Biodegradable Bag

Abstract

The present invention provides a bag made of a non-woven biodegradable material comprising a body portion having at least one side wall and a bottom joined together to define a storage space therebetween and an opening at the top of the body portion, wherein the bag is biodegradable and non-toxic to the environment

Description

FIELD OF THE INVENTION

The present invention relates generally to disposable biodegradable products. In particular, but not exclusively, the present invention relates to a non-woven biodegradable bag.

BACKGROUND TO THE INVENTION

Biodegradable and compostable bags are made of polymers that degrade, or decompose, when exposed to microorganisms in the presence of air, water and/or sunlight. Biodegradable and compostable bags in the marketplace are typically made from resins containing polyethylene, polyester and their blends with starches and/or heavy metals such as cadmium, lead and beryllium.

Whilst current biodegradable and compostable bags provide a solution less harmful to the environment, current biodegradable and regular disposable plastic bags require a similar amount of energy, natural resources and costs to produce. Also mixing of biodegradable and compostable bags in recycling systems with conventional plastic bags creates a strong problem and can render entire batches of recyclable plastic useless.

There is a perception that bag littering could easily increase as people start to believe that biodegradable and compostable bags are less harmful to the environment and will disappear quickly, when it reality it takes at least several months for most current biodegradable and compostable bags to breakdown. Further, the breakdown of starch-based films in water consumes oxygen, resulting in oxygen depletion that contributes to algae blooms and the death of marine life. Consequently, water, soil, and/or crop contamination could result from the use of compost with chemical residues and metabolites from biodegradable bags.

In this specification, the terms ‘comprises’, ‘comprising’ or similar terms are intended to mean a non-exclusive inclusion, such that a non-woven biodegradable bag that comprises a list of elements does not include those elements solely, but may well include other elements not listed.

OBJECT OF THE INVENTION

It is a preferred object of the present invention to provide a non-woven biodegradable and compostable bag which can be used as a recyclable carry bag, that addresses or at least ameliorates one or more of the aforementioned problems of the prior art.

It is a preferred object of the present invention to provide a non-woven biodegradable and compostable bag which is biodegradable and provides a cost-effective compostable alternative to existing products in the marketplace.

SUMMARY OF THE INVENTION

Generally, embodiments of the present invention relate to a non-woven biodegradable bag and method of manufacturing same.

According to one aspect, although not necessarily the broadest or only aspect, embodiments of the present invention reside, in a bag made of a non-woven biodegradable polylactide based material, wherein the material contains polylactic acid, polyethylene glycol and a chain extender such that the bag is biodegradable and degraded products are non-toxic to the environment.

Preferably, the bag is a shopping bag.

Suitably, the bag further comprises a pair of handles, wherein the pair of handles are attached to a top of the body portion at their ends.

Preferably, the bag further comprises at least one strap member.

Suitably, the strap member is attached at or near the top of body portion and extends across the opening of the body portion of the bag.

Suitably, the strap member is permanently secured at a first end to a first side of the body portion, the body portion having a fastening member to releasably secure a second end of the strap member to a second opposing side of the body portion.

Suitably, the bag further comprises a pair of apertures provided at or near the top of the body portion for receiving a prong member therethrough to hold the bag in an open state for example, at the checkout.

Preferably, the biodegradable non-woven material comprises one or more of the following polymers: polylactic acid, polyethylene glycol, chain extender Joncryl—ADR 4370.

Preferably, the material composition of the biodegradable non-woven material is 91-94% polylactic add, 5-8% polyethylene glycol and 1% chain extender.

Preferably, the biodegradable non-woven material has a weight-average molecular weight ratio above 160000, a dispersion coefficient ≦1.5, a melt index between 20-30 and a water content ≦0.9%.

