Preparation of emulsions or other multiphase formulations

The invention relates to new cleavable surface-active compounds (surfactants), processes for their preparation and their use for the preparation of emulsions or other multi-phase formulations.
Surfactants are compounds in which the molecules are built up from hydrophilic and hydrophobic parts. Because of their amphiphilic character, these compounds are surface-active and become enriched at the interface between an aqueous phase and a hydrophobic phase. The hydrophobic phase can be a gas, a liquid or a solid. On enrichment, the surfactants form monomolecular films at the interfaces, which means that the properties of the systems are decidedly influenced, which may lead both to desirable and to undesirable effects.
When classifying surfactants according to their hydrophobic groups, a distinction is made between those having hydrocarbon groups, those having partly fluorinated or perfluorinated hydrophobic radicals and those based on siloxane or polyester.
When classifying them according to hydrophilic groups, a distinction is made between anionic surfactants, the hydrophilic parts of which are formed by anions of the acids of phosphorus or sulphur or of carboxylic acids, cationic surfactants having quaternized nitrogen functions and nonionic surfactants, the hydrophilic groups of which are formed by polyethyleneglycol ethers or polyalcohols.
All these known surfactants have the common feature that they only lose their surface-active properties by biological degradation, by non-specific chemical destruction or, in the case of anionic surfactants, by complexing, for example with Ca.sup.++ or Al.sup.+++. In recent years, however, very interesting possible uses for surfactants have been found, but these require that the surfactants, immediately after they have fulfilled their purpose, are split in the reaction medium into fragments which are no longer surface-active, for example by a change in the pH, and in this way lose their surface-active effect (see (a) J. Org. Chem. 1982, 47, 311-315; (b) 1982, 47, 2221-2223; and (c) 1984, 49, 4545-4547). Cleavable cationic surfactants are described in (a), (b) and (c), and in particular cationic surfactants having ketal groups are proposed in (a) and (b) for use in neutral and basic media; however, these have the disadvantage that they are cleavable only under drastic conditions (at pH values <1), for example with the aid of 5% strength hydrochloric acid. Cationic surfactants which contain monoalkoxysilane units and likewise are cleavable only under drastic conditions (at pH values <1 or >12) are described in (c).
The cleavable surfactants known to date have the disadvantage that on the one hand they can be cleaved only under drastic conditions, that is to say at pH values <1 and >12, and moreover are cationic. In practice, however, nonionic surfactants are required because they are more universally applicable and have a lower sensitivity towards electrolytes, and in particular those nonionic surfactants which are already split under mild conditions, for example at pH values >1 and <11.
Surprisingly, it has been found that silane derivatives of a certain structure have these desired properties.
The invention therefore relates to silane derivatives of the formula ##STR2## in which R.sub.1 denotes H or C.sub.1 -C.sub.4 -alkyl,
n denotes an integer from 2 to 300,
R.sub.2 and R.sub.3 independently of one another denote C.sub.1 -C.sub.16 -alkyl or phenyl,
X denotes --O--, --S--, --NR.sub.5 --(R.sub.5 : hydrogen or C.sub.1 -C.sub.4 -alkyl) or
--O--CH.sub.2 --CH.sub.2 ].sub.r O--
(r=integer from 1 to 100) and
m denotes zero or 1, and
R.sub.4 denotes H, C.sub.1 -C.sub.36 -alkyl, C.sub.2 -C.sub.36 -alkenyl, C.sub.5 -C.sub.36 -cycloalk(en)yl, C.sub.7 -C.sub.36 -aralkyl, C.sub.6 -C.sub.36 -aryl, a radical of the formula (II) ##STR3## in which one of the radicals R.sub.6 and R.sub.7 represents methyl and the other represents H, R.sub.8 denotes C.sub.1 -C.sub.4 -alkyl and x represents an integer from 10 to 300, or a radical of the formula (III) ##STR4## in which R.sub.1 ', R.sub.2 ', R.sub.3 ', X', m' and n' have the meanings given for R.sub.1, R.sub.2, R.sub.3, X, m and n under formula (I) and
A represents a 2-valent hydrophobic radical, for example an alk(en)ylene, oxaalkylene, cycloalk(en)ylene, alkarylene or aryl-alkylene radical containing at least 12C atoms, with the proviso that the sum of the C atoms contained in the radicals R.sub.2, R.sub.3 and R.sub.4 is at least 14.
