JPS6411660B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a fluorosilicone-containing chain terminator,
The present invention relates to new and improved fluorosilicone polydimethylsiloxanes particularly suitable for use as chain terminators in the production of low energy molding (LEM) copolymers and methods for making such chain terminators. For example, [(CH ₃ ) ₂ SiO] ₄ and [CF ₃ (CH ₂ ) ₂ Si
( _CH3 )O] ₃ and can be prepared by equilibration reactions and by the use of readily available catalysts such as calcium hydroxide. Chain terminators have long been needed. Such chain terminators are necessary for use in the preparation of vinyl-terminated fluorosilicone polydimethylsiloxane copolymer compositions. Furthermore, such chain terminators may be used in cases where, for example, the fluorosilicone content in mole % is too low, the vinyl end groups have to be recaptured, or the viscosity has to be reduced for special applications. It can be applied to the regeneration of low energy molding (LEM) copolymers that are out of specification. The present invention provides a process for the production of a fluorosilicone chain terminator, which includes the production of a fluorosilicone polydimethylsiloxane equilibrated chain terminator and a fluorosilicone chain terminator having a range of fluorosilicone contents that make the chain terminator particularly suitable for the aforementioned purposes. provide. Common for the production of these new and improved fluorosilicone polydimethylsiloxane chain terminators useful in reducing the molecular weight of high molecular weight copolymers and useful in reserving vinyl end groups on the copolymer chain. The raw material will be a substandard copolymer characterized by the absence of essential vinyl end groups and reduced density. These characteristics usually make substandard copolymers unsatisfactory as base components for use in low energy molding systems. These requirements include a fluorosilicone content in the range of 30 mol% to 60 mol% and the following formula: (In the formula, R _F represents CF ₃ CH ₂ CH ₂ −, and x is approximately
10-30 and y is about 20-50). To further explain the background art of the present invention and to make the invention easier to understand, low energy molding (LEM) compositions, i.e., used to make thermosetting silicone rubbers by copolymerization, are described below. It should be noted that in the production of higher molecular weight copolymers, the particular chain terminator chosen to terminate the copolymerization process is often determined by the polymerization method to be used. Should.
Other factors considered in making this determination are the desired viscosity of the final product, the desired molecular weight of the final product, and the desired mole percent fluorosilicone content of the copolymer produced. The copolymers which can be advantageously prepared in accordance with the present invention find common uses such as in solvent resistant transparent pipe and electrical cable receptacle pin sealants and aircraft fuel line sealants. Furthermore, such copolymers often retain their physical integrity over a temperature range of, for example, -75°C to +100°C while toluene and
It is formed with a fluorosilicone content of at least 50 mole percent to provide a high degree of resistance to aromatic solvents such as -4 fuels. Additionally, fluorosilicone polydimethylsiloxane chain terminators are often used in the production of low viscosity (300-1000 centipoise) copolymers for use as bases for polytetrafluoroethylene (PTFE)-containing greases. The preparation of the fluorosilicone chain terminators of the present invention is accomplished by a polymerization process commonly referred to as "equilibration." As used herein, the term "equilibrium" refers to the formula: A cyclic monomer such as octamethylcyclotetrasiloxane of MOH (M is an alkali metal, preferably potassium) catalyst and the formula: (where R _F is CF ₃ −CH ₂ −CH ₂ − and Me
is CH ₃ -) with a monomer such as 3,3,3-trifluoropropylmethylsiloxane cyclic trimer, thereby producing linear products and The equilibrium mixture of cyclic products has a linear to cyclic ratio of approximately 80% linear
-90%, cyclic about 10% to about 20%. Furthermore, the distribution between linear and cyclic in the resulting mixture is a function of both the polymerization conditions and the type of catalyst. Furthermore, the fluorosilicone chain terminators of the present invention can be used in conjunction with low molecular weight fluorosilicone polydimethylsiloxanes containing at least 30 mole %, preferably from 30 to 60 mole %, fluorosilicone derived from starting monomers with various activity coefficients. It is a polymer. A mol% content of at least 30 mol% is necessary to ensure solubility of the chain terminator in the equilibrium reaction mixture. Fluorosilicone contents below 30 mole % cause phase separation and thus render the chain terminator inactive. Fluorosilicone contents of more than 60 mole % do not give any more desirable results and result in a waste of expensive cyclic monomer. The term "fluorosilicone" means "containing a 3,3,3-trifluoropropylmethylsiloxane moiety"
is defined as meaning. Highly strained fluorosilicone cyclic trimer from 130℃ to 160℃
The ring opens rapidly with the generation of exothermic heat. Initially, the 3,3,3-trifluoropropylmethylsiloxane cyclic trimer opens to form a homopolymer, then AAAAA- as the octamethylcyclotetrasiloxane ring opens and adds to the growing chain. Separate blocks like BBBB are formed. By continuing the polymerization at 160° C. for about 10 hours, the chains become random due to equilibration. Chain terminators containing 30 to 60 mole percent fluorosilicone are prepared by base-catalyzed equilibration of tetramethyldivinyldisiloxane with octamethylcyclotetrasiloxane cyclic tetramer and 3,3,3-trifluoropropylmethylsiloxane cyclic trimer. It can be manufactured by. The octamethylcyclotetrasiloxane used ensures dryness of the reactant mixture prior to polymerization and controls the amount of methylsiloxane in the resulting copolymer in the range of about 40 mole percent to about 70 mole percent. The components used are expressed in approximate weight percentages and the desired reactions can be obtained using these components and following the procedures described below.