According to another aspect, although again not necessarily the broadest or only aspect, embodiments of the present invention reside in a method of manufacturing a non-woven biodegradable bag comprising the following steps:

preparing a biodegradable non-woven material mixture;

drying the material to remove residual moisture;

extruding a Polylactide (PLA) slicing;

heat melting the extruded PLA slicing;

purifying the melted PLA material;

spinning the material;

cooling and retracting the material;

needling the material onto a roll; and

forming the bag from the roll of material.

Preferably, the material is vacuum dried at 80-90° C. such that the moisture content of the PLA slicing is less than 200 PPM.

Preferably, the extruded PLA slicing is heat melted using a heat screw extruder.

Preferably, the melted PLA material is filtered prior to the spinning process using a high viscosity fondant proportional pump to squeeze out the impurities by rotation.

Further features of the present invention will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be readily understood and put into practical effect, reference will now be made to embodiments of the present invention with reference to the accompanying drawings, wherein like reference numbers refer to identical elements. The drawings are provided by way of example only, wherein:

FIG. 1 is a perspective view of a non-woven biodegradable bag according to an embodiment of the present invention;

FIG. 2 is a perspective view of the non-woven biodegradable bag of FIG. 1 comprising a strap member according to an embodiment of the present invention;

FIG. 3 is a perspective view of an alternative embodiment of the non-woven biodegradable bag of FIG. 1 comprising at least one aperture; and

FIG. 4 is a flow diagram of the method for producing the non-woven bag biodegradable bag of FIGS. 1-3 according to embodiments of the present invention.

Skilled addressees will appreciate that elements in the drawings are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the relative dimensions of some of the elements in the drawings may be distorted to help improve understanding of embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described with reference to a non-woven biodegradable and compostable bag for use as a recyclable and disposable carry bag. However, it should be appreciated that embodiments of the present invention can be used to provide a non-woven biodegradable product which can be used for any other suitable applications such as secondary food packaging including take-away food packaging or the like. It will be appreciated that variations may need to be made as required.

Referring to FIG. 1, the non-woven biodegradable bag 100 is provided in accordance with embodiments of the present invention. According to some embodiments of the invention, the non-woven biodegradable bag is manufactured from a completely biodegradable Polylactide (PLA) non-woven material. PLA is a high crystalloid and linear polymer which satisfies the two primary conditions for wiredrawing to make a non-woven material. PLA or its derivatives, such as L and D type or copolymers, is a degradable polymer having good mechanical properties, the degradable products are natural materials, the degradation time can be varied, the raw material comes from renewable sources such as beet sugar or whey and it can be incinerated without major difficulty or drawbacks. The properties of the PLA non-woven material of the present invention include being a good hydrophilic, soil resistance, deodorisation, fire-resistance and microbial decomposability, all of which provide unique characteristics to the present invention. These properties also make this material the best candidate for a material for use in disposable environmental production. The properties of polymers derived from polylactides vary depending on the type of polymer (L or D type), on the residual amount of monomer (lactide) and, in the case of DL copolymers, on the ratio of D units to L units.

Referring to FIG. 1, the non-woven biodegradable bag 100 comprises a body portion 110 for carrying items therein. According to some embodiments, the body portion 110 comprises at least one side wall 113 and a bottom 114. When joined together, the side wall(s) 113 and bottom 114 define a storage space therebetween with an opening 120 at a top of the body portion 110. A preferred box-like shape for the non-woven biodegradable bag 100 is illustrated in FIG. 1 comprising four side walls 113.

The bag 100 is preferably sized to hold the contents of a conventional grocery shopping bag. However, as will be apparent to those skilled in the art, the body portion 110 can have various shapes and sizes depending on the intended use of the end product. It is envisaged that one skilled in the art can design any number of body configurations according to the invention bearing in mind the limitations and advantages of the materials used and the intended use. For example, a larger body portion 110 can be used if the beg is intended for use as a beach bag or gym bag.

According to some embodiments, a pair of handles 200 is provided for carrying the bag 100. Preferably, the handles 200 are attached by their ends 112 to the top of the body portion 110 of the bag 100 via stitching or any other suitable means enabling permanent attachment. In further embodiments of the present invention, the handles 200 can have an adjustable length to be shorter or longer as is required.

