Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1997-04-02
2002-06-11
Geist, Gary (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S123100, C536S124000, C527S103000, C428S534000
Reexamination Certificate
active
06403787
ABSTRACT:
The present invention relates to new materials consisting of thermoplastic aliphatic polysaccharide carbamic acid derivatives, as well as of mixtures of such derivatives with low-molecular urea derivatives, the preparation of such derivatives and mixtures from polysaccharides or polysaccharide derivatives and aliphatic monoisocyanates in a suitable solvent. The materials according to the invention, after removal of the solvents. are preferably processed as thermoplastic material by injection moulding or extrusion. Mouldings, fibres, films, as well as foams or coatings can be produced.
It is known that thermoplastically processable materials can be produced from polysaccharides, in particular from starches or celluloses, by esterification or etherification of the free hydroxyl groups in a homogeneous reaction process (cf. Encyclopaedia of Polymer Science and Technology Vol. 3, 1985).
Thermoplastic materials are also correspondingly obtained, for example, according to EP 626 392, by esterification of polysaccharide hydroxyalkyl ethers.
JP 142938 and Macromolecules 18, 1985, 1746-1752 describe the reaction of cellulose ethers with acid chlorides or with carboxylic anhydrides.
J. Appl. Polym. Sci. 52. 1994, 755-761. and J. Env. Polym. Degr. 3, 1995, 115-118 describe the preparation of thermoplastic cellulose esters from cellulose and long-chain unsaturated fatty acids in pyridine/DMF.
The thermoplastic processability of polysaccharide derivatives is dependent on the average degree of substitution of the anhydroglucose repeat unit, referred to below as DS, which in the case of thermoplastic aliphatic cellulose ester derivatives, for example, is at least approximately 2.0.
To obtain thermoplastic processability, it is necessary to add further auxiliary substances, especially plasticisers,to these polysaccharide-derivatives (F. Müller, Ch. Leuschke, in Becker/Braun: Kunststoff-Handbuch Vol. 3/1, Hanser Verlag, Munich, 1992).
Whereas the etherification is usually carried out by reacting alkali cellulose with epoxides such as, for example, ethylene oxide or propylene oxide, in an inert suspending medium, esterifications are usually carried out in a solvent process using acids as solvents. Here the swelling process also serves to activate the cellulose (Encyclopaedia of Polymer Science and Technology Vol. 3, 1985).
Comparably, the steady reaction of polysaccharides with substituted isocyanates or substituted isothiocyanates likewise succeeds only in the case of easy accessibility of the cellulose chains in homogeneous solution or in solvents having a very strong swelling effect.
Acta Polymerica 32, 1981, 172-176 specifies that dry cellulose does not react satisfactorily with isocyanates in the absence of solvents and further catalysts. Reactions in solvents which are not capable of at least initiating swelling in the cellulose do not produce satisfactory reactions with the cellulose (Ang. Chem., 59, 1947, 257-288).
B. Polym. J., 18, 1986. 259-262 describes the reaction of wood cellulose with alkyl monoisocyanates. The formation of urethane remains limited to the surface of the polysaccharide fibres.
DE 2358808 describes the reaction with long-chain mono- and diisocyanates, which is limited to the surface of cellulose powders.
L. Disserens, in “Neueste Fortschritte und Verfahren in der chemischen Technologie der Textilfasern”, Birkhäuser Verlag, Stuttgart, 1957, presents a survey of the reactions of textile fibres with mono- and diisocyanates which are limited to the surface. Long-chain alkyl isocyanates are preferably used here for the purpose of hydrophobing the textile material. GB 467 992 describes the heterogeneous reaction with isocyanates of textile fibres which have been previously reacted with alkylene oxides. In the reaction carried out in petroleum spirits, however, no significant swelling of the cellulose results.
In addition the mechanical properties of paper can be influenced by the reaction of isocyanates with the cellulose fibres (Acta Polymerica 32, 1981, 172-176). However, for this preferably multifunctional isocyanates, particularly preferably diisocyanates, are used, which are not the subject matter of the present invention.
