WO2015019061A1

WO2015019061A1 - A method of manufacturing a moulded pulp object

Info

Publication number: WO2015019061A1
Application number: PCT/GB2014/052360
Authority: WO
Inventors: Fuad KHAN
Original assignee: Hpc Healthline UK Ltd
Current assignee: Hpc Healthline UK Ltd
Priority date: 2013-08-07
Filing date: 2014-07-31
Publication date: 2015-02-12
Anticipated expiration: 2016-02-07
Also published as: GB2519059A; GB201314115D0; GB2519059B

Abstract

A method of manufacturing a moulded pulp object comprises providing a pulp slurry including pulp fibres in an aqueous suspension; forming a layer of pulp (6) on the surface of a mould tool (2) to create a three dimensional moulded pulp object having a first surface (10) facing inwardly in contact with the mould tool and a second surface (12) facing outwardly from the mould tool (2); and then applying a surfactant proof coating to the three dimensional moulded pulp object after it has been formed on the mould tool (2). The surfactant proof coating may be applied while the pulp object is retained on the mould tool (2) or while the pulp object is held on the transfer tool (14), or when the pulp object is located on the drying conveyor (18).

Description

A METHOD OF MANUFACTURING A MOULDED PULP OBJECT

The present invention relates to method of manufacturing a moulded pulp object, and in particular a method of forming a surfactant proof moulded pulp receptacle.

Concerns relating to the transfer of infection in in particular the prevalence and persistence of nosocomial infections have lead hospitals to mandate single use utensils rather than traditional utensils that are washed and reused. Disposing of a utensil following a single use avoids the risk of infection being transferred by the subsequent use of the utensil with a different patient. I n addition, single use utensils obviate the time consuming and costly process of washing, sterilising and storing multi use utensils.

The single use disposable nature of the utensils requires them to be low cost. The disposable and high volume nature of the product also requires them to be environmentally friendly. For these reasons paper pulp utensils have become prevalent in hospitals due to their low cost, and environmental benefits. Pulp products are typically formed from recycled paper, and are easily and hygienically disposable through maceration and discharge into the foul line. Washbowls are a commonly used utensil in a hospital for a variety of patient care applications. However, it has not been possible to use common moulded pulp for the formation of washbowls since the pulp material cannot hold liquids containing surfactant such as soaps, oils or gels, which penetrate the pulp and breaks down the pulp material upon contact, leading to ruptures and leaks. Therefore, utensils such as washbowls which are required to come into contact with soap or detergent in use, have not conventionally been able to be formed from moulded paper pulp.

Single use pulp surfactant proof washbowls have been achieved by blending a fluorochemical into the pulp slurry before moulding the utensils. This recent development that have proven popular in hospitals enabling a moulded pulp washbowl that is able to hold water containing soaps, oil or gels. However, this method of manufacturing surfactant proof bowls has proven to be costly and inefficient for several reasons. Fluorochemicals are relatively expensive compared to other chemicals and disproportionately impacts the unit cost of a washbowl. In order to protect the surface of the bowl from surfactant it is necessary to treat the entire bowl with a- fluorochemicals blended through the entire structure at the slurry stage. As such a disproportionate amount of fluorochemical is used through the whole structure, whereas only surface treatment is strictly required. The same is true fo

Furthermore, in order to achieve effective surfactant proofing exact control of the precise mix of chemicals in the slurry is essential to achieve a well performing bowl. This control has proven difficult to achieve in many processes resulting in many cases of bowls having inward leakage and penetration of liquid though to the external surface of the bowl. This has caused some practitioners to double stack bowls before administering to patients to insure against leaks or ruptures thereby doubling the quantity of bowls used.

It is therefore desirable to provide an improved method of providing a barrier coating to a moulded pulp object and in particular for manufacturing a surfactant proof pul p receptacle, and an apparatus for manufacturing the same, which addresses the above described problems and/or which offers improvements generally.

According to the present invention there is provided a method of manufacturing a moulded pulp object as described in the accompanying claims. There is also provided an apparatus for manufacturing a moulded pulp object as described in the accompanying claims.

