DE10130021A1 - Granular highly swellable hydrogel-forming polymer, used for dewatering automobile and machine brake fluids, is held in storage or compensating container - Google Patents

Abstract

Granular highly swellable hydrogel-forming polymer (HFP) is added to brake fluid. The polymer is held in a device, which can be a storage container or compensating container for brake fluids. Independent claims are included for the following: (1) a brake fluid containing a highly swellable hydrogel-polymer in granular form; and (2) a device for holding granular highly swellable hydrogel-forming polymer in brake fluid in storage or compensating containers.

Description

The present invention relates to the use of granular highly swellable hydrogel-forming polymers for drainage of brake fluids and devices for storing them highly swellable hydrogel-forming polymers.

In particular, the present invention relates to the use of absorbing aqueous liquids, in non-aqueous ones Solutions of insoluble, highly swellable hydrogel-forming polymers for drainage of brake fluids, the drainage in the reservoir or expansion tank for brake fluids in the Brake system is carried out.

For the operation of motor vehicles (cars, trucks) and machines Brake fluids and power steering fluids are essential. in the According to the invention, brake fluids are liquids in steering assistance systems and in braking systems, preferably those in Brake systems understood.

Brake fluids for automobiles are subject to their chemical and physical properties are very high Conditions. According to existing standards and Specifications for brake fluids from the US Department of Transportation in the Federal Motor Vehicle Safety Standard FMVSS no. 116 and the SAE published by the Society of Automotive Engineers J 1704 modern brake fluids are said to have a high level Dry boiling points (reflux boiling points, dry [Equilibrium reflux boiling point, "ERBP"]) and high wet boiling points (Reflux boiling points, moist ["wet ERBP"]), on the other hand but also have a viscosity that is within a changes very little over a wide temperature range.

They also have corrosion inhibitors in brake fluids the task of destruction caused by corrosion to prevent metallic materials.

Here, alkali metal salts come from as corrosion inhibitors Phosphoric acid and phosphorous acid, fatty acids such as caprylic, Lauric, palmitic, stearic or oleic acid and their Alkali metal salts, esters of phosphoric acid and phosphorous acid such as ethyl phosphate, dimethyl phosphate, isopropyl phosphate, Diisopropyl phosphate, butyl phosphite or dimethyl phosphite, if appropriate ethoxylated mono- and dialkylamines and their salts with mineral and fatty acids, e.g. B. butylamine, hexylamine, octylamine, Isononylamine, oleylamine, dipropylamine, diisopropylamine or dibutylamine, optionally ethoxylated alkanolamines, e.g. B. mono-, di- or Triethanolamine, N, N'-di-n-butylaminoethanol or 1,1'-iminodipropan-2-ol, cyclohexylamine, benzimidazole, 1H-1,2,4-triazole, Benzotriazole, tolutriazole, hydrogenated tolutriazole, purine, adenine, 6-chloropurine, 2,6-dichloropurine, 6-methoxypurine, 1H-1,2,3-triazolo (4,5B) pyridine, 6-histaminopurine and 6-furfurylaminopurine, and nitro aromatics, e.g. B. 3-nitrobenzaldehyde.

Brake fluids for motor vehicles contain as Main components one or more polyglycol ethers and / or their Boric acid esters.

Suitable polyglycol ethers are above all Ethylene glycol monoalkyl ether with up to 6 ethylene oxide units and with up to 4 Carbon atoms in the alkyl radical, such as methyl diglycol, Methyl triglycol, butyl triglycol or methyl tetraglycol. Farther come with up to ethylene glycol or propylene glycol dialkyl ether 6 alkylene oxide units and each with up to 4 Carbon atoms in the alkyl radicals, such as Triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, Diethylene glycol di-tert-butyl ether, diethylene glycol dibutyl ether, Butyl diglycol tert-butyl ether or Dipropylene dimethyl ether.

Suitable boric acid esters of those mentioned or others Polyglycol ethers are particularly described in EP-B 013 925 (cyclic bis-boric acid esters), DE-C 28 04 535 (nitrogen-containing Boric acid ester), DE-A 24 38 038 (Boric acid-alkylene glycol monoalkyl ether ester) and DE-B 17 68 933 (boric acid tris-alkoxyalkyl ester) described.

Instead of the polyglycol ethers mentioned and / or their Boric acid esters can be used as brake fluids for motor vehicles The main component is also based on carboxylic acid esters, mineral oils or silicone oils.

Brake fluids for motor vehicles can still one or contain several polyglycols.

Suitable polyglycols are primarily higher-boiling Reaction products of ethylene oxide and / or propylene oxide and / or Find butylene oxide with water or diols, in particular corresponding reaction products of mixtures of ethylene oxide and Propylene oxide with water use. The number of alkylene oxide Units in such polyglycols are usually 2 to 10.

The effect of these high-boiling polyglycols is one Lubricant, which essentially indicates an improvement in the Temperature-viscosity behavior is attributable. The Polyglycols give the thin polyglycol ethers at high Temperatures enough viscosity and thus ensure a adequate lubrication. Sufficient lubrication is therefore in the components of the motor vehicle braking system necessary because there Glide rubber or elastomers on metal as wear-free as possible have to.

Other components and aids in brake fluids for Motor vehicles can common antioxidants such. B. Phenothiazine and / or those based on phenol, and usual Be a defoamer.

In addition, the brake fluids of the invention Cyclic carboxylic acid derivatives listed in WO 00/65001 contain which as components for lowering the Low temperature viscosity in the presence of water are suitable.

