WO1992011074A1 - Anti-foaming agent based on carboxylic acid derivatives - Google Patents

Abstract

The use of esters and amides of citric, tartaric, succinic, maleic, nitrilotriacetic and ethylene diamine tetra-acetic acids as anti-foaming agents and anti-foaming mixtures which also contain up to 40 % wt. of an emulsifier with an HLB value of at least 8.

Description

Defoamer based on carboxylic acid derivatives

description

The invention relates to the use of at least partially esterified or at least partially amidated citric acid, tartaric acid, succinic acid, maleic acid, nitrilotriacetic acid and ethylenediaminetetraacetic acid as defoamers and defoamer mixtures which contain these derivatives and an emulsifier.

Due to a high air content in the water cycle of paper machines and due to foam formation, various faults can occur in paper production. If the foam with noted dirt gets onto the paper web during sheet formation, foam spots will appear on the paper. The foam that forms during paper production is generally stable and therefore stays in low-flow areas in the paper machine circuit for a long time, where it can dry up and be carried away in this form by the fabric. Stains also appear in the paper during sheet formation. Defoamers are therefore used which have the tendency to accumulate at the air / water phase boundary and thus counteract foam formation. The air bubbles, for example, interfere with the dewatering process of the paper stock on the paper machine, cause a porous structure of the sheet and can even form holes in the paper web. Since ever higher work speeds are used on the machines in the paper production for reasons of rationalization, the danger of air being mixed into the fiber suspension naturally increases.

As the water cycles of the paper machines are closed more and more, water-soluble substances accumulate in them, which stabilize the foam and sometimes even promote the formation of foam. This also increases the temperature of the water circulating in the paper machine. This

Increasing the temperature has a strong influence on the effect of defoamers. The known defoamers for paper production are water-free or aqueous formulations. The water-free formulations mostly consist of low-viscosity oils, so-called oil defoamers, which are often used in a mixture with suitable emulsifiers or around self-emulsifying fatty acid or fatty alcohol polyethers. This Products have only a limited defoaming, foam-preventing and deaerating effect compared to the aqueous formulations, the so-called emulsion defoamers, which usually have a water content of over 50%.

DE-PS 25 32 888 describes the use of oxyalkylated, straight-chain, saturated fatty alcohols having 12 to 30 carbon atoms, which are reacted by reacting 1 mol of the alcohol with

(a) 5 to 60 moles of propylene oxide and then with

(b) 0.5 to 20 moles of ethylene oxide

are known as fabric deaerators in paper manufacturing. At higher circulating water temperature the

Paper machine, however, reduces the effectiveness of these defoamers.

The invention is based on the object of developing an oil defoamer which is still highly effective even at an elevated temperature of the circulation water of the paper machine. In addition, the defoamers should form emulsions when diluted with water, which are stable for a long time and do not cream.

The object is achieved according to the invention by using at least partially esterified with C 12 -C ₂₂ -alcohols or at least partially amidated with C ₁ -C 6 -C 6 -alkylamines carboxylic acids from the group citric acid, tartaric acid, succinic acid, maleic acid, nitrilotriacetic acid and Ethylenediaminetetraacetic acid as a defoamer. At least 1/3 of the carboxyl groups of the carboxylic acids mentioned are preferably esterified or amidated.

The esters and amides of citric acid, tartaric acid, succinic acid, maleic acid, nitrilotriacetic acid and ethylenediaminetetraacetic acid to be used according to the invention are prepared by known processes. Products effective as defoamers are obtained as soon as one third of the carboxyl groups of the carboxylic acids mentioned are esterified or amidated. C ~ ~ are suitable for the production of esters from the carboxylic acids mentioned

C ₂₂ fatty alcohols, for example methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, n-hexanol, cyclohexanol, 2-ethylcyclohexanol, n-octanol, isooctanol, nonanol, isononanol, decanol, lauryl alcohol, pal ityl alcohol, stearyl alcohol, cetyl alcohol, isotridecanol and mixtures of alcohols in any ratio. Of particular technical interest are those alcohols which can be obtained by the oxo process by adding carbon monoxide and hydrogen to olefins in the presence of catalysts or by the Ziegler process by oxidation of aluminum alkyls and subsequent saponification. These technically easily accessible alcohols are mainly alcohol mixtures from alcohols with 9 to

