Double compartment bag

Abstract

Dual-compartment sachet. Flexible sachet (10) containing at least one composition, comprising at least two walls (12, 13) welded together and delimiting a main compartment (16) and a secondary compartment (17) for a test patch, having a smaller capacity than the main compartment, the main compartment being filled with said composition and the two compartments communicating with each other by at least one passage (18; 18a) of reduced cross-section, the sachet having a first opening zone (30) to be opened to empty the secondary compartment (17), the first opening zone (30) being disposed downstream of the passage (18; 18a) of reduced cross-section, the secondary compartment (17) being arranged to contain a maximum volume of composition of between 0.2 mL and 2 mL, in particular between 0.2 mL and 1 mL. Figure for abbreviation: Fig. 1

Description

Title of the invention: Double compartment bag technical field

[0001] The present invention relates to devices for packaging fluid compositions, and more particularly, but not exclusively, to those intended for packaging a cosmetic composition, especially hair coloring. Prior art

[0002] It is generally recommended that the user of a hair coloring composition perform a test patch prior to applying the composition in order to highlight any possible undesirable physiological reaction of the skin, such as an allergic reaction.

[0003] This "test patch" is preferably carried out 48 hours before using the colouring, by depositing a determined and limited quantity of composition on a skin surface and then checking whether this deposit gives rise to the appearance of redness or other undesirable effect, in which case the application of the composition is not recommended.

[0004] Hair dyes, particularly oxidation dyes, are generally sensitive to oxygen and react when exposed to air for prolonged periods. Therefore, if the sachet containing the composition is opened for the test patch and the remaining contents are exposed to air during the 48-hour waiting period, the composition may deteriorate.

[0005] at least in appearance, which may lead the consumer to think of a defect in the product.

[0006] The composition, for example an oxidation dye, can be used in combination with at least one other composition, for example an oxidant, in a volume ratio of the different compositions determined according to the desired use, for example 1:1 or 1.5:1.

[0007] The user may still wish to test the composition on a strand of hair to see the coloring result. Thus, when carrying out such a test, the volume ratio of the different compositions must be reproduced as faithfully as possible in order to obtain a similar result to subsequent use.

[0008] It is known to package the hair composition in two separate compartments of the same sachet, one used for coloring and the other, of smaller capacity, used for the test patch.

[0009] Application JP2019116300 discloses a bag with two detachable compartments thanks to pre-cuts.

[0010] Patents FR2918038 and EP2758321 disclose bags comprising two separate compartments made by welding two sheets one on top of the other. The

[0011] Manufacturing such pouches with separate compartments is relatively complex. Furthermore, it is relatively difficult to fill a small compartment with a small amount of composition and then seal it neatly, and the size of the pouch may appear disproportionate to the amount of composition available. It is also difficult

[0012] to control the amount of composition in the future compartment and the quality of the seal, because the inner walls of the films will be soiled by the composition.

[0013] Application WO2023 / 099437 discloses a sachet containing a capillary composition, having two openings allowing a test patch to be made by cutting the first opening without exposing the contents of the sachet to oxidation. The composition can exit the sachet through a relatively narrow channel. It is relatively difficult to dose the amount of composition dispensed by squeezing the walls of the sachet upstream of the exit channel.

[0014] Existing sachets do not allow for easy dispensing of a precise dose for the test when a mixture must be prepared in a predefined ratio. The dispensed dose is generally greater than 1.5 mL, which exceeds the actual need, as it is difficult to dispense less. This generally results in product loss. Description of the invention

[0015] There is a need to further improve the packaging devices in order to be able to carry out a reliable test touch with a determined volume of composition without altering the quality of the composition intended for later use, and without the proposed solution causing a significant additional cost for the manufacture of the sachet or posing logistical problems compared to known solutions. Summary of the invention

[0016] The invention aims to meet this need and achieves this by proposing a flexible sachet containing at least one composition, comprising at least two walls welded together and delimiting a main compartment and a secondary compartment for a test strip, of less capacity than the main compartment, the main compartment being filled by said composition and the two compartments communicating with each other by at least one passage of reduced section, the sachet comprising a first opening area to be opened to empty the secondary compartment and preferably a second opening area to be opened to empty the main compartment, the first opening area being disposed downstream of the passage of reduced section, the secondary compartment being arranged to contain a maximum volume of composition between 0.2 mL and 2 mL, for example between 0.2 mL and 1 mL.

