U.S. patent application number 10/505148 was filed with the patent office on 2005-06-09 for polyurethane foam.
Invention is credited to Appelman, Eric, Cameron, Paul A.
Application Number | 20050124711 10/505148 |
Document ID | / |
Family ID | 9931350 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050124711 |
Kind Code |
A1 |
Cameron, Paul A ; et
al. |
June 9, 2005 |
Polyurethane foam
Abstract
A microcellular polyurethane obtainable by reacting a
polyisocyanate, a polyester formed from a dimer fatty acid and/or
dimer fatty diol, and a chain extender. The foam is particularly
suitable for use as a component of shoe soles.
Inventors: |
Cameron, Paul A; (North
Yorkshire, GB) ; Appelman, Eric; (Dordrecht,
NL) |
Correspondence
Address: |
Mayer Brown Rowe and Maw
Intellectual Property Department
1909 K Street N W
Washington
DC
20006-1101
US
|
Family ID: |
9931350 |
Appl. No.: |
10/505148 |
Filed: |
January 12, 2005 |
PCT Filed: |
February 10, 2003 |
PCT NO: |
PCT/GB03/00599 |
Current U.S.
Class: |
521/155 |
Current CPC
Class: |
C08K 5/053 20130101;
C08G 18/10 20130101; C08G 2110/0066 20210101; C08G 2110/0083
20210101; C08G 2120/00 20130101; Y10T 428/249978 20150401; C08G
18/4288 20130101; C08G 18/10 20130101; C08G 18/664 20130101 |
Class at
Publication: |
521/155 |
International
Class: |
C08G 018/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 19, 2002 |
GB |
0203881.8 |
Claims
1. A microcellular polyurethane foam obtainable by reacting a
polyisocyanate, a polyester formed from a dimer fatty acid and/or
dimer fatty diol, and a chain extender.
2. A process for preparing a microcellular polyurethane foam which
comprises (i) reacting a polyisocyanate with a polyester formed
from a dimer fatty acid and/or dimer fatty diol, to form an
isocyanate-terminated prepolymer, and (ii) reacting the prepolymer
with a chain extender.
3. A foam or process according to claim 1 wherein the polyester is
additionally formed from a non-dimer dicarboxylic acid, and
preferably the ratio of dimer fatty acids to non-dimer acids is in
the range from 30 to 70:30 to 70% by weight of the total
dicarboxylic acids.
4. A foam or process according to claim 3 wherein the non-dimer
dicarboxylic acid comprises adipic acid.
5. A foam or process according to claim 1 wherein the chain
extender is a diol having an aliphatic linear carbon chain
comprising in the range from 1 to 10, more preferably 3 to 5 carbon
atoms.
6. A foam or process according to claim 1 wherein the foam retains
at least 60%, preferably at least 80%, of its initial tensile
strength and/or initial elongation at break properties, after being
subjected to hydrolysis for 2 weeks.
7. A foam or process according to claim 1 wherein the foam retains
at least 20%, preferably at least 30%, of its initial tensile
strength and/or retains at least 30%, preferably at least 50% of
its initial elongation at break properties, after being subjected
to hydrolysis for 4 weeks.
8. A foam or process according to claim 1 wherein the foam has a
density in the range from 0.25 to 0.7 gcm.sup.-3, and/or a hardness
in the range from 20 to 60 Shore A, and/or a tensile strength in
the range from 35 to 80 kgcm.sup.-2, and/or an elongation at break
of greater than 250%, and/or a tear strength in the range from 2 to
8 kNm.sup.-1, and/or an impact resilience in the range from 10 to
35%.
9. An isocyanate-terminated prepolymer which is the reaction
product of a polyisocyanate and a polyester which is the reaction
product of dimer fatty acid, adipic acid and diethylene glycol.
10. A shoe sole comprising a microcellular polyurethane foam
obtainable by reacting a polyisocyanate, a polyester formed from a
dimer fatty acid and/or dimer fatty diol, and a chain extender.
Description
FIELD OF INVENTION
[0001] The present invention relates to a microcellular
polyurethane foam, a process of making the foam, and in particular
to the use thereof in shoe soles.
BACKGROUND
[0002] Polyurethanes are extremely versatile materials and have
been used in a wide variety of applications such as foam
insulation, car seats and abrasion resistant coatings.
