Sound deadening material

A sound deadening material is obtained with a very high loading of sound damping materials such as barium sulfate, calcium carbonate or metal powders. These materials are mixed with water and are bound together by adding a water-miscible isocyanate-terminated prepolymer which reacts with the water to form a cross-linked binder.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a sound absorber polymer product containing large 
amounts of a sound absorbing material bound together by a polymer. 
2. Description of the Prior Art 
Sound barrier materials have been made by incorporating sound deadening 
particles into polymer binders. However, the loading levels have been 
relatively low. 
In U.S. Pat. No. 4,110,510 to Oliveira, the sound barrier material 
comprises a polyvinyl chloride impregnated mesh sheet having a coating of 
a chlorinated polyethylene containing barium sulfate. This coated sheet is 
laminated to two sides of an intermediate foam layer. The maximum loading 
of the barium sulfate in the chlorinated polyethylene binder is a weight 
ratio of 2:1 so that there are only two parts of barium sulfate to one 
part of resin binder. 
In U.S. Pat. No. 4,010,818 to Westley, the flexible noise barrier is in the 
form of a mass building coat adhered to a non-woven substrate. The mass 
building coat consists of neoprene and it has dispersed therein particles 
of iron sulfide, iron oxide, barium sulfate or barium oxide. In the recipe 
given the weight of barium sulfate in the neoprene is only equal to the 
weight of the neoprene. The preferred concentration of particles is 45-55% 
with the maximum contemplated, based on the total weight, being 70%. 
In U.S. Pat. No. 4,191,798 to Schumacher et al, the sound-deadening 
sheeting is a highly filled thermoplastic composition. It contains 5-50% 
by weight of an ethylene interpolymer, about 2-15% by weight of processing 
oil and about 50-90% by weight of filler which can be either calcium 
carbonate or barium sulfate. It requires the special combination of resins 
such as vinyl acetate and an ethylene copolymer in addition to the 
processing oil. 
As to hydrogel binders, U.S. Pat. No. 4,246,146 to Wood et al discloses a 
generic class of elastomeric polyurethane hydrogel compositions which 
includes the preferred materials of this invention. However, the 
compositions of the Wood et al patent are mixed with large quantities of 
fire retardant materials to form a coating which provides a barrier for 
fire retardant protection. U.S. Pat. 4,241,537 to Wood discloses a plant 
growth media using polyurethane hydrogel. There is no suggestion in either 
of these patents of making independent structures for sound deadening 
purposes. 
3. Objects of the Invention 
It is an object of this invention to produce a sound deadening composition 
that can be formed into shapes. 
It is a further object to produce a low cost sound deadening composition 
containing a large amount of an inexpensive (on a per pound basis) sound 
deadening material and a relatively small amount of the more expensive 
polymer binder. 
It is a further object of this invention to produce a sound deadening 
composition containing a large quantity of sound absorber particles 
incorporated in a small amount of a polymer binder, which composition can 
be formed into desired shapes. 
It is a further object of this invention to provide a method to incorporate 
a large quantity of particles of a sound deadening material into a polymer 
binder for fabricating into desired shapes. 
It is a further object to produce a flexible sound deadening composition 
having a weight ratio of barium sulfate to polymer binder of greater than 
10:1. 
These and further objects will become apparent as the description of the 
invention proceeds. 
SUMMARY OF THE INVENTION 
A mass of sound deadening material can be formed into a mass damping part 
by mixing together large amounts of the sound absorber such as barium 
sulfate or calcium carbonate in an aqueous suspension with a unique 
hydrophilic prepolymer. By using a water-miscible isocyanate-terminated 
prepolymer as the binder, large amounts of the sound absorber particles 
already in a water suspension can be mixed with the prepolymer at room 
temperature to form a reactive mixture which has sufficient time to permit 
molding the mass to the desired shape before the prepolymer cures to form 
a polymer binder of a polyurethane hydrogel which holds the large mass of 
particles together. Particle loadings of at least 10 times the weight of 
binder are easily achieved and loadings at levels of at least 20 times are 
obtainable. The material can be molded into flexible sheets and applied to 
a fiberous layer for increased strength. Additional latex can be added 
when further strength is desired. 
