The present invention relates to a device for packaging a cosmetic product. More precisely, the invention relates to a packaging sachet. The invention also relates to a method for producing such a sachet.

The expression "cosmetic product" is understood to mean any product as defined in Regulation (EC) No 1223/2009 of the European Parliament and Council of 30 November 2009 relating to cosmetic products.

In the field of devices for packaging metered quantities or samples of cosmetic product, sachets produced from two flexible sheets, the peripheral edges of which are welded together to form a sachet, are known. This type of packaging is easy to produce, low cost and has a small space requirement, particularly after the product it contains has been used.

In order to use the product contained in the sachet, the user breaks the seal, for example by tearing a breakable region of the sachet or by using a pair of scissors, in order to create a dispensing opening.

Thus, documents FR2760436 and US6557731 disclose sachets having a single compartment, which are provided for example in a manner joined together by their free edges. However, each of these sachets is a single- use sachet, because once it has been opened, all of the product contained inside the sachet has to be used in order to avoid it spoiling.

Also known are packaging devices comprising a plurality of compartments in order to use the product that remains in the container several times or to carry out extemporaneous mixtures of products contained in the different compartments.

Thus, EP1021356 discloses a multi-chamber container formed of a deep-drawn thermoplastic component closed by a covering sheet. The use of a deep-drawn thermoplastic component makes manufacturing the container more complex and expensive than a sachet. In addition, this type of container is not suitable for holding certain chemical compositions such as those used in the field of dyeing keratin fibres. In order to make this type of packaging impermeable to light, gases and vapour, the material of which the packaging is made must have at least one layer that forms a barrier, for example a metal sheet. Since the metal sheet is not able to meet all of the conditions placed on a packaging material, in practice, further layers, in particular layers of plastics, are applied to one face or both faces of the metal sheet, in order to obtain a laminated material containing a plurality of layers, making it possible to provide packaging materials that are able to be shaped.

It is also known to adapt this type of material in order to package in sachets products such as compositions containing a basifying agent, in particular those containing aqueous ammonia, for example compositions in the field of dyeing keratin fibres.

For example, the document FR2879170 discloses the use of laminated material suitable for producing sachets containing hair dyeing products. However, these sachets are formed of only one compartment, because the material used is not suitable for the production of compartments separated by a weld, the sealing solidity of which is less than that of the perimeter of the sachet. However, each of these sachets is a single-use sachet, because once it has been opened, all of the product contained inside the sachet has to be used in order to avoid it spoiling. Thus, it is not possible to use either the entire volume, for example for all of the hair, or a partial volume from one or more compartments, for example for shorter hair, or to make mixtures with other products contained in other sachets.

Therefore, the object of the present invention is to provide an improved device for packaging a cosmetic product in order to remedy the abovementioned drawbacks.

To this end, the invention proposes a sachet for packaging a cosmetic product, comprising two flexible sheets secured together along their peripheral edge so as to define a peripheral sealing zone and an interior volume, each sheet forms a multilayer complex comprising a metal layer, a bonding agent comprising a copolymer comprising at least 7% by weight of carboxylic and/or carboxylate units, it being possible for the carboxylic units to be in acid form or in the form of salts, and a layer of peelable polymer joined to the metal layer via said bonding agent.

According to the invention, the sachet is characterized in that it comprises compartments separated by weak welds between the two peelable layers.

According to further features of the invention, the bonding agent can be a copolymer of ethylene and acetic acid.

The layer of peelable polymer can be produced from peelable polyethylene.

The invention will be understood better from reading the following description of non-limiting examples of the implementation thereof with reference to the appended drawings, in which:

- Figure 1 schematically shows an example of a device for packaging a cosmetic product according to the invention;

- Figure 2 is a cross-sectional view of a material used to form the device from Figure 1 ;

- Figures 3 and 4 show variants of the device from Figure 1 ;

- Figure 5 shows the stages in a method for manufacturing the device from Figure 1 .