Polyurethanes are used in a wide variety of forms, for example
non-cellular materials such as elastomers; and cellular materials
such as low density flexible foams, high density flexible foams,
and microcellular foams. Microcellular foams have been used for
energy absorbing bumper mountings and auxiliary suspension units
for wheels, and in particular in shoe soles.
[0003] Microcellular polyurethane foams used in shoe soles require
a wide range of properties such as resistance and durability in
actual use, combined with high flexibility, optimal impact
resilience, low weight, high thermal insulation and cushioning.
There is a need for microcellular polyurethane foams to provide an
improvement in one or more of the aforementioned properties. In
particular, known shoe soling materials tend to have insufficient
flexibility on repeated flexing at low temperature (due to strain
hardening), and hydrolytic instability.
REVIEW OF THE PRIOR ART
[0004] EP-0795572-A is directed to the use of a polyester polyol,
derived from terephthalic acid and adipic acid, to produce
polyurethane foam for shoe soles.
[0005] U.S. Pat. No. 5,856,372 is directed to a microcellular
polyurethane shoe sole component formed from isocyanate-terminated
prepolymers derived from polyoxypropylene diols.
SUMMARY OF THE INVENTION
[0006] We have now surprisingly discovered a microcellular
polyurethane foam which reduces or substantially overcomes at least
one of the aforementioned problems.
[0007] Accordingly, the present invention provides a microcellular
polyurethane foam obtainable by reacting a polyisocyanate, a
polyester formed from a dimer fatty acid and/or dimer fatty diol,
and a chain extender.
[0008] The invention also provides a process for preparing a
microcellular polyurethane foam which comprises (i) reacting a
polyisocyanate with a polyester formed from a dimer fatty acid
and/or dimer fatty diol, to form an isocyanate-terminated
prepolymer, and (ii) reacting the prepolymer with a chain
extender.
[0009] The invention further provides an isocyanate-terminated
prepolymer which is the reaction product of a polyisocyanate and a
polyester which is the reaction product of dimer fatty acid, adipic
acid and diethylene glycol.
[0010] The invention still further provides a shoe sole comprising
a microcellular polyurethane foam obtainable by reacting a
polyisocyanate, a polyester formed from a dimer fatty acid and/or
dimer fatty diol, and a chain extender.
[0011] The polyester used in the present invention is formed from,
ie comprises the reaction product of, at least one dimer fatty acid
and/or dimer fatty diol and/or equivalent thereof. Polyester is
normally produced in a condensation reaction between at least one
polycarboxylic acid and at least one polyol. Dicarboxylic acids and
diols are preferred. The preferred dicarboxylic acid component of
the polyester used in the present invention preferably comprises at
least one dimer fatty acid.
[0012] The term dimer fatty acid is well known in the art and
refers to the dimerisation product of mono- or polyunsaturated
fatty acids and/or esters thereof. Preferred dimer fatty acids are
dimers of C.sub.10 to C.sub.30, more preferably C.sub.12 to
C.sub.24, particularly C.sub.14 to C.sub.22, and especially
C.sub.18 alkyl chains. Suitable dimer fatty acids include the
dimerisation products of oleic acid, linoleic acid, linolenic acid,
palmitoleic acid, and elaidic acid. The dimerisation products of
the unsaturated fatty acid mixtures obtained in the hydrolysis of
natural fats and oils, e.g. sunflower oil, soybean oil, olive oil,
rapeseed oil, cottonseed oil and tall oil, may also be used.
Hydrogenated, for example by using a nickel catalyst, dimer fatty
acids may also be employed.
[0013] In addition to the dimer fatty acids, dimerisation usually
results in varying amounts of oligomeric fatty acids (so-called
"trimer") and residues of monomeric fatty acids (so-called
"monomer"), or esters thereof, being present. The amount of monomer
can, for example, be reduced by distillation. Suitable dimer fatty
acids have a dicarboxylic (or dimer) content of greater than 60%,
preferably greater than 75%, more preferably in the range from 80
to 96%, particularly 85 to 92%, and especially 87 to 89% by weight.
