Note: Descriptions are shown in the official language in which they were submitted.
2~2~
HIG~ PERFORMANCE ONE-PIECE GOLF BALL
~ he present invention relates to a one-piece solid
golf ball and to a one-piece solid core for golf balls.
Golf balls are classi~ied as either wound or solid.
The traditional wound golf ball has a complex structure
consisting of rubber threads wound around the center of the
ball. The process for making such a ball is time-consuming
f - and expensive.
Solid golf balls are classified as one-piece, two-piece
or multi-layer. The one-piece golf ball consists of a single
structure, the two-piece golf ball has a solid core covered
with a cover and the multi-layer ball has three or more
layers with an intermediate layer between the core and the
cover.
There has been great technological advancement in the
production of one-piece and two-piece golf balls; however,
to date there is not in existence a one-piece golf ball
g that embodies both performance and durability
characteristics suitable for use by serious golfers in
tournament play. The two-piece golf ball can be used to the
satisfaction of an average golfer; but, a professional
golfer would not use this type of ball since it lacks feel
and controllability i.e. click of the ball and the ability
to control spin, par~icularly on approach shots. Further, a
high performance one-piece golf ball is not commercially
practical in that it has not been possible to accurately
reproduce it.
Most golf balls are formed from polymerized butadiene.
The polybutadiene elastomer is crosslin~ed by a
crosslinking agent which is a rather large quan~ity of a
-
` 2052~
zinc salt of acrylic or methacrylic acid. An optimal
crosslinker would increase hardness without decreasing
resilience.
The zinc salts of methacrylic and acrylic acids have
shown great promise as crosslinkers for butadiene in the
manufacture of solid golf balls, but so far no suitable
one-piece golf ball for play by tournament caliber golfers
has been made from ~hese materials. Golf ball compounds
crosslinked by acrylic acid zinc salts have generally
demonstrated superior characteristics in terms of resilience
but tend to be les~ durable. Ball forming compounds
crosslinked by methacrylic acid zinc salts produce a ball of
superior durability but at the expense of resilience. The
following discussion of prior art illustrates these points.
Tominaga U.S.Patent No. 4,561,657 teaches that an
improved golf ball can be made from a rubber composition
containing zinc acrylate coated with a fatty acid such as
stearic acid whereby the golf ball exhibits proper hardness,
good impact resilience and good sound and feel when hit.
Another characteristic of this type of rubber composition
is that it creates good roll workability and dipersability
of rubber additives. -
~ ' .
Isaac U.S.Patent No. 4,770,422 discloses an improved
golf ball which is durable with good ~laying characteristics
such as good initial velocity. The composition from which
this ball is formed comprises polybutadiene crosslinked by
zinc diacrylate whereby the amount of free-radical initiator
is substantially below that typically used in the past.
This free-radical initiator is necessary to promote the
crosslinking reaction.
Tominaga U-S.Patent No. 4,556,220 discloses a golf ball
which shows mar~edly superior rebound performance,
durability and flight carry characteristics. This is
achieved by forming the ball from polysulfide type compounds
., '
2~5~0
which regulate the molecular weight of the chains which
result from crosslinking by regulating the length of such
chains.
Llort U.S.Patent No. 4,71~,607 teaches that a better
golf ball is made by using a small amount of zinc diacrylate
to crosslink polybutadiene. Zinc diacrylate is used as a
first crosslinker and zinc dimethacrylate is used as a
second crosslinker. The result is a golf ball with higher
initial velocity and higher compression. Natural rubber can
be added to improve durability.
-3 Reiter U.S.Patent No. 4,688,801 teaches that a
one-piece golf ball can be made with impro~ed compression
and fracture strength while the desired rebound, click and
feel characteristics are maintained. This is achieved by
using a coasent comprising (i) admixture of a polyvalent
metal salt of an unsaturated acid and a~ organic filler or
(ii) a reaction product obtained by reac~ion of an
unsaturated carboxylic acid with an organic filler followed
by further reaction with a polyvalent metal compound in the
presence of said unsaturated carboxylic acid where such
coasent functions as a crosslinking agent with the
polybutadiene elastomer.
'~
The above-noted prior art is directed to
composltions for forming one-piece solid golf balls as well
as rorming the cores of two-piece golf balls. Likewise, the
compositions of the present invention are applicable to
solid one-piece golf balls and the cores of two-piece golf
balls.
