GB2579107A

GB2579107A - Barrier coated paper straw

Info

Publication number: GB2579107A
Application number: GB1905874.2A
Authority: GB
Inventors: Damarell Keith
Original assignee: Havi Global Solutions Europe Ltd
Current assignee: Havi Global Solutions Europe Ltd
Priority date: 2019-04-26
Filing date: 2019-04-26
Publication date: 2020-06-10
Also published as: GB201905874D0

Abstract

A paper drinking straw comprises first 10 and second 12 paper layers each having an inner surface and an outer surface. The straw further comprises a paper core layer 14 having a first surface and a second surface. The inner surface of the first paper layer is bonded to the first surface of the paper core layer and the inner surface of the second paper layer is bonded to the second surface of the paper core layer. Furthermore, the outer surfaces of the first and second paper layers are coated with a water-resistant barrier coating 20, 22. The paper core may comprise a single paper layer or a plurality of paper layers. The inner surfaces of the first and second paper layers may be coated with the water-resistant barrier coating. The water-resistant barrier coating may comprise a styrene free acrylic based coating or a styrene-based coating. The straw may be repulpable, biodegradable and/or recyclable. The bonding may comprise a biodegradable adhesive 30, 32 on the inner surfaces of the first and second paper layers. The straw may be spirally wound and the first and second paper layers may have the same weight. Also disclosed is a method of manufacturing the disclosed straw.

Description

Barrier Coated Paper Straw

Field of the Invention

The present invention belongs to the field of drinking straws. In particular, the invention relates to repulpable and/or recyclable straws comprising paper-based materials.

Background

Paper straws are generally made by combining multiple layers of paper via a spiral winding tube process using a water based glue to adhere the layers together. The papers used to make these straws are generally specified as being a wet strength paper. Wet strength papers typically contain high levels of wet strength resin additives (e.g. epichlorohydrin resin) that helps maintain cellulose fibre bonding even in high water environments. Without the wet strength resin, the hydrogen bonds that provide the paper strength in dry conditions, fail when exposed to water. Typical papers contain chemicals known as sizing agents that impart some water resistance (e.g. AKD, ASA, Rosin size) but sizing alone fails to provide enough wet strength integrity for the paper straw to perform. However, there is a desire to find alternatives which perform to an improved standard.

Some deficiencies seen with paper straws on the market today are as follows: 1 The paper straw starts to soften immediately on immersion in a liquid. Softening continues until the straw integrity fails. Softening can be delayed via the inclusion of wet strength resin but typically a straw will fail after about 30 minutes.

2 The outer surface of a paper straw normally uses an expensive, extra smooth, wet strength paper so the smoothness can provide "lip comfort' for the consumer. Lip comfort, however, begins to deteriorate on exposure to moisture from the mouth and as such, lip comfort with conventional paper straws are inferior to plastic straws.

3 The internal surface of a conventional paper straw has a high level of cellulose fibre exposure due to the way the straws are manufactured. Each individual fibre provides a nucleation site for carbonated beverages. As such, with carbonated beverages, there is a tendency for the dissolved gas within the beverage to be "released" via the nucleation site resulting in an amount of frothing or fizzing of the beverage. This can result in significant beverage spillage from its container.

4 While there is a trend to move away from plastic straws to more environmentally friendly alternatives such as paper straws, wet strength resin containing papers are only repulpable and recyclable with the incorporation of additional steps, specialist chemicals or particular conditions such as high temperature environments, in order to process and remove the resin adhesives.

Such straws are therefore not directly repulpable or recyclable.

Summary

Aspects of the invention are set out in the independent claims and preferred features are set out in the dependent claims.

According to a first aspect there is provided a straw comprising: a first paper layer having an inner surface and an outer surface; a paper core layer having a first surface and second surface, wherein the first surface and the second surface are coated with a water-resistant barrier coating; a second paper layer having an inner surface and an outer surface; wherein the inner surface of the first paper layer is configured to be bonded to the first surface of the paper core layer; wherein the inner surface of the second paper layer is configured to be bonded to the second surface of the paper core layer; and wherein the outer surfaces of the first and second paper layers are coated with a water resistant barrier coating.

