WO2017101974A1

WO2017101974A1 - Polylactic acid-fibers based non-woven, method for manufacturing thereof and its use for making coffee and/or capsules in percolating apparatus

Info

Publication number: WO2017101974A1
Application number: PCT/EP2015/079653
Authority: WO
Inventors: Raymond Volpe; Emilie Picard; Stephen Collins
Original assignee: Ahlstrom Corporation
Priority date: 2015-12-14
Filing date: 2015-12-14
Publication date: 2017-06-22

Abstract

Non-woven comprising fibers consisting of a core containing polylactic acid (PLA-1) coated with an envelope containing polylactic acid (PLA-2) characterised in that: - PLA-1 is a copolymer of lactic acid monomers L1 and lactic acid monomers D1; - PLA-2 is a copolymer of lactic acid monomers L2 and lactic acid D2, whose D2 monomers rate is greater than the monomers rate D1 of PLA-1; - the core further contains a polymeric plasticizer. Use for making coffee and / or capsules in percolating apparatus

Description

POLYLACTIC ACID-FIBERS BASED NON-WOVEN. METHOD FOR MANUFACTURING THEREOF AND ITS USE FOR MAKING COFFEE AND / OR CAPSULES IN PERCOLATING APPARATUS FIELD OF THE INVENTION

The present invention relates to the field of non-woven fabrics, especially non-woven for the food industry. The invention more particularly relates to the field of tea or coffee capsules used in the percolating machines. These machines are more specifically found in the US market (drip coffee).

In the following description, the invention will be more particularly described in relation to the field of coffee although the invention could find other applications especially in the fields of cocoa and infusions.

PRIOR ART

Coffee pods available on the US market must contain about 12g of coffee. The amounts are less for tea. Percolation time of the coffee machines is 30 to 60 seconds for a water volume of about 12 to 30 cl.

According to the applicant, most of the pods for this application are in the form of a plastic container, in particular made of PET, covered with a cap generally made of paper and plastic. This type of pod fully meets the client's expectations apart from the fact they are not environmental-friendly. In fact, there are actually not degradable. This kind of pod is for example sold by San Franciso Bay company. Several information about this product are available on the following links :

https://en.rn. wikipedia.org/wiki/Single-serve_coffee_container

http://www.coffeereview.com/k-cups-cups-capsule-smgle-serve-coffees

http ://www.amazon. com San- Francisco-Bay- Variety

In the food industry, the materials used are regularly subject to increasingly stringent requirements especially regarding environment. Thus, the currently developed products have no longer the unique objective of meeting consumer's tastes. They must also meet the requirements relating to the respect of the environment.

But it is very difficult to recycle those capsules in order to reuse them later on. There is therefore a need to develop capsules that are fully compostable while having a volume suitable for the coffee market especially coffee obtained by percolation.

For this reason, manufacturers have orientated their researches to materials considered to be more acceptable from an environmental point of view, and more particularly to materials that contribute to the biodegradability and/or compostability of the finished product.

According to some studies, the most promising and relevant material is the polylactic acid that is a thermoplastic aliphatic polyester.

However, the use of polylactic acid is difficult due to its limited break elongation properties. In order to receive a relatively large amount of coffee (around 12g) it is actually necessary to produce a container having a certain depth (from 2 to 5 cm). Moreover, a non-woven made of PLA does not achieve this goal since it has, due to the PLA nature, very low elongation.

The invention intends to solve the problem of developing a thermoforming support, based on PLA fibers, that is suitable for use as a filter in a coffee pod obtained by percolation.

The Applicant has developed a non-woven fabric comprising polylactic acid-based fibers to solve this problem. This non-woven has satisfactory mechanical elongation properties for use in a thermoforming process. It can thus be shaped for use as a filter in a drink-supplying capsule. More particularly, this non-woven, once thermo formed, can be used as trickling filter within a coffee and/or tea capsule. DESCRIPTION OF THE INVENTION

The present invention relates to a non-woven fabric comprising fibers having a core/shell structure, i.e having bicomponent fibers. Unlike non-woven of the prior art, it comprises fibers, the nature and more precisely the chemical composition of which makes it possible to obtain elongation mechanical properties compatible with the desired application. This non- woven may actually be thermoformed as to obtain capsules of sufficient depth without breaking the fibers.

