CH648325A5 - SILICONATE-SILYLORGANOPHOSPHONATE AND ITS USE AGAINST METAL CORROSION. - Google Patents

Description

The invention relates to new Siliconat-silyl-organophosphates of the formula I below, furthermore corrosion protection agents and a method for corrosion prevention.

Certain water-soluble silicates are known as metal corrosion inhibitors in aqueous systems. A disadvantage of silicates, however, is the fact that they are unstable because, after use at elevated temperatures, they tend to gel and precipitate out of solution. Many efforts have therefore been made to stabilize silicates in order to improve their corrosion-inhibiting properties.

Combinations of silicones with silicate polymers as corrosion inhibitors are described in US Pat. Nos. 3,312,622 and 3,198,820. Although the patents do not detail the stabilization of the silicates, it is evident from the description that the so-called “novel organosilicon polymer” contributes to the corrosion inhibition of the silicate polymers of the patents. As emphasized there, the novelty is the use of cationic silyl carboxylates in conjunction with the silicates. It is discussed that such materials promote corrosion inhibition in common antifreeze agents, and that they have disadvantages of other known corrosion inhibitors, namely the handling and manufacture of antifreeze agents, a corrosion inhibition selective only for certain metals, a modest storage life, the tendency to attack rubber hoses, eliminate excessive foaming during use and the cause of alcohol decomposition.

In U.S. Patents 3,341,469 and 3,337,496, Pines et al. another system that had proven useful in inhibiting corrosion in aqueous alcohol compositions. It consisted of a mixture of an alkyl sesquisiloxane, a siloxane modified with a cyanoalkyl or carbanol group and a silicate. These materials are described as "remarkably soluble in aqueous liquids". Furthermore, these mixtures are said to overcome many of the disadvantages mentioned above.

Finally, US Pat. No. 3,948,964 describes the stabilization of partially hydrolyzed silicic acid esters using stabilizers selected from organic compounds such as cyclic ethers, ether alcohols, carboxylic acid esters and ketones. Such stabilized materials are used as binders for zinc dust pigments and the like.

However, none of these publications describes the substances according to the invention. These have special advantages, namely both those of the known substances and additional advantages. Most notable are the low cost, improved effectiveness in stabilizing silicates and the durability of the corrosion inhibitor.

This invention has several aspects of the same concept. It initially concerns a substance with the unit formula I,

0

11

MO-P-O-R-SiO i, 5 (I)

1

R '

in which mean:

M is a cation selected from sodium, potassium, lithium, rubidium and tetraorganoammonium ions;

R is a divalent aliphatic hydrocarbon radical having 1 to 3 carbon atoms, or a radical derived from toluene, and

R 'is an optionally halogen-substituted hydrocarbon radical having 1 to 7 carbon atoms.

The Siliconat-silylorganophosphate of formula I is obtained, for example, by reaction of an alkali metal hydroxide with corresponding silanol-containing esters of phosphorus.

The starting phosphorus compound, that is, the silyl alkyl esters of phosphorus, can be prepared by various methods. However, they are preferably represented in the manner described in US Pat. No. 4,093,641. This process is simple to carry out and gives high yields, which is reflected in the low cost of the product obtained. The starting phosphorus compounds are then expediently treated with dilute sodium hydroxide solution and refluxed for several hours

10th

15

20th

25th

30th

35

40

45

50

55

60

65

3rd

648 325

cooked to saponify the phosphonate precursor (percursor). If excess sodium hydroxide is used, the resulting product has the unit formula

I r

0

II

NaOP-O-R-Si-ONa

1 I

R 'O

This is the sodium salt of the sodium silicate silylalkyl phosphate.

In Formula I, M is an alkali metal cation selected from

The resulting product is used alone or in conjunction with silicates, as explained below.

As mentioned above, the products obtained, i.e. alkali siliconate silyl organophosphates, are able to stabilize silicates which are useful as corrosion inhibitors for metals. Such materials can therefore be used in antifreeze mixtures where metal corrosion occurs because of the high temperatures which cause decomposition of the alcohols commonly used as freezing point depressants. If the silicates are the inner metal parts of a cooling system, e.g. in a car engine, protect and if the silicates can be made durable in the aqueous system, then there is a clear advantage.

The invention therefore also relates to a mixture of active ingredients for corrosion protection, in particular for use in an alcoholic medium, with improved corrosion-inhibiting properties, consisting of

(A) 0.1 to 99.9 parts by weight of siliconate silyl organophosphate of the formula I according to claim 1 and

Sodium, potassium, lithium and rubidium, or a tetra-organoammonium cation. Typical tetraorganoammonium cations are tetramethylammonium and tetraethylammonium.

s In the above formula, R represents a divalent aliphatic hydrocarbon residue containing 1 to 3 carbon atoms or a divalent residue derived from toluene. The substance should be water soluble so that there is a limit to the size and type of R.

