JPS6362542B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to phenolic foams, particularly closed cell foams of phenol/formaldehyde resins. The use of foam materials for insulation purposes has already been established. However, many foam materials currently in use have inherent problems such as being easily flammable or emitting toxic gases upon partial combustion. For this reason, many attempts have been made to simultaneously produce foams that have high insulation values while having built-in resistance to combustion. One resin that has been investigated as having desirable properties for producing flame resistant foams is a phenolic resin made by the basic catalyzed copolymerization of phenol and formaldehyde. Such resins are commonly referred to as resols. The first step in the production of phenolic resol is the general formula The purpose is to generate an intermediate having the following. The x/phenolic ring ratio gives the resin an approximate bound phenol/formaldehyde (E/P) ratio. These intermediates then react to form the crosslinking group described below. or gives a structure with structure (), then those of structure () react at high temperature to decompose the formaldehyde and give a bridging group like structure (). Further reactions lead to chain elongation and crosslinking occurs by reaction at other positions on the aromatic ring. Cross-linking and chain extension are not complete at the end of the foaming process, but have proceeded to the extent that the foam can harden and be cut into small pieces. When no crosslinking agent is added, the degree of cure is a function of temperature and, to some extent, time at that temperature.
Therefore, foams that are only subjected to low temperatures have a low degree of hardening. Unfortunately, the problem with producing phenolic foams is that almost all the cells are closed cells if good thermal conductivity is to be maintained. This is not easy. This is because the reaction of phenol with formaldehyde produces water as a by-product and this reduces the effectiveness of the foam as a thermal barrier since it can easily cause bubbles to expand. Although closed cell phenolic foams can be produced by keeping the reaction temperature low, as disclosed in GB 1580565, this is a less cured foam, i.e. high in residual formaldehyde. This results in poor dimensional stability. Such foams may also partially fail if the cell structure is not strong enough to resist the forces to which the foam is exposed during curing and/or thermal cycling. It has long been recognized that the properties of the resol itself are an important factor in attempts to produce phenolic foams with a fine homogeneous cell structure.
U.S. Pat. No. 3,389,094 describes the importance of using resols with less than 10% water content, and U.S. Pat. No. 2,845,396 describes the importance of using resols with less than 5% water content for low density foams. is emphasized. Low moisture is desirable since water present in the foam or generated during curing can evaporate and cause bubble expansion. This point is emphasized in British Patent No. 1580565.
Low moisture content is also important as it increases the viscosity in the resin and provides better control of the foaming operation. In the prior art, closed cell foams can be made from resols with precise rheology, and US Pat.
No. 3953645, No. 4140842 and No.
No. 4,133,931 teaches a method of adjusting the rheology of the resol during foaming by incorporating suitable surfactants, such as those described in US Pat. No. 4,133,931. Both the limited viscosity and the use of surfactants reflect the fact that in order to obtain sufficient closed cell content, the cell walls must be strong enough to withstand the stresses when the resin is foamed and subsequently cured. It is. As the cell expands, the cell walls must be able to stretch without bursting. This is actually a manifestation of the well-known ``Marangoni effect,'' which can be seen, for example, in Fritsch and Saunders' ``Plastic Materials''.
Plastic Foams” Chapter 1, 31-35
(published by Marcel Detzker, 1972). The above-mentioned effect refers to the tendency of a surfactant-containing resin film when stretched, and the tendency of the surfactant concentration on the film surface to be depleted is corrected by supplying resin and surfactant to the stretched region, thus reducing the thickness of the film. means to return to the original state.
