DE4129337C1 - Silane derivs. with bunte salt gps. - used as stabilisers for antifreeze compsns. and prevent pptes. forming on diluting concentrates with hard water - Google Patents

Abstract

Silane derivs. with Bunte salt gps. are of formula (HO)ySi(R)x-CmH2m-O-(CnH2n-O)p-A2-CH2-CH(R')-CH2R" (I). In (I), A is -CH(CH2X)-CH2-O- or -CH2-CH(CH2X)-O-, where X is halogen, pref. Cl; R is 1-4C alkyl or Ph; R' (or R") is OH, and R" (or R') is S2O3M, where M is an alkali metal or pref. substd. NH4 cation; x is 0 or 1 and y is 2 or 3, such that (x+y) is 3; m is 2-6; n is 2 or 3; p is 0-100; and q is 0-5. USE - (I) are stabilisers (0.01-0.50 wt.%) for antifreeze compns. based on glycols and contg. alkali metal silicate, which prevent the formation of pptes. on diluting the concentrates with hard water; and are also surface modifiers for substrates contg. reactive OH gps.

Description

The invention relates to silanes with colored salt groups, a process for their manufacture and their use as additives for antifreezes and as a means of modifying the surface of Substrates that are capable of reacting with OH groups.

In DE-PS 37 35 086 are organopolysiloxanes with over carbon bound Buntesalzgruppen described. These connections can by reacting organopolysiloxanes with epoxy groups with respect to epoxy groups, equimolar amounts of Me₂S₂O₃, where Me an alkali metal or an optionally substituted ammonium radical is to be manufactured. The organopolysiloxanes modified with colored salt groups can be used for permanent finishing of fibers or fiber products or used to treat hair.

DE-PS 34 20 369 relates to the use of salts of sulfuric acid semiesters the general formula

R¹ = lower alkyl radical with 1 to 4 carbon atoms
or phenyl radical,
R² = alkylene radical with 3 to 11 carbon atoms,
X = alkali or ammonium ion,
a = 0 or 1,
b = 2 or 3,
a + b = 3
or their, optionally partial, condensation products as additives for anti-freeze based on polyhydric alcohols, where the anti-freeze may also contain alkali silicates and optionally other additives, in amounts of 0.01 to 0.5% by weight (based on anti-freeze) for prevention the formation of precipitates during or after dilution of the antifreeze with water containing hardening agents to the concentration of use.

The present invention addresses the technical problem of Provision of further organosilicon compounds with colored salt groups and in a special aspect with the provision of such Compounds that are particularly found in antifreezes have favorable properties. Such desired property improvements consist mainly of a stabilization of the Preparations against the formation of precipitates. In investigations these are expressed with antifreeze agents of a defined type Property improvements in the significant extension of the time interval, until precipitation forms and in the reduction of Amount of rainfall formed over time.

The silanes according to the invention with colored salt groups correspond to general formula

where the residues and indices have the following meaning:
R¹ alkyl radical with 1 to 4 carbon atoms or phenyl radical,

R³, R⁴ one of the two residues OH, the other of the two residues -S₂O₃Me,
Me = alkali ion or, optionally optionally substituted, ammonium ion,
a 0 or 1,
b 2 or 3,
a + b 3,
c number from 0 to 100,
d integer from 0 to 5,
m integer from 2 to 6,
n number from 2 to 3.

R¹ preferably has the meaning of an alkyl radical and is in particular straight chain. The alkyl radical is particularly preferred Methyl residue.

R² is a residue that can exist in two isomeric forms:

X is a halogen atom and is preferably a chlorine atom.

R³ and R⁴ are residues resulting from the opening of the oxirane ring from the reaction with thiosulfate: The one of the two residues is an OH residue, while the other residue means an -S₂O₃Me rest has. Me is an alkali ion, especially a Sodium ion, or an optionally substituted ammonium Ion. Examples of this are the tetrabutylammonium, tetramethylammonium or triethanolammonium ion.  

The index a has a value of 0 or 1 and is preferably 1. The index b has a value of 2 or 3 and is preferably 2. Both indices a and b must have a value of 3 together.

The index c indicates the number of oxyalkylene groups and has one Value from 0 to 100, preferably from 0 to 50. About its value and that of the index n can be the hydrophilicity / hydrophobicity of the compound or which is formed from the connection in the respective application Discontinue follow-up products.

The index d has a value from 0 to 5. Its value depends on the manufacturing process and results from the implementation of the not claimed Output connections

with epichlorohydrin. D is preferably 0.

The index m has a value from 2 to 6 and is preferably equal to 3.

The index n has a value of 2 to 3, so that the oxyalkylene group is either an oxyethylene or an oxypropylene group. Lies a Mixture of both oxyalkylene groups before, the index is a broken one Number between 2 and 3.

Examples of compounds according to the invention are:

Another object of the invention is a preferred one Process for the preparation of the compounds according to the invention. The procedure is characterized in that an epoxysilane of the general formula

in which
the radicals R 1, R 2 and the indices a, b, c, d, m and n are as defined above,
with equimolar amounts of Me₂S₂O₃ with respect to epoxy groups at temperatures up to 100 ° C in an aqueous medium, to which polar organic solvents may have been added, in the presence of such amounts of acids that a pH of 5 to 9 is maintained during the reaction .