The reactive end groups of the prepolymer can be made with either the 
conventional aromatic isocyanate terminal groups or with aliphatic 
isocyanate terminal groups which lower the reactivity of the prepolymer to 
permit longer time for shaping the final form of the article. The aromatic 
groups result in a prepolymer that can react with water and cure in about 
30 seconds. 
The main internal portion of the water-miscible polyisocyanate prepolymer 
can be made from a polyether polyol which contains enough oxyethylene 
units to make the prepolymer water-miscible. In order to permit 
cross-linking of the final polymer coating, one embodiment employs a 
polyol which has more than two hydroxyl groups. Each of these hydroxyl 
groups can be capped with conventional diisocyanates such as toluene 
diisocyanate to yield the water-miscible polyisocyanate prepolymer. In 
another embodiment, the cross-linked final polymer structure can be 
obtained by selecting a diol, rather than a polyol, as the basic unit of 
the prepolymer with the isocyanate capping being done with a 
polyisocyanate having greater than two NCO groups per molecule. 
The NCO groups on the prepolymer produce carbon dioxide when contacted with 
water. To insure, in the preferred procedure, that a gel is formed rather 
than a conventional polyurethane foam, the effective amount of NCO groups 
per prepolymer molecule must be reduced. This is done by utilizing 
relatively large polyol molecules between the terminal NCO groups. When 
the hydroxyl groups of a large polyol molecule are capped with the 
diisocyanate groups, for example, the number of average molecular weight 
of the prepolymer obtained is about 2,000 or above. The prepolymer is 
employed in the range of 1 to 100 parts of water and preferably in the 
range of about 1-20 parts per 100 parts of water. Although foaming is not 
a particular problem in making this product, the preferred procedure is 
not to have much foaming. Thus, if a relatively large ratio of prepolymer 
to water in the above range is being used, it may be advisable to employ a 
higher molecular weight prepolymer to lower the resultant number of NCO 
groups so as to avoid any production of foam in the preferred embodiments. 
The water phase also contains large quantities of the sound barrier 
material. When smaller amounts of prepolymer are employed, there will not 
be enough resin to hold together the large amounts of additives. Larger 
amounts of prepolymer can be employed with the added benefit of greater 
strength. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred prepolymer used in making the binder has a relatively large 
molecular weight with a relatively low amount of NCO per unit weight. 
Foams, on the other hand, have a much larger concentration of NCO groups 
per weight of the prepolymer. For example, the foams described in the 
Murch et al U.S. Pat. No. 4,066,578 have about two equivalents of NCO per 
1000 grams of the prepolymer where one equivalent of NCO weighs 42 grams. 
This concentration can also be expressed as two milliequivalents of NCO 
per gram of prepolymer and written as 2 meq. NCO/g. The present 
prepolymers have considerably less NCO groups on the order of about 1.0 
meq. NCO/g or less. Thus there is a great deal more of the hydrophilic 
polymer between each terminal NCO group which by itself is hydrophobic. As 
a result the overall prepolymer is hydrophilic and dissolves completely in 
water. 
One technique for making the low NCO concentration prepolymer is to chain 
extend a polyol with polyoxyalkylene units. Using the triol glycerol with 
the units of ethylene oxide and/or propylene oxide, for example, the 
following prepolymer forming polyol can be obtained 
##STR1## 
with the value of n being about 10 to 50 and where A can be H or CH.sub.3. 
Whan A is H, the bracketed unit is an ethylene oxide (EO) unit and when A 
is CH.sub.3, the unit propylene oxide (PO). The amount of propylene oxide 
(PO) employed must be limited since the prepolymer will not have the 
necessary hydrophilicity if only PO is used. In the case where just PO and 
EO are used, the amount of PO to the total PO+EO should be less than about 
50 percent so the prepolymer will dissolve in water. A further reason for 
this range is that when the PO content increases above 50 percent, the 
fire retardant ability of the resulting polymer diminishes. The property 
may be helpful in some applications. 