The trimer content is suitably less than 40%, preferably in the
range from 2 to 25%, more preferably 5 to 15%, particularly 7 to
13%, and especially 9 to 11% by weight. The monomer content is
preferably less than 10%, more preferably in the range from 0.2 to
5%, particularly 0.5 to 3%, and especially 1 to 2% by weight. All
of the above % by weight values are based on the total weight of
trimer, dimer and monomer present.
[0014] The dicarboxylic acid component of the polyester preferably
also comprises non-dimeric dicarboxylic acids (hereinafter referred
to as non-dimeric acids). The non-dimeric acids may be aliphatic or
aromatic (such as phthalic acid, isophthalic acid and terephthalic
acid), and include dicarboxylic acids and the esters, preferably
alkyl esters, thereof, preferably linear dicarboxylic acids having
terminal carboxyl groups having a carbon chain in the range from 2
to 20, more preferably 6 to 12 carbon atoms, such as adipic acid,
glutaric acid, succinic acid, pimelic acid, suberic acid, azelaic
acid, sebacic acid, heptane dicarboxylic acid, octane dicarboxylic
acid, nonane dicarboxylic acid, decane dicarboxylic acid, undecane
dicarboxylic acid, dodecane dicarboxylic acid and higher homologs
thereof. Adipic acid is particularly preferred.
[0015] A monomeric dicarboxylic acid anhydride, such as phthalic
anhydride, may also be employed as the or as part of the
non-dimeric acid component.
[0016] The polyester is preferably formed from dimer fatty acids to
non-dimer acids present at a ratio in the range from 10 to 100:0 to
90%, more preferably 30 to 70:30 to 70%, particularly 40 to 60:40
to 60%, and especially 45 to 55:45 to 55% by weight of the total
dicarboxylic acids.
[0017] The polyol component of the polyester used in the present
invention suitably has a molecular weight in the range from 50 to
650, preferably 60 to 250, more preferably 70 to 200, and
particularly 100 to 150. The polyol component may comprise polyols
such as pentaerythritol, triols such as glycerol and
trimethylolpropane, and preferably diols. Suitable diols include
straight chain aliphatic diols such as ethylene glycol, diethylene
glycol, 1,3-propylene glycol, dipropylene glycol, 1,4-butylene
glycol, 1,6-hexylene glycol, branched diols such as neopentyl
glycol, 3-methyl pentane glycol, 1,2-propylene glycol, and cyclic
diols such as 1,4-bis(hydroxymethyl)cyclohexane and
(1,4-cyclohexane-dimethanol). Diethylene glycol is a particularly
preferred diol.
[0018] The polyol component may also comprise a dimer fatty diol.
Dimer fatty acids are mentioned above in relation to the
dicarboxylic acid component, and dimer fatty diols can be produced
by hydrogenation of the corresponding dimer fatty acid. The same
preferences above for the dimer fatty acid apply to the
corresponding dimer fatty diol component of the polyester.
[0019] The polyester is preferably formed from dicarboxylic acid to
diol starting materials at a molar ratio in the range from 1:1.0 to
5.0, more preferably 1:1.05 to 3.0, particularly 1:1.1 to 2.0, and
especially 1:1.2 to 1.4. Thus, the diol is preferably present in
molar excess so as to obtain a polyester terminated at both ends
with OH groups.
[0020] In a preferred embodiment, the polyester is formed from
dimer fatty acid, adipic acid, and diethylene glycol, preferably at
a weight ratio in the range from 0.3 to 0.7:0.3 to 0.7:1.0 to 3.0,
more preferably 0.4 to 0.6:0.4 to 0.6:1.1 to 2.0, particularly 0.45
to 0.55:0.45 to 0.55:1.2 to 1.4, and especially approximately
0.5:0.5:1.3.
[0021] The polyester preferably has a molecular weight number
average in the range from 1,000 to 5,000, more preferably 1,700 to
3,000, particularly 1,800 to 2,500, and especially 1,900 to
2,200.
[0022] The polyester preferably has a glass transition temperature
(Tg) value (measured as described herein) in the range from -60 to
0.degree. C., more preferably -50 to -5.degree. C., particularly
-40 to -10.degree. C., and especially -35 to -15.degree. C.
