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
1999-03-19
2001-10-09
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...
C524S592000, C525S380000, C525S381000
Reexamination Certificate
active
06300411
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an aqueous resin composition useful as a coating on various substrates such as wood, metals, and molded resin products; a binder for paints and printing inks; a coating material; and an adhesive. The present invention also relates to an aqueous resin composition which, when dried, can form a tough and highly water resistant film.
2. Description of the Related Art
In the field of coating formation, a switch from emulsions in organic solvents to aqueous emulsions is strongly desired from the points of view of environmental hygiene and savings in resources. However, aqueous emulsions are not fully satisfactory in the water resistance, toughness, and adhesive strength of the resulting coating. A common practice for improving these properties is to introduce a functional group into an aqueous emulsion so that a crosslinked coating is formed. As an aqueous emulsion for formation of the crosslinked coating, a one-pack emulsion comprising a mixture of a curing agent and a polymer is demanded from the aspects of applicability and workability.
To fulfill this demand, U.S. Pat. No. 3,345,336 (Japanese Patent Publication No. 20053/71) discloses the crosslinking of a carbonyl group-containing polymer emulsion with a polyhydrazide compound. An aqueous emulsion used in this method is a one-pack emulsion. After the emulsion is applied for coating, water in the emulsion dries, whereupon the hydrazide groups and the carbonyl groups crosslink as a result of dehydration condensation to form a film. The polyhydrazide compound used here refers to a compound having at least two or more hydrazide groups. Examples of this compound are dihydrazides of an aromatic dicarboxylic acid such as phthalic acid, isophthalic acid, or terephthalic acid. Preferred examples are dihydrazides of an aliphatic saturated dicarboxylic acid having 2 to 10 carbon atoms, such as oxalic acid or sebacic acid. Particularly preferred examples are dihydrazides of adipic acid.
Various improvements have subsequently been made in one-pack crosslinkable aqueous emulsions containing polyhydrazides. Such improvements are described in Deutsche Offenlegungschrift 2819092 (Japanese Unexamined Patent Publication No. 144432/79), Deutsche Offenlegungschrift 2803258 (Japanese Unexamined Patent Publication No. 110248/79), Japanese Unexamined Patent Publication No. 3850/82, Japanese Unexamined Patent Publication No. 3857/82, Japanese Unexamined Patent Publication No. 96643/83, Japanese Unexamined Patent Publication No. 104902/83, Japanese Unexamined Patent Publication No. 38468/85, Japanese Unexamined Patent Publication No. 25163/87, Japanese Unexamined Patent Publication No. 62853/87, Deutsche Offenlegungschrift 3720860 (Japanese Unexamined Patent Publication No. 20256/89), Japanese Unexamined Patent Publication No. 234416/89, Japanese Unexamined Patent Publication No. 68669/91, Japanese Unexamined Patent Publication No. 227947/92 (Deutsche Offenlegungschrift 4016056), Japanese Unexamined Patent Publication No. 249587/92, and WO 96/01252.
Most of these one-pack crosslinkable aqueous emulsions use dihydrazides of aliphatic dicarboxylic acids as polyhydrazide compounds, and often use adipic acid dihydrazide preferably. Adipic acid dihydrazide functions as an effective crosslinking agent, but its solubility in water is insufficient, resulting in insufficient crosslinking. Consequently, the resulting coating is not fully water resistant.
One-pack crosslinkable aqueous emulsions using polyhydrazide compounds having three or more functional groups are also exemplified in some of the previously quoted prior art publications. Japanese Patent Publication No. 6861/86 describes a tri- or tetrahydrazide of pyromellitic acid, and a tri- or tetrahydrazide of nitrilotriacetic acid. Japanese Unexamined Patent Publication No. 38468/85, Deutsche Offenlegungschrift 3720860, and Deutsche Offenlegungschrift 4016056 describe pentane-1,3,5-tricarboxylic acid trihydrazides, hexene-4-1,2,6-tricarboxylic acid trihydrazides, and 3-cyanopentane-1,3,5-tricarboxylic acid trihydrazides.
The use of a hydrazide compound with three or more functional groups can increase the crosslinking density, and is thus expected to enhance the water resistance of a crosslinked coating. However, this does not mean that the higher the functionality of the hydrazide compound, the better outcome is obtained. An excessively high functionality means more hydrazide groups which cannot take part in crosslinking for reasons such as steric hindrance. As a result, the water resistance of the coating declines. Japanese Unexamined Patent Publication No. 234416/89 describes the use of a polyhydrazide formed by polymerizing two or more hydrazine compounds. When such a polyhydrazide is used, this polymeric hydrazide is slightly soluble in water, and cannot be fully dispersed in an aqueous emulsion. This poses difficulty in performing sufficient crosslinking. Japanese Unexamined Patent Publication No. 80619/94 describes a 1,2,3,4-butanetetracarboxylic acid hydrazide as an adsorbent of formaldehyde. This hydrazide is also sparingly soluble in water, and a coating of an emulsion formed by using it as a curing agent is poor in water resistance.
As described above, the use of a conventional aqueous resin composition containing a curing agent and a carbonyl compound still has posed difficulty in forming a crosslinked film having excellent properties such as water resistance and adhesion to a substrate.
It is an object of the present invention to provide a novel aqueous resin composition which has resolved the problems with the earlier technologies. That is, the object of this invention is to provide an aqueous resin composition containing fully dispersed components, and having high storage stability. It is another object of the present invention to provide an aqueous resin composition which, when dried, can form a film excellent in film intactness, transparency, whitening after water immersion, and adhesion after water immersion.
DISCLOSURE OF THE INVENTION
To attain these objects, the inventors of the present invention have conducted extensive studies, including stereostructures of hydrazide compounds. As a result, they have found that an aqueous resin composition having sufficient storage stability can be prepared by the use of a trifunctional hydrazide compound having a specific structure. They have also found that a film excellent in all of film intactness, transparency, whitening after water immersion, and adhesion after water immersion can be formed by drying this aqueous resin composition. The present invention has been presented on the basis of these findings.
That is, the present invention provides an aqueous resin composition containing (A) a copolymer of (a) a monomer having one or more aldehyde groups or ketone groups, and a radical polymerizable unsaturated bond, in a molecule, with (b) a monomer having a radical polymerizable unsaturated bond copolymerizable with the monomer (a); (B) a hydrazine compound of the following formula (1)
where R
1
, R
2
, R
3
and R
4
independently represent a hydrogen atom, or a hydroxyl group, p denotes an integer of 0 to 3, and q denotes an integer of 2 to 8, provided that the relationships p+q≦8 and p<q are satisfied; and
an aqueous medium.
The present invention also provides a polymer crosslinking agent for use in a crosslinking reaction of (A) a copolymer of (a) a monomer having one or more aldehyde groups or ketone groups, and a radical polymerizable unsaturated bond, in a molecule, with (b) a monomer having a radical polymerizable unsaturated bond copolymerizable with the monomer (a), the polymer crosslinking agent containing (B) a hydrazine compound of the above-mentioned formula (1).
The present invention also provides a coating containing (A) a copolymer of (a) a monomer having one or more aldehyde groups or ketone groups, and a radical polymerizable unsaturated bond, in a molecule, with (b) a monomer having a radical polymerizable unsaturated bond copolymer
Hayama Kazuhide
Kinugasa Kazumasa
Kitani Yasuo
Seko Toshiya
Mitsubishi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Yoon Tae H.
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