This "self-healing" effect therefore helps prevent bubble wall collapse during foam formation. Phenolic foams useful as insulation require low thermal conductivity and obviously closed cell foams are highly preferred. This is because they minimize losses due to heat transfer and gas convection. Furthermore, it is desirable that the gas filling the closed cells have as low a thermal conductivity as possible. Gases useful as blowing agents include hydrocarbons and halogenated hydrocarbons (US Pat. No. 2,933,461) and fluorocarbons (US Pat. No. 3,389,094). Other desirable properties of phenolic foams are dimensional stability and low formaldehyde residual. Both of these properties are imparted by heating the foam; however, as discussed above, heating of prior art foams destroys the foam. Accordingly, prior art phenolic foams are typically manufactured at temperatures below about 80°C and are subjected to curing operations at temperatures only up to about 80°C. This produces a foam with a low degree of cure, which is distinct from the higher degree of cure desired for many commercial applications. Improvements have therefore been made to minimize the drawbacks of such prior art. It is therefore a principal object of the present invention to provide a partially cured phenolic foam that resists high temperature curing and imparts dimensional stability to it, while possessing good closed cell content and good thermal insulation properties. Another object of the invention is to provide a method by which the partially cured phenolic foam described above can be produced. The present invention has a density of 30-70Kg/ ^m3 and at least
a phenolic resol with a formaldehyde:phenol molar ratio of 1.2:1 to 2.5:1;
said resol is derived from a composition comprising a surfactant in an amount sufficient to exhibit a Marangoni effect during foaming and a blowing agent having a thermal conductivity of less than 0.016 watts/m<0>C; The thermal conductivity of the foam after 100 days is less than 0.02 watts/m°C and △k/△lnt [△k
(watts/m℃) is k ₁₀₀ −k ₁ and △lnt
(B) the _closed cell content of the _foam is at least ¹⁰
The isotropic pressure required to reduce the amount by 1.75Kg/
It is characterized by being larger than cm ² . Said foam is characterized by a closed cell content of at least 85%, preferably at least 90%. These levels of closed cell content are substantially retained even after curing by heating the partially cured foam to 90° C. or even higher temperatures. This feature is highly unusual since, as mentioned above, curing temperatures tend to destroy cell walls. Preferably, the resol from which the foam is prepared is essentially a conventional phenol/formaldehyde resol having up to 10% by weight of ring-substituted phenolic components such as cresol, xylenol, and the like. The F/P molar ratio of resol is 1.2:1~
2.5:1, but ratios in the higher end of this range are not preferred since excess formaldehyde lengthens the curing process. However, if a ratio that is too small is used, it will be difficult to complete the reaction that produces the foam. The most suitable F/P ratio is
The ratio is 1.5 to 2.2:1. As used throughout the specification, F/P ratio refers to the molar ratio of chemically combined formaldehyde and phenol in the resol. Such a ratio is C13 nuclear magnetic resonance (
¹³ C-NMR).
In the specific technique that has been used, ¹³ -NMR quantitative spectra were obtained using a Jeol FX-900 spectrometer (a product of the Dieol Company, USA) at 50-70% by weight in methanol solvent.
