THERMOPLASTIC STARCH FORMING COMPOSITIONS AND USES THEREOF

FIELD OF THE INVENTION

The invention is broadly in the field of thermoplastics and bioplastics, more precisely in the field of such derived from starch. In particular, the invention concerns a composition suitable for forming a bioplastic or thermoplastic starch derived from pea starch, and its use in producing (bio)degradable films and packaging. More particular the invention relates to cold water soluble starch based films especially for preparing detergent tablets covers.

BACKGROUND OF THE INVENTION

Cold water soluble starch based films for packaging of e.g. detergents allow the detergent release in watery environment at a temperature of 20°C and above. This feature allows the use of lower cleaning temperatures, resulting in less energy consumption for the users and using an environment friendly material.

At the present moment cold water soluble starch blend films are commercially available, and in those formulations, starch is used to substitute a certain percentage of non-biodegradable polymers. In this way the environmental impact is reduced, but problems of compatibility between starch and the other polymers can arise, solubility can decrease in function of the starch percentage component and also some mechanical properties can be lost.

The most important example of such systems are starch blends with polyvinyl alcohol (PVOH). This polymer is biodegradable, but not biosourced/biobased, in fact it is derived by oil refinery processes from fossil fuels. Despite its nature, it has good mechanical properties, elasticity, transparency and solubility and can be considered the gold standard for cold water soluble films.

In order to reduce the environmental impact of PVOH, it is substituted by starch, or starch blends with micro-crystalline hydroxy propyl cellulose and bio-derived swelling polymers such alginate and gums. Those attempts improve the biocompatibility and biodegradability of the film, but the solution in cold water remains around 65% at the best, especially for starch blends with polymers different by PVOH.

Alginate, gums and even starch in its natural form are in fact swelling polymers, that absorb water, increasing the viscosity of the solution. This means they are not naturally dissolving in an aqueous medium. The classical way of increasing the solubility is to increase water temperature under strong agitation, usually close to 60-90°C, depending on the concentration of the solution. However, even with said agitation and heating steps, those solution remain highly viscous. This is a real problem for film application, because even though washing machines and dish washers have good rinsing capabilities, filters and connector tubes can't stand high viscous solutions, with the high risk of tube clogging.

To avoid this problem, starch is often chemically modified through hydroxypropylation, oxidation and functionalization with anhydrides. Starch modification is not simple, because the raw material is a powder, and before to be correctly transformed in films it needs to be transformed in pellets of thermoplastic starch. The most used industrial processes are extrusion, such as reactive extrusion and plastograph mixing. The procedures reported in literature foresee a first mix of starch powder with a plasticizer. A paste is obtained, that needs to swell for a time of between 6 and 24 hours. After this period, the paste is processed in a plastograph, with water and other additives in the desired amount for the desired time. This way thermoplastic starch is obtained, that can be pelleted and extruded into films.

The extrusion processes currently performed in an industrial environment make use of toxic reagents that can be dangerous to the environment and can sometimes destroy the starch structure. As a consequence, although the raw materials to prepare the films are biobased, biocompatible, and biodegradable, the resulting products can contain chemicals residuals, and if starch structure has been highly modified, can be biodegraded less easily.

Summarizing, starch modification processes bear a particularly high environmental cost and present numerous technical constraints.

In order to improve starch processability those skilled in the art combine the raw starch powder with plasticizers. Those are usually polyols, such as sorbitol, mannitol, glycerol, polyethylene glycol, xylitol, and fructose. Among those, glycerol has been chosen because its capability to allow starch swelling, allowing in this way the disruption of granule crystallinity and the transition to an amorph thermoplastic material. Glycerol is also not expensive, non-toxic, biocompatible, and biodegradable. It is a viscous, readily cold water soluble liquid and transparent. Those features help in the production of the final film not only for the mechanical properties but also for the physical properties of the film. As reported in literature, to obtain a homogeneous blend it is important to add maximally 30% w/w of glycerol.

Another important plasticizer is polyethylene glycol. The chain length of polyethylene glycol (PEG) can vary from 300 g/mol to weights of the 10 ⁶ order. Literature reports the use as plasticizer of PEGs with molecular weight between 500 and 4000 g/mol. This compound is often used in pharmaceutical applications, especially in the fabrication of stealth coated drug-delivery systems. This implies that the biocompatibility of PEG is proven due to years of toxicological studies. PEG is also used to improve solubility of hydrophobic polymers such as polylactic acid (PLA), in the formation of micelles, emulsions and other pharmaceutical delivery systems. Many attempts of blends between starch and PEGs are reported in literature, not only to increase starch solubility, but also to give mechanical properties such as elasticity and flexibility. It is important to note that none of those blends make the starch soluble, but the resulting films are soluble in the PEG components and easily disrupted in contact with water.

With ethylene glycol monomers, starch has been extensively functionalized to give hydroxypropyl starch, with cold water solubility between 40 and 60%, depending on starch degree of functionalization. The industrial process, as reported for example in US patent application US3577407A, foresees the use of strong bases as catalysts, notably NaOH, that cannot be completely removed in the final product, and propylene oxide that is an inflammable gas. Even if the industrial process is well known and exploited nowadays, also in alimentary industrial production, the use of dangerous reagents remains an issue and could be improved.

Other attempts to produce cold-water soluble starches have been performed in fast oral dissolving tablets, such explained in US patent US9234049B2. In this patent a superabsorbent powder is prepared, mixing mannitol and starch granules. Starch used in fast dispersing oral tablets has been known since a long time and has been well exploited. However, those kinds of powders if formulated in films (e.g. through thermo-pressing) do not result in a high cold-water solubility. Hence, although the powder form has the appropriate cold-water soluble characteristics, those are not translated in the final film formulation.

From the above, it follows that there is still an unmet need for a starch-based film that is biodegradable and biocompatible and in the use of reagents and, most importantly, in the industrial process of production.

SUMMARY OF THE INVENTION

A first objective of the present invention it is to provide a product that has the required features suitable both for industrial production and formulation of films that have the necessary characteristics of thickness, transparency, cold-water solubility, resistance, and flexibility.

A second objective is to produce a film that is homogeneous in its composition, without compatibility issues with the other polymer(s), that is still biodegradable and biocompatible.

