Vibration-absorbing elastomeric composite, process for making the same, and vibration damper comprising the same

Vibration-absorbing elastomeric composites, having improved vibration-damping properties with improved moldability and resin properties suitable for molded products, are obtained by reacting, insitu in a melted thermoplastic resin such as olefin-diene copolymer, a polyisocyanate with a polyol to form a polyurethane having a nitrogen atom content of at least 3% and having a solubility parameter which is higher by at least 2.5 than that of said thermoplastic resin.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to vibration-absorbing elastomeric composites, 
having improved vibration-damping properties, particularly, those used for 
the purpose of accelerating damping of vibration and decreasing amplitude 
in various apparatuses, equipments or devices, vehicles and so on. 
2. Description of the Prior Art 
Heretofore, as vibration dampers (or vibration insulators), there have been 
known those comprising polymers, such as natural rubber, butadiene rubber, 
isoprene rubber, butyl rubber, ethylene-vinyl acetate copolymer, epoxy 
resin, vinyl chloride resin, or blend of these (for instance JPN Patent 
Lay-open Nos. 227452/1990, 283738/1990 and 759/1991), and those comprising 
these polymers containing dispersed therein inorganic particles, such as 
graphite, calcium carbonate, iron oxides, carbon black, mica and the like 
(for example JPN Patent Lay-open No.227452/1990). 
These vibration dampers, however, have drawbacks, such that 
vibration-damping properties are not satisfied because of insufficient 
damping capacity, effective temperature range remote from room 
temperature, or narrow effective temperature range; and that their uses 
are restricted because of poor moldability, or insufficient rigidity and 
poor shape retention, when they are molded into rubber components to be 
assembled to structures or machines. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a vibration-absorbing 
elastomeric composite having improved damping properties. 
It is another object of this invention to provide a vibration-absorbing 
elastomeric composite effective over a wide temperature range including 
room temperature. 
It is still another object of the invention to provide a 
vibration-absorbing elastomeric composite having improved moldability and 
enough rigidity to be formed into molded products. 
It is yet another object of the invention to provide a vibration damper or 
vibration insulator and a vibration-deadened component or member, having 
improved damping properties. 
Briefly, these and other objects of the present invention as hereinafter 
will become more readily apparent have been attained broadly by a 
vibration-absorbing elastomeric composite, which comprises 
(A) 10-60% by weight of at least one thermoplastic resin and 
(B) 90-40% by weight of a polyurethane resin, prepared by reacting a 
polyisocyanate with a polyol insitu in a melted thermoplastic resin (A); 
wherein said polyurethane has a nitrogen atom content of at least 3% and 
has a solubility parameter which is higher by at least 2.5 than that of 
said thermoplastic resin. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
(A) Thermoplastic resin 
Suitable examples of the thermoplastic resin (A) include olefinic polymers, 
ethylene-unsaturated ester copolymers and natural rubbers. 
Suitable olefinic polymers include (co)polymers (polymers and copolymers; 
similar expressions are used hereinafter) of monoethylenically unsaturated 
hydrocarbon and/or diene, for example, olefins containing 2 to 30 carbon 
atoms (such as ethylene, propylene, butene-1, isobutene, and C5-30 
.alpha.-olefins written in U.S. Pat. No. 4,931,483), styrene and 
homoloques thereof (such as C1-18 alkyl-substituted styrenes), and dienes 
(such as butadiene and isoprene). Illustrative of olefinic polymers are 
(co)polymers of monoethylenically unsaturated hydrocarbon(s), for example, 
ethylene-.alpha.-olefin (C3-30) copolymers (such as ethylene-propylene 
copolymer and ethylene-butene-1 copolymer) and polyisobutylene, 
(co)polymers of diene(s), such as synthetics polyisoprene and 
polybutadiene, and (co)polymers of monoethylenically unsaturated 
hydrocarbon with diene, such as isobutylene-isoprene copolymer, EPDM 
(ethylene-propylene-diene terpolymers) and styrene-diene copolymers. 
