PROCESS FOR MAKING A CONSUMER PRODUCT COMPRISING MODIFIED POLYSACCHARIDES

Abstract

A process for preparing a consumer product including a chemically modified polysaccharide, where the process includes the steps of combining a slurry including polysaccharide with a reactant to form a polysaccharide-reactant mixture, where the reactant includes an ester group; combining a base with the polysaccharide-reactant mixture to form a polysaccharide-reactant-base mixture; and allowing the polysaccharide-reactant-base mixture to form a transesterified polysaccharide mixture, where the transesterified polysaccharide mixture includes an alcohol.

Claims

1. A process for making a consumer product comprising a chemically modified polysaccharide, the process comprising the steps of: a) providing a polysaccharide slurry comprising an undissolved polysaccharide and a liquid carrier; b) combining the polysaccharide slurry with a reactant to form a polysaccharide-reactant mixture, wherein the reactant comprises an ester group; c) combining a base with the polysaccharide-reactant mixture to form a polysaccharide-reactant-base mixture; d) allowing the polysaccharide-reactant-base mixture to form a transesterified polysaccharide mixture, wherein the formed transesterified polysaccharide mixture comprises an alcohol; e) adding the mixture resulting from step d) to an unfinished consumer product or part thereof to make a consumer product.

2. The process according to claim 1 wherein in step d) the polysaccharide-reactant-base mixture is heated to a temperature above the freezing point of the reactant and below the boiling point of the reactant.

3. The process according to claim 1 wherein in step d) the polysaccharide-reactant-base mixture is heated at least 10 C. below the boiling point of the reactant.

4. The process according to claim 1 wherein step d) lasts from 30 minutes to 120 minutes.

5. The process according to claim 1 wherein step d) lasts from 50 minutes to 80 minutes.

6. The process according to claim 1 wherein the polysaccharide comprises monomers selected from the group consisting of glucose, fructose, xylose, mannose, galactose, rhamnose, arabinose, and mixtures thereof.

7. The process according to claim 1 wherein the polysaccharide comprises microfibrillated cellulose.

8. The process according to claim 1 wherein the base is selected from the group consisting of metal alkoxides, alkaline metal hydroxide, organic bases.

9. The process according to claim 1 wherein the base is selected from CsCO.sub.3 and Na.sub.2CO.sub.3, and mixtures thereof.

10. The process according to claim 1 wherein the reactant is selected from the group consisting of acetoacetate alkyl ester, methyl butyrate, ethyl-3-hydroxybutyrate, ethyl valerate, ethyl-5-bromovalerate, ethyl octanoate, ethyl benzoate, ethyl-2-aminobenzoate, ethyl phenylacetate, ethyl-3-phenylpropionate, and mixtures thereof.

11. The process according to claim 1 wherein the reactant an acetoacetate alkyl ester.

12. The process according to claim 1 wherein the water level of the polysaccharide-reactant mixture is less than 10%.

13. The process according to claim 1 wherein the water level of the polysaccharide-reactant mixture is less than 1%.

14. The process according to claim 1 wherein there is no intentional addition of an organic solvent, an ionic liquid, or mixtures thereof, in any of the steps a) to d) and wherein the levels of organic solvent and/or ionic liquid, if present, in any of the steps c and/or d is less than 10%.

15. The process according to claim 1 wherein there is no intentional addition of an organic solvent, an ionic liquid, or mixtures thereof, in any of the steps a) to d) and wherein the levels of organic solvent and/or ionic liquid, if present, in any of the steps c and/or d is less than 0.1%.

16. The process according to claim 1 wherein the chemically modified polysaccharide has a percentage of functionalization of more than 0.5% and less than 50%.

17. The process according to claim 1 further comprises the step: removing the alcohol under vacuum to obtain a transesterified polysaccharide mixture wherein the level of alcohol by weight of the mixture is less than 10%.

18. The process according to claim 1 further comprises the step of cross-linking the transesterified polysaccharide with chitosan or L-lysine.

