FR3113070A1 - Paper and packaging bag, water-repellent, intended for the packaging of various products - Google Patents

Abstract

Paper (10) for making packaging bags of powdery material, comprising:a support structure formed from a matrix of cellulose fibers, at least one moisture resistance agent in a proportion of 0.1 to 10%, of at least one bonding agent in a proportion of 0.01 to 0.5%, of at least one dry strength agent in a proportion of 0.1 to 5%, and of at least one cohesive agent arranged to bind the elements of the support structure, in a proportion of 0.1 to 5%; the cellulose fibers being formed at more than 60% by softwood cellulose fibers; and a hydrophobic agent applied to at least one side of the support structure. Figure 2

Description

Paper and packaging bag, water-repellent, intended for the packaging of various products

The present invention relates to a paper used in the manufacture of powder material packaging.

The invention also relates to a paper bag for packaging powdery material, one ply of which is made from such paper.

The invention further relates to a method for producing such a paper.

STATE OF THE PRIOR ART

For the production of powder material packaging such as cement:

• the paper making up the bag must allow gluing operations, be mechanically resistant or even stretchable, and allow the evacuation of the air trapped in the packaging
• the bag produced must also form a moisture barrier to protect the product contained.

To this end, it is known to use a paper of which at least one face has undergone a plastic coating or is associated with a plastic film.

The problem with these solutions is that the bag or paper thus formed is not compostable and difficult to recycle.

The object of the present invention is in particular to obtain a paper and a bag forming a barrier to humidity, without having recourse to a film or a plastic coating.

In particular, a goal is to provide a solution that meets all or part of at least one of the following objectives:

- obtain a paper for packaging that is resistant to humidity, water-repellent or forming a water barrier, allowing gluing operations, mechanically resistant and possibly stretchable, while being wholly or partly compostable and/or recyclable;

- obtain a bag for packaging powdery material that is resistant to humidity, water-repellent or forms a water barrier, while being wholly or partly compostable and/or recyclable.

This object can be achieved by means of a paper for making packaging bags of powdery material, comprising:
- a support structure formed:
a matrix of cellulose fibers;
at least one humidity resistance agent in a proportion of 0.1 to 10%,
at least one bonding agent in a proportion of 0.01 to 0.5%,
at least one dry strength agent in a proportion of 0.1 to 5%, and
at least one cohesion agent arranged to bind the elements of the support structure, in a proportion of 0.1 to 5%;
the cellulose fibers being formed at more than 60% by resinous cellulose fibers;
-a hydrophobic agent applied to at least one face of the support structure.

Some preferred but non-limiting aspects are as follows.

In one paper implementation, the wet strength agent is polyamide epichlorohydrin.

In one implementation of the paper, the wet strength agent is formed in a proportion of 0.1 to 2%.

In one implementation of the paper, the sizing agent is of the alkenyl succinic anhydride type.

In a paper implementation, the sizing agent is formed in a proportion of 0.05 to 0.3%.

In a paper implementation, the dry strength agent is of the carboxymethyl cellulose type.

In a paper implementation, the dry strength agent is formed in a proportion of 0.2 to 2%.

In a paper implementation, the cohesive agent is of the cationic starch type.

In a paper implementation, the cohesive agent is formed in a proportion of 0.3 to 3%.

In a paper implementation, the hydrophobic agent is impregnated into the support structure.

In a paper implementation, the hydrophobic agent is impregnated with a deposit of between 1 and 8 g/m ² .

In an implementation of the paper, a hydrophobic character is conferred on the support by chromatogeny.

The invention also relates to a bag for packaging pulverulent material, comprising at least a first ply formed with such a paper.

Some preferred but non-limiting aspects of the bag are as follows.

In one implementation of the bag, the bag includes a second ply having a measurement of air permeability of less than 5 seconds according to a GURLEY ISO5636-5 index;
the assembly of the two plies being formed so that air can pass through the second ply and lodge between the first ply and the second ply.

In one implementation of the bag, the material of the second ply is of the kraft type.