of resin solution at ambient temperature. diameter
Samples were analyzed in 10 mm tubes with the addition of 2% tetramethylsilane as a chemical shift standard. The spectrometer was fitted with a lithium 7 isotope external lock. The analyzed spectrum is the tip angle
This was the result of accumulation from 1 to 5000 at 90°. Optimal quantification conditions were used with gate decoupling (proton decoupling only during accumulation) and pulse delay between accumulations of >5T ₁ (relaxation time). The integrated spectra were used to calculate the combined F/P with an accuracy typically better than 4%. The density of the foam is between 30 and 70 Kg/ ^m3 , with preferred foams having a density between 40 and 60 Kg/ ^m3 . Density is obtained by cutting core samples with a diameter of 3.6 cm and a length of 2.9 cm. The core is accurately weighed and the density calculated. The viscosity of the resol measured at room temperature of 25°C is approximately
50000~1000000cps but the best result is 80000~
600000cps viscosity most preferably 80000~
Obtained with a viscosity of 300000cps. At such viscosities, the resol can be foamed to produce substantially closed cell foams using the relatively easily controlled foaming conditions of the present invention. Also,
The reactivity of the resol is very important. This is because if the reactivity is too high, the temperature of the foam composition will become too high, resulting in uncontrolled water vapor destruction of the foam and loss of control of density and closed cell content. On the other hand, if the reactivity time is too low, the processing time becomes long and uneconomical. A suitable test for resole reactivity is described in Example 13 below. Typically, resoles are prepared by conventional base catalysis, and after formation of the resol an acid is used to neutralize the base and stabilize the resin. This naturally involves the formation of salts by reaction between acids and bases. Neutralizing the resol with sulfuric acid or carbon dioxide can result in large insoluble salt particles that can be easily removed before using the resol to make foams. It is also possible to use unfiltered resins, provided that the foaming method employed does not cause sedimentation problems. Generally, if salt particles are present, it is preferred that they be very large or very small, ie, substantially larger than the diameter of the cell or smaller than the thickness of the cell wall. If smaller than the cell wall thickness, the particles will not adversely affect window integrity, but if larger than the bubbles, the number of bubbles that will burst will be reduced. Resols that produce soluble salts upon neutralization are not commonly used due to their water sensitivity. The water sensitivity of such resols is often evidenced by the fact that the insulation and dimensional stability of the resulting foam is adversely affected by ambient humidity.
However, resols containing water-insensitive soluble salts such as alkyl or aromatic calcium sulfate salts or having low water sensitivity can be used. It is preferred to optionally use so-called "dispersed salt" resols in colloidal form, in which the neutralizing acid is oxalic acid and the oxalate produced is highly insoluble and has little tendency to sediment. These resins and foams made therefrom are described, for example, in US Pat. Nos. 4,060,504 and 4,216,295. The composition from which the foam is manufactured has the ability of the resol to exhibit a Marangoni effect during foaming, resulting in cells having windows (membranes between adjacent cells) that remain intact as the cells grow to their final size. surfactant in an amount sufficient to have a surfactant. The amount of surfactant that can be used varies somewhat depending on the surfactant, but typically closed cell foam
It has been found that less than 0.5% by weight of surfactant is difficult to obtain and more than 6.0% by weight does not yield any benefit and is even harmful. The most useful amount of surfactant is 1-5% by weight. All given percentages of surfactant are based on the weight of the resol. The surfactant may be any of those that have shown effectiveness with effervescent resols in the past.
They include nonionic surfactants such as polyethers, polyalcohols, especially condensation products of alkylene oxides with alkylphenols, fatty acids, silanes and silicones, fatty acid esters of polyhydroxyl compounds such as sorbitan or sorbitol, polysilylphosphonates, polydimethylsiloxanes. and U.S. Pat. No. 4,133,931;
There are surfactants described in the specifications of No. 4140842 and No. 4247413. Ionic surfactants such as alkylated quaternary ammonium derivatives can also be used. The presence of surfactants as described above allows the foaming/curing operation to proceed fairly rapidly without destroying the cell structure. However, as a result of using highly reactive resols, excessive velocities can still result in destruction. It is therefore advisable to select an amount of blowing catalyst that produces only a mildly reactive resol and a mild exotherm. The combination of resol reactivity and blowing catalyst concentration is defined in Example 13 below and can be represented by a reactivity number that is between about 2 and about 12. Foaming is catalyzed by acids and commonly used include boric acid, sulfuric acid and sulfonic acids such as toluenesulfonic acid and xylene sulfonic acid. However, other catalytic acids are known to those skilled in the art and can be used.