I n an embodiment of the invention there is provided a method of manufacturing a moulded pulp object comprising providing a pulp slurry comprising pulp fibres in an aqueous suspension; forming a layer of pulp on the surface of a mould tool to create a three dimensional moulded pulp object having a first surface facing inwardly in contact with the mould tool and a second surface facing outwardly from the mould tool; and then applying a barrier coating to the three dimensional moulded pulp object after it has been formed on the mould tool. This may be while the pul p object is retained on the mould tool or while the pulp object is held on the transfer tool, or at any other suitable stage following the formation of the pulp layer on the mould tool, including when the pul p object is located on the drying conveyor. Preferably the barrier coating is a surfactant proof coating. Alternatively or in addition, the barrier coating may include any of the group comprising fluorocarbons, aqueous starch solutions, protein solutions, styrene based polymers, styrene acrylate based polymers, styrene butadiene polymers, non ionic acryl polymer, ammonia salt of modified acrylic copolymers, proteins, or cellulose derivatives, acrylic resins, styrene-acrylic resins, ethylene-vinyl acetate resins, styrene- butadiene rubber resins, polyvinyl alcohol resins, vinylidene chloride resins, waxes, fluorine resins, silicone resins, and copolymers and polyblends of these resins.

Applying a barrier coating to the surface of the pulp object, which is preferably a washbowl but which may be any pulp moulded product, following the moulding operation uses significantly less chemical than by applying the coating throughout the substrate through the addition of the chemical to the slurry prior to moulding. By applying the coating such as fluorochemical onto the surface of the object a greater concentration of the chemical is achieved at the surface for better performance at a significantly reduced cost, with no requirement for the presence of fluorochemical in the body of the washbowl. To achieve the same performance through the addition of fluorochemical or other chemical to the slurry a significantly greater amount would be required, thereby significantly increasing cost.

Preferably the surfactant proof material is sprayed onto the moulded pul p object. Spraying provides an effective means of the applying the fluorochemical solution to the surface of the object in an efficient, rapid and consistent manner.

The surfactant proof material comprises a fluorochemical, preferably containing multiple carbon-fluorine bonds, some of these are commonly known as fluorocarbons or fluoropolymers. Fluoropolymers consist of a linear chain of strong carbon-fluorine bonds with other atoms, polymers or ionic groups attached at one end of the chain. Due to this structure one end of the polymer chain is lipophobic/oleophobic and the other end is hydrophilic. When the bowl's inner surface is coated with fluoropolymer the hydrophilic end of the chain is attracted to the pulp fibre and the lipophobic end becomes the solid interface to air or liquid. These vertical chains, due to their strong attraction to adjacent chains, become a dense film when the coating is dried that is impervious to surfactants. This film, due to the consistent vertical alignment of the chains that is achieved by spraying the fluorochemical, and/or other chemicals as listed above, onto the surface creates a significantly more effective surfactant barrier than if fluorochemical were added to the slurry, in which case the chains are randomly oriented with a far lower number and concentration being vertically aligned at the surface. For the optimum performance from the coating a sizing agent is preferably added to the slurry mix. The sizing assures that the coating does not become absorbed into the surface of the pulp 'felt' and rather floats on top until dried into a film. The coating such as a surfactant proof material is preferably applied to the first surface of the moulded pulp object when it is on the transfer tool. Where the transfer tool is a female tool, the inner first surface of a concave object such as a washbowl is outwardly facing when held on the transfer tool. Therefore spraying while the washbowl is retained on the transfer tool allows the inner first surface of the washbowl, that is initially in contact with the surface of the mould tool prior to transfer the transfer tool, to be coated.

