Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
I. Field of the Invention
The present invention pertains to cellular foam
products. More particularly, the present invention concerns
energy absorbing, semi-flexible cellular foam products.
Even more particularly, the present invention concerns means
and methods for increasing the energy absorbing properties
of semi-flexible cellular foam products.
II. Prior Art
Because of energy shortages considerable efforts
have been directed to creating more fuel efficient vehicles.
While seeking alternate fuel sources, more efficient power
plants and the like, much attention has, also, been focused
on reducing the vehicle weight. By reducing the weight
of the vehicle, less energy is required to drive it.
In reducing the weight of the vehicle, safety
requirements cannot be compromised. Stringent Federal
vehicle safety regulations and standards demand intelligent
energy management systems. Quite often such systems
comprise heavy metallic components, such as bumper beams,
hydraulic shock absorbers and the like. Therefore, in
meeting weight reduction objections, suitable lightweight
plastics must be developed and strategically deployed in the
vehicle.
~5 The prior art is well acquainted with high load
bearing, semi-flexible foams and their energy absorbing pro-
perties in automotive applications. Yet, because of the
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need to further lighten automotive vehicles improved foams
having greater energy absorbing properties are constantly
sought and desired. The present invention, as will
subsequently be detailed, describes means and me-thods for
improving the energy absorbing properties of semi-flexible,
load bearing cellular foam products.
In accordance with the present invention it has
been found that the damping properties and, thus, the
energy absorbing capabilities of semi-flexible cellular foam
products is controlled by regulation of the individual cell
size of the foam product. More precisely, it has been found ,
that by reducing the cell size of the individual cells, in
semi-flexible cellular products, the damping properties
thereof are dramatically improved.
The reduction in individual cell size^is
accomplished, in accordance herewith, by increasing the
levels of catalyst present in the foam formulation. It has
been observed that by increasing catalyst levels from
about 5 to 25 tlmes the amount conventionally employed in
semi-flexible foam formulations, the cell size is
dramatically reduced.
The present invention therefore relates to a method
for improving the damping characteristics of a semi-flexible
cellular polyurethane foam by increasing the number of cells
to at least 100 per linear inch of foam comprising reacting
an organic polyisocyanate and an active hydrogen-containing
compound in the presence of a blowing agent and from about
1 to 10 parts by weight per 100 parts by weight of active
hydrogen-containing compound of a tertiary amine catalyst.
Furtherm~re, further reductions in cell size may be
achieved by incorporating minor amounts of surfactants into
the foam formulation.
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It is, also, contemplated herein that the damping
characteristics of the foam be further increased by filling
the individual cells with a damping fluid, such as mineral
oil or the like.
The catalysts which are used herein are the conven-
tional tertiary amine cata~ysts employed in the preparation
of semi-flexible, cellular foam products.
For a more complete understanding of the present
invention reference is made to the following detailed
description and accompanying examples.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As noted, the present invention provides semi-
flexible cellular foam products of reduced cell size. The
semi-flexible polyurethane cellular products having reduced
cell size are prepared by reacting the components of the
polyurethane formulation in the presence of increased levels
of catalyst. It has been observed that by increasing the
catalyst levels the cell size of the individual cells is
~ dramatically reduced. The reduction in cell size con-
sequently provides cellular products with improved damping
characteristics.
The smaller the cell size of the foam, the greater
the resistance to air flow through the foam mass. The
greater the resistance to air flow the greater the damping
effect of the foam. The greater the damping effect, the
greater the energy absorbing properties of the foam. Hence,
by reducing the individual cell size of the semi-flexible
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foam, there is an increase in the energy absorbing proper-
ties thereof. The air flow res~stance, it should be noted,
is present even though the over-all cell structure of the
foam is open or free of cell walls.
As noted hereinabove, the present invention is par-
ticularly concerned with semi-flexible cellular polyurethane
foam products. Such products are, ordinarily, prepared by
reacting a reactive hydrogen-containing compound with an
organic polyisocyanate in the presence of a suitable cata-
lyst and a blowing agent.
