CA1137698A - Urethane foams utilizing hydrocarbon propellants - Google Patents
Urethane foams utilizing hydrocarbon propellantsInfo
- Publication number
- CA1137698A CA1137698A CA000354307A CA354307A CA1137698A CA 1137698 A CA1137698 A CA 1137698A CA 000354307 A CA000354307 A CA 000354307A CA 354307 A CA354307 A CA 354307A CA 1137698 A CA1137698 A CA 1137698A
- Authority
- CA
- Canada
- Prior art keywords
- prepolymer
- pressurized container
- propellant
- polyols
- viscosity
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
URETHANE FOAMS UTILIZING
HYDROCARBON PROPELLANTS
ABSTRACT
A method of preparing a one component moisture cure polyurethane foam which is suitable for dispensing through an aerosol or pressurized container. The method utilizes a prepolymer having a viscosity of 5,000 to 50,000 centi-poises, a catalyst and an unhalogenated hydrocarbon propellant whose boiling point is not greater than 10°C.
HYDROCARBON PROPELLANTS
ABSTRACT
A method of preparing a one component moisture cure polyurethane foam which is suitable for dispensing through an aerosol or pressurized container. The method utilizes a prepolymer having a viscosity of 5,000 to 50,000 centi-poises, a catalyst and an unhalogenated hydrocarbon propellant whose boiling point is not greater than 10°C.
Description
~3*6~
I. FIELD OF THE INVENTION
The present invention is directed to a urethane foam system which utilizes an unhalogenated hydrocarbon propellant.
Specifically, the invention is concerned with a one component moisture cure system which is suitable for use in an aerosol or pressurized container.
II. DESCRIPTION OF TEIE PRIOR ART
Polyurethane foam plastics are presently enjoying wide use as a building insulation material. They demonstrate excep-tional utili~y as sealants and insulation. This is due to theimperviousness of the foam to the passage of air through its structure. Urethane foams also show usefulness in the filling of gaps in structures, holes in walks etc.
Traditionally polyurethane plastics have been prepared by a multi-component process. Usually they are formed by the reaction of a hydroxy terminated polyether or polyester or other active hydrogen compound and a polyisocyanate in the presence of a blowing agent and a catalyst. In such systems the reaction materials and conditions must be carefully con-trolled since they involve a highly exothermic reaction. There-fore, it has been commercially impractical to produce a foam dispensing system using a conventional multi-component process specifically for use by non professionals or that does not re-quire significant expertise in the preparation of the foam.
The elaborate preparation requirements of multi-component foams render them especially unsuitable for small job applications.
In recent years one component moisture cure urethane foams that can be dispensed by aerosol or pressurized con-tainers have been developed. These products are formed from ;;f, ~3~
polyurethane prepolymers which are the reaction products of organic polyols and organic polyisocyanates and utilize chlo-rofluorocarbons as propellants. These systems can be used in many situations that are unsuitable for multi-component pro-cesses since they are one component and do not involve a per-ceivable exothermic reaction. They are distinguished from "one shot" systems which do not utilize a prepolymer and "quasi-prepolymer" or "prepolymer" process systems which re-quire rapid mixing of a portion of the components prior to dispensing and polymerizillg.
A typical method of producing a one component moisture cure foam product is discussed in U.S. Patent 3,830,760 to Bengtson. Products produced by this proces suffer dèficien---cies due to the use of chlorofluorocarbonsl such as dichloro-difluormethane and trichlorofluoromethane (commonly known as FREON * 12 and FREON * 11 respectively) as a propellant First, the use of chlorofluorocarbons is environmentally damaging ~ $e they are believed to destroy the ozone in the stratosphere.
Second, the products are expensive due to the high cost of chlorofluorocarbons. And third, the products have only a limited shelf life of nine to fourteen months.
In order for the foam prepolymer and catalyst of a one component moisture cure system to be dispersed from an aerosol container it must have a viscosity of approximately 2,000 centi-poise. Conventionally, the prepolymers viscosity is appro~i-mately 60,000 centipoise and therefore is substantially reduced by the solvent nature of the chlorofluorocarbon propellant.
Chloroflurocarbons have been found to have a very pronounced solvent effect on these foam L~repol~vmers. Accardingly, other pneumatogens have been considered unsuitable for use with one component moisture cure systems.
..~.~,.
~ ~376~3~
The present invention is advantageous in that it provides a one-component polyurethane product which is a moisture curing foam that can be packaged in a pressurized can or aerosol container both for professional and non-professional use.
* Trade Mark - 2a -~"~
~3736~
T h e foam is ~nvironmental.ly safe since it does not utili.ze either FREO~ ll or 12 as a propellant, very stable and has a long sheif life.
~ .~ OF HE IN~ENTIO~
The present inveniion provides a method of producing a one component moisture cure polyurethane foam utilizing a isocya-nate terminated prepolymer having a viscosity of from 5,000 to 50,000 centipoise, a catalyst and an unhalogenated hydrocarbon propellant whose boil.ing point or initial boiling point is no greater than 10C at atmospheric perssure. The invention also provides a pressurized container containing a one cornponent moisture cure foam comprising a isocyanate terminated prepolymer having a viscosity of from 5,000 to 50,000 centipoise, a cata-lyst and an unhalogenated hydrocarbon propella.nt whose boiliIIg pOillt or initial boiling point is no greater than lO~C at atmos-pheric pressure~
DESC~IPTION OF THE PREFE~ED E~ODIMæNTS
___ __ . _ The pre~ent invention is directed to a method of makin~
a one componellt moisture cure -~olyureth2ne foam that is suitable for dispensina, from a pressurized or aerosol container. In particular, the invention is direc-ted to a foam which can be dispensed from an aerosol container in an environmentally safe manner. The components for producing the foam comprise a poly~
uxethane prepolymer, a catalyst and an unhalogenated hydrocarbon propellant whose bolling point or initial boiling point is less than 10C at atmospheric pressure~
The prepol.ymer is comprised of the reaction product of an isocyanate and a polyol which produces an isocyanate termin.tted prepolymer, excess unreacted isocyanate but, no residual hydroxyl.