Examples which may be mentioned of representatives of the radicals mentioned for R.sup.4 are: C.sub.1 -C.sub.36 -alkyl radicals, such as the methyl, ethyl, n- and i-propyl, n- and sec-butyl-, 2-ethylhexyl, n-decyl-n-dodecyl-, hexadecyl-, octadecyl- and behenyl(C.sub.22) radical; C.sub.2 -C.sub.36 -alkenyl radicals, such as the propenyl, butenyl, hexenyl, octenyl, hexadecenyl and octadecenyl radical; C.sub.5 -C.sub.36 -cycloalk(en)yl radicals, such as the cyclopentyl, cyclohexyl and cyclopentadienyl radical, and cyclohexyl radicals substituted by alkyl groups, such as the methyl-cyclohexyl, dimethylcyclohexyl and tert.-butylcyclohexyl radical; C.sub.7 -C.sub.36 -aralkyl radicals, such as the benzyl and the .beta.-phenylethyl radical, and benzyl radicals substituted by alkyl groups, such as the methyl-benzyl, nonyl-benzyl and the dodecyl-benzyl radical; and C.sub.6 -C.sub.36 -aryl radicals, such as the phenyl, 4-octyl-phenyl, 4-nonyl-phenyl and 4-dodecyl-phenyl radical.
Examples which may be mentioned of representatives of the 2-valent hydrophobic radicals mentioned for A containing at least 12C atoms are:
C.sub.12 -C.sub.36 -alkylene radicals, such as the dodecylene, hexadecylene and octadecylene radical;
C.sub.6 -C.sub.36 -alkenylene radicals, such as the hexadecenylene and octadecenylene radicals, hydrophobic oxaalkylene radicals, for example poly-(1-methyl-3-oxa)-propylene radicals of the formulae ##STR5## and alkylene-poly-(1-methyl-3-oxy-)propylene radicals of the formulae ##STR6## C.sub.12 -C.sub.36 -cycloalk(en)ylene radicals, such as the cyclohexylene, methylcyclohexylene, cyclohexenylene and the dicyclopentadienedimethylene radical.
Examples which may be mentioned of representatives of the C.sub.1 -C.sub.16 -alkyl radicals mentioned for R.sup.2 and R.sup.3 are: the methyl, ethyl, n- and sec.-butyl-, i-pentyl, n-hexyl, n-decyl, undecyl-, dodecyl-, tridecyl- and hexadecyl radical.
The silane derivatives of the formula (I) are preferred if, in these derivatives,
R.sub.1 denotes C.sub.1 -C.sub.4 -alkyl,
n denotes an integer from 5 to 50,
R.sub.2 and R.sub.3 independently of one another denote C.sub.1 -C.sub.16 -alkyl or phenyl,
X denotes --O--, --S--, --NR.sub.5 -- (R.sub.5 : hydrogen or C.sub.1 -C.sub.4 --alkyl) or
--O--CH.sub.2 --CH.sub.2 ].sub.r O--
(r: integer from 5 to 50) and
m denotes 0 or 1, and
R.sub.4 represents C.sub.1 -C.sub.20 -alkyl, C.sub.2 -C.sub.20 -alkenyl, C.sub.7 -C.sub.20 -aralkyl or C.sub.6 -C.sub.20 -aryl, or represents a radical of the formula ##STR7## in which one of the radicals R.sub.6 and R.sub.7 represents methyl and the other represents H, R.sub.8 is C.sub.1 -C.sub.4 -alkyl and x represents an integer from 10 to 50.
