WO1991013926A1

WO1991013926A1 - Compounds containing polyether chains and quaternary ammonium groups

Info

Publication number: WO1991013926A1
Application number: PCT/EP1991/000376
Authority: WO
Inventors: Ralf Bohlander; Günter Uphues; Uwe Ploog; Maria Liphard
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1990-03-09
Filing date: 1991-03-01
Publication date: 1991-09-19
Also published as: DE4007597A1; AU7333891A

Abstract

The invention relates to water-soluble or water-dispersible compounds containing polyether chains and quaternary ammonium groups, a method for preparing them and their use in the recycling of waste paper.

Description

POLYETHER CHAINS AND QUATERNAR AMMONIUM GROUPS

The invention relates to water-soluble or water-dispersible compounds containing polyether chains and quaternary ammonium groups, a process for their preparation and the use of these compounds in waste paper processing.

For the production of, for example, newspaper printing and hygiene papers, waste paper is used in large quantities today. The quality of these types of paper is determined by their brightness and color. In order to be able to produce high-quality paper types, the printing inks must be removed from the printed waste paper. This is usually done using the deinking process, which essentially takes place in two steps:

1. opening the waste paper, that is to say defibrating in water with simultaneous action of the chemicals and. Required for the detachment of the printing ink particles 2. Elimination of the detached ink particles from the paper suspensions.

The second process step can be carried out by washing or flotation (Ullmann's Enzyclopadie der Technischen Chemie, 4th edition, volume 17, pages 570-571 (1979)). In flotation, in which the different wettability of printing inks and paper fibers is exploited, air is pressed or sucked through the pulp suspensions. Small air bubbles combine with the ink particles and form a foam on the surface of the water, which is removed with fabric hangers.

The deinking of waste paper is usually carried out at alkaline pH values in the presence of alkali hydroxides, alkali silicates, oxidative bleaches and surface-active substances at temperatures between 30 and 50 ° C. Soaps and / or fatty alcohol polyglycol ethers are predominantly used as surface-active substances which bring about the detachment and separation of the printing ink particles (Ullmann's Enzyclopadie der Technischen Chemie, 4th edition, volume 17, pages 571-572 (1979)). The German patent application DE-OS 33 22 330 and the German patent DE-PS 33 47 906 describe the use of alkylamine polyethers for removing printing ink. Furthermore, from JP 84/137587, referenced in Che. Abstr. 102. 80638b (1985) ethyleneimine-ethylene oxide-propylene oxide copolymers and from JP 82/25489, referenced in Chem. Abstr. £ 7, 57393n (1982) ethylene oxide-propylene oxide-alkyl (alkenyl) amine adducts known as deinking chemicals.

The classic printing ink systems, for example based on nitrocellulose, maleate resins and / or shellac, the esters and / or ketones, for example ethyl acetate and / or methyl ethyl ketone, or Alcohols as solvents have been increasingly replaced by water-thinnable printing inks in recent years for environmental reasons. Another reason for the increasing use of water-thinnable printing inks is the incombustibility of water, as a result of which the installation of expensive protective devices necessary when using solvent-containing printing inks is no longer necessary. Most water-thinnable printing inks contain anionic polymers as binders, for example polymers containing carboxyl groups, by neutralizing them with bases the printing inks become water-thinnable.

Although water-thinnable printing inks have decisive advantages over conventional solvent-based printing inks, there are still warnings about the introduction of processes using water-thinning printing inks (flexographic printing inks), since water-thinnable printing inks made from waste paper contain the usual surfactants from the deinking fleet - if at all - can only be removed completely inadequately (Das Papier 42 (10 A), V84-V88 (1988)). The consequence of this is that to date the waste paper that is being produced in ever larger quantities and that has been printed with water-thinnable printing inks has not been reused and is therefore not available as waste paper raw material for newsprint and hygiene paper.

The object on which the invention is based was to provide connections for deinking waste paper, with which it is possible to remove, in particular, satisfactory amounts of water-dilutable printing inks from waste paper.

It has been found that water-thinnable and / or solvent-based printing inks can be found in printed waste paper Have washing deinking or flotation deinking processes in the presence of previously unknown water-soluble or -dispersible compounds containing polyether chains and quaternary ammonium groups removed in surprisingly high amounts.