Surf~ctants and flame retardants are preferably incorporated into the prepclymer~ It has been found that if the viscosity OI t"le prepolymer is between 5,000 centipoise and 50,000 centipoise, preferably between 17,000 and 23,000 centipoise or approximately ~ ~A~ C~ nh~ a~nated h~drocar~on can be used as a 376~8 propellant in a one component moisture cure polyuretnane foam system.
It is important that the prepolymer be 1,near or sub-stantially linear. Therefore, it is preferred that the isocya-nates and polyols be difunctional to trifunctional and that the specific prepolymers be comprised of isocyanates and polyols that are inversely related in futlctionality. That is, i~ the polyol is triunctional (three hydroxy groups per molecule~ the isocya-nate should be difunctional (two NCO groups per molecule). If the polyol is difunctional, the isocyanate shouid be trifunctional.
The latter co~blnation of a difunctional polyol and a trifunctional isocyanate is preferred since the combination has been found to best prevent foam from becoming brittle and is most suitable for use in prepaxing prepolymers whose viscosity is between 5~OGO
centipoise and 50,000 centipoise and that when iurther diluted with unhalogenated h~drocarbon propellarlts are dispersible from pressurized containers.
Ihe averaye functionality o'~ the polyol and isocyanate reactants should be bet:ween 2 and 2 :1/2, preferably 2 1/2. For example: Ifunctionality of the reactants is in parentheses) ~a) isocyanate (3) ~ polyol (2) = 2 1/2 avearae (b) isocyanate (2) + polyol (3) = 2 1/2 average (c) isocyanate (2) + polyol t2) = 2 average Utilizing these reactant combinations allows the formation of substantially linear prepolymers which permits an increasing of the free isocyanate levels in the prepolymer without pro-ducing hrit-tle foams. The increasing of the amount of free isocyanate reduces the viscosity of the prepolymer resin and increases the shelf life of the containerized reactants. High levels of free isocyanate are not feasible in systems containing unhalogenated hydrocarbon propellants since a prepolymer viscosity of approximately 60,000 centipoise is necessary for the dispen-sing of the reactants and to achieve foam stability in such systems.
This is because it has been found that chlorofluorocarbons reduce the viscosity of the reactants to a far greater extent than lln-halogenated hydrocarbons.
Isocvanates suitable for the practice of the invention 37G~
are aromatic and aliphatic polyisocyanates having two to -three reactive isocyanate groups. Examples of suitable polyiso-cyanates are found in U.S. Patent 3,072,582 to Frost and U.S.
Patent 3,830,760 to sengStOn. Examples of such compositions are tolylene diisocyanate ~TDI), especially the 2, 4 and 2, 6 isomers and mixtures thereof. The preferred isocyanate which is safer to handle due to its low vapor pressure is crude poly-meric diphenylmethane diisocyanate (MDI). r~O achieve the afore-mentioned advantages of high free NCO levels in the prepolymer, the free prepolmer NCO should be between 8 and 19% by weight of the prepolymer, preferably 12 to 15% or optimally 14.~%.
r~his compares to free prepolymer NCO levels of 5 to 7% in systems using chlorofluorinated prepellants. Mixtures of poly~
isocyanates can be used.
Organic polyols which are normally formatives of urethane compositions may be utilized to obtain the foams of the inven-tion. Both polyester and polyether polyols with molecular weights of from 300 to 2,500 may be used. Discussions of such pol~ols are found in U.S. Patent 3,830,760 to Bengston. In particular polyether polyols may be preprepared by the reaction of an alkylene oxides with compounds containing a plurality of active hydrogen atoms. The polyols may also be polyesters which are derived from polycarboxylic acids and polyhydric alcohols. soth the polyether or polyester polyol may be mi~-tures. The preferred polyol is a mix-ture of 775 M.W. oxypropy-lated glycol which is the reaction product of propylene glycol and propylene oxide, and a 2000 M.W. polyol which is the reaction product of propylene glycol, propylene oxide, and ethylene oxide.
The prepolymer may contain the standard polyurethane .~ r -- 5 ~
~37~ii~ !3 foam additives including flame retardants, stabili~ers, nucleating agents and cross linking agents. The preferred flame retardant is tris-2-chloroallyl phosphate which is a commonly used retardant in urethane foam products. It is critical that the prepolymer, including the additives, have a viscosity of between 5,000 and 50,000 centipoise, preferably between 17,000 and 23,000 centipoise or approximately 20,000 centipoise.
The foam compositions of the invention may also contain - Sa -~L37~9~3 .,. 6~--conventional catalysts and surfactants. The traditional cata-lysts are tertiary amines. Primary and secondary amlnes are not useful in moisture cure foam products since they will react wi~h the isocyanate and cause gellation. It may also be uscful to employ metal salts, particularly tin catalysts in the prac-tice of the invention~ The surfactants that are normally used in one-component moisture cure urethane foam compositions can be incorporated into the prepolymer. These include organosilicon polymers, prefexrably siloxane-oxyalkylene copolymer.
The propellant is an unhalogenated hydrocarbon whose boil~
ing point or initial boiling point is no greater than 10C at atmospheric pressure (76~ ~lmHg). Not only is the propellan~ en-vironmentally safe bu~ it also produces a oam which has commer-cially acceptable cell sizel foam stability, bubble uniormity, and foam properties. The particular unhalogenated hydrocarbon pro-pellant utilized is not critical, howeverl either propane or a mixture of isobutane or n-butane with propane is preferable. If the unhalogenated hydrocarhon propellant is a mixture then the initial boiling point of the mixture must be less than 10C at atmospheri- pressure. The choice of propellant is dependent upon the strenqth of the contain~ em~loyea. For instance, pro--pane due to its high vapor pressure at room ter;;perature is not suitable for use in a conventional 2Q (180 psig minimum distor-tion; 270 psig minimum b~lrst) strength can.
An important characteristic of the propellant is that i~ does not depend upon exothermic heat of xeaction to expel it quickly from the prepolymer film rollowing di~pensing of the prepolymer from the container, unlike t-e higher boiling blowing agents of the multi-component exothermic systems of the prior art. A foam will not form if the propellant does not immediately boil out of the prepolymer to form the foam cells.
