Hot roll fusers comprising polyarylene elastomers

Hot roll fusers are made with a matrix resin which is an elastomer having a glass transition between 90.degree. C. and 160.degree. C. and a structure represented by the formula X--Ar--Y--Ar--X wherein Ar is an aromatic ring structure, Y is O, S, C.dbd.O, SO.sub.2, C(CH.sub.3).sub.2, C(CF.sub.3).sub.2, CH.sub.2 or (CF.sub.2).sub.n and X is --O--C.tbd.N, --C.tbd.CH or ##STR1##

TECHNICAL FIELD 
The present invention is concerned with hot roll fusers which are used, for 
example, in photocopiers and photoprinters. In particular, it is concerned 
with certain polyarylene elastomers to be used as matrix resins in such 
fusers. 
BACKGROUND ART 
U.S. Pat. Nos. 3,736,293 and 4,232,142 show structures different from, but 
having some similarity to, the elastomers used in the present invention, 
but the patents are entirely silent about hot roll fusers. 
Polydimethylsiloxanes and related structures have commonly been used as 
matrix resins for filled fuser rollers. Unfortunately, the thermal 
oxidative stability of these materials is somewhat limited, leading to 
crosslinking and hardening of the otherwise soft fuser roll. This leads to 
inadequate fusing of the toner on the paper as well as formation of a wear 
track in changing between 11 and 14" wide paper. Traditionally, this has 
been the most costly aspect of maintenance of both photocopiers and 
printers. 
Alternative matrix resins for these composite coatings have primarily 
consisted of perfluoroalkyl ethers. Although these are attractive 
thermally stable elastomers, they have many drawbacks including 
processability, expense, adhesion, filling, conductivity and others which 
limit their utility as fuser roller materials. 
DISCLOSURE OF THE INVENTION 
We have recently taken a completely new approach in the design of thermally 
stable elastomers for use in fuser rolls. Wholly aromatic poly(arylene 
ethers) and related structures have been synthesized with Tg's well below 
the use temperature (170.degree.-185.degree. C) of the fuser roller. When 
these materials are lightly crosslinked, they exhibit excellent 
elastomeric qualities, thermal oxidative stability and resistance to 
wicking oils. 
According to the present invention, a hot roll fuser comprises an elastomer 
having a glass transition temperature between 60.degree. C. and 
160.degree. C. and a structure represented by the formula X--Ar--Y--Ar--X 
wherein Ar is an aromatic ring structure, Y is O, S, C.dbd.O, SO.sub.2, 
C(CH.sub.3).sub.2, C(CF.sub.3).sub.2, C H.sub.2 or (CF.sub.2).sub.n and X 
is --O--C.tbd.N, --C.tbd.CH or 
##STR2## 
It is an unexpected feature of the present invention that these rigid 
aromatic structures become rubbery, rather than leathery, above their 
glass transition temperatures (Tg). 
Poly(arylene ethers, ether sulfones and ether ketones) are thermally stable 
structures which exhibit Tg's between 90.degree. and over 300.degree. C. 
The judicious choice of the monomers and/or a combination of both para and 
meta isomers affords an amorphous-wholly aromatic materials with a low Tg 
(less than 140.degree. C.). A wide variety of interconnecting units 
between the aromatic rings are possible to optimize Tg, flexibility and 
thermal stability.

One series of materials are poly(arylene ether ketones) composed of both 
meta and para linkages affording amorphous materials. Hydroquinone was 
reacted with various compositions of both 2,4'- and 
4,4'-difluorobenzophenone using the NMP/K.sub.2 CO.sub.3 synthetic route. 
Long reaction times (24h) were required to afford high molecular weight 
owing to steric effect associated with the 2-4' isomer. Table 1 contains 
the thermal properties of the polymers synthesized. The mixture of isomers 
affords amorphous materials with polymers composed of 75 mole % and greater 
of the meta isomer. Low Tg's (.gtoreq.145.degree. C.) were also observed 
for these structures. In addition, excellent thermal stability was 
observed for these structures with the onset of degradation occurring at 
approximately 600.degree. C. 
TABLE 1 
______________________________________ 
Mole % Tg Tm 
2,4-difluorobenzophenone 
.degree.C. 
.degree.C. 
______________________________________ 
0 145 345 
15 145 300 
25 145 -- 
50 150 -- 
75 131 -- 
100 145 -- 
______________________________________ 
Another series of poly(arylene ether ketones), l, were synthesized which 
contained fluorine to better control surface effects and also provide 
improved thermal stability. 
##STR3## 
Both high molecular weight and functional oligomers were synthesized as 
shown in Table 2. The Tg's range from 150.degree. to 175.degree. C. 
depending on the molecular weight. Phenolic hydroxyl terminated oligomers 
were synthesized to provide the necessary end group chemistry for 
crosslinking into network structures. 
TABLE 2 
______________________________________ 
Characteristics of Bis-F based Poly(arylene ethers ketones) 
Sample &lt;Mn&gt; [2] Tg 
# g/mol dl/g .degree.C. 
______________________________________ 
1 5,000 0.13 155 
2 12,000 0.22 170 
3 20,000 0.50 175 
______________________________________ 
Another synthetic approach involves the preparation of poly(arylene ethers) 
which do not contain sulfone or ketone moieties. The Ullman reaction was 
used to prepare structures with Tg's in the 90.degree.-120.degree. C. 
range. Several structures have been synthesized in moderate molecular 
weight which have Tg's between 115.degree. and 120.degree. C. 
##STR4## 
Network formation can be achieved by a number of methods by preparing 
functionally terminated oligomers which crosslink with temperature and/or 
catalyst. These reactive groups include biphenylene, cyanato, cyano, 
epoxy, ethynyl, maleimide, nadimide, propargyl, vinyl, benzocyclobutene 
and others. 
It should be obvious to one skilled in the art that the behavior of these 
new more thermally stable fuser elastomers can be further modified with 
appropriate fillers to further enhance properties such as thermal 
conductivity, wear resistance, stability to wicking oils, etc. Although 
one would anticipate use of wicking oils to facilitate interactions 
between the paper and the roll it is felt that one could also fill those 
elastomers with appropriate wicking fluids which would bleed very slowly 
to the surface and thus eliminate the need for adding such fluids to the 
surface. Finally and perhaps most importantly, availability of fuser rolls 
with greatly improved thermal stability permits use of higher fusing 
temperatures, permitting use of a much broader range of low cost toners 
which today cannot be used because they fuse at much higher temperatures.