U.S. patent application number 14/396531 was filed with the patent office on 2015-04-30 for production of polyisocyanurate foam panels.
This patent application is currently assigned to Dow Global Technologies LLC. The applicant listed for this patent is Luigi Bertucelli, Giuseppe Fantera, Paolo Golini. Invention is credited to Luigi Bertucelli, Giuseppe Fantera, Paolo Golini.
Application Number | 20150118476 14/396531 |
Document ID | / |
Family ID | 48539113 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150118476 |
Kind Code |
A1 |
Bertucelli; Luigi ; et
al. |
April 30, 2015 |
PRODUCTION OF POLYISOCYANURATE FOAM PANELS
Abstract
The present invention discloses the production of panels by a
discontinuous process. The panels are produced by injecting a
polyisocyanurate foam forming composition into the mold cavity at
reduced pressure. The combination of certain polyisocyanurate foam
forming formulation and the reduced pressure in the mold cavity
allows production of and resulting sandwich panels in a
discontinuous process where the produced panels are characterized
by improved fire resistance.
Inventors: |
Bertucelli; Luigi; (Reggio
Emilia, IT) ; Fantera; Giuseppe; (Modena, IT)
; Golini; Paolo; (Reggio Emilia, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bertucelli; Luigi
Fantera; Giuseppe
Golini; Paolo |
Reggio Emilia
Modena
Reggio Emilia |
|
IT
IT
IT |
|
|
Assignee: |
Dow Global Technologies LLC
Midland
MI
|
Family ID: |
48539113 |
Appl. No.: |
14/396531 |
Filed: |
May 22, 2013 |
PCT Filed: |
May 22, 2013 |
PCT NO: |
PCT/EP2013/060465 |
371 Date: |
October 23, 2014 |
Current U.S.
Class: |
428/304.4 ;
264/46.5; 264/54 |
Current CPC
Class: |
C08G 18/225 20130101;
C08J 2375/06 20130101; C08J 9/141 20130101; C08J 2203/204 20130101;
B29K 2105/0026 20130101; B29K 2105/04 20130101; C08G 18/14
20130101; C08G 18/546 20130101; C08G 2101/0058 20130101; C08G
2105/02 20130101; C08J 9/0019 20130101; C08J 9/125 20130101; C08J
2375/08 20130101; C08G 18/4027 20130101; C08J 2203/02 20130101;
C08G 18/4829 20130101; C08J 9/08 20130101; C08J 2203/10 20130101;
B29C 44/42 20130101; C08G 18/4883 20130101; C08J 9/0038 20130101;
B29C 44/1233 20130101; B29K 2075/00 20130101; C08G 18/4879
20130101; B29C 44/3415 20130101; C08G 18/092 20130101; C08G 18/4018
20130101; C08G 18/4252 20130101; B29C 44/3403 20130101; C08G
18/0838 20130101; B29L 2009/00 20130101; Y10T 428/249953 20150401;
C08G 2101/0025 20130101; C08J 9/0004 20130101; C08J 2203/14
20130101; C08G 18/7664 20130101; C08J 2203/12 20130101 |
Class at
Publication: |
428/304.4 ;
264/54; 264/46.5 |
International
Class: |
C08J 9/00 20060101
C08J009/00; C08J 9/08 20060101 C08J009/08; B29C 44/12 20060101
B29C044/12; C08J 9/14 20060101 C08J009/14 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2012 |
EP |
12425099.4 |
Claims
1. A method of making a polyisocyanurate (PIR) foam, comprising: A)
injecting into a closed mold cavity, wherein said mold cavity is
under an absolute pressure of from 300 to 950 mbar, a reaction
mixture comprising: a) an organic polyisocyanate; b) a polyol
mixture, wherein the polyol mixture comprises an aromatic polyester
polyol, wherein the aromatic polyester polyol is at least 35 weight
percent of the total amount of polyol; c) a trimerisation catalyst;
d) at least one flame retardant; e) optionally auxiliary
substances; and f) a blowing agent component, wherein said reaction
mixture has an isocyanate index of greater than 250; and B) curing
to form a polyisocyanurate foam.
2. A method of making a sandwich panel having two exterior shells
and an intermediate polyisocyanurate (PIR) structural foam core,
comprising undertaking the method of claim 1, wherein said closed
mold cavity is defined by the two exterior shells and an annular
frame.
3. A method according to claim 1, wherein the aromatic polyester
polyol is at least 50 weight percent of the total amount of
polyol.
4. A method according to claim 1, wherein the reaction mixture has
an isocyanate index of greater than 350.
5. A method according to claim 1, wherein the mold cavity absolute
pressure is from 800 to 950 mbar.
6. A method according to claim 1, wherein the blowing agent
component comprises a physical and chemical blowing agent.
7. A method according to claim 6, wherein the chemical blowing
agent is water, formic acid or a combination thereof.
8. The method according to claim 6, wherein the physical blowing
agent is pentane.
9. A method according to claim 1, wherein the foam has an applied
density of 30 to 75 kg/m.sup.3.
10. A method according to claim 1, wherein the reaction mixture
additionally comprises a silicone surfactant.
11. A method according to claim 1, wherein the flame retardant is a
halogen free flame retardant.
12. A sandwich panel comprising two exterior shells and an
intermediate polyisocyanurate (PIR) structural foam core, wherein
the PIR foam core is produced from a reaction mixture comprising:
a) an organic polyisocyanate; b) a polyol mixture, wherein the
polyol mixture comprises greater than 35% by weight aromatic
polyester polyol and from 10 to 65% by weight novolac initiated
polyol based on the total weight of polyol; c) at least one curing
and/or blowing catalyst; d) at least one trimerisation catalyst; e)
at least one flame retardant; f) optionally at least one silicone
surfactant; g) at least one chemical blowing agent selected from
water and formic acid; and h) pentane, wherein the reaction mixture
has an isocyanate index of greater than 250.
Description
[0001] Polyisocyanurate foams are in general prepared by reacting a
stoichiometric excess of polyisocyanate with a polyol or polyol
mixture in the presence of a catalyst, a blowing agent, and
generally other optional additives such as surfactants and the
like. Polyisocyanurate foams are usually made at an isocyanate
index of between 150 and 500; the term isocyanate index as used
herein is the excess of isocyanate over the theoretical amount for
(1:1) reaction with all active H expressed in percentage terms
(i.e. 1:1=100).
[0002] Polyisocyanurate (PIR) foams, especially those with a high
index (i.e., an index above 250, more preferably above 300),
exhibit improved thermal stability and fire retardant properties
over polyurethane foams. Their better fire retardant properties are
due to the presence of isocyanurate rings, formed by the
cyclotrimerisation reaction of isocyanates. The higher the
isocyanate excess (expressed as isocyanate index), for a given
polyol formulation, the higher the relative concentration of
isocyanurate rings to urethane and/or urea bonds in the polymeric
foam backbone, the better the fire retardant performance will be.
This is the practical outcome of the higher bond energy associated
to quasi-aromatic isocyanurate trimer structure vs. urethane
bonds.
[0003] Such polyisocyanurate foams therefore, are widely used as
insulating materials in the manufacture of sandwich panels used in
the construction industry. Typically these foams are closed-cell,
rigid low density foams containing a low-conductivity gas, such as
a hydrofluorocarbon (HFC) or hydrocarbon, in the cells.
[0004] Sandwich panels with a PIR-foam core are today most commonly
produced with a continuous process. The fabrication features of the
continuous lamination process, including distribution of the
reaction mix across the width of the panel, fast reactivity, etc.
allow great latitude in PR foam chemistry, including use of high
index formulations and/or high content of highly viscous aromatic
polyols. Such versatility in chemistry in turn allows one to attain
excellent foam fire retardant behaviour, even in the case of using
hydrocarbon blowing agent and halogen-free flame retardants.
[0005] For certain application, use of a discontinuous process is
desirable as it allows more versatility in the design of the edges
along the perimeter such as in the production of walk-in coolers
with foamed-in-place locking device and sealing tapes. Such panels
permit easy on-site assembly. Such sandwich panels are
conventionally provided by arranging two spaced apart exterior
shells (of iron sheet or other suitable material) between the
planes of a press, or jig, inside a peripheral frame for retaining
the foam as well the locking device and sealing tapes, and
successively feeding a polyisocyanurate reaction mixture with a
blowing agent, such as a pentane, into the defined foaming cavity
of the panel. However, use of PIR foam chemistry in a discontinuous
closed mold injection process is difficult due to poor flow (high
applied densities), poor bonding strength, etc. Efforts have been
carried out to improve some characteristics, e.g. tensile bond
strength, by use of aliphatic polyesters as disclosed in WO
2010/114695A1, often at expense of other characteristics, e.g.
poorer fire retardant properties.