Typical examples of brake fluids are, for example, in WO 00/65001 or WO 00/46325 described. From BASF For example, joint stock companies use brake fluids Glycol ether base under the name Hydraulan® brands marketed.

Since glycol ether-based brake fluids are hygroscopic, their water content increases over time in the braking system of the Motor vehicle slowly, with too high a water content when Braking to vapor bubbles and thus to malfunction of the Brake system can lead, which is why the automobile manufacturers security reasons a regular change of the Prescribe brake fluid. By adding water-absorbing substances could thus increase safety and security Brake fluid change intervals are extended.

So there are different for every application on the market Products available. The wide product range offers for everyone The right solution to protect machinery and applications Ensure plant parts. Specific additives, such as for example wear protection additives or active ingredients Improvement of aging resistance and corrosion protection enable optimal operating times.

For reasons of environmental protection, there is an increasing tendency to use environmentally friendly brake fluids. The use of offers quickly biodegradable brake fluids in environmentally sensitive areas, the possibility of accidents and Leaks protect the environment as they have little or no damage Cause environmental pollution.

For example, brake fluids are increasingly being used in viticulture renewable raw materials. It acts in detail esterified and natural rapeseed oil as Plant-based brake fluid.

With the development of rapidly biodegradable Brake fluids are suitable for a wide range of applications Solutions are available that make a significant contribution to Environmental relief.

• - Rüböl (natürlicher Ester)
• - Synthetischer Ester oder
• - Polyglykol

Environmentally friendly hydraulic oils are divided into three product groups, depending on the type of base oil component used:

• - rape oil (natural ester)
• - Synthetic ester or
• - polyglycol

The base oil components used in environmentally friendly substances have more favorable lubrication properties than mineral oils. So the load carrying capacity - determined in the FZG test - of rapeseed oil, synthetic esters and polyglycols higher than that of Mineral oils.

While with mineral oils, esters and polyglycols the Products can retain flowability up to the solidification point on a plant basis after only a few days of storage thicken far above and solidify. Generally can however with herbal products from the freezing point no statements about the flow behavior in the low temperature range to meet. Therefore, this is also the case with these products Long-term cold behavior to describe the flowability at deep Temperatures indicated.

Likewise for environmentally friendly reasons, it makes sense Brake fluids do not simply open after a certain operating time dispose of, but clean for reuse. The costs- Benefit analysis of care measures becomes essential from the question influences how many hours of operation substances over which the System manufacturers prescribed change intervals, can remain safely in use. The cleaning facilities are designed to brake fluids and other industrial oils quickly and easy to clean. The cleaning is done for example using the microfiltration method. From the liquids become solid contamination and slurried particles filtered out. This not only reduces operating costs, but it will also make a valuable contribution to protecting our Environment. This eliminates time-consuming changes downtimes are reduced. Associated with it drastic reduction in new brake fluid requirements, as well a significantly lower disposal effort. The environment will less burdened.

Each facility is subject to different criteria, each different effects on aging and wear of the have used substances. It therefore makes sense in any case that Regularly check the quality of the brake fluids; also New brake fluids should be used before, at least to be subjected to random checks and quality controls.

To meet the high demands of modern brake fluids with regard to the purity of the printing medium used filter elements in various subtleties are already starting 3 µm offered.

Prove particularly advantageous for brake fluids Sidestream filtration systems. The bypass filter systems work in Secondary flow during production, that is, they are independent of the system, neither affect the pressure conditions in the System, nor are they for reliable filtering exposed to harmful pressure peaks. In use Brake fluid is best made permanent, or at least regularly Intervals cleaned by bypass filter systems. Oil quality and Purity is achieved by means of meaningful oil analyzes and measuring procedures checked regularly. The filter change takes place either after specified operating hours or by checking the Pressure rise.

If the brake fluid is ultimately disposed of, then generally applies that environmentally friendly materials are not included in the Nature or sewer system may be drained. Esterbasische Products fall under the waste oil law. You can reprocessed or burned in approved facilities. Beet oil and polyglycol-based products are actually covered the Waste Act and are to be classified as hazardous waste to dispose. However, this is not what the legislator intended. So that's why BMU (Federal Ministry for the Environment, Nature Conservation and Reactor safety) made the arrangement that lubricating oils on plant-based can be burned in approved plants, because the calorific value of min. 30 MJ / kg is far exceeded by these products. There is still today no way to reprocess vegetable oils. Polyglycol products are to be disposed of as special waste. Because they are with Mineral oils are not miscible, and the calorific value is lower than in the TA Luft required value of min. 30 MJ / kg.

However, it can still happen due to unforeseen events Damage to the lines in which they occur Lubricating oils. Ingress of contamination, moisture or watery contamination would have been especially with these highly specialized products disastrous consequences. Leaks or small cracks that allow moisture to enter the allow closed circuit of the braking system are in the rarest Cases noticed right away. If the leak is noticed, in As a rule, irreparable damage to the system may also be possible to endanger the life of the user.

Practical studies show that 90% of all Machine failures are due to contamination in the medium. Heat, Moisture, air and solids cause pollution of the liquid media and lead to machine failures, as well undesired downtimes in production. The regular Contamination control on the filter system or the system makes it possible to avoid this and thus helps Reduce maintenance costs drastically. Will the brake fluid kept permanently clean, those tended to wear Zero disturbances.

Previous filter systems are designed to be particulate Contamination is retained even in the smallest dimensions can. This also applies to slurried soiling or Suspended particles. The situation is far more complicated, though it comes to the smallest amount of water or added separate aqueous solution. There are filter systems offered that are also able to remove aqueous contaminants separate. But such a separation is through pure filtering by no means quantitative and complete.

