NZ735104B2 - A process for manufacturing plasterboard liner (PBL) for plaster board - Google Patents

Abstract

process for manufacturing paperboard liner (PBL) for plaster board, including the steps of receiving virgin Kraft fibre ( VKF); receiving recycled paper fibre (RCF); blending the VKF and the RCF to produce multiple fibre blend streams; forming said streams into paper plys; forming the plys into a multi ply paper sheet; chemically sizing the paper sheet to increase hydrophobicity; and drying the multi ply paper sheet over drying drums to produce the PBL, wherein the density of the PBL is no more than 140 grams per square meter (gsm). The liner has reduced weight whilst maintaining the necessary paper tensile strength, and has a light coloured surface. multi ply paper sheet; chemically sizing the paper sheet to increase hydrophobicity; and drying the multi ply paper sheet over drying drums to produce the PBL, wherein the density of the PBL is no more than 140 grams per square meter (gsm). The liner has reduced weight whilst maintaining the necessary paper tensile strength, and has a light coloured surface.

Description

(12) Granted patent specificaon (19) NZ (11) 735104 (13) B2 (47) Publicaon date: 2021.12.24 (54) A process for manufacturing plasterboard liner (PBL) for r board (51) Internaonal Patent Classificaon(s): B32B 13/08 B32B 29/00 B32B 33/00 B32B 37/14 D21H 21/14 D21H 11/14 D21H 19/00 D21H 27/30 D21H 11/04 (22) Filing date: (73) Owner(s): 2016.02.24 VISY R & D PTY LTD (23) Complete specificaon filing date: (74) Contact: 2016.02.24 DAVIES COLLISON CAVE PTY LTD (30) Internaonal Priority Data: (72) Inventor(s): AU 0738 2015.03.03 CLARK, Robert Kenneth MILUNOVIC, Vesna (86) Internaonal Applicaon No.: LE ROUX, Gary Mark 2016/050122 (87) Internaonal Publicaon number: WO/2016/138554 (57) Abstract: A process for cturing oard liner (PBL) for plaster board, including the steps of receiving virgin Kra fibre ( VKF); receiving recycled paper fibre (RCF); blending the VKF and the RCF to produce mulple fibre blend streams; forming said streams into paper plys; forming the plys into a mul ply paper sheet; chemically sizing the paper sheet to increase hydrophobicity; and drying the mul ply paper sheet over drying drums to produce the PBL, wherein the density of the PBL is no more than 140 grams per square meter (gsm). The liner has reduced weight whilst maintaining the necessary paper tensile strength, and has a light ed surface.

NZ 735104 B2 C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 A PROCESS FOR MANUFACTURING PLASTERBOARD LINER (PBL) FOR PLASTER BOARD.

Technical Field of the Invention The present invention relates to a system and process for manufacturing plasterboard liner. The plasterboard liner is preferably light weight Kraft based liner paper for the production of plasterboard.

Background of the Invention As shown in Figure 1, the manufacture of r board has traditionally involved the steps of: 1. rolling out a layer of face plasterboard liner (face PBL ); 2. pouring a slurry of Gypsum over the face PBL; 3. rolling out a layer of back plasterboard liner (back PBL) (also referred to as a base) over slurry of gypsum; 4. cutting the plasterboard into sheets; and 5. drying the plasterboard sheets.

To be suitable for use in plasterboard, plasterboard liner (PBL ) has previously had the following characteristics: 1. a high degree of ional stability with cross-direction wet expansion not exceeding 0.7%; and 2. high degree of tensile th machine direction (MD ) to cross-direction (CD ) tensile ratio in the range of 2.4 to 2.8.

It is also desirable for face PBL to have a light coloured outer surface in anticipation of the rboard being later painted.

A known system for manufacturing PBL is shown schematically in Figures 2a to 2d. As shown, the system uses recycled paper fibre (RCF ) as the main source of paper fibre.

PBL manufactured using a majority of RCF can achieve the necessary end product C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 (plasterboard) market characteristics of: 1. smooth, flat, ripple free surfaces evident by visual inspection; 2. high bending / flexural strength with breaking forc e MD:CD tensile ration not less than 2.4; and 3. face having a light colour with diffuse blue reflectance factor (also known as ISO brightness) not less than 40.

Over the past 15 years, PBL weight has been reduced from greater than 200 gsm to 150 gsm. This has been achieved through various incremental improvements that have allowed for reduced RCF volume and hence weight. These improvements include: a. General increase in RCF strength (due to increased Kraft fibre production from virgin wood and subsequent OCC fibre increase); b. General improvements to equipment, such as lower ply paper machines (i.e. from 7 ply to 3 ply); c. Better process knowledge and y control measures which, for example, has allowed for improved fibre formation; and d. Additives, such as starch, which are used to increase paper tensile strength.

PBL of weight r than 150 gsm ctured using 100% RCF has the advantages of high dimensional stability and tensile strength which is necessary for the subsequent manufacture of plasterboard sheet. However, it is generally desirable to e a plasterboard liner that is lighter in weight and contains an appreciable content of virgin fibre. To this end, the lighter PBL would: 1. Reduce fibre input per PBL unit ; 2. Increase volume of virgin Kraft fibre product per unit ted fibre; 3. Reduce transport cost per PBL unit ; 4. Increase plasterboard unit length per PBL unit weight; and . Reduce plasterboard drying l energy per unit length.

PBL of weight less than 130 gsm manufactured using 100% RCF is not able as it does not meet tensile strength requirements for subsequent plasterboard manufacture. PBL with an appreciable content of virgin Kraft fibre is not marketable C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 as it does not meet the dimensional stability requirements for subsequent rboard manufacture.

Tensile strength for paper is expressed as MD:CD ratio. This is the ratio of the maximum pulling stress before ng of the paper sheet in both the machine direction (MD) and the cross ion (CD). In a paper sheet, fibres oriented in the MD lay in the longitudinal direction of travel of the paper sheet through the paper machine. Fibres oriented in the CD lay dicular to the MD. Traditional PBL of greater than 150 gsm has a high MD:CD ratio for both back and face PBL. This is because there is sufficient fibre available to allow non-specialised fibre orientation in the PBL compared with l paper making in which the predominant fibre orientation is in the MD.

