July 28, 1959
H. c. L. DUNKER
‘
2,896,949
TENNIS BALLS
’ Filed March 15, 1954
2 Air ‘of atmospheric pressure.
\
4v Resinous high styrene-butodiene oopolymer
and rubber.
2 Air at atmospheric pressure
'-
“
v‘
4 Porous resinous hi h st rene
copolymer ond rgbbey.
v
-butooiene
INVENTOR
H‘. C. L. DUNKER
BY
ATTQRNEYYS
United States Patent 0"’
a
W
2,896,949
' ,PatentedaJ-uI-y28,11,959
those. of tennis balls in general .use but'zcontainingzaogas
vquired
?lling at
hardness
atmospheric
and .rebouridmroperties.
pressure, iwhilendisplayinga.
.
‘£896,949 -
Y
Another. object of thainventionais: to: provide :a :tennis
ball‘ comprising‘ a hollow modi?ed.'rubheracorencontaining
a- gas ?lling atatmosphericapressure, and.an;outer'ifelt
‘Henry-i Ghristianioui's ‘Drinker, ‘Halsing‘borg, iSweden
covering, said'ball beingv similar: intappearanee and :play
ing properties to atennisgballsrlwhich satisfy "theiImten
.AmilicatiouMarchf-?y 19.54‘, Serial Nil-#4116358
national and National Tennis Associatihnuneqniremenis
but having;substantially;improvedkeepingtqualities and", as
‘Claims priority, application‘ Sweden August 22,1950
-11':Claims.. :(€l..£7:3—-61)
a consequenqe: ;_t~hereo_f, 1a, pnolongedzplaying ilifer
,
A further object ,of xtheinvention; isntovprovidexaxtennis
ball comprising achollow modi?ed rubber-georecontetin
ingsa .gas ?lling; at. 2atmospheric:eprlessnre;.zandz:an iouter
This applicationiis a continnatienéinipart of applicants
CO-P‘ending application ."Seriial fNo- '23‘8',;19Z,.?1edfIuly 23,
covering, serving to 1give<theéball;the;sur?aizercharacteristics
required ‘in o?iciall match :play, gsaid
1951, and ‘Serial No. ‘266,443, '?l'e'd “January M24', 1952,
{ball ihei'ng
capable of being stored‘; for;aprolongedrtime;periodiwith
both now abandoned.
out any falling-off intitszhardnesstand rebound properties.
.According‘ ‘to the present, :invention, v:the :above land
20 other objects ,?rze :attained {in :artennis .ball, ‘comprising a
Ordinary tennis balls‘generallyeonsist;of;an;inner.hollow
hollow‘ rubber structure by :having incorporated -inw=said
core of rubber ,(rubber ball) having __a .gas _?11ir_1g:.under
,structlme an ingredienhconsisting of auresinousrflrhi
super-atmospheric pressure .anda coveringof, felt. attached
styreneebutadiene ,copolymen.
'<
=to theoutside ,of, said.core., .The structuralcharacteristics
Theaeeompanying drawingdlhistrateszexamples=of§ten
of the _ball,,_such ,as, the composition of .thesrubber, :the 25 nis halls in. accordance .with: :the ‘iPI‘QSeDt :invention.
wall thickness and the , diameter ,of .the. rubber. tame, @-the
Figures. :1 ltoqS, inclusive .rsholwxcross-isections :of tennis
amount ,of super-atmospheric pressure, and .the: nature
:balls till‘ accordance ‘with. 511136 ‘invention’.
of the felt covering, may be varied within relatively ,nar
.‘In ~Figures -.-'1-—_3f, the v‘tennis: :ball icomprises - ahmold‘ed
row limits since these characteristics‘ are“ required ;to 1im
and ;cure.d‘srlihber composition I4 .‘eont-ainingirubher, ‘rub
part‘ predetermined ‘properties to ‘the ‘ball with respect 30 tber processing ingredients ‘and a high .styrene-ibutadiene
to the outer diameter, ‘weight, hardness and rebound.
copolymer,
stantiallyratmosphericzpressure,
the "ball i-being i?l‘led'IIn‘JFigsJI'
'with :a gas
and72*33112
at? cov
‘These requirements are de?ned in "the “Rules of‘Lawn
The presentinvention relates to improvements in tennis
balls.
Tennis” as laid down by;the Internationztl‘Tennis Federa
;ering;of‘.textile~mateiial ids-shown. IInfiFig. 2a cover
‘tion. According -to- these: speci?cations, 'a-tennis 'bal'l shall
ing :c?sponge irubber .‘3' ‘is shown,
’
;be moreet-han 21/2 inches and less‘ than‘ZS/s' inches in di 35
In Figs. 1 and 2, the tennis ‘ball comprises eaad'uril
ameter, and not less than 2 ozs. (56.7 gr.) nor more vthan
layered structure, the: inner".:1ayer"1' ibe‘ing made‘ from
'21A6ozs. (581-5 gr.) in weight, and the ball‘ shall have
a. molded :and rcured rubber composition of 1the Xwel'lf
a minimum reboundof 53 inches (“135 cm;) and a maxi
mum rebound of‘ 58 inches (147 cm.) when dropped
knownutype land the outer ilayer ‘4 beinglcomposed'lo'f‘ia
composition of. rubber, rubber processing ingredients,
il-‘GO‘finches '(25'4-cm.) and a deformation of. not‘l‘ess than 40 and. a: high styrenei-i‘butadieneicopolyrner. Alsurfacedayer
2650f an inch andinotv more than .290 of an inch when
.or1 covering, 3 .of felt Eis. applied‘ ‘to “said; ‘rubber structure.
subjected to a pressure of' 1'8 'lbs'.