The moulded pulp object may be removed from the mould tool using a corresponding transfer tool such that the second surface faces inwardly in contact with the surface of the transfer tool and the first surface faces outwa rdly. The surfactant proof material is applied to the first surface of the moulded pulp object when it is on the transfer tool. It is preferable to form a receptacle such as a washbowl using a male mould which enables the inner surface of the washbowl to be compressed under the action of the vacuum against the surface of the mould tool forming a smooth and non-porous inner surface to the bowl. This is advantageous as the inner surface defines the operable surface in use. Spraying the bowl while it is held on the transfer tool allows the first (inner) surface of the bowl to be surfactant proofed. As it is the first surface that is in direct contact with the liquid in use, coating the first surface obviates the need to coat the additional surfaces of the bowl thereby significantly reducing chemical use and cost. The transfer tool is preferably arranged to transfer the moulded pulp object to a further processing operation. The transfer tool is preferably arranged to transfer the moulded pulp object to a drying operation and the surfactant proof coating is applied to the moulded pul p object on the transfer tool prior to being transferred to the drying operation. Liquid is removed from the layer of pulp material on the mould tool during the formation of the moulded pulp object, and the surfactant coating is preferably applied to the moulded pul p object after the liquid removal stage. As such, the object is coated after de-watering and prior to drying.

I n another aspect of the invention an apparatus for manufacturing a moulded pulp object comprises a pulp slurry container for containing a pulp slurry comprising pulp fibres in an aqueous suspension; a mould tool arranged to be submerged into the pul p slurry container; means for drawing a layer of pulp fibres onto the surface of the mould tool to create a three dimensional pulp object; and means for applying a surfactant proof coating to the three dimensional pulp object after it has been formed on the mould tool.

The means for applying a surfactant proof coating to the three dimensional pulp object preferably comprises a spray for spraying a coating solution comprising fluorocarbon. This advantageously enables the application of a surfactant proof material in an efficient and economical manner.

The mould tool is preferably configured such that when the layer of pulp fibres is formed on the surface of the mould tool a first surface faces inwardly in contact with the mould tool and a second surface facing outwardly from the mould tool. The apparatus preferably further comprises a transfer tool arranged to remove the moulded pulp object from the mould tool and transfer it to a further processing operation. The spray is preferably arranged to apply the surfactant proof coating to the second surface of the moulded pulp object while it is retained on the mould tool. Alternatively or in addition the spray may be arranged to apply the surfactant proof coating to the first surface of the moulded pulp object while it is retained on the transfer tool. The mould tool is preferably a male tool configured to form a moulded pulp receptacle having an inner volume with an inner surface corresponding to the outer surface of the mould tool, and the transfer tool is a female tool inversely corresponding to the shape of the mould tool. It will be appreciate that this arrangement could be inverted. A vacuum source is preferably arranged to remove liquid from the moulded pulp object while it is retained on the mould tool, and control means configured to control the spray to apply the surfactant proof coating to the after the operation of the vacuum source to remove liquid from the moulded pulp object. In another aspect of the invention a moulded pulp liquid receptacle comprises a three dimensional moulded pulp body comprising a base and at least one wall having an inner surface defining a liquid receiving volume; and a surfactant proof layer formed on the inner surface. The present invention will now be described by way of example only with reference to the following illustrative figures in which:

Figure 1 shows a mould tool and transfer tool arrangement according to the present invention with the pulp object retained on the mould tool; Figure 2 shows the arrangement of claim 1 with the transfer tool in engagement with the mould tool;

Figure 3 shows the arrangement of Figure 1 with the pulp object removed from the mould tool by the transfer tool;

Figure 4 shows a moulding process according to an embodiment of the present invention; and Figure 5 shows a spraying operation according to an embodiment of the present invention.

According to the present invention, pulp paper slurry is formed by loading bales of recycled waste paper or virgin pulp into a hydrapulper comprising a water filled tank having a powerful agitator for breaking up the bales into small pieces. The hydrapulper's action defibrillates the paper/pulp into its requisite fibres in an aqueous suspension that is commonly known as slurry. Following the hyrdapulping process the slurry is held in a holding tank with agitators, thus keeping the consistency of the fibre suspension even and preventing settling at the bottom of the tank. A sizing agent may be added to the slurry during the hydrapulping process or just after this process as the slurry is being transferred to a holding tank to water proof the pulp material.

