AU2017243875B2

AU2017243875B2 - Paper sheet, corrugated paper and a process for the manufacture thereof

Info

Publication number: AU2017243875B2
Application number: AU2017243875A
Authority: AU
Inventors: Andrew Conn; Rafik Faltas; Jim SELWAY
Original assignee: Opal Packaging Australia Pty Ltd
Current assignee: Opal Packaging Australia Pty Ltd
Priority date: 2016-03-30
Filing date: 2017-03-30
Publication date: 2021-11-04
Anticipated expiration: 2037-03-30
Also published as: WO2017165919A1; NZ745660A; AU2017243875A1

Abstract

The present invention relates to a paper sheet and a process of making the paper sheet. In one example, the paper sheet may be a corrugated paper and a process may be a process for making a corrugated paper. Ideally, the paper sheet includes an additive such as a clay nano-particles and/or a plasticising agent. The additive may improve one or more mechanical properties of the paper sheet such as: bending stiffness, crush strength and creep resistance.

Description

PAPER SHEET, CORRUGATED PAPER AND A PROCESS FOR THE MANUFACTURE THEREOF FIELD OF THE PRESENT INVENTION

The present invention relates to a paper sheet and a process of

making the paper sheet. In one example, the paper sheet may be

a corrugated paper and a process may be a process for making a

corrugated paper. Corrugated paper can be used in a range of

applications, including making corrugated board and boxes.

BACKGROUND OF THE PRESENT INVENTION

Mechanical properties such as bending stiffness, crush strength

and creep resistance of a sheet of paper is dependent on a

number of factors including the weight (or grammage of the

paper), the type of fibres used and the amount of starch added

to the sheet. For example, the paper sheets used to produce

paper based packaging typically have a starch content in the

range from 5 to 10%wt. Both chemically modified and unmodified

starches can be used to improve the stiffness and strength of

paper.

Depending on the product being produced, silicon or compositions

containing silicon acting as sizing agents may also be added to

increase the hydrophobicity of the paper. The starch material

together with the sizing agents help to give the necessary

stiffness.

Once the paper sheet has been fully formed and dried, if the

paper sheet is going to be used as a liner board for example,

the paper sheet may also be treated in a coating process to

enhance the visual appearance of the sheet, or to laminate the

sheet to other materials. For instance, polymeric films and

metallised foils have been laminated to the sheet, and in other

instances clay has been applied to the outer face of the sheet

to form a smooth high gloss surface. The clay may also

contribute significantly to the weight of the sheet.

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Corrugated board is a high strength product used in the

manufacture cartons that are used for a range of purposes,

including storing fresh food items under moist conditions such

as high humidity topical environments and cold storage. The

cartons are also expected to perform over various time frames

from relative short periods such as a few days, to extended

periods such as a few months or even years. The ability for a

product to resist deterioration or degradation under various

environments, particularly high and cycling humidity

environments, is the product's ability to resist "creep", which

can be an important characteristic depending on the

circumstances.

Moreover, the performance of the corrugated paper of a

corrugated board is dependent on a vast number of different

variables including, but by no means limited to: quality of the

fibre material, particularly virgin fibre versus recycled fibre;

grammage of the corrugated paper; the flute size and geometry of

the corrugated paper; degree of damage resulting from the forces

in the corrugating labyrinth, adhesion of the corrugated paper

to the liner boards; moisture resistance of the corrugated

paper; the humidity of the environment in which the product is

being used; the expected life time and so forth.

In practice the shear and bending stiffness of the corrugated

paper (both material and structural) plays an important role in

the performance of the corrugated paper. Ideally the corrugated

paper is as stiff as possible, as this would have the potential

to reduce the grammage of the liner board required to produce a

corrugated board. However, the grammage of corrugated paper is

generally limited to about 180 gsm. Corrugated paper having a

grammage greater than this is prone to delaminating during the

corrugating process in which the sheet is configured into a

cycling wave shape under heat and pressure. Delaminating

permanently weakens the boards as shear stiffness is greatly

reduced.

18164197_1 (GHMatters) P96760.AU.3 15/10/21

SUMMARY OF THE PRESENT INVENTION

The present invention relates to a paper sheet including one or

more than one ply layer, wherein the paper sheet includes an

additive.

The additive may include a plasticizing agent that allows

relative movement of the internal structure of the sheet to

prevent or reduce fracturing during corrugation of the sheet.

The additive may include nano-particles that can be incorporated

in the sheet which can improve mechanical properties including:

i) crush strength; ii) stiffness of the sheet; iii) creep

resistance of the sheet particularly in cyclic or high humidity

environments, or iv) hydrophobicity or the moisture barrier

properties of the sheet.

An embodiment of the present invention relates to a corrugating

paper treated with an additive including starch and at least

15wt% platelet shaped nanoparticles, the nanoparticles having a

thickness in the range of the 1 to 5nm and bond to any one or a

combination of: starch of the paper sheet, adhesives present in

the paper sheet, cellulose of the paper sheet, and fibre of the

paper sheet, wherein the additive increases the high humidity

load carrying capacity from 1 to 13% compared to an equivalent

paper sheet without the additive, in which the relative humidity

is at least 50%.

An embodiment of the present invention relates to a corrugating

paper treated with an additive including starch and at least

15wt% platelet shaped nanoparticles having a thickness in the

range of the 1 to 5nm, including:

at least two ply layers that are joined together, and

the additive being located between the ply layers that enhances

the bond between the layers joined together, wherein the nano

particles bond to any one or a combination of fibre of the ply

layers, cellulose and starch of the ply layers, wherein the

additive increases the high humidity load carrying capacity from

18164197_1 (GHMatters) P96760.AU.3 15/10/21

1 to 13% compared to an equivalent paper sheet without the

additive, in which the relative humidity is at least 50%.

In one embodiment the paper sheet is a corrugating paper or

corrugating paper.

In other words, the additive helps prevent or reduce fracturing

of the join between the ply/layers compared to an equivalent

paper sheet without the additive.

Another embodiment of the present invention relates to a

corrugating paper treated with an additive including starch and

at least 15wt% platelet shaped nanoparticles having a thickness

in the range of the 1 to 5nmincluding:

at least two ply layers that are joined together to form

the corrugating paper, and

the additive being is present in the corrugating paper and

between the ply layers, wherein the nano-particles bond to

any one or a combination of fibre of the ply layers,

cellulose and starch of the ply layers,

wherein the additive increases the high humidity load carrying

capacity from 1 to 13% compared to an equivalent paper sheet

without the additive, in which the relative humidity is at least

50% and facilitates relative movement of the ply layers to

prevent or reduce fracturing of the join between the ply layers

during corrugation of the sheet.

In one embodiment the paper sheet is a corrugating paper or

corrugating paper.

