CA2173583A1 - Thermoplastically processable starch-based composite materials - Google Patents
Thermoplastically processable starch-based composite materialsInfo
- Publication number
- CA2173583A1 CA2173583A1 CA 2173583 CA2173583A CA2173583A1 CA 2173583 A1 CA2173583 A1 CA 2173583A1 CA 2173583 CA2173583 CA 2173583 CA 2173583 A CA2173583 A CA 2173583A CA 2173583 A1 CA2173583 A1 CA 2173583A1
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- Prior art keywords
- starch
- composite material
- range
- spv
- fatty
- Prior art date
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- Abandoned
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-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L3/00—Compositions of starch, amylose or amylopectin or of their derivatives or degradation products
- C08L3/02—Starch; Degradation products thereof, e.g. dextrin
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L2201/00—Properties
- C08L2201/06—Biodegradable
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L31/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid; Compositions of derivatives of such polymers
- C08L31/02—Homopolymers or copolymers of esters of monocarboxylic acids
- C08L31/04—Homopolymers or copolymers of vinyl acetate
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
- C08L33/04—Homopolymers or copolymers of esters
- C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
- C08L33/08—Homopolymers or copolymers of acrylic acid esters
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
- C08L33/04—Homopolymers or copolymers of esters
- C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
- C08L33/10—Homopolymers or copolymers of methacrylic acid esters
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L75/00—Compositions of polyureas or polyurethanes; Compositions of derivatives of such polymers
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
- Biological Depolymerization Polymers (AREA)
Abstract
The description relates to a shapeable composite material based on thermomechanically hydrolyzed starch in a homogenous mixture with synthetic polymer compounds. To optimise its mechanical strength, synthetic polymer compounds with lateral and/or terminal staight-chained and saturated fatly radicals are added and homogenised with the thermoplasticised starch in selected quantity ratios. The invention also relates to the process for producing such a shape-processable composite material and its use to produce mouldings, e.g. packaging materials such as foils, bottles, jars, boxes and the like.
Description
- - 217~583 THERMOPLASTICALLY PROCESSABLE STARCH BASED COMPOSITE MATERIALS
The invention relates to a shapeable composite starch-based material which has been thermomechanically hydrolyzed in conventional manner - in the following referred to as TPS
- in homogenous mixture with selected synthetic thermoplastic polymer compositions - in the following referred to as SPV. The heart of the invention thereby resides in the selection of certain structural elements of these SPVs and of the amount thereof in the composite material relative to the starch portion.
Numerous proposals of recent years deal with the attempt to enlarge the range of applications of starch, a high molecular weight polymer composition of natural origin. These efforts are based on the conversion of natural starch together with limited amounts of water and/or further additives to a thermoplastic material by way of thermomechanical hydrolysis, which material can be shaped in conventional manner, for example, by injection molding or calendering. This thermomechanical hydrolysis at elevated temperature and pressure is especially possible in conventional extruders which are used in series before the shaping process step. Out of the extensive lile~ e, special reference is hereby made to the publication R.F.T. Stepto et al. Injection Moulding of Natural Hydrophilic Polymers in the Presence of Water, CHIMIA 41 (1987) Nr. 3, 76-81, and to the literature cited therein.
It is known in this context to facilitate the thermomechanical hydrolysis of starch and to improve the product properties of the TPS by using during hydrolysis selected organic additives of low molecular weight. For example, it is proposed to admix additives with the starch which lower the melting point of the starch. Known additives are especially lower polyfunctional alcohols such as ethyleneglycol, propyleneglycol, glycerin, 1,3butandiol, di-glyceride, corresponding ethers and further compositions such as urea.
Numerous proposals deal with the attempt to combine thermoplasticized starch with synthetically derived water-resistant polymeric compositions in such a way that the composite material has an increased resistance to water or hydrophilic solvents, whereby the starch forms a substantial portion of the material.
~1735~
EP-A2 327 505 discloses polymeric material mixtures which are derived from a melt of water-cont~ining destructurized starch and at least one essentially water-insoluble synthetic thermoplastic polymeric composition. The starch and admixed additives are first converted to the TPS and processed into granulates by treatment in an extruder at elevated temperatures.
The water content in the granulate particles is adjusted to about the water content range of natural starch (about 17 wt.-%). The starch granulate is then mixed in the dry condition and at a preselected mixing ratio with synthetic polymer compositions. Further proposals in the relevant field of thermoplastically processable starch-based polymer mixtures are found in EP-A1 0 400 431 and 0 400 532 and in PCT Application WO 90/10 671. The latter priorpublication includes especially extensive details on the mixing and thermoplastic hydrolysis in the presence of water and in suitable extruders of the polymeric starting compositions, and on the at least partial removal of water from the lllixlule, preferably during processing in the extruder.
Materials and/or shaped parts on the basis of thermomechanically hydrolyzed starch in admixture with synthetic thermoplastic polymeric compositions are the subject of DE 40 38 732. These polymer-modified materials are m~nllf~ctured by mixing native starch with aqueous polymer dispersions of the synthetic thermoplastic polymer compositions and, if desired, further plasticizers of low molecular weight; subjecting the multicomponent mixture to elevated temperature and pressure with simultaneous extensive mixing and/or kneading to hydrolyze the starch into thermoplastically processable starch; and, if desired, shaping the homogenized polymer mixture. The water portion which enters into the synthetic polymer compositions by way of the aqueous dispersions is an integral component of the starch hydrolysis process. Suitable, at least substantially water insoluble thermoplastic synthetic polymer compositions according to this proposal are, for example, emulsion-(co)-polymerisates such as polyvinylester, poly(meth)acrylate and/or corresponding copolymers.
Further named are polyester, polyamide and/or polyurethane resins, whereby thosethermoplastic polymer compositions are preferred which have polar groups and possibly combine with molecular components of marketly oleophilic character. The subject of -_ 2:173~8~
DE 41 21 111 are materials and/or shaped parts based on thermomechanically hydrolyzed starch and synthetic thermoplastic polymer compositions whereby synthetic mixture components are used which are made at least partly of base materials derived from renewable resources and are assigned to the class of polyesters and/or polyamines.
The further development described below takes the proposals of the two last mentioned publications DE 41 38 732 and DE 41 21 111 and modifies their teaching in the manner described below. In order to ensure complete and full disclosure of the invention, the disclosures of the two above-referenced applications of the applicant are explicitly made part of the disclosure of the present invention.
It is an object of the further development in accordance with the invention and described in the following to achieve a further optimisation of the properties of the composite material made of thermomechanically hydrolyzed starch (TPS) and the homogeneously admixedsynthetic polymer compositions (SPV). The goal of this optimisation in accordance with the invention is the optimum adjustment of the mechanical strength - determined as tensile strength according to DIN 53455. The concept of this object of the invention is based on the following facts:
The literature describes the capacity of starch to react with fat radicals thereby forming so called inclusion complexes. Non modified starch of natural origin is known to include the two major components of amylose and amylopektin. In starch raw materials of diverse origin which are especially inexpensive and available in large amounts, the amylose portion is the quantitively smaller portion and constitutes normally below about 30 wt.-%, generally in the range of about 20 to 25 wt.-% (wt.-% with respect to the dry matter). Typical representatives of these starch raw materials are the following examples - the respective mean value for amylose wt.-% TS (in brackets): potato starch (22), wheat starch (24), corn starch (21).
However, plant-derived starches are also known which have a significantly higher amylose content possibly as high as at least 50 wt.-%, 70 wt.-% or even 90 wt.-% of the dry matter.
_ 21735~3 -The capacity of the starch to form inclusion complexes with fat radicals is today attributed to the amylose portion in the starch. Fatty radicals are thereby saturated and unbranched hydrocarbon radicals of sufficient length. Corresponding fatty radicals accordingly preferably include at least 6 to 8 carbons atoms, preferably 10 or more carbon atoms in the unbranched saturated hydrocarbyl radical in order to provide for a sufficient complexing through interaction with starch components and formation of the inclusion complexes.
In numerous publications which relate to the production of thermoplastic starch, the use of fat derivatives is disclosed in addition to the joint processing of starch, synthetic polymers and plasticizers. However, the fat derivatives in those cases exclusively function as lubricants.