Dimensional stability for paper means its resistance to change in size as the result of a change in moisture content. Paper fibres have a natural tendency to absorb moisture and hydro expand. A measure of dimensional ity is wet expansion, which is the percentage difference between a paper sheet's dry and wet size. Traditional PBL of greater than 150 gsm has a high dimensional stability in part because it does not contain an appreciable content of virgin Kraft fibre.

Cellulose fibre used for paper making is recyclable. However, each time a fibre is ed, it loses th until it is no longer able to be used. Typically, a cellulose fibre can be recycled for paper making up to about 8 times. The term Kraft fibre is derived from the Kraft process technology for converting wood into wood pulp and extracting virgin cellulose fibres for paper manufacture. This process produces virgin Kraft fibre that has not previously been used for paper manufacture. ‘Kraft’ is a German word for ‘strength’. However, the term Kraft fibre also is used to more broadly refer to cellulose fibres that retain strength similar to that of virgin cellulose fibre and so it can encompass fibres that have been recycled up to about twice.

Kraft fibre is stronger than RCF and its inclusion in PBL can allow for reduced weight whilst maintaining the ary paper tensile strength. However, the inclusion of virgin Kraft fibre in PBL reduces the dimensional stability as virgin Kraft fibre is more reactive in contact with moisture than recycled fibre. This is because the fibre is damaged through each e, which s its strength and also makes it less C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 reactive to t with moisture. The vity of cellulose fibre to contact with water is a known phenomenon to which the paper industry worldwide invests substantial research. This is important in the manufacture of plasterboard sheet as the process involves contact with moisture via the gypsum slurry.

As mentioned, it is also ble for face PBL to have a light coloured outer surface in anticipation of the rboard being later painted. A light coloured surface for PBL face has usly been achieved through the addition of a ‘light colour fibre’ layer during the manufacture process. The process to produce RCF light colour fibre imposes an ongoing operational expense and its feedstock of recovered white paper is becoming less available. Figures 2a to 2d show schematically how this ‘light colour fibre’ layer is produced from recovered white paper feedstock via a ing process during the stock preparation stage.

It is generally desirable to overcome or rate one or more of the above mentioned difficulties, or at least provide a useful alternative.

Summary of the Invention In accordance with the invention, there is ed a process for manufacturing plasterboard liner (PBL ) for plaster board, including the steps of: (a) receiving virgin Kraft fibre (VKF ); (b) receiving recycled paper fibre (RCF ); (c) blending the VKF and the RCF to produce multiple fibre blend streams; (d) forming said streams into paper plys; (e) forming the plys into a multi ply paper sheet; (f) chemically sizing the paper sheet to increase its hydrophobicity; and (g) drying the multi ply paper sheet over drying drums to produce the PBL, wherein a density of the PBL is no more than 140 grams per square meter (gsm).

Preferably, the PBL is no more than 130 grams per square meter (gsm).

Preferably, a Cobb (60 second) value of the PBL is less than 30 gsm.

C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and s\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 Preferably, a cross direction wet expansion of the PBL is no greater than 0.8%.

Preferably, the step of blending results in multiple fibre blend streams each having a substantially even mixture of RCF and VKF. For example, the substantially even mixture includes greater than 35% VKF.

Preferably, the PBL is for a base of the plasterboard and the process includes the step of manipulating fibres of the fibre blend streams so that a machine ion to cross ion tensile ratio (MD:CD) of the PBL is not more than 1.4.

Preferably, the PBL is for a face of the plasterboard and the process includes the step of lating fibres of the fibre blend streams so that a machine direction to cross direction tensile ratio (MD:CD) of the PBL is not less than 2.2. Further, the process advantageously es the step of applying a pigment coating to the face PBL. The pigment coating preferably provides a light colour surface with diffuse blue reflectance factor not less than 30. Alternatively, the pigment coating preferably provides a light colour e with diffuse blue reflectance factor not less than 40.

The present invention also provides plasterboard liner for use in manufacturing rboard formed from the described process.

The present invention also provides base plasterboard liner for use in manufacturing plasterboard formed from the above-described process.

The present invention also provides face plasterboard liner for use in manufacturing plasterboard formed from the above described process.

The present invention also provides plaster board, including gypsum interposed between the above described face plasterboard liner and the above described base plasterboard liner.

The present ion also es a system for manufacturing plasterboard liner (PBL ) for plaster board, including: (a) fibre preparation and blending apparatus, said apparatus for performing the steps of: C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and s\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 (i) receiving virgin Kraft fibre (VKF ); (ii) receiving ed paper fibre (RCF ); and (iii) blending the VKF and the RCF to produce multiple fibre blend s; and (b) paper making apparatus, said paper making apparatus for performing the steps of: (i) receiving the multiple fibre blend streams from the fibre preparation and blending apparatus; (ii) forming said streams into paper plys; (iii) forming the plys into a multi ply paper sheet; (iv) chemically sizing the paper sheet to increase its hydrophobicity; (v) drying the multi ply paper sheet over drying drums to produce the PBL, n a density of the PBL is no more than 140 grams per square meter (gsm).

Preferably, the PBL is no more than 130 grams per square meter (gsm).

Preferably, a Cobb (60 second) value of the PBL is less than 30 gsm.

Preferably, a cross direction wet expansion of the PBL is no greater than 0.8%.

Preferably, the step of blending results in multiple fibre blend streams each having a substantially even mixture of RCF and VKF. For example, the substantially even mixture includes greater than 35% VKF.

Preferably, the PBL is for a base of the plasterboard and the system includes the step of manipulating fibres of the fibre blend streams so that a machine ion to cross direction e ratio (MD:CD) of the PBL is not more than 1.4.

Preferably, the PBL is for a face of the plasterboard and the system includes the step of manipulating fibres of the fibre blend streams so that a machine direction to cross direction tensile ratio (MD:CD) of the PBL is not less than 2.2. Further, the system advantageously includes the step of ng a pigment coating to the face PBL. The C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 pigment g preferably provides a light colour surface with diffuse blue reflectance factor not less than 30. Alternatively, the pigment coating preferably provides a light colour surface with diffuse blue reflectance factor not less than 40.

