Elastomeric podalic pads

Details Elastomeric podalic pads Elastomeric podalic pads

1998-05-27

2001-02-13

Szekely, Peter A. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C523S219000, C524S274000, C524S476000, C524S505000, C524S578000, C524S579000, C036S03200A, C036S037000, C036S071000

Reexamination Certificate

active

06187837

ABSTRACT:

I. FIELD OF THE INVENTION
The present invention relates to cushioning pads for use in connection with human feet. More particularly, the invention relates to elastomeric and viscoelastomeric podalic pads for use in footwear.
II. BACKGROUND OF THE INVENTION
A. Background of Related Art
In the prior art, it was known that cushioning material could be formed from elastomeric gels (see, e.g., U.S. Pat. No. 5,334,646, issued on Aug. 2, 1994 in the name of John Y. Chen), foam rubber, lubricated microspheres (see, U.S. Pat. Nos. 5,421,874 and 5,549,743, issued on Jun. 6, 1995 and Aug. 27, 1996, respectively, both in the name of Tony M. Pearce) and other substances.
The addition of adhesives to elastomeric materials is also well known. For example, REGALREZ® resins have been suggested for use in combination with KRATON® thermoplastic rubbers (see U.S. Pat. No. 4,833,193, col. 2, lines 22-27, issued on May 23, 1989 in the name of David L. Sieverding). Many of those combinations include a substantial amount of KRATON®. Some REGALREZ®/KRATON® combinations of the prior art even include greater amounts of KRATON® than REGALREZ®. Many prior art adhesive elastomeric materials employ small amounts of resins.
U.S. Pat. No. 4,833,193, issued on May 23, 1989 in the name of Sieverding, which is hereby incorporated by reference, discusses pressure sensitive adhesives. Applicant believes that the formulations disclosed in the '193 patent is the closest prior art to the formulations of his invention. It is important to note, however, that Sieverding's work was primarily directed to adhesives, not cushioning. The adhesive materials of that patent contain from about 2 to about 40 weight percent triblock copolymer of the general configuration A-B-A, alone or in combination with a diblock copolymer (col. 12, lines 8-14), at least 20 weight percent of a low molecular weight resin (col. 12, lines 15-18) and up to about 80 weight percent mineral oil having a viscosity of about 200 to about 1,200 (col. 12, lines 19-21).
Sieverding's triblock copolymers are SEBS copolymers, such as those sold by Shell Chemical Company of Houston, Tex. as KRATON® G1651 (col. 12, lines 38-40 and Table, col. 16, line 1 to col. 20, line 42). Sieverding's most preferred high molecular weight SEBS has a styrene to rubber ratio (S:EB or A:B) of about 0.48 to about 0.52 (i.e., about 48:52 to about 52:48)(col. 12, lines 40-45).
Sieverding's preferred tackifying resins are low molecular weight resins commercially available under the trade names REGALREZ® 1018 and 1033, both of which are manufactured by Hercules Incorporated of Wilmington, Del. (col. 13, lines 23, 31-33). The '193 patent states that the REGALREZ® resins desired for use in that material are liquid at room temperature (col. 3, lines 50-52). Sieverding's most preferred resin, REGALREZ® 1018, has an average molecular weight in the range of about 375 to about 430 (col. 13, lines 34-37). The Sieverding '193 patent also teaches the use of a single type of tackifying resin in high concentration in his materials (col. 13, lines 40-55).
The '193 patent does not disclose the tensile strength of the materials described therein. Because Sieverding's preferred triblock copolymers are SEBS copolymers, Applicant believes that the tensile strength of the materials of the '193 patent are low. This is because Applicant has found SEBS to be significantly inferior to his preferred polystyrene-hydrogenated poly(isoprene+butadiene)-polystyrene (S-(I+B)-S or S-(B+I)-S) copolymers. In some uses of his material, Sieverding prefers the use of mineral oil in addition to REGALREZ® 1018, which significantly decreases the visco-elastic properties of the materials. Further, Applicant also believes that Sieverding's material is inadequate for many cushioning and other applications since he prefers to use only one type of tackifying resin (Table, col. 15, line 49 to col. 20, line 43) and because of the narrow softening point ranges of tackifying resins useful in his material (col. 13, lines 40-55). In other words, various characteristics of Sieverding's material, including but not limited to softness and rebound rate, cannot be tailored for any given elastomer to plasticizer ratio. This may not be important in the field of adhesives, but it makes Sieverding's material impractical for wide application in the cushioning art.
B. Chemistry of Plasticizer-Extended Elastomers.
A basic discussion of the chemical principles underlying the characteristics and performance of plasticizer-extended elastomers is provided below to orient the reader for the later discussion of the particular chemical aspects of the invention.
The materials of the present invention are a composition primarily of triblock copolymers and plasticizers, both of which are commonly referred to as hydrocarbons. Hydrocarbons are elements which are made up mainly of Carbon (C) and Hydrogen (H) atoms. Examples of hydrocarbons include gasoline, oil, plastic and other petroleum derivatives.
Referring to
FIG. 1
a
, it can be seen that a carbon atom
110
typically has four covalent bonding sites “•”.
FIG. 1
b
shows a hydrogen atom
112
, which has only one covalent bonding site •. With reference to
FIG. 1
c
, which represents a four-carbon molecule called butane, a “covalent” bond, represented at
116
as “-”, is basically a very strong attraction between adjacent atoms. More specifically, a covalent bond is the linkage of two atoms by the sharing of two electrons, one contributed by each of the atoms. For example, the first carbon atom
118
of a butane molecule
114
shares an electron with each of three hydrogen atoms
120
,
122
and
124
, represented as covalent bonds
121
,
123
and
125
, respectively, accounting for three of carbon atom
118
's available electrons. The final electron is shared with the second carbon atom
126
, forming covalent bond
127
. When atoms are covalently bound to one another, the atom-to-atom covalent bond combination makes up a molecule such as butane
114
. An understanding of hydrocarbons, the atoms that make hydrocarbons and the bonds that connect those atoms is important because it provides a basis for understanding the structure and interaction of each of the components of the present invention.
As mentioned above, the present invention utilizes triblock copolymers. With reference to
FIGS. 2
a
and
2
b,
a triblock copolymer is shown. Triblock copolymers
210
are so named because they each have three blocks—two endblocks
212
and
214
and a midblock
216
. If it were possible to grasp the ends of a triblock copolymer molecule and stretch them apart, each triblock copolymer would have a string-like appearance (as in
FIG. 2
a
), with an endblock being located at each end and the midblock between the two endblocks.
FIG. 3
a
depicts the preferred endblocks of the copolymer used in the present invention, which are known as monoalkenylarene polymers
310
. Breaking the term “monoalkenylarene” into its component parts is helpful in understanding the structure and function of the endblocks. “Aryl” refers to what is known as an aromatic ring bonded to another hydrocarbon group. Referring now to
FIG. 3
b
, benzene
312
, one type of aromatic ring, is made up of six carbon molecules
314
,
316
,
318
,
320
,
322
and
324
bound together in a ring-like formation. Due to the ring structure, each of the carbon atoms is bound to two adjacent carbon atoms. This is possible because each carbon atom has four bonding sites. In addition, each carbon atom C of a benzene molecule is bound to only one hydrogen atom H. The remaining bonding site on each carbon atom C is used up in a double covalent bond
326
,
327
, which is referred to as a double bond. Because each carbon atom has only four bonding sites, double bonding in an aromatic ring occurs between a first carbon and only one of the two adjacent carbons. Thus, single bonds
116
and double bonds
326
alternate around the benzene molecule
312
. With ref

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