BE1025085A1 - COMPOSITION OF DEXTRINES WITH STABLE VISCOSITY WHEN PAPER AND / OR CARDBOARD COATING - Google Patents

Abstract

The present invention relates to a composition of dextrins that exhibits a molecular weight distribution, expressed in the following weight percentages: more than 0.5 of the molecules has a molecular weight of less than 10³ dalton, between 35 and 45% of the molecules a molecular weight contains between 103 and 2.5.104 daltons, between 35 and 50% of the molecules exhibits a molecular weight contains between 2.5.104 and 5.105 daltons, and between 5 and 20% of the molecules exhibits a molecular weight of more than 5.105 daltons. The invention also relates to the composition for surface treatment or coating of paper or cardboard comprising such a composition of dextrins, the method for producing such a composition for surface treatment and / or coating. The invention finally relates to the method for coating a paper or cardboard by applying a coating or surface treatment composition according to the invention and the paper and / or cardboard thus obtained.

Description

(30) Priority data:

(71) Applicant (s):

TEREOS STARCH & SWEETENERS BELGIUM NV

9300, ALST

Belgium (72) Inventor (s):

PERALBA Magalie 9300 AALST Belgium

FREDERIX Sofie 9300 AALST Belgium (54) COMPOSITION OF DEXTRINES WITH STABLE VISCOSITY IN COATING PAPER AND / OR CARDBOARD (57) The present invention relates to a composition of dextrins which has a molecular weight distribution, expressed as the following weight percentages: more than 0.5 of the molecules have a molecular weight of less than 10 ³ daltons, between 35 and 45% of the molecules have a molecular weight between 103 and 2.5104 daltons, between 35 and 50% of the molecules have a molecular weight between 2.5,104 and 5,105 daltons, and between 5 and 20% of the molecules have a molecular weight of more than 5,105 daltons. The invention also relates to the composition for surface treatment or coating of paper or cardboard comprising such composition of dextrins, the method of producing such a composition for surface treatment and / or coating. Finally, the invention relates to the method of coating a paper or cardboard by applying a coating or surface treatment composition according to the invention and the paper and / or cardboard thus obtained.

Fig. 1

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Composition of stable viscosity dextrins when coating paper and / or cardboard

Technical area

The present invention relates to a composition of dextrins, a composition for coating and / or surface treatment of paper or cardboard comprising said composition of dextrins and the paper or cardboard surface-treated and / or coated with such a composition.

Previous state of the art

The prior art describes the use of dextrins for paper coating. However, the dextrins traditionally used in surface treatment and coating tend to exhibit a viscosity that increases rapidly during storage after cooking. After cooking, the dextrins are stored in storage bins. However, depending on the paper mill facilities (volume of storage tanks) and the needs of the paper machine (type of paper being produced or standstill after paper breakdown, for example), the storage time can vary from a few hours to more than 1 day. This storage usually occurs at temperatures from 50 ° C to 90 ° C and involves an increase in the viscosity of the dextrin, which is commonly referred to as retrogradation (Modified starch: properties and uses Otto B. Wurzburg CRC Press 1986) . The retrogradation reduces the performance of the dextrins in surface treatment or coating due to the reduced availability of dextrin chains when bonding to the surface of the paper. In addition, the increase in the viscosity of the dextrin due to the retrogradation changes the characteristics of the composition of the surface treatment or coating due to its behavior during the coating of the paper. This change in composition characteristics during coating may be responsible for paper imperfections. Moreover, this viscosity increase phenomenon is all the more pronounced and difficult to control when the dextrin viscosity is high. Given the importance of these high viscosity dextrins in surface treatment and coating, and given the sensitivity of the coating process to viscosity variations, coating and / or

BE2017 / 5220 surface treatment has a clear need for dextrins that have a high viscosity and high viscosity stability at the same time.

The prior art proposes to use an additional molecule that has the role of anti-viscosity enhancer. For example, international patent application WO2014189999 (CARGILL INC) proposes to use glycerol as an anti-viscosity enhancer. However, while one of the effects of glycerol is to limit the increase in viscosity over time, it can also have other effects such as the decrease in the viscosity of the coating composition. Glycerol can also lead to swelling and / or solubilization of the starch, which is not desirable for an application in papermaking.

The literature shows that the viscous stability of dextrin is mainly related to its degree of branching which is increased in particular during the dextrinization process (Modified starch: properties and uses Otto B. Wurzburg CRC Press 1986p.36-37). In their study, the inventors further demonstrated that increasing the degree of branching of the dextrin did not necessarily increase its viscosity stability.

Another path proposed in the prior art to increase the viscostability of dextrins would be to increase their degree of cross-linking (US 2944913 ANHEUSER BUSCH). However, such a step comes at a cost and increases the changes made to the molecule. Furthermore, we note that this solution involves the use of chemical products such as epichlorohydrin or formaldehyde which, due to their potential toxicity, are subject to fairly strict conditions of use.

