MXPA98002613A - Procedure to produce phenoly foam configure - Google Patents

Abstract

This invention relates to a partially cured or semi-cured foam (2, 12) used to form a pipe insulation. This semi-cured foam is very flexible and can be formed around a tube (4) for a prolonged period of time, after production. The semi-cured phenolic foam board of this invention is of a closed cell foam. This semi-cured foam is further cured in the formed configuration (8, 18). When curing, the foam retains the configuration of the preform. The semi-cured product is very flexible, once cured completely, the insulation becomes rigid

Description

PROCEDURE FOR PRODUCING CONFIGURED PHENOMENAL FOAMS TECHNICAL FIELD The invention relates to a process for producing shaped phenolic foams, from semi-cured or partially cured foams. The configured insulation is typically a tube insulation.

BACKGROUND The industry has produced semi-flexible or flexible phenolic foams, which have 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 soaking agent and a catalyst. The method for producing a semi-flexible or flexible phenolic foam composition, having a substantially open cellular structure, comprises mixing a phenol-aldehyde resin with a surfactant, blowing agent and, optionally, a cell-opening agent. and a soaking agent; cure the mixture by its reaction with an acid catalyst; compress 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.

The U.A. Patent No. 5,057,546 discloses 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. These open cell foams are intended for conventional uses of insulation, fluid absorption, acoustic absorption, and the like. Open cell foams are not intended for pipe insulation. Other processes of the prior art typically spray a liquid on the tube, which foams in place to produce a foam insulation. Liquid systems are difficult to use and should be used on the site immediately. For example, the patent of E. U. A., No. ,292,464 reveals thermal insulation storage tanks or water heaters. The invention uses a jacket that forms a hollow insulation space where the liquid foam insulation is injected into the space. This is a conventional way of forming spuma in place. The patent of E. U. A., No. 5,405,665 shows another conventional insulation of tubes with the foam formed in place. Multiple non-foam layers and foam layers are used. This tube insulation is a multi-layer foam, a heat-shrinkable tube, which also uses a hot melt adhesive. The use of hot melt adhesives presents another complicated stage in production. EXPOSITION OF THE INVENTION The process of this invention uses a partially cured or semi-cured foam to form the insulation of the tube. This semi-cured foam is very flexible and can be formed around a tube after a prolonged period of time following production. The semi-cured phenolic foam board of the invention is a closed cell foam. The semi-cured product is very flexible, once cured completely, the insulation loses its flexibility. The closed-cell, semi-cured phenolic foam tube insulation according to this invention is unique. It provides flexibility, which allows it to be easily wound around a round body, such as a tube, and yet the foam has higher thermal properties compared to open cell foams. The semi-cured foam can be formed around a tube for a prolonged period of time after production. For example, we prepare several pieces of a semi-cured phenolic material in a table; One month later, we rolled a sample of the semi-cured foam produced around a tube with a diameter of 76 mm. The foam was then cured further. After curing, he retained his configuration. The highest quality foam materials can be produced by processes of forming foam material boards that can be produced by casting or spraying processes in place. We can also use a low catalyst foam composition that will have less corrosivity in metal contact applications, due to the control of the time and temperature of curing in the material board process.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a semi-cured foam in a helical wrap design around a tube. Figure 2 shows the semi-cured foam, stamped by pressure, around a tube. Figure 3 shows a semi-cured foam wrapped around a mandrel in a longitudinal direction.

BEST METHOD OF CARRYING OUT THE INVENTION A phenolic foam board was produced in the manner described in U.S. Patent No. 5,407,963. This sheet, when it is produced, maintains its physical dimensions, but can still be folded or molded. The process conditions for the foam are such that it does not fully cure during the material board process, and this board of foam material may be subjected to a subsequent cure cycle to achieve complete cure. The material board is then formed around an adjustment tube or mandrel, and the foam is completely cured. In one embodiment, a foam board with twice the required thickness was produced, and then split into two pieces, before being applied to the tube. The carrier for the sheet forming process will be incorporated in the insulation of the tube. If the foam sheet is split and identical carriers are used for both sides of the foam sheet, a single sheet can form two-sided pieces for insulation. If special barrier properties of a different surface on the inside and outside of the pipe insulation are required, two different surfaces can be used on the top and bottom of a single-thickness foam sheet. The process conditions for the material table can be optimized for the performance of the material as a pipe insulation. The catalyst content of the foam and the temperature of the initial curing kilns will determine the degree of curing in the initial foam sheet and thus its handling capacity, its ability to form a foam in a pipe insulation and its cellular structure and insulation properties.

