CA1186440A - Fire retardant polymer resin - Google Patents
Fire retardant polymer resinInfo
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- CA1186440A CA1186440A CA000373851A CA373851A CA1186440A CA 1186440 A CA1186440 A CA 1186440A CA 000373851 A CA000373851 A CA 000373851A CA 373851 A CA373851 A CA 373851A CA 1186440 A CA1186440 A CA 1186440A
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- Prior art keywords
- aldehyde
- phenol
- acid
- solution
- furfural
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Abstract
ABSTRACT OF THE DISCLOSURE
Flame retardant polymer resins formed by an acid condensation reaction from a mixture of resorcinol and furfural with a molar excess of the aldehyde. In one particular embodiment the resin is formed of a mixture of two prepolymer solutions with at least a boric acid catalyst, one or both of the prepolymer solutions being an acid-condensation reaction product of resorcinol and furfural with excess aldehyde functionality, or one of the prepolymers being a mix of substantially unreacted resorcinol and furfural with a slight molar excess of aldehyde.
Flame retardant polymer resins formed by an acid condensation reaction from a mixture of resorcinol and furfural with a molar excess of the aldehyde. In one particular embodiment the resin is formed of a mixture of two prepolymer solutions with at least a boric acid catalyst, one or both of the prepolymer solutions being an acid-condensation reaction product of resorcinol and furfural with excess aldehyde functionality, or one of the prepolymers being a mix of substantially unreacted resorcinol and furfural with a slight molar excess of aldehyde.
Description
The present invention relates generally to flame-retardant polymer recins, and in particulax to novel synthetic polymer resins which are self-extinguishing and non-punking upon exposure to flames. The invention also contemplates novel processes for producing novel synthetic polymer resins having the aforesaid characteristics. The invention has particula~
utility in connection with the preparation of synthetic polymer resins in foam form for use in thermal insulation systems and will be described in detail in connection with such utility. However, the invention is not limited to the production of polymer foams as will become clear from the description following.
Various synthetic polymer resins are known in the art and have achieved substantial coramercial utility. By way of example, polymer foams based on polyurethane and on polystyrene formulations have achieved substantial use in thermal insulation systems. Polyurethane-based polymer foams offer certain processing advantages in that they may be foamed in situ, and may also be cast in structurally self-support-ing sheet or panel form~ On the other hand, polyurethane and polystyrene-based polymer foams per se are highly flammable.
In order to reduce flammability of polyurethane and polystyrene-i based polymer foams, it has been pxoposed to incorporate phos-phorous and halogen containing additives into the foam forrnulation .
~hile modifying polyurethane and polystyrene based polymer foams in accordance with the foregoing may render the resultant polymer foarns self-extinguishing, the resultant polymer foams generally CIP
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produce toxic smoke when exposed to open flameO More-over, some pyrolysis products of polyurethane and poly-styrene-based polymer ~oams also are flammable, and may cause flash fires if they collect in a closed area. These and other problems and disadvantages have restricted wider commcrcial use of polyurethane and polystyrene based polymer foams in thermal insulation systems.
Polymer foams based on polyimides, polybenzimidazoles, polyphenylquinoxilines, pyrrones, and other highly aromatic polymer materials have also been proposed for use in thermal insulation systems. While polymer foams based on such highly aromatic polymer materials are said to offer extremely high flame retardancy characteristics, none of these polymer foams is believed to have achieved any substantial degree of commercial utilization due to high raw materials cost. Also, limiting commerical utilization of such polymer foams are the requirements for special processiny techniques and apparatus for producing the foams.
Polymer foams based on ureaformaldehyde and phenolformaldehyd , have also been proposed for use in thermal insulating systems, and have achieved some degree of commercial utilization.
Polymer foams based on ureaformaldehyde and phenolformaldehyde ` ~
are relatively inexpensive, and can be foamed in situ using commercially available foaming apparatus. Also, polymer foams based on ureaformaldehyde exhibit good mechanlcal properties but generally generate relatively large quantities of smoke upon exposure to flame, and such polymer foams also are susceptihle to degradation in the presence of moisture~ Polymer foams based on phenol-formaldehyde also exhibit good mechanical properties, and in addition generally are stabl0 in the presence of mois-ture~ Moreover, polymer foams based on phenolformaldehyde exhibit relatively low flame spread and smoke generation on exposure to flames. On the other hand, polymer foams based on phenolformaldehyde generally suffer from so-called "afterglow" or "punking", a phenomenon that causes the foam to be consumed by flameless oxidation after exposure to a fire. While a number of investigators have proposed various solutions for making phenolic foams non-punking, none of such solutions is believed to be entirely sa-tisfactory. Many polymers utilized in foam Eormulations employ alkali or alkaline earth materials as polymerization catalysts and i-t is believed that such materials may in fact cohtribute to combustion of the polymer.
~ccording to an aspect of -the present invention there is provided a method of forming a flame retardant polymer resin, comprising -the steps of: reacting moieties of a first aldehyde and first phenol in the presence of a mineral acid in sufficient proportions to provide an acid-condensation reaction product in the form of a relatively low molecular weigh-t, low viscosity, liquid linear poly-mer having excess aldehyde functionality, the first aldehyde beiny selected from the group consisting of fur-fural and mixtures of furfural and paraformaldehyde, and ,, i, ~
the first phenol. being selected from the group consisting of metacresol, orthocresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols; mixing moieties of a second aldehyde and second phenol to provide a solution of the second phenol in the second aldehyde, which solution contains the second aldehyde in molar excess, the second aldehyde and second phenol being selected from the same groups as the first aldehyde and first phenol; adding to the reaction product a solid, organic, water soluble acid as a polymerization active catalyst; adding to the solution an inorganic acid polymerization catalyst con-taining water of hydration, the inorganic acid being selected from the group consisting of boric acid and boric acid complexes; and reacting the reaction product and solution in the presence of the catalysts to produce con-densation polymerization thereof into the resin According to a further aspect of the present invention there is provided a method of forming a flame retardant pol~mer resin, comprising the steps of: mixing an initially non-a~ueous substantially unreacted solu-ion of a phenol in a liquid aldehyde in molar ratio of about 0.5 to 1 phenol to aldehyde, the phenol being selected from the group consisting of metacresol, orthocresol, 3,5-dimethylphenol, resorci.nol and substituted resorcinol.s, and the aldehyde being selected from the group consisting of furfural and mixtures of furfural and par~formaldehyde;
effecting condensation polymerization of the solution into the resin; and adding to the solution prior to polymeri-zati.on, refractory fibers selected from the group consis-ting of carbon, graphite, silica, and metal oxides and silicates.
~lame retardan-t polymers produced by the above described me~hods are also provided by the present invention.
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According to a further aspect of the invention there is provided a flame retardant composite comprising refractory fibers embedded in a polymeric resin, which resin is a condensation reaction product of an initially non-aqueous substantially unreacted mixture of resorcinol and furfural in a molar ratio of about 0.5 to 1.
The invention accordingly comprises the processes involving the several steps and relative order of one or more such steps with respect to each other, and the materials and products possessing the features, properties and relations of elements which are exemplified in the following detailed disclosure and the scope of the appli-cation of which will be indicated in the claims.
Generally, in the practice of this invention, new phenolic resins based on phenol-aldehyde are derived as the reaction product of a ~olyhydric phenol with an aldehyde polymerized with a catalyst. In one :Form, the resins are derived from a two-part formulation compri.slng:
Part (~) is a stable, low viscosity liquid, low molecula~
weight prepolymer in which is an acid-condensation reaction product of an aldehyde and a polyhydric phenol, containing excess aldehyde functionality, and Part (s) another low viscosity liquid which can either be (1) an acid-conden-sation reaction product a]so of an aldehyde and a poly-hydric phenol, containing excess aldehyde functionality or (2) another low viscosity liquid which is a substan-tially unreacted mixture of aldehyde and polyhydric phenol, containing aldehyde in molar - ~a --excess. In the two part formulation, Part (A) also contains an active polymerization catalystl a solid acid that requires water for initiation, and Part (B) contains a polymerization catalyst which comprises an inorganic Lewis acid containing water of hydra-tion, such as boric acid or a boric acid complex. Both Parts (A) and (B) of the formulation are substantially unreacted until the two parts are mixed together.
In a preferred embodiment of the invention the aldehyde comprises furfural and the polyhydric phenol comprises resorcinolO
Still other obiects and many of the advantages of the present invention will become clear from the description Eollowing.
As used herein the terms l'Part (A)l and "Part (B)" are employed solely for convenience to distinguish the initial aldehyde phenol acid-condensation reaction product part of the two-part formulation containing active polymerization catalyst on the one hand, from the aldehyde/phenol mixture (reacted or unreacted) part of the formulation on the other hand.