It is an object of the present invention to provide
a novel composition capable of producing a one~piece golf
ball or a multi-piece golf baIl.
The presen~ invention is a composition for making a
solid one-piece golf ball with a butadiene base which is
crosslinked by a methacrylic acid zinc salt. The resulting
product is a one-piece golf ball with outstanding
2~2~00
performance which possesses both resilience and durability
and which can be reproduced accuratelY and economically.
This type of golf ball is suitable for play by tournament
caliber golfers. In addition, the material comprising the
composition can be used to form the core of a two-piece or
multi-layer golf ball.
.
At the outset, the present invention is described in
its broadest overall aspects with a more detailed
description following. All embodiments of the invention
involve a composition which includes a polybutadiene
crosslinked with a methacrylic acid zinc salt manufactured
under the tradename Z-Max MA. This zinc salt is present in
the range of 20 to 70 parts by weight per 100 partC of
rubber to be used in ~ormulating the solid one-piece golf
ball and the core of the two-piece golf ball. The term
rubber'is intended to include a major portion of
polybutadiene and may include minor portions of other
2052~0~
.
polymers such as natural rubber, polylsoprene rubber,
styrene-butadiene rubber, ethylene-propylene rubber and
nitrile elastomers. In all embodiments, the rubber com~onent
must include at least 75% by weight of polybutadiene. A
table of the essential ingredients and their use ranges, in
accordance with the present invention, appears below.
TABLE 1
Essential Inqredients PPH
Rubber 100
(at leas~ 75% Polybutadiene by weight)
2 - 20 - 70
Vul Cup R 0.1- 3
(a free-radical initiator)
O~tional Inaredients
Basic lead silicate 0 - 15
Titanium dioxide 0 - 15
Magnesium oxide3 0 - 5
Agerite Resin ~ 0 - 2
CAPOW5KR 9S/H 0 - 2
HVA-2 0 - 2
~ part~ per 100 partsof polybutadiene
2 methacrylic acid zinc salt
t-butyl cumyl peroxide
3 polymerized 1,2-dihydro-2,2,4-trimethylquinoline
titanium IV, 2-propanolato, tris-(dodecyl) benzene
sulfonato-o
N,N~m-phenylene dimaleimide
~ he result of using the composition of the present
invention in forming golf balls is a golf ball with
outstanding performance. Such golf ball's improved
characteristics include resilience, durability and
economical reproducibility.
The key feature of the present invention is the
methacrylic acid zinc salt used to crosslink the butadiene.
6 2 ~ 00
This zinc salt is unique in that its crosslinking energy
is in the same order as or greater than the energy
in commercially acceptable zinc salt made from acrylic
acid, yet the golf ball produced from this salt cross-
linked with polybutadiene is superior to commercially
available balls. Suitably the zinc salt may have a
crosslinking energy of at least about 180 Joules per
gram and/or a xylene-solubility of at least 50~ by weight.
Methacrylic acid zinc salt is traditionally made
by reacting methacrylic acid with zinc oxide. In accordance
with the present invention, the reaction by which the
zinc salt is produced is run in an abundance of air
and suitably with more, e g 10% more, than the stoichiometric
amount of zinc oxide. The introduction of oxygen into
the reaction prevents polymerization of the methacrylic
acid during mixing with polybutadiene rubber. Specifically,
the zinc salt and the polybutadiene are blended in
a roll mill producing a corrugated surface on one side
of the product. This high radiating area keeps the
temperature down and thus delays curing until the molding
step. The temperature is preferably kept down to 75C
which is below polymerization temperature. As a result,
polymerization and curing take place during the molding
step and not during the mixing step.
In accordance with the present invention, the
methacrylic acid zinc salt may be prepared by introducing
a charge of 44 pounds of zinc oxide to 85 pounds of
methacrylic acid along with 0.25 pound of stearic acid.
20 ml of sulfuric acid is added as a catalyst. Prior
to reaction, the zinc oxide and the stearic acid are
dispersed in a solvent which contains heptane and 1,1,1-
trichloroethane in about equal parts by volume and
has a specific gravity of about 0.98. During the reaction
process, the methacrylic acid and sulfuric acid are
added into a rotary vacuum drier and heated to 85-90C.