[Table] Sufficient amount to provide a composition derived from the reaction of the components described above was prepared according to the following method. A stainless steel equilibration reactor equipped with a condenser is first purged with nitrogen to eliminate moisture and oxygen.
The equilibration reactor was then charged with 158 parts of octamethylcyclotetrasiloxane and an excess of 30 parts for drying.
and 262 parts of 3,3,3-trifluoropropylmethylsiloxane cyclic trimer are charged with moderate stirring. The contents of the reactor were heated to 150-160°C and with a nitrogen purge an excess of 30 parts of octamethylcyclotetrasiloxane (typically about a 10% excess of octamethylcyclotetrasiloxane for the charge was 10 ppm moisture). (which would ensure dryness below) to reduce the water content to below 10 ppm. Reduce the reactor temperature to 115-125℃,
48.2 parts of tetramethylvinyldisiloxane and 0.014 g of potassium hydroxide (as a colloid in octamethylcyclotetrasiloxane) are then added. The reaction is exothermic, with a maximum temperature of approximately 127°C ~
Reaching a range of approximately 133℃. When the exotherm begins to subside, the reactor temperature is increased to about 145°C to about 150°C and at that temperature the volatile content of the product is less than 20%;
Hold at 25° C. for 10 hours until the viscosity is in the range of 15 to 22 centistokes and the product density is about 1.090 to about 1.130. The fluorosilicone chain terminator is then neutralized with phosphoric acid, filtered and stored in a clean drum. The results of the analysis have the following composition expressed in approximate weight percent and approximate mole percent.

【table】

[Table] The experimental formula of the fluorosilicone chain terminator obtained was as follows. R _F = CF ₃ CH ₂ CH ₂ -, Vi = CH ₂ = CH -, x =
22,y=38,Me= _CH3- In the preparation of fluorosilicone copolymer liquids having a fluorosilicone content of 30 mol% to 60 mol%, the fluorosilicone chain terminator of the present invention is used in a suitable weight % and as follows: It was effectively used according to the method of

