Modified cellulose ethers and their use in dispersion paints.

0001The invention relates to water-soluble cellulose ethers, to their use and to emulsion paint which contains this compound.

0002When using commercial cellulose ethers which have been hydrophobically modified with long-chain alkyl groups as thickeners in emulsion paints, undesirably high post-thickening occurs during storage. The consistency of the emulsion paint increases sharply after it is produced and can reach more than twice the value after a day of storage. This makes it difficult to adjust / monitor the color consistency at the paint manufacturer. Another disadvantage of these cellulose ethers which have been hydrophobically modified with long-chain alkyl groups is that the dispersion paints thickened with these products only significantly less when processed with a relatively high color consistency of at least 25000-32000 mPa · s (Brookfield rheometer, spindle 6 at 10 rpm) spray as the colors produced with non-hydrophobically modified cellulose ethers. On the other hand, high color viscosities have a disadvantageous effect on the spreadability and gradient of the colors.

0003The object of the invention is to provide water-soluble, hydrophobically modified cellulose derivatives which, when used in emulsion paints, bring about only a slight subsequent thickening of the paints, comparable to non-hydrophobically modified cellulose ethers, and at the same time improve their spray behavior when the paint is applied to the roller to an extent such as this is only achieved with the commercial cellulose ethers modified hydrophobically with long-chain alkyl groups. The invention is also intended to provide cellulose derivatives which, when used in emulsion paints, significantly improve their spray behavior even at relatively low paint viscosities, on the other hand the paint must be easy to spread.

0004This object is achieved according to the invention by the cellulose ether with the features mentioned in claim 1 and by the emulsion paint with the features mentioned in claim 6. The dependent claims indicate appropriate further training.

0005The invention further relates to the use of the cellulose ether according to claim 8.

0006The basic molecular structure of the cellulose derivative consists of the known linear polymer of anhydroglucose units. The number of OH groups etherified per anhydroglucose unit by the non-hydrophobic substituent is expressed by the average degree of substitution, the number of units of the non-hydrophobic etherifying agent added per anhydroglucose unit by the molar degree of substitution. The degrees of substitution in the compound of the invention are in the usual range of cellulose ethers. The molar degree of substitution is, for example for the hydroxyethyl group in hydroxyethyl cellulose 1.5 to 4.0, in particular 2.0 to 3.0. The amount of the non-hydrophobic substituents is not critical as long as it is sufficient to ensure the desired water solubility of the cellulose derivative.

0007The cellulose derivatives according to the invention are water-soluble cellulose ethers with non-hydrophobic substituents and additionally hydrophobic substituents, which contains a fluorine-containing, branched or unbranched alkyl chain of 3-24, in particular 5-18, carbon atoms. In the fluorine-containing substituent, preferably at least 2, in particular at least 3, C atoms are connected to fluorine atoms.

0008The amount of these hydrophobic substituents is comparatively small and corresponds to a fluorine content in the range of 0.05-5, preferably 0.1-1% by weight, based on the dry weight of the cellulose derivative. The fluorine content is determined in the following way: The product is completely freed from salts and any fluorine-containing impurities, which may be adsorptively bound, with an aqueous organic and then with an organic extracting agent and dried at 110 ° C. for 10 hours. The sample is burned using the Schöniger method, the hydrofluoric acid formed is absorbed in water and analyzed with an ion-selective electrode (Lit .: W. Schöniger, Mikrochim. Acta (1955/1, 123ff).

0009In addition to the fluorine-containing substituent (s), the cellulose derivatives contain one or more non-hydrophobic substituents with a non-fluorine-containing radical from the group of hydroxyethyl, hydroxypropyl, methyl, ethyl and carboxymethyl bonded to the cellulose via an ether bond. The amount of these non-hydrophobic substituents is adjusted so that, depending on the intended use, the cellulose derivative is adequately water-soluble. Sufficiently water-soluble cellulose derivatives have a solubility of at least 0.5% by weight in water (20 ° C.).