Advantageously, coating the surfaces with a barrier coating layer, the barrier coating layer provides the paper with waterproof or water resistant qualities without using traditional wet strength or waxed papers. The barrier-coated paper enables the straw to be easily recycled compared to a typical paper straw. In particular, such a straw can be repulped directly without any pre-processing steps. Moreover, the barrier-coated straw increases lip comfort when compared to a conventional paper straw and reduces cellulose fibre exposure on the internal surface of the straw, reducing nucleation in carbonated liquids.

Coating the surfaces of the core layer of the straw with the water-resistant coating as well as coating the two outer surfaces of the straw increases the time taken for a liquid to wet the various paper layers of the straw and therefore maintains the strength and structure of the straw for longer. In particular, since the straw is created by the spiral winding of several layers of paper, the degree of water resistance of paper layers that are internal to the straw may not be considered to be particularly important. However, the inventors have found that, by coating the surfaces of the core paper layer(s) of the straw, the water resistance and strength of the straw as a whole can be increased significantly. This is thought to be due to the fact that the water resistant coating on the surfaces of the core reduce the amount of liquid that can soak into the structure of the straw through the joins in the spiral winding of the paper layers. The claimed arrangement has been found to significantly increase the performance of the straw.

For the avoidance of doubt, it is noted that the outer surface of the first paper layer forms the internal inside surface of the straw and therefore contacts the liquid when in use. The outer surface of the second paper layer forms the external outer surface of the straw and therefore contacts the user's lips when in use.

Optionally, the inner surfaces of the first and second paper layers can also be coated with the water based barrier coating. Optionally, all of the layers of paper that make up the straw can be coated with a barrier coating that provides the paper with a water resistant quality. However, the coating of all layers is generally found to be unnecessary for a standard-use straw and the surfaces can therefore be selectively coated, as set out in claim 1, in order to reduce cost.

The paper core layer comprises at least one, and optionally more than one, paper layer, each paper layer comprising a first and second surface. Optionally, a straw may be made from any number of layers, although a total of three or four layers is typical.

In some embodiments, only the outermost surfaces of the "core" may be coated, however many layers make up the core, wherein the outermost surfaces of the core are the surfaces configured to be bonded with the inner and outer layers. However, optionally, all surfaces of each of the paper layers that make up the core may be coated with the water based barrier coating, such that all the core layers are coated on both surfaces. As noted above, however, while the coating of all surfaces may simplify manufacturing, selective coating of key layers has been found to provide sufficient water resistance while minimizing cost.

The water resistant barrier coating may be an acrylic based coating, optionally a styrene free coating. In one embodiment, the coating may be ethylene acrylic acid or an ethylene acrylic acid co-polymer. The coating is preferably applied using a water based dispersion coating method.

Alternatively, the coating is a styrene based coating, for example a synthetic rubber 113 such as styrene butadiene rubber or styrene butadiene block co-polymer or other styrene acrylic.

Other suitable barrier coatings include polymer dispersion coatings wherein the polymers that can be used include modified ordinary styrene-butadienes, different acrylates and methacrylates, polyolefins, vinylene acetates, copolymers of these or natural biopolymers.

In an alternative implementation, a natural coating may include engineered or modified starch, vegetable oil or a natural wax.

The paper used in the straw, coated with the barrier coating, is optionally free of wet strength chemicals and wet strength resins and is therefore non wet strength paper. Wet strength paper is typically more difficult to recycle than paper coated with a water resistant barrier coating due to the additional chemicals incorporated into the paper to increase its wet strength.

The coating itself is preferably recyclable such that all the elements of the straw that make up the different layers are capable of being easily recycled. In particular, the straw is preferably repulpable directly, without any additional processing steps.

The water resistant barrier coating can be applied to the paper from which the straw will be made via one of: an on machine coater, an off machine coater or a printing machine. Other techniques that can suitably and reliably provide a thin film of coating over the paper may be used.

The paper layers of the straw may be bonded together using an adhesive or glue on the inner surface of the first paper layer and/or the inner surface of the second paper layer. Layers that make up the core may also be bonded together by glue. Optionally, the glue is also biodegradable and recyclable and does not reduce the repulpability of the straw.