In preparing the novel phenolic resins in accordance with the present invention, the fi~st step is to separately prepare the two formulations Parts (A) and (B)u To prepare Part (A), an aldehyde and a polyhydric phenol are mixed together in a ratio of between about two and four moles of the aldehyde for each mole of polyhydric phenol. To fhis mixture is added a relatively small amount (e.g. 0.1 to 1.0 weight percent) of ¦ a mineral acid such as 10~ HCl solution in water. The acid catalyzes the condensation polymerization of the aldehyde and the phenol to form a relatively low molecular weight linear ~M-1~ CIP -5-polymer having excess aldehyde functionality. This polymer is a relativ~ly stable, low viscosity liquid. Part (B) o~ the formulation is prepared either identically to Part A, or by mi~ing an aldehyde and a polyhydric phenol in a ratio between about one and two moles of the aldehyde for each mole of poly-hydric phenol. Preferably, but not necessarily, the aldehyde and the polyhydric phenol in Part (A) of the formulation, and the aldehyde and the polyhydric phenol in Part (s) of the for-mulation, are chemically identical. The resulting mixture (Part B of the formulation) is a relatively stable solution of the polyhydric phenol in the aldehyde, little or no reaction occuring upon mixture of the aldehyde and the polyhydric phenol unless a mineral acid catalyst is added as would be the case where Part B is prepared in the same manner as Part A.
The next step is to incorporate selected catalysts into Parts (A) and (s) of the formulation. A feature and advantage ; of the present invention resides in the selection of, and distribution of a condensation polymerization ac-tive catalyst in one part of the formulation and a polymerization initiation catalyst in the other part of the formulation such that both Parts (A) and (B) of the formulation remain stable, and relatively unre-active until they are mixed. The polymeri~ation active catalyst is added to Part (A) of the formulation, while the polymerization initiation catalyst is added to Part (~) of the formulation. The polymerization active catalys-t added to Part (A) is a solid organ~
ic acid which is water soluble, but i5 substantially i~soluble in .~. . .
FM-l~ CIP -6-Part tA) of the formulation. The acid in solid form is inactive as a polymerization catalyst.
The polymerization initiation catalyst added to Part B
comprises boric acid. The boric acid polymerization initiation S catalyst serves several functions, but primarily acts as an activator to initiate rapid polymerization once Parts (A) ana (B) of the formulation are mixed together. Also, the boric acid is believed to undergo chemical reaction with the low molecular weight polymer of the formulation Part (A) and thereby b~comes an integral par~ of the final cured polymer network.
Upon polymerization, the following reaction is postulated to occur between the boric acid and the resorcinol in Part (B) and also with av2ilable resorcinol hydroxyl groups:
lS B(oB~ ~ ~~~~ ` ~ + H O
The degree to which Reaction I occurs and the actual number of functional sites involved in chemical reaction is not known.
However, it is also believed that the boric acid may also react with free resorcinol or resorcinol that has heen reacted to form the low molecular weight polymer product of Part (A)o PM-18 CIP ¦¦ -7-As mentioned supra, Part (A~ and Part (s) of the formulation are xelatively stable liquids until they are mixed together.
However, once Parts (A) and (B) are mixed together with the catalyst, a condensation polymerization commences, and the solid boric acid partially dissolves in water produced by the conden-sation polymerization reaction, and thus becomes active so as to cataly~e complete cure. One skilled in the art will recognize the use of a solid boric acid catalyst in accordance with the present invention provides the two fold functions of (1) controlling release of active acid catalyst whereby to maintain control over the exothermic condensation polymerization reaction of the polymer, and (2) providing sufficient catalyst release to insure complete cure of the resin over a period o~ time which may be varied. Polymerization generally is initiated within about 60 and 180 seconds following mixing of the formulation Parts (A) and (B), depending on the initial temperature of the materials and catalyst concentration. Complete curing at room temperature generally occurs within several hours thereafter.
Polymerization rate and degree of polymerization can be varied by varying the acid catalyst in Part (~), amount of acid catal~st present in Parts (~) and (B), particle size of acid catalyst (solid acids) and/or degree of hydration of the acid catalyst (solid acids).
The two-part prepolymer compositions are separately Eormulated , and are maintained isolated from one another until the polymer is to be formed. The novel polymer material of the present inven-tion may be formed as a foam by incorporating known foaming agents such as polyhalogenated saturated fluorocarbons in known manner and employing known production equipment, and may be cast as foamed board stock on continuous produckion equipment, or the polymer materials may be foamed in situ. Alternatively, the polymer material of the present invention may be formulated in appropriate weight for use as a fire retardant coating, in a laminate or with ablative materials as will be describ~d in detail hereinafter.
More specifically, the aldehyde compounds used herein comprise a low molecular weight unsaturated aldehyde such as furfuraldehyde (furfural) and mixtures of furfural and para-formaldehyde. The polyhydric phenol comprises resorcinol and substituted resorcinols such as methyl resorcinol. ~esorcinols have been found ko provide polymers which are highly cross~
linked and tend to be thermally stable. Methyl resorcinol used in the present invention tends to produce a stronger, less friable polymer foam than resorcinol, Other phenols may be combined, such as phenol, metacresol, orthocresol, 3,5-dimethylphenol and the like but with at least a minor FM-lB CIP _g_ amount (e.g. 25% or more by weight of th~ polyhydric phenol present. To prepare prepolymer Part A~ a mixture of aldehyde and polyhydric phenol is made, generally in a molar ratio of about three to one. Then a small amount, e.g. about 0.5 weight of dilute inorganic acids such as 10% HCl solution in water is added. An exothermic reaction occurs resulting in the condensation reaction between the aldehyde and the phenol. Since the aldehyde is in substantial molar excess, the condensation reaction product is a li~uid low molecular weight prepolymer with excess aldehyde functionality. The resulting product is a relatively low viscosity liquid. An important feature and advantage of the present invention is to prepare this portion of the prepolymer prior to the polymer foaming operation~ By preparaing the pre-polymer in this manner much of the exothermic reaction occurs prior to actual foaming. This permits foaming to be carried out such that the polymer product may ~e reproduced in a controllable and useful ~anner. A small amount of solid, water soluble organic acid can now be added as a catalyst.
Part (B) of the prepolymer can be a pre-reacted mixture o~
the aldehyde and phenol comprising the same molar ratio as Part ~, or a substantially unreacted mixture of aldehyde and phenol, with the aldehyde in a slight molar excess, e.g. typically the aldehyde is in molar excess relative to the phenol in the range of about 1.25:1 to 1.5:1. The boric acid catalyst is now added.
The resulting mixture compris~s a low viscosity liquid.
~ormulations have also been developed that incorporate furfuryl alcohol in either Part A or Part B or both. Furfuryl alcohol monomer behaves chemically in a manner similar to the initial reaction product between phenols and aldehydes which is also an alcohol. Therefore, from the standpoint of chemical stoichiometry of the resin system, one mole of furfuryl alcohol is the equivalent of one mole of a phenol and one mole of an aldehyde.
Formulations of up to 50 weight % furfuryl alcohol in the overall resin have been prepared. Approximately 9.0 weight g6 is preferred from the standpoint of processing ease and final foam properties. For a 2.65 lb/ft3, foam compressive strength was increased from 9.0 psi to 16 psi by addition of 9.0 weight %
of furfuryl alcohol.
1'he two-part prepolymer system is now ready for use in preparation of polymeric materials of the present invention, particularly for processes of preparing foams, in which processes rapid polymerization time is important to preserve the cellu-lar foam structure. The approach used is to prepare a two~part formulation in the above manner resulting in stable unreactive prepolymer mixtures. If desired, a foaming agent such as one of the Freons (trademark of E.I. DuPont Co. for certain fluorocarbon liquid/gasses refrigerant) may be added tc a mixture of the two prepolymers for producing a polymer foam. Alternatively, PM-18 CIP ~ -11-where the polymeric material is to be employed as a coating, in a laminate or in a composite ablative material, the two parts prepolymers are mixed together without blowing or foaming agents and with, if desired, inert fillers. Also, in such case, the two part system may not be necessary inasmuch as rapid pol~mer-ization is not required.