0010The preferred residue of the non-fluorine-containing non-hydrophobic substituent is hydroxyethyl. The average degree of polymerization of the cellulose ether derivatives according to the invention is approximately 50-2000, in particular 400-1200.

0011In contrast to the cellulose ethers previously used in emulsion paints which have been hydrophobically modified with long-chain non-fluorine-containing alkyl groups, the 1-2% aqueous solutions of the cellulose ether derivatives according to the invention show practically no associative thickening because of their low proportion of hydrophobic fluorine-containing substituents. In aqueous solution, they behave like corresponding unmodified cellulose ethers.

0012The modified fluorine-containing alkyl radicals can be bound to the cellulose substrate via an ether, ester or urethane bond. The ether bond is preferred because it is usually the most resistant to further reactions, for example hydrolytic cleavage from the cellulose backbone.

0013Methods for making mixed fluorine-free cellulose ethers, ie products with more than one modifying, etherifying, non-fluorine-containing residue on the same cellulose molecule, are known in the art. The cellulose derivatives of the invention are produced analogously to the procedure described for mixed, non-fluorine-containing cellulose ethers or by combining corresponding processes for the production of cellulose ethers with non-hydrophobic residues with the known production of cellulose derivatives with only fluorine-containing substituents.

0014The fluorine-containing substituents can accordingly be introduced either before, after or simultaneously with the introduction of hydroxyethyl, hydroxypropyl, methyl, ethyl and / or carboxymethyl ether groups. Preferably, a non-fluorine-containing cellulose ether from the group hydroxyethyl, hydroxypropyl, methyl, ethyl or carboxymethyl cellulose or one of their mixed ethers is preferably prepared by known processes. These are then reacted with the fluorine-containing reagents either with or without intermediate insulation in the presence of bases such as, for example, aqueous alkali metal hydroxides, aqueous alkaline earth metal hydroxides, quaternary ammonium hydroxides or tertiary amines such as pyridine, triethylamine or tripropylamine. The bases serve both as a catalyst for the reaction with the fluorine-containing reagent and as a swelling agent for the cellulose substrate. This ensures that the fluorine-containing reagents react with practically all cellulose ether molecules at the same time. The reaction is preferably carried out in an inert diluent. Suitable such are, for example, lower alcohols, such as isopropanol and t-butanol, ketones such as acetone, aromatic or aliphatic hydrocarbons, such as toluene, or the fluorine-containing reagent used in excess itself. The reaction usually takes place in the temperature range from 20 to 100 ° C. When the reaction has ended, the remaining base is neutralized, the product is recovered, optionally washed with aqueous organic and / or organic solvents and finally dried. In the end product, the cellulose derivatives are in the form of granules or powder and usually have residual moisture levels of less than 10%.

0015Suitable fluorine-containing reagents for forming an ether bond between the cellulose and the fluorine-containing substituent are, for example, alkylene oxides with a fluoroalkyl radical, fluoroolefins, fluorine-containing haloalkanes, fluorine-containing halohydrins, glycidyl ethers of fluoroalcohols and Michael systems such as fluorine-containing acrylonitrile and acrylic ester derivatives.

0016Alkylene oxides with a fluoroalkyl radical to form an ether bond show the formula<chemistry id="chem0001" num="0001"><img file="EP0476507A2_D0001.tif" /></chemistry> in which R is an alkyl radical having 3 to 22, in particular 3 to 16, carbon atoms, at least 3 carbon atoms being fluorinated.