R 'represents a hydrocarbon residue or a halogenated hydrocarbon residue having 1 to 7 carbon atoms and includes, for example, methyl, ethyl, phenyl, halobenzyl and the like.

In current practice, using dichlorobenzyldimethylphosphate as an example, the preparation is as follows:

(z)

(B) 99.9 to 0.1 parts by weight of soluble silicate of the unit formula

50

(MO) aSÌO ± a (II)

2nd

where M has the meaning already given and a is a number from 1 to 3.

The above mixture of active ingredients can be used both in an anhydrous alcoholic environment, but also in one that contains relatively small amounts of water in addition to alcohol and phosphate silicate, as well as in media that contain relatively large amounts of water, i.e. the alcoholic phase can be «concentrate» or «coolant " be.

The alcohols that can be used include both monohydric alcohols, such as methanol, ethanol, propanol and butanol, and polyhydric alcohols, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerin, and mixtures thereof. What is preferred are the alcohols used as common antifreeze agents, especially ethylene glycol.

10th

15

CH2PO (OCH3) 2 Cl

(CH30) 3SiCH2CH2CH2Cl>

/ - \ 9

S \ - CH2POCH2CH2CH2Si (OCH3) 3 \ ==) xi OCH3

(Z) + NaOH water>

Reflux / several hours t

o o n I

CH2POCH2CH2CH2SiONa t 1

Ci

N / A

60

648325

As indicated above, essentially all ratios of phosphate (A) to silicate (B) are capable of providing a metal corrosion inhibiting material. The ratio of (A) to (B) depends on the particular system in which it is used. Therefore, the most effective ratio of (A) to (B) depends in particular on the amount of water in the system, the amount and type of alcohol present, the temperature of the aqueous medium and other additives and chemicals in the system.

The phosphates have been discussed above. The water-soluble silicates are suitable as silicates of the formula II. M has the same meaning as discussed above for M and is a cation that makes the silicate water-soluble. Examples of these silicates are the alkali metal orthosilicates, the alkali metal metasilicates, the alkali metal tetrasilicates, the alkali metal disilicates and the tetraorganoammonium silicates.

Specific examples of these silicates are potassium metasilicate, sodium orthosilicate, potassium disilicate, lithium ortho silicate, lithium metasilicate, lithium disilicate, rubidium disilicate, rubidium metasilicate, mixed silicates (e.g.

NaîO • LÌ2O • 2SÌO2 and K2O • LÌ2O • 4SiCte), tetramethylammonium silicate, tetraethylammonium silicate, phenyltrimethylammonium silicate, benzyltrimethylammonium silicate, guanidine silicate and tetrahydroxyethylammonium silicate. The preferred silicates are sodium and potassium silicates, especially sodium disilicate and potassium disilicate.

As such, the silicate used in the preparation of the phosphonate-silicate inhibitors can be added to the reaction mixture or it can be formed in situ by adding the appropriate alkali hydroxide and silica to the reaction mixture.

It is within the scope of this invention that the combinations of (A) and (B) mixtures of (A) and (B), partial reaction products of (A) and (B) or mixtures of mixtures of (A) and (B) and of partial reaction products of (A) and (B).

The phosphonate-silicate combination can be prepared by simply mixing the components (A) and (B) in the correct ratio and by stirring to homogenize them.

The phosphonate-silicate combination can then be added to the alcohol composition. The order in which the phosphonate, silicate and alcohol are combined is usually not critical as long as the materials are mixed thoroughly.

It has been found that the alcoholic phosphate-silicate combination can be used in other areas besides the use in vehicle engine cooling. So these materials can e.g. in cooling and air conditioning units, cooling coils, heat exchangers and the like.

It has previously been suggested that the phosphonate can also be used effectively without combining it with the silicate prior to use, that is, the phosphonate could be added to the aqueous system without the silicate. The phosphonate compositions and the phosphonate-silicate compositions can also be used in aqueous systems that are not anti-freeze systems, that is, in non-alcoholic aqueous systems that come into contact with metal surfaces, such as uses that are undesirable Keep deposits in geothermal power plants, conventional heat exchange systems and the like under control.

The amount of the combination of (A) and (B) required to protect the metals from corrosion depends on the metal to be protected, the system in which the combination is used, the temperature of the system and other components and additives that are included in the system. In general, the combination of (A) and (B) is used in an amount of 20 ppm up to 2% based on the weight of the aqueous liquid.

When used in automotive engine coolants, it has been found that 200 parts of the phosphonate silicate, based on one million parts of the aqueous, alcoholic coolant, are effective in preventing corrosion. 10 Larger quantities are sometimes required in non-alcoholic aqueous media. The preferred range of use for all such systems encompassed by this invention is from 200 ppm by weight to 2% by weight of the aqueous medium.

