Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1998-09-04
2001-08-14
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C524S556000
Reexamination Certificate
active
06274687
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to powder of agglomerated fine particles of crosslinked allyl copolymer, particularly to powder of agglomerated particles comprising fine particles obtainable by removing an aqueous medium from a crosslinked allyl copolymer fine particles-containing aqueous emulsion. The present powder is useful as a modifying agent for a paint, an adhesive, a varnish or a resin and is very excellent in collapse dispersibility from powder to original fine particles when the powder is dispersed in an organic matrix such as a paint, an adhesive, a varnish or a resin.
RELATED ARTS
Hitherto, in the field of a thermoplastic resin and a thermosetting resin, it is often pointed out that said resins have a defect of so called toughness, namely crack is caused so that a shaped article of said resin is broken, when an external force is applied to the shaped article. In order to eliminate the above defect, there have been used a method comprising adding a rubbery oligomer and dispersing the oligomer as particles having a size of at most several micrometers by a phase separation during the shaping However, in said method, the control of particle diameter and dispersibility of the oligomer not only gives some restrictions, but also the strength such as a flexural strength of the shaped article is unavoidably remarkably decreased.
In order to solve this problem a method of adding powder comprising previously crosslinked rubbery fine particles as the unit particles was developed so that the defect of said oligomer is compensated for the purpose of some types of epoxy resins, as described in, for example, Japanese Patent Kokai Publication No. 117948/1990.
However, said rubbery fine particles have some limitations for the purpose of resins having higher strength. It is pointed out in, for example, Circuit Mounting Society literature, Vol. 11, Page 53 (1996) by Masao TOMOI that the dispersion of harder organic fine particles having an order of submicron in the resins, which is used instead of the rubbery fine particles, has the effectiveness for improving the toughness and preventing the decrease of strength. Although said literature illustrates a method of phase-separating an oligomer having higher glass transition temperature in the resins, the shaping is similarly restricted in view of control of phase separation.
Japanese Patent Application No. 185952/1996 filed by Daiso Co., Ltd. discloses hard organic fine particles which are crosslinked copolymer fine particles comprising diallyl phthalate, &agr;,&bgr;-unsaturated carboxylic acid and an acrylate ester, wherein the content of diallyl phthalate is from 10 to 40% by weight, the content of &agr;,&bgr;-unsaturated carboxylic acid is from 0.1 to less than 5% by weight and a balance is the content of the acrylate ester, and the fine particles are usually prepared by an emulsion polymerization. When the fine particles are mixed with other components such as a resin, it is practically beneficial that the fine particles are separated from the emulsion by the precipitation of particles or the evaporation of aqueous medium so as to give powder. The resultant powder consists of agglomerated fine particles so that it is necessary to disperse to the unit particles when the powder is added to an organic matrix such as a resin. However, it is not necessarily easy to collapse the agglomerate powder into the unit particles, particularly in the case that the powder in a high concentration is added to the resin.
SUMMARY OF THE INVENTION
The present inventors discovered that collapse dispersibility in an organic medium is remarkably improved by decreasing an amount of carboxylic acid which is a hydrophilic group on a surface of a fine particle.
The reason thereof is unclear, but it is supposed to be that an interaction of carboxylic acid between fine particles during the agglomeration or an interaction between carboxylate salt resulting from neutralization of emulsion is decreased, and that a hydrophilic carboxylic acid or carboxylate salt prevents the dispersion in an organic medium having a low dielectric constant.
The present invention provides powder of agglomerated crosslinked allyl copolymer fine particles obtained by emulsion-copolymerizing (a) more than 40% by weight to 80% by weight of diallyl phthalate, (b) 0.05% by weight to 2% by weight of an &agr;,&bgr;-unsaturated carboxylic acid and (c) a balance of at least one vinyl monomer selected from the group consisting of an acrylate ester and methacrylate ester of an alcohol having 1 to 8 carbon atoms in an aqueous medium to give an aqueous emulsion containing crosslinked allyl copolymer fine particles having an average particle diameter of at most 0.5 &mgr;m and separating the aqueous medium from the aqueous emulsion.
DETAILED DESCRIPTION OF THE INVENTION
Diallyl phthalate (a) used in the present invention is a general tern of ortho-, iso- and tere-compounds which are used singly or in combination of at least two.
The &agr;,&bgr;-unsaturated carboxylic acid (b) may be a compound having one carbon—carbon double bond and at least one carboxylic acid group. The &agr;,&bgr;-unsaturated carboxylic acid (b) includes acrylic acid, methacrylic acid (Both of acrylic acid and methacrylic acid are hereinafter referred to as (meth)acrylic acid. Both of an acrylate ester and a methacrylate ester are referred to as a (meth)acrylate ester.), crotonic acid, maleic acid, fumaric acid and itaconic acid. These may be used alone or in combination of at least two.
The vinyl compound (c) is at least one selected from the (meth)acrylate ester. The vinyl compound (c) is preferably the acrylate ester.
The (meth)acrylate ester (c) may be an ester between (meth)acrylic acid and a monohydric alcohol having 1 to 8 carbon atoms. Examples of (meth)acrylate ester (c) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, cyclopentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, methylcyclohexyl (meth)acrylate, octyl (meth)acrylate and 2-ethylhexyl (meth)acrylate. Among them, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are particularly preferable.
A portion of the (meth)acrylate ester may be replaced with other vinyl compound, insofar as the hardness of fine particles and the high collapse dispersibility are not deteriorated. Examples of the other vinyl compound includes &agr;,&bgr;-unsaturated carboxylate esters such as a maleate ester, a fumarate ester, an itaconate ester, acetoacetoxy (meth)acrylate and allyl (meth)acrylate; hydroxyl group-containing (meth)acrylate esters of alcohol having at least two hydroxyl groups, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, (meth)acrylate mono- or di-ester of glycerol, (meth)acrylate mono- or di-ester of trimethylol propane and (meth)acrylate mono-, di- or tri-ester of pentaerythritol; &agr;,&bgr;-unsaturated nitriles such as (meth)acrylonitrile; amides of &agr;,&bgr;-unsaturated carboxylic acid, such as (meth)acrylamide, (meth)acrylisopropylamide, N-methylol (meth)acrylamide and diacetone (meth)acrylamide; and epoxy-containing vinyl compounds such as glycidyl (meth)acrylate and 2-methylglycidyl (meth)acrylate. The amount of the other vinyl compound is from 0 to 40% by weight based on the vinyl compound (c) including the other vinyl compound.
The vinyl compound (c) may be an aromatic vinyl compound such as styrenes and &agr;-methylstyrenes.
Examples of the styrenes include styrene, and styrenes having an aromatic ring substituted by a halogen atom, an alkyl group, a halogenated alkyl group and/or a vinyl group, such as ortho- or para-chlorostyrene, ortho- or para-methylstyrene, ortho- or para-chloro
Aoki Koji
Nakamura Seiji
Shimizu Yasumi
Daiso Co. Ltd.
Foley & Lardner
Michl Paul R.
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