The object of the present invention is to propose a composition of dextrins whose molecular weight distribution provides a sufficiently high viscosity for their use in the surface treatment and coating of paper and which is particularly stable in cooking so that they can be stored in storage tanks without detecting an increase in their viscosity that could compromise the coating step.

Summary of the invention

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The present invention relates to a composition of dextrins that exhibits a molecular weight distribution expressed in the following weight percentages:

- more than 0.5%, preferably more than 1% of the molecules have a molecular weight of less than 10 ³ daltons (Mw)

- between 35 and 45%, preferably between 39 and 43% of the molecules, has a molecular weight between 10 ³ and 2.5.10 ⁴ daltons

- between 35 and 50%, preferably between 35 and 45% of the molecules, has a molecular weight containing between 2.5.10 ⁴ and 5.10 ⁵ daltons

- between 5 and 20%, preferably between 7.5% and 15% of the molecules has a molecular weight of more than 5.10 ⁵ Daltons.

The present invention further relates to a composition for coating and / or surface treatment of paper or cardboard comprising the composition of dextrins according to the invention and optionally, a mineral filler.

The invention also relates to the use of a composition according to the invention for increasing the viscosity of a composition for surface treatment or coating of paper or cardboard.

The invention also relates to the use of a composition according to the invention in the coating of paper or cardboard and in particular during the surface treatment and / or coating of paper or cardboard.

The invention further relates to a method of coating paper or cardboard, said method comprising the steps of (a) providing a composition for surface treatment or coating according to the invention, (b) applying said composition to a paper or cardboard substrate .

Finally, the invention relates to a paper or cardboard which has been coated or the surface of which has been treated with the composition for coating of paper or cardboard according to the invention.

Detailed description of the invention

The invention relates to a composition of dextrins which exhibits a molecular weight distribution, expressed in the following weight percentages:

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- more than 0.5%, preferably more than 1% of the molecules have a molecular weight of less than 10 ³ daltons (Mw)

- between 35 and 45%, preferably between 39 and 43% of the molecules, has a molecular weight between 10 ³ and 2.5.10 ⁴ daltons

- between 35 and 50%, preferably between 35 and 45% of the molecules, has a molecular weight between 2.5.10 ⁴ and 5.10 ⁵ daltons, and

- between 5 and 20%, preferably between 7.5% and 15% of the molecules has a molecular weight of more than 5.10 ⁵ Daltons.

In the present invention, "dextrin" is understood to be a modified starch obtained by dextrinization from a natural starch. Typically, the dextrins of the invention are not subjected to any other modification, especially chemical modification. The dextrins suitable for the present invention are, for example, white dextrins, yellow dextrins or so-called "British GUM" dextrins. The white dextrins are generally obtained by transforming the starch at temperatures often contained between 70 and 170 ° C, in the presence of chemical (s), especially acid, in relatively large amounts. The yellow dextrins are most often obtained by transformation of the starch at higher temperatures, generally contained between 170 and 230 ° C, in the presence of chemical (s), especially acid. Finally, the so-called “British GUM” dextrins are obtained by the action of heat only, at high temperatures, often higher than 230 ° C. A dextrin particularly suitable for the present invention is a wheat or corn based dextrin.

Advantageously, the composition of dextrins of the present invention exhibits a molecular weight to weight / number average molecular weight (Mw / Mn) ratio of greater than 10, more preferably greater than 15, more preferably greater than 20.

When in the present application reference is made to the "average molecular weight", it is understood to mean the weight average molecular weight.

For the purposes of the present invention, the average molecular weight of said dextrin is expressed in daltons and can be determined by those skilled in the art by steric exclusion chromatography using a refractive index detector. The preparation of a sample can be done by 50 mg

BE2017 / 5220 dry weight of a modified starch and in particular dextrin to be dissolved in a solvent formed by DMSO (dimethyl sulfoxide) containing 0.1% (w / v) sodium nitrate. After stirring overnight, the mixture is preheated at 105 ° C for 1 hour and then centrifuged at 5300 rpm for 15 min. A 100 ml volume of the supernatant is injected into a steric exclusion chromatography apparatus whose mobile phase is, for example, DMSO (dimethyl sulfoxide) containing 0.1% (w / v) sodium nitrate at a flow rate of 0.5 ml / min and a temperature of 80 ° C, the columns used being preferably a serial combination of a PLgel 5 μm mixed D column. Calibration is done according to the standards of the pullulans Shodex Viscotek P-82 type.

According to the present invention, the composition of dextrins exhibits a cold solubility of less than 30 mass%. The cold solubility is assessed at room temperature and corresponds to the percentage of solubilized dextrins after vigorous stirring in water for 20 min and with 20 mass% dextrin.