In one implementation of the bag, the bag comprises a bonding scheme making it possible to produce a baffle or a chimney evacuating the air contained between the first ply and the second ply.

The invention further relates to a process for manufacturing such paper, comprising the following successive steps:
a) suspension of cellulose fibers;
b) addition to the suspension obtained in step a) of a dry strength agent for the support structure of the paper;
c) refining a mixture comprising the cellulose fibers and the dry strength agent;
d) addition of a moisture resistance agent to the refined mixture obtained at the end of step c);
e) adding a cohesion agent and a paper sizing agent to the result obtained at the end of step d);
f) shaping the result of step e) in order to conform the support structure in the form of a sheet;
g) application of a hydrophobic agent on at least one side of the sheet obtained in step f) by a surfacing process.

Other aspects, objects, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the appended drawings. on which ones :

There illustrates a perspective view of a paper bag according to the invention, folded and glued, prior to filling with powder material;

There illustrates a perspective view of a bag according to the invention;

There illustrates a schematic view of a method according to the invention.

DETAILED EXPLANATION OF PARTICULAR EMBODIMENTS

In the appended FIGS. 1 to 3 and in the remainder of the description, elements which are identical or similar in functional terms are identified by the same references. In addition, the various elements are not represented to scale so as to favor the clarity of the figures to facilitate understanding. Furthermore, the different modes or examples and variants are not mutually exclusive and can, on the contrary, be combined with one another.

In the remainder of the description, unless otherwise indicated, the terms “substantially”, “approximately”, “overall” and “of the order of” mean “within 10%”.

In the rest of the text, the proportions, in other words the doses, are expressed as a mass percentage with respect to the raw paper production.

The invention relates to a paper 10 for making powder material packaging bags, comprising:
a support structure formed:
a matrix of interwoven cellulose fibres,
at least one humidity resistance agent in a proportion of 0.1 to 10%,
at least one bonding agent in a proportion of 0.01 to 0.5%,
at least one dry strength agent in a proportion of 0.1 to 5%, and
at least one cohesion agent arranged to bind the elements of the support structure, in a proportion of 0.1 to 5%;
the cellulose fibers being formed at more than 60% by resinous cellulose fibers;
a hydrophobic agent applied to at least one side of the support structure.

The paper 10 thus obtained makes it possible to obtain characteristics of water repellency and barrier to humidity as well as mechanical resistance compatible with the creation of packaging of powdery material. Advantageously, this paper 10 is compostable and/or recyclable at least in part. Another advantage is the absence of plastic material.

Paper 10 is made from one or more pulps mixed in a pulper with water. In a preparation step, the dry strength agent is introduced into this diluted paste containing the cellulose fibers. Refining steps follow. Then the moisture resistance agent is added at the outlet of the refiners before being introduced into a mixer. The cohesion/retention agent and the bonding agent are then introduced. In one example, this introduction is carried out during a purification phase. In one example, the introduction of these two agents is carried out between a sub-step of the purification phase implementing cyclone purifiers and a sub-step of the purification phase implementing a volumetric purifier. The paper 10 is then shaped into sheet form by techniques known to those skilled in the art.

The process, illustrated in , can therefore be summarized according to the following successive steps:

a) suspension of cellulose fibers;

b) addition to the suspension obtained in step a) of a dry strength agent for the support structure of the paper 10;

c) refining a mixture comprising the matrix of cellulose fibers and the dry strength agent;

d) adding an agent for resisting the humidity of the support structure of the paper 10 to the refined mixture obtained at the end of step c);

e) adding a cohesion agent and an agent for bonding the support structure of the paper 10, to the result obtained at the end of step d);

f) shaping the result of step e) in order to conform the support structure in the form of a sheet;

g) application of a hydrophobic agent on at least one side of the sheet obtained in step f) by a surfacing process.