In the following description, the term flexible is used to describe a material which deforms under the pressure, typically greater than 10 g, exerted by a user. This term is not synonymous with the term elastic.

With reference to the figures, a sachet 1 for packaging a cosmetic product P comprises two flexible walls 1 1 , 12 secured together along their peripheral edge so as to define a peripheral sealing zone 14 and an interior volume 13 holding the cosmetic product P.

The sachet 1 consists of two flexible walls 1 1 and 12 which are for example approximately rectangular. The flexible walls 1 1 and 12 are produced from multilayer sheets.

A cross-sectional view of a multilayer sheet for producing the sachet 1 is shown in Figure 2. This multilayer sheet having a laminated structure comprises at least the following layers superposed on one another in the following order:

- a metal layer 4, for example made of aluminium foil,

- a bonding agent 5 comprising a copolymer comprising at least 7% by weight of carboxylic and/or carboxylate units, it being possible for the carboxylic units to be in acid form or in the form of salts, and

- a layer of a non-metallic material that forms a first external structure 6 intended to be in contact with the product P. This external structure 6 is for example a layer of plastic such as peelable polyethylene.

These multilayer sheets will be described in more detail in the course of the description.

The rectangular sachet 1 has a bottom edge 15, two side edges 16 and a top edge 17, the latter being the one through which the product P will be dispensed.

The dimensions of the walls 1 1 and 12 that form the sachet are for example between 10 mm and 200 mm for the width and between 20 mm and 300 mm for the length.

The sealing zone 14 on the peripheral edge of the walls 1 1 and 12 is for example obtained by hot welding, adhesive bonding or any other known means for obtaining a strong weld.

The term "sealing" or "strong weld" is understood to mean a definitive weld between two layers, obtained for example by the fusing and mixing together of these two layers, that is to say that the strong weld between two layers cannot be separated without the walls comprising these two layers being damaged.

By contrast, the expression "assembly by bonding" or "weak weld" is understood to mean a non-definitive weld between two layers of identical material, that is to say that the weak weld between two layers can be separated starting from a force threshold, without the walls comprising these two layers being damaged.

A weak weld of two layers of peelable material causes surface bonding between these two layers, whereas a strong weld of these two same layers causes the mixing of these layers, causing them to lose their peelable nature. For example, these two different welds are obtained by varying the pressure threshold and the threshold of the amount of heat supplied during these welding operations, a weak weld being obtained by applying a pressure and an amount of heat that are less than for a strong weld.

By way of example, the sealing zone 14 has a width of between 3 mm and 30 mm starting from the edge of the sachet 1 . In this example, the sealing zone of the top edge 17, of the bottom edge 15 and of the side edges 16 has a width of around 5 mm.

The sealing zone 14 of the top edge 17 can be located at the end of a narrowing of the walls so as to form a neck 18 that defines a dispensing passage 19 defined by said flexible walls 1 1 and 12 and extends along an axis X-X of the interior volume 13 towards the sealed top edge 17 of the sachet 1 . The axis X-X is also the longitudinal axis of the sachet 1 .

The sachet 1 also comprises an opening means 20, for example by way of tearing or cutting with a pair of scissors, that makes it possible to open the upper end of the dispensing passage 19. The opening means is for example a precut line along the top edge 17, passing into the sealing zone 14 on either side of the passage 19 and at the level of the passage 19 so as to be able to detach a portion of the sealing zone 14 of the top edge 17 at the end of the dispensing passage 19.

The precut line can be produced for example by laser, starting with just an outer layer of the multilayer material, which could then be torn easily without a tool.

The sachet 1 may also comprise what is known as a "fine" weld 22.

This type of fine weld is produced for example by ultrasonic welding, which applies a high pressure and great heat to a very small area, such that this weld is also definitive, like a strong weld, but in a very localized manner.