16 carbon atoms. The alcohols are esterified either alone or as a mixture with one another with the abovementioned carboxylic acids in the presence of esterification catalysts. Instead of the carboxylic acids, it is of course also possible to use carboxylic acid derivatives such as anhydrides and acid chlorides, if they can be prepared, to prepare the esters. The esterification catalysts used are preferably p-toluenesulfonic acid, benzenesulfonic acid, hypophosphorous acid, potassium hydrogen sulfate or sulfuric acid. The esterification reaction is generally carried out at temperatures in the range from 100 to 200 ° C. under an inert gas atmosphere in the absence of solvents. The water of reaction formed is distilled off during the esterification. The esterification can be carried out under elevated pressure or under reduced pressure, for example at 100 to 800 mbar. To produce defoamers, the carboxyl groups of the abovementioned carboxylic acids are esterified or amidated to at least 1/3 or completely, preferably 1/3 to 2/3. Citric acid is particularly preferably subjected to the esterification of the above-mentioned carboxylic acids. 1 to 3, preferably 1 to 2, mol of an alcohol or alcohol mixture are used per 1 mol of citric acid. The esterification of the citric acid is preferably carried out with 1 to 2 mol of a Cβ to Cig alcohol or mixtures of alcohols which can be prepared by the oxo process. Defoamers with a particularly advantageous effect are obtained by esterifying citric acid with 1 to 2 mol of saturated Cβ * to C ₂₂ fatty alcohols.

Suitable defoamers are also amides which result from at least partial amidation of citric acid, tartaric acid, succinic acid, maleic acid, nitrilotriacetic acid and ethylenediaminetetraacetic acid with saturated C ₁ -C 6 -alkylamines. At least 1/3 of the carboxyl groups of the above carbon acids is amidated. The fully amidated carboxylic acids mentioned above are also defoamers. Preferably 1/3 to 2/3 of the carboxyl groups of the above carboxylic acids are amidated. Products which act particularly as defoamers are obtained by amidating 1 mol of citric acid with 1 to 2 mol of a primary or secondary saturated C ₁ -C 6 -alkylamine or a mixture of such amines. Cβ * to C 6 ~ alkylamines are preferably used for the amidation of citric acid. Suitable amines are, for example, methylamine, dimethylamine, ethylamine, n-propylamine, isopropylamine, hexylamine, octyla in, decylamine, dodecylamine, tridecyla in, diisotridecylamine and coconut fatty amine. The following are particularly suitable amine mixtures: 2-ethylhexylamine, bis-2-ethylhexylamine, i-tridecylamine, di-i-tridecylamine and coconut fatty amine.

The at least partially esterified or at least partially amidated carboxylic acids to be used according to the invention as defoamers are substances which are liquid at a temperature of 20 ° C. and above. When these defoamers are added to foam-forming aqueous systems, there is a strong reduction in foam formation even in the presence of very small amounts of defoamers. The products to be used as defoamers according to the invention are used in such an amount that there are 0.02 to 0.5, preferably 0.05 to 0.3 part by weight of the defoamer per 100 parts by weight of a foam-forming medium. For example, the pulps that are dewatered in the manufacture of paper are regarded as the foam-forming medium. There are also strong foam-forming media in sulphite pulp boiling as well as in paper coating. In the technical processes mentioned and in the

Foam control in sewage treatment plants, the above-described at least partially esterified or amidated esters of citric acid, tartaric acid, succinic acid, maleic acid, nitrilotetriacetic acid and ethylenediaminetetraacetic acid can be used as defoamers. The defoamers are added directly to the medium to be defoamed or the products mentioned are emulsified in water and the defoamers are used in the form of an oil-in-water emulsion. When the liquid defoamers are metered directly into the aqueous medium to be defoamed, the average particle size of the particles emulsified in water depends on the shear forces present at the metering point, the defoamer component and the type and amount from emulsifiers, which are optionally used together with the products to be used according to the invention as defoamers. The more intensive the distribution of the defoamers in an aqueous medium, the better the defoaming and deaerating effect in the water cycle of the paper machine. A better effect of the defoamers due to a finer distribution can be seen from the fact that the amount used for defoaming can be reduced.