The solvents containing the zinc oxide are then added
to the drier. A one-second blast of air is bled into
the evacuated drier system at 30-second intervals to prevent
polymerization of the zinc salt. After approximately 0.75
2 ~ 0
hour in the rotary vacuum drier, the solvents and water of
reaction are substantially removed by vacuum and the
resulting product is a solid methacrylic acid zinc salt.
The zinc salt is further dried and then reduced to particle
size of 1-30 microns. This salt is currently manufactured by
Yardley Ball Corporation, Milton, Florida, under the name
Z-Max MA (Z-Max) and is referred to herein by that name.
Comparative Examples 1-6 and 8-12 further describe and
define the present invention. Z-Max, Z-Max crosslinked with
polybutadiene as well as two other commercially available
salts, alone and crosslinked with polybutadien~, were
analyzed and compared. The analysis was performed by Arthur
D. Little Laboratories (ADL) of Cambridge, Massachusetts.
The salts compared with Z-Max axe Sartomer 365 manufactured
under this tradename by Sartomer Co., Inc., Exton,
Pennsylvania and ReactRite manufactured under this tradename
by Rockland React-Rite, Inc., Cartersville, Georgia. Two
different samples of Z-Max were analyzed; one sample was
manufactured in the old Yardley Ball Corporation plant in
Pennsylvania and the other sample was manufactured in the
new, currently operating,Florida plant. The Pennsylvania
sample represents Z-Max which has aged before curing and
thus golf balls produced from it would be less resilient and
thus less desirable. Z-Max should preferably be used, i.e.,
cross-linked with polybutadiene, within a week of
production.
Examples 1-6 and 8-12 show that many features
distinguish Z-Max and the polybutadiene cured with it from
other commercially available zinc methacrylate. To begin
with, Z-Max has a higher zinc content and ~resh Z-Max has a
higher exothermic heat of polymerization. The X-raY
diffraction pattern of Z-Max shows a stronger peak between
11 and 12 degrees and the particle sizes of Z-Max are the
smallest of the group analyzed. The FTIR spectrum of Z-Max
has more prominent CO crystalline peaks and the Z-Max
samples had the highest solubility in xylene. The heat of
2~2~
curing is highest for the fresh Z-Max sample and
polybutadiene cured with Z-Max has the highest Shore
Hardness. Finally, Z-Max samples have lower swell lndices
than the other samples tested.
~ xamples 1-6, shown below, provide the results of: 1)
elemental analysis 2) differential scanning calorimetry 3)
X-ray diffraction 4) microscopic examination 5) Fourier
transform in~rared spectroscopy and 6) xylene solubility.
EXAMPLE l
f'`
The analysis for zinc content in the samples was
carried out by plasma analysis. The samples were also
vacuum dried and analyzed for zinc, carbon and hydrogen at
Galbraith Laboratories, Inc., (GLI) in Knoxville, Tennessee.
The results are shown below. 'N.A.' = Not Applicable.
WEIGET % ELEMENT IN ZINC S~LTS
Salt % Zn %C %H %O by
GLI ADL difference
Theoretical Zinc 27.8 N.A. 40.8 4.3 27.2
Methacrylate
PA Z-Max 1-91 30.6 N.A 35.8 3.9 29.7
PA Z-Max 10-90 N.A. 29 37.8 4.0 29
PL Z-Max 28.2 N.A. 38.3 4.1 29-.4
Sartomer 3~5 29.g 29 37.7 3.8 29.1
ReactRite 27.0 27 39.5 4.5 29.0
All samples, except ReactRite, contained more than the
theoretical proportion of zinc; especially the FL Z-Max sample.
All samples, especially the PL Z-Max, contained more than the
theoretical proportion of oxygen and less than the theoretical
proportion of carbon. These results are consis~ent with known
addition of excess zinc oxide in the production of Z-Max and
indicate that the salts had been oxidized; especially the FL
Z-Max. In hydrogen content, the Z-Max and Sartomer samples
20~2~0
.
were below that calculated by ~heory, but the React~ite
hydrogen content was high. This result suggests tha~ React~ite
contained unxeacted methacrylic acid or its polymer.
EX~MPLE 2
.