19. The process according to claim 1 wherein the consumer product is a cleaning or care product.

20. An intermediate composition comprising a polysaccharide, a reactant, and a base wherein a) the reactant comprises an ester, the reactant is selected from the group consisting of ethyl acetoacetate, ethyl-2-methylacetoacetate, ethyl-2-chloroacetoacetate, ethyl-4-chloroacetoacetate, methyl-4-methoxy acetoacetate, methyl butyrate, ethyl-3-hydroxybutyrate, ethyl valerate, ethyl-5-bromovalerate, ethyl octanoate, ethyl benzoate, ethyl-2-aminobenzoate, ethyl phenylacetate, ethyl-3-phenylpropionate, and mixtures thereof; b) the base is selected from the group consisting of metal alkoxides, alkaline metal hydroxide, organic bases, and mixtures thereof; c) the level of organic solvent and/or ionic liquid is less than 5%.

21. A consumer product comprising a chemically modified polysaccharide having formula ##STR00017## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6, are independently selected from hydrogen or from the group consisting of ##STR00018## wherein at least one of R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 is not a hydrogen; wherein n is from 200 to 3000.

Description

DETAILED DESCRIPTION OF THE INVENTION

Definitions

[0011] As used herein, articles such as a and an when used in a claim, are understood to mean one or more of what is claimed or described.

[0012] As used herein, the terms include, includes and including are meant to be non-limiting.

[0013] By consumer product is herein meant a product intended to be used or consumed in the form in which it is sold. Preferably, the consumer product is a liquid or a solid which has been made by processing a liquid even if not all the ingredients of the product were processed in liquid form.

[0014] The consumer product can be baby care, beauty care excluding sun care, fabric and home care, family care, feminine care, snack and/or beverage products intended to be used or consumed in the form in which it is sold, and is not intended for subsequent commercial manufacture or modification. Such products include but are not limited to diapers, bibs, wipes; products for treating hair (human, dog, and/or cat), including bleaching, coloring, dyeing, conditioning, shampooing, styling; deodorants and antiperspirants; personal cleansing; cosmetics; skin care including application of creams, lotions, and other topically applied products for consumer use; and shaving products, products for treating fabrics, hard surfaces and any other surfaces in the area of fabric and home care, including: air care, car care, dishwashing, fabric conditioning (including softening), laundry detergency, laundry and rinse additive and/or care, hard surface cleaning and/or treatment, and other cleaning for consumer or institutional use; products relating to bath tissue, facial tissue, paper handkerchiefs, and/or paper towels; tampons, feminine napkins; products relating to oral care including toothpastes, tooth gels, tooth rinses, denture adhesives, tooth whitening; pet health and nutrition, and water purification; processed food products intended primarily for consumption between customary meals or as a meal accompaniment (non-limiting examples include potato chips, tortilla chips, popcorn, pretzels, corn chips, cereal bars, vegetable chips or crisps, snack mixes, party mixes, multigrain chips, snack crackers, cheese snacks, pork rinds, corn snacks, pellet snacks, extruded snacks and bagel chips); and coffee.

[0015] Preferably, the consumer products are cleaning or care products.

[0016] Unless otherwise noted, all component or composition levels are in reference to the active portion of that component or composition, and are exclusive of impurities, for example, residual solvents or by-products, which may be present in commercially available sources of such components or compositions.

[0017] All percentages and ratios are calculated by weight unless otherwise indicated. All percentages and ratios are calculated based on the total composition unless otherwise indicated.

[0018] All measurements are performed at 25 C. unless otherwise specified.

[0019] As used herein, all boiling and freezing points are measured at atmospheric pressure.

Process for Preparing a Chemically Modified Polysaccharide

[0020] The process for preparing a chemically modified polysaccharide according to the present disclosure comprises the steps: [0021] a) making a slurry comprising an undissolved polysaccharide and a liquid carrier; [0022] b) combining said slurry with a reactant to form a polysaccharide-reactant mixture, wherein the reactant comprises an ester group; [0023] c) combining a base with the polysaccharide-reactant mixture to form a polysaccharide-reactant-base mixture; and [0024] d) allowing the polysaccharide-reactant-base mixture to form a transesterified polysaccharide mixture, wherein the transesterified polysaccharide mixture comprises an alcohol.

[0025] In preferred processes, there is no intentional addition of an organic solvent, an ionic liquid, or mixtures thereof; preferably wherein the levels of organic solvent and/or ionic liquid, if present, in any of the steps c to d is less than 10%, preferably below 5%, even more preferably less than 0.1%.