As mentioned supra an important feature o~ the present inven-tion is to prepare the two-part prepolymer system in such a manner that much of the heat of reaction is produced prior to the actual polymer formation. Still another important feature of the present invention resides in the use of certain solid, water-soluble organic acids as the polymerization catalyst in the two-part systemO By employing an organic acid in inactive solid form, the latter will remain solid in the prepolymer until dissolved in water of condensation produced during polymerization. That is to say, the acid becomes active only as it dissolves in available water. Thls permits controlled release of active acid catalyst whereby control is maintained over the exothermic polymerization reaction of the prepolymers and thereby provides sufFicient cata-lyst release to insure complete cure of the foam over a period of several hours after initial preparation of the foam. Generally, the water-soluble, solid, organic acid catalyst useful in accord-ance with the two part system of the present invention are acids such as citric, fumaric, itaconic, malic, maleic, oxalic and tartaric acidsO Liquid organic acids such as acetic and acrylic can be used, but are not preferred because of their reactivity.
~M-18 CIP ¦¦ - 12-Moreover, the de~ree and rate of polymerization can be varied by varying the paxticular solid or~anic acid catalyst used, amoun-t of that acid catalyst, particle size oi -that acid catalys-t and the de~ree of hydra-tion o~ -tha-t acid catalys-t. For exarnple, polymeriza-tion of the -two-par-t prepolymer resin system can be made to proceed faster if the solid organic acid ca-talys-t has a small particle size, is highly soluble in water and anhydrous initially. In general the higher concentration oE catalyst present, -the faster and further polymerization will occur. Catalysis wi-thout heat by these organic acids requires the presence o~
boric acid.
In addition to solid organic acia ca-talyst materials, certain mineral acids can be employed as polymerization catalysts in accordance with the presen-t invention. Among such acids are phosphoric acid, phosphorous acid, sulphuric acid, hydrochloric ~nd or(~anic acid phosphates such as butyl phosphate and the like. Howe~7er, mineral acids generally are more dif~icul-t to control and -thus generally are not preferred catalys-ts materials except for coa-tings, laminates and ablative composites~ particularly in the one part sys-tem of the present invention As noted, an important feature of the two part system of the present inven-tion is the ~ddition of boric acid -to Part (B) prepolymer. The presence of boric acid in the prepolymer and the resulting polymer provides hea-t absorption in a :Eire environment due to release of large amounts of water o~ hydra-tion available in the boric acid.
rnah/ '' Boric is a Lewis acid and tends to catalyze char formation during pyrolysis which in turn reduces the quantity of combustion gases which might otherwise be generated when the polymer material is exposed to flame. Boric acid is also belie~ed to be coreactive with the prepolymer thereby entering into the polymer structure. Finally, boric acid is a glass-forming material, and such boric oxide glass can melt and thereby add oxidation protection to the charred foam in a fire environment.
The degree to which boron incorporation occurs and actual number of functional sit~s involved in the polymerization reaction inclusion of boron is not known; however, it is believed that boron reaction may also occur on free phenol or phenol that has been reacted into the prepolymer. The boric acid is also believed to function as an activator to initiate polymerization after Parts (A) and (B) of the prepolymers ; are mixed together. This activation is believed to be related to reaction of boric acid with the polymer and its role as a Lewis acid. Thus, if Parts (A) and (B) of the prepolymer are mixed together and the foam prepared without the presence of boric acid, the system is essentially nonreactive and polymerization does not commenc~. On the other hand, the addition of a small amount of boric acid has been found to immediately activate the system causing polymerization : l~ ( to proceed. Polymerization can also proceed without boric acid if a strong mineral acid such as HCl is added; however, polymer-i~ation under these conditions is difficult to initiate unless relatively large amounts of acid are required. Once such poly-merization is initiated it is very exothermic and difficult to control, hence is used herein primarily to form ablative materials from a single-part system of mixed furfural and resorcinol.
Because the nature of some of the primary ingredients used to synthesize the two part resin system are acidic, self-polymeriza-tion will tend to occur gradually over a period of time. It has been found that the use of "acidic" or "basic" inorganic powder fillers can be used to either accelerate self~polymerization or to retard it. As an example, the incorporation of as little as S wt % calcium sulphate hemihydrate will accelerate self-polymerization, while the addition of 5wt% commercial Portland Cement will retard self polymerization. Various fillers such as mica, wollastonite, calcium silicate, titanium dioxide, and aluminum trihydrate have also shown similar behavior.
It is evident that the use of "acidic" and "basic" inorganic fillers can be used to either prolong the storage or shelf life of the prepolymers, or can be used to prime the activity of prepolymers prior to acid cataly~ation in order to control final polymerization and the resulting properties of the foam.
The polymeric materials resulting from mixing prepolymers Parts A and B in th presence of the boric a~id catalyst, if produced in the presence of a foaming agent, may be used ~...... , ~
as thermal insulating systems. Alternatively, by omitting the blowing agent and adjusting catalyst concentrations, the same two-part polymer system may be employed as a fire retardant resin coating, or in a laminate or in conjunction with an ablative composite material, although for the latter, a single-part system is less expensive.
For example, another method of producing a fire retardant resin, particularly useful fox forming ablative matexials, is by a single part system exemplified by the direct reaction of a pheno]
and an aldehyde in the presence of an acid catalyst. The preferrec approach is to form a solution of resorcinol in furfural in molar ratios ranging from about 0.5 to 1. This solution is stable and essentially nonreactive until the catalyst is added. Any of the acid catalysts or catalyst combinations described in the pre-vious disclosure are applicable. The resulting polymer may lack the advantages conferred by the boric acid if the latter is not used, but does constitute an excellent ablative material.
This approach is preferxed for use in formulating fire retarda~t coatings and ablative composites. In producing these coa*ings and composites, additives such as pigments and refractory fibers are combined with the chemical solution. When these addi-tions are properly dispersed, the system is suitable for applica-tion. A catalyst system is then added to initiate the polymer-ization reaction leading to a cured coating or composite. The catalyst is selected to provide a relatively slow ambient temp-erature polymerization without excessive exotherm.
FM-]8 CIP -16-After addition of the catalyst, the formulation can be cast, sprayed or spread depending on the configuration and/or use of the final product. Polymerization to form a cured product occurs at,ambient temperature over a 24-48 hour period.
Heat can be used to accelerate this polymerization.
The following examples, which are illustrative and not meant to be limiting, are given to provide an additonal des-cription of the invention. In order to test for fire resistance the resulting polymeric compositions were exposed to the cutting flame of an oxyacet~lene torch.
EXAMPLE I
A flask equipped with an agitator was charged with a mix-ture of furfural and resorcinol in a mole ratio of 3.6 to 1.
Approximately 2 weight percent of 10~ HCL solution in water was added. The contents were observed to heat up, and the solution was continually stirred for a short period of a few minutes to provide the condensation reaction product between fureural and resorcinol, hereinafter called Part A.
A second flask equipped with an agitator was charged with a mixture of furfural and resorcinol in a molar ratio of 1O3 to 1.
The resorcinol was observed to dissolve in the furfural to provide Part B.
To 168.3 grams of the prepolymer condensation reaction pro-duct of Part A was added 10 grams of tartaric acid. To 152.0 gramc of the mixture of furfural and resorcinol prepared as Part B is added 55 grams of boric acid, 50 grams of Freon 113 (trichloro-trifluoroethane), and 9 grams of a surfactant to aid foaming (UCC5340 non-ionic silicon available from Union Carbide Corporatior ).
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To produce polymeric foam, Part A of the preparation and Part B of the preparation are combined in a ratio of l to l.45 parts by weight and mixed by a motor driven stirrer. Foaming is seen to occur within about 60 to 180 seconds at ambient temp-erature. However, several hours are required before complete cure is obtained. The resulting product is a rigid foam of approxi-mately about l.8 - 2.R pounds per cubic foot density. The foam is tested for flammability by suhjecting the foam product to the flame of the torch. No visible smoke to detectable odor is observed, and no sign of combustion or flammability is noted.
Additional properties of this foam are given in the following table.
The foam, tested for physical properties and flammability has the following characteristics:
Nominal Density l.8 ~ 2.8 lb/ft3 Closed Cell Content 30%
K-Pactor (initial) Et2 ~p hr Water Vapor Permeability 70 Perms Water Absorption 3.6% by Volume 2Q Compressive Strength 9 psi (2 lb/ft3) 3 (parallel to rise) l9 psi (2.8 lb/ft ) Flexural Strength 7.6%
(load deflection @
75% of compression lo~d) Flammability Test Flame SpreadHeat Evolution Factor Factor Flame Spread Index FM-18 CIP ~ -18-Smoke Tes-t (NBS) Specific Optical Density 90 sec 4 min Non-Flaming 0 0 Elaming 0 EXAMPLE II
Prepolymex ~oam resin is prepared by mixing 1,273.9 g furfural, 627~5g resorcinol~ 100.0g surfactant and 5.7g of acid catalyst in a reaction vessel. The catalyst may be a hydro-chloric acid solution such as in Example I. However, a preferred catalyst consists of a mixture of 10 parts by weight organic acid phosphate such as PA-75 (a phosphoric acid derivative sold by -Mobil Oil Co.) to 90 parts Eurfural. After mixing, a slow con-densation reaction occurs between the furfural and the resorcinol.