The reactive hydrogen-containing compound employed
herein is one which is determined by the well-known
Zerewitinoff test, as described by Kohler in Journal of the
American Chemical Society, 49, 3181 (1927) and which is
reactive with an isocyanate group. Such a compound and
its method of preparation is well known. Exemplifying an
active hydrogen-containing compound which is isocyanate
reactive is -0H, -NH-, -COOH, and -SH.
Examples of suitable types of organic compounds
containing at least two active hydrogen-containing groups
which are reactive with an isocyanate group are hydroxyl
terminated polyurethane polymers, polyhydric polythioethers,
alkylene oxide adducts of phosphorus-containing acids,
polyacetal~, aliphatic polyols, aliphatic thiolq including
alkane, alkene and alkyne thiols having two or more --SH
groups; diamines including both aromatic, aliphatic and
heterocyclic diamines, as well as mixtures thereof.
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Compounds which contain two or more different groups within
the above-defined classes may also be used in accordance
with the process of the present invention such as, for
example, amino alcohols which contain an amino group and a
hydroxyl group. Also, compounds may be used which contain
one --SH group and one --OH group as well as those which
contain an amino group and a --SH group.
Any suitable hydroxyl-terminated polyester may be
used such as are obtained, for example, from polycarboxylic
acids and polyhydric alcohols. Any suitable polycarboxylic
acid may be used such as oxalic acid, malonic acid, succinic
acid, glutaric acid, adipic acid, pimelic acid, suberic
acid, azelaic acid, sebacic acid, brassylic acid, thapsic
acid, maleic acid, fumaric acid, glutaconic acid,
~ -hydromuconic acid, ~ -hydromuconic acid, ~ -butyl-
ethyl-glutaric acid, ~ , ~ -diethyl-succinic acid,
isophthalic acid, terephthalic acid, hemimellitic acid, and
1,4-cyclohexane-dicarboxylic acid. Any suitable polyhydric
alcohol, including both aliphatic and aromatic, may be used
such as ethylene glycol, propylene glycol, 1,3-propane diol,
butylene glycol, 1,4-butane diol, 1,3-butane diol, 1,5-
pentanediol, 1,4-pentanediol, 1,3-pentanediol, 1,6-
hexanediol, 1,7-heptanediol, glycerol, 1,1,1-
trimethylolpropane, 1,1,1-trimethylolethane, hexane-1,2,6-
triol,~ -methyl glucoside, pentaerythritol, and sorbitol.
Also included within the term "polyhydric alcohol" are com-
pounds derived from phenol such as 2,-2-bis (4-
hydroxyphenyl) propane, commonly known as Bisphenol A.
~47~0~
The hydroxyl-terminated polyester may also be a
polyester amide such as is obtained by including some amine
or amino alcohol in the reactants for the preparation of the
polyesters. Thus, polyester amides may be obtained by con~
densing an amino alcohol such as ethanolamine with the poly-
carboxylic acids set forth above.
Any suitable polyalkylene ether polyol may be used
such as the polymerization product of an alkylene oxide or
of an alkylene oxide with a polyhydric alcohol. Any
suitable polyhydric alcohol may be used such as those
disclosed above for use in the preparation of the
hydroxylterminated polyesters. Any suitable alkylene oxide
may be used such as ethylene oxide, propylene oxide, buty-
lene oxide, amylene oxide, and mixture~ of these oxides.
lS The polyalkylene polyether polyols may be prepared from
other starting materials such as tetrahydrofuran and alky-
lene oxide-tetrahydrofuran copolymers; epihalohydrins such
as epichlorohydrin; as well as aralkylene oxides such
styrene oxide. The polyalkylene polyether polyols may have
either primary or secondary hydroxyl groups and, preferably,
are polyethers prepared from alkylene oxides having from two
to six carbon atoms such as polyethylene ether glycols,
polypropylene ether glycols, and polybutylene ether glycols.
