DE102007016726A1 - Methylhydroxyethylhydroxypropylcellulose (MHEHPC) in mineral-bonded building material systems - Google Patents

Abstract

The present invention relates to the preparation of methylhydroxyethylhydroxypropylcellulose (MHEHPC) and their use in mineral-bonded building material systems, preferably gypsum-bound building material systems, particularly preferably in plasterboard plaster.

Description

The The present invention relates to the preparation of methylhydroxyethylhydroxypropylcellulose (MHEHPC) and their application in mineral-bound building material systems, preferably in gypsum-bound building material systems, particularly preferred in plaster machine plaster.

The Class of cellulose ethers, in particular the group of binary Alkylhydroxyalkylcelluloses with the commercially exploited representatives Methyl hydroxyethyl cellulose (MHEC) and methyl hydroxypropyl cellulose (MHPC), has been university and university for several decades industrial field of operation and often described. A clear representation of the chemical basics and Principles of Production (Manufacturing Process and Process Steps) as well as a material compilation and description of the properties and applications of various derivatives For example, Houben-Weyl, Methods of Organic Chemistry, Macromolecular substances, 4th edition, Volume E 20, p 2042 (1987). The commercially utilized methylhydroxyalkylcelluloses form Room temperature in water viscous solutions and are in hot Water insoluble at temperatures above the flocculation point.

The Preparation of methylhydroxyalkylcellulose can be summarized as follows be: In an upstream sub-step, the activation takes place of the cellulosic starting material, preferably with caustic. Subsequently, the formed alkali cellulose with methyl chloride and enforced an alkylene oxide forced, where appropriate if necessary, excess alkali with superstoichiometric Amounts of methyl chloride is largely neutralized. In the following Purification step are formed salt and other by-products separated, preferably by hot water washing.

The preparation of ternary Methylhydroxyalkylcellulosen is also known and is for example in the patents US 3,873,518 (= DE 24 57 187 ) EP 0 120 430 A1 and EP 1 180 526 B1 described.

The Alkyl substitution is commonly used in cellulose ether chemistry described the DS. The DS is the average number of substituted ones OH groups per anhydroglucose unit. The methyl substitution becomes, for example as DS (methyl) or DS (M).

Usually the hydroxyalkyl substitution by the MS is described. Of the MS is the mean number of moles of etherifying reagent that per mole of anhydroglucose unit are ether-bound. The etherification with the etherification reagent ethylene oxide is accordingly as MS (hydroxyethyl) or MS (HE) and the etherification with propylene oxide as MS (hydroxypropyl) or MS (HP).

The determination of the DS and MS is carried out according to the Zeisel method known to those skilled in the art, described, for. In PW Morgan, Ind. Eng. Chem. Anal. Ed. 18 (1946) 500-504 and RU Lemieux, CB Purves, Can. J. Res. Sect. B 25 (1947) 485-489 ,

Of the obtained by hot water washing, by-products purified and still water-moist cellulose ethers with a water content of mostly> 50% by weight if necessary after further pretreatment (conditioning) by subsequent drying and grinding into a salable Shape convicted. The cellulose ethers enter the trade preferably in powder or granular form with a water content of about 1-10% by weight.

cellulose ethers are used in building material systems such. B. hand and machine cleaning, and putties as thickening and water retention agents used.

The Properties of these building material systems, in particular the consistency and the setting behavior can be determined by the choice of cellulose ether be strongly influenced.

Especially in gypsum-bound building material systems, d. H. mixed with water gypsum-containing base mixtures, often become lumps, tubers or nodules observed in the worst case to bumps and Rifts can lead and at least delays through intensive reworking.

An attempt has been made to remedy some of these problems with additive combinations. So revealed the WO 99/64368 an additive mixture consisting mainly of cellulose ethers, for example methylhydroxypropylcellulose (MHPC) and small amounts of a polymerized carboxylic acid and a methacrylate or acrylate homo- or interpolymers. Unfortunately, the preparation of this additive mixture is complicated, requires additional mixing units and does not always lead to the reduction of lumps. Darue In addition, the use of aqueous carboxylic acid solutions can lead to pH-induced chain degradation of the cellulose ether. There is no statement about the workability of the plaster.

Therefore there is still a continuing need to provide a cellulose ether, about the processing properties of mineral-bound building material systems to improve, in particular the formation of lumps in gypsum-bound Effectively reduce building material systems while maintaining the processing characteristics to improve.

