WATER-BASED ADHESIVE FOR THE MANUFACTURE OF LAMINATED CELLULOSIC BOARDS COMPRISING MONOLAYER GRAPHENE OXIDE, LAMINATED CELLULOSIC BOARDS OBTAINED THEREWITH, AND METHODS FOR PRODUCTION THEREOF

Abstract

A water-based adhesive for the manufacture of laminated cellulosic boards includes monolayer graphene oxide as a glue enhancer. Laminated cellulosic boards may be obtained by providing cellulosic plies, applying a water-based adhesive, and contacting the surface of another cellulosic ply to the first cellulosic ply. A method for producing the water-based adhesive includes mixing starch, water and glue enhancer. The glue enhancer is a suspension of between 0.1 wt % and 0.001 wt % of monolayer graphene oxide in water.

Claims

1. A water-based adhesive for the manufacture of laminated cellulosic boards, the water-based adhesive comprising: 1) water; 2) between 20.0 wt % and 40.0 wt % starch; 3) optionally, up to 10 wt % of at least one further polymer, selected from natural polymers or soluble synthetic polymers; 4) a glue enhancer, comprising monolayer graphene oxide in water, in an amount such that the water-based adhesive comprises between 0.1 wt % and 10.sup.−7 wt % of monolayer graphene oxide; and 5) at least one further component, selected from fungicides and biocides, and/or stabilizing agents, gelling agents, thickening agents, anti-foaming agents, tackifiers, damp-proofing resins, rheology agents in accordance with the polymer(s).

2. The water-based adhesive according to claim 1, wherein the at least one further component 5) is borax and NaOH, or a mixture of calcium hydroxide and sodium carbonate.

3. The water-based adhesive according to claim 1, wherein the starch is maize starch, wheat starch, potato starch, pea starch, tapioca starch, or mixtures thereof.

4. The water-based adhesive according to claim 1, wherein the at least one further polymer is a natural polymer selected from vegetable sources, protein sources, or animal sources.

5. The water-based adhesive according to claim 1, wherein the at least one further polymer is a soluble synthetic polymer is selected from the group consisting of polyvinyl alcohol, cellulose ethers, methylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, urea-formaldehyde blends, and melamine-formaldehyde blends.

6. The water-based adhesive according to claim 1, wherein the monolayer graphene oxide is in the form of nanoplates as defined in ISO/TR 18401:2017.

7. The use of monolayer graphene oxide as a glue enhancer for a water-based adhesive for the manufacture of laminated cellulosic boards, comprising starch and optionally at least one further polymer, wherein the at least one polymer is selected from natural polymers or soluble synthetic polymers, the water-based adhesive as defined in claim 1.

8. The use of monolayer graphene oxide according to claim 7, wherein the monolayer graphene oxide is in the form of nanoplates as defined in ISO/TR 18401:2017.

9. A method for producing a water-based adhesive as defined in claim 1, comprising mixing starch, water and glue enhancer, said glue enhancer being a suspension of between 0.1 wt % and 0.001 wt % of monolayer graphene oxide in water.

10. The method of claim 9, including the following steps: a) mixing starch into water under stirring and at a temperature between 20.0° C. and 30.0° C., to obtain a first mixture comprising between 20.0 wt % to 40.0 wt % of starch; and b) adding to said first mixture a glue enhancer under stirring, said glue enhancer being a suspension of between 0.1 wt % and 0.001 wt % of monolayer graphene oxide in water, thereby producing a second mixture, comprising between 0.1 wt % and 10.sup.−7 wt % of monolayer graphene oxide.

11. The method according to claim 10, wherein in step a) the first mixture is stirred for at least 20 minutes, and in step b) the second mixture is stirred for at least 10 minutes.