It was therefore the task of an inert additive Add brake fluid to the functioning and rheology the brake fluid is not affected, but still able is, aqueous liquids or aqueous impurities absorb quantitatively and spontaneously, and the one particulate Shape of certain size and strength to the extent that after absorption through a filtration system can be removed, and which also leaves no residue the filtration unit can be removed. In the Filtration unit, the additive should be able to larger To withstand pressure differences without damage in order for filtration to be suitable in the industrial sector. The one through the inert Additive to manage pressure range in industrial filters extends from 60 bar nominal pressure (low pressure filter) to 450 bar Nominal pressure (high pressure filter). Other common filters are Double switching filter (200 bar nominal pressure), bypass filter, suction filter and return filter. Furthermore, the task was based on one To provide system in which the brake fluid not adversely affected by the drying device becomes.

Surprisingly, the above task is solved by the Add granular, highly swellable hydrogel-forming polymers to Brake fluids by using these polymers in one device be kept in the reservoir or expansion tank for brake fluids can be attached and / or by a Device attached to a secondary circuit of the brake fluid is.

Swellable hydrogel-forming polymers, so-called Superabsorbents (Super Absorbing Polymers) are from the prior art Technology known. These are networks more flexible hydrophilic polymers that are both ionic and can be non-ionic in nature. These are watery Absorb and absorb liquids to form a hydrogel bind and are therefore preferred in the absorption of aqueous liquids used. When absorption highly elastic hydrogels of high gel strength formed that too greatest pressure differences without damage, such as B. Can survive collapse of the polymer network and thereby are also designed to be the largest No liquid leakage of the absorbed solutions is recorded.

The hydrogel systems can go beyond the standard ones Filter systems are filtered off and disposed of, with another advantage the swollen hydrogel systems can be composted and thus an environmentally friendly disposal are available. The use according to the invention of the swellable hydrogel-forming Polymers due to the dewatering of lubricants therefore no additional equipment of the already existing standard filter systems for the preparation of the Lubricants and hydraulic oils.

Accordingly, the present invention relates to the use of the highly swellable hydrogel-forming polymers for absorption aqueous fluids in brake fluids.

With the new, highly swellable hydrogel-forming polymers are commercially available superabsorbents, which are used in Powder form are used.

Crosslinked polymers are preferred as hydrogel-forming polymers with acid groups, mainly in the form of their salts, in the Usually alkali or ammonium salts are present. Such polymers swell particularly strongly on contact with aqueous liquids to gel on.

Highly swellable hydrogels with a Particle size larger than 100 µm is used.

Highly swellable hydrogel-forming polymers used in the present invention can preferably be used Absorbance of aqueous liquids from 10 to 1500 fold their own weight.

There are no restrictions on the type of hydrogel-forming Polymers or their manufacturing methodology. Are preferred hydrophilic polymers which have acid groups, which are preferred in Form of their salts, usually alkali or ammonium salts, available. Examples of highly swellable hydrogel-forming polymers include polyacrylates made by inverse Suspension polymerization, or aqueous solution polymerization (adiabatic polymerization, film polymerization), further Graft (co) polymerization, but without being limited to this.

The hydrophilic, highly swellable hydrogels are special Polymers from (co) polymerized hydrophilic monomers, Graft (co) polymers of one or more hydrophilic monomers on a suitable graft base, cross-linked cellulose or Starch ether, cross-linked carboxymethyl cellulose, partly cross-linked polyalkylene oxide or swellable in aqueous liquids Natural products such as guar derivatives, alginates and Carrageenans. Suitable graft bases can be natural or be of synthetic origin. The hydrophilic, highly swellable Hydrogels can also be made by compounding, i.e. H. physical mixtures of cross-linked cellulose or Starch ether, cross-linked carboxymethyl cellulose, partially cross-linked Polyalkylene oxide or swellable in aqueous liquids Natural products such as guar derivatives, alginates and Carrageenans can be made with superabsorbent polymers.

These are preferably polymers, the structural units contain, which are derived from acrylic acid or its esters, or the by graft (co) polymerization of acrylic acid or Acrylic acid esters on a water-soluble polymer matrix were obtained or compounds of acrylic acid or acrylic acid esters with a are water-soluble polymer matrix.

These hydrogels are known to the person skilled in the art and, for example, in US Pat
US-A-4 286 082, DE-C-27 06 135, US-A-4 340 706, DE-C-37 13 601, DE-C-28 40 010, DE-A-43 44 548, DE- A-40 20 780, DE-A-40 15 085, DE-A-39 17 846, DE-A-38 07 289, DE-A-35 33 337, DE-A-35 03 458, DE-A- 42 44 548, DE-A-42 19 607, DE-A-40 21 847, DE-A-38 31 261, DE-A-35 11 086, DE-A-31 18 172, DE-A-30 28 043, DE-A-44 18 881, EP-A-0 801 483, EP-A-0 455 985, EP-A-0 467 073, EP-A-0 312 952, EP-A-0 205 874, EP-A-0 499 774, DE-A-26 12 846, DE-A-40 20 780, EP-A-0 205 674, US-A-5 145 906, EP-A-0 530 438, EP- A-0 670 073, US-A-4 057 521, US-A-4 062 817, US-A-4 525 527, US-A-4 295 987, US-A-5 011 892, US-A- 4,076,663 or US-A-4,931,497.

The content of the above patent documents is expressly part of the present application.