For example, WO 90/010 43 discloses the use of fats, waxes and paraffins as coding agents in the manufacture and processing of TPS. The use of fat as a lubricant in the manufacture of molded TPS-based parts is disclosed in DE 37 12 029. Hardened fats used as processing aids in the hydrolysis of destructurized starch-based polymeric materials is described in EP 404 727. Further reference to the combination of starch and fats is found in US 4,016117 and in DE 1 717 062. US 3,949145 describes the use of sorbitanmonooleate for the manufacture of agro-foils on the basis of a decomposable starch-based material.
Object of the Invention The te;lching~ of the invention are also based on the old object to provide thermoplastic materials which are mainly based on natural raw materials and especially include natural starch as an especially important component. These materials should be thermoplastically processable but distinguished - especially in the shaped form - by optimized strength. The invention thereby especially intends to show a way to m~int~in such optimized strength over a long period of time in the finished moulded product. Although the known aging of such starch-based composite polymer materials by turning brittle and the associated decrease in the mechanical strength cannot be completely prevented, this principally known defect of the TPS
based material mixtures disclosed to date should be largely alleviated. The teachings in accordance with the invention are especially intended to show a way of obtaining shaped parts lq~5~
with significantly improved form stability and made from starch-based materials of the described type.
The teachings in accordance with the invention thereby comply with the above-described object to m~int~in natural starch as the most important raw material portion in the material mixture. In an especially important embodiment, the teachings in accordance with the invention intend to ensure the practically complete decomposition or complete breakdown of the polymer material by biological processes.
The teachings in accordance with the invention are also based on the above-described instruction to plasticize natural starch in the known manner by thermomechanical hydrolysis using plasticizers, and to intim~tely mix it at the same time or at a different point in time with other thermoplastically processable polymer components so that homogenization of the composite materials takes place. In further preferred embodiments of the invention, the synthetic polymeric compositions which are also used as mixture components - in the following referred to SPV - are at least to a major proportion made of base materials from renewable resources.
In another preferred embodiment in accordance with the invention, the SPV components are added in the form of aqueous dispersions to the thermomechanical starch hydrolysis process as described in detail in DE 40 38 732. This allows an especially economical single-step process for the m~nllf;~cture of the below-described starch-based composite materials.
Subject of the Invention Subject of the invention is in a first embodiment a shapeable composite material - in the following occasionally referred to as VM - on the basis of thermomechanically hydrolyzed starch (TPS) with added water and/or plasticizers of low molecular weight and inhomogeneous admixture with synthetic polymer compositions (SPV).
_ 2173~83 The teachings in accordance with the invention are distinguished in that in order to optimize the mechanical strength of the VM - as determined by its tensile strength according to DIN
53455 - the combination of the following parameters is maintained:
Corresponding thermoplastically processable polymer compositions with lateral and/or terminal unbranched saturated carbohydrate groups - in the following referred to as fatty radicals - are used as the SPV component;
The fatty radical substituted SPVs are thereby homogenized with the TPS in such amounts that the fatty radical content of the composite material (wt.-% fatty radicals relative to the water-free starch) lies within the range of 0.5 to 7 wt.-%. Preferred ranges for the weight ratio of fatty radical to starch lie within the range of 1 to 5 wt.-% and especially in the range of about 2 to 4 wt.-%.
In a further embodiment, the teachings in accordance with the invention relate to the use of these thermoplastically processable TPS/SPV-based composite materials, having selected and exact weight ratios of fatty radicals in the SPV, for the manufacture of shaped products, for example, for use as packaging materials such as foils, bottles, cups, boxes and the like.
Finally the teachings in accordance with the invention relate to a process for the manufacture of TPS-based polymer-modified materials and shaped products obtained therefrom in accordance with the above-provided definitions.
Details Of The Teachin~s In Accordance With The Invention The goal of the teachings in accordance with the invention is based in its broadest but simultaneously most concrete concept on the intention to achieve a controlled interaction between the TPS and the SPV by selection and adjustment of a specific structural parameter of the synthetic polymeric compositions (SPV) used for processing together with the starch.
The invention thereby provides the possibility of optimi~ing the mechanical strength of the composite material by selecting the type and amount of the fatty radicals substituents of the SPV relative to the starch portion in the composite material. The individual SPV molecule is thereby distinguished by the presence of a multitude of fatty radicals substituents according to the definition in accordance with the invention. The resulting optimization of the mechanical strength is probably due to the optimal ratio of the relative amounts of the reactive fatty radical substituents to the amylose portions of the starch material and to the reaction of these two groups with one another thereby forming corresponding inclusion complexes. In keeping with this basic nucleus of the process in accordance with the invention, a multitude of variations and a further optimization can be carried out especially in the selection of the respectively used SPV components, in the selection of the additive components for the thermomechanical starch hydrolysis and/or in the process steps for the combination and homogenization of SPV/TPS. The SPVs which are used together with the starch in the process in accordance with the invention are thermoplastically processable polymer components with a principally known mainly linear basic structure. Their molecular weights can vary widely. Appropriate values for the molecular weights lie, for example, in the range of 1.5 x 103 to 10 x 106, whereby preferred lower limits for the molecular weight of these SPV components lie in the range of about 2 to 5 x 103. The SPV components in accordance with the teachings of the invention are consistently distinguished by the presence of a sufficient number of lateral and/or t~rmin~l fatty radicals. The term fatty radical is thereby understood to represent unbranched and saturated hydrocarbon residues with at least 6 carbon atoms, preferably at least 8 carbon atoms. It has been found that the strength of the composite material can be optimized by increasing the length of the carbon chain of the fatty radical so that preferred radicals on average have at least 10 and preferable at least 12 carbon atoms. The respectively used SPV can thereby include the same or different types of these fatty radicals. The preferred ranges for the chain length of these unbranched fatty radicals are 6 to 32 carbon atoms and especially 10 to 24 carbon atoms. The range of about 12 to 18 carbon atoms in at least a substantial portion of the fatty radical substituents present at the SPV can have special significance.
--- 217358~
In this context, the following characteristics must be emph~ci7e~1 The substituents on the especially unbranched basic molecule of the SPV component can also be olefinically mono- and/or poly-unsaturated longer hydrocarbon radicals as often found in materials based on natural substances. For example, olefinically unsaturated C~6-, C~8-, or even higher correspondingly olefinically unsaturated hydrocarbon radicals can be suitable substituents. However, with respect to the mechanical strengthening effect, obviously only the terminal aliphatically unsaturated portion of such an olefinically unsaturated substituent interacts with the starch to form channel-including compositions. The solidifying effect of such substituents of the SPV and thereby the adjustable increase of the physical strength is then limited to the lower carbon number range of the terminal aliphatically unsaturated portion of such substituents. It can be correspondingly preferred in accordance with the invention to select at least a major portion of the fatty radicals on the SPV from aliphatically unsaturated fatty radicals of higher carbon number.
In accordance with the invention, it is further preferred that the starch constitutes at least 40 wt.-% and preferably at least 50 wt.-% of the TPS/SPV based composite material - wt.-%
with respect to the solid material mixture free of low molecular weight plasticizers and water.
Normally, the starch portion of the composite material is about 50 to 80 wt.-% and preferably about 55 to 75 wt.-% - wt.-% is calculated as indicated above.
As stated above, the preferred starches in accordance with the invention are those economically available starch materials which have a limited amylose content below 30 wt.-%
and preferably within the range of about 15 to 25 wt.-% - wt.-% here is in relation to dry matter of starch. The already mentioned starch raw materials derived from potatoes, wheat and/or corn with the already mentioned parameters detennining the amylose content are preferred starting materials for the process in accordance with the invention. The invention is however not limited to these starches. Amylose-rich starches are also appro~fiate starting materials. In fact, when they are used, products can be obtained which are distinguished by even further improved physical properties, for example, by further improved structural stability of the shaped products made, for example, by injection moulding. The use of 2173~83 starches having an amylose content of at least 50 wt.-%, for example, about 65 to 95 wt.-%, and especially from about 70 to 90 wt.-% also falls within the scope of the teachings of the invention.