Figure '4 illustratesv aldetailhofla‘tenni's 'rball'lin a‘modifi
In ,a ‘tennis ‘ball' which'is' made vso as ‘to comply with
cation of :Eig. ‘3f, athevd'etail' consisting of at final ‘layer
the requirements of diameter and‘ weight, the proper
hardness ,and rebound properties are generally attained
‘by suitably adjusting the super-atmospheric pressure of
the gas ?lling within the rubber core. However, the
?nished ball will not keep these ,properties ,unchanged
‘for any considerable ‘period of time, lbecause ,the ,gas
under' pressure ‘gradually ,di?uses out through the .rub
‘ber wall, and‘ thereby results in a reduction ‘of both
the hardness and‘ the-rebound of the ball,
Attempts have .already ‘been made .to avoid .these ,dil?
culties ‘by varying the pressure of ;the. ‘gas ?lling and
‘by increasing the impermeability of‘ the ruhbeneovering.
For example, it has been-proposed tosti?en the rubber
rubber‘rstructure, .in'which» the: inner layer '17 'isr'composetl
of‘ :an ordinary “rubber composition and, the. ‘outer ‘layer
8 of a rubber :composition including a 3high styrene‘
butadiene copol-ymer, said outer‘layer§8¥being:of'a' spongy
character, so that no.1feltcoveriing'iis needed.
:ingsat least 50% by weight sof-styrenerare iknown to'stli?'en
rubber. lit'has been :found ‘that itihey increase the hard
ness andrrigidity .of'the rubber stock. 1In.generallhthey
also improve the rtens'il'e strength, itoug'hness, and-resist;
55 ance to tear ‘and abraSion-ofrubber; "Therefore, such
copolymers ’1'1B.V6'9bBe11 found “useful as stilferiing ‘and "re
inforcing agents in ~rubberisoles v‘and similar articles‘where
core by means of ,a network ,of ,ribs on :the interior
the hardness and‘abrasion resistance‘ of the rubber
surface thereof. ‘However, none of the proposedsolu
60
'The ‘principal- ‘object- of the present invention‘ i's'to
provide an improved "tennis “ball in which ‘the require
"ment of having- a gas ?lling of super-.atmospheriejpres
sure is dispensed with and which, owingto'the' absence
:of apressu-re ‘differential between‘ the inside and outside 65
-_of the modi?ed rubbercore, .willmaintain .its‘ori'ginal
,lproper hardness‘ and rebound properties ‘for alongperiod
=_of time.
It is a further object of‘ the invention to provide a
tennis ball comprising a hollow modi?ed rubber core
‘having an‘ outeridiameter'and 'a“wail“thickness"similar to
of
primary importance, ‘inter saliain 'go-lfball, soft “ball ‘and
tions to the problem of storage has'been successful in
practice;
>
Resinous'copol-ymers of styrene andihutadiene eman- '
basketball covers.
.
Applicant has ‘found by ‘incorporating such resinous
hjgh styrene-butadiene copolymers ‘in’ the'rubber "struc
'ture of ‘tennis balls ‘that properly-matched hardness and
rebound characteristics o'f‘the ?nished "balls may‘j-bejproé
duced in the absence 'ofsuper-atmospheric gas pressure
of‘
?lling
the “within
vknowledge-ofstheinfluence
the hollow rubber" structure.
of" such 'copo‘lynr'ers
On'the on
the'properties of' rubber ‘stock, :it'was'to‘beexpected ‘that
‘balls
an increased
wouldresult
hardness
~from1'the
of the
‘incorporation
rubberstructure
ofthecopdly
mers' ‘in "the-rubber; A ‘similar ‘increase ‘in 'hardness'is
3
2,896,949
4
observed upon adding such well-known ingredients to
the rubber, as inorganic ?llers such as kaolin or chalk.
It was surprising to discover, that despite an increase in
hardness the remaining resilience of the rubber stock is
remarkably effective in tennis balls to permit the objec
tionable super-atmospheric pressure within the balls to be
dispensed with. Particularly, in view of the reduction
in the resilience of the rubber caused by the coplymer, it
In a laminated core construction the copolymer rubber
mix may be even higher in copolymer content in the inner
core to produce a tennis ball meeting the Lawn Tennis
speci?cations and having the same unexcelled storage
characteristics as the single layered core. Further, the
single layered core modi?ed at its surface with a blowing
agent possesses such an excellent balance of properties
within the speci?cation requirements so that the usual
was not expected that tennis balls made from such rubber
felt covering may be entirely dispensed with.
stock and having a gas ?lling of atmospheric pressure 10
The characteristics of the ?nished balls are only slightly
could possess the proper weight and hardness and also
in?uenced by varying other factors, such as the propor
comply with the requisite rebound speci?cation under
tion of kaolin or other ?ller in the rubber blend and the
the international rules.
processing operations, mastication, rate of curing, ‘etc.
One example of a resinous high styrene-butadiene co
' The wall thickness of the rubber body, and the nature of
polymer'which is suitable for the purposes of the present 15 the outer covering are as required for the hardness and
invention is a product sold by the B. F. Goodrich Chem
rebound speci?cations as are also the weight and diameter
‘ical Company under the trade name of “Goodrite Resin
of the balls.