[0023] The polyester preferably has a hydroxyl value (measured as
described herein) in the range from 10 to 100, more preferably 30
to 80, particularly 40 to 70, and especially 50 to 60 mgKOH/g. In
addition, the polyester preferably has an acid value (measured as
described herein) of less than 2, more preferably less than 1.7,
particularly less than 1.3, and especially less than 1.0.
[0024] The polyisocyanate component is preferably at least one
isocyanate which has a functionality of at least 2, and may be an
aliphatic isocyanate such as hexamethylene 1,6-diisocyanate, but
more preferably is an aromatic isocyanate such as tolylene
diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate,
xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate,
hexamethylene diisocyanate, isophorone diisocyanate,
polymethylenepolyphenyl diisocyanate,
3,3'-dimethyl-4,4'-biphenylene diisocyanate,
3,3'-dimethyl-4,4'-diphenylm- ethane diisocyanate,
3,3-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene
diisocyanate, or modified compounds thereof such as
uretonimine-modified compounds thereof. The polyisocyanate monomers
can be used alone or as mixtures thereof. In a preferred
embodiment, 4,4'-diphenylmethane diisocyanate (MDI) is used alone,
or more preferably a mixture of MDI and a uretonimine-modified
4,4'-diphenylmethane diisocyanate (modified MDI) is employed.
[0025] In one embodiment of the invention, at least one of the
aforementioned polyisocyanates is reacted with at least one of the
aforementioned polyesters, to form a prepolymer. The ratio of
polyisocyanate to polyester starting materials which are mixed
together to react to form the prepolymer is preferably in the range
from 20 to 80:20 to 80%, more preferably 35 to 75:25 to 65%,
particularly 45 to 70:30 to 55%, and especially 55 to 65:35 to 45%
by weight. The polyisocyanate is preferably used in molar excess
relative to OH group content of the polyester, so as to obtain a
reaction mixture containing isocyanate-terminated prepolymer and
sufficient unreacted polyisocyanate, such that later addition of
the chain extender can result in reaction to form the polyurethane
foam, without the requirement for adding further
polyisocyanate.
[0026] The prepolymer reaction mixture preferably has an isocyanate
content (measured as described herein) in the range from 5 to 30%,
more preferably 15 to 23%, particularly 17 to 20%, and especially
18 to 19% NCO.
[0027] The chain extender component used to form the polyurethane
suitably comprises a low molecular compound having 2 or more active
hydrogen groups, for example polyols such as ethylene glycol,
diethylene glycol, propylene glycol, 1,4-butylene glycol,
1,5-pentylene glycol, methylpentanediol, 1,6-hexylene glycol,
neopentyl glycol, trimethylolpropane, hydroquinone ether
alkoxylate, resorcinol ether alkoxylate, glycerol, pentaerythritol,
diglycerol, and dextrose; aliphatic polyhydric amines such as
ethylenediamine, hexamethylenediamine, and isophorone diamine;
aromatic polyhydric amines such as methylene-bis(2-chloroaniline),
methylenebis(dipropylaniline), diethyltoluenediamine, trimethylene
glycol di-p-aminobenzoate; alkanolamines such as diethanolamine,
triethanolamine and diisopropanolamine.
[0028] In a preferred embodiment of the invention, the chain
extender is a polyol, more preferably a diol, particularly having
an aliphatic linear carbon chain comprising in the range from 1 to
10, and especially 3 to 5 carbon atoms. Preferred diols include
ethylene glycol, propylene glycol, 1,4-butylene glycol, and
1,5-pentylene glycol. 1,4-butylene glycol is particularly
preferred.
[0029] In a particularly preferred embodiment of the invention, at
least one of the aforementioned polyesters is added together with
the chain extender to react with the prepolymer in order to form
the polyurethane. The molar ratio of chain extender to polyester
employed is preferably in the range from 1 to 10:1, more preferably
1.5 to 8:1, particularly 2 to 5:1, and especially 2.5 to 4:1. The
polyester employed may be the same as or different to the polyester
used to form the prepolymer.
[0030] In one embodiment of the invention, non-dimer (acid or diol)
containing polyester, may also be employed in forming the
microcellular polyurethane foam, in addition to the dimer fatty
(acid and/or diol) containing polyesters described herein. Suitable
non-dimer containing materials include polyesters derived from
adipic acid and common diols such as ethylene glycol, diethylene
glycol, 1,4-butylene glycol, or speciality glycols and other
special ingredients, eg caprolactone.