The polyalkylene polyether polyols may be prepared by any
known process such as, for example, the process disclosed by
Wurtz in 1859 and Encyclopedia of Chemical Technology, Vol.
7, pp. 257-262, published by Interscience Publishers, Inc.
(1951) or in U. S. Patent No. 1,922,459.
3~
Alkylene oxide adducts of Mannich condensation products are
also useful in the invention. Polyethers which are pre-
ferred include the alkylene oxide addition products of tri-
methylolpropane, glycerine, pentaerythritol, sucrose, sor-
bitol, propylene glycol, and 2,2-bis-(4-hydroxyphenol) pro-
pane and blends thereof having equivalent weights of from
250 to 5000.
Alkylene oxide adducts of acids of phosphorus which
may be used, aside from those enumerated in U. S. Patent No.
3,639,542, include those neutral adducts prepared from the
alkylene oxides disclosed above for use in the preparation
of polyalkylene polyether polyols. Acids of phosphorus
which may be used are acids having a P205 equivalency of
from about 72% to about 95%. The phosphoric acids are
preferred.
Any suitable hydroxyl-terminated polyacetal may be
used such as, for example, the reaction product of form-
aldehyde or other suitable aldehyde with a dihydric alcohol
or an alkylene oxide such as those disclosed above.
Any suitable aliphatic thiol including alkane thiols
containing at least two --SH groups may be used such as 1,2-
ethane dithiol, 1,2-propanedithiol, 1,3-propanedithiol, and
1,6-hexane dithiol; alkene thiols, such as 2-butene-1,4-
dithiol, and alkyne thiols such as 3-hexyne-1,6-dithiol.
Any suitable polyamine may be used including aroma-
tic polyamines such as methylene dianiline, polyaryl-
polyalkylene polyamine (crude methylene dianiline),
p-aminoaniline, 1,5-diaminonaphthalene, and 2,4-diaminotoluene;
:`
~.~47~0V
the condensation products of aniline and formaldehyde;
aliphatic polyamines such as methyl amine, ethylene diamine,
1,3-propylenediamine; 1,4-butylenediamine, and 1,3-
butylenediamine, as well as substituted secondary deriva-
tives thereof, such as triisopropanolamine, as well as mix-
tures thereof.
In addition to the above hydroxyl-containing com-
pounds, other compounds which may be employed include graft
polyols. These polyols are prepared by the in situ poly-
merization product of a vinyl monomer in a reactive polyol
medium and in the presence of a free radical initiator. The
reaction is generally carried out at a temperature ranging
from about 40C to about 150C.
The reactive polyol medium generally has a molecu-
lar weight of at least about 500 and a hydroxyl number
ranging from about 30 to about 600. The graft polyol has a
molecular weight of at ~east about 1500 and a viscosity of
less than 40,000 cps. at 10% polymer concentration.
A more comprehensive discussion of the graft
polyols and their method of preparation can be found in
U. S. Patent Nos. 3,383,351; 3,304,273; 3,652,639 and in
U. S. Patent No. 3,823,201.
Also, polyols containing ester groups can be
employed in the subject invention. These polyols are pre-
pared by the reaction of an alkylene oxide with an organic
dicarboxylic acid anhydride and a compound containing a
reactive hydrogen atom. A more comprehensive discussion of
these polyols and their method of preparation can be ~ound
in U. S. Patent Nos. 3,585,185; 3,639,541 and 3/639,542.