The third objective it is that the biocompatibility and biodegradability are still preserved in the final product, i.e. in that the starch structure is not changed too much. Moreover, the entire process of production has the aim to be green, avoiding the use of dangerous or toxic reagents and their release in the environment. The fourth objective it is to maintain this process low cost in terms of economical goods and environmental impact.

Finally, another objective of the present invention is to have a biocompatible final product. Although the final product as such may not be fully (100%) biodegradable i.e. because of the presence of PEGs, the amount of non-biodegradable components is reduced to a minimum and is generally considered to qualify as a biodegradable thermoplastic starch that is almost completely soluble in cold water. In fact, when starch is dissolved in cold water, even if it arrives to the sea water, or enters in the soil, it is still a polymer that can be recognized and eaten by animals and microorganisms naturally present in the environment. This opens the circle of recycling in the best way possible, where used products help the environment and try not to interfere with other biological cycles (cf. e.g. MacNeill et al., 2017, Journal of Experimental Botany, Vol. 68 (16), Pages 4433-4453).

An aspect of the present invention hence provides for a composition for forming a thermoplastic starch (TPS forming composition, briefly referred to herein as "composition"), said composition comprising pulse starch, glycerol, a polycarboxylic acid, an aqueous carrier, and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol. In essence, this implies that PEG800 to PEG3000 is used (respectively having an average molecular weight of about 800 and 3000 dalton).

An aspect provides the use of the composition as taught herein for forming a thermoplastic starch (TPS).

An aspect provides a method for preparing a thermoplastic starch, the method comprising: mixing pulse starch and glycerol, thereby obtaining a mixture of pulse starch and glycerol; placing the mixture of pulse starch and glycerol at room temperature for at least 12 hours, thereby obtaining a swelled starch powder; and mixing the swelled starch powder with the polycarboxylic acid, an aqueous carrier, and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol, thereby obtaining the thermoplastic starch.

The present method allows to produce a thermoplastic starch which can be used for the preparation of a cold water-soluble film with satisfactory mechanical properties such as elongation at break and sufficient solubility. In embodiments of the composition or use as taught herein, said pulse starch is pea starch, more preferably yellow pea starch, faba bean starch or chickpea starch.

Typically, the native starch powder used comprises between 8 and 10% water.

Preferably, the starch used is pea starch, obtainable through wet fractionation, that has a purity on dry mass of above or equal to 95%, preferably above or equal to 98% (in contrast to pea starch obtained by dry fractionation which only has a purity of about 65%).

In embodiments of the composition or use as taught herein, the polycarboxylic acid is citric acid or tartaric acid; preferably the polycarboxylic acid is citric acid.

In embodiments of the composition or use as taught herein, the PEG has a molecular mass of about 1000 g/mol to about 2500 g/mol; preferably the PEG has a molecular mass of about 2000 g/mol. In essence, this implies that preferably PEG1000 to PEG2500 is used (respectively having an average molecular weight of about 1000 and 2500 dalton), and more preferably PEG2000 (PEG having an average molecular weight of about 2000).

In embodiments of the composition or use as taught herein, the composition comprises an aqueous carrier; preferably the composition comprises water.

In embodiments of the composition or use as taught herein, the composition comprises from about 5% to about 30% by weight of the aqueous carrier.

In embodiments of the composition or use as taught herein, the TPS forming composition comprises: from about 60% to about 95% by weight of pulse starch; from about 2% to about 30% by weight of glycerol; from about 2% to about 30% by weight of an aqueous carrier; from about 1.5% to about 3% by weight of the polycarboxylic acid; and/or from about 1.5% to about 3% by weight of the PEG.

Preferably, said TPS forming composition comprises: from about 60% to about 75% by weight of pulse starch; from about 10% to about 15% by weight of glycerol; from about 2% to about 30% by weight of an aqueous carrier; from about 1.5% to about 3% by weight of the polycarboxylic acid; and/or from about 1.5% to about 3% by weight of the PEG.

Preferably, said TPS forming composition comprises: from about 65% to about 75% by weight of pulse starch; from about 10% to about 15% by weight of glycerol; from about 2% to about 30% by weight of an aqueous carrier; from about 1.5% to about 3% by weight of the polycarboxylic acid; and/or from about 1.5% to about 3% by weight of the PEG.

In embodiments of the composition or use as taught herein, said pulse starch is pea starch, more preferably yellow pea starch, faba bean starch or chickpea starch.

In embodiments of the composition or use as taught herein, said TPS forming composition comprises an aqueous carrier water which is present in a concentration of between 10 and 25% w/w, such as between 10 and 20 %w/w, or between 10 and 15 % w/w.

In embodiments of the composition or use as taught herein, the composition further comprises a natural gum; preferably selected from the group consisting of: sodium alginate, gellan gum, xanthan gum, agar, alginic acid, carrageenan, gum arabic, gum ghatti, gum tragacanth, karaya gum, guar gum, locust bean gum, beta-glucan, dammar gum, glucomannan, psyllium seed husks, and tara gum. In some embodiments, said natural gum can be a natural gum obtained from seaweeds, a natural gum produced by bacterial fermentation, or a natural gum obtained from non-marine botanical resources.

A further aspect provides a thermoplastic starch (TPS) obtained from the composition as taught herein. In essence, said thermoplastic starch (TPS) composition obtained comprises pea starch, glycerol, PEG, citric acid, and aqueous carrier.

A further aspect relates to a cold water-soluble film formed by the thermoplastic starch as defined herein. In preferred embodiments said film comprises pulse starch, glycerol, PEG, citric acid, and aqueous carrier, preferably from about 8 to 12 % water, such as about from 9 to 11 % water. Preferably said pulse starch is pea starch, more preferably yellow pea starch, faba bean starch or chickpea starch. Without wanting to be bound to any theory it is believed that the different components are (fully or partially) linked as esters/ethers and/or through hydrogen bonds to the pulse starch. In embodiments of the film as taught herein, the film has a solubility in an aqueous medium at room temperature ( between 15 and 25 °C) of at least 75%; preferably of at least 80%.

The solubility of the film may be determined by methods as known in the art. For instance, the solubility of the film may be determined by dissolving a predetermined amount (e.g., 1 gram) of the film in an amount (e.g., 20 ml) of water such as distilled water; mixing the solution for instance with a vortex (e.g., for 2 min); centrifuging the solution (e.g., at 4000 rpm for 10 minutes); lyophilizing the upper solution; and drying the obtained precipitate for instance in a vacuum oven (e.g., at 60°C for at least 5h). The solubility (in percentage) may then be calculated as the ratio of the weight of the dried obtained precipitate to the weight of the film at start, times 100. For instance, in case the weight of the dried obtained precipitate is 0.76 g and the weight of the film at start is 1.00 g, the solubility (in percentage) is 76%, i.e. 100 x 0.76/1.00.

