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
1998-12-11
2001-06-26
Moore, Margaret G. (Department: 1712)
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...
C525S100000, C526S279000, C524S548000, C524S806000, C524S808000, C524S809000
Reexamination Certificate
active
06251986
ABSTRACT:
The present invention relates to a paint resin emulsion for use as an aqueous painter binder having improved weatherability. More particularly, the invention provides a resin emulsion having improved resistance against degradation due to exposure to ultra-violet or visible light. The resin emulsion according to the present invention will find a variety of applications including, but not limited to, application as a binder to be contained in paint for domestic electric appliances, steel-made machinery, large construction works, automobiles, building constructions, building materials, wood materials or the like.
In recent years, in consideration of the environmental pollution or effect on human body, there has been a general shift from solvent-based paint to water-based paint. In particular, water-based or aqueous paint using an acrylic resin emulsion as a binder has been often used because it satisfies the requirements as paint resin such as paint-film forming ability, adhesion to the substrate, pigment dispersion stability or the like.
However, as for a conventional acrylic resin emulsion paint, an accelerated weathering test using a sunshine meter conducted thereon has revealed that this resin can retain its gloss for approximately 100 hours only. Therefore, this type of resin has problem for application demanding a long-term weatherability. Then, in order to improve the long-term weatherability, the prior art has further suggested adding to the resin paint those additives generically referred to as anti-weathering agent such as ultra-violet absorbent for absorbing ultra-violet ray which significantly contributes to degradation of the molecular chain of the resin, antioxidant or the like.
Further, the Japanese laid-open patent gazette Hei. 3 (1991)-128978 discloses the technology of copolymerizing ultra-violet stabilizing monomers enabling to be polymerized.
In more recent years, fluorine resin, silicone resin or the like has been put into use as paint resin having improved long-term weatherability capable of retaining gloss as long as 4000 to 5000 hours as determined in the accelerated weathering test using the sunshine weather meter.
Notwithstanding the above, in the case of acrylic resin paint added with the anti-weathering agent, although some improvement may be recognized indeed in terms of the long-term weatherability, the resin still has the problem of poor durability against effusion due to e.g. rain after evaporation or bleed-out of the anti-weathering agent Then, in order to restrict such effusion, according to the art of the Japanese laid-open patent gazette Hei. 3 (1991)-128978 discussed supra, a trial for improvement was attempted by using a monomer containing cycloalkyl group as another essential component thereof. However, the level of the weatherability achieved with this attempt has proven still insufficient.
On the other hand, the fluorine resin and the silicone resin are inferior to the acrylic resin in the respect of such properties as gloss, pigment dispersion stability.
Then, the primary object of the present invention is to provide improved acrylic resin which has the gloss-retaining ability almost as good as that of the fluorine resin or silicone resin while maintaining the advantages of conventional acrylic resin paint binder such as the gloss-retaining ability or pigment dispersion stability.
In order to a ccomplish the above-noted object, the paint resin emulsion having improved weatherability, according to the present invention, comprises in 100 wt. % of the resin component in the emulsion thereof:
(a) 0.1 to 10 wt. % of a monomer containing light stabilizing group; and
(b) 0.1 to 10 wt. % of a monomer containing alkoxysilyl group.
In the above, the light stabilizing group contained in such a monomer containing the light stabilizing group may be an amino group of a hydroxyl group surrounded by a bulky substituent having steric hindering effect, i.e. a functional group commonly referred to as a hindered amino group or hindered hydroxyl group. As such the light stabilizing group is bonded with a polymerizing unsaturated group, the monomer containing the light stabilizing group is formed.
Then, by copolymerization of such a monomer with the polymerized chain of the binder resin, there is obtained the paint resin emulsion which suffers less degradation from effusion due to rain after evaporation or bleeding-out of the anti-weathering agent therefrom and which yet provides improved weatherability due to the cross linking effect of the resin molecules.
Referring the above component (a), i.e. a monomer containing the light stabilizing group, if the amount of this monomer is present less than 0.1 wt. % in the resin, then, the monomer cannot provide its effect sufficiently. Conversely, an amount thereof greater than 10 wt. % will not provide any additional effect, only resulting in cost increase. Also, referring to the other component (b), if the amount of this component is less than 0.1 wt. %, the effect thereof will be insufficient. And, an amount thereof greater than 10 wt. % will only result in cost increase, without providing any additional effect.
According to the invention as set forth in claim
2
, the construction of claim
1
further comprises the additional component (c), i.e. 0.1 to 10 wt. % of a monomer containing ultra-violet absorbent group.
Such a monomer containing the ultra-violet absorbent group as this component (C) is a compound capable of contributing to further improvement of weatherability by absorbing ultra-violet ray which can excite and cut off the chemical bond of the resin molecules. Then, by addition of this further component (c), the weatherability may be further improved.
Like the amount of the components (a) and (b) discussed above, if the amount of the component (c) is smaller than the lower limit of 0.1 wt. %, the component cannot provide its effect sufficiently and an amount thereof greater than 10 wt. % will only result in cost increase, without providing any additional effect.
Preferably, a monomer containing the light stabilizing group is represented by the following chemical formula (chemical formula 4):
(wherein R
1
is H or CN; R
2
and R
3
respectively are H, CH
3
, or C
2
H
5
, with R
2
and R
3
being same as or different from each other; R
4
is alkyl group having a carbon number ranging between 1 and 18 or —CO—C(R
2
)═CH(R
3
) [R
2
and R
3
. respectively are H, CH
3
or C
2
H
5
, with R
2
and R
3
being same as or different rom each other]; and X is a nitrogen or oxygen atom).
Incidentally, if X is a nitrogen atom, there is provided an amino group, hich may be either —NH— or —NR—(R is lower alkyl group).
It is believed that the improvement of the weatherability is attributable mainly to the nitrogen atom to which R
4
of the compound represented by the above chemical formula 4 is an alkyl group.
Further, preferably, a monomer containing the alkoxysilyl group is represented by the following chemical formula (chemical formula 5):
(wherein R
5
is H or CH
3
; R
6
is an alkyl group having a carbon number ranging between 1 and 3; Y is an alkylene group having a carbon number ranging between 1 and 6).
Incidentally, in the above total three units of R
6
may be same as or different from one another.
By copolymerization of this monomer containing the alkoxysilyl group, it is believed that the formation of cross linking among the resin binder molecules mainly contributes to the improvement of the weatherability, the anit-solvent resistance, and so on.
Preferably, a monomer containing the ultra-violet absorbent group employed in the present invention is represented by the following chemical formula (chemical formula 6):
(wherein R
7
is H or CH
3
; Z is an alkylene group having a carbon number ranging between 1 and 6).
It is believed that the weatherability of the resin emulsion of the invention may be significantly improved through absorption of ultra-violet ray due to the conjugated double bond in the molecule represented by the formula 6 in combination with the above-described effect of the mono
Ide Hiroshi
Takagi Motoyuki
Moore Margaret G.
National Starch and Chemical Investment Holding Corporation
Roland Thomas F.
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