Dispersed resins for use in coating compositions

Details Dispersed resins for use in coating compositions Dispersed resins for use in coating compositions

2000-09-11

2002-05-14

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...

C524S035000, C524S271000, C524S394000, C524S398000, C528S336000

Reexamination Certificate

active

06388002

ABSTRACT:

The present invention relates to dispersed resins used in coating compositions such as paints.
In recent years, apart from emulsion paints, there has been an increase in demand for water-based paints. These paints are prepared by emulsifying the resin or other film forming materials and incorporating pigment, if appropriate, in the emulsified composition. In order to assist the emulsification it is common practice to incorporate a surfactant. However, one of the problems associated with the use of a surfactant is that although it does facilitate the emulsification of the resin it also has a tendency to make the resulting coating more susceptible to water penetration. This is particularly noticeable when the water-based paint is applied over a ferrous metal because in damp conditions rust will form under the coating. The surface activities of the surfactant causes this effect. Thus the very property which makes the surfactant useful in preparing the formulation has an adverse effect on the coating produced from it.
It has now been found, surprisingly, that a particular surfactant system, while being effective in the emulsification of resins and the like, subsequently loses its surfactant effect such that the deleterious effect of ordinary surfactants is not observed or greatly reduced.
An aqueous composition which comprises a reaction product of
(i) at least one carboxylic acid containing from 3 to 22 carbon atoms; and
(ii) at least one unsubstituted or substituted aliphatic amine or polyfunctional aromatic amine, containing from 2 to 25 carbon atoms;
(iii) a complex crosslinking agent of a metal which is zinc, aluminium, titanium, copper, chromium, iron, zirconium or lead.
(iv) a resin or oil, the weight ratio of the resin or oil to the sum of (i), (ii) and (iii) being at least 2.5:1; and
(v) a thickener, a continuous dry layer obtained by applying the composition to Western Red Cedar providing a contact angle with water not exceeding 80°.
The upper limit of the resin or oil (hereafter referred simply as the “resin”) is not particularly critical but, in general, the weight ratio will be from 2.5:1 to 100:1 or more. More usually the weight ratio is from 5:1 to 75:1 and, in particular from 10:1 to 60:1. The preferred ratio will depend on the type of coating composition for which the emulsified resin is intended. A particularly preferred range for a primer will be from 2.5:1 or 2.6:1 to 20:1 while for a paint it will be from 30:1 to 50:1.
It will be understood that the emulsified resin formulation can be used as such as a coating composition or the usual ingredients such as pigments can be incorporated.
It will be appreciated that components (i) and (ii) are reacted together. In some instances, in particular where the acid is solid, it is necessary to cause the components to react, typically by melting the solid acid (solid amine is generally readily water-soluble). Subsequently i.e. once the composition has been applied to the substrate, the crosslinking agent will react with this reaction product, thus making the coating more resistant to water penetration.
The time taken for the coating to dry will, of course, depend on various factors such as the water content and atmospheric conditions. Typically, though it will be dry in 24 hours by which time the crosslinking agent will have reacted with the reaction products of (i) and (ii). Substantial crosslinking occurs in a significantly shorter time than this. For example 80% crosslinking can occur in 6 hours.
In order to prevent premature reaction of the crosslinking agents, the composition should be stored in a confined space before use.
Typically, the solids content of the emulsified formulation will vary from 15% to 75% by weight, generally from 25% to 75% by weight and, more particularly, from 35% to 55% by weight. The concentration of the reaction product will generally be from 0.1 to 10%, preferably from 0.5% to 3%, especially 0.5 to 1.5%, by weight.