The defoamer formulation can be used in addition to those of the invention

Products up to 40 wt .-%, based on the mixture, contain emulsifiers. Emulsifiers with an HLB value of at least 8 are particularly suitable. In some cases, the mixing of the defoamers to be used according to the invention leads to an increase in activity.

Defoamers suitable for technical purposes are therefore often mixtures which are essential components

(a) carboxylic acids from the group citric acid, tartaric acid, succinic acid, maleic acid, nitrilotriacetic acid and ethylenediamine tetraacetic acid and at least partially esterified with C 1 -C ₂₂ -alcohols or at least partially amidated with primary or secondary saturated C ₁ -C 6 -alkylamines

(b) Emulsifiers with an HLB value of at least 8 in the weight ratio (a) :( b) from 95: 5 to 60:40

contain. As is known, the HLB value is understood to mean the hydrophilic-lipophilic balance of an emulsifier, cf. WC Giffin, 3rd Soc. Cosmet. Chem., 1, 311 (1950). Suitable emulsifiers of this type are, for example, hydrophilic water-soluble products which can be obtained by ethoxylation of alkylphenols, fatty alcohols, fatty acids and fatty amines, and PO-EO block polymers with an ethylene oxide content of 10 to 80%. In particular, the addition products of ethylene oxide or propylene oxide to fatty alcohols having 8 to 18 carbon atoms are used as emulsifiers, or ethylene oxide and then propylene oxide and, if appropriate, ethylene oxide are added to the fatty alcohols, so that block copolymers are formed. The alkoxylation products can also add small amounts of butylene oxide contain. Also suitable are addition products which are formed by the addition of propylene oxide and then ethylene oxide to fatty alcohols or in which butylene oxide and then ethylene oxide are initially added to a fatty alcohol or a fatty alcohol mixture. The alkoxylation of the fatty alcohols can of course also be carried out using mixtures of the alkylene oxides. In the latter case, however, statistically structured addition products are obtained. CQ to Ciβ *, in particular Cio * to Ci _ß alcohols are preferably subjected to the alkoxylation, 3 to 80, preferably 10 to 30, mol of alkylene oxide being reacted per mol of alcohol. Of the alkylene oxides, ethylene oxide is preferred. The products are essentially characterized in that they have an HLB value of at least 8 and are water-soluble.

Of particular interest are the above-mentioned citric acid esters obtained from 1 mol of citric acid with 1 to 2 mol of a saturated C 6 -C ₂₂ alcohol or from mixtures of such alcohols and emulsifiers based on C 6 -C 6 alcohols, preferably obtainable by the oxo process Alcohols with an ethylene oxide content of 3 to 12. Products of this type can be used universally as defoamers. They act as foam dampers, foam preventers and fabric deaerators, in particular in the manufacture of paper and in paper coating colors.

Examples

Manufacture of defoamers

Defoamer 1

210 g of citric acid monohydrate and 288 g of isononanol are heated in a molar ratio of 1: 2 together with 2.5 g of potassium bisulfate to a temperature of 150 ° C. and stirred for 8.5 hours at this temperature. The water of reaction formed is continuously distilled off during this time. The condensation has ended as soon as the reaction product has an acid number of 136. The saponification number of the citric acid ester obtainable in this way is 387. Defoamer 2

160 g (0.8 mol) of i-tridecanol and 84 g (0.4 mol) of citric acid monohydrate are heated together with 1.4 g of p-toluenesulfonic acid as a catalyst to a temperature of 155 ° C. and stirred at this temperature for 4 hours . The water of reaction formed is continuously distilled off during this time. After completion of the reaction, it can be almost completely removed at 120 ° C. and a pressure of 20 bar. 223 g of a yellow, viscous liquid with an acid number of 103 and a saponification number of 303 are obtained.

Defoamer 3

One heats 133.35 g (0.35 mol) of di-i-tridecylamine

Temperature of 90 ° C under a nitrogen atmosphere. As soon as the temperature of 90 ° C. is reached, 73.5 g (0.35 mol) of citric acid monohydrate are added in portions with stirring and the reaction mixture is heated to a temperature in the range from 150 to 160 ° C. After a reaction time of 9 hours at the temperature indicated, the reaction mixture was cooled to a temperature of 120 ° C. and the remaining water was removed within 2 hours at a pressure of 20 mbar. Citric acid di-i-tridecylamide was obtained as a light brown viscous liquid with an acid number of 62 and an amine number of 22.