Principally, all polymers of this type are suitable as fatty radical - substituted SPV
components whereby the biologically decomposable or compostable compositions of this type are especially preferred. In this sense, SPVs of the type of fatty radical cont~ining acrylate and/or methacrylate polymers are applopl;ate and especially fatty radical side groups including SPVs from the field of polyesters, polyamides, polyurethanes and/or polyvinylalcohol esters, which include long chain fatty radicals in at least part of their ester groups. One can here refer to the pertinent knowledge on the constitution and manufacture of the corresponding polymer components with lateral and/or terminal fatty radical groups. In a special embodiment, once again those SPV-types are suitable which are at least partly made from renewable raw materials. The corresponding instructions for the classes of polyester, polyamide and/or polyurethane compounds are found in DE 41 21 111 which has beenincorporated into this disclosure. In the field of PVA-derivatives, this element of the invention can be complied with by using fatty acids of natural origin, for example, corresponding esters of carbonic acids with 10 to 24 carbon atoms, especially with 12 to 22 carbon atoms. In an important embodiment, such fatty radicals can be present in the PVA
based polymer in admixture with radicals of shorter carbonic acid chains, for example, C2 4-carbonic acids. Especially suited representatives thereof are PVAc-types modified with longer-chain fatty acid esters - copolymers of vinyl acetate and monomers of vinyl alcohol esters with longer-chain fatty acids (for example, C~2 l8-fatty acids). The fatty radicals can thereby be present in minor amounts relative to the total number of the acid radicals.
Wholely vinyl alcohol-based esters which include at least a portion of fatty radicals according to the definition in accordance to the invention - especially from the acid groups used for ester formation - can have a special importance because of the following aspects: It has been shown that corresponding mixtures of TPS/SPV can be of special importance in the shaping process. Foils as well as shaped products of higher material thickness, such as bottles, cups - ~173~83 -etc., and with good product characteristics can be manufactured according to principally known processes. At the same time, it is known that the quantitative microbiological breakdown of SPVs based on esters of PVA - illustrated by way of the example of polyvinyl acetate - takes place especially quickly and completely, not only with respect to the ester splitting and breakdown of the acid component but also with respect to the polyvinyl alcohol molecule formed - see the publication by H. Kastien et al. "Der quantitative mikro-biologische Abbau von Lackkunstharzen und Polymerdispersionen", Farbe & Lack, 1992, 505-508. Thus, by selecting corresponding completely microbiologically decomposable components in accordance with the invention on the part of the SPV, a simultaneous optimization of the structural strength of the shaped product and of the degradation by natural decomposition processes can be insured.
The teachings of the invention used in an important embodiment the elements of DE 40 38 732 included into the present disclosure. Correspondingly, the SPV which are substituted with fatty radicals according to the present teachings can be used in the form of aqueous dispersions which are combined together with the aqueous phase with the starch to be processed to the thermoplastic condition. If desired, further required low molecular weight plasticizers are admixed. The m~mlf~cture of the finished composite materials is then achieved by subjecting the multiple component mixture to an elevated temperature and pressure, simultaneously intensively mixing and/or kneading the mixture during starch hydrolysis to form the composite material of TPS/SPV and, if desired, shaping the homogenized polymer mixture. The water portion introduced by way of the aqueous SPV
dispersion here becomes an integral part of the process which part is used in the starch hydrolysis and effective in breaking down the starch.
In accordance with the invention, the thermomechanical hydrolysis of starch to athermoplastic material as previously known requires the use of water and/or lower organic softeners and/or additives. Especially lower polyfunctional alcohols such as ethylene glycol, propylene glycol, butanediol, glycerine and/or their esters, especially partial esters, are appropriate. The use of urea as one of the additives of concern here is also known and can ~1 73583 -be exploited in accordance with the invention. The relative amount of water in the mixture to be processed can be, for example, in the range of 5 to 40 wt.-%, preferably 5 to 30 wt.-% -wt.-% is relative to the whole mixture. The relative amount of the also used low molecular weight organic additives such as glycerine is usually at least about 3 wt.-%, more suitably in the range of at least about 5 to 10 wt.-% and especially at about 10 to 50 wt.% - again relative to the whole mixture.
The individual components of the mixture can be fed separately and preferably continuously to the input area of the respectively used apparatus, for example, the extruder, and in the respectively required amount. Especially the desired homogenizing and mixing takes place in the upstream portions of the extruder and during the transport of the multi component mixture in the extruder. A processing portion follows which is m~int~ined at product temperatures and pressures which result in the desired thermomechanical hydrolysis of the starch. The product temperature lies here above at least 100C and preferably at or above 120C, whereby process conditions in that area of up to about 170C and at least in the final phases of the mixing and starch hydrolysis can be preferred. The resulting working pressure usually corresponds to the internal pressure of the water-cont~inin~ component mixture at the respective working temperature. The residence times of the multi-component mixture under these working conditions are generally not higher then at most about 30 minutes, preferably at most about 20 minutes. It may be expedient to operate with mixture residue times of about 0.5 to 10 minutes, preferably in the range of about 2 to 5 minutes at least in the area where the elevated temperature and pleS~ule conditions required for starch hydrolysis are present.
The homogenized polymer blend can be obtained as an extrudate and subjected at a later point in time, for example, to a molding process. However, it is also possible to subject the mixed polymers produced to a molding operation immediately subsequent to its production as described for pure thermoplasticized starch in the above cited publication in CHIMIA (1987) supra.
-^ 21735~
-Prior to the molding process and usually in the end stage of the hydrolysis in the extruder at least a portion of the water added for mixing and hydrolysis is removed. It is principally accepted that starch based materials, when stored under ambient conditions, will automatically reach the natural water content of starch which is known to be in the range of 15 to 20 wt.-%
- relative to the amount of starch.
For details of the hydrolysis process reference is once again made to the repeatedly cited patents DE 40 38 732 and DE 41 21 l l l .
The following general information applies to the apparatus and raw materials used in the examples below:
a) Apparatus The production of TPS (thermoplastic starch)-blends requires the following process steps:
- conveying in an extruder the components which are present in the form of a liquid, dispersion, granulate, or powder;
- compressing the extrusion mass to a compact solid material;
- melting of the extrusion mass;
- homogenization of the melt;
- pumping of the melt through an extrusion die.
Principally suitable for this process are worm extruders of various constructions, for example, single worm extruders or parallel or counter-rotating dual worm extruders. Because of the advantages of - self cleaning of the worm - narrow residence times spectrum - even product loading ~173~
as known from the literature (see Handbuch der Kunststoffextrusionstechnik, Band l, Hanser-Verlag, 1989), a parallel, dual worm extruder with the following characteristics has been used in the following examples:
- type Continua C37, manufacturer Werner & Pfleiderer - power input 7.6 KW
- length of the worms 960 mm - L~D ratio 26.
Conveying, plastifying, homogenizing, pressurizing and degassing zones were realized with a component system of worms and housings. Furthermore, the worm housing was separated into two independently controllable heating zones of equal length. Input of the liquid or solid components was achieved by way of gravimetrically controlled dosing units (Schenck Company). In general, the following extrusion parameters were used:
- temperature lO0 - 150C
- worm rotation speed lO0 rpm - total throughput 6 - 18 kg/h b) Raw Materials The following raw materials were used for the manufacture of TPS-Blends on the basis of starch/SPV:
- potatoe starch (for example Sudstarke GmbH or Emsland-Starke) with a water content of 17 - 20%, or wheat starch with a water content of lO - 15%.
- fatty radical substituted synthetic polymer compositions (SPV) according to the specific definition respectively provided below.
The invention relates to a shapeable composite starch-based material which has been thermomechanically hydrolyzed in conventional manner - in the following referred to as TPS
- in homogenous mixture with selected synthetic thermoplastic polymer compositions - in the following referred to as SPV. The heart of the invention thereby resides in the selection of certain structural elements of these SPVs and of the amount thereof in the composite material relative to the starch portion.