Typically, cold solubility is measured as follows:

g of dextrin dry matter is collected and dispersed in 100 ml of demineralized water for 20 minutes with vigorous stirring, after which the resulting suspension is centrifuged (7000 rev). 50 ml of the supernatant are collected and the mass of the dry dextrin is evaluated (evaporation at 120 ° C, with slow stirring, for 3 hours).

The solubility expressed as a percentage is calculated as follows: Solubility = mass of dry supernatant x 10

The composition of dextrins of the present invention exhibits a viscosity containing between 50 and 400 mPa.s (brookfield, 70 ° C, 31% DS), more preferably between 100 and 300 mPa.s.

The viscosity of the dextrin is measured after cooking (boiled to a dry matter content of 40% with a jet cooker at 130 ° C for 3 min). The viscosity is measured with a brookfield viscometer (model RVDV-E) at 70 ° C for a solution with a dry matter content of 31% at a speed of 20 rpm with spindle 3, the value is read after 10 s rotations.

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More specifically, after boiling the dextrin, the dry matter content of the solution is adjusted to 31% in a 11 beaker, then cooled to 70 ° C (with gentle stirring). The measurement is done with a Brookfield viscometer (model RVDV-E) at a speed of 20 rpm with the spindle 3. 400 ml of the dextrin-ορ discharge is poured into a 600 ml beaker. The module is soaked in the boiled dextrin until the spindle's indicator line, the value is read after 10 s revolutions.

The composition of dextrins according to the invention shows a viscosity ratio containing between 1 and 7, more preferably between 1 and 5, more preferably between 1 and 3.

The "viscosity ratio" of a composition is the ratio of the viscosity at 50 ° C of the composition after cooking at 130 ° C for 3 minutes in a jet cooker followed by 22 hours of incubation in a 50 ° C water bath to the viscosity at 70 ° C of the composition after cooking at 130 ° C for 3 minutes in a jet cooker.

The purpose of this measurement is to simulate the reality as observed by the user, in particular to assess the viscosity of the composition before and after 22 hours of storage at 50 ° C, where the viscosity at 70 ° C of a composition after cooking is the reference measurement.

The present invention also relates to a composition for surface treatment or coating of paper or cardboard comprising the composition of dextrins according to the invention and optionally at least one mineral filler, said composition preferably having a dry matter content between 2 and 80%. Typically, the surface treatment composition has a dry matter content of 2 and 30%, typically between 5 and 25%, even more preferably between 6 and 20%. Typically, the coating composition exhibits a dry matter content of 45 and 80%, typically between 45 and 75%, even more preferably between 50 and 72%

"Composition for coating paper or cardboard" means a composition which is particularly suitable for coating paper or cardboard. It is an aqueous formulation typically comprising water, at least one mineral filler, typically one or more binders and optionally different additives.

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Advantageously, the coating composition according to the invention comprises in bulk parts:

100 parts of mineral filler (typically 80 parts of calcium carbonate, for example of the type Hydrocarb 90® and 20 parts of kaolin, for example of the type Hydragloss 90®) to 20 parts of binder, typically a synthetic binder up to 20 of the composition of dextrins according to the invention

- Between 0 and 10 parts of different additives (carboxymethyl cellulose, optical bleach ...).

Typically, the coating composition has a dry matter content between 45 and 80%.

By "paper or board surface treatment composition" is meant a composition which is particularly suitable for treating the paper or board surface. According to the present invention, surface treatment composition is understood to mean an aqueous formulation containing the composition of dextrins of the invention, optionally a mineral filler, and optionally various additives (such as a binder or insolubilizing agent).

By "binder" is meant a compound which has the function of adhering the particles of the mineral filler (or pigments) together and keeping the layer on the surface of the paper. The composition of dextrins fulfills this role of binder.

Advantageously, the composition has a dry matter content of between 45 and 80%, preferably between 50 and 78%.

Typically, the coating composition further comprises a modified starch and / or a synthetic adhesive,

For the purposes of the present invention, "modified starch" means any starch that can be chemically or physically treated.

The modified starch molecules present in the present invention may come from a vegetable source such as grains, tubers, carrots, vegetables and fruits. For example, it or the starches may come from a vegetable source selected from corn, peas, potato, sweet potato, banana, barley, wheat, rice, oats, sago, tapioca, and sorghum.