According to some embodiments, the bag 100 has at least one printable area 111 for displaying a company logo, advertising or any other suitable information. Preferably, the material of the bag 100 is such that information can be printed directly onto the bag material using a suitable biodegradable ink and standard printing machine to minimise production costs.

Referring now to FIG. 2, the non-woven biodegradable bag 100 can have one or more optional features attached to the body portion 110. According to some embodiments, the bag 100 further comprises at least one strap member 300 which acts as a tension member for the bag 100. According to some embodiments, the strap member 300 is attached at or near the top of body portion 110 and extends across the opening 120 of the bag 100. In FIG. 2, one strap member 300 is shown. However, in further embodiments, more strap members 300 can be included to provide additional support for the bag 100.

The strap member 300 is preferably permanently secured at a first end 301 to a first side of the body portion 110. The body portion 110 has a fastening member 310 provided on a second opposing side of the body portion 110 to releasably secure a second end 302 of the strap member 300 to the body portion 110. In an alternative embodiment, both ends 301, 302 of the strap member 300 can be releasably secured to the body portion 110. Preferably, the fastening member 310 for releasably securing the strap member 300 to the body portion is a snap fastener but any other suitable fastening device can also be used. For example, hook and loop type fasteners can be used.

According to an alternative embodiment illustrated in FIG. 3, the non-woven biodegradable bag 100 comprises a pair of apertures 120 provided at or near the top of the body portion 110. Preferably, the apertures 120 are provided on the first and second opposing sides of the body portion 110 of the bag 100. The apertures 120 are adapted to receive a prong member or the like provided at a shopping counter for holding the bag 100 in an open state. As illustrated in FIG. 3, in an alternative embodiment of the non-woven biodegradable bag, the pair of handles 200 can be omitted.

In further embodiments of invention, it is envisaged that the non-woven biodegradable bag can have additional features to provide added functionality for the bag and/or suit other applications. The non-woven biodegradable bag 100 can have provided one or more pockets (not illustrated). These pockets can be sized to hold or secure specific items such as, for example, a cell phone, wallet, keys, or glasses or the like. The interior of the body portion 110 can also have provided one or more dividers for enabling the separation of items and organising packing of items within the bag 100.

Referring now to FIG. 4, a schematic diagram of a method 400 for producing the non-woven biodegradable product is illustrated. The main equipment required for the production of PLA non-woven material includes a plastic particle dry system, a spinning unit, a drafting lay-down system, a needling unit and a roil unit. According to some embodiments, the material composition of the non-woven PLA material is as follows:

1. PLA—91˜44%

Technical requirement

• • Weight-average molecular weight ratio is between 150000 to 220000
  • Melting point 160˜170° C.
  • Crystallization temperature 50˜80° C.
  • Moisture content 5500 ppm

2. Polyethylene Glycol (PEG)—5˜8%

Technical requirement

• • Weight-average molecular weight ratio is between 5000 to 20000
  • Melting point 50˜65° C.
  • dynamic viscosity 30˜35 mm²/s,
  • pH value: 4˜7
  • The PEG used PEG4000—molecular formula is HO(CH2CH2O)nH

• • It mainly provides a toughening reagent when used in molten extrusion wiredrawing while still allowing adjustment of the melt molten index to facilitate easy drawing.

3. Chain extender ADR4370 1%

• • The Joncryl—ADR4370 maximises melt viscosity through branching where high melt strength is needed for steady parisons, non-sagging profiles, and dosed-cell, low-density foams. Its every molecule has eight epoxy groups which can react with the hydroxyl group in the polylactic acid molecules, forming a chain structure. The main aim of We using the chain extender is to increase the products intensity, and partial repair the cut molecular chain during the manufacture process when the molecular chain is cut by the twin-screw extruder.

