Process for producing urethane foam having a high density skin layer

A process is provided for producing a polyurethane foam having a high-density skin layer by reacting a polyol with a polyisocyanate in a short time. The reaction is allowed to proceed in the presence of a blowing agent, a catalyst, and optionally an additive, the blowing agent being composed only of water, and the catalyst being an amine represented by formula (I) below and/or an organic acid salt thereof: ##STR1## where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are, independently, an alkyl group of 1 to 12 carbons, or R.sub.1 and R.sub.2, and/or R.sub.3 and R.sub.4 may be linked to form a cycloalkyl or heterocyclic ring together with the adjacent nitrogen atom; and R.sub.5 is hydrogen, an alkyl group of 1 to 12 carbons, a phenyl group, or a cycloalkyl group. This process does not use halogenated hydrocarbons which cause ozone layer destruction.

BACKGROUND OF THE INVENTION 
Field of the Invention 
The present invention relates to a process for producing a flexible, 
semi-rigid, or rigid polyurethane foam which has a high-density skin 
layer. More particularly, the present invention relates to a process for 
producing a polyurethane foam having a high-density skin layer, generally 
called a polyurethane integral skin foam, without using halogenated 
hydrocarbons as blowing agents. 
Discussion of the Background 
Polyurethane foam is usually produced by mixing a polyisocyanate 
instantaneously with a polyol premix containing a polyol, a catalyst, a 
blowing agent (a halogenated hydrocarbon and/or water) and optionally 
other additives to expand the mixture. 
Polyurethane integral skin foams are used in many application fields owing 
to their light weight, soft touch, and high impact strength, for example, 
for interior and exterior materials of automobiles including steering 
wheels, air spoilers, bumpers, head rests, arm rests, and structural 
materials. 
Methods for producing such products are known, see for example, the methods 
described in Keiji Iwata (ed.), "Polyurethane Jushi Handobukk 
(Polyurethane Resin Handbook)", pp. 220-221, and the methods described in 
Gunter Oertel, "Polyurethane Handbook", pp. 314-369. According to any of 
these methods, a polyurethane integral skin foam is produced through one 
injection step with one system liquid as an integrated molded product 
which has a high-density skin layer and a low-density core portion, with 
high productivity. 
This advantage is achieved by a higher over-packing percent with a highly 
reactive polyol system by a RIM process (reaction injection molding), the 
system requiring CFC-11 (trichloromonofluorocarbon) as the essential 
blowing agent. Generally, a catalyst therefor is employed, such as 
triethylenediamine, tin compounds, and the like. The formation of the 
high-density skin layer of the integral skin foam is based on the 
principle that the CFC-11, a FREON type blowing agent, condenses 
physically at the surface layer portion of the resin in the mold because 
of the pressure rise owing to the high over-packing ratio and because of 
the low temperature at the surface layer portion owing to the absorption 
of the reaction heat by the mold. Therefore, the use of CFC-11 is 
indispensable. 
The CFC-11, which is a halogenated hydrocarbon type blowing agent and is an 
ozone layer-destroying substance, will be prohibited internationally after 
the end of this century. Accordingly, a system and a production technique 
are strongly needed which enables the production of integral skin foam 
without using CFC-11 as the blowing agent. Proposed substitutes for the 
CFC-11 are low-boiling solvents such as pentane, and so-called alternative 
Freons which exhibit a lower ozone layer destruction coefficient such as 
HCFC-123, HCFC-22, and HCFC-141b. However, low-boiling solvents involve 
the disadvantage of inflammability, and the alternative Freons still 
exhibit a non-zero ozone layer destroying coefficient and will be 
prohibited in the future. Therefore, neither the low-boiling solvents nor 
the alternative Freons cannot be substituted for the CFC-11. 
Another non-polluting type of process is a gas loading method which employs 
dry air or gaseous nitrogen. This method is also not applicable to the 
integral skin foam because of difficulty in formation of the high-density 
skin layer owing to non-occurrence of the aforementioned physical 
condensation. Further, a method using water, which evolves carbon dioxide 
gas by reaction with an isocyanate, as the blowing agent is not suitable 
because of the difficulty in obtaining a high-density skin layer in 
comparison with the use of CFC-11, although water is safe and causes no 
environmental problem. To improve the water-blowing process, a special 
catalyst has been investigated (Japanese Patent Application Laid-Open Nos. 
