PROCESS FOR PRODUCING SHAPED PHENOLIC FOAMS

Abstract: This invention is a partially- or semi-cured foam (2, 12) used to form the pipe insulation. The semi-cured foam is very flexible and can be formed around a pipe (4) for a long period of time after production. The semi-cured phenolic foam board of this invention is a closed-cell foam. The semi-cured foam is further cured in the formed shaped (8, 18). Upon curing the foam retains the shaped of the perform. The semi-cured products is very flexible; once fully cured, the insulation becomes rigid.

Description: PROCESS FOR PRODUCING SHAPED PHENOLIC FOAMS TECHNICAL FIELD This invention relates to a process for producing shaped phenolic foams from semi-cured or partially cured foams. The shaped insulation typically is pipe insulation. BACKGROUND Industry has produced semi-flexible or flexible phenolic foams having a substantially open cellular structure. The foams are the reaction product of a mixture of a phenol-aldehyde resin, a surfactant, a blowing agent; optionally a wetting agent and a catalyst. The method for producing a semi-flexible or flexible phenolic foam composition having a substantially opened cellular structure comprises mixing a phenol-aldehyde resin with a surfactant, a blowing agent, and optionally a cell opening and wetting agent; curing the mixture by reacting it with an acid catalyst; compressing the cured or semi-cured product below its original thickness; and releasing the pressure, thereby obtaining the desired semi-flexible or flexible phenolic foam composition. U.S. Patent No. 5,057,546 discloses such a semi-flexible or flexible phenolic foam composition. This foam composition is a substantially open cellular structure. Open-cell phenolic foams have about half the R value of closed-cell phenolic foams. The open-cell foams are intended for conventional insulation uses, fluid absoφtion, sound absoφtion cushioning, and the like. The open-cell foams are not intended for pipe insulation Other prior art processes typically spray a liquid on the pipe which foams in place to produce foam insulation. The liquid systems are difficult to use and must be used on site immediately. For example, U.S. Patent No. 5,292,464 discloses thermally insulating storage tanks or water heaters. The invention uses a jacket which forms a hollow insulation space where a liquid foam insulation is injected into the space. This is the conventional way of foaming in place. U.S. Patent No. 5,405,665 shows another conventional foam-in-place pipe insulation. Multiple non-foam layers and foam layers are used. This pipe insulation is a multi-layer foam, heat-shrinkable tube which also uses a hot- melt adhesive. The use of hot-melt adhesives presents another complicating step in production. DISCLOSURE OF INVENTION The process of this invention uses a partially or semi-cured foam to form the pipe insulation. The semi-cured foam is very flexible and can be formed around a pipe after a long period of time following production. The semi-cured phenolic foam board of this invention is a closed-cell foam. The semi-cured product is very flexible; once fully cured, the insulation looses its flexibility. The semi-cured, closed-cell phenolic foam pipe insulation of this invention is unique. It provides flexibility which allows it to be easily wrapped around a round body such as a pipe, yet the foam has higher thermal properties than open-cell foams. The semi-cured foam can be formed around a pipe for a long period of time after production For example, we prepared several pieces of semi-cured phenolic boardstock, a month later, we wrapped a sample ofthe semi-cured foam produced around a 3 -inch-diameter (76 mm) pipe. The foam was then further cured. After curing, it retained its shape. Higher quality foam materials can be produced by boardstock foam processes than could be produced by pour- or spray-in-place processes Also, we can use a low-catalyst foam composition that would have less corrosivity in metal contact applications because ofthe control of cure time and temperature in the boardstock process BRIEF DESCRIPTION OF DRAWINGS Figure 1 shows semi-cured foam in a screw wrap design around a pipe Figure 2 shows pressure stamping semi-cured foam around a pipe Figure 3 shows semi-cured foam wrapped around a mandrel in a longitudinal direction BEST MODE FOR CARRYING OUT THE INVENTION We produce a phenolic foam board in the manner of U.S Patent No. 5,407,963. This sheet, when produced, maintains its physical dimensions, but it may still be bent or molded. The processing conditions for the foam are such that it is not fully cured during the boardstock process, and