TW201710075A - Starch compositions and use thereof - Google Patents

Abstract

There is provided a starch composition comprising a crosslinked starch. The composition may be useful in a variety of applications, for example, in thermoformed articles or as a component in multilayer films.

Description

Starch composition and its use field

A starch composition is provided comprising at least one crosslinked starch. These compositions find particular use in packaging applications, even if not proprietary.

background

In recent years, research has focused on the use of starch as an industrial raw material, which reduces dependence on non-renewable resources. It has been recognized that the starch system consists of two components, a linear amylose component and a branched amylopectin component. Starches from different sources (eg, potato, corn, tapioca, and rice) are characterized by different relative ratios of amylose to amylopectin components, such as gelatinization, water absorption, and physicochemical properties of melt viscosity. [Determination of Amylose Content in Different Starches Using Modulated Differential Scanning Calorimetry, using Mobility Differential Scanning Calorimetry, Moorthy, SN et al, Starch, 58 (2006) 209-214] . Several methods have been developed for the production of high amylose or amylopectin starches, including physical separation means, traditional plant planting, and genetic engineering improvements in plants such that a starch is primarily produced.

In general, the physical properties of products containing starch are improved when the amylose content is high. However, high amylose starches are more expensive than 'natural' low amylose starches (sometimes referred to as commercial starches), often resulting in a compromise between price and performance.

Natural starch can also be modified by chemical, biochemical, and/or physical means to produce certain properties. For example, chemically modified methods such as etherification or esterification delay the re-coagulation of the starch and effectively plasticize the starch to behave like the same thermoplastic.

While the efficacy of such particular and improved starches has been recognized, the cost of such products inhibits the commercial acceptability of products made therefrom. Furthermore, replacement of a proportion of commercial low amylose starch, for example, high amylose starch may adversely affect physical properties, even if it provides a generally lower cost starch composition.

Therefore, there is a need to provide a starch composition having desirable physical properties and using inexpensive renewable materials.

summary

Provided is a starch composition comprising: a) at least one first starch having an amylose content of greater than or equal to 50% by weight based on the dry weight of the first starch; and b) at least one second starch, Having an amylose content of less than or equal to 40% by weight based on the dry weight of the second starch; wherein the at least one first starch and the at least one second starch are chemically modified to be selected from the group consisting of ethers a class of esters or esters and a mixture of such Sexually substituted hydroxy functionality; and wherein the at least one first starch is uncrosslinked starch and the at least one second starch is a crosslinked starch.

The at least one second starch may be present in an amount of at least 5% by weight, based on the total dry weight of the starch in the composition. The at least one second starch may be at least 10% by weight, or at least 15% by weight, or at least 20% by weight or at least 25% by weight, or at least 30% by weight, or at least, based on the total dry weight of the starch in the composition. It is present in an amount of 35 wt%, or at least 40 wt%, or at least 45 wt%, or at least 50 wt%.

The at least one second starch may be from 0.001 to 5% by weight, or from 0.001 to 2% by weight, or from 0.001 to 1% by weight, or from 0.001 to 0.5% by weight, based on the dry weight of the second starch. One or more crosslinkers are treated with one of the starches. Crosslinkers can be one of the functionalities known in the art to crosslink starch. Exemplary but non-limiting crosslinkers include phosphorus oxychloride, epichlorohydrin, hydrophobic cationic epoxides, sulfates, dianhydrides, such as adipic anhydride, and by being positive with sodium or potassium. Phosphate derivatives prepared by the reaction of phosphate or tripolyphosphate, and combinations thereof.

Illustrative, but non-limiting examples of both the first and second starches are wheat starch, corn starch, tapioca starch, potato starch, tapioca starch, pea starch, oat starch, gelatin gold starch, barley starch, or rice starch, And a mixture of these.

The at least one first starch is a high amylose starch, i.e., containing at least 50% by weight of amylose based on the dry weight of the first starch. Based on the dry weight of the first starch, it can be used here. The high amylose starch has at least 50% by weight, or at least 55% by weight, or at least 60% by weight, or at least 65% by weight, or at least 70% by weight, or at least 80% by weight, or at least 90% by weight Any starch with a chain starch content. While high amylose corn starch is suitable, other starches that may be used include any plant species derived from starch that produces or can produce a high amylose content, such as cassava, peas, wheat, and rice. Alternatively, the high amylose starch may be obtained by separating or isolating, such as by fractionating a natural starch material, or by blending isolated amylose with a natural starch.

The at least one first starch may be a corn starch or a tapioca starch having an amylose content of greater than or equal to 50% by weight based on the weight of the at least one first starch dried.

The at least one second starch is a low amylose starch, that is, containing less than or equal to 40% by weight of amylose, or less than or equal to 35% by weight based on the dry weight of the second starch. Amylose, or less than or equal to 30% by weight of amylose, or less than or equal to 25% by weight of amylose, or less than or equal to 20% by weight of amylose. While low amylose corn starch or low amylose tapioca starch is suitable, other starches that may be used include any plant species derivative that produces starch that produces or produces a low amylose content, for example, Bowl of beans, barley, potatoes, wheat, and rice. Alternatively, the low amylose starch may be obtained by separating or isolating, such as by fractionating a natural starch material, or by blending isolated amylose with a natural starch.

Based on the dry weight of the second starch, the at least one second lake The powder may be a corn starch or a tapioca starch having an amylose content of less than or equal to 40% by weight.