Hei-3-32811 and Hei-3-33120). This improved process, however, is not 
satisfactory for obtaining a sufficiently high density of the skin layer, 
and involves the problem of low productivity owing to delayed demolding 
times. 
Accordingly, a technique is strongly needed to produce a polyurethane foam 
having a high-density skin layer in high productivity without 
environmental pollution. 
The inventors of the present invention have investigated comprehensively 
the use of water alone as the blowing agent, without use of any 
halogenated hydrocarbon, for producing a polyurethane integral skin foam. 
As a result, the inventors have found that use of a guanidine type amine 
compound and/or its organic acid addition salt makes the density of the 
skin layer high and advances the mold release time, and have completed the 
present invention on the basis of this finding. 
SUMMARY OF THE INVENTION 
The present invention provides a process for producing polyurethane 
integral skin foam in high yield by use, as the blowing agent, of water 
alone with no halogenated hydrocarbon. 
The present invention provides a process for producing a polyurethane foam 
having a high-density skin layer by reacting a polyol with a 
polyisocyanate in the presence of a blowing agent, a catalyst, and 
optionally an additive, the blowing agent being composed only of water, 
and the catalyst, being an amine represented by the general formula (I) 
below, and/or an organic acid salt thereof: 
##STR2## 
where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are, independently, an alkyl 
group of 1 to 12 carbons, or R.sub.1 and R.sub.2, and/or R.sub.3 and 
R.sub.4 may be linked to form a ring together with the adjacent nitrogen 
atom; and R.sub.5 is hydrogen, an alkyl group of 1 to 12 carbons, a phenyl 
group, or a cycloalkyl group.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The process of the present invention for producing a polyurethane foam 
having a high-density skin layer comprises mixing a polyisocyanate with a 
polyol premix containing a polyol, a catalyst, water, and optionally an 
additive, and injecting the resulting liquid mixture into a mold to expand 
the mixture. 
The catalyst employed is a guanidine type amine represented by the general 
formula (I) and/or an organic acid addition salt thereof: 
##STR3## 
where R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are as defined above. 
Preferably, R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are, independently, 
alkyl groups of 1-8 carbon atoms, more preferably 1-6 carbon atoms. When 
R.sub.1 and R.sub.2 or R.sub.3 and R.sub.4 form a ring together with the 
adjacent nitrogen atom, the ring is preferably a 5-8 membered ring, more 
preferably a 5-6 membered ring containing 1-3 nitrogen atoms. When R.sub.1 
and R.sub.2 or R.sub.3 and R.sub.4 form a ring together with the adjacent 
nitrogen atom, one ring nitrogen atom will, of course, be contributed by 
the adjacent nitrogen atom. R.sub.5 is preferably an alkyl group of 1-8, 
preferably 1-6 carbon atoms, a cycloalkyl group of 5-8 carbon atoms or 
hydrogen. 
The guanidine type amine includes N,N,N',N'-tetramethylguanidine, 
N,N,N',N',N"-pentamethylguanidine, 
N,N,N',N'-tetramethyl-N"-cyclohexylguanidine, 
N,N-diethyl-N',N'-dimethylguanidine, 
N,N-diethyl-N',N'-dimethyl-N"-methylguanidine, and 
N,N-diethyl-N',N'-dimethyl-N"-cyclohexylguanidine. Of the above amines, 
N,N,N', N'-tetramethylguanidine is preferred. 
Such a guanidine type amine compound hydrolyzes gradually and loses its 
catalytic activity in the presence of water. Accordingly, the amine, when 
used with water as the blowing agent as in the present invention, exhibits 
catalytic activity for a short time after mixing into the polyol premix. 
This short activity is offset by using the guanidine type amine in a form 
of a salt of an organic acid. Suitable organic acids include aliphatic 
saturated carboxylic acids, aliphatic unsaturated carboxylic acids, 
aromatic carboxylic acids, and amino acids. Preferably, the acids having 
an acid dissociation constant, pKa, of from 3 to 6. Specific examples 
include formic acid, acetic acid, 2-ethylhexanoic acid, oleic acid, 
acrylic acid, crotonic acid, citric acid, adipic acid, succinic acid, 
benzoic acid, 4-aminobutyric acid, and the like. Of these, higher fatty 
acid salts such as 2-ethylhexanoic acid and oleic acid are preferred 
because of the higher catalytic activity. Weaker acids having an acid 
dissociation constant (pKa) of higher than 6 do not inhibit the 
hydrolysis, causing gradual hydrolysis of the catalyst amine and loss of 
catalyst activity. On the other hand, strong acids having an acid 
dissociation constant (pKa) of lower than 3 such as hydrochloric acid and 
dichloroacetic acid, inhibit the hydrolysis, but the salts have low 
catalytic activity. 