Any propellant retained by the prepolymer prevents a foam from setting up since the retained propellant reduces the viscosity of the prepolymer too low fox stable foam formation. Therefore the propellant must have a boiling point or initial b~iling point lower than 1~C. If the boiling point or initial boi]ing ~3'76 -- 7~
point of the propellant is greater than 10C in a one-componellt moisture cure system it will remain as a liquid dissolved in the prepo1~ner at atmospheric pressure and room temperatl!re an~
thereby prevent ~he formation of a stable foam~
It may be desirable to utilize other gases with unh~lo-genated hydroca~bon gases to form che propell~nt. For example:
rela~ively small amounts (less than 50~ by volume) of chloro-carbon or chlorofluorocarbon gases can be used to reduce -the flamability of the propellant. Significant amounts of these gases diminish the ad~antages of the invention. In for-mulating a propellant mixture it is important that the propellant not be a strong solvent of the prepolymer. If the prvpellant totally solubilizes the prepolyrner there will be insufficient nucleating ma-'erial to form a foam when the mixture is dlspensed.
A porl:ion of the prepolymer must be insoluble in the propellant and present as emulsion droplets. The emulsion droplets act as a nucleating agent to form the foam cel].s. Sirce the viscosity of th~ prepol~ner is relatively low, it is easily totally solu-bilized by strong solvents. Therefore, in formulating a pro-pellant mi~ture a lo~ overall hydxogen bonding capacity and Hildebrand solubility parameter is desirable. Unlike multi-component systems, a one component moisture cure system does not rely upon a highly exothermic reaction for the formation of the foam. The foarning of the prepolymer is effectuated by the release of pressure and not by ~aporization due to the heat of a reaction as in a multicomponent system. Accordingly, the higher the vapor pressure or lower the boiling point of the, propellant the better the foam produced since it evacuates from the prepolymer more quickly.
The preferable rnethod of producing the foam of the inven-tion is to mix the isocyanate, polyol, surfactant and fire retar-dant and heat in the absence of a catalyst to forr~ a prepoly~er.
The prepolymer and catalyst are then introduced into a container which is pressurized by the propellant. The size of the contair.er s not critical and both hand-held cans and large cornmercial n~ L~ ~kP ~r~ition~l method of re~ctin~
~76i9~3 the ingredients of the prepolymer with the catalyst in a batch process prior to introduction into a pressurized contalner and gassing can also be utilized. M;xing and reacting all of the materials within the dispensing container is also feasible. When this is done, it is important that provision be made for shaking the container and cooling it to remove the heat of reaction. The preferred method, of forming an uncatalyzed prepolymer, provides a stable system which can be stored for long periods prior to filling.
As previously noted, it is critical that the prepolymer or resin have a viscosity of 5,000 to 50,000 centipoise, pre-ferable 17,000 to 23,000 or approximately 20,000 centipoise. It is also important that the boiling point of the propellant be less than 10C. The quantity of propellant can also be important due to the solvent nature of the propellant and is preferably between 10% and 30% by weight so that the viscosity of the foam mixture contained within a dispensing container will be between 100 to 2,000 centipoise. This is a similar viscosity as those one component foams whose prepolymer viscosity is approximately 60,000 centipoise but whose propellant is a chlorofluorocarbon.
An unhalogenated hydrocarbon has been found to reduce tne viscosi-ty of a prepolymer substantially less than a chlorofluorinated propellant. Therefore, chlorofluorinated propellants are unsuit-able for use with the prepolymers of the present invention since they would reduce the viscosity to levels below which they can form a foam product~ Also, the foam s~stems of the present in-vention have shelf lives of approximately two -years, which is significantly greater than the shelf life of the one component moisture cure systems of the prior art.
The following table illustrates the principles of the invention:
~37~
J~ rr~ W rr~ I crZ ~ H ~ZZ ~ ¦ ~J ~ .^Z
Z~Z ~ t.`t O _ O C I rt O Ul ,_. ~ Il~ ~~~ ~ rt -t C O ~D t~p~ tr pJ r o ~ . o ~,_ o v- H 3 c r~ X~ 1-- r- ~ 15 :~ U 'a 3 ~ z o o ~ ~D C~
r~- Hl ¦ I t ~ rt tD u) ~D g ~ a ~. X -~ . ~ rt ~D
i- ~t ~ pJ~D rt iD ~ rt ~ i~ ~ ~, I R~ Z a 3 ~D i I_~ C P~ u~ ~ ~ R~ 3 tD :~, . O j_ O
tD tD H) :~, j_Z C~ ~- C ~D rt tD . I ~r ~D 1~
(D i~~ 1_. ~J. ~ r, ~D r~ O l o I ~~ '~, rt ~ ' rt I H ' r l ~ (D ~ '~ C ¦ t '-- tD
(D I ~Z ~ l l tD I_ ~ c~
S?~ C ¦ ~ ~ ~ x ~ o I ra ¦ Z_ 1 3 (D ~ ~ ~ O ~ tD ~ O ~ ~t ~D
~ W~
~ ~ ~ ~ ¦ _ - ~tt t-- PROPELTZAI~;Z'T E~LE~
tD I x l X o I x tll I tn I ¦ ~ 1 ¦ o ~ 5 0~ 5 0 vol . /vol .
;~ - 1- 1 1 1~P 111~J~ I I ~ 1w 10 10 1~ I ProE)ar~e/isobutane I I l I I 1'~ 1 1~ 1 ul lo 1~ Iw 1~ 1 ~ I
X X t~ ~ t~ ~t O ~ O ~ ~ i;~ ~C ~ U~ ~ 50~50 vol./vol.