Suitable ethylene-unsaturated ester copolymers ethylene-unsaturated acid 
copolymers include, for example, copolymers of ethylene with vinyl esters 
(such as vinyl acetate, vinyl propionate and vinyl butyrate), unsaturated 
carboxylic acids [such as (meth)acrylic, ethacrylic, crotonic, sorbic, 
maleic, fumaric, itaconic and sinnamic acids], and/or esters (such as 
C1-18 alkyl esters) of these unsaturated acids [such as methyl, ethyl, n- 
and i- propyl and butyl, n-octyl, 2-ethylhexyl, lauryl and stearyl 
(meth)acrylates]. 
Suitable natural rubbers include those obtained from latex of Hevea 
brasiliensis. 
Among these thermoplastic resins (A), preferred are isobutylene-isoprene 
copolymer and ethylene-propylene copolymer, particularly 
isobutylene-isoprene rubber and ethylene-propylene rubber (EP rubber). 
Weight average molecular weight of these thermoplastic resins (A) is 
usually about 10,000 to about 3,000,000, preferably about 10,000 to about 
1,000,000. 
(B) Polyurethane Resin 
Polyurethane resin (B) can be prepared by reacting a polyisocyanate (B1) 
with a high molecular weight polyol (B2) and a chain extender (B3) insitu 
in a melted thermoplastic resin (A) as mentioned above. 
In producing said polyurethane resin (B), there may be used any of organic 
polyisocyanates, conventionally employed for production of polyurethanes. 
Suitable polyisocyanates (B1) include, for example, aromatic 
polyisocyanates containing 6-20 carbon atoms [except carbon atoms in NCO 
groups], such as 1,3- and 1,4-phenylenediisocyanates, 2,4- and 
2,6-tolylenediiso-cyanates [TDI], diphenylmethane-2,4'-and 
4,4'-diisocyanates [MDI], naphthalene-1,5-diisocyanate, 
triphenylmethane-4,4',4'-triisocyanate, 
polymethylenepolyphenylenepolyisocyanates [PAPI] obtainable by 
phosgenation of aniline-formldehyde condensation products, and m- and 
p-isocyanatophenylsulfonylisocyanate; aliphatic polyisocyanates containing 
2-18 carbon atoms, such as ethylenediisocyanate, 
tetramethylenediisocyanate, hexamethylenediisocyanate, 
dodecamethylenediisocyanate, 1,6,11-undecanediisocyanate, 
2,2,4-trimethylhexanediisocyanate, lysine diisocyanate, 
2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl fumarate, 
bis(2-isocyanatoethyl) carbonate and 
2-isocyanatoethyl-2,6-diisocyanato-hexanoate; alicyclic polyisocyanates 
containing 4-15 carbon atoms, such as isophorone diisocyanate, 
dicyclohexylmethane diisocyanates, cyclohexylene diisocyanates, 
methylcyclohexylene diisocyanates and bis(2-isocyanatoethyl) 
4-cyclohexene-1,2-dicarboxylate; araliphatic polyisocyanates containing 
8-15 carbon atoms, such as xylylene diisocyanates and diethylbenzene 
diisocyanates; and modified polyisocyanates of these polyisocyanates, 
containing urethane, carbodiimide, allophanate, urea, biuret, urethdione, 
urethimine, isocyanurate and/or oxazolidone groups, such as 
urethane-modified TDI, carbodiimide-modified MDI, urethane-modified MDI, 
and the like; as well as mixtures of two or more of them. 
Among these polyisocyanates, preferred are aromatic diisocyanates, 
particularly TDI [including 2,4- and 2,6-isomers, mixtures of them and 
crude TDI] and MDI [including 4,4'- and 2,4'-isomers, mixtures of them and 
crude MDI], and modified polyisocyanates containing urethane, 
carbodiimide, allophanate, urea, biuret and/or isocyanurate groups, 
derived from TDI and/or MDI. 