A fine weld can thus have a width of less than 1 mm. This fine weld makes it possible advantageously to limit the spoiling of the product that can be contained in the sachet at the time of welding. In the example in Figure 1 , a fine weld 22 is produced transversely to the axis X-X in the dispensing passage 19, each end connecting the sealing zone 14 so as to obtain an end compartment 13a located between the top edge 17 and the fine weld 22. This end compartment 13a of small volume makes it possible for example to remove a small amount of product in order to carry out a sensitivity test of the product before applying all of the product contained in the sachet 1 .

To this end, two opening means 20 are positioned on either side of the fine weld. The opening means located between the top edge 17 and the fine weld 22 makes it possible to open the end compartment 13a, while the other opening means 20 makes it possible to open the sachet 1 to discharge the product contained in the rest of the interior volume 13.

According to the invention, the interior volume 13 of the sachet 1 comprises at least one weak weld 21 , each end of which is connected to the sealing zone 14 so as to define on each side each weak weld of the compartments (13b, 13c, 13d, 13e) in the interior volume 13, the weak weld making it possible to obtain leaktightness between the compartments in order to avoid a product contained in a first compartment passing into a second compartment.

However, when the user applies a pressure to the flexible sachet in the region of a compartment, such a weak weld separates under the force of the pressure transmitted by the product to the weak weld, thereby allowing the passage and mixing of the product from one compartment with that of the adjacent compartment.

In Figure 1 , the sachet comprises three weak welds 21 transverse to the axis X-X of the sachet 1 , so as to delimit four compartments (13b, 13c, 13d, 13e).

The multilayer sheets are chosen to package a cosmetic product, the layer of non-metallic material 6 forms a first external structure 6 that is able to be brought into contact with the product, and the metal layer 4 may furthermore be covered, on a side opposite the one on which the first external structure 6 is held, by a second external structure 2. This second external structure 2 may be produced from one or more mutually bonded layers of paper, cardboard and/or thermoplastics such as vinyl plastics for example based on polyvinyl chloride (PVC), polyesters, polyolefinic plastics or polyamides.

Examples of plastics based on polyvinyl chloride (PVC) are vinyl plastics containing vinyl chloride units in their structure, such as copolymers of vinyl chloride with vinyl esters of aliphatic acids, copolymers of vinyl chloride with esters of acrylic or methacrylic acid or with acrylonitrile, copolymers of vinyl chloride with diene bonds and unsaturated dicarboxylic acids or anhydrides thereof, copolymers of vinyl chloride and vinylidene chloride with unsaturated aldehydes, ketones, etc., or polymers and copolymers of vinylidene chloride with vinyl chloride or other polymerizable compounds. The thermoplastics based on vinyl can also be rendered flexible in a manner known per se by means of primary or secondary plasticizers. The PVC sheets can, as the case may be, also be drawn monoaxially (oPVC) or biaxially.

Examples of plastics based on polyesters are poly(alkylene terephthalate)s or poly(alkylene isophthalate)s having alkyl groups or radicals containing from 2 to 10 carbon atoms or alkyl groups containing from 2 to 10 carbon atoms which are interrupted at least by one -O-, such as, for example, poly(ethylene terephthalate) (PET sheets), poly(propylene terephthalate), poly(butylene terephthalate) (poly(tetramethylene terephthalate)), poly(decamethylene terephthalate), poly(1 ,4-cyclohexyldimethylol terephthalate) or poly(ethylene 2,6 naphthalenedicarboxylate), or copolymers of poly(alkylene terephthalate) and poly(alkylene isophthalate), the proportion of isophthalate being, for example, from 1 to 10 mol%, copolymers and terpolymers, and also block polymers and grafted alternative forms of the abovementioned substances. Other appropriate polyesters, such as polyethylene naphthalate, are known in the technical field under the abbreviation PEN.