Slurry Comprising Polysaccharide

[0026] With the term slurry we herein mean a composition comprising an undissolved polysaccharide into a liquid carrier. Preferably, the liquid carrier is an aqueous solution. Preferably the aqueous solution comprises a bactericide to control bacterial growth within the slurry.

[0027] The level of undissolved polysaccharide is preferably from 0.1 to 40%, more preferably from 0.5 to 20%, even more preferably from 0.5 to 10% by weight of the polysaccharide slurry. Higher levels of undissolved polysaccharide lead to higher viscosities and hence more difficult handling of the slurry.

[0028] Preferably, the polysaccharide comprises monomers selected from the group consisting of glucose, fructose, xylose, mannose, galactose, rhamnose, arabinose, and mixtures thereof, preferably the monomers are condensed through glycosidic bonds, more preferably the monomers are condensed through beta-1,4-glycosidic bonds or alpha-1,3-glycosidic bonds; even more preferably the polysaccharide is cellulose; most preferably, the polysaccharide is cellulose fiber. With cellulose fibers we herein mean microfibrillated cellulose and nanocellulose. Cellulose fibers provide efficient structuring properties when formulated into liquid compositions; e.g. liquid consumer products.

[0029] The cellulose fibers can be of bacterial or botanical origin, i.e. produced by fermentation or extracted from vegetables, plants, fruits or wood. Cellulose fiber sources may be selected from the group consisting of citrus peels, such as lemons, oranges and/or grapefruit; fruits, such as apples, bananas and/or pear; vegetables such as carrots, peas, potatoes and/or chicory; plants such as bamboo, jute, abaca, flax, cotton and/or sisal, cereals, and different wood sources such as spruces, eucalyptus and/or oak. Preferably, the cellulose fiber source is selected from the group consisting of wood or plants, in particular, spruce, eucalyptus, jute and sisal.

[0030] The content of cellulose in the cellulose fibers will vary depending on the source and treatment applied for the extraction of the fibers, and will typically range from 15% to 100%, preferably above 30%, more preferably above 50%, and even more preferably above 80% of cellulose by weight of the cellulose fibers.

[0031] Such cellulose fibers may comprise pectin, hemicellulose, proteins, lignin and other impurities inherent to the cellulose based material source such as ash, metals, salts and combinations thereof. The cellulose fibers are preferably substantially non-ionic. Such fibers are commercially available, for instance Citri-Fi 100FG from Fiberstar, Herbacel Classic from Herbafood, and Exilva from Borregaard.

[0032] The cellulose fibers may have an average diameter from 10 nm to 350 nm, preferably from 30 nm to 250 nm, more preferably from 50 nm to 200 nm.

[0033] In one aspect when the liquid carrier of the slurry is an aqueous composition, prior to combining the undissolved polysaccharide with reactant, the slurry is washed with a solvent, preferably wherein the solvent is ethanol or propane-1,2-diol, even more preferably wherein the solvent is ethanol.

Polysaccharide-Reactant Mixture

[0034] According to step b) of the present disclosure, a slurry comprising polysaccharide is combined with a reactant to form a polysaccharide-reactant mixture. The reactant is essential to provide a chemical functionality to the polysaccharide. The reactant of the present invention comprises an ester group which is essential to enable transesterification in the process according to the present invention.

[0035] Preferably, the boiling point of the reactant is above 80 C., more preferably above 100 C., even more preferably above 120 C., to reduce evaporation of the reactant during the reaction.

[0036] Non-limiting examples of preferred reactants with their CAS number, chemical structure, and boiling point are listed in Table 1. More preferably, the reactant is selected from the list consisting of acetoacetate alkyl ester, methyl butyrate, ethyl valerate, ethyl-2-aminobenzoate, and mixtures thereof; most preferably the reactant is an acetoacetate alkyl.

