Heat-sealing paper with reduced noise, for packaging a solid product

Abstract

The invention relates to a heat-sealing paper (1) for packaging a solid product, comprising at least one layer of cellulose fibres (2), said cellulose fibres having a density of between 1.2 and 1.7 g / cm3 and a porosity of between 30% and 80%, and at least one layer of hot-melt adhesive (3). According to the invention, the at least one hot-melt adhesive layer (3) is deposited on the cellulose fibre layer (2) in a discontinuous manner over the entire length and width of the cellulose fibre layer, the hot-melt adhesive layer having a melting point at a temperature above 80°C

Description

Description Title of the invention: NOISE-REDUCING HEAT-SEALING PAPER FOR PACKAGING A SOLID PRODUCT technical field

[0001] The invention relates to the technical field of heat-sealing papers suitable for use in packaging, more particularly the packaging of a solid product, such as sanitary napkins.

[0002] The invention also relates to a method for manufacturing heat-sealing paper for packaging a solid product. State of the art

[0003] It is necessary to package solid products, such as sanitary napkins, in protective packaging, particularly during transport. The packaging for this type of consumer product should be discreet so as not to disturb the users.

[0004] Generally, the packaging for these solid products, such as sanitary napkins, is in the form of a film made mostly of plastic.

[0005] However, in recent years, legislation in many countries has been reducing the use of plastic in all types of industries. Therefore, manufacturers of plastic films for packaging products, especially solids, must find alternative packaging materials to maintain their properties, such as low cost and good protection.

[0006] For this purpose, manufacturers of packaging films for products, especially solids, have replaced plastic with paper fiber packaging materials where the fibers are glued to a specific location, where the weld for closing the packaging is made.

[0007] However, such a method requires a high degree of adaptability of the machines to accommodate differences in the dimensions of the solid products to be packaged, such as sanitary napkins.

[0008] Indeed, sealing the packaging by gluing then requires modifying the packaging devices according to the different dimensions of the solid products.

[0009] Thus, in order to adapt to different dimensions, these devices must undergo heavy modifications resulting in a heavy and costly packaging process.

[0010] Alternatively, manufacturers have developed heat-sealable paper packaging incorporating a layer of plastic, usually polyethylene terephthalate (PET), which allows for sealing the plastic. This eliminates the issue of machine compatibility, thereby reducing the cost of the process. However, the use of plastic, even in small quantities, raises environmental concerns.

[0011] Another method involves a water-based heat-sealing paper made by coating the paper with a cold, water-based adhesive.

[0012] This method requires applying a layer of aqueous-phase glue and then removing all the water present in the aqueous-phase glue, the glue being composed of approximately 60% water, in order to leave only pure glue or glue extract.

[0013] Thus, in order to leave only the minimum quantity necessary for this process, it is impossible to make this deposit in one go because the quantity of water deposited would be too great and would have the effect of damaging, or even breaking, the paper strip.

[0014] Therefore, manufacturers apply several successive layers of water-based glue, each layer being smaller. Each glue-coating step is followed by a hot-drying step to reduce the water content of the glue during the coating process. Consequently, this process is energy-intensive and expensive, making paper use very costly and thus limiting its use.

[0015] Moreover, to meet the need for discretion when using paper for packaging sanitary napkins, for example, the paper must have specific characteristics that prevent the use of aqueous glue because the latter is absorbed by the layer of cellulose fibers specific to this use.

[0016] The invention therefore falls within this context and seeks to resolve all of the aforementioned drawbacks.

[0017] Thus, the invention seeks to produce a less expensive, ecological heat-sealing paper, adaptable to different packaging devices for solid products, including sanitary napkins, all while having reduced noise during its use, particularly when crumpling. Presentation of the invention

[0018] The invention relates to a heat-sealing paper that is less expensive, ecological and adaptable to different machines for packaging solid products, including sanitary napkins, while having reduced noise during use, particularly when crumpling.

[0019] An additional object of the invention relates to a method for manufacturing a fast and less expensive heat-sealing paper according to the invention, said paper being suitable for packaging, in particular sanitary napkins.