Hydrogel-forming polymers are, in particular, polymers made from (Co) polymerized hydrophilic monomers, graft (co) polymers from one or more hydrophilic monomers to a suitable one Graft base, cross-linked cellulose or starch ether, cross-linked Carboxymethyl cellulose, partially cross-linked polyalkylene oxide or natural products swellable in aqueous liquids, such as for example guar derivatives, alginates and carrageenans. This Progf bases can also be used as a component for compounds Serve superabsorbents.

Suitable graft bases can be of natural or synthetic origin. Examples are starch, cellulose or cellulose derivatives and other polysaccharides and oligosaccharides, polyvinyl alcohol, polyalkylene oxides, in particular polyethylene oxides and polypropylene oxides, polyamines, polyamides and hydrophilic polyesters. Suitable polyalkylene oxides have, for example, the formula


R ¹ and R ² independently of one another are hydrogen, alkyl, alkenyl or acrylic,
X is hydrogen or methyl and
n is an integer from 1 to 10,000.

R ¹ and R ^{2 are} preferably hydrogen, (C ₁ -C ₄ ) alkyl, (C ₂ - C ₆ ) alkenyl or phenyl.

Crosslinked polymers are preferred as hydrogel-forming polymers with acid groups, mainly in the form of their salts, in the Usually alkali or ammonium salts are present. Such polymers swell particularly strongly on contact with aqueous liquids to gel on.

Polymers produced by crosslinking polymerization are preferred or copolymerization of acid-bearing monoethylenic unsaturated monomers or their salts are obtained. Further it is possible to add these monomers without crosslinking agents (co) polymerize and subsequently crosslink.

Monomers bearing such acid groups are, for example, monoethylenically unsaturated C ₃ -C ₂₅ -carboxylic acids or anhydrides such as acrylic acid, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid and fumaric acid. Also suitable are monoethylenically unsaturated sulfonic or phosphonic acids, for example vinylsulfonic acid, allylsulfonic acid, sulfoethyl acrylate, sulfomethacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy-3-acryloxypropylsulfonic acid, 2-hydroxy-3-methacryloxypropylsulfonic acid, stylphosphonic acid, allylphosphonic acid, allylphosphonic acid, allylphosphonic acid, acrylamido-2-methyl propane sulfonic acid. The monomers can be used alone or as a mixture with one another.

Monomers used with preference are acrylic acid, methacrylic acid, Vinylsulfonic acid, acrylamidopropanesulfonic acid or mixtures these acids, e.g. B. mixtures of acrylic acid and Methacrylic acid, mixtures of acrylic acid and acrylamidopropanesulfonic acid or mixtures of acrylic acid and vinyl sulfonic acid.

To optimize properties, it can be useful to use additional monoethylenically unsaturated compounds which do not carry any acid groups, but which can be copolymerized with the monomers bearing acid groups. These include, for example, the amides and nitriles of monoethylenically unsaturated carboxylic acid, e.g. As acrylamide, methacrylamide and N-vinylformamide, N-vinyl acetamide, N-methyl-vinyl acetamide, acrylonitrile and methacrylonitrile. Other suitable compounds are, for example, vinyl esters of saturated C ₁ - to C ₄ -carboxylic acids such as vinyl formate, vinyl acetate or vinyl propionate, alkyl vinyl ethers with at least 2 C atoms in the alkyl group, such as, for. B. ethyl vinyl ether or butyl vinyl ether, esters of monoethylenically unsaturated C ₃ - to C ₆ -carboxylic acids, for. B. esters of monohydric C ₁ - to C ₁₈ alcohols and acrylic acid, methacrylic acid or maleic acid, half-esters of maleic acid, for. B. maleic acid mono-methyl ester, N-vinyl lactams such as N-vinyl pyrrolidone or N-vinyl caprolactam, acrylic acid and methacrylic acid esters of alkoxylated monohydric, saturated alcohols, e.g. B. of alcohols with 10 to 25 carbon atoms, which have been reacted with 2 to 200 moles of ethylene oxide and / or propylene oxide per mole of alcohol, and monoacrylic acid esters and monomethacrylic acid esters of polyethylene glycol or polypropylene glycol, the molecular weights (Mn) of the polyalkylene glycols, for example, up to Can be 2000. Other suitable monomers are styrene and alkyl-substituted styrenes such as ethylstyrene or tert-butylstyrene.

These monomers which do not contain acid groups can also be used in Mixture with other monomers are used, for. B. Mixtures of vinyl acetate and 2-hydroxyethyl acrylate in any ratio. These monomers bearing no acid groups the reaction mixture in amounts between 0 and 50 wt .-%, preferably less than 20 wt .-% added.

crosslinkers

Crosslinked polymers bearing acid groups are preferred monoethylenically unsaturated monomers, which may or may not be present or after the polymerization into their alkali or ammonium salts be transferred, and from 0-40 wt .-% based on it Total weight no acid-bearing monoethylenically unsaturated Monomers.

Crosslinked polymers of monoethylenically unsaturated C ₃ to C ₁₂ carboxylic acids and / or their alkali metal or ammonium salts are preferred. In particular, crosslinked polyacrylic acids are preferred, the acid groups of which are 25-100% as alkali or ammonium salts.