TABLE-US-00001 TABLE 1 preferred reactants with their CAS number chemical structure and boiling point. Reactant name CAS number Chemical structure Boiling point Ethyl acetoacetate 141-97-9 [00001] 181 C. Ethyl-2-methylacetoacetate 609-14-3 [00002] 187 C. Ethyl-2-chloroacetoacetate 609-15-4 [00003] 107 C. Ethyl-4-chloroacetoacetate 638-07-3 [00004] 115 C. Methyl-4-methoxy acetoacetate 66762-68-3 [00005] 89 C. Methyl butyrate 623-42-7 [00006] 102-103 C. Ethyl-3-hydroxybutyrate 5405-41-4 [00007] 170 C. Ethyl valerate 539-82-2 [00008] 144-145 C. Ethyl-5-bromovalerate 14660-52-7 [00009] 104-109 C. Ethyl octanoate 106-32-1 [00010] 206-208 C. Ethyl benzoate 93-89-0 [00011] 212 C. Ethyl-2-aminobenzoate 87-25-2 [00012] 129-130 C. Ethyl phenylacetate 101-97-3 [00013] 229 C. Ethyl-3-phenylpropionate 2021-28-5 [00014] 247-248 C.

[0037] To further improve the efficiency of the transesterification process of step d), the level of aqueous carrier in the polysaccharide-reactant mixture is less than 10%, preferably less than 5%, more preferably less than 3%, even more preferably less than 1%. It is believed that the presence of water hinders the transesterification process.

Polysaccharide-Reactant-Base Mixture

[0038] In step c) according to the present disclosure, a base is brought in contact with the polysaccharide-reactant mixture to form a polysaccharide-reactant-base mixture.

[0039] In preferred polysaccharide-reactant mixtures the water level is less than 10%, preferably less than 5%, more preferably less than 3%, even more preferably less than 1%. A low water level in the polysaccharide-reactant mixture further improves the transesterification process.

[0040] The base is used to catalyse the transesterification reaction between the reactant and the polysaccharide within the polysaccharide-reactant-base mixture. Suitable bases include alkaline metal alkoxides, alkaline metal hydroxides, and non-ionic organic bases. Preferred bases are carbonates because of their low toxicity and low corrosivity. In addition, carbonates are easy to use and have the advantage to form bicarbonate instead of water as a by-product and hence help to avoiding ester hydrolysis. Especially preferred bases are Na.sub.2CO.sub.3, Cs.sub.2CO.sub.3, K.sub.2CO.sub.3, and mixtures thereof. Most preferably, the base catalyst is Na.sub.2CO.sub.3 and/or Cs.sub.2CO.sub.3.

[0041] In one aspect of the invention the polysaccharide-reactant-base mixture is an intermediate mixture wherein the reactant comprises an ester; preferably the reactant is selected from the group consisting of ethyl acetoacetate, ethyl-2-methylacetoacetate, ethyl-2-chloroacetoacetate, ethyl-4-chloroacetoacetate, methyl-4-methoxy acetoacetate, methyl butyrate, ethyl-3-hydroxybutyrate, ethyl valerate, ethyl-5-bromovalerate, ethyl octanoate, ethyl benzoate, ethyl-2-aminobenzoate, ethyl phenylacetate, ethyl-3-phenylpropionate, and mixtures thereof; most preferably the reactant is an acetoacetate alkyl ester; wherein the base is selected from the group consisting of metal alkoxides, alkaline metal hydroxide, organic bases, and mixtures thereof, preferably the base is selected from the group consisting of K.sub.2CO.sub.3, CsCO.sub.3, Na.sub.2CO.sub.3, and mixtures thereof; wherein the level of organic solvent and/or ionic liquid is less than 10%, preferably less than 5%, more preferably less than 0.1%.

Transesterification

[0042] The chemical modification of the polysaccharide according to the present disclosure in step d) is a transesterification process. The transesterification occurs in the polysaccharide-reactant-base mixture wherein the reactant reacts with the polysaccharide to form a transesterified polysaccharide mixture wherein the transesterified polysaccharide mixture comprises an alcohol as a result of the transesterification process.

[0043] The process may comprise a further step of removing the alcohol, preferably removing the alcohol under vacuum to obtain a transesterified polysaccharide mixture wherein the level of alcohol by weight of the mixture is less than 10%, preferably less than 5%, even more preferably less than 1%.

[0044] In case the boiling point of the reactant is below the reaction temperature, a reflux system is required to avoid loss of the reactant. In a preferred process, the polysaccharide-reactant-base mixture is heated to a temperature above the freezing point of the reactant and below the boiling point of the reactant, preferably at least 10 C. below the boiling point of the reactant, more preferably at least 20 C. below the boiling point of the reactant, most preferably 30 C. below the boiling point of the reactant to improve the transesterification process.