Brief Description of the Drawings Preferred embodiments of the t invention are hereafter described, by way of non-limiting example only, with reference to the accompanying drawing in which: Figure 1 is a schematic diagram g steps performed by a known system for manufacturing plaster board from plasterboard liner and gypsum slurry; Figure 2a is a schematic diagram showing steps performed by a known system for manufacturing plasterboard liner from mainly recycled paper fibre; Figure 2b is a schematic diagram g steps med for stock preparation by the known system shown in Figure 2a; Figure 2c is a tic diagram showing steps performed for paper making by the known system shown in Figure 2a; Figure 2d is a schematic diagram showing steps performed for paper strengthening by the system shown in Figure 2a; Figure 3a is a schematic diagram showing steps performed by a system for manufacturing plasterboard liner; Figure 3b is a schematic diagram showing steps performed for fibre preparation and ng by the system shown in Figure 3a; Figure 3c is a tic diagram showing steps performed for paper making by the system shown in Figure 3a; Figure 3d is a schematic diagram showing steps performed for pigment coating by the system shown in Figure 3a; and Figures 4 to 9 show test data for plasterboard liner ed by the system shown in Figure 3a.

Detailed Description of Preferred Embodiments of the Invention The system 10 shown in s 3a includes apparatus 12 for manufacturing plasterboard liner (PBL ) 14 of less than 140 grams per square meter ( gsm ). For example, the system 10 can advantageously produce PBL ranging between 110gsm C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 and 130gsm. Advantageously, the system 10 achieves PBL of less than 140 gsm with one or more of the following:  Back PBL MD:CD tensile ratio not greater than 1.4;  Face PBL MD:CD tensile ratio not less than 2.2;  CD wet expansion less than 0.8%;  Cobb value (60 seconds) less than 40 gsm; and  Face PBL light colour e not less than ISO brightness 30.

The PBL thus achieves the necessary characteristics of dimensional stability, and tensile strength for the combined back and face to make it suitable for uent rboard sheet manufacture. The system 10 achieves these results using a substantially even ratio of recycled paper fibre (RCF ) 16 and virgin Kraft fibre (VKF ) 18, for example. Alternatively, the system uses any other suitable ratio of RCF and VKF to achieve a PBL 14 of less than 140 gsm.

The system 10 is also suitable for manufacturing plasterboard liner (PBL ) 14 of less than 130 grams per square meter (gsm ). For example, the system 10 can advantageously produce PBL ranging between 110gsm and 125gsm. Advantageously, the system 10 achieves PBL of less than 130 gsm with one or more of the following:  Back PBL MD:CD tensile ratio not greater than 1.4;  Face PBL MD:CD tensile ratio not less than 2.2;  CD wet expansion less than 0.8%;  Cobb value (60 seconds) less than 30 gsm; and  Face PBL light colour surface not less than ISO ness 40.

The PBL thus achieves the ary characteristics of dimensional stability, and tensile th for the combined back and face to make it suitable for subsequent plasterboard sheet manufacture. The system 10 achieves these results using a substantially even ratio of ed paper fibre (RCF ) 16 and virgin Kraft fibre (VKF ) 18, for example. Alternatively, the system uses any other suitable ratio of RCF and VKF to achieve a PBL 14 of less than 130 gsm.

In either case, the lighter PBL 14 is advantageous across a number of manufacturing C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 and commercial aspects including:  The market units of lighter PBL are increased for the same weight of paper ed and this has a commercial advantage for transporting the PBL 14;  The paper product volume is increased for the same weight virgin Kraft fibre by mixing with RCF and this has a manufacturing advantage for a pulp mill in reducing the bottle neck imposed by the rate and cost of pulp production to output of paper products; and  The plasterboard sheet manufacture drying energy is reduced for the same unit length of rboard sheet due to the reduced weight of the PBL 14.

The system 10 also advantageously solves the problem of a light ed PBL face without additional fibre layer. The system 10 includes an option to apply a pigment coating 24 to PBL to achieve an ivory coloured e with ISO brightness not less than 30, for example. Alternatively, the system 10 includes an option to apply a pigment coating 24 to PBL to achieve an ivory coloured surface with ISO brightness not less than 40, for example. This is achieved using an application process to the PBL surface. The advantage of the solution is that PBL face with a light coloured e is ctured without the need to use light coloured RCF and this avoids the need for RCF recovered white paper feedstock and the stock preparation de-inking process or the purchase of white fibre feedstock.

The apparatus 12 includes: 1. fibre preparation and blending apparatus 20; 2. paper making apparatus 22; and 3. pigment g tus 24.

By way of non limiting example, a detailed description on the operation of each apparatus 20 to 24 is set out below. 1. Fibre Preparation & Blending Apparatus 20 The fibre preparation and blending apparatus 20 receives RCF 16 and VKF 18 from preceding ated manufacturing processes. The VKF 18 is manufactured using the C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 Kraft process technology and refined to e paper properties using known process technology. For example, Visy's Tumut Kraft Mill in Australia produces high quality kraft paper for domestic and international markets using ips from softwood plantations in southern NSW supplemented by recyclable wastepaper. The RCF 16 is manufactured using recovered paper/cardboard from which recyclable cellulose fibres are extracted using known process technology.

RCF 16 and water 32 are added to the RCF pulper tank 26. The contents of the pulper tank 26 is then passed through contaminant screens 30 to remove contaminant materials such as plastic and metal in a known step common to paper making using RCF. The RCF is then sent to the blend tank 34.

VKF 18 and water 32 are added to the Kraft fibre pulper & pre-treatment tank 28.

Charge control chemicals are added to maximise reactivity of the VKF 18 with sizing chemicals later added by the al additive apparatus 38 (described below in further detail with reference to the paper making tus 22).. For example, adding anionic trash tor (ATC) at 1 to 2 KG per tonne to achieve 500 to 1000 uEq/l. The pre-treated VKF is then sent to the blend tank 34.

The blend tank 34 takes the pre-treated VKF 18 and the screened RCF 16 and tes multiple fibre blend streams of ntially even mixtures. As above mentioned, it is anticipated that other mixtures of RCF 16 and VKF 18 can be used with a view to obtaining PBL of less than 140 gsm or 130 gsm. For example, the mixture may be 40% VKF. However, for ease of description, the system 10 is described below with reference to the mixture being substantially even.

Each stream forms a ply of the multi ply paper machine 36 of the paper making tus 22 with a substantially even fibre g on the total PBL of RCF 16 and VKF 18.

All paper products have a natural tendency to absorb moisture and hydro expand (called wet expansion). Even with internal and surface applied chemical sizing technology, wet expansion results in dimensional changes on the paper relative to the original paper in the dry state.

C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 n fibres have a greater potential to reabsorb moisture than others. In the example of PBL, RCF has a lower level of wet expansion than VKF. However, RCF has a lower tensile strength than VKF.

