Process for the production of alkyl sulfate pastes having improved flow properties

The alkylsulphate pastes disclosed can be prepared by sulphonating mixtures containing a)50-90% by weight of at least one aliphatic primary alcohol with 6-22 carbon atoms and b)1-50% by weight of at least one unsaturated fatty acid glyceride ester derived from fatty acids having 16-22 carbon atoms and having one, two or three double bonds, with gaseous sulphur trioxide and subsequently neutralizing and hydrolysing the reaction products with aqueous bases in such a way that pastes with solids contents of 30-80% by weight are obtained.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process for the production of alkyl sulfate 
pastes having improved flow properties by co-sulfonation of aliphatic 
alcohols and unsaturated fatty acid glyceride esters and subsequent 
neutralization and hydrolysis of the reaction products formed. 
2. Statement of Related Art 
Anionic surfactants of the alkyl sulfate type, particularly those 
containing C.sub.16-18 alkyl radicals, show excellent detergent properties 
and are used in particular in powder-form detergents. 
Powder detergents of the type in question are produced from 
water-containing alkyl sulfate pastes. In order to avoid unnecessary mass 
transport during spray drying, the water-containing surfactant pastes 
advantageously have a high solids content. However, alkyl sulfate pastes 
can only be concentrated to a certain solids content. Beyond this limit, 
their viscosity generally reaches such high values that the surfactant 
solutions can no longer be pumped, even at elevated temperatures. 
There has been no shortage of attempts in the past to solve the problem 
posed by the high viscosity of anionic surfactant pastes. For example, the 
use of secondary alkane sulfonates and hydroxycarboxylic acid salts as 
viscosity-reducing agents for anionic surfactant concentrates is known 
from German patent applications DE-A-34 47 859 and DE-A-22 51 405. The 
viscosity of alkylbenzene sulfonate pastes can be reduced by alkoxylated 
alcohols [DE-A-37 18 896] or aliphatic hydrocarbons [DD-A-240 025]. Other 
known viscosity reducers are sulfonated aromatic compounds [DE-A-23 05 
554], cumene sulfonate or acidic phosphoric acid esters [DE-B-16 17 160], 
polyhydric alcohols, carboxylic acids or esters thereof [EP-A-0 008 060] 
or mono and/or disulfates of polyalkylene glycol ethers [EP-B-0 024 711]. 
However, the viscosity reducers mentioned fail in cases where the viscosity 
of water-containing alkyl sulfate pastes has to be reduced. 
Accordingly, the problem addressed by the present invention was to provide 
a process for the production of alkyl sulfate pastes having improved flow 
properties. 
DESCRIPTION OF THE INVENTION 
The present invention relates to a process for the production of alkyl 
sulfate pastes having improved flow properties, characterized in that 
mixtures containing 
a) 50 to 99% by weight of at least one aliphatic primary alcohol containing 
6 to 22 carbon atoms and 
b) 1 to 50% by weight of at least one unsaturated fatty acid glyceride 
ester derived from fatty acids containing 16 to 22 carbon atoms and 1, 2 
or 3 double bonds, 
are sulfonated with gaseous sulfur trioxide and the reaction products are 
subsequently neutralized with aqueous bases and hydrolyzed so that pastes 
having solids concentrations of 30 to 80% by weight are obtained. 
It has surprisingly been found that, after sulfonation, neutralization and 
hydrolysis, mixtures of components a) and b) which contain these 
components within the limits mentioned have a distinctly lower viscosity 
than sulfonation products derived from the pure starting materials. The 
invention includes the observation that the sulfonated mixtures produced 
by the process according to the invention are distinguished by improved 
pumpability and a lower energy demand in the spray drying process. 
The aliphatic primary alcohols used as component a) in accordance with the 
invention are fatty alcohols such as, for example, caproic alcohol, 
caprylic alcohol, capric alcohol, lauryl alcohol, myristyl alcohol, cetyl 
alcohol, stearyl alcohol or behenyl alcohol. It is preferred to use fatty 
alcohols containing 12 to 18 carbon atoms and preferably 16 to 18 carbon 
atoms. 
Other suitable alcohols are technical alcohol cuts of the type obtained, 
for example, in the hydrogenation of technical fatty acid methyl ester 
mixtures of natural origin or aldehydes from Roelen's oxo synthesis. 