It is part of this invention that various additives are added that have special properties, such as anti-foaming agents (both organic and siloxane-based), dyes, pH indicators, other inhibitors, thickeners and the like.

20 The following examples are presented to illustrate the invention and are not intended to be construed to cover the scope thereof.

25th

example 1

As mentioned above, the known corrosion inhibitors are exposed to very unfavorable conditions which affect their stabilizing properties. The materials according to the invention were therefore subjected to extreme conditions in the following manner:

In this example, Nyacof 215, a commercial silica sol manufactured by Nyanza Inc., Ashland, Maine (USA) was used. The 10.5 pH sol that was 3S Na + stabilized contained approximately 15% silica with a particle size of approximately 2 nm. The pH was lowered using 10% aqueous HCl solution as shown in Table 1. The thaw freeze cycle consisted of placing glass vials with 28.35 g of the solution in a freezer and allowing to freeze for twelve hours. The vials were then removed from the freezer and allowed to thaw. The solutions were then examined for the appearance of a precipitate, which would indicate that they are not stable.

Example 2

To demonstrate the versatility of the material, 50 a second colloidal silica was treated similarly and subjected to similar adverse conditions (see Table II). The silicate was Ludox® from E.I. DuPont de Nemours and Co., Wilmington, Delaware. The sol contains 30% silica and is ammonium stabilized. The pH of the 55 Sois was 9.4 and the average particle size was 13-14 nm. The pH was lowered by adding 10% aqueous HCl solution as indicated in Table II.

60 Example 3

This example illustrates the stabilizing effect of the material in Nalcoag® 1034A from Nalco Chemical Co., Chicago, Illinois (USA). The sol is H + stabilized and contains 34% silica. It is acidic with pH 3.4 and the average particle size is 16-22 nm. The «Nalcoag» was made less acidic by adding ammonia before it was tested as shown in Table III.

5

648325

Example 4

This example shows the stabilizing effect of the material in Ludox® SM 30 by E.I. DuPont de Nemours and Co., Wilmington, Delaware. The sol is Na + stabilized, has a pH of 9-10 and an average particle size of 7-8 nm. The solutions were tested, as listed in Table IV, after the pH had been increased by adding 10% aqueous HCl- Solution had been lowered.

Example 5 io

This example illustrates the effect of pH on stability. The stability of silicate / siliconate mixtures is generally at a minimum at pH 8.

A molar ratio of sodium silicate “G” to product of 7.5: 1 was used. The silicate "G" was a sodium silicate manufactured by Philadelphia Quartz Co. with a Si0a / Na20 weight ratio of 3.22 and a pH of 10.8. The product of this invention was a one molar aqueous silicate, i.e. the unit formula

sample

Aging time at room temperature

Stability at pH 8

A

lOsec.

30 sec.

B

1 min.

70 sec.

C.

5 min.

20 min.

D

15 minutes.

> 1 week

E

45 min.

> 1 week

Samples D and E were still stable about four weeks after they were made.

Example 7

This example shows the effect of sodium metasilicate, a low molecular weight silicate. A two molar sodium metasilicate solution was mixed with a two molar product, i.e.

O

O

(XsSicmcmcmopoNa

OuSiCHîCHîCHzOPONa.

CH3

After aging for one day, the mixture was acidified to various pH with 10% aqueous HCl solution and observed for gel time.

pH

Gel time

4th

6

7

8th

9 10

> 1 week

> 1 week

> 1 week 13A hours 9 hours

> 1 week

CH3

25 mixed in a molar ratio of 7: 3. After aging for six months at room temperature, the equilibrated solution was further diluted with sodium metasilicate as indicated. The pH was then adjusted to 8 with 10% aqueous HCl solution and the stability of the 30 solutions was observed.

Mole ratio

Na metasilicate / phosphonate

7: 3 4: 1

6: 1

Stability at pH 8

> 1 week 1 week

16 min.

The sample at pH 4 showed no gel formation within one year.

It can thus be observed that a mixture of sodium metasilicate with a phosphonate according to the invention in a ratio of 4: 1 brings stable corrosion inhibitors which do not gel when neutralized. A fresh mixture at a ratio of 4: 1 gelled at pH 8 within 6-45 minutes, indicating that a period of time to equilibrate is beneficial for the solution.

Example 6

This example illustrates the impact of aging. A mixture of the same type as that prepared in Example 5 above was used for this example, except that the ratio of silicate to product in the one-molar solution was 5: 1.

Example 8

so stabilization of a potassium silicate (Kasil 6).

A one molar potassium silicate solution with a weight ratio SÌO2 / K2O of 2.10 (molar ratio 3.3: 1), manufactured by Philadelphia Quartz, was mixed with two parts of one molar siliconate solutions. After standing for 15 minutes, the pH was brought to 8 with 10% aqueous HCl solution.

sample

Siliconate

Stability at pH?