[0006] Due to the poor ability of high index polyisocyanurate
formulations, in particular when containing high levels of viscous
aromatic polyesters, to flow and fill the foam cavity of a
discontinuous panels, such panels, in general, require a certain
extra-charge of the polyisocyanurate reactive mixture (overpacking)
in order to obtain a complete filling up of the foaming cavity, and
a suitable distribution of materials to give foam with acceptable
mechanical and thermal properties. In addition, at the end of the
expansion phase of the foam, the panel is to be maintained between
the planes of the press or jig for a long period of time to oppose
the thrust exerted by the polyisocyanurate material during foaming,
as removal of the panel too early can cause an unacceptable
post-expansion and bulging of the polyisocyanurate foam core.
[0007] It is now known that reducing the pressure of the mold
cavity below atmospheric pressure has a positive effect on the
filling process. For example, WO 2007/058793 and EP 0854025 both
demonstrate the production of an improved polyurethane foam using
vacuum/sub-atmospheric pressure injection technology. The process
allows for homogeneous filling of the mold cavity, therefore
avoiding voids, and also allows the polyurethane mixture to be
injected in a lower quantity than in the absence of reduced
pressure. The review "Sandwich Panels: Innovative Solutions using
Vacuum-assisted Foam Injection" by Taverna et al (Cannon at UTECH
2000), states that vacuum/sub-atmospheric pressure injection
technology is also useful in the production of polyisocyanurate
sandwich panels.
[0008] However, there is still a need for an improved method to
produce sandwich panels using a discontinuous process, having foam
performance attributes similar to the ones currently attainable
with the continuous process; in particular, sandwich panels having
improved flame retardant properties while still maintaining good
bonding to facers.
[0009] The objectives of the present invention are achieved by
incorporating a proper amount of aromatic polyester polyol in a
polyol formulation, including a flame retardant and injecting the
polyol formulations, an isocyanate and blowing agent into a closed
panel mold under reduced atmospheric pressure. The edges of the
mold are constructed such that the finished panel has edges along
the perimeter to allow for easy assembly.
[0010] In a first aspect, the present invention provides a method
of making a polyisocyanurate foam comprising:
A) injecting into a closed mold cavity, wherein said mold cavity is
under an absolute pressure of from 300 to 950 mbar, a reaction
mixture comprising: [0011] a) an organic polyisocyanate; [0012] b)
a polyol mixture, wherein the polyol mixture comprises an aromatic
polyester polyol, wherein the aromatic polyester polyol is at least
35 weight percent of the total amount of polyol; [0013] c) a
trimerisation catalyst; [0014] d) at least one flame retardant;
[0015] e) optionally auxiliary substances; and [0016] f) a blowing
agent component, wherein said reaction mixture has an isocyanate
index of greater than 250; and B) curing to form a polyisocyanurate
foam.
[0017] In a second aspect, the present invention provides a method
of making a structural or self-supporting sandwich panel having two
exterior shells and an intermediate polyisocyanurate foam core
bonded to the said shells, comprising:
A) injecting into a closed mold cavity, wherein said mold cavity is
under an absolute pressure of from 300 to 950 mbar, a reaction
mixture comprising: [0018] a) an organic polyisocyanate; [0019] b)
a polyol mixture, wherein the polyol mixture comprises an aromatic
polyester polyol, wherein the aromatic polyester polyol is at least
35 weight percent of the total amount of polyol; [0020] c) a
trimerisation catalyst; [0021] d) at least one flame retardant;
[0022] e) optionally auxiliary substances; and [0023] f) a blowing
agent component, wherein said closed mold cavity is defined by the
two exterior shells and an annular frame, wherein said reaction
mixture has an isocyanate index of greater than 250; and B) curing
to form a polyisocyanurate foam bonded to the exterior shells.
[0024] The present invention is also a polyisocyanurate foam
produced according to the method of the first aspect, wherein the
PIR foam core is produced from a reaction mixture comprising:
[0025] a) an organic polyisocyanate; [0026] b) a polyol mixture,
wherein the polyol mixture comprises greater than 35% by weight
aromatic polyester polyol and from 10 to 65% by weight novolac
initiated polyol based on the total weight of polyol; [0027] c) at
least one curing and/or blowing catalyst; [0028] d) at least one
trimerisation catalyst; [0029] e) at least one flame retardant;
[0030] f) optionally at least one silicone surfactant; [0031] g) at
least one chemical blowing agent selected from water and formic
acid; and [0032] h) pentane, wherein the reaction mixture has an
isocyanate index of greater than 250.
[0033] The present invention is also a sandwich panel produced
according to the method of the second aspect comprising two
exterior shells and an intermediate polyisocyanurate structural
foam core, wherein the PR foam core is produced from a reaction
mixture comprising: [0034] a) an organic polyisocyanate; [0035] b)
a polyol mixture, wherein the polyol mixture comprises greater than
35% by weight aromatic polyester polyol and from 10 to 65% by
weight novolac initiated polyol based on the total weight of
polyol; [0036] c) at least one curing and/or blowing catalyst;
[0037] d) at least one trimerisation catalyst; [0038] e) at least
one flame retardant; [0039] f) optionally at least one silicone
surfactant; [0040] g) at least one chemical blowing agent selected
from water and formic acid; and [0041] h) pentane, wherein the
reaction mixture has an isocyanate index of greater than 250.
[0042] In a further embodiment, the flame retardant in the above
noted embodiments is a halogen free flame retardant.
Various terms used in the text of the present invention have the
following meaning: Polyol Mixture: The polyol mixture is a blend of
polyols used in production of the PIR foam. Polyol Formulation: The
polyol mixture in combination with any additives, such as
catalysts, flame retardants, surfactants and chemical blowing
agents, but excluding physical blowing agent. Pressure: The reduced
pressure within the mold as used herein refers to absolute pressure
with the unit mbar (or hPa). The reference pressure is 1000
mbar=1000 hPa=approx 1 atmosphere at sea level=0 bar gauge. While
reference is made to atmospheric pressure at sea level, it should
be understood the gauge pressure will be at least 50 mbar lower
than the measured atmospheric pressure. To further illustrate, an
absolute pressure of 800 to 950 mbar at sea level, approximates a
gauge pressure of -50 to -200 mbar.
[0043] The low internal pressure maintained within the
polymerization cavity helps the polyisocyanurate reactive mixture
to more evenly fill the available space, and therefore reduces the
required overpacking and resulting extra pressure on the press
planes. In the present invention, more viscous components either
due to the type of polyols or isocyanates and/or faster reactive
systems can be processed. The present invention may also allow for
a reduction in the absolute level of physical blowing agent which
may reduce the polyisocyanurate formulation costs, in particular
when using newly developed blowing agents such as
hydro-fluoroolefins, and volatile organic compound emissions upon
disposal of an article containing such a foam.
[0044] The composition contains various components which are
described in more detail below.
[0045] All features described in connection with any aspect of the
invention can be used with any other aspect of the invention.
[0046] Suitable polyisocyanates used in the present invention are
aliphatic, cycloaliphatic, arylaliphatic, aromatic polyisocyanates
and derivatives thereof. Such derivatives include allophanate,
biuret and NCO terminated prepolymer. Aromatic isocyanates,
especially aromatic polyisocyanates are preferred. It is preferred
to use aromatic diisocyanates such as isomers of toluene
diisocyanate (TDI), crude TDI, isomers of diphenyl methane
diisocyanate, and higher functional polymethylene polyphenyl
polyisocyanates (pMDI).
[0047] Mixtures of isocyanates and crude polyisocyanates as well as
MDI and TDI prepolymers, blends thereof with polymeric and
monomeric MDI may also be used in the practice of this invention.
The total amount of polyisocyanate used to prepare the foam in the
present inventions should be sufficient to provide an isocyanate
reaction index of from 250 to 500. Preferably the index is from 300
to 450. More preferably the index is from 300 to 400. An isocyanate
reaction index of 100 corresponds to one isocyanate group per
isocyanate reactive hydrogen atom present, such as from water and
the polyol mixture.