[0031] When the optional non-dimer containing polyester is present,
the microcellular polyurethane foam is formed from dimer-containing
polyester to non-dimer containing polyester (both used as the
polyester and/or in isocyanate-terminated prepolymer form)
preferably at a ratio in the range from 10 to 95:5 to 90, more
preferably 30 to 90:10 to 70, particularly 40 to 80:20 to 60, and
especially 50 to 70:30 to 50% by weight.
[0032] The dimer fatty acid and/or dimer fatty diol content of the
polyurethane foam is preferably in the range from 5 to 50%, more
preferably 8 to 40%, particularly 12 to 30%, and especially 15 to
20% by weight.
[0033] In the present invention, the chain extender composition may
optionally contain other additives such as blowing agents, urethane
promoting catalysts, surfactants, stabilizers and pigments.
[0034] Suitable blowing agents include water, and fluorocarbons
such as trichlorofluoromethane, dichlorodifluoromethane and
trichlorodifluoroethane. The blowing agents may be used alone or as
mixtures thereof.
[0035] Examples of urethane catalysts include tertiary amines such
as triethylamine, 1,4-diazabicyclo[2.2.2.]octane (DABCO),
N-methylmorpholine, N-ethylmorpholine,
N,N,N',N'-tetramethylhexamethylene- diamine, 1,2-dimethylimidazol;
and tin compounds such as tin(II)acetate, tin(II)octanoate,
tin(II)laurate, dibutyltin dilaurate, dibutyltin dimaleate,
dioctyltin diacetate and dibutyltin dichloride. The catalysts may
be used alone or as mixtures thereof.
[0036] Suitable surfactants include silicone surfactants such as
dimethylpolysiloxane, polyoxyalkylene polyol-modified
dimethylpolysiloxane and alkylene glycol-modified
dimethylpolysiloxane; and anionic surfactants such as fatty acid
salts, sulfuric acid ester salts, phosphoric acid ester salts and
sulfonates.
[0037] Examples of the stabilizers include hindered phenol radical
scavengers such as dibutylhydroxytoluene,
pentaerythrityl-tetrakis[3-(3,5-
-di-t-butyl-4-hydroxyphenyl)propionate] and
isooctyl-3-(3,5-di-t-butyl-4-h- ydroxyphenyl)propionate;
antioxidants such as phosphorous acid compounds such as
triphenylphosphite, triethylphosphite and triphenylphosphine;
ultraviolet absorbing agents such as
2-(5-methyl-2-hydroxyphenyl)benzotri- azole and a condensation
product of methyl-3-[3-t-butyl-5-(2H-benzotriazol-
e-2-yl)-4-hydroxyphenyl]propionate and polyethylene glycol.
Suitable pigments include inorganic pigments such as transition
metal salts; organic pigments such as azo compounds; and carbon
powder.
[0038] The microcellular polyurethane foam according to the present
invention may be produced by efficiently mixing the prepolymer with
a chain extender composition, preferably in an injection moulding
polyurethane machine. The chain extender composition is preferably
prepared by simple pre-mixing of, for example, the chain extender,
polyester and other additives (such as blowing agent, and/or
urethane catalyst, and/or surfactant). In the polyurethane
synthesis, the NCO/OH ratio employed is preferably in the range
from 1 to 1.2:1, more preferably 1 to 1.1:1, and particularly 1 to
1.03:1.
[0039] The microcellular polyurethane foam according to the present
invention is suitably defined as an elastomer of cellular structure
containing mostly closed cells which are difficult to see with the
naked eye (cell size of the order of approximately less than 0.1
mm). The foam preferably has a density (measured as described
herein) in the range from 0.2 to 0.9, more preferably 0.25 to 0.7,
particularly 0.3 to 0.6, and especially 0.35 to 0.5 gcm.sup.-3.
[0040] The microcellular polyurethane foam preferably has a
hardness (measured as described herein) in the range from 10 to 70,
more preferably 20 to 60, particularly 25 to 55, and especially 30
to 50 Shore A.
