FR2731227A1 - SILICON BALANCING CATALYST AND POLYCONDENSATION AND / OR REARRANGEMENT METHOD USING SUCH A CATALYST - Google Patents

Abstract

Disclosed is a silicone equilibration catalyst, which is the reaction product of a linear phosphonitrilic halide, such as a linear phosphonitrilic chloride, and a triorganosiloxy terminated polydiorganosiloxane. This catalyst is used for the polycondensation and rearrangement of various polydiorganosiloxanes, in particular low molecular weight siloxane oils.

Description

I Balancing silicone catalyst and polycondensation process

  and / or rearrangement using such a catalyst. The present invention relates to a silicone balancing catalyst, in the form of a reaction product of a liquid silicone having triorganosiloxy end units and of a linear phosphonitrilic halide (LPNQ), Q denoting a halogen atom and preferably a chlorine atom. The present invention further relates to the use of an LPNQ-silicone catalyst for carrying out the condensation and / or balancing of liquid silanols and their mixtures with liquid silicones having patterns.

triorganosiloxy terminals.

  Silicone gums were prepared by balancing cyclic diorganosiloxanes, such as octamethylcyclotetrasiloxane, with triorganosiloxy-terminated polydiorganosiloxanes, such as hexamethyldisiloxane. Balancing can be carried out using a strong base or a strong acid such as sulfuric acid. Although interesting results have been obtained with such methods, the resulting high-chain, stopped-chain polydiorganosiloxanes often have to be freed of undesirable oligomeric cyclic products from side reactions

catalytic parasites.

  Other organopolysiloxane balancing methods use an LPNQ catalyst, and in particular a linear phosphonitrilic chloride (LPNC) corresponding to the formula: Cl3P (NPCl2) nNPCl3.PC16, (1) in which n represents a number equal to 0- 4, preferably 1 or 2. The LPNC catalyst can be prepared by the methods described in US Pat. No. 3,839,388, the content of which is incorporated herein by reference. Silydol-terminated polydiorganosiloxanes can be condensed therebetween using an LPNQ catalyst. Mixtures of such silanol-terminated polydiorganosiloxanes and of diorganosiloxanes having triorganosiloxy end units can be balanced using an LPNQ catalyst, such as the LPNC catalyst of formula (1). For example, US Pat. No. 2,990,419 describes a process for the preparation of organopolysiloxane oils by balancing a diorganosiloxane blocked at the chain end with a hydroxy group and a diorganosiloxane blocked at the chain end with a triorganosilyl group , by means of a compound containing phosphorus and nitrogen, such as a phosphonitrilic halide. Although good results are obtained by this process, it has been found necessary to continuously blow air into the mixture, for several days, at different temperatures, to stabilize the siloxane oil. As shown in US Pat. No. 3,835,388, there are other methods using a phosphonitrilic halide as a balancing catalyst for carrying out the condensation and / or balancing of liquid silanols and their mixtures, these methods involving the use of vacuum

to facilitate condensation.

  U.S. Patent No. 5,008,229 relates to solutions of phosphonitrilic chlorides in an organic solvent and the use of such compositions to accelerate the condensation and / or equilibration of diorganosiloxanes blocked at the chain end by the hydroxy group. Better results are thus obtained, but the use of an organic solvent such as ethyl acetate to facilitate the dissolution of phosphonitrilic chloride, can cause environmental problems. German patent application 3,725,377 describes a process in which the use of an organic solvent is avoided by using as a catalyst a reaction product of a phosphorus and nitrogen chloride and a cyclic diorganosiloxane such as octamethylcyclotetrasiloxane. However, experience shows that the reaction products of phosphorus and nitrogen chloride and octamethylcyclotetrasiloxane often have viscosities exceeding several thousand centipoises, which can make such products unsuitable as catalysts for polymerizations in the reactor. of an extruder. It is therefore desirable to develop balancing catalysts and improved methods for balancing polydiorganosiloxanes, which minimize environmental problems. The present invention is based on the discovery that a linear phosphonitrilic chloride (LPNC) of formula (1) can be reacted with a linear siloxane oil corresponding to the formula: R (RI) 2si [OSi (R ') 2 ] mOSi (R1) 2R, (2) in which R represents a hydrogen atom or a monovalent organic group with C1 to C18, R1 represents a monovalent organic group with C1 to C13, preferably a methyl, vinyl or phenyl group, and m represents an integer equal to 0 to 100, limits included, to produce an LPNC-siloxane catalyst in the form of a homogeneous mixture. Furthermore, contrary to what happens in the case of the reaction product of German patent application 3 725 377, the reaction of the products of formulas (1) and (2) does not lead to a significant increase in viscosity. In addition, the resulting LPNC-siloxane reaction product was found to be effective as

  balancing catalyst for the preparation of organopolysiloxanes.

  According to a first aspect, the present invention relates to a silicone balancing catalyst, having a viscosity in the range from approximately 1 to approximately 1000 centistokes and being in the form of a reaction product of approximately 0 , 1 to about 3.0 parts by weight of a phosphonitrilic halide for

  parts of a linear siloxane oil of formula (2).

