DE2415331A1 - Polyorganosiloxane resins - contg. silanol groups produced by hydrolysis of organohalosilane mixts. - Google Patents

Abstract

Polysiloxane resins contg. silanol gps. are prepd. by hydrolysis of organohalosilane mixts. in the presence of a hydrogen carbonate or hydrogen sulphate salt, water, a water miscible solvent and a water immiscible solvent. The water miscible solvent is also miscible in the water immiscible solvent. The salts may be partially replaced by other materials which as bases and hydrolysis is carried out at pH 6-8. This method allows the reaction to be carried out in a practically homogeneous phase making it almost independent of temp. and reaction time. The aq. phase with its high salt content allows for easy sepn. from resin phase.

Description

Process for the preparation of organopolysiloxane resins containing silanol groups Organopolysiloxane resins containing silanol groups are in addition to the alkoxyl groups containing the most important prepolymers for the production of various combination resins, which are mostly used as paint binders.

Their production is difficult because of the silicon-bonded OH groups tend towards siloxane condensation. So conditions must be created that allow cohydrolysis of the chlorosilanes without complete condensation entry.

For this reason, silanol-containing polysiloxanes have so far only been used two processes are produced: 1) According to German Offenlegungsschrift 2 005 762 an organochlorosilane mixture, optionally mixed with acetone and cooled with such a rate to a mixture of water and toluene or xylene given that the temperature of 400C, possibly 720C is not exceeded.

When the addition is complete, the mixture is stirred briefly and allowed to settle, the phases become separated, and the resin phase is freed from the solvent, optionally in vacuo.

2) US Pat. No. 2,646,441 describes the reaction of organochlorosilanes with sodium or calcium hydrogen carbonates or sulfites in anhydrous acetone or ether according to After filtration and removal of the solvent, a non-gelling hydroxypolysiloxane is obtained.

The former method has the disadvantage that the resulting resin very sensitive to the rate of addition, the stirring method and the reaction temperature is dependent. It is true that the polysiloxane is said to be in the organic phase of 1 condensation catalysis be withdrawn by the hydrochloric acid in the aqueous phase, but because of the narrow Both phases come into contact with stirring and the absorption of hydrogen chloride the toluene or xylene can only partially achieve this effect. Leading to the fact that gel formations already during the production from certain chlorosilane mixtures can be done. It is also possible that incompletely hydrolyzed and thus chlorine-containing components migrate into the resin phase, which later act as a condensation catalyst during storage split off effective hydrogen chloride, which can lead to gelling of the resin.

Since in the second-mentioned process, an excess of carbonate, or at least carbonate amounts equivalent to the chlorosilanes used are used neither during manufacture nor during storage is likely to form a gel. On the other hand, this method has all the disadvantages of a heterogeneous reaction, E.g. longer reaction time, strong agitation dependency and, if the reaction only at the surface takes place, possibly poor implementation the bicarbonate particles.

The present invention now relates to a method for production of organopolysiloxane resins containing silanol groups by hydrolysis of organohalosilane mixtures, which is characterized in that the hydrolysis in the presence of a hydrogen carbonate or a hydrogen sulfite and in the presence of water, one immiscible with water organic solvent and one in both water and the organic Solvent soluble component is carried out.

Surprisingly, it has been found that the disadvantages the above method can be avoided when following the inventive Process is worked and the reaction which otherwise takes place in a heterogeneous phase now takes place in a practically homogeneous phase. This is the inventive Process almost independent of temperature and reaction time, and the aqueous phase can be removed from the resin phase without any difficulty because of its high salt content separate.

Suitable starting components for the process according to the invention Organochlorosilanes of the general formula XnSiR4 n (n = 1,2 or)) where X for chlorine or bromine and R for an optionally inertly substituted, alkyl, Aryl or aralkyl radical.

Examples of R are methyl, ethyl, propyl, butyl, pentyl, hexyl, Phenyl, chlorophenyl, benzyl, tolyl, xylyl. The method according to the invention is preferred with cheap substances such as methyltrichlorosilane, dimethyldichlorosilane, diphenyldichlorosilane, Phenyltrichlorosilane, propyltrichlorosilane or hexyltrichlorosilane.

Preferred hydrogen carbonates or hydrogen sulfites are sodium, Potassium and / or ammonium salts into consideration. As organic, immiscible with water Solvents are e.g. benzene, chlorobenzene, xylenes, toluene, cyclohexane or Decahydronaphthalene.

As soluble in both water and organic solvent Component can e.g. methyl ethyl ketone, t-butanol, 1,4-dioxane, dimethoxyethane, ethyl glycol acetate or cyclohexanone can be used.

The method according to the invention is preferably carried out in such a way that to a stirred mixture of water, organic solvents and hydrogen carbonate respectively.

sulfite was added dropwise a mixture of the halosilanes in question is, the rate of addition being adjusted so that the temperature of the Reaction mixture does not rise above 700C, preferably not above 300C.

The pH of the reaction mixture should be approximately between 6 and 8; it may be necessary to also use hydrogen carbonate during the addition of the halosilane or sulfite must be added in order to carry out the hydrolysis in the optimal pH range.