Compounds which have at least two can function as crosslinkers have ethylenically unsaturated double bonds. examples for Compounds of this type are N, N'-methylenebisacrylamide, Polyethylene glycol diacrylates and polyethylene glycol dimethacrylates, the each of polyethylene glycols with a molecular weight of 106 to 8500, preferably 400 to 2000, Trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, Ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate Propylene glycol dimethacrylate, butanediol diacrylate, Butanediol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, Allyl methacrylate, diacrylates and dimethacrylates of block copolymers from ethylene oxide and propylene oxide, twice or more with Acrylic acid or methacrylic acid esterified polyhydric alcohols, such as glycerol or pentaerythritol, triallylamine, Dialkyldiallylammonium halides such as dimethyldiallylammonium chloride and Diethyldiallylammonium chloride, tetraallylethylenediamine, divinylbenzene, Diallyl phthalate, polyethylene glycol divinyl ether from Polyethylene glycols with a molecular weight of 106 to 4000, Trimethylolpropane diallyl ether, butanediol divinyl ether, Pentaerythritol triallyl ether, reaction products of 1 mole of ethylene glycol diglycidyl ether or polyethylene glycol diglycidyl ether with 2 moles Pentaerythritol triallyl ether or allyl alcohol, and / or Divinylethylenharnstoff. Preferably, water-soluble crosslinking agents are used, e.g. B. N, N'-methylenebisacrylamide, polyethylene glycol diacrylates and Polyethylene glycol dimethacrylate, which differs from addition products 2 to 400 moles of ethylene oxide to 1 mole of a diol or polyol derive vinyl ethers from addition products from 2 to 400 mol Ethylene oxide on 1 mole of a diol or polyol, Ethylene glycol diacrylate, ethylene glycol dimethacrylate or triacrylates and Trimethacrylates of addition products of 6 to 20 moles of ethylene oxide 1 mole of glycerol, pentaerythritol triallyl ether and / or Divinylurea.

Also suitable as crosslinkers are compounds which at least one polymerizable ethylenically unsaturated group and contain at least one further functional group. The functional group of these crosslinkers must be able to use the functional groups, essentially the acid groups, the React monomers. Suitable functional groups are for example hydroxyl, amino, epoxy and aziridino groups. Can be used for. B. Hydroxyalkyl esters of the above mentioned monoethylenically unsaturated carboxylic acids, for. B. 2-hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, Hydroxyethyl methacrylate, hydroxypropyl methacrylate and Hydroxybutyl methacrylate, allyl piperidinium bromide, N-vinylimidazoles such as. B. N- Vinylimidazole, 1-vinyl-2-methylimidazole and N-vinylimidazolines such as N-vinylimidazoline, 1-vinyl-2-methylimidazoline, 1-vinyl-2-ethylimidazoline or 1-vinyl-2-propylimidazoline, which in Form of free bases, in quaternized form or as a salt the polymerization can be used. They are also suitable Dialkylaminoethyl acrylate, dimethylaminoethyl methacrylate, Diethylaminoethyl acrylate and diethylaminoethyl methacrylate. The basic ones Esters are preferably in quaternized form or as a salt used. Furthermore, e.g. B. also glycidyl (meth) acrylate be used.

Also suitable as crosslinkers are compounds which contain at least two functional groups that are capable are, with the functional groups, essentially the To react acid groups of the monomers. The suitable ones functional groups have already been mentioned above, i. H. hydroxyl, Amino, epoxy, isocyanate, ester, amido and aziridino groups. Examples of such crosslinkers are ethylene glycol, Diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, Glycerin, polyglycerin, triethanolamine, propylene glycol, Polypropylene glycol, block copolymers of ethylene oxide and Propylene oxide, ethanolamine, sorbitan fatty acid esters, ethoxylated Sorbitan fatty acid esters, trimethylolpropane, pentaerythritol, 1,3-butanediol, 1,4-butanediol, polyvinyl alcohol, sorbitol, starch, Polyglycidyl ethers such as ethylene glycol diglycidyl ether, Polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol polyglycidyl ether, Diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, Sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, Propylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether, Polyaziridine compounds such as 2,2-Bishydroxymethylbutanoltris [3- (1-aziridinyl) propionate], 1,6-hexamethylene diethylene urea, diphenylmethane-bis-4,4'-N, N'-diethylene urea, Haloepoxy compounds such as epichlorohydrin and α-methylepifluorohydrin, Polyisocyanates such as 2,4-tolylene diisocyanate and Hexamethylene diisocyanate, alkylene carbonates such as 1,3-dioxolan-2-one and 4-methyl-1,3-dioxolan-2-one, further bisoxazolines and Oxazolidones, polyamidoamines and their reaction products with Epichlorohydrin, also polyquaternary amines such as condensation products of Dimethylamine with epichlorohydrin, homo- and copolymers of Diallyldimethylammonium chloride and homo- and copolymers of Dimethylaminoethyl (meth) acrylate, optionally with for example, methyl chloride are quaternized.

Other suitable crosslinkers are polyvalent metal ions, which in are able to develop ionic networks. examples for such crosslinkers are magnesium, calcium, barium and Aluminum ions. These crosslinkers are, for example, as Hydroxides, carbonates or hydrogen carbonates are used. Further suitable crosslinkers are multifunctional bases, which are also in are able to form ionic networks, for example Polyamines or their quaternized salts. Examples of polyamines are ethylenediamine, diethylenetriamine, triethylenetetramine, Tetraethylene pentamine, pentaethylene hexamine and polyethyleneimines as well Polyamines with molecular weights of up to 4,000,000 each.

The crosslinkers in the reaction mixture are, for example, from 0.001 to 20 and preferably from 0.01 to 14 wt .-% present.

