EP4604906A1

EP4604906A1 - Solid surfactant compositions

Info

Publication number: EP4604906A1
Application number: EP23797681.6A
Authority: EP
Inventors: Rossana COLOMBO; Stefano Monti; Alessandro D'ALOIA; Tamara Verzotti
Original assignee: Lamberti SpA
Current assignee: Lamberti SpA
Priority date: 2022-10-21
Filing date: 2023-10-18
Publication date: 2025-08-27
Also published as: IT202200021849A1; CN120051267A; WO2024083905A1

Abstract

The present invention relates to solid surfactant compositions comprising an anionic carboxylic ester of C₈-C₂₀ alkyl polyglycosides and a C₈-C₂₂ N-acyl amino acid, which can be easily formulated into self-thickening rinse-off formulations with remarkable foaming properties, and to personal care formulations containing said solid surfactant compositions.

Description

SOLID SURFACTANT COMPOSITIONS

TECHNICAL FIELD

The present invention relates to solid surfactant compositions, comprising an anionic ester of C8-C20 alkyl polyglycosides and a C8-C22 N-acyl amino acid, and to personal care formulations containing said solid surfactant compositions.

PRIOR ART

Given recent concerns for the preservation of the environment, together with the desire of consumers and conscious companies to take care of the planet, there is a strong boost to reduce the environmental footprint of personal care products, including consumer products. Traditional personal care rinse-off compositions, such as shampoos and body washes, typically contain water as predominant ingredient of the formulation. This leads to the need for large plastic packaging, as well as an increase in cost and CO2 emissions during transportation. Traditionally, the personal care market is almost totally dependent on plastic packs, sparingly recycled or difficult to recycle, as paper-based or biodegradable materials are not entirely satisfactory for aqueous compositions or liquid-based cosmetics. Besides the formulations of personal care products, therefore, packaging provides another opportunity to reduce a product environmental footprint.

With this goal in mind, efforts have been made to develop and sell personal care products in concentrated or, in particular, in solid form, and therefore, to provide products that comprise less or no water. Solid, low-water content or water-less personal care products, can be provided in sustainable and recyclable packaging. They are also generally more concentrated, a fraction of the size of their liquid counterparts, keeping packaging to a minimum and being lighter and easier to transport, therefore generating lower emissions. Formulating with low water content, anyhow, can be challenging, as all the properties that consumers demand must be guaranteed: ease of use, agreeable foam, mildness, nice hair and skin feel. New solid and sustainable ingredients are therefore essential to deliver safe, effective, water-conscious personal care products.

Sustainable alkyl polyglycosides (APG) based surfactants have been known and appreciated for a long time. Even, anionic ester of alkyl polyglycosides, such as APG sulfosuccinates, APG tartrates and APG citrates, are known. In particular anionic ester of APG without sulfate or sulfonate groups such as APG tartrates and APG citrates, are appreciated in the personal care sector because their mildness toward the hair, skin and mucous membranes.

However, APG surfactants and their derivatives are mainly provided as water solutions and are really difficult, almost impossible, to desiccate and to provide them in solid form.

Surprisingly, it has now been found that surfactant mixtures, comprising an anionic carboxylic ester of C8-C20 alkyl polyglycoside and a salt of a Os-Cis acyl aminoacid can be easily dried and can be provided in the form of solid compositions, such as powders, granules, compressed tablets or pellets. These surfactant compositions quickly dissolve in water and can be used to prepare both solid and concentrated personal care formulations. Moreover, both ingredients are bio-based materials with excellent surface properties, low potential toxicity and low environmental impact.

As far as the Applicant knows, the solid surfactant compositions of the present disclosure have never been described.

WO 2021/087492 describes a substantially anhydrous, concentrated surfactant composition comprising a sugar-based surfactant, such as an alkyl polyglucoside citrate; an amino acid based surfactant; a polyglycerol ester or a polyhydroxy ether, or a combination of a polyglycerol ester and a polyhydroxy ether; and, optionally, a glycol. According to WO 2021/087492, however, a carrier is typically needed to help solubilize the composition and a glycol is therefore included in the surfactant compositions in an amount between about 10 wt% and less than 40 wt%. Solid surfactant compositions are not described nor suggested. Only liquid surfactant compositions are exemplified.

