US-20260125191-A1 - ALGINATE-STARCH FILMS

US20260125191A1US 20260125191 A1US20260125191 A1US 20260125191A1US-20260125191-A1

Abstract

This invention relates to the field of heat-sealable, highly biodegradable films comprising polymers of fully natural plant origin, comprising salts of alginic acid and carbohydrates. The inventive films can be used for packing products, such as powder and liquid products, in sachets using current heat sealing equipment and at commercially viable production rates. In particular, the inventive films can be used in Vertical-Form-Fill-Seal (VFFS) packing equipment without requiring equipment modification. The inventive films use natural materials that are readily available, of low price and that have not required extensive or expensive chemical modifications. The films do not comprise synthetic polymers and are rapidly and completely biodegradable. The films can be soluble or non-soluble.

Inventors

Hugo Thomas Barroux
Georgios GKOTSIS
Marc Rodriguez Garcia
Nigel Patrick Somerville-Roberts
James Alexander Aiken
Christian BEALE
Stephen Arnold NICHOLLS

Assignees

XAMPLA LIMITED

Dates

Publication Date: 20260507
Application Date: 20230929
Priority Date: 20221003

Claims (17)

1 . A film comprising: a first layer comprising based on the total weight of the first layer: at least 20 wt.-% of one or more monovalent salts of alginic acid, and at least 5 wt.-% of one or more organic plasticisers; a second layer comprising based on the total weight of the second layer: one or more carbohydrates other than alginic acid and any of its salts, at least 5 wt.-% of one or more organic plasticisers, and less than 20 wt.-% of alginic acid salts; wherein one surface of the second layer is sealed to one surface of the first layer.
2 . The film of claim 1 , wherein the film has a thickness of between 20 μm and 120 μm.
3 . The film of claim 1 , wherein the first layer further comprises one or more divalent alginic acid salts selected from calcium alginate and magnesium alginate.
4 . The film of claim 1 , wherein the second layer has an onset melting temperature in the range of from 55° C. to 85° C.
5 . The film of claim 1 , wherein the second layer comprises a starch and/or pullulan.
6 . The film of claim 1 , wherein the film comprises based upon the total weight of the film 3-90 wt.-% of one or more alginic acid salts as measured by HPLC.
7 . The film of claim 1 , wherein the film has a heat sealing strength of at least 40 N/m as measured by ASTM F88/F88M-15 at 55% relative humidity and 20° C. after the film has been conditioned at 55% relative humidity and at 20° C. for at least one hour and then sealed at a temperature of 120° C. and a pressure of between 1 and 3 bar applied for a time of 1 second.
8 . The film of claim 1 , wherein the organic plasticiser in the first layer is selected from glycerol, polyethylene glycol, propylene glycol, sorbitol, mannitol, xylitol, triethyl citrate, oleic acid, glucose, mannose, fructose, sucrose, urea, lecithin, waxes, amino acids, lactic acid, citric acid, glycolic acid, malic acid, tartaric acid, and mixtures thereof.
9 . The film of claim 1 , wherein the organic plasticiser in the second layer is selected from glycerol, polyethylene glycol, sorbitol, mannitol, xylitol, triethyl citrate, glucose, mannose, fructose, sucrose, urea, lecithin, amino acids, lactic acid, citric acid, glycolic acid, malic acid, tartaric acid, and mixtures thereof.
10 . A process for preparing a film of claim 1 , comprising the steps of: (i) providing a first layer comprising based on the total weight of the first layer: at least 20 wt.-% of one or more monovalent salts of alginic acid, and at least 5 wt.-% of one or more organic plasticisers; (ii) providing a second layer comprising based on the total weight of the second layer: one or more carbohydrates other than alginic acid and any of its salts, at least 5 wt.-% of one or more organic plasticisers, and less than 20 wt.-% of alginic acid salts; and (iii) sealing one surface of the second layer to one surface of the first layer.
11 . A product enclosed by a film according to claim 1 .
12 . The product of claim 11 , wherein the film is more than 75% biodegradable, according to ASTM D6691 after 28 days testing.
13 . A method of enclosing a product, comprising the steps of: (i) wrapping the product in a film of claim 1 , such that the first layer is the outer layer; and (ii) heat sealing the film around the product to form a sachet.
14 . The method of claim 13 , wherein the duration of step (ii) is less than 2 seconds, and wherein step (ii) is conducted at a temperature of less than 160° C.
15 . (canceled)
16 . A sachet prepared by the method of claim 13 .
17 . A method of releasing a product enclosed in the film of claim 1 , comprising the steps of: (i) placing the enclosed product in water; and (ii) allowing the film to disperse, thereby releasing the product.