This particular trifunctional polyol is then reacted with a diisocyanate to 
provide the urethane linkage and the terminal isocyanate groups as follows 
##STR2## 
The selection of the polyoxyalkylene component depends on the conditions 
employed when the isocyanate capped prepolymer is subsequently dissolved 
in water to form the gel. A polyoxyalkylene made of just ethylene oxide 
units will be hydrophilic and dissolve in water, but it is a solid at room 
temperature. This can cause a problem during use. While waiting for the 
last of the solid prepolymer to slowly dissolve in water, the part that 
has already dissolved may prematurely begin to form a gel, as will be 
explained later, so that a homogeneous gel is not obtained. To avoid this 
problem, it is advantageous to have the prepolymer in a liquid form so it 
can readily dissolve without heating, which increases the gelation rate, 
and mix with the water to form a gel with the high loading of sound 
deadening particles. A prepolymer which is a liquid at room temperature 
can be obtained by incorporating various amounts of a relatively 
hydrophobic comonomer into the ethylene oxide based polymerization 
product. Comonomers such as propylene oxide (PO) described in the example 
above or butylene oxide (BO) may be copolymerized as a random copolymer, a 
block copolymer, or both, such that the resulting copolymer remains 
hydrophilic. Random copolymerization is especially preferred to insure 
obtaining a liquid prepolymer having a low viscosity. 
The addition of these comonomers also provides other desirable features for 
certain applications, namely improved low temperature flexibility, 
resilliency and the like. As discussed earlier, up to about 50 mole 
percent of a relatively hydrophobic comonomer such as propylene oxide may 
be copolymerized with the ethylene oxide monomer and still yield 
hydrophilic crosslinked network binders when those products are used as 
polyol intermediates in practicing the present invention. Preferred 
prepolymers have only up to about 30 mole percent of the relatively 
hydrophobic comonomer. Thus, throughout this text the term 
"polyoxyethylene polyol" is intended to include not only a homopolymer of 
ethylene oxide, but also hydrophilic copolymers of ethylene oxide such as 
those described above wherein all of the polyol derivatives have a 
hydroxyl functionality of about two or greater. The ethylene oxide content 
is generally greater than about 50 mole percent so that the resulting 
prepolymer will be miscible with water. 
However, as indicated in the Asao et al U.S. Pat. No. 3,719,050 which is 
referred to in the Wood et al U.S. Pat. No. 4,241,537, larger amounts of 
alkylene oxides other than ethylene oxide might be employed to obtain a 
workable system involving an emulsion rather than a true solution. 
The prepolymers do not have to be liquid. If the binder forming operation 
is carried out at an elevated temperature, then the prepolymer can be 
melted to the liquid state at that higher temperature. This liquid melt 
can then readily mix with the water to form the homogeneous gel. In 
addition, if the capping isocyanate is selected as one having a relatively 
low reactivity, then it may be acceptable to use a solid prepolymer and to 
wait for the solid to dissolve at room temperature because the gel forming 
reaction will not yet have begun. 
Prepolymers can be made by reacting EO, PO or BO with polyols such as 
glycerol, 
1,2,6-hexanetriol, 
1,1,1,-trimethylolpropane, 
3-(2-hydroxyethoxy)-1,2-propanediol, 
3-(2-hydroxypropoxy)-1,2-propanediol, 
2,4-dimethyl-2-(2-hydroxyethoxy)-methylpentanediol-1,5, 
1,1,1-tris[(2-hydroxyethoxy)methyl]ethane, 
1,1,1,-tris-[(2-hydroxypropoxy)methyl]propane, 
triethanolamine, triisopropanolamine, pyrogallol and phloroglucinol. 
One example of a suitable chain-extended polyol is the polyether triol XD 
1421 which was made by the Dow Chemical Company. It had a molecular weight 
of around 4900. It was composed of a ratio of three oxyethylene units 
randomly copolymerized per one unit of oxypropylene, and it had a hydroxy 
content of 0.61 meq. OH/g. Another example of a material which is 
commercially available is Pluracol.RTM. V-7 made by BASF Wyandotte which 
is a high molecular weight liquid polyoxyalkylene polyol. 