The silane derivatives of the formula (I) are particularly preferred if, in these derivatives,
R.sub.1 denotes methyl or ethyl,
n denotes an integer from 5 to 50
R.sub.2 and R.sub.3 independently of one another denote for C.sub.1 -C.sub.16 -alkyl or phenyl,
X denotes --0--, --S--, --NH-- or --O--CH.sub.2 CH.sub.2 ].sub.r O, where r=n,
m denotes 1 and
R.sub.4 denotes C.sub.8 -C.sub.20 -alkyl, C.sub.8 -C.sub.20 -aralkyl or
C.sub.6 -C.sub.20 -aryl, or R.sub.4 =R.sub.1.
The compounds listed in the following table I may be mentioned as examples of representatives of the cleavable silane derivatives of the formula (I) according to the invention; the preparation of the compounds 1-13 is described in Examples 1-13.
TABLE 1__________________________________________________________________________Preparationdescribed inExample Silane derivatives according to the invention formula__________________________________________________________________________ (I)1, 2 and 3 ##STR8## n = 10, 16, 304, 5, 6 and 7 ##STR9## n = 10, 16, 30, 45 ##STR10##9 ##STR11##10 and 11 ##STR12## n = 15, 3012 and 13 ##STR13## n = 15, 30 ##STR14## ##STR15##14-18 ##STR16## n = r = 5, 7, 10, 16, 30 m = 11 (65%) m = 13 (35%)__________________________________________________________________________
The surfactants according to the invention are distinguished by an excellent emulsifier action in the pH range from 5 to 10; the emulsions prepared with these are stable for weeks in this pH range. In contrast, outside this pH range the surfactants according to the invention are rapidly cleaved into surface-inactive fragments. The emulsions prepared with these surfactants therefore break down outside the pH range of 5-10 into their aqueous and hydrophobic phases. The surfactants according to the invention are therefore particularly suitable as emulsifiers for the treatment of textiles and fibres, for metalworking and for oil recovery.
The invention furthermore relates to the processes for the preparation of the silane derivatives of the formula (I) according to the invention. The silane derivatives of the formula (I) are obtained--in the case where m=1--by a process in which silanes of the formula (V) ##STR17## in which R.sub.2 and R.sub.3 have the meaning given under formula (I) and
Y denotes a hydrolysable atom or a hydrolysable group,
are first reacted either with compounds containing reactive hydrogen, of the formulae
R.sub.1 --O--CH.sub.2 CH.sub.2 --O].sub.n H (VI),
in which R.sup.1 and n have the meaning given under formula (I), or
R.sub.4 --X--H (VII)
in which R.sub.4 and X have the meaning given under formula (I), to give silane compounds of the formulae ##STR18## in which R.sub.1, R.sub.2, R.sub.3, R.sub.4, n and X have the meaning given under formula (I) and Y has the meaning given under formula (V); and these silane compounds (VIIIa) or (VIIIb) are then reacted again in a second reaction stage with the compounds of the formulae (VII) or (VI), and in particular the silane compounds (VIIIa) are reacted with the compounds of the formula (VII) and the silane compounds (VIIIb) are reacted with the compounds of the formula (VI).
The silane compounds of the formula (I) are obtained in a particularly simple manner if, in these compounds, m is 1, X is --[OCH.sub.2 CH.sub.2 ].sub.r --O-- (where r=n) and R.sub.4 is R.sub.1, that is to say if the radical X--R.sub.4 is R.sub.1 O--[CH.sub.2 CH.sub.2 --O].sub.n. These compounds are obtainable in a single-stage reaction of the compound (V) with 2 mol of the compound of the formula (VI). It is also possible to use mixtures of various compounds of the formula (V) instead of one compound of the formula (V).
The silane derivatives of the formula (I) according to the invention, if m is 0 in these, are obtained by reaction of silanes of the formula (IX) ##STR19## in which R.sub.2, R.sub.3 and R.sub.4 have the meaning given under formula (I) and Y has the meaning given under formula (V), with compounds containing reactive hydrogen, of the formula (VI).
Examples which may be mentioned of Y as a group which can be split off hydrolytically are alkoxy groups, such as methoxy or ethoxy groups, or carboxylate groups and pseudo-halides, such as cyanide groups or thiocyanate groups, and as atoms which can be split off by hydrolysis halogen atoms, preferably Cl and bromine atoms.