DESCRIPTION OF THE INVENTION

It is therefore an object of the present invention a solid surfactant composition comprising: a) from 10 to 45 % by weight (wt%) of an anionic carboxylic ester of C8-C20 alkyl polyglycosides and b) from 20 to 75 wt%, of a C8-C22 N-acyl amino acid salt, with the proviso that the sum of a) and b) make up at least 50 wt%, preferably at least 65 wt%, of the composition.

A further object of this invention is a personal care formulation comprising from 0.5 to 70 wt% of said solid surfactant composition. DETAILED DESCRIPTION OF THE INVENTION

The term "solid", as used herein and common in the art, applies to substances in a state of matter having constant volume and shape at normal conditions, which means that the physical state of the surfactant composition is that of a solid at temperature of 20°C and a pressure of 1 atmosphere.

The solid surfactant composition may be in powder, granule, compressed tablet, stick or pellet form. Preferably, composition is in powder or granule form. More preferably it is in powder form.

The term "powder" means a composition in pulverulent form, with a particle size comprised between 0.1 pm and 3 mm, preferably between 0.3 pm and 1 mm.

The term "granules" means small fractionated objects formed from solid particles that are aggregated together, of variable shapes and sizes. They may be in regular or irregular form. They may in particular be in spherical form or in square, rectangular or elongated form such as small sticks. Spherical granules are most preferred.

The solid surfactant composition may be in the form of a compressed tablet, stick or pellet form, which can be obtained, for example, by manual or mechanical press or by extrusion. The solid surfactant composition of the invention comprises from 10 to 45 wt%, preferably from 15 to 40 % wt, more preferably from 20 to 40 wt%, of an anionic carboxylic ester of alkyl polyglycosides.

The anionic carboxylic ester of alkyl polyglycosides may be represented by the formula (I): [R-O-(G)x]n -(D)_y (I) wherein:

R is an aliphatic alkyl group, saturated or unsaturated, linear or branched, having from 6 to 20 atoms of carbon, preferably from 8 to 14 carbon atoms;

G is a residue of a reducing saccharide, preferably of glucose, connected to R-O by means of an ethereal O-glycosidical bond;

O is an oxygen atom;

D is the acyl residue of a carboxylic acid selected from the group consisting of citric acid, tartaric acid, maleic acid, malic acid, sulfosuccinic acid and mixtures thereof, in acid or salt form; n is a number between 1 and m-1, where m is the number of carboxylic groups in the acid that originates D; x is a number from 1 to 5, representing the average degree of polymerization of G; y is a number from 1 to 5, representing the average degree of esterification.

The above mentioned anionic esters of alkyl polyglycosides of formula (I) are known and they can be prepared as described, for example, in EP 258 814 or EP 510 564.

In a preferred embodiments, the anionic ester of alkyl polyglycosides is synthesized from alkyl polyglucosides with an alkyl group containing 8 to 14 carbon atoms and having an average degree of polymerization x between 1.0 and 2.5.

Preferably, in formula (I), D is the acyl residue of a carboxylic acid selected from the group consisting of citric acid, tartaric acid and mixtures thereof.

Anionic esters of alkyl polyglucosides of formula (I) in which R is an alkyl group having from 8 to 14 atoms of carbon, the average degree of polymerization x is between 1.0 and 2.5 and D is the acyl residue of citric acid (citric esters of Cg-Cu alkyl polyglucosides) gave the best results.

The solid surfactant composition of the invention comprises from 20 to 75% wt, more preferably from 30 to 70% wt, more preferably from 35 to 70 wt%, of a C8-C22 N-acyl amino acid salt.

The type of amino acid that is used to produce said salt is not particularly limited. Examples include glutamic acid, glycine, alanine, phenylalanine, sarcosine, tyrosine, threonine, aspartic acid and the like. As the acyl group, for example, a saturated or unsaturated, straight or branched fatty acyl group having from 8 to 22 carbon atoms, preferably from 8 to 18 carbon atoms, can be used. Examples of the acyl group include 2-ethylhexanoyl, capryloyl, caproyl, lauroyl, myristoyl, stearoyl, isostearoyl, oleoyl, behenoyl, cocoyl, palmitoyl groups, and the like.