The heat of reaction by thermal analysis is known in the
art to correlate with chemical reactivity in curing
polybutadiene. Each sample was analyzed using a DuPont 910
Differential Scanning Calorimeter (DSC) with a 20 C/minute
oven ramp, nitrogen atmosphere,to 300 C in hermetically sealed
pans. Each sample showed an exothermic peak due to heat of
polymerization. The peak temperature in degrees centigrade and
the heat of polymerization in ~oules per gram (J~g) were
recorded. The older Z-Mzx sample also showed an endothermic
heat of melting, apparently of a crystalline species formed on
storage. It is noted that the structure of the cured polym~r
is influenced by the rate of cooling.
DSC RESULTS WITH æN SALTS
Property/Salt PA Z-Max FL Z-Max React Rite Sartomer 365
Endgtherm, 28.6 J/g None None None
130 C
Exotherm, OJ/g 138 170 61 73.9
Peak Temp. C 140 217 115 225
i~.~3
Exotherm J/g 2~3 No N.A. 62.7
after
anngaling at
125 C 15 min.
and slow cooling
Peak O
Temp. C 209 N.A. N.A. 218
Melted,
Polymerized
and quench
cooled with
liquid
nitrogen J/g 57.5 N.A. N.A. 70.9
Temp. Peaks C 213,248,
260 N.A. N.A. 221
` ~ 2~2~00
EXAMPLE 3
To perform the X-ray diffraction spectroscopy, the dry
powders were each pressed in an aluminium frame. The
diffraction patterns with CuK alpha radiation show no zinc
oxide left in the samples.
X-RAY DIPFRACTION PEAK ANGLES
Angle, PA Z-M æ FL Z-Max React Rite Sartomer 365
Degrees
7.3 Strong Absent Absent Weak
9.8 Strong Strong Strong Very Strong
10.6 Medium Medium Somewhat Very Strong
Strong
11.6 Somewhat Somewhat Weak Medium
Strong Strong
Extent of 2 3 4(Least) l(Most)
Crystalline
Part
The ReactRite sample clearly has the largest amorphous
phase and fewer crystals of one of the phases shared by the
other two samples. The Z-Max and Sartomer samples appeared to
contain mostly crystals and all samples had at least four
crystalline planes. The Sartomer sample had particularly
strong bands in the peaks at 9 to 10 and at 10 to 11 degrees
and showed the most complicated crystalline pattern. As a
check, an X-ray spectrum was run o~ a known zinc acrylate and
compared to a methacrylate sample.
After treatment with ethyl alcohol, the X-ray spectra of
the PA Z-Max and the Sartomer 365 samples were shown to be
similar, with strong peaks between 9 and 10 degrees and just
below 11 degrees. After alcohol treatment, the ReactRite had
only one crystalline peak just below 11 degrees and a broad
amorphous peak just below that.
2~2'~0~
EXAMPLE 4
The various zinc methacrylate samples were examined under
the microscope at 150 and 300 x magnification. The Z-Max
particles were the smallest and most rounded, the Sartomer
~articles were the largest and constituted highly crystalline
acicular ~lat planes. The ReactRite particles in xylene showed
birefringence, suggesting a transition between amorphous and
crystalline forms.
f ~ICROSCOPICAL EXAMINATION
~ethod P~ Z-Max FL Z-Max React Rite Sart~mer 365
Mlcroscopy
Microns, Mostly 3-10 1-5 5-25 5-200
Dia. Up to 35 Up to 200
Shape All Irreg. Irreg. Round ~ Needles
Needles
Crystals Some particles Rectangular
crystalline ~ Crystalline
amorphous or Plates
poorly
crystallized
The finer particle size of the Z-Max samples corresponds
with larger surface area for increased reactivity. The Florida
Z-Max appeared to be less completely crystalline than the
Sartomer. The particle sizes of the Z-Max were much smaller
than those of the two other salts. The Sartomer sample
appeared to be highly crystalline, in agreement with X-raY
observation. The ReactRite sample had a mixture o~ acicular
crystals and irregular roundish amorphous-looking particles.
As a check, a known Sartomer zinc acrylate was examined
microscopically and compared to methacrylate.
EXAMPLE 5
over 40 scans were taken with a Bio-Rad FTS
spectrophotometer with the averages used to provide results.
The infrared spectra differed among the samples, in that the
`` 20~2~0
12
Z-Max samples had an additional band at 1090 reciprocal cm
where carbon-to-oxygen bonds generally appear. The Z-Max
samples also showed a greater number of crystalline peaks. The
crystal form of Z-Max is clearly different from that of the
other salts analyzed.
