DE19935323A1 - Use of optionally substituted with methyl and optionally hydroxyalkyl sulfoalkylmodifizierten cellulose ethers as non-associative thickener for aqueous coating systems and a process for the preparation of hydroxyalkyl-methyl-sulfoalkylcellulose - Google Patents

Abstract

The invention relates to the use of sulfoalkyl-modified cellulose ethers, which are optionally substituted by hydroxyalkyl groups, as non-associatively active thickeners for aqueous coating systems such as dispersion paints, silicone resin paints or silicate paints. The invention also relates to a method for producing hydroxyalkyl-methyl-sulfoalkyl celluloses suited for this intended use.

Description

The invention relates to a new class of water-soluble, ionic cellulose ethers and their use as an additive for aqueous coating compositions, in particular Facade colors, such. B. emulsion paints, silicone resin paints and silicate paints.

Water-soluble cellulose ethers, such as hydroxyethylcellulose (HEC), methylcellulose (MC) and carboxymethylcellulose (CMC) as well as mixed ethers of both ionic and ionic cellulose ethers have long been used as protection colloids or auxiliaries for controlling rheology and water retention in Used paints. Usually, products based on carboxy methylcellulose (CMC) and differently substituted methylcellulose or Hydroxyalkyl methylcellulose ethers (HEMC, MC, HPMC) and hydroxyethylcellu loose ether (HEC) used. The amounts used are usually in the range of about 0.3-0.8% (Ullmanns Enzyklopadie der technischen Chemie, Volume 9, 4th edition 1975, page 209). Changes in consumer habits as well as those at The formulation of the coating colors makes it necessary to determine the properties of the coating Thickeners usually used to improve further.

So there is a general desire to use emulsion paints, which are characterized by a high thickening performance, good storage stability and easy processing and environmentally friendly application. Furthermore, the products should be in different recipes consistently good performance engineering own (low tendency to spill, good color surface, slight spread availability, high abrasion resistance, good pigment distribution and the like ä.). In addition, they should ver be technically fast and easy and inexpensive to produce. Out For economic reasons, therefore, the etherifying agents used should be economical  used; The degree of etherification should therefore be as low as possible without it application disadvantages for the end user are connected.

It is known that products with high degrees of substitution by hydroxyethyl groups are highly hygroscopic, which can lead to processing problems (see US 4,902,733). Other products, such as Guar ether (e.g., hydroxy propylguar) show problems due to low thickening, bad Water retention, lack of delay and insufficient storage or organic stabilities. In addition, it is known that the use of non-ionic, highly hydro phobic products, such. Hydroxypropyl, methyl, methyl hydroxypropyl, Methyl hydroxyethyl or ethyl cellulose ethers under extreme conditions Consistency problems. At higher temperatures it comes in use corresponding products in the paint to a reduced water retention or to flocculate the thickener. By the use of z. B. ionic Cellulose ethers based on carboxymethylcellulose can be such problems avoid. However, such products are especially polyvalent ones Cations incompatible, resulting in coagulation and associated Ver succeeded, bad color surfaces and viscosity losses is connected (See L. Brandt in Ullmanns Encyclopedia of Industrial Chemistry, Vol. Verlag Chemie, Weinheim / New York, 1986, page 479 ff., See also DE-OS 31 26 489).

The use of associative thickeners (see, for example, J.W. Schermann in "Dispersion Silicate Systems", W. Schultze et al., Expert Verlag (1996), p. 408- 438) depending on the type and amount of stock in the formulation which in turn means the universal use of such associative thickeners not allowed or only to a very limited extent.

Object of the present invention was to use a cellulose ether as an additive for aqueous coating systems to provide the o. g. Disadvantages ver avoids, is easy to produce and in good yields and compared to the previous  commercially available thickeners to improved performance properties leads.

Surprisingly, it has been found that the use of water-soluble binary and ternary sulfoalkyi-modified cellulose ether in aqueous coating systems with improved performance characteristics. The Class of binary cellulose ethers and their preparation are in the Literature (eg DE 42 03 530 A1 or EP 0 554 749 B1).

The sulfoalkyl-modified cellulose ethers act as non-associative thickeners.

The sulfoalkyl-modified cellulose ethers have very good acid and alkali properties in contrast to products based on carboxymethylcellu loosely with a large number of especially polyvalent cations (especially calcium) and aluminum ions) are excellently compatible.