The amount of the catalyst used in the process of the present invention is 
generally in the range of from 0.02 to 10 parts by weight per 100 parts by 
weight of the polyol. A larger amount of the catalyst raises the 
reactivity of the system and advances the demolding time, but is less 
economical, while a smaller amount of the catalyst delays the demolding 
time. Therefore, the catalyst is preferably used in the range of 0.5 to 
5.0 parts by weight relative to 100 parts by weight of the polyol. 
A known cocatalyst such as a tertiary amine and/or an organic acid salt 
thereof, and an organometallic compound may be used in an account such 
that the function of the catalyst of the present invention is not 
impaired. Suitable amine cocatalysts include triethylenediamine, 
1-methyl-4-(2-dimethylaminoethyl)piperazine, 1-methyl-4-(2-hydroxyethyl) 
piperazine, bis(2-dimethylaminoethyl)ether, 
tetramethylhexamethylenediamine, 1-methylimidazole, 1,2-dimethylimidazole, 
1-isobutyl-2-methylimidazole, and 
tris(dimethylaminopropyl)hexahydro-s-triazine, and organic acid salts 
thereof. These amines improve the moldability in the process of the 
present invention. 
The organometallic compound cocatalyst includes for example, organotin 
compounds and alkali metal salts of carboxylic acids; such as 
di(C.sub.3-10 alkyl)tin di(C.sub.2-15 alkanoate)s and lithium, sodium and 
potassium C.sub.2-15 alkanoates, e.g., dibutyltin diacetate, dibutyltin 
dilaurate, dioctyltin dilaurate, dibutyltin bis(isooctylmercaptoacetate), 
potassium acetate, potassium 2-ethylhexanoate, etc. In particular, in the 
process of the present invention, the organotin compound advances the 
demolding time. 
Any of the above cocatalysts may be combined with any of the guanidine type 
amine compounds and/or the salts thereof of the present invention. The 
combinations of a guanidine type amine and/or its organic acid salt with 
an amine cocatalyst are preferred. Further, addition of an organotin 
compound to the above combination, namely combinations of three components 
are more preferred, for producing a foam having a skin layer of higher 
density, produced in a short time with high moldability. The ratio of the 
three components in the combination is 1 part by weight of the guanidine 
type amine and/or its organic acid salt, 0.1 to 5.0 parts by weight of the 
amine cocatalyst, and 0 to 0.5 part by weight of the organotin compound. 
As the blowing agent, water, which evolves carbon dioxide on reaction with 
isocyanate, is solely used in the present invention. The amount of water 
to be used depends on the density of the intended product, a larger amount 
of water giving a lower density product, and a smaller amount of water 
giving a higher density product. The water is usually used in an amount of 
5% by weight or less relative to 100 parts by weight of the polyol. 
Known aromatic polyisocyanates are useful as the polyisocyanate in the 
process of the present invention. The known aromatic polyisocyanates 
includes toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, and 
polymeric isocyanates thereof; isocyanate-terminated prepolymers derived 
by reaction of the above isocyanate with a polyol, e.g., toluene 
diisocyanate prepolymers, and diphenylmethane-4,4'-diisocyanate 
prepolymers; modified isocyanates derived by modification with 
carbodiimide or the like; and the mixtures of the above isocyanates. 
Highly reactive polyisocyanates are preferred, such as 
diphenylmethane-4,4'-diisocyanate, polymeric isocyanates thereof, and 
isocyanate-terminated prepolymers thereof, modified isocyanates thereof, 
and mixed polyisocyanates thereof, for advancing the mold release time. 
Aliphatic isocyanates and alicyclic isocyanates are slightly less reactive 
and require slightly longer demolding times. 
Known polyols and crosslinking agents, and optionally an additive such as a 
foam stabilizer, may be used in the process of the present invention. 
