Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-10-26
2001-11-06
Peselev, Elli (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S090000, C536S091000
Reexamination Certificate
active
06313287
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
The present invention is described in the German priority application No. 19849442.4 filed Oct. 27, 1998 which is hereby incorporated by reference as is fully disclosed herein.
The present invention relates to water-soluble, sulfoalkyl-containing, hydrophobically modified cellulose ethers, to processes for preparing them and to their use, and to emulsion paints comprising these compounds.
Commercially customary emulsion paints possess pronounced pseudoplasticity. This stands in contrast to the processor's requirements for paints having more Newtonian rheology, which offer distinct advantages in terms of brushability, flow and drip. By using cellulose ethers modified hydrophobically with long-chain alkyl groups as thickeners, or by using conventional cellulose ethers in combination with synthetic associative thickeners, a more Newtonian rheology can be established in emulsion paints.
A disadvantage of the commercial thickeners comprising cellulose ethers modified hydrophobically using long-chain alkyl groups is the undesirably high level of bodying of the emulsion paint on storage. The consistency of emulsion paint increases sharply following its preparation and can more than double after one day of storage. This complicates the deliberate adjustment/monitoring of paint consistency by the paint manufacturer. A further disadvantage is the sharp reduction in the water solubility of the hydrophobically modified cellulose ethers even at low degrees of substitution.
DESCRIPTION OF THE RELATED ART
In EP-A-0 307 915 the attempt is made to improve the solubility of hydrophobically modified cellulose ethers by the additional introduction of a carboxymethyl group. A disadvantage, however, is the sensitivity of the carboxymethyl group to pH: it is protonated even in the weakly acidic range and so takes on a hydrophobic character itself. The carboxymethyl group is also sensitive to divalent ions, such as calcium ions, for example. Calcium compounds, however, are frequently used as fillers in aqueous emulsion paints.
P. Talaba, I. Srokova, P. Hodul and G. Cik in Chem. Papers 50 (2), 101 (1996) describe hydrophobically modified sulfoethylcelluloses. High degrees of substitution are necessary in these compounds, however, because of the absence of other substituents. They are water-soluble only at low degrees of polymerization, and possess a strong tendency to form foam, which is undesirable for use in emulsion paints.
EP-A-0 781 780 describes sulfoalkylated cellulose ethers modified hydrophobically using C
10
-C
40
alkyl chains, these ethers likewise possessing a high surfactant action and being used as thickeners in cosmetic formulations. For these compounds a degree of sulfoalkylation of from 0.1 to 1 is claimed.
SUMMARY OF THE INVENTION
The object of the present invention is to provide water-soluble, hydrophobically modified cellulose derivatives which when used in emulsion paints cause only minimal bodying of the paints, comparable with that of cellulose ethers not hydrophobically modified, and which at the same time improve the non-drip characteristics of the paints when applied with a roller to an extent similar to that of the commercial cellulose ethers modified hydrophobically using long-chain alkyl groups. The invention also intends to provide cellulose derivatives which when used in emulsion paints bring about a substantial improvement in their non-drip characteristics even at relatively low paint viscosities, while at the same time allowing the paint to be easily spread (by brush or roller, etc.). In addition, the emulsion paint must attain good abrasion resistance.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention accordingly provides water-soluble ionic cellulose ethers from the group of hydroxyalkylcelluloses which are substituted by on average from 0.001 to 1.0, preferably from 0.001 to 0.2, alkyl group per anhydroglucose unit and carry from 0.01 to 0.1 sulfoalkyl group per anhydroglucose unit.