Both high and low amylose starches can be chemically modified to the same or different degrees. By chemical modification, it is meant that the starch can be derivatized or modified by typical methods known in the art, for example, esterification or etherification. Chemically modified starches may include esters such as acetates and dicarboxylic acids/anhydrides, especially alkenyl succinic acids/anhydrides and ethers such as hydroxyethyl and hydroxypropyl starch. class. These and other traditional improvements in starch are described, for example, in "Starch: Chemistry and Technology", Second Edition, edited by Roy L. Whistler et al., Chapter X; Starch Derivatives: Productionion and Uses, Academy of MWRutenberg et al. In the literature of Press, Inc., 1984.

One of the particularly advantageous high and low amylose starches is etherified with alkylene oxides, especially those containing 2 to 6, or 2 to 4, carbons. Ethylene oxide, propylene oxide, and butylene oxide are useful as exemplary compounds for the etherification of starting starch materials, and propylene oxide is particularly preferred. Different amounts of these compounds can be used depending on the desired properties and economy. The chemical modification of the first and second starches may independently comprise a monohydroxyalkyl C _2-6 group or a product of the reaction of the first or second starch with an anhydride of a monocarboxylic acid.

Another modification of the particularly advantageous high and amylose starch is acetylation to form a starch acetate. Different degrees of acetylation can be used according to the nature of the desire and economy.

The chemical modification of the first and second starches may independently comprise a monohydroxyalkyl C _2-6 group, or a product of the first or second starch reacted with an anhydride of a monocarboxylic acid to form an ester.

The first starch and the second starch may be modified with a hydroxyalkyl C _2-6 group. The first starch may be modified with a hydroxyalkyl C _2-6 group, and the second starch may be formed by oxime modification, for example, acetate starch.

The first and second starches can be chemically modified to independently have a degree of substitution from 0.05 to 3.0. The degree of substitution defines the average number of substituents per anhydroglucose unit. Therefore, by definition, the maximum possible degree of substitution of starch is 3.0.

The starch compositions disclosed herein present different advantages. Although the composition contains a proportion of low amylose starch, the physical properties of the articles prepared from such compositions can be maintained relative to articles prepared from compositions comprising only high amylose starch. It is expected that cross-linking will result in a harder and more rigid material that is less tough and tends to have a higher fracture. However, this has not been found to be the case. While not wishing to be bound by theory, it is contemplated that the introduction of a crosslinked starch produces a 'rubber toughened' phase in the starch matrix, improving physical properties, e.g., improving impact strength by avoiding rupture extension. Thus, a lower cost starch composition can be prepared wherein a proportion of the uncrosslinked high amylose starch is replaced with a crosslinked bottom amylose starch.

The starch composition may further comprise one or more filler or nanomaterials. These may be present in one or both of the first or second starch or may be added during formation of the starch composition. The nanomaterial will peel off in a starch nanocomposite. Exemplary nanomaterials include clay, carbon nanotubes, cellulose nanobes, and chitin. Exemplary clays include montmorillonite, bentonite, Bede stone, mica, hectorite, magnesium bentonite, iron bentonite, zinc bentonite, vermiculite, illite, magadisite, sodaite, strontite, chrome bentonite, or a mixture of these. Nanomaterials or fillers can be modified. The nanomaterial or filler can be modified by hydrophobicity. The nanomaterial can be a modified clay, especially a 'hydrophobic modified layered silicate clay'.

A 'hydrophobic modified layered silicate clay' or 'hydrophobic clay' may be a surfactant comprising a long chain alkyl group, such as a long chain alkyl ammonium ion, for example, Mono- or di-C ₁₂ -C ₂₂ alkyl ammonium ions, exchanged and modified one of the clays. Polar substituents such as hydroxy or carboxy are preferably not attached to the long chain alkyl group. Examples of suitable clays include CLOISITE® 20A or CLOISITE® 25A from Southern Clay Products Inc.

The filler or nanomaterial may be present in an amount up to 20% by weight, or up to 10% by weight, or up to 5% by weight, or up to 3% by weight, based on the total dry weight of the starch composition.

The starch composition may further comprise fatty acids or fatty acid salts. These may be present in one or both of the first or second starch or may be added during the formation of the starch composition. Exemplary but non-limiting fatty acids include a _C12-22 fatty acid and/or a _C12-22 fatty acid salt. The fatty acid or fatty acid salt may be present in the starch composition from 0.1 to 5% by weight based on the total dry weight of the starch composition. If the filler is used in the starch composition, the fatty acid or fatty acid salt is preferably absent in some cases.

The starch composition may further comprise a polymer. This polymer can be a water soluble polymer. The polymer may be present in one or both of the first or second starch or may be added during the formation of the starch composition. Starch group The starch composition may comprise up to 20% by weight of one polymer, or from 4 to 12% by weight of one polymer, based on the total dry weight of the product. Polyvinyl alcohol is a polymer which is exemplified but not limited to this one.

The starch composition may further comprise one or more plasticizers. The plasticizer can be water or one or more polyols. The plasticizer may be present in an amount up to 20% by weight, based on the total weight of the starch composition.

The starch composition may also comprise any combination of the foregoing features.

Also provided is a thermoformed article comprising a starch composition according to any of the preceding embodiments. The exemplified thermoformed article can include a tray, a container, or a lid.

Also provided is an injection molded product comprising a starch composition according to any of the preceding embodiments.

Also provided is a multilayer film comprising a starch composition according to any of the preceding embodiments.