The method includes the steps of: providing a foam composition of a resin, a blowing agent, a surfactant and a catalyst; mix the composition to start the formation of foam and produce a resol foam; and curing the foam at a density ranging from 8 to 48 g / m3. This process allows the formation of foam of phenol-formaldehyde resins, which have a very high viscosity and cure the foams at a very low density. The resin is a phenol-formaldehyde resole, which does not have substantially free formaldehyde and which has a water content of 4 to 8% and a viscosity that varies from 5,000 to 40,000 cps, to 40sc. The foams are prepared from resoles that have been obtained using conventional molar ratios starting from phenol to formaldehyde, in the present case in the range from 1: 1 to 1: 4.5, preferably from 1: 1.5 to 1: 2.5. High molar ratio materials are the bases for resins that are substantially free of phenol and that can be treated with a co-reactant or formaldehyde scavenger, to reduce the content of free, initially high formaldehyde. This resin is concentrated to reduce the free water content of the resin. A typical viscosity resin used for the manufacture of the 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 of high viscosity resins, according to the present invention, the resin used will preferably have a viscosity of the order of 5,000 to 20,000 cps, at 402C. The blowing agent may be selected from a number of HCFC chlorofluorocarbons or hydrofluorocarbons (HFC). Specific examples of these blowing agents include 1-chloro-l, 1-difluoroethane (142b), dichlorofluoroethane (22); 2-chloro-l, 1,1, 2-tetrafluoroethane (124); 1,1-difluoroethane (152a); pentafluoroethane (125) and 1,1,1,2-tetrafluoroethane, dichlorofluoroethane (141b); and others. This blowing agent may include a perfluoroalkane, in which this perfluoroalkane comprises from 1 to 5 weight percent of the weight of the total blowing agent. Preferably, the perfluoroalkane is represented by the formula: cnHxFy in which 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 of the perfluoroalkane include dodecafluoropentane, tetradecafluorohexane, hexadecafluoroheptane.

Preferably, the perfluoroalkane comprises from 1 to 3 weight percent and more preferably from 1 to 2 weight percent of the weight of the total blowing agent. Alkanes such as butane, pentane or cyclopentane can also be used. The surfactants that are generally used for the manufacture of phenolic foam are traditionally non-ionic in nature. Surface-active agents of polyethylene-polypropylene oxide, such as Pluronic (trademark of BASF yandotte), particularly high molecular weight F-127, F-108 and F-98, and Harfoam Pl (Huntsman Chemical Co.) are use Silicon-containing surfactants, such as the ethylene oxide / propylene oxide copolymers of alkoxy silanes, polysilicon / phosphonate copolymers, polydimethylsiloxane and polyoxyalkylene may also be used. Examples of suitable commercial silicon-containing surfactants are the trademarks of Dow Corning DC-190 and DC-193, and the trademarks of Union Carbide L-530, L-5310 and L-5410. The concentrations of the surfactants can vary from 2 to 10% of the total weight of the formulation. The preferred level for the resoles described herein is 2 to 5%. To produce closed cell foams containing the blowing agent in sufficient quantities, to provide higher thermal values, careful selection of the resin and the properties of the surfactant is required. The catalysts used are usually acidic.

