With very special thanks to Mr. L. Paul Brossette for
his contribution!
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Reproduction of original patent available here: http://members.aol.com/imwpeddler/ |
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United
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3,241,834HIGHLY RESILIENT POLYBUTADIENE BALL Norman H. Stingley, Garden Grove, Calif., assignor to Wham-O Manufacturing Company, San Gabriel, Calif., a corporation of CaliforniaFiled Aug. 25, 1965, Ser. No. 482,5843 Claims. (Cl. 273—58) This is a continuation-in-part of
application Serial No. 462,081 filed June 7, 1965, and now abandoned. This invention relates to a toy and more
particularly to a ball or sphere having extremely high resilience and a high
coefficient of friction. The resilience of rubber balls is one of
their most important characteristics.
This is because the resilience of the ball material determines the
“liveliness” and “bounce” of the ball and hence its utility in various sporting
games and attractiveness as a toy for children. The resilient material normally used for making rubber balls is
a polymer such as natural rubber or some synthetic analog of natural rubber
such as polyisoprene. The present invention is concerned with a
material other than rubber and polyisoprene as the base polymer in rubber
toys and sporting articles. It has
been found that this new material imparts some highly unusual qualities to
articles fabricated with it. Such
articles have been found to have a substantially greater resiliency than those
manufactured from more conventional materials. The greater resiliency is thought to be due to the nature of
the base polymer used in the mixture and the unique quality of the mixture
which comprises the article of being able to conserve the energy which is
imparted to it rather than dissipating a substantial portion of it in the
form of heat. The higher resilience
means that balls made from the material of this invention have a resilience
factor in excess of 90%. This
resilience factor is the resilience of the material as measured by the
Yerzley method, ASTM D945-59. Another unusual quality of balls and toys
of this invention is their coefficient of friction. In this instance the coefficient friction is substantially
higher than in other similar items.
This quality combined with the significantly higher resilience causes
a ball to react in an extraordinary and unpredictable manner when bounced or
struck. This higher coefficient of
friction also provides a means whereby the spin or “English” on a thrown,
struck or dropped ball can be accentuated resulting in unusual reactions by
the ball whenever rebounds from a hard surface. This novel combination of qualities means that one natural
application for balls manufactured with the base polymer with which this
invention is concerned is in trick ball uses. In addition, as a sports implement a ball of this invention
presents a greater challenge to the user.
As an article of play, the eccentricity of reaction makes the ball a
highly entertaining and amusing toy. The invention in the present case
contemplates a molded, vulcanized, highly resilient ball comprising a mixture
of Polybutadiene, a sulfurous vulcanizing agent and a Polybutadiene
reinforcing agent. In addition to the inherent resilience of
the base polymer, the degree of cross linkage between polymer chains is
important in optimizing the bounce or liveliness of balls fabricated with
it. The degree of cross linkage is
primarily determined by the amount of vulcanizing agent used. By limiting the amount of vulcanizing
agent introduced into the mixture to the quantities specified below, a ball
having a Yerzley resilience in excess of 90% is obtained. Such a resilience factor is substantially
higher that that found in balls manufactured from natural rubber or
polyisoprene. In addition to resilience and cross
linkage, the ability |
5 10 15 20 25 30 35 40 45 50 55 60 65 70 |
of
the material to conserve energy is of importance. It has been found that balls manufactured according to the
present invention dissipate very little energy imparted to it in the form of
heat. The present invention embodies
these and other properties as will be observed from the following detailed
description. The accompanying diagrammatic drawing with
legends illustrates the ball. Products according to this invention are
manufactured from a formulation consisting of the following:
In
the formulation above Polybutadiene is the base polymer of the mixture. To produce cross linkage between
polybutadiene chains, that is, to vulcanize or cure the polymer, sulfur is
added to the mixture. A greater
amount of vulcanizing agent is used in the mixture than in such products as
tires thereby producing a greater degree of vulcanization. Put another way, the degree of cross
linkage relative to saturation (hard rubber) is increased over tires and the
like. The more complete vulcanization
is believed to result in the improved resilience of the finished
product. The addition of sulfur in
the range indicated will result in balls having a Yerzley Resilience in
excess of 90%. Oil extended
polybutadiene having as much as 50 parts by weight of oil per hundred parts
by weight of polybutadiene can also be used as the base polymer. Because the natural curing rate of a
mixture of polybutadiene and sulfur is quite slow, certain other additives
are combined with this basic mixture to initiate the curing cycle and
accelerate the rate of vulcanization.
The zinc oxide and stearic acid are added to the basic mixture to
provide this activation function.
Acceleration accomplishes two purposes, one, it shortens the length of
the molding cycle, and two, it equalizes heat throughout the mixture during
the curing cycle. In the preceding
formulation, the accelerators are N-oxydiethylene benzothiazole 2
sulfenamide, di-orthotolylguanidine and bismuth dimethyldithiocarbonate. For ease of reference, the trade names
AMAX, DOTG and Bismate respectively will be used to designate the
accelerators. This activation of these accelerators
occurs as the mixture reaches a specific temperature. For Bismate and DOTG the activation
temperature is approximately 230° F, while that of AMAX is approximately 260° F. By insuring that the heat of reaction is
equalized throughout the mixture a more uniform rate of vulcanization and
improved consistency in the end product is obtained. Hydrated silica is added to the mixture as
a filler. As specific hydrated silica
suitable for use in this mixture is marked under the trademark Hi-Sil
233. This material and certain other
materials perform the function of providing tear and abrasion
resistance. The basic criteria for
selection of the filler material is its ability to improve the durability of
polybutadiene with unduly increasing the specific gravity. Carbon black and lithium oxide have also
been found to fill these requirements and are satisfactory substitutes for
hydrated silica. |
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3,241,834 |
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In addition to the ingredients just
previously discussed, 4 methyl-6 tertiary-butyl phenol is also added to the
mixture. This substance has been given
the trade name of Antioxidant 2246 and prevents discoloration and staining
and inhibits aging of the finished product.
