SK50495A3 - Method of production of reaction products from poly (diorganosiloxanes) and alcoxysilanes - Google Patents

Abstract

The novel feature in the reaction of polysiloxanes with alkoxysilanes is that fluoride ions are present as activator, such ions pref. having as their source: (i) an alkali metal fluoride; or (ii) a non-metallic cpd. esp. a tetra-alkylammonium fluoride and/or NH4F as well as trialkylamine-HF and other polyhydrofluorides or tert. org. amines.

Description

Technical field

The invention relates to a process for the production of reaction products from poly (diorganosilanes) and alkoxysilanes.

BACKGROUND OF THE INVENTION

The purpose of the reaction of poly (diorganosiloxanes) with alkoxysilanes is to produce poly (diorganosiloxanes) with diorganyloxy-organosilyl or triorganyloxysilyl end groups. According to literature, the following paths were taken:

1. the reaction of alpha, omega-dihydroxy-poly (diorganosiloxanes) with alkoxysilanes in the presence of suitable catalysts, and

2. the reaction of alpha, omega-dihydroxy-poly (diorganosiloxanes) with mixed functional silanes, such as alkoxyamidosilanes (DE-PS 1 247 646), and alkoxy-acetoxysilanes of catalysts.

alkoxy-oximosilanes (US-PS 3 269 165) without (EP 98 369) additional

In the first process described above, amines (EP 21 859), amines in admixture with metal carboxylates (US-PS 3 161 614) and amines in admixture with carboxylic acids (EP 137 883), ammonium carbamates, preferably (CH ₃ ) ₂ NH ₂ OCON (CH ₃ ) 2 (DE-PS 3 523 206) and hydroxylamine derivatives (EP 70 786).

However, long reaction temperatures are required for all the alkoxy-terminated catalysts and the high catalysts or systems that have been used to produce polysiloxanes. To do this, the catalysts must be used in a substantial amount, and their removal from the polymer is usually difficult or not at all possible. These disadvantages could be overcome by using alkali metal hydroxides and alcohols (DE-OS 4 022 661, EP-A 457 693, EP-A 376 696) as catalysts. However, extreme activation by hydroxide and alcoholate ions leads to undesirable side reactions, such as polymer rearrangements, so that the catalyst must be inactivated by neutralization as soon as possible after the reaction has proceeded.

silanes unlike reactive, so with alpha, omega but expensive possibly impossible.

In the second process described, the pure organyloxyorganosilanes used are sufficiently reacted without the use of dihydroxy-poly (siloxanes) catalysts. Silage production and removal of fission products is difficult,

Particularly from an economic point of view, the reaction of alpha, omega-dihydroxy-poly (diorganosiloxanes) with alkoxysilanes using suitable catalysts is preferable to the latter process.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a process for the reaction of poly (diorganosiloxanes) with alkoxysilanes which in particular allows the production of poly (diorganosiloxanes) with diorganyloxy-organosilyl or triorganyloxysilyl end groups at a short reaction time already at room temperature.

Surprisingly, it has now been found that the reaction of poly (diorganosiloxanes) and alkoxysilanes in the presence of fluorides leads to the production of poly (diorganosiloxanes) end-alkoxy groups at room temperature for a few minutes, and the fluorides supplied in this mixture are suitable for targeted degradation. high molecular weight poly (diorganosiloxanes).

Accordingly, the present invention provides a process for preparing reaction products from poly (diorganosiloxanes) and alkoxysilanes, wherein the reaction is carried out in the presence of fluoride ions as activator.

The polysiloxane according to the present invention is a polysiloxane or a mixture of polysiloxanes of the formula I

R ² O

R ¹

Si-O - R ³ (I)

R -

in which

R @ 1 and R @ 1 - denote an alkyl or alkoxy group having from 1 to 18 carbon atoms, a phenyl group, a substituted phenyl group and an alkenyl or alkoxyalkyl group having 2 to 18 carbon atoms, wherein R and R ^{@ 1} may be the same or different. .

R and R are hydrogen, alkyl of 1 to 18 carbon atoms, aryl of 6 to 14 carbon atoms, and SiR ' ₃ in which

R 'represents an alkyl or alkoxy group having 1 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms and an alkenyl or alkoxyalkyl group having 2 to 18 carbon atoms, wherein R ² and R ³ may be the same or different and x is a number of 10 to 10 000.

In a preferred embodiment of the present invention, the polysiloxanes have a reticulated structure.