A mixture of two or more N-acyl amino acids having acyl groups of different chain lengths may be used for the preparation of the surfactant composition of the invention.

The type of salt of the C8-C22 N-acyl amino acid is also not particularly limited. The salt may be chosen among those commonly used in the art. Examples include alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as calcium salts and magnesium salts, ammonium salts, organic amine salts such as monoethanolamine salts, diethanolamine salts and triethanolamine salts, basic amino acid salts such as arginine salts and lysine salts. Alkali metal and ammonium salts are preferred, and the sodium salts are the most preferred.

Specific examples C8-C22 N-acyl amino acid salts suitable for the realization of the present invention are the sodium or ammonium or potassium salts of N-lauroyl sarcosinate, N- cocoyl sarcosinate, N-lauroyl glutamate, N-cocoyl glutamate, N-myristoyl glutamate, N- lauroyl alaninate, N-cocoyl alaninate, N-myristoyl alaninate, N-lauroyl glycinate, N-cocoyl glycinate, N-myristoyl glycinate, and mixtures thereof.

C8-C22 N-acyl glutamate and glycinate salts are preferred amino acid based surfactants for the preparation of the solid surfactant compositions of the present invention. Cs-Cis acyl glutamate salts are particularly preferred.

The solid surfactant composition of the invention can further comprise from 3 to 25 wt%, preferably from 5 to 20 wt%, of an alkyl polyglycoside. Suitable alkyl polyglycosides have Formula II:

R-O-(G)_X II wherein R, O, G and x have the same meaning reported above for Formula I.

The solid surfactant composition in powder form can be prepared by means of solvent evaporation, spray-drying, freeze-drying and electrospraying starting from the composition in form of aqueous solution. Preferably, the solid surfactant composition of the invention is prepared by spray-drying.

The solid surfactant composition in granule form can be prepared by means of a fluidized bed, a rolling or a spray drying apparatus, starting from the composition in powder form. Preferably, the granulation is performed by means of a rolling granulating apparatus.

The pellets can be prepared, for example, by dry pressing or extrusion of the composition in powder form or in form of solution, preferably by extrusion.

The disclosed solid surfactant composition can be utilized for preparing personal care formulations, which comprise from 0.5 to 70 wt%, preferably from 1 to 60 %wt%, more preferably from 2 to 50 wt%, of said surfactant composition. The personal care formulations of the invention can further comprise from 0.1 to 50 wt%, preferably from 0.5 to 45 wt%, more preferably from 5 to 40 wt %, of at least another surfactant selected among anionic surfactants, amphoteric surfactants, cationic surfactants, zwitterionic surfactants, non-ionic surfactants, and mixture thereof.

Anionic surfactants include alkyl sulfates, alkyl ether sulfates, alkyl sulfonates, alkylamido sulfonates, alkylaryl sulfonates, alkylamido ether sulfates, alkylaryl polyether sulfates, monoglycerides sulfates, alpha-olefin sulfonates, paraffin sulfonates, alkyl and alkylaryl phosphates, alkyl ether and alkylaryl ether phosphates, alkyl sulfosuccinates, alkyl ether sulfosuccinates, alkylamide sulfosuccinate, alkylsulfoacetate, alkylsarcosinates, acyl sarcosinates, alkyl carboxylates, fatty acids salts (soaps), alkyl ether carboxylates, nonacylated alkyl isethionates, acyl taurates, acyl glycinates, and mixtures thereof.

The amphoteric or zwitterionic surfactants which can be used in the compositions of the present disclosure are those which can be broadly described as derivatives of aliphatic amines or quaternary ammonium compounds, containing an anionic water-solubilizing group, e.g. a carboxylate, sulfonate, sulfate, phosphate or phosphonate group.

Cationic surfactants useful in the compositions of the present disclosure contain amino or quaternary ammonium moieties, which are positively charged when dissolved in the aqueous composition of the present invention. Examples of cationic surfactants are long- chain alkyl trimethyl ammonium chlorides, long-chain alkyl benzyl dimethyl ammonium chlorides, alkylamine hydrochlorides, alkylamine acetates and di(long-chain alkyl) dimethyl ammonium bromides.

In the case of anionic, cationic or amphoteric surfactants, the counter-ion can be monoatomic or polyatomic, inorganic or organic. Examples of counterions are: alkali metal, alkaline earth metal, transition metal, chloride, bromide, iodide, ammonium, pyridinium, triethanol amonium and methyl sulfate.