Average degrees of conversion of cellulose with isocyanates are obtained using solvents and catalysts especially when the cellulose is in the swollen condition. This can be achieved through the use of a suitable solvent or else through the use of a derivative of the cellulose or of a polysaccharide together with a suitable solvent. The formation of the urethane bond can also be brought about here by an additional back process (Cell. Chem. Technol. 1, 1967, 23-32).
The swelling of the cellulose can be achieved by initial swelling in water and subsequent exchange for a polar aprotic solvent.
Alternatively, solvents having a strongly swelling or solvent effect on cellulose, such as DMAc, DMSO, DMAc/LiCl or DMSO/formaldehyde mixtures, can also be used directly (U.S. Pat. Nos. 4,129,451, 4,129,640, 4,097,666). Surveys of solvent systems are published in Nevell and Zeronian: Cellulose chemistry and its applications, Wiley, N.Y., 1985, Acta Polym. 36 (1985), 697-698 and Polymer News 15, (1990), 170-175.
Also described as being good swelling or dissolving systems are, for example, morpholine/piperidine mixtures (J. Appl. Polym. Sci., 22, (1978), 1243-1253, as well as amine-N-oxides (Acta Polymerica, 39, (1988), 710-714, U.S. Pat. No. 3,508,941) and metal cation/solvent systems such as Cu/NH
3
or Cd/ethylenediamine (Polymer 31, (1990), 348-352).
The reaction of phenyl isocyanate with cellulose in DMSO/paraformaldehyde mixtures is described in J. AppI. Pol. Sci. 27, (1982), 673-685, J. Appl. Pol. Sci. 42, (1991), 821-827, and in Nevell and Zeronian: Cellulose chemistry and its applications, Wiley, N.Y., 1985.
High degrees of conversion are favoured especially by the addition of catalysts, by a reaction period of an appropriately chosen length or by elevated temperatures. On the other hand, the formation of isocyanurates is catalysed by means of amines in DMAc, DMSO or DMF as swelling agents or solvents (Eur. Polym. J., 26 (11), (1990), 1217-1220).
The patents and publications listed below describe the reaction of soluble cellulose acetate having degrees of substitution DS<3.0 with isocyanates. isocyanate prepolymers or isocyanate-functionalised polymers or oligomers in homogeneous solution. After the formation of the urethane, the acetate groups can be saponified and the urethane derivatives of the unsubstituted cellulose can be isolated.
J. Macromol. Sci. Chem. A 16 (1981) 473. Polym. Prepr. Am. Chem. Soc. Div. Poly. Chem. 20 (1979) 574, J. Poly. Sci. Polym. Lett. ed. 111 (12) (1973) 731-735, Macromol. Synth. 7, 101-105, Polymer 21 (1980) 648-650, Polym. Prepr. Am. Chem. Soc. Div. Poly. Chem. 3 (1990) 642, U.S. Pat. No. 3,950,28.
Thermoplastically processable aliphatic carbamates starting from polysaccharides or polysaccharide hydroxyalkyl ethers are not known.
The object of this invention is to identify reaction conditions for the reaction of polysaccharide derivatives. preferably those from renewable raw materials and derivatives of these, with isocyanates, such that average to high degrees of conversion are obtained. For this was required in particular a reaction under homogeneous conditions, that is. a solution of the polysaccharide derivative in the solvent, and at least a solvent having a very strong swelling effect.
Surprisingly, it has now been found that cellulose derivatives, and particularly preferably cellulose alkyl ethers which are not soluble or highly swellable in the solvents used according to the invention, pass into solution or begin to swell strongly during the reaction with alkyl monoisocyanates and consequently lead to average to high degrees of conversion.
Examples of polysaccharide components which may be mentioned in particular are hydroxypropyl cellulose and hydroxyethyl cellulose. Aprotic polar and nonpolar solvents, preferably cyclic ethers or substituted aromatics, particularly preferably dioxane and toluene, can be used a
Dijkstra Dirk-Jacques
Engelhardt Jürgen
Koch Rainhard
Müller Hanns-Peter
Simon Joachim
Geist Gary
Norris & McLaughlin & Marcus
Owens, Jr. Howard V
Wolff Walsrode AG
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