The chain extended polyol can then be capped with a polyisocyanate to form 
the prepolymer. Suitable polyisocyanates useful in preparing this type of 
prepolymer include toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, 
commercial mixtures of toluene-2,4- and 2,6-diisocyanates, ethylene 
diisocyanate, ethylidene diisocyanate, propylene-1,2-diisocyanate, 
cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, 
m-phenylene diisocyanate, 
3,3'-diphenyl-4,4'-biphenylene diisocyanate, 
4,4'-biphenylene diisocyanate, 
3,3'-dichloro-4,4'-biphenylene diisocyanate, 
1,6-hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, 
1,10-decamethylene diisocyanate, 
1,5-naphthalenediisocyanate, cumene-2,4-diisocyanate, 
4-methoxy-1,3-phenylenediisocyanate, 
4-chloro-1,3-phenylenediisocyanate, 
4-bromo-1,3-phenlenediisocyanate, 
4-ethoxy-1,3-phenylenediisocyanate, 
2,4'-diisocyanatodiphenylether, 
5,6-dimethyl-1,3-phenylenediisocyanate, 
2,4-dimethyl-1,3-phenylenediisocyanate, 
4,4'-diisocyanatodiphenylether, benzidinediisocyanate, 
4,6-dimethyl-1,3-phenylenediisocyanate, 
9,10-anthracenediisocyanate, 4,4'-diisocyanatodibenzyl, 
3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, 
2,6-dimethyl-4,4-diisocyanatodiphenyl, 
2,4-diisocyanatostilbene, 
3,3'-dimethyl-4,4'-diisocyanatodiphenyl, 
3,3'-dimethoxy-4,4'-diisocyanatodiphenyl, 4,4'-methylene 
bis(diphenylisocyanate), 4,4'-methylene 
bis(dicyclohexylisocyanate), isophorone diisocyanate, PAPI (a polyaryl 
polyisocyanate commercial product sold by the Upjohn Company as defined in 
U.S. Pat. No. 2,683,730), 
1,4-anthracenediisocyanate, 2,5-fluorenediisocyanate, 
1,8-naphthalenediisocyanate and 2,6-diisocyanatobenzfuran. 
Also suitable are aliphatic polyisocyanates such as the triisocyanate 
Desmodur N-100 sold by Mobay which is a biuret adduct of 
hexamethylenediisocyanate; the diisocyanate Hylene W sold by du Pont, 
which is 4,4'-dicyclohexylmethane diisocyanate; the diisocyanate IPDI or 
Isophorone Diisocyanate sold by Thorson Chemical Corp., which is 
3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate; or the 
diisocyanate THMDI sold by Verba-Chemie, which is a mixture of 2,2,4- and 
2,4,4-isomers of trimethyl hexamethylene diisocyanate. 
Another technique to produce the prepolymer is to use a polyfunctional 
isocyanate having a functionality greater than 2 in combination with a 
chain extended diol. 
Suitable starting diols for chain extension useful in this method for 
preparing prepolymers include ehtylene glycol, propylene glycol, 
trimethylene glycol, 
1,2-butylene glycol, 1,3-butanediol, 1,4-butanediol, 
1,5-pentanediol, 1,2-hexylene glycol, 1,10-decanediol, 
1,2-cyclohexanediol, 2-butene-1,4-diol, 
3-cyclohexene-1,1-dimethanol, 
4- methyl-3-cyclohexene-1,1-dimethanol, 
3methylene-1,5- pentanediol, diethylene glycol, 
resorcinol, hydroquinone, 4,6-di-tertiarybutyl catechol, and catechol. 
Suitable polyisocyanates useful in this technique include PAPI (a polyaryl 
polyisocyanate commercial product sold by the Upjohn Company as defined in 
U.S. Pat. No. 2,683,730), 2,4,6-toulene-triisocyanate and 
4,4'4"-triphenylmethane triisocyanate. 
Other techniques to prepare the hydrophilic capped polyoxyethylene polyol 
reaction product having an average isocyanate functionality greater than 
two are disclosed in the Wood et al U.S. Pat. No. 4,137,200, incorporated 
herein by reference. 
As discussed above, particularly useful gels may be prepared by first 
capping a polyoxyethylene polyol with a polyisocyanate such that the 
capped product has a reaction functionality greater than 2. Thereafter, 
the resin is reacted by dissolving it in water such that a crosslinked gel 
results. 