Nonionic surfactants can be broadly defined as compounds containing a hydrophobic moiety and a nonionic hydrophilic moiety. Examples of the hydrophobic moiety can be alkyl, alkyl aromatic and aryl aromatic. Examples of nonionic hydrophilic moieties are polyoxyalkylenes, amine oxides, hydroxyl groups and alkanol amides. Examples of nonionic surfactants are alkoxylated fatty alcohols, alkoxylated fatty acids, (poly)glycerol alkyl esters, alkoxylated di- and tri-stiryl phenols, fatty sugar esters and polyesters, fatty alkoxylated sugar esters, sorbitan and alkoxylated sorbitan fatty acid esters, block copolymers of polyethylene glycol and polypropylene glycol. Other examples of nonionic emulsifiers include alkyl polyglycosides, such as those represented by Formula II described above.

In a preferred embodiment of the invention, the further surfactant of the personal care formulation of the invention is a nonionic surfactant or a mixture of nonionic surfactants. Preferred nonionic surfactants are alkyl polyglycosides.

The personal care formulation of the invention can also comprise from 0.01 to 4.0 wt%, preferably from 0.05 to 3.0 wt%, of at least one thickening agent. Examples of thickening agents that can be used in the formulation of the invention include inorganic and organic thickening agents. Suitable inorganic thickening agents are clays and silicas. Suitable synthetic organic thickening agents include anionic, cationic, hydrophobically-modified and amphoteric acrylic copolymers (such as crosslinked homopolymers of acrylic acid or of acrylamidopropyl sulfonic acid (AM PS) or crosslinked copolymers of (meth)acrylic acid, a C1-C4 acrylate ester and a C8-C40 substituted polyethylene glycol acrylate ester). Suitable natural and semisynthetic organic thickening agents include cellulose and nonionic, cationic, anionic and amphoteric cellulosic polymers (such as hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose and cationic hydroxypropyl cellulose); nonionic, anionic, hydrophobically-modified, amphoteric and cationic polysaccharides (such as xanthan gum, chitosan, alginate, guar gum, carboxymethyl guar, hydroxypropyl guar, cationic guar, cationic hydroxypropyl guar; potato starch, wheat starch, rice starch, methyl hydroxypropyl starch, starch phosphate, carboxymethyl starch, hydroxyethyl starch and hydroxypropyl starch). Mixtures of different thickening agents can be also used.

The preferred thickening agent is xanthan gum.

In a particularly preferred embodiment, the personal care formulation of the invention is an aqueous liquid formulation, comprising from 1 to 8 wt% of the composition of the invention, from 1 to 15 wt% of an alkyl polyglicoside of formula II and from 0.05 to 1.0 wt% of xanthan gum.

In another particularly preferred embodiment, the personal care formulation of the invention is a solid formulation, comprising from 25 to 50 wt% of the solid composition of the invention, from 5 to 20 wt% of an alkyl polyglicoside of formula II and from 0 to 20 wt% of at least one further surfactant.

The pH of the personal care formulation is an important factor. Preferably, the pH range is between 3.5 and 7.0, more preferably between 4.0 and 6.5. A wide variety of acids, bases, and buffers can be utilized to adjust and/or maintain the pH of the compositions of the present invention. Examples of materials useful for adjusting and/or maintaining the pH include, without limitation, ammonia, sodium carbonate, sodium hydroxide, triethanolamine, hydrochloric acid, phosphoric acid, sodium hydrogen phosphate, sodium dihydrogen phosphate, citric acid, lactic acid and the like.

Beside the above described ingredients, the cosmetic formulation of the invention can comprise further additives commonly used in the field. Examples of these additives are: humectants, emollients, consistency factors and sensorial additives, chelating agents, solubilizers; fillers, pigments, dyes; polyquatemary ammonium compounds, such as cationic polysaccharides, as conditioning agents; perfumes, fragrances and/or, essential oils; water and/or oil soluble vitamins or derivatives or precursors; antioxidants and/or preservatives; pearlescing agents; peeling and or scrubbing agents; plant extracts, particularly water soluble plant extracts; hydroxy-, particularly alpha-hydroxy, and/or polyunsaturated acids; phospholipids; proteins and/or amino acids and/or derivatives; electrolytes; NM F (natural moisturising factor); foam boosters and/or stabilisers e.g. mono- and/or di-ethanolamides and/or amine oxides; and sucrose ester derivatives.

