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
1998-04-14
2001-10-09
Woodward, Ana (Department: 1711)
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...
C524S276000, C524S277000, C524S487000, C524S490000, C524S570000, C524S571000, C524S574000
Reexamination Certificate
active
06300398
ABSTRACT:
The subject invention is directed to polymer compositions having improved elongation. In particular, the subject invention is directed to polymer compositions which comprise a homogeneous linear or substantially linear ethylene polymer, a wax which has a low molecular weight and which has a higher crystalline melting point than the homogeneous linear or substantially linear ethylene polymer, and a nucleating agent.
Homogeneous ethylene polymers having a density less than about 0.910 g/cm
3
, particularly less than about 0.900 g/cm
3
, preferably less about 0.890 g/cm
3
, and most preferably less than about 0.880 g/cm
3
, have good elongation properties, that is, such as a high elongation at break and the ability to withstand high degrees of stress before breaking, with the degree of elongation properties increasing as the density of the polymer decreases. However, homogeneous ethylene polymers having such elongation properties lack a highly crystalline fraction that imparts increased upper use temperature and favorably high onset of crystallization temperatures.
To compensate for the poor upper use temperature and low onset of crystallization temperature characteristic of homogeneous ethylene polymers having a density less than about 0.910 g/cm
3
, it may be desirable to blend therewith a higher crystallinity material, such as a higher density homogeneous ethylene polymer or a traditional wax. However, while the addition of such a higher crystallinity material may increase the upper use temperature and provide a higher onset of crystallization temperature, it causes a highly deleterious loss of elongation properties.
Those in industry would find great advantage in polymer compositions which have favorable upper use temperatures and high onset of crystallization temperatures, but which retain favorable elongation at break and the ability to withstand high degrees of stress before breaking which is characteristic of homogeneous ethylene polymers having a density less than about 0.910 g/cm
3
.
Hot melt adhesives comprising homogeneous linear or substantially linear ethylene polymers are further known. See, for instance, WO 97/33921, WO 92/12212, and WO 94/10256, each of which is incorporated herein by reference. While such hot melt adhesive formulations exhibit many commercially attractive attributes, it would be desirable for certain formulations to improve the elongation at break of these compositions. Those in industry would further find great advantage in hot melt adhesive formulations for use in formulations which require a high elongation at break, without incurring a detrimental effect on yield or break stress, such as, for instance, in bookbinding adhesives.
Accordingly, the subject invention provides a polymer composition comprising:
(a) a homogeneous ethylene/x-olefin interpolymer;
(b) a wax; and
(c) a nucleating agent,
wherein the nucleating agent is provided in an effective amount such that the percent elongation at break of the polymer composition is at least fifty percent greater than the percent elongation at break of a comparative composition which lacks the nucleating agent.
In preferred embodiments, the homogeneous ethylene/&agr;-olefin interpolymer will be a homogeneous linear or substantially linear ethylene/&agr;-olefin interpolymer, which in turn preferably has a density less than about 0.910 g/cm
3
, more preferably less than about 0.900 g/cm
3
, even more preferably less than about 0.890 g/cm
3
, and most preferably less than about 0.880 g/cm
3
.
In preferred embodiments, the wax will be a paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polyethylene or polyethylene by-product wax, or homogenous wax, which is preferably characterized as having a M
w
of no more than about 3000, and which has a density greater than that of the homogeneous ethylene polymer of component (a).
In preferred embodiments, the nucleating agent will be provided in an amount of at least about 0.01 weight percent, more preferably at least about 0.05 weight percent, even more preferably at least about 0.1 weight percent, and most preferably at least about 0.2 weight percent; preferably no more than about 10 weight percent, more preferably no more than about 5 weight percent, even more preferably no more than about 1 weight percent, and most preferably less than about 0.5 weight percent.
Preferred polymer compositions of the invention will exhibit a percent elongation at break which is at least four times greater than the percent elongation at break of a comparative composition which lacks the nucleating agent.
The subject invention further provides a hot melt adhesive composition comprising:
(a) an olefin polymer;
(b) a nucleating agent; and
(c) optionally, one or more of a tackifier, plasticizer or wax.
These and other embodiments are more fully described in the following detailed description, wherein:
FIG. 1
is a bar chart representation of the elongation properties of polymer compositions of the invention and comparative compositions lacking a nucleating agent
The polymer compositions of the invention comprise at least one homogeneous ethylene/&agr;-olefin interpolymer which is an interpolymer of ethylene and at least one C
3
-C
20
(&agr;-olefin. The term “interpolymer” is used herein to indicate a copolymer, or a terpolymer, or a higher order polymer. That is, at least one other comonomer is polymerized with ethylene to make the interpolymer.
The homogeneous ethylene/&agr;-olefin interpolymer is a homogeneous linear or substantially linear ethylene/&agr;-olefin interpolymer. By the term “homogenous”, it is meant that any comonomer is randomly distributed within a given interpolymer molecule and substantially all of the interpolymer molecules have the same ethylene/comonomer ratio within that interpolymer. The melting peak of homogeneous linear and substantially linear ethylene polymers, as obtained using differential scanning calorimetry, will broaden as the density decreases and/or as the number average molecular weight decreases. However, unlike heterogeneous polymers, when a homogeneous polymer has a melting peak greater than 115° C. (such as is the case of polymers having a density greater than 0.940 g/cm
3
), it does not additionally have a distinct lower temperature melting peak.
In addition or in the alternative, the homogeneity of the polymer may be described by the SCBDI (Short Chain Branching Distribution Index) or CDBI (Composition Distribution Breadth Index), which are defined as the weight percent of the polymer molecules having a conomomer content within 50 percent of the median total molar comonomer content. The SCBDI of a polymer is readily calculated from data obtained from techniques known in the art, such as, for example, temperature rising elution fractionation (abbreviated herein as “TREF”), which is described, for example, in Wild et al., Journal of Polymer Science, Poly. Phys. Ed., Vol. 20, p. 441 (1982), in U.S. Pat. No. 4,798,081 (Hazlitt et al.), or in U.S. Pat. No. 5,089,321 (Chum et al.), each of which is incorporated herein by reference. The SCBDI or CDBI for the homogeneous ethylene/&agr;-olefin interpolymers useful in the invention is preferably greater than about 50 percent, more preferably greater than about 70 percent, with SCBDI's and CDBI of greater than about 90 percent being easily attained.
The homogeneous ethylene/&agr;-olefin interpolymers useful in the invention are characterized as having a narrow molecular weight distribution (M
w
/M
n
). For the homogeneous ethylene/&agr;-olefins useful in the polymer compositions of the invention, the M
w
/M
n
is from about 1.5 to about 2.5, preferably from about 1.8 to about 2.2, most preferably about 2.0.
Substantially linear ethylene interpolymers are homogeneous interpolymers having long chain branching. Due to the presence of such long chain branching, substantially linear ethylene interpolymers are further characterized as having a melt flow ratio (
10
/I
2
) which may be varied independently of the polydispersity index, that is, the molecular weight distribution M
w
/M
n
. This fe
Jialanella Gary Lee
McKeand, Jr. Thomas J.
Sehanobish Kalyan
The Dow Chemical Company
Woodward Ana
LandOfFree
Polymer compositions having improved elongation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polymer compositions having improved elongation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymer compositions having improved elongation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2580686