Note: Descriptions are shown in the official language in which they were submitted.
j.
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PROCESS FOR THE PRODUCTION OF RIGID POLYURETHANE
MOLDINGS HAVING AN INTEGRAL STRUCTURE
BACKGROUND OF THE INVENTION
The present invention provides a process for the production of rigid
polyurethane
moldings having a compacted peripheral zone and a cellular core, so-called
compact skin foams, in which cyclopentane and a mixture of C4-C7 hydrocarbons
having a boiling point in the range of 45°-80°C are used as the
blowing agent.
Until its ozone-damaging behavior became known, monofluoro-trichloromethane
(R11) was virtually the only blowing agent used to form the compacted
peripheral
zone and cellular internal structure of rigid polyurethane moldings.
Recognition of
these findings was accompanied by the development and investigation of many
novel blowing gases of the hydrochlorofluorocarbon (HCFC) type and hydro-
1 S fluorocarbon (HFC) type. Hydrocarbons were included in these
investigations at an
early stage, as may be seen from some patent publications such as, for
example,
U.S. Patent 3,178,490, U.S. Patent 3,182,104, U.S. Patent 4,065,410, and U.S.
Patent 3,931,106, and DE-A 3,430,285, DE-A 2,622,951 and DE-A 2,544,560.
Once the ozone-damaging behavior of fluorocarbons became known, numerous
attempts were made to use other types of blowing agents to produce cellular
polyurethanes. EP-A 364,854 thus describes a process for the production of
moldings having a compacted peripheral zone and a cellular core, preferably
shoe
soles, from per se known starting materials, but using low-boiling, aliphatic
and/or
cycloaliphatic hydrocarbons having 4 to 8 carbon atoms per molecule.
As replication of the process described in EP-A 364,854 has shown, the
mechanical properties of the polyurethane moldings produced using aliphatic
hydrocarbons, such as iso-pentane and n-pentane, are not satisfactory,
especially
with regard to surface hardness as a significant material criterion, since low
Shore
D hardness values are obtained. However, hydrocarbons such as n-heptane and
cyclohexane are also unsatisfactory as deficient surface quality is also
achieved
when these hydrocarbons are used.
This was especially surprising as the above-stated European published patent
application describes and claims iso-pentane and n-pentane as particularly
suitable
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blowing agents. Example 1 of this European patent publication shows n-pentane
and iso-pentane to provide similarly good mechanical properties as monofluoro-
trichloromethane (R11).
It has surprisingly now been found that, by using cyclopentane and/or a
mixture of
C4 to C~ hydrocarbons having a boiling point in the range of 45°C to
80°C as the
blowing agent, rigid polyurethane moldings having an integral structure may be
produced which have particularly high surface hardness and differ distinctly
from
the hardness brought about by n-pentane. Furthermore, the flow behavior of the
raw material components is excellent, even at low raw material processing
temperatures.
SUMMARY OF THE INVENTION
The present invention accordingly provides a process for the production of
rigid
polyurethane moldings having a compacted peripheral zone and a cellular core,
by
reacting
a) at least one organic polyisocyanate, modified organic polyisocyanate, or
polyisocyanate prepolymer,
with
b) an isocyanate-reactive component comprising:
1) at least one polyol component having an OH value of 300 to 1850
and a functionality of 2 to 8,
in the presence of
c) water
and
d) at least one blowing agent selected from the group consisting of:
1) cyclopentane
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2) a mixture of C4 to C~ hydrocarbons, wherein the mixture is
characterized by a boiling point in the range of 45°C to 80°C,
preferably 45°C to 75°C,
and
3) a mixture of cyclopentane with at least one hydrocarbon having
from 4 to 7 carbon atoms, wherein the mixture is characterized by a
boiling point in the range of 45°C to 80°C, preferably
45°C to
75°C.
The rigid polyurethane moldings having a compact skin produced according to
the
present invention are characterized by Shore D hardness values (DIN 53,505) of
25 to 45, preferably of 25 to 40. The bulk density of these compact skin foams
is
100 to 700 kg/m3, preferably 100 to 600 kg/m3, more preferably 100 to
400 kg/m3.