Suitable high molecular weight polyols (B2) employed for producing 
polyurethanes include, for example, polyether polyols, polyester polyols, 
polyolefin polyols, and mixtures of two or more of them. 
Suitable polyether polyols include alkylene oxide (hereinafter referred to 
as AO) adducts of compounds containing at least two active hydrogen atoms, 
such as polyhydric alcohols, polyhydric phenols, amines, polycarboxylic 
acids, phosphrous acids and the like. Suitable examples of polyhydric 
alcohols include diols, such as ethylene glycol, propylene glycol, 1,3- 
and 1,4-butane diols, 1,6-hexane diol, neopentyl glycol, diethylene 
glycol, bis(hydroxymethyl)cyclohexane and bis(hydroxyethyl)benzene; and 
polyols having 3-8 or more hydroxyl groups, such as glycerol, trimethylol 
propane, trimethylol ethane, hexane triol, pentaerythritol, diglycerol, 
alpha-methylglucoside, sorbitol, xylitol, mannitol, glucose, fructose, 
sucrose, and the like. Exemplary of suitable polyhydric phenols are mono- 
and poly-nuclear phenols, such as hydroquinone, catechol, resorcin, 
pyrogallol, and bisphenols [bisphenol A, bisphenol F, bisphenol sulfon and 
the like], as well as phenol-formaldehyde condensation products. Suitable 
amines are inclusive of ammonia; alkanol amines, such as mono-, di- and 
tri- ethanol amines, isopropanol amines and the like; aliphatic, aromatic, 
araliphatic and alicyclic monoamines, such as C.sub.1 -C.sub.20 alkyl 
amines [methyl, ethyl, isopropyl, butyl, octyl and lauryl amines, and the 
like], aniline, toluidine, naphthyl amines, benzyl amine, cyclohexyl amine 
and the like; aliphatic, aromatic, araliphatic and alicyclic polyamines, 
such as C.sub.2 -C.sub.6 alkylene diamines [ethylene diamine, 
tetramethylene diamine, hexamethylene diamine and the like], diethylene 
triamine, tolylene diamines, phenylene diamines, benzidine, 
methylenedianilines, diphenylether diamines, xylylene diamines, 
tetramethylxylylene diamines, isophorone diamine, 1,4-diaminocyclohexane 
and 4,4'-diaminodicyclohexylmethane; and heterocyclic polyamines, such as 
piperazine, N-aminoethylpiperazine, and other heterocyclic polyamines, 
written in JPN Patent Publication No.21044/1980. Suitable AO, employed for 
producing polyether polyols, include, for example, ethylene oxide 
(hereinafter referred to as EO), propylene oxide (herein-after referred to 
as PO), 1,2-, 2,3-, 1,3- and 1,4-butylene oxides, styrene oxide, 
epichlorohydrin and the like, as well as combinations of two or more of 
them. Among these, preferred are PO and combination of PO/EO [Weight 
ratio: usually 30/70-100/0, preferably 70/30-95/5]. Addition of AO to 
active hydrogen atom-containing compounds can be carried out in the usual 
way, with or without catalysts [such as alkaline catalysts, amine 
catalysts and acidic catalysts], under normal or elevated pressure, in a 
single step or multi-stages. Addition of different AO's [PO and EO] may be 
performed by random-addition, block-addition or combination of them [for 
instance, random-addition followed by block-addition]. Illustrative of 
such polyether polyols are polyethylene glycol, polypropylene glycol, 
polyethylene/propylene(block or random) glycol, 
polyethylene/tetramethylene(block or random) glycol, 
polytetramethylene-ether glycol and polyhexamethyleneether glycol. 