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More specifically, the reactions for modification can be realized, for example:

• by pre-gelatinisation via splitting of the starch granules (for example drying and cooking in a tumble dryer);

• by wet acid hydrolysis using, for example, strong acids or by enzymatic hydrolysis, • by oxidation using, for example, strong oxidizing agents, leading to the introduction of carboxyl groups in the starch molecule and to the depolymerization of the starch molecule (for example, by treating an aqueous starch solution with sodium hypo chlorite);

• by cross-linking with functional agents that can react with the hydroxyl groups of the starch molecules which will thus be bound together (for example with glyceryl and / or phosphate groups); for example, phosphorus compounds are obtained from mono-starch phosphates (type Am-0-P0 (OX) 2), di-starch phosphates (type Am-O-PO- (OX) -O-Am) or even from tri starch ( of the type Am-0-PO- (0-Am) 2) or mixtures thereof. X stands for, for example, alkali or alkaline earth metals, • by esterification in an alkaline medium for the grafting of functional groups, in particular C1-C6-acyl (acetyl), C1-C6-hydroxyalkyl (hydroxyethyl, hydroxypropyl), carboxymethyl, octenyl succinate. In particular, we can mention the starches modified by sodium carboxymethyl;

Suitable modified starches include, but are not limited to, pregelatinized starches, low viscosity starches (e.g. hydrolysed starches, oxidized starches), stabilized starches (e.g. starch esters, starch ethers), cross-linked starches and starches that have received a combination of treatments (e.g. cross-linking and gelatinization) and mixtures thereof.

In the context of the present invention, the adhesive is preferably synthetic. An example of a synthetic adhesive suitable for the present invention is a latex, a vinyl acetate, a polyvinyl alcohol, sodium carboxymethyl cellulose and hydroxyethyl cellulose.

The term "latex" refers to an aqueous polymer dispersion that corresponds to a colloidal dispersion of synthetic polymers in a

BE2017 / 5220 aqueous phase, i.e. a dispersion of microparticles of polymers in suspension in a water phase, sometimes also referred to as suspension or emulsion of polymers. Examples of latex suitable for the present invention are selected from the group consisting of styrene-butadiene latexes, polyvinyl alcohol latexes and acrylic copolymer latexes, preferably the styrene-butadiene type latex.

The surface treatment compositions do not necessarily include mineral fillers. Typically, the surface treatment compositions comprise between 50 and 70 parts of dextrin, from 0 to 80 parts of mineral pigment, from 0 to 7 parts of additives. The surface treatment composition shows a dry matter content between 2 and 20%.

Generally, in the coating mass, the imported mineral filler is transferred in the form of an aqueous suspension. Typically, this filler is a calcium carbonate suspended in water by a dispersant. Typically, a mineral filler particularly suitable for a coating composition comprises a sufficiently high degree of whiteness (greater than 80% of the whiteness of barium sulfate at 457 nm), a particle size distribution of 0 to 10 μm at most (where the average particle size is between 0.2 and 2 μm) and a minimum degree of agglomeration of the particles. The mineral filler can be selected, for example, from the group consisting of Calcium carbonates, clay for coatings, fine calcined clay, alumina trihydrate, talc and titanium dioxide.

The term "calcium carbonate" includes ground calcium carbonate (GCC), that is, a calcium carbonate obtained from natural sources such as limestone, marble, calcite or lime. The term "calcium carbonate" also includes precipitated calcium carbonate (PCC), i.e., a synthesized substance usually obtained by precipitation after a reaction of carbon dioxide and calcium hydroxide (lime hydrate) in an aqueous environment or by precipitation of a calcium source and carbonate in water.

The composition of the invention may also include other agents such as one or more dispersants. By "dispersant" is meant an agent having the function of keeping the particles of the mineral filler in an electrostatic dispersion state. For example, the dispersant is selected from the group consisting of sodium polyacrylate, tetrasodium polyphosphate, tetrasodium pyrophosphate, pentasodium tripolyphosphate, sodium tetraphosphate, and sodium silicate.

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The composition may also include at least one lubricant, typically selected from the group consisting of sodium stearate, calcium steara, sulfonated oils, sulfated tallow fatty acid and polyethylene emulsions.

The composition may further comprise at least one insolubilizing agent selected from the group consisting of urea resins, melamine resins, glyoxal, zinc compounds, formaldehyde and dimethylolurea.

The invention also relates to a method of producing the surface treatment or coating composition according to the invention, comprising the following steps:

mixing a composition of dextrins according to the invention and a mineral filler, optionally an adhesive and / or at least one binder including at least one modified starch,

- addition of water to the obtained mixture to obtain a composition containing a dry matter content which is between 2 and 80%, optionally the addition of water is done with the mineral filler and / or the modified starch.

Typically, during the method of producing the surface treatment or coating composition of the invention, the composition of dextrins may be water soluble, and preferably undergo a boiling step before mixing with the adhesive. Independently, the mineral filler can be previously dissolved in the water before being mixed with the binders.

The invention also relates to a method of coating a paper or a cardboard, said method comprising the steps of (a) providing a composition for surface treatment or coating according to the invention, (b) applying said composition to a paper- or carton substrate.