The amount of catalyst used in the foaming mixture can vary widely depending on the particular resol and catalyst used. Based on the weight of the resol from about 0.5 to about
Amounts of 3.0% by weight, preferably 1.0-2.0% by weight can be used. The blowing agent used should have a thermal conductivity of less than 0.016 watts/m°C, preferably less than 0.014 watts/m°C. Typically, this range includes blowing agents such as methylene dichloride and various chlorofluorocarbons such as monofluorotrichloromethane, difluorodichloromethane, monofluorodichloromethane, difluoromonochloromethane, trifluorotrichloromethane and tetrafluorodichloroethane. Freon 114 (1,2-dichlorotetrafluoroethane available from DuPont under the above trade name) is particularly preferred. The amount of blowing agent used in the foaming mixture depends on the molecular weight and foam density of the blowing agent. An amount of about 5 to about 25% by weight, preferably 10 to 20% by weight of Freon 114 based on the weight of the resol, from about 30 to 70 Kg/m ³
It can be used for the following forms. In addition to the catalyst residue produced when neutralizing the base that catalyzes the reaction that causes the resol to foam, the resol contains a latent neutralizing additive that removes any remaining traces of curing acid to a neutral form. It may be included. Suitable latent neutralizing agents are described, for example, in U.S. Pat.
It is described in the specifications of No. 4207400 and No. 4207401. In addition to the previously mentioned ingredients, the foam may also contain other additives, such as anti-punching additives and particulate or fibrous fillers, such as glass fibers, to improve the fire resistance or physical properties of the resulting foam.
Can include talc and the like. It can also include ingredients added after resol formation, such as lignin materials, urea or melamine as extenders or formaldehyde scavengers. U.S. Patent Application No. 219165 (December 1980)
The hydrated alumina taught therein is effective in increasing closed cell content and is therefore a desirable component of the foam. The process of producing closed cell phenolic foams is very sensitive to changes in conditions and formulation.
The basic methods described in the prior art require extruding the foamable mixture under conditions such that the resol foams and cures at a compatible rate. However, within these wide conditions it has not been demonstrated to date that it has been possible to obtain a foam with the remarkable performance of the foam of the present invention. In producing the foams of the present invention, the components from which the foams are produced include resoles, surfactants, acidic catalysts, and blowing agents. These components are selected according to the principles described above and mixed at temperatures and pressures calculated to effect rapid expansion in the extrusion head. Mixing can be carried out in any equipment capable of providing an effective fine (less than 10 microns) and uniform dispersion of blowing agent in the mixture. Suitable mixer equipment for this stage of operation is a short residence time, high shear pin mixer such as an Oakes mixer. Suitable blowing agents are fed by conventional means to the mixer under air or nitrogen pressure. The foamable mixture is passed from the mixer to the extrusion head. Expansion from the head is rapid and deposits a stream of foam onto the substrate. The extrusion head may be in the form of a slit so as to deposit a continuous sheet of foam. however,
In a preferred method, the extrusion head is a valved pipe that reciprocates transversely to the direction of extrusion so as to deposit a continuous ribbon form on the moving substrate in parallel lines that solidifies as the foaming progresses. be. In a further preferred feature, the molding member limits expansion so that a uniformly molded plate of foamed resin is produced. Although the molded part may have a suitable surface finish applied to its surface, it is advantageous to apply such a surface finish after the expanded foam has hardened. As foaming progresses, the foam is conventionally held at a constant temperature of about 60°C. This is done by passing the produced sheet through an oven at that temperature so that on leaving the oven after about 20 minutes it is sufficiently cured to be cut into plates and then stored at 60°C for 18 hours. After this, the board is in a partially cured state. As used herein, the term "partially cured" refers to a foam that has been subjected to a temperature of at least 60°C for at least 18 hours. Although other low temperature cure conditions can be used, such as lower temperatures and longer times, the foams of the present invention achieve at least a partial cure after 18 hours at 60°C. It is often desirable to apply a facing to the surface after a suitable period of curing. This may include cardboard, asphalt/asbestos composites, aluminum foil