[0048] In certain embodiments the polyisocyanates are polymeric MDI
products, which are a mixture of polymethylene polyphenylene
polyisocyanates in monomeric MDI, having an average isocyanate
functionality of from 2.5 to 3.3 isocyanate groups/molecule and an
isocyanate equivalent weight of from 130 to 170. Suitable
commercially available products of that type include PAPI.TM. 27,
Voranate.TM. M229, Voranate.TM. 220, Voranate.TM. M595 and
Voranate.TM. M600, Voranate M647 all available from The Dow
Chemical Company.
[0049] In the present invention, isocyanates having viscosities up
to 2,000 cps, measured at 25.degree. C. may be preferably used.
[0050] The polyol mixture of the present invention comprises an
aromatic polyester polyol. The aromatic polyester polyol is based
on inter-esterification product of at least one aromatic component
and at least one polyhydroxy component.
[0051] As used herein, "aromatic" refers to organic compounds
having at least one conjugated ring of alternate single and double
bonds, which imparts an overall stability to the compounds. The
term "polyester polyol" as used herein includes any minor amounts
of unreacted compound, for example, polyhydroxy compound remaining
after the preparation of the polyester polyol. Preferably the
aromatic component is based on a phthalic acid based material such
as phthalic anhydride, phthalic acid, isophthalic acid,
terephthalic acid, methyl esters of phthalic, isophthalic, or
terephthalic acid, dimethyl terephthalate, trimellitic anhydride,
pyromellitic dianhydride, or mixtures thereof. While the aromatic
polyester polyol may be prepared from substantially pure reactant
materials, more complex starting materials, such as polyethylene
terephthalate, may be advantageous. Other residues are dimethyl
terephthalate (DMT) process residues, which are waste or scrap
residues from the manufacture of DMT.
[0052] Suitable polyhydroxy components are those having a molecular
weight of from 60 to 1000. In a further embodiment the molecular
weight is less than 800, less than 600 or even less than 500. In a
further embodiment the molecular weight is less than 400. Examples
of suitable polyhydroxy compounds, such as glycols, include
ethylene glycol, propylene glycol, diethylene glycol (DEG),
dipropylene glycol, triethylene glycol; polyethylene glycol (PEG)
and polypropylene glycol.
[0053] Generally, the aromatic component comprises at least 20, 23,
25 or at least 28 weight percent of the final polyester polyol. In
a further embodiment, the aromatic component comprises less than
50, 45, 40 or less than 35 weight percent of the polyester polyol.
The remaining weight percent of the polyester polyols is comprised
of the polyhydroxy component.
[0054] In one embodiment, the polyester polyol is based on
terephthalic acid, DEG and PEG as disclosed in publication
WO2010/015642.
[0055] The polyester polyols are formed by the
polycondensation/transesterification and polymerization of the
aromatic and polyhydroxy component under conditions well known in
the art. See for Example G. Oertel, Polyurethane Handbook, Carl
Hanser Verlag, Munich, Germany 1985, pp 54-62 and Mihail Ionescu,
Chemistry and Technology of Polyols for Polyurethanes, Rapra
Technology, 2005, pp 263-294. In general, the reaction is done at
temperature of 180 to 280.degree. C. In another embodiment the
reaction is done at a temperature of at least 200.degree. C. In a
further embodiment the reaction is done at a temperature of
215.degree. C. or greater. In a further embodiment the
transesterification is done at a temperature of 260.degree. C. or
less.
[0056] While the reaction may take place under reduced or increased
pressure, the reaction is generally carried out near atmospheric
pressure conditions.
[0057] The aromatic and polyhydroxy compounds are generally reacted
in a ratio to give an aromatic polyester polyol with a hydroxyl
number from 150 mg .sub.KOH/g to 400 mg .sub.KOH/g, preferably from
175 mg .sub.KOH/g to 300 mg .sub.KOH/g and in a further embodiment
from 200 mg .sub.KOH/g to 250 mg .sub.KOH/g.
[0058] The aromatic polyester polyol is preferably used in an
amount of at least 35 weight percent of the total amount of polyol
mixture, preferably the aromatic polyester polyol is at least 40
weight percent of the total amount of polyol, more preferably the
aromatic polyester polyol is at least 50 weight percent of the
total amount of polyol. In some embodiments the aromatic polyester
polyol is at least 60 weight percent of the total amount of polyol.
The aromatic polyester polyol is preferably less than 90 weight
percent of the total amount of polyol; preferably the aromatic
polyester polyol is less than 80 weight percent of the total amount
of polyol.
[0059] In a particular embodiment of the present invention a
Novolac-type polyether polyol is used in the polyol mixture in
addition to the polyester polyol.
[0060] Novolac-type polyether polyols are the alkoxylation products
of a phenol-formaldehyde resin. Novolac-resins are prepared by
condensing phenol with formaldehyde in the presence of an acid
catalyst. Methods for the production of novolac polyols are known
in the art, as described, for example, in U.S. Pat. Nos. 2,838,473;
2,938,884; 3,470,118; 3,686,101; and 4,046,721.
[0061] In general, suitable acidic catalysts for the novolac resin
reaction include oxalic acid, zinc acetate, hydrochloric acid,
glacial acetic acid, hydrochloric, sulphuric acid or a combination
thereof. The condensation reaction is generally done at a reaction
temperature of between 60 and 160.degree. C.
[0062] Phenols which may be used to prepare the Novolac initiator
include: o-, m-, or p-cresols, ethylphenol, cardanol (including
that obtained from cashew nuts), nonylphenol, p-phenylphenol,
2,2-bis(4-hydroxyphenol)propane, beta-naphthol,
beta-hydroxyanthracene, p-chlorophenol, o-bromophenol,
2,6-dichloro-phenol, p-nitrophenol, 4-nitro-6-phenylphenol,
2-nitro-4-methylphenol, 3,5-dimethylphenol, p-isopropylphenol,
2-bromo-4-cyclohexylphenol, 4-t-butylphenol,
2-methyl-4-bromophenol, 2-(2-hydroxypropyl)phenol,
2-(4-hydroxyphenol)ethanol, 2-carbethoxyphenol,
4-chloro-methylphenol, and mixtures thereof. It is especially
preferred that the phenols used to prepare the Novolac-type
polyether polyols be unsubstituted.
[0063] While formaldehyde or a derivative thereof, such as
trioxane, is generally used as the aldehydic reactant,
acetaldehyde, propionaldehyde or butyraldehyde may also be
used.
[0064] Typically, Novolac starting materials are prepared by
reacting a phenol (for example, a cresol) with from about 0.8 to
about 1.0 moles of formaldehyde per mole of the phenol in the
presence of an acidic catalyst to form a polynuclear condensation
product containing from 2.1 to 12, preferably from 2.2 to 6, and
more preferably from 2.5 to 5 phenol units per molecule.
[0065] The Novolac resin is then reacted with an alkylene oxide
such as ethylene oxide, propylene oxide, butylene oxide, or
isobutylene oxide to build molecular weight to a desired level.
Generally the final polyol will desirably have a molecular weight
from about 300 to about 1500, and in certain non-limiting
embodiments, from about 400 to about 1000. Preferred Novolac
polyols are those having an average of from 3 to 6 hydroxyl
moieties per molecule and an average hydroxyl number of from about
100 to about 500 mg .sub.KOH/g, preferably from about 100 to about
300 mg .sub.KOH/g.
[0066] The Novolac polyol is preferably used in an amount of at
least 10 weight percent of the total amount of polyol mixture,
preferably the Novolac polyol is at least 15 weight percent of the
total amount of polyol, more preferably the Novolac polyol is at
least 20 weight percent of the total amount of polyol, more
preferably the Novolac polyol is at least 30 weight percent of the
total amount of polyol mixture. The Novolac polyol is preferably
less than 65 weight percent of the total amount of polyol,
preferably the Novolac polyol is less than 60 weight percent of the
total amount of polyol, and in a further embodiment, less than 50
weight percent of the polyol mixture.
[0067] The polyol mixture of the present invention may also
comprise one or more other polyols other than the above desired
aromatic polyester and Novolac polyols. Examples of additional
polyols include polyether polyols and aliphatic polyesters.