Numerous proposals of recent years deal with the attempt to enlarge the range of applications of starch, a high molecular weight polymer composition of natural origin. These efforts are based on the conversion of natural starch together with limited amounts of water and/or further additives to a thermoplastic material by way of thermomechanical hydrolysis, which material can be shaped in conventional manner, for example, by injection molding or calendering. This thermomechanical hydrolysis at elevated temperature and pressure is especially possible in conventional extruders which are used in series before the shaping process step. Out of the extensive lile~ e, special reference is hereby made to the publication R.F.T. Stepto et al. Injection Moulding of Natural Hydrophilic Polymers in the Presence of Water, CHIMIA 41 (1987) Nr. 3, 76-81, and to the literature cited therein.
It is known in this context to facilitate the thermomechanical hydrolysis of starch and to improve the product properties of the TPS by using during hydrolysis selected organic additives of low molecular weight. For example, it is proposed to admix additives with the starch which lower the melting point of the starch. Known additives are especially lower polyfunctional alcohols such as ethyleneglycol, propyleneglycol, glycerin, 1,3butandiol, di-glyceride, corresponding ethers and further compositions such as urea.
Numerous proposals deal with the attempt to combine thermoplasticized starch with synthetically derived water-resistant polymeric compositions in such a way that the composite material has an increased resistance to water or hydrophilic solvents, whereby the starch forms a substantial portion of the material.
~1735~
EP-A2 327 505 discloses polymeric material mixtures which are derived from a melt of water-cont~ining destructurized starch and at least one essentially water-insoluble synthetic thermoplastic polymeric composition. The starch and admixed additives are first converted to the TPS and processed into granulates by treatment in an extruder at elevated temperatures.
The water content in the granulate particles is adjusted to about the water content range of natural starch (about 17 wt.-%). The starch granulate is then mixed in the dry condition and at a preselected mixing ratio with synthetic polymer compositions. Further proposals in the relevant field of thermoplastically processable starch-based polymer mixtures are found in EP-A1 0 400 431 and 0 400 532 and in PCT Application WO 90/10 671. The latter priorpublication includes especially extensive details on the mixing and thermoplastic hydrolysis in the presence of water and in suitable extruders of the polymeric starting compositions, and on the at least partial removal of water from the lllixlule, preferably during processing in the extruder.
Materials and/or shaped parts on the basis of thermomechanically hydrolyzed starch in admixture with synthetic thermoplastic polymeric compositions are the subject of DE 40 38 732. These polymer-modified materials are m~nllf~ctured by mixing native starch with aqueous polymer dispersions of the synthetic thermoplastic polymer compositions and, if desired, further plasticizers of low molecular weight; subjecting the multicomponent mixture to elevated temperature and pressure with simultaneous extensive mixing and/or kneading to hydrolyze the starch into thermoplastically processable starch; and, if desired, shaping the homogenized polymer mixture. The water portion which enters into the synthetic polymer compositions by way of the aqueous dispersions is an integral component of the starch hydrolysis process. Suitable, at least substantially water insoluble thermoplastic synthetic polymer compositions according to this proposal are, for example, emulsion-(co)-polymerisates such as polyvinylester, poly(meth)acrylate and/or corresponding copolymers.
Further named are polyester, polyamide and/or polyurethane resins, whereby thosethermoplastic polymer compositions are preferred which have polar groups and possibly combine with molecular components of marketly oleophilic character. The subject of -_ 2:173~8~
DE 41 21 111 are materials and/or shaped parts based on thermomechanically hydrolyzed starch and synthetic thermoplastic polymer compositions whereby synthetic mixture components are used which are made at least partly of base materials derived from renewable resources and are assigned to the class of polyesters and/or polyamines.
The further development described below takes the proposals of the two last mentioned publications DE 41 38 732 and DE 41 21 111 and modifies their teaching in the manner described below. In order to ensure complete and full disclosure of the invention, the disclosures of the two above-referenced applications of the applicant are explicitly made part of the disclosure of the present invention.
It is an object of the further development in accordance with the invention and described in the following to achieve a further optimisation of the properties of the composite material made of thermomechanically hydrolyzed starch (TPS) and the homogeneously admixedsynthetic polymer compositions (SPV). The goal of this optimisation in accordance with the invention is the optimum adjustment of the mechanical strength - determined as tensile strength according to DIN 53455. The concept of this object of the invention is based on the following facts:
The literature describes the capacity of starch to react with fat radicals thereby forming so called inclusion complexes. Non modified starch of natural origin is known to include the two major components of amylose and amylopektin. In starch raw materials of diverse origin which are especially inexpensive and available in large amounts, the amylose portion is the quantitively smaller portion and constitutes normally below about 30 wt.-%, generally in the range of about 20 to 25 wt.-% (wt.-% with respect to the dry matter). Typical representatives of these starch raw materials are the following examples - the respective mean value for amylose wt.-% TS (in brackets): potato starch (22), wheat starch (24), corn starch (21).
However, plant-derived starches are also known which have a significantly higher amylose content possibly as high as at least 50 wt.-%, 70 wt.-% or even 90 wt.-% of the dry matter.
_ 21735~3 -The capacity of the starch to form inclusion complexes with fat radicals is today attributed to the amylose portion in the starch. Fatty radicals are thereby saturated and unbranched hydrocarbon radicals of sufficient length. Corresponding fatty radicals accordingly preferably include at least 6 to 8 carbons atoms, preferably 10 or more carbon atoms in the unbranched saturated hydrocarbyl radical in order to provide for a sufficient complexing through interaction with starch components and formation of the inclusion complexes.
In numerous publications which relate to the production of thermoplastic starch, the use of fat derivatives is disclosed in addition to the joint processing of starch, synthetic polymers and plasticizers. However, the fat derivatives in those cases exclusively function as lubricants.
For example, WO 90/010 43 discloses the use of fats, waxes and paraffins as coding agents in the manufacture and processing of TPS. The use of fat as a lubricant in the manufacture of molded TPS-based parts is disclosed in DE 37 12 029. Hardened fats used as processing aids in the hydrolysis of destructurized starch-based polymeric materials is described in EP 404 727. Further reference to the combination of starch and fats is found in US 4,016117 and in DE 1 717 062. US 3,949145 describes the use of sorbitanmonooleate for the manufacture of agro-foils on the basis of a decomposable starch-based material.
Object of the Invention The te;lching~ of the invention are also based on the old object to provide thermoplastic materials which are mainly based on natural raw materials and especially include natural starch as an especially important component. These materials should be thermoplastically processable but distinguished - especially in the shaped form - by optimized strength. The invention thereby especially intends to show a way to m~int~in such optimized strength over a long period of time in the finished moulded product. Although the known aging of such starch-based composite polymer materials by turning brittle and the associated decrease in the mechanical strength cannot be completely prevented, this principally known defect of the TPS
based material mixtures disclosed to date should be largely alleviated. The teachings in accordance with the invention are especially intended to show a way of obtaining shaped parts lq~5~
with significantly improved form stability and made from starch-based materials of the described type.
The teachings in accordance with the invention thereby comply with the above-described object to m~int~in natural starch as the most important raw material portion in the material mixture. In an especially important embodiment, the teachings in accordance with the invention intend to ensure the practically complete decomposition or complete breakdown of the polymer material by biological processes.
The teachings in accordance with the invention are also based on the above-described instruction to plasticize natural starch in the known manner by thermomechanical hydrolysis using plasticizers, and to intim~tely mix it at the same time or at a different point in time with other thermoplastically processable polymer components so that homogenization of the composite materials takes place. In further preferred embodiments of the invention, the synthetic polymeric compositions which are also used as mixture components - in the following referred to SPV - are at least to a major proportion made of base materials from renewable resources.
In another preferred embodiment in accordance with the invention, the SPV components are added in the form of aqueous dispersions to the thermomechanical starch hydrolysis process as described in detail in DE 40 38 732. This allows an especially economical single-step process for the m~nllf;~cture of the below-described starch-based composite materials.
Subject of the Invention Subject of the invention is in a first embodiment a shapeable composite material - in the following occasionally referred to as VM - on the basis of thermomechanically hydrolyzed starch (TPS) with added water and/or plasticizers of low molecular weight and inhomogeneous admixture with synthetic polymer compositions (SPV).