A corrugating paper is a medium that can be imparted with crests

and troughs to form a corrugated paper.

In other words, the bond between the base sheets post

corrugation is enhanced compared to an equivalent corrugated

paper without the additive between the paper base sheets.

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Enhancing the bond between the paper base sheets may enhance one

or more of the performance characteristics of the corrugating

paper. For example, increasing the bond between the base sheets

may increase the ultimate loading point at which the corrugated

paper fails when subjected to a load. In some situations, crush

strength, the bending stiffness or the shear stiffness of the

corrugated paper may be increased at any one point in time after

manufacture or setting. It will be appreciated however, that an

increase in shear stiffness and bending stiffness does not

necessitate an increase in the ultimate load point of the

material. Moreover, it is possible that increasing the shear

and/or bending stiffness may in fact have no effect on the

ultimate load point, increase the ultimate load point, or even

reduce the ultimate load point of the corrugated paper.

An embodiment of the present invention relates to a paper sheet

including nanoparticles that can bond to any one or a

combination of: starch of the paper sheet, adhesives in the

paper sheet, cellulose of the paper sheet, and fibre of the

paper sheet.

The bond between the nano-particles and the starch, adhesives,

and/or cellulose may be in the form of physical bonding, but is

ideally in the form of a chemical bond.

The term "adhesives" in the specification embraces materials

such as: starch, PVA, and other compatible polymeric materials.

Without wanting to be limited by theory, it is believed that

certain types of the nano-particles may occupy spaces or voids

in the sheet and/or starch coating and thereby define a tortuous

path by which moisture is required to take in order to reach the

inner core of the sheet. As a result, one the properties

changed is that the sheet may exhibit an increase in the

hydrophobicity or the moisture barrier property of the sheet.

In addition, the nano-particles can occupy spaces that would

otherwise be voids. Occupying the voids can limit the mobility

of the matrix of starch, cellulose and fibre of the paper sheet.

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It is believed that restricting the matrix mobility on this scale can increase the stiffness and creep resistance of the paper sheet.

Throughout this specification the term "paper sheet", or variations thereof such as a "sheet of paper" or "sheet" embraces any fibrous or cellulosic containing material and embraces material including a single ply layer, multiple plies and other laminated structures. The term "paper sheet" therefore embraces any one or a combination of a corrugated paper that has been corrugated, corrugating paper prior to being corrugated, namely a flat planar sheet, or paper layers joined together, or optionally joined to non-paper materials such as polymeric film, metallic foil, coatings of wax and so forth.

Nanoparticles

The additive may include nano-particles.

The nano-particles may include cellulose nano-particles or derivatives thereof, including nanocrystalline cellulose, cellulose nanocrystals, cellulose whiskers, nanofibrillated cellulose, cellulose nanofibrils, microfibrillated cellulose, carboxymethylated cellulose, microcrystalline cellulose, and cellulose filaments.

Examples of other nano-particles that may be present in the paper sheet include graphite or graphene platelets, carbon nanotubes, and ZnO or TiO 2 nano-particles.

The nano-particles may include clay nano-particles.

The additive may include a combination of clay nano-particles, cellulose nano-particles and starch. The additive may include any proportion of clay and cellulose nano-particles. For instance, the additive may include from 0% to 100% clay nano particles and from 100% to 0% cellulose nano-particles, and any mix in between. By way of example, the weight ratio of clay nanoparticles and cellulose nanoparticles may be in the ranges of 10 to 90 : 90 to 10 respectively. Specifically, the weight

18164197_1 (GHMatters) P96760.AU.3 15/10/21 ratio of clay nanoparticles to cellulose nanoparticles may be any one of 50:50, 40:60, 30:70, 20:80, 60:40, 70:30 and 80:20 respectively.

Without wanting to be limited by theory, nanoparticles have the

ability to limit the mobility of molecules for a starch and by

bonding to and bridging between adjacent starch particles.

Nano-particles have a large surface area per unit weight or

volume hence significant amounts of the matrix can be affected.

Restricting the matrix molecule mobility on this minute scale

can increase stiffness and in addition improve creep performance

in cyclic or high humidity conditions.

For instance, an additive comprising clay nano-particles and

additional starch added to the surface of the paper sheet at a

weight of up to 5gsm can increase a ring crush strength of the

paper sheet from 1 to 8% compared to an equivalent paper sheet

without the additive. The additive may, for example, comprise

from 85 to 75wt% starch and from 15 to 25wt% clay nano

particles.

The nano-particles may have a size in the range of equal to, or

less than 500nm, and even more suitably the nano-particles may

have a size in the range of equal to less than 100nm. Ideally,

the nano-particles may be platelets having a thickness in the

range of the 1 to 5nm, and suitably approximately 1 nm, and a

diameter in the range of 0.1 to 10ptm.

The nano-particles may be have any suitable shape and are

suitably platelets shaped nano-particles. Even more suitably,

the nano-particles are in the form of clay nano-particles having

a platelet shape and may have the size ranges mentioned above.

The bond between the nano-particles and the starch and/or

cellulose may be in the form of physical bonding, but is ideally

a chemical bond.

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The nano-particles may chemically bond to the starch of the

substrate, for example, by hydrogen bonding.

The nano-particles, and especially clay nano-particles, provide

the synergistic benefit of increased cyclic or high humidity

creep resistance, stiffness and possibly the fail strength by

forming bonds to starch and/or cellulose, and improving the

moisture barrier property. In other words, the presence of

nano-particles, paper creep will show a noticeable improvement

in performance in moist or humid environments.

Ideally, the additive slows time dependent deformation (creep)

of the paper sheet subjected to a load in a high

humidity/moisture environment in which the relative humidity is

at least 50%, compared to an equivalent paper sheet without the

additive. Depending on the preferred conditions, the relative

humidity may be at least 65%, and even more preferably at least

75%.

For instance, an additive comprising clay nano-particles and

additional starch added to interface between two of the base

sheets to from a single sheet at a weight in the range of the

9gsm can increases the high humidity load carrying capacity from

1 to 13% compared to an equivalent paper sheet without the

additive. The additive may, for example, comprise from 85 to

75wt% starch and from 15 to 25wt% clay nano-particles.

Plasticizing agent

The additive may include a plasticizing agent that can form a

thermoplastic with starch. The starch may be contained within

the ply layers, or included in the additive.

The additive may include a combination of a plasticizing agent

and starch at an interface between the ply layers of the paper

sheet, or between an interface between base sheets. Examples of

a plasticizing agent that can be used with starch are glycerol

and sorbitol. Glycerol may be included in the additive by

itself or in combination with other agents such as sorbitol.

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Similarly, sorbitol may be included in the additive by itself or

in combination with other agents such as glycerol.

Ideally the additive may have an ability to soften when

subjected to a temperature above ambient temperature, and harden

at temperatures at or below ambient temperatures. Ambient

temperature may, for example, be 25, 35 or 45 degrees Celsius.