~ 1' ' ~ 1- . 1 1 ~ I I I I ~ W 1 1 1 ~ I Propane/n-bu-tant, ;~ l`q It~ X 13 1 ~ ~ OO~o ProI~al;e I I I I I I I I I ~ 10 lo I I I I I I I o 1 l 1 1 I~n lo lo lw ~n ¦ ~ ~ ¦ ~ h~ o ; 10 Il' O I 1~ 1 o I I lo I ~o 1~ IUl 5 ~ ~ o ~tD ~ 00% isobutarle I I l I I I o I 1 1 l IU` I" I IW I'J` I ' ~
1 3 u~ I t~ ~ 0 1 ItD ~ ¦x I I ItD 1~ P' 1~ ¦ IU~ !, 1~ ¦, 1 1 1~ -- IU ¦ 30/70 vol ./vol.
~? ~ It 1- 1 o IU~ w ¦o lo ~ Propa~-le/isobl~tan~
I I I I I I ~ o lo lw ~
Ix o 1~ t~ 13 ¦ O Ul ~ c lo ~0 ~ o~J70 Vc~ vtJl.
~ 1 ' ~ w ¦ ¦ ¦~ ¦ ~ ¦ Prt~pallefiso~utane Ix tn ILq 1~ t~ 10 O ¦? ¦~ ~ ¦ ~ U' ¦ 40/60 vol./vol.
¦- ¦ ¦~o ¦ I ¦o ¦ I ¦~ ¦o 1o 1 ¦~ ¦ ~ ¦ Propane/isobutane l~ tn It~ lr~ ~ 3 1 o I 1~
I~ o ¦? ~ ~ I I 1 1 1 1~ 1~ 1~ ¦ U ¦ 40~G0 vc~ ol.
1- ~ 1 1 i- 1~ 1- O 1O 1~ 1~ 11 1~ Iw lo 1O ~ Propane/n-butane I l I I l I I I 1~ o lo lw ~
I ~ t~ ¦t~ 1~ ¦t~ L~ 13~ ¦ ¦~ ~ ~ ¦ . 1 55~45 vol./vol.
1 1 ~ ~ lo ~ '?ropane/n-~utane ~D I I Ix lo Ix lr, Itn ~ O 1 ¦'' ¦~ 40/60 vol./vol.
In ~ I'J 1~ 10 IU~ 10 10 IW ~ PrOPane/iSObUtane tn ~ d I ~ ~x lo 1~- 10 lo 1~ 1 o I lo I I lo lo 1~
l O 1- IO ~ 10 IO ~ 1 . 11 1~ l00~ n-butane Lo L~ I ~ lo lo 1~ la' I a~ I
9_ 3~6~
Bubble Size: small-less than a 32nd of an inch -~edium-bet~Jeen 16th to 1/4 of an inch large-is between 1/4 to 1 inch oam Stability: poor-unusable since it is completely flat fair-unusable since it is substantially flat good-sags slightly excellent--does nGt sag after rising Density: low-less than 25 g/l medium~between 25 g/l and 5~ g/l high-greater than 50 g/' ertical hang up: poor-all of product drips off of ceiling or wall fair-mlos-t of p~oduct remains on ceiling or wall excellent-all of product xemains on ceiling or wall Shelf life: air to poor-approximately one year excellent-approximately two years Tack free and cure time: slow-l to 3 hours tack free; 24+ hours cure medium-20 to 60 minutes tack free, 12 to 24 hours cure very fast-less than 10 minutes tack free;
I. FIELD OF THE INVENTION
The present invention is directed to a urethane foam system which utilizes an unhalogenated hydrocarbon propellant.
Specifically, the invention is concerned with a one component moisture cure system which is suitable for use in an aerosol or pressurized container.
II. DESCRIPTION OF TEIE PRIOR ART
Polyurethane foam plastics are presently enjoying wide use as a building insulation material. They demonstrate excep-tional utili~y as sealants and insulation. This is due to theimperviousness of the foam to the passage of air through its structure. Urethane foams also show usefulness in the filling of gaps in structures, holes in walks etc.
Traditionally polyurethane plastics have been prepared by a multi-component process. Usually they are formed by the reaction of a hydroxy terminated polyether or polyester or other active hydrogen compound and a polyisocyanate in the presence of a blowing agent and a catalyst. In such systems the reaction materials and conditions must be carefully con-trolled since they involve a highly exothermic reaction. There-fore, it has been commercially impractical to produce a foam dispensing system using a conventional multi-component process specifically for use by non professionals or that does not re-quire significant expertise in the preparation of the foam.
The elaborate preparation requirements of multi-component foams render them especially unsuitable for small job applications.
In recent years one component moisture cure urethane foams that can be dispensed by aerosol or pressurized con-tainers have been developed. These products are formed from ;;f, ~3~
polyurethane prepolymers which are the reaction products of organic polyols and organic polyisocyanates and utilize chlo-rofluorocarbons as propellants. These systems can be used in many situations that are unsuitable for multi-component pro-cesses since they are one component and do not involve a per-ceivable exothermic reaction. They are distinguished from "one shot" systems which do not utilize a prepolymer and "quasi-prepolymer" or "prepolymer" process systems which re-quire rapid mixing of a portion of the components prior to dispensing and polymerizillg.
A typical method of producing a one component moisture cure foam product is discussed in U.S. Patent 3,830,760 to Bengtson. Products produced by this proces suffer dèficien---cies due to the use of chlorofluorocarbonsl such as dichloro-difluormethane and trichlorofluoromethane (commonly known as FREON * 12 and FREON * 11 respectively) as a propellant First, the use of chlorofluorocarbons is environmentally damaging ~ $e they are believed to destroy the ozone in the stratosphere.
Second, the products are expensive due to the high cost of chlorofluorocarbons. And third, the products have only a limited shelf life of nine to fourteen months.
In order for the foam prepolymer and catalyst of a one component moisture cure system to be dispersed from an aerosol container it must have a viscosity of approximately 2,000 centi-poise. Conventionally, the prepolymers viscosity is appro~i-mately 60,000 centipoise and therefore is substantially reduced by the solvent nature of the chlorofluorocarbon propellant.
Chloroflurocarbons have been found to have a very pronounced solvent effect on these foam L~repol~vmers. Accardingly, other pneumatogens have been considered unsuitable for use with one component moisture cure systems.
..~.~,.