It is also possible to use an isocyanate capped polyoxyethylene polyol 
having a functionality approximating 2, in which case a polyfunctional 
reactive member such as one having three or up to about eight reactive 
amine, hydroxy, thio or carboxylate sites per average molecule is included 
to form a three dimensional crosslinked product. The reactive member 
preferably is one that is reactive enough to compete with the reaction of 
the water with the isocyanate groups. Useful polyfunctional reactive 
members are amines which include materials such as diethylenetriamine, 
triethylenetetramine, tetraethylenepentamine, polyethyleneimine, 
tolylene-2,4,6-triamine, ethylenediamine, trimethylenediamine, 
tetramethylenediamine, pentamethylenediamine,hexamethylenediamine, 
aminoethanol, diethanolamine,hydrazine, triethanolamine, 
4,4',-methylenebis (p-chloraniline), and the like. 
To produce the binder structure the prepolymer is dissolved in water which 
also contains the sound barrier particulate materials. Some of the 
terminal NCO groups react with water to form a carbamate compound which is 
unstable at room temperature and which breaks down to form an amine. The 
amine in turn reacts with another chain terminated NCO group to form a 
urea linkage to join the two chains. The reaction can be illustrated as 
follows: 
##STR3## 
Various types of sound barrier materials can be incorporated into the 
binder. Most of the materials are first suspended or dissolved in the 
aqueous phase to form the slurry or solution and then the prepolymer is 
mixed with the slurry. The amount of materials to be added to the water 
can vary from about 10 parts of material per 100 parts of water up to 
about 300 parts of material per 100 parts of water. If concentrations are 
employed below the lower amount, there may not be enough sound barrier 
material present in the resulting binder. On the other hand, if more 
material is added to the water than the upper specified amount, then a 
very viscous paste will form which will not mix well with the prepolymer. 
This discussion on the amount of sound deadening additives is based on 
materials having a density such as a specific gravity of around 4.5, as 
possessed by barium sulfate. Of course, if much heavier particles are 
employed, such as lead, having a specific gravity of 11.3, then larger 
amounts by weight could be added to the aqueous slurry before a limiting 
thick paste is obtained. In some instances a part of the sound absorbing 
material can initially be mixed with the prepolymer instead of being added 
to the aqueous slurry or solution, but this is not the preferred 
procedure. 
The sound deadening fillers can be any of the conventionally empolyed 
materials such as iron sulfide, iron oxide, barium sulfate, calcium 
carbonate, bauxite, gypsum, lead and other dense powders such as metal 
powders. Particularly preferred materials are barium sulfate, calcium 
carbonate, and metal powders. 
In addition, reinforcing agents can also be added to the mixture to improve 
the strength of the resulting composition. Many types of fibers can be 
used for this purpose, such as wood, carbon, glass, polyolefin, polyester, 
polyamide, cellulosic and polyvinyl alcohol fibers; mineral wool; metal 
fibers; etc. 
The sound deadening composition can also be applied to a layer of woven or 
nonwoven fibers to improve the resulting strength. Typical fibers include 
polyester, cotton, steel, glass and other conventional reinforcing 
materials. 
In making a sound deadening product there are other factors to be 
considered than just being able to obtain a large amount of sound 
deadening material in a relatively small amount of polymer binder. The 
sound deadening product must also have the desired strength properties, 
density, modulus and shrinkage resistance. 
The tensile strength values obtained for this hydrogel binder system appear 
to depend on the amount of hydrogel prepolymer used. Under some conditions 
even a small amount of 5 grams of prepolymer can give a respectable 
strength when as much as 300 grams of the filler are employed. The tensile 
strength is also related to the amount of filler employed. As with any 
filler containing polymer system, the more filler that is used the lower 
will be the tensile strength. 
There is also a relationship between the modulus which is the measure of 
the stiffness as a function of the amount of the filler employed. Lower 
modulus values are preferred as they permit the film or sheet to be 
flexible and to be able to easily fit around an object to be quieted. If 
too little polymer binder is present for a given amount of filler then the 
sheet becomes too stiff. Flexibility is desired since it also aids in the 
ability of the material to absorb more sound. 