Optionally, in a particular embodiment, the weight of paper used for each of the first paper layer, the second paper layer and the core is less than 120gsm, preferably 100gsm, further preferably 80gsm. In some embodiments, the weight of paper used for each of the first paper layer, the second paper layer and the core is the same for each layer. However, the weight of paper of each of the layers may also be different.

The finished straw comprises a hollow cylinder and may be formed by being spirally wound and then bonded together.

According to another aspect, there is provided a method of manufacturing a straw comprising: providing a first paper layer having an inner surface and an outer surface; providing a paper core layer having a first surface and second surface, wherein the first and second surfaces are coated with a water resistant barrier coating; providing a second paper layer having an inner surface and an outer surface; winding the first paper layer, the paper core layer and the second paper layer in an overlapping spiral pattern to form a hollow cylinder; bonding the inner surface of the first paper layer to the first surface of the paper core layer; bonding the inner surface of the second paper layer to the second surface of the paper core layer; and providing the outer surfaces of the first and second paper layers with a water resistant barrier coating.

Optionally, the method includes cutting the straw to a predetermined length and/or pre-treating at least one paper layer of the straw with a water resistant barrier coating.

Of course, as the skilled person will appreciate, the steps of the method set out above may be implemented in a different order. For example, the outer surfaces of the first and second paper layers may be provided with a water-resistant barrier coating prior to any winding of the paper layers in an overlapping spiral pattern. In particular, the paper forming the straw may be provided pre-coated with all necessary coatings prior to any formation of the straw.

Moreover, the layers of the straw may all be wound together at the same time or the layers may each be wound sequentially on top of the preceding layer. Therefore, the bonding steps may occur simultaneously or sequentially.

There may be an additional step in the manufacturing process of applying an adhesive to one or more layers to bond the layers together.

The straw may also be dried (for example by building a drying time into the process or by heating and cooling the straw), cut to length as required and/or painted or coated with a coloured layer.

Brief Description of the Drawings

Exemplary embodiments are illustrated in the accompanying figures in which: Figures 1 and 2 illustrate exemplary structural compositions of a three layer drinking straw according to embodiments; Figures 3 and 4 illustrate exemplary structural compositions of a two layer drinking straw; Figure 5 is a perspective view of an exemplary straw according to one embodiment; Figure 6 is a schematic illustration of a paper straw according to one embodiment.

Detailed Description

Figure 1 illustrates the layers of a barrier coated straw. The layers comprise paper layers, barrier coatings disposed on the layers, and adhesive or glue to stick the layers 30 together.

The straw 1 comprises a first paper layer 10 and a second paper layer 12, which surround a further paper layer comprising a paper core 14.

A first barrier coating 20 is applied to the first paper layer 10, on a first external or outer surface of the first paper layer. The first surface faces outwards, away from the other layers of the straw, and is therefore referred to herein as an outer surface. When the straw is spirally bound, the surface on which the barrier coating 20 is disposed provides what will be the inner surface of the hollow cylinder of the straw, through which liquid is drawn up during drinking.

A second barrier coating 22 is applied to the second paper layer 12 on a first surface of the second paper layer. The first surface of the second paper layer 12 faces outwards and is therefore also described herein as an outer surface. When the straw is spirally bound, the outer surface on which the barrier coating 22 is disposed provides what will be the outer surface of the straw in a hollow cylinder formation, and is therefore the surface around which a user places their lips at one end, and that is placed in the liquid at the other, opposing end.

A first layer of glue or adhesive 30 is applied between the first paper layer 10 and a paper core 14, and a second layer of glue 32 is applied between the second paper layer 12 and the paper core 14. The glue may comprise water-based PVA glue or another glue approved for food contact.

The paper layers 10, 12, 14 of the straw form the main structural body of the straw when bound. The barrier coatings 20 and 22 seal the paper, including the core paper layer 14, against moisture. The glue 30, 32 between the layers allows them to be bonded together.

The layers are bound together in a spiral winding to create a hollow tube with a desired diameter that can be cut to a desired length. In use, the straw is disposed in a liquid at one end and remains in air at the other end and is available for a user to draw the liquid up into their mouth.