~,
..~ ,~. r
The organic polyisocyanate used to prepare the
foams hereof correspond to the formula:
R" (NCO)æ
Wherein R" is a polyvalent organic radical which is either
aliphatic, aralkyl, alkaryl, aromatic or mixtures thereof,
and z is an integer which corresponds to the valence of R"
and is at least two. Representative of the organic polyiso-
cyanates contemplated herein includes9 for example, the aro-
matic diisocyanates, such as 2,4-toluene diisocyanate, 2,6-
toluene diisocyanate, mixtures of 2,4- and 2,6-toluene
diisocyanate, crude toluene diisocyanate, methylene diphenyl
diisocyanate, crude methylene diphenyl diisocyanate and
the like, the aromatic triisocyanates such as 4,4', 4"-
triphenylmethane triisocyanate, 2,4,6-toluene triisocyanates;
the aromatic tetraisocyanates, such as 4,4'-dimethyldi-
phenylmethane-2,2'-5, 5'-tetraisocyanate, and the like;
arylalkyl polyisocyanates, such as xylylene diisocyanate;
aliphatic polyisocyanates, such as hexamethylene-1,6-
diisocyanate, lysine diisocyanate methylester and the like,
and mixtures thereof. Other organic polyisocyanates include
polymethylene polyphenylisocyanate, hydrogenated methylene
diphenylisocyanate, m-phenylene diisocyanate, naphthalene-
1,5-diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, 4,4'-
biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl
diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate and
3,3'-dimethyldiphenylmethane-4,4'-diisocganate.
--1 0--
These polyisocyanates are prepared by conventional
methods known in the art such as the phosgenation of the
corresponding organic amine.
Still another class of organic polyisocyanates con-
templated for use herein are the so-called "quasi-
prepolymers". Three quasi-prepolymers are prepared by
reacting an excess of organic polyisocyanate or mixtures
thereof with a minor amount of an active hydrogen containing
compound such as those described hereinabove.
The catalysts which are employed in preparing the
semi-flexible, cellular products are the well known tertiary
amine urethane catalysts. Any such tertiary amine catalyst
can be used herein. Representative of such catalyst is, for
example, triethylenediamine, triethylamine,
diethylcyclohexylamine, dimethylethanolamine, N-methyl
morpholine, trimethylpiperazine, N-ethylmorpholine, diethyl-
ethanolamine, 2,4,6-tris (dimethylolmethyl) phenol, 1-
methyl-4-dimethylamine, ethyl piperazineS 3-methoxy-N-
dimethyl propyl amine, N-dimethyl-N-methyl isopropyl propy-
lene diamine, N,N-diethyl-3-diethylaminopropylamine,
dimethyl benzyl amine and the like, as well as mixtures
thereof.
Water is conventionally employed as the blowing
agent. However, fluorocarbon blowing agents or methylene
chloride can be used either alone or in combination with water.
In a preferred embodiment of the present invention,
the reactive hydrogen-containing compound is a polyhydroxyl-
containing compound or mixtures thereof and the organic
polyisocyanate is crude methylenediphenyldiisocyanate.
~4'7~00
As is known to those skilled in the art to which
the present invention pertains, the amine catalyst is con-
ventionally employed in an amount ranging from about 0.01
parts to about 1 part thereof per 100 parts, by weight, of
active hydrogen-containing compound. In accordance herewith
the catalyst is employed in an amount ranging from about 1
to 10 parts by weight thereof per 100 parts by weight of
active hydrogen-containing compound. Preferably, the cata-
lyst is present in an amount ranging from about 2 to 7 parts
by weight thereof per 100 parts of active hydrogen-
containing compound. By operating within the prescribed
range shrinkage of the foam is not encountered. Greater
levelq of catalyst, if employed, may result in shrinkage of
the foam.
The present invention, also, contemplates the use
of a surfactant in the foam formulation. The surfactant
contributes to reduction in cell size. Although optional,
where used, the surfactant is employed in an amount ranging
from about 0.5 to about 5 parts by weight, per 100 parts by
weight of polyol and, preferably, from about 0.2 to about
2.5 parts by weight thereof per 100 parts by weight of
polyol. The surfactants contemplated for use are the sili-
cone surfactants, such as alkyl polysiloxane and
polyalkylsiloxanes.
The improvement in damping effect attributable to
cell size reduction because of catalyst levels can be still
further enhanced, if desired. By saturating the cellular
product of reduced cell size with a suitable damping fluid,
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the cells become filled with the fluid. Filling the cells
in thi~ manner further increases the resistance to air flow
of the mass. Suitable damping fluids include mineral oil,
and other viscous materials which are non-reactive with the
foam. The damping fluid is employed by immersing the foam
product therewithin or by any other suitable mode. Where
used, the foam is subsequently encapsulated to prevent loss
of the fluid.