Typical resins which can be used in the present invention include silicones, alkyd resin, rosin esters, polyurethanes and acrylic polymers. Oils can be used in place of these resins. It will be appreciated that in some formulations it is desirable to use a combination of these in order to obtain particular effects. In particular for primers, it is preferred to use two different types of resin, for example an alkyd resin and a rosin, such that one of the resins penetrates the substrate somewhat, for example the alkyd resin, while the other stays on the surface, for example the rosin, and acts as a “key” for the subsequent paint layer.
The silicone resins used in the present invention will generally have the formula
M
&agr;
D
&bgr;
T
&ggr;
Q
67
(OR)
&egr;
  (I)
where, M=R
1
R
2
R
3
SiO
1/2
D=R
4
R
5
SiO
2/2
T=R
6
SiO
3/2
Q=SiO
4/2
R
1
, R
2
, R
3
R
4
R
5
and R
6
, which can be the same or different, represent a C
1
-C
12
especially C
1
-C
8
, hydrocarbon radical
R: a hydrogen atom or a linear or branched C
1
-C
4
alkyl radical,
the copolymer comprising at least one T or Q grouping;
the symbols &agr;, &bgr;, &ggr;, &dgr; representing, independently, numbers corresponding to the number of atoms of silicon of the type M, D, T and Q relative to an atom of silicon of in the resin of formula (I); the symbol &egr; representing the molar fraction of the ends ≡SiOR relative to an atom of silicon the resin of formula (I); these symbols having the following limits:
&agr;: 0 to 0,5
&bgr;: 0 to 0,95
&ggr;: 0 to 0,9
&dgr;: 0 to 0,8
&egr;: 0,05 to 2
with a &agr;+&bgr;+&ggr;+&dgr;=1.
The groups M can be the same or different when more than one is present; similar comments apply to the groupings D and T. Likewise the groupings OR can be the same or different.
According to a preferred mode of the present invention, the resin is a copolymer of formula (I) where R
1
to R
6
, which are the same or different, represent a C
1
-C
8
linear or branched alkyl radical, R is a hydrogen atom or a C
1
-C
4
linear or branched alkyl radical the copolymers containing at least one T grouping (the symbol &ggr; being a number other than 0) associated with one or more groupings M and D.
Preferred resins are those of formula A and B below:
A: copolymers M
&agr;
D
&bgr;
T
&ggr;
Q
67
(OR)
&egr;
(II) where
A1. according to a first definition:
R
1
to R
6
C
1
-C
8
identical or different alkyl radicals;
R: a hydrogen atom or a C
1
-C
4
alkyl radical
&agr;: 0,1 to 0,3
&bgr;: 0,1 to 0,5
&ggr;: 0,4 to 0,8
&egr;: 0,08 to 1,5
with &agr;+&bgr;+&ggr;=1.
A2. according to a second definition:
R
1
to R
6
: C
1
-C
3
alkyl radicals
R: a hydrogen atom or a C
1
-C
4
alkyl radical
&agr;: 0,1 to 0,3
&bgr;: 0,1 to 0,5
&ggr;: 0,4 to 0,8
&egr;: 0,08 to 1,5
with &agr;+&bgr;+&ggr;=1.
B: The copolymers D
&bgr;
T
&ggr;
(OR), (III) where
B1. according to the first definition:
R
4
to R
6
which may be the same or different represent C
1
-C
8
linear or branched alkyl radical;
R: a hydrogen atom or a C
1
-C
4
linear or branched alkyl radical, at least 25% of one or more of the substituents R
4
to R
6
being a C
3
-C
8
linear or branched alkyl radical.
&bgr;: 0,2 to 0,9
&ggr;: 0,1 to 0,8
&egr;: 0,2 to 1,5
B2. According to a more preferred definition:
R
4
and R
5
: which are the same and represent a C
1
-C
2
alkyl radical,
R
6
: a C
3
-C
8
linear or branched alkyl radical;
R a hydrogen atom or a C
1
-C
3
linear alkyl radical,
&bgr;: 0,2 to 0,6
&ggr;: 0,4 to 0,8
&egr;: 0,3 to 1,0
In general each of radicals R
1
to R
6
can be a linear or branched alkyl radical, for example methyl, ethyl, propyl, butyl or isobutyl; an alkenyl radical such as vinyl; an aryl radical such as phenyl or naphthyl; an arylalkyl radical such as benzyl or phenylethyl; an alkylaryl radical such as tolyl or xylyl; or an araryl radical such as biphenyl.
Typical alkyd resins can be used in the present invention include both drying and non-drying alkyd resins. Thus suitable alkyd resins include oil type using oils having a long carbon chain, eg. C
16
-C
22
, e

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