As sulfoalkyl-modified cellulose ethers may optionally with hydroxy alkyl groups, in particular with hydroxyethyl or hydroxypropyl substitui tuierte sulfoalkylcelluloses be used. Preference is given to the hydroxy alkylcelluloses, in particular hydroxyethyl-sulphoethylcellulose (HESEC), hydroxy propyl sulfoethyl cellulose (HPSEC) and hydroxyalkyl hydroxypropyl sulfoethyl cellulose. In a further variant, the binary with hydroxyalkyl groups are sub substituted sulfoalkylcelluloses as so-called ternary cellulose ethers additionally substituted with methyl groups. These compounds are so-called hydroxyalkyl Methyl-Sulfoalkylcellulosen. Preference is given to the hydroxyalkyl-methyl-sulfo ethylcellulose, most preferably the hydroxyethyl-methyl-sulfoethylcellulose (HEMSEC).

The sulfoalkyl-modified cellulose ethers used according to the invention have average degrees of substitution (DS) by sulfoalkyl, especially sulfo ethyl groups of <0.5, in particular <0.4, preferably ≦ 0.3. The average  Liche degree of substitution by hydroxyalkyl groups (MS-HA) with the catalytic Amounts of alkali-reacting compounds ethylene oxide and / or propylene oxide is at MS <1.0, in particular at <1, 2, preferably ≧ 1.8. Preference is given to ethylene oxide used as hydroxyalkylating agent.

In the case of the hydroxyalkyl-methyl-sulfoalkylcelluloses, the average Degree of substitution by hydroxyethyl groups (HA) with catalytic amounts Alkali-reacting compounds ethylene oxide and / or propylene oxide are preferred <1, preferably 1.5-4.5, especially at 1.8-3.5. Preferred is ethylene oxide as Hydroxyalkylating used. The average degree of substitution by Methyl groups (ME) is at ME = 0.01-2.0, especially at 0.2-2.0, before zugt 0.4-1.2, more preferably 0.6-1.0. The average degree of substitution by sulfoalkyl groups (SE), in particular sulfoethyl groups, is <0.3, preferably at 0.001-0.2, more preferably at 0.01-0.2.

The abovementioned sulfoalkyl-modified cellulose ethers can be used as non-associative thickeners (additives) for aqueous coating systems such as facade paints, in particular special emulsion paints, silicone resin paints or silicate paints. The additive according to the invention achieves the following advantages for the colors in comparison with the conventional cellulose ethers:

• 1. Good or even significantly improved storage stability.
• 2. Good or significantly improved abrasion resistance.
• 3. Improved spreadability.
• 4. Good or improved gradient.
• 5. Significantly less tendency to spray and thus significantly improved Appli cation of color.

The cellulose ethers used according to the invention have average degrees of polymerization (DP) of 30-4,000, in particular 300-2,500, and in 2% by weight aqueous solution have viscosities of 5-80,000 mPa.s (rotational viscometer) at a shear rate of D = 2.5 s ^-1 and a temperature of 20 ° C. The cellulose ethers described above have no flocculation point <100 ° C in water.

The cellulose ethers used according to the invention can be prepared by various methods Process are produced. The preparation of the invention claimed Hydroxyalkyl sulfoethylcelluloses is preferably based on those in the literature (see for example EP 0 554 749 B1, DE 42 03 530 A1, EP 0 487 988 A3).

Another object of the invention is a process for the preparation of the ternary cellulose ethers of the hydroxyalkyl-methyl-sulfoalkylcellulose type. In this case, the etherification of the cellulose is carried out with chloromethane, at least one hydroxyalkyl groups transmitting compound such. Example, ethylene oxide or propylene oxide and at least one sulfoalkyl group-transferring compound, in particular the sodium salt of vinyl sulfonic acid, according to the following steps:

• a) alkalization of the cellulose
• b) before, during or after a) addition of chloromethane,
• c) before, during or after a) or b) adding at least one Sulfoalkyl group transferring compound,
• d) optionally neutralizing a portion of the alkalizing agent,
• e) optionally adding additional alkalizing agent,
• f) neutralization of excess alkalizing agent, in which
• g) the addition of the hydroxyalkylating agent takes place after step a), wherein min at least 50% by weight of the hydroxyalkylating agent, based on the total amount of hydroxyalkylating agent, after process step c) but before the process step f) are added.