50” and consisting of about 85% styrene and 15% buta
A typical example of a rubber-copolymer composition
diene. This resin is described for example in an article
within the above-mentioned limits which may be used for
“Rubber or Plastics” in the “Modern Plastics,” July 1948. 20 making tennis balls as described is as follows:
Other examples are a product sold by the Marbon Cor
EXAMPLE 1
poration under the name of “Marbon B” and a product
sold by the Dewey and Almy Chemical Co. under the
name of “Darex Copolymer 3,” both consisting of 70%
styrene and 30% butadiene.
Parts by weight
Rubber
___________________________________ __
100
A further example is a 25 Resinous copolymer (85 % styrene, 15 % buta
product sold by the Polymer Corporation, Ltd., of Can
diene)
_____ _i ___________________________ __
30
ada, under the same of 58-250, and consisting of 55%
styrene and 45% butadiene. Still another example is a
Zinc oxide ________________________________ __
5
Kaolin ____________________________________ _._
20
product sold by the Goodyear Tire & Rubber Company
Stearic acid _______________________________ _._
2
under the name of “Pliolite 8-3.” The important char 30
acteristics of this product are explained in an article
Accelerator
“Styrene-Diene Resins in Rubber Compounding” by
A. M. Borders et al. in the “Industrial and Engineering
_______________________________ __
1
Sulphur ___________________________________ _._
2.5
The rubber blend is processed as is usual in rubber
manufacture, and the ball cores are made therefrom
Chemistry,” vol. 38-—l946. Further examples of suitable
using any well-known forming and curing technique
copolymers are products sold by the Marbon Corpora 35 except that the means for developing super-atmospheric
tion and known under the names of “Marbon S and S1,”
pressure within the cores are dispensed with. The appli—
vwhich are described in an article “High Styrene Resins in
Rubber Compounding” by A. G. Susie et al. in the “Rub<
cation of the outer covering of felt material or any other
equivalent material is also carried out in the well-known
ber Age,” August 1949.
manner.
A tennis ball embodying the present invention may 40 It is within the purview of the invention to produce
consist of an inner hollow rubber body having uniformly
tennis balls in which the hollow rubber structure includes
incorporated therein by conventional rubber handling
an inner hollow rubber core containing a gas ?lling of
procedures a high styrene-butadiene copolymer and an
atmospheric pressure and a rubber layer surrounding
outer covering of the usual felt material or a material
said core and having the resinous high styrene-butadiene
having characteristics equivalent to those of such felt 45 copolymer incorporated therein. Since the said rubber
material, such as sponge rubber, the said body enclosing
layer containing the copolymer is here relied upon to
a gas ?lling, preferably air at ordinary atmospheric pres
sure. The rubber blend from which the said rubber body
is made may, apart from ordinary ?llers and processing
properties, otherwise obtained by having the gas ?lling
ingredients such as kaolin, accelerators, and sulphur, pref~
stitutes only part of the thickness of the rubber struc
impart to the balls the necessary hardness and rebound
at super-atmospheric pressure, and since this layer con
erably contain from about 65 to about 90 parts of rubber
ture as a whole, the range of percentages of the copolymer
and from about 10 to about 35 parts of a high styrene
in the rubber of said layer will be moved upwardly to
,butadiene copolymer. Where a copolymer very high in
some extent. For example, in using a copolymer
styrene, e.g. containing about 85% styrene and about
containing 85% styrene and 15% butadiene (“Goodrite
.15 % butadiene (“Goodrite Resin 50"), is used, an amount 55 Resin 50”) at least 15% of this copolymer may have
of said copolymer at the lower part of said range is re
to be included in the rubber blend, and in using a co
quired, whereas a copolymer lower in styrene will as a
polymer containing 70% styrene and’30% butadiene
rule be added to the rubber in amounts nearer the upper
(“Marbon B”) the proportion of copolymer in the rubber
limit of said range, in order that the ?nished tennis balls
blend may be increased towards 50%. Typical examples
shall have the desired hardness and rebound properties. 60 of rubber-copolymer compositions which may be used
However, the application is not restricted to the exact
for this variety of tennis balls are as follows (the ?gures
ranges of the constituents mentioned above, since these
being parts by weight):
may be varied somewhat so that the proportions may
sometimes be a little outside of these ranges.
Example"
It is to be understood that the amount of resinous high 65
styrene-butadiene copolymer incorporated with the rub
same time the amount is su?icient to render the core sub
stantially impermeable so that it will have the compressi
jbility, hardness, wall thickness and weight characteristics
despite modi?cation by conventional ?ller ingredients. 75,
3
4
Natural Rubber __________________________________ __
Synthetic Rubber (“GR-S”)
ber is an amount su?icient to prevent the resilience of the
“Marbon S" __________________ __
?nished ball from dropping below a minimum value
“Marbon S1” __________________ __
oxide,
which will reduce the rebound properties as are necessary 70 Zinc
Stearie acid
to comply with the Lawn Tennis speci?cation, and at the
2
10
2
Mineral oil- _~_ ____________________________________ __
Accelerator
1. 7
Antioxidant ______________________________________ _.
0.5
ulphur- _
2. 5
The rubber blends, after being processed, are prefer
assets“
,
= 36.,
._
remains- 1A.
ably’ formed-into ‘sheets: in :alpressure curing operation
icarrieduontrin- a wellahnownimanners *From these‘: sheets
ith'en stamped. piecesof a desiredgshap'e which :are
coated ‘with, a cement and applied‘ as ‘a covering around
.the inner cured‘ rubber core.