_ 2173~83 The teachings in accordance with the invention are distinguished in that in order to optimize the mechanical strength of the VM - as determined by its tensile strength according to DIN
53455 - the combination of the following parameters is maintained:
Corresponding thermoplastically processable polymer compositions with lateral and/or terminal unbranched saturated carbohydrate groups - in the following referred to as fatty radicals - are used as the SPV component;
The fatty radical substituted SPVs are thereby homogenized with the TPS in such amounts that the fatty radical content of the composite material (wt.-% fatty radicals relative to the water-free starch) lies within the range of 0.5 to 7 wt.-%. Preferred ranges for the weight ratio of fatty radical to starch lie within the range of 1 to 5 wt.-% and especially in the range of about 2 to 4 wt.-%.
In a further embodiment, the teachings in accordance with the invention relate to the use of these thermoplastically processable TPS/SPV-based composite materials, having selected and exact weight ratios of fatty radicals in the SPV, for the manufacture of shaped products, for example, for use as packaging materials such as foils, bottles, cups, boxes and the like.
Finally the teachings in accordance with the invention relate to a process for the manufacture of TPS-based polymer-modified materials and shaped products obtained therefrom in accordance with the above-provided definitions.
Details Of The Teachin~s In Accordance With The Invention The goal of the teachings in accordance with the invention is based in its broadest but simultaneously most concrete concept on the intention to achieve a controlled interaction between the TPS and the SPV by selection and adjustment of a specific structural parameter of the synthetic polymeric compositions (SPV) used for processing together with the starch.
The invention thereby provides the possibility of optimi~ing the mechanical strength of the composite material by selecting the type and amount of the fatty radicals substituents of the SPV relative to the starch portion in the composite material. The individual SPV molecule is thereby distinguished by the presence of a multitude of fatty radicals substituents according to the definition in accordance with the invention. The resulting optimization of the mechanical strength is probably due to the optimal ratio of the relative amounts of the reactive fatty radical substituents to the amylose portions of the starch material and to the reaction of these two groups with one another thereby forming corresponding inclusion complexes. In keeping with this basic nucleus of the process in accordance with the invention, a multitude of variations and a further optimization can be carried out especially in the selection of the respectively used SPV components, in the selection of the additive components for the thermomechanical starch hydrolysis and/or in the process steps for the combination and homogenization of SPV/TPS. The SPVs which are used together with the starch in the process in accordance with the invention are thermoplastically processable polymer components with a principally known mainly linear basic structure. Their molecular weights can vary widely. Appropriate values for the molecular weights lie, for example, in the range of 1.5 x 103 to 10 x 106, whereby preferred lower limits for the molecular weight of these SPV components lie in the range of about 2 to 5 x 103. The SPV components in accordance with the teachings of the invention are consistently distinguished by the presence of a sufficient number of lateral and/or t~rmin~l fatty radicals. The term fatty radical is thereby understood to represent unbranched and saturated hydrocarbon residues with at least 6 carbon atoms, preferably at least 8 carbon atoms. It has been found that the strength of the composite material can be optimized by increasing the length of the carbon chain of the fatty radical so that preferred radicals on average have at least 10 and preferable at least 12 carbon atoms. The respectively used SPV can thereby include the same or different types of these fatty radicals. The preferred ranges for the chain length of these unbranched fatty radicals are 6 to 32 carbon atoms and especially 10 to 24 carbon atoms. The range of about 12 to 18 carbon atoms in at least a substantial portion of the fatty radical substituents present at the SPV can have special significance.
--- 217358~
In this context, the following characteristics must be emph~ci7e~1 The substituents on the especially unbranched basic molecule of the SPV component can also be olefinically mono- and/or poly-unsaturated longer hydrocarbon radicals as often found in materials based on natural substances. For example, olefinically unsaturated C~6-, C~8-, or even higher correspondingly olefinically unsaturated hydrocarbon radicals can be suitable substituents. However, with respect to the mechanical strengthening effect, obviously only the terminal aliphatically unsaturated portion of such an olefinically unsaturated substituent interacts with the starch to form channel-including compositions. The solidifying effect of such substituents of the SPV and thereby the adjustable increase of the physical strength is then limited to the lower carbon number range of the terminal aliphatically unsaturated portion of such substituents. It can be correspondingly preferred in accordance with the invention to select at least a major portion of the fatty radicals on the SPV from aliphatically unsaturated fatty radicals of higher carbon number.
In accordance with the invention, it is further preferred that the starch constitutes at least 40 wt.-% and preferably at least 50 wt.-% of the TPS/SPV based composite material - wt.-%
with respect to the solid material mixture free of low molecular weight plasticizers and water.
Normally, the starch portion of the composite material is about 50 to 80 wt.-% and preferably about 55 to 75 wt.-% - wt.-% is calculated as indicated above.
As stated above, the preferred starches in accordance with the invention are those economically available starch materials which have a limited amylose content below 30 wt.-%
and preferably within the range of about 15 to 25 wt.-% - wt.-% here is in relation to dry matter of starch. The already mentioned starch raw materials derived from potatoes, wheat and/or corn with the already mentioned parameters detennining the amylose content are preferred starting materials for the process in accordance with the invention. The invention is however not limited to these starches. Amylose-rich starches are also appro~fiate starting materials. In fact, when they are used, products can be obtained which are distinguished by even further improved physical properties, for example, by further improved structural stability of the shaped products made, for example, by injection moulding. The use of 2173~83 starches having an amylose content of at least 50 wt.-%, for example, about 65 to 95 wt.-%, and especially from about 70 to 90 wt.-% also falls within the scope of the teachings of the invention.
Principally, all polymers of this type are suitable as fatty radical - substituted SPV
components whereby the biologically decomposable or compostable compositions of this type are especially preferred. In this sense, SPVs of the type of fatty radical cont~ining acrylate and/or methacrylate polymers are applopl;ate and especially fatty radical side groups including SPVs from the field of polyesters, polyamides, polyurethanes and/or polyvinylalcohol esters, which include long chain fatty radicals in at least part of their ester groups. One can here refer to the pertinent knowledge on the constitution and manufacture of the corresponding polymer components with lateral and/or terminal fatty radical groups. In a special embodiment, once again those SPV-types are suitable which are at least partly made from renewable raw materials. The corresponding instructions for the classes of polyester, polyamide and/or polyurethane compounds are found in DE 41 21 111 which has beenincorporated into this disclosure. In the field of PVA-derivatives, this element of the invention can be complied with by using fatty acids of natural origin, for example, corresponding esters of carbonic acids with 10 to 24 carbon atoms, especially with 12 to 22 carbon atoms. In an important embodiment, such fatty radicals can be present in the PVA
based polymer in admixture with radicals of shorter carbonic acid chains, for example, C2 4-carbonic acids. Especially suited representatives thereof are PVAc-types modified with longer-chain fatty acid esters - copolymers of vinyl acetate and monomers of vinyl alcohol esters with longer-chain fatty acids (for example, C~2 l8-fatty acids). The fatty radicals can thereby be present in minor amounts relative to the total number of the acid radicals.
Wholely vinyl alcohol-based esters which include at least a portion of fatty radicals according to the definition in accordance to the invention - especially from the acid groups used for ester formation - can have a special importance because of the following aspects: It has been shown that corresponding mixtures of TPS/SPV can be of special importance in the shaping process. Foils as well as shaped products of higher material thickness, such as bottles, cups - ~173~83 -etc., and with good product characteristics can be manufactured according to principally known processes. At the same time, it is known that the quantitative microbiological breakdown of SPVs based on esters of PVA - illustrated by way of the example of polyvinyl acetate - takes place especially quickly and completely, not only with respect to the ester splitting and breakdown of the acid component but also with respect to the polyvinyl alcohol molecule formed - see the publication by H. Kastien et al. "Der quantitative mikro-biologische Abbau von Lackkunstharzen und Polymerdispersionen", Farbe & Lack, 1992, 505-508. Thus, by selecting corresponding completely microbiologically decomposable components in accordance with the invention on the part of the SPV, a simultaneous optimization of the structural strength of the shaped product and of the degradation by natural decomposition processes can be insured.