7.5: 1

5: 1

A B

OuSiCmCHaCOONa OusSiCH-CHaCHzCOONa O

3 min.

> 1 week

> 1 week

O i, 5SiCH2CH2CH2P (ONa) 2

0.5 min.

1 min.

648325

sample

Siliconate o

Stability at pH 8

7.5: 1

5: 1

D

0i, 5SiCH2CH2CH20P (0Na> 10 min.

> 1 week

O

II

E

II

OuSiCmCEhCmOPONa 10 min.

I.

> 1 week

1

Cm

(Samples A-D: comparison)

Samples A, β, D and E still showed excellent stability at a ratio of 5: 1 after 4 weeks.

Table I

Stability under unfavorable conditions depending on the time

Colloidal silica (silicate) percent siliconate room temp.

Freeze-thaw cycle

pH 5

Nyacol215

0 0.4h

70% rainfall

0.2 O H

Nyacol215

II

OuSiCmCEbCmOPONa 2 h

67% rainfall

1

cm

2.0 O

II

Nyacol215

II

OuSiCmCmcmOPONa 32 h

No precipitation,

1

stable

CH3

2.0 O

II

Nyacol215

II

Oi, 5SiCH2CH2CH2OPONa 1.3 h

No precipitation,

|

stable

OH

Table!!

Stability under unfavorable conditions depending on the time

Colloidal silica (silicate)

Percent siliconate room temp. pH 5

O.lNNaOHpHó freeze-thaw cycle

Ludox AS

Comparative standard 2 h

0.5 h gel

0.2 O

H

Ludox AS

II

Oi.sSiCmcmCmOPONa> 50 h

I.

50 h gel

1

CHs

2.0 O

M

Ludox AS

II

Oi.sSicmcmcmopoNa> 100 h

> 144 h no precipitation

1

cm

648325

Table II (continued)

Stability under unfavorable conditions depending on the time

Colloidal silica (silicate) percent siliconate room temp. pH 5 O.INNaOHpHö freeze-thaw cycle

2.0 O

II

Ludox AS Oi.sSiCmCHiCH-OPONa> 100 h> 144 h No precipitation

I.

OH

Table III

Stability under unfavorable conditions depending on the time

Colloidal silica (silicate) percent siliconate pH 7/95 ° C

pH 6/60 ° 0.1N HCl freeze-thaw cycle

Nalcoag 1034A

Nalcoag 1034A

Nalcoag 1034A

Nalcoag 1034A

Comparison standard 0.2 O

II

OusSiCHìCrnCHìOPONa

I.

CH3

2.0 O

II

Ot.sSiCHzCHaCHiOPONa CHs

2.0 O

II

OusSiCHzCmCmOPONa

I.

OH

24 hours

36 h

72 h

24 hours

0.5 h

0.7 h cloudy

gel

> 120 h

gel

> 120 h clear

Table IV

Stability under unfavorable conditions depending on the time

Colloidal silica (silicate) percent siliconate

Room temp. pH 5

Freeze-thaw cycle

Ludox SM

Ludox SM

Ludox SM

Ludox SM

Comparative standard 2 h

0.2 O

II

OuSiCmCHzCmOPONa 50 h

I.

CHs

2.0 O

II

OusSicmcmcmopoNa 20 h

I.

CHs

2.0 O

II

OusSiCmCmCHiOPONa 120 h

I.

OH

gel

Gel clear clear

B

Claims (6)

648325 1 R ' in which mean: M is a cation selected from sodium, potassium, lithium, rubidium and tetraorganoammonium ions; R is a divalent aliphatic hydrocarbon radical having 1 to 3 carbon atoms, or a divalent radical derived from toluene, and R 'is an optionally halogen-substituted hydrocarbon radical having 1 to 7 carbon atoms. 1. Siliconate-silylorganophosphonate of the unit formula 0 11 m MO-P-O-R-SiOi. 5 W. 2nd where M has the meaning already given and a is a number from 1 to 3. 2. Active ingredient mixture for corrosion protection, consisting of (A) 0.1 to 99.9 parts by weight of Siliconat-Silylorganophos-phonat of formula I according to claim 1 and (B) 99.9 to 0.1 parts by weight of soluble silicate of the unit formula (M0) aSÌ04-a (II) 2nd PATENT CLAIMS 3. Corrosion protection agent, containing the active ingredient mixture according to claim 2 in a corrosion-inhibiting effective amount in an alcohol. 4. A method for preventing corrosion of metals in an aqueous medium, characterized in that a compound of formula I according to claim 1 is added to the aqueous medium. 5. The method according to claim 4, characterized in that an active ingredient mixture according to claim 2 is added to the aqueous medium. 6. The method according to claim 4, characterized in that a corrosion protection agent according to claim 3 is added to the aqueous medium.