I
I'The: hollow rubber structure, comprising the inner
~holl'owrrubbericore andthewouter lcovering :of a :rubber
eopolymer'xomposition, ‘may :have :a surface ‘layer or
the: usual‘ feltmateriali ‘applied1 thereto». ‘ Itiis‘ a; further
The rubber material
aspecttof :the invention that the said’ covering- -.of ‘a
nuhber-copolymerlcomposition may "be- made spongy and,
fit-desired, :formedlzwith: any suitable surface pattern “to
the bars hallfsprssrwere
tested as explained above. 7
The results are given irr'th'e following Tables I and II.
make the said covering more ‘or vl'es's-Aeqliiyla'll‘en't' {to a
felt layer andI to provide-a- ‘bet'ten griplto'vthe ball- and
raster _
‘con?ne it to‘ aisrnooth path through the-air, thereby
vmaking ‘an. additional Jfelt vzsur?ace ‘layer super?uous.
i’li‘hewcovering-may be made spongy by ‘adding 'to the
>-mhber-copolymer compositions, 'for‘example those men
‘ iRllbberzeompound-ié
= ‘
Rubber
u |~ "+
:1 wstwmnprbumlenp
admixture
tioned :as .“Example'Nos‘. '2, ‘3. and‘ 4' above, so called
agents‘, ez'g. ‘ammonium (carbonate, =bi'rcarbonate
Oycllged rubber
copolymer
i Hardnes ‘riteslllenee, Hardness #3981119“?
‘
I
l
.
.
(of soda, ammonium :nitrate, iaz'o compounds rtsomethne‘s
oi
as
p0,»?
65L»
:used under :the trade names‘ 1of' “Unicelg” “*Vlilkaeel,”
“Porofor,” etc.) and others, in amounts of about 6 to=7
$15:
69 1
358%‘
6%-
‘:39...
.82.
parts in the formulas of Examples 2, 3 and 4.
s
'
‘
{Q0
>
"52
. ..3.1
TABLEHII
oncyclizedfrnbbenj
‘
_v
,
Copolymer ‘ Cyellzed
rubber
‘varying- t-he composition o£¥1the=rubber4copolymer Eblend},
particularly the ratio- of- ‘rubber ‘to copolymer- ‘and the
Eainount- ‘or blowing agent, vthe ‘rebound and hardness
of the ?nished tennis- balls may thereby be effectively
i'Rahmmrl ‘
-
.Eompresslon=.-__._._
“
110.v .. l
To illustrate the improvement achievedtby the inven
.. _ _
_.
“Weight, g‘. .1. .... _-
535
_
_
[BallemsdeztromaS? partsembbnr-iéwpartestyrene-butadiene eopolymer
less spongy. The vsponginess of- the eovering-ma‘kes ,it
lighter and reduces the rebound and hardnesscharacter
iistics of the ‘tennis ‘balls, which has ‘to betalien into
account in ‘designing the rubber structure. “Thus, by
_
V
Owing
tov the gases which these substances-release on ‘heating
when the rubber is ‘cured, the rubber becomes more or
controlled.
,.
@1150
3'05
‘
The, rubber blendeentained-aa-relatively high ~percent~
age :o? 'ikaolin;
tion a number of rubber compositions and tennis" alls
made therefrom, ?lled atatmospheric pressure have been
tested, and an account thereof -iS-,giV¢I1F below.’ Int-hose
tests the rubber blends of various compositions are "420
,mixed with various proportions of a ‘high styrenerbntap
results indicated’ in arable: I=.'.show
that .by- .isuhstitutinghigh: stynenerhutai?ene ‘for :part:
the :rubber atrubber' material havingoipcrensedzhandness
reduced IEBSliiCBQQAQ?H i‘he tolatailieth.v :zlh'tcompaaiison,
~cycjlizrd rubber, :gives :alnmos'treanalincreasesin;rh'ardik
diene copolymer or other ingredients (cyclized rubber,
ness‘
II it =hutza
may be
greater
seen reduction
that a ball in
\resiliencet:
‘which the:rFrom
rubber ma
coumarone resin, or kaolin), the hardness and resilience
terial contains 15% oopolymer, calculated on the basis
of the rubber made from such rubber-copolymer mixtures
of rubber+copolymer, has properties which might make
are determined, tennis balls are made from these rubber 45 it suitable as a tennis ball, while a ball having part of
mixtures, and the compression (the inyerse-lo?fliardness)
the rubber replaced by cyclized rubber appears to be
less suitablebecausethe rebound has dropped too much.
and the rebound of the balls determined. The hardness
‘of the rubber mafe'ri'ahis determined by means of the
well-known ‘Shore durometer “A,” and the resilience is
(The bare ball cores, such as tested, ought to have
vslightly greater amounts of rebound and compression
'teste'dbymeans of a’Schob pendulum in which the degree
than required ‘for v;_t,h;§>:“?nished balls.)
of resilience of the t'estgpiece‘isntietermined- by the, rebound
‘IL-Investigation 70)‘ the connection between hardness and
resilience -of~~rubber~and rebound and compression of
.balls imade. .t-herefromf
‘pendulum;
,
.
Tennisiihall cores. were made from ‘the rubber mixtures 55 The rubber blendsnsed in these experiments di?ered
ii'n=the ordinary way. In some of'the experiments, bare
slightly ‘from those employed in the experiments re
ball core'sé(with'ont an outer-‘felt towering), were tested
ported under -I-.
1
'in respect to the rebounding. capacity and compression;
<A~?rst<series -of~runs-'were conducted with two differ
of the pendulum aaftertalling' down onto said piece, the,
test valtle expressed in percent- of the-total ~-fall~off“the" “'
in others both bare ball cores and ?nished (felt covered)
balls were tested, as indicated below.