Other polyesters are copolymers of terephthalic acid and of another polycarboxylic acid with at least one glycol. Copolyesters of terephthalic acid, of ethylene glycol and of an additional glycol are appropriate. Glycol-modified polyesters, which are known in the technical field under the name PETG, are preferred.

Appropriate polyesters are composed of poly(alkylene terephthalate)s having alkyl groups or radicals comprising 2 to 10 carbon atoms and poly(alkylene terephthalate)s having alkyl groups or radicals containing 2 to 10 carbon atoms which are interrupted by 1 or 2 -O-.

Other preferred polyesters are poly(alkylene terephthalate)s having alkyl groups or radicals containing 2 to 4 carbon atoms and preference is very particularly given to poly(ethylene terephthalate)s. These poly(ethylene terephthalate)s also include A-PET, PETP and the PETG mentioned or the G- PET.

Examples of polyolefin materials are polyethylenes (PE), for example high density polyethylene (HDPE, density of greater than 0.944 g/cm ³ ), medium density polyethylene (MDPE, density of 0.926 to 0.940 g/cm ³ ), linear medium density polyethylene (LMDPE, density of 0.926 to 0.940 g/cm ³ ), low density polyethylene (LDPE, density of 0.910 to 0.925 g/cm ³ ) and linear low density polyethylene (LLDPE, density of 0.916 to 0.925 g/cm ³ ), for example in the form of nonoriented sheets (PE sheet) or monoaxially or biaxially oriented sheets (oPE sheet), polypropylenes (PP), such as axially or biaxially oriented polypropylene (oPP sheet) or cast polypropylene (cPP sheet), amorphous or crystalline polypropylene or blends thereof or atactic or isotactic polypropylene or blends thereof, poly(l -butene), poly(3-methylbutene), poly(4 methylpentene) and copolymers thereof, then polyethylene with vinyl acetate, vinyl alcohol or acrylic acid, such as, for example, ionomer resins, such as copolymers of ethylene, of acrylic acid, of methacrylic acid, of acrylic esters, tetrafluoroethylene or polypropylene, in addition random copolymers, block copolymers or olefin polymer/elastomer blends. The polyolefin materials can also comprise cycloolefins as monomer of a homopolymer or of copolymers.

Preference is given to high density polyethylenes and to polypropylenes, and also to ionomers, for example known under the trade name Surlyn. Examples of polyamides (PA) for the plastic sheets are composed, for example, of polyamide 6, ε-caprolactam homopolymer (polycaprolactam); polyamide 1 1 ; polyamide 12, co-lauryllactam homopolymer (polylauryllactam); polyamide 6,6, homopolycondensate of hexamethylenediamine and of adipic acid (poly(hexamethylene adipamide)); polyamide 6,10, homopolycondensate of hexamethylenediamine and of sebacic acid (poly(hexa-methylene sebacamide); polyamide 6,12, homopolycondensate of hexamethylenediamine and of dodecanedioic acid (poly(hexamethylene dodecanamide)) or polyamide 6-3-T, homopolycondensate of trimethylhexamethylenediamine and of terephthalic acid (poly(trimethylhexamethylene terephthalamide)), and blends thereof. The polyamide sheets are drawn monoaxially or biaxially (oPA).

The second external structure 2 is preferably composed of poly(alkylene terephthalate), for example of poly(ethylene terephthalate), so as to improve the impact strength of the material 1 finally produced, in particular to improve the resistance to impacts which might be experienced from the outer perimeter of the packaging device at least in part delimited by a flexible sheet forming a first wall produced from this material 1 .

The second external structure 2 generally has a thickness of between 12 μιτι and 25 μιτι.