The invention accordingly relates to water-soluble or water-dispersible compounds containing polyether chains and quaternary ammonium groups, obtainable by reacting halohydrin and / or epoxy compounds containing quaternary ammonium groups and

Connections of the general formula I

in the R a z-valent alkoxy radical, AO 1 to 100 alkylene oxide units, which are composed of 0 to 100 C2H4θ units, 0 to 50 C3H5Ö units and 0 to 30 C ^ gO units, shark chlorine and / or Bromine atoms, p is an integer between 0 and 3 and q 0 or 1, with the proviso that the sum p + q is not equal to 0 and z is an integer from 1 to 10,

with ammonia,

aliphatic di- and / or polyamines and / or amino sugars.

Another subject matter of the invention is a process for the preparation of water-soluble or water-dispersible compounds containing polyether chains and quaternary ammonium groups, which is characterized in that halohydrin and / or epoxy compounds containing quaternary ammonium groups and Compounds of the general formula I

in the R a z-valent alkoxy radical, AO 1 to 100 alkylene oxide units, which are composed of 0 to 100 C2H4θ units, 0 to 50 C3H θ units and 0 to 30 CHgO units, shark chlorine and / or bromine atoms , p is an integer between 0 and 3 and q is 0 or 1, with the proviso that the sum p + q is not equal to 0, and z is an integer from 1 to 10,

with ammonia,

aliphatic di- and / or polyamines and / or amino sugars at temperatures between 40 and 120 ° C.

In contrast to the compounds according to the invention, the compounds described in DE-PS 38 03 213 have significantly lower molar masses and only have terminal quaternary ammonium groups and at least one oxirane group.

The polyether chains and compounds containing quaternary ammonium groups can be obtained by reacting halohydrin and / or epoxy compounds containing quaternary ammonium groups and compounds of the general formula I with ammonia,

Cl-22 " ^A T ^c yl ^am '' ^nβn f aliphatic di- and / or polyamines and / or amino sugars (NH compounds) preferably in the presence of alkali metal hydroxides at temperatures between 40 and 120 ° C, preferably between 60 and 95 ° C. The alkali metal hydroxides used are, for example, sodium hydroxide and / or potassium hydroxide, preferably sodium hydroxide, and the reactions can be carried out with or without a solvent the reactions are carried out in aqueous, alcoholic or aqueous-alcoholic solutions. The reactions are terminated by adding inorganic and / or organic acids, for example sulfuric acid, acetic acid and / or lactic acid.

0.8 to 1.2 halohydrin groups are used per NH group.

For the preparation of the compounds according to the invention, aliphatic di- and / or polyamines can first be modified with halohydrin and / or epoxy compounds containing quaternary ammonium groups, 0.1 to 1 mol of these quaternary ammonium groups containing halohydrin and / or epoxy compounds per mole A be used. Modification means that some of the primary and secondary amine groups contained in the di- and / or polyamines are converted into the corresponding secondary and tertiary amine groups. The modified di- and / or polyamines are then reacted with compounds of the general formula I, optionally with the addition of NH compounds. Another possibility for the preparation of the compounds according to the invention is that halohydrin and / or epoxy compounds containing quaternary ammonium groups are reacted together with compounds of the general formula I and NH compounds. However, it is also possible first to react only a portion of the quaternary ammonium halohydrin and / or epoxy compounds with compounds of the general formula I and NH compounds and then the remaining amount of quaternary ammonium groups containing halohydrin and / or add epoxy compounds to the reaction mixture. In the two last-mentioned process variants, halohydrin and / or epoxy compounds containing quaternary ammonium groups are used in such amounts used that 1 to 30 mol% of the nitrogen atoms can be modified. Furthermore, quaternary ammonium halogen-containing and / or epoxy compounds can be added after the reaction of the compounds of general formula I with NH compounds. Halogen-hydrine and / or epoxy compounds containing quaternary ammonium groups are used in amounts such that 0.1 to 10 mol% of the amine nitrogen atoms originally present can be modified.

Examples of suitable quaternary ammonium groups containing halohydrin and / or epoxy compounds are 2,3-epoxypropyltrimethylammonium chloride and / or 3-chloro-2-hydroxypropyltriethylammonium chloride. These compounds are commercially available products and are offered, for example, by Degussa under the name "QUAB".

