JPH11512131A - Method for producing phenolic resin foam - Google Patents

Abstract

(57) Abstract The present invention relates to the production of low density resole foam from resole resins. The resole foam has a density of 9.0 pounds per cubic foot (144.166 kg / m ³ ) or less and is manufactured using a halogen-free hydrocarbon blowing agent such as pentane.

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a low-density phenolic resin foam having excellent thermal performance, high heat retention, and excellent fire prevention performance. The method uses a non-ozone-depleting blowing agent. BACKGROUND The damage to the ozone layer by chlorofluorocarbons (CFCs) and to a lesser extent their hydrochlorofluorocarbons (HCFCs), and the activity of those substances as greenhouse gases, which have recently become apparent, are: It poses a problem for their future viability as blowing agents for foam materials. While the development of non-ozone-depleting hydrofluorocarbons (HFCs) is ongoing, it is questionable whether suitable candidates with acceptable properties can be obtained at a reasonable cost. A disadvantage of alkanes is that their thermal conductivity is inferior to CFCs. With the increasing trend for higher energy efficiency, the insulating role of foam materials is becoming increasingly important. Thus, meeting these demands with a gas having a low heat insulating effect is an important attempt for foam manufacturing technology. Phenolic resin foam has been used as an insulating material for many years. Its good thermal and aging thermal performance is well known. Closed cell phenolic foam retains blowing agent gas for a longer period of time than urethane, isocyanurate, and polystyrene foams, and has less air ingress. Maintaining thermal conductivity for a long time due to the low permeability of the phenolic foam to the blowing agent gas and atmosphere provides better thermal barrier performance over the life of the product. Phenolic resin materials are also known to have superior fire protection and lower smoke emission properties than other types of foam materials. DISCLOSURE OF THE INVENTION We have discovered that the production of phenolic foams with alkane blowing agents results in self-extinguishing resole foams. Alkane blowing agents have much higher flammability than CFC and HCFC. Many foams currently manufactured, made with non-flammable blowing agents, are themselves flammable, and the use of alkanes in the blowing agent of those foams is not possible in the absence of flame retardant additives. Increases flammability. The present invention is a significant improvement in the technology available in producing low density insulation materials with high flammability blowing agents. The low permeability of the phenolic resin matrix provides an excellent barrier to both blowing agent and air and produces good thermal performance even at very low densities. The fire protection of these materials is much better than urethane foam made with comparable blowing agents. BEST MODE FOR CARRYING OUT THE INVENTION The method comprises the steps of: (a) containing little or substantially no free formaldehyde, having a water content of 4 to 8%, and having a viscosity of 5,000 to 40,000 cps at 40 ° C. Providing a foaming composition of a phenol formaldehyde resole resin, (b) a foaming agent, (c) a surfactant, and (d) a catalyst, mixing the composition and starting foaming to produce a resol foam; Curing the resole foam to a density of 0.5 to 9.0 pounds per cubic foot (8.01 to 144.166 kg / m ³ ). By this method, a phenol formaldehyde resin having a high viscosity can be foamed and the foam can be cured at a very low density. Commonly used blowing agents are hydrocarbons, including aliphatic and cycloaliphatic alkanes. Preferred blowing agents are aliphatic alkanes, including pentane. Preferably, the aliphatic alkane contains at least 4, but no more than 7, carbon atoms. For example, pentane, hexane, heptane, isobutane and isopentane. Also included are unsaturated hydrocarbons such as pentene and hexene. Cycloaliphatic hydrocarbons having at least 4, but not more than 7, carbon atoms may be saturated or unsaturated. Examples of saturated alicyclic hydrocarbons include cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane. Examples of unsaturated alicyclic hydrocarbons include cyclopentene, cyclohexene, and 1,3-cyclohexadiene. Although not preferred, mixtures such as cyclopentane and acetone can also be used. Although mixtures of halogen free hydrocarbons with CFCs and HCFCs have been suggested for foams other than resole foams, we believe that the blowing agent for resole foams should be CFC and HCFC free. The foam is prepared from a resole made using a conventional initial molar ratio of phenol to formaldehyde, in this case 1: 1 to 1: 4.5, preferably 1: 1.5 to 1: 2.5. High molar ratio materials are based on resins that are substantially phenol free and can be treated with formaldehyde co-reactants or scavengers to reduce the initial high free formaldehyde content. The resin is concentrated to reduce the free water content of the resin. Typical resins used for resol foam production have viscosities on the order of 4,000 to 40,000 cps and a free water content of 4-8%. However, during the production of phenolic foams from high viscosity resins according to the present invention, it may be desirable for the resin utilized to have a viscosity at 40 ° C. on the order of 5,000 to 20,000 cps. The effervescent