[0045] In a further preferred process, the transesterification process lasts from 30 minutes to 120 minutes, preferably from 40 minutes to 100 minutes, most preferably from 50 minutes to 80 minutes.

[0046] The percentage of functionalization influences the compatibility of the modified polysaccharide with other ingredients when formulated into a consumer product. However, when the percentage of functionalization is high, the rheological properties of the modified polysaccharide are reduced. Preferably, the chemically modified polysaccharide has a percentage of functionalization of more than 0.5% and less than 50%. More preferably the percentage of functionalization is more than 0.5% and less than 30%, even more preferably more than 0.5% and less than 20%, most preferably more than 0.5% and less than 10%. With percentage of functionalization we herein mean the degree of substitution and is determined as described in the Methods.

[0047] In one aspect of the invention, the chemically modified polysaccharide has a formula

##STR00015##

wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6, are independently selected from hydrogen or from the group consisting of

##STR00016##

wherein at least one of R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 is not a hydrogen; wherein n is from 200 to 3000, preferably from 300 to 2800, more preferably from 500 to 2500. The wavy line represents where the R group links to the polysaccharide structure.

Cross-Linking

[0048] Optionally, the process further comprises a cross-linking step wherein the transesterified polysaccharide is cross-linked preferably with chitosan or L-lysine. The optional additional cross-linking further improves the compatibility with other ingredients when formulated into a liquid composition and still have a dynamic yield stress. The Applicants believe that the improved compatibility is a result of the cationic charge provided by chitosan and L-lysine. Once the modified polysaccharide is obtained, it is added to an un-finised consumer product or part thereof to give rise to a finished consumer product. The product is preferably a cleaning or a care product.

Use of an Esterified Polysaccharide

[0049] The invention further relates to the use of an esterified polysaccharide obtainable according to the process of the present invention in a liquid composition, preferably a fabric care composition, to provide yield stress and improved compatibility with other ingredients of the composition.

Methods

IR Spectroscopy

[0050] Instrument details: Attenuated total reflection (ATR) Fourier transformation infrared spectroscopy (FTIR) was used to determine the main functional groups of synthesized derivatives. All the spectra are obtained by an Alpha Bruker Spectrometer apparatus in a wavenumber range of 4000-550 cm.sup.1.

[0051] Sample preparation: approximately 0.65 grams of transesterified polysaccharide slurry were weighed in a glass vial (Alemania Glas GmBH, 26.5 mm diameter). The samples were placed in the oven (Memmert GmBH) at 150 C. to remove the water until a dry solid residue was obtained. The resulting solid residue (approximately 20 mg) was placed onto the sample holder of the equipment without any further treatment.

[0052] Result: The formation of the transesterified polysaccharide was verified by IR spectroscopy. The IR spectra of the synthesized transesterified polysaccharide displays the characteristic band of the ester bond in the region 1,720-1,750 cm.sup.1.

Degree of Substitution (DS) and % of Functionalisation

[0053] The degree of substitution of each transesterified polysaccharide was determined by titration. The titration was performed in triplicate.

[0054] Determination of dry matter: After the transesterification reaction, about 2 g of each aqueous transesterified polysaccharide slurry was weighed in a vial (Alemania Glas GmBH, 26.5 mm diameter). The samples were dried in the oven (Memmert GmBH) at 150 C. until complete removal of water. The samples were then weighed again to calculate the dry matter, which was obtained as a percentage. Each measurement was performed three times.

[0055] The dry matter is calculated using the following equation:

Dry matter %=(weight of dry sample100)/(weight of the aqueous transesterified polysaccharide slurry)

[0056] Sample preparation and titration: each sample (about 3 g) is dispersed as an aqueous slurry in a solution of aqueous ethanol (70%, Ethanol AbsolutFisher and Milli-Q water) in a 20 mL of total volume of solvent (including the water content of the slurry) in a 100 mL round bottom flask. The resulting suspension was stirred for 30 minutes using a magnetic stirrer (Yellow LineMST Basic C) at 20 C. at a 600 rpm rotational speed. After 30 minutes, sodium hydroxide 0.5 M (20 mL, Sigma Aldrich) was added. The reaction was performed for 48 or 72 hours under mixing at 600 rpm at 20 C. The round bottom flask is closed with a rubber top and sealed with parafilm to prevent solvent evaporation. After this time, the excess of sodium hydroxide is back titrated with hydrochloric acid 0.5 M (Sigma Aldrich) in the presence of phenolphthalein (Sigma Aldrich5 drops) as an indicator. The addition of hydrochloric acid is stopped when a colour change from pink to transparent was observed, therefore the volume of hydrochloric acid added varied each time depending on the % of functionalisation. A blank measurement was performed each time.

