Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-12-17
2003-05-06
Metzmaier, Daniel S. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C516S059000, C516S924000, C528S010000
Reexamination Certificate
active
06559224
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates a process for producing a polyorganosiloxane latex.
2. Description of Related Art
A polyorganosiloxane latex can be used as various polymeric materials such as adhesives, sealants, and impact resistant resins. As a process for producing such a polyorganosiloxane latex, a process in which a liquid mixture containing an organosiloxane, which is a monomer, an initiator, a surface active agent, and water is emulsified, and the emulsion is heated to allow polymerization to occur therein, and a process in which a polyorganosiloxane, which is a polymer, is dispersed to form an emulsion using an emulsifying and dispersing machine have been known. However, there has been a problem that in the case when the water content is large with respect to the organosiloxane, the emulsion is unstable and phase separation of the organosiloxane and water occurs with the passage of time. Therefore, there have been problems that the process of polymerization of the organosiloxane is retarded, the organosiloxane is not effectively used for the polymerization, and unpolymerized organosiloxane emerges on the surface of the latex.
On the other hand, in the process in which a polyorganosiloxane is dispersed in water using an emulsifying and dispersing machine, a special emulsifying and dispersing machine is required as described in Japanese Unexamined Patent Application, First Publication (Kokai), No. Hei 8-198969, or there is a disadvantage that the particle diameters of the polyorganosiloxane become as large as 0.4 &mgr;m or larger, which degrades the transparency of the coated film obtained from the latex.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a process for producing a polyorganosiloxane latex according to which polymerization of a cyclic organosiloxane proceeds easily, the cyclic organosiloxane effectively becomes a polyorganosiloxane from which cyclic organosiloxane does not emerge, and the weight-average diameter of the polyorganosiloxane is controlled to under 0.4 &mgr;m.
The subject matter of the present invention is a process for producing a polyorganosiloxane latex, the process comprising polymerizing a paste which contains at least a cyclic organosiloxane, a surface active agent, an initiator, and water, and which is an emulsified dispersion of the cyclic organosiloxane, in which the water content is in a proportion of 1 to 66 parts by weight with respect to 100 parts by weight of the cyclic organosiloxane.
By producing the polyorganosiloxane latex according to the above production process, phase separation of the organosiloxane and water does not occur during the polymerization of the paste. Accordingly, polymerization of the cyclic organosiloxane proceeds easily, and a pasty polyorganosiloxane latex from which the cyclic organosiloxane does not emerge can be produced. In addition, by diluting the pasty polyorganosiloxane latex with water and dispersing the polyorganosiloxane in the water, a polyorganosiloxane latex which is stable without emergence of the cyclic organosiloxane can be obtained.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the paste for producing the polyorganosiloxane latex contains at least a cyclic organosiloxane, a surface active agent, an initiator, and water, and is obtained by emulsifying a dispersion of a mixed liquid having the composition such that the water content is 1 to 66 parts by weight with respect to 100 parts by weight of the cyclic organosiloxane using an emulsifying and dispersing machine.
The water content in the paste for producing the polyorganosiloxane latex is in a proportion of 1 to 66 parts by weight with respect to 100 parts by weight of the cyclic organosiloxane. A paste having a water content of less than 1 part by weight would not be able to exist stably. A water content of 1 to 66 parts by weight would not cause separation of the cyclic organosiloxane and water, which would emerge as a problem if the water content exceeded 66 parts by weight. This is attributed to the fact that a paste having a water content of 1 to 66 parts by weight has a high viscosity and no fluidity in comparison with an emulsion with a water content of more than 66 parts by weight. Since a paste having a water content of 1 to 66 parts by weight does not cause separation of the cyclic organosiloxane and water, the cyclic organosiloxane is effectively polymerized to form a polyorganosiloxane by heat polymerization of the paste.
If the water content is small, it is sometimes difficult to obtain a paste by feeding a liquid mixture, prepared in advance by combining the entire amounts of the cyclic organosiloxane, the surface active agent, the initiator and water, into an emulsifying and dispersing machine. In such a case, a paste can be obtained by feeding the cyclic organosiloxane into the emulsifying and dispersing machine, and mixing the cyclic organosiloxane with the surface active agent, the initiator, and water in the emulsifying and dispersing machine to disperse the cyclic organosiloxane to form an emulsion. For example, a paste having a small water content can be obtained by feeding the surface active agent, the initiator, and water into the emulsifying and dispersing machine in advance and mixing them to prepare a liquid mixture, and adding the cyclic organosiloxane dropwise to the liquid mixture while successively mixing the cyclic organosiloxane with the above-described liquid mixture in the emulsifying and dispersing machine so as to successively disperse the cyclic organosiloxane to form an emulsion.
As the emulsifying and dispersing machine which is used when preparing the paste, a known type of emulsifying and dispersing machine for use in emulsification and dispersing such as a homomixer, a line mixer, a colloid mill, and a homogenizer can be used. A single emulsifying and dispersing machine or a combination of two or more emulsifying and dispersing machines may be used. The paste which is an emulsified dispersion of the cyclic organosiloxane in water can be obtained using such an emulsifying and dispersing machine.
The thus-obtained paste is polymerized by heating or the like to form a pasty polyorganosiloxane latex (hereinafter occasionally referred to as “polymerized paste”). The heating temperature for polymerizing the cyclic organosiloxane in the paste is not particularly limited. However, in view of the production of the polyorganosiloxane latex within a short period of time, a heating temperature of 30° C. or higher is preferable, and a heating temperature of 50° C. or higher is particularly preferable.
The polymerization of the cyclic organosiloxane is an equilibrium reaction, and the conversion in general under equilibrium condition is about 80 to 90%. According to the production process of the present invention, the paste is preferably polymerized so that a conversion of 80 to 90% can be achieved.
By diluting the above-obtained polymerized paste with water and dispersing the polymerized paste in the water, a polyorganosiloxane latex which has a low concentration of polyorganosiloxane and has a low viscosity can be obtained. This latex diluted with water is stable, and the cyclic organosiloxane does not emerge. Accordingly, production of a latex having a desired concentration of polyorganosiloxane and which has excellent coating properties is easy according to the present invention. Furthermore, normally the dilution of the polymerized paste with water is carried out so that the concentration of the polyorganosiloxane becomes about 20 to 45% by weight.
An example of the cyclic organosiloxane is one expressed by a general formula represented by the following Chemical Formula 1.
(in the formula, n is a positive integer, preferably 3 to 8, and each of R
1
and R
2
, which may be the same or different, indicates a hydrogen atom or a hydrocarbon group such as a methyl group, an ethyl group, a propyl group, and a phenyl group).
Specific examples of the cyclic organosiloxane are hexamethylcyclotrisiloxane, octamethy
Kikuya Nobuyuki
Sasaki Akinobu
Sato Haruki
LandOfFree
Process for producing polyorganosiloxane latex does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing polyorganosiloxane latex, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing polyorganosiloxane latex will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3068441