Note: Descriptions are shown in the official language in which they were submitted.
L6~1
SPECIFICATION
.
The degree of hardness is one basis of classification of
polyurethane foams, and one usually distinguishes between flexible foam,
semi-rigid foam, and rigid foam. The hydroxyl content or number of the
polyether polyol used principally determines the degree of hardness. A
step forward in the development of polyurethane foam less hard or softer
than what is re-Eerred to as flexible foam is the so-called supersoft foam,
obtained by reacting a polyisocyanate with a polyol of suitable properties
in a weight ratio such that the isocyanate index, i. e. the ratio between
isocyanate groups and hydroxyl ~roups present in the reaction mixture,
does not e}~ceed 1. 0. Also, certain softening agents and blowing a~ents
may in some cases decrease the hardness of the foam.
Hypersoft; polyurethane foams (i. e. foams of very low
hardness) have been prepared by the process disclosed in French patent
- 15 No. 2,172,860, using a mixture of two mutually insoluble polyethel polyols,
in which case the mixture of the t~vo polyols must conform to the following
specifications:
(a) The mixture of polyether polyols contains from 50 to 70~C
by weight of oxyethylene units, i. e., units derived from ethylene oxide;
(b) The proportion of primary hydroxyl groups compared to
the total amount of hydro~yl groups is from 35 to 50~c;
(c) The ratio between the percenta~e by weight OI oxyethylene
units, i. e. units derived from ethylene oxide,according to ~a~ and the
- percentage of primary hydro~Yyl groups according to ~) is from 1.1 to 1. 7.
These so~t foarns have a considerably lower degree of hardness,
'`'' ' '
35~6~
i. e. a~e softer, than the pre~iously mentioned supersoft foams. This is
why this category of foam is usually designated hypersoft.
In accordance with the present invention, polyurethane foams
softer than hypersoft foams~ i. e. of still lower hardness than those poly-
5 urethane foams prepared according to the process of French patent No.2,172, 860, are obtained by using a polyether polyol mixture containing an
unusu~lly high proportion of primary hydroxyl groups, within a carefully
selected ratio of the amount of polyisocyanate to polyol. More particularly~
the present invention prwides a process Eor the preparation oP super-
lQ hypersoft polyurethane foam, of a low degree of hardness, that is alsohighly hydrophilic,by reacting polyisocyanate with a polyether polyol
mixture of at least two mutually insoluble poly~mctional polyether polyols
containing from about 50 to about 70~/c by weight oxyethylene units (derived
from ethylene oxide) in the presence of catalyst, blowing agent, foam
15 stabili~er and, if desired, any other additives commonly used in the
preparation of polyurethane foam. The terni "polyfunctional" as used
herein refers to triEunctional alld higher, and excludes mono and bifunctional.
The polyether poly~l mixture used in the process of the
irlvention has a hydroxyl number of from 35 to 45, and from 55 to 80~
20 primary hydroxyl groups of the total number of hydroxyl groups in the
polyether polyol mixture. The amounts oF polyisocyanate and polyether
polyol are selected so that the ratio of isocyanate groups to hydroxyl
groups is from 0. 85 to 1. 05, preferably from 0. 90 to 0. 98.
The hydro~yl number and the proportion of primary hydroxyl
25 groups are determined according to the method described in Analytical
Chemistr;y 33 896 (1961).
.
:.' ' ' ' :
5~6~
Extensive ir~vestigations have shown that one single polyol
having properties corresponding to that of the polyol mixture does not
produce a polyurethane from having the desiredproperties, nor does a
poly~l mixture having properties other than those stated above.
An especially remarkable feature of the poiyurethane oams
prepared according to the invention is that the extremely low hardness
(i. e., super hypersoEtness~ can be combined with e2~cellent physical
properties, such as elongation at break, tensile strength and compression
set. Further, during the -Eoaming process the foam shows excellent
stability. Thus, it is of decisive importance that the conditions according
to the invention be met, since otherwise the stated beneEits of the invention
will not be obtained.
The polyether polyols employed in the process of the
invention are obtained by adding at least two different alkylene oxides, o-f
--15 which one is ethylene oxide, to a poly~unctiDnal nucleus having at least
three reactive hydrogens. This nucleus can be a polyol having at least
three hydroxyl groups. Triols such as glycerol and trimethylolpropane
are preferred, but trihydroxy alkanol amines such as triethanolamine are
also useful. ~ The oxyethylene units of the polyether polyol mixture deriyed
from ethylene oxide is from 50 to 70% by weight; the remaining oxyalkylene
units derived from higher alkylene oxides can be from propylene oxide,
butylene oxide, or migtures of these.