The reactions of the silanes of the formulae (V), (VIIIa), (VIIIb) and (IX) are carried out in an inert gas atmosphere in organic solvents which are inert under the reaction conditions and in the presence of bases at temperatures of 0.degree.-100.degree. C.
The silanes of the formula (V) are reacted with the compounds containing reactive hydrogen in a molar ratio of 3-6:1, and the silanes of the formulae (VIIIa), (VIIIb) and (IX) are reacted in a molar ratio of 1:1.
Tertiary amines, for example triethylamine and pyridine, have proved to be particularly suitable bases.
Examples which may be mentioned of organic solvents which are inert under the reaction conditions are aliphatic, cycloaliphatic and aromatic hydrocarbons; cyclohexane, benzene and toluene have proved to be particularly suitable. The solvents are preferably employed in an amount such that the weight ratio of reactants: solvent is 1:1 to 1:20.
The bases are preferably employed in excess, based on the amount of hydrolysable groups or atoms to be split off. If tertiary amines are used, the ammonium salts which are particularly easy to separate off are formed and the excess amine can be removed by distillation after the reaction. Molar ratios of tertiary amine/hydrolysable groups (atoms) to be split off of 1.05-1.1:1 have proved to be particularly suitable.
The conversion in the reaction can be monitored in a simple manner by a quantitative determination of the ammonium salt formed. When the reaction has ended, the ammonium salt can be separated off by filtration and the surfactant according to the invention can be isolated by removal of the solvent.
The starting compounds (V), (VI), (VII) and (IX) required for the preparation of the silane derivatives of the formula (I) according to the invention are either commercially available or can be prepared by reactions which are known per se (see, for example, Houben-Weyl Methoden der organischen Chemie [Methods of organic chemistry], 4th edition, volume 13/5, page 106, volume E 20, page 1367).
The invention furthermore relates to the use of the silane derivatives of the formula (I) according to the invention as surfactant.

EXAMPLES
EXAMPLES 1-9
(A) Preparation of the silane compounds of the formual (VIIIa) (general procedure)
To 5 mol of dichlorodimethylsilane in a reaction vessel filled with dry nitrogen there are added simultaneously
a) a 50% strength by volume solution of one mol of a compound containing reactive hydrogen (compound of formula (VII)) in anhydrous toluene and
b) a 50% strength by volume solution of 1.05 mol of triethylamine in anhydrous toluene
at 30.degree. C., while stirring. The reaction mixture is heated to 70.degree. C. and stirred at this temperature for 2 hours. The ammonium salt precipitate is then filtered off with suction and the filtrate is freed from the solvent and excess dichlorodimethylsilane by vacuum distillation.
(B) Preparation of the silane derivatives of the formula (I) according to the invention
A 50% strength by volume solution of a compound of the formula (VII) in dry toluene and a 50% strength by volume solution of 1.05 mol of triethylamine in dry toluene are added to 1 mol of the silane compound obtained in stage (A). The reaction mixture is stirred at 50.degree. C. for 4 hours. The ammonium salt is then filtered off with suction and the filtrate is freed from the solvent by vacuum distillation. The compounds containing reactive hydrogen, of the formula (VI), used in stage (A) for the reaction of the 5 mol of dichlorodimethylsilane, the silane compounds of the formula (VIIIa) obtained in stage (A) and the compounds containing reactive hydrogen, of the formula (VII), used in stage (B) for the reaction of the chlorosilane compounds (VIIIa) are listed in the following Table 2.