In embodiments of the film as taught herein, the film has an elongation at break of at least 5% such as at least 10%. In embodiments, the film has an elongation at break of 5% to 10%.

The elongation at break can be measured for example by using a Traction machine from Zwick Roell Z2.5, with a Load Cell Type XForce P Nominal Force 500N. DogBones specifics: about 9 mm width in the extremities and about 3mm width in the central segment. Preferably, the elongation at break of the film is measured after conditioning of the film in a controlled atmosphere between 40% and 70% relative humidity for between 5h and 24h. For instance, the elongation at break of the film is measured after conditioning of the film in a controlled atmosphere between 40% and 70% relative humidity for between lOh and 16h. More preferably, the elongation at break of the film is measured after conditioning of the film in a controlled atmosphere at 60% relative humidity for 12h.

In embodiments of the film as taught herein, the film has an elongation at break of at least 5% such as at least 10% after conditioning of the film in a controlled atmosphere between 40% and 70% relative humidity for between 5h and 24h, e.g., after conditioning of the film in a controlled atmosphere at 60% relative humidity for 12h.

In embodiments of the film as taught herein, the film has a thickness of 15pm to 200pm; preferably the film has a thickness of 30pm to 150pm, more preferably the film has a thickness of from 30pm to 100 pm, such as from 30pm to 75pm or from 75pm to 100pm; and/or the film is transparent and/or flexible.

As mentioned above, a further aspect provides a method for preparing a thermoplastic starch (TPS) as defined herein, the method comprising: mixing pulse starch and glycerol, thereby obtaining a mixture of pulse starch and glycerol; placing the mixture of pulse starch and glycerol at room temperature for at least 12 hours, thereby obtaining a swelled starch powder; mixing the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG; and collecting the thermoplastic starch.

In a preferred embodiment, said pulse starch is pea starch, more preferably yellow pea starch, faba bean starch or chickpea starch.

In embodiments of the method as taught herein, the aqueous carrier is mixed together with the polycarboxylic acid and the PEG into the swelled starch powder.

In embodiments of the method as taught herein, the mixing of the swelled starch powder with the polycarboxylic acid and the PEG is performed for about 2.5 minutes to about 3.5 minutes at about 105°C to about 145°C or equal temperature/time ratios. In embodiments of the method as taught herein, the mixing of the swelled starch powder with the polycarboxylic acid and the PEG is performed for about 2.5 minutes to about 3.5 minutes at about 105°C to about 115°C or equal temperature/time ratios.

A further aspect relates to a thermoplastic starch (TPS) obtained by the methods as taught herein. In essence, said thermoplastic starch (TPS) composition obtained comprises pea starch, glycerol, PEG, citric acid, and aqueous carrier.

A further aspect provides a thermoplastic starch (TPS) comprising pulse starch, glycerol, a polycarboxylic acid, an aqueous carrier, and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol.

A further aspect relates to a method for preparing a cold water-soluble film, preferably a film as defined herein, the method comprising: preparing a thermoplastic starch as defined herein; extruding the thermoplastic starch, thereby obtaining an extruded starch; and thermo-pressing casting or calendering of the extruded starch, thereby obtaining the cold water-soluble film.

In embodiments of the method as taught herein, the extrusion is performed for about 2.5 minutes to about 3.5 minutes at about 125°C to about 135°C. In embodiments of the method as taught herein, the thermo-pressing is performed for about 8 minutes to about 12 minutes at about 115 °C to about 125°C and about 10 bar to about 12 bar.

In embodiments of the method as taught herein, the thermo-pressing comprises the prior steps of contacting the extruded starch with the thermo-pressing system; and/or alternating pressing and depressing the extruded starch.

A further aspect provides the use of a cold-water soluble film as defined herein or a cold water soluble film obtained by the method as defined herein, for packaging an anhydrous composition; preferably wherein the composition is a dishwashing composition, a laundry detergent, a toiletcleaning composition, a fabric softening composition, a bath salt composition, or a food composition. In some embodiments, said packaged composition can be in granular form, or wherein the composition is in liquid form.

A further aspect relates to a packaged composition for the delivery of a composition into an aqueous medium, the package composition comprising: a container made of the film as defined herein, or obtained by the method as defined herein, and an anhydrous composition inside said container; preferably wherein the composition is a dishwashing composition, a laundry detergent, a toilet-cleaning composition, a fabric softening composition, a bath salt composition, or a food composition.

A further aspect relates to a method of delivering a composition to an aqueous medium, the method comprising contacting the packaged composition as defined herein with the aqueous medium; preferably immersing the packaged composition as defined herein in the aqueous medium.

The above and further aspects and preferred embodiments of the invention are described in the following sections and in the appended claims. The subject-matter of appended claims is hereby specifically incorporated in this specification.

DESCRIPTION OF THE DRAWINGS

Figure 1: Evaluation of solubility of the films according to invention. Composition N29 was used (cf. Example 1) A) solubility tests in distilled water and B) tap water, both before centrifugation.

A becomes C, and B becomes D after centrifugation, showing the precipitate. E) is Lactips, a prior art thermoplastic based on proteins, solubilized in distilled water and F) is again N29 solubilized in distilled water, both before centrifugation. E becomes G, and F becomes H after centrifugation.

Figure 2: Tensile properties and elasticity of starch films according to invention

Figure 3: Tensile properties and elasticity of films obtained from blends with Gums and Seaweed- derivatives

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise.

The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements, or method steps. The terms also encompass "consisting of" and "consisting essentially of".

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

The term "about" as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of and from the specified value, in particular variations of +/-10% or less, preferably +/-5% or less, more preferably +/-1% or less, and still more preferably +/-0.1% or less of and from the specified value, insofar such variations are appropriate to perform in the disclosed invention. It is to be understood that the value to which the modifier "about" refers is itself also specifically, and preferably, disclosed.

Whereas the term "one or more", such as one or more members of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members.

All documents cited in the present specification are hereby incorporated by reference in their entirety.