The addition o-E the all~ylene oxides is carried out by
conventional methods. Ethylene oxide and higher alkylene oxi~es can be
added either in admixture or separately, in one or more increments or
,
- 3 ~ ~
..
- . . .. . . . .
' " ' ' ' ~ . ' " ' ' , .. ' ' . `~ . ', ,' ., .. . ' . ' .', ' , . , ' . ,
L600
batches. In order to obtain high so~tness it is essential that the two p~lyethe-r
polyols be mutually insoluble, i. e. that they have different hydrophilicity.
The weight ratio of the polyether polyols should fall within the range from
1:lQ to 10:1.
One of the two polyols should be soluble in water, and should
preferably have an HLB value of at least 15, and a turbidity p~int of at
least 88C. Its a~erage molecular weight is from 3000 to 5000.
The other polyether polyol should be considerably more
hydrophobic, alld should have an HLB ~alue not exceeding 5, and a turbidity
10 point of below 70C. The average molecular weight of this polyether polyol
can be somewhat higher, and range from 3aoo to 70Q0.
The HLB values a:re calculated according to W. C. Griffin,
Oficiai Digest, June 1956, 447, and the turbidity points are calculated
according to Lowe et al~ Journal of Cellular Plastics, January 1965, 121.
Illustrative examples of suitable polyols according to the
invention are the following:
EXAMPLE A
.
O~ta. 92 parts by weight of glycerol there are first condensed
4, 000 parts by weight of propylene oxide, and thereupon 1300 parts by
weight of ethylene oxide are condensed thereoll. The resulting polyether
polyol adduct has a hydro~yl number of 36 and 75~c primary hydro~yl
groups.
EXAM:?LE B
Onto 92 parts by weight of glycerol there are first condensed
470 parts by weight of propylene oxide, and thereupon 3440 parts by weight
of a mi~ture comprising 18~C of propylene o~ide and 82C/C of ethylene o~{ide
,
... . . . .. . .
.
. .. .. , ~ , .
~os~oo
are condensed thereon. The resulting polyetller polyol adduct has a hydroxyl
number of 42, and 5~c/c primary hydroxyl groups.
EXAMPLE C
-
Onto 134 parts by weight of trimethylolpropane there are
first condensed 3000 parts by wei~ht of a mixture comprising 18'3ic of
propylene oxide ancl 82% of ethylene oxide, and thereupon 300 parts by
weight of propylene oxide and finally 350 parts by weight of ethylene oxide
are condensed thereon. The resultmg polyol has a hydroxyl numbsr of 42,
and ~3% primary hydro~yl groups.
EX~PLE D
r _ '
Onto~ 99 parts by wei~ght of glycerol there are first condensed
5000 parts by weight of propylene oxide and then 100 parts by weight of
ethylene oxide. The resulting polyol has a hydroxyl number of about 34,
and 7537c primary hydroxyl groups.
-- 15 The polyisocyanate to be used according to the present
invention is at least bifunctional, but it can also be polyfunctional. Examples
of suitable isocyanates are toluene diisocyanate, hexamethylene diisocyanate~
diphenylmethane diisocyanate, polyphenylpolymethylenepolyi$ocyanate, and
mixtures thereof. The preferred isocyanate is toluene diisocyanate, which `
can be in its isomeric 2,4-form, or 2~6-form, or as mixtures of these
isomeric forms. A suitable isomer mixture comprises about 80% of
2, 4-isomer and 20% of 2, 6-isomer, but other proportîons can also be used
success~ully. The amount of isocyanate added should be adapted to the
remaining components contained in the reaction mixture in such a way that
the isocyanate index, i. e. the ratio between isocyanate groups an~ hydroxyl -
. ~ ' .
~
~ '
~ .
~ ~C3 5~60C~
groups present in the mi~ture, is from about 0. 85 to about 1. 05, preferably
from 0. 90 to û. 98 .
The reaction between isoc:yanate and polyether polyol is
carried out in the presence of an amine catalyst, preferably a tertiary
amine, such as triethylenediamine, dimethylaminoethanol; and tetramethvl-
ethylenediamine. One can also use organometallic salt catalysts, such as
tin-2-ethylhexoate, tin dibutyl dilaurate, lead naphthenate, and cobalt
naphthenate; such salts are preferably used in small amounts, and in
combinatlon with amine catalysts.