the foam boardstock does not undergo a postcure cycle to achieve full cure The boardstock is then formed around a pipe or sizing mandrel, and the foam fully cured. In one embodiment, we produce the foam board at double the required thickness, and then it is slit into two pieces before being applied to the pipe The earner for the sheet forming process would be incoφorated into the pipe insulation If the foam sheet was slit and identical carriers were used on both sides ofthe foam sheet, a single sheet could form two-faced pieces for insulation If special barner properties were required from a facer diffeπng on the inside and outside ofthe pipe insulation, two diffeπng facers could be used on the top and bottom of a single-thickness foam sheet The processing conditions for the boardstock could be optimized for the performances ofthe matenal as a pipe insulation The catalyst content ofthe foam and the temperature ofthe initial cuπng ovens would deteπnine the degree of cure in the initial fυam sheet, and thus its handlability, its ability to be post-foamed into a pipe insulation, and its cell structure and insulation properties The processing includes the steps of providing a foaming composition of a resin, blowing agent, a surfactant, and a catalyst, mixing the composition to initiate foaming and to produce a resol foam, and cuπng the foam to a density ranging from 0 5 to 3 0 pounds per cubic foot (8 009 to 48 055 kg m 3 ) This process allows us to foam phenol formaldehyde resms which have a very high viscosity and cure the foams to a very low density The resin is a phenol formaldehyde resol resm having substantially no free formaldehyde and having a water content of 4 to 8% and a viscosity ranging from 5,000 cps to 40,000 cps at 40°C The foams are prepared from resols which have been made using conventional starting mole ratios of phenol to formaldehyde, in the present case in the range of 1 1 to 1 4 5, preferably 1 1 5 to 1 2 5 The high mole ratio matenals are the basis for resms which are substantially free of phenol and which can be treated with a formaldehyde co-reactant or scavenger to reduce the initially high free formaldehyde content The resin is concentrated to reduce the free water content ofthe resm A typical viscosity resin used for manufacturing resol foam has a viscosity in the order of 5,000 to 40,000 cps and a free water content of 4 to 8% However, during the manufacture of phenolic foams from high-viscosity resins in accordance with the present invention, the resin utilized will preferably have a viscosity in the order of 5,000 to 20,000 cps at 40°C The blowing agent can be selected from a number of HCFCs or hydrofluorocarbons (HFCs). Specific examples of these blowing agents include 1-chloro- 1,1-difluoroethane (142b); dichlorofluoro-methane (22); 2-chloro-l,l,l,2- tetrafluoroethane (124); 1,1-difluoroethane (152a); pentafluoroethane (125); and 1,1,1,2- tetrafiuoroethane, dichlorflouro ethane (141b); or others. The blowing agent also may include a perfluoroalkane wherein the perfluoroalkane comprises 1 to 5 weight percent ofthe total blowing agent weight. Preferably, the perfluoroalkane is represented by the formula: CnHχF y wherein n is an integer ranging from 4 to 20, x is zero or an integer ranging from 2 to 10, and x + y = 2n + 2. Specific examples ofthe perfluoroalkane include dodecafluoropentane, tetradecafluorohexane, hexadecafluoroheptane. Preferably the perfluoroalkane comprises 1 to 3 weight percent and more preferably 1 to 2 weight percent of total blowing agent weight. Alkanes like butane, pentane, or cydopentane also could be employed. Surfactants which are generally used for phenolic foam manufacture are typically non-ionic in nature. Polyethylene-polypropylene oxide copolymer surfactants such as Pluronic (trademark of BASF Wyandotte), particularly the high-molecular- weight F-127, F-108, and F-98, and Harfoam PI (Huntsman Chemical Co.) are used. Surfactants containing silicon, such as the silicon ethylene oxide/propylene oxide copolymers of alkoxy silanes, polysilyl/phosphonates, polydimethylsiloxane, and polyoxyaikylene copolymers can also be used. Examples of suitable commercial silicon-containing surfactants are the Dow Corning Trademarks DC- 190 and DC-193 and the Union Carbide Trademarks L-530, L-5310, and L-5410. Surfactant concentrations can vary from 2 to 10% of the total formulation weight. The preferred level for the resols described herein is 2 to 5%. To produce closed- cell foams which contain the blowing agent in sufficient amounts to give superior thermal values, careful selection of resin and surfactant properties is required. The