Thus, the specific structure and properties of the fibers make the non-woven fabric suitable for the manufacture of coffee and/or tea capsules by thermoforming. This non-woven especially enables the percolation of coffee or tea. More specifically, the present invention relates to a non-woven fabric comprising fibers having a core containing polylactic acid (PLA-1) coated with an envelope containing polylactic acid (PLA-2). This non-woven is characterised in that:

- PLA-1 is a copolymer of lactic acid monomer Lj and lactic acid monomer Dj;

- PLA-2 is a copolymer of lactic acid monomer L₂ and lactic acid monomer D₂, whose D2 monomers rate is greater than the monomers rate Dl of PLA-1;

- the core further contains a polymeric plasticizer.

In a preferred embodiment, the non-woven of the invention consists exclusively of the above- identified fibers.

The non-woven fabric of the invention is advantageously compostable and/or biodegradable. In other words, it degrades over time, possibly through the action of microorganisms and, in the presence or absence of oxygen. Thus, the non-woven of the invention meets the ASTMD6400 standard.

It is meant by "Dl monomers rate" the ratio and by "D2 monomers rate" the

ratio

with D1 and L1 referring to the monomers of PLA-1 polymer and D₂, L₂ referring to the monomers of PLA-2 polymer. In addition, each monomers rate Dl and D2 is expressed in %.

It is meant by "plasticizer", any chemical compounds, which after incorporation into a polymer material increases the polymer chains mobility so as to reduce the brittleness of the material and improve its elongation properties. In this case, it is a polymeric plasticizer. According to the invention, the plasticizer may be in the form of a mixture containing a polymeric plasticizer, additives such as, for instance, comptabilisants agents. In practice, the additives account for up to 5% by weight of plasticizer, preferably up to 3% by weight.

As already mentioned, the invention consists of a non-woven of polylactic acid-based fibers having a core/shell structure. This non-woven has mechanical elongation properties enabling its shaping by thermoforming. These thermoforming properties are primarily due to the polymeric nature of the plasticizer and respectively monomers rates Dl and D2. In general, polylactic acid (PLA-1) is more crystalline than polylactic acid (PLA-2), the monomers rate Dl being less than the monomers rate D2. Thus, PLA-1 has elongation properties less than that of PLA-2. Furthermore, given the monomers rates, PLA-1 has a melting point greater than that of PLA-2.

The incorporation of a polymeric plasticizer in the fibers core makes it possible to improve the elongation properties of the PLA-1 therefore of the non-woven. The plasticizer reduces the interactions between the polymer chains which lead to a greater mobility amongst them. Thus, the polymeric chains have less ability to crystallize and the fibers core is therefore even more ductile.

Generally, the presence of the polymeric plasticizer does not significantly affect the melting temperature of PLA-1. Thus, the plasticizer improves the elongation properties of the fibers core.

The polymeric plasticizer is preferably a polymer or copolymer of monomers selected from the group comprising the monomers: (meth)acrylic, olefin, caprolactone, ethylene, hydroxyalkanoate, ethylene glycol, propylene glycol, others diacids and other dialcohols. It may especially be an ethylene copolymer-type polymer, acrylic acid and / or methacrylic acid, polycaprolactone, polyhydroxyalkanoates, polyethylene glycol, polypropylene glycol, copolyesters.

The plasticizer may represent, by weight percentage relative to the fiber's weight, 1 to 5%, preferably 2 to 3%.

In practice, the plasticizer may represent, by percentage weight, from 1,5 to 8% of the non- woven fabric fiber's core of the invention preferably 3 to 7%. Advantageously, polylactic acid (PLA-1) has a CAS number is 26100-51-6.

In general, polylactic acid (PLA-1) has a monomers rate Dl that is less than 2%, preferably less than 1%, advantageously less than 0.5%. PLA-1 may have a viscosity index in the melt at 210°C advantageously between 20 and 25g 10 min, more preferably between 22 and 24 g 10 min.

PLA-1 may have a crystallinity of preferably between 50 and 70%. PLA-1 may represent, by weight percentage relative to fiber's weight, from 50 to 80%, preferably from 60 to 70%.