Examples of such polysiloxanes having a mesh-like structure are vulcanized elastomers, such as high temperature vulcanized (HV) elastomers, liquidsilicone (LSR) elastomers, and room temperature vulcanized (RTV) elastomers, which are single-component (1K) or two-component (2K).

The net-like structure of the polysiloxanes may be formed, among others, in the following units.

R

I

T-unit = Si-O-Si-O-Si p

I

ABOUT

I

Si Ξ or

Si =

I

ABOUT

I

Q-unit with Si - O - Si - O - Si p

I o

I

Si =

Groups which are formed by hydrosilylation or peroxidic crosslinking reactions are, for example, alkylene groups.

The alkoxysilane used in the context of the present invention is at least one alkoxysilane or a mixture of several alkoxysilanes of the general formula II

R ² n Si (OR ¹ ) ₄ - _n (II) wherein

R ¹ represents an alkyl group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 8 carbon atoms or a cycloaliphatic hydrocarbon radical having 5 to 7 carbon atoms,

R ² represents an optionally substituted alkyl of 1 to carbon atoms or alkenyl having 2 to 10 carbon atoms, phenyl or substituted phenyl and n is 0, 1 or 2 above.

Particularly preferred alkoxysilanes are tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane and dimethyldimethoxysilane. Also suitable are alkoxysilanes substituted on an alkyl group, such as XCH ₂ CH ₂ CH ₂ Si (OR ¹ ) ₃ , where X = HS-, H ₂ N, R ₂ N 2 Cl- and other substituents.

Activators within the meaning of the present invention are soluble metal and non-metal fluorides in the system.

The metal fluorides within the meaning of the present invention are preferably alkali metal fluorides such as sodium fluoride or potassium fluoride. Non-metallic fluorides are preferably used as the fluoride source. Ammonium fluoride and / or tetraalkylammonium fluoride is particularly preferred, tetrabutylammonium fluoride as well as trialkylamine hydrofluorides such as triethylamine trisulfofluoride [(C ₂ H ₅ ) ₃ N ₃ HF] and other tertiary ammonium polyhydrofluorides are particularly preferred. The activators can be added to the reaction mixture both in pure form and in dissolved form in suitable solvents or alkoxysilanes. Alcohols and alkoxysilanes are particularly suitable solvents.

With the present invention, it has been found that very low concentrations of fluorides are sufficient to function as an activator in the reaction. In the process for producing reaction products from polysiloxanes and alkoxysilanes according to the present invention, preferably 0.001 to 5% by weight, in particular 0.001 to 1% by weight, particularly preferably 0.001 and 0.5% by weight, of fluorides are used, based on the total mixture.

The process of the present invention is carried out at a temperature in the range of 0 ° C to 300 ° C.

In a preferred embodiment of the process according to the invention, the reaction of the polysiloxanes with alkoxysilanes in the presence of fluoride ions after the production of poly (diorganosiloxanes) with triorganylsilyl or diorganyloxyorganosilyl end groups is terminated by precipitation of fluoride ions in the form of sparingly alkaline fluorides they have at least one OH function. Preference is given to using polysiloxanes with a content of 0.01 to 19% by weight of SiOH, based on the polymer, particularly preferably alpha, omega-dihydroxy-poly (diorganosiloxanes).

Likewise, all of the above-described alkoxysilanes of the formula II as well as all of the above-described alkali metal and non-metal fluorides are also applicable. The interruption of the reaction can be achieved by the addition of alkaline earth metal ions. This results in the formation of sparingly soluble alkaline earth metal fluorides which no longer have an activating effect on the system. Any alkaline earth metal salts which are soluble in this system are suitable as the alkaline earth metal compounds. Calcium chloride is particularly suitable. In order to achieve a good dispersion in the reaction mixture and short reaction times, alkaline earth metal salts are added to the reaction mixture in dissolved form. Alcohols such as methanol and ethyl alcohol have proved to be particularly suitable solvents.

The amount of alkaline earth metal compounds used is controlled by the concentration of fluoride ions in the reaction mixture. The alkaline earth metal ions must be used at least in a stoichiometric ratio, based on fluoride ions, and a 20% to 100% excess, based on the stoichiometrically used amounts of fluoride, has proven suitable.