A radical polymerization is preferably carried out. The As usual, polymerization is carried out by an initiator triggered. Also initiation of the polymerization by Effect of electron beams on the polymerizable, aqueous Mixing is possible. However, the polymerization can also take place in Absence of initiators of the type mentioned above Exposure to high energy radiation in the presence of photoinitiators to be triggered. All can be used as polymerization initiators decomposing into radicals under the polymerization conditions Connections are used, e.g. B. peroxides, hydroperoxides, Hydrogen peroxides, persulfates, azo compounds and the so-called redox catalysts. The use of is preferred water-soluble initiators. In some cases it is advantageous To use mixtures of different polymerization initiators z. B. mixtures of hydrogen peroxide and sodium or Potassium. Mixtures of hydrogen peroxide and Sodium peroxodisulfate can be used in any ratio become. Suitable organic peroxides are, for example Acetylacetone peroxide, methyl ethyl ketone peroxide, tert-butyl hydroperoxide, Cumene hydroperoxide, tertiary amyl perpivalate, tertiary butyl perpivalate, tert-butyl perneohexanoate, tert-butyl perisobutyrate, tert-butyl per-2-ethylhexanoate, tert-butyl perisononanoate, tert-butyl permaleate, tert-butyl perbenzoate, di- (2-ethylhexyl) peroxidicarbonate, dicyclohexyl, Di- (4-tert-butylcyclohexyl) peroxidicarbonate, dimyristilperoxidicarbonate, Diacetyl peroxydicarbonate, allyl perester, cumyl peroxyneodecanoate, tert-butylper-3,5,5-trimethylhexanoate, acetylcyclohexylsulfonyl peroxide, Dilauryl peroxide, dibenzoyl peroxide and tert-amyl perneodecanoate. Particularly suitable polymerization initiators are water-soluble azo starters, e.g. B. 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (N, N'-dimethylene) isobutyramidine dihydrochloride, 2- (carbamoylazo) isobutyronitrile, 2,2'-azobis [2- (2'-imidazolin-2-yl) propane] dihydrochloride and 4,4'-azobis (4-cyanovaleric acid). The above Polymerization initiators are used in conventional amounts, e.g. B. in amounts of 0.01 to 5, preferably 0.05 to 2.0 wt .-%, based on the polymerizing monomers.

Redox catalysts are also suitable as initiators. The redox catalysts contain at least one of the above-mentioned per compounds as the oxidizing component and as reducing component, for example, ascorbic acid, glucose, sorbose, ammonium or alkali metal hydrogen sulfite, sulfite, thiosulfate, hyposulfite, pyro sulfite or sulfide, metal salts, such as iron ( II) ions or sodium hydroxymethyl sulfoxylate. Ascorbic acid or sodium sulfite is preferably used as the reducing component of the redox catalyst. Based on the amount of monomers used in the polymerization, 3 × 10 ^-6 to 1 mol% of the reducing component of the redox catalyst system and 0.001 to 5.0 mol% of the oxidizing component of the redox catalyst are used, for example.

If the polymerisation by exposure to high energy Radiation is usually used as an initiator so-called photoinitiators. This can be, for example so-called α-splitters, H-abstracting systems or azides act. Examples of such initiators are Benzophenone derivatives such as Michlers ketone, phenanthrene derivatives, fluorene derivatives, Anthraquinone derivatives, thioxanone derivatives, cumann derivatives, Benzoin ethers and their derivatives, azo compounds such as those above radical generator, substituted hexaarylbisimidazoles or Acylphosphine. Examples of azides are: 2- (N, N-dimethylamino) ethyl-4-azidocinnamate, 2- (N, N-dimethylamino) ethyl 4-azidonaphthyl ketone, 2- (N, N-dimethylamino) ethyl 4-azidobenzoate, 5-azido-1-naphthyl-2 '- (N, N-dimethylamino) ethyl sulfone, N- (4-sulfonyl azidophenyl) maleimide, N-acetyl-4-sulfonyl azidoaniline, 4-sulfonylazidoaniline, 4-azidoaniline, 4-azidophenacyl bromide, p-azidobenzoic acid, 2,6-bis (p-azidobenzylidene) cyclohexanone and 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone. The If they are used, photoinitiators are usually used in Amounts of 0.01 to 5 wt .-% based on those to be polymerized Monomers applied.

As a technical process for the manufacture of these products all processes are used, which are usually used in the Production of superabsorbents are used, such as. B. in Chapter 3 in "Modern Superabsorbent Polymer Technology", F.L. Buchholz and A. T. Graham, Wiley-VCH, 1998.

Polymerization in aqueous solution is preferred as so-called gel polymerization. 10 to 70% by weight aqueous solutions of the monomers and, if appropriate, a suitable one Graft base in the presence of a radical initiator Utilization of the Trommsdorff-Norrish effect polymerized.

The polymerization reaction can take place in the temperature range between 0 ° C and 150 ° C, preferably between 10 ° C and 100 ° C, both at Normal pressure as well as under increased or reduced pressure be performed. As usual, the polymerization can also be carried out in a protective gas atmosphere, preferably under nitrogen, be carried out.

By reheating the polymer gels for several hours in the Temperature range 50 to 130 ° C, preferably 70 to 100 ° C, can Quality properties of the polymers can still be improved.

The crosslinked polymers are preferably neutralized used. However, the neutralization can also be carried out only partially his. The degree of neutralization is preferably 25 to 100%, in particular 50 to 100%. As neutralizing agents come in Question: Alkali metal bases or ammonia or amines. Preferably sodium hydroxide solution or potassium hydroxide solution is used. The neutralization but can also with the help of sodium carbonate, Sodium hydrogen carbonate, potassium carbonate or potassium hydrogen carbonate or others Carbonates or bicarbonates or ammonia made become. In addition, prim., Sec. And tert. Amines can be used.