From this same prepolymer mixture, Part ~A) and Part (B) are prepared. Part ~A) consists of 1,012.1g of prepolymer, 198.3g tartaric acid, and 406.7g of freon 113. Part (B) consists of 995g prepolymer and 608g boric acid.
To produce a foam, equal volumes ~1:1) of Part (Al and Part (B) are mixed together using a high shear laboratory mixer.
E'oaming is seen to occur within about 60 to 180 seconds at ambient temperature. As in Example 1, several hours are required before complete cure is obtained. The resulting product is a rigid foam of approximately 2 to 3 pounds per cubic foot density with physical properties and Eire retardant properties similar to the foam described in Example 1.
FM--1~ CIP -19-~ 4~
EXAMPLE III
To prepare fire retardant coating, prepolymer Part A i5 ormed by mixing together the following by weight: furfural 43%, resorcinol 10.5%, acetal (Formvar 15/95E) 3.5%, titanium dioxide 31.5%, aluminum trihydrate 10.5%, surfactant DC 193 1.0%, with a trace of 85% phosphoric acid to serve as a catalyst. Titanium dioxide is added simply as a pigment to change the normal black color of the cured resin to a battleship gray. The acetal is added to provide toughness and flexibility to the cured resin coat-ing when applied to substrates such as aluminum and steel, without sacrificing fire retardancy.
Prepolymer Part B is formed by mixing together th~ following ky weight: furfural 37~, resorcinol 34%, boric acid 29%.
A formulation consisting of 63.8% Part A and 36.2% Part B
from this example is used to coat mild steel plates measuring 1/4" x 12" x 18" using a nylon paint brush. The coatings will gel within one to two hours and are then heat cured for several hours at 150F. When the coatinys are exposed to the flame of an oxyacetylene torch they will not burn or propagate a flame.
EX~MPLE IV
The preparation of fixe retardant laminates using fiberglass cloth embedded in a cured resin matrix is accomplished by pre-paring the resin in the same manner as the coating resin described previously in Example III with the exception that no pigments are used. However7 the use of a pigment is technically feasible.
As with the coatings, no blowing agent is used and the acid catalyst is modified to suit the particular requirements for polymerization of the laminate-resin structure.
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Once again the incorporation of n acetal such as Formavar 15/95E is believed to improve the adhesion of the resin to the surface of the fiberglass, and the resulting laminate will exhibit no burning or flam0 propagation when subjected to the flame of the torch.
EXAMPLE V
The preparation o a fire retardant ablative composite material is accomplished from a single part mixture in the follow-ing manner: 1,641g of furfural are mixed with 867g of resorcinol using a high shear mixer. To this resin mixture 418g of a refrac-tory type fiber are added while the resin is being mlxed.
Ideally a Banbury or Hobart type mixer should be used for beating the fibers into the resin mix to minimize breakdown. These fibers may be carbon, graphite or silica; however, graphite fibers are preferred.
The resin-fiber mixture can be catalyzed by any of the pre-viously mentioned acids in sufficient quantity. However, a pre-ferred catalyst consists of a mixture of 25 parts by weight of an phosphoric acid derivative such as PA-75, to 75 parts furfural.
Typically up to 50ml of the catalyst mixture will initiate a controllable room temperature cure within 24 hours. In this example, the resin/fiber batch is transfexred into a gallon metal container and the catalyst is added. Uniform mixing of the cata-lyst and batch is achieved by immediately closing the metal con-tainer and shaking it for approximately five minutes on a gyratory type paint shaker. Alternatively, larger batches may be catalyzed using a rotating mortar mixer, or a Banbury or Hobart type mixer.
llF~44~0 Such an ablative material as described above can be cast into moulded shapes using vibrating equipment or manual tamping of the mould. The density of the finished part can vary from 80 to 100 lbs/Et3 depending on the amount of entrained air that is removed during the casting process.
EXAMPLE VI
In another example of an ablative material to the same mix-ture as described in Example V, up to lOPHR high surface area carbon black is added prior to catalyzation. The carbon black absorbs excess resin during castiny, minimizing resin run-out. In addition, the carbon black imparts a thixotropic nature to the resin allowing it to be troweled onto vertical surfaces without slumping or falling off.
Since certain changes may be made in the above method without departing from the scope of the invention herein invovled, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted in an illustrative and not in a limiting sense.
utility in connection with the preparation of synthetic polymer resins in foam form for use in thermal insulation systems and will be described in detail in connection with such utility. However, the invention is not limited to the production of polymer foams as will become clear from the description following.
Various synthetic polymer resins are known in the art and have achieved substantial coramercial utility. By way of example, polymer foams based on polyurethane and on polystyrene formulations have achieved substantial use in thermal insulation systems. Polyurethane-based polymer foams offer certain processing advantages in that they may be foamed in situ, and may also be cast in structurally self-support-ing sheet or panel form~ On the other hand, polyurethane and polystyrene-based polymer foams per se are highly flammable.
In order to reduce flammability of polyurethane and polystyrene-i based polymer foams, it has been pxoposed to incorporate phos-phorous and halogen containing additives into the foam forrnulation .
~hile modifying polyurethane and polystyrene based polymer foams in accordance with the foregoing may render the resultant polymer foarns self-extinguishing, the resultant polymer foams generally CIP
~ 3~
produce toxic smoke when exposed to open flameO More-over, some pyrolysis products of polyurethane and poly-styrene-based polymer ~oams also are flammable, and may cause flash fires if they collect in a closed area. These and other problems and disadvantages have restricted wider commcrcial use of polyurethane and polystyrene based polymer foams in thermal insulation systems.
Polymer foams based on polyimides, polybenzimidazoles, polyphenylquinoxilines, pyrrones, and other highly aromatic polymer materials have also been proposed for use in thermal insulation systems. While polymer foams based on such highly aromatic polymer materials are said to offer extremely high flame retardancy characteristics, none of these polymer foams is believed to have achieved any substantial degree of commercial utilization due to high raw materials cost. Also, limiting commerical utilization of such polymer foams are the requirements for special processiny techniques and apparatus for producing the foams.
Polymer foams based on ureaformaldehyde and phenolformaldehyd , have also been proposed for use in thermal insulating systems, and have achieved some degree of commercial utilization.
Polymer foams based on ureaformaldehyde and phenolformaldehyde ` ~
are relatively inexpensive, and can be foamed in situ using commercially available foaming apparatus. Also, polymer foams based on ureaformaldehyde exhibit good mechanlcal properties but generally generate relatively large quantities of smoke upon exposure to flame, and such polymer foams also are susceptihle to degradation in the presence of moisture~ Polymer foams based on phenol-formaldehyde also exhibit good mechanical properties, and in addition generally are stabl0 in the presence of mois-ture~ Moreover, polymer foams based on phenolformaldehyde exhibit relatively low flame spread and smoke generation on exposure to flames. On the other hand, polymer foams based on phenolformaldehyde generally suffer from so-called "afterglow" or "punking", a phenomenon that causes the foam to be consumed by flameless oxidation after exposure to a fire. While a number of investigators have proposed various solutions for making phenolic foams non-punking, none of such solutions is believed to be entirely sa-tisfactory. Many polymers utilized in foam Eormulations employ alkali or alkaline earth materials as polymerization catalysts and i-t is believed that such materials may in fact cohtribute to combustion of the polymer.