Preferably, before the alkalization (step a), the addition of chloromethane (Step b) and at least one sulfoalkyl group-transferring compound (Step c).

Preference is given by this process according to the invention hydroxyalkyl Methyl-sulfoethylcelluloses, more preferably hydroxyethyl-methyl-sulfoethyl cellulose (HEMSEC).

The process steps a) to f) can advantageously in the presence of a suspension be carried out by means of, as suspending agent is an organic water miscible solvent or a mixture of organic water-miscible Solvents is used. Preference is given to dimethyl ether as suspending agent or a mixture of dimethyl ether and an organic water-miscible Solvent used. For organic water-miscible solvents these are, for example, aliphatic alcohols, ketones and ethers, preferably tertiary butanol, iso-propanol, methyl ethyl ketone, acetone, tetrahydrofuran, Dimethoxyethane or dioxane.

As sulfoalkyl groups transferring compound is advantageously the sodium salt the vinyl sulfonic acid used.

After the etherification reaction, the cellulose ethers are purified. The cleaning The cellulose ether is done by means of water-miscible organic solvents or mixtures of water-miscible organic solvents or Ver wetting of the cellulose ethers with bifunctional carbonyl compounds soluble derivatives with water. Preference is given to the purification of the cellulose ethers after conversion of the cellulose ethers with glyoxal to water-insoluble, reversible crosslinked derivatives are carried out with water.

The level of water retention of the sulfoalkylated cellulose ethers is in the essentially determined by the degree of sulfoalkyl substitution. The below  listed examples show that even the use of small amounts of Sulfoalkylierungsreagenz sufficient to the application properties significantly improve. The setting of degrees of substitution by Sulfoalky sulfoethyl groups of <0.5 is therefore neither of application Reasons still required for procedural and economic reasons. Preferred sulfoalkyl group-transferring compounds are sulfoethyl groups transferring compounds such as chloroethanesulfonic acid, bromoethanesulfonic acid, Vinylsulfonic acid and its salts, in particular their sodium salts.

The invention will be explained in more detail with reference to embodiments and comparative examples. In the examples and tables given below, quantities are parts by weight. The viscosities were measured with a Physika viscometer at a shear rate of D = 2.5 s ^-1 and a temperature of T = 20 ° C. For the determination of the viscosities in aqueous solution, 2% strength by weight solutions in distilled water were measured. The cellulose ethers were all screened out prior to their testing in the color by means of a screening machine with sieves according to DIN 4188. Fractions of 100% <0.315 mm and a maximum of 40% <0.063 mm were used.

Examples Production of HESEC (Table 1, No. 1)

In a 5 liter autoclave, 257 g of cotton linters are evacuated and Injection with nitrogen rendered inert. Subsequently, 1180 g of dimethyl ether, 221 g of water and 131 g of a 30 wt.% Aqueous solution of vinylsulfonic acid sodium salt and 240 g of a 50 wt.% Aqueous sodium hydroxide solution with stirring sprayed the cellulose. After stirring for another 60 minutes at 25 ° C is the mixture heated to 70 ° C. After being stirred at 70 ° C for 80 minutes, 463 g of ethylene oxide are gradually metered into the reactor within 45 minutes and then reacted at 70 ° C for 60 minutes. After evacuation and Ab cooled to 50 ° C, 193 g of acetic acid and 2 l of acetone are metered into the reactor. The Crude product is purified with acetone and acetone / methanol mixtures. The Solvent-moist cellulose ether is stored at 55 ° C in a convection oven dried and then ground.

The hydroxyethylsulfoethylcellulose ether has a degree of substitution Hydroxyethyl groups (MS-HE) of 2.29 and a degree of substitution by sulfo ethyl groups (DS-SE) of 0.08 and a sodium acetate content of 0.07 wt .-%. Its viscosity in 2% aqueous solution is 22227 mPa.s.

Example for the preparation of HESEC (Table 1, No. 2)

In a 5 liter autoclave, 257 g of cotton linters are evacuated and Injection with nitrogen rendered inert. Subsequently, 1200 g of dimethyl ether, 248 g of water and 79 g of a 30 wt.% Aqueous solution of vinylsulfonic acid sodium salt and 242 g of a 49.5 wt.% Aqueous sodium hydroxide solution with stirring sprayed on the cellulose. After stirring for 60 minutes at 25 ° C. the mixture is heated to 70 ° C. After stirring at 70 ° C for 60 minutes is gradually metered within 30 minutes 264 g of ethylene oxide in the reactor  and then reacted at 70 ° C for 60 minutes. After evacuation and Ab are cooled to 50 ° C, 320 g of 65 wt.% Nitric acid and 2 l of acetone in the Metered reactor. The crude product is mixed with acetone / methanol mixtures and Acetone cleaned.