[0017] The reduced section passage and the secondary compartment have widths chosen to allow the user to ensure complete filling of the

[0018] secondary compartment before opening it, by forcing the composition to flow from the main compartment to the secondary compartment by pressing the walls together with his fingers, for example.

[0019] The sachet can thus be opened in the first opening area after the secondary compartment has been completely filled with the composition.

[0020] Thanks to the invention, it is possible to dispense a measured quantity of the composition by emptying the secondary compartment, since the latter can be completely filled before opening the secondary compartment with a predefined volume determined by the shape of said compartment. The volume of the latter allows sufficiently easy circulation of the composition within it to expel any air that may be present when the user forces the composition from the main compartment to the secondary compartment.

[0021] Preferably, the sachet has a second opening area to be opened to empty the main compartment. The relative positions of the first and second opening areas then advantageously allow, when the sachet is fully opened according to the second opening, the part of the sachet which may contain a small amount of composition whose appearance has deteriorated following exposure to ambient air since the initial opening to be eliminated.

[0022] Preferably, the secondary compartment is arranged to contain a maximum composition volume of between 0.2 mL and 0.5 mL. Such a volume corresponds to a dose particularly suitable for carrying out a test stain, in particular by mixing an oxidation dye with a color oxidant.

[0023] Preferably, the reduced-section passage has a width of between 3 and 15 mm, better 5 and 10 mm, even better 4 and 10 mm, and especially 7 mm. Such a width is well suited to obtaining the desired volume without unduly hindering the flow of product for filling the second compartment.

[0024] The length of the secondary compartment can be between 12 and 50mm, better between 15 and 30mm, even better 15 and 25mm, or even between 20 and 50mm.

[0025] The reduced cross-section passage may be delimited by at least one projection formed by welding the walls of the bag together. This passage may, in particular, be formed between two such projections, which may be symmetrical to each other.

[0026] The portion of the sachet defining the secondary compartment may form a tab protruding from the rest of the sachet. This can facilitate access to the first opening area and make it easier for the user to locate. It can also facilitate manipulation of the sachet to force the product into the secondary compartment. Furthermore, it allows the tab to be separated from the rest of the sachet to dispense the contents of the main compartment.

[0027] Preferably, the secondary compartment widens downstream of the reduced cross-section passage. This facilitates the complete filling of the secondary compartment.

[0028] The ratio Wmax / Wmin between the maximum width Wmax of the secondary compartment and the minimum width Wmin of the reduced section passage is preferably between

[0029] between 1 and 3, the maximum width Wmax of the secondary compartment preferably being between 12 and 50mm, better between 15 and 25mm.

[0030] The first opening zone and the second opening zone can be materialized in different ways, by printing, color contrast, reliefs or notches constituting tear initiation points.

[0031] The first zone and the second opening zone may in particular include an impression of a cutting line, in particular an impression of a discontinuous line.

[0032] The first and second opening zones can be arranged respectively on either side of the reduced section passage.

[0033] The width of the passage defined by the first opening zone, in the open state, can be between 5 and 15mm, preferably between 7 and 10mm.

[0034] The width of the passage defined by the second opening zone, in the open state, is preferably greater than that of the passage defined by the first opening zone, and the width of the passage defined by the second opening zone can be between 10 and 50mm, better between 15 and 25mm.