  According to a second aspect, the present invention relates to a process for polycondensation and / or rearrangement of organosiloxanes containing silanol groups, having an average ratio of 1.9 to approximately 2.1 organic groups per silicon atom, said organic groups being bound to silicon by carbon-silicon bonds, a process which comprises: (1) stirring a mixture comprising an organosiloxane containing silanol groups and approximately 2 to approximately 200 ppm by weight of a balancing catalyst, a temperature of about 30 to about 150 C, and (2) quenching the balancing catalyst in the mixture from (1), when the desired level of silanol has been reached, said balancing catalyst being a silicone having a viscosity in the range of from about 1 to about 1000 centipoise and in the form of a reaction product of 0.1 to 3.0 parts of a phosphonitrilic halide per 100 part s

  of a linear siloxane oil of formula (2).

  Among the organic groups represented by R in formula (2), mention may be made of C1 to C8 alkyl groups, for example methyl, ethyl, propyl and butyl groups, and haloalkyl groups such as the trifluoropropyl group. In addition, R may be a C2 to C8 alkenyl group, such as a vinyl or allyl group, a C3 to C8 cycloalkyl group, such as the cyclopropyl group, and a cycloalkenyl group such as the cyclopentenyl group. R can also represent a C6 to C13 aryl group, such as a phenyl, tolyl, xylyl or naphthyl group, or a haloaryl group, for example a chlorophenyl group. R preferably represents a methyl, vinyl or phenyl group. The groups represented by R1 in formula (2) are all the monovalent organic groups in C1 to C13, mentioned previously for R. The expression "organosiloxane containing silanol groups"

  used in the description of the present invention, encompasses the

  liquid polydiorganosiloxanes corresponding to the formula: HO- [Si (R1) 2-O] xH, (3) and mixtures thereof with liquid polydiorganosiloxanes corresponding to the formula: RI [(R1) 2SiO] yH, (4) x and y representing whole numbers having a value of from about 5 to about 10,000, limits included, preferably from about 20 to about 1000, limits included. These liquids can have viscosities in the range of from about 5 to about 500,000 centipoise, preferably in the range of from about 10 to about 30,000 centipoise. The liquids of formula (3) can be prepared by hydrolysis of a diorganosilane such as dimethyldichlorosilane, using a controlled amount of water, in the presence of an appropriate acid or basic catalyst. The liquids of formula (4) can be prepared by balancing a mixture of compounds containing triorganosiloxy units and diorganosiloxy units. The liquids of formulas (3) and (4) may contain from about 0.02 to about 8.0% by weight of hydroxy groups bound to silicon. Processes for the preparation of liquids of formulas (3) and (4) are described in U.S. Patent No. 3,541,044, the content of which is

  incorporated here for reference.

  The linear siloxane oil of formula (2) can be prepared by balancing a mixture of a cyclic polydiorganosiloxane and a disiloxane blocked at the end of the chain by a triorganosiloxy group, in the presence of a conventional balancing catalyst , such as a strong acid such as sulfuric acid, or a hydroxide of

  alkali metal such as potassium hydroxide.

  The balancing catalyst or LPNQ-siloxane catalyst of the present invention can be prepared by heating and vigorously stirring a mixture of the linear siloxane oil and LPNQ for 1 to 8 hours, at a temperature of 90 ° C. to 140 ° C. C. It is preferred to carry out the reaction under an inert atmosphere, for example under an inert gas such as nitrogen. After forming a clear solution, the volatiles can be removed by distillation under reduced pressure. In place of linear phosphonitrilic chloride (LPNCl), the balancing catalyst may contain phosphonitrilic bromide

  linear (LPNBr) or linear phosphonitrilic fluoride (LPNF).

  Balancing or polycondensation of the organosiloxanes containing silanol groups of formulas (3) and (4) can be carried out, using an effective amount of the LPNQ-siloxane catalyst as defined above. Although it is preferred initially to heat the organosiloxane containing silanol groups at a temperature in the range of 90 ° C. to 140 ° C., before the addition of the LPNQ-siloxane catalyst, the order of addition of the various ingredients is not of fundamental importance. I have also found it advantageous to stir the mixture under reduced pressure, such as 0.1-10.0 torr, while heating it. After a reaction time of about 2 to about 20 minutes, the reaction can be stopped by adding a quencher for the LPNQ-siloxane catalyst. An extinguisher suitable for the catalyst can be used at a rate of 10 to 200% by weight relative to the LPNQ-siloxane catalyst. Among the useful catalyst extinguishers, mention may be made of organosilazanes such

  than hexamethyldisilazane, the lithium salt of hexa-

  methyldisilazane, lithium trimethylsilanolate, silylamines, and

  amines such as triethylamine, pyridine and butylamine.

  Organopolysiloxanes, such as silicone gums and liquid silicones, prepared in accordance with the process of the present invention, can be used as filament lubricants, transformed into elastomers or used in the production of silicone compositions vulcanizable at ordinary temperature,

catalyzed with platinum.

  The invention is illustrated by the following examples in

  which all parts are by weight, unless otherwise indicated.