Suitable polyester polyols are inclusive of condensation products of low 
molecular weight polyols [dihydric alcohols (such as ethylene glycol, 
propylene glycol, 1,3- and 1,4-butane diols, 1,6-hexane diol, 
3-methyl-1,5-pentane diol, neopentyl glycol, 
1,4-dihydroxymethylcyclohexane and diethylene glycol) and/or trihydric 
alcohols (such as glycerol and trimethylolpropane) and the like] and/or 
polyether polyols [such as those described above] with dicarboxylic acids 
[aliphatic dicarboxylic acids (such as succinic, adipic, sebacic, 
glutaric, azelaic, fumaric and maleic acids) and/or aromatic dicarboxylic 
acids (such as phthalic, iso-phthalic and terephthalic acids] or 
ester-forming derivatives thereof [anhydrides and lower alkyl esters, such 
as maleic and phthalic anhydrides, dimethyl terephtharate, and the like], 
for example, polyethylene adipate, polybutylene adipate, polyhexamethylene 
adipate, polyneopentyl adipate, polyethylene/butylene adipate, 
poly-3-methyl-1,5-pentane adipate and polybutylene iso-phthalate; 
ring-opening polymerization products of lactones [such as 
.epsilon.-caprolactone, 3-methyl-valerolactone], for instance, 
polycaprolactone diol and triol, and poly-3-methyl-valerolactone diol; and 
polycarbonate polyols, such as polyhexamethylene carbonate diol. 
Illustrative of polyolefin polyols are polydiene polyols (such as 
polybutadiene glycol and polyisoprene glycol) and hydrogenated products of 
them. 
Among these high molecular weight polyols, preferred are polyether polyols. 
Preferable polyether polyols are ones obtainable by PO/EO [Weight ratio: 
preferably 70/30-95/5], particularly polyethylene/propylene (random or 
block) glycol. 
These high molecular weight polyols have usually 2-8 hydroxyl groups, 
preferably 2-4 hydroxyl groups, and have OH equivalent weight of usually 
250-4,000, preferably 400-3,000. 
Suitable chain extenders (B3) include low molecular weight compounds 
containing at least two [preferably 2-5] active hydrogen atom-containing 
groups (such as Hydroxyl group and/or amino groups) and having an 
equivalent weight [molecular weight per active hydrogen atom-containing 
group] of at least 30 and less than 250, for example, low molecular weight 
polyols, polyamines and amino alcohols. Illustrative of suitable low 
molecular weight polyols are dihydric and trihydric alcohols as mentioned 
above as raw materials for polyether polyols (such as ethylene glycol, 
diethylene glycol, propylene glycols, 1,3- and 1,4-butane diols, 
1,6-hexane diol, glycerol, trimethylolpropane and the like), and low mole 
AO adducts of these polyols and/or amines, as well as mixtures two or more 
of them. Examples of suitable polyamines include aliphatic, aromatic, 
araliphatic and alicyclic polyamines as mentioned above as raw materials 
for polyether polyols (such as ethylene diamine, tetramethylene diamine, 
hexamethylene diamine, diethylene triamine, tolylene diamines, phenylene 
diamines, benzidine, methylene dianilines, xylylene diamines, 
tetramethylxylylene diamines, isophorone diamine, 1,4-diaminocyclohexane 
and 4,4'-diaminodicyclohexylmethane), as well as mixtures two or more of 
them. Amino alcohols, include, for instance, alkanol amines as mentioned 
above (such as ethanol amine), and low mole AO adducts of the 
above-mentioned diamines (such as N-hydroxyethylethylene diamine). Among 
these chain extenders (B3), preferred are low molecular weight polyols, 
particularly diols. 
In the present invention, polyisocyanate (B1), high molecular weight polyol 
(B2) and chain extender (B3) are reacted in such a ratio to give said 
polyurethane resin (B) having a content of nitrogen atoms (contained in 
the urethane groups) of at least 3%, preferably at least 5%, more 
preferably 6-10% by weight. Use of polyurethane resin having a nitrogen 
atom content of less than 3% results in poor vibration-damping properties. 