An advantage provided by this aspect is that ply layers can move

relative to each other more readily when subject to heat,

enabling the sheet to be treated in a corrugating step with a

reduced risk of the join between ply layers fractured, or the

ply layers themselves within the paper sheet fracturing.

An advantage in using a plasticizing agent that can form a

thermoplastic with starch is that the thermoplastic is heat

softenable, thereby enabling, for instance the sheet to be

heated after being dried to allow the ply layers to move

relatively. In one example, the sheet may be manufactured with

the additive contained in the paper sheet, and the paper sheet

stored for a period during which the paper sheet can cool. The

plasticising agent can then be softened, for example by being

heated and optionally moistened, and the paper sheet can then be

corrugated while heated.

The additive may include one or a combination of the nano

particles, particularly clay nano-particles, cellulose nano

particles, a plasticizing agent, and starch.

Structure

The additive may be located at any section of the paper sheet.

For example, and without limitation, the additive may be

distributed evenly throughout the entire thickness of the paper

sheet, isolated to one of the ply layers of the paper sheet,

located in two or more of the ply layers if present, located at

the interface between two or more of the ply layers if present

in the paper sheet, or located on the outer faces of the paper

sheet.

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In the situation in which the paper sheet has two ply layers or

base sheets that are joined to each other, that is without any

additional ply layers therebetween, the additive may be located

at the interface between the ply layers, and may penetrate into

the plies to a degree.

In the situation where the paper sheet includes more than two

ply layers or base sheets, the additive may be located between

any two juxtaposed ply layers or base sheets, i.e., at the

interface between the layers.

As well as being present at the interface between the ply

layers, the additive may also penetrate the ply layers to some

extent. For example, although the additive may have been

applied to a surface of one of the ply layers while the ply

layer contains a high water content at the wet end of the paper

making machine, or incorporated into the ply layer by being

added to the slurry from which the ply layer is made, the

additive can migrate away from the interface between the ply

layers.

For example, the additive may migrate nearly entirely through

each ply layer, but may also migrate only to a smaller extent,

for example, up to 50% of the thickness of the ply layers, or

only up to 30% of the thickness of the ply layers.

In addition to being located at the interface between the ply

layers. The additive may also be present within the thickness

of the paper sheet, i.e., within each of the ply layers. For

example, the additive may be distributed throughout the

thickness of one of the ply layers. In another example, the

additive may be distributed throughout the thickness of two ply

layers, and suitably each of the ply layers of the paper sheet.

The additive may increase the strength of the bond between the

fibres, cellulose and starch within the paper sheet, including

within each of the ply layers, and/or between the ply layers.

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Enhancing the bond between the ply layers and within the ply

layers may enhance the performance characteristics of the paper

sheet and particularly a corrugated paper made from the paper

sheet. For example increasing the bond between the ply layers

and within the ply layers may increase the ultimate loading

point at which the sheet or corrugated paper fails. In some

situations, the enhanced bond may increase shear stiffness and

bending stiffness of the paper sheet including corrugated papers

made therefrom. It will be appreciated however, that an

increase in shear stiffness and bending stiffness does not

necessitate an increase in the ultimate loading point.

In an embodiment, the additive may be absent from the outer face

of the paper sheet.

In an embodiment, the additive may be incorporated into one or

more than of the ply layers. For example, the additive may be

added to a paper pulp slurry feed to the headbox of a

papermaking machine so that the additive is distributed through

the ply layer of the headbox. The additive can be added as a

wet slurry or in pre-mixed and dried powered form. In this

instance, the additive distributed in the ply layer will be

present at the interface with an adjacent ply layer that may not

have the additive distributed therethrough. The additive may

migrate from the ply layer having the additive distributed

therein to the ply layer in which the additive is not

distributed therein.

In an embodiment, the additive may be applied to a face of the

ply layer that is discharged from a paper machine headbox. For

instance, the additive is sprayed onto the ply layer on the wire

at the wet end of the paper machine and another ply layer laid

on top.

In the situation in which the paper sheet may include three or

more ply layers, the additive is suitably present at the between

each of the ply layers.

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The ply layers may be joined together by, for example, laminating the ply layers together. The ply layers may be

laminated together without or without an adhesive. In the

situation where there is no adhesive, starch may assist in

bonding the ply layers together, and the fibre of the ply layers

may intertwine to some extent.

In an embodiment, the additive may be applied to one face, and

suitably to opposite faces of the paper sheet in a coating step.

The additive, such as nano-particles may penetrate up to 100

microns from the outer face of the paper sheet during the

coating process. The degree of penetration can be controlled to

some extent during coating depending on coating viscosity, nip

pressure, web moisture, and so forth. An embodiment relates to

controlling the penetration depth of the additive into the paper

sheet during the coating step. Bending and printing properties

can be enhanced if the nano-particles are located predominantly

near the surface (as would be suitable for linerboards). While

shear properties are enhanced if the nano-particles penetrate to

near the centre of the sheet (as would be suitable for

corrugating papers).

The paper sheet may be a corrugated paper having crests and

troughs. The corrugated paper may also include other adhesives,

such as starch and/or PVA to bond the sheets together.

Another benefit of the present invention is that paper sheet

made entirely of recycled fibre can be used to in situations

where only virgin (not previously used in paper) fibres may have

needed while maintaining the same or having an improved creep

resistance can be manufactured.

Generally speaking, papers containing recycled fibres, compared

to virgin fibre have an inherent increased rate of creep, and

therefore, in situations where creep needs to be controlled,

higher cost virgin fibres are required. One benefit is that

paper made from solely or predominately from recycled fibres can

be used because the nano-particles help to reduce creep. Creep,

18164197_1 (GHMatters) P96760.AU.3 15/10/21 refers to the undesirable property of paper based packing to deform and weaken over time under load, particularly in humid or cycling humidity environments. An embodiment relates to controlling the creep resistance of the paper sheet by adjusting the weight of additives, in particular, nano-particles in the paper sheet. In one example, the paper sheet may be made entirely of recycles fibre. In another example, the paper sheet may be made of 50% recycled fibre.

Process

An embodiment relates to a process of manufacturing a

corrugating paper from a paper sheet, the process including the

steps of:

forming the paper sheet including one or more than one ply

layer;

treating the paper sheet with an additive including starch

and at least 15wt% platelet shaped nanoparticles having a

thickness in the range of the 1 to 5nm; and

corrugating the sheet into a corrugating paper;

wherein the nano-particles bond to any one or a combination of

fibre of the ply layers, cellulose and starch of the ply layers,

and the additive increases the high humidity load carrying

capacity from 1 to 13% compared to an equivalent corrugating

paper without the additive, in which the relative humidity is at

least 50% and facilitates relative movement of internal sheet

structure and/or the ply layers to prevent or reduce fracturing

of the internal structure and/or join between the ply layers

during corrugation of the sheet.