Methylhydroxyethylhydroxypropylcelluloses (MHEHPC) are well known as thickeners in dipresion-bound paints ( US 3,873,518 respectively. DE 24 57 187 ). After the apprenticeship of DE 2457187 MHEHPC with a DS (methyl) of 0.396 to 1.216, an MS (hydroxyethyl) of 0.335 to 1.087 and an MS (hydroxypropyl) of 0.381 to 1.286 are used which have a thermal gel point of> 70 ° C. and preferably both as well as methanol soluble. Higher degrees of substitution, in particular with regard to the DS (methyl), are not advantageous, so that their suitability for property improvement in dispersion-bound systems such as emulsion paints is heavily dependent on the degree of substitution.

Surprisingly it has now been found that the processing properties are mineral bonded building material systems, in particular gypsum-bonded system by Improve the addition of methylhydroxyethylhydroxypropylcellulose (MHEHPC) to let. This effect is exacerbated when at the Preparation for drying and granulation a grinding drying step is passed through, wherein the feed material in this case a very specific Has moisture.

object he invention are therefore containing mineral bound building material systems Methylhydroxyethylhydroxypropylcellulose (MHEHPC).

preferred mineral-bound building material systems are gypsum-bound building material systems, particularly preferred gypsum plaster.

The Methylhydroxyethylhydroxypropylcelluloses to be used according to the invention (MHEHPC) typically have a DS (methyl) of> 1.30, preferably> 1.45, more preferably from> 1.55, especially preferably> 1.65.

The upper limit of the DS (methyl) is chosen so that the Product is soluble in water at room temperature, preferably if the DS <2,3, more preferably <2.1 and most preferably <1.95.

The lower limit of MS (hydroxyethyl) is typically 0.10, preferably 0.20, more preferably 0.25 and most especially preferably 0.30. The upper limit of MS (hydroxyethyl) is chosen so that the MHEHPC a thermal flocculation point in water of <100 ° C having. The upper limit of MS (hydroxyethyl) is therefore typically 0.70, preferably 0.60, and more preferably 0.50.

The lower limit of MS (hydroxypropyl) is typically 0.20, preferably 0.30, more preferably 0.35 and most especially preferably 0.40. The upper limit of MS (hydroxyethyl) is typically 0.80, preferably 0.70 and most preferably 0.60.

Prefers the values for MS (hydroxyethyl) and MS (hydroxypropyl) the above data, wherein the value of MS (hydroxyethyl) the 0.3 to 1.3 times, more preferably 0.4 to 1.2 times and most preferably 0.5 to 1.1 times the value of MS (hydroxypropyl) is.

The methylhydroxyethylhydroxypropylcelluloses (MHEHPC) essential to the invention are typically prepared by grinding and drying the water-moist cellulose ether obtained after the reaction of cellulose with methyl chloride, ethylene oxide and propylene oxide and subsequent purification with hot water. The reaction and purification of methylhydroxyethylhydroxypropylcelluloses (MHEHPC) is carried out according to the prior art. For example, the purification may be carried out using centrifuges or hydrocyclones, optionally followed by ultrafiltration as in EP 0 632 056 disclosed. In a preferred cleaning method, a rotary pressure filter is used, such as in the EP-B 1 652 860 described.

The water-moist filter cake can be conditioned before grinding, for example, by adding additives, modifiers or other water, the water-moist filter cake cooled or is compressed mechanically.

It has proved to be particularly advantageous when in the Mill drying methylhydroxyethylhydroxypropyl used (MHEHPC) doing a special Mahlgutfeuchte in terms of water content exhibit.

object The present invention is therefore also a process for the preparation of ground methylhydroxyethylhydroxypropylcellulose (MHEHPC), in which as a feed material water and possibly alcohol Methylhydroxyethylhydroxypropylcellulose with a DS (methyl) of ≥ 1.30, an MS (hydroxyethyl) of ≥ 0.10, an MS (hydroxypropyl) of ≥ 0.20 and a water content of 35 to 63% by weight is subjected to grinding drying.

Prefers the water content is at most 61% by weight, most preferably at most 57% by weight, especially preferably at most 53% by weight, and most preferably at most 50% by weight.

Prefers but the water content is at least 38 wt .-%, especially preferably at least 40 wt .-%, most preferably at least 42% by weight, and most preferably at least 44% by weight. lower Water contents in the filter cake are only disproportionate long filtration times or pre-drying of the filter cake to reach.

to Adjustment of the above-mentioned moisture content may be too low Values added water or filter cake with higher humidity become. To lower the humidity of a filter cake, it is preferable already dried and ground cellulose ether powder or granules admix.