Compounds of the general formula I can be prepared from alcohols having 1 to 10 OH groups which are alkoxylated by known industrial processes with ethylene oxide, propylene oxide and / or butylene oxide ("Chemical Technology", Volume 7, pages 131-132, Carl-Hanser -Verlag, Munich - Vienna 1986)). The alkoxylated alcohols, if desired in a mixture with the corresponding nonalkoxylated alcohols, are prepared with epihalohydrins, preferably with epichlorohydrin, preferably in the presence of catalysts, for example boron trifluoride diacetic acid and / or tin tetrachloride, at temperatures between 50 and 150 ° C. ¬ preferably implemented between 60 and 95 ° C. Epihalohydrins are used in amounts of 0.3 to 4 mol, based on an OH group. Suitable alcohols with 1 to 10 OH groups are, for example, linear, branched-chain and / or cyclic, primary and / or secondary, monohydric alkyl alcohols with 1 to 22 carbon atoms, such as methanol, ethanol, butanol, isopropanol, cyclohexanol, 2-ethylhexanol and / or lauryl alcohol, dihydric alcohols of the general formula H0- (CH2) 2-12 ~ ^0H _< Bisphenol A, glycerol, di-, tri- and / or tetraglycerol, trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol and / or mannitol. Alcohols with 2 to 4 OH groups are preferred.

Suitable NH compounds are ammonia, C22 alkylamines, for example dodecylamine, 2-ethylhexylamine, coconut amine and / or tallow amine, aliphatic linear branched-chain and / or cyclic, optionally alkoxylated di- and / or polyamines with optionally amide groups in the aliphatic radicals , for example ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, dihexaethylenetriamine, 1,2-dihydroxyethyldiaminoethane, piperazine, polyethyleneamine with average molecular weights between 200 and 10,000, bis- [3,3-aminopropyl] methylamine, N, N-dimethylaminopropylamine, N-stearylpropylenediamine and / or N-acylamidoamine, which can be prepared by aminolysis of natural fats and / or oils or by amidation of fatty acids with polyamines, for example reaction products of beef tallow with tetraethylene pentamine or stearic acid with diethylene triamine, and / or amino sugar, for example glycamine. Alkoxylated, preferably ethoxylated, di- and / or polyamines must have at least one N-H group. Ci-22 "alkylamines and / or aliphatic di- and / or polyamines are preferably used.

The compounds of the invention which are accessible by reacting compounds of the general formula I and quaternary ammonium groups-containing halohydrin and / or epoxy compounds with NH compounds are aqueous solutions or with Gels which form aqueous solutions and contain the compounds according to the invention in amounts of 10 to 80% by weight, preferably 40 to 60% by weight.

The compounds according to the invention are suitable for removing water-dilutable and / or solvent-containing printing inks from printed waste paper and / or paper cycle water. Accordingly, the present invention relates to the use of water-soluble or water-dispersible compounds containing polyether chains and quaternary ammonium groups, obtainable by reacting halohydrin and / or epoxy compounds containing quaternary ammonium groups and

Compounds of the general formula I

in which R is a z-valent alkoxy radical, AO 1 to 100 alkylene oxide units, which are composed of 0 to 100 C2H4θ units, 0 to 50 C3H5θ units and 0 to 30 C4Hg0 units, shark chlorine and / or bromine atoms, p is an integer between 0 and 3 and q is 0 or 1, with the proviso that the sum p + q = 0 and z is an integer from 1 to 10,

with ammonia, C22 alkylamines, aliphatic di- and / or polyamines and / or amino sugars,

for removing printing inks from printed waste paper and / or paper circuit water. The compounds according to the invention are added to paper stock suspensions, preferably in amounts of 0.02 to 2% by weight, particularly preferably from 0.1 to 0.5% by weight, in each case based on air-dry paper stock. Air-dry paper stock means that an equilibrium state of internal moisture has occurred in the paper stock. This state of equilibrium depends on the temperature and the relative humidity of the air.