The cellulose fibers are advantageously formed at more than 60% by resinous cellulose fibers. This rate can be increased to use cellulose fibers made from 100% softwood. By increasing this rate, it is possible to increase the mechanical strength of the paper 10. Thus, by going from 60% to 100% in the rate of cellulose fibers derived from resinous trees, it is possible to increase the tear resistance of the paper by 30%. paper 10. Softwood fiber levels of 70, 80 or even 90% are entirely possible, but all values between 60% and 100% are plausible.

The moisture resistance agent consists in introducing into the fibrous suspension or chemical pulp, being developed, cationic polymers adsorbing on the surface of the fibers. After the formation of the sheet of paper 10, the wet sheet is dried and it is during this stage that the crosslinking of these polymers begins. It leads to the formation of a three-dimensional polymer network in the fibrous matrix. This network allows the paper 10 to retain its mechanical properties when in contact with water.

In an advantageous example, the moisture resistance agent is formed in a proportion of 0.1 to 2%. This proportion is calculated in active material relative to paper 10.

In one example, the wet strength agent may be polyamide epichlorohydrin (PAA-E). However, other moisture resistance agents can be used such as urea-formaldehyde (UF) resins, or glyoxal resins.

The sizing agent is used to impart water resistance properties to the paper 10 in order to control the penetration of liquids into the papers, mainly for printing and converting operations. Thus introduced into the fibrous suspension and adsorbed by the fibers before the formation of the sheet, they lower the surface energy of these fibers. Alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA) can be used as fining agent. They thus make it possible to produce a strongly glued paper. They can be implemented in a neutral or alkaline medium, thus making it possible to add mineral fillers such as calcium carbonate. In other examples, it is possible to use modified natural resins (resin-based glues), starch or modified starch. This reinforces the natural origin of the components of the paper 10.

In a preferred example, the bonding agent is formed in a proportion of 0.05 to 0.3%.

The dry strength agent improves the strength of the paper 10 in the dry state.

The dry strength agent can be chosen from starch, starches, latex, hemicelluloses, galactomannans, gelatins or polyamide-epichlorohydrin resins, taken alone or as a mixture. Advantageously, carboxymethylcelluloses (CMC) can be used as dry strength agent.

In an advantageous example, the dry strength agent is formed in a proportion of 0.2 to 2%.

The cohesive agent is arranged to bind the elements of the support structure. In one example, cationic starch can be used as a cohesive agent. It ensures the formation of a strong bond by forming bridges between the cellulose fibers due to the cationic charge. It also increases the dry strength and durability of the paper 10. The cationic starch also allows better retention of the sizing agent.

In a preferred example, the cohesion agent is formed in a proportion of 0.3 to 3%.

The paper support obtained before surfacing is advantageously manufactured with low air permeability and a closed structure, in order to deposit the hydrophobic agent mainly on the surface of the paper.

In one example, the hydrophobic agent is applied by impregnation by the so-called “size press” method, well known to those skilled in the art, of a hydrophobic agent on the support. This impregnation is done once the paper 10 is put in the form of a sheet. The impregnation can also take place from both sides, this makes it possible to increase the characteristics of barrier to humidity, of resistance to the wet state and the hydrophobic character of the paper 10. The impregnation consists in causing the fibers to penetrate the hydrophobic agent. This has the advantage of making the paper 10 hydrophobic and moisture barrier in the mass and not just on the surface as is the case with offline film coating techniques. This facilitates recycling and compostability. In this example, the hydrophobic agent is applied during a drying phase. The hydrophobic agent can also be applied by impregnation between a pre-drying sub-step of the drying phase and a post-drying sub-step of the drying phase, this step possibly including infrared drying.

In one example, the hydrophobic agent is impregnated until a deposit of between 1 and 8 g/m ² is reached.

In another example, the hydrophobic character is obtained by chromatogeny treatment of the support. In one example, the hydrophobic agent is applied after the drying phase.

The invention also relates to a paper bag for packaging pulverulent material, comprising at least the first outer ply formed with a paper as described above. This gives the bag 20 its moisture barrier characteristic. The paper illustrated on the , is thus shaped, folded, glued to form a container. The paper bag 20 thus formed is intended for manufacturers packaging powdery materials as illustrated in the .