RESULTS FRO~ INFRARED SPECTROSCOPY
CO Peaks PA Z-Max FL Z-Max React Rite Sartomer 365
1090 CO Band CO Band No extra CO No extra CO
1545
and 710 Yes More Fewer Fewer
~i~ Suggesting
Crystallinity
EXAMPLE 6
Excess xylene was mixed thoroughly with a weighed sample
of zinc salt. The excess of solvent was decanted off. A he~t
lamp was used to evaporate xylene from both the soluble and
insoluble portions ~efore weighing. The weight percentages
recovered (some was lost on evaporation) are given below.
XYLENE SOLUBILITY
PA Z-Max FL Z-M~x React Rite
Soluble Insoluble Soluble Insoluble Soluble Insoluble
.,
~-~J 72 19 62 29 38 S7
The FL Z-Max had about-10~ more insoluble material than
the PA Z-Max sample. The ash contents o~ PA Z-~ax corresponded
to between 29 and 30% zinc for both the soluble and insoluble
phases. The FL Z-Max had similar results. For ReactRite, the
soluble portion ash content corresponded to 32% zinc and the
insoluble portion to 26%.
At this point a discussion regarding the usual composition
of the base of the solid one-piece golf ball or the core of
the two-piece golf ball is appropriate. Such a descriPtiOn
follows.
'''' ''`'''''''`''~''''''''''''
20~24~0
.
13
Bu~ad~ene rubber, that is cis-1,4-polybutadiene rubber,
is the primary elastomer component, but other elastomers may
also be present in smaller quantities. Natural rubber,for
example, may be added to lower modulus and improve durability.
In addltion to the methacrylic acid zinc salt constituent and
the free-radical or peroxide initiator, numerous other
ingredients may be incorporated into the solid ball compound.
The composition usually contains fillers such as zinc oxide,
barium sulfate, lead oxide, basic lead silicate, or the like,
used singularly or in combination, to control the weight of the
ball. Other additives may include: magnesium oxide, calcium
carbonate as fillers and/or acid acceptors; mildly reinforcing
fillers and/or nucleating agents such as silicas, carbon
blacks, clays and the like; silanes and/or titanates as co-plin~
and/or dispersing agents; antioxidants for improving process,
heat and shelf aging properties; co-curing agents such as
HVA-2, TMPTA, TMPTMA and the like; cure modifying agents such
as sulfur and sulfur-bearing compounds; granular or powdered
high molecular weight polymeric materials as im~act modifiers;
pigments and other ingredients for imparting various
characteristics known by those skilled in the art of rubber
compounding for golf balls.
This composition is then kneaded by a suitable kneader,
mixer or blender such as a roll mill or a Banbury mixer. Next,
the rubber composition is molded using, for instance, heat-
pressure molding. A one-plece golf ball is prepared by
heat-pressure molding the rubber composition into a ball
having the size suitable for a golf ball. A two-piece golf
ball is prepared by heat-pressure molding the rubber
composltion in a core mold having a suitable size to from a
solld core and covering the core with a suitable cover. The
cover can be prepared from compositions comprising, for
lnstance, an ionomer resin as a main component and optionally a
filler or coloring agent such as a titanium dioxide or zinc
oxlde. The solid core is covered with two covers previously
molded in the form of a hemispherical shell and is then
.
.
! ' ~ '
,
29~2~0~
14
heat-pressure molded to fuse the two shells together to give a
finished golf ball. Injection molding is also used to introduce
the covering material around the core.
One important embodiment of the composition of the present
invention comprises high cis polybutadiene as the primary
elastomer, Z-Max MA crosslinker in the range of between 20 to
70 parts, based on 100 parts of elastomer, basic leAd silicate
as filler-for-weight in the range of 5 to 15 parts, titanium
dioxide pigment in the range of 0 to 15 parts, magnesium oxide
acid acceptor in the range of 0 to 5 parts, AgeRite Resin D
antioxidant in the range of 0 to 2 parts, CAPOW KR 9S/H
i titanate in the range of 0 to 2 parts, Vul Cup R peroxide
initiator in the range of 0.1 to 3 parts, and HVA-2 co-curing
agent in the range of 0 to 2 parts. The compound is mixed at
a temperature of 20 to 150C in a Banbury mixer or a roll mill,
then molded for 20 minutes at 175C in a 1.727-inch golf
ball mold.