The polyol includes polyetherpolyols, polymer polyols, and polyesterpolyols 
having two or more reactive hydroxyl groups. The polyetherpolyols include 
addition products prepared by adding ethylene oxide or propylene oxide to 
an active hydrogen compound such as a polyhydric alcohol, e.g., glycol, 
glycerin, pentaerythritol, sucrose, etc.; ammonia; an aliphatic polyamine, 
e.g., ethylenediamine, etc.; an aromatic amine, e.g., toluene diamine, 
diphenylethane-4,4'-diamine, etc.; and mixtures thereof. The polymer 
polyols include reaction products prepared by reacting the above 
polyetherpolyol with an ethylenically unsaturated monomer, e.g., 
butadiene, acrylonitrile, styrene, etc. in the presence of a radical 
polymerization catalyst. The polyesterpolyols include reaction products of 
a dibasic acid with a polyhydric alcohol, e.g., polyethylene adipates and 
polyethylene terephthalates, which may be regenerated products derived 
from waste materials. For relatively elastic flexible foams and semi-rigid 
foams, two- to three-functional polyols are preferably used, and for 
relatively less elastic rigid foams, three- or more-functional polyols are 
preferably used. 
Suitable crosslinking agents include known two- or more functional low 
molecular weight polyols, i.e. polyols such as ethylene glycol, diethylene 
glycol, butanediol, trimethylolpropane, and glycerin; and amine type low 
molecular weight polyols such as triethanolamine and diethanolamine. These 
low molecular weight polyols may be used singly or in combinations of two 
or more. 
The foam stabilizer includes nonionic surfactants such as 
organopolysiloxane-polyoxyalkylene copolymers, silicone-glycol copolymers, 
and mixtures thereof, and is used optionally. The amount to be used is not 
specially limited, but is usually in the range of from 0 to 2.5 parts by 
weight per 100 parts by weight of the polyol. 
Other known additives may be added in the present invention, if necessary. 
The known additives include flame retardants, colorants, fillers, 
antioxidants, and ultraviolet light absorbers. 
The mixing ratio of the polyol premix to the polyisocyanate, namely the 
index number, is in the range of from 60 to 150, preferably from 80 to 
120. The resulting liquid mixture is blended by a blowing machine, and 
then injected into a mold and blown therein. Thereafter the foamed product 
is released from the mold. Either a high-pressure blowing machine or a 
low-pressure blowing machine may be used. High-pressure blowing machines 
having high mixing performance, are preferred. The liquid mixture is 
injected into the mold, in a so-called over-packing state. A higher 
over-packing ratio provides a higher density skin layer. 
The mold may be an open mold, a closed mold, or a RIM. The RIM is preferred 
because it enables shorter demolding times. A lower mold temperature gives 
a higher density skin layer. However, the lower temperature of the mold 
lowers the resin formation velocity, and requires a longer time before the 
demolding. Therefore, the temperature is preferably in the range of from 
30.degree. to 60.degree. C. 
Examples of the products produced by the process of the present invention 
are exterior and interior materials for automobiles such as steering 
wheels, instrument panels, head rests, arm rests, door panels, air 
spoilers, bumpers, and other structural foams as structural materials. 
The novel process of the present invention gives, without destruction of 
the global environment, products having the same properties at the same 
productivity as the products of conventional processes which employ a 
halogenated hydrocarbon. 
The present invention is described in more detail by reference to examples 
without limiting the invention in any way. 
EXAMPLES 
Examples 1-6, and Comparative Examples 1-6 
Foaming tests were conducted by changing the catalyst in the material 
mixing ratios (namely the formulations) below. In Example 1, the water was 
used in an amount of 0.8 parts by weight to produce a foam of relatively 
low density. In Example 2, the water was used in an amount of 0.5 parts by 
weight and larger amount of the liquid was injected into the mold to 
produce a foam of higher density. In Example 3, the mold temperature was 
set at 50.degree. C. which is higher by 10.degree. C. than in Example 1. 
In Examples 4 to 6 and Comparative Examples 1 to 5, the foaming conditions 
were the same as in Example 1 except for the catalyst. In each Example, 
the catalyst was used in such an amount that the same reaction rate (rise 
time of about 60 seconds) was obtained. 
The resulting foams were evaluated in a manner described below. The results 
are shown in Table 1. 