By coating method according to the invention is meant a method during which a surface treatment or coating composition is spread on the surface of a paper or cardboard. The step of spreading said composition for surface treatment or coating on a paper or cardboard substrate can be done with the aid of a coating sheet, a

BE2017 / 5220 coating pin, a threaded rod, through a size-press curtain coating or a film press or any other technique known to those skilled in the art. Typically, the application step is at a temperature comprised between 25 and 60 ° C.

Typically, said surface treatment or coating composition is applied to at least one side of said paper or cardboard substrate in an amount containing between 1 g / m ² and 15 g / m ² , preferably between 3 g / m ² and 10 g / m ² .

The invention also relates to a paper or cardboard which is coated or whose surface has been treated with the composition for surface treatment or coating of paper or cardboard according to the invention.

The invention also relates to the use of a composition according to the invention in the coating of paper and / or cardboard, in particular for the pigmented or non-pigmented surface treatment and / or coating.

The invention also relates to the use of a composition according to the invention for increasing the viscosity of a composition for surface treatment or coating of paper or cardboard.

Although they have different meanings, the terms include, "contain", "consist of" and their derivatives have been used interchangeably in the description of the invention and may be substituted for one another.

The invention will be more clearly understood by reading the following figures and examples, which are given by way of example only.

FIGURES

Figure 1: Distribution of the molecular weight (LogMw) of dextrins I, J, K, L and of a commercially available dextrin

Figure 2: Evolution of the Brookfield Viscosity over time of the compositions of dextrins I, J, K, L and a commercially available dextrin

Examples

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Materials and methods

MW measurement

The average molecular weight of the dextrins, expressed in daltons, was measured via steric exclusion chromatography coupled to a refractive index detector. The sample was prepared by dissolving 50 mg of the dry weight of dextrin in a solvent formed by DMSO (dimethyl sulfoxide) containing 0.1% / V sodium nitrate. After stirring overnight, the mixture is preheated at 105 ° C for 1 hour and then centrifuged at 5300 rpm for 15 minutes. A volume of 100 ml of the supernatant is injected into the steric exclusion chromatography, the mobile phase of which is formed by DMSO (dimethyl sulfoxide) containing 0.1% (w / v) sodium nitrate, at a flow rate of 0.5 ml / min and at a temperature of 80 ° C. The columns used are a serial combination of the PLgel 5 μm mixed D column. Calibration is done according to the pullulans Shodex Viscotek P-82 standards.

Brookfield viscosity

The viscosity of the composition of dextrins is measured after cooking (boiled to a dry matter content of 40% with a jet cooker at 130 ° C for 3 min). The dry matter content of the cooked dextrins composition is then adjusted to 31% in an 11 beaker, and the solution is cooled to 70 ° C (by mixing everything until temperature drops). The measurement is carried out with a Brookfield viscometer (model RVDV-E), the measurement is made at a speed of 20 rpm with the spindle 3. 400 ml of the dextrin composition is poured into a 600 ml beaker. The module is soaked in the boiled dextrin until the spindle's indicator line, the value is read after 10 s revolutions.

To measure the viscosity, the previous composition with a dry matter content of 31% is cooled after cooking (jet cooking at 130 ° C for 3 min.) With stirring until a temperature of 50 ° C is reached. The beaker containing the composition is then placed in a water bath at 50 ° C and incubated for 22 hours. Throughout the process, the beaker is covered with a sheet of aluminum to prevent any evaporation of water and to maintain a constant dry matter content. The Brookfield viscosity measurement is performed every hour (model RVD-E, speed 20 rpm). In the examples below, the spindle used to assess the viscosity can be adjusted in function of the analyte

BE2017 / 5220 composition. If the viscosity is above the measuring limit of the spindle, the spindle that allows the measurement and which has the lowest number is selected in this way. If no spindle allows to perform the measurement, it is considered that the viscosity of the composition cannot be assessed. The viscosity stability ratio of a composition is the ratio of the viscosity at 50 ° C of the composition after cooking at 130 ° C for 3 minutes in a jet cooker and incubation for 22 hours in a water bath at 50 ° C to the viscosity at 70 ° C of the composition after cooking at 130 ° C for 3 minutes in a jet cooker.

Results

Example 1:

Compositions of dextrins A, B, C were developed. These dextrins were prepared according to a method known to those skilled in the art (Food polysaccharides and their applications, Alistair Μ. Stephen, Glyn O. Phillips, CRC Press 2016, p.93) with addition of hydrochloric acid in a starch milk to adjust the pH between 1 and 4, after which the starch milk was dried to a moisture content of 2 to 10%. The preparation is then warmed to a temperature of 70 to 100 ° C for an acid conversion for 30 to 120 minutes. The acidity is then neutralized with sodium carbonate.

To characterize these dextrins, measurements of molecular weight distribution, viscosity, and viscosity ratio were performed.