The multilayer film may comprise: (a) at least one layer comprising a starch composition according to any of the preceding embodiments; and (b) at least one other layer.

The at least one other layer may have a water vapor permeability coefficient measured to be less than 1 g.mm/m ² .24 hr.atm at 38 ° C and 90% relative humidity.

The at least one layer comprising a starch composition may also comprise up to 50% by weight of natural unmodified starch.

A multilayer film according to any of the preceding embodiments is also provided for packaging, preferably for the purpose of packaging food.

There is also provided a fabricated article comprising a multilayer film according to any of the preceding embodiments. Exemplary articles of manufacture include food packages such as containers, lids, bags, stretch wraps, and films.

The use of the terms "comprising" or "comprising" or variations of the grammatical expressions thereof, as used in the specification, is used to clarify the existence of the described features, components, steps, or components, but does not exclude Reference is made to the presence or addition of one or more other features, ingredients, steps, components, or groups.

For the sake of brevity, only certain ranges are explicitly disclosed herein. However, a range from any lower limit may be combined with any upper limit to describe a range that is not explicitly described, and any range from the lower limit may be combined with any other lower limit to describe a range that is not explicitly described, in the same manner, from any The range of upper limits may be combined with any other upper limit to describe a range that is not explicitly described.

Brief description of the schema

Figure 1 is a graph showing the viscosity data of crosslinked and uncrosslinked starch.

Detailed description

The disclosure will now be conveniently described with reference to particular embodiments and examples. The examples and examples are merely illustrative and are not to be construed as limiting the scope of the disclosure. It will be apparent to those skilled in the art that the disclosed changes are within the scope of this disclosure. Similarly, the disclosure can find applications in areas not explicitly described in this disclosure, and certain applications are not The facts clearly stated should not be considered as limiting the overall application of this disclosure.

High amylose starch

The high amylose starch component can be an uncrosslinked starch of hydroxypropylated high amylose starch. Other substituents may be hydroxyethyl or hydroxybutyl groups to form hydroxy ether substitutions, or anhydrides such as maleic anhydride, phthalic anhydride or octenyl succinic anhydride may be used to produce ester derivatives. The degree of substitution (the average number of hydroxyl groups substituted in a glucose) may be from 0.01 to 2.0, or may be from 0.01 to 1.5, or may be from 0.02 to 1.5, or may be from 0.02 to 1.0, or may be from 0.05 to 1.5. A preferred high amylose starch is a high amylose corn starch. Further preferred high amylose starch is a high amylose tapioca starch. A preferred modified high amylose starch component is a hydroxypropylated high amylose starch. For example, ECOFILM®, marketed by National Starch and Chemical Company, or Gelose® A939, marketed by Penford.

Low amylose starch

The low amylose starch may be any commercially available starch. This can be derived, for example, from wheat, corn, cassava, potato, rice, oats, gemkin, and bowl of beans. A preferred low amylose starch is a hydroxypropylated low amylose starch. Other substituents may be hydroxyethyl or hydroxybutyl groups to form hydroxy ether substitutions, or anhydrides such as maleic anhydride, phthalic anhydride, or octenyl succinic anhydride may be used to produce ester derivatives. Further preferred low amylose starch is an acetated starch. The degree of substitution (the average number of hydroxyl groups substituted in a glucose) may be from 0.01 to 2.0, or may be 0.01 To 1.5, or may be 0.02 to 1.5, or may be 0.02 to 1.0, or may be 0.05 to 1.5.

The hydroxyl group on the starch reacts with the polyfunctional reagent to form a crosslinked starch. Crosslinks are produced with low reagents. The low amylose starch is crosslinked and can be derived from 0.001 to 5% by weight, or 0.001 to 2% by weight, or 0.001 to 1% by weight, or 0.001, based on the dry weight of the low amylose starch. One of the starch is treated to one or more of 0.5% by weight of the crosslinking agent. The low amylose starch may be treated from 0.002 to 0.1% by weight of one or more crosslinking agents, based on the dry weight of the low amylose starch. The low amylose starch may be treated from 0.005 to 0.05% by weight of one or more crosslinking agents, based on the dry weight of the low amylose starch. Exemplary but non-limiting crosslinkers include phosphorus oxychloride, epichlorohydrin, hydrophobic cationic epoxides, sulfates, dianhydrides, and orthophosphates or tripolyphosphates with sodium or potassium. a phosphate derivative prepared by a salt reaction, and combinations thereof.

The measurement of the viscosity of a starch provides insight into one of the cross-linking efficacies and provides guidance on the amount of cross-linking required to produce the desired effect. One technique uses a Rapid Visco Analyser (RVA), which measures viscosity depending on temperature and time. This method uses a relatively long period of time during which the starch is exposed to high temperatures (95 ° C) under low/medium shear. The crosslinked starch tends to increase viscosity during the test, while the uncrosslinked starch is easily decomposed, resulting in a decrease in viscosity.

The National 7 starch used in the example is an uncrosslinked low amylose starch, and the viscosity is measured at 95 ° C over time. Reduced, indicating starch breakdown. Conversely, National Frigex®, which is a low-amylose starch that has been cross-linked, is also used in the formula and exhibits a much higher viscosity when exposed to high temperature/time distribution.

In a preferred embodiment, the first starch is a hydroxypropylated starch of high amylose starch and the second starch is a hydroxypropylated starch of a low amylose starch. Low amylose starch is crosslinked.