Example 1

  A mixture of 20.5 g of phosphorus pentachloride, 2.7 g of ammonium chloride and 50 ml of tetrachloroethane is stirred and heated under reflux for 8 hours. The mixture is then poured into petroleum ether. A light yellow precipitate is formed. After removing traces of solvent by vacuum distillation, 14 g of light yellow crystals are obtained. According to the preparation process, the

  product is a linear phosphonitrilic chloride (LPNC1).

  A mixture of 100 g of a trimethylsiloxy-terminated polydimethylsiloxane oil having a viscosity of centistokes and 2.0 g of LPNC1 is stirred vigorously for 8 hours at 100 ° C. under a nitrogen atmosphere. Once a clear homogeneous mixture has been formed, the products with low boiling point are eliminated by heating the mixture to 100 ° C. under reduced pressure (1.0 torr) for 15 minutes. 97 g of a clear oil are thus obtained,

  hereinafter referred to as "LPNCl-trimethylsiloxy catalyst".

Example 2

  The procedure of Example 1 is repeated, except that the liquid polydimethylsiloxane with trimethylsiloxy termination is replaced by a liquid polydimethylsiloxane with vinyldimethylsiloxy termination, having a viscosity of 250 centistokes. We

  96 g of a clear "LPNCl-vinyldimethylsiloxy catalyst" are obtained.

Example 3

  A mixture of 60 g of a silanol-terminated polydimethylsiloxane, having a viscosity of 1000 centistokes, and 1 g of decamethyltetrasiloxane is heated to 100 C. The LPNC1-trimethylsiloxy catalyst is then added to the mixture 20 ppm (60 μl). The mixture is stirred under a pressure of 1 torr, at 100 C. There is initially a rapid increase in viscosity, which is followed by a reduction in viscosity. After 5 minutes, the catalyst is quenched by the addition of 0.002 g of hexamethyldisilazane. The effectiveness of the LPNCl-trimethylsiloxy catalyst as a balancing catalyst is demonstrated by the formation of 60 g of a trimethylsiloxy-terminated polydimethylsiloxane, having a viscosity of 200 centistokes and containing less than 50 ppm of groups.

silanol terminals.

Example 4

  The procedure of Example 3 is repeated, except that the LPNCl-trimethylsiloxy catalyst is replaced by 20 ppm of the LPNCl-vinyldimethylsiloxy catalyst. A substantially equivalent amount of trimethylsiloxy-terminated polydimethylsiloxane is obtained, having a viscosity of 200 centistokes and

  containing less than 50 ppm of silanol end groups.

Claims (10)

  1. A silicone balancing catalyst having a viscosity in the range of from about 1 to about 1000 centistokes and in the form of a reaction product from about 0.1 to about 3.0 parts by weight of a phosphonitrilic halide per 100 parts of a linear siloxane oil corresponding to the formula: R (R ') 2Si [OSi (RI) 2] mOSi (R') 2R, (2) in which R represents a hydrogen atom or a monovalent organic group in C1 to C18, RI represents a monovalent organic group in C1 to C13 and m represents an integer equal to 0 to , terminals included.   2. silicone balancing catalyst according to claim 1, characterized in that the phosphonitrilic halide is a phosphonitrilic chloride.   3. silicone balancing catalyst according to claim 1, characterized in that the linear siloxane oil is   a trimethylsiloxy-terminated polydimethylsiloxane.   4. silicone balancing catalyst according to claim 1, characterized in that the linear siloxane oil is   a vinyldimethylsiloxy-terminated polydimethylsiloxane.   5. Process for polycondensation and / or rearrangement of organosiloxane containing silanol groups, having an average ratio of approximately 1.9 to approximately 2.1 organic groups per silicon atom, said organic groups being linked to silicon by carbon-silicon bonds, characterized in that it comprises: (1) stirring a mixture comprising an organosiloxane containing silanol groups and approximately 2 to approximately 200 ppm by weight of a balancing catalyst, at a temperature from about 30 to about C, and (2) quenching the balancing catalyst in the mixture from (1) when the desired level of silanol has been reached, said balancing catalyst being a silicone having a viscosity included in the range of about 1 to about 1000 centipoise and in the form of a reaction product of 0.1 to 3.0 parts of a phosphonitrilic halide per 100 parts of a linear siloxane oil meets ant to the formula: R (R ') 2Si [OSi (R1) 2] mOSi (R1) 2R, (2) in which R represents a hydrogen atom or a monovalent organic group C1 to C18, R1 represents a group monovalent organic in C1 to C13 and m represents an integer equal to O to , terminals included.   6. Method according to claim 5, characterized in that the balancing catalyst is a reaction product of a phosphonitrilic chloride. 7. Method according to claim 6, characterized in that the balancing catalyst is a reaction product of a   trimethylsiloxy-terminated polydimethylsiloxane.   8. Method according to claim 6, characterized in that the balancing catalyst is a reaction product of a   vinyldimethylsiloxy-terminated polydimethylsiloxane.   9. Method according to claim 5, characterized in that the   catalyst is quenched using an organosilazane.   10. Method according to claim 9, characterized in that   the organosilazane is hexamethyldisilazane.