The following is an example of the preferred embodiment.
20~2~00
-
EXAMPLE 7
HIGH PE~FORMANCE ONE-PIECE GOLF ~AL~
Com~ound: GB-1 Parts bv weight
Polybuta~iene (high cis) 100
Z-Max MA 48
Basic lead silicate 6
Titanium dioxide 3
Magnesium oxide
AgeRite Resin3D2 0.03
CAPOW KR 4S/H 0.20
Vul C~p R 0.53
HVA-2 0.16
Total158.98
2 methacrylic acid zinc salt - Yardley Ball Corp.
polymerized 1,2-dihydro-2,2,4-trimethylquinoline - R.T. Van
3derbilt Company
titanium IV, 2-propanolato, tris-(dodecyl~ benzene
~ulfonato-O - Kenrich Petrochemicals, Inc.
t-butyl cumyl peroxide - Hercules, Inc.
N,N-m-phenylene dimaleimide - E.I. DuPont de Nemours & Co.
The resulting typical ball properties are:
Shore C 93
Compression 122
~,~ COR 0.796.
I.V. ft/sec 254.6
Comparative Examples 8-12 which appear below show the
differences between the conventional salt-polybutadiene
compositions and the Z-Max-polybutadiene compositions. The
compositions were prepared in accordance with the teachlngs of the
present invention. The following analyses were performed: 1)
heats of crystallizing and curing rubbers 2) exothermic
recrystallization heat of cured samples 3) Shore hardness and
4) swell index.
' ~
2~52400
16
EXAMPLE 8
The below-listed ingredients were mixed with a Type
PL-V302 Brabender PlastiCorder, Serial Number 177518, with
electrical heating, air cooling and variable speed one
horsepower Type GP 100 Drive. Titanium dioxide, an inert
pigment, was omitted to facilitate examination by infrared
spectrophotometry.
Grams Inqredients
34.5 High cis-polybutadiene from Dunlop Slazenger,
Greenville, South Carolina
0.138 AgeRite Resin D, R. T. Vanderbilt,poly(~rimethyl
dihydroquinoline) antioxidant
0.3485 Magnesium Oxide, to neutralize acid
0.069 Capow KR 9S/H, Kenrich Pe~rochemical,monoalkoxy
titanate coupling agent on a hydroxylated
silicon dioxide carrier
These materials were mixed at a temperature in the 90 to
100 C range to masticate the rubber for 11 or 12 minutes. The
mixture was then allowed to cool to about 96 - 108 C by
reducing the s~irring speed. Next, 15.962 gof one of the four
zinc salts of methacrylic acid was added: Sartomer 365,
ReactRite, PA Z-Max or FL Z-Max. After a dozen minutes of
stirring, during which time the temperature was not allowed to
exceed 113 C, the stirrer was slowed and the temperature
allowed to fall to about 102 C for the addition of the curing
agents which are listed below.
Grams Inqredients
0.1242 Di Cup R from Hercules, dicumyl peroxide
0.1242 Vul Cup R from Hercules, t-butyl cumyl peroxide
0.0552 HVA-2 from DuPont, N.N'-m-phenylenebismaleimide
` 2~2~00
,
17
These ingredients were blended for 6 mlnutes with the
temperature keot down to 100 - 102 C to prevent premature
curing. Cylindrical moldings about 6 mm thick and 32 mm wide
were produced by curing at 160 C for 20 minutes in a press at
10,000 pounds on a 4-inch ram. The round mold was about 2
inches in outer diameter.
EXAMPLE 9
The samples in the compound with rubber were cured in the
DSC and the heats of crystallizing and curing of the rubbers
were measured. This important exothermic heat was determined
at 20 C/mlnute. The preceding crystallization exotherms were
determined at both 5 and 20 C.
DSC HEATS OF CURING AND CRYSTALLIZ~TION
Zinc Salt PA Z-Max PL Z-Max Sartomer 365 React Rite
20C/Minute
Rate of
Increase
Heat of Curing
J/g
Initial Spike5.50 8.78 6.14 17.28
Broad Secondg6.21 95.80 46.93 22.96
Temperatures, C
Pirst Peak:
Onset 159.1 158.8 159.2 159.1
Peak 162.1 161.6 162.0 161.8
Second Peak:
Peak 190.4 189.5 192.2 196.4
5C/Minute
Rate of
Increase
~irst Pgak:
(at 159 C):
Heat, J/g 5.48 6.93 6.37 5.49
20~4~0
18
The above-shown results show that the FL Z-Max sample
cured more ~han twice as energetically as the Sartomer 365.