The process may include allowing the paper sheet that has been

treated with the additive to cool, and thereafter heating the

paper sheet prior to and/or during the corrugating step.

Corrugating the paper sheet into a corrugated form may also

include passing the paper sheet between a pair of co-operating

18164197_1 (GHMatters) P96760.AU.3 15/10/21 rollers having mating surfaces with crests and troughs that impart a corrugated profile.

In one embodiment, the process may also include forming the ply

layers. Forming the ply layers may include creating a paper

pulp slurry containing the paper fibre, and delivering the

slurry onto a travelling wire at the wet end of a paper making

machine.

While it is possible that the additive may be added to the one

or both of the paper pulp slurry that from the ply layers,

ideally the additive is applied to one or both of the faces of

the ply layers prior to the ply layers being overlaid during

joining the ply layers.

The step of incorporating the additive in the paper sheet may

include any one or a combination of the following.

i) Adding the additive in a paper pulp slurry feed to the

headbox of a papermaking machine so that the additive is

distributed through the ply layer of the headbox. The

additive can be added as a wet slurry, or in pre-mixed

and dried powered form. In this instance, the additive

distributed in the ply layer will be present at the

interface with an adjacent ply layer that may not have

the additive distributed therethrough.

ii) Applying the additive to a face of the ply layer that is

discharged from a paper machine head box. For

instances, the additive may be sprayed onto face of one

or more ply layers on a wire at the wet end of the paper

machine and another ply layer laid thereover top.

iii) Applying the additive to the paper sheet after the ply

layers have been joined together. For example, the play

layers may be dried in a drier and the additive applied

to the paper sheet in size press. In another example,

the additive may be applied by meter press roll.

According to either example, the additive can migrate

18164197_1 (GHMatters) P96760.AU.3 15/10/21 into the paper sheet, including to the interface between the ply layers.

An embodiment also relates to a process of manufacturing a paper

sheet, the process including the steps of:

forming a paper sheet including one or more than one ply

layer; and

incorporating nano-particles into the paper sheet, wherein

the nanoparticles bond to any one or a combination of:

starch of the paper sheet, cellulose of the paper sheet,

and fibre of the paper sheet.

Forming the paper sheet may include mixing a paper pulp slurry

containing the paper fibre, and delivering the slurry onto a

travelling wire at the wet end of a paper making machine.

The nano-particles may be incorporated into the paper sheet by

being added to the paper slurry that forms one or both of the

ply layers.

The step of incorporating the nano-particles into the paper

sheet may include any one or a combination of the following.

i) Applying the nano-particles to the paper sheet after the

ply layers have been joined together. For example, the

play layers may be dried in a drier and the nano

particles applied to the paper sheet in size press. In

another example, the nano-particles may be applied by

meter press roll. According to either example, the

additive can migrate into the paper sheet. The nano

particles may be applied to the paper as a dispersion

that is formed by suspending the nano-particles in

water, for example, separating the sheets of the nano

particles in the high shear mixer or agitator. The

dispersion may also include additional agents for

treating the web prior to drying. The additional agents

include any one or a combination of sizing agents such

18164197_1 (GHMatters) P96760.AU.3 15/10/21 as silicon, colouring agents such as whitening agents, starch and so forth.

ii) Adding the nano-particles in a paper pulp slurry feed to

the headbox of a papermaking machine so that the nano

particles is distributed through the ply layer of the

headbox. The additive can be added as a wet slurry, or

in pre-mixed and dried powered form.

iii) Applying the nano-particles to a face of the ply layer

that is discharged from a paper machine head box. For

instances, the nano-particles may be sprayed onto face

of one or more ply layers on a wire at the wet end of

the paper machine and another ply layer laid thereover

top.

Another embodiment relates to a process of manufacturing a

corrugating paper, the process including:

treating two base sheets with an additive including starch

and at least 15wt% platelet shaped nanoparticles having a

thickness in the range of the 1 to 5nm to locate the

additive between the two base sheets;

joining the base sheets together with the additive

therebetween to form a medium; and

corrugating the medium into the corrugating paper;

wherein the additive enhances the bond between the sheets and

the nano-particles bond to any one or a combination of the fibre

of the base sheets or starch of the base sheets, and increases

the high humidity load carrying capacity from 1 to 13% compared

to an equivalent base sheet without the additive, in which the

relative humidity is at least 50%.

Ideally, the additive is a wet additive.

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Corrugating the paper sheet into a corrugated form may also

include passing the paper sheet between a pair of co-operating

rollers having mating surfaces with crests and troughs that

impart a corrugated profile.

The additive may be applied to one or both of the joined faces

of the sheets prior to the sheets being joined together.

The additive may be applied using any suitable means including

spraying the additive onto the paper sheet and applying the

additive by means of roller application.

The process may also include applying at least one liner board

to the corrugated paper after the corrugating step. The

corrugated paper may be bonded to any number of other sheets

including liner boards, internal dividing sheets, and other

corrugated papers. The other corrugated papers may also be made

according to the process of the present invention.

The process of the present invention may include any one or a

combination of the features paper sheet described herein.

Similarly, the paper sheet may include any one or a combination

of the features of the process described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment will now be described with reference to

the accompanying Figures, of which:

Figures la and lb are schematic perspective views of a paper

sheet and a corrugated paper respectively;

Figures 2a, 2b and 2c are alternative schematic cross-sectional

views of the section shown in the dashed circle in Figure la;

Figure 3a, 3b and 3c are alternative schematic cross-sectional

views of the section in the dashed circle in Figure 1b;

Figure 4 is a schematic illustration of a process of making a

paper sheet that can be converted into a corrugated paper or a

18164197_1 (GHMatters) P96760.AU.3 15/10/21 paper sheet shown in Figures la or lb respectively in which the process includes forming two ply layers, joining the ply layers together with the additive located at the interface between the layers or incorporated in the ply layers to improve the performance of the corrugated paper;

Figures 5a and 5b are schematic illustrations of two processes for applying the additive to the surface of the paper sheet, in which Figures 5a and 5b are representative of the process steps of block 20 of Figure 3;

Figure 6 is a schematic illustration of a process for corrugating a corrugating paper (or paper sheet) to form the corrugated paper of any one of Figures 1b, 3a, 3b and 3c, in which the paper sheet is heated to soften the thermoplastic of the paper sheet;

Figure 7 is a schematic illustration of a process of making the corrugated paper shown any one of Figures lb and 3a in which the process includes joining two sheets and applying an additive to the interface between the layers to improve the performance of the corrugated paper formed therefrom;

Figure 8a is a graph illustrating the improved performance of the single sheet of 100gsm paper that has been treated with starch and nano-clay at a weight of approximately 4.5gsm;

Figure 8b is a graph illustrating the improved performance of a sandwich of the two 100gsm sheets of paper in which starch and nano-clay has been applied at a weight of approximately 9gsm bewteen the sheets; and

Figure 8c is a graph illustrating the improved performance of a single sheet of 135gsm paper that has been treated with starch and nano-clay at a weight of approximately 4.5gsm.