Unless otherwise specified, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions may be included to better appreciate the teaching of the present invention. An aspect of the invention relates to a method for preparing a thermoplastic starch, the method comprising: mixing pulse starch and glycerol, thereby obtaining a mixture of pulse starch and glycerol; placing the mixture of pulse starch and glycerol at room temperature for at least 12 hours, thereby obtaining a swelled starch powder; and mixing the swelled starch powder with a polycarboxylic acid, an aqueous carrier, and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol, thereby obtaining the thermoplastic starch.

As used herein the term "pulse" encompasses all dried seeds of legume. There are in general 11 types of pulses: dry beans, dry broad beans, dry peas, chickpeas, cow peas, pigeon peas, lentils, Bambara beans, vetches, lupins and pulses nes (minor pulses).

The term "legume" refers to a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant.

Dry beans (Phaseolus spp. including several species in Vigna) are selected from the group consisting of Adzuki Beans, Anasazi Beans, Appaloosa Beans, Baby Lima Beans, Black Calypso Beans, Black Turtle Beans, Dark Red Kidney Beans, Great Northern Beans, Jacob's Cattle Trout Beans, Large Faba Beans, Large Lima Beans, Mung Beans, Pink Beans, Pinto Beans, Romano Beans, Scarlet Runner Beans, Tongue of Fire, White Kidney Beans and White Navy Beans.

Dry peas (Pisum spp.) are selected from garden pea (Pisum sativum var. sativum) and protein pea (Pisum sativum var. arvense). Dry peas are represented by: Black-Eyed Peas, Green Peas, Marrowfat Peas, Pigeon Peas, Yellow Peas and Yellow-Eyed Peas.

Chickpeas or chick peas (Cicer arietinum) are selected from gram or Bengal gram, garbanzo or garbanzo bean (kabuli), or Egyptian pea.

Vicia faba, also known as the Broad bean, fava bean, faba bean, field bean, bell bean, or tic bean, is a species of flowering plant in the pea and bean family Fabaceae native to North Africa southwest and south Asia, and extensively cultivated elsewhere.

Lentils (Lens Culinaris) are selected from Beluga Lentils, Brown Lentils, French Green Lentils, Green Lentils, or Red Lentils.

As used herein, the term "pea" refers to the round seeds contained in the pod of Pisum sativum and its subspecies, varieties or cultivars. Preferably, the peas are yellow peas, preferably dry yellow peas, i.e. yellow peas which have been harvested in a dry state. Different varieties of peas may be for examples smooth pea or wrinkled pea. The term "pea" may also refer to chickpea or Vicia faba. The chickpea or chick pea (Cicer arietinum) is a legume of the family Fabaceae, subfamily Faboideae. Its different types are variously known as gram, or Bengal gram, garbanzo or garbanzo bean, or Egyptian pea. Vicia faba, also known as the broad bean, fava bean, faba bean, field bean, bell bean, or tic bean, is a species of flowering plant in the pea and bean family Fabaceae native to North Africa southwest and south Asia, and extensively cultivated elsewhere.

As used herein, the term "starch" refers to a polymeric carbohydrate encompassing a large number of glucose units joined by glycosidic bonds. As used herein, the starch is in the native form. As used herein, the term "native" refers to starch that has not been modified by enzymatic or chemical processing methods. Native starch may however have been modifying by physical methods such as thermal treatment, extrusion and/or processing. According to the invention, starch may be precooked and pregelatinized.

As used herein the term "pulse starch" encompasses starch extracted from any kind of pulse.

As used herein, the term "pea starch" encompasses starch extracted from peas and in its native form is rich in amylose (up to 35%). According to the invention, pea starch can be isolated using techniques such as pin milling and air classification. Air classification is the most commonly used commercial method for pea starch isolation. The process requires a very high degree of particle size reduction (achieved by pin milling) in order to separate the starch granules from the protein matrix. The major fraction from the air classification process is the low-protein starch fraction, which is separated from the fine protein fraction during the process. The starch concentrate contains about 65% of starch. Residual protein associated with air classified field pea starch granules is derived from protein bodies, agglomerates, chloroplast membrane remnants (which enclose the starch granule) and from a water-soluble fraction which is presumably derived from the dehydrated starch. Re-milling and reclassifying the starch fraction removes most of the protein bodies and agglomerates while water washing results in removal of most of the remainder of the attached protein. The above purification procedure results in a protein content of 0.25% in the washed starch. The purity of starch obtained by wet processing is higher than that obtained by airclassification. Smooth pea starch could be extracted in high yields (93.8—96.7%) from its flour, after protein extraction at pH 9 using different sieving (200—60 pm) and washing conditions. The starches were found to be contaminated mainly by cell wall polysaccharides (less than 4%). The protein content in the starch ranged from 0.3-0.4%. (Starch 54 (2002) 217-234; Pea starch: Composition structure and properties - A review). Nastar® is native pea starch from yellow peas, and commercially available product from Cosucra Warcoing, Belgium. Nastar® comprises minimally 88% dry matter, i.e. native pea starch. Pea starch for use in the present invention can be obtained from Cosucra Warcoing, Belgium.

The two major components of starch are amylose and amylopectin. Generally, legume starches are characterized by a high amylose content (24-65%). But the amylose content of smooth pea, pea mutants and wrinkled pea starches range from 33.1-49.6%, 8-72% and 60.5-88% respectively. Amylose, the minor component, consists mainly of a (1-4) (amylose) linked D-glucopyranosyl residues. The molecular weight of amylose varies between 105-106 Da. Amylopectin is the major component of field pea starch with a Mw of the order 107-109 Da. Amylopectin is composed of linear chains of (1-4) a-D-glucose residues connected through (1- 6)-a-linkages (5-6%). The granule size of smooth pea starch is variable and ranges from 2-40 pm. Most of the granules are oval, although spherical, round elliptical and irregularly shaped granules are also found. Pea starch has a low temperature of gelatinisation and syneresis of pea starch after gelation is significant.

The term The term "polycarboxylic acid" refers to an organic carboxylic acid whose chemical structure contains at least two carboxyl functional groups (-COOH). In embodiments, the polycarboxylic acid is a dicarboxylic acid, a tricarboxylic acid, or a mixture thereof. Preferred examples are tartaric acid and citric acid.