0017These compounds react to form cellulose derivatives of the formula<ul id="ul0001" list-style="none"><li>(a)         R - CH (OH) - CH₂ - O - cellulose ether. Fluorine-containing halohydrins have the formula         R - CH (OH) - CH₂Cl (Br), in which R has the same meaning. They react in the presence of bases with elimination of HCl or HBr to give the alkylene oxide and this in the same way as described above for the cellulose derivative. Fluoroolefins are fluorine-containing hydrocarbons         R - CF = CF - R¹ with a total of 3-24, in particular 5-18 carbon atoms and at least one double bond, at least the carbon atoms on a double bond and a third carbon atom being fluorinated. R and R¹ are alkyl radicals. Cellulose derivatives of the formula are obtained</li><li>(b)         Cellulose ether - O - CFR - CHFR¹ or</li><li>(c)         Cellulose ether - O - CFR¹ - CHFR. Fluorine-containing haloalkanes consist of saturated hydrocarbons RX with at least 3 fluorinated carbon atoms in the alkyl radical R and one carbon atom with a chlorine, bromine or iodine atom (= X). The total number of carbon atoms is 3 to 24, in particular 5 to 18. The cellulose derivative has the formula</li><li>(d)         Cellulose ether - O - R. Glycidethers of fluoroalcohols have the formula<chemistry id="chem0002" num="0002"><img file="EP0476507A2_D0002.tif" /></chemistry> in which R is an alkyl radical having 3 to 21, in particular 3 to 15, carbon atoms. The compound contains at least 3 fluorinated carbon atoms. The resulting cellulose derivative has the formula</li><li>(e)         Cellulose ether - O - CH₂ - CH (OH) - CH₂ - OR. Fluorine-containing acrylonitriles and acrylic esters show the formulas         CX₂ = CX - Y         R²CX = CX - Y in which X represents hydrogen and / or fluorine. R² is either H or an alkyl radical having 1 to 22, in particular 3 to 16, carbon atoms, Y is -CN or -CO₂R³, where R³ is an alkyl group having 1 to 22, in particular 3 to 16, carbon atoms. These compounds contain at least 3 fluorine-containing carbon atoms. You react to</li><li>(f)         Cellulose ether - O - CX₂ - CHX - Y or</li><li>(G)         Cellulose ether - O - CXR² - CHX - Y. The introduction of the fluorine-containing radicals into cellulose or cellulose ether via an ether linkage of the fluorinated group takes place under reaction conditions analogous to those in the known production of cellulose ethers with various non-fluorine-containing radicals. Here one starts from cellulose or from cellulose and introduces the non-fluorine-containing residue and the fluorine-containing residue by reaction with a hydroxyl group of the cellulose in the basic madium one after the other or simultaneously. When introducing fluorine-containing substituents through an ester or urethane linkage, practically the same procedures are used as when forming an ether linkage with the fluorine-containing reagents. Suitable fluorine-containing reagents for forming an ester or urethane bond are, for example Fluoroalkylene oxides, fluorine-containing ketenes, fluorine-containing carboxylic acid halides, especially chlorides and bromides, or fluorine-containing isocyanates. Fluoroalkylene oxides to form an ester bond have the formula<chemistry id="chem0003" num="0003"><img file="EP0476507A2_D0003.tif" /></chemistry> in which R is an alkyl radical having 1 to 24, in particular 5 to 18, carbon atoms. Fluorine atoms are present on at least 2, preferably at least 3, C atoms of this compound. These compounds react to cellulose derivatives of the formula (h)</li><li>(H)         RCF₂ - CF₂ - O (CFR-CF₂-O)_n - CFR - CO - O - cellulose ether         n = 0-3 or</li><li>(i)         R - CF₂ - CO - O - cellulose ether. Fluorine-containing ketenes show the structure<chemistry id="chem0004" num="0004"><img file="EP0476507A2_D0004.tif" /></chemistry> R² represents an H atom or a fluorine-containing alkyl radical, R a fluorine-containing alkyl radical, R and R² have a total of 2 to 24 C atoms, at least 2, preferably at least 3 C atoms being fluorinated. These compounds react to form cellulose derivatives of the formula</li><li>(j)         HCRR² - CO - O - cellulose ether. Fluorine-containing carboxylic acid halides R - COX (X = Cl, Br) have a fluorinated alkyl group with 3 to 24, in particular 5 to 18, carbon atoms, at least 2, preferably at least 3, carbon atoms being fluorinated. They react to cellulose derivatives of the formula</li><li>(k)         R - CO - O - cellulose ether. Fluorine-containing isocyanates have the formula         R - N = C = O, in which R is a fluorinated alkyl group having 3 to 24, in particular 5 to 18, carbon atoms, at least 2, preferably at least 3, carbon atoms being fluorinated. You react to</li><li>(l)         R - NH - CO - O - cellulose ether.</li></ul>