The Addition of dried and ground cellulose ether powder or granules to the optionally conditioned water-moist filter cake can be continuous at various points after filtration or batchwise. The addition is preferably carried out outside the grinding chamber. The mixing can z. B. in a commercial Mixer or carried out in a screw conveyor become. Preferably, between the place of addition and the mill a mixing element and / or a conveyor line, which a ensures adequate mixing.

Prefers is used for moisture adjustment dried and already ground cellulose ether powder or granules by means of a metering device added, which is the targeted setting of the desired Range of the total moisture of the composition allowed. The cellulose ether powder may be completely or partially removed during grinding consist of existing oversize, which continuously or batchwise to the possibly conditioned water-moist filter cake is dosed.

The Flowability of the optionally conditioned moist filter cake is made by adding the dried and ground cellulose ether powder or granules mostly clear improved, thus can blockages and caking be reduced in the system.

By the mixture of the water-moist filter cake with dried Cellulose ether powder or granules can Mahlgutfeuchten be adjusted by economic filtration methods can not be reached.

The Ground material consisting of either a possibly conditioned water-moist Filter cake of a MHEHPC or a composition, in addition dried and ground cellulose ether powder or granules is subsequently by known methods crushed and dried.

Prefers no (pre-) drying takes place before the grinding, more preferably Drying takes place simultaneously with the grinding.

Especially Preferably, a reduction takes place simultaneously with the comminution the water content such that the difference in water content in% by weight, based on the total mass, between mill inlet and output more than 10 wt .-%, preferably more than 20 wt .-%, especially preferably more than 35 wt .-% is.

Processes for the simultaneous comminution and drying of cellulose ethers are known, for example from the teaching of GB 2 262 527 . DE 38 39 831 . EP 1 127 910 and EP 1 127 895 , Various mill types can be used, for example, pin, bowl, hammer, Siebkorb-, blow cross and impact mills. The drying action is preferably supported by the use of gases or gas mixtures heated to temperatures of> 80 ° C., preferably> 100 ° C., in the comminuting device. The milling drying can be followed by further grinding and / or drying steps. Preferably, however, the grinding is single-stage and as a mill, a sieveless high-speed impact mill is used.

To the grinding and drying stage, the product stream can be classified and the oversize grain in whole or in part, batchwise or continuously be traced back to the process.

in the Connection to the grinding and drying, which preferably simultaneously in the form of a Malt drying, the Methylhydroxyethylhydroxypropylcelluloses (MHEHPC) a residual moisture content based on water content in the solid of 0.1 to 15 wt .-%, preferably 1 to 10 wt .-%, particularly preferably 1.5 to 7 wt .-%.

One Another object of the invention are those according to the invention Process obtainable methylhydroxyethylhydroxypropylcelluloses (MHEHPC).

The methylhydroxyethylhydroxypropylcelluloses according to the invention preferably have the following grading curve: undersize percent <315 μm 95 to 100 <250 μm 90 to 100 <200 μm 80 to 100 <160 μm 70 to 99.9 <125 μm 50 to 95 <100 μm 30 to 90 <63 μm 10 to 70

The viscosity of the products at 23 ° C., measured as solution in water of 2% by weight with a Haake Rotovisko at 2.55 s ^-1 , is preferably from 10 to 200 000 mPa · s, more preferably from 100 to 150 000 mPa · s, most preferably about 1000 to 100,000 mPa.s, and most preferably 10,000 to 80,000 mPa.s.

The Bulk density of the products, measured on a loose bed is preferably 200 to 700 g / l, more preferably 250 to 650 g / l and most preferably about 300 to 600 g / l.

The Essential to the invention cellulose ethers allow the production of mineral-bonded building material systems, preferably gypsum-bound Building material systems with particularly advantageous properties. Especially show such gypsum-bound building material systems in the mix with Water for the production of plaster-bound building material systems reduced lumping and improved processability over the prior art.

The Methylhydroxyethylhydroxypropylcellulose (MHEHPC) is in Amounts of 0.01 to 5 wt .-%, preferably 0.1 to 0.8 wt .-% and especially preferably used 0.2 to 0.4 wt .-%, in each case based on the Dry matter of the mineral-bonded building material system.

