HEAT-SEALING PAPER FOR FILTERING AND PACKAGING SOLID PRODUCTS

Abstract

The invention relates to a heat-sealable paper (1) for packaging a solid product comprising at least one layer of cellulose fibers (2) and at least one layer of hot-melt adhesive (3). According to the invention, the at least one layer of hot-melt adhesive (3) is deposited discontinuously on the layer of cellulose fibers (2) along 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.

Description

Title of the invention: HEAT-SEALING PAPER FOR FILTERING AND PACKAGING A SOLID PRODUCT technical field

[0001] The invention relates to the technical field of heat-sealing papers suitable for use for filtration, more particularly filtration in order for example to allow flavors to pass through while retaining impurities such as for example as tea or coffee bag paper or as paper to allow liquids or vapors to pass through.

[0002] The invention also relates to a method for manufacturing heat-sealable paper for use, in particular, as filter paper. Prior art

[0003] It is sometimes necessary to have packaging that allows fluids to pass through, depending on the application. Indeed, some applications require that flavors pass through while preventing impurities from passing through, such as tea bags or coffee filters. Whereas in other applications, such as the packaging of garments after dry cleaning, the packaging must allow water to pass through so that it evaporates; otherwise, the garment cannot dry effectively. Generally, the packaging for these garments is in the form of a film made primarily of plastic.

[0004] 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 product packaging, particularly clothing, must find alternative packaging materials to maintain their properties, such as low cost, good protection, and good ventilation.

[0005] For this purpose, manufacturers of product packaging films have replaced plastic with paper fiber packaging materials, the latter of which are glued at a precise location, on which the weld for closing the packaging is made.

[0006] However, such a method requires a high degree of machine adaptability to accommodate the varying dimensions of the solid products to be packaged, such as clothing, but also tea bags. Indeed, sealing the packaging material by gluing necessitates modifying the packaging devices according to the different dimensions of the solid products.

[0007] Thus, in order to adapt to different dimensions, these devices must undergo heavy modifications resulting in a heavy and costly conditioning process.

[0008] Alternatively, manufacturers have produced a heat-sealable paper packaging comprising a layer of plastic, generally polyethylene terephthalate known as "PET," which allows the plastic to be sealed. This eliminates the problem of machine compatibility, thereby reducing the cost of the process. However, the use of plastic, even in small quantities, raises environmental concerns.

[0009] Another method consists of an aqueous phase heat-sealing paper made by coating the paper with a cold aqueous glue.

[0010] This method requires depositing a layer of aqueous-phase glue and then removing all the water present in the aqueous-phase glue, said glue being composed of approximately 60% water, in order to leave only pure glue or glue extract.

[0011] 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 large and would have the effect of damaging, or even breaking, the paper strip.

[0012] Consequently, 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 phase of the glue during the coating process. This process is therefore energy-intensive and costly, making the use of paper very expensive and thus limiting its use.

[0013] Moreover, the nature of the cellulose fibers present in the paper for these uses is such that coating is almost impossible. Indeed, since the cellulose fiber layer is open, that is to say, having numerous pores, the aqueous glue passes through and / or is absorbed by the cellulose fiber layer, rendering the bonding ineffective.

[0014] The invention therefore falls within this context and seeks to resolve all of the aforementioned drawbacks.

[0015] Thus, the invention seeks to produce a less expensive, environmentally friendly heat-sealing paper adaptable to various garment packaging devices, while allowing for effective filtration and ventilation. Presentation of the invention

[0016] The invention relates to a heat-sealing paper that is less expensive, ecological and adaptable to different garment packaging machines, while allowing efficient filtration and aeration.

[0017] 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 clothing, but also suitable for filtration.

[0018] For this purpose, a heat-sealing paper has been developed for the filtration and packaging of a solid product comprising at least one layer of cellulose fibers, said cellulose fibers comprising a density between 0.9 and 1.6 g / cm3, a porosity between 50% and 90%, a surface treatment with hydrophobic or hydrophilic agents and at least one layer of hot-melt adhesive.

[0019] According to the invention, at least one layer of hot melt glue is deposited on the cellulose fiber layer, discontinuously over the entire length and width of the cellulose fiber layer, the hot melt glue layer having a melting point at a temperature above 80°C.

[0020] 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 depositing the adhesive.