The acetone-wet cellulose ether is then in a 5 l autoclave by Eva kuieren and pressurized with nitrogen. Subsequently, 1723 g Dimethyl ether and 61 g of a 49.5 wt.% Aqueous sodium hydroxide solution with stirring sprayed onto the cellulose ether. After stirring at 25 ° C for 60 minutes is the mixture is heated to 70 ° C. Then gradually within 30 minutes 132 g of ethylene oxide metered into the reactor and then for a further 60 minutes 70 ° C implemented. After evacuation and cooling to 50 ° C, 73 g 65 wt.% Nitric acid and 2 l of acetone are metered into the reactor. The crude product is cleaned with acetone and acetone / water mixtures.

The solvent-moist cellulose ether is dried at 55 ° C. in a circulating air dried and then ground.

The hydroxyethylsulfoethylcellulose ether has a degree of substitution Hydroxyethyl groups (HS-HE) of 2.78 and a degree of substitution by sulfo ethyl groups (DS-SE) of 0.04 and a sodium nitrate content of 0.05 wt .-%. Its viscosity in 2% aqueous solution is 8,799 mPa.s.

Example for the Preparation of HPSEC (Table 1, No. 3)

In a 2 liter autoclave 87 g of wood pulp in 1356 ml of tert-butyl alcohol elutriated. The mixture is added with stirring 19.7 g of a 50 wt.% aqueous solution of Vinylsulfonsäurenatriumsalzes and 68 g of water and added rendered inert by evacuation and nitrogen. Then be 120 g of a 50 wt.% Aqueous sodium hydroxide solution and 203 g of propylene oxide in the Metered reactor and then stirred at 25 ° C for 80 minutes. The mixture is  heated to 80 ° C within 60 minutes and then 120 minutes at this Temperature maintained. Then 90 g of acetic acid and 15 g of 37 wt.% Hydrochloric acid placed in the reactor. The mixture is cooled to 25 ° C and purified slurried the crude product three times in aqueous methanol and each over a Nutsche separated. The solvent-moist cellulose ether is at 55 ° C in dried in a convection oven and then ground.

The hydroxypropylsulfoethylcellulose ether has a degree of substitution Hydroxypropyl groups (MS-HP) of 1.31 and a degree of substitution by sulfo ethyl groups (DS-SE) of 0.09. Its viscosity is in 2% aqueous solution 14,910 mPa.s.

Example for the preparation of HEMSEC (Table 1, No. 4)

In a 5 liter autoclave, 257 g of cotton linters are evacuated and Injection with nitrogen rendered inert. Subsequently, 486 g of dimethyl ether, 136 g of chloromethane, 52 g of a 30 wt.% Aqueous solution of vinylsulfone acid sodium salt and 262 g of a 50 wt.% Aqueous sodium hydroxide solution Stirring sprayed on the cellulose. After stirring at 25 ° C for 60 minutes 66 g of ethylene oxide are metered into the reactor and the mixture is heated to 65 ° C. After being stirred at 65 ° C for 30 minutes, it is brought to 85 ° C heated and held at this temperature for 60 minutes. After cooling to 75 ° C At this temperature, another 264 g of ethylene are gradually added within 40 minutes oxide metered into the reactor. Subsequently, a further 40 minutes at 75 ° C vice sets and then cooled. At 50 ° C then 29 g of 65 wt.% Nitric acid in 1000 g of acetone and 166 g of 50 wt.% Glyoxylsäure in 250 g of acetone in the Given reactor.

The mixture is mixed with 61 g of 40 wt.% Aqueous glyoxal and intensively touched. The glyoxal-crosslinked crude product is separated on a suction filter and at  Dried 55 ° C in a convection oven, at the same time the Glyoxalver reinforced. For purification, the cellulose ether is added twice in 4 l each Slurried water and separated after 3 minutes on a suction filter. The water-moist cellulose ether is stored at 55 ° C in a convection oven dried and then ground.