Defoamer 4 (comparison)

Commercial defoamer based on an addition product of ethylene oxide with a Ciε alcohol.

Defoamer 5

Mixture of the defoamer 1 and an addition product of 11 moles of ethylene oxide with 1 mole of a C 1 -C ₀ -oxoalcohol in a weight ratio of 4: 1.

Defoamer 6

Mixture of defoamer 2 and an addition product of 30 moles of ethylene oxide with 1 mole of a mixture of Cχ3-Ci5-0xoalcohol in a weight ratio of 4: 1. Defoamer 7

Mixture of defoamer 2 and an addition product of 11 moles of ethylene oxide with 1 mole of a Cio-oxo alcohol in a weight ratio of 4: 1.

The defoamers described above were tested as follows:

Determination of the foam value:

5 l of a foam-developing pulp suspension consisting of 0.1% wood pulp, 0.002% resin glue, 0.004% alum and 0.016% casein are pumped for 5 minutes in a channel made of a transparent plastic. The amount of foam formed on the surface of the stock suspension is then with the help of a

Grid on the wall of the channel measured in units of area (cm2) and given as a so-called foam value to assess the effectiveness of a defoamer.

If the pulp suspension is pumped around in the absence of a defoamer, the foam value after 5 minutes is 1200 cm 2. By adding 2 mg / l of an effective defoamer (a total of 10 mg solid) to the pulp suspension, this foam value is significantly reduced, so that it represents a measure of the effectiveness of a defoamer.

Checking the defoamers:

The temperature of the pulp suspension is kept constant by means of a immersion heater connected to a controller and, depending on the test, is 30, 50 or 60 ° C.

Since the zero foam value differs at 30, 50 and 60 ° C, the effectiveness of a defoamer is shown as% residual foam.

The% residual foam (R) is calculated as S _e • 100

R = where S _{e is} the foam value which is after adding the defoamer and S _{0 is} the foam zero value, ie the value which is measured in the absence of a defoamer. In this terminology the defoamer is better the smaller R is.

The values for the residual foam R given in the table below were obtained for the defoamers described above.

Example defoamer R No. No. 30 ° C 50 ° C 60 ° C

40 60 66

Claims

Claims 1. Use of carboxylic acids from the group of citric acid, tartaric acid, succinic acid, maleic acid, nitrilotriacetic acid and ethylenediaminetetraacetic acid which are at least partially esterified with saturated C 1 -C ₂₂ -alcohols or at least partially amidated with saturated C ₁ -C 6 -alkylamines as defoamers . 2. Use according to claim 1, characterized in that at least 1/3 of the carboxyl groups of the carboxylic acids mentioned are esterified or amidated. 3. Use according to claim 1, characterized in that citric acid esters are used, which are obtainable by esterification of 1 mole of citric acid with 1 to 3 moles of a saturated Cχ ~ to C ₂ 2 ~ alcohol or a mixture of such alcohols. 4. Use according to claim 1, characterized in that Citric acid esters are used, which can be obtained by esterifying 1 mole of citric acid with 1 to 2 moles of a saturated Cg to C ₂₂ alcohol or a mixture of such alcohols. 5. Use according to claim 1, characterized in that A ide of citric acid are used, which can be obtained by amidating 1 mol of citric acid with 1 to 2 mol of a primary or secondary Cβ ~ to C ₂₆ alkylamine or a mixture of such amines. 6. Use according to one of claims 1 to 5, characterized in that additionally emulsifiers with an HLB value of at least 8 in amounts up to 40 wt .-%, based on the mixture, are also used. 7. defoamer, characterized in that they are essential components (a) at least partially esterified ₂ 2 ^_ alcohols with Cι ~ C until at least partially or with primary or secondary CJ to C ₂₂ alkylamines amidated Carboxylic acids from the group citric acid, tartaric acid, succinic acid, maleic acid, nitrilotriacetic acid and ethylenediaminetetraacetic acid and (b) Emulsifiers with an HLB value of at least 8 in the weight ratio (a) :( b) from 95: 5 to 60:40.