cationic or anionic functional groups are added to the extruder to react with the starch during the extrusion process.

43. A process according to any of claims 37-42 where a cross linker is added to the extruder and/or where a cross linker has already been added to the mixture of feed starch and aqueous liquid before adding it to the extruder.

44. A process according to any of claims 37-43 where one or more chemical reagents are added to the extruder and/or where one or more chemical reagents have already been added to the mixture of feed starch and aqueous liquid before adding it to the extruder.

45. A process according to any of claims 37-44 where a hydroxylic liquid is injected in the last stages of the extruder and the mixture is dispersed inside the extruder or outside the extruder or both inside and outside the extruder to obtain a dispersion with a solid content between 20 wt.% and 50 wt.%, wherein the hydroxylic liquid used in the extruding process is water, a mixture of water and alcohol or alcohol, wherein the dispersion obtained has a solid content between 20 wt.% and 50 wt.%, optionally it can be directly added to the paper stock or after previous dilution with old water.

46. A process according to any of claims 37-45 where the highly viscous starch melt leaves the extruder at the outlet with a dry content of at least 65 wt.%, wherein the remaining water is evaporated to less than 14 wt.% or less than 10 wt%, wherein upon cooling down, the viscous material becomes a brittle solid that can be crushed into small pieces in a hammer mill, using cryogenic grinding or in a similar crushing step/device, wherein the resulting powder product can be characterized by being in a completely amorphous state showing no signs of birefringence and by providing a stable dispersion of starch particles with particle sizes between 0,2 and 100 pm when mixed with cold water a solid concentration of 1 wt.%, wherein the starch powder dispersed in water is added to the thick stock and/or the thin stock of the paper machine or earlier during pulp stock preparation operations, preferably wherein the starch powder is directly added to the paper stock under thick stock and/or thin stock conditions forming a dispersion with the liquid component of the paper stock.

47. A process according to any of claims 37-46 where the solid content of starch in the final pulp composition is between 500 g dry starch per ton of dry paper fiber and 50 kg dry starch per ton of dry paper.

48. A process according to any of claims 37-47, where the drying section of the paper making process at least partly consists of a Yankee Cylinder type device.

49. A process according to any of claims 37-48 wherein the extruded starch is characterized by an RSS that is 92% or less.