12. A method for producing a laminated cellulosic board, the method including the following steps: i) providing at least two cellulosic plies; ii) applying, to at least a part of the surface of a cellulosic ply, an adhesive comprising: 1) water; 2) between 20.0 wt % and 40.0 wt % starch; 3) optionally, up to 10 wt % of at least one further polymer, selected from natural polymers or soluble synthetic polymers; 4) a glue enhancer, comprising monolayer graphene oxide in water, in an amount such that the water-based adhesive comprises between 0.1 wt % and 10.sup.−7 wt % of monolayer graphene oxide; and 5) at least one further component, selected from fungicides and biocides, and/or stabilizing agents, gelling agents, thickening agents, anti-foaming agents, tackifiers, damp-proofing resins, rheology agents in accordance with the polymer(s); iii) contacting the surface of a further cellulosic ply to first cellulosic ply of step ii); and iv) optionally repeating once or more times steps ii) and iii), to obtain a laminated cellulosic board.

13. The method according to claim 12, wherein step iii) further comprises applying, to at least a part of the surface of the further cellulosic ply, the adhesive.

14. The method according to claim 12, wherein the cellulosic ply is a paper or cardboard ply.

15. A laminated cellulosic board comprising: at least two cellulosic plies attached one to another, wherein the at least two cellulosic plies are attached one to another with an adhesive according to claim 1.

16. The laminated cellulosic board according to claim 15 or obtained by a method including the following steps: i) providing at least two cellulosic plies; ii) applying, to at least a part of the surface of a cellulosic ply, the adhesive; iii) contacting the surface of a further cellulosic ply to first cellulosic ply of step ii); and iv) optionally repeating once or more times steps ii) and iii), to obtain a laminated cellulosic board, wherein at least one of the cellulosic plies is a corrugated ply.

17. The laminated cellulosic board according to claim 15, a method including the following steps: i) providing at least two cellulosic plies; ii) applying, to at least a part of the surface of a cellulosic ply, the adhesive; iii) contacting the surface of a further cellulosic ply to first cellulosic ply of step ii); and iv) optionally repeating once or more times steps ii) and iii), to obtain a laminated cellulosic board, wherein at least one of the cellulosic plies is a laminated paper.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] To complete the description and in order to provide for a better understanding of the disclosure, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the disclosure, which should not be interpreted as restricting the scope of the disclosure, but just as an example of how the disclosure can be carried out. The drawings comprise the following figures:

[0083] FIG. 1 shows a corrugated laminated cellulose board comprising 5 layers.

[0084] FIG. 2 shows a corrugated laminated cellulose board comprising 3 layers.

[0085] FIGS. 3 and 4 show results of dry peeling tests performed with different Samples:

[0086] FIG. 3 corresponds to a dry peeling test performed with a corrugated board prepared using an adhesive without the glue enhancer according to the disclosure.

[0087] FIG. 4 corresponds to a dry peeling test performed with a corrugated board prepared using an adhesive comprising the glue enhancer according to the present disclosure.

[0088] FIG. 5 shows schematic representations of the adhesives, obtained by some of the different methods of preparation described above.

[0089] FIGS. 6a and 6b schematically show the steps of the Stein Hall process described above.

DETAILED DESCRIPTION OF THE DRAWINGS

[0090] FIG. 1 shows a corrugated laminated cellulose board with a plurality of plies, particularly five, numbered 25-29, attached one to another with an adhesive, for instance an adhesive according to the present disclosure, i.e., comprising monolayer graphene oxide as glue enhancer.

[0091] The corrugated laminated cellulose board comprises a first planar ply 25, a first corrugated ply 26, which is attached underneath the first planar ply 25; a second planar ply 27, which is attached underneath the first corrugated ply 26; a second corrugated ply 28, which is attached underneath the second planar ply 27; and a third planar ply 29, which is attached underneath the second corrugated ply 28. In this particular example, the first corrugated ply 26 has a smaller fluting than the fluting of the second corrugated ply 28. This should in no case be considered a limitation of the disclosure, as the flutings of different corrugated plies may be the same or different.

[0092] One of the two major surfaces of the first and third planar plies 25 and 29 (i.e., the external liners) are attached with an adhesive to a major surface of the first and second corrugated plies 26 and 28, respectively. Each of the second planar ply 27, first corrugated ply 26 and second corrugated ply 28 have the two major surfaces thereof attached with an adhesive to a major surface of another ply. Depending on the properties of the adhesive, the plies are glued together with more or less adherence. The adhesive and the adherence influence the mechanical properties of the corrugated laminated cellulose board 20, because a resistance of a ply may be enhanced by resistance of the other plies, which depends, among other features, upon how strongly the plies are glued together.