Under certain circumstances, the foam can be generated only by the application of heat without the use of a catalyst. However, in practice a catalyst is necessary to complete the cure of the foams. Numerous acidic catalysts, both organic and inorganic, are known and described in the prior art. Examples of inorganic acids include hydrochloric, sulfuric, nitric acids and various phosphoric acids. Examples of organic acids include aromatic sulfuric acids, such as benzenesulphonic acid, toluenesulfonic acid, xylene sulfonic acid, phenol sulfonic acid and naphthalene sulphonic acid; latent acid catalysts, such as the 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-ketones and aldehydes, and several dienes; mono- and polycarboxylic acids, such as acetic acid, formic acid, propionic acid, oxalic acid, maleic acid and substituted strong organic acids, such as trichloroacetic acid. A mixture of toluenesulphonic and xylene sulfonic acids is usually preferred.

The acid catalyst sold under the trademark Ultra TX (itco Chemical Company) is especially preferred. The foam is encapsulated on a semipermeable surface, which acts as a carrier for the healing foam. The surface is incorporated in the final foam product. This surface can be a spun polyester mat, glass mat, a reinforced or unreinforced fabric, felt, cloth, sheet metal, plastic film, or a combination of them. The cured resol foam has a density that varies from 8 to 128 kg / m3. Preferably, the density of the resol foam varies from 11.2 to 28.8 kg / m3, for use in the insulating material. Figure 1 shows a semi-cured foam 2 in a helical envelope design around the tube 4. The winding of the foam material board around a rotating mandrel, which moves on the longitudinal axis at a rate that will produce a cover uniform foam around the tube. The foam 2 is then heated and cured in its formed position. The foam sheet is cut to the appropriate width. The tube 4 is rotated about its axis and moved transversely in its longitudinal direction. The width of the foam, the speed of rotation of the tube and the longitudinal speed are adjusted to form a continuous coverage on the tube.

Figure 2 shows a semi-cured foam 2, stamped by pressure, around the tube 4 or a removable mandrel. A section of the material table is pressed around a mandrel or die and cured in position. The foam sheet is placed in the lower mandrel block 6. The center adjustment mandrel 8 is then placed on the foam and the shape of the lower mandrel block 6 is shaped. The upper adjustment blocks 10 are then moved to form the foam 2 to the configuration of the center adjustment mandrel 8. The molded parts are heated and the foam 2 is removed from the mold, removing the upper adjustment blocks 10, removing the pressure of the center adjustment mandrel 8 and ejecting the foam from the lower mandrel block 6. Figure 3 shows a semi-cured foam 12 of longitudinal formation around the mandrel 18. This foam 12 is molded around the mandrel 18 just after it has been formed. The foam 12 is then cured and removed from the mandrel 18. In an alternative, not shown, the foam 12 moves within a forming shoe around an inner mandrel that is supported at one end. The foam from any alternative is then cured in an oven and then removed from the mandrel and cut to length.

Example 1 - Preparation of Resol The resole resin used in the production of these foams uses a formaldehyde: phenol molar ratio of 2.3: 1, which uses 52% formaldehyde and 99% phenol. The reaction is carried out under basic conditions at elevated temperatures, with a 50% caustic solution. When the Ostwal viscosity of the resin reaches 62 cst (measured at 252C), the reaction is cooled and neutralized with 50% aqueous aromatic sulfonic acid. Urea was added as a formaldehyde scavenger at a level of 77% per mole of 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 mass mixture of a nonionic surfactant based on ethylene oxide, Pluronic F127, from BASF and Harfoam Pl from Huntsman Chemical Co., was then added in a molten state to 3.5% by weight of the resin and mixed in the resin to form a homogeneous mixture. The final viscosity of the resin was 9,000-12,000 cps (measured at 402C).