[0041] The microcellular polyurethane foam suitably has a tensile
strength (measured as described herein) of greater than 20,
preferably greater than 30, more preferably in the range from 35 to
80, particularly 40 to 75, and especially 50 to 70 kgcm.sup.-2.
[0042] The elongation at break (measured as described herein) of
the microcellular polyurethane foam is suitably greater than 150%,
preferably greater than 200%, more preferably greater than 250%,
particularly in the range from 300 to 550% and especially 350 to
400%.
[0043] The tear strength (measured as described herein) of the
microcellular polyurethane foam is preferably greater than 1.2,
more preferably in the range from 1.6 to 6, particularly 2 to 5,
and especially 2.5 to 4 kNm.sup.-1.
[0044] The impact resilience (measured as described herein) of the
microcellular polyurethane foam is suitably less than 45%,
preferably in the range from 10 to 35%, more preferably 15 to 30%,
particularly 18 to 27%, and especially 20 to 25%.
[0045] A particular advantage of the microcellular polyurethane
foam according to the present invention is that it is resistant to
hydrolysis. Thus, the foam after being subjected to hydrolysis for
2 weeks, as described under test procedures herein, suitably has a
tensile strength and/or elongation at break, within the respective
preferred values given above. The foam suitably retains at least
40%, preferably at least 60%, more preferably at least 80%,
particularly at least 90%, and especially at least 100% of its
initial tensile strength and/or initial elongation at break
properties, after being subjected to hydrolysis for 2 weeks.
[0046] In addition, the microcellular polyurethane foam preferably
retains at least 20%, more preferably at least 30%, particularly at
least 40%, and especially at least 50% of its initial tensile
strength properties, after being subjected to hydrolysis for 4
weeks. The foam preferably has a tensile strength of greater than
10, more preferably in the range from 15 to 45, particularly 20 to
40, and especially 25 to 35 kgcm.sup.-2 after being subjected to
hydrolysis for 4 weeks. The foam also suitably retains at least
30%, preferably at least 50%, more preferably at least 70%,
particularly at least 85%, and especially at least 95% of its
initial elongation at break properties after being subjected to
hydrolysis for 4 weeks. The foam suitably has an elongation at
break of greater than 100%, preferably greater than 150%, more
preferably greater than 200%, particularly in the range from 250 to
450% and especially 300 to 400% after being subjected to hydrolysis
for 4 weeks.
[0047] The microcellular polyurethane foam according to the present
invention is suitable for use, inter alia, as shock
absorbers/"spring aids" for automotive suspension, tyres (energy
absorbing wheels for buggies, trollies) and technical parts (car
seat components), and is particularly suitable for use in shoes.
The foam can be used in dual density outsoles, single density
boots, single density casual/formal, single density sandals, single
density insoles, and especially in dual and single density
midsoles.
[0048] The invention is illustrated by the following non-limiting
examples.
[0049] In this specification the following test methods have been
used.
[0050] (a) For Polyester and Prepolymer
[0051] (i) The glass transition temperature (Tg) was measured by
Differential Scanning Calorimetry (DSC) at a scan rate of
20.degree. C./minute using a Mettler DSC30.
[0052] (ii) Molecular weight number average was determined by end
group analysis.
[0053] (iii) The hydroxyl value is defined as the number of mg of
potassium hydroxide equivalent to the hydroxyl content of 1 g of
sample, and was measured by acetylation followed by hydrolysation
of excess acetic anhydride. The acetic acid formed was subsequently
titrated with an ethanolic potassium hydroxide solution.
[0054] (iv) The acid value is defined as the number of mg of
potassium hydroxide required to neutralise the free fatty acids in
1 g of sample, and was measured by direct titration with a standard
potassium hydroxide solution.
[0055] (v) The isocyanate value is defined as the weight % content
of isocyanate in the sample and was determined by reacting with
excess dibutylamine, and back titrating with hydrochloric acid.
[0056] (b) For Microcellular Polyurethane Foam
[0057] (i) Density
[0058] Determined by measuring the mass and volume of the specimen
(to within 1% accuracy) and calculating density (=mass/volume).
[0059] (ii) Hardness
[0060] Measured using a Shore A meter on a 10 mm thick sample. Mean
value of 10 readings calculated.
[0061] (iii) Tensile Strength
[0062] Determined according to ISO 37/DIN 53504 using a Z82B29
sample die.