[0035] The sachet may have a single reduced-section opening between the two compartments. Alternatively, the sachet has two reduced-section openings, with the first opening located between them. This allows the secondary compartment to be detached from the rest of the sachet before emptying its contents, which can facilitate handling of the secondary compartment; in this case, the sachet retains one reduced-section opening that helps to close the main compartment, and the other reduced-section opening can help to retain the contents in the secondary compartment once it has been detached.

[0036] The secondary compartment may include an enlarged portion and an outlet channel of lesser width than the enlarged portion, this outlet channel communicating with the enlarged portion, the first opening area being located at the outlet channel, the enlarged portion preferably having a width between 12 and 25mm, in particular between 15 and 25mm and the outlet channel preferably having a width between 7 and 10mm, in particular between 8 and 10mm.

[0037] The bag may have at least one notch creating a tear initiation point at at least one opening area, and preferably at least one such notch at each opening area, and even more preferably, the bag has two notches creating tear initiation points at each of the opening areas. These notches may serve as visual guides allowing

[0038] to allow the user to view the location of the opening areas, in the form of a straight line joining said notches.

[0039] The secondary compartment may have its longitudinal axis coincident with that of the main compartment. Alternatively, the secondary compartment may have its longitudinal axis forming a non-zero angle with that of the main compartment, in particular a perpendicular or oblique angle.

[0040] The welded walls can each be formed of a multilayer film, preferably with a thickness between 70 and 160 microns, in particular PET-M-PE, PE-M, in particular monoPE-M or PP-M, in particular monoPP-M, M designating a metal, in particular aluminium, but can also each be formed of a film having a single layer of PE or PP, with if necessary an oxygen barrier layer, formed for example by a metallisation or a layer of an oxide, in particular silica oxide SiOx.

[0041] The invention further relates to a method of manufacturing a bag according to the invention, as defined above, in which two films are welded together to form the main and secondary compartments and the reduced section passage, in particular two films formed by folding a single sheet or by two separate sheets.

[0042] The invention also relates to an assembly comprising at least one sachet according to the invention, containing a first hair coloring composition,

[0043] in particular an oxidant (respectively an oxidative dye), and at least a second composition intended to be mixed with the first in a predefined ratio, in particular an oxidative dye (respectively an oxidant). The ratio ranges, for example, from 1:1 to 1:3 or 3:1.

[0044] The second composition can be contained in a sachet according to the invention, for example identical to that containing the first composition, or differing from it only in the dimension of the secondary compartment, in order to contain a different volume of composition when the mixing ratio is different from 1:1.

[0045] The invention further relates to a cosmetic treatment process, in particular for hair coloring, using at least one composition contained in a sachet according to the invention, comprising the following steps: • With the sachet unopened, ensure the secondary compartment is full by forcing the contents of the main compartment into the secondary compartment through the narrow opening, for example by pressing on the sachet with your fingers and sliding them towards the secondary compartment to push the contents towards it. • Open the sachet in the first opening area, • Dispense the contents of the secondary compartment onto a test area or into a container intended for mixing the composition contained in the sachet with another composition. • Once the test is completed, distribute the contents of the main compartment, and • Perform the cosmetic treatment with the composition thus extracted from the main compartment, possibly mixed with said other composition.

[0046] When the contents of the secondary compartment are delivered, the latter may still belong to the sachet or be separated from it, depending on the positioning of the first

[0047] opening zone, at one end of the secondary compartment or between the two compartments.

