Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2000-06-19
2003-07-29
Riley, Jezia (Department: 1637)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S050000, C536S084000, C536S090000, C536S099000, C536S111000, C536S120000, C536S123100, C536S123120
Reexamination Certificate
active
06600033
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to hydrophobically modified cellulose ethers and to the use thereof.
Cellulose ethers, such as carboxymethyl cellulose, are employed in a wide variety of applications to treat the rheological properties of aqueous solutions in particular. Objects of use include, for example, foods, medicines, cosmetic preparations, detergents, agricultural chemicals, textiles, printing inks, paper coating agents, construction materials, adhesives, paints, ceramic materials, and additives of polymerisation.
Cellulose ethers can be modified by attaching different substituents to hydroxyl groups in cellulose. In this way, the solubility or the hydrophobicity of cellulose ether in particular can be affected.
There is a lot of literature concerning the hydrophobic modification of polysaccharides.
U.S. Pat. No. 4,228,277 describes the modification of non-ionic cellulose ethers, such as methyl cellulose, methyl hydroxypropyl cellulose, hydroxypropyl cellulose, and particularly hydroxyethyl cellulose, by using epoxyalkanes having a length of the alkyl group of 10 to 24 carbons. According to the patent, one advantage of the modification is that even small amounts of hydrophobically modified cellulose ether make the viscosity of an aqueous solution increase so that the dosage of the cellulose ether can be decreased. The cellulose ether thus modified can be used in paints. The modification is carried out by using a cellulose ether as a starting material, and the reaction times are long, 2 to 5 hours. However, it is uncomfortable to use epoxy compounds because they are detrimental to health.
In FI Patent No. 95138, carboxymethyl hydroxyethyl cellulose is modified by an alkyl group having 8 to 25 carbons in an amount of 0.1 to 4% by weight. This product is also applied to paints. The alkyl reagent can be halide, halohydride, or epoxide, all of which are hazardous to environment and health. Hydroxyethylation, hydrophobic modification, and carboxymethylation are carried out in sequence, therefore the reaction time is long, more than 4 hours.
U.S. Pat. No. 5,302,196 describes cellulose ethers which are modified by a fluorine-containing alkyl group having 3 to 24 carbon atoms, the fluorine content being 0.05 to 5% by weight. The cellulose ether is especially hydroxyethyl cellulose, hydroxyethyl carboxymethyl cellulose or methyl hydroxyethyl cellulose. The fluorine-containing alkyl reagent is preferably epoxide, bromide or perfluoroolefin. This product is also developed for paints. The reaction is long, the modification requires a reaction time of 6 hours.
In EP Patent Application No. 384167, cellulose ether, especially hydroxyethyl cellulose, is modified with an aromatic alkyl group having at least 10 carbons, the content being 0.001 to 0.1 moles per one mole of a glucose repeat unit of the cellulose ether. The alkyl reagent can be, for example, halide, oxirane, acid, (thio)isocyanate or halohydrin. The product can be used in latex paints. This manufacturing process also has a long reaction time, 6 or up to 12 hours.
GENERAL DESCRIPTION OF THE INVENTION
According to the independent claim 1, hydrophobically modified cellulose ethers have been invented. The dependent claims disclose some preferred embodiments of the invention.
This invention introduces a new type of hydrophobically modified cellulose ether in which the modifying agent is alkylketene dimer. The cellulose ether is preferably carboxymethyl cellulose or sodium carboxymethyl cellulose (CMC, NaCMC).
Cellulose ether modified with alkylketene dimer is easy to manufacture. The process is safe, simple, and quick. The modification can also improve the dispersability of cellulose ether in water.
