Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-06-01
2001-05-22
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S103000, C526S209000, C502S080000, C502S081000, C502S083000
Reexamination Certificate
active
06235859
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a production process for polyvinyl ether and a catalyst used for the same. Polyvinyl ether is a useful material which is widely used as a raw material for pressure sensitive adhesive agents, adhesives and paints.
RELATED ART
Polyvinyl ether is industrially produced by homogeneous cationic polymerization in which a Lewis acid catalyst such as boron trifluoride is used. However, there are the problems that a low temperature of 0° C. or lower which is industrially disadvantageous is required in order to obtain a high molecular polymer and that resulting polyvinyl ether is colored.
On the other hand, known as well is polymerization of polyvinyl ether in a heterogeneous system in which solid acids such as chromium (III) oxide and silica-alumina are used. In this case, however, there is the problem that the polymerization activity is low and if the polymerization goes on, resulting polyvinyl ether is colored or decomposed.
Further, it is known that when polyvinyl ether is polymerized using sulfate or acid clay as a catalyst, it is polymerized at a high temperature of not lower than a room temperature, but there has been the problem that the catalyst has a low polymerization activity and both the molecular weight and the polymerization rate are not raised so much (Kobunshi Kagaku, vol. 18, No. 197 (1961), p. 561 to 566). A solid acid catalyst can be used in a large amount in order to make up for the low polymerization activity, but there have been the problems that the high viscosity of the resulting polymer solution makes it difficult to remove the catalyst after the polymerization and that the quality of the product is reduced.
With respect to a method for solving the problems described above to obtain a polymer at a temperature of not lower than a room temperature, it is disclosed in U.S. Pat. No. 5,691,430 to use a catalyst (sea sand and kaolin) comprising silicon dioxide and at least one metal oxide selected from aluminum oxide, magnesium oxide, iron oxide and titanium oxide. However, the catalyst is subjected to no any treatment for raising an activity, and a natural mineral is used as it is. Accordingly, the activity as a polymerization catalyst is low, so that it takes as long time as 8 hours to one month to obtain the desired polymer.
[Problems to be Solved by the Invention]
An object of the present invention is to solve the problems described above, that is, to provide a process for producing polyvinyl ether at a temperature of not lower than a room temperature which is advantageous for industrial production for short time at a good productivity, and a catalyst used for the above process. [Means for Solving the Problems]
Investigations continued by the present inventors in order to achieve the above object have resulted in finding that a material obtained by subjecting an acid clay mineral to acid treatment to strengthen an activity reveals a surprisingly high activity as a polymerization catalyst for polyvinyl ether, and thus they have come to complete the present invention. The material obtained by subjecting an acid clay mineral to acid treatment includes, for example, a material called ┌Factivated clay┘. The activated clay is obtained by subjecting an acid clay mineral to acid treatment to turn it to a porous structure material having a far larger specific surface area than that of the original acid clay mineral. Since this material has a high specific surface area and a porous structure, it has a very high adsorbing capacity of chemical matters and is used as an adsorbing agent for refining mineral oils and decoloring organic chemicals. However, there have so far been no examples in which it is tried to use this material as a catalyst for cationic polymerization.
Thus, according to the present invention, provided is a production process for polyvinyl ether by polymerizing vinyl ether in the presence of a catalyst, characterized by using an acid clay mineral subjected to acid treatment as the catalyst described above.
The vinyl ether described above is represented by the following Formula (
1
):
CH
2
═CHOR (1)
wherein R represents an alkyl group allowed to have a substituent, a cycloalkyl group, an alkenyl group, an aryl group, an aralkyl group or a silyl group.
The catalyst described above is used usually in an amount falling in a range of 10 to 5000 ppm based on the weight of vinyl ether.
Further, according to the present invention, provided is a catalyst characterized by comprising an acid clay mineral subjected to acid treatment as a catalyst useful for polymerizing vinyl ether to produce polyvinyl ether.
[Embodiment of the Invention]
The catalyst according to the present invention is a catalyst comprising a material obtained by subjecting an acid clay mineral to acid treatment. The acid clay mineral specified in the present invention is a composite oxide containing SiO
2
and Al
2
O
3
as principal components and Fe
2
O
3
, MgO and CaO as trace components. Suitable examples of such acid clay mineral include a group of clay minerals called acid clays such as kaolinite and montmorillonite.
The acid used for the acid treatment shall not specifically be restricted, and mineral acids such as sulfuric acid, hydrochloric acid and nitric acid are usually used.
It is known that the acid clay mineral described above is treated with an acid such as a mineral acid and the like to elute a part of Al
2
O
3
, Fe
2
O
3
, MgO and CaO, whereby a porous structure material having a far larger specific surface area than that of the original acid clay mineral is obtained. This material has a high specific surface area and a porous structure and therefore has a very high adsorbing capacity of chemical matters. In the present invention, it is considered that these high specific surface area and porous structure act effectively to reveal the high activity as an acid catalyst for polymerizing vinyl ether.
Publicly known methods can be used as a method for the acid treatment described above. Included are, for example, (i) a method in which the acid clay mineral is treated with 10 to 50% sulfuric acid at 80 to 90° C. for 1 to 5 hours and then sufficiently washed with water to remove water soluble components, followed by drying and (ii) a method in which the acid clay mineral is immersed in 50 to 80% sulfuric acid for several days to several weeks and then sufficiently washed with water to remove water soluble components, followed by drying. The method (i) is preferred since it is simple and efficient.
The catalyst prepared in the manner described above has a specific surface area of 150 to 300 m
2
/g. The specific surface area is increased to a large extent while the acid clay mineral has a specific surface area of 50 to 100 m
2
/g.
The material obtained by subjecting an acid clay mineral to acid treatment includes, for example, a material called activated clay. The activated clay is obtained by subjecting an acid clay mineral to acid treatment to turn it to a porous structure material having a far larger specific surface area than that of the original acid clay mineral.
The catalyst according to the present invention has a very high activity, and therefore even if the use amount of the catalyst is 100 ppm or less based on vinyl ether, the polymerization reaction goes on sufficiently well, but the catalyst amount may be increased if necessary. The use amount of the catalyst is usually 10 to 5000 ppm, preferably 50 to 1000 ppm based on the amount of vinyl ether. Too much catalyst amount causes discoloration of the yielded material or reduces the quality of the product.
Vinyl ether used as a raw material monomer in the present invention is, for example, the compound represented by Formula (1) described above. To be specific, suitable examples thereof include methyl vinyl ether, ethyl vinyl ether, isopropyl vinyl ether, n-propyl vinyl ether, isobutyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, n-octyl vinyl ether, cyclohexyl vinyl ether, phenyl vinyl ether, benzyl vinyl
Naka Akio
Shimasaki Yuuji
Choi Ling-Siu
Nippon Shokubah Co Ltd
Wu David W.
LandOfFree
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