~ ~376~3~
The present invention is advantageous in that it provides a one-component polyurethane product which is a moisture curing foam that can be packaged in a pressurized can or aerosol container both for professional and non-professional use.
* Trade Mark - 2a -~"~
~3736~
T h e foam is ~nvironmental.ly safe since it does not utili.ze either FREO~ ll or 12 as a propellant, very stable and has a long sheif life.
~ .~ OF HE IN~ENTIO~
The present inveniion provides a method of producing a one component moisture cure polyurethane foam utilizing a isocya-nate terminated prepolymer having a viscosity of from 5,000 to 50,000 centipoise, a catalyst and an unhalogenated hydrocarbon propellant whose boil.ing point or initial boiling point is no greater than 10C at atmospheric perssure. The invention also provides a pressurized container containing a one cornponent moisture cure foam comprising a isocyanate terminated prepolymer having a viscosity of from 5,000 to 50,000 centipoise, a cata-lyst and an unhalogenated hydrocarbon propella.nt whose boiliIIg pOillt or initial boiling point is no greater than lO~C at atmos-pheric pressure~
DESC~IPTION OF THE PREFE~ED E~ODIMæNTS
___ __ . _ The pre~ent invention is directed to a method of makin~
a one componellt moisture cure -~olyureth2ne foam that is suitable for dispensina, from a pressurized or aerosol container. In particular, the invention is direc-ted to a foam which can be dispensed from an aerosol container in an environmentally safe manner. The components for producing the foam comprise a poly~
uxethane prepolymer, a catalyst and an unhalogenated hydrocarbon propellant whose bolling point or initial boiling point is less than 10C at atmospheric pressure~
The prepol.ymer is comprised of the reaction product of an isocyanate and a polyol which produces an isocyanate termin.tted prepolymer, excess unreacted isocyanate but, no residual hydroxyl.
Surf~ctants and flame retardants are preferably incorporated into the prepclymer~ It has been found that if the viscosity OI t"le prepolymer is between 5,000 centipoise and 50,000 centipoise, preferably between 17,000 and 23,000 centipoise or approximately ~ ~A~ C~ nh~ a~nated h~drocar~on can be used as a 376~8 propellant in a one component moisture cure polyuretnane foam system.
It is important that the prepolymer be 1,near or sub-stantially linear. Therefore, it is preferred that the isocya-nates and polyols be difunctional to trifunctional and that the specific prepolymers be comprised of isocyanates and polyols that are inversely related in futlctionality. That is, i~ the polyol is triunctional (three hydroxy groups per molecule~ the isocya-nate should be difunctional (two NCO groups per molecule). If the polyol is difunctional, the isocyanate shouid be trifunctional.
The latter co~blnation of a difunctional polyol and a trifunctional isocyanate is preferred since the combination has been found to best prevent foam from becoming brittle and is most suitable for use in prepaxing prepolymers whose viscosity is between 5~OGO
centipoise and 50,000 centipoise and that when iurther diluted with unhalogenated h~drocarbon propellarlts are dispersible from pressurized containers.
Ihe averaye functionality o'~ the polyol and isocyanate reactants should be bet:ween 2 and 2 :1/2, preferably 2 1/2. For example: Ifunctionality of the reactants is in parentheses) ~a) isocyanate (3) ~ polyol (2) = 2 1/2 avearae (b) isocyanate (2) + polyol (3) = 2 1/2 average (c) isocyanate (2) + polyol t2) = 2 average Utilizing these reactant combinations allows the formation of substantially linear prepolymers which permits an increasing of the free isocyanate levels in the prepolymer without pro-ducing hrit-tle foams. The increasing of the amount of free isocyanate reduces the viscosity of the prepolymer resin and increases the shelf life of the containerized reactants. High levels of free isocyanate are not feasible in systems containing unhalogenated hydrocarbon propellants since a prepolymer viscosity of approximately 60,000 centipoise is necessary for the dispen-sing of the reactants and to achieve foam stability in such systems.
This is because it has been found that chlorofluorocarbons reduce the viscosity of the reactants to a far greater extent than lln-halogenated hydrocarbons.
Isocvanates suitable for the practice of the invention 37G~
are aromatic and aliphatic polyisocyanates having two to -three reactive isocyanate groups. Examples of suitable polyiso-cyanates are found in U.S. Patent 3,072,582 to Frost and U.S.
Patent 3,830,760 to sengStOn. Examples of such compositions are tolylene diisocyanate ~TDI), especially the 2, 4 and 2, 6 isomers and mixtures thereof. The preferred isocyanate which is safer to handle due to its low vapor pressure is crude poly-meric diphenylmethane diisocyanate (MDI). r~O achieve the afore-mentioned advantages of high free NCO levels in the prepolymer, the free prepolmer NCO should be between 8 and 19% by weight of the prepolymer, preferably 12 to 15% or optimally 14.~%.
r~his compares to free prepolymer NCO levels of 5 to 7% in systems using chlorofluorinated prepellants. Mixtures of poly~
isocyanates can be used.
Organic polyols which are normally formatives of urethane compositions may be utilized to obtain the foams of the inven-tion. Both polyester and polyether polyols with molecular weights of from 300 to 2,500 may be used. Discussions of such pol~ols are found in U.S. Patent 3,830,760 to Bengston. In particular polyether polyols may be preprepared by the reaction of an alkylene oxides with compounds containing a plurality of active hydrogen atoms. The polyols may also be polyesters which are derived from polycarboxylic acids and polyhydric alcohols. soth the polyether or polyester polyol may be mi~-tures. The preferred polyol is a mix-ture of 775 M.W. oxypropy-lated glycol which is the reaction product of propylene glycol and propylene oxide, and a 2000 M.W. polyol which is the reaction product of propylene glycol, propylene oxide, and ethylene oxide.
The prepolymer may contain the standard polyurethane .~ r -- 5 ~
~37~ii~ !3 foam additives including flame retardants, stabili~ers, nucleating agents and cross linking agents. The preferred flame retardant is tris-2-chloroallyl phosphate which is a commonly used retardant in urethane foam products. It is critical that the prepolymer, including the additives, have a viscosity of between 5,000 and 50,000 centipoise, preferably between 17,000 and 23,000 centipoise or approximately 20,000 centipoise.