In another preferred embodiment, the first starch is a hydroxypropylated starch of a high amylose starch and the second starch is a low amylose acetalized starch. The low amylose acetalized starch is crosslinked.

polymer

The polymeric component of the starch composition, when present, is compatible with the starch, may be water soluble, may be biodegradable, and may have a low melting point that is compatible with the starch processing temperature. Exemplary but non-limiting polymers may be selected from the group consisting of polyvinyl acetate, polyvinyl alcohol, or mixtures of such. A preferred concentration range is from 4 to 12% by weight, more preferably from 8% to 12% by weight, based on the dry weight of the starch composition.

Plasticizer

A range of plasticizers and humectants can be added to the starch to aid in the processing and control and stability of the mechanical properties. The desired level of plasticizer is primarily determined by the processing behavior desired during processing and subsequent blowing or stretching processes, and the desired mechanical properties of the final product.

The plasticizer may be water, and/or one or more polyols such as glycerol, maltitol, mannitol, erythritol, and xylitol, even ethylene glycol and diethylene glycol. used. Water system is a preferred plasticizer.

The content of water and/or multiparticulates may be up to 20% by weight of the starch composition, depending on the particular application.

Other plasticizers or humectants

The plasticizer can be polyethylene glycol, polyethylene oxide, epoxidized linseed oil, epoxidized soybean oil, tributyl citrate, 2,2,4 trimethyl-1,3- One or more of pentanediol diisobutyrate or ethyl citrate triethyl citrate. These plasticizers are additionally used in addition to or in addition to the above polyols or water.

One or more of such things as red algae, tri-sac, gum arabic, guar gum, gelatin, sugar, glucose, red algae, gelatin, sansonic gum, gum arabic, guar gum, and triacetin A humectant can be added to the starch composition.

Fatty acid and / or fatty acid salt

The fatty acid and/or fatty acid salt may be present in the starch composition based on the total dry weight of the starch composition. The starch composition may comprise from 0.1 to 5% by weight of one _C12-22 fatty acid and/or one _C12-22 fatty acid salt. The fatty acid and/or fatty acid salt component may be present at a concentration of from 0.6 to 1% by weight, based on the total dry weight of the starch composition. Stearic acid is a particularly preferred component. Sodium and potassium stearates can also be used. The cost can be one of the factors in selecting this component, but lauric acid, myristic acid, palmitic acid, linoleic acid, and azelaic acid are suitable.

Barrier property

The film formed from the starch composition disclosed herein exhibits improved gas and moisture barrier properties as compared to the starch composition of the crosslinked starch lacking a low amylose starch. For example, including the starch composition disclosed herein The oxygen permeability of the film of the article may be less than that of the uncrosslinked starch (first starch) comprising high amylose starch and the crosslinked starch (second starch) lacking low amylose starch. The water vapor transmission rate can be similarly improved.

Compared to the composition of the crosslinked starch comprising a low amylose starch, the uncrosslinked starch comprising a high amylose starch (first starch) and a low amylose starch uncrosslinked starch Films formed from starch compositions exhibit poor gas and moisture barrier properties. For example, a film comprising a high amylose uncrosslinked starch (first starch) and a low amylose uncrosslinked starch may have a water vapor transmission rate greater than that of a high amylose starch. a film of the crosslinked starch (second starch) of the linked starch (first starch) and a low amylose starch, or may be larger than the uncrosslinked starch (first starch) containing a high amylose starch and lacking A film of low amylose crosslinked starch (second starch). Oxygen penetration rate will also be negatively affected.

application

The starch composition can be used in a variety of applications. For example, the starch composition can be thermoformed into articles using methods known in the art. An exemplary thermoformed article can include a tray, a container, or a lid. The starch composition can also be used as a component in a multilayer film comprising, for example, a barrier tray to extend the storage of perishable foods including meat, poultry, fish, pasta, dishes, prepared meat and cheese. period. The starch composition can also be used in modified atmosphere packaging (MAP) where gas permeation is required.

Multilayer film

The starch composition can be used to make a multilayer film comprising: (a) at least one layer comprising any of the previously described embodiments. a starch composition; and (b) at least one other layer.

The multilayer film may comprise: a) at least one layer comprising: i. at least one first starch having an amylose content of greater than or equal to 50% by weight based on the dry weight of the first starch; and ii. a second starch having an amylose content of less than or equal to 40% by weight based on the dry weight of the second starch; wherein the at least one first starch and the at least one second starch are chemically modified To replace the hydroxy functionality with a functional group selected from the group consisting of ethers or esters and the like; and wherein the at least one second starch is a crosslinked starch; and b) at least one other layer.

The at least one other layer may have a water vapor transmission coefficient of less than 1 g.mm/m ² .24 hr.atm at 38 ° C and 90% relative humidity.

The total thickness of the at least one layer comprising a starch composition can be greater than 20% of the total thickness of the multilayer film. The at least one first starch and the at least one second starch may have a degree of substitution of less than 1.5.

The water vapor transmission coefficient of the at least one other layer may be less than 0.5 g.mm/m ² .24 hr. atm at 38 ° C and 90% relative measurement, or at 38 ° C and 90% relative measurement system Less than 0.2 g.mm/m ² .24 hr. atm.

The total thickness of the at least one layer comprising a starch composition can be greater than 30% of the total thickness of the multilayer film, or greater than 40% of the thickness of the multilayer film, or greater than 50% of the total thickness of the multilayer film. Containing at least one layer of a starch composition The total thickness can be greater than 60% of the total thickness of the multilayer film.