[0020] For this purpose, a heat-sealable paper has been developed for packaging a solid product comprising at least one layer of cellulose fibers, said cellulose fibers having a density of between 1.2 and 1.7 g / cm³. 3 and a porosity between 30% and 80% and at least one layer of hot melt adhesive.

[0021] According to the invention, at least one layer of hot-melt adhesive is deposited on the cellulose fiber layer, discontinuously over the entire length and width of the cellulose fiber layer, the hot-melt adhesive layer having a melting point at a temperature above 80°C.

[0022] It is therefore understood that the layer of hot melt adhesive does not contain water and is deposited hot, avoiding the long and costly process of cold application of the adhesive.

[0023] Thus, a heat-sealable paper without a layer of plastic material is obtained, allowing it to be produced in an environmentally friendly and less expensive way, so that when the paper is exposed to a temperature above 80°C, the layer of hot-melt glue melts and forms a bond with the cellulose fibers to create a rigid and resistant structure.

[0024] Furthermore, the presence of a hot-melt adhesive layer eliminates the successive coating and drying steps required when using a cold, water-based adhesive, a process that is both cumbersome and expensive. Indeed, using a waterless adhesive applied with heat avoids the need for multiple layers of water-based glue.

[0025] Furthermore, the presence of a heat-activated hot-melt adhesive layer makes the heat-sealable paper suitable for any packaging device for solid products, including sanitary napkins. Indeed, to seal the heat-sealable paper to itself for packaging, it is simply necessary to heat the heat-sealable paper sufficiently to reactivate the hot-melt adhesive.

[0026] Depositing the hot melt adhesive layer onto the cellulose fiber layer in a discontinuous manner creates a heat-sealing paper with a hot melt adhesive layer that is not evenly distributed over the cellulose fiber layer.

[0027] The term "discontinuous" refers to the fact that the hot melt adhesive layer is distributed unevenly across the entire width and length of the cellulose fiber layer.

[0028] Indeed, following the deposition of the hot melt adhesive layer on the cellulose fiber layer, said hot melt adhesive layer groups together into small aggregates arranged in an uncontrolled manner over the entire length and width of the cellulose fiber layer.

[0029] It is therefore understood that the term discontinuous relates to the random way in which the small aggregates of glue will be distributed on the layer of cellulose fibers and not to a discontinuous distribution because it is not continuous.

[0030] Similarly, it is understood that the layer of cellulose fibers, by the density and porosity of its fibers, makes it possible to produce a packaging paper that is not noisy during its use, more particularly during, for example, a crumpling operation of said paper according to the invention.

[0031] The paper can have a density of between 20 g / m 2 and 40 g / m 2The paper can have a porosity ranging from 2800 cm³ (min-l-cm²) to 6200 cm³ (min-l-cm²). The application of a layer of hot, waterless glue in a paste-like consistency on the surface prevents water from penetrating the paper through its porosity. It is this porous nature that gives the paper its quiet characteristics.

[0032] The term "porosity between 30% and 80%" refers to the fact that the porosity of cellulose fibers can be measured in terms of the volume of the pores relative to the volume total cellulose fiber.

[0033] In a particular embodiment, the hot melt adhesive layer comprises a hot melt resin mixture in contact with the cellulose fiber layer, such that when the paper is exposed to a temperature above 80°C, the hot melt resin adhesive layer melts and forms a bond with the cellulose fibers and the thermoplastic polymer layer.

[0034] Preferably, the hot melt adhesive layer is deposited on the cellulose fiber layer with a density of 1 to 8 g / m². 2 .

[0035] In a more preferred embodiment, the hot melt adhesive layer is deposited on the cellulose fiber layer with a density of 2 to 5 g / m². 2

[0036] Preferably, the hot melt adhesive layer is deposited on the cellulose fiber layer in a single pass.

[0037] The term "density" refers to the fact that on a surface of one square meter of cellulose fiber, there are between 1 and 8 grams of hot melt glue.