[0068] Additional polyether polyols may be a polyoxypropylene, a
polyoxyethylene or combination thereof, either as a block copolymer
or a random copolymer. Initiators for such polyols include, for
example, polyhydric alcohols, such as, glycerol, pentaerythritol,
ethanediol, 1,2- and 1,3-propanediol, diethylene glycol,
dipropylene glycol, 1,4-butanediol, 1,6-hexanediol,
trimethylolpropane, for example, and sugars, such as sorbitol,
sucrose, glucose, fructose or other sugars Polyols may also be
formed from mixtures of initiators such as a high functionality
starter (sorbitol/sucrose) and a lower functionality starter such
as glycerin to give co-initiated polyols having functionality of
from 3 to 5 and preferably a hydroxyl value from 300 to 550 mg
.sub.KOH/g. Other polyols may be selected from both aliphatic and
aromatic amine-containing compounds. Examples of such initiator
molecules include aliphatic and aromatic, unsubstituted or N-mono-,
N,N- and N,N'-dialkyl-substituted diamines having from 1 to 4
carbon atoms Examples alkyl amine initiators include unsubstituted
or mono- or dialkyl-substituted ethylenediamine,
diethylenetriamine, triethylenetetramine, 1,3-propylene-diamine,
1,3- and 1,4-butyl-enediamine, 1,2-, 1,3-, 1,4-, 1,5- and
1,6-hexamethylene-diamine, Examples of initiators containing an
aromatic amine include, aniline, phenylene-diamines, 2,3-, 2,4-,
3,4- and 2,6-tolylenediamine, and 4,4'-, 2,4'- and
2,2'-diaminodiphenylmethane.
[0069] Other suitable initiator molecules are alkanolamines, for
example, ethanolamine, N-methyl- and N-ethylethanolamine;
dialkanolamines, for example, diethanolamine, N-methyl- and
N-ethyldi-ethanolamine, and trialkanolamines, for example,
triethanolamine.
[0070] Another class of aromatic based polyether polyols which may
be used are an alkylene oxide adduct of
phenol/formaldehyde/alkanolamine resin, frequently called a
"Mannich" polyol such as disclosed in U.S. Pat. Nos. 4,883,826;
4,939,182; and 5,120,815.
[0071] An example of a phenol based polyol which can be used is the
alkoxylation product of bisphenol A. Bisphenol A is produced by the
condensation product of acetone with two phenols.
[0072] If present, the polyether polyol, excluding the
Novolac-initiated polyol, is used in an amount of at least 2 weight
percent of the total of polyol mixture. The polyether polyol may be
present in at least 5 weight percent of the total amount of polyol,
10 weight percent of the total amount of polyol, or 20 weight
percent of the total amount of polyol. The polyether polyol is
preferably less than 55 weight percent of the total amount of
polyol; preferably the polyether polyol is less than 50 weight
percent of the total amount of polyol, more preferably the
polyether polyol is less than 45 weight percent of the total amount
of polyol.
[0073] When used the polyether polyol has a hydroxyl number from 20
mg .sub.KOH/g to 700 mg .sub.KOH/g, more preferably from 25 mg
.sub.KOH/g to 700 mg .sub.KOH/g.
[0074] The polyol mixture of the present invention may also
comprise one or more aliphatic polyester polyols.
[0075] Illustrative aliphatic polyester polyols may be prepared
from organic dicarboxylic acids having from 2 to 12 carbon atoms
and polyhydric alcohols, preferably diols, having from 2 to 12,
preferably from 2 to 8 and more preferably 2 to 6 carbon atoms.
Examples of dicarboxylic acids are succinic acid, glutaric acid,
adipic acid, suberic acid, azelaic acid, sebacic acid,
decanedicarboxylic acid, malonic acid, pimelic acid,
2-methyl-1,6-hexanoic acid, dodecanedioic acid, maleic acid and
fumaric acid. Such acids may be used individually or as mixtures.
Examples of dihydric and polyhydric alcohols include ethanediol,
diethylene glycol, Methylene glycol, 1,2- and 1,3-propanediol,
dipropylene glycol, 1,4-butanediol and other butanediols,
1,5-pentanediol and other pentanediols, 1,6-hexanediol,
1,10-decanediol, glycerol, and trimethylolpropane. Illustrative of
the polyester polyols are poly(hexanediol adipate), poly(butylene
glycol adipate), poly(ethylene glycol adipate), poly(diethylene
glycol adipate), poly(hexanediol oxalate), poly(ethylene glycol
sebecate), and the like.
[0076] If present, the polyester polyol is preferably at least 1
weight percent of the total amount of polyol, preferably the
polyester polyol is at least 2 weight percent of the total amount
of polyol, more preferably the polyester polyol is at least 5
weight percent of the total amount of polyol. The polyester polyol
is preferably less than 55 weight percent of the total amount of
polyol; preferably the polyester polyol is less than 50 weight
percent of the total amount of polyol, more preferably the
polyester polyol is less than 45 weight percent of the total amount
of polyol.
[0077] The polyol mixture will generally have a hydroxyl number of
from 100 mg .sub.KOH/g to 400 mg .sub.KOH/g. Preferably the
hydroxyl number is from 150 mg .sub.KOH/g to 350 mg .sub.KOH/g and
more preferably from 200 mg .sub.KOH/g to 30 mg .sub.KOH/g.
[0078] The polyol mixture forms the bulk of the polyol formulation.
It is preferred that the polyol mixture comprises from 30 to 95
weight percent of the polyol formulation, preferably from 40 to 85
weight percent and more preferably from 45 to 80 weight
percent.
[0079] The balance of the polyol formulation is made up of
catalysts, cross-linkers, chain extenders, surfactants, fillers,
flame retardants, chemical blowing agents and other additives.
[0080] In a preferred embodiment of the present invention, there is
provided one or more catalysts.
[0081] Polyisocyanurate catalysts provide three main purposes,
namely to act as curing catalysts, blowing catalysts and
trimerisation catalysts. The present invention employs at least a
trimerisation catalyst. It is preferred that the catalytic package
of the present invention provides at least at least one additional
curing or blowing catalyst. It is further preferred that all three
catalyst types are present. The inclusion of a trimer catalyst is
intended to allow isocyanurate ring formation, essential for the
reaction to fire property, while the use of the other mentioned
catalyst types must be fine-tuned in order to get the desired
reaction profile and optimized processability performance,
providing gel time as reactivity parameter longer than 50 seconds,
measured on foam injected by means of high pressure foaming machine
at typical environment temperature (20-25.degree. C.).
[0082] Trimerisation catalysts are able to promote the reaction of
isocyanate on itself. Examples of trimerisation catalysts include
tris(dialkylaminoalkyl)-s-hexahydrotriazines such as
1,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine; potassium
acetate, potassium ethyl hexanoate; tetraalkylammonium hydroxides
such as tetramethylammonium hydroxide; alkali metal hydroxides such
as sodium hydroxide; alkali metal alkoxides such as sodium
methoxide and potassium isopropoxide; and alkali metal salts of
long-chain fatty acids having 10 to 20 carbon atoms and, in some
embodiments, pendant hydroxyl groups. Examples of Commercially
available trimerisation catalysts include DABCO.TM. TMR-30;
DABCO.TM. K-2097, POLYCAT.TM. 41, POLYCAT.TM. 43, POLYCAT.TM. 46,
DABCO.TM. TMR, CURITHANE.TM. 52, DABCO K15.
[0083] The trimerisation catalyst is preferably at least 0.3 weight
percent of the total amount of polyol formulation, preferably at
least 0.6 weight percent of the total amount of polyol formulation,
and more preferably at least 0.7 weight percent of the total amount
of polyol formulation. In addition, the trimerisation catalyst is
less than 5 weight percent of the total amount of polyol
formulation, preferably less than 4 weight percent of the total
amount of polyol formulation, and more preferably less than 3
weight percent of the total amount of polyol formulation.
[0084] Some of these catalysts are solids or crystals and can be
dissolved in the proper solvent which can be the polyol, water,
dipropylene glycol or any other carrier compatible with the
polyisocyanurate foaming composition.
[0085] While it is known that some catalysts may promote both
blowing and curing (so-called "balanced" catalysts), such are
conventionally differentiated by their tendency to favour blow
reaction (urea or water and isocyanate reaction), in the case of
the blowing catalyst, or the curing reaction (urethane or polyol
and isocyanate reaction), in the case of the curing catalyst. In
some non-limiting embodiments, a catalyst that technically may
catalyze both blowing and curing may be selected for its favoured
tendency, e.g., curing, and combine with another catalyst directed
more toward the other purpose, e.g., blowing, and vice versa.