PLA-1 represents, by weight percentage relative to fiber's core weight, between 92 and 98.5% of the non-woven fibers core, preferably between 93 and 97%.

Advantageously, polylactic acid (PLA-2) has a CAS number is 26100-51-6.

Preferably, polylactic acid (PLA-2) has a monomers rate D2 between 2 and 12%, preferably 5 to 12%, advantageously between 8 and 12%.

PLA-2 may have a viscosity index in the melt at 210°C comprised between 10 and 20g 10min more preferably between 15 and 17g/10 min. PLA-2 may represent, by weight percentage relative to a fiber's weight, 20 to 50%, preferably 30 to 40%.

PLA-2 represents 100% by weight of the envelope. Thus the non-woven may comprise fibers that each contain, by weight percentage relative to the fiber's weight:

- between 55 and 69% PLA-1;

- between 30 and 40% PLA-2;

- between 1 and 5% plasticizer.

Depending on the desired application, the skilled person knows how to adapt the respective amounts of PLA-1, PLA-2 especially the amount of plasticizer present in the core of fibers of the non-woven. Generally, the non-woven may advantageously be composed of fibers having:

- a diameter of between 15 and 35 micrometers, more preferably between 20 and 30 micrometers; and/or

- a linear density of between 2 and 10 deniers, more preferably between 4 and 8 denier. Moreover, the non-woven of the invention may advantageously have:

- a weight of between 60, preferably between 80 and 160 g/m2, preferably between 120 and 140g/m² more preferably of 130 g/m²; and/or

- a thickness between 450 and 650 micrometers, advantageously between 500 and 600 micrometers.

The present invention also relates to a method for producing a non-woven as above-described. This method comprises the following steps:

a) preparing, by melting, fibers consisting of a core containing polylactic acid (PLA-1) coated with an envelope containing polylactic acid (PLA-2),

b) forming a non-woven by partial cooling followed by stretching and deposition of the obtained fibers on a forming mat;

c) calendering the non-woven fabric thus obtained. Step a) of the process consists in preparing fibers with core/shell structure based on polylactic acid. It is advantageously carried out with two extruders that are simultaneously extruding the core of the fibers and the envelope of the fibers.

According to an advantageous embodiment, this step is performed using at least two couples of two extruders for forming two layers of fibers. As already said, a single couple of extruders can also be used.

Each couple of extruders El comprises an extruder El to form the core of the fibers and an extruder E2 to form the envelope of the fibers.

When four extruders are used, a first couple of extruders CI is dedicated to the formation of the first fiber layer, while a second couple C2 can form the second fiber layer.

The two extruders (El, E2) are independently from each other supplied in polymers and when necessary in a polymeric plasticizer. Indeed, El is supplied with polylactic acid (PLA-1) and with a polymeric plasticizer unlike E2 which is supplied with polylactic acid (PLA-2).

The polymeric materials PLA-1, PLA-2 and the polymeric plasticizer may be added in solid form such as granules, powders.

In addition, PLA-1 and the polymeric plasticizer may be introduced simultaneously or separately. They are advantageously prepared beforehand in a single master-batch in amounts that are depending on the desired application. In a preferred embodiment, the master-batch preferably comprises 75% of PLA-1 and 20 to 25% of polymeric plasticizer and up to 5% of comptabilisants.

When the PLA-1, PLA-2 and the polymeric plasticizer are introduced into extruders (El, E2), the molten material from each extruder El and E2 is then driven to a die by means of distribution plates. At the end of the die, fibers having a core containing PLA-1 + plasticizer, such core being coated with a envelope containing PLA-2.

Generally, the fibers exiting the die have a diameter of between 0.3 and 0.7 millimeter, more preferably between 0.4 and 0.6 mm, and even more preferably of close to 0.5 millimeters.

A quenching step (quench) partially cools the fibers so that they have an optimum temperature for the spinning step. A spinning step by means of a "drawjet" is then used to stretch the fibers by spunlaid. This step is preferably carried out using compressed air, the so-called "spunbond" process and reduces the diameter of the fibers by stretching them.

Then the fibers fell onto a forming belt to form a web of fibers. The fibers are then conducted by the belt, and take an orientation that is induced by the machine direction.