DETAILED DESCRIPTION

18164197_1 (GHMatters) P96760.AU.3 15/10/21

A preferred embodiment will now be described with reference to

the accompanying figures. To assist in identifying the various

features reference numerals have been includes in the text and

figures. The same reference numerals have been used on similar

or alike features of the various embodiments. However, in order

to maintain clarity of the figures, not all of the reference

numerals have been used in each of the figures.

With reference to the Figures, Figure la illustrates a paper

sheet 10 suitable for a corrugating paper including two base

sheets 11 and 12 (or ply layers 11 and 12), with an additive 13

at the interface therebetween. It will be appreciated that the

paper sheet 10 may be of any form, including for example,

corrugated paper, liner boards for cartons, liner boards for

corrugated paper and liner boards for plaster board.

Figures 2a and 2b are schematic cross-section views of the

corrugated paper shown in the dashed circle in Figure 1 in which

the dots 13 represent the additive in the paper sheet 10. The

additive 13 may be present in one or more of the various

sections of the paper sheet, including being distributed through

the thickness of the paper sheet 10, or on an outer surface and

section immediately inward of the outer surface only, or on

inner sections of the paper sheet 10 only, for example, at the

interface between the base sheets 11 and 12 (or the ply layers

11 and 12). Figure 2a illustrates the situation in which the

additive 13 is present at the interface between the base sheets

11 and 12 (or the ply layers 11 and 12), and has migrated to

some extent through the base sheets 11 and 12 (or ply layers 11

and 12). Figure 2b illustrates the situation in which the

additive 13 is incorporated throughout the base sheets 11 and 12

(or ply layers 11 and 12).

Figure 2c illustrates the situation in which the additive 13 is

located on an outside of the paper sheet 10 and has penetrated a

small distance into the paper sheet 10.

18164197_1 (GHMatters) P96760.AU.3 15/10/21

Figure lb is a schematic illustration of a paper sheet 10 in the

form of a corrugated paper having one or more than type of

additive 13 that are described herein to improve the performance

of the corrugated paper. Figures 3a to 3c are enlarged

schematic cross-sectional views of the portion shown in the

dashed circle in Figure lb. Specifically, figure 3a illustrates

the situation in which an additive 13 is located at the

interface between base sheets 11 and 12, and the situation in

which the additive 13 has migrate to a small extent into the

base sheets 11 and 12. Figure 3b illustrates the situation in

which the additive 13 is distributed through the thickness of

the base sheets 11 and 12. Figure 3c illustrates the situation

in which the additive 13 has been applied to an outside surface

of the paper sheet 10 and migrated to an extent into the paper

sheet 10.

The additive may include any one or a combination of the

following.

a) A plasticizing agent that can form a thermoplastic with

starch that is heat softenable. Examples of

plasticizing agents include glycerol and sorbital.

b) Nano-particles, including for example, clay nano

particles and cellulose nano-particles, having a size

in the range of equal to, or less than 500nm, and

suitably equal to, or less than 100nm. The nano

particles may have a platelet shape having a thickness

in the range of the 1 to 5nm, and suitably

approximately 1 nm, and a diameter in the range of 1 to

10ptm. Clay nano-particles can bond, for example by

physical or chemical bonding, to the starch and/or

cellulose of the ply layers and, in turn, increase the

stiffness of the paper sheet. Examples of other nano

particles that could be used include graphite or

graphene platelets, carbon nanotubes (fibers/whiskers),

ZnO and TiO 2 .

18164197_1 (GHMatters) P96760.AU.3 15/10/21

A non-exhaustive list of characteristics that may be improved by

the additive are as follows.

1. The additive 13 may allow or facilitate relative

movement of the ply layers 11 and 12 (or the base sheets

11 and 12) when the paper sheet 10, for example, is in

the process of being corrugated, which typically

involves being subjected to heat, pressure and moisture.

Advantageously however, after the sheet 10 has been

corrugated and cooled, the additive 13 may have an

ability to harden and, without wanting to be limited by

theory, increase the bond between fibre, cellulose and

starch within the base sheets 11 and 12 (or the ply

layers 11 and 12), and between the base sheets 11 and 12

(or the ply layers 11 and 12), thereby potentially

improving the structure and performance of the sheet 10.

2. The additive 13 may include either one or both of the

plasticizing agents and nano-particles and during a

corrugating step, the paper sheet and ideally the

interface between the ply layers will soften when heated

and "slip" avoiding delamination. After the corrugation

step is complete, the interface will cool and stiffen.

3. The additive 13 may produce two practical advantages.

Higher grammage ply layers that are inherently stiffer

can be used on account that the ply layers are less

likely to delaminate, thereby enabling a corrugated

paper to be made with a higher stiffness.

4. Thermoplastic additive can increase the shear stiffness

of the paper sheet particularly when cooled and devoid

of significant corrugating damage. Furthermore, clay

platelet shaped nano-particles can, in addition to allow "slippage" of the ply layer during corrugation, increase

the stiffness and creep resistant properties of the

18164197_1 (GHMatters) P96760.AU.3 15/10/21 paper sheet, and slow moisture uptake which can result in a better resistance to creep in cyclic and high humidity conditions.

5. When the additive 13 includes nano-particles, the nano particles can occupy voids between the starch molecules, cellulose and the fibre of the paper sheet, thereby reducing the mobility of the matrix structure of the paper sheet 10, making the paper sheet 10 stiffer than equivalent paper sheets at without nano-particles.

6. In addition to making the paper sheet 10 stiffer, the nanoparticles can infill voids in the matrix structure of the paper sheet 10, increasing the hydrophobicity of the paper sheet 10. In turn, the paper sheet 10 will have an increased stiffness and better creep resistant properties in a cyclically and high humidity conditions.

The manner in which the additive 13 is included in the paper sheet 10 can be achieved by several means.

Figure 4 is a schematic illustration of the process for making a paper sheet 10 in which the process includes forming the ply layers 11 and 12 by delivering sequentially, two suspensions 11s and 12s of paper fibre (paper pulp slurry) onto a wire 17 at the wet end of paper making machine so that the ply layers 11 and 12 are overlaid in a stagewise manner.

The additive 13 can be added to the suspensions 11s and 12s, for example, in upstream mixing vessels 21 in which the suspensions 11s and 12s are prepared. The suspensions 11s and 12s are then fed to the headboxes 18. It is also possible that the additive 13 can be added directly to the headboxes 18.