catalysts employed are usually acids. Under certain circumstances, foam may be generated solely by the application of heat without the use of a catalyst. In practice, however, a catalyst is necessary to complete the curing ofthe foams. Numerous acid catalysts, both organic and inorganic, are known and disclosed in the prior art. Examples of inorganic acids include hydrochloric acids, sulfuric acids, nitric acid, and the various phosphoric acids. Examples of organic acids include aromatic sulfuric acids, such as benzene sulfonic acid, toluene sulfonic acid, xylene sulfonic acid, phenol sulfonic acid, and naphthalene sulphonic acid, latent acid catalysts such as phenol esters of carboxylic acids including phenyl trifluoroacetate and phenyl hydrogen maleate, and various sulfur dioxide containing compounds such as the sulfur of a, β- unsaturated ketones and aldehydes, and vanous dienes, mono and poly carboxylic acids such as acetic acid, formic acid, propionic acid, oxalic acid, maleic acid and strong substituted organic acids such as tπchloracetic acid An admixture of toluene sulphonic acids and xylene sulphonic acids is usually preferred The acid catalyst sold under the trademark Ultra TX (Witco Chemical Company) is especially preferred The foam is encapsulated in a semi-permeable facer that acts as a earner for the cuπng foam The facer is incoφorated into the final foam product The facer could be a spun bond polyester matt, a glass mat, a reinforced or unreinforced tissue, felt, cloth, metal foil, plastic film, or a combination of these The cured resol foam has a density ranging from 0 5 to 8 0 pounds per cubic foot (8 009 to 128 148 kg/m 3 ) Preferably the resol foam density ranges from 0 7 to 1 8 pounds per cubic foot (11 213 to 28 833 kg m 3 ) for use as m insulating matenal Figure 1 shows semi-cured foam 2 in a screw wrap design around pipe 4 The wrapping ofthe foam boardstock around a rotating mandrel that is moving in the longitudinal axis at a rate that will produce an even covenng of foam around the pipe Foam 2 is then heated and cured in its formed position The foam sheet is cut to width Pipe 4 is rotated along its axis and moved transversely in its length direction The foam width, pipe rotation speed, and longitudinal speed are set so as to form a continuous coveπng on the pipe Figure 2 shows pressure stamping semi-cured foam 2 around pipe 4 or a removable mandrel A section of boardstock is pressed around a mandrel or die and cured in position The foam sheet is placed in lower mandrel block 6 Center sizing mandrel 8 is then placed onto the foam forming it to the shape of lower mandrel block 6 Top sizing blocks 10 are then moved to form foam 2 to the shape of center sizing mandrel 8 The molded parts are heated, and foam 2 is removed from the mold by removal of top sizing blocks 10, removing pressure from center sizing mandrel 8 and ejecting the foam from lower mandrel block 6 Figure 3 shows longitudinal forming semi-cured foam 12 around mandrel 18 Foam 12 is molded around mandrel 18 just after it has been formed Foam 12 is then cured and removed from mandrel 18 In an alternative not shown, Foam 12 is moved into a forming shoe around an interior mandrel that is supported on one end The foam from either alternative is then cured in an oven and then removed from the mandrel and sawn to length 5 Example 1 - Preparation of Resol The resol resin used in the production of these foams used a formaldehyde phenol (F/P) mole ratio of 2 3 1, using 52% formaldehyde and 99% phenol The reaction was carried out under basic conditions at elevated temperatures with 50% caustic solution Wrien the Ostwald viscosity ofthe resin reached 62cst (measured at 10 25°C), the reaction was cooled and neutralized with 50% aqueous aromatic sulphonic acid Urea was added as a formaldehyde scavenger at a level of 77% by mole ofthe residual formaldehyde The resin was passed through a thin film evaporator to reduce the water content from about 30% to 4-8% A 50/50 blend by mass of an ethylene oxide based nonionic surfactant Pluronic F127 from BASF and Harfoam PI from Huntsman 15 Chemical Co was then added in the molten state at 3 5% by weight ofthe resin and mixed into the resin to form a homogeneous mixture The final viscosity ofthe resin was 9,000- 12,000 cps (measured at 40°C) Example 2 - Preparation of Resol Foam The resol foam was prepared by mixing together the resol resin and 20 surfactant with the blowing agent and acid catalyst using a high-shear short residence, rotor/stator continuous mixer The blowing agent was saturated with nitrogen at 200 psi (1379 kPa) prior to introduction to the high-shear