~ccording to an aspect of -the present invention there is provided a method of forming a flame retardant polymer resin, comprising -the steps of: reacting moieties of a first aldehyde and first phenol in the presence of a mineral acid in sufficient proportions to provide an acid-condensation reaction product in the form of a relatively low molecular weigh-t, low viscosity, liquid linear poly-mer having excess aldehyde functionality, the first aldehyde beiny selected from the group consisting of fur-fural and mixtures of furfural and paraformaldehyde, and ,, i, ~
the first phenol. being selected from the group consisting of metacresol, orthocresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols; mixing moieties of a second aldehyde and second phenol to provide a solution of the second phenol in the second aldehyde, which solution contains the second aldehyde in molar excess, the second aldehyde and second phenol being selected from the same groups as the first aldehyde and first phenol; adding to the reaction product a solid, organic, water soluble acid as a polymerization active catalyst; adding to the solution an inorganic acid polymerization catalyst con-taining water of hydration, the inorganic acid being selected from the group consisting of boric acid and boric acid complexes; and reacting the reaction product and solution in the presence of the catalysts to produce con-densation polymerization thereof into the resin According to a further aspect of the present invention there is provided a method of forming a flame retardant pol~mer resin, comprising the steps of: mixing an initially non-a~ueous substantially unreacted solu-ion of a phenol in a liquid aldehyde in molar ratio of about 0.5 to 1 phenol to aldehyde, the phenol being selected from the group consisting of metacresol, orthocresol, 3,5-dimethylphenol, resorci.nol and substituted resorcinol.s, and the aldehyde being selected from the group consisting of furfural and mixtures of furfural and par~formaldehyde;
effecting condensation polymerization of the solution into the resin; and adding to the solution prior to polymeri-zati.on, refractory fibers selected from the group consis-ting of carbon, graphite, silica, and metal oxides and silicates.
~lame retardan-t polymers produced by the above described me~hods are also provided by the present invention.
, ~
~, rnab/l~
According to a further aspect of the invention there is provided a flame retardant composite comprising refractory fibers embedded in a polymeric resin, which resin is a condensation reaction product of an initially non-aqueous substantially unreacted mixture of resorcinol and furfural in a molar ratio of about 0.5 to 1.
The invention accordingly comprises the processes involving the several steps and relative order of one or more such steps with respect to each other, and the materials and products possessing the features, properties and relations of elements which are exemplified in the following detailed disclosure and the scope of the appli-cation of which will be indicated in the claims.
Generally, in the practice of this invention, new phenolic resins based on phenol-aldehyde are derived as the reaction product of a ~olyhydric phenol with an aldehyde polymerized with a catalyst. In one :Form, the resins are derived from a two-part formulation compri.slng:
Part (~) is a stable, low viscosity liquid, low molecula~
weight prepolymer in which is an acid-condensation reaction product of an aldehyde and a polyhydric phenol, containing excess aldehyde functionality, and Part (s) another low viscosity liquid which can either be (1) an acid-conden-sation reaction product a]so of an aldehyde and a poly-hydric phenol, containing excess aldehyde functionality or (2) another low viscosity liquid which is a substan-tially unreacted mixture of aldehyde and polyhydric phenol, containing aldehyde in molar - ~a --excess. In the two part formulation, Part (A) also contains an active polymerization catalystl a solid acid that requires water for initiation, and Part (B) contains a polymerization catalyst which comprises an inorganic Lewis acid containing water of hydra-tion, such as boric acid or a boric acid complex. Both Parts (A) and (B) of the formulation are substantially unreacted until the two parts are mixed together.
In a preferred embodiment of the invention the aldehyde comprises furfural and the polyhydric phenol comprises resorcinolO
Still other obiects and many of the advantages of the present invention will become clear from the description Eollowing.
As used herein the terms l'Part (A)l and "Part (B)" are employed solely for convenience to distinguish the initial aldehyde phenol acid-condensation reaction product part of the two-part formulation containing active polymerization catalyst on the one hand, from the aldehyde/phenol mixture (reacted or unreacted) part of the formulation on the other hand.
In preparing the novel phenolic resins in accordance with the present invention, the fi~st step is to separately prepare the two formulations Parts (A) and (B)u To prepare Part (A), an aldehyde and a polyhydric phenol are mixed together in a ratio of between about two and four moles of the aldehyde for each mole of polyhydric phenol. To fhis mixture is added a relatively small amount (e.g. 0.1 to 1.0 weight percent) of ¦ a mineral acid such as 10~ HCl solution in water. The acid catalyzes the condensation polymerization of the aldehyde and the phenol to form a relatively low molecular weight linear ~M-1~ CIP -5-polymer having excess aldehyde functionality. This polymer is a relativ~ly stable, low viscosity liquid. Part (B) o~ the formulation is prepared either identically to Part A, or by mi~ing an aldehyde and a polyhydric phenol in a ratio between about one and two moles of the aldehyde for each mole of poly-hydric phenol. Preferably, but not necessarily, the aldehyde and the polyhydric phenol in Part (A) of the formulation, and the aldehyde and the polyhydric phenol in Part (s) of the for-mulation, are chemically identical. The resulting mixture (Part B of the formulation) is a relatively stable solution of the polyhydric phenol in the aldehyde, little or no reaction occuring upon mixture of the aldehyde and the polyhydric phenol unless a mineral acid catalyst is added as would be the case where Part B is prepared in the same manner as Part A.
The next step is to incorporate selected catalysts into Parts (A) and (s) of the formulation. A feature and advantage ; of the present invention resides in the selection of, and distribution of a condensation polymerization ac-tive catalyst in one part of the formulation and a polymerization initiation catalyst in the other part of the formulation such that both Parts (A) and (B) of the formulation remain stable, and relatively unre-active until they are mixed. The polymeri~ation active catalyst is added to Part (A) of the formulation, while the polymerization initiation catalyst is added to Part (~) of the formulation. The polymerization active catalys-t added to Part (A) is a solid organ~
ic acid which is water soluble, but i5 substantially i~soluble in .~. . .
FM-l~ CIP -6-Part tA) of the formulation. The acid in solid form is inactive as a polymerization catalyst.
The polymerization initiation catalyst added to Part B
comprises boric acid. The boric acid polymerization initiation S catalyst serves several functions, but primarily acts as an activator to initiate rapid polymerization once Parts (A) ana (B) of the formulation are mixed together. Also, the boric acid is believed to undergo chemical reaction with the low molecular weight polymer of the formulation Part (A) and thereby b~comes an integral par~ of the final cured polymer network.
Upon polymerization, the following reaction is postulated to occur between the boric acid and the resorcinol in Part (B) and also with av2ilable resorcinol hydroxyl groups:
lS B(oB~ ~ ~~~~ ` ~ + H O
The degree to which Reaction I occurs and the actual number of functional sites involved in chemical reaction is not known.
However, it is also believed that the boric acid may also react with free resorcinol or resorcinol that has heen reacted to form the low molecular weight polymer product of Part (A)o PM-18 CIP ¦¦ -7-As mentioned supra, Part (A~ and Part (s) of the formulation are xelatively stable liquids until they are mixed together.
However, once Parts (A) and (B) are mixed together with the catalyst, a condensation polymerization commences, and the solid boric acid partially dissolves in water produced by the conden-sation polymerization reaction, and thus becomes active so as to cataly~e complete cure. One skilled in the art will recognize the use of a solid boric acid catalyst in accordance with the present invention provides the two fold functions of (1) controlling release of active acid catalyst whereby to maintain control over the exothermic condensation polymerization reaction of the polymer, and (2) providing sufficient catalyst release to insure complete cure of the resin over a period o~ time which may be varied. Polymerization generally is initiated within about 60 and 180 seconds following mixing of the formulation Parts (A) and (B), depending on the initial temperature of the materials and catalyst concentration. Complete curing at room temperature generally occurs within several hours thereafter.
Polymerization rate and degree of polymerization can be varied by varying the acid catalyst in Part (~), amount of acid catal~st present in Parts (~) and (B), particle size of acid catalyst (solid acids) and/or degree of hydration of the acid catalyst (solid acids).
The two-part prepolymer compositions are separately Eormulated , and are maintained isolated from one another until the polymer is to be formed. The novel polymer material of the present inven-tion may be formed as a foam by incorporating known foaming agents such as polyhalogenated saturated fluorocarbons in known manner and employing known production equipment, and may be cast as foamed board stock on continuous produckion equipment, or the polymer materials may be foamed in situ. Alternatively, the polymer material of the present invention may be formulated in appropriate weight for use as a fire retardant coating, in a laminate or with ablative materials as will be describ~d in detail hereinafter.
More specifically, the aldehyde compounds used herein comprise a low molecular weight unsaturated aldehyde such as furfuraldehyde (furfural) and mixtures of furfural and para-formaldehyde. The polyhydric phenol comprises resorcinol and substituted resorcinols such as methyl resorcinol. ~esorcinols have been found ko provide polymers which are highly cross~
linked and tend to be thermally stable. Methyl resorcinol used in the present invention tends to produce a stronger, less friable polymer foam than resorcinol, Other phenols may be combined, such as phenol, metacresol, orthocresol, 3,5-dimethylphenol and the like but with at least a minor FM-lB CIP _g_ amount (e.g. 25% or more by weight of th~ polyhydric phenol present. To prepare prepolymer Part A~ a mixture of aldehyde and polyhydric phenol is made, generally in a molar ratio of about three to one. Then a small amount, e.g. about 0.5 weight of dilute inorganic acids such as 10% HCl solution in water is added. An exothermic reaction occurs resulting in the condensation reaction between the aldehyde and the phenol. Since the aldehyde is in substantial molar excess, the condensation reaction product is a li~uid low molecular weight prepolymer with excess aldehyde functionality. The resulting product is a relatively low viscosity liquid. An important feature and advantage of the present invention is to prepare this portion of the prepolymer prior to the polymer foaming operation~ By preparaing the pre-polymer in this manner much of the exothermic reaction occurs prior to actual foaming. This permits foaming to be carried out such that the polymer product may ~e reproduced in a controllable and useful ~anner. A small amount of solid, water soluble organic acid can now be added as a catalyst.
