Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2003-06-17
2004-09-21
Zalukaeva, Tatyana (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S079000, C526S203000, C526S319000, C526S318200, C526S346000, C526S347100
Reexamination Certificate
active
06794465
ABSTRACT:
RELATED APPLICATION
This application claim the priority of Japanese Patent application No. 2002-179255 filed on Jun. 20, 2002, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of preparing an acrylic copolymer, and particularly to a method of preparing an acrylic copolymer at a high temperature of 150° C. or higher.
2. The Prior Art
In order to reduce environmental burdens, so-called high solid type coatings, which contain a lesser amount of organic solvents, are drawing attention. For the binder ingredient of a high solid type coating, an acrylic polymer with a high solid content ratio having a molecular weight of several thousands is commonly used because of its application workability. In order to obtain such an acrylic polymer, it was necessary to raise the polymerization temperature to 130-140° C., which is higher than usual, to increase the amount of the initiator, and/or to jointly use a chain transfer agent. However, a polymer usually obtained under such conditions has a lower solid content ratio and an additional process of removing the organic solvent by means of distillation is required to achieve the target solid content ratio. Also, the increase in the amount of initiator and/or chain transfer agent is not preferable considering the cost.
An example of solutions to this problem is a method in which the aforementioned polymerization is carried out at a high temperature, i.e. 150° C. or higher. By using this method, a polymer having a relatively low molecular weight can be obtained with a high solid content ratio. However, methacrylate monomers at high temperatures go through polymerization and depolymerization simultaneously. Because of this, when the ratio of the methacrylate monomer ingredient is high in the acrylic polymer, there is a problem in that unreacted monomers remain in the system.
The object of the present invention is to provide a method of preparing an acrylic copolymer with a low amount of unreacted monomers using high temperature polymerization at 150° C. or higher.
BRIEF SUMMARY OF THE INVENTION
The method of preparing an acrylic copolymer of the present invention is a method of preparing an acrylic copolymer using as a raw material a monomer mixture comprising 50 mole % or more of a monomer having a polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded wherein, after the polymerization is carried out at a polymerization temperature of 150° C. or higher, further heating at 80-130° C. is done. The aforementioned monomer having a polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded can be a methacrylate monomer, &agr;-methylstyrene, itaconic acid, itaconic acid anhydride, citraconic acid, or citraconic acid anhydride.
Also, a second monomer mixture consisting of a monomer having a polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded and/or an initiator can be added at the time of heating after the aforementioned polymerization reaction. The aforementioned monomer having a polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded can be a polymerizable aromatic compound and/or acrylate monomer. Also, the aforementioned monomer having a polymerizable double bond formed by two carbon atoms to which a hydrogen atom is bonded can be part of the monomers that are constituents of the aforementioned monomer mixture.
DETAILED DESCRIPTION OF THE INVENTION
In the method for preparing an acrylic copolymer of the present invention, first the polymerization reaction is carried out at a polymerization temperature of 150° C. or higher, using as a raw material a monomer mixture comprising 50 mole % or more of a monomer having a polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded.
The aforementioned polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded is a structure represented by a methacrylate group. A description using ethylene as an example follows. In this example structure, both hydrogen atoms bonded to one carbon atom that is a constituent of ethylene are replaced by carbon atoms, and two hydrogen atoms bonded to the other carbon atom stay unchanged or only one hydrogen atom is replaced by a carbon atom. A double bond having such a structure is known to go through polymerization and depolymerization simultaneously at high temperatures.
Examples of the aforementioned monomer having a polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded include methacrylate monomers. Specific examples of the methacrylate monomer include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, phenyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, t-butylcyclohexyl methacrylate, dicyclopentadienyl methacrylate, dihydrodicyclopentadienyl methacrylate, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, glycidyl methacrylate, methacryl alcohol, adduct of hydroxyethyl methacrylate and &egr;-caprolactone, methacrylamide, N-methylol methacrylamide, N-butoxymethyl methacrylamide, N,N-dimethyl methacrylamide, N,N-dibutyl methacrylamide, N,N-dioctyl methacrylamide, N-monobutyl methacrylamide, N-monooctyl methacrylamide, N-(2-hydroxyethyl) methacrylamide, methacrylonitrile, and &ohgr;-carboxy polycaprolactone monomethacrylate.
Examples other than a methacrylate monomer include &agr;-methylstyrene, itaconic acid, itaconic acid anhydride, citraconic acid, and citraconic acid anhydride. The aforementioned monomer having a polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded can be of more than one type.
In the aforementioned mixture, the content of the monomer having a polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded is 50 mole % or more. If it is less than 50 mole %, then the amount of unreacted monomers in the high temperature polymerization is not very problematic.
The aforementioned monomer mixture can contain a monomer having a polymerizable double bond formed by two carbon atoms to which a hydrogen atom is bonded, in addition to the monomer having a polymerizable double bond formed by a carbon atom to which no hydrogen atom is bonded and a carbon atom to which a hydrogen atom is bonded.
The aforementioned polymerizable double bond formed by two carbon atoms to which a hydrogen atom is bonded is a structure represented by a styryl group and acrylate group. Just as above, a description using ethylene as an example follows. In this example structure, hydrogen atoms bonded to two carbon atoms that are constituents of ethylene are left as they are, or, one hydrogen atom from one or both carbon atoms is replaced by a carbon atom. A double bond having such a structure would not go through polymerization and depolymerization simultaneously even at high temperatures.
Examples of the aforementioned monomer having a polymerizable double bond formed by two carbon atoms to which a hydrogen atom is bonded include an acrylate monomer, polymerizable aromatic compounds, carboxylic acid compounds having a double bond, &agr;-olefin compounds, and vinyl compounds. Of these, an acrylate monomer and polymerizable aromatic compounds are preferable because of their copolymerizability and also because they are easy to handle.
Specific examples of the acrylate
Asai Tomohito
Nakajima Koji
Oohata Masatoshi
Nippon Paint Compnay, Ltd.
Townsend & Banta
Zalukaeva Tatyana
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