TABLE 2__________________________________________________________________________ Cl-silane compounds of the Compound of Compounds of the formula (VIIIa) the formulaExample formula (VI) obtained in stage (A) (VII)__________________________________________________________________________1 CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.10H ClSi(CH.sub.3).sub.2 [OCH.sub.2 CH.sub.2 ] .sub.10OCH. sub.3 n-C.sub.12 H.sub.25 OH2 CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.16H ClSi(CH.sub.3).sub.2 [OCH.sub.2 CH.sub.2 ] .sub.16OCH. sub.3 n-C.sub.12 H.sub.25 OH3 CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.30H ClSi(CH.sub.3).sub.2 [OCH.sub.2 CH.sub.2 ] .sub.30OCH. sub.3 n-C.sub.12 H.sub.25 OH4 CH.sub. 3 O[CH.sub.2 CH.sub.2 O] .sub.10H ClSi(CH.sub.3).sub.2 [OCH.sub.2 CH.sub.2 ] .sub.10OCH. sub.3 ##STR20##5 CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.16H ClSi(CH.sub.3).sub.2 [OCH.sub.2 CH.sub.2 ] .sub.16OCH. sub.3 ##STR21##6 CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.30H ClSi(CH.sub.3).sub.2 [OCH.sub.2 CH.sub.2 ] .sub.30OCH. sub.3 ##STR22##7 CH.sub.3 O[CH.sub.2 CH.sub.2 O ] .sub.45H ClSi(CH.sub.3).sub.2 [OCH.sub.2 CH.sub.2 ] .sub.45OCH. sub.3 ##STR23##8 CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.30H ClSi(CH.sub.3).sub.2 [OCH.sub.2 CH.sub.2 ] .sub.30OCH. sub.3 ##STR24##9 CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.30H ClSi(CH.sub.3).sub.2 [OCH.sub.2 CH.sub.2 ] .sub.30OCH. sub.3 n-C.sub.12 H.sub.25 NH.sub.2__________________________________________________________________________
EXAMPLES 10-13
(A) Preparation of the silane derivatives of the formula (I) according to the invention in which n is 0 (general procedure)
A 50% strength by volume solution of a compound containing reactive hydrogen, of the formula (VI), in dry toluene and a solution of 1.05 mol of pyridine in 200 ml of dry toluene are added simultaneously to a 50% strength by volume solution of 1 mol of silane compound of the formula (IX) in dry toluene in a reaction vessel filled with dry nitrogen at room temperature, while stirring. The reaction mixture is heated to 70.degree. C. and stirred at this temperature for one hour. The ammonium salt precipitate is then filtered off with suction and the filtrate is freed from the solvent in vacuo. The silane compounds of the formula (IX) used and the compounds containing active hydrogen, of the formula (VI), are listed in the following Table 3.
TABLE 3______________________________________Ex- Silane compound of Compound of theample the formula (IX) formula (VI)______________________________________10 [n-C.sub.6 H.sub.13 ] .sub.3SiCl CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.10H11 [n-C.sub.6 H.sub.13 ] .sub.3SiCl CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.16H12 ##STR25## CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.30H13 ##STR26## CH.sub.3 O[CH.sub.2 CH.sub.2 O] .sub.10H______________________________________
EXAMPLES 14-18
(A) Preparation of the silane derivatives of the formula (I) according to the invention, in which R.sub.1 =R.sub.4 =CH.sub.3, m is 1 and x is --[O--CH.sub.2 --CH.sub.2 --].sub.r --O--, where r is n (general procedure)
A 20% strength by volume solution of 2.0 mol of a compound containing reactive hydrogen, of the formula (VI), in dry toluene and the solution of 2.05 mol pyridine in 200 ml of dry toluene are simultaneously added to a 20% strength by volume solution of a mixture of 0.65 mol of dichloromethylundecylsilane and 0.35 mol of dichloromethyltridecylsilane in dry toluene in a reaction vessel filled with dry nitrogen at room temperature, while stirring. The reaction mixture is heated to 70.degree. C. and stirred at this temperature for one hour. The ammonium salt precipitate is then filtered off with suction and the filtrate is freed from the solvent in vacuo.
The dichlorosilane compounds of the formula (V) used and the compounds containing active hydrogen, of the formula (VI), are listed in the following Table 4.