[0021] Thus, a heat-sealing paper without a layer of plastic material is obtained, allowing it to be produced in an environmentally friendly and less expensive manner, 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.

[0022] Furthermore, the presence of a layer of hot-melt adhesive eliminates the successive coating and drying steps required when using a cold-applied water-based adhesive, which makes the process cumbersome and expensive. Indeed, using a waterless adhesive applied with heat avoids the need to apply multiple layers of water-based adhesive.

[0023] Furthermore, the presence of a heat-activated hot-melt adhesive layer makes the heat-sealable paper adaptable to any packaging device for solid products, particularly press copies. 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.

[0024] Depositing the hot melt adhesive layer on the cellulose fiber layer in a discontinuous manner makes it possible to create a heat-sealing paper comprising a hot melt adhesive layer that is not distributed homogeneously on the cellulose fiber layer.

[0025] The term "discontinuous" means that the hot melt adhesive layer is distributed unevenly over the entire width and length of the cellulose fiber layer.

[0026] 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.

[0027] 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.

[0028] Similarly, it is understood that the layer of cellulose fibers, by the density and porosity of its fibers, as well as by the treatments it undergoes depending on its use, makes it possible to produce a filtering or aerating packaging paper during its use, more particularly when used, for example, as a tea bag or as packaging paper for clothes coming out of the dry cleaners.

[0029] The term "porosity between 50% and 90%" means that the porosity of cellulose fibers can be measured in terms of the volume of the pores relative to the total volume of the cellulose fiber.

[0030] The treatment with hydrophobic or hydrophilic agents on the cellulose fibre layer can be total or partial depending on the use of the heat-sealing paper.

[0031] 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.

[0032] Preferably, the hot melt adhesive layer is deposited on the cellulose fiber layer with a density of 1 to 8 g / m2.

[0033] 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

[0034] More preferably, the hot melt adhesive layer is deposited on the cellulose fiber layer in a single pass.

[0035] By the term “density”, we mean to define the fact that on a surface of one square meter of cellulose fiber, we find between 1 and 8 grams of hot melt glue.

[0036] Thus, using a small amount of hot melt glue makes it possible to reduce the cost of manufacturing such paper, while producing a heat-sealing paper whose bonding is sufficient for packaging solid products, including clothing, or even as tea bags.

[0037] In a particular embodiment, the cellulose fiber layer and the hot melt adhesive layer are arranged such that the deposition of the hot melt adhesive layer onto 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.

[0038] 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.

[0039] Thus, the layer of hot melt adhesive, by its surface tension, groups together in points of aggregates linked to the cellulose fibers.

[0040] Indeed, the amount of hot melt adhesive is such that the surface tension of the hot melt adhesive creates a layer of hot melt adhesive with irregular deposition, forming areas with a lower quantity of adhesive than other areas with a higher quantity; these areas with a higher quantity of adhesive form the deposits. This non-uniform distribution of the hot melt adhesive is due to the small amount of hot melt adhesive deposited on the cellulose fiber layer.

[0041] Consequently, the hot melt glue is difficult to spread, which forms aggregates of hot melt glue on the cellulose fiber layer.

[0042] Thus, such a layer of hot melt adhesive provides sufficient bonding for packaging solid products, particularly clothing. However, the uneven distribution of the hot melt adhesive deposits prevents a watertight seal and is therefore poorly suited for use with liquid products, for example.

[0043] In a preferred embodiment, the hot melt adhesive deposits are distributed inhomogeneously on the cellulose fiber layer.

[0044] The random distribution of the hot melt adhesive deposits is due to the particular way the hot melt adhesive is spread. Because the adhesive is spread over a large surface area, it clumps together in small aggregates in random areas on the cellulose fiber layer.

[0045] More particularly, 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.

[0046] In a particular embodiment, the cellulose fiber layer comprises a mixture of long and short cellulose fibers.

[0047] In a particular embodiment, the proportion of long cellulose fibers is greater than the proportion of short cellulose fibers

[0048] In one embodiment, the cellulose fiber layer comprises a thickness of between 20 and 50 micrometers.

[0049] Preferably, the heat-sealing paper comprises a thickness of between 0.1 and 0.4 millimeters.

[0050] Preferably, the cellulose fiber layer comprises between 20% and 80% long fibers and between 20% and 80% short fibers.