The term "polyethylene glycol" or "PEG" refers to the a polyether compound comprising polymers of ethylene-oxide derived from petroleum with many applications, from industrial manufacturing to medicine. PEG is a hydrophilic flexible water-soluble polymer. PEGs exist in many different molecular weights, indicated by the number following the PEG designation. For example "PEG1000" refers to a PEG polymer having an average molecular weight (Mw) of about 1000 dalton (lkDa), "PEG2000" to a PEG polymer having an average molecular weight (Mw) of about 2000 dalton (2kDa) etc.

The thermoplastic starch forming composition of the invention can further comprise a natural gum selected from the group consisting of sodium alginate, gellan gum, xanthan gum, agar, alginic acid, carrageenan, gum arabic, gum ghatti, gum tragacanth, karaya gum, guar gum, locust bean gum, beta-glucan, dammar gum, glucomannan, psyllium seed husks, and tara gum. In some embodiments, said natural gum can be a natural gum obtained from seaweeds, a natural gum produced by bacterial fermentation, or a natural gum obtained from non-marine botanical resources.

In embodiments of the methods as taught herein, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be performed prior to the extrusion step. In embodiments of the methods as taught herein, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be performed for about 2.5 minutes to about 3.5 minutes at about 105°C to about 145°C or equal temperature/time ratios. In embodiments of the methods as taught herein, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be performed for about 2.5 minutes to about 3.5 minutes at about 105°C to about 140°C, at about 105°C to about 135°C, at about 105°C to about 130°C, at about 105°C to about 125°C, at about 105°C to about 120°C, or at about 105°C to about 115°C, or equal temperature/time ratios.

In embodiments of the methods as taught herein, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be performed for about 1 minute to about 15 minutes. In embodiments, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be performed for about 1.5 minutes to about 10 minutes, about 2 minutes to about 8 minutes, about 2.5 minutes to about 6 minutes, or about 3 minutes to about 5 minutes.

In embodiments, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be performed at room temperature, i.e., a temperature between 15°C and 25°C, e.g., at about 20°C. In embodiments of the methods as taught herein, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be performed at room temperature for about 1 minute to about 15 minutes. In embodiments, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be performed at room temperature for about 1.5 minutes to about 10 minutes, about 2 minutes to about 8 minutes, about 2.5 minutes to about 6 minutes, or about 3 minutes to about 5 minutes. For instance, the mixing step may be performed in a mixing chamber of the extruder in order to mix the compounds homogenously prior to extrusion. In embodiments, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be performed during the extrusion step. In embodiments, the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG may be the same step as the extrusion step.

In embodiments of the methods as taught herein, the polycarboxylic acid may be citric acid or tartaric acid; preferably the polycarboxylic acid is citric acid.

In embodiments of the methods as taught herein, the PEG may have a molecular mass of about 1000 g/mol to about 2500 g/mol; preferably the PEG has a molecular mass of about 2000 g/mol. In embodiments of the methods as taught herein, the composition may comprise from about 2% to about 30% by weight of the aqueous carrier, preferably water. In embodiments of the methods as taught herein, the composition may comprise from about 5% to about 30% by weight of the aqueous carrier, preferably water.

In embodiments of the methods as taught herein, the following amounts of components are used: from about 60% to about 95% by weight of pulse starch; from about 2% to about 30% by weight of glycerol; from about 2% to about 30% by weight of an aqueous carrier; from about 1.5% to about 3% by weight of the polycarboxylic acid; and/or from about 1.5% to about 3% by weight of the PEG.

In embodiments of the methods as taught herein, the pulse starch may be pea starch, preferably the pulse starch is yellow pea starch, faba bean starch or chickpea starch.

As aspect provides the use of a composition comprising: pulse starch; glycerol; a polycarboxylic acid - preferably citric acid or tartaric acid; an aqueous carrier; and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol, for forming a thermoplastic starch (TPS), preferably for forming a TPS according to the methods as defined herein.

A further aspect provides a thermoplastic starch (TPS) obtained by the methods as taught herein or by the use as taught herein. In an embodiment, the TPS comprises pulse starch, glycerol, a polycarboxylic acid, an aqueous carrier, and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol.

A related aspect or embodiment provides a TPS or TPS forming composition comprising pulse starch, glycerol, a polycarboxylic acid, an aqueous carrier, and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol.

A further aspect provides a cold water-soluble film prepared from the thermoplastic starch as defined in herein; preferably wherein the film has a thickness of 15 pm to 200 pm; more preferably wherein the film has a thickness of 20 pm to 120 pm; and/or wherein the film is transparent and/or flexible.

The phrases "cold-water soluble" or "soluble in an aqueous medium at room temperature" may be used interchangeably herein.

The term "cold water" as used herein refers to any aqueous medium at room temperature (and is not limited to but preferably water at room temperature). The term "room temperature" refers to a temperature between 15°C and 25°C, e.g., at about 20°C.

Hence, in embodiments, the film may be soluble in an aqueous medium at room temperature, such as in an aqueous medium at a temperature between 15°C and 25°C, e.g., at about 20°C. For instance, the film may be soluble in an aqueous medium at a temperature between 18°C and 22°C.

In embodiments of the film as taught herein, the film has a solubility in an aqueous medium at room temperature (i.e., between 15 and 25 °C, e.g. at 20°C) of above 65%, such as of at least 70%, of at least 75%; preferably of at least 80% or more, such as of at least 85%, or at least 90%, or at least 99%, or 100%. Such films have sufficient solubility in cold water (e.g., in water at a temperature between 15 and 25°C, e.g. at 20°C), as desired or required for certain applications as taught herein. A further aspect provides a method for preparing a cold water-soluble film as defined herein, the method comprising: preparing a thermoplastic starch (TPS) according to the methods as taught herein, according to the use as defined herein, or providing a TPS as defined herein; extruding the thermoplastic starch, thereby obtaining an extruded starch; and thermo-pressing, casting, or calendering of the extruded starch, thereby obtaining the cold water-soluble film.

A further aspect provides a method for preparing a thermoplastic starch film, such as a cold water- soluble thermoplastic starch film, the method comprising: mixing pulse starch and glycerol, thereby obtaining a mixture of pulse starch and glycerol; placing the mixture of pulse starch and glycerol at room temperature for at least 12 hours, thereby obtaining a swelled starch powder; extruding the swelled starch powder with a polycarboxylic acid, an aqueous carrier, and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol, thereby obtaining a thermoplastic starch; and thermo-pressing, casting, or calendering of the thermoplastic starch, thereby obtaining the thermoplastic starch film. Such thermoplastic starch film advantageously is a cold water soluble film suitable for packaging an anhydrous composition such as a dishwashing composition, a laundry detergent, a toilet-cleaning composition, a fabric softening composition, a bath salt composition, or a food composition.