The blend tank 34 maintains a balance between RCF 16 and VKF 18 content of the fibre streams for each ply of the multi ply paper machine 36. It uses fibre slurry consistency and flow rate to achieve a specified RCF 16 and VKF 18 composition of the multiple outflow fibre streams. Each outflow fibre stream forms a ply and the multiple plys are combined through the paper making apparatus 22 to form a multi ply paper sheet. The bution of RCF and VKF is very important within the respective paper plys as well as the ply split within the composite PBL. The blending of RCF 16 and VKF 18 to achieve the necessary fibre blend of the fibre streams is fied schematically in Figure 3b.

An advantage of RCF is than it has a lower level of wet ion and icantly cheaper raw material to manufacture PBL. A disadvantage with RCF is that manufactured PBL has a lower tensile strength than, for example, an equivalent weight PBL using virgin Kraft fibre. The advantage of virgin Kraft fibre is that manufactured PBL has a vastly or tensile strength. The disadvantage of virgin Kraft fibre is that manufactured PBL has a high level of wet expansion.

To obtain an optimal balance n the benefits of using VKF 18 to obtain higher tensile strength and minimising wet ion, the blend tank 34 provides a substantially even mixture of RCF 16 and VKF 18 in multiple streams for the paper making apparatus 22. This results in an even fibre ratio across the total multi ply PBL sheet, for example. 2. Paper Making Apparatus 22 The paper making apparatus 22 includes: a. a multi ply paper machine 36, including: i. paper fibre formation apparatus 37 (also known as paper machine wet end); ii. chemical additive apparatus 38; and rs\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 iii. speed control tus 40; and b. drying drums 42.

The operation of each one of the above is below described in further detail. a. Multi Ply Paper Machine 36 The multi ply paper machine 36 manufactures paper sheet by first forming multiple fibre plys that are then ed into a multi ply paper sheet prior to drying. The formation of paper sheet using a 2 ply paper machine is shown schematically in Figure 3c, for example. i. Paper Fibre Formation tus 37 The paper machine wet end 37 receives fibre from the blend tank 34 in multiple s and this is carefully manipulated to achieve the required basis weight of the combined ply paper sheet, for example 130gsm, and composition of RCF 16 and VKF 18, for example, greater than 35% virgin Kraft fibre.

Importantly, the paper machine wet end 37 -wire ratio is carefully manipulated to control the physical fibre orientation of the paper sheet. This ratio, which is the difference between the speed of the fibre forming n jet and that of the forming section wire, is used to fine-tune a PBL's fibre structure. It also ively determines the dominant directional tensile strength of the paper sheet in either the machine direction (MD) or cross direction (CD).

Traditionally the jet-to-wire ratio is less than unity, and the fibre content is high, and this 'draws' or 'drags' the fibres out in the MD and achieves a high MD:CD tensile ratio. For PBL the jet-to-wire ratio is carefully controlled to either 'drag' or 'rush' (when jet-to-wire ratio is greater than unity) the paper sheet to manipulate the proportion of fibre alignment in the CD. Combined with the low fibre content, this achieves MD:CD tensile ratios that differ substantially between back and face PBL. For example: PBL Jet-to-wire Fibre content MD:CD tensile ratio C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 ratio Back 1.000 120 gsm 1.1 Face 1.015 125 gsm 2.6 Importantly the jet-to-wire ratio and resultant fibre orientation also affects the dimensional stability through the degree of wet expansion. The advantages of very low MD:CD tensile ratio for back PBL is that it attains a lower CD wet expansion, for example 0.8%. ii. The Chemical Additive Apparatus 38 The chemical additive apparatus 38 chemically sizes the multiple paper substrate plys to increase hydrophobicity of both RCF 16 and VKF 18 y reducing the multi ply paper s tendency to absorb liquid. The following steps are performed in that regard: a. the VKF 18 is pre-treated at the fibre preparation and blending apparatus 20 with charge control chemical technology to maximize the virgin Kraft fibre’s ability to react with sizing chemicals; internal sizing chemical technology is d to the multi ply paper sheet by the chemical additive apparatus 38 using for example the following cationic rosin >12 kg/t, aluminum sulphate (Alum) >24 kg/t, and Alkyl Ketene Dimer >3 kg/t In addition, surface sizing chemical technology is applied at the coating machine 44 by the surface sizing apparatus 46, as shown in Figure 3d.

The steps med by the multi ply paper e 36, as described above, are shown schematically in Figure 3c, using a 2 ply paper machine for example. They result in improved dimensional ity and tensile strength and of PBL containing substantial content of VKF 18.

The PBL manufactured by the system 10 includes the use and sizing of VKF 18 to achieve the necessary dimensional stability and tensile th suitable for the subsequent manufacture of plasterboard sheet. This, in turn, s the plasterboard sheet to achieve its required market characteristics of flat, ripple free surfaces and high blending strength.

C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 The system 10 solves the problem of d VKF 18 which is reactive to contact with moisture and this makes it unsuitable for use in PBL as the required dimensional stability is not ed. The manufacture of plasterboard sheet requires the PBL to be in contact with gypsum slurry as it is sandwiched between the face and back PBL. Too much wet expansion through water absorption from the slurry during pressing to adjust thickness can result in subsequent rippling of the end product surfaces following drying of the slurry to produce the plasterboard sheet.

The system 10 can use various functional sizing al technology for PBL . A combination of sizing chemicals is used, for example: a. cationic rosin >12 kg/t; b. aluminum sulphate (Alum) >24 kg/t; c. Alkyl Ketene Dimer >3 kg/t; and d. e sizing agent 3-12 kg/t.

Both VKF 18 and RCF 16 are d with internal sizing chemical technology to manufacture PBL grades.

Functional sizing chemical technology reduces the natural tendency of fibres to reabsorb moisture after paper has been dried. Internal sizing chemical technology reduces the paper tendency to absorb water by attaching hydrophobic les to the fibres. These molecules effectively repel water before water is able to penetrate into the fibre structure.

To further enhance hydrophobicity, surface sizing al technology is also applied at the surface sizing chemical apparatus 46 of the coating machine 44. Here a limited amount of sizing chemical is applied as a layer to create surface r to reduce water ation into the PBL. 2(a)(iii) & 2(b). Speed Control Apparatus 40 & Drying Drums 42 The speed control apparatus 40 acts to reduce the draw between successive processes on the formed paper sheet through its pressing and drying. This reduces the tendency C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 for formed paper sheet to react when contacted with water thereby reducing the hydro expansion. This feature is identified schematically in Figure 3c.