The results are presented in the table below in which three different molecular weight distributions are observed. They differ in the following way: the short chains (<10 ³ dalton) vary between 0.1 and 0.3%; the chains between 10 ³ and 2.5 10 ⁴ Da vary between 33.8% and 41%; the chains between 2.5.10 ⁴ and 5.10 ⁵ Da vary between 53.1 and 63.2% and the long chains (> 5.10 ⁵ Da) vary between 1.7 and 5.3%.

<10 ³ (Da) 1O ³ -2.5.1O ⁴ (Da) 2.5.10 ⁴ - 5.10 ⁵ (Da) > 5.10 ⁵ (Da) Mw / Mn Dextrin A 0.6 41.0 53.1 5.3 H, 7 Dextrin B ο, ι 35.3 63.3 1.7 5.7 Dextrin C ο, ι 33.8 63.2 2.9 6.7

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Table 1: Distribution of the molecular weight of the composition of dextrins A, B, C (by weight).

These differences in the molecular weight distribution are the cause of the differences in properties as seen in Table 2.

Viscosity (mPa.s) V isco stability ratio Dextrin A 254 Not measurable Dextrin B 168 Not measurable Dextrin C 146 31

Table 2: Measurement of viscosity and visco stability ratio of the compositions of dextrins A to C

The 3 dextrins A to C develop a fairly high viscosity (> 100 MPa.s) with a higher viscosity for dextrin A due to a higher percentage of high molecular weight (5.3% compared to 1.7% for dextrin B and 2.9 for dextrin C). However, despite these variations in the molecular weight distribution, the viscostability of these 3 dextrins is unacceptable for papermaking. It is the case that the dextrins A and B have such a high viscosity after 22 hours of storage that it is no longer possible to measure them. The compositions of dextrins A and B have become gels that can no longer be used for coating paper or cardboard. The return to an acceptable viscosity is then no longer possible. For the papermaker this is therefore a pure loss because he will find a gel after 22 hours of storage in the box.

None of the molecular weight distribution profiles of these dextrins allow to significantly improve their viscosity.

Example 2:

As proposed in the prior art ("Modified starch: properties and uses" Otto B. Wurzburg CRC Press 1986 p.36-37), the dextrinization process as explained in Example 1. Dextrin D was obtained at a higher temperature than dextrin E to promote the increase in branching. The amount of acid was adjusted to provide the same viscosity to the dextrin.

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Two dextrins (dextrin D, E) were obtained with different degree of branching, with that of dextrin D being significantly higher than that of dextrin E. The degrees of branching were assessed by ¹ H-NMR by a technique known in the prior art ( Nilsson, GS; Bergquist, K.-E .; Nilsson, U .; Gorton, L. Starch / Sta'rke 1996, 48, 352-357 and the measurements were performed by the IBiSA platform "Biopolymers-Structural Biology" in the center of the INRA of (INRA Research Unit 1268 BIA)). The measurements showed that the degree of branching of dextrin D is higher than that of dextrin E (see Table 3).

Branching (%) Dextrin D 4.3 Dextrin E 3.8

Table 3: Measurement of the degree of branching of dextrins D and E in percent

Dextrins D and E have molecular weight distributions that are close to each other, and since dextrin D has the highest degree of branching, it is therefore believed to have better viscosity than dextrin E. However, the observed viscosity properties do not correspond to these. expectation (table 4).

V isco stability ratio Dextrin D 18.2 Dextrin E 5.7

Table 4: Measurement of the viscostability ratio of the compositions of dextrins D and E

Thus, and contrary to popular belief, increasing the degree of branching of a dextrin during the dextrinization process does not allow to improve its viscosity.

Example 3:

To improve the viscosity of the dextrins, new formulations have been developed by blending different dextrins to adapt the viscosity and viscosity to the needs of paper manufacturers.

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The composition of dextrins which served as the starting composition was the composition of dextrins F, the molecular weight distribution of which is given in Table 5 below:

<10 ³ (Da) 10 ³ -2.5.10 ⁴ (Da) 2.5.10 ⁴ - 5.10 ⁵ (Da) > 5.10 ⁵ (Da) Mw / Mn Dextrin F 0.4 45.7 52.4 1.4 6.3

Table 5: Distribution of the molecular weight of the composition of dextrins F (in percentage by weight).

Dextrin F was obtained in the same manner as in Example 1. The viscosity measurement of this composition shows a low viscosity (see Table 6).

Viscosity (mPa.s) Dextrin F 97

Table 6: Measurement of the viscosity of the composition of dextrins F.

To give it the desired properties (viscosity in the vicinity of 200 mPa.s), the composition of dextrins F was mixed with other dextrins obtained according to Example 1. Thus, the compositions of dextrins G and H were obtained. Their characteristics are given in Table 7 below.

