Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-03-22
2002-07-02
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S099000, C524S240000, C524S257000, C528S288000, C528S289000
Reexamination Certificate
active
06414058
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to color stability, and more particularly to improvement of the color stability of compositions containing arylate-comprising polymers.
Photoyellowing of polymers over time is a known phenomenon which is undesirable for aesthetic reasons. It is generally the result of absorption of ultraviolet (UV) radiation by the polymer, said radiation causing photochemical reactions which typically form yellow materials. Such base polymers as polycarbonates are particularly sensitive to photoyellowing. This can severely impede the fabrication of light-colored articles such as white or blue articles, since the yellowing tendency can obliterate the white or blue coloring with the passage of time. Alternatively, a higher proportion of the desired colorant can be introduced during fabrication but there will still be a change in appearance over time.
A recent development which can minimize photoyellowing is the use of a polymer comprising arylate structural units, for example one with structural units derived from resorcinol and a mixture of isophthalic and terephthalic acids, which may be blended with a base polymer, may form a copolymer therewith or may constitute a separate, external layer thereover. Such polyarylates undergo a Fries rearrangement to form hydroxybenzophenone moieties, which serve as ultraviolet absorbers and protect the base polymer from photoyellowing.
However, the polyarylates themselves may develop a yellow color with the passage of time, dissipating to at least some extent the benefits of UV absorption. This is because, while they absorb primarily in the range between about 360 nanometers and about 390 nanometers (nm) in the near ultraviolet portion of the spectrum, their absorption extends a small distance into the visible area, resulting in the yellow color development.
One known method of compensating for color development is to introduce into the polymer a photobleachable compound which absorbs in the same region of the spectrum as the hydroxybenzophenone moieties. Yellow dyes generally absorb in this range. Such a dye, if photobleachable, turns colorless at approximately the same rate as that of photoyellowing and the overall color of the polymer remains fairly constant. This method is disclosed in various patents, of which examples in the polyphenylene ether art include U.S. Pat. Nos. 4,493,915 and 5,478,878.
However, the absorption of most photobleachable yellow dyes continues into the range between about 400 nanometers and about 450 nanometers in the visible region of the spectrum, farther than that of the hydroxybenzophenone moieties. This means that their presence initially introduces a yellow tinge of greater intensity than that produced as hydroxybenzophenone moieties are formed. Under such conditions it is at best difficult, and at worst impossible, to produce light colored articles with consistent coloration over the passage of time. New methods for color suppression continue to be sought in the art.
SUMMARY OF THE INVENTION
The present invention is based on the discovery that color development as the result of the formation of hydroxybenzophenone moieties in arylate-comprising polymers can be suppressed by the addition of photobleachable compounds having absorption limited, within the near ultraviolet and visible portions of the spectrum, to the aforementioned region of between about 360 nm and about 390 nm. It has further been discovered that aminocinnamic compounds have such absorption properties.
Accordingly, in one embodiment the invention is a resinous composition comprising the following:
(A) at least one thermoplastic polymer comprising structural units derived from at least one 1,3-dihydroxybenzene and at least one organodicarboxylic acid, and
(B) at least one 4-aminocinnamic compound of the formula
wherein:
each of R
1
and R
2
is an alkyl radical, or R
1
and R
2
together with the nitrogen atom separating them form a heterocyclic radical;
R
3
is COOR
4
, C(O)R
4
, or CN;
R
4
is hydrogen, alkyl or aryl; and
each of R
5
and R
6
is hydrogen, alkyl, or aryl; or R
5
and R
6
together with the carbon atoms connecting them form an alicyclic radical;
said 4-aminocinnamic compound absorbing radiation in the range between about 360 nanometers and about 390 nanometers.
In another embodiment the invention is a resinous composition comprising the following:
(A) at least one thermoplastic polymer comprising structural units derived from at least one 1,3-dihydroxybenzene and at least one organodicarboxylic acid, and
(B) at least one 4-aminocinnamic compound of the formula
wherein:
each of R
1
and R
2
is an alkyl radical, or R
1
and R
2
together with the nitrogen atom separating them form a heterocyclic radical;
R
3
is COOR
4
, C(O)R
4
, or CN;
R
4
is hydrogen, alkyl or aryl;
R
5
is hydrogen, alkyl, or aryl; and
each of R
7
and R
8
is hydrogen or an alkyl radical, or R
7
and R
8
together form an alicyclic radical;
said 4-aminocinnamic compound absorbing radiation in the range between about 360 nanometers and about 390 nanometers.
In another embodiment the invention is a resinous composition comprising the following and any reaction products thereof:
(A) at least one thermoplastic polymer comprising structural units derived from at least one 1,3-dihydroxybenzene and at least one organodicarboxylic acid, and
(B) at least one 4-aminocinnamic compound of the formula
wherein:
each of R
1
and R
2
is an alkyl radical, or R
1
and R
2
together with the nitrogen atom separating them form a heterocyclic radical;
each of R
5
and R
6
is hydrogen, alkyl, or aryl; or R
5
and R
6
together with the carbon atoms connecting them form an alicyclic radical; and
each of R
7
and R
8
is hydrogen or an alkyl radical, or R
7
and R
8
together form an alicyclic radical;
said 4-aminocinnamic compound absorbing radiation in the range between about 360 nanometers and about 390 nanometers.
DETAILED DESCRIPTION; PREFERRED EMBODIMENTS
For the sake of brevity, the constituents of the compositions of this invention are defined as “components” irrespective of whether a reaction between said constituents occurs at any time. Thus, the compositions may include said components and any reaction products thereof. As used herein the term polymer comprises homopolymers, copolymers, interpolymers, higher order copolymers, and higher order interpolymers, but is not limited to these specific genera of polymeric materials.
Component A in the compositions of the invention is a thermoplastic polymer comprising structural units derived from at least one 1,3-dihydroxybenzene and at least one organodicarboxylic acid. Suitable polymers for this purpose, specifically arylate-comprising polymers, are disclosed for example in commonly owned U.S. Pat. No. 5,916,997, the disclosure of which is incorporated by reference herein. Arylate-comprising polymers having a glass transition temperature of at least about 80° C. and no crystalline melting temperature, i.e., those that are amorphous, are preferred.
In one embodiment the polymer comprising a polyarylate is one with structural units derived from a 1,3-dihydroxybenzene and either isophthalic acid or terephthalic acid or a mixture thereof comprising structural units of the formula
wherein each R
9
is a substituent, especially halo or C
1-12
alkyl, and p is 0-3, optionally in combination with structural units of the formula
wherein R
9
and p are as previously defined and R
10
is a divalent C
3-22
aliphatic, alicyclic or mixed aliphatic-alicyclic radical. Moieties represented by R
10
are often referred to as “soft block” units.
It is within the scope of the invention for other acid groups, such as those derived from aliphatic dicarboxylic acids such as succinic acid, adipic acid or cyclohexane-1,4-dicarboxylic acid, or from other aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, to be present, preferably in amounts no greater than about 30 mole percent. Most typically, however, component A may consist of units of formula IV, optionally in combination with units of f
Brown S. Bruce
General Electric Company
Johnson Noreen C.
Yoon Tae H.
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