The foam compositions of the invention may also contain - Sa -~L37~9~3 .,. 6~--conventional catalysts and surfactants. The traditional cata-lysts are tertiary amines. Primary and secondary amlnes are not useful in moisture cure foam products since they will react wi~h the isocyanate and cause gellation. It may also be uscful to employ metal salts, particularly tin catalysts in the prac-tice of the invention~ The surfactants that are normally used in one-component moisture cure urethane foam compositions can be incorporated into the prepolymer. These include organosilicon polymers, prefexrably siloxane-oxyalkylene copolymer.
The propellant is an unhalogenated hydrocarbon whose boil~
ing point or initial boiling point is no greater than 10C at atmospheric pressure (76~ ~lmHg). Not only is the propellan~ en-vironmentally safe bu~ it also produces a oam which has commer-cially acceptable cell sizel foam stability, bubble uniormity, and foam properties. The particular unhalogenated hydrocarbon pro-pellant utilized is not critical, howeverl either propane or a mixture of isobutane or n-butane with propane is preferable. If the unhalogenated hydrocarhon propellant is a mixture then the initial boiling point of the mixture must be less than 10C at atmospheri- pressure. The choice of propellant is dependent upon the strenqth of the contain~ em~loyea. For instance, pro--pane due to its high vapor pressure at room ter;;perature is not suitable for use in a conventional 2Q (180 psig minimum distor-tion; 270 psig minimum b~lrst) strength can.
An important characteristic of the propellant is that i~ does not depend upon exothermic heat of xeaction to expel it quickly from the prepolymer film rollowing di~pensing of the prepolymer from the container, unlike t-e higher boiling blowing agents of the multi-component exothermic systems of the prior art. A foam will not form if the propellant does not immediately boil out of the prepolymer to form the foam cells.
Any propellant retained by the prepolymer prevents a foam from setting up since the retained propellant reduces the viscosity of the prepolymer too low fox stable foam formation. Therefore the propellant must have a boiling point or initial b~iling point lower than 1~C. If the boiling point or initial boi]ing ~3'76 -- 7~
point of the propellant is greater than 10C in a one-componellt moisture cure system it will remain as a liquid dissolved in the prepo1~ner at atmospheric pressure and room temperatl!re an~
thereby prevent ~he formation of a stable foam~
It may be desirable to utilize other gases with unh~lo-genated hydroca~bon gases to form che propell~nt. For example:
rela~ively small amounts (less than 50~ by volume) of chloro-carbon or chlorofluorocarbon gases can be used to reduce -the flamability of the propellant. Significant amounts of these gases diminish the ad~antages of the invention. In for-mulating a propellant mixture it is important that the propellant not be a strong solvent of the prepolymer. If the prvpellant totally solubilizes the prepolyrner there will be insufficient nucleating ma-'erial to form a foam when the mixture is dlspensed.
A porl:ion of the prepolymer must be insoluble in the propellant and present as emulsion droplets. The emulsion droplets act as a nucleating agent to form the foam cel].s. Sirce the viscosity of th~ prepol~ner is relatively low, it is easily totally solu-bilized by strong solvents. Therefore, in formulating a pro-pellant mi~ture a lo~ overall hydxogen bonding capacity and Hildebrand solubility parameter is desirable. Unlike multi-component systems, a one component moisture cure system does not rely upon a highly exothermic reaction for the formation of the foam. The foarning of the prepolymer is effectuated by the release of pressure and not by ~aporization due to the heat of a reaction as in a multicomponent system. Accordingly, the higher the vapor pressure or lower the boiling point of the, propellant the better the foam produced since it evacuates from the prepolymer more quickly.
The preferable rnethod of producing the foam of the inven-tion is to mix the isocyanate, polyol, surfactant and fire retar-dant and heat in the absence of a catalyst to forr~ a prepoly~er.
The prepolymer and catalyst are then introduced into a container which is pressurized by the propellant. The size of the contair.er s not critical and both hand-held cans and large cornmercial n~ L~ ~kP ~r~ition~l method of re~ctin~
~76i9~3 the ingredients of the prepolymer with the catalyst in a batch process prior to introduction into a pressurized contalner and gassing can also be utilized. M;xing and reacting all of the materials within the dispensing container is also feasible. When this is done, it is important that provision be made for shaking the container and cooling it to remove the heat of reaction. The preferred method, of forming an uncatalyzed prepolymer, provides a stable system which can be stored for long periods prior to filling.
As previously noted, it is critical that the prepolymer or resin have a viscosity of 5,000 to 50,000 centipoise, pre-ferable 17,000 to 23,000 or approximately 20,000 centipoise. It is also important that the boiling point of the propellant be less than 10C. The quantity of propellant can also be important due to the solvent nature of the propellant and is preferably between 10% and 30% by weight so that the viscosity of the foam mixture contained within a dispensing container will be between 100 to 2,000 centipoise. This is a similar viscosity as those one component foams whose prepolymer viscosity is approximately 60,000 centipoise but whose propellant is a chlorofluorocarbon.
An unhalogenated hydrocarbon has been found to reduce tne viscosi-ty of a prepolymer substantially less than a chlorofluorinated propellant. Therefore, chlorofluorinated propellants are unsuit-able for use with the prepolymers of the present invention since they would reduce the viscosity to levels below which they can form a foam product~ Also, the foam s~stems of the present in-vention have shelf lives of approximately two -years, which is significantly greater than the shelf life of the one component moisture cure systems of the prior art.