In many cases, the deinking result, the distance that is of printing inks from printed wastepaper, be increased when compounds of the invention in combination with spielsweise Cιo- 2 "F ^ettsäureπ ι ^w"> ^e 01inor ^R 4010, 01inor ^R 4020, and / or 01inor ^R DG40 (manufacturer of all Henkel KGaA products), ethoxylated alkyl alcohols with 6 to 22 carbon atoms, ethoxylated alkylphenols, polymers such as polyacrylamides and / or polydimethylaminoethyl methacrylates and / or copolymers, described, for example, in DE 3839479, in amounts of 0 , 01 to 1 wt .-%, based on air-dry paper stock, and / or with in situ precipitated layer compounds of the general composition

M (II) ₁ _ _x M (III) _x (0H) 2 (A ^Z -) _x / ₂ -nH ₂ 0

where M (II) stands for divalent metal cations, M (III) for trivalent metal cations and A ^z ~ for anions of mono- and / or polybasic acids, the indices x a number between 0.01 and 0.5 and n is a number between 0 and 20, described in DE 39 09 568, are used. The molar ratio of divalent metal cations to trivalent metal cations in layer compounds precipitated in situ is preferably between 20: 1 and 1: 1. Based on air-dry paper stock, trivalent metal cations can be used in amounts between 0.3 and 2% by weight. In the presence of compounds according to the invention, water-thinnable and / or solvent-containing printing inks, in particular water-thinning printing inks, can be used alone or in combination with solvent-containing printing inks, for example newspaper rotary inks, letterpress printing inks, off-set printing inks, illustration gravure printing inks, flexographic printing inks, laser printing inks and / or packaging gravure inks from printed waste paper, for example newspapers, magazines, computer papers, magazines, brochures, forms, telephone books and / or catalogs. The waste papers deinked by the process according to the invention are distinguished by very high degrees of whiteness.

Printed waste papers are, for example, between 1 and 5% by weight in a cloth dissolver in aqueous solution, typically 0 to 1.5% by weight hydrogen peroxide (100%), 0 to 2.5% by weight 99% .-% NaOH and 0 to 4.0 wt .-% soda water glass with a solids content of 35 wt .-% (37 to 40 ^β Be) - all wt .-% refer to air-dry paper - contains Crushed temperatures between 20 and 60 ° C. The pulp suspensions are then stirred into water or water is added, so that 0.6 to 1.6% by weight pulp suspensions are obtained. After a residence time of between 60 and 120 minutes at temperatures between 20 and 60 ^° C., 0.02 to 2% by weight of compounds according to the invention are added, based on air-dry paper stock, and the detached ink particles are then washed out or flotated in a manner known per se excreted the pulp suspensions. Flotation is preferably carried out in a manner known per se, for example in a Denver flotation cell. If one or more of the substances mentioned above, for example fatty acids, ethoxylated alkyl alcohols and / or alkyl phenols, polymers, copolymers and / or layer compounds precipitated in situ, are used, these can be added to the pulp suspensions before or during the crushing of the pulp or together with the compounds according to the invention.

When using the compounds according to the invention, printing inks are removed both from the waste paper and from the circulating water. The compounds according to the invention can also be used for the separate cleaning of paper circulation waters. In these cases, after the addition of 2 to 100 mg of compounds according to the invention per liter of circulating water, the ink particles are removed, for example by filtration or flotation.

Examples

Production of water-soluble or water-dispersible. Polyether chains and compounds containing quaternary ammonium groups

AI. 330 g (1 mol) of QUAB 181 (a 60% strength by weight aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride) were added to 131 g (1 mol) of dipropylenetriamine at 60 to 70 ° C. in the course of 2 hours. given and then stirred at this temperature for one hour.

A2. 2 g of the yellow solution obtained according to AI were mixed with 200 g of water, 13 g (0.1 mol) of dipropylenetriamine and 200 g (0.25 mol) of bischlorohydrin ether, prepared by reacting polyethylene glycol with an average molecular weight of 600 with 2 mol of epichlorohydrin, mixed and heated to 90 ° C. After the addition of 28 g of 37% strength by weight sodium hydroxide solution, the mixture was stirred at this temperature for 2 hours. After adding 10 g of 50% by weight acetic acid, a 50% by weight, clear yellow-orange colored solution with a viscosity (measured according to Höppler at 20 ^° C.) of 3000 mPas was obtained.