[0051] The term “long fibers” means cellulose fibers measuring over 2 millimeters, preferably between 2 and 3 millimeters.

[0052] As for "short fibers", we mean cellulose fibers measuring less than 2 millimeters, preferably between 1 and 2 millimeters.

[0053] In a particular embodiment, the cellulose fiber layer comprises between 40% and 60% long fibers and between 40% and 60% short fibers.

[0054] In a preferred embodiment, the cellulose fiber layer comprises 45% long fibers and 55% short fibers.

[0055] In a particular embodiment, the cellulose fiber layer comprises cellulose fibers having a diameter between 10 and 30 micrometers.

[0056] Such dimensions of cellulose fibers make it possible to obtain fine cellulose fibers that can be organized in a three-dimensional way so as to create so-called "open" papers, that is to say, having enough space between the fibers in order to have such porosity, but also so as to create a paper that can filter effectively or that can condition an object while allowing the latter to be aerated.

[0057] In a preferred embodiment, the cellulose fiber layer comprises between 50% and 80% microscopic pores ranging from 0.5 to 2 micrometers and between 20% and 50% macroscopic pores ranging from 5 to 50 micrometers.

[0058] Still with the aim of forming a filtering and aerating layer of cellulose fibers, the cellulose fiber layer comprises a composition with numerous microscopic and macroscopic pores.

[0059] The composition of cellulose fiber, particularly in terms of the distribution of microscopic and macroscopic pores, varies according to its use.

[0060] Preferably, the microscopic and macroscopic pores are distributed uniformly in the cellulose fiber layer.

[0061] The invention also relates to a method for manufacturing a heat-sealable paper according to the invention and comprises at least the steps of continuously supplying paper comprising at least one layer of cellulose fibers, treating the cellulose fiber layer with hydrophobic or hydrophilic agents, 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 adhesive hot melt on the cellulose fiber layer and continuous winding of the heat-sealing paper.

[0062] Indeed, the hot melt adhesive is hot-coated over the entire length and width of the cellulose fiber layer, which makes it possible to obtain a simple and efficient coating step.

[0063] The hot melt glue 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 glue in a single coating.

[0064] In a particular embodiment, the coating step is carried out by a lip nozzle.

[0065] Preferably, the hot melt adhesive coating step applies a quantity of hot melt adhesive so as to form discontinuous deposits of said hot melt adhesive on the cellulose fiber layer

[0066] The coating step is such as to form inhomogeneous deposits of said hot melt glue on the cellulose fiber layer.

[0067] 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 clothing or tea or coffee.

[0068] Furthermore, the fact that the hot coating step is carried out on the entire surface of the paper allows for a high degree of adaptability of the process to different packaging machines and, consequently, significant cost savings due to the absence of modifications to packaging machines for solid products, particularly press copies. Indeed, paper packaging films are usually glued and sealed at specific points. However, these specific points vary depending on the dimensions of the solid objects to be packaged, such as press copies, making the processes specific to each packaging machine.

[0069] Preferably, the hot melt adhesive is applied to at least one side of the cellulose layer in a single pass.

[0070] Thus, the manufacturing process of the heat-sealable paper is accelerated because it does not require plus the successive application of several layers of glue, separated from each of them by a drying stage in order to reduce the proportion of water in the glue so as not to weigh down the layer of cellulose fibers, which can cause a break in said cellulose fibers. Brief description of the figures

[0071] 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:

[0072] [Fig-1] is a schematic side view representation of the heat-sealing paper, according to the invention.

[0073] [Fig.2] is a schematic perspective representation of the heat-sealing paper.

[0074] [Fig.3] is a schematic representation of the paper manufacturing process heat sealant, according to the invention.

[0075] In the following description, identical elements, by structure or by function, appearing on different figures retain, unless otherwise specified, the same references. Description of the implementation methods

[0076] 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 clothing or tea or coffee.

[0077] 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.

[0078] More specifically, and in order to obtain a heat-sealing paper 1 that can effectively filter tea as packaging paper, the cellulose fiber layer 2 comprises a density of 1 g / cm3, as well as a porosity of 80%.

[0079] Similarly, and again in order to filter the tea effectively, more specifically to allow the flavors to diffuse into the water without any solid particles remaining, the cellulose fibers undergo treatment with hydrophobic agents. Without departing from the scope of the invention, this treatment may be partial or total.

[0080] 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.