[0057] Blank measurement: sodium hydroxide 0.5 M (20 mL) was stirred in a solution of aqueous ethanol (70% 20 mL) in a 100 mL round bottom flask for 48 or 72 hours. After this time, sodium hydroxide was titrated with hydrochloric acid 0.5 M in the presence of phenolphthalein (5 drops) as an indicator. The addition of hydrochloric acid was stopped when a colour change from pink to transparent was observed.

[0058] Degree of substitution (DS): The degree of substitution is obtained from the following equation:

DS=M.W..sub.monomer[(vol HCl.sub.blankconc)(vol HCl.sub.titrationcone)]/w[(vol HCl.sub.blankconc)(vol HCl.sub.titrationcone)]M.W..sub.grafted ester functionality}

[0059] wherein

[0060] M.W..sub.monomer=molecular weight of monomer unit

[0061] Vol=volume (L)

[0062] Conc=concentration of hydrochloric acid (M)

[0063] M.W..sub.grafted ester functionality=molecular weight of the grafted ester functionality

[0064] w=weight of the solid content in the aqueous slurry.

[0065] Percentage of functionalisation: The percentage of functionalisation is obtained from the following equation:

% functionalisation=DS100/number of OH groups present in the monomer

Water Determination Via Karl Fisher

[0066] Water percentage in the reaction media was determined via Karl Fisher titration using a Mettler DL 31, Metrohm 795 Volumetric Karl Fischer Titrator or equivalent in drift control mode using a two-component volumetric reagents. First, a blank was titrated, then 0.5 gram sample were added into the titrator filled with HYDRANAL Solvent (Honeywell) and titrated with HYDRANAL Titrant 5. The instrument provided the % of water in the sample already taking into account the water in the blank.

Dynamic Yield Stress

[0067] Sample preparation for dynamic yield stress measurement: transesterified polysaccharide aqueous slurry was added to a surfactant model matrix and mixed for 5 minutes at 21.000 rpm using a ultra-turrax with S25N-10G dispersing element. Final composition was:

TABLE-US-00002 Ingredient wt % Linear Alkylbenzene Sulphonic Acid (HLAS) 10 transesterified polysaccharide (as dry material) 0.25 Monoethanolamine to pH 8 Water to 100%

[0068] Dynamic yield stress was measured using a controlled stress rheometer (such as an HAAKE MARS from Thermo Scientific, or equivalent), using a 60 mm 1 cone-plate and a gap size of 0.052 microns at 20 C. The dynamic yield stress was obtained by measuring quasi steady state shear stress as a function of shear rate starting from 10 s.sup.1 to 10.sup.4 s.sup.1, taking 25 points logarithmically distributed over the shear rate range. Quasi-steady state is defined as the shear stress value once variation of shear stress over time is less than 3%, after at least 30 seconds and a maximum of 60 seconds at a given shear rate. Variation of shear stress over time was continuously evaluated by comparison of the average shear stress measured over periods of 3 seconds. If after 60 seconds measurement at a certain shear rate, the shear stress value varies more than 3%, the final shear stress measurement was defined as the quasi state value for calculation purposes. Shear stress data was then fitted using least squares method in logarithmic space as a function of shear rate following a Herschel-Bulkley model:

=.sub.0+ky.sup.n

wherein is the measured equilibrium quasi steady state shear stress at each applied shear rate .sub.0 is the fitted dynamic yield stress. k and n are fitting parameters.

Examples

[0069] The undissolved polyssacharide used for examples 1-16 was microfibrillated cellulose (MFC) provided by Borregaard as a slurry of undissolved microfibrillated cellulose in an aqueous carrier (Exilva Forte, level of 3% microfibrillated cellulose by weight of the slurry) and was used as supplied. All the other commercial reagents and solvents were purchased from Sigma-Aldrich, VWR, Fisher and Alfa Aesar.