In preparing foams in accordance herewith, ordi-
narily, the active hydrogen-containing compound, catalyst,
blowing agent and ~urfactant, if any, are blended together.
Then, the isocyanate is admixed therewith to commence the
reaction. Ordinarily, the reaction is carried out at
ambient conditions. If desired, the foam produced thereby
can, then, be saturated wlth a damping fluid ln the manner
described above.
For a more complete understanding of the present
invention reference is made to the following specific
example thereof. In the example, which i9 to be construed
as illustrative and not limitative of the invention, all
parts are by weight absent indications to the contrary.
EXAMPLE
To test the efficacy of the present inventlon a
series of semi-rlexible polyurethane foams were prepared by
the following procedure:
Into one-quart capacity mixing cups, at room tem-
perature was added a blend of (a) a polyol blend, (b) water
as a blowing agent, (¢) a silicone surfactant, where used, and
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(d) dimethylethanolamine, as a catalyst. The mixture was
stirred with a light duty bench top drill press equipped
with a 1~ inch diameter shrouded mixing blade. The stirring
was timed by a stop watch. Mixer speed was 3400 rpms. The
stop watch and mixer were started simultaneously and the
mixture was stirred initially for 30 seconds. While mixing,
to the container was, then, added quickly crude methylene
diphenyldiisocyanate (MDI) as the isocyanate reactant. After
the isocyanate was added, mixing continued for about 5 to 10
seconds. The foam compositions were then poured into a 9" x
9" x 12" aluminum molds pretreated with a release agent and
were retained in the mold for twenty-five minutes to ensure
complete reaction. The foams were, then, removed from the
mold and tested for physical properties.
The following table sets forth the ingredients and
their respective amounts, the processing conditions and the
physical tests and the results thereof carried out on the
sample foams.
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TABLE
. _
SAMPLE
A. Ingredient, amt., Pbw 1 2 3
Polyol(l) 100. 100. 100.
Water 2.2 2.2 2.2
Dimethylethanolamine0.125 2.5 2.5
Surfactant( 2) ~ 1.0
Crude MDI 45.0 45.0 45.0
Isocyanate Index 103. 90. 90.
_ _ Processing Conditions
Cream Time, sec. 40. 10. 10.
Free-rise time, sec.400. 60. 60.
C. ProPertie~( 3)
Density, pcf 6.99 6.99 7.12
ILD, lb. 1 sq. in.
25% 45.3 37.1 48.8
65% 62.7 53 - 4 58.8
25% return 5.6 6.2 6.4
SAG factor ( 4) 1.38 1.44 1.20
Guide factor (5) 6.50 5.3 6.9
Recovery, % (6) 12.4 16.7 13.0
Decreasing Cell Size
(1)a polyol blend of (a) triol-based styrene-acrylonitrile
graft polyol having an OH No. of about 23,
tb) an ethoxylated and propoxylated glycerine-based
polyol having an OH No. of about 35, and
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(c) an ethoxylated and propoxylated ethylenediamine
having an OH No. of about 450, the polyols (a), (b) and
(c) being present in a, respective, weight ratio of r
4:1:0.263.
(2) a silicone surfactant sold under the name NIAX
Surfactant L-5302 (trademark) t
(3) each sample property based on an average of three foams
per sample
(4) defined as the ratio of 65% ILD/25% ILD
(5) defined as the ratio of 25~ ILD/density
(6) defined as the ratio of 25% return ILD/25% ILD
It is to be observed from the Table that the load
bearing level of the smaller cell sized foams are equivalent
to those of the larger cell sized foams (Sample 1), even
though the isocyanate index for the smaller cell sized foams
is lower than that of SAMPLE 1. Ordinarily, the lower the
isocyanate index the softer the foam. E
Having, thus, described the invention what is
claimed is:
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