If appropriate, this second external structure 2 is bonded to the metal layer 4 by means of a layer 3 of a second bonding agent produced from appropriate laminating adhesives that may contain solvents or be devoid of solvents and also contain water. Examples of laminating adhesives consist of acrylate adhesives that contain solvents, are devoid of solvents or are aqueous, or of polyurethane-adhesive systems. However, it is also possible to use adhesives which cure under the effect of electromagnetic radiation (for example under UV radiation or electron beams). It is also possible to produce this layer 3 from diisocyanates or aliphatic polyesters, or from appropriate lacquers, such as, for example, acrylate-based lacquers, epoxy resins, melamine resins, urea resins, polyurethanes, cellulose nitrate, polyesters and mixtures thereof. The lacquers can, for example, be solvent-based or aqueous-based or can be systems comprising one, two or more components. The lacquers can, for example, be cured by drying, thermally, chemically and/or using radiation (UV; electron beam; IR).

Preferably, the layer 3 is produced from polyurethane. It has, for example, a thickness of between 2 and 5 μιτι, preferably around 4 μιτι.

In a variant, which is not shown, the second external structure 2 is a varnish that is able to be bonded directly to the metal layer 4.

The metal sheet 4 according to the invention can be made of iron, steel, nickel, copper, tin, bronze, brass, aluminium, etc. Advantageously, the metal sheet 4 is made of aluminium having a degree of purity of 99.95% to 97% (% by weight), the rest being inevitable impurities or alloying elements.

Examples of alloys are those having aluminium as main component and Fe; Si;

Mg; Mn; Ti and/or Cu as alloying elements, such as, for example, the alloys

AIFe1 .5Mn, AIFeSi or AlFeSiMn, respectively having a purity of greater than

97.5%, and preferably greater than 98.5% (% by weight) of aluminium.

In particular, the metal layer 4 is produced from aluminium and has a thickness of between 6 and 12 μιτι, preferably around 12 μιτι.

The faces of the metal layer 4 may have improved adhesion for the bonding agent by virtue of a pretreatment that tends in particular to increase the surface tension of these faces, for example brushing, chromating, ionization treatment, ozone treatment, corona treatment, flame treatment or plasma treatment.

The layer 5 of bonding agent comprises a copolymer comprising at least 7% by weight of carboxylic and/or carboxylate units, it being possible for the carboxylic units to be in acid form or in the form of salts. In particular, the carboxylic and/or carboxylate units are present in an amount of between 7% and 19%, and preferably of around 9.7% by weight.

In particular, the layer 5 is a copolymer which comprises at least one first monomer according to the following unit

R ₃ = H or CH ₃ , R ₂ = H or a linear or branched unsubstituted alkyl group, such as a methyl, ethyl, propyl or isobutyl group, or R ₂ represents a C ₄ to Ci cycloalkyl group,

and m being selected such that this first monomer represents between 7 and 19% by weight of the copolymer.

In particular, this copolymer comprises at least one second monomer formed of an alkylenic unit containing 1 to 10 carbon atoms, and in particular having an ethylenic unit according to the following formula:

(-CH ₂ -CH ₂ -) _n

n being chosen such that this second monomer represents between

71 and 92% by weight of the copolymer.

Preferably, the copolymer forming the layer 5 is a copolymer of ethylene and ethyl acrylate comprising 9.7% by weight of ethyl acrylate and/or a copolymer of ethylene and acrylic acid comprising 9.7% by weight of acrylic acid. The layer 5 generally has a thickness of between 10 and 40 μιτι, preferably around 25 μιτι.

Finally, this layer 5 of bonding agent serves to bond the metal layer 4 to the first external structure 6, the latter being produced from a peelable thermoplastic, for example, a material comprising a mixture of polyethylene and polybutene. The proportions of the mixture are defined so as to have a sufficient difference in separating force (peelabilty) between a strong weld and a weak weld when each weld is produced at a sufficiently different temperature. For example, with such a material, a strong weld carried out at 160°C opens with a force of 335 N, and a weak weld carried out at 100°C opens with a force of 210 N.

The first external structure 6 can itself be produced from one or more layers bonded together and produced from materials that may be different from one another.