In conformity with the accepted requirements quoted
ent rubber blends mixed with high styrene-butadiene co
60 polymer (“Goodrite Resin 50”).
The formulas of these
blends are given below, and the results are summarized
in the corresponding Tables III and IV for various
above, the rebound of the balls Was measured after
allowing the balls to fall from a height 0525mm, and
amounts of high styreneabutadiene copolymer.
the compression was determined by means ofa “Major
FORMULA B
'& Stevens?" machine, in which the deformation of’ the a5 _'
balls by "a- predetermined load ‘is measured in thou-7 ‘Natural.rubber,,.,.,____,., ____________________ ..-
100
,‘Zinc carbonate __-_,, ______________________ __
Kaolin
'
10
10
. sands of inches.
L~C0mpara1ive tests of rubber mixed with tvariozas“ .
amounts #0)‘ high. .styrene-‘butadiene copolymer" tor I " - Stearine
'
‘70 'R'os'in
.nyclizeirubber
' ‘iI-Iigh styrenedfbutadiene copolymer‘ (“Gpodrite Resin
Minerali oii _'
25.07’) andé-Lcyclizedz rubber; respectively, was‘ mixed with
jaqrubber'tzblend of? the following; gompositgion in paints
fEliphenrlsufalti.idine
by wisht:
_
..
.
v Mercaptobenzothiazole '
.uLSulphur
.___.._
1.5
.5
'5
1.6
-8
3Q
2,896,949
FORMULA 0
Natural rubber ’
, ,Zmc
.
carbonate
. _Stéarine ‘
R -
which isv clearly seen in ‘Table HI. The bareball cores
I
_________ --r-.--a ____________ __
Kaolin
_-___
100
‘also dlsplay a maximum of rebound‘ at a content of about
1O
5 to 10% copolymer
1n the rubber, which
con?rms
_the
. .
_
_
2
____
05m
7
_v
5
fact that good resilience of the rubber
is of importance
_
L5 5 for the rebound of the ball. With such low copolymcr
5
content, however, the compression of, the ball is much
.
Minera1 oil
Mercaptobenmthiaz01 e ____________________ __
.
.
Sul but
P
1_____ ___ _________________ __
.
.
too high. To produce a. ball having the desired prop
L6
erties and not contaimng a gas ?lling‘ at super-atmos
1.8
phenc
pressure .a rubber-copolymer mlxture
contalnmg
.
.
.
. .
D1phenylguan1d1ne
.
‘5
3 O 10 a h1gher proportion of the copolymer is used while tak
""""""""""""""""""""" n
'
ing into account that the rebound is reduced at the same
TABLE III
time, and all the more as the amount of kaolin in th
rubber blend is increased.
Rubber-i-Styrene-
R
Bare ball core
Styrene" Butadiene o°p°lymer
ubberin
,
'
Other series v0f runs were carried 01111 With additional
15 rubber blends according torthe following Formulas D, E,
butadiene
.
FormulaB _copolymer
.
.
.
.
,
and F m1xed with various proportions of kaolm, cou
Hardness Resilience 003388‘ Rebmmd
marone resin, or high styrene-‘butadiene copolymer
(“Goodrite resin 50”), ‘respectively. In these experi
0
50
66
~70O
660
10
w h 69
70
27??
gig
g2
35
86
47
180
ments the compression, the rebound, and the weight of
186 20 the bare ball cores, on the one hand, and the ?nished
(felt covered) balls, on the other hand, were examined.
71
130
The results are found in the following Tables V VI
an
T
d VII .
’
-
N
FORNIIIL'A D
25 Natural rubber ___________________________ __ 100
Rubber
R bb m
11
bsttyrgine-
91'
118
Formula C
,
St
ene-
Bare ball core
Butadienel-cogglymer
6H6
Compres-
Rebound
31°11
o
27.6
35,
20
courilarone resm """""""""""""""""" ""
Hardness Resilience
13
8
Magneswm carbonate --------------------- -_
.
copolymer
Y
Zinc oxide
_____________________________ __ "‘
.
54
70
a a
a
83
87
62
30
620
136
61
3
steal'lne
1.5
Benzoic ‘acid _
___
___
_
1
180
Mercaptobenzothiazolebisul?de __ ____________ __
11,2
a:
‘stilftylw’l‘dme """""""""""""""""" "
3'2
149
124 35
p
1‘
_________________________________ ___
.
FORMULA E
Natural rubber ___________________________ __ 100
It is seen from Tables HI ‘and IV above that the hard-
Zinc carbonate
ness of the rubber increases rapidly with an increased
percentage of copolymer. The resilience of the rubber,
___
_
12
Kaolin __________________________________ __
Stearine
_____
____.
____
‘8
1
on the other hand, instead of steadily falling off with an
Mercaptobenzothiazoledisul?de ______________ __
increasing percentage of copolymer, passes through a 40 Diphenylguanidine ________________________ __
slight maximum at a content of about 10% copolyrner,
Sulphur
____
’
1,5
.18
2.8
TABLE V
Kaolin per 100
parts of rubber in
FormulaD
Rubber+Kaolin
Hardness
Resilience,
Bare ball core
Finished ball
Gonipres-
Re-
Weight,
sion,
bound,
g.
(Shore °)
Percent
inches .103
64
59
66
70
7a
73
68
69
66
61
60
58
636
613
436
340
320
262
cm.
164
166
158
165
164
160
Oompres-
Re-
Weight,
sion,
bound,
g.
inches .103
44. 2
47. 9
53. 1
66. 4
67. 4
60. 0
610
453
e14
251
231
216
cm.