In another example, part of the additive 13 such as clay nano particles can be added to the upstream mixing vessels 21, and another part of the additive 13, such as a plasticizing agent

18164197_1 (GHMatters) P96760.AU.3 15/10/21 can be added to the suspension in the head boxes 18, or vice versa.

By including the additive 13 in the suspensions 11s and 12s, the additive 13 will be distributed throughout the entire thickness of the respective ply layers 11 and 12 discharged from the respective headbox 18, which can product the structures shown in figures 2b and 3b. In some situations, the additive 13 need only be present, and preferably, but not necessarily, at the interface between the ply layers 11 and 12 to benefit the paper sheet 10, as shown in Figure 2a and 3a.

Figure 4 also illustrates a step of applying the additive 13 to the face of the first ply layer 12. Specifically, the first ply layer 12 is discharged from a first headbox 18 onto the wire 17, and the additive 13 is applied to the upper face of the first ply layer 12 prior to the second ply layer 11 being delivered onto the first ply layer 12. For example, the additive 13 may be sprayed onto the upper face of the first ply layer 12 by a sprayer 19. Thereafter the ply layers 11 and 12 are joined together in a joining step 14. The joining step 14 may include dewatering and drying the paper sheet 15 in a drier.

The additive 13 can be added to the paper sheet 15 by means of either one or a combination of: i) adding the additive to the suspensions 11s and 12s in the mixing vessels 21 or the head boxes 18, or ii) applying a solution containing the additive to the surface of one of more of the ply layers using, for example, sprayer 19. Although Figure 4 illustrates the sprayer 19 in a located for applying the additive to ply layer 12, it will be appreciated that the sprayer 19 could be arranged to spray the inner face of the ply layer 11. It is also possible that other sprayers could be arranged to apply the additive 13 to the outer face of ply layers 11 and 12. In any event, when the sprayer 19 is used to apply the additive 13, the interface between the ply layers 11 and 12, the structure shown in figures 2a and 3a can result.

18164197_1 (GHMatters) P96760.AU.3 15/10/21

As shown in Figure 4, the process may optionally include applying the additive to the outer face of the paper sheet 15 in step 20, which is described in detail below with reference to Figures 5a and 5b. Following step 20 the paper sheet 15 can be rolled into a roll 22 for storage where the paper sheet can cool. The roll 22 can be called from storage for further product as desired.

Figures 5a and 5b illustrate two process steps for treating the surface of the paper sheet 15 with the additive 13. Moreover the processes illustrated in Figures 5a and 5b can be used with, and in addition to the process illustrated in Figure 4. It is possible that the additive 13 may not be included in the suspension 11s and 12s, or applied to the surface of the ply layers via sprayer 19 in accordance with Figure 4, but rather, the additive may be applied solely to the outside face of the paper sheet 15 according to the processes shown in Figures 5a and 5b.

The processes of Figure 5a and 5b include forming an aqueous solution of the additive 13, such as plasticising agent and optionally nano-particles, suitably clay nano-particles. A solution of the clay nano-particles is formed by dispersing the nano-particles supplied in a powder/aggregate form in a high shear mixing tank 25. The additive 13 may also include one or more plasticising agents for forming a thermoplastic polymer with starch as described herein. From the mixing tank 25, the dispersion is supplied to a pool 27. The process illustrated in Figures 5a and 5b can be used alternately or in combination.

Figure 5a illustrates the pool 27 formed in a size press comprising two engaging rollers 26 with the paper sheet 15 being conveyed through the nip of the rollers 26. The pool 27 may also include other agents such as addition starch, sizing agents, brightness enhancers and so forth. After being conveyed through the size press, the paper sheets 15 can be dried in an after drier 28 and rolled.

18164197_1 (GHMatters) P96760.AU.3 15/10/21

Figure 5b illustrates the pool 27 being arranged to feed to meter roller having grooves or indentations on the surface of the metered roller 30 that receives the solution and applies the solution containing the additive to the paper sheet 15. A transfer roller 31 may convey the solution from the pool 27 to metered roller 30. A backing roller 32 may be used to ensure adequate contact between the paper sheet 15 and the meter roller 30. Moreover, the amount of the additive applied to the sheet 15 passing through the pool 27 can be controlled by adjusting one or more of, the speed of the meter roller 30, the number of the grooves on the meter roller 30, the residence time of the paper sheet 15 in the pool, or the nip pressure between the rollers 26, or between the rollers 30 and 32. Moreover, the process may include controlling the degree of migration, penetration of the additive into the paper sheet, for example, by adjusting the nip pressure between the rollers 26, or between the rollers 30 and 32.

The processes shown in Figures 5a and 5b can product the structures shown in figures 2c and 3c.

Figure 6 illustrates the process of corrugating the paper sheet 15. The process may include a preliminary heating step 33 for heating the paper sheet 15 and activate the additive 13 prior to corrugating the paper sheet 15. Activating the additive 13, preferably including a plasticising agent, allows the starch to behave in a thermoplastic manner. The paper sheet 15 is then conveyed through a mating pair of rollers 16 that include co operating crests and troughs to impart a corrugating profile on the paper 15. The paper sheets 15 can also be moistened prior to passing through the corrugation rollers 16 or subjected to any other treatment to ready the paper sheet 15 for corrugation. During the corrugating step, the additive allows the ply layer 11 and 12 to move relative to each other to some extent, reducing the risk of delamination of the ply layers 11 and 12.

18164197_1 (GHMatters) P96760.AU.3 15/10/21

Figure 6 also illustrates that steps of attaching two liner boards 34 and 35 to the opposite faces of the paper sheet 15 have a corrugated conformation.

Figure 7 is a schematic illustration of a process for converting two preformed paper base sheets 11 and 12 into a corrugated paper 10. The preformed paper sheets 11 and 12 may be provided in a roll formation and can be obtained from any source and may each, for example, have a grammage ranging from 20 to 200 gsm. As shown in figure 7, the additive 13 may be applied to one or both of the surfaces of the preformed sheets 11 and 12 that face each other using a spray box 19. However, it will be appreciated that any suitable method such as roller application, meter rollers, or even passing the preformed sheets through a bath/pool containing the additive can be used.

The amount of the additive 13 applied to the paper sheets 11 and 12 can be controlled. For example, controlling the amount of additive 13 applied may include adjusting the rate at which the additive solution is sprayed from the sprayer 19, or adjusting the speed of the paper sheets 11 and 12 passing the sprayer 19. In addition the degree of the penetration of the additive into the base sheets 11 and 12 can be controlled by adjusting the nip pressure between the rollers 14 and the amount of the additive solution sprayed onto the base sheets 11 and 12.