[0093] It is readily apparent that other laminated cellulose boards, both corrugated or not, are possible within the scope of the present disclosure, for instance corrugated laminated cellulose board having a first planar ply and a first corrugated ply, or having a first planar ply, a first corrugated ply and a second planar ply, or having additional planar and/or corrugated plies, etc. Moreover, the fluting of the corrugated plies may be the same or different. It is also readily apparent that different types of paper or cardboard may be used to prepare laminated cellulose boards, such as semi-chemical paper, kraft paper, or plastic paper, for example.

[0094] In FIG. 2 there is shown a corrugated laminated cellulosic board having three plies, particularly comprising a first planar ply, a corrugated ply, which is attached underneath the first planar ply; and a second planar ply, which is attached underneath the corrugated ply.

[0095] In FIG. 3 there is shown a corrugated laminated cellulosic board having three plies as described with reference to FIG. 2, the plies being glued with an adhesive not including a glue enhancer according to the present disclosure. As may be observed, the first planar ply separates from the corrugated ply quite easily, without the ply delaminating, due to the weak adherence of the plies one to another.

[0096] In FIG. 4 there is shown a corrugated laminated cellulosic board having three plies as described with reference to FIG. 2, the plies being glued with an adhesive including glue enhancer according to the present disclosure. As may be observed, the first planar ply in this case delaminates (i.e. both the planar and the corrugated layers break), due to a stronger adherence due to the glue enhancer according to the disclosure comprised in the adhesive used to attach the plies one to another.

EXAMPLES

[0097] In the following, the disclosure will be further illustrated by means of Examples and Comparative Examples. The Examples should in no case be interpreted as limiting the scope of the disclosure, but only as an illustration of the disclosure.

Example 1: Preparation of an Adhesive According to the Disclosure

[0098] An adhesive is produced as follows: providing a volume of water of 1800 L; heating the volume of water up to 25.0° C.; adding an amount of modified starch of 550 kg; agitating the resulting mixture for 20 minutes; adding a volume of glue enhancer of 1.5 L to the mixture, the solvent comprising water and 0.01 wt % of monolayer graphene oxide; and agitating the resulting mixture for 10 minutes. The resulting exemplary adhesive thus has, approximately, 0.0000064 wt % of monolayer graphene oxide.

Example 2: Dry Peeling Test

[0099] A dry peeling test was performed on several samples of corrugated laminated cellulose boards with and without adhesive according to the disclosure, i.e., with and without monolayer graphene oxide therein. In the dry peeling test, two plies glued one to another are peeled apart. The average load required to separate the two, over the length of the specimen is recorded, and expressed in N.

[0100] Particularly, the dry peeling test was performed on boards comprising three layers, as shown in FIG. 2. The 3 layers were the following: [0101] superior ply: planar ply: T14; paper type: Test, grammage of 140 gr [0102] interior ply: corrugated ply, fluting SQ15; paper type: Semichemical, grammage of 150 gr [0103] inferior ply: T14; paper type: Test, grammage of 140 gr.

[0104] Sample 1 is a corrugated laminated cellulose board according to the above, prepared by using a glue or adhesive not comprising the glue enhancer according to the disclosure.

[0105] Sample 2 is a corrugated laminated cellulose board according to the above, prepared by using a glue or adhesive comprising the glue enhancer according to the disclosure.

[0106] The results of the tests are provided in Table 1, wherein two rows of values are indicated: the first row corresponding to the dry peeling between the superior, planar ply and the interior, corrugated ply; and the second row corresponding to the dry peeling between the corrugated ply and the inferior planar ply.