[0038] Thus, using a small amount of hot melt glue reduces the manufacturing cost of such paper, while producing a heat-sealable paper with sufficient bonding for packaging solid products, including sanitary napkins.

[0039] In a particular embodiment, the cellulose fiber layer and the hot melt adhesive layer are arranged so that the deposition of the hot melt adhesive layer on the cellulose fiber layer forms several deposits of said hot melt adhesive on the cellulose fiber layer, said deposits being interconnected with each other on the cellulose fiber layer.

[0040] Thus, the surface tension of the hot melt glue and that of the cellulose fiber layer form several deposits of said hot melt glue on the cellulose fiber layer, said deposits remaining connected to each other on the cellulose fiber layer.

[0041] Thus, the layer of hot melt glue, through its surface tension, groups together into points of aggregates linked to the cellulose fibers.

[0042] Indeed, the amount of hot melt adhesive is such that its surface tension creates an unevenly deposited layer, forming areas with less adhesive than areas with more. These areas with more adhesive form the deposits. This uneven distribution of the hot melt adhesive is due to the small amount of adhesive applied to the cellulose fiber layer.

[0043] Consequently, the hot melt glue is difficult to spread, which forms aggregates of hot melt glue on the cellulose fiber layer.

[0044] Thus, such a layer of hot melt adhesive allows for sufficient bonding to The packaging of solid products, particularly sanitary napkins. However, the uneven distribution of the hot melt adhesive deposits does not allow for a watertight bond and is therefore poorly suited for use with liquid products, for example.

[0045] In a preferred embodiment, the hot melt adhesive deposits are distributed inhomogeneously over the cellulose fiber layer.

[0046] The random distribution of hot melt adhesive deposits is due to the specific way the hot melt adhesive is spread. Because the adhesive is spread over a large area, it clumps together in small aggregates in random areas on the cellulose fiber layer.

[0047] More specifically, the surface tension of the glue does not allow the formation of a uniform glue layer and creates a non-uniform coating which forms a network of random glue beams.

[0048] In a particular embodiment, the cellulose fiber layer comprises a mixture of long cellulose fibers having a length greater than 2 mm and short cellulose fibers having a length less than or equal to 2 mm.

[0049] Blending long and short cellulose fibers can optimize mechanical strength. Long fibers can form a strong structural network that improves the paper's tensile and tear resistance. Short fibers can fill the spaces between the long fibers, creating a denser, more cohesive structure. Short fibers can also contribute to a smoother, more uniform surface, facilitating the even application of hot melt adhesive. Blending short and long fibers allows for fine-tuning mechanical properties by offering an optimal balance between rigidity and flexibility.

[0050] In a particular embodiment, the proportion of long cellulose fibers is greater than the proportion of short cellulose fibers.

[0051] In one embodiment, the cellulose fiber layer comprises a thickness of between 20 and 50 micrometers.

[0052] Preferably, the heat-sealing paper has a thickness between 0.1 and 0.4 millimeters.

[0053] Preferably, the cellulose fiber layer comprises between 20% and 80% long fibers and between 20% and 80% short fibers.

[0054] These proportions of long and short fibers can ensure an optimal balance between the structural strength provided by the long fibers and the surface density provided by the short fibers, enabling optimal heat sealing. Furthermore, these proportions can reduce dimensional changes during heating and cooling during the heat-sealing process. In particular, these proportions can allow for stable and reproducible manufacturing with consistent properties.

[0055] The term "long fibers" refers to cellulose fibers measuring over 2 millimeters. preferably between 2 and 3 millimeters.

[0056] As for "short fibers", this refers to cellulose fibers measuring less than 2 millimeters, preferably between 1 and 2 millimeters.

[0057] In one particular embodiment, the cellulose fiber layer comprises between 40% and 60% long fibers and between 40% and 60% short fibers.

[0058] In a preferred embodiment, the cellulose fiber layer comprises 55% long fibers and 45% short fibers.

[0059] In a particular embodiment, the cellulose fiber layer comprises cellulose fibers having a diameter between 10 and 40 micrometers.