The following application of the additive 13, the two sheets 11 and 12 are then joined together. The joining step may include pressing the sheets 11 and 12 together, for example, by passing through a nip of a pair of pressure rollers 14 to form an intermediate sheet 15. The intermediate sheet 15 is then corrugated by passing between a mating pair of co-operating rollers 16 that include co-operating crests and troughs which impart a corrugated profile to the paper sheet. The corrugated sheet 10 can then be cut to length as desired.

In other processes (not illustrated in the figures of the specification), the pressure rollers 14 may not be required and

18164197_1 (GHMatters) P96760.AU.3 15/10/21 the sheets 11 and 12 may be simultaneously joined and corrugated between the corrugating rollers 16.

Once the intermediate sheet 15 has been conveyed through the corrugating rollers 16, liner board 20 may be bonded, for example using an adhesive, to the undulations of one or both of the faces of the corrugated paper 10.

When an additive in the form of nano-particles is present on the outer face of the corrugated paper 10, the nano-particles may, in addition to affecting the mechanical properties of the corrugated paper 10, enhance the bond between the corrugated paper 10 and the liner board 20.

The additive may be included in a solution that is applied to one or both of the sheets 11 and 12 prior to the sheets being joined and corrugated. Ideally, the additive includes nano particles such as either one or a combination of clay nanoparticles and cellulose nano-particles. However, the additive may also include other types of the nano-particles such as those mentioned herein.

Ideally the clay nano-particles have a size in the range of equal to, or less than 500nm, and suitably equal to or less than 100nm. Ideally, the nano-particles may be platelets having a thickness in the range of the 1 to 5nm, and suitably approximately 1 nm, and a diameter in the range of 1 to 1011m. The nanoparticles, particularly clay nano-particles can bond, for example by physical or chemical bonding, to the starch and/or cellulose of the corrugated paper 10 and increase the stiffness of the paper 10.

Trials

A set of trials have been carried to measure the performance of a paper sheet that has been treated according to a preferred embodiment. The standard test methods we used are a ring crush strength (RCS) test, and a high humidity load carrying capacity

18164197_1 (GHMatters) P96760.AU.3 15/10/21

(HHLCC) test. Both tests are standard test methods and were carried out on i) untreated paper for use a control, and a paper treated with an additive in accordance with the embodiments described herein. The RCS test method involves a compression force being exerted on a sample of paper held in a ring form in a sample holder that is placed between two platens of a compression machine in which platen is driven toward a rigid platen at a uniform speed until the sample collapses. The sample is pre-conditioned in a controlled environment having a 50% relative humidity at 23°C.

The HHLCC test method is the same as the RCS test method described above, save for the additional following steps:

i) The sample is exposed to an environment in which the humidity changes stepwise between 50% relative humidity and 90% relative humidity over a three hour cycle. ii) A constant load is applied and the time to collapse measured (i.e. creep test) iii) The load and time to collapse is used to determine and measure creep performance in a cyclic high humidity environment.

Trial one

A 100gms paper sheet was surface treated using a mixture of starch and nano-clay at a weight of 4.5gsm. The mixture may be applied to the surface of the paper sheet using the size press methodology shown in figures 5a and 55, or sprayed onto the surface of the paper sheet. The treated paper sheet had a structure as shown in figure 3c and the mixture comprised starch and nano-clay in proportions of 85% starch and 15% nano-clay.

Figure 8a shows the test results of the treated and untreated paper sheets. As can be seen, the RCS of the paper sheet increased by approximately 8% and the HHLCC of the same paper sheet increased by approximately 13%. This is considered to be a considerable improvement.

18164197_1 (GHMatters) P96760.AU.3 15/10/21

Trial two

Two layers, each of 100gms, where sandwiched together using a mixture of starch and nano-clay that was applied at a weight of approximately 9gsm between the sheets. The mixture may be applied to either dry or wet layer, for example by means of the spray boxes 19 in figures 4 and 7, or by suitable means such as roller application, meter rollers, or even passing the preformed sheets through a bath containing the additive. In any event, the layers may form a paper sheet having the structure shown in figures 2a or 3a. The mixture comprised 25% nano-clay and 75% starch.

Figure 8b is a graph illustrating the improved performance of the sandwich paper sheet. The RCS of the sandwich does not increase significantly, however, the HHLCC of the same sample of paper increases by approximately 13%.

Trial three

A 135gms paper sheet was surface treated using a mixture of starch and nano-clay at a weight ratio of 4.5gsm. The mixture may be applied to the surface of the paper sheet using the size press methodology as shown in figures 5a and 55, or sprayed onto the surface of the paper sheet. In any event, the paper sheet had a structure as shown in figure 3c and the mixture comprised 85% starch and 15% nano-clay.

Figure 6c is a graph illustrating the improved performance of the paper sheet. Specifically, the RSC of the paper sheet increased by approximately 5%, and the HHLLC of the same sample increases by approximately 4%.

One of the benefits of the present invention is that the performance characteristics, such as ultimate load strength, shear stiffness and bending stiffness can be improved by the additive. This means that a corrugated paper containing a higher percentage of the recycled fibres can be produced with characteristics more akin to a product made from virgin fibre.

18164197_1 (GHMatters) P96760.AU.3 15/10/21

Similarly, when applied to a paper sheet comprising virgin

fibre, the embodiments could further improve the performance of

the product compared to other corrugated paper of similar

grammage made of the virgin fibre.

It will be understood to persons skilled in the art of the

invention that many modifications may be made to embodiments

described above without departing from the spirit and scope of

the invention.

18164197_1 (GHMatters) P96760.AU.3 15/10/21

Claims

1. A corrugating paper treated with an additive including

starch and at least 15wt% platelet shaped nanoparticles, the

nanoparticles having a thickness in the range of the 1 to 5nm

and bond to any one or a combination of: starch of the paper

sheet, adhesives present in the paper sheet, cellulose of the

paper sheet, and fibre of the paper sheet, wherein the additive

increases the high humidity load carrying capacity from 1 to 13%

compared to an equivalent paper sheet without the additive, in

which the relative humidity is at least 50%.

2. A corrugating paper treated with an additive including

starch and at least 15wt% platelet shaped nanoparticles having a

thickness in the range of the 1 to 5nm, including:

at least two ply layers that are joined together, and the

additive being located between the ply layers that

enhances the bond between the layers joined together,

wherein the nano-particles bond to any one or a

combination of fibre of the ply layers, cellulose and

starch of the ply layers, wherein the additive increases

the high humidity load carrying capacity from 1 to 13%

compared to an equivalent paper sheet without the

additive, in which the relative humidity is at least 50%.

3. The corrugating paper according to either claim 1 or 2,

wherein the nano-particles include cellulose nano-particles or

derivatives thereof, including nanocrystalline cellulose,

cellulose nanocrystals, cellulose whiskers, nanofibrillated

cellulose, cellulose nanofibrils, microfibrillated cellulose,

carboxymethylated cellulose, microcrystalline cellulose, and

cellulose filaments.