TABLE-US-00001 TABLE 1 Comparison of dry peeling tests between corrugated laminated cellulose boards with and without glue enhancer according to the present disclosure. Sample 1: Sample 2: Adhesive Adhesive without glue Standard with glue Standard enhancer Deviation enhancer deviation Dry peeling 7.93N 0.98 delamination (superior planar ply - corrugated ply) Dry peeling 2.13N 1.05 4.74N 0.853 (corrugated ply - inferior planar ply)

[0107] In Sample 2, i.e. having glue enhancer according to the present disclosure, the dry peeling between the superior planar ply and the corrugated ply results in delamination (refer to FIG. 4). Delamination is a consequence of the high strength of the adhesive, and both planar and corrugated layers break.

[0108] In contrast, for Sample 1, i.e. without the glue enhancer according to the present disclosure, the dry peeling between the superior planar ply and the corrugated ply the measured force was 7.93 N.

[0109] In the dry peeling test between the corrugated ply and the inferior planar ply, Sample 2 required a force of 4.74 N for the dry peeling, which is greater than the force for the dry peeling of the Sample 1 (2.13 N).

[0110] Therefore, in both cases the resistance against dry peeling of Sample 2 (comprising glue enhancer) is greater than the resistance of Sample 1 (without glue enhancer) (refer to FIG. 4 versus FIG. 3, delamination versus peeling off, without delamination).

Example 3: Determination of the Water Resistance of the Glue Bond: FEFCO Testing Method #9

[0111] Also, water resistance of the glue bond by immersion of corrugated laminated cellulose boards, manufactured with and without the adhesive comprising glue enhancer according to the present disclosure, is tested, in accordance with FEFCO Testing Method #9. The water resistance of the glue of corrugated board is expressed by the amount of time that a predetermined combination of glue lines, immersed in water, resist the pulling of a suspended weight (having a mass of 250 grams) in the plane vertical to the axis of the cellulosic board, at a right angle with respect to the glue lines.

[0112] Particularly, the dry peeling test was performed on boards comprising five layers, according to the shown in FIG. 1. The five layers, listed from up to bottom, were the following: [0113] superior, exterior planar ply: T200; paper type: Test, grammage of 200 gr [0114] first corrugated ply: small fluting, SQ150; paper type: Semichemical, grammage of 150 gr [0115] interior ply (interior liner): T140; paper type: Test, grammage of 140 gr [0116] second corrugated ply: large fluting, SQ150; paper type: Semichemical, grammage of 150 gr [0117] inferior, exterior planar ply: T200; paper type: Test, grammage of 200 gr.

[0118] Sample 3 is a corrugated laminated cellulose board according to the above, prepared by using a glue or adhesive not comprising the glue enhancer according to the disclosure.

[0119] Sample 4 is a corrugated laminated cellulose board according to the above, prepared by using a glue or adhesive comprising the glue enhancer according to the disclosure.

[0120] It can be observed in Table 2 that Sample 4 (with the adhesive comprising glue enhancer according to the present disclosure), features a longer time before it breaks, in comparison to Sample 3 (with the adhesive not including glue enhancer). In this Table 2, the water resistance is measured between each pair of plies; also, the standard deviation of the measured times in different tests is indicated.

TABLE-US-00002 TABLE 2 Comparison of water resistance of the glue bond between corrugated laminated cellulose boards with and without glue enhancer according to the present disclosure. Sample 3: Sample 4: Adhesive Adhesive without Glue Standard with Glue Standard enhancer Deviation enhancer deviation Water resistance 30 s 2.3 70 s 12.2 of the glue bond (superior planar ply-first corrugated ply with large fluting) Water resistance 29 s 3.8 78 s 20.4 of the glue bond (first corrugated ply with large fluting - interior planar ply) Water resistance break break of the glue bond (interior planar ply - second corrugated ply with small fluting) Water resistance break break of the glue bond (second corrugated ply with small fluting - inferior planar ply)

[0121] “Break” in table 1 means that the paper breaks before the adhesive unglues.

[0122] In this text, the terms first, second, etc. have been used herein to describe several substances or elements, it will be understood that the substances or elements should not be limited by these terms since the terms are only used to distinguish one substance or element from another.

[0123] In this text, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.

[0124] On the other hand, the disclosure is obviously not limited to the specific embodiment(s) described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the disclosure as defined in the claim.