Examples of substitutes for Antioxidant 2246 are phenyl B
naphthylamine, alkyl diphenylamine, and hindered alkyl phenols. Pigmenting agents for obtaining the
desired color of the end product are optional additives. The
mixture and molding of the constituents of this formulation proceeds
according to the following steps. The
various elements of the formulation are brought together in a mixing machine
and agitated thoroughly to insure uniform mixing and distribution of the
elements throughout the mixture. The
result is a plastic mass ready for insertion in a mold. To complete the process, the mixture is
placed in a mold and subjected to a pressure of between 500 and 3,000 p.s.i.
for a period of approximately 10-30 minutes.
Simultaneously, the temperature of the mixture is raised to
approximately 285-340° F. To a certain extent the
length of the molding operation, the pressure, and the temperature to which
the formulation is subjected are co-variant and one may be adjusted to
compensate for a variation of the other.
Preferably the time and temperature for the molding operation is 15-20
minutes at approximately 320° F. and 1,000 p.s.i. An alternate formulation to the one
outlined above is as follows:
The above formulation is mixed in the same manner
as the preceding formulation. To
insure a good dispersion of all ingredients in the mixture, the batch is
normally given a two-pass mix. In the
above formulation, the zinc oxide and the stearic acid perform the same
functions, viz., activation of polymer curing, as they did in the first
formulation. Akron 544 Red and Akron
626 Blue are trade designations for organic coloring agents manufactured by
Akron Chemical Co. Titanium dioxide
is also a coloring agent. These three
constituents in combination are the pigmenting agent for the mixture. Zeolex is a proprietary brand name for a
series of precipitated, highly hydrated sodium silico-aluminates and sodium
calcium silico-aluminates. Its
function is to strengthen the finished product and to act as a filler in the
same manner as the Hi-Sil 233 does in the preceding formulation. Sulfur is the vulcanizing agent. Vandex is a proprietary name for finely
ground selenium. Its function is to
supplement sulfur as a vulcanizing agent. As in the first formulation, several
constituents of the mixture (AMAX and M. Tuads) are added to serve as
accelerators for the polymerization. |
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As is normal in molding techniques, the
curing temperature must be carefully selected in order to prevent
imperfections in the finished product.
Too high a molding temperature will contribute to a condition designated
”backrind.” This condition is characterized
by an indented fracture around the body of the molded product defining the
point where the two halves of the mold are brought together and is due to
thermal expansion in this area during and after the molding cycle. Subject to the proper choice of injection
pressure, injection time, and the combination of mixture constituents,
preheat, and mold temperature, this mixture can also be molded by means of a
conventional injection-molding technique. Combinations of ingredients of which the
two formulations listed above are representative have been found to result in
a product with a specific gravity of approximately 1.0 to 1.3. For greatest resilience, it has been found
that a sufficient amount of filler should be added to produce a product
having a specific gravity of 1.02. What is claimed is: 1. A highly resilient solid ball in the
form of a sphere, the ball material having a specific gravity of from about 1
to about 1.3, and comprising in combination a vulcanized polymer
characterized by the use of 100 parts by weight of polybutadiene and 0.5 to
15 parts by weight of a sulfur vulcanizing agent, and further comprising, in
addition to any activators and accelerators used for vulcanization, 5 to 15
parts by weight of an inorganic reinforcement material. 2. A ball is in accordance with claim 1
in which the reinforcing material is selected from the class consisting of
hydrated silica, carbon black and lithium oxide. 3. A ball in accordance with claim 2 in which the sulfur vulcanizing agent is approximately 5.25 parts by weight and the reinforcing material is approximately 7.5 parts by weight. References
Cited by the Examiner UNITED STATES PATENTS
FOREIGN PATENTS
OTHER REFERENCES “Rubber and Plastics Age,” vol. 38, No. 10,
October 1957, pages 880-883, 885, 887, 889, 891 and 892. “Rubber Chemistry and Technology,” vol.
XXXII, No. 2, April-June 1959, pages 614-627. “Rubber and Plastics Age,” March 1961,
pages 276-282. DELBERT
B. LOWE, Primary Examiner. G.J.
MARLO, Assistant Examiner. |
March 22, 1966 |
N.
H. STINGLEY
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3,241,834 |
HIGHLY RESILIENT POLYBUTADIENE BALL
Filed Aug. 25, 1965
BALL
MATERIAL:
SPECIFIC GRAVITY - 1-1.3
POLYBUTADIENE - ABOUT 100 PARTS
SULFUR VULCAN. AGENT - 0.5 to 15 PARTS
HYDRATED SILICA or }
CARBON BLACK or } - 5 to 15 PARTS
LITHIUM OXIDE }
INVENTOR
NORMAN H.
STINGLEY
BY
Christie, Packer
& Hale
ATTORNEYS