[0060] Such dimensions of cellulose fibers make it possible to obtain fine cellulose fibers that can be organized in a three-dimensional way in order to create so-called "open" papers, that is to say, having enough space between the fibers in order to have such porosity, but also in order to create a paper with reduced noise during its use, in particular during a crumpling operation.

[0061] In a preferred embodiment, the cellulose fiber layer comprises between 50% and 80% by volume of microscopic pores with a diameter between 10 and 50 micrometers and between 20% and 50% by volume of macroscopic pores with a diameter between 50 and 200 micrometers, said volume percentages and pore diameters being determined by porosimetry.

[0062] Microscopic pores allow for controlled penetration of the molten adhesive, creating effective mechanical anchoring and thus optimized adhesion of the hot melt glue. The specific pore distribution can create multiple anchoring points that reinforce adhesion and resist delamination. Macroscopic pores, in limited proportions, can prevent excessive adhesive penetration that would reduce the effectiveness of the heat seal. Furthermore, the specific pore distribution maintains the sealing properties necessary for packaging while allowing adhesion. This porous structure can also improve resistance to thermal stresses during the heat-sealing process.

[0063] Still with the aim of forming a low-noise cellulosic fiber layer, the cellulose fiber layer comprises a composition with numerous microscopic and macroscopic pores.

[0064] The invention also relates to a method for manufacturing a heat-sealable paper according to the invention and includes at least the steps of continuously supplying paper comprising at least one layer of cellulose fibers, continuously hot-coating the hot-melt adhesive onto at least one face of the cellulose fiber layer, said hot-melt adhesive coating being carried out so as to deposit between 1 and 8 grams of hot-melt adhesive onto the surface of the cellulose fiber layer per square meter, so as to form discontinuous deposits of said hot-melt adhesive on the cellulose fiber layer, and cooling the hot-melt adhesive on the fiber layer. cellulose and continuous winding of heat-sealable paper.

[0065] Indeed, the hot melt adhesive is hot-coated over the entire length and width of the cellulose fiber layer, resulting in a simple and efficient coating step.

[0066] The hot melt adhesive coating step is carried out continuously and in a single pass of the paper, that is to say that the side of the paper suitable for gluing receives the entire hot melt adhesive in a single coating.

[0067] In one particular embodiment, the coating step is carried out by a lip nozzle.

[0068] The coating stage is such as to form inhomogeneous deposits of said hot melt glue on the cellulose fiber layer.

[0069] Thus, a low grammage of glue per square meter of cellulose fiber layer makes it possible to obtain a saving of raw materials, but also to carry out the coating step in a single pass, consequently reducing production time and therefore increasing productivity, all while having sufficient bonding for the packaging of solid products, in particular sanitary napkins.

[0070] Furthermore, the fact that the hot coating step is applied to the entire surface of the paper allows for great adaptability of the process to different packaging machines, resulting in significant cost savings due to the absence of modifications to packaging machines for solid products, particularly sanitary napkins. Indeed, paper packaging films are usually glued and sealed at specific points. However, these points vary depending on the dimensions of the solid objects being packaged, such as sanitary napkins, making the processes specific to each packaging machine.

[0071] Preferably, the hot melt adhesive is applied to at least one side of the cellulose layer in a single pass.

[0072] Thus, the manufacturing process of heat-sealable paper is accelerated because it no longer requires the successive application of several layers of glue, each separated by a drying step to reduce the glue's water content and prevent it from weighing down the cellulose fiber layer, which can lead to breakage of the cellulose fibers. Brief description of the figures

[0073] Other advantages and features of the present invention are now described by means of purely illustrative and in no way limiting examples of the scope of the invention, and from the accompanying drawings, in which the various figures represent:

[0074] [Fig. 1] is a schematic side view representation of the heat-sealing paper, according to the invention.

[0075] [Fig. 2] is a schematic perspective representation of the heat-sealing paper.

[0076] [Fig. 3] is a schematic representation of the process for manufacturing heat-sealing paper, according to the invention.