The hydrocarbon blowing agents, used in the process according to the
invention,
are typically present in quantities of 0.5 to 15, preferably of 2 to 12, more
preferably of 3.5 to 11 parts by weight, based on the total weight of
component
b), the isocyanate-reactive component.
In addition to cyclopentane, suitable blowing agents for the present invention
include mixtures of hydrocarbons containing from 4 to 7 carbon atoms, provided
that the mixture has a boiling point in the range of from 45 to 80°C.
Some
examples of hydrocarbons include compounds such as i-butane, n-butane, n
pentane, iso-pentane, cyclohexane, cyclopentane, methylcyclopentane, 2-methyl
pentane, 3-methylpentane, 2,2-dimethyl-butane, 2,3-dimethylbutane,
cyclohexane,
n-hexane, n-heptane, 3-methylhexane, 2-methylhexane, 2,2-dimethylpentane,
2,3-dimethylpentane, 3,3-dimethylpentane and/or 2,4-dimethylpentane.
Preferred mixtures of these C4 to C~ hydrocarbons include those mixtures
having
i) at least one compound selected from the group consisting of n-butane, iso-
butane, n-pentane and iso-pentane,
and
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ii) at least one compound selected from the group consisting of cyclohexane,
methylcyclopentane, 2-methylpentane, 3-methylpentane, 2,2-dimethyl
butane, 2,3-dimethylbutane, cyclohexane, n-hexane, n-heptane, 3-methyl
hexane, 2-methylhexane, 2,2-dimethylpentane, 2,3-dimethylpentane, 3,3
dimethylpentane and 2,4-dimethylpentane,
wherein the mixture is characterized by a boiling point in the range of
45°C to
80°C, and preferably of 45°C to 75°C.
In addition, suitable blowing agents for the present invention include a
mixture of
1) cyciopentane,
and
2) at least one hydrocarbon having from 4 to 7 carbon atoms,
wherein the mixture is characterized by a boiling point in the range of
45°C to
80°C, preferably 45°C to 75°C.
Another preferred blowing agent for the present invention includes a mixture
of
1) cyclopentane
and
d)2)i) at least one compound selected from the group consisting of n-butane,
iso-
butane, n-pentane and iso-pentane,
wherein the mixture is characterized by a boiling point in the range of
45°C to
80°C, and preferably of 45°C to 75°C.
Another preferred blowing agent for the present invention includes a mixture
of
1) cyclopentane
and
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d)2)ii) at least one compound selected from the group consisting of
cyclohexane,
methylcyclopentane, 2-methylpentane, 3-methylpentane, 2,2-dimethyl
butane, 2,3-dimethylbutane, cyclohexane, n-hexane, n-heptane, 3-methyl
hexane, 2-methylhexane, 2,2-dimethylpentane, 2,3-dimethylpentane, 3,3
dimethylpentane and 2,4-dimethylpentane,
wherein the mixture is characterized by a boiling point in the range of
45°C to
80°C, and preferably of 45°C to 75°C.
Cyclopentane, mixtures of cyclopentane with d)2)ii), and mixtures of d)2)i)
with
d)2)ii) result in compact skin foams especially in the low bulk density range
of
100-400 kg/m3 having surprisingly high surface hardness, good fluid behavior
and
good surface structure at raw material temperatures of around 25°C.
As already mentioned, water is additionally used as a blowing agent in the
process
according to the invention. The quantity of water additionally incorporated
into the
polyurethane formulation is conventionally 0.05 to 0.6 parts by weight,
preferably
1 S 0.1 to 0.4 parts by weight, based on the total weight of component b), the
isocyanate-reactive component.
Organic polyisocyanates a) which are suitable for the present invention
include
aliphatic, cycloaliphatic, araliphatic and preferably aromatic polyfunctional
isocyanates, as are disclosed in, for example, in EP-A 364,854.
Particularly suitable isocyanates are tolylene diisocyanates and
diphenylmethane
diisocyanates, the modification products thereof or the corresponding
prepolymers
thereof, which may be modified by urethane, urea, biuret, allophanate,
carbodiim-
ide or uretidione groups. Aromatic polyisocyanates which may in particular be
mentioned are: 4,4-diphenyl-methane diisocyanate, mixtures of 2,4'- and 4,4'-
diphenylmethane diisocyanate or crude MDI grades and/or 2,4- and/or 2,6-
tolylene
diisocyanate and the mixtures thereof with each other.