In producing said polyurethane resin (B), the amount of chain extender (B3) 
is generally not more than 60%, preferably 4-50%, based on the total 
weight of high molecular weight polyol (B2) and chain extender (B3). The 
average molecular weight of high molecular weight polyol (B2) and chain 
extender (B3) is usually not more than 600, preferably not more than 500 
and at least 100. 
In general, polyisocyanate (B1) is used in such an amount providing 
NCO-index of 80-120, preferably 90-110. 
Polyurethane resins can be produced in known manners, including one-shot 
process, semi-prepolymer process and prepolymer process. 
It is essential that said polyurethane resin (B) has a solubility parameter 
(hereinafter referred to as SP) which is higher by at least 2.5 than that 
of said thermoplastic resin (A). The difference between the SP of 
polyurethane resins (B) and the SP of resin (A) is usually 2.5-5.0, 
preferably 3.0-4.5. SP of thermoplastic resin (A) are usually 7.0-9.0% 
preferably 7.5-8.5. In the above, SP can be determined according to Robert 
F. Fadors, Polymer Engineering & Science, Vol. 14, p. 151, and is 
represented by a squre root of quotient of cohesive energy density divided 
by molecular volume: SP=.sqroot. .DELTA.E/V wherein .DELTA.E is cohesive 
energy density and V is molecular volume. 
(C) Compatiblilizer or Dispersant 
In producing said polyurethane resin (B) by reacting a polyisocyanate (B1) 
with a high molecular weight polyol (B2) and a chain extender (B3) insitu 
in a melted thermoplastic resin (A), the reaction may be carried out in 
the presence of a compatiblilizer or dispersant (C). Suitable 
compatiblilizers or dispersants (C) include, for example, those disclosed 
in GB Patent Application No. 9115301.5. Such dispersants include (I) those 
having both (i) a moiety having substantially the same SP as said 
thermoplastic resin (A) or said polyurethane resins (B) and (ii) at least 
one reactive group (such as carboxylic, carboxylic anhydride, amino, 
hydroxyl, isocyanate and epoxy groups), and (II) those having both (i) a 
moiety having substantially the same SP as said thermoplastic resin (A) 
and (ii) a moiety having substantially the same SP as said polyurethane 
resins (B). In the above, substantially same SP means that the difference 
in SP between the moiety and the resin is not more than 0.5. Illustrative 
of (C) are maleic (anhydride)-modified polypropylene, maleic 
(anhydride)-modified polyethylene, amino-modified low molecular weight 
polypropylene, amino-modified low molecular weight polyethylene, 
hydroxyl-terminated hydrogenated maleic-modified polypropylene, 
hydroxyl-terminated hydrogenated maleic-modifled polyethylene, and 
mixtures of 2 or more of them. Among these, preferred are maleic 
(anhydride)-modified polypropylene and maleic (anhydride)-modified 
polyethylene. These compatiblilizers or dispersants (C) have a 
number-average molecular weight of usually about 800--about 3,000,000, 
preferably about 1,000--about 1,000,000 
Composite 
In the elastomeric composite of the present invention, the content of 
thermoplastic resin (A) is usually 10-60%, preferably 20-40%, the content 
of polyurethane resin (B) is 90-40%, preferably 80-60%, and the content of 
compatiblilizer or dispersants (C) is generally 0-20%, preferably 2-10%. 
In the above and hereinafter, % represents % by weight. 
The elastomeric composite of this invention may be produced by reacting a 
polyisocyanate (B1) with a high molecular weight polyol (B2) and a chain 
extender (B3) insitu in a melted thermoplastic resin (A), optionally in 
the presense of a compatiblilizer or dispersant (C), within any known 
mixing machine. Suitable mixing machines include, for example, extruders 
(such as twin-screw extruder), kneaders, Banbury mixers and planetary 
mixers. The reaction can be carried out at a temperature of generally 
10.degree.-350.degree. C., preferably 100.degree.-300.degree. C., under a 
normal pressure or under pressure of upto 20 atm., preferably upto 10 atm. 