resole mixture (resin, surfactant, blowing agent, catalyst) can be divided into a batch or continuous process. In a batch process, the foamable mixture is poured into a mold preheated to 80 ° C, sealed, and cured in an 80 ° C oven for 20 minutes. After removal from the mold, the foam is further cured at 80 ° C. for 2 hours. In a continuous process, the foamable composition is dispensed onto a carrier sheet moving from equally spaced tubes and nozzles. The parallel lines of foam in the foam tie so that the foam spreads to form a continuous sheet and travels through a conveyor oven at about 80 ° C. The plate is transferred to a separate oven for further curing. The cured resole foam has a density of 0.5 to 9.0 pounds per cubic foot (8.01 to 144.166 kg / m ³ ). Example 1-Preparation of resole The resole resin used in the production of the above foam used 52% formaldehyde and 99% phenol with a formaldehyde: phenol (F / P) molar ratio of 2.3: 1. The reaction was carried out at high temperature under alkaline conditions using a 50% caustic solution. When the Ostwald viscosity of the resin reached 62 cst (measured at 25 ° C.), the reaction was cooled and neutralized with 50% aqueous aromatic sulfonic acid. Urea was added as a formaldehyde scavenger at 77 mole% of the residual formaldehyde. The resin was passed through a thin film evaporator to reduce the water content from about 30% to 4-8%. The final viscosity of the resin was 4,000-12,000 cps (measured at 40 ° C.). Example 2-Preparation of resole foam Take 47.75 g of a phenol resole, prepared according to Example 1, having a formaldehyde / phenol ratio of 2.3, containing 7% water and having a viscosity of 5,200 cps at 40 ° C. Was mixed with 2.25 g of a 1: 1 (w: w) blended surfactant of an ethoxylated alkylphenol, Harfoam PI (Huntsman Chemical Co.) and an ethylene oxide-propylene oxide block copolymer Pluronic F127 (BASF). To the mixture in the cup was added with stirring 4.5 g of n-pentane. The mixture was stirred until the n-pentane was completely dispersed in the resol and the surfactant. Then, while stirring, 5 g of a catalyst consisting of a blend of toluenesulfonic acid and xylenesulfonic acid, diethylene glycol and resorcinol were quickly added. The volume of then 8X8x2in ³ the contents of the cup (203x203x51mm ^3), was transferred to a rectangular steel mold preheated to 75 ° C.. The mold was sealed and placed in a furnace preheated to 75 ° C. After 20 minutes, the foam was removed from the mold and further cured at 70 ° C. for 3 hours. The properties of the resulting foam are shown in Table 1. The foam had a density of 1.54 pcf (24.668 kg / m ³ ) and a thermal conductivity of 0.145 Btu.in/hft ² ° F (0.021 w / mK). After 200 days of aging at room temperature, the thermal conductivity was found to be 0.164 Btu.in/hft ² ° F (0.024w / mK). A sample of the foam was placed on a laboratory Bunsen burner. When removed from the burner flame, the foam flame disappeared. Example 3 Preparation of Resol Foam 38.0 g of the resol of Example 1 was blended with 1.7 g of the surfactant of Example 2. To this was added 5.1 g of n-pentane and stirred until the pentane was uniformly dispersed. With stirring, 5 g of the catalytic material of Example 2 was quickly added to the formulation. The resulting formulation was transferred to a mold preheated to 70 ° C as in Example 2. The mold was placed in a 70 ° C. oven for 20 minutes, removed from the mold, and further cured at 70 ° C. for 3 hours. The foam has a density of 1.12 pcf (17.941 kg / m ³ ), an initial thermal conductivity of 0.154 Btu.in/hft ² ° F (0.022 w / m.K), and 0.166 after aging at room temperature for 200 days. Btu.in/hft had a thermal conductivity of ² ° F (0.024w / mK). Example 4-Preparation of resole foam 30 g of a blend of the resole of Example 1 and the surfactant of Example 2 in a proportion of 3.5% of the total weight were mixed with 2% by weight of a perfluoroalkane (3M performance fluid 5050). )) And 5.0 g of n-pentane. To this was added 5.0 g of the quick catalyst of Example 2 with stirring. The resulting mixture was transferred to a steel mold preheated to 80 ° C as described in Example 2, and then the mold was transferred to a furnace preheated to 80 ° C. After 20 minutes, the foam was removed from the mold and the foam was further cured at 80 ° C. for 2 hours. The foam had a density of 0.87 pcf (13.94 kg / m ³ ) and had a thermal conductivity of 0.171 Btu.in/hft ² ° F (0.025 w / mK). Example 5-Preparation of foam (control) 20 g of Alkapol SOR 490 (Rhone Poulenc) were blended with 4 g of n-pentane. To this formulation was added 20 g of MondurMR (Mobay). The mixture was mixed thoroughly. Then the mixture was stirred while 4 drops of DabcoT9 (Air Products) were added. The mixture was then transferred from the cup to a flat sheet of aluminum foil and allowed to cure. A sample of the foam was placed in a Bunsen burner flame. The foam continued to burn violently when removed. ¹ X = Material has extinguished O = Material has continued to burn Table 1 shows that low density resole foam can be made with a non-ozonant alkane blowing agent. Both the initial thermal conductivity and the thermal performance after 200 days are excellent, demonstrating the high thermal efficiency of the low density resole foam. Further, as shown in Table 1, the foam in Example 2 has excellent flame resistance, and the fire was extinguished when the foam was removed from the flame source. I continued to burn when I took it off.