Material Drying Process

The PLA grade required for the preparation of the present invention is fibre-grade PLA material having a weight-average molecular weight above 160000, a dispersion coefficient ≦1.5, a melt index between 20-30 and a water content ≦0.5%. Polylactide physical properties, especially the tensile strength parameters will increase as the molecular weight is increased. By using different molecular weights, the PLA fiber can also have different tensile strength. For example, using a molecular weight below 150,000 polylactic acid to produce polylactic acid fiber, the tensile strength is low and can not reach strength requirements for the non-woven material and bag. If the molecular weight were higher than 220,000 polylactic add, although its fibre strength is high, because of the high viscosity of molten body of the PLA material, shear stress is larger and hard to withstand for the production equipment. For example, for 150,000 molecular weight of polylactide, its production of fibre tensile strength is 1.1 Mpa, but for 220,000 molecular weight of polylactide, its production of fibre tensile strength can reach 2.6 Mpa.

The moisture content is the most important of the above parameters because PLA is hydrolysable at high melt temperatures causing the molecular chain to rupture and the molecular weight to decrease. This kind of circumstance can make the output of the strength of fiber lower and very easy to be broken. Thus, it is necessary to let the raw material dry fully. In order to avoid this issue, the material undergoes a further drying process to desiccate the PLA polymer and remove residual moisture to reduce the moisture content to a level where hydrolysis is insignificant. Preferably, the moisture content of a PLA slicing should be less than 200 PPM and is achieved by vacuum drying at 80-90° C. The drying process can be carried out utilising a rake vacuum drying system or the like.

According to experience value, a PLA raw material used for producing film must be dried to a moisture content of below 200 PP and a PLA raw material used for producing fibre must dried to moisture content of 30 PPM below.

Melt Extrusion Process

In this process, the polymer is melted and extruded by means of a heated single-screw or twin-screw extruder and then conveyed to a spinning pump. If a double screw extruder is chosen the length-diameter ratio of the screws should be considered. The specification of the extruder diameter can be 135 mm. Care must be taken while kneading during the extrusion process so as not to destroy the PLA polymer chain in the processing cycle and then influence the stretch of the tactile fibre and break the fibre or decline the single fibre tenacity.

Using custom made extruders for this process, for extruder specifications the diameter is 135 mm, length-diameter ratio is 1:25, dividing into six district for heating and cooling zone before first district; the cooling district and the first district is the area for feeding section, second and third district is compressed section, forth district and fifth district is measurement section, sixth district is mixing section.

After PLA resin is melted by the screw extruder, the PLA fondant impurities must be removed which is achieved by introduction of a filter film head with a filter level of 20 μm. After the PLA fondant is passed through the filter film it goes through a high viscosity fondant proportional pump to squeeze out the impurities by rotation. The proportional pump frequency is controlled according to the output and product features required. The proportional pump with temperature control provides uniform flow of the molten polymer.

On leaving the pump, the stream of molten polymer is conveyed through the filter to the spinneret, which contains a series of small holes (0.2 to 2.0 mm in diameter), usually of the order of several thousand holes. The polymer is spun through the spinneret and conveyed to the cooling and drawings sections. The specification selected in this instance for the non-woven spinneret plate bore diameter is 0.25-0.35 mm. This is based on a preferred narrow processing window for the PLA material and the allowed processing temperature range. According to some embodiments, the diameter of plate bore is according to the requirement of silk flock. In this case, every flock of silk is 90˜96 roots, so the the diameter of plate bore is 10 mm. When spinning, the lowest melt temperature for the melting point is around 170° C., otherwise material cannot melt and also cannot be spun. The highest temperature is around 210° C., if higher, poly lactic add will very easily decompose. The lowest draw ratio is 80.