[0086] Examples of suitable blowing catalysts that may tend to
favour the urea reaction are short chain tertiary amines or
tertiary amines containing at least an oxygen and may include
bis-(2-dimethylaminoethyl)ether; pentamethyldiethylene-triamine,
triethylamine, tributyl amine, N,N-dimethylaminopropylamine,
dimethylethanolamine, or N,N,N',N'-tetra-methylethylenediamine. In
one embodiment, a combination of bis(dimethylaminoethyl)ether and
dipropylene glycol may be an effective blowing catalyst, for
example, in a 70/30 weight percent ratio. Combinations of any of
the above may also be selected.
[0087] The amount of blowing catalyst is added to give a gel time
of at least 50 seconds. The adjustment of the catalyst levels to
obtain the desired gel time is known to those skilled in the art.
In general the blowing catalysts is at least 0.1 weight percent of
the total amount of polyol formulation, preferably at least 0.15
weight percent, and more preferably at least 0.2 weight percent of
the total amount of polyol formulation. In addition, the blowing
catalyst is preferably less than 0.4 weight percent of the total
amount of polyol formulation.
[0088] Examples of suitable curing catalysts that may tend to
favour the urethane reaction include, generally, amidines, tertiary
amines, organometallic compounds, and combinations thereof. These
may include, but are not limited to, amidines such as
1,8-diazabicyclo[5.4.0]undec-7-ene and
2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, and their salts.
[0089] Organometallic compounds may include organotin compounds,
such as tin(II) salts of organic carboxylic acids, e.g., tin(II)
diacetate, tin(II) dioctanoate, tin(II) diethylhexanoate, and
tin(II) dilaurate, and dialkyltin(IV) salts of organic carboxylic
acids, e.g., dibutyltin diacetate, dibutyltin dilaurate, dibutyltin
maleate and dioctyltin diacetate. Bismuth salts of organic
carboxylic acids may also be selected, such as, for example,
bismuth octanoate. The organometallic compounds may be selected for
use alone or in combinations, or, in some embodiments, in
combination with one or more of the highly basic amines listed
hereinabove.
[0090] If present, the curing catalysts are generally at least 0.05
weight percent of the total amount of polyol formulation,
preferably at least 0.1 weight percent of the total amount of
polyol formulation. In addition, the curing catalysts is generally
less than 0.4, preferably less than 0.3 weight percent of the total
amount of polyol formulation.
[0091] Example of catalysts able to promote both blowing and curing
reactions are tertiary amines such as triethylamine, tributylamine,
dimethylbenzylamine, N-methyl-, N-ethyl-, and
N-cyclohexylmorpholine, N,N,N',N'-tetra-methylethylenediamine,
N,N,N',N'-tetramethylbutanediamine and -hexanediamine,
tetramethyldiaminoethyl ether, bis(dimethylamino-propyl)urea,
dimethylpiperazine, dimethylcyclohexylamine,
1,2-dimethyl-imidazole, 1-aza-bicyclo[3.3.0]octane,
triethylenediamine (TEDA).
[0092] Another class of catalysts for both blowing and curing
reactions are alkanolamine compounds, such as triethanolamine,
triisopropanolamine, N-methyl- and N-ethyldiethanolamine, and
dimethylethanolamine may also be selected. Combinations of any of
the above may also be effectively employed.
[0093] Examples of commercially available blowing, curing or
blowing/curing catalyst include NIAX A-4, NIAX A6, POLYCAT 6,
POLYCAT 5, POLYCAT 8, Niax A1; POLYCAT 58, DABCO T, DABCO NE 300,
TOYOCAT RX 20, DABCO DMDEE, JEFFCAT ZR 70, DABCO.TM. 33 LV, NIAX
A-33, DABCO R-8020, NIAX TMBDA, POLYCAT 77, POLYCAT 6, POLYCAT 9,
POLYCAT 15, JEFFCAT ZR 50, TOYOCAT NP, TOYOCAT F94, DABCO NEM, etc.
POLYCAT and DABCO catalysts are available from Air Products;
TOYOCAT catalysts are available from Tosho Corporation; NIAX
Catalysts are available from Momentive Performance Material; and
JEFFCAT catalysts are available from Huntsman.
[0094] Some of these catalysts being solids or crystals are
dissolved in the proper solvent which can be polyol, water, blowing
agent, DPG or any carrier compatible with the polyisocyanurate foam
forming components.
[0095] In one particular embodiment of the present invention, the
combined amount of catalysts, not considering the solvents, is from
0.6 to 5 weight percent, preferably from 0.7 to 4 weight percent,
more preferably from 0.8 to 3 weight percent, based on the weight
of the polyol formulation.
[0096] As known to those skilled in the art, the amount of catalyst
can vary based on the temperatures of the materials.
[0097] According to the method of the present invention, one or
more flame retardants are present.
[0098] Flame retardants are chemical additives used across a
variety of consumer products, such as plastics, textiles, leather,
paper, rubber, etc, to inhibit or resist the spread of fire. The
flame retardants interfere with a particular stage of combustion,
i.e., during heating, decomposition, ignition or flame spread,
through physical or chemical actions.
[0099] Chemicals which may be used as flame retardants can be
mineral, halogen containing, nitrogen containing and phosphorus
containing chemicals, silicon based chemicals, etc. The term
"retardant" represents a class of use and not a class of chemical
structure.
[0100] In recent years, there have been growing concerns about the
safety of halogenated flame retardant chemicals, and the impact
they have on the environment. There is a high demand therefore, for
polyisocyanate foam sandwich panels that use non-halogenated flame
retardant materials. Initiatives, such as The U.S. Green Building
Council (US GBC) Leadership in Energy and Environmental Design
(LEED) certification scheme, are in place in the U.S. to promote
buildings that are environmentally responsible, profitable and
healthy places to live and work. The LEED Green Building Rating
System is a voluntary standard that recognizes the life cycle
assessment (LCA) and life cycle costing (LCC) of building
construction. The selection of building insulation products may
contribute to LEED credits in several categories such as energy
performance and indoor air quality.
[0101] In one embodiment of the present invention therefore, there
is provided a method of making a polyisocyanurate foam comprising
only halogen-free flame retardants.
[0102] Examples of suitable halogen free flame retardants include
metal hydroxides such as aluminium and magnesium hydroxide,
phosphorus based flame retardants including organic and inorganic
phosphates, phosphonates, phosphites, phosphinates, etc. and
nitrogen based flame retardants such as melamine and melamine
derivatives (e.g., melamine cyanurate, melamine polyphosphate,
melem, melon). Examples of suitable phosphorous-containing organic
compounds are described in EP 1023367 B 1, paragraphs [0026] to
[0032], the referenced paragraphs included herein by reference.
[0103] Preferably the halogen-free flame retardant is an organic
phosphate such as triethyl phosphate (TEP).
[0104] Preferably, the halogen-free flame retardant is an organic
phosphonate such as diethyl ethyl phosphonate (DEEP).
[0105] In general, the halogen-free flame retardants are added at a
level of from 5 to 50 parts by weight, preferably from 10 to 40
parts by weight, more preferably from 15 to 30 parts by weight of
the flame retardant per 100 parts per weight of the polyol
formulation.
[0106] Since certain types of halogenated flame retardants are
still considered useful however, the present invention also
provides a method of making polyisocyanurate foams using at least
one halogenated flame retardant.
[0107] Generally such flame retardants are halogenated aromatic
compounds, or halogen-substituted phosphates. Common
halogen-substituted phosphates include
tris(2-chloroethyl)phosphate, tris(1,3-dichloropropyl)phosphate,
tris(2-chloropropyl)phosphate, tris(2,3-dibromopropyl)phosphate,
chloropropyl bis(bromopropyl)phosphate and
tetrakis(2-chloroethyl)ethylene diphosphate.
[0108] Halogenated polyols, which are reactive and permanently
bonded in the polymer, may be used. Examples of commonly used
halogenated polyols are PHT-4 diol and/or SAYTEX RB79.