Most of the materials made in the following examples have a rubbery to 
leathery feel which indicates the good flexibility that is obtained. 
One would expect the dry density in pounds per cubic foot to be nominally a 
function of the amount of filler employed. Because there is only a small 
amount of resin present, one would expect the density relationship to be 
directly proportional to the amount of filler added. The fact that the 
relationship is not a constant value based on the amount of filler present 
suggests that there is air entrapped in the samples. It is hypothesized 
that when more of the filler is used, the water and filler slurry becomes 
more viscous and thus traps more air in the mixture. Air may also be 
trapped when the hydrogel prepolymer is mixed in the final mixing. 
The shrinkage of the resulting product is a function of the amount of the 
filler used. If there were no filler added a sample made of the resin 
binder would shrink to a much higher degree than with the presence of the 
filler. 
The failure strain for the sheets containing BaSO.sub.4 as the sound 
dampener appears to be dependent primarily on the amount of the prepolymer 
that is used in the formulation. As the relative amount of the polymer 
decreases, the percent strain at failure also decreases. 
The sound damping composition disclosed herein can have the relative 
amounts of filler and binder varied over a fairly broad range depending on 
the properties desired. By using the unique water-miscible prepolymer it 
is possible to incorporate very large amounts of the filler into the 
composition. This lowers the cost of the sound deadening unit and it 
lowers the amount of shrinkage of the product when it dries. Additional 
binder can be added when the product is desired, to be stronger and more 
rubbery and when it is desired to provide ease of processing and to lower 
the energy requirements. 
A latex emulsion can also be added to the formulation to increase the 
tensile strength. Latex emulsions such as Versaflex.RTM. 1 and 
Everflex.RTM. 81L manufactured by W. R. Grace& Co. can be added in amounts 
of up to about 20 times the amount of prepolymer binder. Good results have 
been achieved with latex emulsions being employed in amounts up to 10 
times the weight of the binder.

Having described the basic aspects of our invention, the following examples 
are given to illustrate specific embodiments thereof 
PREATION EXAMPLE 1 
Twelve thousand two hundred grams of the polyether triol XD1421 made by Dow 
Chemical Company and composed of a ratio of three oxyethylene units 
randomly copolymerized per one oxypropylene to a molecular weight of 
around 4900 and having 0.61 meq. OH/g. was dried by vacuum stripping to a 
moisture content of 0.038% and the pH was adjusted with benzoyl chloride 
to the point where a 5% solution of the triol had a pH of 4.25. It was 
reacted at 57.degree. C. for 41 hours with 1,452.8 g. of Type II toluene 
diisocyanate produced by Olin Chemical Co. This commercial grade of 
toluene diisocyanate is an 80/20 mixture made of 80 parts of 2,4-toluene 
diisocyanate and 20 parts of 2,6-toluene diisocyanate. The reaction 
product is a pale yellow liquid of 10,000 to 13,000 cps at 25.degree. C. 
and it has 1.00 meq. NCO/g. 
PREATION EXAMPLE 2 
Sixteen thousand eighty four and five tenths grams of the polyester triol 
XD1421 made by Dow Chemical Company and composed of a ratio of three 
oxyethylene units randomly copolymerized per one oxypropylene to a 
molecular weight of around 4900 and having 0.061 meq. OH/g. was dried by 
vacuum stripping to a low moisture content of less 0.1% and the pH was 
adjusted with benzoyl chloride to the point where a 5% solution of the 
triol had a pH of 4.24. It as reacted at 140.degree. F. for 8 hours with 
1,819.5 g. of Type II toluene diisocyanate produced by Olin Chemical Co. 
This commercial grade of toluene diisocyanate is an 80/20 mixture made of 
80 parts of 2,4-toluene diisocyanate and 20 parts of 2,6-toluene 
diisocyanate. The reaction product is a pale yellow liquid of about 11,250 
cps at 25.degree. C. and it has 0.55 meq. NCO/g. 
EXAMPLES 1-7 
These examples illustrate the properties of sheets obtained when increasing 
amounts of the filler barium sulfate, BaSO.sub.4, are mixed with different 
amounts of the hydrogel binder. 