Preferred cellulose ethers are those of the formula
[C
6
H
7
O
2
(OR
1
)(OR
2
)(OR
3
)]
m
where
C
6
H
7
O
2
is an anhydroglucose unit,
m is 50-3000, especially 100-1000,
and R
1
, R
2
, R
3
independently of one another are each a polyalkylene oxide chain of the formula
where
X=H, C
n
H
2n+1
, C
n
H
2n−1
O, CH
2
—CH
2
—SO
3
Y or CH
2
—CHOH—CH
2
SO
3
Y,
n=4-20
and Y=H, Na or K,
and in which
p, q, and r independently of one another in R
1
, R
2
and R
3
can each independently assume values from 0 to 4, the sum of all (p+q+r) added over R
1
, R
2
and R
3
per anhydroglucose unit is on average greater than 1.3 and less than 4.5, preferably from 1.5 to 3.0, the sequence of the oxyalkylene units in the polyalkylene oxide chain is arbitrary, and the average number of hydrophobically modified groups per anhydroglucose unit (DS HM) is from 0.001 to 0.2, preferably from 0.01 to 0.04, and the average number of sulfoalkyl groups per anhydroglucose unit is from 0.01 to 0.1, preferably from 0.01 to 0.09. The sulfoalkyl groups are preferably sulfoethyl groups.
The present invention also provides processes for preparing the cellulose ethers of the invention by etherifying cellulose with an etherifying agent from the group of the alkylene oxides and etherifying with an alkyl halide or an alkyl glycidyl ether and a sulfonate, with base catalysis, or by etherifying ethers from the group of hydroxyalkylcelluloses with an alkyl halide or an alkyl glycidyl ether and a sulfonate, with base catalysis, preferably
A) by etherifying cellulose with ethylene oxide, propylene oxide and/or glycidyl alcohol and an alkyl halide or an alkylene oxide or an alkyl glycidyl ether and an alkenylsulfonate or chloroalkylsulfonate, with base catalysis, preferably in a suspension medium;
B) by etherifying hydroxyethylcellulose, hydroxypropylcellulose, dihydroxypropylcellulose or a cellulose ether having two or more of said hydroxyalkyl substituents with an alkyl halide or an alkylene oxide or an alkyl glycidyl ether and an alkenylsulfonate or chloroalkylsulfonate, with base catalysis, preferably in a suspension medium.
Suspension media preferably used are lower alcohols or ketones, an example being isopropanol, tert-butanol or acetone, in a weight ratio to the cellulose of from 3:1 to 30:1, preferably from 8:1 to 15:1. As the base it is usual to use aqueous solutions of alkali metal hydroxides, especially sodium hydroxide. The molar ratio of base to anhydroglucose unit is determined by the carbohydrate (derivative) used. When using cellulose (method A) the molar ratio is preferably from 1.0 to 1.5; for products which are already etherified (method B) it is preferably from 0.1 to 1.0 mol of base per anhydroglucose unit.
The water content of the reaction mixture is preferably from 5 to 30, in particular from 10 to 20, mol of water per anhydroglucose unit.
After the suspension medium has been introduced as initial charge, the cellulose added and the batch rendered alkaline with the aqueous base, the batch is homogenized thoroughly and stirred without supply of heat, with cooling if desired, for preferably from 0.5 to 2 hours. The etherification reagents (epoxyalkanes, alkyl glycidyl ethers and/or alkyl halides and sulfonic acid derivatives) are subsequently added in unison or in succession. The batch is then brought preferably to a temperature in the range from 60 to 120° C., with particular preference from 80 to 100° C., and is heated for preferably from 2 to 6 hours. After cooling, it is neutralized with an acid, preferably hydrochloric acid, nitric acid and/or acetic acid, preferably to a pH of from 6 to 8. The suspension medium is removed by decantation or filtration. The crude cellulose mixed ether can be freed from the adhering byproducts, such as polyglycols, glycol ethers and salts, by extraction with aqueous alcohols or ketones having a preferred water content of from 10 to 50% by weight, especially isopropanol, ethanol and acetone. After drying under reduced pressure or at atmospheric pressure at from 50 to 120° C., t
Doenges Reinhard
Kirchner Juergen
Clariant GmbH
Hanf Scott E.
Peselev Elli
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