Successive paper machine sections (press, dryer and reel) relative speed controls are carefully lled by the speed control apparatus 40 to minimize fibre draw in the MD before application to the drying drums 42 to minimise sheet shrinkage to less than 2% for example. 3. Pigment g apparatus 24 The pigment coating apparatus 24 includes: a. a coating machine 44; b. surface sizing chemical apparatus 46; c. pigment ation tus 48; and d. drying drums 50.

Traditional Ivory PBL utilizes de-inked RCF from recovered white paper feedstock to manufacture the face (Ivory) grades. With the incorporation of the coating machine 44, for example a film press, there is the option of pigment coating the PBL 14 to resemble the ivory sheet appearance for face PBL, or any other desired colour. The coating refers to a layer of material from a single stage application, for e including pigment formulation, starch and sizing agent.

This offers the t of improved strength gains associated with starch to offset the negative effect of the pigment coating and an overall benefit of lower cost of pigment.

Figure 3d shows schematically how the coating machine 44 is used for this feature.

The advantage of pigment coating is that g can be formulated to achieve the d surface appearance, for example light coloured face PBL of ISO brightness not less than 30. atively, the coating can be formulated to achieve the desired surface appearance, for example light coloured face PBL of ISO brightness not less than 40. Pigment coating is significantly r than light coloured RCF used in traditional Ivory grades. A disadvantage is that pigment coating chemicals do not have any tensile strength enhancement of the PBL. As such, the tensile strength must be C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 derived from the VKF 18 and the RCF 16.

The coating machine 44 works by enabling a finite amount of pigment coating film to be metered onto one (or two) rolls through which paper runs. The pigment coating film effectively transfers onto the sheet once the paper passes through the rolls. The amount of pigment coating is carefully controlled by the coating recipe, its solid content, the applicator rod ion and contact time on the rolls.

The pigment g recipe includes a mixture of different clay and/or calcium carbonate pigments and binders.

Coating machines for single stage applications have previously been installed on paper machines to enhance dry strength with the application of modified starches. In the example shown in Figure 3d, the coating machine 44, for example a film press, includes the pigment ation apparatus 48 and the surface sizing chemical apparatus 46. The incorporation of the pigment application apparatus 48 allows the coating machine 44 to add a coating pigment in addition to the applied starch. The reason for the addition of pigment is to affect the surface appearance of the face PBL.

The addition of the surface sizing chemical apparatus 46 to the coating e 44 allows for blending surface sizing chemical technology with starch, water or coating pigment to enhance hydrophobicity of the paper and e a coating thickness of 7- 8 ml/m2 for example. In this application the surface sizing chemical is 100% retained on the face PBL sheet. Figure 3d shows schematically how the coating machine 44, for e a film press, is used for this feature.

The advantages of the coating e 44 is that cheaper alternative pigments eg. clay and calcium carbonate can be precisely metered onto the PBL sheet to ate an Ivory ply for face PBL. Other ages are that the appearance can be modified with recipe of coating and ation loading. atives to a coating machine 44 are: a. For light colour: to use a de-inked RCF from red white paper feedstock on the face PBL (Ivory ply); C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 b. For dry strength enhancement: to use lized dry strength chemicals in the fibre ; and c. For surface sizing: there is no effective alternative as only internal sizing chemicals can be applied using the paper e.

Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention. To this end, the apparatus for manufacturing plasterboard liner 12 has been above described, by way of non-limiting example, with reference to the following being separate apparatus: 1. fibre preparation and blending apparatus 20; 2. paper making apparatus 22; and 3. pigment coating apparatus 24.

However, in ce, the above is alternatively formed as one unit, or many separate units.

Sizing for paper means the use of chemicals to reduce its tendency to absorb liquid.

Internal sizing chemicals are applied during paper formation to be incorporated throughout the paper sheet h bonding to ose fibres to increase their hydrophobicity. Surface sizing chemicals are d as a thin coating on the paper sheet and have a hydrophillic end that joins to the cellulose fibre and a hydrophobic end that faces away to make the paper surface more ant to the penetration of liquid. A measure of resistance to liquid absorption is the Cobb value, which is the surface water absorption in grams per square meter over 60 seconds. As the manufacture of plasterboard sheet requires PBL to be in t with moisture via the gypsum slurry, PBL is 'hard sized' paper. This means it is in the category of papers with the highest water resistance.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge in Australia In this specification and the claims that follow, unless stated otherwise, the word "comprise" and its variations, such as "comprises" and "comprising", imply the rs\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 inclusion of a stated integer, step, or group of integers or steps, but not the exclusion of any other integer or step or group of integers or steps.

References in this specification to any prior publication, information derived from any said prior publication, or any known matter are not and should not be taken as an acknowledgement, admission or suggestion that said prior publication, or any information derived from this prior publication or known matter forms part of the common general knowledge in the field of endeavour to which the ication relates.

C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 Summary of Paper Trials: Trial 1 Initial base line study to ine quality at normal ply loading at 30% RCF substitution to the top wire (TW ) (also referred to as the "bottom ply").

Trial 2 Second ne study based on 50:50 ply loading. RCF loading increased to 40% and ng study to understand impact on ty. Secondary objective to establish the impact of the BW FormMaster.

Moderate water absorption test performed on paper (COBB ) 1’ 25-30 at maximum CRS size dosage for normal wet end chemistry. The test resulted in significant rippling associated with Wet Expansion.

Trial 3 Trial to test the baseline to understand %RCF and Tensile ratio on Wet Expansion.

Also TOPKraft jumbo. The trial also included manufacture K110PB at low Tensile ratio and TOPKraft jumbo.

The trial resulted in significant ement in back rippling. That is, it was less defined and finer. The TopKraft paper did not show any benefit. That is, it appeared easier to delaminate.

Lower tensile ratio  260-280 N MD breaking strength MD (AS/NZ minimum 360N).

Trial 4 Implement trial 3 machine set up at lowest Tensile ratio. Focus on improving wet end chemistry for maximum or HIGH SIZE cationic rosin size efficiency. That is, the lowest COBB capability.