The pulp slurry is pumped to the moulding tank. En route to the moulding tank the slurry is diluted to a consistency amenable to moulding. Dilution can be achieved through several methods, the two most common being through a Ύ' connection where the pipe from the water tank and the slurry storage tank converge into one pipe causing dilution of the slurry. An alternative method uses a dilution tank where fixed amounts of white water and slurry are mixed. At the moulding tank the pulp fibres in aqueous suspension are drawn onto a tool 2 having a porous surface capable of having a vacuum drawn therethrough. Typically the tool may include vacuum holes and preferably covered by a porous surface layer such as a stainless steel gauze 4, as shown in Figure 1. Alternatively, the surface of the tool itself may be formed from a porous material obviating the requirement for a separate gauze. This is done by dipping or submerging the tool 2 into the moulding tank and applying vacuum to the tool 2. The tool 2 is a male tool for forming a hollow receptacle such as a washbowl. The male tool defines the internal volume of the washbowl. The application of vacuum causes pulp fibres to be drawn to the gauze 4 as the white water of the slurry is sucked through the gauze 4 forming a layer 6 of pulp on the outer surface of the tool 2. With a layer of pulp fibres 6 formed on the tool 2, the tool 2 is retracted from the moulding tank. The layer 6 of pulp forms a 'felt' of pulp covering the gauze in the shape of the outer surface of the mould tool 2, defining a three dimensional pulp washbowl 8. It will be appreciated that while the following description describes the object as a washbowl this is not limiting and the process may apply to any suitable three dimensional object and in particular to a pulp receptacle.

Once the mould tool 2 has been removed from the moulding tank a further vacuum is then applied to dewater the layer 6 of pulp retained on the mould to remove as much of the water held within the pulp material as much as possible. As the pulp object 8 is formed onto the mould tool 2 under the action of the vacuum the porous surface of the mould tool 2 creates a corresponding relatively 'smooth' inner surface of the bowl which is typically lightly textured though smoother than the outer surface. The surface of the mould tool may be stainless steel or any other suitable material. The outer surface 12 of the washbowl 8 retains a relatively rougher texture due to the pulp material not having been compressed against a mould surface.

Following dewatering the moulded pulp washbowl is removed from the moulding tool 2 using a transfer tool 14. At this stage, when held on the transfer tool the pul p has a water content of between 40-80% and more preferably between 50-70% by weight. I n the embodiment described the water content upon application is approximately 68% by weight. The transfer tool 14 is a corresponding female tool that is the inverse shape of the moulding tool 2 with a smooth inner surface 16 comprising vacuum holes. The two tools meet and the inner surface 16 of the transfer tool 14 is brought into engagement with the outer surface 12 of the moulded pulp object 8 or 'felt'. The moulded pulp object 8 is then transferred to the transfer tool 14 by application of a vacuum to the transfer tool 14 which hold the pulp object 8 in engagement with the transfer tool 14. The vacuum force applied by the transfer tool is sufficient to hold the pulp object in engagement with the transfer tool, but is significantly less than the vacuum force applied by the tool to draw the pulp onto the tool and/or dewater the pulp. Depending on the type of moulding machine, the transfer tool 14 then either deposits the mould onto a conveyor for drying through a hot air tunnel or to a set of drying tools if the mould is being dried between heated tools, commonly known as 'thermoformed', 'dry in place', or 'press to dry' processes. The transfer tool 14 may be heated to assist in the drying process. In the arrangement shown in Figure 4 the transfer tool 14 removes the washbowl 8 from the moulding tool 2 following dewatering and transfers the washbowl 8 to a conveyor 18. The conveyor 18 carries the washbowls 8 through a drying tunnel 20 in which a heater 22 directs heated air onto the washbowls 8 to dry the pulp and remove the remaining water content. The sizing agent in the pulp material which was added during the slurry stage makes the dried pulp washbowl 8 waterproof. As such, clean water may be poured into the washbowl 8 and held without leakage. However, the presence of surfactants such as soaps, oils or gels pulp in the water, which are typically present during most hospital applications where a washbowl is required, act to break down the pulp material upon contact, leading to ruptures and leaks.