The teachings of the invention used in an important embodiment the elements of DE 40 38 732 included into the present disclosure. Correspondingly, the SPV which are substituted with fatty radicals according to the present teachings can be used in the form of aqueous dispersions which are combined together with the aqueous phase with the starch to be processed to the thermoplastic condition. If desired, further required low molecular weight plasticizers are admixed. The m~mlf~cture of the finished composite materials is then achieved by subjecting the multiple component mixture to an elevated temperature and pressure, simultaneously intensively mixing and/or kneading the mixture during starch hydrolysis to form the composite material of TPS/SPV and, if desired, shaping the homogenized polymer mixture. The water portion introduced by way of the aqueous SPV
dispersion here becomes an integral part of the process which part is used in the starch hydrolysis and effective in breaking down the starch.
In accordance with the invention, the thermomechanical hydrolysis of starch to athermoplastic material as previously known requires the use of water and/or lower organic softeners and/or additives. Especially lower polyfunctional alcohols such as ethylene glycol, propylene glycol, butanediol, glycerine and/or their esters, especially partial esters, are appropriate. The use of urea as one of the additives of concern here is also known and can ~1 73583 -be exploited in accordance with the invention. The relative amount of water in the mixture to be processed can be, for example, in the range of 5 to 40 wt.-%, preferably 5 to 30 wt.-% -wt.-% is relative to the whole mixture. The relative amount of the also used low molecular weight organic additives such as glycerine is usually at least about 3 wt.-%, more suitably in the range of at least about 5 to 10 wt.-% and especially at about 10 to 50 wt.% - again relative to the whole mixture.
The individual components of the mixture can be fed separately and preferably continuously to the input area of the respectively used apparatus, for example, the extruder, and in the respectively required amount. Especially the desired homogenizing and mixing takes place in the upstream portions of the extruder and during the transport of the multi component mixture in the extruder. A processing portion follows which is m~int~ined at product temperatures and pressures which result in the desired thermomechanical hydrolysis of the starch. The product temperature lies here above at least 100C and preferably at or above 120C, whereby process conditions in that area of up to about 170C and at least in the final phases of the mixing and starch hydrolysis can be preferred. The resulting working pressure usually corresponds to the internal pressure of the water-cont~inin~ component mixture at the respective working temperature. The residence times of the multi-component mixture under these working conditions are generally not higher then at most about 30 minutes, preferably at most about 20 minutes. It may be expedient to operate with mixture residue times of about 0.5 to 10 minutes, preferably in the range of about 2 to 5 minutes at least in the area where the elevated temperature and pleS~ule conditions required for starch hydrolysis are present.
The homogenized polymer blend can be obtained as an extrudate and subjected at a later point in time, for example, to a molding process. However, it is also possible to subject the mixed polymers produced to a molding operation immediately subsequent to its production as described for pure thermoplasticized starch in the above cited publication in CHIMIA (1987) supra.
-^ 21735~
-Prior to the molding process and usually in the end stage of the hydrolysis in the extruder at least a portion of the water added for mixing and hydrolysis is removed. It is principally accepted that starch based materials, when stored under ambient conditions, will automatically reach the natural water content of starch which is known to be in the range of 15 to 20 wt.-%
- relative to the amount of starch.
For details of the hydrolysis process reference is once again made to the repeatedly cited patents DE 40 38 732 and DE 41 21 l l l .
The following general information applies to the apparatus and raw materials used in the examples below:
a) Apparatus The production of TPS (thermoplastic starch)-blends requires the following process steps:
- conveying in an extruder the components which are present in the form of a liquid, dispersion, granulate, or powder;
- compressing the extrusion mass to a compact solid material;
- melting of the extrusion mass;
- homogenization of the melt;
- pumping of the melt through an extrusion die.
Principally suitable for this process are worm extruders of various constructions, for example, single worm extruders or parallel or counter-rotating dual worm extruders. Because of the advantages of - self cleaning of the worm - narrow residence times spectrum - even product loading ~173~
as known from the literature (see Handbuch der Kunststoffextrusionstechnik, Band l, Hanser-Verlag, 1989), a parallel, dual worm extruder with the following characteristics has been used in the following examples:
- type Continua C37, manufacturer Werner & Pfleiderer - power input 7.6 KW
- length of the worms 960 mm - L~D ratio 26.
Conveying, plastifying, homogenizing, pressurizing and degassing zones were realized with a component system of worms and housings. Furthermore, the worm housing was separated into two independently controllable heating zones of equal length. Input of the liquid or solid components was achieved by way of gravimetrically controlled dosing units (Schenck Company). In general, the following extrusion parameters were used:
- temperature lO0 - 150C
- worm rotation speed lO0 rpm - total throughput 6 - 18 kg/h b) Raw Materials The following raw materials were used for the manufacture of TPS-Blends on the basis of starch/SPV:
- potatoe starch (for example Sudstarke GmbH or Emsland-Starke) with a water content of 17 - 20%, or wheat starch with a water content of lO - 15%.
- fatty radical substituted synthetic polymer compositions (SPV) according to the specific definition respectively provided below.
2 17358~
- polyols with a boiling point of at least 150C were used as plasticizers such as propylene glycol or, preferably, glycerine, and, if required, further additives such as urea and/or derivatives thereof.
Example 1 The dependency of the strength characteristics of TSP/SPV-blends on the fatty radicals content of the respectively used SPV component in accordance with the invention is examined by way of the following exemplary prepalalions which are labelled with experiment numbers 1 to9.
Three related polymer types are subjected to homogenization with starch as part of the thermomechanical hydrolysis:
Experiments 1, 4 and 7:
Aqueous polyvinyl acetate dispersion which is subjected, in accordance with the teachings of DE 40 38 732 and jointly with potatoe starch and a low molecular weight plasticizer (especially glycerine) to an extrusion and the thermomechanical hydrolysis associated therewith.
Experiments 2, 5 and 8:
Instead of the aqueous PVAc-dispersion a comparable dispersion of a copolymer of vinyl acetate (VAc) and vinyllaureate (VL) having a VAc: VL mole ratio of 50: 2.5 is used. The synthetic polymer component used here includes as lateral substituents and in fixed distribution the long chain alkyl residues of the vinyllaureate component. Correspondingly, the biological breakdown of this polymer and, thus, its decomposability is ensured.
Experiments 3, 6 and 9:
The synthetic polymer type used for ~(lmixing with the starch and for the thermomechanical hydrolysis corresponds to the one used in experiments 2, 5 and 8, however, with the modification that the mole ratio of VAc: VL is shifted to the value of 47.8: 5Ø
The type and amount of the mixture components are shown below in Table 1 for theexperiment groups which are combined in the groups of three of 1 to 3, 4 to 6 and 7 to 9.
Table 1 Experiment Sta~ch PVAc P(VAc-co-VL) P(VAc-co-VL) Urea Glycerin Water No. wt.-% wt.-%VAc:VL=50:2.5VAc:VL=47.8:5.0 wt.-% wt.-% wt.-%
wt.-% wt.-%
18.3 - - - 16.7 25 2 40 - 18.3 - - 16.7 25 3 40 - - 18.3 - 16.7 25 4 40 20.4 - - 5.6 7.4 26.7 - 20.4 - 5.6 7.4 26.7 6 40 - - 20.4 5.6 7.4 26.7 7 36.9 21.2 - - 11.5 3.9 26.5 8 36.9 - 21.2 - 11.5 3.9 26.5 9 36.9 - - 21.2 11.5 3.9 26.5 217 ~583 Table 2 below lists for experiment numbers 1 to 9 the calculated numerical values of the ratio of "starch:polymer" in parts per weight, of the ratio "starch:fat (according to the definition in accordance with the invention)", and of the "fat content (according to the definition in accordance with the invention)" in the polymer in weight percent.
The tensile strength in N/mm2 according to DIN 53455 (testing speed 20 mm/min.) associated with the respective experiment numbers is shown in the last column of Table 2.