• Incorporating anionic trash collection application C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 • Establish effect on Wet ion at extreme e ratio set-up • Rewetting paper at VPC to reduce internal strain with water uptake on gypsum application • Third Plasterboard trial 14/06/2013 at Boral Port Melbourne • Rippling for low Tensile ratio was as good as second trial • High Tensile ratio paper was not tested Trial 5 • ASA (Alkyl Succinic Anhydride) size conversion trial  achieve as low COBB as possible • Substitute 60% RCF for 110 gsm and 115 gsm • Rewetting paper at VPC to reduce internal strain with water uptake on gypsum application • Fourth rboard trial 11/07/2013 at Boral Pinkenba • General consensus hard sized ASA compared with hard sized Rosin sized paper for rippling • 60% RCF substitution reel gave the best OVERALL result on rippling • med by the lowest Wet Expansion < 0.8% Trial 6 Objective to establish the max. and min. Tensile MD at 110 gsm and 125 gsm.

Standardize 50% RCF for 115 gsm and 125 gsm. Rewetting paper at VPC to reduce internal strain with water uptake on gypsum application.  ation max. and min. Tensile ratio was ran for FACE and BASE  Max. Tensile MD paper acceptable for FACE break strength  MD Break Strength K110PB 280 N ; K125PB 380 N (Spec 360N)  BASE rippling is almost acceptable but more work required to achieve PN150 flatness C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 Process Capability and Expected Quality: 1. Minimum Wet Expansion (BASE) K110PB K125PB a. Tensile MD 50-52 N.m/g 7 kN/m 6.25-6.5 kN/m b. Tensile CD 40-42 N.m/g 4.4 – 4.6 5.0-5.25 kN/m c. Tensile ratio 1.0 – 1.1 d. Porosity 250 – 300 ml/min e. ASA Sizing. COBB does not correlate with wet expansion. EMCO s on Trial 4 and Trial 5 indicates a significant ence in initial water hold out (40-80%) with ASA hard sized paper. f. Higher RCF substitution up to 60% g. Minimum refining levels h. Lowest risk of rippling at Wet Expansion 0.7- 1.0% 2. Balanced Tensile Strength (BASE) K110PB K125PB a. Tensile MD 55-60 N.m/g 6.0–6.6 kN/m 6.9-7.5 kN/m b. e CD 45 N.m/g 5.0 kN/m 5.6 kN/m c. Tensile ratio 1.2– 1.5 d. Porosity 230 – 250 ml/min e. ASA Sizing. f. Higher RCF substitution up to 50% g. Moderate refining levels CSF 500-550 CSF h. Higher risk of ng with Wet Expansion 1.0-1.5% 3. Highest e Strength (FACE) K110PB K125PB a. Tensile MD 70-73 N.m/g 7.7–8.0 kN/m 8.8-9.12 kN/m b. Tensile CD 23 - 30 N.m/g 2.5-3.3 kN/m 2.9-3.75 kN/m c. Tensile ratio >2.7 d. Porosity 200 – 220 ml/min e. High Size Cationic Rosin High Size. f. RCF substitution up to 50% g. Max refining levels < CSF 500 CSF h. Highest risk of rippling with Wet Expansion > 1.5% C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 4. Chemical additives a. Fibre preparation sizing:  Anionic trash collector 3kg/t 500-1000uEq/l b. Paper making internal sizing:  Cationic rosin > 12 kg/t  Aluminum sulphate > 24 kg/t  AKD (Alkyl Ketene Dimer) > 3 kg/t c. Film press surface sizing  Surface sizing agent 3-12 kg/t General: 1. BASE ation best option is Capability 1 (lowest tensile ratio) K125PB: a. Expect plasterboard MD ng strength 300 N ( in combination with PV170) b. ASA hard sized 4.5-5 kg/Adt c. Lowest risk of rippling 2. FACE ation best option is Capability 3 (highest tensile ratio) K125PB and high sized ROSIN: a. Rosin hard sized 10-11 kg/Adt b. Expect plasterboard MD breaking strength >360 N ( in combination with PV170) c. Lowest risk of board break on the gypsum line 3. Although COBB does not correlate well with Wet ion, EMCO testing indicates a difference between hard sized ASA vs ROSIN: a. ASA appears to have superior initial water hold-out rs\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 Glossary TW Top Wire (Bottom ply) GSM Grams per square meter BW Bottom Wire (Top ply) FormMaster Name of papermaking Equipment COBB Water absorptiveness (cobb value) is the mass of water absorbed in a specific time by one square meter of paper, board, or ated fibreboard under one centimetre of water.

CRS cationic Rosin Size (rosin is a chemical added to achieve water holdout). jumbo jumbo / master reels of paper K110PB Paper grade MD Machine Direction - paper direction along the le ngth of the paper machine.

VPC Visy Paper Coatings K125PB Paper grade CD Cross Direction - paper direction across the width of the paper machine.

EMCO Water absorption test equipment name.

CSF Canadian Standard Freeness. A measure of the ge of paper pulp linked to refining and pulp quality.

PV170 170gsm Ivory Face paperboard liner TSI e Stiffness Index. Ultrasonic, non-destructive test method for determining the strength of paper, and plaster board liner.

ABB AWP Moisturising bar from ABB used at VP9 furnish paper going to pulping stage of papermaking.

WIS Web Inspection System - hole detector WW White Water - aking water removed from wet sheet and recycled back into the process water.

PSD Paper machine shutdown WRV Water ion Value - laboratory test for delivering how much water a pulp will hold under controlled conditions.

Mutec Laboratory equipment for measuring charge in water.