As the temperature increases, the flow of viscosity is well controlled and the uniformity and theological characteristic of the PLA material can be property maintained. The high volume heated airflow attenuates the filaments in a high-output and controlled manner. The spinability is increased gradually as the maximum draw ratio and natural draw ratio is raised, thereby increasing the single fibre tenacity. If the PLA fondant melt temperature is too high, the PLA material may itself tends to degrade making the screw pressure produced undulate. Consequently, the spinning blowout is not a continuous state and could lead to stretching the fibre, making the spinning process difficult and increasing the fuzziness' of the PLA material.

For the production process of PLA, in order to improve the spinability, the primary fiber does not need to have a high crystallinity, otherwise in the drafting process it is very easy to break, which reduces the product's intensity in the process of melt-spurt spinning. The crystallinity in general before drafting is about 40%, in the best conditions of cooling temperature and time (cooling temperature is 20° C.), and guarantee that the highest airflow velocity is 5000 m/min, realizing the best melt-spinning spinability.

In the process of crystallization drying, the crystallization temperature and the drying temperature are controlled between around 110-120° C., extruder temperature from district one to six increases from 170-210° C. and spinning temperature is controlled at 210° C. plus or minus 0.1° C. Drafting speed is 5000 m/min, drafting pressure is 0.46˜0.6 MPa, cycloid rate is around 50 H and the speed of nets machine and hot-rolled machine is 17 m/min.

Cooling and Retraction

When cooling the undrawn filament yarns (UDY) from the spinning plate, the cooling speed should be controlled. If the cooling is not managed, the crystalline nature of the stretched undrawn filament yarns can not be controlled properly and can be difficult to retain for longer time period.

After the cooling of PLA undrawn filament yarns, the undrawn filament yarns should pass through the high-speed traction stretch where the molecular chain of PLA silk is re-arranged again, the degree of orientation of fibre molecules is increased, the strength of fibre silk is raised in multiples and the product quality is improved.

Needling Binding to Roll

After the cooling and retraction process, the fibre silk is introduced in the needle machine. The needling depth is selected according to the production requirement, a depth too deep could damage the fibre and a depth too shallow will result in not enough binding. In general the density of needling is large and the fibre tangle degree and the production strength is high. The mixed fibres were processed using needle punching and thermal bonding to create PLA nonwoven fabric. The PLA fibre non-woven material can be chosen according to the customer requirement of width and roil length.

In further embodiments of the present invention the one or more of the following parameters can also be adopted:

A Conveying capacity: once 2 t/h, Saul Sates tan transportation; Secondary transmission is control sending, conveyance medium: dry air.

B: Dry capacity: 500 Kg/h, way for filling type is continuous spray drying tower.

C: The spinning mode is melt spinning, through a single screw extruder extrusion melting and measuring mixing (speed 30˜40 turn/min is best), entering wick-type filter, filtered melt passing into the metering pump and then measuring extrusion (metering pump rotation speed is in 18˜≅turn/min for the best) into the silk spray head ventage. From silk spray head outbursts primary fiber goes through quench air cooling wind into moulding (wind speed is 0.6 m/min; temperature is 20˜22° C.), then enters into the draft tube for drafting (draft speed is 5000 m/min), the air needed for drafting must be dry air to go through air compressor and air dryer (pressure is 0.5 Mpa). The flock silk after drafting then preliminarily goes into the net through pendulum silk machine (fluctuating frequencies is 45˜50 Hz, the pendulum deflection is 14 degrees) and nets machine (the nets machine is negative pressure suction type, namely through air volume of 150000 mcubic meters/hour, using the frequency adjustable fan of 2000 Pa for sucking the below of nets machine, making the two tightly adherent in the surface of net unit), adopting the hot-rolled method for molding.

Hence, the non woven biodegradable bag 100 of the present invention thus provides a solution to the aforementioned problems of the prior art by providing a non-woven biodegradable bag 100 which is biodegradable and cost-effective to manufacture. Thus, after the biodegradable bag has been used and disposed of, it can biodegrade into carbon dioxide and water by microorganism in composting condition. The non-woven PLA material complies with international sustainable development demands by having the characteristics of a complete natural cycle and biodegradable product. Tests conducted have revealed that the present invention is biodegradable within seven days with earth worm and soil tests confirming that the biodegraded product is non-toxic to the environment.