4. The corrugating paper according to any one of claims 1 to

3, wherein the nano-particles include clay nano-particles.

18164197_1 (GHMatters) P96760.AU.3 15/10/21

5. The corrugating paper according to any one of claims 1 to 4, wherein the additive includes a combination of clay nano particles, cellulose nano-particles in which a weight ratio of clay nanoparticles and cellulose nanoparticles is in the ranges of 10 to 90 : 90 to 10 respectively.

6. The corrugating paper according to any one of claims 1 to 5, wherein the additive increases the ring crush strength from 1 to 8% compared to an equivalent corrugating paper without the additive.

7. The corrugating paper according to any one of claims 1 to 6, wherein the additive slows time dependent deformation (creep) of the corrugating paper that is subject to a load in a high humidity/moisture environment in which the relative humidity is at least 50%, compared to an equivalent corrugating paper without the additive.

8. The corrugating paper according to any one of claims 1 to 7, wherein the nano-particles are distributed throughout the corrugating paper.

9. The corrugating paper according to any one of claims 1 to 8, wherein the corrugating paper has one or more ply layers, and the nano-particles are distributed throughout the or each ply layer.

10. The corrugating paper according to any one of claims 1 to 9, wherein the nano-particles are applied to the outer faces of the corrugating paper.

11. A corrugating paper treated with an additive including starch and at least 15wt% platelet shaped nanoparticles having a thickness in the range of the 1 to 5nm including:

at least two ply layers that are joined together to form the corrugating paper, and

18164197_1 (GHMatters) P96760.AU.3 15/10/21 the additive being is present in the corrugating paper and between the ply layers, wherein the nano-particles bond to any one or a combination of fibre of the ply layers, cellulose and starch of the ply layers, wherein the additive increases the high humidity load carrying capacity from 1 to 13% compared to an equivalent paper sheet without the additive, in which the relative humidity is at least 50% and facilitates relative movement of the ply layers to prevent or reduce fracturing of the join between the ply layers during corrugation of the sheet.

12. The corrugating paper according to claim 11, wherein the

additive further includes a plasticizing agent that can form a

thermoplastic with starch.

13. The corrugating paper according to claim 12, wherein the

plasticizing agent includes at least one of glycerol or

sorbitol.

14. The corrugating paper according to any one of claims 11 to

13, wherein the additive slows time dependent deformation

(creep) of the corrugating paper that is subject to a load in a

high humidity/moisture environment in which the relative

humidity is at least 50%, compared to an equivalent corrugating

paper without the additive.

15. The corrugating paper according to any one of claims 11 to

14, wherein the additive is located at the interface between the

ply layers, and penetrates into the plies to a degree.

16. The corrugating paper according to any one of claims 11 to

15, wherein the additive is located entirely through each ply

layer.

17. The corrugating paper according to any one of claims 11 to

16, wherein the additive is added to a paper pulp slurry feed to

18164197_1 (GHMatters) P96760.AU.3 15/10/21 the headbox of a papermaking machine so that the additive is distributed through the ply layer at the headbox.

18. The corrugating paper according to any one of claims 11 to 17, wherein the additive is applied to a face of the ply layer that is discharged from a paper machine headbox.

19. A process of manufacturing a corrugating paper from a paper sheet, the process including the steps of:

forming the paper sheet including one or more than one ply layer;

treating the paper sheet with an additive including starch and at least 15wt% platelet shaped nanoparticles having a thickness in the range of the 1 to 5nm; and

corrugating the sheet into a corrugating paper;

wherein the nano-particles bond to any one or a combination of fibre of the ply layers, cellulose and starch of the ply layers, and the additive increases the high humidity load carrying capacity from 1 to 13% compared to an equivalent corrugating paper without the additive, in which the relative humidity is at least 50% and facilitates relative movement of internal sheet structure and/or the ply layers to prevent or reduce fracturing of the internal structure and/or join between the ply layers during corrugation of the sheet.

20. The process according to claim 19, wherein the process includes allowing the paper sheet to cool, and thereafter heating the paper sheet prior to and/or during the corrugating step.

21. The process according to claim 19 or 20, wherein the step of corrugating the paper sheet into a corrugating paper includes passing the paper sheet between a pair of co-operating rollers

18164197_1 (GHMatters) P96760.AU.3 15/10/21 having mating surfaces with crests and troughs that impart a corrugated profile.

22. The process according to any one of claims 19 to 21,

wherein the step of forming the sheet including one or more ply

layers includes creating a paper pulp slurry containing the

paper fibre, and delivering the slurry onto a travelling wire

from a headbox at the wet end of a paper making machine and the

step of incorporating the additive in the paper sheet includes

any one or a combination of the following:

i) adding the additive to the paper pulp slurry feed to the

headbox of a papermaking machine so that the additive is

distributed through the ply layer of the headbox; or

ii) applying the additive to a face of the ply layer that is

discharged from a paper machine head box onto the wire.

23. The process according to any one of claims 19 to 22,

wherein the step of treating the paper sheet with the additive

includes forming a pool including the additive and conveying the

paper sheet through the pool.

24. The process according to any one of claims 19 to 23,

wherein the step of treating the paper sheet with the additive

includes controlling the penetration depth of the additive into

the paper sheet.

25. A process of manufacturing a corrugating paper, the

process including:

treating two base sheets with an additive including starch

and at least 15wt% platelet shaped nanoparticles having a

thickness in the range of the 1 to 5nm to locate the

additive between the two base sheets;

joining the base sheets together with the additive

therebetween to form a medium; and

corrugating the medium into the corrugating paper;

18164197_1 (GHMatters) P96760.AU.3 15/10/21 wherein the additive enhances the bond between the sheets and the nano-particles bond to any one or a combination of the fibre of the base sheets or starch of the base sheets, and increases the high humidity load carrying capacity from 1 to 13% compared to an equivalent base sheet without the additive, in which the relative humidity is at least

50%.

26. The process according to claim 25, wherein the additive is

a wet additive.

27. The process according to claim 25, wherein the additive is

applied to one or both of the joined faces of the sheets prior

to the sheets being joined together.

28. The process according to claim 27, wherein the additive is

applied by means of either: i) spraying the additive onto the

base sheet, or ii) applying the additive by means of roller

application.

29. The process according to any one of claims 25 to 28,

wherein corrugating the medium into the corrugating paper

includes passing the medium between a pair of co-operating

rollers having mating surfaces with crests and troughs that

impart a corrugated profile before drying the additive.

30. The process according to any one of claims 25 to 29,

wherein the process includes applying at least one liner board

to the corrugating paper after the corrugating step.

18164197_1 (GHMatters) P96760.AU.3 15/10/21