The hydroxyethylmethylsulfoethylcellulose ether has a degree of substitution by hydroxyethyl groups (MS-HE) of 2.09 and a degree of substitution Methyl groups (DS-ME) of 0.74 and a degree of substitution by sulfoethyl groups (DS-SE) of 0.04 and a NaCl content of 0.8 wt .-%. His Viscosity in 2% aqueous solution is 22,872 mPa.s.

The prepared anionic cellulose ethers are exemplified in a Formu Tested for Dispersioninnenwandfarben.

Table 1 shows the product-specific characteristics of the used sulfoethyl-substituted cellulose ether listed. Table 2 shows the recipe for Preparation of the dispersion inner wall paint reproduced.

In the preparation of the emulsion paints, the procedure is as follows

In a 2 liter water-cooled dissolver cup, the cellulose ethers are under Stir in water at 2000 rpm. Subsequently, the in Table 2 added under position 3 and 4 designated components. After 10 minutes stirring at 2000 rpm, the compo registered. Then the binder (position 16) is added with stirring 2000 rpm and 10 min. Homo with the dissolver at 2000 rpm genisiert. About a concentration series is in advance the amount of the respective Cellulose ether determined, which is required in the emulsion paint, a Visko from 11,000 to 13,000 mPa.s. With the color obtained in this way  Various technical applications were carried out. The results this is shown in Table 3.

Table 3

The assessment of the performance parameters specified in Table 3 are carried out in detail as follows:

ink viscosity

The examination of the coating colors is carried out in such a way that isoviscose coating colors viscosities of 11,000-13,000 mPa.s. This is usually distinguished between two thickening mechanisms. Denoted in Table 1 Neten, non-associatively thickening cellulose ether of the type hydroxyethylsulfone ethylcellulose (HESEC) and hydroxyethylmethylsulfoethylcellulose (HEMSEC) be with the commonly used in the market thickeners of the type HEC (Natrosol 250 MHBR or Natrosol 250 HBR, Aqualon) compared.

Stormer viscosity

The determination of the Stormer viscosity is carried out according to ASTM-D 562. The specification of the Viscosity takes place in cancer units (KU). The determination of the Stormer viscosity pursues the goal of setting the consistency of the color to a uniform level. Usually, Stormer viscosities of about 108-112 Krebs units (KU) sought.

To determine the Stormer viscosity, the dispersion paint for 30 s of Hand stirred. Then the paint is filled in a 500 ml plastic cup and centered on the adjustable platform of the viscometer (Stormer Krebs Viscometer,  Type 000.0407, Mayer & Wonisch, Neheim-Huesten). The standard Whisk is dipped to the mark on the shaft in the color. By the Use of rheometer weights can now be determined accurately How much weight is needed to reach a revolution of 200 rpm. The standard whorl is powered by weights. The included weights range up to 1 kg, gradations are made with 5 g each with a minimum weight of 50 g. These are placed on the weight hitch, with the crank Pulled up and down by pulling down the locking screw calmly. The required weights are used to determine the Stormer viscosity added together and according to the following table in cancer units expelled.

Weight [g] Cancer Units [Ku] 400 104 425 106 450 108 475 110 500 112 525 114 550 116

storage stability

After adjustment of the viscosity required for the color examination of approx. 11,000-13,000 mPa.s, the storage stability is exceeded by storage of the color 15 days at 40 ° C. The color viscosity after storage is recorded, to simulate the viscosity reduction after 6 months. It is as follows addressed.  

The emulsion paint is stirred for 30 seconds with a spoon spatula. The viscosity of the paint is previously determined rheologically (Physica MC 20 rotational viscometer, measuring system Z 3, D = 2.5 s ^-1 , T = 20 ° C.) in order to obtain the initial viscosity. Then about 100 g are filled into a screw-cap jar and stored for 14 days at 40 ° C in a drying oven. On the 14th day, the color is placed in a tempering bath for 1 h at 20 ° C. It is then stirred for 30 seconds with a spatula and then measured with the rheometer (measuring system Z 3, D = 2.5 s ^-1 , T = 20 ° C). The storage stability is given by the following formula:

Viscosity losses indicate an inhomogeneous distribution of the substituents along the cellulose chain or on a concomitant degradation out.

liters weight

With a color pycnometer, the density is determined over the weight of the liter, so to determine whether the products have surface-active properties (foam ne tion), which could then have a negative impact on further testing (Evaluation of the color surface and the like). To determine the weight of the liter is like follows.