[0048] To distribute the contents of the main compartment, the bag can be opened in a second opening area, located upstream of the reduced section passage. Brief description of the drawings

[0049] The invention will be better understood upon reading the detailed description that follows, the non-limiting examples of its implementation, and upon examination of the accompanying drawing, on which:

[0050] [Fig. 1] [Fig. 1] represents in a partial and schematic manner an example of an assembly according to the invention,

[0051] [Fig.2] [Fig.2] represents in isolation, in a partial and schematic manner, an example of a sachet according to the invention, in its unopened state,

[0052] [Fig.3] [Fig.3] is a section along 111-111 of [Fig.2],

[0053] [Fig.4] [Fig.4] is a view analogous to [Fig.2] of a variant embodiment of the bag,

[0054] [Fig. 5] [Fig. 5] is a view analogous to [Fig. 2] of an alternative embodiment of the sachet, and

[0055] [Fig.6] [Fig.6] is a view analogous to [Fig.2] of another variant embodiment of the sachet. Detailed description

[0056] In the following, the terms "top", "bottom", "upper", "lower", "vertical" refer to a bag resting by its base against a horizontal flat surface and oriented vertically. The vertical edge may correspond to a long side of the bag, when the latter is rectangular.

[0057] The terms "cut" and "cutting" should be understood in a broad sense, that is to say, designating any action enabling the opening in the bag to be made, whether

[0058] manually, for example by tearing, or with the aid of a cutting tool such as scissors, a knife, a cutter or any other suitable means.

[0059] By "opening zone" is meant the region where the cut which forms the opening is made.

[0060] The term "upstream" should be understood in view of the direction of flow of the product when it is distributed from the bag.

[0061] Figure 1 shows a set 1 (also called a kit) intended for carrying out a cosmetic treatment, for example coloring, comprising sachets 10 and 10' according to the invention, containing respective compositions A and B, for example an oxidation dye and an oxidant.

[0062] The 10 and 10' bags may be identical except for their contents, or may have different dimensions and / or different internal configurations.

[0063] In an unillustrated variant, the 10 or 10' sachet is replaced by a different container.

[0064] Assembly 1 may contain a container 2 for mixing compositions A and B, and a spatula 3.

[0065] All the components of the assembly 1 can be packaged together in a packaging device 5 such as a box, a bag, or otherwise, for example in a blister pack.

[0066] In the following description, only sachet 10 is described, but this description applies to sachet 10'.

[0067] The bag 10 comprises two walls 12, 13, visible in [Fig. 3], joined by a fastening zone 14 extending around their periphery. The width of the fastening zone is, for example, between 4 and 6 mm, being, for example, 5 mm.

[0068] The walls 12 and 13 can be formed of a complex comprising at least one gas barrier layer, for example a metallized layer, in particular in

[0069] aluminium, a silicon oxide-based coating layer, or any other suitable layer, in a manner known per se.

[0070] Each wall 12 or 13 is, for example, formed by a multilayer film, preferably heat-sealable, the attachment area 14 then being a weld area. The multilayer film is, for example, of PET-A1-PE structure, and its thickness is, for example, approximately 150 microns.

[0071] The bag 10 can be formed in different ways, for example by folding and sealing a single sheet onto itself, or by means of two separate sheets welded together.

[0072] The walls 12 and 13 delimit between each other a main compartment 16 and a secondary compartment 17, visible on the [Fig.2].

[0073] Communication between these compartments 16 and 17 is achieved by at least one passage 18 of reduced cross-section, formed in the example of [Fig.2] between a projection 21

[0074] of the fixing zone 14 and a portion 20 of the fixing zone 14 adjoining the edge opposite the projection 21.

[0075] The secondary compartment 17 belongs to a tab 22 which protrudes from the rest of the bag, and extends in the example considered along an axis

[0076] longitudinal Y which makes an angle with the longitudinal axis X of the main compartment 16, for example an angle between 30 and 60°

[0077] The sachet 10 may have on at least one of its faces, or even on each of its faces, information indicating the location of an opening area to deliver the contents of the associated compartment.

[0078] In the example of [Fig.2], the bag 10 has a first impression of a continuous or discontinuous line, materializing a cutting line constituting a first opening area 30, and a second similar impression materializing a cutting line constituting a second opening area 40.

[0079] The first zone 30 is located at the end of the secondary compartment 17 and allows the contents of the latter to be distributed, and the second zone 40 that of the main compartment 16.