The ReactRite peak was not only smaller in area but more spread
out. The heat of curing is highest for FL Z-Max and lowest for
Reac~Rite.
When the uncured compound is heat d at 20 C/minute, the
heat flow after the first peak subsides to the base line
followed by an excursion to the second peak. Because other
sharp exothermic spikes occur at the same temperature in cured
rubbers as in the uncured compound, when the temperature is
increased at the same rate, the first exothermic peak is
considered due to crystal reorganization and the second to the
curing reaction. The ReactRite sample, which appeared least
crystalline by microscope and X-ray, had the largest
crystallization exotherm at the 20 C/minute heating rate but
one of the lowest heats at the 5 C/minute rate. This
difference suggests that the sample is not homogeneous.
ExAMæLE 10
The exothermic recrystallization heat of the cured samples
was measured. Since curing had been carried on for 20 minutes,
the transitions in the cured compounds as noted below are
concluded to have been physical rather than chemical. In every
case, spike exotherms of the cured rubbers began at 157.5 C
and peaked at 158 to 159 C. When the cured rubbers were
~rogrammed in the DSC at a 5 C/minute increase ln temperature,
they revealed spike exotherms at about 159 C which are
considered dtle to reorganization in structure.
EXOTHERMIC TRANSITION
zinc Salt Exothermic Heat, J/g at 158-159C
PA Z-Max 15.4
FL Z-Max 15.8
Sartomer 365 19 . O
React Rite 7.64
2052400
19
The samples were close in heat of crystallization except
for cured ReactRite which was significantly lower. This may be
due to a less desirable form of cross-linking, such as the
carbon-carbon bonds formed by peroxides, especially when zinc
methacrylate is absent or less active.
EXAMPLE 11
Shore hardness measurements were performed on all samples.
Each molding was measured after aging for at least five days.
The five measureme~ts were at least 0.5 inch in from the edge
as prescribed by ASTM. Averages of the measurements were taken
and are shown below.
S~ORE HARDN~SS
zinc Salt Hardness Readings Average
PA Z-~ax 4g 47 50 49 51 49.2
FL Z-Max 49 52 53 51 54 51.8
Sartomer 365 47 48 48 48 48 47.8
React Rite 26 28 26 26 26 26.4
It is important to note that the Z-Max samples were
harder than the other two samples,indicating a higher degree of
cross-linking reaction for the same proportion of reagent.
EXAMPLE 12
The swell index was measured for each sample. This index
represents the equilibrium weight of toluene absorbed by a
cured rubber divided by the initial weight of the rubber. For
example, an uptake of 69~ is a swell index of 0.69. Parts of
the moldings described above were weighed into an excess of
freshly opened scintillation grade toluene and obcerved over
four days of aging. Each day the swollen rubber samples were
blotted and weighed in grams. The following results may vary
in the last figure due to variability in blotting technique.
~ ;
,.
2~52~
.~
WEIGHTS OF POLYBUTADIENE WIl~I TOLUENE
Zinc Salt/days 0 1 2 3 4
PA Z-Max 2.267 3.652 3.693 3.755 3.828
FL Z-Max 2.281 4.534 4.752 4.752 4.708
Sartomer 365 1.992 3.989 4.136 4.243 4.291
React Rite 2.508 5.771 5.819 5.870 5.932
After four days, the solvent up~ake was 69 weight percent
toluene for the PA Z-Max, 106~ for the FL Z-Max, 115% for
Sartomer and 136~ for ReactRite. This difference indicates
,. .
that the polybutadiene cured with Z-Max was more resistant to
solvent and therefore more cross-linked than the polybutadiene
cured with the other salts.
The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The present embodiments are therefore to be
considered in all respects as illustrative and not restrictive,
the scope of the invention being indicated by the appended
claims rather than by the foregoing description, ~nd there is
no intention to exclude any equivalence thereof. Hence, it is
recognized that various modifications are possible when within
the scope of the present invention as claimed.
,