[0081] The heat-sealing paper 1 comprises a layer of hot-melt adhesive 3 deposited on the layer of cellulose fibers 2 with a density of three g / m2.

[0082] Thus, three grams of hot melt glue 3 are obtained on a surface of one square meter of the cellulose fiber layer 2.

[0083] In this way, the heat-sealing paper 1 has non-uniform hot melt adhesive dots 3, forming a random network of hot melt adhesive dots 3.

[0084] 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 separated from each other on the cellulose fiber layer 2.

[0085] 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.

[0086] The heat-sealing paper 1 comprises a mixture of long and short cellulose fibers 2, more particularly the proportion of long cellulose fibers 2 represents 80% of the total cellulose fibers 2, i.e. 20% of short cellulose fibers.

[0087] The cellulose fibre layer 2 is 50 micrometres thick, for a heat-sealing paper thickness of 0.1 of 0.5 millimetres.

[0088] Still with the aim of obtaining a heat-sealing filter paper 1, the cellulose fiber layer 2 comprises 80% microscopic pores with an average of 0.8 micrometers and 20% macroscopic pores with an average of 23 micrometers.

[0089] As illustrated in [Fig.3], the process 10 for manufacturing heat-sealable paper 1 successively implements a step of continuous paper supply comprising a layer of cellulose fibers 2, treatment of the layer of cellulose fibers 2 with hydrophobic agents, continuous hot coating of the 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.

[0090] The process for packaging solid products, in particular tea, includes welding and cutting steps of the heat-sealing paper 1 by a welding system comprising a blade and at least one hot press device for the heat-sealing paper 1. Thus, the cooled hot melt adhesive 3 is reactivated, which makes it possible to properly bond two parts of the heat-sealing film together, in order to obtain packaging of solid products, satisfactory in particular for tea.

[0091] 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 the heat-sealable paper 1 at a precise point intended to be cut. The hot pressure reactivates the hot-melt adhesive and allows two parts of the heat-sealable paper to be sealed together.

[0092] The coating step is carried out by a lip nozzle in a single pass of the cellulose fiber layer 2 over the lip nozzle.

[0093] The process 10 applies three grams of hot melt adhesive 3 per square meter to one face of the cellulose fiber layer 2, over the entire width and length of the cellulose fiber layer 2.

[0094] The coating step 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.

[0095] The coating step is such as to form random deposits of said hot melt glue 3 on the cellulose fiber layer 2.

[0096] The preceding description clearly explains how the invention makes it possible to achieve the objectives it has set for itself, namely the reduction of the cost of production of a packaging of solid products, while being ecological and allowing a great adaptability of the process to the different packaging devices of solid products, all while providing a filtering and aerating paper.

[0097] In any event, the invention cannot be limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically operative combination of these means.

Claims

Demands

1. Heat-sealable paper (1) for filtering and packaging a solid product comprising: - At least one layer of cellulose fibers (2), said cellulose fibers having a density between 0.9 and 1.6 g / cm3, a porosity between 50% and 90%, a surface treatment with hydrophobic or hydrophilic agents; 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, 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.

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 fibre layer (2) comprises a mixture of long and short cellulose fibres (2).

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 fibre of cellulose comprising a diameter between 10 and 30 micrometers.

8. Paper (1) according to any one of the preceding claims, characterized in that the cellulose fibre layer (2) comprises between 50% and 80% microscopic pores ranging from 0.5 to 2 micrometres and between 20% and 50% macroscopic pores ranging from 5 to 50 micrometres.

9. Paper (1) according to the preceding claim, characterized in that the microscopic and macroscopic pores are uniformly distributed in the cellulose fiber layer (2).

10. A method (10) for manufacturing a heat-sealable paper (1) according to any one of claims 1 to 5, characterized in that it comprises at least the steps of: - Continuously supplying a paper comprising at least one layer of cellulose fibers (2); - Treating the layer of cellulose fibers (2) with hydrophobic or hydrophilic agents; - Continuously hot-coating a hot-melt adhesive (3) onto at least one face of the layer of cellulose fibers (2), said coating of the hot-melt adhesive (3) being carried out so as to deposit between 1 and 8 grams of hot-melt adhesive (3) onto 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 the hot-melt adhesive (3) on the layer of cellulose fibers (2); and - Continuous winding of the heat-sealing paper (1).

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