Suitable isocyanate-reactive components b) include 1) at least one polyol
having
an OH value of from 300 to 1850, preferably of 350 to 1850, and a
functionality
of 2 to 8, preferably 3 to 6. Polyols which have proved particularly suitable
include those selected from the group of polyether polyols and polyester
polyols,
as are obtained by addition of alkylene oxides, such as ethylene oxide and
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propylene oxide, onto polyfunctional starters, such as ethylene glycol,
propylene
glycol, glycerol, trimethylolpropane, sorbitol and/or ethylenediamine, or by
condensation of dicarboxylic acids, such as adipic acid, succinic acid,
glutaric
acid, suberic acid, sebacic acid, malefic acid, phthalic acid, with
predominantly
difunctional hydroxyl components, such as ethylene glycol, propylene glycol,
diethylene glycol. Polyether polyols synthesized from ethylene oxide and
propylene oxide together with glycerol, trimethylolpropane, ethylenediamine,
propylene glycol, ethylene glycol, sorbitol and mixtures thereof as the
starter, are
particularly preferred.
The polyether and polyester polyols may be used both individually and as
mixtures with each other.
The process according to the invention is particularly suitable for the
production
of rigid polyurethane moldings which preferably have bulk densities of 100 to
400 kg/m3 and also exhibit very good toughness and low temperature properties.
The flow behavior of the reaction components, being the sum of all the
reactants,
is not problematic, even at lower raw material processing temperatures.
The good toughness and low temperature properties are attained when the
isocyanate-reactive component b) additionally comprises 2) at least one polyol
component having an OH value of 15 to 299, preferably of 25 to 299, and a
functionality of 2 to 3.
This polyol component, i.e., b)2), is added to the previously stated polyol
component b)1) in quantities of 5 to 40 wt.%, preferably of 7 to 25 wt.%,
based
on the total weight of b) 1 ). Suitable compounds to be used as polyol
components
b)2) include ethylene glycol and propylene glycol, and the addition products
thereof with propylene oxide and/or ethylene oxide. Mixtures having a
functionality of 2 to 3, preferably of 2 to 2.6, may be established in
component
b)2) by also using, for example, glycerol or trimethylolpropane as a starter.
Polyol components b)2) may also be added to component b)1) individually or as
a
mixture with each other.
The stabilizers, activators, solubilizing agents, fillers and flame retardants
as
described in, for example, EP 0,364,854, may additionally be present in the
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process according to the invention. The quantities of the known additives is
determined by the particular application of the polyurethane moldings produced
according to the invention and may readily be determined by appropriate
preliminary testing.
Production of the moldings according to the invention is also familiar to the
person skilled in the art and need not be described in greater detail. Such
details
are also set forth in, for example, EP-A 364,854.
The polyurethane moldings having a compact skin produced using the process
according to the invention exhibit, in conjunction with a low bulk density, a
surprisingly high surface hardness. This property makes these polyurethane
moldings particularly suitable for applications in the consumer, electrical or
automotive sectors, for example for imitation stucco, decorative profiles,
imitation
profiles, imitation wood, ventilation components, door surround components in
the
automotive sector and furniture profiles.
The following examples further illustrate details for the process of this
invention.
The invention, which is set forth in the foregoing disclosure, is not to be
limited
either in spirit or scope by these examples. Those skilled in the art will
readily
understand that known variations of the conditions of the following procedures
can
be used. Unless otherwise noted, all temperatures are degrees Celsius and all
percentages are percentages by weight.
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EXAMPLES
Description of raw materials:
Pol~ol_ 1: Polyether polyol having an OH value of 515, produced by
addition of propylene oxide onto propylene glycol as a
starter.
PolXol 2: Polyether polyol having an OH value of 475, produced by
addition of propylene oxide onto a starter mixture of 80%
sucrose and 20% polypropylene glycol as a starter.
Po-Col 3: Polyether polyol having an OH value of 1000, produced by
addition of propylene oxide onto trimethylolpropane as a
starter.
Po~rol 4: Polyether polyol having an OH value of 640, produced by
addition of propylene oxide onto ethylenediamine as a
starter.
Po_~ol 5: Polyether polyol having an OH value of 480, produced by
addition of propylene oxide onto ethylenediamine as a
starter.
