Aqueous dispersion and process for producing the same

Details Aqueous dispersion and process for producing the same Aqueous dispersion and process for producing the same

2001-03-23

2002-09-17

Yoon, Tae H. (Department: 1714)

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...

C524S832000, C523S205000, C523S206000, C523S335000

Reexamination Certificate

active

06451901

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an aqueous dispersion and to a method for producing it. The aqueous dispersion of the invention has good adhesiveness, especially airtight adhesiveness to various substrates, and has good storage stability, good weather resistance and good hydrophobicity.
BACKGROUND ART
Polyolefin resins such as polypropylene have good resin properties including workability, water resistance and oil resistance, and are inexpensive. Therefore, they are much used for plastics for electric and electronic appliances for household use and for automobile parts. To add further value thereto, polyolefin moldings are coated with paint or are formed into laminates with other resins. As having low polarity, however, polyolefins are problematic in that they are poorly adhesive to ordinary paint and to other resins.
To solve the problem, pre-treating the surface of polyolefin moldings with chromic acid, flame, corona discharge, plasma, solvent, etc. to thereby increase the polarity of the surface of the moldings and to improve the adhesiveness thereof to paint and to other resins has heretofore been tried. However, the treatment requires complicated working steps and requires a large amount of corrosive chemicals, and is therefore often dangerous.
Given that situation, a method of undercoating the surface of polyolefin moldings with a primer that comprises, as the essential ingredient, a chloropolyolefin has been proposed. When used, however, the chloropolyolefin is dissolved in an aromatic organic solvent such as toluene, xylene or the like harmful to human bodies, and using it is therefore undesirable from the viewpoint of environmental safety. A method of dispersing such a chloropolyolefin in water has been proposed (see Japanese Patent Laid-Open No. 256556/1989). Even in this method, however, it is still difficult to prepare the aqueous dispersion without using such an aromatic organic solvent at all, and, in addition, the weather resistance of the coating film formed is poor.
Use of an aqueous dispersion of a modified polyolefin for primer has been proposed (see Japanese Patent Laid-Open No. 73250/1994). However, since the modified polyolefin is a graft copolymer, the aqueous dispersion comprising it must contain a large amount of surfactant to ensure its stability, but the adhesiveness of the coating film formed is thereby lowered. In addition, when an inorganic filler having been subjected to surface treatment with the aqueous dispersion of a modified polyolefin is added to a polyolefin, it detracts from the mechanical properties of the polyolefin since the adhesiveness between the polyolefin and the inorganic filler is poor.
Accordingly, the object of the present invention is to provide an aqueous dispersion having good adhesiveness, especially airtight adhesiveness to various substrates, and having good storage stability, good weather resistance and good hydrophobicity, and to provide a method for producing it.
DISCLOSURE OF THE INVENTION
According to the invention, the above-mentioned object can be attained by providing an aqueous dispersion of a block copolymer composed of polymer blocks (A) consisting essentially of olefin monomer units and polymer blocks (B) comprising from 2 to 100 mol % of units of vinyl monomers having a carboxyl group or a carboxylic acid anhydride group and from 0 to 98 mol % of units of other vinyl comonomers capable of copolymerizing with the vinyl monomers, dispersed in an aqueous solution of at least 0.05 equivalents, relative to the carboxyl group or the carboxylic acid anhydride group, of a basic substance; and a method for producing the aqueous dispersion by dispersing a block copolymer composed of polymer blocks (A) Consisting essentially of olefin monomer units and polymer blocks (B) comprising from 2 to 100 mol % of units of vinyl monomers having a carboxyl group or a carboxylic acid anhydride group and from 0 to 98 mol % of units of other vinyl comonomers capable of copolymerizing with the vinyl monomers, in an aqueous solution of at least 0.05 equivalents, relative to the carboxyl group or the carboxylic acid anhydride group, of a basic substance, at a temperature not lower than the melting point of the block copolymer.
BEST MODES OF CARRYING OUT THE INVENTION
The block copolymer in the invention is composed of polymer blocks (A) and polymer blocks (B) mentioned below, and it includes, for example, AB-type diblock copolymer, ABA-type triblock copolymer, BAB-type triblock copolymer, etc. Of those, preferred is the AB-type diblock copolymer.
The polymer blocks (A) that constitute the block copolymer consist essentially of olefin monomer units. The olefin monomer unit content of the polymer blocks (A) preferably falls between 50 and 100 mol %, more preferably between 70 and 100 mol %, even more preferably between 80 and 100 mol %, based on the number of mols of all the constituent units of the polymer blocks (A).
The olefin monomer units include, for example, those derived from ethylene; &agr;-olefins such as propylene, 1-butene, 2-methyl-1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-octadecene, etc.; 2-butene; isobutylene; conjugated dienes such as butadiene, isoprene, etc.; cyclopentadiene, vinylcyclohexane, &bgr;-pinene, etc. The polymer block (A) may contain one or more of these units. Preferably, the polymer block (A) contains units derived from ethylene or propylene. More preferably, it contains units derived from propylene, or contains units derived from propylene and units derived from other &agr;-olefins than propylene. In case where the olefin monomer units are derived from conjugated dienes such as butadiene, isoprene, cyclopentadiene, etc., the remaining unsaturated bonds may be hydrogenated.
The polymer block (A) may optionally contain from 0 to 50 mol % of units derived from vinyl comonomers capable of copolymerizing with the olefin monomers. The comonomer content of the polymer block (A) preferably falls between 0 and 30 mol %, more preferably between 0 and 20 mol %.
The vinyl comonomers capable of copolymerizing with the olefin monomers include, for example, (meth)acrylonitrile; vinyl esters such as vinyl acetate, vinyl pivalate, etc.; (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, dodecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc.; (meth)acrylamide, N-vinyl-2-pyrrolidone, etc. One or more of these comonomers may be copolymerized with the olefin monomers. Of those, preferred are methyl acrylate, ethyl acrylate, and vinyl acetate. The polymer blocks (A) may be modified. The modification may be effected in various known methods of halogenation such as chlorination or bromination, or chlorosulfonation, epoxidation, hydroxylation, acid anhydride-carboxylation, acid-carboxylation, etc.
The polymer blocks (B) that constitute the block copolymer in the invention contain from 2 to 100 mol %, based on the number of mols of all the constituent units of the polymer blocks (B), vinyl monomer units having a carboxyl group or a carboxylic acid anhydride group. Preferably, the vinyl monomer unit content of the polymer blocks (B) falls between 2 and 50 mol %, more preferably between 2 and 30 mol %.
The carboxyl group-having vinyl monomers include, for example, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, maleic acid etc. The polymer block (B) may contain one or more of these monomer units. Of those, preferred are acrylic acid and methacrylic acid.
The vinyl monomers having a carboxylic acid anhydride group (represented by —CO—O—CO—) include, for example, maleic anhydride, itaconic anhydride, citraconic anhydride, butenylsuccinic anhydride, tetrahydrophthalic anhydride, etc. The polymer block (B) may contain one or more of these monomer units. Of those, preferred is maleic anhydride.
The polymer blocks (B) may contain from 0 to 98 mol %, preferably from 50 to 98 mol %, more preferably from 70 to 98 mol %, based on the number of mols of all the constituent units of the polymer blocks (B),

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