It is preferred for inhibitiong thermal degradation to carry out the 
reaction within a period of time as short as possible, for instance, 
0.8-60 minutes, preferably 1-30 minutes. 
In producing composites according to this invention, there may be used, if 
necessary, any known materials, such as catalysts [for example, 
organo-matal compounds (particularly organo-tin compounds, such as 
dibutyltin dilaurate, dioctyltin dilaurate and stannous octoate) and/or 
amine compounds (such as triethyl amine, triethylene diamine and 
diazabicycloundecene); mold-release agents (such as hydrocarbon waxes and 
silicone compounds), lubricants, plasticizers, colorants (pigments and 
dyes), blowing agents [halogenated hydrocarbons (such as methylene 
chloride, chloroform, ethylidene dichloride, vinylidene chloride, 
trichlorofluoromethane, dichlorofluoromethane) and/or water], stabilizers 
(weathering stabilizers and thermal stabilizers, such as age antioxidants 
and resistors), flame-retardants (such as phosphorus compounds, halogen 
compounds and Sb.sub.2 O.sub.3), surfactants (such as silicone 
surfactants), coupling agents, germicides, fillers (such as carbon black, 
titanium dioxide, diatomaceus earth, glass fiber, shattered glass fiber, 
talc, mica, silica, sand, aluminum powder, graphite and asbestos) and 
other auxiliaries, usually employed in producing polyurethanes. 
Composites of the invention may be molded according to any known method, 
for example, by injection molding, extrusion molding and compression 
molding. Injection molding is preferred in view of workability and 
productivity. 
Composites according to the present invention show high vibration-damping 
properties (such as Tan .delta. of 0.1 or more) over a wide temperature 
range (such as -20.degree. C. to 60.degree. C.). Besides, these composites 
have, over such a wide temperature range, high resin strengths, such as 
modulus of 10.sup.7 -10.sup.9 dyne/cm.sup.2 and Shore A hardness of at 
least 20. 
Accordingly, composites of this invention are useful as vibration dampers 
or vibration insulators in various applications, for example, as 
vibration-deadened components or members, in transports, including 
vehicles, such as automobiles and railway rolling stocks, aircrafts and 
water craft; members, requiring damping properties, in various industrial 
machines, various electrical, electronical or other apparatuses or 
appliances (such as computers, printers, air-conditioners, washing 
machines, cleaners, acoustic or audio systems, pianos, organs and so on; 
noize-reducing members in various noise sources in factories and 
residences; innersoles for sports shoes and the like. 
Having generally described the invention, a more complete understanding can 
be obtained by reference to certain specific examples, which are included 
for purposes of illustration only and are not intended to be limiting 
unless otherwise specified. 
In the following examples, parts represents parts by weight, and raw 
materials and measuring methods used therein are as follows: 
(1) Raw materials 
IIR: isobutylene-isoprene rubber (JSR Butyl 065, produced by Japan 
Synthetic Rubber K.K.). 
EPR: ethylene-propylene rubber (propylene content:30%, number-average 
molecular weight:70,000). 
PEPG: EO adduct of polypropylene glycol (MW:900, EO content:10%). 
EG: ethylene glycol. 
BG: 1,4-butane diol. 
MDI: 4,4'-diphenylmethane diisocyamate 
PP-MA: maleic anhydride-modified polypropylene (combined maleic 
anhydride:10%, number-average molecular weight 5,000: U-Mex 1010, produced 
by Sanyo Chemical Industries, Ltd.). 
PEA: polyethylene adipate diol (number-average molecular weight: 2,000). 
(2) Tan .delta. and modulus: measured with use of Vibron produced by 
Orienteck Co., at frequency of 100 Hz and rate of temperature increase of 
2.degree. C./minute. 
(3) Hardness: Shore A in accordance with JIS K6301.