Part (B) of the prepolymer can be a pre-reacted mixture o~
the aldehyde and phenol comprising the same molar ratio as Part ~, or a substantially unreacted mixture of aldehyde and phenol, with the aldehyde in a slight molar excess, e.g. typically the aldehyde is in molar excess relative to the phenol in the range of about 1.25:1 to 1.5:1. The boric acid catalyst is now added.
The resulting mixture compris~s a low viscosity liquid.
~ormulations have also been developed that incorporate furfuryl alcohol in either Part A or Part B or both. Furfuryl alcohol monomer behaves chemically in a manner similar to the initial reaction product between phenols and aldehydes which is also an alcohol. Therefore, from the standpoint of chemical stoichiometry of the resin system, one mole of furfuryl alcohol is the equivalent of one mole of a phenol and one mole of an aldehyde.
Formulations of up to 50 weight % furfuryl alcohol in the overall resin have been prepared. Approximately 9.0 weight g6 is preferred from the standpoint of processing ease and final foam properties. For a 2.65 lb/ft3, foam compressive strength was increased from 9.0 psi to 16 psi by addition of 9.0 weight %
of furfuryl alcohol.
1'he two-part prepolymer system is now ready for use in preparation of polymeric materials of the present invention, particularly for processes of preparing foams, in which processes rapid polymerization time is important to preserve the cellu-lar foam structure. The approach used is to prepare a two~part formulation in the above manner resulting in stable unreactive prepolymer mixtures. If desired, a foaming agent such as one of the Freons (trademark of E.I. DuPont Co. for certain fluorocarbon liquid/gasses refrigerant) may be added tc a mixture of the two prepolymers for producing a polymer foam. Alternatively, PM-18 CIP ~ -11-where the polymeric material is to be employed as a coating, in a laminate or in a composite ablative material, the two parts prepolymers are mixed together without blowing or foaming agents and with, if desired, inert fillers. Also, in such case, the two part system may not be necessary inasmuch as rapid pol~mer-ization is not required.
As mentioned supra an important feature o~ the present inven-tion is to prepare the two-part prepolymer system in such a manner that much of the heat of reaction is produced prior to the actual polymer formation. Still another important feature of the present invention resides in the use of certain solid, water-soluble organic acids as the polymerization catalyst in the two-part systemO By employing an organic acid in inactive solid form, the latter will remain solid in the prepolymer until dissolved in water of condensation produced during polymerization. That is to say, the acid becomes active only as it dissolves in available water. Thls permits controlled release of active acid catalyst whereby control is maintained over the exothermic polymerization reaction of the prepolymers and thereby provides sufFicient cata-lyst release to insure complete cure of the foam over a period of several hours after initial preparation of the foam. Generally, the water-soluble, solid, organic acid catalyst useful in accord-ance with the two part system of the present invention are acids such as citric, fumaric, itaconic, malic, maleic, oxalic and tartaric acidsO Liquid organic acids such as acetic and acrylic can be used, but are not preferred because of their reactivity.
~M-18 CIP ¦¦ - 12-Moreover, the de~ree and rate of polymerization can be varied by varying the paxticular solid or~anic acid catalyst used, amoun-t of that acid catalyst, particle size oi -that acid catalys-t and the de~ree of hydra-tion o~ -tha-t acid catalys-t. For exarnple, polymeriza-tion of the -two-par-t prepolymer resin system can be made to proceed faster if the solid organic acid ca-talys-t has a small particle size, is highly soluble in water and anhydrous initially. In general the higher concentration oE catalyst present, -the faster and further polymerization will occur. Catalysis wi-thout heat by these organic acids requires the presence o~
boric acid.
In addition to solid organic acia ca-talyst materials, certain mineral acids can be employed as polymerization catalysts in accordance with the presen-t invention. Among such acids are phosphoric acid, phosphorous acid, sulphuric acid, hydrochloric ~nd or(~anic acid phosphates such as butyl phosphate and the like. Howe~7er, mineral acids generally are more dif~icul-t to control and -thus generally are not preferred catalys-ts materials except for coa-tings, laminates and ablative composites~ particularly in the one part sys-tem of the present invention As noted, an important feature of the two part system of the present inven-tion is the ~ddition of boric acid -to Part (B) prepolymer. The presence of boric acid in the prepolymer and the resulting polymer provides hea-t absorption in a :Eire environment due to release of large amounts of water o~ hydra-tion available in the boric acid.
rnah/ '' Boric is a Lewis acid and tends to catalyze char formation during pyrolysis which in turn reduces the quantity of combustion gases which might otherwise be generated when the polymer material is exposed to flame. Boric acid is also belie~ed to be coreactive with the prepolymer thereby entering into the polymer structure. Finally, boric acid is a glass-forming material, and such boric oxide glass can melt and thereby add oxidation protection to the charred foam in a fire environment.
The degree to which boron incorporation occurs and actual number of functional sit~s involved in the polymerization reaction inclusion of boron is not known; however, it is believed that boron reaction may also occur on free phenol or phenol that has been reacted into the prepolymer. The boric acid is also believed to function as an activator to initiate polymerization after Parts (A) and (B) of the prepolymers ; are mixed together. This activation is believed to be related to reaction of boric acid with the polymer and its role as a Lewis acid. Thus, if Parts (A) and (B) of the prepolymer are mixed together and the foam prepared without the presence of boric acid, the system is essentially nonreactive and polymerization does not commenc~. On the other hand, the addition of a small amount of boric acid has been found to immediately activate the system causing polymerization : l~ ( to proceed. Polymerization can also proceed without boric acid if a strong mineral acid such as HCl is added; however, polymer-i~ation under these conditions is difficult to initiate unless relatively large amounts of acid are required. Once such poly-merization is initiated it is very exothermic and difficult to control, hence is used herein primarily to form ablative materials from a single-part system of mixed furfural and resorcinol.
Because the nature of some of the primary ingredients used to synthesize the two part resin system are acidic, self-polymeriza-tion will tend to occur gradually over a period of time. It has been found that the use of "acidic" or "basic" inorganic powder fillers can be used to either accelerate self~polymerization or to retard it. As an example, the incorporation of as little as S wt % calcium sulphate hemihydrate will accelerate self-polymerization, while the addition of 5wt% commercial Portland Cement will retard self polymerization. Various fillers such as mica, wollastonite, calcium silicate, titanium dioxide, and aluminum trihydrate have also shown similar behavior.
It is evident that the use of "acidic" and "basic" inorganic fillers can be used to either prolong the storage or shelf life of the prepolymers, or can be used to prime the activity of prepolymers prior to acid cataly~ation in order to control final polymerization and the resulting properties of the foam.
The polymeric materials resulting from mixing prepolymers Parts A and B in th presence of the boric a~id catalyst, if produced in the presence of a foaming agent, may be used ~...... , ~
as thermal insulating systems. Alternatively, by omitting the blowing agent and adjusting catalyst concentrations, the same two-part polymer system may be employed as a fire retardant resin coating, or in a laminate or in conjunction with an ablative composite material, although for the latter, a single-part system is less expensive.
For example, another method of producing a fire retardant resin, particularly useful fox forming ablative matexials, is by a single part system exemplified by the direct reaction of a pheno]
and an aldehyde in the presence of an acid catalyst. The preferrec approach is to form a solution of resorcinol in furfural in molar ratios ranging from about 0.5 to 1. This solution is stable and essentially nonreactive until the catalyst is added. Any of the acid catalysts or catalyst combinations described in the pre-vious disclosure are applicable. The resulting polymer may lack the advantages conferred by the boric acid if the latter is not used, but does constitute an excellent ablative material.
This approach is preferxed for use in formulating fire retarda~t coatings and ablative composites. In producing these coa*ings and composites, additives such as pigments and refractory fibers are combined with the chemical solution. When these addi-tions are properly dispersed, the system is suitable for applica-tion. A catalyst system is then added to initiate the polymer-ization reaction leading to a cured coating or composite. The catalyst is selected to provide a relatively slow ambient temp-erature polymerization without excessive exotherm.