More particularly, the first external structure 6 forms a layer of peelable polyethylene. Moreover, it has a thickness of between 40 and 150 μιτι, and preferably of around 75 μιτι. The layers and/or respectively structures 2, 3, 5 and 6 may be transparent, translucent or opaque and may be clear or partially or completely coloured.

At least one of the external faces of the material, respectively represented by the external structures 2 and 6, and preferably the first, can be covered with a printed pattern, which itself may be covered with a lacquer. It is also possible to provide these external faces with a lacquer, it being possible, as the case may be, for this lacquer also to be printed and/or to be able to be printed on the packaging installations, for example by means of UV radiation, solvents, laser beams or electron beams.

In the case where the external layers or structures are produced from plastics, these may be extruded. In particular, the material is obtained by laminating layers over one another.

According to one particular embodiment of the multilayer material, this material may also comprise an arrangement of layers and/or structures that are symmetrical to one another on either side of the metal layer 4.

Preferably, this material can be produced in the form of an endless material, such as rolls, and subsequently be cut into sections to be joined together to form a multitude of packaging sachets 1 . The method for manufacturing sachets 1 will be described below.

The cosmetic product P intended to be contained in the sachet 1 is for example a makeup product such as a foundation, a care product such as a face cream, a hair dyeing product or a haircare product such as a shampoo.

The presentation form of the product P can be of any type, such as a product in the form of a powder, a gel, a cream or a liquid.

In particular, the multilayer material is used to contribute to the packaging of cosmetic products such as compositions for dyeing keratin fibres, in particular compositions for oxidation dyeing containing a basifying agent.

Mention may be made, as examples of basifying agents, of aqueous ammonia, alkaline carbonates, alkanolamines such as mono-, di- and triethanolamines and derivatives thereof, sodium hydroxide or potassium hydroxide and compounds of the following formula (II): N W N

/ \

^Rc % l)

in which W is a propylene residue optionally substituted with a hydroxyl group or a Ci-C ₄ alkyl radical; and R _a , Rb, R _c and Rd, which may be identical or different, represent a hydrogen atom or a Ci-C ₄ alkyl or Ci-C ₄ hydroxyl radical.

According to one preferred embodiment, the basifying agent is chosen from aqueous ammonia and/or ethanolamine.

Conventionally, the compositions for the oxidation dyeing of keratin fibres, in particular human hair, comprise, in an appropriate medium, at least one oxidation base and optionally one or more couplers.

Mention may be made, as oxidation bases, of para- phenylenediamines, bisphenylalkylenediamines, para-aminophenols, bis-para- aminophenols, ortho-aminophenols, heterocyclic bases and the addition salts thereof.

The oxidation base or bases are generally each present in an amount of between 0.001 and 10% by weight approximately relative to the total weight of the dyeing composition, preferably between 0.005 and 6%.

Mention may in particular be made, as couplers present in the dyeing composition, of meta-phenylenediamines, meta-aminophenols, meta-diphenols, naphthalene couplers, heterocyclic couplers and the addition salts thereof.

In the composition of the present invention, the coupler or couplers are each generally present in an amount of between 0.001 and 10% by weight approximately relative to the total weight of the dyeing composition, preferably between 0.005 and 6%.

Generally, the addition salts of the oxidation bases and the couplers that can be used within the context of the invention are in particular chosen from the addition salts with an acid, such as hydrochlorides, hydrobromides, sulphates, citrates, succinates, tartrates, lactates, tosylates, benzenesulphonates, phosphates and acetates, and the addition salts with a base, such as sodium hydroxide, potassium hydroxide, aqueous ammonia, amines or alkanolamines. The dyeing composition may also contain direct dyes. These direct dyes that can be used according to the invention are chosen, for example, from neutral, acid or cationic nitrobenzene direct dyes, neutral, acid or cationic azo direct dyes, neutral, acid or cationic quinone and in particular anthraquinone direct dyes, azine direct dyes, triarylmethane direct dyes, indoamine direct dyes and natural direct dyes.