[0077] In the description that follows, identical elements, by structure or by function, appearing on different figures retain, unless otherwise specified, the same references. Description of the implementation methods

[0078] With reference to [Fig. 1] to [Fig. 2], the present invention relates to a heat-sealing paper 1 for the packaging of a solid product, in particular sanitary napkins.

[0079] The heat-sealing paper 1 comprises a layer of cellulose fibers 2 and a layer of hot melt adhesive 3, said layer of hot melt adhesive 3 is in contact with the layer of cellulose fibers 2, so that when the paper 1 is exposed to a temperature of 180°C, the layer of hot melt adhesive 3 melts and forms a bond with the cellulose fibers 2.

[0080] More specifically, and in order to obtain a heat-sealable paper 1 that makes little or no noise when used as packaging paper, particularly for sanitary napkins, the cellulose fiber layer 2 has a density of 1.5 g / cm² 3 , as well as a porosity of 60%.

[0081] The hot melt adhesive layer 3 is deposited on the cellulose fiber layer 2 discontinuously over the entire length and width of the cellulose fiber layer 2, the hot melt adhesive layer having a melting point above a temperature of 100°C.

[0082] The heat-sealable paper 1 comprises a layer of hot-melt adhesive 3, which is deposited on the layer of cellulose fibers 2 with a density of three g / m² 2 .

[0083] Thus, three grams of hot melt glue 3 are obtained on a surface of one square meter of the cellulose fiber layer 2.

[0084] In this way, the heat-sealable paper 1 has non-uniform hot melt glue dots 3, forming a random network of hot melt glue dots 3.

[0085] The cellulose fiber layer 2 and the hot melt adhesive layer 3 are arranged so that the hot melt adhesive layer 3 is deposited on the cellulose fiber layer 2 forms several deposits of said hot melt glue 3 on the cellulose fiber layer 2, said deposits being separated from each other on the cellulose fiber layer 2.

[0086] The surface tension of the hot melt adhesive 3 forms several deposits of the hot melt adhesive 3 on the cellulose fiber layer 2, said deposits being separated from each other on the cellulose fiber layer 2. The deposits of the hot melt adhesive 3 are distributed inhomogeneously on the cellulose fiber layer 2.

[0087] Heat-sealing paper 1 comprises a mixture of long and short cellulose fibers 2, more specifically the proportion of long cellulose fibers represents 75% of the total cellulose fibers 2, i.e. 25% of short cellulose fibers.

[0088] The cellulose fiber layer 2 is 37 micrometers thick, for a heat-sealing paper thickness of 0.25 of 1 millimeter.

[0089] Still with the aim of obtaining a heat-sealable paper that is not too noisy, the layer of fibers Cellulose 2 comprises 60% microscopic pores with an average size of 26 micrometers and 40% macroscopic pores with an average size of 123 micrometers.

[0090] As illustrated in [Fig. 3], the process 10 for manufacturing heat-sealable paper 1 successively implements a step of continuous supply of paper comprising a layer of cellulose fibers 2, continuous hot coating of hot melt adhesive 3 on one face of the layer of cellulose fibers 2, said coating of the hot melt adhesive 3 is carried out so as to deposit between 1 and 8 grams of hot melt adhesive 3 on the surface of the layer of cellulose fibers 2 per square meter, so as to form discontinuous deposits of said hot melt adhesive on the layer of cellulose fibers, cooling of the hot melt adhesive 3 on the layer of cellulose fibers 2 and continuous winding of the heat-sealable paper 1.

[0091] The process for packaging solid products, in particular sanitary napkins, includes welding and cutting steps of the heat-sealable paper 1 by a welding system comprising a blade and at least one hot press device for the heat-sealable paper 1. Thus, the cooled hot melt adhesive 3 is reactivated, which allows two parts of the heat-sealable film to be properly bonded together, in order to obtain packaging for solid products, satisfactory in particular for a sanitary napkin.

[0092] Indeed, in order to cut and seal the heat-sealable paper 1, the heat-sealable paper 1 is hot-pressed on either side of a blade to stretch it at a precise point intended for cutting. The hot pressure reactivates the hot-melt adhesive and allows the two parts of the heat-sealable paper to be sealed together.