______________________________________ 
(a) Formulation 
______________________________________ 
Polyol*.sup.1 100 parts by weight 
water 0.5 or 0.8 parts by weight 
crosslinking agent*.sup.2 
8.0 parts by weight 
Catalyst*.sup.3 See Table 1 
Isocyanate*.sup.4 
(NCO/OH = 1.05) 
______________________________________ 
*.sup.1 Three-functional polyetherpolyol, OHV = 33 mg KOH/g 
(FA-703, made by Sanyo Chemical Industries, Ltd.) 
*.sup.2 Ethylene glycol (made by Nisso Yuka K.K.) 
*.sup.3 Catalyst, and abbreviation thereof in Tables 
TMG: N,N,N',N'-tetramethylguanidine 
PMG: N,N,N',N',N"-pentamethylguanidine 
CHMG: N,N,N',N'-tetramethyl-N"-cyclohexylguanidine 
L33E: 33% triethylenediamine solution in ethylene 
glycol (TEDA-L33E, made by Tosoh Corporation) 
POLYCAT-41: tris(dimethylaminopropyl)hexahydro-S- 
triazine (made by Air Products Co.) 
POLYCAT-42: mixture of tris(dimethylaminopropyl)- 
hexahydro-S-triazine and organometal salt 
(made by Air Product Co.) 
NMIZ: N-methylimidazole 
DBU: phenol salt of 1,8-diazabicyclo[5.4.0] 
undecene-7 (U-CATSAI, made by Sun Apro K.K.) 
*.sup.4 Crude MDI: MR-200 (NCO concentration: 31.0%, made 
by Nippon Polyurethane Industry Co., Ltd.) 
(b) Foaming conditions 
Raw material liquid temperature: 25.degree..+-.1.degree. C. 
Stirring: 6000 rpm (6 seconds) 
(c) Measurement items 
1. Free foaming 
A reaction liquid mixture was poured into a 500 ml polyethylene cup and the 
mixture was allowed to foam. The reactivity was evaluated by the following 
criteria. 
Cream time: length of time before initial foam rising (seconds) 
Gel time: length of time for resinification (or threading; seconds) 
Rise time: length of time before stoppage of rising (seconds) 
2. Mold foaming 
A liquid reaction mixture was poured into a temperature-controlled aluminum 
mold having inside dimensions of 15 cm.times.20 cm.times.1 cm, then 
immediately the mold was closed with a top cover, and foaming was allowed 
to proceed. Four minutes later, the foamed product was released from the 
mold, and the following items were evaluated. 
Mold releasability: Foam hardness (Shore C) of the released product was 
measured and compared after 4 minutes of foaming in the mold. 
Final hardness: One day after the foaming, the hardness (Shore C) was 
measured and compared. 
Foam density: Samples were taken from three spots in central portion of the 
foam, and the average density was calculated from the dimension and the 
weight of the samples as the overall density of the foam. Two samples 
having a size of 2.5 mm of the skin layer (top face and bottom face) were 
cut out and the average of the densities were calculated as the skin layer 
density. Core density was calculated from the central foam portion after 
removal of the skin layer. A large difference between the densities of the 
skin layer and the central portion means a higher density ratio for the 
skin layer. 
As shown in Tables 1-1 and 1-2, the foams produced by use of the catalyst 
of the present invention had high hardness after demolding, and had a skin 
layer of high density in comparison with the foams produced by use of the 
catalyst of the Comparative Examples. 
Examples 7-10, and Comparative Examples 6-9 
The catalysts prepared by reacting 1 mol of TMG (tetramethylguanidine) with 
1 mol of an acid, and TMG itself were tested for storage stability in a 
polyol premix. The abbreviations of the catalyst salts, the compositions 
thereof, and the method of the storage stability test are described below. 
The test results are shown in Table 2. 
1. Preparation of TMG-acid salt catalyst 
A predetermined amount of TMG and ethylene glycol (EG) or water as the 
solvent were placed in a 300 ml round bottom flask. The acid was added 
thereto with stirring to obtain the TMG-acid salt catalyst. The 
compositions of the catalysts are shown below. The numerals indicate 
percentages by weight. 