Technical coconut oil or tallow fatty alcohol cuts are preferably used. 
These are primary fatty alcohols which, on average, have the following C 
chain distribution: 
______________________________________ 
Coconut oil Tallow fatty 
fatty alcohol alcohol 
______________________________________ 
C.sub.10 : 
0-3% by weight 
C.sub.12 : 
48-58% by weight 
C.sub.14 : 
19-24% by weight 0-3% by weight 
C.sub.16 : 
9-12% by weight 45-55% by weight 
C.sub.18 : 
11-14% by weight 45-55% by weight 
C.sub.20 : 0-3% by weight 
______________________________________ 
The fatty acid glyceride esters used as component b) in accordance with the 
invention are unsaturated mono-, di- and/or triglycerides having iodine 
values of 60 to 210 and preferably 100 to 130 which may be of natural or 
synthetic origin. The fatty acid component may contain 16 to 22 carbon 
atoms and 1, 2 or 3 double bonds. The glycerides of palmitoleic acid, 
oleic acid, elaidic acid, petroselic acid, ricinoleic acid, linoleic acid, 
linolenic acid or erucic acid are mentioned as examples. 
As usual in oleochemistry, these glycerides may also be present in the form 
of technical mixtures, for example as rapeseed oil, sunflower oil, olive 
oil, peanut oil, coriander oil, cottonseed oil, castor oil or fish oil. In 
this form, the fatty acid component may also contain C.sub.6-22 fatty 
acids. Rapeseed oil rich in oleic acid from new plants is preferably used. 
In the process according to the invention, components a) and b) may be used 
in a ratio by weight of 99:1 to 50:50. Alkyl sulfate pastes having 
particularly advantageous performance properties are obtained when the 
components are used in a ratio of a to b of 95:5 to 70:30 and, more 
particularly, 95:5 to 90:10. 
The sulfonation of the mixtures containing components a) and b) is carried 
out with gaseous sulfur trioxide in the same known manner as for fatty 
acid lower alkyl esters [J. Falbe (ed.), "Surfactants in Consumer 
Products", Springer Verlag, Berlin-Heidelberg, 1987, pages 61 to 63], 
reactors operating on the falling-film principle being preferred. The 
sulfur trioxide is diluted with an inert gas, preferably air or nitrogen, 
and used in the form of a gas mixture containing the sulfonating agent in 
a concentration of 1 to 8% by volume and, more particularly, 2 to 5% by 
volume. 
The molar ratio between the mixtures containing components a) and b) and 
the gaseous sulfur trioxide may be from 1:0.95 to 1:1.5. To obtain a high 
degree of sulfonation on the one hand and to guarantee minimal 
discoloration of the products on the other hand, ratios of 1:1.05 to 1:1.3 
have proved to be optimal. The sulfonation reaction is carried out at 
temperatures of 50.degree. to 90.degree. C. and preferably at temperatures 
of 40.degree. to 80.degree. C. 
The acidic sulfonation products accumulating during the sulfonation 
reaction are stirred into aqueous bases, neutralized and adjusted to a pH 
value of 7.5 to 10.5. Suitable neutralization bases are alkali metal 
hydroxides, such as sodium, potassium and lithium hydroxide, alkaline 
earth metal oxides and hydroxides, such as magnesium oxide, magnesium 
hydroxide, calcium oxide and calcium hydroxide, ammonia, mono-, di- and 
tri-C.sub.2-4 -alkanolamines, for example mono-, di- and triethanolamine 
and primary, secondary or tertiary C.sub.1-4 alkyl amines. The 
neutralization bases are preferably used in the form of 5 to 55% by weight 
aqueous solutions, 5 to 25% by weight aqueous sodium hydroxide solutions 
being preferred. 
In the co-sulfonation of the aliphatic alcohols and the fatty acid 
glyceride esters, the corresponding alkyl sulfates are formed. The 
unsaturated glycerides may react off with the sulfur trioxide in various 
ways. For example, addition products of the SO3 with the olefinic double 
bond and various glyceride sulfates are formed. Finally, soaps and 
sulfonated soaps are also present. To avoid afteracidification, the 
products have to be subjected to an aftertreatment in which the 
neutralized products are hydrolyzed for 30 to 240 mins. at temperatures of 
50.degree. to 90.degree. C. and at pH values of 7.5 to 8.5. 