756 g (1.27 mol) of polyethylene glycol with an average molecular weight of 600 were reacted with 236 g (2.6 mol) of epichlorohydrin in the presence of 19.5 g of BF3 ~ acetic acid to give the corresponding bischlorohydrin ether. 85 g of coconut amine (0.44 mol) were then added to the reaction mixture at 80 ° C. in the course of 30 minutes. • 10 ³ Pa and 110 ^β C Subsequently volatile Bestand¬ parts by distillation and then the insoluble matter was removed by filtration first at second B2. 300 g of the filtrate obtained according to B1 were mixed with 15.7 g (0.12 mol) of dipropylenetriamine, 5 g of the product obtained according to AI and 270 g of water and heated to 80 ^° C. After the addition of 28 g of 37% strength by weight sodium hydroxide solution, stirring was continued at 80.degree. After 2.5 hours the viscosity no longer rose and 8 g of 37% strength by weight sodium hydroxide solution were added again. After 45 minutes the reaction product had the desired viscosity (measured in situ with a 25 ml pipette; leakage method calibrated for Höppler at 20 ° C)

2500 mPas. The reaction was then stopped by adding 25 g of 80% by weight lactic acid. A yellow solution with a viscosity (measured at 20 ^° C. according to Höppler) of

3500 mPas and 50 wt .-% compound according to the invention.

C. 330 of the filtrate obtained according to B1 were mixed at 60 ° C. with 16 g triethylenetetramine, 305 g water and 32 g 37% by weight sodium hydroxide solution. The reaction mixture was then heated to 70 ^° C. After 90 minutes the reaction mixture had a viscosity (in situ measurement with a 25 ml pipette; leakage method calibrated for Höppler at 20 ° C) of 800 mPas. Then 10 g of QUAB 151 (50% strength by weight aqueous solution of 2,3-epoxypropyltrimethylammonium chloride), 100 g of water and 5 g of 37% strength by weight sodium hydroxide solution were added and stirring was continued at 80.degree. After 30 minutes, the reaction was terminated by adding 20 g of 50% by weight sulfuric acid. A cloudy, 50% by weight solution with a viscosity (measured at 20 ° C. according to Höppler) of 2500 mPas was obtained.

D. A mixture consisting of 240 g of bischlorohydrin ether, prepared by reacting polyethylene glycol with an average molecular weight of 600 with 2 mol of epichlorohydrin, 18 g of dipropylenetriamine, 15 g (0.05 mol) of QUAB 181 solution and 210 g of water were stirred at 90 ° C for 20 minutes. Then 41 g of 37% strength by weight sodium hydroxide solution and after a further 30 minutes 15 g of QUAB 181 solution were added. After 30 minutes the reaction mixture had the desired viscosity of 6000 mPas (in situ measurement with a 25 ml pipette; leakage method calibrated for Höppler at 20 ° C). The reaction was then ended by adding 10 g of 98% strength by weight acetic acid and 30 g of water. A clear, 50% by weight solution with a viscosity (measured at 20 ° C. according to Höppler) of 6,500 mPas was obtained.

Application examples

20 g air-dry (= 18.4 g dry at 8.3% moisture; ^' dry = absolutely dry) printed waste paper (100 daily newspapers), printed with flexographic printing inks, were in 520 ml aqueous solution containing 2.0% by weight Soda water glass, solids content: 35% by weight (37 - 40 ° Be), 0.7% by weight 100% hydrogen peroxide and 1.0% by weight sodium hydroxide, 99% by weight (all% by weight - Data based on air-dry paper stock) in a starch mix, stage 2, at 45 ° C. for 10 minutes. The paper pulp was then diluted to 1.84 l with water and left to stand at 45 ^° C. for 1.5 hours. Then, to each 600 ml of this paper stock suspension, based on air-dry paper stock, 0.2% by weight of compounds according to the invention were added with stirring and 12 minutes at 45 ° C. at a pH of 8.5 in a Denver laboratory flotation cell (600 ml) floated at 3,000 revolutions per minute. After the flotation, the paper pulp was separated from the water (circulating water) on a suction filter and formed into a sheet between 2 filter papers on a photo drying press and dried at 100 ° C. for 90 minutes. The deinking results are summarized in Table 1. The deinkability index (DEM) was calculated from the reflection factors R457 nm (whiteness) of the printed (BS), deinked (DS) and unprinted (US) paper stock using the following formula:

Whiteness (DS) - Whiteness (BS)

DEM (%) = x 100

Whiteness (US) - Whiteness (BS)

(0% means no ink removal, 100 H means quantitative ink removal). The quality of the circulating water was determined with the aid of a transmission measurement (Photometer 662, Metrohm, Herisau, Switzerland) (the higher the transmission T in%, the better the circulating water can be assessed: 100% T means clear circulating water).