[0063] (iv) Elongation at Break
[0064] Measured according to ISO 37/DIN 53504 using a Z82B29 sample
die.
[0065] (v) Tear Strength
[0066] Determined using a procedure analogous to ASTM D3574 test F,
except that the sample used was 100.times.25.times.10 mm with a 40
mm cut in the centre of the 25.times.10 mm face, parallel to the
25.times.100 mm face. The crosshead speed was 200 mm/min. The
maximum load from the start of tearing over a 20 mm tear was
recorded, and the tear strength calculated by dividing by the
thickness (25 mm).
[0067] (vi) Impact Resilience
[0068] Measured according to ASTM D3574 (falling ball rebound
test).
[0069] (vii) Hydrolysis
[0070] Samples were aged by placing dumbells of the material in a
climate chamber at 70.degree. C. and >98% relative humidity for
periods of 2 and 4 weeks. The tensile strength and elongation at
break of the "aged" samples were determined as above and the values
compared to the original figures (on percentage retention
terms).
[0071] All the above tests were performed after the foam samples
had been conditioned for a minimum of 24 hours, undeflected and
undistorted at 23.degree. C. and 50% relative humidity.
EXAMPLES
Example I
[0072] (a) 902 g of adipic acid, 902 g of PRIPOL 1017 (trade mark,
ex Uniqema (dimer acid)) and 1051 g of diethylene glycol were
reacted at 225.degree. C. in the presence of 50 ppm of tetrabutyl
titanate catalyst. On completion of the reaction, the excess
diethylene glycol was removed in vacuo and the dimerate polyester
product was purified by filtration. Hydroxyl value was found by
titration to be 54 mg KOH/g.
[0073] (b) 586 g of the polyester produced above was placed in a
flask and dried by heating for 2 hours at 120.degree. C. and 50
mbar. 860 g of flake pure MDI (ex Bayer) was added at a temperature
of 50 to 60.degree. C. over 1 hour period at atmospheric pressure.
161 g of modified MDI (Suprasec 2021, ex Huntsman Polyurethanes)
was then added, and the reaction was heated at 55.degree. C. for a
further hour, and then at 85.degree. C. for a further two hours.
The product was discharged and stored at 50.degree. C. The
prepolymer material was found to have an isocyanate content of
18.5% NCO.
[0074] (c) A chain extender composition was prepared by mixing the
following components in the following ratio:
1 Polyester prepared in (a) 100 DABCO DC193 silicone surfactant (ex
Air Products) 0.4 1,4-butylene glycol (dry) 12 DABCO crystal
(triethylene diamine, ex Air Products) 0.5 Distilled water 0.5
[0075] (d) The prepolymer (prepared in (b)) and the chain extender
composition (prepared in (c)) were mixed using an injection
moulding polyurethane machine, with an isocyanate index of 100 to
103, and a mixing temperature of 35 to 45.degree. C. The cream time
was 5 to 10 seconds. The mould was coated in silicone release agent
and was at a temperature of 65.degree. C. A polyurethane foam sheet
of 150.times.150 mm was yielded (step mould resulted in 4 mm thick
and 10 mm thick sections). The foam was demoulded after 8
minutes.
[0076] The resulting polyurethane foam had the following
properties, measured as described above;
[0077] (i) The density (of 10 mm thick section) was 0.37
gcm.sup.-2,
[0078] (ii) The hardness was 35 Shore A,
[0079] (iii) The tensile strength was 33.9 kgcm.sup.-2 (the modulus
at 100% was 15 kgcm.sup.-2),
[0080] (iv) The elongation at break was 300%, and
[0081] (v) The tear strength was 2.2 kNm.sup.-1.
[0082] The polyurethane foam was subjected to hydrolysis conditions
for 2 weeks and 4 weeks as described above, and the following
properties were remeasured;
[0083] Two Weeks--
[0084] (i) The tensile strength was 30.9 kgcm.sup.-2 (=91%
retention of initial value), and
[0085] (ii) The elongation at break was 253% (=84% retention of
initial value).
[0086] Four Weeks--
[0087] (i) The tensile strength was 14.6 kgcm.sup.-2 (=43%
retention of initial value), and
[0088] (ii) The elongation at break was 122% (=41% retention of
initial value).