The term "extruding" encompasses any process of forming sheet-like films of biopolymer. In essence the extruding process encompasses a high-volume manufacturing process in which raw thermoplastic pellets are heated (melted) and formed into a continuous profile. Extrusion produces items such as films and sheeting, and thermoplastic coatings. This process starts by feeding the bioplastic material (pellets, granules, flakes or powders) into the extruder. The material is gradually heated (melted) by the mechanical energy generated by turning screws and if needed by heaters arranged along the extruder. The molten biopolymer is then forced into a die, which shapes the polymer into a shape that hardens during cooling.

The term "thermo-pressing" or "thermal pressing" or "hot pressing" encompasses any technology wherein a biopolymer film is sandwiched between two (heated) plates, thereby forming a reduced film of the required thickness.

Alternatively to thermo-pressing, the biopolymer can be cast into a sheet form for a wide variety of ongoing uses. In the film casting process, the process comprises evaporation (under vacuum or not) of the solvent in which the material is readily soluble and then the molten polymer is usually extruded through a slot die onto an internally cooled chill roll and then passes through a series of rollers which will determine the nature and properties of the cast film including thickness. The cast film is then cut as required by saws, shears or hot wire methods.

As a further alternative, the biopolymer can be made into a film through calendering. Calendering is the process of forming a continuous sheet of controlled size by squeezing a softened thermoplastic material between two or more horizontal rolls. The biopolymer (e.g. in powder or pellets) is first fluxed, i.e., heated and worked until it reaches a molten or dough-like consistency, and discharged to a calender either in a continuous strip or in batches. When an extruder is used for fluxing, the extrudate is fed directly to the calender. Alternatively, the biopolymer can in some cases be fed directly to the calender. After passage through the calender, the continuous sheet of hot plastic is stripped off the last calender roll with a small, higher-speed stripping roll. The hot sheet is cooled as it travels over a series of cooling drums. The film or sheeting is finally cut into individual sheets or wound up in a continuous roll.

In embodiments of the method as taught herein, the extrusion may be performed for about 2.5 minutes to about 3.5 minutes at about 125°C to about 135°C.

In embodiments of the method as taught herein, the extrusion may be performed for about 2.5 minutes to about 3.5 minutes at about 105°C to about 145°C. In embodiments, the extrusion may be performed for about 2.5 minutes to about 3.5 minutes at about 105°C to about 140°C, at about 105°C to about 135°C, at about 105°C to about 130°C, at about 105°C to about 125°C, at about 105°C to about 120°C, or at about 105°C to about 115°C. Such extrusion step advantageously results in a film having better mechanical properties such as an increased elongation at break. In embodiments of the method as taught herein, the extrusion may be performed for about 1 minute to about 15 minutes. In embodiments, the extrusion may be performed for about 1.5 minutes to about 10 minutes, about 2 minutes to about 8 minutes, about 2.5 minutes to about 6 minutes, or about 3 minutes to about 5 minutes. Preferably, the extrusion may be performed for about 2.5 minutes to about 3.5 minutes. Such extrusion timing advantageously results in a film having better mechanical properties such as an increased elongation at break.

In embodiments of the method as taught herein, the extrusion may be performed at about 105°C to about 145°C. In embodiments, the extrusion may be performed at about 105°C to about 140°C, at about 105°C to about 135°C, at about 105°C to about 130°C, at about 105°C to about 125°C, or at about 105°C to about 120°C. In embodiments, the extrusion may be performed at about 105°C to about 115°C.

In embodiments of the method as taught herein, the extrusion may be performed for about 1 minute to about 15 minutes at about 105°C to about 145°C. In embodiments, the extrusion may be performed for about 1.5 minutes to about 10 minutes, about 2 minutes to about 8 minutes, about 2.5 minutes to about 6 minutes, or about 3 minutes to about 5 minutes at about 105°C to about 145°C.

A further aspect relates to the use of a cold-water soluble film as defined herein, for packaging an anhydrous composition; preferably wherein the composition is a dishwashing composition, a laundry detergent, a toilet-cleaning composition, a fabric softening composition, a bath salt composition, or a food composition.

A further aspect relates to a packaged composition for the delivery of a composition into an aqueous medium, the package composition comprising: a container made of the film as defined herein, and an anhydrous composition inside said container; preferably wherein the composition is a dishwashing composition, a laundry detergent, a toilet-cleaning composition, a fabric softening composition, a bath salt composition, or a food composition.

The present application also provides aspects and embodiments as set forth in the following Statements:

Statement 1. A method for preparing a thermoplastic starch, the method comprising: mixing pulse starch and glycerol, thereby obtaining a mixture of pulse starch and glycerol; placing the mixture of pulse starch and glycerol at room temperature for at least 12 hours, thereby obtaining a swelled starch powder; and mixing the swelled starch powder with the polycarboxylic acid, an aqueous carrier, and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol, thereby obtaining the thermoplastic starch.

Statement 2. The method according to statement 1, wherein the mixing of the swelled starch powder with the polycarboxylic acid, the aqueous carrier, and the PEG is performed for about 2.5 minutes to about 3.5 minutes at about 105°C to about 115°C or equal temperature/time ratios.

Statement 3. The method according to statement 1 or 2, wherein the polycarboxylic acid is citric acid or tartaric acid; preferably wherein the polycarboxylic acid is citric acid.

Statement 4. The method according to any one of statements 1 to 3, wherein the PEG has a molecular mass of about 1000 g/mol to about 2500 g/mol; preferably wherein the PEG has a molecular mass of about 2000 g/mol.

Statement 5. The method according to any one of statements 1 to 4, comprising from about 5% to about 30% by weight of the aqueous carrier, preferably water.

Statement 6. The method according to any one of statements 1 to 5, wherein the following amounts of components are used: from about 60% to about 95% by weight of pulse starch; from about 2% to about 30% by weight of glycerol; from about 2% to about 30% by weight of an aqueous carrier; from about 1.5% to about 3% by weight of the polycarboxylic acid; and/or from about 1.5% to about 3% by weight of the PEG.