TABLE 4______________________________________Ex-am- Dichlorosilane compound Compound of theple of the formula (V) formula (VI)______________________________________14 ##STR27## CH.sub.3 O(CH.sub.2 CH.sub.2 O).sub.5 H m = 11 (65%) m = 13 (35%)15 ##STR28## CH.sub.3 O(CH.sub.2 CH.sub.2 O).sub.7 H m = 11 (65%) m = 13 (35%)16 ##STR29## CH.sub.3 O(CH.sub.2 CH.sub.2 O).sub.10 H m = 11 (65%) m = 13 (35%)17 ##STR30## CH.sub.3 O(CH.sub.2 CH.sub.2 O).sub.16 H m = 11 (65%) m = 13 (35%)18 ##STR31## CH.sub.3 O(CH.sub.2 CH.sub.2 O).sub.30 H m = 11 (65%) m = 13 (35%)______________________________________
EXAMPLE 19
(A) Determination of the emulsifier properties and of the stability of the silane derivatives according to the invention as a function of the pH of the aqueous phase of the emulsions prepared with the aid of these derivatives.
Emulsions were prepared from the following components:
Aqueous phase:
a) Aqueous buffer solution containing 50 mmol of KH.sub.2 PO.sub.4 /l; this aqueous buffer solution is brought to the desired pH by addition of HCl and NaOH;
b) Surfactant solution: This contains 6% by weight of the surfactant under investigation, dissolved in distilled water;
Hydrophobic phase:
c) Isododecane
Preparation of the emulsions:
Components (a), (b) and (c) are mixed in a volume ratio of 2:2:1 and the mixture is homogenized with a rotor-stator at 10,000 revolutions/minute for 1 minute. The 50% strength by volume oil-in-water emulsion formed contains 3% by weight of surfactant (silane derivative), based on the volume of the organic phase.
The stability of the resulting emulsion was assessed after one day and after a standing time of three weeks, the following ratings being used: Stability=I: the emulsion separates into a concentrated white upper layer (cream layer) and a milky-cloudy to clear aqueous phase in the course of a few days. The cream layer retains its white colour throughout the observation period and does not change. No formation of a separate isododecane layer takes place.
Stability=II: a cream layer forms in the course of a few hours; after one day, the cream layer has a glassy consistency (signs of droplet enlargement/coalescence).
In addition, the formation of an isododecane layer on the cream layer is already detectable after one day; the volume of this isododecane layer increases in the course of the observation period.
Stability=III: the emulsion separates into an aqueous phase and into an isododecane phase in the course of a few minutes. No cream layer forms or a cream layer forms only in some parts.
The stability values obtained for the individual surfactants according to the invention at the various pH values are listed in the following Table 5.
For comparison, the stability values of two structurally related surfactants belonging to the prior art have furthermore been stated.
TABLE 5__________________________________________________________________________Stabilities Surfac- Surfac- Surfac- Surfac- Surfac- Surfac-pH of the tant ac- Sur- tant ac- Sur- tant ac- tant ac- tant ac- tant ac-aqueous cording to factant cording to factant cording to cording to cording to cording tophase Example 1 A Example 3 B Example 6 Example 8 Example 17 Example 18__________________________________________________________________________3 III I III I III III III III4 III I III I II II II II5 III I III I I II I I6 I I I I I I I I7 I I I I I I I I8 I I I I I I I I9 I I I I I I I I10 I I I I I I I11 II I II I II II II II12 III I III I III III II III13 III I III I III III III III__________________________________________________________________________ Sufactants according to the prior art: ##STR32## ##STR33##

Number	Name	Date
2917480	Bailey et al.	Dec 1959
3308149	Schenck et al.	Mar 1967
3359212	Bailey et al.	Dec 1967
3600418	Bailey et al.	Aug 1971
4060538	Kotzsch et al.	Nov 1977
4160776	Scardera	Jul 1979
4226794	Scardera et al.	Oct 1980
4306035	Baskent et al.	Dec 1981
4698178	Huttinger et al.	Oct 1987

Preparation of emulsions or other multiphase formulations

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Entry
Synthesis, Nr. 3, Mar. 1977, pp. 184-186; H. Lehmkuhl et al.
Chemical Abstracts, Band 83, 1975, p. 241, 62401d.
Chemical Abstracts, Band 82, 1975, p. 181, 60453c.
Chemical Abstracts, Band 83, 1975, p. 268, 118483b.