In addition to the cellulose ether, the mineral binder and water may be included in such mineral bound building material systems, for example, but not limited to, the following ingredients: • hydrated lime 0-30% by weight • Mineral aggregates (eg quartz sand, limestone sand, grits, flour, mica) 0-30% by weight • lightweight aggregate (eg perlite) 0-20% by weight • plastic dispersion powder 0-20% by weight • fibers (eg cellulose fibers) 0-2% by weight • accelerator 0-0.8% by weight • additional thickener (eg starch and guar derivatives, synthetic thickeners, polyacrylamide, polyvinyl alcohol) 0-0.5% by weight • Retarder 0-0.5% by weight • Air entrainment agent 0-0.1% by weight

The Water / solids ratio in the inventive mineral bound building material systems is preferred 0.3 to 0.9, more preferably 0.4 to 0.8.

the It is known to the skilled worker that cellulose ethers are customary not alone, but with a range of aggregates and / or Modifying agents can be used in the masterbatches. So z. B. in building material mixtures find use Methylhydroxypropylcellulosen mixed with small amounts of Auxiliaries and additives z. B. Defoamers, swelling agents, Fillers, lightweight aggregates, polyacrylates, polyacrylamides, Air entrainers, dispersants, water repellents, condensers, Superabsorbents, stabilizers and synthetic, semi-synthetic as well as natural thickeners.

Examples

One water-moist filter cake of a Methylhydroxyethylhydroxypropylcellulose with a DS (methyl) = 1.69, an MS (hydroxyethyl) = 0.43 and a MS (hydroxypropyl) = 0.54 after hot water washing divided into two subsets. One subset each becomes one Adjusted water content of 48 wt .-% and 63 wt .-%.

Subsequently Each subset is separated in a sieveless high speed gas flow rotary mill with vertically arranged drive shaft and seven grinding tracks, the equipped with impact plates, which profiled against a Work countermill, crushed and dried. As a drying and transport gas is nitrogen, which the gas circulation at various Positions is supplied.

Of the Mill downstream is a cyclone, where the main part of the finely ground product. The gas flow is then in a downstream bag filter of Residual dust freed.

Clean gas side is arranged a radial fan, which controls the dust-free gas flow transported in a heat exchanger, where the transport gas heated to the required drying temperature and finally is directed back to the mill. The water vapor content of the circulating gas is in front of the mill in one after the cyclone arranged gas scrubber removed from the recycle gas, so that maintain a nitrogen-rich carrier gas composition becomes.

excess Circulating gas is discharged via a valve from the gas cycle.

Various MHPC (MHPC 1 and 2) are prepared by the same method. attempt MHEHPC 1 invention (preferred embodiment) MHEHPC 2 invention MHPC 1 comparison MHPC 2 comparison DS (methyl) 1.69 1.69 1.64 1.75 MS (hydroxyethyl) 0.43 0.43 - - MS (hydroxypropyl) 0.54 0.54 1.02 0.51 Moisture of the conditioned filter cake,% by weight 48 63 60 49 Product moisture in% by weight 3.20 2.94 3.23 5.36 Bulk density in g / L 394 365 451 351 Flock point, ° C 64 64 54 56 Proportion <63 μm,% laser diffraction (Helios) 20.8 24.9 22.3 26.4 Viscosity V2 atro in mPas 35180 35,750 57840 49340

Application in a plaster machine plaster

The products MHEHPC 1 and 2 as well as MHPC 1 and 2 were used in a gypsum machine plaster base mixture (0.24 wt .-% cellulose ethers, based on the total base mixture) and applied by means of a plastering machine on a wall. The workability, the formation of lumps and the surface area according to school grades were assessed, with 1 (very good) the best grade and 5 (poor) the worst. Note is. The following symbols are used: Very good: ++, good +, satisfactory o, sufficient -, poor - -. spraying test A (invention, preferred embodiment) B (invention) C (comparison) D (comparison) template MHEHPC 1 MHEHPC 2 MHPC 1 MHPC 2 DS (methyl) 1.69 1.69 1.64 1.75 MS (hydroxyethyl) 0.43 0.43 - - MS (hydroxypropyl) 0.54 0.54 1.02 0.51 Moisture of the conditioned filter cake,% by weight 48 63 60 49 Pressure (bar) 8-10 9-10 8-10 8,5-10 Water in l / h 740 740-750 740-750 740-750 Consistency after application Comment + ++ good running + + Workability when pulling first + ++ O - Note g good sliding very good sliding hardly sticks sticks something Lump after 1. pulling remark + less than MHEHPC 2 O - extremely many - extremely many Workability on the 2nd drawing remark O + good editing O - Sufficient gliding Surface image after 2nd drawing + / ++ area OK + / 0 several deepening - - area not OK, many rolled up lumps, very many depressions - Area not OK, many wells

The best surface image is achieved with the MHEHPC 1. The educated Lumps are destroyed during processing again. With the MHEHPC 2, which produced with higher regrind moisture was, some lumps remain below the plaster surface hidden, which lead to bumps in the surface. The comparison samples show a pronounced lump formation, which are not compensated in the course of further processing can be.