────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Wilson Jennifer M             United States Ohio 43081 C             Estherville Staple Chase             5389

Claims (1)

[Claims] 1. A method for producing a closed-cell resol foam, comprising: (a) phenol formaldehyde substantially free of free formaldehyde, having a water content of 4-8%, and having a viscosity of 4,000 cps to 40,000 cps at 40 ° C. Providing a foamed composition of a resole resin, (b) a halogen-free hydrocarbon foaming agent, (c) a surfactant, and (d) a catalyst; and mixing the composition to initiate foaming. A method comprising making a resole foam and curing the resole foam to a density of 0.5 to 9.0 pounds per cubic foot (8.01 to 144.166 kg / m ³ ). 2. The method according to claim 1, wherein the blowing agent is an aliphatic or cycloaliphatic alkane. 3. The method of claim 1, wherein the blowing agent contains 4 to 7 carbon atoms. 4. The method of claim 1, wherein the blowing agent is saturated or unsaturated. 5. The method according to claim 1, wherein the blowing agent is pentane, isopentane or cyclopentane. 6. The method of claim 1 wherein the resole resin has a viscosity at 40 ° C of 5,000 cps to 20,000 cps. 7. The method of claim 1 wherein the density of the phenolic foam is 0.5 to 2.0 pounds per cubic foot (8.01 to 32.037 kg / m ³ ). 8. The method of claim 1 wherein the density of the phenolic foam is 0.7 to 1.8 pounds per cubic foot (11.21 to 28.833 kg / m ³ ). 9. A low density resol foam made according to the method of claim 1. Ten. A low density resole foam made according to the method of claim 5.