[0080] The minimum width Wmin of passage 18 is chosen so as to limit the movement between compartments 16 and 17, while not preventing the composition from being manually forced to cross said passage.

[0081] This width can be chosen according to the flexibility of the walls 12 and 13 and the viscosity of the composition.

[0082] For example, it is in the order of 6 to 8 mm.

[0083] The secondary compartment 17 has a maximum width Wmax, measured perpendicular to the longitudinal axis Y, greater than Wmin.

[0084] To use the sachet 10, the user first ensures that the secondary compartment 17 is full, by pushing out the contents with their fingers.

[0085] main compartment 16 to secondary compartment 17, through passage 18 of reduced section.

[0086] During this operation, the secondary compartment 17 is filled with a predefined volume of composition, determined by the geometry of the compartment 17, its dimensions, and the flexibility of the walls 12 and 13. Any air initially present in the secondary compartment 17 is forced towards the main compartment 16 by the composition forced to fill the compartment 17.

[0087] Once this operation has been carried out, the bag 10 can be cut in the first opening area 30, for example with scissors or otherwise, the location of the area to be cut being facilitated for example by the presence of notches constituting tear starting points.

[0088] After opening, the contents of the secondary compartment 17 can be distributed, for example into the container 2, in order to be mixed with the contents of the compartment

[0089] secondary of the 10' sachet, in order to respect a predefined mixing ratio, for example 1:1.

[0090] Once the mixture has been made, it can be used to make a test patch in order to determine, for example, the absence of an allergic reaction and / or the result of the coloring.

[0091] Pending the result of the test, the main compartment 16 remains substantially isolated from the ambient air by the walls of the secondary compartment 17, which are joined together, between the first opening zone 30 and the passage 18.

[0092] When the contents of the main compartment 16 need to be delivered, the user can open it along the second opening area 40, using, for example, scissors.

[0093] As the second opening zone 40 is located upstream of the passage 18, the exit section is greater than that of the passage 18 and the emptying of the main compartment 16 can be carried out relatively quickly and without difficulty.

[0094] The secondary compartment 17 can be made differently without departing from the scope of the present invention.

[0095] Figure 4 illustrates the possibility of achieving the reduced section passage 18 by forming a bend 50 with the peripheral fixing zone 14, the concavity of the bend 50 being oriented outwards.

[0096] In this example, the tab 22 has its longitudinal axis Y oriented approximately at 90° to the longitudinal axis X of the main compartment.

[0097] The free end of the tab 22 is located, for example, as illustrated, in the vertical alignment of the edge of the bag located under the tab 22.

[0098] The second opening zone 40 is preferably located, as illustrated, between the elbow 50 and the opposite portion 51 of the fixing zone 14, the opening zone 40 being preferably oriented perpendicular to the X axis.

[0099] The first opening area 30 is located at the end of the tab 22, preferably being oriented obliquely relative to the Y axis, with an angle for example of about 20° with the X axis, so as to present the desired width and slightly encroach on the secondary compartment 17.

[0100] Figure 5 shows an alternative embodiment of the bag 10, in which the secondary compartment 17 communicates with the main compartment 16 by

[0101] via two successive passages of reduced section 18a and 18b. These latter are for example identical.

[0102] The secondary compartment 17 is defined, in this example, by a tab 22 which has the same longitudinal axis as the X axis of the main compartment 16.

[0103] The first opening zone 30 is located between passages 18a and 18b, being for example materialized by a line located between notches 60 constituting tear initiations, this line being for example perpendicular to the X axis as illustrated, and preferably located at an equal distance from passages 18a and 18b.

[0104] The width of the channel formed between passages 18a and 18b can increase between them, for example, being 10 mm, whereas the width of passages 18a and 18b is, for example, 7 mm. The distance a, along the X-axis, between passages 18a and 18b can be on the order of 10 mm. The distance b, between the beginning of passage 18b and the end of the secondary compartment 17, is, for example, 35 mm. Each passage 18a or 18b can be formed between projections 80 whose sides 81 are, for example, oriented at 45° with respect to the X-axis.