The product is suitable to be used in any water-based application. The hydrophobic group renders the substance properties that are advantageous to, for example, detergents, paper coating mixtures, paints, dispersing agents, and oil drilling muds.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, alkylketene dimer (AKD) is used to modify the cellulose ether. The general formula of AKD is
in which R
1
and R
2
are alklyl or alkenyl chains having 5 to 22, preferably 13 to 20 carbons. R
1
or R
2
can also be substituted or they can contain heteroatoms in a chain. R
1
or R
2
can in particular have a straight chain and contain 14 to 18 carbons.
AKD reacts with the hydroxyl group of cellulose or cellulose ether, forming the following formula:
Elevated temperatures, such as 30-120° C., preferably 50-90° C., and most preferably 60-85° C., enhance the reaction, so that at the elevated temperatures AKD is melted first. High temperature and alkaline pH improve the reactivity of AKD with cellulose ether. AKD can react with the substituent, for example carboxymethyl group in cellulose ether. AKD can also react with other compounds which contain an OH group. These include water, alcohol, and sodium glycolate which are generated in the preparation of CMC. The thus generated compounds also have an effect on the hydrophobicity of the product.
The reacted AKD concentration in the cellulose ether can be analysed by using gas chromatography. The unreacted AKD or AKD reacted with other OH containing compounds are extracted with a suitable solvent. The sample is hydrolysed causing the cleavage of alkyl ketene group. The reacted AKD is extracted with a suitable solvent and analysed with gas chromatograph.
The AKD can be in a solid state or dispersed in water or other solvents.
The content of AKD in the cellulose ether can be 0.001-10% by weight. The content is preferably 0.01-2% by weight.
The molecular weight (Mw) of the cellulose ether can be 10 000-1 000 000, preferably 20 000-700 000. The cellulose ether can be, for example, alkyl, hydroxyalkyl or carboxyalkyl substituted or a mixed ether of these.
According to the invention, cellulose ether that is modified by AKD can be used in any water-based application. It can be used, for example, in paper or board coating mixtures, in the wet end in paper or board manufacturing, paints, construction materials, adhesives, oil drilling mud, detergents, cosmetic products, and as a dispersion agent.
The cellulose ether is preferably carboxymethyl cellulose (CMC). Its degree of substitution (DS, i.e., the average number of substituted hydroxyl groups in a glucose ring) can be for example, 0.2-2.0, preferably 0.4-1.5, most preferably 0.4-1.2. Its molecular weight is preferably 40 000-500 000. It can be applied to all the above-mentioned objects.
The cellulose ether can also be, e.g., hydroxyethyl cellulose (HEC). Its molecular weight can be, for example, 90 000-1 300 000 and the molar substitution (MS) 1.5-4. HEC can be used in coating, construction materials, and cosmetic preparations in particular.
The cellulose ether can also be, e.g., hydroxypropyl cellulose (HPC). Its molecular weight can be, for example, 80 000-1 150 000 and the molar substitution (MS) 1.5-4. HPC can be used in foods, medical preparations, and coating in particular.
There is a lot of literature about the manufacture of cellulose ethers. Generally, cellulose ethers are prepared by mixing wood-based or cotton wool-based raw material with a reaction medium, such as alcohol or acetone, and by mercerising it with an alkalic substance, such as sodium hydroxide, to activate the cellulose. An etherifying chemical is added and it is allowed to react. The complete product is neutralised. The viscosity can be reduced if needed. By-products, such as salts generated in the reaction, are washed out with alcohol, for example, when purified cellulose ether is manufactured, but they can also be left in the product or only remove partly (technical or crude cellulose ether). The solvent used is separated and the product is dried. The particle size and the bulk density can be adjusted by grinding the product into powder or by granulating it. The product can also be screened.
Cellulose ether can be modified with AKD by various methods. AKD can be added to the cellulose ether at any stage of the production, for example, in merce
Gosselink Eugene Paul
Känköhen Heidi
Kloow Göran
Lähteenmäki Mikko
Leupin Jennifer Ann
Metsa Specialty Chemicals Oy
Millen White Zelano & Branigan P.C.
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