[0109] In general, the halogenated flame retardants are added at a
level of from 5 to 60 parts by weight, preferably from 5 to 50
parts by weight, more preferably from 10 to 40 parts by weight of
the flame retardant per 100 parts per weight of the polyol
formulation.
[0110] If desired, various additives can be incorporated into the
reaction mixture for producing the foams of the present invention.
Examples are chain extenders, crosslinking agents, surface-active
substances, foam stabilizers, cell regulators, fillers, dyes,
pigments, hydrolysis inhibitors, fungistatic and bacteriostatic
substances.
[0111] In one preferred embodiment chain extenders and/or
crosslinking agents are included to help adjusting the polymer
crosslinking. Unlike the polyols, these are not polymers in their
own right. Chain extenders are generally grouped as having a
functionality equal to 2. They are usually represented by
relatively short chain or low molecular weight molecules such as
hydroquinone di(.beta.-hydroxyethyl)ether, ethylene glycol (EG),
diethylene glycol (DEG), triethylene glycol, tetraethylene glycol,
propylene glycol, dipropylene glycol, tripropylene glycol,
1,3-propanediol, 1,3-butanediol, 1,4-butanediol (BDO), neopentyl
glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol,
methyldiethanolamine, phenyldiethanolamine, combinations thereof,
and the like. Particularly frequently used are dipropylene glycol
(DPG), 1,4-butanediol (BDO), diethylene glycol (DEG) and
combinations thereof.
[0112] The crosslinking agents are generally grouped as having a
functionality equal to 3 or more. They also are usually represented
by relatively short chain or low molecular weight molecules such as
glycerine, ethanolamine, diethanolamine, trimethylolpropane (TMP),
1,2,6-hexanetriol, triethanol-amine, pentaerythritol,
N,N,N',N'-tetrakis(2-hydroxypropyl)-ethylenediamine,
diethyl-toluenediamine, dimethylthiotoluenediamine, combinations
thereof, and the like. Particularly frequently used are glycerine,
1,4-trimethylolpropane (TMP), and combinations thereof.
[0113] Those skilled in the art will be familiar with a wide range
of suitable chain extenders and/or crosslinking agents. When used,
the crosslinker and/or chain extender may be used in amount up to 8
wt % of the polyol formulation.
[0114] Suitable surface-active substances (surfactants and
emulsifiers) are, for example, compounds which serve to aid the
homogenization of the starting materials and may also be suitable
for regulating the cell structure of the foam.
[0115] Surfactants, including silicone-based and organic ones, may
be added to serve as cell stabilizers. Some representative
materials are, generally, polysiloxane polyoxylalkylene block
copolymers, such as those disclosed in U.S. Pat. Nos. 2,834,748;
2,917,480; and 2,846,458, the disclosures of which are incorporated
herein by reference in their entireties. Also included are organic
surfactants containing polyoxyethylene-polyoxybutylene block
copolymers, as are described in U.S. Pat. No. 5,600,019, the
disclosure of which is incorporated herein by reference in its
entirety. Other surfactants include polyethylene glycol ethers of
long-chain alcohols, tertiary amine or alkanolamine salts of
long-chain allyl acid sulfate esters, alkylsulfonic esters, alkyl
arylsulfonic acids, and combinations thereof.
[0116] Surfactants, such as NIAX.TM. L-6900 or DABCO.TM. DC5598,
may be included in any amount ranging from 0 to 6 parts. (NIAX.TM.
L-6900 is available from Momentive, DABCO.TM. DC5598 is available
from Air Products).
[0117] Surface-active substances also comprise emulsifiers, such as
the sodium salts of castor oil sulfates or of fatty acids and also
amine salts of fatty acids, e.g., diethylamine oleate,
diethanolamine stearate, diethanolamine ricinoleate, salts of
sulfonic acids, e.g., alkali metal or ammonium salts of
dodecylbenzene- or dinaphthylmethanedisulfonic acid and ricinoleic
acid. Other foam emulsifiers include, for example, ethoxylated
alkylphenols, ethoxylated fatty alcohols, paraffin oils, castor oil
or ricinoleate esters.
[0118] The emulsifier substances are usually employed in amounts of
from 0.01 to 5 parts by weight, preferably 1 to 5 parts per 100
parts of polyol formulation.
[0119] Agents, such as perfluoroalkanes are important additives in
the field of rigid foams since they help regulate foam cell
structure, hence they can be used with the present invention.
[0120] Examples of fillers include talcs, clays, silicas, calcium
carbonates, graphites, glass, carbon black, glass fibers or other
ceramics, or powdered polymers such as polyamide, propylene, ABS or
recycled polyurethane foam. Fillers can be used in an amount of up
to 20% by weight of the polyol formulation.
[0121] The method of the present invention is undertaken in the
presence of a physical blowing agent. Suitable physical blowing
agents for use in the present invention are those having a boiling
point above freezing (0.degree. C.). Preferably at least one
blowing agent has a boiling point above 10.degree. C. and more
preferably 15.degree. C. or higher.
[0122] The blowing agent composition includes at least one physical
blowing agent which is a hydrocarbon, hydrofluorocarbon (HFC),
fluorocarbon, dialkyl ether or a fluorine-substituted dialkyl
ether, hydrochlorofluoroolefin (HCFO), hydrofluoroolefin (HFO) or a
mixture of two or more thereof. Blowing agents of these types
include, for example, propane, isopentane, n-pentane, n-butane,
isobutane, isobutene, cyclopentane, dimethyl ether,
1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1,3,3-pentafluorobutane
(HFC-365mfc), 1,1-difluoroethane (HFC-152a),
1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), and
1,1,1,3,3-pentafluoropropane (HFC-245fa). Examples of HFO and HCFO
blowing agents include pentafluoropropenes, such as HFO-1225yez and
HFO-1225ye; tetrafluoropropenes, such as HFO-1234yf
(2,3,3,3-tetrafluoropropene) and HFO-1234ze
(1,3,3,3-tetrafluoropropene); chlorofluoropropenes, such as,
HCFO-1233zd (1,1,1-trifluoro-3-chloropropene), HCFO-1223
dichlorotrifluoropropene); HCFO-1233xf
(2-chloro-3,3,3-trifluoropropene); and
1,1,1,4,4,4-hexafluoro-2-butene (FEA-1100). Such blowing agents are
disclosed in numerous publications, for example, publications
WO2008121785A1 WO2008121790A1; US 2008/0125506; US 2011/0031436;
US2009/0099272; US2010/0105788 and US2011/0210289. Methyl formate
and dimethyoxymethane are additional examples of physical blowing
agent which may be utilized. The hydrocarbon and hydrofluorocarbon
blowing agents are preferred. In a further embodiment the
hydrocarbon blowing agent utilized is cyclopentane.
[0123] Due to the in-mold reduced pressure, blowing agents having a
high boiling point, that is, above 50.degree. C., such as
cyclohexane or methyl-cyclohexane can be used in the present
invention. Optionally products having a boiling point below
0.degree. C., such as for instance isobutene, can be combined with
the other blowing agents listed heretofore.
[0124] Other blowing agents which may be used in combination with
these compounds are rare gases such as Argon, Krypton or Xenon.
[0125] All aforementioned physical blowing agents can be used as
pure components as well as mixtures of these various physical
blowing agents.
[0126] The method of the present invention also uses at least one
chemical blowing agent, such as water or formic acid. The total
amount of chemical blowing agent is present in a level of from 0.1
weight percent to 5 weight percent, based on the total weight of
the polyol formulation. Preferably, the amount of chemical blowing
agent is from 0.5 to 4 weight percent.
[0127] A chemical blowing agent content which is too high can lead
to increased brittleness (due to increased content of polyurea
linkages) and increase in thermal conductivity (due to the higher
molar ratio of carbon dioxide to the physical blowing agent in the
cell gas composition).
[0128] The polyisocyanurate foam of the present invention is made
by mixing the polyol formulation and the isocyanate components at
approximate 20.degree. C. in the presence of the physical blowing
agent and injecting into a closed mold cavity which has an internal
air pressure below atmospheric pressure and under such conditions
that the polyols and polyisocyanate(s) react and cure.
[0129] It is usually not necessary to pre-heat the components or
apply heat to the reaction mixture in order to obtain a good
reaction and cure but heating may be used if desired. However, the
in-mold cavity is generally heated, preferably at 30 to 60.degree.