Examples of personal care formulations of the invention are hair- and skin- cleansing compositions, shampoos, 2-in-1 shampoos, body and shower gels, bath foams, cleansing soaps and bars, cleansing powders and concentrates, make-up removers, impregnating liquids for wet wipes, cleansing foams and mousses, liquid soaps, scrubbing/peeling formulations, dentifrices, shaving creams and other products for similar applications.

EXAMPLES

In the Examples the following surfactants were used:

DSCG = Disodium Cocoyl Glutamate, 27 wt% aq. solution;

APG Citrate = Disodium Coco-Glucoside Citrate, 30 wt% aq. solution;

SCA = Disodium Cocoyl Alaninate, 26 wt% aq. solution; LPG = Lauryl Polyglucoside, 50 wt% water solution;

DPG = Decyl Polyglucoside, 50 wt% water solution;

Example 1

A solid surfactant composition according to the invention was prepared by carefully mixing 8.75 Kg of APG Citrate and 16.25 Kg of DSCG. The mixture was then spray dried with a laboratory spray-dryer (APT-5.0 from APTSOL, evaporative capacity max: 5 Kg/h)

The spray-drying process begins with the atomization of liquid mixture in a droplets nebulization. The feeding of the material to be processed takes place via a peristaltic pump, at the same time an air jet causes the liquid coming out as a fine spray through a nozzle. The droplets come into contact with the air in co-current respect to the nebulization flow. This takes place inside the drying chamber, with consequent evaporation of the liquid and formation of dry particles. The spray dryer settings are reported in Table 1:

Table 1

5.85 kg of a fine pale yellow powder having a particle size distribution (volume based) reported in Table 2 were obtained.

Table 2

Example 2

A solid surfactant composition according to the invention was prepared by carefully mixing 150 g of APG Citrate and 220.7 g of DSCG. The mixture was then spray dried with a laboratory spray-dryer (APT-2.0 from APTSOL, evaporative capacity max: 2 Kg/h). The spray dryer settings are reported in Table 3. Table 3

A fine pale yellow powder was obtained.

Example 3

A solid surfactant composition according to the invention was prepared by carefully mixing 140 g of APG Citrate and 260 g of SCA. The mixture was then spray dried with a laboratory spray-dryer (APT-2.0 from APTSOL, evaporative capacity max: 2 Kg/h). The same spray dryer settings of Example 2 were used.

A fine pale yellow powder was obtained.

Critical Micellar Concentration, Surface Tension and Contact Angle

The Critical Micellar Concentration (CMC, mg/l) and the Surface Tension (mN/m) were determined with a tensiometer (K100 from KRUSS) on a 0.10 wt% active matter deionized water solution (pH 5.5).

The contact angle over the time was determined on Parafilm® M surface with a Pocket Goniometer (PGX from Rycobel) using the same solutions used for the CMC determination.

The following Tables report the Critical Micellar Concentration (CMC, mg/l) and the Surface Tension (mN/m) of Examples 1-3 (Table 4) and the Contact Angle over the time of the solid surfactant composition of Example 1 (Table 5).

Table 4 Table 5

Foamability Evaluation

The foamability of the solid surfactant composition of Examples 1-3 and the stability of the foam produced after 5 min was determined according the Ross-Miles method on 0.10 wt% (as active matter) solutions in deionized water and water with a hardness of 30 °F. The pH of the solutions was brought to about 5.5 with citric acid. The test was performed both a 25 and 40 °C. Solutions of the solid surfactant composition of Example 1 and lauryl polyglucoside or decyl polyglucoside in a ratio by weight of 1.22:1 were also evaluated. The results in millimeters are shown in Table 6 and 7, for the deionized and hard water respectively, together with the results of the comparative surfactants.

Table d

* Comparative

ND = Not Determined Table ?

* Comparative

ND = Not Determined

NA = Not Applicable

The surfactant composition of the invention has excellent foaming properties, comparable or better than surfactants widely recognized for their foamability, such as decyl polyglucoside. The combination of the surfactant composition of the invention and an alkyl polyglucoside maintain remarkable foaming power, even when the alkyl polyglucoside shows very poor performances, i.e. lauryl polyglucoside in hard water.