An aqueous mixture was formed by adding barium sulfate in the amounts 
listed in Table 1A below to 50 grams of water and stirring the mixture. 
The hydrogel prepolymer of Preparatory Example 1 was added in the amount 
listed in Table 1A and the mixture was stirred for 10 seconds. The table 
expresses the amount of the 2 ingredients in the resulting product in two 
ways. One is to express the amount of binder as the weight % of binder 
which is the fraction of binder to the total of binder and BaSO.sub.4. The 
second is to express the amount of BaSO.sub.4 on the basis of 100 parts of 
the resin binder which is abbreviated phr. The mold mixture was next 
poured into a 6 inch.times.6 inch picture frame having a thickness of 
0.091 inch. A sheet of polyethylene was placed under the frame and after 
the material was poured into the frame, a second sheet of polyethylene was 
placed on top. The material was uniformly spread out by using an 18 pound 
rolling pin. 
TABLE 1A 
______________________________________ 
Polymer BaSO.sub.4 
wt. % BaSO.sub.4 
Example g. g. Polymer 
phr 
______________________________________ 
1 5 150 3.25 3000 
2 5 200 2.44 4000 
3 5 300 1.64 6000 
4 10 150 6.25 1500 
5 10 200 4.80 2000 
6 10 300 3.22 3000 
7 20 300 6.25 1500 
______________________________________ 
The properties of the resulting product are set forth in Table 1B. 
Shrinkage occured upon drying the material in the amount set forth in 
Table 1B. This percentage shrinking was determined by measuring the final 
area as compared to the area of the initial mold. 
The dry density was determined by weighing the sample and dividing the 
weight by the volume of the sample. 
The stress and strain values for failure were obtained from the 
strss-strain curve and the modulus was calculated from the initial slope 
of the curve. This modulus is a measure of the flexibility of the sample. 
TABLE 1B 
______________________________________ 
Ex- Dry % Thick- F F 
am- Density Shrinkage ness Stress 
Strain 
ple lb/ft.sup.3 
on Drying inch Modulus 
psi % 
______________________________________ 
1 136 8.5 .0972 775 14 271 
2 160 5.9 .0954 950 13 97 
3 304 2.3 .1133 2142 18 30 
4 152 13.0 .0969 4946 57 255 
5 154 8.7 .0989 3293 56 238 
6 146 3.4 .1159 4671 44 116 
7 125 5.2 .1335 2777 51 236 
______________________________________ 
By increasing the amount of the barium sulfate for a fixed amount of 
polymer there is generally an increase in the modulus value indicating an 
increase in stiffness. There is also a decrease in the strain value 
showing the lesser amount of flexibility. 
These examples show that a relatively small amount of this unique polymer 
is able to bind or encapsulate a large amount of dense filler which gives 
a leathery to rubbery feel which is a key property that a mass damping 
material possesses. 
EXAMPLES 8-11 
These examples illustrate the addition of barium sulfate to the hydrogel 
prepolymer with the addition of a latex material which constributes 
further advantageous properties such as increased tensile strength to the 
resulting product. 
In these examples the amount of barium sulfate was maintained the same at 
200 grams and the amount of the hydrogel prepolymer of Preparatory Example 
1 used and the amount was varied as set forth in Table 2A below. Two 
different latexes were added. The latex identified as "V" in the table was 
Versaflex.sup..RTM. 1 which is an acrylic terpolymer made by W. R. Grace & 
Co. This material contains 54-56% solids. The other latex was the product 
Everflex.sup..RTM. 81L which is a polyvinyl acetate copolymer made by W. 
R. Grace & Co. and which contains 49% solids. The procedure involved 
adding barium sulfate to the aqueous latex and mixing the two together. 
After they were mixed, the hydrogel prepolymer was added and mixed for an 
additional 10 seconds. Again, the materials were poured into a square mold 
having a dimension of 6 inches .times.6 with a height of 0.091 inch. The 
same rolling procedure was used as in Examples 1-7 to obtain sheets having 
the properties set forth in Table 2B. 
