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
2002-02-27
2004-08-31
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...
C523S201000, C525S384000
Reexamination Certificate
active
06784238
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a primer composition for coating and bonding molded articles of polyolefins such as polypropylene or the like, particularly, relates to a primer composition showing excellent storage stability for storing under mixing with water-containing substances such as pigments, water or moisture.
BACKGROUND OF THE INVENTION
Conventionally, molded articles of polyolefins such as polypropylene have been enhanced in their values by application of paints or formation of resin layers other than polyolefin to the surfaces thereof. However, polyolefins generally have a small polarity and inferior adhesion to general coating materials or other resins. On this account, the adhesion of a polyolefin molded article to coating materials or the like has conventionally been improved by enhancing the surface polarity thereof with treatment of the polyolefin molded article surface using chromic acid, flame, corona, plasma or solvents.
These methods, however, have defects that they require complicated treatments, are accompanied with danger of using corrosive chemicals and also require strict process control for obtaining stable adhesiveness.
The present applicant discloses, in JP-B-62-21027/1987 and JP-B-59-42693/1984, that using, as a primer (surface treating agent), a solution of dissolving a graft copolymer obtainable by graft co-polymerization of a propylene/ethylene copolymer or ethylene/propylene copolymer with maleic anhydride in an organic solvent, the adhesion between a coated object (for example, polyolefin molded articles such as polypropylene molded articles) and a coating material or adhesive is improved to attain good adhesion.
These primer compositions can exert good adhesion between a substrate (coated object) and a coating material or adhesive. However, when they are kept for a long time under water or moisture contact conditions, the problem of increasing their viscosities will be induced, and when water-containing products such as pigments are added to them, foreign matters will be produced or increasing their viscosities will be induced.
In order to solve these problems, the present applicant proposed, in JP-B-61-11250/1986, a primer composition (surface treating agent) prepared by dissolving a modified ethylene/propylene copolymer, which is obtainable by grafting a mono-olefin dicarboxylic acid monoalkyl ester, in an organic solvent.
The above problems for the primer compositions are solved, however, they are found to have a defect of lowering the adhesion with a specific coating material or a specific adhesive.
Therefore, the advent of primer compositions having excellent adhesion between a polyolefin molded article, which is a substrate (coated object) and various materials (coating materials, adhesives or the like), and excellent storage stability and pigment-loading properties has been desired.
The present invention is intended to solve the problems associated with the prior art as mentioned above. It is an object of the invention to provide a primer composition having excellent adhesion between a polyolefin molded article, which is a substrate (coated object) and various materials (coating materials, adhesives or the like), and excellent storage stability and pigment-loading properties.
DISCLOSURE OF THE INVENTION
The primer composition of the present invention comprises:
(I) a modified copolymer obtainable by addition of a polar group represented by the following formula (1) or (2) to at least one (co)polymer selected from
(A) an olefin (co)polymer,
(B) a halogenated olefin (co)polymer
(C) a styrene/conjugated diene/styrene tri-block copolymer or its hydrogenated product and
(D) a halogenated styrene/conjugated diene/styrene tri-block copolymer or its hydrogenated product, and
(II) an organic solvent,
wherein the modified copolymer contains the polar group in an amount of from 1×10
−3
to 250×10
−3
mol based on 100 g of the modified copolymer,
in the formulas (1) and (2), R
1
is hydrogen or an alkyl group of 1 to 6 carbon atoms, R
2
is an alkylene group of 1 to 6 carbon atoms and n is an integer of 1 to 20.
The primer composition of the present invention preferably has a content of the organic solvent (II) of from 100 to 4000 parts by weight based on 100 parts by weight of the modified copolymer (I).
BEST MODE OF CARRYING OUT THE INVENTION
The primer composition of the present invention will be described in detail hereinafter.
The primer composition of the present invention comprises (I) the specific modified copolymer and (II) the organic solvent.
Modified Copolymer (I)
The modified copolymer (I) used for the invention is a graft-modified product of at least one (co)polymer selected from (A) an olefin (co)polymer, (B) a halogenated olefin (co)polymer, (C) a styrene/conjugated diene/styrene tri-block copolymer or its hydrogenated product and (D) a halogenated styrene/conjugated diene/styrene tri-block copolymer or its hydrogenated product, and has the specific polar group.
[(A) Olefin (Co)polymer]
The olefin (co)polymer (A) used for the invention is a homopolymer of at least one &agr;-olefin or a copolymer comprising at least two &agr;-olefins.
Exemplary &agr;-olefins are &agr;-olefins of 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms, and specifically may include ethylene, propylene, 1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-hexene, 2-methyl-1-pentene, 1-heptene and 1-octene.
Among of the &agr;-olefin (co)polymers, it is preferred to use a propylene/ethylene copolymer, propylene/1-butene copolymer and ethylene/1-octene copolymer as the olefin (co)polymer (A).
The intrinsic viscosity [&eegr;] as measured in decalin at 135° C. of the olefin (co)polymer (A) is desirably in the range of 0.05 to 5.0 dl/g, preferably 0.1 to 2.0 dl/g.
[(B) Halogenated Olefin (Co)polymer]
The olefin (co)polymers for the halogenated olefin (co)polymer (B) used in the invention may include, for example, the above-described olefin (co)polymers (A).
Examples of the halogen used in the halogenation of the olefin (co) polymer (A) may include fluorine, chlorine and bromine.
The degree of halogenation varies depending on the kinds of substrate to be subjected to primer treatment and coating objects such as coating materials and adhesives, and further, is desirably in the range of generally 5 to 40% by weight, preferably 10 to 30% by weight based on 100% by weight of the olefin (co) polymer before the halogenation.
[(C) Styrene/Conjugated Diene/Styrene Tri-Block Copolymer or Its Hydrogenated Product]
The styrene/conjugated diene/styrene tri-block copolymer or its hydrogenated product (C) used in the present invention is a copolymer which comprises a polymer block (S) having at least one recurring structural unit derived from styrene in its molecule and a conjugated diene polymer block (Di) having at least one recurring structural unit derived from conjugated diene in its molecule and has, for example, a structure represented by the following formula:
—(S-Di-S)
n
—
in the formula, n is an integer of 1 or more.
Examples of the conjugated diene for the styrene/conjugated diene/styrene tri-block copolymer may include isoprene and butadiene. The tri-block copolymer may contain the conjugated diene singly or in combination with two or more.
Preferably, the styrene content of the tri-block copolymer is generally 10 to 55% by weight, particularly 15 to 50% by weight.
The styrene/conjugated diene/styrene tri-block copolymer or its hydrogenated product used in the invention has a number average molecular weight (Mn) of preferably from 1×10
4
to 18×10
4
, more preferably 1.5×10
4
to 12×10
4
. In the present invention, the number average molecular weight (Mn) is determined using tetrahydrofurane as a solvent at 40° C. by gel permeation chromatography (GPC).
[(D) Halogenated Styrene/Conjugated Diene/Styrene Tri-Block Copolymer or its Hydrogenated Product]
The styrene/conjugated diene/styrene tri-block copolymer or its hydrogenated product for the h
Birch & Stewart Kolasch & Birch, LLP
Mitsui Chemicals Inc.
Yoon Tae H.
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