The multilayer film can have a low oxygen permeability coefficient (OPC). The multilayer film has an OPC of less than 0.6 cm ³ mm/m ² .24 h.atm at 50% relative humidity (RH). The multilayer film may have an OPC of less than 0.3 cm ³ mm/m ² .24 h.atm at 50% RH, or an OPC of less than 0.2 cm ³ mm/m ² .24 h.atm at 50% RH. The multilayer film may have an OPC of 50% RH system less than 0.1 cm ³ mm/m ² .24 h.atm, or the multilayer film may have an OPC of 50% RH system less than 0.05 cm ³ mm/m ² .24 h.atm .

The multilayer film may have an OPC of less than 1.2 cm ³ mm/m ² .24 h.atm at 75% relative humidity (RH). The multilayer film may have an OPC of 75% RH system of less than 0.6 cm ³ mm/m ² .24 h.atm, or an OPC of 75% RH system of less than 0.2 cm ³ mm/m ² .24 h.atm. The multilayer film may have an OPC of 75% RH system less than 0.1 cm ³ mm/m ² .24 h.atm, or the multilayer film may have an OPC of 75% RH system less than 0.05 cm ³ mm/m ² .24 h.atm .

The OPC can be maintained at 50% RH below 0.05 cm ³ mm/m ² .24 h. atm for an extended period of time. OPC can be maintained at 50% RH below 0.05cm ³ mm/m ³ .24h.atm for at least 10 days, or OPC can be maintained at 50% RH below 0.05cm ³ mm/m ² .24h.atm for 20 Days, or OPC, can be maintained at less than 0.05 cm ³ mm/m ² .24 h. atm for 30 days at 50% RH. The OPC can be maintained at less than 0.05 cm ³ mm/m ² .24 h. atm for 30 days at 50% RH.

Therefore, the multilayer film has enhanced properties with respect to oxygen barrier properties over an extended period of time. The time to reach equilibrium moisture content can be extended with other layers of controlled water vapor transmission. Due to the % phase in other layer materials For the humidity/% moisture content gradient, the equilibrium % moisture content within the starch layer can be lower.

The shelf life of perishable foods that extend the life of the extended barrier to gas barrier properties is clearly desirable.

Advantageously, from a renewable point of view, the multilayer film may contain a high proportion of biodegradable starch.

The thickness of each of the multilayer film and the layers within the multilayer film can vary depending on the true nature of the end use application.

The total thickness of the multilayer film can be between 10 and 1000 microns. The total thickness of the multilayer film can be between 10 and 100 microns, or between 20 and 80 microns. The total thickness of the multilayer film can be between 100 and 1000 microns, or between 200 and 800 microns.

The total thickness of the at least one layer comprising a starch composition can be between 5 and 600 microns. The total thickness of the at least one layer comprising a starch composition can be between 5 and 50 microns, or between 10 and 40 microns. The total thickness of the at least one layer comprising a starch composition can be between 100 and 600 microns, or between 150 and 450 microns.

The total thickness of the at least one other layer can be between 5 and 400 microns. The total thickness of the at least one other layer can be between 5 and 25 microns, or between 10 and 20 microns. The total thickness of the at least one other layer can be between 30 and 400 microns, or between 30 and 300 microns.

The at least one layer comprising a starch composition can have a total thickness between 100 and 600 microns, and the at least one other layer can have a total thickness between 10 and 400 microns. The at least one layer comprising a starch composition can have The total thickness between 100 and 400 microns, and the at least one other layer may have a total thickness between 40 and 250 microns.

The at least one layer comprising a starch composition can have a total thickness between 10 and 60 microns, and the at least one layer can have a total thickness between 5 and 40 microns.

The at least one layer comprising a starch composition may comprise water, preferably up to 20% by weight water, more preferably up to 12% by weight water. Water can be used as a plasticizer.

The moisture content of the at least one layer comprising a starch composition can be an average moisture content at ambient % relative humidity. For example, the equilibrium moisture content can range from about 4% of the low % RH to more than 15% of the high % RH.

The at least one layer comprising a starch composition may also comprise up to 50% by weight of natural unmodified starch.

The layer comprising a starch composition and/or other layers may comprise a colorant.

Other layer

Other layers may be selected to impart certain physical and aesthetic properties to the finished multilayer film. Such properties may include, for example, anti-fog, strength, heat sealability, color, or transparency. Other layers may be those having a low water vapor transmission rate.

The at least one other layer may comprise polyolefin, polyethylene terephthalate, polyethylene terephthalate, polylactic acid, nylon, polyvinyl chloride, polyvinylidene chloride, cellulose, a water resistant protein A layer comprising a water resistant layer of cerium oxide, or a mixture thereof. Each of these other layers may comprise a mixture of components. One or more of these other layers may be It consists of the same material layer. Each of these other layers may comprise different materials. These layers can be solvent cast or spray coated.

Suitable polyolefins for the preparation of polyolefin film layers may be selected from ethylene homopolymers, propylene homopolymers, heteropolymers of ethylene and propylene, and heterogeneous ethylene or propylene with one or more C ₄ -C ₁₀ α-olefins. A group of copolymers, cyclic olefin polymers and copolymers, biaxially oriented polypropylene, and mixtures thereof.

Suitable polyolefins may be selected from the group consisting of ethylene or a copolymer of propylene and one or more alpha-olefins. Both high density polyethylene and linear low density polyethylene can be used.