Example 2 - Preparation of the Resol Foam The resole foam was prepared by mixing together the resole resin and the surfactant with the blowing agent and the acid catalyst, using a continuous short residence mixer, high cut, rotor / stator The blowing agent was saturated with nitrogen at 1279 kPa before introduction to the high cut mixer. The foaming catalyst was a mixture of resorcinol, diethylene glycol and a mixture of xylene- and toluene-sulfonic acids. (See U.S. Patent Nos. 4,883,824 and 4,945,077.) Resole resin, blowing agent and catalyst were continuously dosed to the mixer by means of suitable devices that dose the flow, in the following ratios: resin / surfactant 100 HCFC141b 8.63 Catalyst 11.8 The foamable mixture (resin / surfactant, blowing agent, catalyst) exited the mixer through tubes and nozzles, evenly spaced, to form continuous foam strips on a mobile tissue surface, reinforced with glass . This resulted in parallel lines of foam that were woven together as the foam expanded to form a continuous sheet. The foam sheet was then moved through a conveyor oven at a temperature of about 80ac at a fixed rate to produce a board, which was cured sufficiently for handling. The resulting foam had a density of 59 kg / m3. This foam was left semi-cured and was not post-cured.

Example 3 The foam sheet of Example 2 was cut to a thickness of 12.7 mm and then wound around an inner 254 mm mandrel and held in place by steel bands. This set was placed inside a pre-heated oven at 70 ° C and was cured for three hours.The resulting foam remained in the configuration of the internal mandrel Example 4 A foam board, 25.4 mm thick, a density of 24 kg / m3 and coated on both sides with a polyester mat bound by spinning, was produced according to the method described in Examples 1 and 2. The sheet was kept at the temperature environment for a month. The foam sheet was then wrapped around a 76 mm diameter tube and held in place with metal bands. The foamed sheet was not split during this training process. The whole was placed in a preheated oven at 702C for three hours for curing. The foam maintained the configuration of the tube mandrel, after curing.

Claims (14)

1. CLAIMS 1. A process for producing a closed-cell, semi-cured, flexible resol foam, which comprises the steps of: providing a foaming composition of: (a) a phenol formaldehyde resin resin, which has substantially no formaldehyde and has a water content of 4 to 8% and a viscosity ranging from 4,000 to 40,000 cps, at a temperature of 402C; (b) a blowing agent; (c) a surfactant; and (d) a catalyst; mix the composition to start the formation of foam and produce a resol foam; and partially curing the resol foam, so that it remains flexible enough to wrap around a shaped body.
2. 2. A process, according to claim 1, wherein the blowing agent is a hydrogenated chlorofluorocarbon (HCFC), a hydrogenated fluorocarbon (HFC) or an alkane.
3. 3. A process, according to claim 1, wherein the HCFC is 1-chloro-l, 1-difluoroethane, chlorodifluoromethane, or mixtures thereof.
4. 4. A process, according to claim 1, wherein the perfluoroalkane is represented by the formula: cnHxFy in which n is an integer that varies from 4 to 20, x is zero or an integer that varies from 2 to 10 and x + y = 2n + 2.
5. 5. A process, according to claim 1, wherein the perfluoroalkane is dodecafluoropentane.
6. 6. A method for isolating a shaped body, including the steps of: winding the flexible, semi-cured, open cell foam of claim 1 around a shaped body; and completely cure the foam to a point where it retains its configuration around the body.
7. 7. A method, according to claim 6, in which the foam is a tube insulation and the configured body is a tube.
8. 8. A method, according to claim 6, wherein the insulation is removed from the shaped body, after curing.
9. 9. A method, according to claim 6, in which the foam composition is obtained from a phenol-formaldehyde resole resin, which is substantially free of formaldehyde and has a water content of 4 to 8% and a viscosity ranging from 5,000 to 40,000 cps, at a temperature of 402C, where the resulting foam composition is a closed cell resol foam.
10. 10. A method, according to claim 6, in which the foam is completely cured at a density ranging from 8 to 48 kg / m3.
11. 11. A method, according to claim 6, in which the fully cured foam is inflexible.
12. 12. A method, according to claim 6, wherein the shaped body is a storage tank of a water heater and the foam is an insulator of the water heater.
13. 13. A method, according to claim 6, in which the foam is cured naturally by the heat supplied by the body configured during service.
14. 14. A method, according to claim 6, in which the configured body is an aircraft or a submarine, and the foam is an insulator of the aircraft or the submarine.