C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 INDEX Figure 1 A Plasterboard liner - face B Gypsum slurry C Plasterboard liner - back D Cutter E Plasterboard sheets F Drying Figure 2a G Recovered paper - newsprint H red paper – Office white I Recovered paper - mixed J Recovered cardboard - mixed K Recovered cardboard – high content Kraft fibre L Water M Stock preparation N RCF Slurry O Paper making P Paper strengthening Q Paper board liner C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 Figure 2b R Recovered paper - newsprint S Recovered paper – Office white T red paper - mixed U Recovered cardboard - mixed V Recovered cardboard – high content Kraft fibre W Water X RCF pulper Y Contaminant screens Z Detergent AB Floatation tank AC Disperser AD RCF blending (as required) AE RCF De-Inking (Face PBL only) AF RCF Slurry Figure 2c AG RCF Slurry AH 3 ply machine Paper sheet formation AI Paper making AJ Drying drums Figure 2d AK Starch bath AL Paper strengthening AM Drying drums AN Plasterboard liner C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and s\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 Figure 3a AO Virgin Kraft fibre AP Recovered cardboard AQ RCF AR Water AS Fibre ation and blending AT Paper making AU Pigment coating AV Kraft Plasterboard liner Figure 3b AW Water AX Virgin Kraft fibre AY RCF AZ Kraft fibre pulper & pre-treatment BA RCF pulper BB Contaminant screens Figure 3c BC Fibre preparation & blending BD Paper fibre formation BE Chemical additive apparatus BF Speed control apparatus BG Multi Ply Paper Machine BH Drying drums Figure 3d BI Surface sizing chemical apparatus BJ Pigment application apparatus BK Coating machine BL Drying BM Kraft Plasterboard liner C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 Claims Defining the Invention 1. A process for manufacturing plasterboard liner (PBL ) for plaster board, including the steps of: (a) ing virgin Kraft fibre (VKF ); (b) receiving recycled paper fibre (RCF ); (c) blending the VKF and the RCF to produce multiple fibre blend streams; (d) forming said s into paper plys; (e) forming the plys into a multi ply paper sheet; (f) chemically sizing the paper sheet to increase hydrophobicity; and (g) drying the multi ply paper sheet over drying drums to produce the PBL, wherein a density of the PBL is no more than 140 grams per square meter (gsm). 2. The process claimed in claim 1, wherein the density of the PBL is no more than 130 grams per square meter (gsm). 3. The process claimed in claim 1 or claim 2, wherein a Cobb (60 second) value of the PBL is less than 30 gsm. 4. The process claimed in any one of claims 1 to 3, wherein cross ion wet expansion of the PBL is no greater than 0.8%.

. The process claimed in any one of claims 1 to 4, wherein the step of blending s in multiple fibre blend streams each having a substantially even mixture of RCF and VKF. 6. The process claimed in claim 5, wherein the ntially even mixture includes greater than 35% VKF. 7. The process claimed in any one of claims 1 to 6, n the density of the plasterboard liner ranges between 110gsm and . 8. The process claimed in any one of claims 1 to 6, wherein the density of the plasterboard liner ranges between 110gsm and 130gsm.

C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 9. The process claimed in any one of claims 1 to 8, wherein the step of chemically sizing the VKF and RCF includes the step of applying internal sizing chemicals to the paper sheet.

. The process claimed in claim 9, wherein the internal sizing als include:  Cationic rosin > 12 kg/t  Aluminum sulphate > 24 kg/t  AKD (Alkyl Ketene Dimer) > 3 kg/t 11. The process d in claim 9 or claim 10, wherein the step of chemically sizing the VKF includes the step of applying surface sizing chemicals to the multi ply paper substrate. 12. The s claimed in claim 11, wherein the surface sizing chemicals include surface sizing agent 3 to 12 kg/t. 13. The process claimed in any one of claims 9 to 12, wherein the step of chemically treating the VKF includes the step of pre-treating the VKF to improve the VKF's ability to react with the sizing chemicals. 14. The process d in claim 13, wherein the sizing chemicals include anionic trash collector 3kg/t to achieve 500 to1000uEq/l. 15. The process d in any one of claims 1 to 14, wherein the PBL is for a base of the plasterboard and the process es the step of manipulating fibres of the fibre blend streams so that a machine direction to cross direction e ratio (MD:CD) of the PBL is not more than 1.4. 16. The process claimed in any one of claims 1 to 14, wherein the PBL is for a face of the plasterboard and the process includes the step of manipulating fibres of the fibre blend streams so that a machine direction to cross direction tensile ratio (MD:CD) of the PBL is not less than 2.2. 17. The process d in claim 16, including the step of applying a pigment C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 57(21827042.1).doc-4/08/2021 coating to the face PBL. 18. The process claimed in claim 17, wherein the step of applying the pigment coating to the face PBL includes the step of ing dry strength with application of modified starches. 19. The process claimed in claim 17 or claim 18, wherein the pigment g provides a light colour surface with diffuse blue reflectance factor not less than 40. 20. The process claimed in claim 17 or claim 18, wherein the t coating provides a light colour surface with diffuse blue reflectance factor not less than 30. 21. Plasterboard liner for use in manufacturing plasterboard formed from the process claimed in any one of claims 1 to 20. 22. Base plasterboard liner for use in manufacturing plasterboard formed from the process claimed in claim 15. 23. Face plasterboard liner for use in manufacturing plasterboard formed from the process claimed in any one of claims 16 to 19. 24. Plaster board, including gypsum interposed between the face plasterboard liner claimed in claim 23 and the base plasterboard liner claimed in claim 22. 25. A system for manufacturing plasterboard liner (PBL ) for plaster board, ing: (a) fibre preparation and blending apparatus, said apparatus for performing the steps of: (i) receiving virgin Kraft fibre (VKF ); (ii) receiving recycled paper fibre (RCF); and (iii) blending the VKF and the RCF to produce multiple fibre blend s; and (b) paper making apparatus, said paper making apparatus for performing the steps of: (i) receiving the multiple fibre blend streams from the fibre C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 preparation and blending apparatus; (ii) g said streams into paper plys; (iii) forming the plys into a multi ply paper sheet; (iv) chemically sizing the paper sheet to increase hydrophobicity; and (v) drying the multi ply paper sheet over drying drums to produce the PBL, wherein a density of the PBL is no more than 140 grams per square meter (gsm). 26. The system claimed in claim 25, wherein the density of the PBL is no more than 130 grams per square meter (gsm) 27. The system claimed in claim 25 or claim 26, wherein a Cobb (60 second) value of the PBL is less than 30 gsm. 28. The system d in any one of claims 25 to 27, wherein cross direction wet expansion of the PBL is no greater than 0.8%. 29. The system claimed in any one of claims 25 to 28, wherein the step of blending results in multiple fibre blend streams each having a substantially even mixture of RCF and VKF.

. The system claimed in claim 29, wherein the substantially even mixture includes r than 35% VKF. 31. The system claimed in any one of claims 25 to 30, wherein the density of the plasterboard liner ranges between 110gsm and . 32. The system claimed in any one of claims 25 to 30, n the density of the plasterboard liner ranges between 110gsm and 130gsm. 33. The system claimed in any one of claims 25 to 32, wherein the step of chemically sizing the VKF and the RCF includes the step of applying internal sizing chemicals to the paper sheet.