[0105] The presence of two passages 18a and 18b of reduced section makes it possible to limit the risk of emptying of compartments 16 and 17 in the absence of action by the user on them, after separation of the tab 22.

[0106] To use the sachet 10, the user ensures that the secondary compartment 17 is full, then cuts it along the first opening area 30, for example by tearing the sachet using the notches 60, or better by using scissors.

[0107] The tab 22 is then separated from the rest of the sachet, and the user can empty the contents of the secondary compartment 17 by squeezing it between their fingers.

[0108] The user can then open the bag according to the second opening zone 40 located upstream of passage 18a.

[0109] The variant of sachet 10 shown in [Fig.6] includes a tab 22 whose longitudinal axis coincides with the longitudinal axis X of the main compartment 16.

[0110] The passage 18 is formed between two extensions 65 of the attachment zones 14.

[0096] Opposing pairs of notches 66 and 67 constituting tear initiators

[0111] materialize the opening zones 40 and 30.

[0112] In this example, the tongue 22 has a narrowing in its distal part, which forms a distribution channel 69, the width c of which is, for example, greater than that Wmin of passage 18 but less than the maximum width Wmax of the secondary compartment. The width c is, for example, 9 mm while Wmin is 7 mm.

[0113] The first opening zone 30 is located, for example, near the distal end of this distribution channel 69, preferably less than 3mm away, for example at 2mm.

[0114] The secondary compartment 17 can have a constant width d over a distance between 15 and 25mm, for example a width of 18mm over a length of 20mm.

[0115] The sachet 10 may have a width which is constant over most of its length, then decreases in a transition zone 70 towards the tab 22.

[0116] The second opening zone 40 can be located in the channel 90 formed between this transition zone 70 and the passage 18. The edges 91 of the channel 90 can converge towards the passage 18, with, for example, an angle of 10° between each side of the channel 90 and the X-axis. The flanks 92 of the extensions 65 can be oriented at 45°. The second opening zone 40 can be located at a distance from the flanks 92 of, for example, between 2 and 4 mm, for example 3 mm.

[0117] Of course, the invention is not limited to the examples just described.

[0103] For example, if in the examples illustrated in Figures 5 and 6 the bags 10

[0118] have a symmetrical shape with respect to a median plane containing the longitudinal axis X, it is possible, without departing from the scope of the invention, to produce the bags with a shape that is not symmetrical with respect to a median plane.

[0119] The first opening area and / or the second opening area may include various indications on the cutting to be carried out, for example an impression of a cutting line, in particular an impression of a dotted line with a cutting tool such as scissors.

[0120] The ranges of values ​​indicated must be understood inclusive of the limits, unless the limits are explicitly excluded.

Claims

Demands

1. Flexible sachet (10) containing at least one composition, comprising at least two walls (12, 13) welded together and delimiting a main compartment (16) and a secondary compartment (17) for a test patch, of less capacity than the main compartment, the main compartment being filled by said composition and the two compartments communicating with each other by at least one passage (18; 18a) of reduced cross-section, the sachet comprising a first opening zone (30) to be opened to empty the secondary compartment (17), the first opening zone (30) being disposed downstream of the passage (18; 18a) of reduced cross-section, the secondary compartment (17) being arranged to contain a maximum volume of composition of between 0.2 mL and 2 mL, in particular between 0.2 mL and 1 mL.

2. Sachet according to claim 1, the secondary compartment (17) being arranged to contain a maximum volume of composition between 0.2 mL and 0.5 mL.

3. Bag according to any one of the preceding claims, the reduced section passage (18; 18a) having a width between 3 and 15mm, better between 5 and 10mm, even better between 4 and 10mm, in particular 7mm.

4. Bag according to any one of the preceding claims, the reduced section passage being delimited by at least one projection (21; 80; 65) formed by welding the walls (12, 13) together.