The barrier coating on the surfaces of the paper provides a water resistance that prevents moisture from getting into the paper and destroying the structural integrity of the straw. Moisture can pervade the layers of the straw from both ends; from the liquid in which it may be placed, and from the moisture of the mouth and lips where the user contacts the straw. In use, the inside of the straw is exposed to the liquid being drawn up to the users mouth, so water resistance along the full length of the straw is desirable. Barrier coatings can be applied using a water-dispersion method and examplary barrier coatings are set out above.

Figure 2 shows the same initial configuration of the layers of paper, barrier coating and glue as Figure 1, with additional barrier coating layers 24, 26 applied to the paper core layer 14. Barrier coating 24 is applied to a first surface of the paper core 14, the first surface of the paper core 14 being adjacent the first paper layer 10. A further barrier coating 26 is applied to a second surface of the paper core 14, the second surface of 113 the paper core being adjacent the second paper layer 12.

Applying barrier coatings to the surfaces of the core paper layer 14 provides sealant against moisture and is particularly beneficial when the straw has been spirally bound. The joins between windings of the spiral bound straw can be weak points that enable some ingress of moisture, even if there is an overlap of the layer between subsequent windings. This can expose the core layers of the paper straw to moisture and cause these inner layers of the straw to weaken and reduce the strength of the straw as a whole.

Barrier coatings 24, 26 on both surfaces of the core paper layer 14 help reduce the intake of water into the core of the straw by providing further water resistance even if the moisture seeps through the external or internal surfaces of the straw. In turn, this provides improved structural integrity for the straw for a longer period when it is disposed in a liquid.

In particular embodiments, a straw's useful operational performance time can be improved from around 30 minutes to a couple of hours or more.

In other words, despite the outer and inner layers of traditional paper straws having a water resistant coating on the outer surfaces, the spiral winding process leaves microscopic gaps or weak points on the surface of the straw. Liquid can penetrate through to the inner layers at these weak points and reach the inner layer(s), which can destroy the strength and structural integrity of the straw. Therefore, the present inventors have appreciated that, although the barrier coating can be applied just to the internal and external layers of the straw construction, if the middle or core layer(s) of the straw themselves are barrier coated where they meet the outer and inner (first and second) paper layer, robustness against moisture pervasion can be significantly improved. By providing a barrier coating to each side of the core layer(s), liquid penetration and resulting failure of the straw can be significantly delayed.

Figure 3 shows a variant of the straw, which has only the first paper layer 10 and the second paper layer 12. The outer surfaces of the paper layers are covered by the barrier coatings 20 and 22 The glue 30 is provided between the interface of the two paper layers and allows them to be bonded to one another.

Figure 4 illustrates a variant of the straw having two paper layers, as in Figure 3, wherein each of the paper layers is additionally coated on the inner surface (at the interface which is to be bonded to the other layer) with a barrier coating 21 and 23.

Figure 5 illustrates a perspective view of an exemplary straw according to one embodiment. The layers of the straw have been spirally bound, such that the outer surface of the straw is the second paper layer 12. The spiral winding process leaves weak points 50 on both surfaces of the straw that can be susceptible to liquid penetration. The straw comprises a hollow cylinder. In use one end of the straw is placed in a liquid whilst the other end is placed in a user's mouth.

Figure 6 is a schematic illustration of a paper straw according to one embodiment. The straw comprises an inner surface 10, a core 14, and an outer surface 12. The layers are spirally wound to create the hollow tubular structure as illustrated.

It will be appreciated that any number of paper layers can be used in the straw composition, and that each of these layers may be coated on one or both sides with a barrier coating to provide the paper with a water resistant quality. In addition, it is also possible to have different layers of the straw having different numbers of coated surfaces in any combination. For example, the first paper layer may have an outer surface coating only, the middle (or core) layer may have coatings on both surfaces, and the second paper layer may also be coated on both surfaces.