Pool 6: Polyether polyol having an OH value of 35, produced by
addition of 86 wt.% of propylene oxide and 14 wt.% of
ethylene oxide onto trimethylolpropane as a starter, and
having predominantly primary OH groups.
Pol i~5ranate 1: Polymethylene poly(phenylisocyanate) mixture obtained by
phosgenation of an aniline/formaldehyde condensation
product and having an isocyanate content of 31.5%. This
mixture contains 60% by weight of methylene diphenyl-
diisocyanate and 40% by weight of higher functional
homologues.
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The raw material formulations described below are introduced, as is
conventional
for mechanical processing of polyurethanes, into a sheet mold of dimensions
190 X 155 x 20 mm heated to 50°C and removed from the mold after 10
minutes.
The temperature of the raw materials is 25°C.
Polyol Formulation A:
Polyol I 15 parts by
weight
Polyol 2 35 parts by
weight
Polyol 3 18 parts by
weight
Polyol 6 15 parts by
weight
Water 0.25 parts by
weight
Stabilizer B*8423 (Goldschmidt)1.5 parts by
weight
Desmorapid*726b (Bayer AG) 1.0 part by
weight
Desmorapid*PV 1.0 part by
weight
Emulsifier PU*1747 (Bayer 3.0 parts by
AG) weight
Polvol Formulation B:
Polyol I 17 parts by weight
Polyol 2 40 parts by weight
Polyol 4 37 parts by weight
Water 0.25 parts by weight
Stabilizer B 8423 1.3 parts by weight
Desmorapid 726b 0.1 parts by weight
Desmorapid PV 0.1 parts by weight
PU 1747 3.0 parts by weight
Oleic acid 1.0 part by weight
Po. 13ro1 Formulation C:
Polyol 1 15 parts by weight
Polyol 2 45 parts by weight
Polyol 4 20 parts by weight
Polyol 5 20 parts by weight
Water 0.25 parts by weight
Stabilizer B 8423 1.5 parts by weight
Desmorapid 726b 0.1 parts by weight
Desmorapid PV 0.1 parts by weight
Oleic acid I.0 part by weight
*trade-mark
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Blowing Agents: (m = mole in the mixtures below)
I. Cyclopentane (bp: 49°C)
II. Mixture of 0.8 m of cyclohexane and 0.2 m of iso-pentane; having a
boiling point of 62°C
III. Mixture of 0.9 m of cyclohexane and 0.1 m of n-butane; having a boiling
point of 60°C
IV. Mixture of 0.25 m of iso-pentane and 0.75 m of n-heptane; having a
boiling point of 65°C
V. Mixture of 0.15 m of iso-pentane and 0.85 m of methylcyclopentane;
having a boiling point of 60°C
VI. Mixture of 0.1 m of n-butane and 0.9 m of methylcyclopentane; having a
boiling point of 55°C
VII. Mixture of 0.15 m of iso-pentane and 0.85 m of 2-methylhexane; having a
boiling point of 72°C
VIII. Mixture of 0.9 m of cyclopentane and 0.1 m of n-heptane; having a
boiling
point of 52°C
IX. Mixture of 0.9 m of cyclohexane and 0.1 m of iso-pentane; having a
boiling point of 70°C
X. Mixture of 0.1 m of methylcyclopentane and 0.9 m of cyclopentane; having
a boiling point of 51°C
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Foam Examples 1 to 4:
Tabte 1
Parts by wt.! 1 2 3 4
Foam no.