Once the fibers web formed by the first couple CI reaches the zone on the forming belt facing the second couple C2 of extruders, the second fibers web is deposited onto the first web so as to form a single layer of fibers.

This layer of fibers subsequently undergoes a calendering step in which the fibers pass between two heated and pressurized rollers.

The calendering temperature can be comprised between 125 and 135°C preferentially between 128 and 130 °C and a pressure ranges from 110 to 150 kPa preferably from 125 to 135 kPa.

In practice, the calendering is carried out with two rollers. The upper roller is advantageously provided with a template, a pattern, an etching or the like for forming fixation points by localized fusing points of the fibers. In other words, the presence of a pattern on the upper roller makes it possible to melt some predetermined areas of the layer of fibers to form the non-woven. When exiting the calender rolls, the non-woven is generally in the form of a single fibrous layer, even when four extruders are used.

According to another embodiment, the threading step may be performed by hot-melt also called "meltblown". In this case, hot compressed air is applied directly at the die outlet. Thus, the fibers obtained have a diameter smaller than those of fibers obtained by "spunbond". The method "meltblown" does not require a calendering step, the fibers being sufficiently hot at the die outlet to bind to each other during their deposition on the forming belt. Due to its ability to be thermoformed, the non-woven according to the invention can particularly be used in the production of coffee capsules and/or tea and more precisely as a percolating filter.

The non-woven of the invention can be shaped by thermoforming, advantageously at a temperature between 80 and 110°C, more preferably between 90 and 100°C.

Thermoforming is generally carried out according to techniques known to those skilled in the art, particularly using a preheated form. Generally, the non-woven according to the invention can be thermoformed so as to undergo deformation advantageously between 2 and 5 cm, more preferably between 3 and 4 cm

Thus, the present invention also relates to a coffee and/or tea capsule, comprising as a thermoformed filter, the non-woven above-described.

The capsule can also comprise a collar and a seal.

The collar enables to maintain the capsule in a brewing machine. The seal may consist of a non-woven fibers material selected from the group consisting of paper, non-woven, compostable film, and mixtures thereof.

In practice, the depth of the thermoformed filter is between 2 and 5 centimeters. The invention also relates to the use of the non-woven as above-described as a filter for pod in a brewing machine. The invention and its related advantages are shown in the following examples as an illustration and are thus not limited to those.

Figure 1 is a schematic representation of the thermoforming test conducted according to invention.

Four different sets 1 to 4 are carried out, each set comprising four non-woven supports. The supports have the configurations as detailed below. In each set, the nature of the plasticizer varies.

- Support 1: 100% by weight of monocomponent fibers of PLA 6100D supplied by NATURWORKS

- Support 2: 100% by weight of monocomponent fibers made of a mixture comprising 93% by weight of fibers of PLA 6100D and 7% by weight of plasticizer.

- Support 3: 100% by weight of bicomponent fibers consisting of a core of PLA 6100D representing 80% by weight of the fiber and an envelope made of PLA 6302D representing 20% by weight of the fiber. In this case, the core is plasticizer-fiee.

- Support 4 (invention): 100% by weight of bicomponent fibers consisting of a core containing PLA 6100D (93% by weight relative to the weight of the core) and plasticizer (7% by weight relative to the weight of the core), which core reprsents 80% by weight of the fiber and an envelope made of PLA 6302D reprsenting 20% by weight of the fiber.

For each set, the nature of the plasticizer is varying:

- Set 1 represents the case where the plasticizer is an ethylene-acrylic copolymer marketed by Arkema under the trademark "Biostrenght". - Set 2 represents the case where the plasticizer is a copolyester commercially available from BASF under the Trademark "Ecoflex".

- Set 3 represents the case where the plasticizer is essentially a polyhydroxyalkanoate sold by the company Danimer.

- Set 4 represents the case where the plasticizer is essentially a polyhydroxyalkanoate sold by the company Metabolix. The substrates are manufactured, at a laboratory scale, according to the method below.

a) preparing fibers by meting and partial cooling

b) forming a non-woven by stretching the fibers and depositing them on a forming belt; c) calendering the non-woven fabric obtained.

A thermoforming test is carried out for each support according to the following method illustrated on figure 1. .

