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
2001-02-28
2002-09-10
Henderson, Christopher (Department: 1713)
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...
C524S819000, C524S832000
Reexamination Certificate
active
06448330
ABSTRACT:
TECHNICAL FIELD
This invention relates to an aqueous emulsion of a homopolymer or copolymer of at least one monomer selected from the group consisting of an acrylic acid ester monomer, a methacrylic acid ester monomer, a styrenic monomer and a diene monomer, and to a process for producing the aqueous emulsion.
BACKGROUND ART
Emulsions of homopolymers and copolymers prepared by polymerizing various ethylenically unsaturated monomers and diene monomers, such as a styrene-butadiene copolymer emulsion, an acrylic acid ester resin emulsion, a methacrylic acid ester resin emulsion and a vinyl ester resin emulsion, are widely used as an adhesive, a coating composition, a binder, a fiber-treating agent and a mortar-ingredient.
The above-mentioned emulsions are produced usually by emulsion-polymerizing an ethylenically unsaturated monomer and/or a diene monomer in the presence of a surface active agent or a water-soluble high-molecular-weight compound such as polyvinyl alcohol (hereinafter abbreviated to “PVA”) or hydroxyethyl cellulose.
By using a surface active agent for polymerization, standing stability, mechanical stability, chemical stability, freeze-thaw stability and pigment-miscibility of the polymer emulsion can be maintained at a certain level but the level is not satisfactorily high. The polymer emulsion produced by an emulsion polymerization procedure using a surface active agent as an emulsifier generally has a low viscosity, and therefore, when the polymer emulsion is used in a field where a high viscosity is required, a thickening agent must be added or a unsaturated acid must be copolymerized followed by alkali addition for increase of viscosity. The addition of a thickening agent and the copolymerization of an unsaturated acid lead to deterioration of water resistance of a final product of the emulsion. Further, the surface active agent is liable to migrate in the final product with the result of deterioration of various properties.
A polymer emulsion prepared by polymerizing vinyl acetate or vinyl chloride in the presence of a water-soluble high-molecular-weight compound such as a PVA polymer as an emulsion stabilizer is satisfactory in various dispersion stabilities such as mechanical stability and chemical stability and in the fact that a desired viscosity is obtained by controlling the polymerization procedure and conditions. However, these advantages can be achieved only with limited polymer emulsions prepared from monomers having a high free-radical polymerizability such as vinyl acetate and vinyl chloride. Stable polymer emulsions cannot be prepared from monomers having a relatively low free-radical polymerizability such as a styrenic monomer, a diene monomer, an acrylic acid ester monomer and a methacrylic acid ester monomer.
A proposal of conducting a polymerization of a styrenic monomer, a diene monomer, an acrylic acid ester monomer or a methacrylic acid ester monomer by using a PVA polymer having a mercapto group as an emulsion stabilizer was made in Japanese Unexamined Patent Publication (hereinafter abbreviated to “JP-A”) No. S60-197229. But, research of the present inventors has revealed that good polymerization stability can be obtained only when a special initiator, such as potassium bromate, capable of generating a free-radical due to the reaction with a mercapto group in the PVA polymer is used. Good polymerization stability cannot be obtained with ordinary initiators. Further, it is pointed out that the use of the PVA polymer having a mercapto group has a problem such that polymerization inevitably stops when the whole amount of mercapto group is consumed.
A process for producing an aqueous polymer emulsion wherein an ethylenically unsaturated monomer or a diene monomer is polymerized by using PVA as a dispersing agent in the presence of a small amount of a chain transfer agent having a mercapto group is described in JP-A H8-325312. This process has a problem such that gelation occurs during polymerization due to the presence of the chain transfer agent (see Comparative Example 6 given below). A process for producing an aqueous emulsion of a homopolymer or copolymer from an acrylic acid ester monomer, a methacrylic acid ester monomer, a styrenic monomer, a diene monomer or a halogenated vinyl monomer is described in JP-A H8-104703. In this process, a special vinyl alcohol polymer must be used as a dispersing agent, which satisfies the special requirements for the viscosity average degree of polymerization, the ratio of weight average molecular weight
umber average molecular weight, and the maximum peak of molecular weight in the molecular weight distribution, and therefore, this process is limited in utilization.
Thus, a process for stably producing an aqueous emulsion of a homopolymer or copolymer from an acrylic acid ester monomer, a methacrylic acid ester monomer, a styrenic monomer, a diene monomer or a halogenated vinyl monomer has not proposed, wherein these monomers are polymerized by using a protective colloid of a general water-soluble high-molecular-weight compound as a dispersing agent.
DISCLOSURE OF THE INVENTION
A primary object of the present invention is to provide an aqueous polymer emulsion having an extremely enhanced stability, and a process for producing the aqueous polymer emulsion by homopolymerizing or copolymerizing an acrylic acid ester monomer, a methacrylic acid ester monomer, a styrenic monomer or a diene monomer by using as a dispersing agent a water-soluble high molecular-weight compound having an alcoholic hydroxyl group which is a protective colloid of a general water-soluble high-molecular-weight compound.
Through a research into a process for stably producing an aqueous polymer emulsion from an acrylic acid ester monomer, a methacrylic acid ester monomer, a styrenic monomer or a diene monomer by using as a dispersing agent a protective colloid of a general water-soluble high-molecular-weight compound, the present inventors have found that the above-mentioned object can be achieved by a process wherein the polymerization is carried out by using a vinyl alcohol polymer as a dispersing agent, while the monomer or monomers are incorporated into a polymerization system in a special manner. Based on this finding, the present invention has been completed.
Thus, in one aspect of the present invention, there is provided an aqueous emulsion of a homopolymer consisting of units of a monomer selected from the group consisting of an acrylic acid ester monomer, a methacrylic acid ester monomer, a styrenic monomer and a diene monomer, or a copolymer predominantly comprised of units of at least one monomer selected from said group of monomers, which is dispersion-stabilized with a water-soluble high-molecular-weight compound having a molecular weight of at least 300 and having an alcoholic hydroxyl group;
characterized in that said homopolyme or copolymer is in the form of particles having an average particle diameter of 0.05 &mgr;m to 5 &mgr;m and said aqueous emulsion has a calcium chloride chemical stability index of at least 20 and a surface tension of at least 45 mN/m as measured at a solid content concentration of 30% by weight;
that the amount of the water-soluble high-molecular-weight compound having an alcoholic hydroxy group is in the range of 0.01 to 100 parts by weight based on 100 parts by weight of the homopolymer or the copolymer;
that at least part of the water-soluble high molecular-weight compound having an alcoholic hydroxyl group is graft-bonded to the homopolymer or copolymer; and further
that the amount of the homopolymer or copolymer having graft-bonded thereto the water-soluble high-molecular-weight compound having an alcoholic hydroxyl group is in the range of 0.5% to 30% by weight based on the sum of the homopolymer or copolymer having grafted thereto the water-soluble high-molecular-weight compound having an alcoholic hydroxyl group and the homopolymer or copolymer, to which the water-soluble high-molecular-weight compound having an alcoholic hydroxyl group has not been grafted.
In another aspect of th
Haneda Hidekazu
Inoue Toshihiro
Henderson Christopher
Zeon Corporation
LandOfFree
Aqueous emulsion and process for producing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous emulsion and process for producing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous emulsion and process for producing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2876629