In one example, the bag 20 includes a second ply whose air permeability measurement is less than 5 seconds GURLEY ISO5636-5 index. The assembly of the two plies is formed so that the air can pass through the second ply and lodge between the first ply and the second ply.

In one example, the fixing agent for the paper sheets is a glue.

In one example, the material of the second ply is of the kraft type.

Bag 20 may include at least one valve for filling operations. This valve can be formed in whole or in part by paper.

The diagram of the collages made is suitable for creating a baffle or deaeration chimney allowing the air contained between the first and the second ply to be evacuated.

Claims (17)

Paper (10) for making powder material packaging bags, comprising:
a support structure formed:
a matrix of cellulose fibers,
at least one humidity resistance agent in a proportion of 0.1 to 10%,
at least one bonding agent in a proportion of 0.01 to 0.5%,
at least one dry strength agent in a proportion of 0.1 to 5%, and
at least one cohesion agent arranged to bind the elements of the support structure, in a proportion of 0.1 to 5%;
the cellulose fibers being formed at more than 60% by resinous cellulose fibers;
a hydrophobic agent applied to at least one side of the support structure. The paper (10) for making powder material packaging bags according to claim 1, wherein the wet strength agent is polyamide epichlorohydrin. Paper (10) for making powder material packaging bags according to any one of claims 1 or 2, wherein the wet strength agent is formed in an amount of 0.1 to 2%. Paper (10) for making powder material packaging bags according to any one of claims 1 to 3, in which the sizing agent is of the alkenyl succinic anhydride type. Paper (10) for making powder material packaging bags according to any one of claims 1 to 4, in which the sizing agent is formed in a proportion of 0.05 to 0.3%. Paper (10) for making powder material packaging bags according to any one of claims 1 to 5, in which the dry strength agent is of the carboxymethyl cellulose type. Paper (10) for making powder material packaging bags according to any one of claims 1 to 6, wherein the dry strength agent is formed in an amount of 0.2 to 2%. Paper (10) for making powder material packaging bags according to any one of claims 1 to 7, in which the cohesive agent is of the cationic starch type. Paper (10) for making powder material packaging bags according to any one of claims 1 to 8, in which the cohesive agent is formed in a proportion of 0.3 to 3%. Paper (10) for making powder material packaging bags according to any one of claims 1 to 9, wherein the hydrophobic agent is impregnated into the support structure. Paper (10) for making powder material packaging bags according to claim 10, in which the hydrophobic agent is impregnated with a deposit of between 1 and 8 g/m ² . Paper (10) for making powder material packaging bags according to any one of Claims 1 to 9, in which a hydrophobic character is conferred on the support by chromatogeny. Bag (20) for packaging pulverulent material, comprising at least a first ply formed with the paper (10) according to any one of Claims 1 to 12. A powder material packaging bag (20) according to claim 13, comprising a second ply having a measurement of air permeability of less than five seconds according to a GURLEY ISO5636-5 index;
the assembly of the two plies being formed so that air can pass through the second ply and lodge between the first ply and the second ply. A bag (20) for packaging powder material according to claim 14, in which the material of the second ply is of the kraft type. Bag (20) for packaging pulverulent material according to any one of Claims 14 or 15, comprising a bonding pattern making it possible to produce a baffle or a chimney evacuating the air contained between the first ply and the second ply. Process for manufacturing a paper (10) according to one of Claims 1 to 12, comprising the following successive steps:
a) suspension of cellulose fibers;
b) addition to the suspension obtained in step a) of a dry strength agent for the support structure of the paper;
c) refining a mixture comprising the cellulose fibers and the dry strength agent;
d) addition of a moisture resistance agent to the refined mixture obtained at the end of step c);
e) adding a cohesion agent and a paper sizing agent (10), to the result obtained at the end of step d);
f) shaping the result of step e) in order to conform the support structure in the form of a sheet;
g) application of a hydrophobic agent on at least one side of the sheet obtained in step f) by a surfacing process.