The emulsion paint is stirred for 30 seconds with a spoon spatula. The empty one Pycnometer (type 290, Erichsen GmbH & Co. KG, Hemer) is weighed and with the paint at room temperature while avoiding air bubbles brimming filled. The lid is placed under a slight twisting motion and the off The overflow hole escaping substance stripped with a rubber wiper.  

Thereafter, the filled pycnometer is weighed again. The density results the quotient of the weight difference and the volume.

color gradient

The determination of the flow properties of an emulsion paint is given by a Grading test blade included. A paint is usually easy to pass his. This is a certain viscosity adjustment and a related Course behavior required. A paint, recognizable on the brushstrokes those who are not leveled do not have optimal grading behavior.

The test procedure is as follows:
A glass plate is laid lengthwise on the work table. Then put on a Leneta foil (type 255 [dimensions 335 mm × 225 mm × 0.25 mm, Erichsen GmbH & Co. KG, Hemer). The emulsion paint to be tested is stirred with a spoon spatula for 30 s. Immediately thereafter, the paint is poured into the frame formed by the drawing and end faces of the doctor blade. The frame must be filled to 1/3. At the end, the test doctor (type 419, Erichsen GmbH & Co. KG, Hemer) is moved over a flat surface at a uniform speed. The distance between the individual links of each filmstrip pair is initially the same size. The film strips are allowed to run into one another in a horizontal position. Depending on the flow properties of the color, the distances between the individual pairs of links are reduced. The evaluation takes place after complete drying of the paint. The procedure is that the webs are assessed visually for good and bad course behavior. The leveling doctor blade contains 5 pairs of columns each with a width of 1.6 mm and a distance between the pairs of 2.5 mm. When calculating the percent gradient, the center bar is used as a reference. The non-running surface is measured with a thread counter. The calculation is performed as follows:
2.5 mm (100%) - x mm (measured) = y mm (gradient)
y mm (gradient) ÷ 2.5 mm. 100% = z% (= specification of the course in%)

The Prüfangabe takes place as a percentage course with an associated school note (1-6 [1 = very good, 6 = insufficient]) according to the following guideline values. Grade 1 (<60% gradient), Grade 2 (52% gradient), Grade 3 (48% gradient), Grade 4 (44 % Gradient), Grade S (30% gradient), Grade 6 (<30% gradient).

color surface

For the evaluation of the color surface as well as the washing and abrasion resistance Color films are produced with a semi-automatic film applicator (Filmzieh device type 335/1, Erichsen GmbH & Co. KG, Hemer; Doctor blade 200 μm, type 335, Erichsen). This is a color with a constant wet film thickness and constant Speed applied to a defined surface. In detail, how follows.

The film applicator is switched on, the direction switch to standstill (vertical right position) and removed the protective plate. A Lenetafolie (Typ 255, Erichsen GmbH & Co. KG, Hemer) is placed on the plate of the device. In front of the squeegee slider, a 200 μm doctor blade is applied. The foil is going through Applying a slight vacuum (water jet pump) fixed on the ground. The dispersion paint is stirred for 30 seconds with a spoon spatula and then in entered the squeegee. At a feed of 19.2 mm / s, the squeegee with the in the dispersion paint located in it over the film. The film will be on Finally, place it on a worktable and heat at room temperature for 2 hours dries.

The color surface is assessed visually in comparison to the respective reference sample with a magnifying glass. The goal is to set homogeneous and smooth color surfaces. The information is given here in the form of school grades (1-6 [1 = very good, 6 = insufficient]). All colors were evaluated with grades from 1 to a maximum of 2
(Grade 1: smooth and homogeneous color surface;
Grade 2: largely smooth and homogeneous color surface with very few holes;
Grade 3: rough surface with small holes;
Grade 4: rough surface with many small and medium to larger holes;
Grade 5: rough surface with many large holes;
Grade 6: rough, inhomogeneous color surface with many holes and filler particles).

pigment distribution

The influence of thickeners on the pigment distribution in a dispersion paint is tested. For this purpose, the emulsion paint is prepared with the thickener to be tested and then mixed with a small amount of a critical pigment. The paint is then applied in defined thickness on an uncoated, white cardboard. Subsequent trituration may result in further disruption of the pigment, recognizable by increased color intensity at the respective site. In detail, the procedure is as follows:

The dispersion paint is prepared according to the following recipe:
Water: 72.3 g
Calgon N: 0.5 g
Pigment distributor: 0.2 g
Defoamer: 1.0 g

Subsequently, the following materials are added:
Bayer Titan RD: 65.0 g
Omyacarb 2-GU: 67.5 g
Thickener to be tested: 1.2 g.