Hydrogel-forming polymers are preferred post-crosslinked. The surface post-crosslinking can in itself known way with dried, ground and sieved Polymer particles happen.

For this purpose, compounds with the functional groups of the Polymers can react with crosslinking, preferably in the form a water-based solution on the surface of the Hydrogel particles applied. The water-based solution can be water-miscible contain organic solvents. Suitable solvents are Alcohols such as methanol, ethanol, i-propanol or acetone.

In the subsequent crosslinking, polymers are formed by the Polymerization of the above monoethylenically unsaturated Acids and optionally monoethylenically unsaturated Comonomers were produced and which have a molecular weight greater than 5000, preferably have greater than 50,000, reacted with compounds which at least two groups reactive towards acid groups exhibit. This reaction can take place at room temperature or at elevated temperatures up to 220 ° C. Suitable reactive Groups are e.g. B. hydroxyl, amino, epoxy, isocyanate, ester, Amido and aziridino groups.

Examples of such crosslinkers are polyols such as ethylene glycol, Diethylene glycol, triethylene glycol, tetraethylene glycol, Polyethylene glycol, glycerin, di- and polyglycerol, triethanolamine, Propylene glycol, polypropylene glycol, the oxyethylates of these polyols and their esters with carboxylic acids or carbonic acid such as Ethylene carbonate or propylene carbonate, block copolymers Ethylene oxide and propylene oxide, ethanolamine, Sorbitan fatty acid esters, ethoxylated sorbitan fatty acid esters, trimethylolpropane, Pentaerythritol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, Methyl triglycol, polyvinyl alcohol, sorbitol, starch, di- or Polyglycidyl compounds such as ethylene glycol diglycidyl ether, Polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, Glycerol polyglycidyl ether, diglycerol polyglycidyl ether, Polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, Pentaerythritol polyglycidyl ether, propylene glycol diglycidyl ether and Polypropylene glycol diglycidyl ether, phosphonic acid diglycidyl ether or bischlorohydrin ether of polyalkylene glycols, di- and poly-N-methylol compounds such as for example methylenebis (N-methylol-methacrylamide) or Melamine-formaldehyde resins, alkoxysilyl compounds, Polyaziridine compounds or compounds containing aziridine units Based on polyethers or substituted hydrocarbons, such as bis-N-aziridinomethane, 2,2-Bishydroxymethylbutanoltris [3- (1-aziridinyl) propionate], 1,6-hexamethylene diethylene urea, diphenylmethane-bis-4,4'-N-N'-diethylene urea, Haloepoxy compounds such as epichlorohydrin and a-methylepifluorohydrin, Di- and polyisocyanates such as 2,4-tolylene diisocyanate and Hexamethylene diisocyanate, compounds with two or more blocked Isocyanate groups such as Trimethylhexamethylene diisocyanate blocked with 2,2,3,6-tetramethyl-piperidinone-4, Alkylene carbonates such as 1,3-dioxolan-2-one and 4-methyl-1,3-dioxolan-2-one, carbonic acid derivatives such as urea, thiourea, Guanidine, dicyandiamide, 2-oxazolidinone and its derivatives, Bisoxazolines, polyoxazolines, and oxazolidones, polyamines or Polyamidoamines and their reaction products with epichlorohydrin, further polyquaternary amines such as condensation products of dimethylamine with epichlorohydrin, homo- and copolymers of Diallyldimethylammonium chloride, as well as homo- and copolymers of Dimethylaminoethyl (meth) acrylate, optionally with, for example Methyl chloride are quaternized.

If necessary, acidic catalysts such as p-toluenesulfonic acid, phosphoric acid, boric acid or Ammonium dihydrogen phosphate can be added.

Particularly suitable post-crosslinking agents are di- or Polyglycidyl compounds such as ethylene glycol diglycidyl ether, the Reaction products of polyamidoamines with epichlorohydrin and 2-oxazolidinone.

The crosslinking agent solution is preferably applied by Spraying a solution of the crosslinker in conventional Reaction mixers or mixing and drying systems such as Patterson-Kelly mixer, DRAIS turbulence mixer, Lödige mixer, Screw mixer, plate mixer, fluid bed mixer and Schugi Mix. After spraying the crosslinker solution, a Follow the temperature treatment step, preferably in a downstream one Dryer, at a temperature between 80 and 230 ° C, preferred 80-190 ° C, and particularly preferably between 100 and 160 ° C, about a period of 5 minutes to 6 hours, preferably 10 minutes up to 2 hours and particularly preferably 10 minutes to 1 hour, whereby both cleavage products and solvent components are removed can be. Drying can also be done in the mixer itself done by heating the jacket or blowing one preheated carrier gas.

In a particularly preferred embodiment of the invention, the hydrophilicity of the particle surface of the hydrogel-forming polymers is additionally modified by the formation of complexes. The complexes are formed on the outer shell of the hydrogel particles by spraying on solutions of di- or polyvalent metal salt solutions, the metal cations being able to react with the acid groups of the polymer to form complexes. Examples of divalent or polyvalent metal cations are Mg ²⁺ , Ca ²⁺ , Al ³⁺ , Sc ³⁺ , Ti ⁴⁺ , Mn ²⁺ , Fe ^{2 + / 3 +} , Co ²⁺ , Ni ²⁺ , Cu ^{+ / 2 +} , Zn ²⁺ , Y ³⁺ , Zr ⁴⁺ , Ag ⁺ , La ³⁺ , Ce ⁴⁺ , Hf ⁴⁺ , and Au ^{+ / 3 +} , preferred metal cations are Mg ²⁺ , Ca ^{2 +} , Al ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ and La ³⁺ , and particularly preferred metal cations are Al ³⁺ , Ti ⁴⁺ and Zr ⁴⁺ . The metal cations can be used either alone or in a mixture with one another. Of the metal cations mentioned, all metal salts are suitable which have sufficient solubility in the solvent to be used. Metal salts with weakly complexing anions such as chloride, nitrate and sulfate are particularly suitable. Water, alcohols, DMF, DMSO and mixtures of these components can be used as solvents for the metal salts. Water and water / alcohol mixtures, such as water / methanol or water / 1,2-propanediol, are particularly preferred.