After neutralization and hydrolysis, the sulfonation products may be 
bleached in known manner by addition of hydrogen peroxide or sodium 
hypochlorite solution. 0.2 to 2% by weight hydrogen peroxide, expressed as 
100% substance, or corresponding quantities of sodium hypochlorite, based 
on the solids content of the solution of sulfonation products, are used 
for this purpose. The pH value of the solutions may be kept constant using 
suitable buffers, for example sodium phosphate or citric acid. In 
addition, it is advisable to add preservatives, for example formaldehyde 
solution, p-hydroxybenzoate, sorbic acid or other known preservatives, for 
stabilization against bacterial contamination.

The following Examples are intended to illustrate the invention without 
limiting it in any way. 
EXAMPLES 
Examples 1 to 4 
General Procedure for the Preparation of Tallow Alkyl 
Sulfate/Sulfotriglyceride Mixtures 
600 g of a mixture of 70 to 95 parts by weight C.sub.16/18 tallow alcohol 
(Hydrenol.RTM. DD, hydroxyl value 215, a product of Henkel KGaA) and 5 to 
30 parts by weight rapeseed oil rich in oleic acid (oleic acid content&gt;80% 
by weight) were introduced into a 1 liter sulfonation reactor equipped 
with jacket cooling and a gas inlet pipe and reacted at T =80.degree. C. 
with sulfur trioxide in a molar ratio of mixture to SO.sub.3 of 1:1.05. 
The sulfur trioxide was driven out by heating from a corresponding 
quantity of 65% by weight oleum, diluted with nitrogen to a concentration 
of 5% by volume and introduced into the starting product over a period of 
50 minutes. The crude sulfonation product was then neutralized with 
aqueous 25% by weight sodium hydroxide and hydrolyzed over a period of t=2 
h at a temperature T of 80.degree. C. and at a pH value of 8. The 
resulting approx. 25% by weight paste was bleached with 2% by weight, 
based on the solids content of the paste, of a 35% by weight hydrogen 
peroxide solution. The product was then adjusted to pH 7.5 with 
hydrochloric acid and buffered with 1% by weight, based on the solids 
content, of citric acid. Particulars of the reaction mixtures and the 
characteristic data of the products are set out in Tables 1 and 2. 
The anionic surfactant content (WAS) and the unsulfonated components (US) 
were determined by the DGF-Einheitsmethoden, Stuttgart, 1950-1984, 
H-III-10 and G-II-6b. The sulfate content was calculated as sodium sulfate 
and the water content was determined by the Fischer method. 
TABLE 1 
______________________________________ 
Sulfonation of tallow alcohol/triglyceride mixtures 
a:b a b SO.sub.3 
Ex. Pts. by wt. 
g = mol g = mol g = mol 
______________________________________ 
1 95:5 570 2.22 30 0.03 187 2.34 
2 90:10 540 2.10 60 0.06 182 2.27 
3 80:20 480 1.87 120 0.12 168 2.10 
4 70:30 420 1.63 180 0.18 152 1.90 
______________________________________ 
a = C.sub.16/18 tallow alcohol 
b = Rapeseed oil rich in oleic acid 
Legend: Pts. by wt. = parts by weight 
TABLE 2 
______________________________________ 
Characteristic data of the products 
WAS US SO.sub.4 .sup.2- 
H.sub.2 O 
Ex. % % % % 
______________________________________ 
1 18.8 3.6 0.6 77.0 
2 21.0 1.0 0.0 77.0 
3 20.7 1.7 0.5 77.0 
4 20.5 2.1 0.4 77.0 
______________________________________ 
II. VISCOSITY OF TALLOW ALKYL SULFATE/SULFOTRIGLYCERIDE MIXTURES 
Examples 5 to 8 
The viscosity of the sulfonated mixtures according to Examples 1 to 4 was 
determined with a Brookfield viscosimeter at a temperature of 80.degree. 
C. The results of the viscosity measurements are shown in Table 3. 
TABLE 3 
______________________________________ 
Viscosity measurements 
Mixture of 
Viscosity 
Ex. Example mPas 
______________________________________ 
5 1 1925 
6 2 635 
7 3 3500 
8 4 9500 
______________________________________