Statement 7. The method according to any one of statements 1 to 6, wherein said pulse starch is pea starch, more preferably yellow pea starch, faba bean starch or chickpea starch.

Statement 8. Use of a composition comprising: pulse starch; glycerol; a polycarboxylic acid - preferably citric acid or tartaric acid; an aqueous carrier; and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol, for forming a thermoplastic starch (TPS). Statement 9. A thermoplastic starch (TPS) obtained by the method according to any one of statements 1 to 7 or by the use according to statement 8.

Statement 10. A cold water-soluble film prepared from the thermoplastic starch as defined in statement 9; preferably wherein the film has a thickness of 15 pm to 200 pm; more preferably wherein the film has a thickness of 20 pm to 120 pm; and/or wherein the film is transparent and/or flexible.

Statement 11. A method for preparing a cold water-soluble film as defined in statement 10, the method comprising: preparing a thermoplastic starch (TPS) according to the method of any one of statements 1 to 7 , according to the use of statement 8, or providing a TPS as defined in statement 9; extruding the thermoplastic starch, thereby obtaining an extruded starch; and thermo-pressing, casting, or calendering of the extruded starch, thereby obtaining the cold water-soluble film.

Statement 12. The method according to statement 11, wherein the extrusion is performed for about 2.5 minutes to about 3.5 minutes at about 125°C to about 135°C.

Statement 13. Use of a cold-water soluble film as defined in statement 10, for packaging an anhydrous composition; preferably wherein the composition is a dishwashing composition, a laundry detergent, a toilet-cleaning composition, a fabric softening composition, a bath salt composition, or a food composition.

Statement 14. A packaged composition for the delivery of a composition into an aqueous medium, the package composition comprising: a container made of the film as defined in statement 10, and an anhydrous composition inside said container; preferably wherein the composition is a dishwashing composition, a laundry detergent, a toilet-cleaning composition, a fabric softening composition, a bath salt composition, or a food composition.

Statement 15. A thermoplastic starch (TPS) comprising pulse starch, glycerol, a polycarboxylic acid, an aqueous carrier, and a polyethylene glycol (PEG) having a molecular mass of about 800 g/mol to about 3000 g/mol.

The above aspects and embodiments are further supported by the following non-limiting examples. EXAMPLES

Materials and methods

1. Materials

The pea starch used in the study has been provided by COSUCRA, Warcoing, Belgium. Glycerol used as plasticizer in this study has been purchased from Alfa Aesar. Polyethylene glycol (PEG) and citric acid monohydrate used as solubilizing additives have been purchased from Sigma Aldrich. Tartaric acid used as dispersing agent has been purchased from Supelco. Sodium Alginate, purchased by PanReac AppliChem and Gellan Gum were purchased from Alfa Aesar, have been used as reinforcing agents. Glucuronic acid, used as agent promoting the film elastic behaviour, has been purchased from Sigma Aldrich. Distilled water served as plasticizer to prepare thermoplasticized starch.

2. Film Preparation

2.1. Starch swelling with plasticizer

Pea starch (40g) and glycerol (8 g) have been mixed in a plastic bag manually for 5 minutes. After this time the mixture has been left to swell for 24h.

2.2. Starch blend in internal kneader Brabender

In a glass beaker the following components were exactly weighted: distilled water (8 g), PEG (2000 g/mol, lg) and citric acid monohydrate ( 1 g). After the total dissolution of PEG and citric acid inside the aqueous medium, it is blended inside a Brabender® internal kneader, pre-warmed at 110°C. The final TPS forming composition tested hence is as follows:

40g pea starch 69% w/w

8 g glycerol 13.8% w/w

8 g dist. H2O 13.8% w/w l g PEG 1.7% w/w lg citric acid 1.7% w/w

In order to obtain the correct thermoplastic starch (TPS) form, in a first step starch swelled powder previously prepared in step 2.1. has been added inside the machine, with the screws rotating at 30 rpm and in the shortest time possible (usually around 1 minute), then the water solution with PEG and Citric acid is added and only as last step the screw speed is increased to 100 rpm. The blend process last for 3 minutes, then the screw speed is decreased till 0 rpm. The mixing room is opened and the product is recovered (yield: 100%). Before the next step the, TPS so obtained, is left to cool down to room temperature. Once the TPS is cold, it is pelleted.

2.3. Melt-blending of TPS inside a twin-screw DSM micro-compounder, 15 cc

A DSM micro-compounder is heated at 130°C. The pelletized starch, ~12g, is inserted in the shortest time possible (usually 2 minutes) in the extrusion chamber where screws co-rotate at 30 rpm speed. After the total insertion of the raw material, screw speed is increased at 100 rpm and the extrusion lasts for 3 minutes. Then the extrusion room is opened, and the polymer is collected (~75%, because the process is semi-continuous).

The filament of extruded starch is left to cool down at room temperature and pelletized as aforementioned.

2.4. Thermo-pressing of extruded starch

About 2 g of so prepared extruded starch is pressed at 120°C, 11 bar for 10 minutes. The thermopressing process for 10 minutes at 120°C, 11 bar. After this time, the polymer is cooled down till 20°C, always at 11 bar pression (time to cool down: 4 minutes). The film so obtained are cold water soluble (20°C), ~80 pm thick, transparent, flexibles.

3. Solubility test

In a plastic vial adapt to centrifuge, about l g of film it is mixed with 20 mL of water and then shaken for 2 minutes, using a vortex. The so obtained solution is then centrifuged for 10 minutes at 4000 rpm. This process gives a white solid on the bottom of the vial and a transparent water phase. Those are divided through decantation and the solid is dried in a vacuum oven at 60°C for at least 5 hours. After this is exactly weighted and the solubility percentage is obtained by subtraction.