The direct dye or dyes preferably represent from 0.001 to 20% by weight approximately relative to the total weight of the ready-to-use composition, and even more preferably from 0.005 to 10% by weight approximately.

At the time of use, the oxidation dyeing composition as defined above is mixed with an oxidizing agent such as hydrogen peroxide, persalts such as persulphates or an oxidase enzyme such as uricase or laccase.

According to one particular embodiment, the composition is a direct dyeing composition, that is to say one devoid of oxidation base and coupler, containing one or more direct dyes as defined above in a cosmetic medium containing at least one basifying agent. This composition may also contain an oxidizing agent such as hydrogen peroxide, in order to obtain lightening of the keratin fibres.

The medium appropriate for dyeing, also known as dyeing vehicle, generally consists of water or a mixture of water and at least one organic solvent in order to dissolve the compounds which would not be sufficiently soluble in water.

The solvents are preferably present in proportions preferably of between 1 and 40% by weight approximately and even more preferably between 5 and 30% by weight approximately relative to the total weight of the dyeing composition.

The dyeing composition may also include various adjuvants which are used conventionally in compositions for dyeing hair, such as anionic, cationic, nonionic, amphoteric or zwitterionic surface-active agents or mixtures thereof, anionic, cationic, nonionic, amphoteric or zwitterionic polymers or mixtures thereof, inorganic or organic thickening agents and in particular anionic, cationic, nonionic and amphoteric polymeric associative thickeners, antioxidants, penetration agents, sequestering agents, fragrances, buffers, dispersing agents, conditioning agents, such as, for example, volatile or nonvolatile and modified or unmodified silicones, film-forming agents, ceramides, preservatives or opacifying agents.

The above adjuvants are generally present in an amount, for each of them, of between 0.01 and 20% by weight, relative to the weight of the composition.

The dyeing composition may be provided in various forms, such as in the form of liquids, creams or gels, or in any other form which is appropriate for carrying out dyeing of the keratin fibres, in particular human hair.

Thus, each compartment of the sachet may contain the same product or different products, which for example react with one other such that they must be mixed just before or at the moment of application. For example, one compartment may contain an oxidation dyeing composition and another may contain an oxidizing agent.

The advantage of the weak weld with the multilayer material described above is that is makes it possible to have sufficient leaktightness to avoid any migratory flow from one compartment to the other, it being possible for the reaction between the two products to emit a gas and cause the destruction of the sachet by explosion if the pressure becomes too high.

Preferably, all of the compartments comprise the same product.

This sachet is used as follows. Optionally, for example if the user is using the product for the first time and if this product has an allergenic factor, the user only tears the opening means 20 between the top edge and the fine weld in order to have access to the amount of product that is useful for a sensitivity test.

Next, when the user wishes to use the product, he will first of all determine how much will be the necessary amount. This amount can be determined by the possibility of wishing to mix the product contained in one compartment with the product contained in another compartment, in order to personalize the expected effect, or else by the fact that a user needs only one part of the packaging to meet his needs, for example if it is a product provided for long hair, a user who has short hair may only require a part thereof and will be happy to keep the other part for a new application at a later time. On the other hand, two compartments may comprise a different dye that can be used on its own or in a mixture in order to obtain a third colour.

The user then exerts a pressure close to the weak weld located between the compartments containing the products intended to be mixed, in order to open the weak weld in question. This weak weld is the one closest to the dispensing passage. The user can also open a plurality of weak welds for a single application. A large compartment formed from a plurality of adjacent compartments, the weak welds of which have been opened, thus contains the product to be applied.

In the case in which the compartments comprise different products, the user can massage this large compartment in order to homogenize the mixture.

The user then tears the second opening means in order to open the dispensing passage 19 so as to be able to remove the mixed product and then to apply it.

If the compartments have not been opened, the user can then keep the product for another use, during which it will suffice to open the remaining weak weld or welds in order to dispense the product through the already open dispensing passage 19.