Polyol Formulation100 100 100 100
A
Polyisocyanate 135 135 135 135
1
Cyclopentane 9 - -
n-pentane - g _ _
R11 - - 15 -
R 365 - - _ 17
Cream time (sec)21 19 23 20
Fiber time (sec)95 103 84 98
Bulk density, 53 55 58 56
free
(kg/m )
Bulk density, 180 180 180 180
mold
(kg/m )
Shore D hardness
after 24 h 30 20 23 26
after 120 h 38 23 29 27
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Foam Examples 5 to 7:
Table 2:
Parts by weight/Foam no. 5 6 7
Polyol Formulation B 100 100 100
Polyisocyanate 1 140 140 140
Rll 15 - -
n-pentane - g _
Cyclopentane - - 9
Cream time (sec) 24 22 22
Fiber time (sec) 75 79 77
Bulk density, free (kg/m3)67 64 63
Bulk density, mold (kg/m3)180 180 180
Shore D hardness
after 24 h 20 20 28
after 120 h 23 22 34
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Foam Examples 8 to 10:
Table 3
Parts by weight/foam no. 8 9 10
Polyol Formulation C 100 100 100
Polyisocyanate 1 130 130 130
R11 15 - -
n-pentane - 9 -
Cyclopentane - - g
Cream time (sec) 25 23 22
Fiber time (sec) 76 77 78
Bulk density, free (kg/m3)66 64 64
Bulk density, mold (kg/m3)180 180 180
Shore D hardness
after 24 h 21 20 28
after 120 h 24 22 32
The elevated hardness brought about by cyclopentane is evident from Examples
1,
7 and 10, while the hardness brought about by n-pentane as seen in Examples 2,
6
and 9 is much lower. It is also surprising that the foams produced using
halogenated blowing gases (in Examples 3, 4, S and 8) do not achieve the
surface
hardness of foams produced using cyclopentane, and that these halogenated
blowing gases must be used in a larger quantity in order to be able to
establish the
desired bulk density of 160 kg/m3 in the molding. This hardening effect of the
cyclopentane allows, for example, the weight of compact skin foam moldings to
be reduced without impairing the important material characteristic of
hardness.
With cyclopentane as a blowing agent, hardness values may now be achieved in
the lower bulk density range which were previously achieved only at higher
bulk
densities.
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This effect applies not only to cyclopentane but also, surprisingly, to any
desired
mixtures of C4 to C7 hydrocarbons of a boiling range of 45°C to
80°C, preferably
of 45°C to 75°C.
Examules 11-14:
Table 4
Parts by wt./ 11 12 13 14
Foam no.
Polyol Formulation100 100 100 100
A
Polyisocyanate 140 140 140 140
1
Blowing Agent 10
II
Blowing Agent 10
III
Blowing Agent 10
IV
Blowing Agent 10
V
Cream time (sec)23 24 24 24
Fiber time (sec)90 88 79 84
Bulk density, 58 56 55 57
free
(kg/m )
Bulk density, 180 180 180 180
mold
(kg/m )
Shore D hardness
after 24 h 30 31 31 30
after 120 h 3 7 3 8 3 8 3 9
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Examples 15-18:
Table 5
Parts by wt./ 15 16 17 18
Foam no.
Polyol Formulation100 100 100 100
A
Polyisocyanate 140 140 140 140
1
Blowing Agent 10
VI
Blowing Agent 10
VII
Blowing 10
Agent VIII
Blowing Agent 10
IX
Cream time (sec)23 22 24 23
Fiber time (sec)88 90 91 92
Bulk density, 58 59 59 57
free
(kg/m )
Bulk density, 180 180 180 180
mold
(kg/m )
Shore D hardness
after 24 h 29 31 3 0 31
after 120 h 3 9 40 3 8 3 8 ''
These surface hardness results demonstrate that Blowing Agent Mixtures II-X
are
also suitable for increasing the surface hardness values in the lower bulk
density
range. This is surprising since these individual hydrocarbons such as, for
example,
n-pentane, iso-pentane, cyclohexane, and particularly cyclohexane and heptane,
are
not suitable for achieving equally satisfactory elevated surface hardness,
flow
behavior and good surface structure.
The hydrocarbon mixtures of the present invention have a boiling point in the
range of 45-80°C, preferably of 45-75°C, while compounds such as
n-pentane and
iso-pentane have distinctly lower values for boiling points, namely
36°C and 28°C,
respectively. In light of this, it is surprising that
monofluorotrichloromethane (R11)
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which also has a low boiling point (23.7°C), is superior to n- and iso-
pentane with
regard to surface hardness. However, R11 does not achieve anywhere near the
surface hardness of cyclopentane and/or the C4 to C~ hydrocarbon mixtures of
the
present invention, which was not expected.
Although the invention has been described in detail in the foregoing for the
purpose of illustration, it is to be understood that such detail is solely for
that
purpose and that variations can be made therein by those skilled in the art
without
departing from the spirit and scope of the invention except as it may be
limited by
the claims.