0018The presence of bases is essential for the implementation of these fluorine-containing reagents with cellulose or cellulose ethers to form an ester or urethane bond, as in the formation of an ether bond. The bases ensure sufficient swelling of the cellulose or the cellulose ethers before the reaction with the fluorine-containing reagent, so that the modifying fluorine-containing reagents can react practically uniformly with all cellulose or cellulose ether molecules. If the reaction is not largely uniform, the desired improvement in performance will not be achieved.

0019Suitable reaction apparatuses for producing the cellulose ether derivatives according to the invention are, for example, stirred kettles, mixers and kneaders. In principle, all reaction apparatuses can be used which are also common in the production of cellulose derivatives with non-hydrophobic substituents and which permit sufficient mixing of the cellulose or the water-soluble cellulose ether with the non-hydrophobic reagents.

0020The invention is illustrated by the following examples. All percentages refer to percent by weight. The following fluorine-containing reagents are used:<chemistry id="chem0005" num="0005"><img file="EP0476507A2_D0005.tif" /></chemistry><ul id="ul0002" list-style="none"><li>(4)         C₇F₁₅CH₂Br</li><li>(5)         CF₃ - CF = CF₂</li><li>(6)         C₅F₁₁ - CF = CF₂</li></ul>

example 1

002160 g air-dry spruce pulp are suspended in a mixture of 586.4 g 95% t-butanol and 60 g isopropanol. The suspension is transferred to a 2 l autoclave, rendered inert by evacuation and blanketing with nitrogen, and a solution of 15.35 g of sodium hydroxide solution in 45 g of water is added dropwise while stirring. After stirring for a further 30 minutes at room temperature, 94.6 ml of ethylene oxide are added to produce hydroxyethyl cellulose. The reaction is then carried out at 40 ° C. for 2 hours, partially neutralized with 30.43 g of 65% nitric acid and the reaction is completed at 80 ° C. within 2 hours. 0.8 g of alkylene oxide of the formula (1) is added and the mixture is reacted at 90 ° C. for a further 6 h. After cooling, the mixture is neutralized with 4.6 g of acetic acid, extracted salt-free with 80% acetone, dehydrated with 1 l of acetone, washed twice with 1 l of gasoline and the product is dried at 60 ° C.

0022The hydroxyethyl cellulose derivative has a molar degree of substitution of 4.0 and a fluorine content of 0.09%. Its viscosity in 2% aqueous solution is 9300 mPa · s.

Example 2

002370 g air-dry hydroxyethyl cellulose with a molar degree of substitution of 2.4 and a viscosity of 5600 mPa · s in 2% aqueous solution are suspended in 371 g 95% t-butanol. The suspension is transferred to a 2 l autoclave, rendered inert by evacuation and blanketing with nitrogen, and a solution of 2 g of sodium hydroxide solution in 26.2 g of water is added with stirring. After stirring for 30 minutes at room temperature, 5.9 g of alkylene oxide of the formula (2) are added. The reaction is carried out at 90 ° C. for 6 h, the mixture is cooled, neutralized with 3.3 g of acetic acid and worked up as in Example 1.

0024The hydroxyethyl cellulose derivative has a fluorine content of 0.29% and a viscosity in 2% aqueous solution of 3800 mPa · s.

Example 3

0025Following the same procedure as in Example 2, instead of the alkylene oxide of the formula (2) is reacted with 8.8 g of the alkylene oxide of the formula (3). The resulting hydroxyethyl cellulose derivative has a fluorine content of 0.16% and a viscosity in 2% aqueous solution of 2400 mPa · s.