Lower aliphatic are preferably used as organic polar solvents Alcohols such as B. ethanol, isopropanol or propylene glycol, used, each 1 part by volume of water preferably 0.5 up to 5 parts by volume of organic solvent can be used.

The reaction is already running at room temperature or moderately elevated temperatures from. An upper temperature of 120 ° C should not be exceeded will.

It is essential that a pH range of 5 until 9 is observed. This is conveniently done by adding a preferably dilute acid, such as. B. dilute hydrochloric acid. The The choice of acid can also be of importance for the application technology Suitability of the product when the salt of the acid is not  is removed from the product. Examples of suitable acids are acetic acid, Glycolic acid, citric acid, benzoic acid, tartaric acid, ethylhexanoic acid and adipic acid. You can also use acid releasing compounds or use suitable ion exchangers loaded with acidic groups. This ensures that the reaction of the thiosulfate with the epoxy groups of the silane completely. It is not allowed the acid necessary to neutralize the released base to add from the beginning, because in this case you are affected by acid Medium would decompose the colored salt formed. Rather, it is important maintain the required pH range of 5 to 9 during the reaction. This requires controlled and constant addition of acid.

Another reason for the invention is the use of the Compounds according to the invention as additives for antifreezes based on polyhydric alcohols, which alkali silicates and optionally contain other conventional additives, in amounts of 0.01 to 0.5 wt .-% (based on antifreeze) for prevention the formation of precipitates during or after dilution of the antifreeze with hardness-forming water to use concentration.

It is known to add an anti-freeze to the cooling water in order to to lower the freezing point of the cooling water. As an antifreeze are polyhydric alcohols or their partial methyl or Ethyl ether, preferably ethylene glycol, is used. Ethylene glycol oxidized in the cooling water during prolonged use. Hereby there is a drop in the pH value. To prevent corrosion on the metal parts Avoid antifreezes Corrosion inhibitors and buffer substances added. As corrosion inhibitors water-soluble alkali silicates have proven to be effective. They are usually combined with other corrosion inhibitors, such as sodium nitrite, Benzotriazole or sodium mercaptotriazole used. Suitable Buffer substances are alkali borates or alkali benzoates.  

The antifreezes are sold in concentrated form brought and generally contain only so much water that the additives stay in solution. The concentrates are added before use Diluted water in amounts such that the desired freezing point depression is achieved.

When using alkali silicate as a corrosion inhibitor, it can already in the antifreeze concentrate to form turbidity come. If the antifreeze concentrate is diluted with water, which contains hardness can also precipitate Alkali calcium silicates are formed. The amount of precipitation increases when the diluted antifreeze preparation is heated. These precipitates can accumulate on the walls of the cooling system discontinue and impair the heat transfer or the cables of the cooling system or reduce the water cycle.

To reduce the amount of precipitation formed, one already has as mentioned at the beginning, according to DE-PS 34 20 369 compounds the general formula

R¹ = lower alkyl radical with 1 to 4 carbon atoms
or phenyl radical,
R² = alkylene radical with 3 to 11 carbon atoms,
X = alkali or ammonium ion,
a = 0 or 1,
b = 2 or 3,
a + b = 3
used.

In the European patent application 00 29 728 to avoid the Formation of gel particles by adding an effective amount of glycol ether modified Siloxanes recommended.

Surprisingly, it has been found that the colored salt groups according to the invention containing silanes are effective agents to the formation of Precipitation in antifreeze concentrates and their dilutions to delay or the amount of precipitates above that to reduce the achievable level with comparable additional quantities.

Components of the antifreeze concentrates can be glycols, such as preferably ethylene glycol, but also diethylene glycol, propylene glycol, Dipropylene glycol and / or glycol ether, such as methyl, ethyl, propyl, Be butyl ether of ethylene glycol. From the multitude of usable Examples of corrosion inhibitors are: guanidine, Citrates, coal tar derivatives, thiocyanates, phenols, thioureas, Tannin, quinoline, morpholine, triethanolamine, tartrate, glycol monorizoleate, organic nitrites, mercaptans, mercaptobenzoetriazoles, polytriazoles, sulfonated hydrocarbons, fats, soaps and inorganic Salts, such as sulfates, sulfides, fluorides, alkali metal chromates, Nitrates, nitrites, phosphars, borates, tungstates, molybdates, vanadates, Carbonates and silicates. In addition, defoamed can be effective Means be included.

In the following Examples 1 and 2, the preparation of the invention Connections explained in more detail. In an application technology Example 3 shows that the compounds of the invention the state of the art products in terms of delay the formation of precipitates in antifreeze and in are superior in reducing the amount of precipitates.  

I. Manufacturing examples example 1

Preparation of an anti-freeze stabilizer [sodium (3- (3- trihydroxysilylpropyloxy) -2-hydroxypropylthiosulfate)] from glycidoxy propyltrimethoxysilane and sodium thiosulfate using Acetic acid as a neutralizing agent.