Examples 4-11

The Ross-Miles foamability (mm) of surfactant systems close to those of personal care formulations prepared by dissolving in deionized water different amount of the solid surfactant composition of Example 1 and of lauryl polyglucoside was determined. The pH of the surfactant solutions was brought to about 5.0 with citric acid. Table 8 shows the amount (wt%) of the ingredients, as active substance, their ratio by weight and the Brookfield viscosity in mPa*s of the formulations.

The viscosity was determined with a Brookfield RVT viscometer at 25 °C and 20 rpm. Table 8

Naturally derived surfactants, such as amino-acid based surfactants, can prove to be extremely difficult to thicken. On the contrary, the solid composition of Example 1 can be easily formulated into self-thickening rinse-off compositions, with remarkable foaming properties.

Example 12

A rinse-off personal care composition containing the surfactant composition of Example 1 was prepared with the ingredient reported in Table 9.

Table

RVT, 20 rpm, 25°C The liquid rinse-off personal care composition containing Example 1 can be thickened by means of polymers, such as natural or natural-derived gums, without compromising the foaming nor other sensorial attributes.

Example 13 A solid cleansing bar, containing the surfactant composition of Example 1 as primary surfactant, was prepared according to Table 10.

Table 10

The solid bar delivers a mild yet effective cleansing action, providing a pleasant and creamy foam.

Claims

1) Solid surfactant composition comprising: a) from 10 to 45 % by weight (wt%) of an anionic carboxylic ester of C8-C20 alkyl polyglycosides and b) from 20 to 75 wt%, of a C8-C22 N-acyl amino acid salt, with the proviso that the sum of a) and b) make up at least 50 wt% of the composition.

2) The surfactant composition of claim 1 comprising: a) from 15 to 40 % wt of an anionic carboxylic ester of alkyl polyglycosides and b) from 30 to 70% wt of a C8-C22 N-acyl amino acid salt.

3) The surfactant composition of claim 1, wherein the anionic carboxylic ester of alkyl polyglycosides may be represented by the formula (I):

[R-O-(G)x]n -(D)_y (I) where:

R is an aliphatic alkyl group, saturated or unsaturated, linear or branched, having from 6 to 20 atoms of carbon;

G is a residue of a reducing saccharide, connected to R-O by means of an ethereal O- glycosidical bond;

O is an oxygen atom;

D is the acyl residue of a carboxylic acid selected from the group consisting of citric acid, tartaric acid, maleic acid, malic acid, sulfosuccinic acid and mixtures thereof, in acid or salt form; n is a number between 1 and m-1, where m is the number of carboxylic groups in the acid that originates D; x is a number from 1 to 5, representing the average degree of polymerization of G; y is a number from 1 to 5 representing the average degree of esterification.

4) The surfactant composition of claim 3, wherein, in formula (I), D is the acyl residue of a carboxylic acid selected from the group consisting of citric acid, tartaric acid and mixtures thereof.

5) The surfactant composition of claim 4, wherein, in formula (I), R is an alkyl group having from 8 to 14 atoms of carbon, the average degree of polymerization x is between 1.0 and 2.5 and D is the acyl residue of citric acid. ) The surfactant composition of claim 1, further comprising from 3 to 25 wt% of an alkyl polyglycoside of Formula II:

R-O-(G)_X II wherein

O is an oxygen atom. ) Personal care formulation comprising from 0.5 to 70 wt% of a solid surfactant composition comprising: a) from 10 to 45 wt% of an anionic carboxylic ester of C8-C20 alkyl polyglycosides and b) from 20 to 75 wt%, of a C8-C22 N-acyl amino acid. ) The personal care formulation of claim 7, further comprising from 0.1 to 50 wt% of at least another surfactant selected among anionic surfactants, amphoteric surfactants, cationic surfactants, zwitterionic surfactants, non-ionic surfactants, and mixture thereof. ) The personal care formulation of claim 8, wherein said at least another surfactant is an alkyl polyglycoside. ) The personal care formulation of claim 7, further comprising from 0.01 to 4.0 wt% of at least one thickening agent.