<10 ³ (Da) 1O ³ -2.5.1O ⁴ (Da) 2.5.10 ⁴ - 5.10 ⁵ (Da) > 5.10 ⁵ (Da) Mw / Mn Dextrin G 0.4 39.1 50.1 10.4 16.9 Dextrin H 0.3 38.9 53.2 7.6 H, 1

Table 7: Distribution of the molecular weight of the compositions of dextrins G and H (by weight).

The compositions of dextrins G and H differ mainly in their percentage chains longer than 2.5.10 ⁴ Da. The composition of dextrins G indeed contains more chains longer than 5.10 ⁵ Da and the composition of dextrins H more chains between 2.5.10 ⁴ and 5.10 ⁵ Da. This difference is of the order of 3% by weight.

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Viscosity (mPa.s) V isco stability ratio Dextrin G 217 9 Dextrin H 201 14

Table 8: Measurement of the viscosity and the visco stability ratio of the compositions of dextrins G and H

Reading Table 8, we first and foremost establish that the two compositions of dextrins develop viscosities that are close to each other. However, the composition of dextrins G has a better visco stability. Indeed, we establish a visco stability ratio of 9 to 14 for the composition of dextrins H. Thus, after 22 hours of storage, the viscosity increases 9 times instead of 14 times. Likewise, even small differences in the molecular weight distribution involve large differences in visco stability.

Example 4:

To determine the ideal molecular weight distribution for good viscostability and thus demonstrate the importance of this parameter for viscostability, compositions of dextrins exhibiting different molecular weight distributions but developing the same viscosity were produced. This is accomplished by mixing various compositions of dextrins produced by the method described above.

Their molecular weight distributions are evaluated and described in Table 9 below. The molecular weight distribution of a commercially available dextrin is also evaluated.

<10 ³ (Da) 10 ³ -2.5.10 ⁴ (Da) 2.5.10 ⁴ - 5.10 ⁵ (Da) > 5.10 ⁵ (Da) Mw / Mn Dextrin I 1.7 44.4 41.5 12.4 28.7 Dextrin J 1.6 44.0 46.3 8.1 16.1 Dextrin K. 0.2 36.6 50.5 12.7 18.2 Dextrin L 0.1 35.0 54.9 9.9 H, 7 On the market 2.3 35.8 52.1 9.8 14

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available dextrin

Table 9: Distribution of the molecular weight of the compositions of dextrins I to L and a commercially available dextrin (by weight).

Four dextrins were developed, with the following molecular weight distributions:

The composition of dextrins L contains the lowest amount of chain shorter than 10 ³ Da but the largest amount of chains between 2.5.10 ⁴ and 5.10 ⁵ Da.

The composition of dextrins K contains less chains containing between 2.5.10 ⁴ and 5.10 ⁵ Da than dextrins L, but more longest chains (> 5.10 ⁵ Da).

The composition of dextrins J contains more short chains (<10 ³ Da) than dextrins K and L, and more chains between 10 ³ and 2.5.10 ⁴ Da, but on the other hand, fewer chains between 2.5.10 ⁴ and 5.10 ⁵ Da.

The composition of dextrins I is similar to the composition of dextrins J but contains more chains between 2.5.10 ⁴ and 5.10 ⁵ Da and more long chains (> 5.10 ⁵ Da).

The compositions of dextrins J, K and L differ from the composition of dextrins I due to the fact of a lower ratio Mw / Mn, a very low amount of chains <10 ³ Da, and a very high amount of chains between 2.5.10 ⁴ and 5.10 ⁵ Da.

Regarding the commercially available dextrin, the molecular weight distribution differs mainly in a large amount of short chains (<10 ³ Da) close to that of dextrin I but also in a larger amount of chains between 2.5.10 ⁴ and 5.10 ⁵ Da closer to dextrin L.

To illustrate the difference in molecular weight distribution, we have presented them in Figure 1.

As we can see in Figure 1, the commercially available dextrin has a molecular weight distribution different from that of the dextrins of the invention. In fact, the molecular weight distributions of dextrins I, J, K and L are typical of dextrins obtained by mixing dextrins. We indeed find 2 peaks in figure 1, one at about 10 ⁶ Da and the other at about 10 ⁵ Da. And it is this distribution, this heterogeneity in it

BE2017 / 5220 weight that gives the sought-after visco stability properties. The mixture of dextrins allows to create a molecular weight distribution that is ideal for this application, it cannot be obtained by a single dextrin.

To assess the impact on their properties, the compositions of dextrins were boiled with a jet cooker at 130 ° C for 3 min and their viscosities and viscosity ratio were assessed (Table 10).

Viscosity (mPa.s) V isco stability ratio Dextrin I 215 1.9 Dextrin J 205 2.6 Dextrin K. 208 5.4 Dextrin L 234 6.4 On the market available dextrin 230 7.8

Table 10: Measurement of post-viscosity and viscosity ratio of the compositions of dextrins I to L and of a commercially available dextrin

The viscosities developed by these different compositions of dextrins are very close to each other.

