Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-11-01
2002-03-26
Fonda, Kathleen Kalher (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S032000, C536S037000, C536S038000, C536S056000, C536S066000, C536S124000, C525S054200, C428S508000, C428S532000
Reexamination Certificate
active
06362330
ABSTRACT:
The present invention relates to novel thermoplastic materials based on polysaccharide ethers which are simultaneously substituted by carboxylic acid ester groups and carbamate groups, together with mixtures of such derivatives with low molecular weight aliphatic urea derivatives.
The invention additionally relates to the production of such derivatives and mixtures of polysaccharide ethers and aliphatic or aromatic carboxylic acids or carboxylic acid derivatives and aliphatic monoisocyanates in a suitable solvent. After removal of the solvents, the materials according to the invention are preferably processed as thermoplastic materials by injection moulding or extrusion. Moulded articles, fibres, films and also foams or coatings may be produced.
It is known that melt processable materials may be produced from polysaccharides, in particular from starches or celluloses, by esterification or etherification of the free hydroxyl groups when the reaction is performed homogeneously (cf Encyclopedia of Polymer Science and Technology Vol. 3, 1985).
Thermoplastic materials are also 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 acid anhydrides.
J. Appl. Polym. Sci. 52, 1994, 755-761 and J. Env. Polym. Degr. 3, 1995, 115-118 describe the production of thermoplastic cellulose esters from cellulose and long chain unsaturated fatty acid esters in pyridine/DMF.
The melt processability of polysaccharide derivatives is dependent on the average degree of substitution of the anhydroglucose repeat unit, abbreviated below as DS, which may amount for example to at least approximately 2.0 in the case of thermoplastic aliphatic cellulose ester derivatives.
For melt processing, auxiliary substances, in particular plasticisers, which reduce the viscosity of the material to be softened, have to be added to these polysaccharide derivatives (F. Muller, Ch. Leuschke in Becker/Braun Kunststoff-Handbuch Vol. 3/1, Hanser Verlag Munich 1992). At elevated temperatures >220° C., it is possible to observe decomposition and discolouration of polysaccharide derivatives.
While etherification is conventionally carried out by reacting alkali cellulose with epoxides, such as for example ethylene oxide or propylene oxide, in an inert suspending agent, esterification is conventionally carried out in a solution process using acids as the solvent. In such an instance, the swelling process also serves to activate the cellulose (Encyclopedia of Polymer Science and Technology Vol. 3, 1985).
Synthesis of the known polysaccharide carboxylic and dicarboxylic acid half esters is effected in pyridine or acetic acid with basic salts such as for example sodium acetate as the catalyst (J. Env. Pol. Degr. 3, 1995, 115-119). The products may be liberated from these solvents only with considerable effort. Because they accelerate corrosion, these solvents require specially designed installations for synthesis thereof. Syntheses carried out in standard organic solvents would be advantageous in this respect.
Economic derivatisation of celluloses using acid derivatives with a degree of substitution <<3 and homogeneous random distribution of the acid derivatives has hitherto required complete substitution of the cellulose (DS approx. 3.0) with subsequent partial hydrolysis (U.S. Pat. No. 1,984,147, U.S. Pat. No. 2,129,052, U.S. Pat. No. 5,478,386).
Thermoplastic cellulose derivatives with DS <3.0 and homogeneous random substituent distribution have not hitherto been economically directly available. This is primarily because of the poor, incomplete solubility of partially substituted celluloses in suitable organic solvents.
Likewise, it is possible to achieve uniform reaction of polysaccharides with substituted isocyanates or substituted isothiocyanates only in the case of good accessibility of the cellulose chains in homogeneous solution or in solvents with a very strong swelling action.
Acta Polymerica 32, 1981, 172-176 describes how dry cellulose reacts in an unsatisfactory manner with isocyanates in the absence of solvents and other catalysts. Reactions in solvents which are not in a position at least to initiate swelling of 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 lignocellulose with alkyl monoisocyanates. Urethane formation remains restricted to the surface of the polysaccharide fibres.
DE 23 58 808 describes the reaction with long chain mono- and diisocyanates restricted to the surface of cellulose powder.
In “Neueste Fortschritte und Verfahren in der chemischen Technologie der Textilfasern”, Birkhäuser Verlag, Stuttgart, 1957, L. Disserens provides a summary of the reactions, restricted to the surface, of textile fibres mono- and diisocyanates. In this context, long chain alkyl isocyanates are preferably used for the purpose of hydrophobising textile material. GB 467 992 describes the heterogeneous reaction with isocyanates of textile fibres previously reacted with alkylene oxides. In the case of the reaction carried out in benzin, however, no significant swelling of the cellulose occurs.
Average degrees of conversion of cellulose with isocyanates are obtained, with solvents and catalysts, in particular when the cellulose is initially present in a swollen state. This may be achieved by using a suitable solvent or by using a derivative of cellulose or a polysaccharide together with a suitable solvent. Formation of the urethane bond may also be effected by a subsequent baking process (Cell. Chem. Technol. 1, 1967, 23-32).
Swelling of the cellulose may be achieved by initiating said swelling in water, which is subsequently replaced by a polar aprotic solvent.
Alternatively, direct use may also be made of solvents with a strong swelling or dissolving action in relation to cellulose, such as DMAc, DMSO, DMAc/LiCl or DMSO/formaldehyde mixtures (U.S. Pat. No. 4,129,451, U.S. Pat. No. 4,129,640, U.S. Pat. No. 4,097,666). Solvent systems are summarised 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.
Examples of other systems described as having a good swelling or dissolving action are, for example, morpholine/piperidine mixtures (J. Appl. Polym. Sci., 22, (1978), 1243-1253) together with amine-N-oxides (Acta Polymerica, 39, (1998), 710-714, U.S. Pat. No. 3,508,941) and metal cation/solvent systems such as Cu/NH3 or Cd/ethylene diamine (Polymer 31, (1990), 348-352).
The reaction of phenyl isocyanate with cellulose in DMSO/paraformaldehyde mixtures is described in J. Appl. 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 promoted, in particular, by the addition of catalysts, by a correspondingly long reaction period or by elevated temperature. On the other hand, where DMAc, DMSO or DMF is used as a swelling agent or solvent, the formation of isocyanurates is catalysed with amines (Eur. Polym. J., 26 (11)(1990) 1217-1220).
The patents and publications listed below describe the reaction of soluble cellulose acetate with degrees of substitution DS<3.0 with isocyanates, isocyanate prepolymers or isocyanate-functionalised polymers or oligomers in homogeneous solution. After formation of the urethane, the acetate groups may be saponified and urethane derivatives of the unsubstituted cellulose may 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. 395,028).
The reaction of polysaccharide derivatives with aliphatic isocyanates to form thermoplastic materia
Dijkstra Dirk Jacques
Müller Hanns-Peter
Simon Joachim
Weber Gunter
Fonda Kathleen Kalher
Franks James R.
Gil Joseph C.
Maier Leigh C.
Preis Aron
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