The reaction conditions for the reaction of poly (diorganosiloxanes) with alkoxysilanes are determined by the reactivity of the alkoxysilane used and the desired reaction products. The process of the present invention is carried out at temperatures ranging from 0 to 300 ° C, preferably 15 to 60 ° C, particularly preferably 18 to 40 ° C, and very particularly preferably at room temperature. The reaction time is at least 3 minutes, preferably 5 to 30 minutes. The reaction time depends on the desired degree of occupancy of the end groups. A particularly preferred reaction time at room temperature is less than 10 minutes.

When a polymer is to be used for the production of RTV-1K- (at room temperature vulcanizing 1-component -) - masses, a one-pot process in a mixing unit is offered.

In another embodiment of the present invention, the reaction of the polysiloxanes with alkoxysilanes in the presence of fluoride ions at a temperature in the range of 0 to 300 ° C takes at least 5 minutes.

Polysiloxanes of the formula I may be used in this embodiment. Preferably, however, the aforementioned polysiloxanes with a cross-linked structure are used. However, all of the previously described alkoxysilanes analogous to formula II as well as all the above-described metal and non-metal fluorides are equally applicable.

In this embodiment of the process of the present invention, compounds of formula III are preferably produced as low molecular weight siloxanes.

R ¹

I

I — Si-O

R ¹ i

Si - (III) in which

R and R ¹ represent linear or branched alkyl or alkoxy having 1 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms, alkoxyalkyl or alkenyl having in each case 2 to 18 carbon atoms, wherein R and R ¹ may be the same or different, and y is a number of 3 to 20, preferably 3 to 6, particularly preferred.

In another embodiment, linear and / or branched short-chain siloxanes of the formula IV r ⁴ o • Si-OR (IV) are produced as low molecular weight siloxanes in which:

R @ ¹ and R @ ¹ denote an alkyl or alkoxy group having 1 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms and an alkoxyalkyl or alkenyl group each having from 2 to 18 carbon atoms, wherein R ^{@ 1} and R ^{@ 1} may be the same or different; C 1 -C 18 or -SiR ' ₃ , wherein

R 'represents an alkoxy or alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms and an alkenyl or alkoxyalkyl group having 2 to 18 carbon atoms and is a number of 1 to 200, preferably 3 to 100, particularly preferably 3 to 10 .

The low molecular weight, branched siloxanes of the formula IV can also be used with the low molecular weight cyclenes of the formula III.

with short chain formed in the mixture

The reaction can be carried out both at room temperature and at elevated temperatures. The reaction time depends on the type of poly (diorganosilane) used and the temperature. It can vary between a few hours and several days. Volatile reaction products such as cyclic diorganosilanes can be separated from the reaction mixture by distillation under reduced pressure. The reaction of the polysiloxanes with alkoxysilanes in the presence of fluoride ions can also be carried out in the presence of suitable solvents. Suitable solvents here are any organic solvents such as, for example, toluene, xylene, alcohols or else low-viscosity poly (diorganosilanes) or cyclic diorganosiloxanes.

DETAILED DESCRIPTION OF THE INVENTION

The process according to the present invention using the following examples.

is explained in more detail

In order to test the end examples and the comparative products of the groups, the products were tested as follows.

1. Determination of viscosity using a Haake rotary viscometer;

2. cross-linking test a

3. determination of SiOH content by FT-IR-differential spectroscopy.

For the cross-linking test referred to in point 2, 20 parts by weight of the test mixture are mixed with 1 part by weight of the test solution. This test solution is prepared by dissolving 40% dibutyltin oxide in tetraethyl silicate at 100 ºC. When a rapid increase in the viscosity of the mixture is observed after the addition of the test solution, the mixture gels, this is evaluated as evidence of incomplete reaction of the SiOH groups. If such behavior is not detected and the material is cured under the influence of atmospheric moisture, it can be concluded that the end groups are bound.

Example 1

In a planetary mixer, parts of poly (dimethylsiloxane) are charged with a mixture of 55 parts by weight with OH-terminated groups of 29 parts by weight with a viscosity of 80 poly (diorganosilane)

Pa. and with trimethylsilyl end groups having a viscosity of 100 mPa.s. To this mixture was added 2.5 parts by weight of methyltrimethoxysilane containing 1 part by weight of tetrabutylammonium fluoride. After 10 minutes by weight of a solution of 1 weight of calcium in ethyl alcohol.

0.55 parts of chloride are added

The polymer blend had a viscosity of 15.7 Pa · s immediately after production, which did not change after repeated measurements after one day or seven days. No SiOH groups could be detected by FT-IR spectroscopy. The cross-linking test shows no rapid gelling but provides complete cured test specimens after 24 hours in the presence of moisture on a 2 mm thick layer. From the results it can be deduced that the desired end closure has occurred.