Example 4

0026Following the same procedure as in Example 2, the reaction is carried out with 3.1 g of alkylene oxide of the formula (2) in 371 g of 77% isopropanol. The hydroxyethyl cellulose derivative has a fluorine content of 0.35% and a viscosity in 2% aqueous solution of 5100 mPa · s.

Example 5

002760 g air-dry spruce pulp are suspended in 500 g t-butanol, 31 g acetone and 50 g water. The suspension is transferred to a 2 l autoclave, rendered inert by evacuation and blanketing with nitrogen, a solution of 23.8 g of sodium hydroxide solution in 46.6 g of water is added, the mixture is stirred at room temperature for 30 minutes, mixed with 34.8 ml of ethylene oxide and can react at 55 ° C for 45 min. A further portion of 52.2 ml of ethylene oxide and 4.1 g of bromide of the formula (4) is then added and the mixture is reacted at 70 ° C. for 45 min and at 95 ° C. for 2.5 h. The mixture is allowed to cool to 70 ° C., 14.1 g of monochloroacetic acid dissolved in 34.5 g of t-butanol are added and the mixture is left to react at 70 ° C. for 1 hour. After cooling, neutralized with 29 g of 65% nitric acid and 1.7 g of acetic acid and worked up as in Example 1.

0028The hydroxyethylcarboxymethyl cellulose derivative has a molar degree of substitution of hydroxyethyl of 2.7 and an average degree of substitution of carboxymethyl of 0.25. Its fluorine content is 0.32%. The viscosity of the 2% aqueous solution is 20,100 mPa · s.

Example 6

002970 g air-dry methylhydroxyethylcellulose with an average degree of substitution of 1.4 in methyl and a molar degree of substitution of 0.14 in hydroxyethyl and a viscosity of 2600 mPa · s in 2% aqueous solution are suspended in 300 g 95% t-butanol. The suspension is transferred to a 2 l autoclave, rendered inert by evacuation and blanketing with nitrogen, a solution of 2.4 g of sodium hydroxide solution in 38.8 g of water is added dropwise while stirring, the mixture is stirred for 30 minutes at room temperature and a solution of 1.5 g of perfluoroolefin of the formula (5) in 20 g of t-butanol. The reaction is then carried out at 90 ° C. for 6 h. The mixture is allowed to cool, neutralized with 4 g of acetic acid and worked up as in Example 1.

0030The methylhydroxyethyl cellulose derivative has a fluorine content of 0.6% and a viscosity in 2% aqueous solution of 1870 mPa · s.

Example 7

0031Analogously to Example 6, 2.6 g of perfluoroolefin of the formula (6) are used for the reaction. The methylhydroxyethyl cellulose derivative obtained has a fluorine content of 0.4% and a viscosity in 2% aqueous solution of 2100 mPa · s.

0032The cellulose derivatives prepared in Examples 2 and 3 are incorporated as thickeners in an internal dispersion paint and their effect is compared with the prior art thickeners.

0033The emulsion paints examined contain the following master batch:<tables id="tabl0001" num="0001"><img file="EP0476507A2_D0006.tif" /></tables>

0034Production of the finished color:<tables id="tabl0002" num="0002"><img file="EP0476507A2_D0007.tif" /></tables><dl id="dl0001"><dt>Sample A:</dt><dd>Thickener cellulose derivative of Example 2</dd><dt>Sample B:</dt><dd>Thickener cellulose derivative of Example 3</dd></dl>

0035For comparison with the cellulose derivatives of the invention, the following prior art thickeners are used. All viscosity values ​​(mPa · s) of the thickeners were determined in a 2% aqueous solution at 20 ° C. in accordance with DIN 53 015 in a Höppler falling ball viscometer.<dl id="dl0002"><dt>Sample C:</dt><dd>Thickener hydroxyethyl cellulose viscosity 6000 mPas / 2%</dd><dt>Sample D:</dt><dd>Thickener methylhydroxyethylcellulose, viscosity 6000 mPas / 2%</dd><dt>Sample E:</dt><dd>Thickener hydroxyethyl cellulose with long chain alkyl residue, viscosity 6000 mPas / 2%</dd><dt>Sample F:</dt><dd>Thickener ethyl hydroxyethyl cellulose, hydrophobically modified, viscosity 6000 mPa · s / 2%</dd></dl>