As shown in Figure 5, a spray 22 is provided that is configured to spray a barrier coating onto the washbowl. The surface barrier coating may comprise any barrier coating for a pulp product, and preferably from the group of surface barriers including a fluorocarbons, aqueous starch solutions, protein solutions, styrene based polymers, styrene acrylate based polymers, styrene butadiene polymers, non-ionic acryl polymer, ammonia salt of modified acrylic copolymers, proteins, or cellulose derivatives, acrylic resins, styrene- acrylic resins, ethylene-vinyl acetate resins, styrene-butadiene rubber resins, polyvinyl alcohol resins, vinylidene chloride resins, waxes, fluorine resins, silicone resins, and copolymers and polyblends of these resins. For surfactant proofing it is preferable that a surface coating solution is provided containing a fluorocarbon as an active ingredient. I n the embodiment shown in Figure 5 the spray 22 is used to apply a coating of surfactant proofing fluorocarbon solution to the inner surface 10 of the washbowl 8 while it is held on the transfer tool 14. The inner surface 10 of the washbowl 8 defines the liquid containing volume of the washbowl 8 and is the surface in immediate contact with the liquid contained by the washbowl. Therefore, providing the inner surface 10 is surfactant proofed, the remaining body of the washbowl 8 is protected from degradation.

I n addition, or alternatively, the 'rough' outer surface 12 of the washbowl may be coating with the surfactant proofing solution by spraying the outer surface 12 of the washbowl 8 while it is still retained on the mould tool 2. Preferably this spraying stage is conducted after the pulp layer 8 has been dewatered. A common spray 22 may be used to spray both the inner surface 10 and outer surface 12. Alternatively a separate spray bar (not shown) may be positioned above the moulding tool for spraying the pul p layer 8 following dewatering and prior to transfer. The addition of a sizing agent to the pulp slurry ensures that when the surfactant proofing solution is sprayed onto the surface of the washbowl 8 a film is created by preventing penetration and ensuring that it is not drawn into the pulp. I nstead the surfactant proofing solution remains on the surface and forms a surfactant proof film during the drying stage. This maximises the concentration of the surfactant proofing material at the surface of the washbowl providing a dense surface film.

I n an alternative embodiment the fluorochemical is both hydrophobic and lipo/oliophobic and as such both waterproofs and provides surfactant resistance. In this embodiment a sizing agent may not be required, although the addition of the sizing agent would still assist in floating the sprayed fluorochemical layer on the surface creating the surface film. While the above barrier coatings are described as being applied to a pulp product including a sizing agent, the invention is not limited to this combination a nd it is contemplated that the above described coatings may alternatively be applied to a pul p that does not include a sizing agent.

While the mould tool 2 is described as being a male tool, with the transfer tool 14 being a corresponding female tool, in an alternative arrangement the mould tool may be a female 2, with the transfer tool 14 being a corresponding male tool. I n this embodiment, if the inner surface of the washbowl, which means the inner surface of the washbowl in use rather than relative to the mould tool, is to be sprayed with a surfactant proofing solution then the spraying is conducted while the washbowl is retained on the mould tool during which time the inner surface of the washbowl is outwardly facing away from the surface of the mould tool. Similarly, if the outer surface of the washbowl is to be sprayed then this is done while the washbowl is retained on the transfer tool.

It is preferable that the spray is applied to the pulp object 8 when it is held on the transfer tool. The relatively high vacuum force applied by the mould tool 2 may act to draw the surfactant proof solution into the pulp material, thereby reducing the surface concentration and hence the efficacy of the surface film and/or requiring the spraying of additional chemical solution to counter absorption. The vacuum force of the transfer tool is of a low enough level to avoid such action.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A method of manufacturing a moulded pulp object comprising:

providing a pulp slurry comprising pulp fibres in an aqueous suspension; forming a layer of pulp on the surface of a mould tool to create a three dimensional moulded pulp object having a first surface facing inwardly in contact with the mould tool and a second surface facing outwardly from the mould tool; and

applying a coating to the three dimensional moulded pulp object after it has been formed on the mould tool.