Description

FIELD OF THE INVENTION This invention relates to the field of heat-sealable, highly biodegradable films comprising polymers of fully natural plant origin, comprising salts of alginic acid and carbohydrates. The inventive films can be used for packing products, such as powder and liquid products, in sachets using current heat sealing equipment and at commercially viable production rates. In particular, the inventive films can be used in Vertical-Form-Fill-Seal (VFFS) packing equipment without requiring equipment modification. The inventive films use natural materials that are readily available, of low price and that have not required extensive or expensive chemical modifications. The films do not comprise synthetic polymers and are rapidly and completely biodegradable. The films can be soluble or non-soluble. BACKGROUND Packaging materials made from renewable materials are of increasing interest and importance as environmental pressures dictate a move away from oil-based feedstock. Such packaging materials include films which are especially useful for wrapping and/or encapsulating products. Examples of products using films for packaging include sachets and bags. It is highly preferred if the packaging material, as well as being sourced from renewable materials, is highly biodegradable so as to minimise the problems of waste disposal. Typically, products made from renewable, natural feedstock, are highly biodegradable provided that they have not been chemically modified. Chemical modification can dramatically lower the biodegradability profile. Some packaging films combine natural and synthetic materials. Such products typically have an improved environmental profile compared to equivalent products that use only synthetic materials. Plus, they can give an optimum balance of physical properties, such as strength and barrier resistance. However, the use of synthetic, typically non-biodegradable materials, inherently means that the biodegradability profile is not as good as materials that use fully natural raw materials. Water-soluble films made from polyvinyl alcohol are widely available and widely used—for example in packaging of detergents. Often, they are marketed as being environmentally friendly. Examples include Monosol M-8630 from Monosol (now Kuraray). Typically, such films are soluble but actually have poor biodegradability in marine biodegradation tests and can accumulate in the environment. Some products and packaging applications require the packaging material itself to be edible. In this context, by “edible” it is meant that all of the materials are classified as being safe to eat whether or not they are digestible by humans or can provide human nutrition. Many biopolymers, or materials of natural origin, can be used to make packaging films. Widely used examples of biopolymer films include starches and cellulose-based films. Starches are especially widely used due to their low cost and ready availability. Typically, the starches are chemically modified to improve their processability and functionality. One example of a modified starch is hydroxypropylated amylose starch. Other substituents may be hydroxyethyl or hydroxybutyl to form hydroxyether substitutions, or anhydrides such as maleic phthalic or octenyl succinic anhydride can be used to produce starch ester derivatives. Starch films typically have high tensile strengths at moderate humidity (such as between 30% and 50% at 20° C.) but typically become much weaker at higher humidity unless they have been highly chemically modified. In particular, many starch films are very susceptible during storage at low temperatures, as starches are prone to retrogradation. Many starch-based products, such as compostable bags, include significant levels of polybutene adipate terephthalate or PBAT to improve their processability and physical properties. PBAT is a biodegradable synthetic polymer. However, it is obviously obtained from non-renewable feedstock. Examples of starch-based films are those sold by Plantic Technologies Ltd (now part of Kuraray). Plantic films comprise modified starch and are available as both monolayer and multi-layer films. Cellulose-based polymers and materials can also form films and are also widely used. Commonly, cellulose films are made from so-called “regenerated” cellulose wherein cellulose fibers are dissolved in carbon disulphide under alkaline conditions to form viscose. The viscose is then contacted with an acidic solution to “regenerate” the cellulose. Such processes are resource and energy intensive, and the resulting cellulose films are not water-soluble or water-dispersible at all, and they do not heat seal. Regenerated cellulose is used in NatureFlex films, which are cellulose-based compostable packaging films sold by Futamura. Other cellulose-materials include Hyproxypropyl Methyl Cellulose (HPMC) and Carboxymethyl Cellulose (CMC). HPMC films have long been used in the medical field as a coating for tablets. However,