TMG-FA: TMG 40.0; formic acid (95%) 17.0; EG 43.0 
TMG-AA: TMG 40.0; acetic acid 20.9; EG 39.1 
TMG-HA: TMG 30.0; 2-ethylhexanoic acid 37.6; EG 32.4 
TMG-P: TMG 35.0; phenol 28.6; EG 36.4 
TMG-C: TMG 40.0; carbon dioxide 15.3; EG 34.7; water 10.0 
TMG-DA: TMG 30.0; dichloroacetic acid 33.6; EG 36.4 
TMG-CA: TMG 30.0; hydrochloric acid 9.5; EG 43.6; water 16.9 
2. Test method for storage-stability 
TMG or the above TMG-acid salt catalyst was added to a formulation having 
the same composition as in Example 1 (polyol 100 parts by weight; water 
0.8 parts by weight; and ethylene glycol 8 parts by weight) in an amount 
shown in Table 2 to prepare a premix. The premix was subjected to the 
foaming test immediately after preparation and after storage for 6 days in 
an oven at 50.degree. C. to measure the reactivity, whereby the activity 
and the stability of the catalysts were compared. 
As shown in Table 2, TMG exhibited decreased activity after 6 days of 
storage, showing less stability. The formate, acetate and 2-ethylhexanoate 
of TMG had activity almost unchanged after the storage, showing high 
stability. On the other hand, the TMG salts of carbonic acid and phenol 
which have an acid dissociation constant (pKa) of higher than 6 exhibited 
low activity, showing less stability. The TMG salts of hydrochloric acid 
and dichloroacetic acid exhibited low catalytic activity, and could not 
serve as the catalyst. 
Example 11-18, and Comparative Example 10-12 
With the same formulation as in Example 2, the foaming test was conducted 
by use of the combined system of the TMG-HA or TMG-FA with an amine 
cocatalyst or an organotin compound. In the test, the amount of the 
catalyst was increased to raise the reactivity, and demolded after 2 
minutes. The moldability of the resulting foam was evaluated with the 
evaluation standard shown below. The results are shown in Table 3. The 
chemical names of the amine cocatalysts and organotin compounds used and 
abbreviation thereof are shown below. 
1. Evaluation standard 
.circleincircle.: no void found 
.largecircle.: a few voids found 
.DELTA.: voids found 
X: many voids found 
2. Catalyst and abbreviation thereof 
TMNAEP: 1-methyl-4-(2-dimethylaminoethyl)piperazine (TOYOCAT-NP, made by 
Tosoh Corporation) 
MHEP: 1-methyl-4-(2-hydroxyethyl)piperazine (TOYOCAT-HP, made by Tosoh 
Corporation) 
BDAEE: 70 wt. % solution of bis(2-dimethylaminoethyl)ether in dipropylene 
glycol (TOYOCAT-ET, made by Tosoh Corporation) 
DBTDL: dibutyltin dilaurate (TEDA-T411, made by Tosoh Corporation) 
DBTM: Dibutyltin bis(isooctylmercaptoaceate) (TEDA-T40S, made by Tosoh 
Corporation) 
As shown in Table 3, the foams prepared with the catalyst of the present 
invention had high hardness after mold release, high moldability, and 
higher-density skin layer. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein. 
TABLE 1-1 
__________________________________________________________________________ 
Example No. 
1 2 3 4 5 6 
__________________________________________________________________________ 
Water 0.8 0.5 0.8 0.8 0.8 0.8 
part (by weight)*.sup.1 
Catalyst 
Catalyst name TMG TMG TMG PMG CHMG TMG/L33E 
parts (by weight)*.sup.1 
0.60 
0.65 
0.60 
0.47 
0.72 0.3/0.5 
Reactivity 
Cream time (sec) 
19 20 19 18 20 17 
Gel time (sec) 
42 39 42 41 43 38 
Rise time (sec) 
60 58 60 59 62 59 
Mold foaming 
Mold temperature (.degree.C.) 
40 40 50 40 40 40 
Mold releasability (Shore C) 
43 45 49 43 42 48 
Hardness at mold release 
(released after 4 min) 
Final hardness (Shore C) 
70 74 71 72 69 75 
Foam density (kg/cm.sup.3) 
Overall 431 668 424 427 433 425 
Skin 493 803 462 487 486 485 
Center portion 
319 506 307 317 322 315 
Density difference 
174 297 155 170 164 170 
(skin-core) 
__________________________________________________________________________ 
*.sup.1 Parts to 100 parts by weight of polyol 
TABLE 1-2 
__________________________________________________________________________ 
Comparative Example No. 