126
126
134
140
140
142
67. 0
61. s
66. 9
69. 6
70. 6
73. 0
TABLE VI
cm?ggie
0
Bare ball core
‘Finished ball
Ooumarone per 100
6 parts of rubber-in
FormulaD
Hard-
Resilience,
Oompression,
Rebound,
Weight,
g.
636
164
44.2
610
126
57 0
680
680
680
158
130
112
44. 6
44.6
44.3
515
663
660
120
115
104
58 2
67 s
67 6
680
40
44.4
760
30v
67 6
Percent
inches .103
68
62
62
as
cm.
Oompression,
inches .10a
.
Rebound,
cm.
Weight,
g.
123896349
“ 1o
,Ruhber-i-
‘ Bamhallcore
‘Oopol‘ymer
Oggglymergger 1310
p Fb‘imr?ia I?
v
'
'Hardl‘
‘
,Einished ball
‘
i
Resil- ‘i'o'ompres-l' ' "Re-
ness. i. 111mm,».
51011,,
Y v(Shore °). Percent, ?nches .10‘,
54;
as
61":
70-,
‘68’
My
81,
52‘
,
:Weight, ‘Compres- '
I“?b0m?,'
.g.
A1011,
cm; ;
r
Re- ‘ Weight,
hound,»
g.‘
estllls,v {a gem. J
v‘636;’
16L 5
44,2
.510“
126'
57.0
‘539’
:3’18 ;.
182'
. ‘1822'
"-44.2
44.3
‘395 '
284.“
"140
‘144;
67.6
52.29
g 163‘,
r156:v
44.4
B8
67.8
v .157;
As will appear ‘from ‘the above-‘tables, :the:
‘
balls are slightly harder-and have‘lessreboundtlramthe
'bare'ballfcores.
'
.
v“
._
‘I
Example»--__________________________________ __-r
20
With amajor proportion ‘of iIkao'h‘n incorporated ‘in ,
v
.
_
,,
.
v
,
l.
I
v
I
J
a
a
.
.
v
5 ‘I
,
_
m0
lGopolymer>(86%-s
the rubber, balls may be'manufactured whlohhave-qulte
100“,
v12=
,30,
V53
1o
.10‘
11552 a
5
1-. 6:
“"125
5
g
1.6 ‘
1..,6
‘duce the weight, the ‘hardness. is reduced and the re-
,gllggrvlguamdme ---
“bound is also altered. ‘With less kaolin 'the'ha‘rdness as
.,
kg ; 3-73’.
' l:
'
.
v
.a
,
I
l
'well' as "the rebound become too :low. "Thu'stiit, .is not
a
_
>100
acceptable rebound and ‘hardness charabtel‘lstwsg ‘as‘seen
ggglrligj; ----- -j ----------------------------- --.'
in Table "V. However, ‘the "weight of "the balls ‘becomes
1R7£ige1raloiln
v
‘
too'great. If the'WaLu of the 'bans is mad?
to I?‘ 125 Mercaptobenzothiazole _______________ __»_____.f
.
zinc pgrbonate_______ __
7-,‘
‘
VNatural-tubber..- »
l
6 f
,
_
--
--
~
",7 """" "f """"""""""""""" "
311mm=Cblmlylmel‘:@‘IJPI‘OXii -------------- f 89:11
possible by incorporatingv kaolin. intherubber to arrive
‘
r
.
g ,
.
‘
5
.at a ball which has the properlhardness,.,freboundeand r30 ,Exampleua ______________________________ __;
weight characteristics, without ‘using an internal i-super-
-
'
N f,
.
atmospheric pressure mr-thejball.
>
_
.
_
I ’
Coumaroneresm .(Table VI)_;wh1ch:hasz-approx1matel~y
the same speci?c gravity as
‘l
,
a
I
11m
r11
s
zinc carbonate._._.____._i____
_.
I:
g
.15" I
greater amounts withoutvapprecialbly-affectmg"weight
.of "the 'ball. However, it reduces :thethardnessaand re-
5 I
7 136 .
silience of the rubber mater'i'alandalsoeauseslairedue
B phur _______________ __
:tion ‘of the rebound and hardness-characteristicsofthe
'-
o
-
a
i '
3.10‘
_ 100
v
‘
r,
41 _
,79
2% .
1:5
1:5 ruff;
5
.lss, ‘-
_
, 7
65:85
m0
_
I6.‘
I
3-3
I, _'
,
>
‘
_,
7723
100 ,
91"-
,
v
M
eopolymermqo Styrene)_____
10
.2
i138
'
'
- I
5%
p
0
33311, Therefore, such'resin, alone,Yismétstiitatblehs a 40 nubberi'copolxmer’?ppmx'"f"“ """"""I "8614”: 70 30
my’
rubber modi?er ‘for the present invention.
When using‘ ‘the extreme :rubber-copol-ymer composi
The speci?c gravity ‘of "high- styrene-britadiene ‘co:
polymer also differs insigni?oantlyfrom‘that of‘rubber.
It increases the hardness of the rubber material .con
ttionssrepresentednby the‘ aboveExampl‘es 5, 7,'8v and 110,
considerable rdifliculti'es are experienced to have-the com
‘rpressibility, rebound‘. ‘and weight ‘within: the ‘limits re
'siderably, and ‘reduces the ‘resilience thereof. 'It lowers "45 ;qui-redzforltennis balls. This-is. borneoutfbyithel?guresfin
the rebound slightly butnot more thanl'raolin.