Suitable linear low density polyethylene (LLDPE) may comprise a copolymer of ethylene and an alpha olefin (about 5 to about 15 weight percent). The α -olefin may include 1-butene, 1-hexene, 1-octene, etc., and mixtures thereof. The density of the LLDPE is in the range of from about 0.865 to about 0.925 g/cm ³ .

Suitable high density polyethylene (HDPE) may comprise an ethylene homopolymer, and a copolymer of ethylene and an alpha olefin (about 0.1 to about 10 weight percent). Suitable alpha -olefins may include 1-butene, 1-hexene, 1-octene, and the like, and mixtures thereof. The density of HDPE is preferably from about 0.940 to about 0.970 g/cm ³ .

Suitable cyclic olefin polymers and copolymers may include polymers of norbornene or tetrachlorododecene, and copolymers of norbornene or tetrachlorododecene with one or more alpha-olefins. Examples include cyclic olefin polymer systems Topas (Ticona) and Apel (Mitsui).

Blends of polyolefins with other polymers can be advantageously used. Cast polypropylene (cPP) or biaxially oriented polypropylene (BOPP) due to improved strength And low WVTR was chosen. Polyethylene terephthalate (PET) can be selected for strength and shrinkage.

Modified polyolefins such as grafted polyolefins can be used. A preferred grafted polyolefin is a polyolefin grafted with maleic anhydride.

Polyolefin

Suitable LLDPE, HDPE and polypropylene can be made by Ziegler, single site, or any other olefin polymerization catalyst. Ziegler catalysts and cocatalysts are known in the art. The metallocene single site catalyst is a transition metal compound containing a cyclopentadienyl (Cp) or Cp derived ligand. For example, U.S. Patent No. 4,542,199 teaches the preparation of metallocene catalysts. Non-metallocene single site catalysts containing heteroaromatic ligands (e.g., boron heteroaryl, pyrrolyl, azaborolinyl, or quinolinyl) are also known in the art.

HDPE can also be multimodal. By "multimodal" it is meant that the polymer comprises at least two components, one having a relatively low molecular weight and the other having a relatively high molecular weight. Multimodal polyethylene can be made by polymerization using conditions that produce a multimodal polymer product. This can be achieved by using a catalyst system having one or two different catalytic sites, or by using two or more stages of polymerization processes and having different processing conditions at different stages (eg, different temperatures, pressures, polymerization media, Completed by hydrogen partial pressure, etc.). Multimodal HDPE can be produced by a multistage ethylene polymerization reaction using a series of reactors and adding comonomers to only one of the reactors.

The at least one other layer may comprise one or more materials derived from one or more recycled materials. Polyethylene or polypropylene can be regenerated from one or more Material derived. The polyethylene can be freely produced, for example, from sugar cane, sugar beets, or wheat grain derived ethanol. Polyethylene terephthalate can be derived from biopolyols.

Adhesive

The at least one other layer can be secured to at least one layer comprising a starch composition via the use of a suitable adhesive. This can help minimize slippage and, therefore, maintain excellent barrier properties. Several suitable adhesives are readily apparent to those skilled in the art. The adhesive can be selected to chemically bond at least one layer comprising a starch composition. Useful adhesives can include one or more polyurethanes or epoxides.

Advantageously, the use of an adhesive can overcome or minimize this need for other layers that are modified or grafted as a bonding layer. Thus, for example, a standard film polyethylene grade can be successfully used as the other layer of polyolefin in the multilayer film. This can be done by cost considerations.

Other suitable adhesives may include EVA copolymers, acrylic copolymers and terpolymers, ionomers, metallocene-derived polyethylene, maleic anhydride-modified polyethylene, ethylene acrylate terpolymers, and ethylene. Vinyl acetate terpolymer.

Those skilled in the art will be familiar with other adhesive lamination techniques suitable for adhering various types of plastics, including systems for thermal activation and UV activation. Exemplary adhesives can include polyurethanes, epoxies, nylons, acrylics, and acrylates.

Polyurethane-based adhesives are particularly suitable for immobilizing other layers to a layer comprising a starch composition. Polyurethane adhesive can be Prepared in situ by reaction of one or more isocyanates with starch. The carbamate functionality is formed by reaction of the surface hydroxyl functionality of the starch with the isocyanate. Preferred isocyanates are diisocyanates. Those skilled in the art will be able to select suitable isocyanates from a wide range of techniques typically employed in the synthesis of polyurethanes.

Additionally, the polyurethane adhesive may comprise one or more polyols. Such two component systems comprising diisocyanates and polyols are known in the art.

The adhesive may or may not contain a solvent. The solvent may be organic or water based.

Exemplary isocyanates include methylene diphenyl diisocyanate and toluene diisocyanate. Exemplary polyols include polyether polyols such as polyethylene glycol or polypropylene glycol, and polyester polyols such as polyols based on adipates.

Method for preparing multilayer film

Multilayer films can be made by a variety of methods. Multilayer films can be made by coextrusion, coating, extrusion coating, extrusion lamination, and other lamination methods. The film can also be produced by a casting or blown film process. T

Coextrusion tends to use a tie layer and other modified layers, such as modified (grafted) polyolefins. Co-extrusion generally achieves a thin overall specification. Laminated systems are more suitable for thicker multilayer films using adhesives. Extrusion coating produces a coated product in a line process. Extrusion coating can be applied to a substrate using a suitable adhesive resin to coat a polymer layer of a relatively thin polyolefin or polyester.