C., more preferably from 40 to 50.degree. C., to provide suitable
surface cure and efficient adhesion of the foam to the plastic
and/or metal liner.
[0130] The mold has an internal pressure, according to this
invention, which is sufficient to provide a good filling with the
used foaming composition. The internal mold pressure can vary
between 300 and 950 mbar, preferably between 400 and 950 mbar, and
more preferably from 500 to 900 mbar. The internal air pressure is
controlled in such that the moulded density can be obtained with
the right balance of filling vs. gelling time.
[0131] Alternatively, applying a vacuum just after the injection of
the foaming composition may be done, but this is not the preferred
option. By injection under reduced in-mold pressure, or applying
vacuum just after injection, allows the foaming composition to flow
and fill the cavity quicker and more efficiently than with the
conventional process at atmospheric pressure, hence more viscous,
or more reactive, foam formulations can be used with the present
invention. Techniques for applying a partial vacuum to a mold
cavity are known in the art, see for example U.S. Pat. Nos.
5,454,582 and 5,972,260. Prior to injection under reduced pressure
in the closed mold cavity, the cavity may be purged with an inert
gas, such as nitrogen, for safety reasons when flammable blowing
agents are used in the foam formulation.
[0132] The molded density of the foam is generally from 30 to 75
kg/m.sup.3, preferably from 35 to 70 kg/m.sup.3, more preferably
from 35 to 65 kg/m.sup.3. To obtain the foams within the desired
density range under the partial vacuum employed and to assure the
entire mold cavity is properly filled, the mold is generally filled
to a packing factor of greater than 1.03 and is not higher than
1.9. Preferably the packing factor is set from 1.06 to 1.6 and more
preferably from 1.1 to 1.5.
[0133] Advantageously, the polyisocyanurate foams prepared in the
present invention may exhibit improved flame retardant behavior
when compared with conventional foams produced at similar density
using conventional formulations and conventional process done at
atmospheric pressure.
[0134] As used herein, the term "improved flame retardant behavior"
refers to the capability of the foam to have a flame height of not
higher than 15 centimeters when tested according to EN ISO 11925/2.
In certain embodiments the invention may be useful in satisfying
reaction-to-fire requirements of building products based on new
Euroclasses regulations (European Standard EN 13501).
[0135] The polyisocyanurate sandwich panels produced from the
process of the present invention are preferably used in the
assembly of structures for cold storage and transportation, such as
walk in coolers, refrigerated trucks, refrigerated rail cars,
etc.
[0136] The following examples are given to illustrate the invention
and should not be interpreted as limiting in anyway.
[0137] Unless specific, values in the working examples are parts by
weight. A description of the raw materials used in the examples is
as follows:
Polyol 1 is an aromatic polyester polyol; hydroxyl number 215 based
on 31.5% TPA (terephthalic acid) 8.5% DEG (diethylene glycol) and
60% PEG200 (polyethylene glycol, 200 MW). Polyol 2 is an aromatic
resin-initiated oxypropylene-oxyethylene polyether polyol; hydroxyl
number approximately 200, average functionality of about 3.3; where
the resin is a condensate of phenol and formaldehyde. Polyol 3 is a
sucrose/glycerine initiated polyether polyol, with a functionality
of about 7, equivalent weight about 200, and hydroxyl number of
280, available from The Dow Chemical Company under the tradename
VORANOL.TM. 280. Polyol 4 is a glycerol-initiated
polyoxyethylene/polyoxypropylene polyether polyol; hydroxyl number
32-35; 1,675 equivalent weight; available from The Dow Chemical
Company as VORANOL.TM. CP-1421 Additive 1 Dimethyl adipate
Flame Retardant 1 (FR 1) Triethyl Phosphate (TEP)
[0138] Flame Retardant 2 (FR 2) Diethyl ethyl phosphonate
(DEEP)
Flame Retardant 3 (FR 3) Tris(chloroisopropyl)phosphate (TCPP)
[0139] Surfactant DABCO.TM. DC-5598, silicone surfactant; available
from Air Products Catalyst 1 Potassium acetate (32%) in glycol;
Dabco K2097, available from Air Products Catalyst 2
N,N-dimethylcyclohexyl amine (DMCHA) Isocyanate VORANATE.TM. M-220
(polymethylene polyphenylisocyanate with a total isocyanate content
of about 31% and an average functionality of 2.7).
[0140] All foams are made using a high pressure Cannon machine
equipped with a mix-head attached to the mold injection hole, in a
laboratory where the atmospheric pressure is about 1,000 mbar (or
hPa). Premix (polyol formulation plus blowing agent) and isocyanate
are impinged in the mixing head at a pressure of 90 bars or higher,
and injected in the mold. The mold is made of aluminum with
dimensions of 194.times.35.times.6 cm and has no venting to allow
the creation of an under pressure in the mold during foaming,
therefore there is no extrusion of the foaming mass. The internal
pressure of the mold is controlled via a pipe connected to a 500
liter buffer tank that is connected to a medium capacity vacuum
pump (1500 l/min). The vacuum in the buffer tank, and thus the in
mold air pressure, is maintained with control valves. The foams
produced in this mold can be used to measure molded density,
density distribution, compression strength, thermal conductivity
and reaction-to-fire. The temperature of the mold is about
50.degree. C. The release agent applied to the mold is ACMOS
37-7900, supplied from Acmos.
Cream Time is the time lapse in seconds from the beginning of the
mixing process until a visual change of the reactants (color change
and/or start of rise) occurs Gel Time is the lapse of time in
seconds from the beginning of the mixing process until a string can
be pulled from the rising foam using a probe like a tongue
depressor. Free Rise Density (FRD) in kg/m.sup.3 is the density
measured from a 100.times.100.times.100 mm block obtained from the
center of a free-rising foam (at ambient air pressure) produced
from a total system formulation weight of 200 grams or more. FRD is
reported in kg/m.sup.3. Minimum Filling Density (MFD) is the
density determined from the minimum weight needed to fill the mold
completely (packing factor=0%) and the volume of this mold. MFD is
reported in kg/m.sup.3. Flow Index is the ratio of the minimum fill
density/free rise density, the latter measured at atmospheric
pressure. Average density deviation is a number calculated on the
base of the variation of density measured on different specimens
(minimum of 17 samples) 35.times.10.times.6 cm cut from molded
panel 194.times.35.times.6 cm). Applied Density is the density
determined from the injected weight in the in-mold cavity and the
volume of this in-mold cavity. Applied density is reported in
kg/m.sup.3. Foam compressive strength in kPa is measured
perpendicular to the main faces of the molded panel, according to
EN ISO 844 (2009). Thermal Conductivity at 10.degree. C. in
mWm.degree. K is measured, heat-flow perpendicular to the main
faces of the molded panel), according to European standard EN12667.
Flame height in cms is measured according EN ISO 11925-2. Total
heat release in MJ/m.sup.2; peak of heat release in kW/m.sup.2; and
total smoke production in m.sup.2/m.sup.2 are measured using a cone
calorimeter equipment according to (ISO-5660-1).
EXAMPLES
[0141] Halogen flame retardant based formulations were produced
according to the components in Table 1.
TABLE-US-00001 TABLE 1 System No. 1 2 3 4 Polyol 1 25.43 25.43
25.43 25.43 Polyol 2 22.1 22.1 22.1 22.1 Polyol 3 Polyol 4 Additive
1 FR1 FR2 8.51 8.51 8.51 8.51 FR3 33.81 33.81 33.81 33.81
Surfactant 4 4 4 4 Catalyst 1 2.05 2.05 2.05 2.05 Catalyst 2 0.25
0.25 0.25 0.25 Formic acid 3.4 3.4 3.4 3.4 water 0.45 0.45 0.45
0.45 Total 100 100 100 100 Index 400 300 400 300 c/i-pentane* 6 6
10 10 Isocyanate 216 162 216 162 *Is a 70/30 wt/wt blend of
cyclo-/isopentane.
The polyol formulations/blowing agents were mixed with the
isocyanate and injected into a mold at ambient pressure of about
1000 mbar to produce standard foam (Comparative Examples 1-4) and
molds maintained at 900 mbar (Examples 1-4). The properties of the
produced foams are shown in Table 2. Formulations 3 and 4
(comparative examples 3 and 4) utilize a higher level of
hydrocarbon blowing agent to obtain densities comparable to those
obtained in Examples 1 and 2.