‘
v'liables
and IN, whichreferi'to rubber-copolymerrcom~
'positibnsis'imilarto those disted :ajbove;
- - I '
:It can ‘clearly be seen from Table 'VII, ihoweverrthat
' Where the rubber‘structurerof-the tennis balls isimad'e
'the rebound of the'balls'has a~.certainl~maximum which
‘.lies at a higher proportionof thecopolymer component
sin-omen: inner-,rubber-‘core ‘('not containing copollymer)
than the slight maximumwhich ‘can be: found for the 50 and an outer covering of rubbersopol'ymer~_cornposition,
resilience of the rubber material.
proportion of copolymer will have to be slightly
,
vAs exempli?ed by Table VII, a'certain‘. amountnf
kaolin may advantageously; be: incorporated in the rubber
material. "Other well-‘known. ?llers: may'rfal‘so :beprese'nt.
.It should be noted, however‘, zthat'xsuch1 ?llers-are [not
necessary‘ingredients in the rubber, ‘when‘high’styr‘ene
butadiene copolymers are added, but they are used as
means for the purpose of‘slightlyadjustingthe ‘properties
of the rubber and thebal-ls made‘Ytheref'rom.
[From Table VII it may be seeni'zthat the properties 10f
thebare ball cores and those. ofathezfelt coveredballs
do not vary quite in unison, withzvarying proportions-of
copolymer in the rubber.. Thnsgwhile‘a sdtt‘btrll‘be
greater, as already pointed out, andfor ‘this reason, ithe
compositions :of Examples ‘5 land‘ -8 I-will‘hardly \be practi~
,cabl'e insuclr caseywhile Examples 6’, 7, ‘9‘ and 110 may
perfomrxsatisfactorily'. Where a copolymer containing
-86:%:sty1'ene=is: usedi, atpractical- upper limit tor ithedpro
zportionlof-tlre copolymer'in thecomposition-‘appearsltoibe
aboutI45j%-..
'
'
~
5
- ~ It“ is ‘I thought that :thezinvention: and its -=.adlvantages~ :will
.be understood from the ‘lforegoingadescriptionu and 'it-ii's
apparentithat various changes may be ‘made in the-J-forml,
construction and-,arrangement-of the :p'ant's withoubde
parting; ‘from, the spiritaand. scope ' of. the» invention 11m‘
comes considerably less compressible through the felt ’
‘sacri?cing its material advantages, the ‘forms --hereinbe
fore described ,andlillustrated in ether-drawings beingmere
covering, a hard ball does not change"'very much inre
.lygpreferred emhodimentszthereof.
spect .of compressibility ‘by the‘ application iofthe ‘I'felt
'
-
' uHavingtthus. disclosedthesinvention: What is ' claimedzis:
covering. Similarly the rate of decrease of therébound,
with increasing. ‘percentages: of :ifeopolym'er 33in
" rubber,
1.,Al tennis. ball, comprising :a- .hollow ‘:Slil’llCt’llIl?-J?f
rubber, and a resinous high- styreneebutadienecopolyrmer
is diminished by the felt-covering.- '
‘incorporated in at least a spherical annulus of said struc
ture in a proportion of 10 to 45 parts thereof per 90
to 55 parts of rubber, calculated on the basis of 85%
styrene in said Icopolymer, and a gas ?lling within said
'
1
'
" "
Some further speci?c examples of rubber-copolymer
compositions suitable for making tennis balls, having a
gas ?lling of atmospheric pressure only, according to the
vpresent invention will now be given.
hollow structure at substantially atmospheric pressure.
‘11
2,896,949
2. A tennis ball, comprising a hollow structure at sub
stantially atmospheric inner pressure having a diameter
of 2% to 2% inches and a weight of 2 to 2%6‘ozs, at
least a core portion of said structure being of rubber, and
at least a spherical layer of said core portion having‘.
incorporated therein a resinous high styrene-butadiene
copolymer in a proportion of 12 to 80 parts thereof,
12
inorganic ?ller material per 100 parts of rubber, to im
part concurrently to said structure a deformation char
' acteristic of 0.265 to 0.290 of an inch under a pressure of
18 lbs. and a rebound characteristic of 53 to 58 inches
after a drop of 100 inches.
8. A tennis ball, comprising a hollow structure of rub—
her, a resinous high styrene-butadiene copolymer incorpo
calculated on the basis of 85% styrene in said copolymer,
per 100 parts of rubber to impart concurrently to said
rated in at least a spherical layer of said structure in a
proportion of 10 to 45 parts thereof per 90 to 55 parts of
structure a deformation characteristic of 0.265 to 0.290 of 10 rubber, calculated on the basis of 85 % styrene in said
an inch under a pressure ‘of 18 lbs. and a rebound charac
teristic of 53 to 58 inches after ‘a drop of 100 inches.