[0070] Equivalent to 1 gram of dry polysaccharide, the polysaccharide aqueous slurry was weighed in a 250 mL beaker, diluted with 100 mL of demineralized water and stirred for 5 mins at 600 rpm with a magnetic stirrer (Yellow LineMST Basic C). The slurry was filtered on a sintered glass funnel by vacuum filtration using a Vacuubrand GmBH+CO pump. The filtrate was mixed with 50 mL ethanol Absolut (Fisher) on the filter and filtered again under vacuum. This last step was repeated twice. The resulting filtrate was transferred into a 100 mL beaker and stirred with 50 mL ethanol for 5 minutes on the magnetic stirrer. Then, the slurry was filtered again on a sintered glass funnel by vacuum filtration. This step was performed twice. The resulting filtrate with a water level of less than 10% was transferred into a 100 mL beaker and stirred with 50 mL of the selected reactant to form a microfibrillated cellulose-reactant mixture.

[0071] The microfibrillated cellulose-reactant mixture was stirred at a 600 rpm with the magnetic stirrer. The mixture was heated to 105-110 C. using an oil bath and the base (such as Na.sub.2CO.sub.3, Cs.sub.2CO.sub.3 supplied from Acros Organics) was added to form a microfibrillated cellulose-reactant-base mixture.

[0072] The microfibrillated cellulose-reactant-base mixture was allowed to transesterify at this temperature. The reaction time was varied to vary the degree of substitution.

[0073] Once the transesterification reaction was considered completed, stirring was stopped and the beaker was removed from the oil bath. 50 mL Ethanol were added and the transesterified polysaccharide was collected by vacuum filtration. The transesterified polysaccharide is then mixed on the filter with 50 mL ethanol and filtered again under vacuum. The resulting transesterified polysaccharide filtrate was subsequently transferred into a 100 mL beaker and stirred with 50 mL ethanol for 5 mins with the magnetic stirrer. The transesterified polysaccharide filtrate was collected by vacuum filtration. This same procedure was performed twice with ethanol (250 mL) and it is repeated for three times using water as dispersing agent (350 mL). The final product was homogenized using an Ultra-Turrax homogenizer (IKA) for 5 mins at 21,000 rpm. The formation of the ester bond and the absence of starting material were confirmed by IR spectroscopy. 33.33 grams MFC slurry were used in each example.

TABLE-US-00003 TABLE 2 Detailed composition of examples 1-16. In the examples with an asterisk, a reflux system was applied the since reaction temperature was above the boiling point of the reactant. The reaction time in example 3 was 2 hrs while in the other examples 1-2, 4-16 the reaction time was 1 hour. Reaction Base temper- % function- addition ature alization Ex. Reactant Base [mg] [ C.] [%] 1 Ethyl acetoacetate Cs.sub.2CO.sub.3 60.31 105 C. 15.7% 2 Ethyl acetoacetate Cs.sub.2CO.sub.3 40.20 105 C. 3.33% 3 Ethyl acetoacetate Cs.sub.2CO.sub.3 40.20 105 C. 3.67% 4 Ethyl acetoacetate Na.sub.2CO.sub.3 29.43 105 C. .sup.17% 5 Ethyl acetoacetate Na.sub.2CO.sub.3 19.62 105 C. 7.33% 6 Ethyl acetoacetate Na.sub.2CO.sub.3 13.08 105 C. 1% 7 Ethyl-2- Na.sub.2CO.sub.3 29.43 110 C. 3.33% methylacetoacetate 8* Ethyl-2- Na.sub.2CO.sub.3 29.43 110 C. 3.67% chloroacetoacetate 9* Ethyl-4- Na.sub.2CO.sub.3 29.43 110 C. 10.33% chloroacetoacetate 10* Methyl-4-methoxy Na.sub.2CO.sub.3 29.43 110 C. 4% acetoacetate 11* Methyl butyrate Na.sub.2CO.sub.3 29.43 110 C. 2.9% 12 Ethyl-3- Na.sub.2CO.sub.3 29.43 110 C. 13.67% hydroxybutyrate 13 Ethyl valerate Na.sub.2CO.sub.3 29.43 110 C. 33.33% 14 Ethyl benzoate Na.sub.2CO.sub.3 29.43 110 C. 5.33% 15 Ethyl-2- Na.sub.2CO.sub.3 29.43 110 C. 13.33% aminobenzoate 16 Ethyl phenylacetate Na.sub.2CO.sub.3 29.43 110 C. 17.67%

[0074] Examples 1 to 16 demonstrates that the process according to the present invention results in transesterification. In addition, examples 1-6 illustrate the effect of base, base level, and reaction temperature on the percentage of functionalization. To better control the level of functionalization % we did not remove the alcohol formed in the above examples.