The following table illustrates the principles of the invention:
~37~
J~ rr~ W rr~ I crZ ~ H ~ZZ ~ ¦ ~J ~ .^Z
Z~Z ~ t.`t O _ O C I rt O Ul ,_. ~ Il~ ~~~ ~ rt -t C O ~D t~p~ tr pJ r o ~ . o ~,_ o v- H 3 c r~ X~ 1-- r- ~ 15 :~ U 'a 3 ~ z o o ~ ~D C~
r~- Hl ¦ I t ~ rt tD u) ~D g ~ a ~. X -~ . ~ rt ~D
i- ~t ~ pJ~D rt iD ~ rt ~ i~ ~ ~, I R~ Z a 3 ~D i I_~ C P~ u~ ~ ~ R~ 3 tD :~, . O j_ O
tD tD H) :~, j_Z C~ ~- C ~D rt tD . I ~r ~D 1~
(D i~~ 1_. ~J. ~ r, ~D r~ O l o I ~~ '~, rt ~ ' rt I H ' r l ~ (D ~ '~ C ¦ t '-- tD
(D I ~Z ~ l l tD I_ ~ c~
S?~ C ¦ ~ ~ ~ x ~ o I ra ¦ Z_ 1 3 (D ~ ~ ~ O ~ tD ~ O ~ ~t ~D
~ W~
~ ~ ~ ~ ¦ _ - ~tt t-- PROPELTZAI~;Z'T E~LE~
tD I x l X o I x tll I tn I ¦ ~ 1 ¦ o ~ 5 0~ 5 0 vol . /vol .
;~ - 1- 1 1 1~P 111~J~ I I ~ 1w 10 10 1~ I ProE)ar~e/isobutane I I l I I 1'~ 1 1~ 1 ul lo 1~ Iw 1~ 1 ~ I
X X t~ ~ t~ ~t O ~ O ~ ~ i;~ ~C ~ U~ ~ 50~50 vol./vol.
~ 1' ' ~ 1- . 1 1 ~ I I I I ~ W 1 1 1 ~ I Propane/n-bu-tant, ;~ l`q It~ X 13 1 ~ ~ OO~o ProI~al;e I I I I I I I I I ~ 10 lo I I I I I I I o 1 l 1 1 I~n lo lo lw ~n ¦ ~ ~ ¦ ~ h~ o ; 10 Il' O I 1~ 1 o I I lo I ~o 1~ IUl 5 ~ ~ o ~tD ~ 00% isobutarle I I l I I I o I 1 1 l IU` I" I IW I'J` I ' ~
1 3 u~ I t~ ~ 0 1 ItD ~ ¦x I I ItD 1~ P' 1~ ¦ IU~ !, 1~ ¦, 1 1 1~ -- IU ¦ 30/70 vol ./vol.
~? ~ It 1- 1 o IU~ w ¦o lo ~ Propa~-le/isobl~tan~
I I I I I I ~ o lo lw ~
Ix o 1~ t~ 13 ¦ O Ul ~ c lo ~0 ~ o~J70 Vc~ vtJl.
~ 1 ' ~ w ¦ ¦ ¦~ ¦ ~ ¦ Prt~pallefiso~utane Ix tn ILq 1~ t~ 10 O ¦? ¦~ ~ ¦ ~ U' ¦ 40/60 vol./vol.
¦- ¦ ¦~o ¦ I ¦o ¦ I ¦~ ¦o 1o 1 ¦~ ¦ ~ ¦ Propane/isobutane l~ tn It~ lr~ ~ 3 1 o I 1~
I~ o ¦? ~ ~ I I 1 1 1 1~ 1~ 1~ ¦ U ¦ 40~G0 vc~ ol.
1- ~ 1 1 i- 1~ 1- O 1O 1~ 1~ 11 1~ Iw lo 1O ~ Propane/n-butane I l I I l I I I 1~ o lo lw ~
I ~ t~ ¦t~ 1~ ¦t~ L~ 13~ ¦ ¦~ ~ ~ ¦ . 1 55~45 vol./vol.
1 1 ~ ~ lo ~ '?ropane/n-~utane ~D I I Ix lo Ix lr, Itn ~ O 1 ¦'' ¦~ 40/60 vol./vol.
In ~ I'J 1~ 10 IU~ 10 10 IW ~ PrOPane/iSObUtane tn ~ d I ~ ~x lo 1~- 10 lo 1~ 1 o I lo I I lo lo 1~
l O 1- IO ~ 10 IO ~ 1 . 11 1~ l00~ n-butane Lo L~ I ~ lo lo 1~ la' I a~ I
9_ 3~6~
Bubble Size: small-less than a 32nd of an inch -~edium-bet~Jeen 16th to 1/4 of an inch large-is between 1/4 to 1 inch oam Stability: poor-unusable since it is completely flat fair-unusable since it is substantially flat good-sags slightly excellent--does nGt sag after rising Density: low-less than 25 g/l medium~between 25 g/l and 5~ g/l high-greater than 50 g/' ertical hang up: poor-all of product drips off of ceiling or wall fair-mlos-t of p~oduct remains on ceiling or wall excellent-all of product xemains on ceiling or wall Shelf life: air to poor-approximately one year excellent-approximately two years Tack free and cure time: slow-l to 3 hours tack free; 24+ hours cure medium-20 to 60 minutes tack free, 12 to 24 hours cure very fast-less than 10 minutes tack free;
2 to 8 hours cure All percentages are percentage by weight. The components of the resin were mixed and heated together. They were then introduced in an aerosol container with a catalyst. The container was gassed with a propellant. Upon activation of the container's nozæle a foam product was dispensed which demonstrated the above characteristics.
The invention may be embodied in other specific forms without departing from the spirit of essential characteristics thereof. ~he presen~ embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the append claims rather than by the foregoing description, and all charges which come within the meaning and range of equi~alency of the claims a~e therefore intended to be embraced therein.
The invention may be embodied in other specific forms without departing from the spirit of essential characteristics thereof. ~he presen~ embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the append claims rather than by the foregoing description, and all charges which come within the meaning and range of equi~alency of the claims a~e therefore intended to be embraced therein.
Claims (43)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of preparing a one component moisture cure poly-urethane foam comprising the step of dispensing from a container an isocyanate terminated prepolymer having a free isocyanate content of 8% to 19% by weight of the prepolymer and a catalyst with an unhalogenated hydrocarbon propellant whose boiling point or initial boiling point is not greater than 10°C at atmospheric pressure.
2. The method of claim 1 wherein the viscosity of said pre-polymer is between 17,000 and 23,000 centipoises.
3. The method of claim 1 wherein said propellant is between 10% and 30% by weight of said prepolymer, catalyst, propellant mixture.