3. A tennis ball, comprising a hollow structure at sub
stantially atmospheric inner pressure having a diameter
. copolymer, a surface layer of a material having surface
‘ characteristics equivalent to those of felt material, and a
’ gas ?lling'within said hollow structure at substantially at
mospheric pressure.
of 21/2 to 2% inches and a weight of 2 to 2%“; 02s., at 15
9. A tennis ball, comprising a hollow structure at sub
least a core portion of said structure being of rubber, and
stantially atmospheric inner pressure having a diameter
.at. leasta spherical layer of said ~core portion having
of ‘21/2 to 2% inches and a weight of 2 to 21/16 02s., at
incorporated therein 12 to 80 parts of a resinous high
least a core portion of said structure being of rubber, the
.styrene-butadiene copolymer, calculated on the basis of
rubber in at least a spherical layer of said core portion
85% styrene in said copolymer, and 10 to 47 parts of 20 having incorporated therein a resinous high styrene-buta
inorganic ?ller material per 100 parts of rubber, to im
diene copolymer in a proportion of 12 to 80 parts thereof,
part concurrently to said structure a deformation charac~
calculated on the basis of 85 % styrene in said copoly
teristic of 0.265 to 0.290 of an inch under a pressure of
mer, per 100 parts of rubber, to impart concurrently to
18 lbs. and a rebound characteristic of 53 to 58 inches
said structure a deformation characteristic of 0.265 to
25 0.290 of an inch under a pressure of 18 lbs. and a re
after a drop of 100 inches.
4. A tennis ball, comprising a hollow structure at sub
bound characteristic of 53 to 5 8 inches after a drop of 100
stantially atmospheric inner pressure having a diameter
inches, and a surface layer of a material having surface
of 21/2 to 2% inches and a weight of 2 to 21716 02s., at
characteristics equivalent to those of felt material.
least a core portion of said structure comprising rubber,
10. A tennis ball, comprising a hollow structure at sub
30
12 to 53 parts of a resinous high styrene-butadiene co
stantially atmospheric inner pressure having a diameter
polymer, calculated on the basis of 85 % styrene in said
of 21/2 to 2% inches and a weight of 2 to 2%“; 02s., at
copolymer, and 10 to 40 parts of inorganic ?ller material
least a core portion of said structure being of rubber, the
per 100 parts of rubber, .to impart concurrently to said
rubber in a spherical outer layer of said core portion hav
structure a deformation characteristic of 0.265 to 0.290
ing incorporated therein 30 to 5 3 parts of a resinous high
of an inch under a pressure of 18 lbs. and a rebound 35 styrene-butadiene copolymer, calculated on the basis of
characteristic of 53 to’ 58 inches after a drop of 100
in'ches.
.
5. A tennis ball, comprising a hollow structure at sub
stantially atmospheric inner pressure having a diameter
85% styrene in said copolymer, and 10 to 25 parts of in
organic?ller material per 100 parts of rubber, to impart
concurrently to said structure a deformation characteristic
of 0.265‘to 0.290 of an inch under a pressure of 18 lbs.
of 21/2 to 2% inches and a weight of 2 to 2%‘; 02s., at 40 and a rebound characteristic of 53 to 58 inches after a
least a core portion of said structure comprising rubber,
drop of 100 inches, and a surface layer of material hav—
the outer spherical layer of said core portion having
ing.
slurface characteristics equivalent to those of felt ma
incorporated therein 30 to 53 parts of a resinous high
eria .
vst-yrene-butadiene copolymer, calculated on the basis of
'11. A tennis ball, comprising a hollow structure at sub
85% styrene in said copolymer, and 10 to 25 parts of 45 stantially atmospheric inner pressure having a diameter
inorganic ?ller material per 100 parts of rubber, to im~
of 2% to 25/; inches and a weight of 2 to 21/16 ozs., said
part concurrently to said structure a deformation charac
structure having a spherical inner layer of rubber and a
teristic of 0.265 to 0.290 of an inch under a pressure of
spherical outer layer of spongy rubber, the rubber of
18 lbs. and a rebound characteristic of 53 to 58 inches
which the spongy rubber is formed having incorporated
50
after a drop of 100 inches.
therein 30 to 5 3 parts of a resinous high styrene-butadiene
6. A tennis ball, comprising a hollow structure at sub
copolymer, calculated on the basis of 85% styrene in said
stantially atmospheric inner pressure having a diameter
copolymer, and 10 to 25 parts of inorganic ?ller material
per 100 parts of rubber to impart concurrently to said
least a core portion of said structure comprising rubber,
a deformation characteristic of 0.265 to 0.290
16 to 79 parts of a resinous high styrene-butadiene copoly 55 structure
of an. Inch under a pressure of 18 lbs. and a rebound char
mer, calculated on the basis of 70% styrene in said co
acteristic of 53 to 58 inches after a drop of 100 inches.
polymer, and 15 to 47 parts of inorganic ?ller material
per 100 parts of rubber, to impart concurrently to said
References :Cited in the ?le of this patent’
of 2%. to 2% inches and a weight of 2 to 21/16 02s., at
structure a deformation characteristic of 0.265 to 0.290 of
an inch under a pressure of 18 lbs. and a rebound char 60
UNITED STATES PATENTS
acteristic of 53 to 58 inches after a drop of 100 inches.
7. A tennis ball, comprising a hollow structure at
1,402,682 ,
Takashima ___________ __ Jan. 3
1,614,853 .
Schwartz ____________ __ Jan. 18’, 1927
substantially atmospheric inner pressure having a diameter
2,131,756
2,452,999
Roberts ______________ __ Oct. 4, 1938
Daly et a1. ___________ __ Nov. 2, 1948
of 21/2 to 2% inches and a weight of 2 to 2146 02s., at 65
least a core portion of said structure being of rubber, the
rubber in a spherical layer of said core portion having
incorporated therein 41 to 79 parts of a resinous high
styrene-butadiene copolymer, calculated on the basis of
70% styrene in said copolymer, and 15 to 32 parts of
_
OTHER REFERENCES
Industrial and Engineering Chemist
pp‘ 95.5457.
1922
‘
S t
b
ry, ep em er 1946,
India Rubber World, January 1948, pp. 487-491.
Modern Plastics, February 1950, pp. 72-74.