The method for manufacturing such a sachet will now be described with reference to Figure 5.

The manufacturing method is advantageously implemented by what is known as a vertical machine that makes it possible to form, fill and seal a continuous series of sachets 1 in order to obtain high manufacturing rates and a low production cost. The vertical axis is perpendicular to the longitudinal axis X-

X of the sachets.

The multilayer sheets of each wall (1 1 , 12) are packaged on a reel

(not shown). Thus, two reels unroll from the top of the machine, the multilayer sheets forming the front wall 1 1 and the rear wall 12 of the sachet 1 , said walls being brought face to face, the layers that form the first external structures 6 comprising the peelable thermoplastic being located opposite.

In the example of Figure 5, the width of each sheet corresponds substantially to the length of a sachet. However, the assembly can be repeated in width, thereby creating as much packaging and thus multiplying the manufacturing rate by the number of packages created by width.

The reels are unwound in a stepwise manner. Each manufacturing step will now be described. Each step is carried out more or less simultaneously in order to produce a set of sachets, the manufacturing stages of which are offset by one step.

The first step 101 , known as the "strong weld" step, makes it possible to connect the two sheets 1 1 and 12 of the multilayer complex in a definitive manner, by producing a strong weld 14 on the top edge 15 and bottom edge 17 of the sachet 1 , said edges being positioned laterally in the manufacturing method. The side edges 16 are not welded.

The reels are then unwound by one step. The sachet being manufactured is moved downwards by the value of one step, in other words by the width of a sachet.

The second step 102, known as the "weak welds" step, makes it possible to produce weak welds 21 that delimit the compartments along the axis X-X.

The reels are then unwound by one step. The machine thus comprises as many product filling tubes 30 as there are compartments to be filled. These tubes are fixed, passing through the compartments preformed in the previous steps (101 , 102), and their end is located approximately at the level of this third step 103.

During the third step 103, known as the "filling step", the filling tubes deliver the desired amount of product P. This amount is for example the same in all of the compartments, but it is also possible for the volumes delivered to be different from one another.

The filled sachet drops by another step. The fourth step 104 makes it possible to close the filled sachet definitively and hermetically with the aid of a strong weld 14 that makes it possible to seal the side edge 16 which is positioned at the top of the sachet in the method. This strong weld also makes it possible to seal a side edge 16 of the following sachet positioned at the bottom in the previous step 103. In this way, the filling only starts once this strong weld has been created, that is to say there is an offset between the execution of the fourth step of forming a sachet and the third step 103 of forming the following sachet.

If necessary, a fifth step 105 consists in creating a sub-compartment 13a with the aid of a fine weld 22, followed by a sixth step 106 in which the opening means 20 is or are created for example by laser precuts.

Finally, the process of creating a sachet is finished by a seventh step 107 of a final cut, separating the sachet in the seventh step 107 for the others still being manufactured in steps 101 to 106. This cutting phase also makes it possible to remove the portions 23 of external walls of the sachet, which are thus useless, on each side of the neck 18, and/or to create any notches for the opening means 20.

On complex machines, it is possible to carry out a plurality of steps at once, for example the first and second steps can be combined and/or the fourth, fifth and sixth steps.

Variants of sachets according to the invention are shown in Figures 3 and 4.

The sachet in Figure 3 comprises a multitude of opening means 20, such as precuts, such that after being emptied, the compartments can be separated from the unused compartments of the sachet 1 . In this example, each compartment also comprises a dispensing passage 19.

The sachet in Figure 4 comprises two opposite dispensing passages 19 for making it easier for the product coming from the compartments furthest away from the first dispensing passage to emerge.

The invention is not limited to the examples illustrated. The features of the various examples can in particular be combined as parts of variants which are not illustrated. The expression "comprising a" should be understood as meaning "comprising at least one", unless specified to the contrary.