The batch is carried out for 3 min at 1500 rpm and then with 1.5 g Ammonia (25%) and 40.0 g of Acronal 290 D added. After another 3 min Stirring time is weighed from the base batch 100 g, with 0.5 g Luconylviolett 5894 added and stirred again for 2 min. The white cardboard is placed on the glass plate and the paint is applied with the squeegee. 90 s after the squeegee will be at 2 places of the color film (double determination) with the index finger intensely circular rubbed. The evaluation takes place after the color has completely dried out. The color intensity is compared between the rubbed and the un rubbed Area of the color film. If there is no difference in color intensity, it is assumed that the pigment has been completely digested. Is the color intensity on the grated surface compared to the surrounding more intense it has been assumed that the pigment digestion was incomplete. The grading is based on grades 1 to 6 (grade 1 = very good, Grade 6: insufficient).

Abrasion resistance

The determination of the washing and abrasion resistance is carried out according to DIN 53 778 T2. aim is to set color surfaces that are characterized by high levels of rub resistance Marked are. The information is given in double strokes. The assessment of a Dis Perspective color with regard to their washing and abrasion resistance is the principle a temporally limited stress of a disperse color film of a Festge lay dry film thickness on a defined surface according to defined Drying time with a defined cleaning liquid in a scrubber based on scrubbing brushes being pulled back and forth. The through management is carried out as indicated below.

The emulsion paint to be tested is prepared as described above (see under Color Surface) aufgerakelt on a Lenetafolie and ge for 28 days at room temperature ge  dries. For further assessment, the required amount of cleaning liquid produced. For this purpose, the washing liquid (Marlon A 350, Fa. Huls, Marl) with a dissolver disc for about 3 min at 1500 rpm mixed. to closing is a 0.25% solution of Marlon A 350 in deionized water manufactured. The cleaning fluid is used after 48 hours of storage. For the determination of the washing and abrasion resistance is a scrub tester (Model 494, Erichsen, Hemer) with two scrub brushes according to DIN 53 777-A (Erichsen) and a metering pump (model 494, Erichsen) used. The Disperse paint scrape-on to the leneta foil is adjusted to the size of the glass plate cut and then with screw clamps on the rough side of the glass plate in the tub with the Scheuernestgerät attached. The color film is using of a brush quickly wetted with washing liquid until a liquid layer on the sample remains. After 1 min, the possibly still existing over Carefully wash liquid washing liquid with a soft, moistened sponge wiped off. Subsequently, both brushes as quickly as possible on the same Set wet weight and each with the same narrow sides to the engine in the Brush box used. The dosing pump for the washing liquid is activated closed on; when the first drop of washing liquid emerges, it will Device put into operation.

To obtain a uniformly scoured, evaluable sample coating, the painting surface must be evenly washed during the whole test be wetted liquid. If in midfield at a length of 10 cm, under not Observe the two outermost tracks, two of the three middle tracks together hanging through are scrubbed, the test is terminated. After each individual exam The brushes are washed out with tap water, dipped in Marlon solution and again durchgewalkt. Then the number of double strokes is counted factory read. If the brushes have a different number of cycles need to clear the tracks, both numbers are written down. at At least 1000 scouring cycles, the color is washable, after at least 5,000 Scouring cycles, she is resistant to scrubbing.  

spreadability

For the determination of the processability or spreadability of the dispersion color is proceeded as follows:

In a 100 g plastic cup about 60 g of paint are filled. With a long hair brush (4.5 long bristles [China bristles]) will increase the quality of the spreadability (Rheology) on a gypsum cardboard board rated qualitatively. The evaluation is done compared to a standard in the form of grades (grade 1: very good (easy common), Grade 6: insufficient (very stiff, braking Elapse)).