Application in a synthetic resin plaster I (comparative experiment)

For producing a synthetic resin plaster after the DE-A 24 23 618 a solution of 2 wt .-% of the cellulose ether MHEHPC 1 and 2 and the MHPC 1 and 2 is prepared. To this is added a quantity of 7 g of cellulose ether with stirring in 343 g of water. The agitator used was an RW20 DZ from Jahnke & Kunkel, which was operated at 2000 rpm and equipped with a propeller stirring tool. For all cellulose ethers used, intensive lump formation during littering was likewise observed.

Application in a synthetic resin plaster II (comparative experiment)

In another attempt was made according to DE-A 102 38 242 method and a binder premix of 2 wt .-% cellulose ether and 4 wt .-% of a redispersible powder based on a vinyl acetate homopolymer prepared. The cellulose ethers used in each case are the MHEHPC 1 or MHEHPC 2 according to the invention or, for comparison, MHPC 1 or 2. For this purpose, 329 g of water were stirred at 2000 rpm using a propeller stirrer, and 7 g of cellulose ether and 14 g of a redispersible powder based on a vinylacetate homopolymer were added. After stirring at this speed for 15 minutes, lumps were still visible, regardless of the cellulose ether used.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 3873518 [0004, 0014]
• - DE 2457187 [0004, 0014, 0014]
• EP 0120430 A1 [0004]
• EP 1180526 B1 [0004]
• WO 99/64368 [0012]
• - EP 0632056 [0023]
• EP 1652860 B [0023]
• - GB 2262527 [0037]
• - DE 3839831 [0037]
• - EP 1127910 [0037]
• - EP 1127895 [0037]
• - DE 2423618 A [0057]
• - DE 10238242 A [0058]

Cited non-patent literature

• - PW Morgan, Ind. Eng. Chem. Anal. Ed. 18 (1946) 500-504 [0007]
• - RU Lemieux, CB Purves, Can. J. Res. Sect. B 25 (1947) 485-489 [0007]

Claims (10)

Containing mineral-bound building material systems Methylhydroxyethylhydroxypropylcellulose (MHEHPC). Mineral bonded building material systems according to claim 1, characterized in that it is gypsum-bonded systems is. Mineral bonded building material systems according to claim 1 or 2, characterized in that the methylhydroxyethylhydroxypropylcellulose in amounts of 0.01 to 5 wt .-% based on the dry matter of mineral-bound building material system is included. Process for the preparation of ground-dried methylhydroxyethylhydroxypropylcellulose (MHEHPC), in which as a feed material water and possibly alcohol Methylhydroxyethylhydroxypropylcellulose with a DS (methyl) of ≥ 1.30, an MS (hydroxyethyl) of ≥ 0.10, an MS (hydroxypropyl) of ≥ 0.20 and a water content of 35 to 63% by weight is subjected to grinding drying. A method according to claim 4, characterized characterized in that the water content of the feed by mixing of at least two methylhydroxyethylhydroxypropylcelluloses of different Humidity is set. A method according to claim 5, characterized characterized in that for the adjustment of moisture at least one Methylhydroxyethylhydroxypropylcellulose having a moisture content from 0.1 to 15 wt .-% is used. Method according to one of the claims 4 to 6, characterized in that for the provision of the feedstock at least one methylhydroxyethylhydroxypropylcellulose having a Water content of less than <62 Wt .-%, but more than 44 wt .-% is used. Method according to one of the claims 4 to 7, characterized in that the method operated so is that the ground-dried Methylhydroxyethylhydroxypropylcellulose a residual moisture content based on water of 1.5 to 7 wt .-% having. Grind-dried methylhydroxyethylhydroxypropylcellulose obtainable by a method according to one of claims 4 to 8. Mineral-bound building material systems according to a of claims 1 to 3, characterized in that a Grind-dried methylhydroxyethylhydroxypropylcellulose according to claim 9 is used.