Table 1

R457 R457 R457 DEM (%) T (%) compounds according to the invention used (US) (BS) (DS) according to the example

A2 51.2 27.2 41.5 59 100

B2 55.0 28.2 48.0 73 98

C 55.0 28.2 42.3 53 90

D 55.0 28.2 43.3 56 92

Claims

1. Water-soluble or water-dispersible compounds containing polyether chains and quaternary ammonium groups, obtainable by reacting halohydrin and / or epoxy compounds containing quaternary ammonium groups and

Compounds of the general formula I

in which R is a z-valent alkoxy radical, AO 1 to 100 alkylene oxide units which are composed of 0 to 100 C2H4θ units, 0 to 50 C3Hö0 units and 0 to 30 C4HgO units, shark chlorine and / or bromine atoms, p is an integer from 0 and 3 and q is 0 or 1, with the proviso that the sum p + q is not equal to 0 and z is an integer from 1 to 10,

with ammonia, Cι_22-alkylamines, aliphatic di- and / or polyamines and / or amino sugars.

2. Compounds according to claim 1, characterized in that in the general formula IR a 2- to 4-valent alkoxy radical, A0 1 to 100 alkylene oxide units, which are composed of 0 to 100 C2H4θ units, 0 to 50 CsHßO units and 0 to Compose 30 C4H8θ units, shark chlorine atoms, p is an integer from 0 and 3 and q is 0 or 1, with the proviso that the sum p + q is not equal to 0, and z is an integer from 2 and 4 .

3. A process for the preparation of water-soluble or water-dispersible compounds containing polyether chains and quaternary ammonium groups, characterized in that halohydrin and / or epoxy compounds and quaternary ammonium groups and

Compounds of the general formula I

H

in which R is a z-valent alkoxy radical, AO 1 to 100 alkylene oxide units which are composed of 0 to 100 C2H4θ units, 0 to 50 C3H5θ units and 0 to 30 C4H8θ units, shark chlorine and / or bromine atoms, p is an integer between 0 and 3 and q is 0 or 1, with the proviso that the sum p + q is not equal to 0, and z is an integer between 1 and 10,

with ammonia, Cι.22 " ^A ^ ylamines, aliphatic di- and / or polyamines and / or amino sugars at 40 to 120 ° C.

4. The method according to claim 3, characterized in that the implementations in the presence of alkali metal hydroxides are carried out.

5. The method according to one or both of claims 3 to 4, characterized in that the reactions are carried out at temperatures between 60 and 95 ° C.

6. The method according to one or both of claims 3 to 5, characterized in that compounds of the general formula I in which R is a 2- to 4-valent alkoxy radical, AO 1 to 100 alkylene oxide units, which are composed of 0 to 100 C2H4θ units , 0 to 50 C3HsO units and 0 to 30 C4HgO units, Shark chlorine atoms, p is an integer between 0 and 3 and q 0 or 1, with the proviso that the sum p + q is not equal to 0, and z is an integer between 2 and 4.

7. Use of water-soluble or water-dispersible compounds containing polyether chains and quaternary ammonium groups, obtainable by reacting halohydrin and / or epoxy compounds containing quaternary ammonium groups and

Compounds of the general formula I

in which R is a z-valent alkoxy radical, A0 1 to 100 alkylene oxide units which are composed of 0 to 100 C2H4θ units, 0 to 50 C3H5θ units and 0 to 30 C4HgO units, shark chlorine and / or bromine atoms, p is an integer between 0 and 3 and q is 0 or 1, with the proviso that the sum p + q is not equal to 0, and z is an integer between 1 and 10, with ammonia, Cι_22-alkylamines, aliphatic di- and / or polyamines and / or amino sugars

for removing printing inks from printed waste paper and / or paper circuit water.