Example 2 (comparative)

Example 1 was repeated without the addition of a catalyst using methyltrimethoxysilane. The mixture had a viscosity of 16.5 Pa.s and a SiOH content of 0.16% by weight. When the test solution is added in the crosslinking test, a strong gelation occurs.

Example 3 (comparative)

Example 1 is repeated without the addition of a calcium chloride solution. The viscosity of the polymer is greatly reduced, reaching about 1 Pa.s after 24 hours. The SiOH content is max. 0.01% by weight. In the cross-linking test, neither gelation nor cross-linking of the material occurs after 24 hours.

Example 4

Example 1 was repeated with the addition of 0.92 parts by weight of a solution of 1% by weight of calcium chloride in ethyl alcohol. The viscosity of the polymer blend is 15.0 Pa.s and does not change over 7 days. SiOH groups are not detectable and there is no gelling in the crosslinking test. After 24 hours, a fully cured molded body is formed.

Example 5

The procedure of Example 1 is carried out with the addition of 1.25 parts by weight of methyltrimethoxysilane with 1% by weight of tetrabutylammonium fluoride. After 12 minutes, 0.27 parts by weight of a 1% solution of calcium chloride in ethyl alcohol was added. SiOH groups are no longer detectable and the viscosity remains unchanged for 7 days at 18.2 Pa.s. No gelling was observed in the crosslinking test.

Example 6

The procedure of Example 1 was carried out using 0.25 parts by weight of methyltrimethoxysilane and 0.25 parts by weight of a solution of 10% tetrabutylammonium fluoride in methanol. The inactivation of the fluoride ions is performed by adding 0.6 parts by weight of a solution of 1% calcium chloride in ethyl alcohol after 10 minutes. The crosslinking test does not result in gelling and the SiOH content is max. 0.01%.

Example 7

This example is intended to show the possibility of using the process of the present invention for the production of RTV-1K-mass in a one-pot process during the consolidation.

55 parts by weight of an OH-terminated poly (dimethylsiloxane) having a viscosity of 80 Pa.s with 29 parts by weight of a trimethylsilyl-terminated poly (dimethylsiloxane) having a viscosity by weight of a solution in methyltrimethoxysilane are introduced into a planetary mixer and wait for

100 mPa.s. Thereafter, 2.5 1% tetrabutylammonium fluoride is mixed for 10 minutes. addition

0.55 parts by weight of a solution of 1% calcium chloride in ethyl alcohol is terminated. Then 9.5 parts by weight of hydrophobized pyrogenic silica (BET surface 110 m ² / g) are added and mixed. One part by weight of diisobutoxy-bis-acetoacetic acid ethyl ester titanate is then added and mixed. The incorporation of the titanium complex proceeds without difficulty. Since the use of OH-terminated polymers usually does not give rise to an undesirable increase in viscosity after the addition of the titanium catalyst, it can be concluded that termination of the polymer has been completed.

The mixture is filled into cartridges. To test the mechanical data, 2 mm thick membranes are drawn and after 14 weeks curing at 23 ° C and 50% relative atmospheric humidity, a tensile and elongation test according to DIN 53504 is carried out.

Tensile stress at 100% elongation 0.32 MPa

Tensile strength 1.80 MPa

Elongation at break 670%

Hardness (after 21 days, DIN 53505) 21 Shore A

The paste did not show any significant change in properties when compared to fresh goods after three months of storage in cartridges at room temperature or at 50 ° C when repeating the mechanical tests.

Example 8

42 parts by weight of OH-terminated poly (dimethylsiloxane) having a viscosity of 80 Pa.s. and 18 parts by weight of trimethylsilyl-terminated P ° (dimethylosiloxane) having a viscosity of 100 mPa.s are introduced into a planetary mixer. Then 2 parts by weight of a solution of 1% tetrabutylammonium fluoride in methyltrimethoxysilane are added, and after a ten-minute break, 0.55 parts by weight of a solution of 1% calcium chloride in ethyl alcohol is added. Then 30 parts by weight of hydrophobized ground chalk stearic acid and 5.5 parts by weight of hydrophobized silica (BET surface 110 m ² / g) are added and mixed. Then, 1 part by weight of diisobutoxy-bis-acetoacetic acid ethyl ester titanium chelate is added and mixed. The incorporation of the titanium complex proceeds without difficulty. Mechanical properties tests were performed as described in Example 7, with the following results.