In one embodiment, a three layer film is provided comprising an inner layer comprising the starch composition and a second outer polyolefin layer. In other embodiments, an adhesive layer can be used between the layer comprising the starch composition and the polyolefin layer, thereby producing a five layer film.

In another embodiment, the starch layer can be extrusion coated onto a film substrate, for example, a biaxially oriented polypropylene or paper substrate, and then, another layer, such as a polyolefin or polyester layer. It can be extrusion coated on the starch layer.

Multilayer film application

Those skilled in the art will appreciate that one or three or five layers of film are only one of many possible embodiments for the use of starch and other layers. The number of layers and their relative thickness can be adjusted depending on the function or end use of the film.

In addition, further layers comprising other materials commonly used in barrier film applications are contemplated. Further film layers exemplified include metallized films, non-polymer films, and the like.

Multilayer films can have many applications, including grocery bags, stretch wraps, food wrap films, packaging containers, and packaging lids where low water vapor and oxygen permeability are required.

example

As reviewed in Table 1, three chemically modified low amylose starches were obtained from Ingredion Incorporated. Each of these starches has an amylose content of less than 40% by weight.

¹ % improvement

² degree of substitution

³ % cross-linking % is the weight % of cross-linking agent relative to the weight of dry starch

Such low amylose starch (second starch) replaces an uncrosslinked hydroxypropyl modified with an amylose content of between about 0% and 50% by weight of a starch composition. High amylose starch (first starch). Each of these starch compositions was thermally processed with polyvinyl alcohol, stearic acid, and Cloisite 20A to form a sheet which was then thermoformed into a tray in a thermoforming machine at 120 °C. The total amount of the first and second starches in the composition is about 90% by weight based on the total dry weight of the composition. The amounts of PVA, stearic acid, and Cloisite 20A are each about 10% by weight, 0.5% by weight, and 2% by weight.

Table 2 summarizes the compositions prepared. Note that each of these compositions having 0% of the second starch component is a comparative composition.

Fall test

The thermoformed tray made from the sheet material was loaded with 125 grams of weight, sealed in a carton and conditioned at 23 ° C and 35% RH or 50% RH for 48 hours. The conditioned sample is then adjusted for trays that are 35% humidity regulated. A height of 0.9 m (equal to 1.1 J impact energy) fell, and the tray adjusted for 50% humidity was dropped at 1.5 m (equal to 1.8 J impact energy). The results of the drop test were evaluated according to the following definitions and graded as described in Table 3.

Rupture: Stretched from the edge or inside of the tray.

Small piece: A piece of sheet that is separated from the edge of the tray. The dimensions are the largest dimensions of the detached portion and do not include any associated rupture.

Hole: Occurs in the middle of a tray. The dimensions are the largest dimensions of the detached portion and do not include any associated rupture.

Separator: A large piece of 75% or more that is detached from the tray.

Due to the rigorous nature of this test and the critical defect points contained in the thermoformed tray, a drop of about 3 or less is considered to be acceptable. Accepted. This test was developed to effectively classify the starch composition, and the less stringent test did not distinguish any improvement in performance. Table 4 collects the drop test results of the trays made from various compositions. A comparative composition containing only high amylose starch was tested prior to testing each of these compositions. This is equal to the result referred to as 0% in Table 4 (compositions 1, 8, and 13). Additional compositions containing National 7 (uncrosslinked starch) are also considered to be comparative.

Comparing the results of compositions 1 to 7, noting that one was uncrosslinked The low amylose starch (National 7) replaces the high amylose starch in Composition 1 resulting in poor drop test performance, especially at higher replacement levels.

Conversely, comparing the results of compositions 8 to 12, replacing the high amylose starch of up to 30% and even up to 40% of composition 8 with a crosslinked low amylose starch (National Frigex) Accept the drop test performance.

Comparing the results of Compositions 13 to 17, the replacement of up to 40% of the high amylose starch of Composition 3 with a crosslinked low amylose starch (National 1658) also resulted in acceptable drop test performance.

Another series of tests were carried out using commercially available acetylated low amylose tapioca starch. Details of these starches are presented in Table 5.

¹ % improvement

² degree of substitution

³ % cross-linking % is the weight % of cross-linking agent relative to the weight of dry starch

The acetalized starch (second starch) replaces 20% by weight or 40% by weight of an uncrosslinked hydroxypropyl group having an amylose content of about 70% by weight in a starch composition. High amylose starch (first starch). Each of these starch compositions was thermally processed with polyvinyl alcohol, stearic acid, and Cloisite 20A to form a sheet which was then thermoformed into a tray in a thermoforming machine at 120 °C. The total amount of the first and second starches in the compositions is about 90% by weight based on the total dry weight of the composition. The amounts of PVA, stearic acid, and Cloisite 20A are each about 10% by weight, 0.5% by weight, and 2% by weight.

A sheet sample of about 250 μm thickness was reduced to about 60 μm thick in a thermoforming machine. The reduced samples were evaluated for impact strength using a Spencer tester (ASTM D3420).

Sheets and trays were tested for impact properties and the results were collected in Table 6. The 0% by weight item was a comparative example using an uncrosslinked hydroxypropyl modified high amylose starch (first starch).

The results confirmed that Elastitex 2, an uncrosslinked low-linear lake The acetalized starch of the powder replaces the high amylose starch, resulting in a decrease in impact properties. Substituting Purity® 69, a cross-linked, low amylose acetalized starch, replaces high amylose starch, resulting in less impact strength reduction, especially at 40% replacement. This is significant because the acetylated low amylose tapioca starch is less expensive than the hydroxypropylated high amylose corn starch.