C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 34. The system claimed in claim 33, wherein the internal sizing chemicals include:  Cationic rosin > 12 kg/t  Aluminum sulphate > 24 kg/t  AKD (Alkyl Ketene Dimer) > 3 kg/t . The system claimed in claim 33 or claim 34, wherein the step of ally sizing the PBL includes the step of ng surface sizing chemicals to the multi ply paper sheet. 36. The system claimed in claim 35, wherein the surface sizing chemicals include surface sizing agent 3 to 12 kg/t. 37. The system claimed in any one of claims 33 to 36, including the step of presizing the VKF to improve the VKF's y to react with the sizing chemicals. 38. The system d in claim 37, wherein the sizing chemicals include anionic trash tor 3 kg/t to achieve 500 to 1000uEq/l. 39. The system claimed in any one of claims 25 to 38, wherein the PBL is for a base of the plasterboard and the s includes the step of manipulating fibres of the fibre blend streams so that a machine direction to cross direction tensile ratio (MD:CD) of the PBL is not more than 1.4. 40. The system claimed in any one of claims 25 to 39, wherein the PBL is for a face of the plasterboard and the process includes the step of manipulating fibres of the fibre blend streams so that a machine direction to cross direction tensile ratio (MD:CD) of the PBL is not less than 2.2. 40. The system d in claim 40, further including pigment coating tus, said coating apparatus for performing the step of applying a pigment coating to the PBL. 41. The system claimed in claim 40, wherein the pigment coating apparatus includes a film press for performing the step of enhancing dry strength with application of modified starches. rs\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and s\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-4/08/2021 42. The system claimed in claim 41, wherein the pigment coating apparatus includes a pigment coater for adding said coating t to the applied starches. 43. The system claimed in claim 42, wherein the pigment coating apparatus includes surface sizing chemical apparatus for blending surface sizing als in with starch, water or coating pigment to enhance hydrophobicity of the PBL. 44. The system claimed in any one of claims 41 to 43, wherein the t coating provides a light colour surface with diffuse blue reflectance factor not less than 40. 45. The system claimed in any one of claims 41 to 43, wherein the pigment coating provides a light colour surface with diffuse blue tance factor not less than 30. 46. The system claimed in any one of claims 25 to 44, wherein the paper making apparatus performs the steps of reducing a draw between successive processes so as to reduce the tendency for dried paper to react when contacted with water thereby reducing the hydro expansion. 47. The system claimed in claim 46, wherein reducing the draw results in paper with very low tensile ratio (ratio of machine direction to cross direction) so that it has a low wet expansion. 1/12 Figure 1 2/12 I M N Figure 2a X Y Z AB AC X Y AF 3/12 U X Y Figure 2b AG 4/12 – AH AI Figure 2c Figure 4 5/12 Figure 2d 6/12 18 AR AP AQ Figure 3a AW 28 AZ 7/12 AY BB 16 30 26 34 Figure 3b 37 38 40 BD BF 8/12 36 42 Figure 3c 46 48 50 14 BI BJ 9/12 BK BL Figure 3d /12 Fig 1 VP9 K110PB Tensile MD Index vs. Tensile Ratio Tensile MD Index [N.m/g] 80.0 70.0 60.0 50.0 Trial 3.2 40.0 Trial 4 .0 Trial 5 .0 Trial 6 .0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Tensile Ratio Figure 4 Fig 2 VP9 K110PB Tensile MD Index vs. ty Tensile MD Index [N.m/g] 80.0 70.0 60.0 50.0 Trial 3.2 40.0 Trial 4 .0 Trial 5 .0 Trial 6 .0 0 50 100 150 200 250 300 350 400 Bendsten porosity [ml/min] Figure 5 11/12 Fig 3 VP9 K110PB %Wet Expansion vs. Tensile Ratio Wet Expansion [%] Trial 3.2 Trial 4 Trial 5 Trial 6 0.0 0.5 1.0 1.5 2.0 2.5 3.0 e Ratio Figure 6 Fig 4 VP9 K110PB COBB vs. % Wet Expansion 1'COBB [gsm] BOTTOM 0.4 0.6 0.8 Wet Expansion [%]1 1.2 1.4 1.6 Figure 7 12/12 Fig 5: Top Sheet EMCO Comparison High Sized Rosin vs ASA K110PB 3.5 tB = inital wetting time tS = time to max. adsorp.rate 3 S = max. rate 2 High Size Rosin:Alum 1.5 High Size ASA tB [sec] tS [sec] S [% r/s] Figure 8 Fig 6: Bottom Sheet EMCO Comparison High Sized Rosin vs ASA K110PB tB = inital wetting time tS = time to max. adsorp.rate S = max. absop.rate 3 High Size Rosin:Alum 2 High Size ASA tB [sec] tS [sec] S [% r/s] Figure 9

Claims (8)

Claims Defining the Invention

1. A process for manufacturing plasterboard liner (PBL ) for plaster board, including the steps of: 5 (a) ing virgin Kraft fibre (VKF ); (b) receiving recycled paper fibre (RCF ); (c) blending the VKF and the RCF to produce multiple fibre blend streams; (d) forming said s into paper plys; (e) forming the plys into a multi ply paper sheet; 10 (f) chemically sizing the paper sheet to increase hydrophobicity; and (g) drying the multi ply paper sheet over drying drums to produce the PBL, wherein a density of the PBL is no more than 140 grams per square meter (gsm). 15

2. The process claimed in claim 1, wherein the density of the PBL is no more than 130 grams per square meter (gsm).

3. The process claimed in claim 1 or claim 2, wherein a Cobb (60 second) value of the PBL is less than 30 gsm.

4. The process claimed in any one of claims 1 to 3, wherein cross ion wet expansion of the PBL is no greater than 0.8%.

5. The process claimed in any one of claims 1 to 4, wherein the step of blending 25 s in multiple fibre blend streams each having a substantially even mixture of RCF and VKF.

6. The process claimed in claim 5, wherein the ntially even mixture includes greater than 35% VKF.

7. The process claimed in any one of claims 1 to 6, n the density of the plasterboard liner ranges between 110gsm and .

8. The process claimed in any one of claims 1 to 6, wherein the density of the 35 plasterboard liner ranges between 110gsm and 130gsm. C:\Users\tld\AppData\Roaming\iManage\Work\Recent\35272257NZ A system and process\Spec. inc. 2SPA clean pgs - 35272257(21827042.1).doc-