248.18 g Na₂S₂O₃ * 5H₂O (1 mol), 118.86 g water and 39.46 g Ethanol are placed in a 2 liter flask and gassed with nitrogen. Thereafter, a mixture of 236.34 g of glycidoxypropyltrimethoxysilane (1 mol) and 102.88 g of ethanol were added dropwise over 30 minutes. The Temperature rises due to exothermic reaction by additional Heating from 20 ° C to 80 ° C. Dilute by adding drops Acetic acid, prepared from 283.84 g water and 60.05 g acetic acid (1 mol), the pH of the reaction mixture is in the range of 8 held to 9. After 3.5 hours the pH no longer changes, and no further acetic acid has to be added. It will still be Stirred at 80 ° C for 30 min, cooled to 50 ° C and diluted with the Acetic acid adjusted to pH 7.0. 11 g of the dilute acetic acid are not used, this results in a turnover of 97%.

Example 2

Preparation of an anti-freeze stabilizer [sodium (3- (3- trihydroxysilylpropyloxy) -2-hydroxypropylthiosulfate)] from glycidoxy propyltrimethoxysilane and sodium thiosulfate using 2-ethylhexanoic acid as neutralizing agent.

248.18 g Na₂S₂O₃ * 5H₂O (1 mol), 323.8 g water and 142.34 g Ethylene glycol are placed in a 2 liter flask and filled with nitrogen fumigated. Then 236.34 g of glycidoxypropyltrimethoxysilane (1 mol) added dropwise during 30 min. The temperature rises due to exothermic Reaction by additional heating from 20 ° C to 80 ° C. By dropwise addition of 144.2 g of 2-ethylhexanoic acid (1 mol)  pH of the reaction mixture kept in the range of 8 to 9. To The pH does not change for 3.5 hours and there is no need for another Ethylhexanoic acid are added more. It is still 1 hour at 80 ° C stirred, cooled to 50 ° C. and adjusted to pH 7.0 with ethylhexanoic acid, which is completely used up.

II. Application example 3

In 86.6 g of ethylene glycol, 1 g of sodium tetraborate decahydrate, 9 g 25% by weight aqueous solution of sodium benzoate, 1 g 33.3% by weight aqueous solution of sodium nitrite, 0.9 g 33.3% by weight aqueous solution of sodium nitrate, 1 g of 10% by weight aqueous solution of sodium metasilicate (Na₂SiO₃) and 0.07 g benzotriazole at room temperature solved.

To prepare the solutions to be examined, this antifreeze concentrate is used the following active ingredients are dissolved:

Solution A: without further addition
Solution B: 0.1% by weight of a polyether siloxane of the following average formula

according to EP-OS 00 29 728
Solution C: 0.1 wt .-% (HO) ₃Si (CH₂) ₃OSO₃NH₄ according to DE-PS 34 20 369
Solution D: 0.025 wt .-% (HO) ₃Si (CH₂) ₃OSO₃NH₄ according to DE-PS 34 20 369
Solution E: 0.1% by weight of the product according to the invention according to Example 1
Solution F: 0.1% by weight of the product according to the invention according to Example 2
Solution G: 0.025% by weight of the product according to the invention according to Example 1
Solution H: 0.025% by weight of the product according to the invention according to Example 2

50 ml of solutions A to F are mixed with 50 ml of a saline solution Water added, per liter 150 mg Na₂SO₄, 165 mg NaCl, Contains 140 mg NaHCO₃ and 275 mg CaCl₂. The samples are closed Vessel stored at 80 ° C and open at regular intervals examined the formation of precipitation. After 4 weeks of storage the solutions 10 minutes at 3500 revolutions / min. centrifuged. The amount of precipitation is determined volumetrically. The results are reproduced in the following table:

table

The table shows the superior effectiveness of the products according to the invention assuming comparable concentrations too remove.

Claims (3)

1. Silanes with colored salt groups of the general formula where the residues and indices have the following meaning:
R¹ alkyl radical with 1 to 4 carbon atoms or phenyl radical, R³, R⁴ one of the two residues OH, the other of the two residues -S₂O₃Me,
Me = alkali ion or, optionally optionally substituted, ammonium ion,
a 0 or 1,
b 2 or 3,
a + b 3,
c number from 0 to 100,
d integer from 0 to 5,
m integer from 2 to 6,
n number from 2 to 3. 2. A process for the preparation of the compounds of claim 1, characterized in that an epoxysilane of the general formula wherein the radicals R¹, R² and the indices a, b, c, d, m and n are as defined above, with equimolar amounts of Me₂S₂O₃ with respect to epoxy groups at temperatures up to 100 ° C in an aqueous medium, which optionally polar organic solvent added are, in the presence of such amounts of acids that a pH of 5 to 9 is maintained during the reaction. 3. Use of the silanes of claim 1 as an additive for antifreeze based on polyhydric alcohols, which alkali silicates and optionally contain other customary additives, in quantities of 0.01 to 0.5% by weight (based on antifreeze with tel).