[Table] Sufficient amount of fluorosilicone copolymer derived from the above-mentioned components was prepared according to the following method. 1750 g of 3,3,3-trifluoropropylmethylsiloxane cyclic trimer, octamethylcyclotetrasiloxane in a stainless steel equilibration reactor.
Charge 2330 g (including 200 g excess for purge drying) and 271 g fluorosilicone chain stopper. The reaction system is heated to about 120° C. and excess tetramer is purged with nitrogen to reduce the water content to less than 10 ppm water. The reaction is carried out at about 120° C. with 0.12 g of potassium hydroxide catalyst (as a colloid in octamethylcyclotetrasiloxane) and is an exothermic reaction. When the temperature begins to subside (after 4-10 minutes), the reactor temperature is increased to about 155°C to about 160°C and held at that temperature for about 7 hours, then neutralized with phosphoric acid. The reaction yielded 3428 g (83% recovery) of a copolymer having a viscosity of about 15,000 to about 25,000 centipoise and a density of about 1.100 to about 1.200 at 25°C. The use of the novel fluorosilicone chain terminators of the present invention is effective for the regeneration of off-spec copolymers characterized by the substantial absence of vinyl end groups and reduced density. A representative copolymer suitable for modification by this method can be characterized by the following empirical formula. where the molecular weight is greater than or equal to 50,000 to about 250,000, x is equal to about 250 to about 1200, and y is about 200 to about 250,000.
equals about 1150 and R is CH ₃ −CH ₂ =CH− or
OH and R _F is CF ₃ CH ₂ CH ₂ −. After treatment according to the invention, this copolymer has x
is from about 185 to about 200, y is from about 180 to about 195, the total molecular weight is from about 40,000 to about 50,000, and R is _CH2 =CH-. A typical mixture useful in this method consists of the following components:

[Table] The copolymers shown first here are about 50,000 to about
has a molecular weight of 250,000, x equals about 250 to about 1200, y equals about 200 to about 1150, and R is _CH3- ,
CH ₂ = CH- or OH and R _F is
CF ₃ CH ₂ CH ₂ −. The following example is an example of a method for using fluorosilicone chain terminators to regenerate off-spec copolymers. Ingredients are expressed in approximate weight percentages and methods are as outlined below.

[Table] Sufficient amount of copolymer that was out of specification was regenerated by the following method. 2290 g of off-spec copolymer, 750 g of 3,3,3-trifluoropropylmethylsiloxane cyclic trimer, octamethyl in a clean, dry reactor equipped with a means of evacuation, a heating element and an agitator for moderate agitation. 160 g of cyclotetrasiloxane and 118 g of fluorosilicone chain terminator were introduced. The system was heated to 120°C and the octamethylcyclotetrasiloxane was purged with nitrogen to reduce the water content.
The amount was reduced to below 10ppm. Sufficient potassium hydroxide to give a catalyst level of 60 ppm was added with moderate stirring. When the exotherm subsided, the reaction temperature was raised to 160°C and held at 160°C for 6 hours. The catalyst was then neutralized with phosphoric acid and the temperature of the reaction system was reduced to 145
The volatile content was reduced to less than 3.0% by vacuum stripping at 40-70 mm of mercury while maintaining between 160°C and 160°C. The regenerated copolymer had a recovery of 73.4% (2506 g) and had a Bruckfield viscosity at 25°C of about 15,000 to about 25,000 centipoise and a density of about 1.1580 to about 1.1800. Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to these specific embodiments, but includes all modifications within the scope of the claims.

Claims (1)

[Claims] 1. It has the following empirical formula and the viscosity at 25°C is approximately
30-70 centipoise, density approximately 1.09-1.130
Fluorosilicone polydimethylsiloxane equilibration chain terminator: Here, R _F is CF ₃ CH ₂ CH ₂ −, and X is approximately 10~
30, Y is approximately 20-50. 2. The chain terminator according to claim 1, which has the following general analytical composition. [Table] 3 The viscosity at 25℃ including the following steps is approximately 30
Process for Preparing ~70 Centipoise Fluorosilicone Polydimethylsiloxane Equilibrated Chain Termination Agent: (A) At an approximate temperature of 145-155°C in the presence of 30-55 ppm alkali metal hydroxide catalyst, (i) 30-60 wt. % of 3,3,3-trifluoropropylmethylsiloxane cyclic trimer, (ii) 25-65% by weight of octamethylcyclotetrasiloxane, and (iii) 5-15% by weight of tetramethyldivinyldisiloxane. react a mixture of
and (B) after achieving equilibration, the catalyst in the reaction mixture is neutralized with phosphoric acid.