Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Carbohydrate doai
Reexamination Certificate
2000-03-13
2001-11-06
Peselev, Elli (Department: 1623)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Carbohydrate doai
C525S054240
Reexamination Certificate
active
06313105
ABSTRACT:
The invention relates to mixtures which can be thermoplastically processed to give shaped biodegradable articles and which comprise, as components, dialdehyde starch, starch or modified starch, if desired also other polymers, in particular biopolymers, such as proteins, and also plasticizers and, if desired, conventional additives, such as antioxidants, mold-release agents, lubricants, dyes and the like. The invention further relates to the use of these mixtures for producing shaped articles which may be used in particular in the sectors of food and drink and pharmaceutical products.
Constantly growing environmental awareness, and also ever stricter regulations relating to waste disposal or recycling, have led to a marked increase in efforts to utilize biodegradable materials for producing shaped articles. Increasing efforts are also being made, wherever possible, to use materials and in particular polymers based on renewable raw materials instead of materials based on mineral oil. Substances from natural sources are moreover in many cases less physiologically hazardous.
Starch, and also modified starch, alone or else mixed with other polymers, in particular with biopolymers, are renewable raw materials which are of constantly increasing importance, especially for producing shaped articles, e.g. foils or films. Processors encounter a wide variety of problems here. To process starch, modified starch or else mixtures with other polymers by shaping, very intimate mixing is required, i.e. homogenization of the components, in particular if the materials are to be processed thermoplastically. It is also important that during the shaping process the mixture has been adequately plasticized, in order to avoid having to accept excessively high shaping temperatures and the associated decomposition of the components. The shaped article moreover should have not only good biodegradability but also highly homogeneous internal structure and good mechanical properties, such as strength and elasticity. A particular further requirement for most applications is very low brittleness and abrasion. The plasticizer should also be environmentally friendly, i.e. biodegradable, and preferably physiologically nonhazardous.
Some publications are known concerning molded compositions based on starches and on proteins with dialdehyde starch as an additive.
In DE-A 1470882, for example, a process is described for producing transparent films for packaging food or drink. Here, from 2 to 50% of protein and from 5 to 70% of a plasticizer in aqueous solution at from 22 to 50° C. are mixed with from 0.01 to 20% by weight, based on the dry substances, of a dialdehyde polysaccharide, e.g. dialdehyde starch. The dialdehyde starch serves to crosslink the protein. Free amino groups in the protein react with the aldehyde groups. This process is awkward and requires a great deal of energy since about ten times the amount of water, based on protein, is used in the production of the films, and this has to be evaporated. In addition, there are two curing steps
U.S. Pat. No. 5,397,834 describes a composition made of from 10 to 35% by weight of protein and from 65 to 70% by weight of aldehyde starch. To prepare compositions of this type, from 0.5 to 2 parts of protein are dissolved in from about 2 to 6 parts of a solubilizing solvent, e.g. a 75% strength aqueous ethanol solution. This solution is then mixed with from 2 to 8 parts of an aldehyde starch. The aldehyde starch is to have a low degree of oxidation, preferably from 10 to 20%, to ensure effective crosslinking of the protein and of the aldehyde starch. After the mixing, the solvent is evaporated. This procedure again leads to crosslinked materials which are not suitable for thermoplastic further processing.
WO 93/19125 describes mixtures made from starch or, respectively, modified starch and from proteins, in which crosslinking agents, inter alia dialdehyde starch, are also used. Here, again, these are materials which are not within the scope of the present invention.
U.S. Pat. No. 4,220,264 describes the production of shaped articles, such as foils, from amylose and amylose starch, with concomitant use of crosslinking agents and of a liquid, such as dimethyl sulfoxide. The amount of the liquid needed is from about 10 to 20 times that of the starch used. The foils obtained in Examples 11 and 12, in which dialdehyde starch is used as crosslinking agent, are all easily fractured.
Finally, EP-A1-0 599 535 describes a process in which extrusion is used to shape mixtures composed of starch and of a starch degradation product, such as a starch hydrolysis product with DE (dextrose equivalent) values of from 1 to 40, and of oxidized starches and of pyrodextrins. The oxidized starches used here exhibit the typical starch color reaction with iodine. This is a clear indication that the hydroxymethylene group of the starch has been oxidized, or the degree of oxidation of a dialdehyde starch is only very low.
Although there is a wide variety of known processes and compositions for producing shaped articles in which dialdehyde starch is used, there remains a need for improved processes and improved compositions which allow the production of moldings which have good and improved properties and are versatile in use.
It is therefore an object of the invention to provide compositions which comprise dialdehyde starch and at least one other biodegradable component based on starch or on modified starch, and also comprise plasticizers and, if desired, other biopolymers, and also other conventional additives, which can be produced simply and cost-effectively and are thermoplastically processable to give shaped articles with industrially useful properties, which do not have the disadvantages which arise in the crosslinking of starch components, and which are homogeneous and which give shaped articles with a homogeneous structure.
This object is achieved by a thermoplastic mixture as claimed in patent claim
1
.
Other advantageous embodiments are described in claims
2
to
10
. The invention also provides a process as claimed in patent claims
11
to
13
. Advantageous uses are given in patent claims
14
to
18
.
A group of starches which can be used for the purposes of the invention comprises the starches obtained from vegetable raw materials. These include starches made from tubers, such as potatoes, cassava, maranta or sweet potato, from seeds, such as wheat, com, rye, rice, barley, millet, oats or sorghum, from fruits, such as chestnuts, acoms, beans, peas and other pulses or bananas, or from plant pith, for example of the sagopalm.
The starches which can be used for the purposes of the invention are composed substantially of amylose and amylopectin in varying proportional quantities.
Particularly good results are achieved with, inter alia, starches made from potatoes (e.g. ®Toffena from Süidstärke) or corn (e.g. Maize Starch from National Starch), or else from polyglucans, which feature a perfectly linear structure of the polymers.
The molecular weights of the starches which can be used according to the invention may vary over a wide range. The starches which can be used as a basis for the novel thermoplastic mixture are those which are composed substantially of a mixture of amylose and amylopectin, with molecular weights M
w
within the range from 5×10
4
to 1×10
7
. Preference is given to relatively long-chain polymers with molecular weights M
w
of from 1×10
6
to 5×10
6
.
Preference is also given to linear starches, preferably polyglucans, in particular 1,4-&agr;-D-polyglucan, with molecular weights M
w
within the range from 5×10
2
to 1×10
5
, preferably with molecular weights M
w
of from 1×10
3
to 5×10
4
.
Besides molding compositions based on starches of native vegetable origin, the invention also includes thermoplastic mixtures or molding compositions with starches which have been chemically modified, have been obtained by fermentation, are of recombinant origin or have been prepared by biotransformation (biocatalysis). The ter
Bengs Holger
Böhm Gitte
Grande Jürgen
Schneller Arnold
Schuth Silke
Aventis Research and Technologies GmbH & Co KG
Connolly Bove & Lodge & Hutz LLP
Peselev Elli
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