Example 2
[0089] (a) The procedure according to Example 1(a) was used except
that the starting materials were 879 g of adipic acid, 879 g of
dimer acid (containing 88% by weight dimer and 10% by weight
trimer) were reacted with 1042 g of diethylene glycol. Hydroxyl
value of the resultant polyester was 54 mg KOH/g.
[0090] (b) The procedure according to Example 1(b) was employed
except that 706 g of the polyester produced above was reacted with
960 g of flake pure MDI (ex Bayer) and 185 g of modified MDI
(Desmodur CD, ex Bayer). The prepolymer material had an isocyanate
content of 18.5% NCO.
[0091] (c) The procedure according to Example 1(c) was employed
except that polyester produced in Example 2(a) above was used.
[0092] (d) The procedure according to Example 1(d) was employed
except that materials produced in Example 2(b) and (c) above were
used.
[0093] The resulting polyurethane foam had the following
properties, measured as described above;
[0094] (i) The density (of 10 mm thick section) was 0.48
gcm.sup.-2,
[0095] (ii) The hardness was 46 Shore A,
[0096] (iii) The tensile strength was 74 kgcm.sup.-2 (the modulus
at 100% was 27 kgcm.sup.-2),
[0097] (iv) The elongation at break was 341%,
[0098] (v) The tear strength was 2.5 kNm.sup.-1, and
[0099] (vi) The impact resilience was 25%.
[0100] The polyurethane foam was subjected to hydrolysis conditions
for 2 weeks and 4 weeks as described above, and the following
properties were remeasured;
[0101] Two Weeks--
[0102] (i) The tensile strength was 70 kgcm.sup.-2 (=95% retention
of initial value), and
[0103] (ii) The elongation at break was 397% (=16% increase over
initial value).
[0104] Four Weeks--
[0105] (i) The tensile strength was 33 kgcm.sup.-2 (=45% retention
of initial value), and
[0106] (ii) The elongation at break was 339% (=99% retention of
initial value).
Example 3
[0107] This is a comparative example not according to the
invention. The procedure according to Example 1 was repeated except
that Daltorez P716 (adipate polyester, ex Huntsman Polyurethanes)
was used as polyester, and Suprasec 2980 (polyester modified MDI,
ex Huntsman Polyurethanes) was used as the as prepolymer.
[0108] The resulting adipate derived polyurethane foam had the
following properties, measured as described above;
[0109] (i) The density (of 10 mm thick section) was 0.42
gcm.sup.-2,
[0110] (ii) The hardness was 38 Shore A,
[0111] (iii) The tensile strength was 60 kgcm.sup.-2 (the modulus
at 100% was 16 kgcm.sup.-2),
[0112] (iv) The elongation at break was 516%,
[0113] (v) The tear strength was 4.1 kNm.sup.-1, and
[0114] (vi) The impact resilience was 37%.
[0115] The polyurethane foam was subjected to hydrolysis conditions
for 2 weeks and 4 weeks as described above, and the following
properties were remeasured;
[0116] Two Weeks--
[0117] (i) The tensile strength was 11 kgcm.sup.-2 (=18% retention
of initial value), and
[0118] (ii) The elongation at break was 104% (=20% retention of
initial value).
[0119] Four Weeks--
[0120] (i) The tensile strength was 0 kgcm.sup.-2 (=0% retention of
initial value), and
[0121] (ii) The elongation at break was 0% (=0% retention of
initial value).
Example 4
[0122] This is a comparative example not according to the
invention. The procedure according to Example 1 was repeated except
that the starting materials were adipate polyester (Desmophen 2000
MZ, ex Bayer (468 g)), flake pure MDI (ex Bayer (640.4 g)) and
modified MDI (Suprasec 2021, ex Huntsman Polyurethanes (123.1
g)).
[0123] The resulting adipate derived polyurethane foam was
subjected to hydrolysis conditions for 4 weeks as described above,
and the following properties were measured;
[0124] (i) The tensile strength was 6 kgcm.sup.-2, and
[0125] (ii) The elongation at break was 42%.
[0126] The above examples illustrate the improved properties of a
microcellular polyurethane foam according to the present
invention.
* * * * *