Tensile stress at 100% elongation Tensile strength Elongation at break Hardness (after 21 days, DIN 53505)

0.49 MPa 1.71 MPa 599%

Shore A

Claims (12)

PATENT CLAIMS Process for producing reaction products from polysiloxanes and alkoxysilanes, characterized in that the reaction is carried out in the presence of fluoride ions as activator. Process according to Claim 1, characterized in that a polysiloxane or a mixture of polysiloxanes of the formula I is used. R ² O R ¹ Si-O - R ³ (I) R - * x in which R and R ¹ represent an alkyl or alkoxy group having 1 to 18 carbon atoms, phenyl, substituted phenyl and the alkenyl or alkoxyalkyl having 2 to 18 carbon atoms, wherein R and R ¹ can be identical or different, 2 3 R and R are hydrogen, alkyl of 1 to 18 carbon atoms, aryl of 6 to 14 carbon atoms, and SiR ' ₃ in which R 'represents an alkyl or alkoxy group having 1 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms and an alkenyl or alkoxyalkyl group having 2 to 18 carbon atoms, wherein R ² and R ³ may be the same or different and x is a number of 10 to 10 000. Method according to either of Claims 1 and 2, characterized in that the polysiloxane has a net-like structure. Process according to one of Claims 1 to 3, characterized in that at least one alkoxysilane or a mixture of several alkoxysilanes of the general formula II is used as alkoxysilane. R ² n Si (OR ¹ ) ₄ - _n (II) wherein R ¹ represents an alkyl group having 1 to 6 carbon atoms, an alkoxyalkyl group having 2 to 8 carbon atoms or a cycloaliphatic hydrocarbon radical having 5 to 7 carbon atoms, R2 represents an optionally substituted alkyl group having from 1 to ² carbon atoms; N is 0, 1, or 2, or a C10 -C10 alkenyl group, a C10 -C10 alkenyl group, a phenyl group or a substituted phenyl group; Method according to one of Claims 1 to 4, characterized in that non-metal fluorides are used as the fluoride ion source. Method according to one of Claims 1 to 5, characterized in that tetraalkylammonium fluoride and / or ammonium fluoride, such as trialkylamine hydrofluorides and other polyhydrofluorides of tertiary organic amines, is used as the fluoride ion source. Method according to one of Claims 1 to 4, characterized in that alkali metal fluorides are used as the fluoride ion source. • Process according to one of Claims 1 to 7, characterized in that 0.001 to 5% by weight, in particular 0.001 to 1% by weight, particularly preferably 0.001 to 0.5% by weight, of fluorides, based on the total mixture, are used in the reaction. Process according to one of Claims 1 to 8, characterized in that the reaction after the production of triorganyloxysilyl-terminated or diorganyloxyorganylsilyl-terminated poly (diorganosiloxanes) is terminated by precipitation of fluoride ions as sparingly soluble alkaline earth metal fluorides, the polysiloxanes used. of the formula I have at least one OH function. • The process according to claim 1, wherein the reaction is carried out at a temperature in the range of 0 to 300 ° C for at least 5 minutes. Process according to one of Claims 1 to 4 and 19, characterized in that the compounds of formula III are produced as low molecular weight siloxanes. Γ R ¹ I I --You are about R R ¹ i Si-η R (III) wherein R and R ¹ represent linear or branched alkyl or alkoxy -C 18 carbon atoms, an aryl group having 6 to 14 carbon atoms, alkoxyalkyl or alkenyl having in each case 2 to 18 carbon atoms, wherein R and R ¹ may be the same or different, and y means the number 3 to 20. Process according to one of Claims 1 to 4 and 10, characterized in that linear or branched short-chain siloxanes of the general formula IV are produced as low molecular weight siloxanes. R The R-Si-OR R '(IV) _It is T R @ 1 and R @ 2 are alkyl or alkoxy of 1 to 18 carbon atoms, aryl of 6 to 14 carbon atoms and alkoxyalkyl or alkenyl of 2 to 18 carbon atoms, wherein R and R ^{@ 1} may be the same or different, R ⁴ represents an alkyl group having from 1 to 18 carbon atoms or a -SiR ' ₃ group wherein: R 'represents an alkoxy or alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms and an alkenyl or alkoxyalkyl group having 2 to 18 carbon atoms and z represents a number of 1 to 200.