Example 1: Preparation of the film according to the invention

1.1 Thermoplastic starch

An internal kneader Brabender® of 40 g capacity was used to prepare a thermoplastic starch. A solution of distilled water (20% by weight of matter to starch reference), PEG (2000 g/mol, 2.5% by weight of matter to starch reference) and citric acid monohydrate (20% by weight of matter to starch reference) was prepared. Then the internal kneader was charged as follow: 1. mixture of starch and glycerol (20% by weight of matter to starch reference) added in 1 minute; 2. water solution. The extrusion was performed at 100 rpm for 3 minutes at the temperature of 110°C and then the raw material was collected, which is subsequently referred to as thermoplastic starch (TPS). When the TPS was cooled down to room temperature it was transformed in pellets of about 0.5 cm length and width. 1.2 Thermoplastic starch with solubilizing agents

The process was carried out as described above, while varying the parameters listed in table 1 and the nature of solubilizing additives as follows:

N28 and N29: the nature of polycarboxylic acid was changed from citric acid (AC) that has 3 - COOH groups to tartaric acid (AT) that has 2 -COOH groups

N37 and N38: the length of the PEG was changed, respectively from PEG8000 to PEG300.

N50 and N56: the percentage of PEG1000 is changed from 1.75 to 2.5%

N51 and N52: the nature and percentage of the polycarboxylic acid is changed, using an excess amount of AC and a mixture of AC and AT - N53 and N54: the ratio between polycarboxylic acid and PEG length is changed

N55: the water percentage is tested and shows that if more water is added the solubility is decreased

N57: the tartaric acid forms a suspension

N58.1, N58.2, N59, N60: the PEG content is varied Table 1: Compositions of Films tested and their solubility In order of solubility: N29, N55, N28, N59, N50, N56, N52 - N60, N57, N54, N53, N37, N58.2, N38, N58.1 - N51.

From this scheme, we can summarize:

1. The optimal PEG length is between 1000 and 2000 g/mol in a maximum amount of 2.5 - 3% w/w.

2. The optimal water content is between 20-30%. If more water is added, the solubility of the final product starts to decrease.

3. The higher the number of carboxylic groups in the Polycarboxylic acid, higher the solubility of the final product.

4. We obtained a soluble film made by about 70% of pure starch, which has to our knowledge never been achieved before.

1.3 Pellets extrusion

A DSM micro-compounder Explore® of 15 cc is used to extrude the TPS. About 12 g of TPS pellets are inserted in the extruder machine and warmed up at 130°C. They are mixed for 3 minutes at 130°C and then the extruded starch (ES) will be collected in the shape of flexible, transparent filaments. The ES is allowed to cool down to room temperature and then it is pelleted in squares of about 0.5 cm.

1.4 Thermo-pressing

The pellets obtained in 1.3 are pressed at 11 bar for 10 minutes at a temperature of 120°C. The obtained film is allowed to cool down under pressure until a temperature of about 20°C is reached after which the thermoplastic film is collected.

Example 2: Solubility of thermoplastic films according to invention and comparisons

The characteristics of the thermoplastic films according to invention were also compared with three other series prepared as reference to describe the synergic effect of PEG and citric acid. The following compositions were tested:

PEG2000 -2.5:

40g pea starch 70.2% w/w

8 g glycerol 14% w/w

8 g dist. H2O 14% w/w

1 g PEG 1.8% w/w PEG 2000 -5:

40g pea starch 69% w/w

8 g glycerol 13.8% w/w

8 g dist. H2O 13.8% w/w

2 g PEG 3.4% w/w

PEG2000 -10:

40g pea starch 66.67% w/w

8 g glycerol 13.33% w/w

8 g dist. H2O 13.33% w/w

4 g PEG 6.67% w/w

Citric acid - 2.5:

40g pea starch 70.2% w/w

8 g glycerol 14% w/w

8 g dist. H2O 14% w/w

1 g Citric Acid 1.8% w/w

Citric acid - 5:

40g pea starch 69% w/w

8 g glycerol 13.8% w/w

8 g dist. H20 13.8% w/w

Citric Acid 3.4% w/w

Citric acid - 10:

40g pea starch 66.67% w/w

8 g glycerol 13.33% w/w

8 g dist. H20 13.33% w/w

Citric Acid 6.67% w/w Mix 5:

40g pea starch 66.67% w/w

8 g glycerol 13.33% w/w

8 g dist. H2O 13.33% w/w 2 g PEG 3.335% w/w

2g Citric Acid 3.335% w/w

Mix 10:

40g pea starch 62.5% w/w

8 g glycerol 12.5% w/w 8 g dist. H2O 12.5% w/w

4 g PEG 6.25% w/w

4g Citric Acid 6.25% w/w

Mix 20:

40g pea starch 55.6% w/w 8 g glycerol 11.11% w/w

8 g dist. H20 11.11% w/w

8 g PEG 11.11% w/w

8g Citric Acid 11.11% w/w

Table 2: Solubility of different films tested

The solubility values listed in Table 2 show a synergistic effect of combining PEG and Citric acid as solubilizing agents.

Example 3: Evaluation of solubility of the films according to invention

Solubility of the samples has been performed dissolving lg of the starch based cold water soluble film obtained above in 20 ml of distilled water. The solution has been mixed for 2 minutes with a vortex, and then centrifuged at 4000 rpm for 10 minutes. Subsequently, the upper solution was lyophilized, and the precipitate dried in a vacuum oven at 60°C for 5h at least. Then the % solubility was calculated based on the weight of the obtained dried precipitate versus the weight of the film started with (lg).

As can be seen in Figure 1, the grey precipitate is present only and exclusively with the mixture of citric acid and PEG. That means, it is a side reaction that arrives when those two components interact. This has been confirmed through a pilot reaction between citric acid and PEG2000 performed in a batch reactor of 15 cc, at 110°C under vacuum (but not under nitrogen).

Another interesting feature is the formation of foam in the upper part of the solution, which may indicate a surfactant-like behaviour.

The solution after centrifugation is not totally transparent, but more opaque. This behaviour, although to less extent, is also seen for PVA solutions and Lactips (see also Example 5).

Example 4: Tensile properties and elasticity of starch films according to invention

The film has been cut in dog-bone shape and tensile test have been performed on the samples so obtained. Elongation at break has been measured with a cellule of 500N, until the sample was totally broken (cf. Figure 2).

Example 5: Blends with Gums and Seaweed-derivatives

The process of step 1.2 of mixing the thermoplastic starch with solubilizing agents has been modified using Alginate and Gellan Gum to improve mechanical properties. The procedure and %w/w in relation to starch haven't been changed. The solubility of those films has been tested at 60°C because gellan gum (ROQUETTE) and alginate (Lycagel®) are not soluble in water, but they swell at high temperature, increasing water viscosity. Tensile tests have been performed as described in Example 4 and are depicted in Figure 3.