0036Immediately after completion of the color and after conditioning at 20 ° C / 50% moisture / 1 day, the color viscosities were measured with the Brookfield rheometer (spindle 6 at 10 and 100 rpm, 20 ° C).

0037The viscosity values ​​measured result in less thickening of the products according to the invention (samples A and B) compared to conventional cellulose ethers and the hydrophobically modified cellulose ethers (samples E and F).<tables id="tabl0003" num="0003"><img file="EP0476507A2_D0008.tif" /></tables>

0038Conditioned emulsion paints with a reference viscosity of 25,000 mPa · s (Brookfield rheometer, spindle 6, 10 rpm, 1 min measuring time, 20 ° C.) are used to assess the yield of the thickeners.

0039The products according to the invention show a higher yield in comparison. The following quantities (% by weight based on the total weight of the paint) are required to set the reference consistency:<dl id="dl0003"><dt>Sample A</dt><dd>0.44 - 0.50% by weight</dd><dt>Sample B</dt><dd>0.44 - 0.50% by weight</dd><dt>Sample C</dt><dd>0.55 - 0.60% by weight</dd><dt>Sample D</dt><dd>0.58 - 0.63% by weight</dd><dt>Sample E</dt><dd>0.50 - 0.55% by weight</dd><dt>Sample F</dt><dd>0.52 - 0.57% by weight</dd></dl>

0040The following test is carried out to quantitatively assess the spraying behavior of an emulsion paint, which simulates the application of the paint with the paint roller:

0041A conditioned paint roller is loaded with a defined amount (35 ml) of emulsion paint and rolled out several times with motorized strokes on a paint wiper that is common in practice. The contact pressure of the paint roller is kept constant. At the bottom of a bowl that serves as a support for the rectangular grid, there is a black cardboard box. The color splashes that hit it are quantified in terms of number and area coverage with a photo-electronic image analyzer.

Results (paint splash test)

0042<tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="2" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">sample</entry><entry namest="col2" nameend="col2" align="center">Area covered with paint splashes (%)</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">A</entry><entry namest="col2" nameend="col2" align="char" char=",">0,4 - 0,5</entry></row><row><entry namest="col1" nameend="col1" align="left">B</entry><entry namest="col2" nameend="col2" align="char" char=",">0,4 - 0,5</entry></row><row><entry namest="col1" nameend="col1" align="left">C.</entry><entry namest="col2" nameend="col2" align="char" char=",">1,7 - 2,1</entry></row><row><entry namest="col1" nameend="col1" align="left">D</entry><entry namest="col2" nameend="col2" align="char" char=",">0,7 - 0,9</entry></row><row><entry namest="col1" nameend="col1" align="left">E</entry><entry namest="col2" nameend="col2" align="char" char=",">0,4 - 0,5</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">F</entry><entry namest="col2" nameend="col2" align="char" char=",">0,4 - 0,5</entry></row></tbody></tgroup></table></tables>

0043When the cellulose derivatives according to the invention are processed in emulsion paints, they show a comparable reduction in the tendency to spray compared to cellulose derivatives hydrophobized with long alkyl chains. However, they lead to a lower thickening of the color when stored and have a higher yield and thus increased effectiveness with regard to the thickening effect in the color. Compared to the cellulose ethers without hydrophobic modification, the cellulose derivatives according to the invention achieve a significantly reduced spray behavior of the emulsion paint. To achieve the desired color consistency, a smaller amount of thickener is also required compared to these compounds.

0044The cellulose derivatives are also suitable as protective colloids for suspension / emulsion polymerization and can also be used as surface-active compounds.