FM-]8 CIP -16-After addition of the catalyst, the formulation can be cast, sprayed or spread depending on the configuration and/or use of the final product. Polymerization to form a cured product occurs at,ambient temperature over a 24-48 hour period.
Heat can be used to accelerate this polymerization.
The following examples, which are illustrative and not meant to be limiting, are given to provide an additonal des-cription of the invention. In order to test for fire resistance the resulting polymeric compositions were exposed to the cutting flame of an oxyacet~lene torch.
EXAMPLE I
A flask equipped with an agitator was charged with a mix-ture of furfural and resorcinol in a mole ratio of 3.6 to 1.
Approximately 2 weight percent of 10~ HCL solution in water was added. The contents were observed to heat up, and the solution was continually stirred for a short period of a few minutes to provide the condensation reaction product between fureural and resorcinol, hereinafter called Part A.
A second flask equipped with an agitator was charged with a mixture of furfural and resorcinol in a molar ratio of 1O3 to 1.
The resorcinol was observed to dissolve in the furfural to provide Part B.
To 168.3 grams of the prepolymer condensation reaction pro-duct of Part A was added 10 grams of tartaric acid. To 152.0 gramc of the mixture of furfural and resorcinol prepared as Part B is added 55 grams of boric acid, 50 grams of Freon 113 (trichloro-trifluoroethane), and 9 grams of a surfactant to aid foaming (UCC5340 non-ionic silicon available from Union Carbide Corporatior ).
~ R/~
~`
To produce polymeric foam, Part A of the preparation and Part B of the preparation are combined in a ratio of l to l.45 parts by weight and mixed by a motor driven stirrer. Foaming is seen to occur within about 60 to 180 seconds at ambient temp-erature. However, several hours are required before complete cure is obtained. The resulting product is a rigid foam of approxi-mately about l.8 - 2.R pounds per cubic foot density. The foam is tested for flammability by suhjecting the foam product to the flame of the torch. No visible smoke to detectable odor is observed, and no sign of combustion or flammability is noted.
Additional properties of this foam are given in the following table.
The foam, tested for physical properties and flammability has the following characteristics:
Nominal Density l.8 ~ 2.8 lb/ft3 Closed Cell Content 30%
K-Pactor (initial) Et2 ~p hr Water Vapor Permeability 70 Perms Water Absorption 3.6% by Volume 2Q Compressive Strength 9 psi (2 lb/ft3) 3 (parallel to rise) l9 psi (2.8 lb/ft ) Flexural Strength 7.6%
(load deflection @
75% of compression lo~d) Flammability Test Flame SpreadHeat Evolution Factor Factor Flame Spread Index FM-18 CIP ~ -18-Smoke Tes-t (NBS) Specific Optical Density 90 sec 4 min Non-Flaming 0 0 Elaming 0 EXAMPLE II
Prepolymex ~oam resin is prepared by mixing 1,273.9 g furfural, 627~5g resorcinol~ 100.0g surfactant and 5.7g of acid catalyst in a reaction vessel. The catalyst may be a hydro-chloric acid solution such as in Example I. However, a preferred catalyst consists of a mixture of 10 parts by weight organic acid phosphate such as PA-75 (a phosphoric acid derivative sold by -Mobil Oil Co.) to 90 parts Eurfural. After mixing, a slow con-densation reaction occurs between the furfural and the resorcinol.
From this same prepolymer mixture, Part ~A) and Part (B) are prepared. Part ~A) consists of 1,012.1g of prepolymer, 198.3g tartaric acid, and 406.7g of freon 113. Part (B) consists of 995g prepolymer and 608g boric acid.
To produce a foam, equal volumes ~1:1) of Part (Al and Part (B) are mixed together using a high shear laboratory mixer.
E'oaming is seen to occur within about 60 to 180 seconds at ambient temperature. As in Example 1, several hours are required before complete cure is obtained. The resulting product is a rigid foam of approximately 2 to 3 pounds per cubic foot density with physical properties and Eire retardant properties similar to the foam described in Example 1.
FM--1~ CIP -19-~ 4~
EXAMPLE III
To prepare fire retardant coating, prepolymer Part A i5 ormed by mixing together the following by weight: furfural 43%, resorcinol 10.5%, acetal (Formvar 15/95E) 3.5%, titanium dioxide 31.5%, aluminum trihydrate 10.5%, surfactant DC 193 1.0%, with a trace of 85% phosphoric acid to serve as a catalyst. Titanium dioxide is added simply as a pigment to change the normal black color of the cured resin to a battleship gray. The acetal is added to provide toughness and flexibility to the cured resin coat-ing when applied to substrates such as aluminum and steel, without sacrificing fire retardancy.
Prepolymer Part B is formed by mixing together th~ following ky weight: furfural 37~, resorcinol 34%, boric acid 29%.
A formulation consisting of 63.8% Part A and 36.2% Part B
from this example is used to coat mild steel plates measuring 1/4" x 12" x 18" using a nylon paint brush. The coatings will gel within one to two hours and are then heat cured for several hours at 150F. When the coatinys are exposed to the flame of an oxyacetylene torch they will not burn or propagate a flame.
EX~MPLE IV
The preparation of fixe retardant laminates using fiberglass cloth embedded in a cured resin matrix is accomplished by pre-paring the resin in the same manner as the coating resin described previously in Example III with the exception that no pigments are used. However7 the use of a pigment is technically feasible.
As with the coatings, no blowing agent is used and the acid catalyst is modified to suit the particular requirements for polymerization of the laminate-resin structure.
~ X/~
Once again the incorporation of n acetal such as Formavar 15/95E is believed to improve the adhesion of the resin to the surface of the fiberglass, and the resulting laminate will exhibit no burning or flam0 propagation when subjected to the flame of the torch.
EXAMPLE V
The preparation o a fire retardant ablative composite material is accomplished from a single part mixture in the follow-ing manner: 1,641g of furfural are mixed with 867g of resorcinol using a high shear mixer. To this resin mixture 418g of a refrac-tory type fiber are added while the resin is being mlxed.
Ideally a Banbury or Hobart type mixer should be used for beating the fibers into the resin mix to minimize breakdown. These fibers may be carbon, graphite or silica; however, graphite fibers are preferred.
The resin-fiber mixture can be catalyzed by any of the pre-viously mentioned acids in sufficient quantity. However, a pre-ferred catalyst consists of a mixture of 25 parts by weight of an phosphoric acid derivative such as PA-75, to 75 parts furfural.
Typically up to 50ml of the catalyst mixture will initiate a controllable room temperature cure within 24 hours. In this example, the resin/fiber batch is transfexred into a gallon metal container and the catalyst is added. Uniform mixing of the cata-lyst and batch is achieved by immediately closing the metal con-tainer and shaking it for approximately five minutes on a gyratory type paint shaker. Alternatively, larger batches may be catalyzed using a rotating mortar mixer, or a Banbury or Hobart type mixer.
llF~44~0 Such an ablative material as described above can be cast into moulded shapes using vibrating equipment or manual tamping of the mould. The density of the finished part can vary from 80 to 100 lbs/Et3 depending on the amount of entrained air that is removed during the casting process.
EXAMPLE VI
In another example of an ablative material to the same mix-ture as described in Example V, up to lOPHR high surface area carbon black is added prior to catalyzation. The carbon black absorbs excess resin during castiny, minimizing resin run-out. In addition, the carbon black imparts a thixotropic nature to the resin allowing it to be troweled onto vertical surfaces without slumping or falling off.
Since certain changes may be made in the above method without departing from the scope of the invention herein invovled, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted in an illustrative and not in a limiting sense.