The paper layers can be made from the same type of paper, although they may comprise different thicknesses or grammages (in gsm) of paper, for example. It will be appreciated that different papers could be used on each of the different paper layers. The outer or second layer, for example, may have a smaller gsm to the inner and core paper layers. The second paper layer 12 may be decorated, for example, with a different colour or pattern to the other layers so as to be more pleasing or interesting to a consumer.

Due to the improved performance of the straw, the thickness of the paper used to form the various layers can be reduced, and hence the cost of the straw and the amount of raw material to make the straw can be reduced. Previous straws are typically made of two layers of 120gsm paper with a finer outer layer of 80gsm. However, the straw described herein may be made of three layers of 100gsm or 80sgm paper, or two layers of 100gsm with an outer layer of 80gsm. There may be some advantage in using papers of the same grammage in all three layers in terms of simplifying the machinery used to manufacture the straws and simplifying the materials used in its as manufacture.

Since the barrier coating on the external surface of the straw improves the mouth feel, the paper of the outer layer of the straw no longer needs to be an 80gsm or finer paper, but can be made using a heavier and coarser 100gsm or even 120gsm weight zo paper.

Replacing the wet strength paper layers, which are typically used to make a paper straw, with non wet strength papers coated with water resistant barrier coatings advantageously provides for an improved paper straw that provides improved water resistance and avoids the straw becoming soggy or limp, whilst having the ability to be recyclable and repulpable.

Non wet strength papers are of a similar grammage (in gsm) to the existing papers used, and thus look and feel similar to conventional paper straws. The straws pertaining to this application comprise papers which are water resistant by virtue of their barrier coating, and do not employ water resistance by virtue of compounds added to the paper material itself. The water based coating imparts, when dry, a high level of grease and water resistance to the paper surface, giving additional structure and integrity to the paper. The papers used are conventionally repulpable without additional processing steps to first remove any of the coating layers or additives and/or biodegradable for example through composting.

In contrast, wax coated papers are unsuitable for recycling and many existing straws made using wet strength papers require separation and additional processing at recycling plants in order to break down the chemicals and additives used to improve the paper strength and are therefore difficult to recycle in conventional recycling centres.

The coatings used are typically food safe, styrene-free, acrylic based coatings but can include styrene-butadiene, styrene acrylics and other lattices known to provide water resistance, or any of the coating materials described above.

The coatings can be applied via: on-machine coaters at the paper machine, off-machine coaters or via printing processes. The printing of the coating may depend on the coating weight or required thickness as well as placement.

Coatings can be dispersed by application to the surface of paper, or other easily pulpable, suitable materials, to form a solid, non-porous film. After the film is dried, it provides a barrier layer against water (and/or water vapour) and other substances such as grease, oil and other gases.

A food safe, smooth, barrier coating applied to the outer layer of the straw, provides the user with a comfortable surface on which to place the lips without the need for expensive, extra smooth papers. Lip comfort is maintained for longer periods of time than a conventional straw, and has shown similar performance to a plastic straw.

The inner surface of the paper straw is coated with a food safe barrier coating, this provides for the cellulose fibres, which are normally exposed, to be covered. As such, the barrier coated paper straw construction improves the frothing or fizzing problem seen with conventional paper straws when used with carbonated beverages.

Tests may be undertaken to determine the performance of the straws made according to the methods described above.

In one test, the water absorption of the straw is tested in a method including the steps of 1) Weigh the straw 2) Submerge 50% of the length of the straw in cold water for 15 minutes 3) Remove the straw from the water and blot dry.

4) Shake the straw 3 times to remove excess water droplets 5) Weigh the straw In this test, the % increase in weight of the straw was, on average, around 17%, compared to a % increase in weight of around 28% for the control group of prior art straws. Hence the water absorption of embodiments of the straw according to the invention described herein is significantly lower than that of the test group of existing straws, enabling the straws described herein to retain their strength and functionality for longer.

In a further nucleation test, the level of "fizz" created by inserting the straw into a carbonated beverage is tested.

a) In a static test, a straw is inserted into a freshly opened can of carbonated beverage and observed for 2 minutes.

b) In a dynamic test, a straw is inserted into freshly opened can of carbonated beverage, stirred for 30 seconds and observed for 2 minutes.