TABLE 2A 
______________________________________ 
Polymer Latex BaSO.sub.4 
BaSO.sub.4 
Example g. g. g. phr* 
______________________________________ 
8 5 V-50 200 4,000 
9 10 V-50 200 2,000 
10 5 E-50 200 4,000 
11 10 E-50 200 2,000 
______________________________________ 
*where the resin is the hydrogel polymer. 
TABLE 2B 
______________________________________ 
Dry Thick- F F 
Density ness Stress 
Strain 
Example 
lb/ft.sup.3 
inch Modulus psi % 
______________________________________ 
8 129.2 .1256 22,902 185 8.43 
9 131.8 .1238 21,753 147 23 
10 123.0 .1404 45,194 469 1.23 
11 123.8 .1176 33,182 241 4.31 
______________________________________ 
The addition of the latex significantly improved the strength of the 
resulting product as seen by the increased stress values. However, it also 
substantially increased the modulus value which rendered the product 
stiffer. This may detract from the viscoelastic damping of the binder. 
EXAMPLES 12-17 
These examples illustrate the properties of sheets obtained when increasing 
amounts of the filler calcium carbonate, CaCO.sub.3, are mixed with 
different amounts of the hydrogel binder. 
The same procedure was used as in Examples 1-7 except that the prepolymer 
of Preparatory Example 2 was used and the prepolymer was preheated to 
approximately 42.degree. C. to make it easier to measure and pour before 
using. The ingredients for each example are listed in Table 3A and the 
properties of the products are in Table 3B. 
TABLE 3A 
______________________________________ 
Polymer CaCO.sub.3 
wt. % CaCO.sub.3 
Example g. g. Polymer 
phr 
______________________________________ 
12 5 97.7 5.1 1954 
13 5 130 3.8 2600 
14 5 140 3.6 2800 
15 10 97.7 10.2 977 
16 10 130.2 7.1 1302 
17 10 140 7.1 1400 
______________________________________ 
TABLE 3B 
______________________________________ 
Dry % F F 
Density Shrinkage Stress 
Strain 
Example 
lb/ft.sup.3 
on Drying Modulus 
psi % 
______________________________________ 
12 140 19.57 4,210 66 61 
13 103 12.42 2,916 49 82 
14 92.2 11.39 4,247 50 93 
15 141 22.28 5,452 78 179 
16 95 10.26 4,701 70 286 
17 106 11.07 3,575 61 239 
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These are also rubbery to leathery in feel and thus are good sound damping 
materials. Since the densities are less than BaSO.sub.4, the sheets would 
have to be thicker to obtain the same mass per unit area. 
EXAMPLE 18 
This example illustrates the properties of a sheet obtained when a 
surfactant is added to a mixture of calcium carbonate and the hydrogel 
binder. 
The same procedure as in Example 15 was followed except that the initial 
aqueous slurry also had added 0.5 g. of the surfactant Pluronic P-75 made 
by BASF Wyandotte. The properties are set forth in Table 4. 
TABLE 4 
______________________________________ 
Dry % F F 
Density Shrinkage Stress 
Strain 
Example 
lb/ft.sup.3 
on Drying Modulus 
psi % 
______________________________________ 
18 116 18.09 2,544 62 345 
______________________________________ 
This shows the significant decrease in modulus caused by the surfactant 
which results in a much more flexible sheet. 
EXAMPLE 19 
This example illustrates the use of a non-woven backing to provide 
additional strength to the sound deadening composition. 
An aqueous mixture of 50 g. water and 150 g. BaSO.sub.4 was first mixed 
together. Then 5 g. of the prepolymer made in preparatory Example 2 was 
added with further mixing for 10 seconds. The mixture was cast on to a 
layer of unbonded nontreated Kodel Polyester fibers. The layer of fibers 
was on a sheet of polyethylene and then after coating a second sheet was 
placed on top and the sandwiched layer was rolled out with an 18 pound 
rolling pin. 
The resulting product had the following properties as set forth in Table 5. 
TABLE 5 
______________________________________ 
F F 
Thickness Stress 
Strain 
Example Inch Modulus psi % 
______________________________________ 
19 .047 5,621 292 25 
______________________________________ 
This shows the very significant increase in tensile strength when compared 
to Example 1 by using the non-woven backing.