A non-woven sample (1) is fixed with a mounting ring (6) on a non-heated support (2). A heated spare punch (3) is applied on the non-woven with gradual depths ranging from 2 to 4.5 cm For this purpose, a succession of rings (4) is used with 0.5 cm in height. The tests were carried out on 4 samples of each the supports. The arrow 5 designates the thermoforming direction.

For each set, the thermoforming depth results are the following:

- for the support 1 , the thermoforming depth is 2,5 cm.

- for the support 2, the thermoforming depth is 3 cm maximum.

- for the support 3, the thermoforming depth is 2,5 cm.

- the support 4 of the invention, thermoforming depth is 4.5 cm.

Beyond these depths, the support breaks or has some holes which are not compatible with the use, especially coffee.

The results show that the presence of a bicomponent structure of PLA fibers whose core contains a polymeric plasticizer is necessary to obtain a sufficient thermoforming depth.

Claims

1. Non-woven comprising fibers consisting of a core containing polylactic acid (PLA-1) coated with an envelope containing polylactic acid (PLA-2) characterised in that:

- PLA-1 is a copolymer of lactic acid monomers Li and lactic acid monomers Di;

PLA-2 is a copolymer of lactic acid monomers L₂ and lactic acid D₂, whose D2 monomers rate is greater than the monomers rate Dl of PLA-1;

the core further contains a polymeric plasticizer.

2. A non-woven fabric according to claim 1, characterised in that it consists exclusively of fibers made of core containing a polylactic acid (PLA-1) coated with an envelope containing polylactic acid (PLA-2):

PLA-1 is a copolymer of lactic acid monomers Li and lactic acid monomers Di; PLA-2 is a copolymer of lactic acid monomers L₂ and lactic acid monomers D₂, D2 monomers having a rate which is greater than the monomers rate Dl of PLA-1 ;

the core further contains a polymeric plasticizer.

3. Non-woven fabric according to claim 1 or 2, characterised in that the polymeric plasticizer is a polymer or copolymer of monomers selected from the group comprising the monomers: (meth) acrylic, olefin, capro lactone, ethylene, hydroxyalkanoate, ethylene glycol, propylene glycol, diacides, dialcohols.

4. A non-woven fabric according to one of the claims 1 to 3, characterised in that the monomer rate Dl is less than 1%, preferably less than 0.5%.

5. Non-woven fabric according to one of claims 1 to 4, characterised in that the monomers rate D2 is between 2 and 12%, preferably between 8 and 12%.

6. A non-woven fabric according to one of the claims 1 to 5, characterised in that PLA-1 represent, by weight percentage relative to the weight of a fiber, from 50 to 80%, preferably from 60 to 70%.

7. A non-woven fabric according to one of the claims 1 to 6, characterised in that PLA-2 represents by weight percentage relative to the weight of a fiber, from 20 to 50%, preferably from 30 to 40%.

A non-woven fabric according to one of the claims 1 to 7, characterized in that the polymeric plasticizer represents, by weight percentage relative to the weight of the fiber, from 1 to 5%, preferably from 2 to 3%.

A non-woven fabric according to one of the claims 1 to 8, characterized in that fibers have:

a diameter of between 15 and 35 micrometers, more preferably between 20 and 30 micrometers; and/or

a linear density of between 2 and 10 deniers, more preferably between 4 and 8 denier.

. A non-woven fabric according to one of the claims 1 to 10, characterized in that it has : a weight of between 60 and 160 g/m2, preferably between 120 and 140g/m2 more preferably of 130 g/m2; and/or

a thickness between 450 and 650 micrometers, advantageously between 500 and 600 micrometers.

11. A method for making a non-woven according to any of claims 1 to 10 comprising the steps of:

a) preparing, under melting, fibers consisting of a core containing polylactic acid (PLA- 1) coated with an envelope containing polylactic acid (PLA-2),

c) calendering the non-woven fabric thus obtained.

12. Capsule coffee and / or tea including, as a filter which is thermoformed, the non-woven according to any of claims 1 to 10.

13. Capsule according to claim 12, characterised in that the depth of the thermoformed filter is between 2 cm and 4.5 cm

14. Use of the non-woven according to one of the claims 1 to 10 as a filter pod in a brewing machine.