The measurement of the viscosity after cooking and the viscosity ratio clearly demonstrate that the composition of dextrins I exhibits the best characteristics in terms of viscosity. In fact, the composition of dextrins I develops a viscosity comparable after cooking but exhibits better viscosity properties (viscosity ratio of 1.9; thus viscosity is multiplied only by 1.9 which is very good and not visible on paper handling applications). In fact, the viscostability ratio is better (lower, so a smaller increase of the

BE2017 / 5220 viscosity) which allows to store this composition of dextrins in storage bins without deterioration of the properties. If we compare the results obtained between the composition of dextrins I and the compositions K and L whose molecular weight distribution deviates, we see on reading Table 10 that the compositions of dextrins K and L have a viscosity ratio of 5.4 and 6.4. This means that a very large increase in their viscosity has taken place during the 22h in the water bath and so they cannot be stored for a long time in these same conditions without deterioration of their properties.

Regarding the commercially available dextrin, we find a viscosity ratio of 7.8, ie higher than that of the compositions of dextrins I to L. Thus, the viscosity of this dextrin is less good than that of the compositions of dextrins I to L. The molecular weight distribution of this dextrin may explain the observed viscostability. This dextrin actually contains many chains between 2.5.10 ⁴ and 5.10 ⁵ Da.

The evolution of the Brookfield viscosity of a dextrin composition over time reflects its viscosity. To illustrate this statement, the Brookfield viscosity of the compositions of dextrins I through L, as well as that of the commercially available dextrin was measured every hour for 22 hours (Figure 2).

We observe quite different behaviors with the different compositions. The compositions of dextrins I and J are very different from the compositions of dextrins K and L and the dextrins available on the market. In fact, the variations in viscosity after 22 hours of storage are very limited. This confirms the special importance of the compositions of dextrins according to the invention.

The latter results demonstrate the effect of molecular weight distribution on the viscosity and viscosity of a composition of dextrins and show that a change in molecular weight distribution of a dextrin simultaneously changes its viscosity and viscostability.

BE2017 / 5220

Claims (10)

CONCLUSIONS A composition of dextrins which has a molecular weight distribution, expressed as the following weight percentages: - more than 0.5%, preferably more than 1% of the molecules have a molecular weight of less than 10 ³ daltons, - between 35 and 45%, preferably between 39 and 43% of the molecules, has a molecular weight between 10 ³ and 2.5.10 ⁴ daltons, - between 35 and 50%, preferably between 35 and 45% of the molecules, has a molecular weight between 2.5.10 ⁴ and 5.10 ⁵ daltons, and - between 5 and 20%, preferably between 7.5% and 15% of the molecules has a molecular weight of more than 5.10 ⁵ Daltons. The composition of dextrins according to claim 1, characterized in that it exhibits a viscosity ratio comprising between 1 and 7, said ratio of the viscosity at 50 ° C of the composition after cooking at 130 ° C for 3 minutes in a jet cooker and 22 hours incubation in a 50 ° C water bath to the viscosity at 70 ° C of the composition after boiling at 130 ° C for 3 minutes in a jet cooker. The composition according to any one of claims 1 or 2, characterized in that it has a brookfield viscosity at 70 ° C which contains between 50 and 400 mPa.s, preferably between 100 and 300 mPa.s. Composition for the surface treatment or coating of paper or cardboard, characterized in that it comprises the composition of dextrins according to any one of claims 1 to 3 and at least one mineral filler, said composition preferably having a dry matter content, contains between 2 and 80%. Coating composition according to claim 4, characterized in that it has a dry matter content, containing between 45 and 80%. Surface treatment composition according to claim 4, characterized in that it has a dry matter content, containing between 2 and 30%. BE2017 / 5220 A method of preparing a surface treatment or coating composition according to any one of claims 4 to 6, comprising the following steps: mixing a composition of dextrins according to any one of claims 1 to 3 and a mineral filler, optionally an adhesive and / or at least one binder including at least one modified starch, - addition of water to the obtained mixture to obtain a composition containing a dry matter content which is between 2 and 80%, optionally the addition of water is done with the mineral filler and / or the modified starch. Use of a dextrin composition according to any one of claims 1 to 3 for increasing the viscosity of a composition for the coating and / or surface treatment of paper and / or cardboard. A method of coating a paper or a cardboard, said method comprising the steps of (a) providing a surface treatment or coating composition according to any one of claims 4 to 6, (b) applying said composition to a paper or cardboard substrate. Paper or cardboard that has been coated or the surface of which has been treated with the composition for surface treatment or coating of paper or cardboard according to any one of claims 4 to 6. BE2017 / 5220