Table 2 Experiment Starch :PolymerStarch : "Fat""Fat" in the Tensile No. Polymer Strength wt.-% N/mm2 68.6 31.4 100 0 0 5.8 2 68.6 31.4 97.9 2.1 4.8 7.4 3 68.6 31.4 95.8 4.2 9.5 6.0 4 66.2 33.8 100 0 0 15.3 66.2 33.8 97.6 2.4 4.8 19.7 6 66.2 33.8 95.4 4.6 9.5 14.9 7 63.5 36.5 100 0 0 5.1 8 63.5 36.5 97.3 2.7 4.8 8.7 9 63.5 36.5 94.8 5.2 9.5 7.9 ~ 3 5 ~ 3 The optimization of the tensile strength in experiments 2, 5 and 8 is apparent from the measured numerical values.
Example 2 Three further synthetic polymer compositions which included lateral fatty radical substituents according to the definition in accordance with the invention were used in form of an aqueous dispersion and mixed with potatoe starch in different amounts, and the thermomechanical starch hydrolysis and the homogenization with the respectively used synthetic polymer was carried out in the extruder.
The following three polymer types were tested:
Experiments 10, 11 and 12:
A polyurethane including fatty radicals according to the definition in accordance with the invention, commercial product "Fondoflex P202" of the applicant. The fatty radicals of this polyurethane based synthetic polymer are derived from ricinoleic acid. Thus, only C7 alkyl groups are available for clathrate formation with the starch. Table 3 below shows the relatively smallest strengths for this type of polymer which can be explained by the reduced tendency of complex formation. The portion of dampened castor oil relative to the PU melt (without water) is 12 wt.-% in the product used.
Experiments 13, 14 and 15:
The synthetic polymer component used here is a C16"8-fatty alcohol-methacrylate-homopolymer (Mw = 166,000; Mn = 31,000).
~173~83 Experiments 16, 17 and 18:
The polymer component (acrylate polymer) is a poly(butyl-co-behenyl)-acrylate where the molar ratio of butyl to behenyl-acrylate is 4: 1 (MW = 74,000; Mn = 20,000).
In a series of experiments with the three polymer types according to experiments 10 to 18 the respective maximum strength was determined - here again determined as tensile strength according to DIN 53455. The following Table 3 combines the weight ratios of starch: "fat"
(according to the definition in accordance with the invention) with a respective maximum strength in the series of experiments.
Table 3 Experiment Polymer Starch: Starch: "Fat" in Strength No. Polymer "Fat" the Polymer N/mm2 wt.-% wt.-% wt.-%
89.2%10.8% 98.6% 1.4% 7 11 PU 84.8%15.2% 97.9% 2.1% 12.0% 9 12 80.2%19.8% 97.1% 2.9% 4 13 99.0%1.0% 99.2% 0.8% 19 14 Methacrylate 96.0%4.0% 96.9% 3.1% 77.0% 23 93.0%7.0% 94.5% 5.5% 10 16 98.3%1.7% 99.4% 0.6% 11 17 Acrylate 93.3%6.7% 97.6% 2.4% 35.0% 23 18 88.4%11.6% 95.6% 4.4% 13
- polyols with a boiling point of at least 150C were used as plasticizers such as propylene glycol or, preferably, glycerine, and, if required, further additives such as urea and/or derivatives thereof.
Example 1 The dependency of the strength characteristics of TSP/SPV-blends on the fatty radicals content of the respectively used SPV component in accordance with the invention is examined by way of the following exemplary prepalalions which are labelled with experiment numbers 1 to9.
Three related polymer types are subjected to homogenization with starch as part of the thermomechanical hydrolysis:
Experiments 1, 4 and 7:
Aqueous polyvinyl acetate dispersion which is subjected, in accordance with the teachings of DE 40 38 732 and jointly with potatoe starch and a low molecular weight plasticizer (especially glycerine) to an extrusion and the thermomechanical hydrolysis associated therewith.
Experiments 2, 5 and 8:
Instead of the aqueous PVAc-dispersion a comparable dispersion of a copolymer of vinyl acetate (VAc) and vinyllaureate (VL) having a VAc: VL mole ratio of 50: 2.5 is used. The synthetic polymer component used here includes as lateral substituents and in fixed distribution the long chain alkyl residues of the vinyllaureate component. Correspondingly, the biological breakdown of this polymer and, thus, its decomposability is ensured.
Experiments 3, 6 and 9:
The synthetic polymer type used for ~(lmixing with the starch and for the thermomechanical hydrolysis corresponds to the one used in experiments 2, 5 and 8, however, with the modification that the mole ratio of VAc: VL is shifted to the value of 47.8: 5Ø
The type and amount of the mixture components are shown below in Table 1 for theexperiment groups which are combined in the groups of three of 1 to 3, 4 to 6 and 7 to 9.
Table 1 Experiment Sta~ch PVAc P(VAc-co-VL) P(VAc-co-VL) Urea Glycerin Water No. wt.-% wt.-%VAc:VL=50:2.5VAc:VL=47.8:5.0 wt.-% wt.-% wt.-%
wt.-% wt.-%
18.3 - - - 16.7 25 2 40 - 18.3 - - 16.7 25 3 40 - - 18.3 - 16.7 25 4 40 20.4 - - 5.6 7.4 26.7 - 20.4 - 5.6 7.4 26.7 6 40 - - 20.4 5.6 7.4 26.7 7 36.9 21.2 - - 11.5 3.9 26.5 8 36.9 - 21.2 - 11.5 3.9 26.5 9 36.9 - - 21.2 11.5 3.9 26.5 217 ~583 Table 2 below lists for experiment numbers 1 to 9 the calculated numerical values of the ratio of "starch:polymer" in parts per weight, of the ratio "starch:fat (according to the definition in accordance with the invention)", and of the "fat content (according to the definition in accordance with the invention)" in the polymer in weight percent.
The tensile strength in N/mm2 according to DIN 53455 (testing speed 20 mm/min.) associated with the respective experiment numbers is shown in the last column of Table 2.
Table 2 Experiment Starch :PolymerStarch : "Fat""Fat" in the Tensile No. Polymer Strength wt.-% N/mm2 68.6 31.4 100 0 0 5.8 2 68.6 31.4 97.9 2.1 4.8 7.4 3 68.6 31.4 95.8 4.2 9.5 6.0 4 66.2 33.8 100 0 0 15.3 66.2 33.8 97.6 2.4 4.8 19.7 6 66.2 33.8 95.4 4.6 9.5 14.9 7 63.5 36.5 100 0 0 5.1 8 63.5 36.5 97.3 2.7 4.8 8.7 9 63.5 36.5 94.8 5.2 9.5 7.9 ~ 3 5 ~ 3 The optimization of the tensile strength in experiments 2, 5 and 8 is apparent from the measured numerical values.
Example 2 Three further synthetic polymer compositions which included lateral fatty radical substituents according to the definition in accordance with the invention were used in form of an aqueous dispersion and mixed with potatoe starch in different amounts, and the thermomechanical starch hydrolysis and the homogenization with the respectively used synthetic polymer was carried out in the extruder.
The following three polymer types were tested:
Experiments 10, 11 and 12:
A polyurethane including fatty radicals according to the definition in accordance with the invention, commercial product "Fondoflex P202" of the applicant. The fatty radicals of this polyurethane based synthetic polymer are derived from ricinoleic acid. Thus, only C7 alkyl groups are available for clathrate formation with the starch. Table 3 below shows the relatively smallest strengths for this type of polymer which can be explained by the reduced tendency of complex formation. The portion of dampened castor oil relative to the PU melt (without water) is 12 wt.-% in the product used.
Experiments 13, 14 and 15:
The synthetic polymer component used here is a C16"8-fatty alcohol-methacrylate-homopolymer (Mw = 166,000; Mn = 31,000).
~173~83 Experiments 16, 17 and 18:
The polymer component (acrylate polymer) is a poly(butyl-co-behenyl)-acrylate where the molar ratio of butyl to behenyl-acrylate is 4: 1 (MW = 74,000; Mn = 20,000).
In a series of experiments with the three polymer types according to experiments 10 to 18 the respective maximum strength was determined - here again determined as tensile strength according to DIN 53455. The following Table 3 combines the weight ratios of starch: "fat"
(according to the definition in accordance with the invention) with a respective maximum strength in the series of experiments.