1 2 3 4 5 
__________________________________________________________________________ 
Water 0.8 0.8 0.8 0.8 0.8 
part (by weight)*.sup.1 
Catalyst 
Catalyst name L33E 
POLYCAT-41 
POLYCAT-42 
NMIZ 
DBU 
parts (by weight)*.sup.1 
1.00 
1.30 1.30 2.60 
1.30 
Reactivity 
Cream time (sec) 
14 12 15 12 32 
Gel time (sec) 
40 39 38 35 41 
Rise time (sec) 
60 59 59 59 57 
Mold foaming 
Mold temperature (.degree.C.) 
40 40 40 40 40 
Mold releasability (Shore C) 
32 39 32 30 5 
Hardness at mold release 
(released after 4 min) 
Final hardness (Shore C) 
72 66 70 64 60 
Foam density (kg/m.sup.3) 
Overall 422 425 409 426 388 
Skin 460 447 444 467 458 
Center portion 
334 365 339 324 305 
Density difference 
126 82 105 143 153 
(skin-core) 
__________________________________________________________________________ 
*.sup.1 Parts to 100 parts by weight of polyol 
TABLE 2 
__________________________________________________________________________ 
Example No. Comparative Example No. 
7 8 9 10 6 7 8 9 
__________________________________________________________________________ 
Catalyst 
Catalyst name 
TMG TMG-FA 
TMG-AA 
TMG-HA 
TMG-P 
TMG-C 
TMA-DA 
TMG-CA 
Parts (by weight)*.sup.1 
0.8 2.2 2.5 2.9 2.5 2.0 2.2 2.2 
pKa -- 3.8 4.8 4.9 10.0 6.4 1.3 below 1 
Reactivity just 
after premixing 
Cream time (sec) 
12 24 23 16 11 13 180 &gt;500 
Gel time (sec) 
20 69 43 28 17 26 360 -- 
Rise time (sec) 
23 84 30 32 19 30 600 -- 
Reactivity after storage 
at 50.degree. C. for 6 days 
Cream time (sec) 
16 24 23 16 29 17 181 &gt;500 
Gel time (sec) 
40 69 42 29 55 38 357 -- 
Rise time (sec) 
60 83 60 33 70 59 603 -- 
__________________________________________________________________________ 
*.sup.1 Parts to 100 parts by weight of polyol 
TABLE 3 
__________________________________________________________________________ 
Comparative 
Example No. Example No. 
11 12 13 14 15 16 17 18 10 11 12 
__________________________________________________________________________ 
Catalyst 
(parts by weight)*.sup.1 
TMG-HA 2.84 
1.50 
-- 2.00 
2.00 
1.07 1.00 
1.00 0.60 
-- -- 
TMG-FA -- -- 1.30 -- -- -- -- -- -- -- -- 
L33E -- 0.75 
0.92 -- -- 0.54 -- -- -- 0.80 
-- 
TMNAEP -- -- -- 0.60 
-- -- 0.60 
-- -- -- -- 
MHEP -- -- -- -- 1.24 
-- -- 1.00 -- -- -- 
BDAEE -- -- -- -- -- 0.50 -- -- -- -- -- 
DBTDL -- -- -- -- -- -- 0.05 
-- 0.20 
-- 0.30 
DBTM -- -- -- -- -- -- -- 0.10 -- 0.10 
-- 
Reactivity 
Cream time (sec) 
18 16 16 16 16 14 14 15 15 12 15 
Gel time (sec) 26 25 26 26 25 26 26 24 25 22 23 
Rise time (sec) 
31 31 32 30 30 31 33 28 29 25 26 
Mold foaming 
Mold temperature (.degree.C.) 
40 40 40 40 40 40 40 40 40 40 40 
Mold releasibility (Shore C) 
68 62 63 63 61 60 69 70 71 65 67 
Hardness at mold release 
(released after 2 min) 
Final hardness (Shore C) 
83 84 79 80 79 76 80 79 82 80 80 
Foam density (kg/m.sup.3) 
Overall 697 704 685 709 690 678 684 679 695 692 701 
Skin 855 813 809 818 811 782 810 810 819 767 771 
core 519 522 521 523 518 505 509 507 512 524 525 
Density difference 
336 291 288 295 293 277 301 303 307 243 246 
(skin-core) 
Moldability .DELTA. 
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X X X 
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*.sup.1 Parts by weight to 100 parts by weight of polyol