PLA (polylactic add) is an ideal raw material for leading-edge sustainable applications since it is derived from the natural fermentation of corn-based products and represents a renewable resource. PLA also has the ability to form fibers, films or foams and is easily extruded into a variety of forms that have applicability to unique markets. Depending on the process formulation, PLA can be exploited by combining it with other natural hydrophilic or hydrophobic materials, making PLA an ideal candidate for developing flexible solutions.

PLA's degradation properties, wherein PLA polymers break down into lactic add or its oligomeric lactide forms that are easily metabolized, provides a green alternative where biodegradability is an important consideration.

Furthermore, domestically-sourced PLA resins we equally cost competitive with petroleum-based resins, providing additional options for customers.

Throughout the specification the aim has been to describe the invention without limiting the invention to any one embodiment or specific collection of features. Persons skilled in the relevant art may realize variations from the specific embodiments that will nonetheless fall within the scope of the invention.

Claims

1. A bag made of a non-woven biodegradable polylactide based material comprising a body portion having at least one side wall and a bottom joined together to define a storage space therebetween and an opening at the top of the body portion, wherein the material contains polylactic acid, polyethylene glycol and a chain extender such that the bag is biodegradable and biodegraded products are non-toxic to the environment.

2. The bag of claim 1, wherein the bag is suitable for use as a shopping bag.

3. The bag of claim 1, further comprising a pair of handles, wherein the pair of handles are attached to a top of the body portion at their ends.

4. The bag of claim 1, further comprising at least one strap member.

5. The bag of claim 4, wherein the strap member is attached at or near the top of the body portion and extends across the opening of the body portion of the bag.

6. The bag of claim 4, where the strap member is permanently secured at a first end to a first side of the body portion, the body portion having a fastening member to releasably secure a second end of the strap member to a second opposing side of the body portion.

7. The bag of claim 1, further comprising a pair of apertures provided at or near the top of the body portion for receiving a prong member therethrough to hold the bag in an open state.

8. The bag of claim 1, wherein the biodegradable non-woven material comprises one or more of the following polymers: polylactic acid, polyethylene glycol, chain extender Joncryl—ADR 4370.

9. The bag of claim 8, wherein the material composition of the biodegradable non-woven material is 91-94% polylactic acid, 5-8% polyethylene glycol and 1% chain extender.

10. The bag of claim 8, wherein the biodegradable non-woven material has a weight-average molecular weight ratio above 160000, a dispersion coefficient ≦1.5, a melt index between 20-30 and a water content ≦0.5%.

11. A method of manufacturing a bag made of a non-woven biodegradable polylactide based material comprising a body portion having at least one side wall and a bottom joined together to define a storage space therebetween and an opening at the top of the body portion, wherein the material contains polylactic acid, polyethylene glycol and a chain extender such that the bag is biodegradable and biodegraded products are non-toxic to the environment, the method comprising the following steps:

preparing a biodegradable non-woven material mixture;

drying the material to remove residual moisture;

extruding a polylactide (PLA) slicing;

heat melting the extruded PLA slicing;

purifying the melted PLA resin;

spinning the material;

cooling and retracting the material;

needling the material onto a roll; and

forming the bag from the roll of material.

12. The method of claim 12, wherein the material has a weight-average molecular weight ratio above 160000, a dispersion coefficient ≦1.5, a melt index between 20-30 and a water content ≦0.5%.

13. The method of claim 12, wherein the material is vacuum dried at 80-90° C. such that a moisture content of the PLA slicing is less than 200 PPM.

14. The method of claim 12, wherein the extruded PLA slicing is heat melted using a heat screw extruder.

15. The method of claim 12, wherein the melted PLA material is filtered prior to the spinning process using a high viscosity fondant proportional pump to squeeze out the impurities by rotation.