TABLE-US-00002 TABLE 2 System 1 System 2 System 3 System 4 Comp Ex
1 Ex 1 Comp Ex 2 Ex 2 Comp Ex 3 Comp Ex 4 Mold pressure (bar) 1 0.9
1 0.9 1 1 Cream Time (s) 7 4 10 7 Gel Time (s) 64 51 90 60 Free
Rise Density (kg/m.sup.3) 33.2 27.5 30.5 26.5 MFD (g/l) 46.5 41.05
39.3 35.05 41.93 37.8 Flow Index 1.401 1.236 1.429 1.275 1.375
1.426 Applied Density (g/l) 51.96 43.20 45.76 39.14 46.80 41.60
Average Density Deviation 1.248 0.811 0.938 0.568 0.805 n.d.
Compressive Strength (kPa) 287 181 209 141 205 134 EN ISO 11925-2,
flame height (cm) 6 5 8 6 11 12 ISO 5660-1, Peak of heat release
86.7 81.0 76.1 68.1 87.3 n.d. (kW/m.sup.2)
Halogen-free flame retardant formulations were produced according
to the components in Table 3.
TABLE-US-00003 TABLE 3 System No. 5 6 7 8 9 10 Polyol 1 48.3 49.2
49.2 49.2 23 23 Polyol 2 20.6 20.6 20.6 20.6 10.6 10.75 Polyol 3 35
35 Polyol 4 7 Additive 1 7 FR 1 15 15 15 15 15 FR 2 8.5 8.5 8.5 8.5
8.5 8.5 FR 3 Surfactant 4 4 4 4 4 4 Catalyst 1 1.1 1.1 0.9 1.2 1.25
1 Catalyst 2 0.2 0.2 0.2 0.2 0.35 0.25 Formic acid 1.8 1.1 0.5 1.8
1.8 1.8 water 0.5 0.3 0.2 0.5 0.5 0.5 Total 100 100 99.1 100 100
99.8 Index 350 350 350 350 350 230 c/i-pentane 6.5 10 12.5 6.8 7.5
5 % mols HC/tot. 57.4 77.4 88.8 50.9 60.9 64.2 mmoles B.A
Isocyanate (parts by 191 168 149 191 213 139 weight)
The polyol formulations/blowing agents were mixed with the
isocyanate and injected into a mold at ambient pressure of about
1000 mbar to produce standard foam (Comparative Example 5 and
Comparative Example 8) and molds maintained at 900 mbar (Examples
3-6 and Comparative Examples 10 and 12). Comparative examples 6, 7,
9, 11 are produced by pouring the reactive mixture into a bag and
measuring reactivity and FRD.
TABLE-US-00004 TABLE 4 System 5 System 6 System 7 System 8 System 9
System 10 Comp Comp Comp Comp Comp Comp Comp Comp Ex 5 Ex 3 Ex 6 Ex
4 Ex 7 Ex 5 Ex 8 Ex 6 Ex 9 Ex 10 Ex 11 Ex 12 Mold pressure 1 0.9 1
0.9 1 0.9 1 0.9 1 0.9 1 0.9 (absolute bar) Cream Time (s) 11 10 10
9 12 8 Gel Time (s) 75 60 63 74 97 78 Free Rise Density 38.55 34.82
33.8 35.2 39.06 35.3 (kg/m.sup.3) MFD 50.degree. C. (g/l) 60.3
54.28 n.d. 49.26 n.d. 50.47 55.2 51.15 n.d. 51.05 n.d. 50.48 Flow
Index 50.degree. C. 1.56 1.408 n.d. 1.41 n.d. 1.49 1.57 1.45 n.d.
1.31 n.d. 1.43 Applied Density n.d. 57 51.7 53 58.7 53.7 53.6 53
(g/l) Average Density 0.655 0.62 0.63 0.56 0.63 0.63 Deviation
Compressive n.d. 228 136 129 174 196 184 172 Strength (kPa) Thermal
22.31 22.4 21.62 21.65 22.96 23.12 Conductivity 10.degree. C. (mW m
.degree. K) EN ISO 11925-2, 5.5 4 6.5 7.5 5 8 10 flame height (cm)
ISO-5601-1, Total n.d. 15.7 14.5 16 17.5 14.3 15.6 n.d. heat
release (MJ/m.sup.2) ISO 5660-1, Total n.d. 338 225 243 331 206 394
n.d. smoke production (m.sup.2/m.sup.2)
TABLE-US-00005 TABLE 5 System 5 Ex 3 Ex 3a Ex 3b Ex 3c Ex 3d Brett
Mold Pressure at 0.9 0.8 0.8 0.7 0.7 50.degree. C. (bar) Applied
Density (g/l) 57 57.7 52 57.3 52.1 Average Density Deviation 0.655
0.4 0.43 0.39 0.5 Compressive Strength (kPa) 228 279.3 194.2 274.7
224.6 Thermal Conductivity 10.degree. 22.31 22.15 22.64 23.24 22.7
C. (mW/m .degree. K) Aesthetics good Very good Very good good good
filling OK OK OK OK OK
[0142] To determine the versatility of the present process, System
5 is used to produce foams at various pressures to determine the
applied density and to visually observe the aesthetic properties of
the produced insulated panels. The obtained results are given in
Table 5 above. Aesthetics refers to visual observation of quantity
and size of the voids.
[0143] The results in Table 2 and 4 show that the foams of the
present invention (Examples 1-6) meet the requirements for
reaction-to-fire Euroclass E according to EN ISO 11925-2 standard
(flame height of less than 15 cm) and exhibit a good reaction
profile.
[0144] As can be seen from Examples 1 and 2 in Table 2, the foams
of the present invention (molded at 900 mbar) show reduced flame
height properties as compared to foams of the same formulation,
produced under standard pressure conditions. For instance, the
flame height of system 1, molded at 1000 mbar is 6 cm, whereas the
flame height of system 1 molded at 900 mbar is only 5 cm.
[0145] Examples 1 and 2 also demonstrate that peak of the heat
release produced by the foams molded at 900 mbar is lower than that
of the foams molded at 1000 mbar.
[0146] As can be seen from Table 4, the halogen-free formulation of
Example 3 and 6 molded at 900 mbar, also has significantly improved
fire properties than the foam of the same formulation molded at
1000 mbar. The 10 percent reduction in mold air pressure leads,
together with the reduced applied densities, to a reduction in EN
ISO 11925-2 flame height, in a reduction of total heat release, and
a significant reduction in the total smoke produced.
[0147] System 9 and 10 do not fall within the scope of the present
invention. System 9 does not comprise a polyol mixture that is at
least 35 weight percent aromatic polyester polyol. System 10
similarly does not comprise a polyol mixture that is at least 35
weight percent aromatic polyester polyol and also does not have an
isocyanate index of greater than 250
[0148] As can be seen from Table 4, the systems of the present
invention (i.e., examples 3-6 comprising a polyol mixture made up
of at least 35 weight percent aromatic polyester polyol and having
an isocyanate index of greater than 250), result in foams having
improved fire properties over the foams of systems 9 and 10, when
molded at 900 mbar. For example, the flame height of system 10,
molded at 900 mbar is 10 cm, whereas the flame height of examples
3-6, molded at 900 mbar are all less or equal than 7.5 cm. In
addition the total smoke produced by system 9, molded at 900 mbar,
is significantly greater that the total smoke produced by any of
examples 3-6 when molded at 900 mbar.
[0149] As can be seen from Table 4 and 5 the method of the
invention allows the production of PIR foams characterized by
excellent thermal insulation. Moreover, as shown in Table 5 the
method allows to easily control the cavity filling and the material
distribution (density deviation), by adjusting the absolute
pressure in the mold cavity.
[0150] Whilst the invention has been described with reference to a
preferred embodiment, it will be appreciated that various
modifications are possible within the scope of the invention.
[0151] In this specification, unless expressly otherwise indicated,
the word `or` is used in the sense of an operator that returns a
true value when either or both of the stated conditions is met, as
opposed to the operator `exclusive or` which requires that only one
of the conditions is met. The word `comprising` is used in the
sense of `including` rather than in to mean `consisting of`. All
prior teachings acknowledged above are hereby incorporated by
reference. No acknowledgement of any prior published document
herein should be taken to be an admission or representation that
the teaching thereof was common general knowledge in Australia or
elsewhere at the date hereof.
* * * * *