mixer The foaming catalyst was a blend of resorcinol, diethylene glycol, and a mixture of xylene and toluene sulphonic acids (See U S Patent Nos 4,883,824 and 4,945,077 ) The resol resin, blowing agent, and 25 catalyst were continuously metered to the mixer by means of suitable flow metering devices in the following ratios resin/surfactant 100 HCFC141b 8 63 catalyst 11 8 30 The foamable mixture (resin/surfactant, blowing agent, catalyst) exited the mixer through evenly spaced tubes and nozzles to form continuous beads of froth on a moving glass-reinforced tissue facer This resulted in parallel lines of foam which knitted together, as the froth expanded, to form a continuous sheet The foam sheet then moved through a conveyor oven at approximately 80°C at a fixed rate to produce a board that was cured enough to handle. The resultant foam had a density of 3.7 pcf (59.268 kg/m 3 ). The foam was left semi-cured and not post-cured. Example 3 The foam sheet from Example 2 was slit Vi-inch- (12.7-mm-) thick and then wrapped around a 10-inch (254 mm) inner mandrel and held in place by steel banding. This assembly was placed in an oven preheated to 70°C and cured for three hours. The resultant foam remained in the shape ofthe inner mandrel. Example 4 A foam board, 1-inch- (25-mm-) thick, 1.5 pcf (24.028 kg/m 3 ) density, and faced on both sides with spun-bond polyester mat was produced according to the method described in Examples 1 and 2. The sheet was kept at room temperature for one month. The foam sheet was then wrapped around a 3-inch- (76-mm-) diameter pipe and held in place with metal banding. The foamed sheet did not crack during this forming process. This assembly was placed in an oven preheated at 70°C for three hours to cure. The foam maintained the shape ofthe pipe mandrel after curing.

Claims: CLAIMS 1 A process for producing a flexible, semi-cured, closed-cell resol foam (2,12) comprising the steps of: providing a foaming composition of: (a) a phenol formaldehyde resol resin having substantially no free formaldehyde and having a water content of 4 to 8% and a viscosity ranging from 4,000 cps to 40,000 cps at 40°C, (b) a blowing agent, (c) a surfactant, and (d) catalyst mixing the composition to initiate foaming and to produce a resol foam, and partially curing the resol foam such that it remains flexible enough to wrap around a shaped body 2 A process according to claim 1 wherein the blowing agent is a hydrogenated chlorofluorocarbon (HCFC), hydrogenated fluorocarbon (HFC), or an alkane 3 A process according to claim 1 wherein the HCFC is 1 -chloro- 1,1- difluoroethane, chlorodifluoromethane, or a mixture thereof 4 A process according to claim 1 wherein the perfluoralkane is represented by the formula wherein n is an integer ranging from 4 to 20, x is zero or an integer ranging from 2 to 10, and x + y = 2n + 2 5 A process according to claim 1 wherein the perfluoroalkane is dodecafluoropentane 6 A process for insulating a shaped body, including the steps of wrapping the flexible, semi-cured closed-cell resol foam (2,12) of claim 1 around a shaped body (4,8,18), and fully curing the foam to a point where it retains its shape around the body 7 A process according to claim 6 wherein the foam (2) is pipe insulation and the shaped body is a pipe (4) 8. A process according to claim 6 where the insulation is removed from the shaped body (8,18) after curing. 9. A process according to claim 6 wherein the foam composition is made from a phenol formaldehyde resol resin having substantially no free formaldehyde and have a water content of 4 to 8% and a viscosity ranging from 5,000 cps to 40,000 cps at 40°C, wherein the resulting foam composition is a closed-cell resol foam. 10. A process according to claim 6 wherein the foam is fully cured to a density ranging from 0.5 to 3.0 pounds per cubic foot (8.009 to 48.055 kg/m 3 ). 11. A process according to claim 6 wherein the fully cured foam is inflexible. 12. A process according to claim 6 wherein the shaped body is a waterheater storage tank and the foam is a waterheater insulator. 13. A process according to claim 6 where the foam naturally cures by the heat supplied by the shaped body in service. 14. A process according to claim 6 wherein the shaped body is an aircraft or submarine and the foam is an aircraft or submarine insulator.

Inventors: FAUSEY WILLIAM HERBERT, GRINSHPUN VYACHESLAV SLAVA, HULLS BYRON JEFFREY, FAUSEY, WILLIAM, HERBERT, GRINSHPUN, VYACHESLAV, SLAVA, HULLS, BYRON, JEFFREY
Applicants: OWENS CORNING FIBERGLASS CORP, OWENS CORNING
Application year: 1996
Main classification: C08G8
IPC codes: C08G8, C08J9, C08L61, F16L59