5. Bag according to any one of the preceding claims, the part of the bag defining the secondary compartment constituting a tab (22) projecting from the rest of the bag.

6. Bag according to any one of the preceding claims, the secondary compartment (17) widening downstream of the reduced section passage.

7. Bag according to the preceding claim, the ratio Wmax / Wmin between the maximum width Wmax of the secondary compartment and the minimum width Wmin of the reduced cross-section passage being between

1. and 3, the maximum width of the secondary compartment preferably being between 12 and 50mm, better between 15 and 25mm.

8. Bag according to any one of the preceding claims, comprising a second opening area (40) to be opened to empty the main compartment (16).

9. Bag according to the preceding claim, the first opening area (30) and the second opening area (40) having an impression of a cutting line, in particular an impression of a discontinuous line.

10. Bag according to any one of claims 8 and 9, the first and second opening zones being arranged respectively on either side of the reduced section passage (18; 18a).

11. Bag according to any one of the preceding claims, comprising a single passage (18) of reduced cross-section between the two compartments (16, 17).

12. Bag according to any one of claims 1 to 10, comprising two passages (18a, 18b) of reduced section, the first opening zone (30) being located between them.

13. Bag according to any one of the preceding claims, the secondary compartment (17) comprising an enlarged portion and an outlet channel (69) of lesser width than the enlarged portion, this outlet channel communicating with the enlarged portion, the first opening area (30) being located at the outlet channel, the enlarged portion preferably having a width between 15 and 25mm, and the outlet channel (69) preferably having a width between 7 and 10mm.

14. Bag according to any one of the preceding claims, comprising at least one notch (60; 66; 67) creating a tear initiation point at at least one opening area, and preferably at least one such notch at each opening area, and more preferably the bag comprising two notches creating tear initiation points at each of the opening areas.

15. Bag according to any one of the preceding claims, the length of the secondary compartment being between 20 and 50mm.

16. Bag according to any one of the preceding claims, the secondary compartment having its longitudinal axis coincident with that (X) of the main compartment.

17. Sachet according to any one of claims 1 to 15, the secondary compartment having longitudinal axis (Y) making a non-zero angle with that of the main compartment, in particular a perpendicular or oblique angle.

18. Bag according to any one of the preceding claims, the welded walls (12, 13) each being formed of a multilayer film, preferably of a thickness between 70 and 160 microns, in particular PET-M-PE, monoPE-M or monoPP-M, M designating a metal, in particular aluminium, or the walls each being formed of a film having a single layer of PE or PP, with if necessary an oxygen barrier layer, formed in particular by a metallization or a layer of an oxide, in particular silica oxide SiOx.

19. A method of manufacturing a bag (10) as defined in any one of the preceding claims, wherein two films are welded together to form the main and secondary compartments and the reduced section passage, in particular two films formed by folding a single sheet or by two separate sheets.

20. Assembly (1) comprising at least one sachet (10) as defined in any one of the preceding claims, containing a first hair coloring composition (A), in particular an oxidant, and at least a second composition (B) intended to be mixed with the first in a predefined ratio, in particular an oxidation dye.

21. Together according to the preceding claim, the second composition (B) being contained in a sachet (10') as defined in any one of claims 1 to 17.

22. A cosmetic treatment method, in particular for hair coloring, using at least one composition contained in a sachet (10) as defined in any one of claims 1 to 18, comprising the following steps: • With the sachet not opened, ensure the filling of the secondary compartment (17) by forcing some of the composition contained in the main compartment (16) into the secondary compartment by passing through the reduced cross-section passage (18; 18a), • Open the sachet in the first opening area (30), Dispense the contents of the secondary compartment (17) onto a test area or into a container intended for mixing the composition contained in the sachet with another composition. Once the test has been carried out, dispense the contents of the main compartment (16), and Perform the cosmetic treatment with the composition thus taken from the main compartment, possibly mixed with the said other composition.