Claims (17)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Method of forming a flame retardant polymer resin, comprising the steps of:
reacting moieties of a first aldehyde and first phenol in the presence of a mineral acid in sufficient pro-portions to provide an acid-condensation reaction product in the form of a relatively low molecular weight, low viscosity, liquid linear polymer having excess aldehyde functionality, said first aldehyde being selected from the group consisting of furfural and mixtures of furfural and paraformaldehyde, and said first phenol being selected from the group consisting of metacresol, orthocresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols;
mixing moieties of a second aldehyde and second phenol to provide a solution of said second phenol in said second aldehyde, which solution contains said second aldehyde in molar excess, said second aldehyde and second phenol being selected from the same groups as said first aldehyde and first phenol;
adding to said reaction product a solid, organic, water soluble acid as a polymerization active catalyst;
adding to said solution an inorganic acid poly-merization catalyst containing water of hydration, said inorganic acid being selected from the group consisting of boric acid and boric acid complexes; and reacting said reaction product and solution in the presence of said catalysts to produce condensation polymerization thereof into said resin.
reacting moieties of a first aldehyde and first phenol in the presence of a mineral acid in sufficient pro-portions to provide an acid-condensation reaction product in the form of a relatively low molecular weight, low viscosity, liquid linear polymer having excess aldehyde functionality, said first aldehyde being selected from the group consisting of furfural and mixtures of furfural and paraformaldehyde, and said first phenol being selected from the group consisting of metacresol, orthocresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols;
mixing moieties of a second aldehyde and second phenol to provide a solution of said second phenol in said second aldehyde, which solution contains said second aldehyde in molar excess, said second aldehyde and second phenol being selected from the same groups as said first aldehyde and first phenol;
adding to said reaction product a solid, organic, water soluble acid as a polymerization active catalyst;
adding to said solution an inorganic acid poly-merization catalyst containing water of hydration, said inorganic acid being selected from the group consisting of boric acid and boric acid complexes; and reacting said reaction product and solution in the presence of said catalysts to produce condensation polymerization thereof into said resin.
2. Method of forming a resin according to claim 1, wherein said organic acid is selected from the group consisting of citric, acetic, fumaric, acrylic, ita-conic, malic, maleic, oxalic and tartaric acids.
3. Method of forming a resin according to claim 1, wherein said first and second phenol are resor-cinol, and said first and second aldehyde are furfural;
said reaction product being formed from a mixture of fur-fural and resorcinol in a mole ratio of about 3.6 to 1;
and said solution being formed from a mixture of furfural and resorcinol in a mole ratio of about 1.3 to 1;
said reaction product being formed from a mixture of fur-fural and resorcinol in a mole ratio of about 3.6 to 1;
and said solution being formed from a mixture of furfural and resorcinol in a mole ratio of about 1.3 to 1;
4. Method of forming a resin according to claim 1, 2 or 3, including adding a foaming agent prior to com-pletion of the reaction of said reaction product and solution.
5. A flame retardant polymer resin prepared according to the method comprising the steps of:
reacting moieties of a first aldehyde and first phenol in the presence of a mineral acid in sufficient proportions to provide an acid-condensation reaction pro-duct in the form of a relatively low molecular weight, low viscosity, liquid linear polymer having excess aldehyde functionality, said first aldehyde being selected from the group consisting of furfural and mixtures of furfural and paraformaldehyde, and said first phenol being selected from the group consisting of metacresol, orthocresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols;
mixing moieties of a second aldehyde and second phenol to provide a solution of said second phenol in said second aldehyde, which solution is separate from said reaction product and contains said second aldehyde in molar excess, said second aldehyde and second phenol being selected from the same groups as said first aldehyde and first phenol;
adding to said reaction product a solid, organic, water-soluble acid as a polymerization active catalyst;
adding to said solution an inorganic acid polymerization catalyst containing water of hydration, said inorganic acid being selected from the group con-sisting of boric acid and boric acid complexes; and reacting a mixture of said reaction product and said solution in the presence of said catalysts to produce condensation polymerization thereof into said resin.
reacting moieties of a first aldehyde and first phenol in the presence of a mineral acid in sufficient proportions to provide an acid-condensation reaction pro-duct in the form of a relatively low molecular weight, low viscosity, liquid linear polymer having excess aldehyde functionality, said first aldehyde being selected from the group consisting of furfural and mixtures of furfural and paraformaldehyde, and said first phenol being selected from the group consisting of metacresol, orthocresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols;
mixing moieties of a second aldehyde and second phenol to provide a solution of said second phenol in said second aldehyde, which solution is separate from said reaction product and contains said second aldehyde in molar excess, said second aldehyde and second phenol being selected from the same groups as said first aldehyde and first phenol;
adding to said reaction product a solid, organic, water-soluble acid as a polymerization active catalyst;
adding to said solution an inorganic acid polymerization catalyst containing water of hydration, said inorganic acid being selected from the group con-sisting of boric acid and boric acid complexes; and reacting a mixture of said reaction product and said solution in the presence of said catalysts to produce condensation polymerization thereof into said resin.
6. Method of forming a flame retardant polymer resin, comprising the steps of:
mixing an initially non-aqueous substantially unreacted solution of a phenol in a liquid aldehyde in molar ratio of about 0.5 to 1 phenol to aldehyde, said phenol being selected from the group consisting of meta-cresol, orthocresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols, and said aldehyde being selected from the group consisting of furfural and mixtures of fur-fural and paraformaldehyde;
effecting condensation polymerization of said solution into said resin; and adding to said solution prior to polymerization, refractory fibers selected from the group consisting of carbon, graphite, silica, and metal oxides and silicates.
mixing an initially non-aqueous substantially unreacted solution of a phenol in a liquid aldehyde in molar ratio of about 0.5 to 1 phenol to aldehyde, said phenol being selected from the group consisting of meta-cresol, orthocresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols, and said aldehyde being selected from the group consisting of furfural and mixtures of fur-fural and paraformaldehyde;
effecting condensation polymerization of said solution into said resin; and adding to said solution prior to polymerization, refractory fibers selected from the group consisting of carbon, graphite, silica, and metal oxides and silicates.
7. Method of forming a resin according to claim 1, wherein furfural alcohol is substituted on the basis of one mole of said furfural alcohol being chemically equivalent to one mole of said phenol and one mole of said aldehyde, up to 50% by weight of the final product.
8. Method of forming a resin according to claim 1, wherein said condensation polymerization is effected by addition of an acid catalyst in sufficient amount to produce said polymerization.
9. Method of forming a resin according to claim 1, wherein said condensation polymerization is effected by addition of a polyfunctional amine curing agent in sufficient amount to product said polymerization.
10. Method of forming a resin according to claim 1, wherein said condensation polymerization is effected by the addition to said solution of heat and a latent amine complex curing agent which undergoes thermal decomposition to release a polyfunctional amine upon addition of said heat.
11. Method of forming a resin according to claim 8, wherein said acid catalyst is selected from the group consisting of phosphoric acid, phosphorous acid, sulfuric acid, hydrochloric acid and organic acid phos-phates.
12. Method of forming a resin according to claim 9, wherein said curing agent is selected from both aliphatic and aromatic amines.
13. Method of forming a resin according to claim 10, wherein said latent curing agent is an amine complex.
14. A flame retardant polymer resin prepared according to the method comprising the steps of:
forming a solution of a phenol in a solvent which is a liquid aldehyde in molar ratio of about 0.5 to 1 phenol to aldehyde and in the absence of any other solvent for said phenol or aldehyde, said phenol. being selected from the group consisting of metacresol, ortho-cresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols, and said aldehyde being selected from the group consisting of furfural and mixtures of furfural and paraformaldehyde;
effecting condensation polymerization of said solution into said resin; and adding to said solution prior to polymerization, refractory fibers selected from the group consisting of carbon, graphite, silica, and metal oxides and silicates.
forming a solution of a phenol in a solvent which is a liquid aldehyde in molar ratio of about 0.5 to 1 phenol to aldehyde and in the absence of any other solvent for said phenol or aldehyde, said phenol. being selected from the group consisting of metacresol, ortho-cresol, 3,5-dimethylphenol, resorcinol and substituted resorcinols, and said aldehyde being selected from the group consisting of furfural and mixtures of furfural and paraformaldehyde;
effecting condensation polymerization of said solution into said resin; and adding to said solution prior to polymerization, refractory fibers selected from the group consisting of carbon, graphite, silica, and metal oxides and silicates.
15. A flame retardant composite comprising refractory fibers embedded in a polymeric resin, which resin is a condensation reaction product of an initially non-aqueous substantially unreacted mixture of resorcinol and furfural in a molar ratio of about 0.5 to 1.
16. A flame retardant composite according to claim 15, wherein said fibers are selected from the group consisting of carbon, graphite, silica, and metal oxides and silicates.
17. A flame retardant composite as defined in claim 15 or 16, wherein said non-aqueous mixture also includes a polyfunctional amine.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000373851A CA1186440A (en) | 1981-03-25 | 1981-03-25 | Fire retardant polymer resin |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000373851A CA1186440A (en) | 1981-03-25 | 1981-03-25 | Fire retardant polymer resin |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1186440A true CA1186440A (en) | 1985-04-30 |
Family
ID=4119544
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000373851A Expired CA1186440A (en) | 1981-03-25 | 1981-03-25 | Fire retardant polymer resin |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1186440A (en) |
-
1981
- 1981-03-25 CA CA000373851A patent/CA1186440A/en not_active Expired
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