The cell formation and accordingly the density of the poly-
urethane foam is controlled by adjusting, in a conventional way, theamount
of water added and any other blowing agents, such as trichloroEluoromethane
or methylene chloride. The addition af foam stabilizers, such as silicone
oil, will ensure a good foam stability, and good physical strength properties.
In addition to the above-s$ated additives7 other addîtives can be added, if
desired, using well-known techniques.
The following Examples in the opinion of the inventors
represent preferred embodiments of thelr invention.
EX~IPLES 1 to 3
With the aid of a Eive-component laboratory foaming machine,
a polyether polyol corresponding to 3xample A above was mixed with a
polyether polyol corresponding to Example B above, waterJ silicone oil,
triethylenediamine, dimethylaminoethanol and trichlorofluorome$hane in
the parts by weight stated in Table I below, together with toluene diisocyanate
(80% 2,4-isomer, 20~C 2,5-isomer) in an amount to bring the isocyanate
~,
1~516~
index to 0. 95. The mixture was poureA into a 50 x 50 x 30 cm mold and the
resulting foam allowed to set for one day at room temperature. Upon con-
ditioning for 24 hours in a cvnstant temperature room, physical tests were
carried out. The following results were obtained:
T~13LE I
P rts by Weigh$
Formulation Example 1 Example 2 E~ample 3
Polyether polyol of Example A 25 25 25
Polyether polyol of Example B 75 75 75
Water - 3. 5 3. 5 3 5
Silicone oil 1.5 1.5 1.i5
Triethylenediamine (33%) 0.2 0.2 0.2 `
Dimethylaminoethanol 0. 8 0. 8 0. 8
Trichlorofluoromethane 15 7. 5 o -: :~
Toluene diisocyanate an amount to gîve - .
an isocyanate index of 0~ 95 `~
Physical properties (ASTM D 1564-62g~
Density, kg/m3 19.7 23.i5 27 . ~:
Tensile strength, kg/cm2 1.2 1. 3 1~ 7 . ~ ::
Elongation at break, ~c. 490 420 395
Teiar strength, kg/cm 0. 5 0.4 Q. 6 ~-
90% corr~ression set, % 10 10 10 ;
Impact resilience, ~c . 50 50 50 -
Hardness, 25(7c compression, kp/dm2 0.6 0~9 1
Hardness, 6D% connp ession, kp/dma7.2 I. 7 Z. 1
. . ' '' ' .
. . . .
60q~
From the results it is evi~ent that the foams are quite soft,
i. e., they have an extremely low hardness. For comparison, the foam
prepared according to the French patent specification No. 2,172, 860 at
about the same density and about the same physical properties, has a
5 hardness twice that of Example 2.
EX~MPLES 4 TO 5
With the ald of a fi~e component laboratory foaming machine
polyether polyol of Example D was mixed with polyether polyol of Example B
(which were mutually in~olu~le),water, silicone oil, triethylene diamine
10 and dimethylaminoethanol in the amounts stated in Table II below, together
with toluene diisocyanate (80'3~c 2,4-isomer, 20% 2,6-isomer) in an amount
to give an isocyanate inde~ of 0.~5. The mixture was poured into a
50 x 50 x 30 cm mold and the resulting foam was allowed to set for one day
at room temperature. Upon conditioning for 24 hours in a constant
- 15 temperature room, physical tests were carried out. The following result~ -
were-obtained:
- ~s~6~ff~
TABLE II
Parts by Weight
Formulation Example 4 Example 5
Polyether polyol of Example.D 20 30
Polyether polyol of Example B 80 ~ 70
Water 3. 5 3 5
Silicone oil 1.5 1.5
~friethylenediamine (33%) 0.15 0.15f
Dimethylaminoethanol 0. 55 0. 55
Toluene diisoc~anate an amount to give
an isocyanate index of 0.95
Physical properties (ASTM D ff 5f64-629)
... .
Density, kg/m3 29 29 -
; . .
Hardness~ 25% compression, kpf/dm2 . 1.3 . 1.ffJ -~
.,;, :: :
Ha~dness, 65% compression, kp/dm2 2. 5 ~. 0
The polyurethane fofams prepared showed, in af~dition to
low hardness, exf~ellf3nt physical properties, such as a regular cell
structure, a high elongation at breal~, and a high tensile strength. During i ~:
Ihe ioaming, no shrinkage is observed. ~
.
g ~ - .
~, .