Elastitex 2 and Purity® 69 starch were analyzed using a Rapid Visco Analyser and the results are shown in Figure 1. These analyses provide information on the swelling and gelation behavior of starch. The crosslinked starch shows higher expansion before gelation, less set back, and higher final viscosity.

The starch composition was also tested for barrier properties. Table 7 collects the results of oxygen permeability and water vapor transmission rate. OTR is measured using ASTM F 1927-98 and WVTR is measured using ASTM F 1249-01.

The barrier performance results indicate that the cross-linked starch of low amylose replaces the uncrosslinked starch of 30% high amylose to reduce oxygen permeability. The results also indicate that the uncrosslinked starch of 30% high amylose starch is replaced with unamed starch of low amylose to increase water vapor transmission.

Collectively, the results confirmed a significant proportion of expensive high amylose starch The starch may be replaced by a crosslinked low amylose starch, and the thermoformed article formed therefrom has desirable physical properties, particularly impact properties and barrier properties.

Claims (24)

A starch composition comprising: a) at least one first starch having an amylose content of greater than or equal to 50% by weight based on the dry weight of the first starch; and b) at least one second starch, And having an amylose content of less than or equal to 40% by weight based on the dry weight of the second starch; wherein the at least one first starch and the at least one second starch are chemically modified to be selected from The functionality of the ether or ester and mixtures thereof replaces the hydroxy functionality; and wherein the at least one first starch is uncrosslinked starch and the at least one second starch is a crosslinked starch. The starch composition of claim 1 wherein the at least one second starch is present in an amount of at least 5% by weight based on the total dry weight of the starch in the composition. The starch composition of claim 1 or 2, wherein the at least one second starch is present in an amount from 5% by weight to 50% by weight based on the total dry weight of the starch in the composition. The starch composition of any one of claims 1 to 3, wherein the at least one second starch is derived from from 0.001 to 5% by weight, based on the dry weight of the uncrosslinked starch or The uncrosslinked starch is treated with a plurality of crosslinkers. The starch composition of claim 4, wherein the crosslinking agent is selected from the group consisting of phosphorus oxychloride, epichlorohydrin, hydrophobic cationic epoxides, sulfates, a dianhydride, and a phosphate derivative prepared by reacting with sodium or potassium orthophosphate or tripolyphosphate, and combinations thereof. The starch composition according to any one of claims 1 to 5, wherein the chemical modification independently comprises a monohydroxyalkyl C _2-6 group or a product of a reaction of a starch with an anhydride of a monocarboxylic acid. The starch composition of any one of claims 1 to 6, wherein the first and second starches are chemically modified so as to have a degree of substitution independently from 0.01 to 1.5. The starch composition according to any one of claims 1 to 7, wherein the first or second starch is independently selected from the group consisting of wheat starch, corn starch, tapioca starch, potato starch, tapioca starch, bean starch, oatmeal Starch, turmeric, or rice starch, or a mixture of these. The starch composition according to any one of claims 1 to 8, wherein the first starch is a corn starch having an amylose content of 50% by weight or more based on the dry weight of the first starch or A tapioca starch. The starch composition according to any one of claims 1 to 9, wherein the second starch is a corn starch having an amylose content of less than or equal to 40% by weight based on the total weight of the second starch Or a tapioca starch. The starch composition according to any one of claims 1 to 10, wherein the first starch is a hydroxypropylated starch of a high amylose starch, and the second starch is a hydroxypropyl group of a low amylose starch. Starch. The starch composition according to any one of claims 1 to 10, wherein the first starch is a hydroxypropylated starch of a high amylose starch, and the second starch is a acetaminophen of a low amylose starch. Starch. The starch composition of any one of claims 1 to 12, further comprising one or more fillers or nanomaterials. The starch composition of claim 13, wherein the filler is present in an amount up to 20% by weight based on the total dry weight of the starch composition. The starch composition according to any one of claims 1 to 14, further comprising one or more fatty acids or salts thereof. The starch composition of claim 15 comprising from 0.1 to 5% by weight, based on the total dry weight of the starch composition, of one C _12-22 fatty acid and/or one C _12-22 fatty acid salt. The starch composition of any one of claims 1 to 16, further comprising polyvinyl alcohol. The starch composition of any one of claims 1 to 17, further comprising water. The starch composition according to any one of claims 1 to 18, wherein an oxygen permeability coefficient of a film comprising one of the starch compositions is relative to a film comprising the at least one first starch and lacking a film of the second starch / or the water vapor transmission coefficient is reduced. A thermoformed article comprising the starch composition of any one of claims 1 to 19. A multilayer film comprising the starch composition of any one of claims 1 to 19. The multilayer film of claim 21, comprising: (a) at least one layer comprising the starch composition of any one of claims 1 to 19; and (b) at least one other layer; wherein the at least one other layer has The water vapor permeability coefficient was less than 1 g.mm/m ² .24 hr.atm measured at 38 ° C and 90% relative humidity. The multilayer film of claim 21 or 22, wherein the other layer comprises a polyolefin, polyethylene terephthalate, nylon, polyvinyl chloride, polyvinylidene chloride, cellulose, a water resistant protein layer, and a mixture of these. Use of a multilayer film according to any one of claims 21 to 23 for packaging, in particular packaged food.