[0075] Example 17: 0.402 gram of chitosan (molecular weight 200000 g/mol, Glentham Life Sciences LTD) were dissolved in 40 mL of a 1% aqueous solution of acetic acid and a gel was instantly formed. 0.5 grams of transesterified polysaccharide from example 1 was added. The mixture was diluted with 60 mL water to facilitate mixing. The reaction was stirred for 3 hours at 20 C. and product formation was monitored every hour by IR spectroscopy. After 3 hours, the reaction was stopped and the product was purified by multiple washing with water (450 mL). The final chitosan cross-linked transesterified polysaccharide was homogenized using an Ultra-Turrax for 5 mins at 21000 rpm. The formation of the enamine bond was confirmed by IR spectroscopy.

[0076] Example 18: 0.451 grams L(+)-Lysine monohydrochloride (99%, Acros Organics NV) was dissolved in 25 mL water. 0.5 grams of transesterified polysaccharide from example 1 was added and the composition was stirred for 24 hours at 20 C. The obtained product was purified by multiple washing with water (450 mL). The final L-lysine cross-linked transesterified polysaccharide was homogenized using an Ultra-Turrax for 5 mins at 21000 rpm. The formation of the enamine bond was confirmed by IR spectroscopy.

Example A (Comparative): Transesterification Using Ball Milling

[0077] Initially, 1 gram of wood derived cellulose fibers pulped and bleached without being defibrillated (10% activity) was added to each of the two zirconium oxide chambers (Planetary Micro Mill, PULVERISETTE 7 premium line from Fritsch). Each chamber (80 mL volume) was filled with 25 zirconium oxide milling balls (10 mm diameter). The process was carried out at 400 and 800 rpm rotational speed and between 2 and 10 minutes. After 2 minutes, there was no change in the cellulose fibers. However, when increasing the milling time, fibers were burnt. Since suitable conditions without burning the fibers could not be identified, no reactant was added.

[0078] Without being bound by theory, it is believed that burning of fibers was due to the bleaching. Therefore, raw jute fibers (no treatment) were used instead and 1 gram of dried jute fibers was added to each of the two zirconium oxide chambers (Planetary Micro Mill, PULVERISETTE 7 premium line from Fritsch) together with 0.14 g ethyl acetoacetate and 0.020 equivalents of sodium carbonate. Each chamber (80 mL volume) was filled with 25 zirconium oxide milling balls (10 mm diameter). The process was carried out at 800 rpm rotational speed for 2 minutes. The percentage of functionalization obtained was 5%. However, because the size of the fibers was modified, they have no rheology modification properties. Modified fibers precipitate at the bottom of the bottle not being possible to perform rheology characterization.

TABLE-US-00004 TABLE 3 The dynamic yield stress of the different examples as described in the Methods section. Dynamic Yield Example Stress (Pa) 1 0.29 11 0.22 12 0.14 13 0.21 15 0.23 17 0.04 18 0.15 A (Comparative) <0.001

[0079] No yield stress was measured with the chemically modified polysaccharide of comparative example A even though the % of functionalization was similar to example 1-6. It is believed that the lack of a dynamic yield stress with comparative example A was caused because the size of the fibers was modified during the milling. In addition, the chemically modified fibers of comparative example A precipitated at the bottom of the recipient when added to the surfactant model matrix (see Methods).

[0080] From example 1, 11-18 it is clear that a dynamic yield stress was still obtained after the chemical modification according to the present invention when the chemically modified polysaccharide was formulated into the model surfactant matrix (see Methods). Furthermore, it is clear that L-lysine cross-linking (ex. 18) resulted in a higher dynamic yield stress than cross-linking with chitosan (ex. 17).

[0081] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as 40 mm is intended to mean about 40 mm.

[0082] Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0083] While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.