spattering

The influence of cellulose ethers on the tendency to spatter of a standard Emulsion paint. For this purpose, a standard emulsion paint with the to be tested Cellulose ether produced. A mint lambskin role is equal to a wetted moderate amount of paint and in a well-defined period of time over an Eternit plate, which has a Lenetafolie underlayed, rolled. The different number of Thickness of paint splashes, influenced by different cellulose ethers, becomes assessed visually in comparison to the respective reference sample. It is presented as such go that the freshly prepared isoviskos set to 11,000-13,000 mPa.s Dispersion paints are used. An Eternit plate is raised at a 90 degree angle a Lenetafolie laid. The rolling direction is transverse to the Eternit plate. Of the color Add about 50-60 g to a paint tray and moisten the tared lambskin roller through some rolling operations with the paint until it has assumed 30 g ± 0.5 g of color. It will now be 30 seconds with the stopwatch running with the lambskin roller on the Eternit rolled plate, without rewetting the paint roller with paint. In this before The aim is to achieve approx. 40 roll operations. It should be with even Pressure and rolled at the same speed.  

The evaluation takes place after complete drying of the splashes of paint on the Leneta sheet. It assesses the strength and number of paint spatters that occur during the process Rolling process have arisen. An assessment is based on standardized Spray cards with school grades of 1-6 (grade 1 = very good (no spraying), school note 6 = insufficient (very many big splashes)).  

Table 1

Product-specific characteristics of the sulfoethyl-modified cellulose ethers used

Table 2

Formulation for 1 kg of a dispersion inner wall paint

Claims (11)

1. Use of optionally substituted with hydroxyalkyl groups sulfoalkyl-modified cellulose ethers as non-associative Ver Thickener for aqueous coating systems. 2. Use of cellulose ethers according to claim 1, characterized marked records that the aqueous coating systems emulsion paints, silicone resin paints or silicate paints. 3. Use according to one of the preceding claims, characterized characterized in that optionally substituted with hydroxyalkyl sulfo alkyl-modified cellulose ethers optionally with hydroxyalkyl group pen substituted sulfoethyl cellulose is. 4. Use according to claim 3, characterized in that the sulfoethyl cellulose is substituted with hydroxyalkyl groups and as hydroxyalkyl Sulfoethylcellulose an average degree of substitution by sulfo ethyl groups (DS-SE) of <0.5. 5. Use according to claim 4, characterized in that the hydroxy alkyl sulfoethyl cellulose an average degree of substitution Hydroxyalkyl groups (MS-HA) of <1.0. 6. Use according to claim 5, characterized in that the hydroxy Alkyl sulfoethyl cellulose, a hydroxyethyl sulfoethyl cellulose or a Hydroxypropyl sulfoethyl cellulose having an average substituent Degree of sulfoethyl groups (DS-SE) of <0.5 and a through average degree of substitution by hydroxyethyl or -propylgruppen (MS-HA) of <1.0.   7. Use according to claim 1, characterized in that the cellulose ether is a methyl ether substituted cellulose ether. 8. Use according to claim 7, characterized in that it is Hydroxyalkyl-methyl-sulfoalkylcelluloses with a degree of substitution by sulfoethyl groups (DS-SE) of ≦ 0.3, a degree of substitution Methyl groups (DS-ME) of at least 0.01, and a degree of substitution by hydroxyalkyl groups (MS-HA) from 1.5 to 4.5. 9. A process for the preparation of hydroxyalkyl-methyl-sulfoalkylcelluloses by etherification of cellulose in an alkaline medium with chloromethane and at least one sulfoalkyl group-transferring compound and at least one hydroxyalkylating agent comprising the process steps:

• a) alkalization of the cellulose
• b) before, during or after process step a) addition of chloromethane,
• c) before, during or after the process steps a) or b) addition of at least one sulfoalkyl group-transferring compound;
• d) optionally neutralization of a subset of the alkalization means,
• e) optionally adding additional alkalizing agent,
• f) neutralization of excess alkalizing agent, wherein
• g) the addition of the hydroxyalkylating agent takes place after step a), wherein at least 50% by weight of the hydroxyalkylating agent, based on the total amount of hydroxyalkylating agent, is added after process step c), but before process step f),

he follows. 10. The method according to claim 9, characterized in that the method Steps a) to f) in the presence of an organic water-miscible solution by means of or a mixture of organic water-miscible solutions be carried out as a suspending agent. 11. hydroxyalkyl methyl sulfoethyl cellulose, characterized in that this a degree of substitution by sulfoethyl groups (DS-SE) of 0.3, one Degree of substitution by methyl groups (DS-ME) of at least 0.01, and a degree of substitution by hydroxyalkyl groups (MS-HA) of <1.0 has.