2. A method of manufacturing a moulded pul p object according to claim 1 wherein the coating is a barrier coating.

3. A method of manufacturing a moulded pul p object according to claim 2 wherein the barrier coating includes at least one of a group comprising fluorocarbons, aqueous starch solutions, protein solutions, styrene based polymers, styrene acrylate based polymers, styrene butadiene polymers, non ionic acryl polymer, ammonia salt of modified acrylic copolymers, proteins, or cellulose derivatives, acrylic resins, styrene-acrylic resins, ethylene-vinyl acetate resins, styrene-butadiene rubber resins, polyvinyl alcohol resins, vinylidene chloride resins, waxes, fluorine resins, silicone resins, and copolymers and polyblends of these resins.

4. A method of manufacturing a moulded pulp object according to any preceding claim wherein the coating is sprayed onto the moulded pulp object.

5. A method of manufacturing a moulded pul p object according to claim 4 wherein coating is a surfactant proof material comprising fluorochemical.

6. A method of manufacturing a moulded pulp object according to any preceding claim wherein the moulded pulp object is removed from the mould tool using a corresponding transfer tool such that the second surface faces inwardly in contact with the surface of the transfer tool and the first surface faces outwardly; and wherein the coating is applied to the first surface of the moulded pulp object when it is on the transfer tool.

7. A method of manufacturing a moulded pul p object according to claim 6 wherein the transfer tool is arranged to transfer the moulded pulp object to a further processing operation.

8. A method of manufacturing a moulded pul p object according to claim 7 wherein the transfer tool is arranged to transfer the moulded pulp object to a drying operation and the surfactant proof coating is applied to the moulded pulp object on the transfer tool prior to being transferred to the drying operation.

9. A method of manufacturing a moulded pulp object according to any preceding claims wherein the coating is applied to the moulded pulp object when the water content is between 40 and 80% by weight.

10. A method of manufacturing a moulded pulp object according to any preceding claims wherein the coating is applied to the moulded pulp object when the water content is between 50 and 70% by weight.

11. A method of manufacturing a moulded pulp object according to any preceding claim wherein liquid is removed from the layer of pulp material on the mould tool during the formation of the moulded pulp object, and the surfactant coating is applied to the moulded pulp object after the liquid removal stage.

12. An apparatus for manufacturing a moulded pulp object comprising:

a pulp slurry container for containing a pul p slurry comprising pulp fibres in an aqueous suspension;

a mould tool arranged to be submerged into the pulp slurry container; means for drawing a layer of pulp fibres onto the surface of the mould told to create a three dimensional pulp object; and

means for applying a coating to the three dimensional pul p object after it has been formed on the mould tool.

13. An apparatus for manufacturing a moulded pul p object according to claim 12, wherein the means for applying a coating to the three dimensional pulp object comprises a spray for spraying a coating solution.

14. An apparatus for manufacturing a moulded pul p object according to claim 10 wherein the mould tool is configured such that when the layer of pulp fibres is formed on the surface of the mould tool a first surface faces inwardly in contact with the mould tool and a second surface facing outwardly from the mould tool, the apparatus further comprising a transfer tool arranged to remove the moulded pulp object from the mould tool and transfer it to a further processing operation and the spray is arranged to apply the surfactant proof coating to the first surface of the moulded pulp object while it is retained on the transfer tool.

15. An apparatus for manufacturing a moulded pulp object according to any one of claim 14 wherein the mould tool is a male tool configured to form a moulded pul p receptacle having an inner volume with an inner surface corresponding to the outer surface of the mould tool and transfer tool is a female tool inversely corresponding to the shape of the mould tool.

16. An apparatus for manufacturing a moulded pulp object according to any one of claims 12 to 15 further comprising a vacuum source arranged to remove liquid from the moulded pulp object while it is retained on the mould tool, and control means configured to control the spray to apply the surfactant proof coating to the after the operation of the vacuum source to remove liquid from the moulded pul p object.

17. A moulded pulp liquid receptacle comprising: a three dimensional moulded pul p body comprising a base and at least one wall having an inner surface defining a liquid receiving volume; and

a surfactant proof layer formed on the inner surface.