4. The method of claim 1 wherein said propellant comprises more than one gas.
5. The method of claim 1 wherein said prepolymer is formed from difunctional to trifunctional isocyanates and difunctional to trifunctional polyols.
6. The method of claim 5 wherein said prepolymer is formed from difunctional polyols and trifunctional isocyanates.
7. The method of claim 1 wherein the viscosity of said prepolymer is 20,000 centipoise.
8. The method of claim 1 wherein said catalyst comprises tertiary amines.
9. The method of claim 1 wherein the viscosity of said prepolymer is from 5,000 to 50,000 centipoises.
10. The method of claim 5 wherein said isocyanate comprises crude polymeric diphenylmethane diisocyanate.
11. The method of claim 1 wherein said prepolymer further contains a flame retardant.
12. The method of claim 1 wherein said prepolymer further contains a surfactant.
13. The method of claim 1 wherein said propellant comprises a mixture of isobutane and propane.
14. The method of claim 1 wherein said free prepolymer NCO
percentage is from 12 to 15%.
percentage is from 12 to 15%.
?? ??????????????????????????????????????????????????????
is 14.4%.
is 14.4%.
16. The method of claim 1 wherein said propellant comprises a mixture of n-butane and propane.
17. The method of claim 1 wherein said propellant comprises propane.
18. The method of claim 5 wherein the average functionality of said isocyanates and polyols is 2 to 2 1/2.
19. The method of claim 5 wherein said polyol is oxypropylated glycol.
20. The method of claim 5 wherein the functionality of the isocyanates and polyols are inversely related.
21. The method of claim 1 wherein the prepolymer is sub-stantially linear.
22. The method of claim 5 wherein the polyol comprises a polyether polyol.
23. A pressurized container containing a one-component moisture cure polyurethane foam comprising an isocyanate terminated prepolymer having a free isocyanate content of 8% to 19% by weight of the prepolymer, a catalyst and an unhalogenated hydrocarbon propellant whose boiling point or initial boiling point is not greater than 10°C at atmospheric pressure.
24. The pressurized container of claim 23 wherein the viscosity of said prepolymer is between 17,000 and 23,000 centipoises.
25. The pressurized container of claim 23 wherein said propellant comprises 10 to 30% by weight of the prepolymer, catalyst, propellant mixture.
26. The pressurized container of claim 23 wherein said propellant comprises more than one gas.
27. The pressurized container of claim 23 wherein said prepolymer is formed from difunctional to trifunctional isocyanates and difunctional to trifunctional polyols.
28. The pressurized container of claim 27 wherein said prepolymer is formed from difunctional polyols and trifunctional isocyanates.
29. The pressurized container of claim 23 wherein the viscosity of said prepolymer is 20,000 centipoises.
30. The pressurized container of claim 23 wherein said catalyst comprises a tertiary amine.
31. The pressurized container of claim 23 wherein the viscosity of the said prepolymer is from 5,000 to 50,000 centipoises.
32. The pressurized container of claim 27 wherein said iso-cyanate comprises crude polymeric diphenylmethane diisocyanate.
33. The pressurized container of claim 23 wherein said pre-polymer further contains a flame retardant.
34. The pressurized container of claim 27 wherein said free prepolymer NCO percentage is from 12 to 15%.
35. The pressurized container of claim 34 wherein said free NCO percentage is 14.4%.
36. The pressurized container of claim 23 wherein said propellant comprises a mixture isobutane and propane.
37. The pressurized container of claim 23 wherein said propellant comprises a mixture n-butane and propane.
38. The pressurized container of claim 23 wherein said propellant comprises propane.
39. The pressurized container of claim 27 wherein the average functionality of said isocyanates and polyols is 2 to 2 l/2.
40. The pressurized container of claim 27 wherein said polyol is oxypropylated glycol.
41. The pressurized container of claim 27 wherein the functionality of the isocyanates and polyols are inversely related.
42. The pressurized container of claim 27 wherein the prepolymer is substantially linear.
43. The pressurized container of claim 27 wherein the polyol comprises a polyether polyol.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/049,339 US4274075A (en) | 1976-11-18 | 1979-06-18 | Electronic multi-range variable resistor |
| US49,339 | 1979-06-18 | ||
| US12777580A | 1980-03-06 | 1980-03-06 | |
| US12,775 | 1980-03-06 | ||
| US15743180A | 1980-06-09 | 1980-06-09 | |
| US157,431 | 1980-06-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1137698A true CA1137698A (en) | 1982-12-14 |
Family
ID=27367520
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000354307A Expired CA1137698A (en) | 1979-06-18 | 1980-06-18 | Urethane foams utilizing hydrocarbon propellants |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1137698A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4596725A (en) * | 1984-05-04 | 1986-06-24 | Henkel Kommanditgesellschaft Auf Aktien | Polyurethane insulating foam |
| US10350617B1 (en) | 2016-02-12 | 2019-07-16 | Konstantin Dragan | Composition of and nozzle for spraying a single-component polyurethane foam |
| US10702876B2 (en) | 2016-06-03 | 2020-07-07 | Konstantin Dragan | System, composition, and method for dispensing a sprayable foamable product |
| US10815353B1 (en) | 2016-06-03 | 2020-10-27 | Konstantin Dragan | Composition of and nozzle for spraying a single-component polyurethane foam |
-
1980
- 1980-06-18 CA CA000354307A patent/CA1137698A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4596725A (en) * | 1984-05-04 | 1986-06-24 | Henkel Kommanditgesellschaft Auf Aktien | Polyurethane insulating foam |
| US10350617B1 (en) | 2016-02-12 | 2019-07-16 | Konstantin Dragan | Composition of and nozzle for spraying a single-component polyurethane foam |
| US10702876B2 (en) | 2016-06-03 | 2020-07-07 | Konstantin Dragan | System, composition, and method for dispensing a sprayable foamable product |
| US10815353B1 (en) | 2016-06-03 | 2020-10-27 | Konstantin Dragan | Composition of and nozzle for spraying a single-component polyurethane foam |
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