In the nucleation test, straws according to the present invention did not cause any significant foaming of the beverage in either the static or the dynamic test and all contents of the drink remained within the can.

Prior art straws caused foaming of the beverage such that the beverage rose up the straw during the static test, but the foaming dissipated and the beverage remained within the can. However, in the dynamic test, significant foaming of the beverage occurred and the contents of the can spilled over and out of the can.

Finally, in a lip comfort test, two straws were inserted into a new beverage can, one prior art straw and one straw according to the present invention. The beverage was then consumed through both straws side by side over 10-15 minutes. Initially, both straws have an equivalent feel, however as beverage is consumed and the straws get wet, the feel of the prior art paper straw becomes uncomfortable. The coated paper straw according to the present invention remains smooth and comfortable throughout testing.

There are a wide range of paper straws in terms of size and dimensions. Paper straws vary in diameter, thickness and length but each has similar overall characteristics. Paper straws made in the above manner may advantageously be made in a number of sizes, and configurations and maintain the integral strength to withstand being disposed in a liquid.

It will be appreciated from the above description that many features of the different examples are interchangeable and combinable. The disclosure extends to further examples comprising features from different examples combined together in ways not specifically mentioned. Indeed, there are many features presented in the above examples and it will be apparent to the skilled person that these may be advantageously combined with one another.

Claims

Claims 1 A straw comprising: a first paper layer having an inner surface and an outer surface; a paper core layer having a first surface and second surface, wherein the first and second surfaces are coated with a water resistant barrier coating; a second paper layer having an inner surface and an outer surface; wherein the inner surface of the first paper layer is configured to be bonded to the first surface of the paper core layer; wherein the inner surface of the second paper layer is configured to be bonded to the second surface of the paper core layer; and wherein the outer surfaces of the first and second paper layers are coated with a water resistant barrier coating.
2. The straw of any preceding claim wherein the inner surfaces of the first and second paper layers are coated with the water resistant barrier coating.
3. The straw of any preceding claim wherein the paper core layer comprises a single layer of paper.
4. The straw of any preceding claim wherein the paper core layer comprises a plurality of paper layers.
5. The straw of claim 4 wherein each surfaces of each layer of the plurality of paper layers is coated with the water resistant barrier coating.
6. The straw of any preceding claim wherein the water resistant barrier coating is an acrylic based coating.
7. The straw of claim 6 wherein the acrylic based coating is styrene free.
8. The straw of any of claims 1 to 5 wherein the water resistant barrier coating is a styrene based coating.
9. The straw of any preceding claim wherein the paper layers are free of wet strength chemicals and wet strength resins.
10. The straw of any preceding claim wherein the straw is repulpable.
11. The straw of any preceding claim wherein the straw is biodegradable and/or recyclable.
12. The straw of any preceding claim wherein the water resistant barrier coating is applied via one of: an on-machine coater; an off-machine coater; and/or a printing process.
13. The straw of any preceding claim wherein the bonding comprises an adhesive on the inner surface of the first paper layer and/or the inner surface of the second paper layer.
14. The straw of claim 13 wherein the adhesive is biodegradable.
15. The straw of any preceding claim wherein the weight of paper used for each of the first paper layer, the second paper layer and the core is less than 120gsm, preferably 100gsm, further preferably 80gsm.
16. The straw of claim 15 wherein the weight of paper used for each of the first paper layer, the second paper layer and the core is the same for each layer.
17. The straw of any preceding claim wherein the straw comprises a hollow cylinder.
18. The straw of any preceding claim wherein the straw is configured to be bonded by being spirally wound.
19. A method of manufacturing a straw comprising: providing a first paper layer having an inner surface and an outer surface; providing a paper core layer having a first surface and second surface, wherein the first and second surfaces are coated with a water resistant barrier coating; providing a second paper layer having an inner surface and an outer surface; winding the first paper layer, the paper core layer and the second paper layer in an overlapping spiral pattern to form a hollow cylinder; bonding the inner surface of the first paper layer to the first surface of the paper core layer; bonding the inner surface of the second paper layer to the second surface of the paper core layer; and providing the outer surfaces of the first and second paper layers with a water resistant barrier coating.