[0093] The coating step is carried out by a lip nozzle in a single pass of the cellulose fiber layer 2 over the lip nozzle.

[0094] The 10-layer process involves applying three grams of hot melt glue 3 per square meter on one face of the cellulose fiber layer 2, over the entire width and length of the cellulose fiber layer 2.

[0095] The coating stage and the surface tension of the hot melt adhesive 3 form discontinuous deposits of said hot melt adhesive 3 on the cellulose fiber layer 2.

[0096] The coating step is such as to form random deposits of said hot melt glue 3 on the cellulose fiber layer 2.

[0097] The preceding description clearly explains how the invention achieves its objectives, namely reducing the production cost of packaging for solid products, while being environmentally friendly and allowing great adaptability of the process to different packaging devices for solid products, all while providing a quiet paper during its use.

[0098] In any event, the invention is not limited to the embodiments specifically described in this document, and extends in particular to all means equivalents and to any technically operative combination of these means.

Claims

Demands

1. Heat-sealable paper (1) for packaging a solid product comprising: At least one layer of cellulose fibres (2), said cellulose fibres comprising a density of between 1.2 and 1.7 g / cm² 3 measured by pycnometry and a porosity between 30% and 80% measured by porosimetry; and At least one layer of hot melt adhesive (3), Characterized in that at least one layer of hot melt adhesive (3) is deposited on the layer of cellulose fibers (2) discontinuously over the entire length and width of the layer of cellulose fibers (2), the layer of hot melt adhesive having a melting point at a temperature above 80°C.

2. Paper (1) according to claim 1, characterized in that the hot melt adhesive layer (3) is deposited on the cellulose fiber layer (2) with a density of 1 to 8 g / m² 2 .

3. Paper (1) according to claim 2, characterized in that the cellulose fiber layer (2) and the hot melt adhesive layer (3) are arranged so that the deposition of the hot melt adhesive layer (3) on the cellulose fiber layer (2) forms several deposits of said hot melt adhesive (3) on the cellulose fiber layer (2), said deposits being interconnected with each other on the cellulose fiber layer (2).

4. Paper (1) according to claim 3, characterized in that the deposits of the hot melt glue (3) are distributed inhomogeneously on the layer of cellulose fibers (2).

5. Paper (1) according to any one of the preceding claims, characterized in that the cellulose fiber layer (2) comprises a mixture of long cellulose fibers (2) having a length greater than 2 mm and short cellulose fibers (2) having a length less than or equal to 2 mm.

6. Paper (1) according to the preceding claim, characterized in that the cellulose fibre layer (2) comprises between 20% and 80% long fibres and between 20% and 80% short fibres.

7. Paper (1) according to any one of the preceding claims, characterized in that the cellulose fibre layer (2) comprises cellulose fibres comprising a diameter between 10 and 40 micrometres.

8. Paper (1) according to any one of the preceding claims, characterized in that the cellulose fibre layer (2) comprises between 50% and 80% by volume of microscopic pores having a diameter of between 10 and 50 micrometers and between 20 and 50% by volume of macroscopic pores with a diameter between 50 and 200 micrometers, said volume percentages and pore diameters being determined by porosimetry.

9. A method (10) for manufacturing a heat-sealable paper (1) according to any one of claims 1 to 8, characterized in that it comprises at least the steps of: Continuous supply of paper comprising at least one layer of cellulose fibres (2); Continuous hot coating of a hot melt adhesive (3) on at least one face of the cellulose fiber layer (2), said coating of the hot melt adhesive (3) is carried out so as to coat between 1 and 8 grams of hot melt adhesive (3) on the surface of the cellulose fiber layer (2) per square meter, so as to form discontinuous deposits of said hot melt adhesive on the cellulose fiber layer; Cooling of the hot melt adhesive (3) on the cellulose fiber layer (2); and Continuous winding of the heat-sealing paper (1). Claim 10] Method (10) according to the preceding claim, characterized in that the coating of the hot melt adhesive (3) on at least one face of the cellulose fiber layer (2) is carried out in a single pass.

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