After the reaction has taken place, the reaction mixture is known per se Wise worked up and the resin solution cleaned if necessary.

In a particular embodiment of the method according to the invention it is also possible to carry out the hydrolysis in the presence of additional other water-soluble, basic compounds such as NaOH, KOH, Na2COD, K2CO). The amount of hydrogen carbonate or hydrogen sulfite can be replaced by up to about 67% will.

The resins obtainable by the process according to the invention are storage-stable and are suitable for the production of combination resins, with a reactive prepolymer, e.g. an R-functional polyester (R can be OH, alkoxy, NH2, etc.), with cleavage of R-H is boiled in a known manner with the polysiloxane. The resulting Combination resins have proven to be excellent paint binders.

The method according to the invention will now be based on the following examples are explained in more detail (% figures mean - unless otherwise stated is - in each case wt .-%).

In a 6 l three-necked flask stirring apparatus were vigorously stirred mixture of 1.7 l of water, 570 ml of xylene and 600 ml of acetone 0.5 kg of sodium hydrogen carbonate slurried, forming a mixture of pH 7.8. A mixture of 2 moles (= 235 ml) methyltrichlorosilane, 2.6 mol (= 313.5 ml) dimethyldichlorosilane and 2 mol (= 519.5 ml) phenyltrichlorosilane is cooled under the surface of the ice / table salt introduced mixture introduced. Before a third of the chlorosilanes have been added, were-again entered 0.5 kg of sodium hydrogen carbonate, and before two thirds of the chlorosilanes have been added, a further 0.5 kg of carbonate.

After half an hour to an hour, the addition was complete, and the The contents of the flask were stirred for a further 15 minutes. After sitting for 15 minutes, the upper Phase separated from the saline solution and after filtering in vacuo (0.4 - 1.0 mm) freed from water and organic solvents to such an extent that about 650 g of an approx. 70 suitable clear, pale yellow resin solution lead into its solids A ratio of C6H5: HCH3: HOH = 60: 129: 6.5 was determined by 1H-NMR spectroscopy became. This corresponds to the theoretical phenyl: methyl ratio of 1 / 3.6 and is permitted the arithmetic determination of an OH content of 3.1%. The molecular weight of the solid was 1100.

Example 2: Compared to the method according to Example 1, only that Chlorosilane mixture changed, now from 4.05 mol (= 477 ml) methyltrichlorosilane and 2.7 moles (= 326 ml) of dimethyldichlorosilane. There were about 500 g of one 80% clear xylene resin solution obtained, from its 1H-NMR data HCH3: HOH 204.5: 11.5 an OH content of 5.5% can be calculated. The solid had a Molecular weight of about 1450.

Example 3: In an otherwise unchanged process according to Example 1 a mixture of 2.7 mol (= 318 ml) methyltrichlorosilane and 1.8 mol (= 217 ml) Dimethyldichlorosilane to a slurry of 0.6 kg of potassium hydrogen carbonate in 2 liters of water, 380 ml of xylene and 400 ml of methyl ethyl ketone with a pH of 7.5 are added. After half the amount of chlorosilane had been added dropwise, a further 570 g of carbonate were introduced. Approx.

250 g of an approximately 70% clear resin solution behave for their Solid from the 1H-NMR ratio of HOCH: HOH = 188.5: 13 3 an OH content of 6.9% is to be calculated.

Example 4: Compared to Example 1, the following were changed: the chlorosilane mixture, which here consisted of 4 moles of phenyltrichlorosilane and 1 mole of hexyltrichlorosilane, and the amount of sodium hydrogen carbonate, of which 700 g are presented here and after the feed half the amount of chlorosilane was added 650 g. A silicone resin was obtained with 6.7% OH and a molecular weight of approx. 1500.

Example 5: Instead of the slurry described in Example 3 a solution of 1.22 kg of sodium hydrogen sulfite in those listed in Example 3 was found Liquids used, which corresponded to the total amount of sulfite required. Under The chlorosilane mixture from Example 3 was used to produce a resin with approx. 6.6% OH obtain.

Example 6: A chlorosilane mixture according to Example 1 was under introduced the surface of a slurry prepared according to Example 1 until almost a third of the chlorosilanes was added. Then 2.3 l of a 5 N sodium hydroxide solution are added (corresponding to 11.5 mol) simultaneously with the remaining amount of chlorosilane so slowly added dropwise that the chlorosilane and alkali amounts added per unit of time as possible are equivalent, the reaction mixture in no case being clearly alkaline may be. After the addition has ended, work-up is carried out as in Example 1. The received Resin contained 3.4% OH.

Claims (3)

Patent claims: t W Process for the production of organopolysiloxane resins containing silanol groups by hydrolysis of organohalosilane mixtures, characterized in that the Hydrolysis in the presence of a hydrogen carbonate or a hydrogen sulfite and in Presence of water, an organic solvent immiscible with water and a component soluble in both water and the organic solvent is carried out. 2) Method according to claim 1, characterized in that the hydrolysis is carried out at a pH between 6 and 8. 3) Method according to one of claims 1 to 2, characterized in that that the hydrogen carbonate or hydrogen sulfite is partly basic due to others reacting substances is replaced.