Table 3 Experiment Polymer Starch: Starch: "Fat" in Strength No. Polymer "Fat" the Polymer N/mm2 wt.-% wt.-% wt.-%
89.2%10.8% 98.6% 1.4% 7 11 PU 84.8%15.2% 97.9% 2.1% 12.0% 9 12 80.2%19.8% 97.1% 2.9% 4 13 99.0%1.0% 99.2% 0.8% 19 14 Methacrylate 96.0%4.0% 96.9% 3.1% 77.0% 23 93.0%7.0% 94.5% 5.5% 10 16 98.3%1.7% 99.4% 0.6% 11 17 Acrylate 93.3%6.7% 97.6% 2.4% 35.0% 23 18 88.4%11.6% 95.6% 4.4% 13
Claims (17)
1. Shapeable composite material on the basis of thermomechanically hydrolyzed starch (TPS) obtained with the addition of water and/or low molecular weight plasticizers, in homogeneous admixture with synthetic polymer compositions (SPV), characterized in that in order to optimize its mechanical strength (determined by way of the tensile strength according to DIN 53455) synthetic polymer compositions with lateral and/or terminal unbranched and saturated hydrocarbon radicals (fatty radicals) are homogenized with the TPS in such a ratio that the fatty radical content in the composite material (wt.-% fatty radicals relative to the water-free starch) is in the range of 0.5 to 7 wt.-%.
2. Composite material according to claim 1, characterized in that the weight ratio of the fatty radicals to the starch is in the range of 1 to 5 wt.-%, preferably in the range of 2 to 4 wt.-%.
3. Composite material according to claims 1 and 2, characterized in that SPVs with at least predominately linear base structure and lateral as well as terminal fatty radical groups is homogenized into the TPS.
4. Composite material according to claims 1 to 3, characterized in that the fatty radicals have a chain length of at least 6 carbon atoms, preferably 8 carbon atoms and especially predominately at least 12 carbon atoms, whereby fatty radicals of the same and/or different chain lengths can be present in the SPV material and lie preferably in the range of 6 to 32 carbon atoms, especially in the range of 10 to 24 carbon atoms, for example, in the range of 12 to 18 carbon atoms.
5. Composite material according to claims 1 to 4, characterized in that the biologically degradable or decomposable SPV is homogeneously combined with the TPS.
6. Composite material according to claim 1 to 5, characterized in that SPVs including lateral fatty radicals from the group of polyesters, polyamides, polyurethanes and/or polyvinylalcohol esters, and possibly also fatty radicals-containing polymeric compositions of the poly(meth)acrylate type, are admixed with the TPS.
7. Composite material according to claims 1 to 6, characterized in that at least a portion of the SPV is derived from renewable raw materials.
8. Composite material according to claims 1 to 7, characterized in that its content of SPV
is derived from corresponding polymer dispersions which include the polymer compositions as dispersed phase in an aqueous liquid phase and have been incorporated into the starch together with the aqueous phase.
is derived from corresponding polymer dispersions which include the polymer compositions as dispersed phase in an aqueous liquid phase and have been incorporated into the starch together with the aqueous phase.
9. Composite material according to claims 1 to 8, characterized in that it contains the starch in amounts of at least 40 wt.-%, preferably at least 50 wt.-% - wt.-% relative to the solid materials mixture free of water and low molecular weight plasticizers.
10. Composite material according to claims 1 to 9, characterized in that it includes at least 3 wt.-%, preferably at least 5 to 10 wt.-% of water and/or low molecular weight plasticizers, relative to the composite material.
11. Composite material according to claims 1 to 10, characterized in that it includes lower polyfunctional alcohols, especially glycerin and/or there ethers as low molecular weight plasticizers and preferably in a proportion within a range of about 10 to 50 wt.-0%, practically within the range of about 15 to 35 wt.-%, relative to the total mixture.
12. Composite material according to claims 1 to 11, characterized in that it includes as the starch portion in the composite material starches of a mean amylose content in the range below 30 wt.-%, preferably in the range of 15 to 25 wt.-%, (relative to starch dry matter), whereby potato starch or corresponding wheat and/or corn starch is preferred, but whereby the use of starches with amylose contents of at least 50 wt.-%, for example, 70 to 90 wt.-% may be preferred.
13. Use of the composite materials according to claims 1 to 12 for the manufacture of shaped products, for example, packaging materials, such as foils, bottles, cups, boxes and the like.
14. Process for the manufacture of polymer modified materials on the basis of TPS and shaped products made therewith according to claims 1 to 13, characterized in that native starch is mixed with aqueous dispersions of the SPV, if desired, further low molecular weight plasticizers and/or water, the multi-component mixture is subjected to starch hydrolysis at elevated temperatures and pressures and simultaneous mixing and/or kneading to form the TPS, and the homogenized polymeric mixture is shaped, if desired.
15. Process according to claim 14, characterized in that product temperatures are used at least in the terminal faces of the mixing and starch hydrolysis process which lie above 100°C
and preferably above 120°C, especially in the range of about 120 to 150°C.
and preferably above 120°C, especially in the range of about 120 to 150°C.
16. Process according to claims 14 and 15, characterized in that the residence times of the multi-component mixture under process conditions is in the range of about 30 minutes, preferably in the range of about 0.5 to 10 minutes and thereby especially with a continuous process and under the inherent pressures which are generated in the system at the process temperature.
17. Process according to claims 14 to 16, characterized in that the mixing and the hydrolysis of the polymer components is carried out in heated extruders to which the starch -preferably as powdered starch - and the aqueous SPV dispersions as well as the possibly also used further molecular weight plasticizers are separately fed in the input portion thereof, while the homogenized and hydrolyzed polymer mixture - if desired after a partial expulsion of excess water - is obtained as extrudate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19934333858 DE4333858A1 (en) | 1993-10-05 | 1993-10-05 | Thermoplastic composite materials based on starch |
| DEP4333858.5 | 1993-10-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2173583A1 true CA2173583A1 (en) | 1995-04-13 |
Family
ID=6499405
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2173583 Abandoned CA2173583A1 (en) | 1993-10-05 | 1994-09-27 | Thermoplastically processable starch-based composite materials |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0722475A1 (en) |
| JP (1) | JPH09505613A (en) |
| CA (1) | CA2173583A1 (en) |
| DE (1) | DE4333858A1 (en) |
| WO (1) | WO1995009888A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2493975B1 (en) * | 2009-10-30 | 2017-03-29 | Stichting Kennis Exploitatie RB | Starch-based biodegradable polymer; method of manufacture and articles thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5614544A (en) * | 1979-07-14 | 1981-02-12 | Nippon Synthetic Chem Ind Co Ltd:The | High polymer composition with excellent compatibility |
| US4835198A (en) * | 1986-06-06 | 1989-05-30 | Kuraray Co., Ltd. | Polymer composition and textile sizing agent made therefrom |
| US5087650A (en) * | 1990-12-05 | 1992-02-11 | Fully Compounded Plastics, Inc. | Biodegradable plastics |
| DE4122212C2 (en) * | 1991-07-04 | 1994-06-16 | Inventa Ag | Thermoplastically processable mass of starch and acrylate copolymers |
| DE4209095A1 (en) * | 1992-03-20 | 1993-09-23 | Henkel Kgaa | THERMOPLASTICALLY MANUFACTURED MATERIALS BASED ON STAEREE BASE, MOLDED PARTS AND METHOD OF PRODUCTION THEREOF |
-
1993
- 1993-10-05 DE DE19934333858 patent/DE4333858A1/en not_active Withdrawn
-
1994
- 1994-09-27 JP JP7510594A patent/JPH09505613A/en active Pending
- 1994-09-27 EP EP94927656A patent/EP0722475A1/en not_active Withdrawn
- 1994-09-27 CA CA 2173583 patent/CA2173583A1/en not_active Abandoned
- 1994-09-27 WO PCT/EP1994/003229 patent/WO1995009888A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0722475A1 (en) | 1996-07-24 |
| WO1995009888A1 (en) | 1995-04-13 |
| DE4333858A1 (en) | 1995-04-06 |
| JPH09505613A (en) | 1997-06-03 |
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