Spraying the metal salt solution onto the particles of the Hydrogel-forming polymer can be used both before and after Surface post-crosslinking of the particles take place. In one particular preferred method is the spraying of the metal salt solution in the same step as spraying the crosslinker solution, whereby both solutions are separated one after the other or simultaneously two nozzles are sprayed, or crosslinker and Metal salt solution can be sprayed together via a nozzle.

Optionally, a further modification of the hydrogel-forming polymers can be carried out by adding finely divided inorganic solids, such as, for example, silica, aluminum oxide, titanium dioxide and iron (II) oxide, which further enhances the effects of surface treatment. The addition of hydrophilic silica or of aluminum oxide with an average size of the primary particles of 4 to 50 nm and a specific surface area of 50-450 m ² / g is particularly preferred. The addition of finely divided inorganic solids is preferably carried out after the surface modification by crosslinking / complex formation, but can also be carried out before or during these surface modifications.

The present invention further relates to the use of the above mentioned highly swellable hydrogel-forming polymers for Absorption of aqueous fluids in brake fluids.

In particular, the present invention relates to the use of absorbing aqueous liquids, in non-aqueous ones Solutions insoluble, highly swellable hydrogel-forming polymers for the drainage of brake fluids.

The highly swellable hydrogel-forming polymers can be used in any Shape, size and / or morphology are used. Under granular polymer is understood to mean particulate polymer. This are z. B. powders, granules, flakes, aggregates or their Mixtures, especially powders.

Powdery material is preferably in the form of individual Particles used. Material with a particularly preferred Grain size of more than 100 µm is used. In particular lies the particle size at greater than 300 microns and / or less than 3 mm or 2 mm, in particular less than 1 mm.

In the application according to the invention, the highly swellable hydrogel-forming polymers excellent as Absorbent for water and aqueous liquids, so they advantageous as an aid in the drainage of brake fluids can be used.

The highly swellable hydrogel-forming polymers can do that too added directly to draining brake fluids and lubricating oils become. In practice, however, it is more advantageous to do this Polymer a filter in the system or one for the Brake fluid permeable reservoir in the brake system or in To provide expansion tanks. Such The device for storing the superabsorbers must be permanent or be in contact with the brake fluid at least regularly. she must be permeable to the brake fluid but should Super absorber in swollen and unswollen condition hold back. It can be fixed in the construction of a compensation or Storage container be installed and z. B. from the container material be constructed. On the other hand, it can also in the compensation or Storage containers are designed to be floating. It is advantageous if the device is prevented from compensating or Leaving storage containers (e.g. in a dimension larger than Outlet from container, flexible fixation to the container by chain, Tape etc). Advantageously, the devices in the Expansion tank or reservoir attached so that easily checked whether the superabsorbent has already absorbed water and possibly the device or possibly only the Superabsorbent (advantageously in an extra container integrated) can be easily replaced. Under compensation or Storage tanks are also low pressure storage, reserve storage as understood in WO 97/02973. Further refinements from Braking systems are e.g. B. in WO 01/07307, WO 98/17516 or WO 99/30943 find the devices in their containers or secondary circuits can be attached for dewatering. Under secondary circuits such circuits are understood that either as "bypass" are designed for the brake circuit or such Refinements in which the brake fluid on the device can flow past without the braking function essentially increasing impair, e.g. B. by a superabsorbent restrained, Brake fluid permeable container in a widened Line of the brake circuit is inserted that the Brake fluid can also flow past the container.

Claims (10)

1. Use of granular, highly swellable hydrogel-forming polymer in a device for storing highly swellable hydrogel-forming polymer in the expansion tank or reservoir for brake fluid for drainage the brake fluid. 2. Use of granular, highly swellable hydrogel-forming polymer in a device for storing highly swellable hydrogel-forming polymer in one Auxiliary circuit of the brake fluid to drain the Brake fluid. 3. Use according to one of claims 1 or 2, wherein it is in the highly swellable hydrogel-forming polymer Networks of flexible hydrophilic polymers of ionic and / or is non-ionic in nature. 4. Use according to any one of claims 1 to 3, wherein it is in the highly swellable hydrogel-forming polymer cross-linked polymers with acid groups, mainly in farm their salts are present. 5. Use according to one of claims 1 to 4, wherein it is in the highly swellable hydrogel-forming polymer crosslinked polymers with acid groups, predominantly in the form of Alkali or ammonium salts are present. 6. Use according to any one of claims 1 to 5, wherein highly swellable hydrogel-forming polymers with a particle size of larger than 100 µm are used. 7. Brake fluid containing highly swellable hydrogel-forming polymer in granular form. 8. Device for storing granular highly swellable hydrogel-forming polymer in the expansion tank or Brake fluid reservoir. 9. Device for storing granular highly swellable hydrogel-forming polymers in a secondary cycle of Brake fluid. 10. Device according to one of claims 8 or 9, containing granular, highly swellable hydrogel-forming polymers.