plastic moisture barriers, layers or glass fiber sheet material optionally impregnated with resin or asphalt. These facings improve the surface of the foam and provide some dimensional stability. However, it should be noted that the cured foam has inherent three-dimensional stability up to the approximate temperature at which it is cured. Because the foams of the present invention can be cured at temperatures higher than those likely to be experienced in use, the facing materials selected need not be selected with dimensional change considerations in mind. Although the process has been described for the production of continuous sheets, it is of course also possible to carry out the batch process and extrude the foamable mixture into a mold to produce a single foam. Since the foam material is primarily useful as an insulator, it is important that it provide a good barrier to heat transfer. However, it is insufficient that the fresh foam has good thermal barrier properties. Their properties must be retained over a long period of time after insulation. The thermal insulation properties of closed cell foams are determined primarily by the rate at which heat moves through the foam by conduction through the cell skeleton and the gas filling the cells and by radiation through the cell structure. Therefore, the nature of the gas is a critical factor in determining conductivity, as is the extent to which the gas is retained within the bubbles. It will also be appreciated that as the bubble becomes stronger and thicker, the bubble window becomes weaker and can retain a more desirable gas composition for a longer period of time than a thinner window. As the foam matures, air diffuses in and blowing agent diffuses out. Air typically has a much higher thermal conductivity than the blowing agent, so the thermal barrier properties are substantially reduced. This is common with most insulating foams and has required the use of barrier films on major surfaces to prevent blowing agent escape. however,
Such films lose their usefulness when they are perforated. Although this reduction in thermal barrier properties occurs gradually, a useful indicator of long-term performance has been found to be the thermal conductivity 'k' after 100 days of storage at 23°C and 50% RH (relative humidity). . If the cell windows in the foam are broken or very thin, the blowing agent will be diluted with enough air to increase the k value significantly. In this specification, "k" (k ₁₀₀ ) after 100 days is
This is the thermal conductivity of the partially cured foam of the present invention 100 days after production. The partially cured foam of the present invention is
It has a k ₁₀₀ less than 0.020 watts/m°C. A measure of the rate of increase in thermal conductivity of the partially cured foams of the present invention over time can be expressed as the value of the equation Δk/Δlnt (also known as the k-retention value). In the formula, △k is k ₁₀₀ − _{k 1} , △lnt is the natural logarithm of t ₁₀₀ − natural logarithm of _{t 1} , and k is 100
Watts/m℃ on day (k ₁₀₀ ) and day 1 (k ₁ )
is the thermal conductivity of a 2.54 cm thick sample measured at and t is the number of days elapsed. The partially cured foams of the present invention have k retention values not greater than 0.5 x 10 ^-3 . Although the k ₁₀₀ value gives a good indication of the barrier properties of a foam structure, it is not necessarily a good indication of the strength of the structure, ie its ability to withstand internal pressures. This indicator indicates that the closed cell content is at least
It is given by the "burst pressure" which is the isotropic pressure which is reduced by 10%. A good insulation form must be able to withstand high pressures such as those generated during curing or thermal cycling such as may be experienced during use. The foam of the present invention requires a burst pressure greater than 1.75 Kg/cm ² . This, along with the k ₁₀₀ value,
A new type of partially cured foam not provided by the prior art is suitably defined, which has the potential for the production of high quality fully cured foams. The invention will now be described with respect to specific compositions intended for illustrative purposes only. This is not intended to limit the scope of the invention. Closed cell content is ASTM to obtain open cell content
Measured by air pycnometer using the technique described in D-2856 (Method C). Closed cell content is
100 - open cell content. The thermal conductivity of the foam is measured using the technique described in ASTM C-518-76 to a thickness with a width and length of at least 20.3 cm.
Measurements were made on a 2.54 cm sample. The top surface of the sample is 32
℃ and the lower side to 15.5 ℃ to bring the average temperature of the entire sample to 24 ℃. A heat flow thermal conductivity meter constructed according to such a method and available as Rapid-K from Dynatech R/D Company was used. The resol used in each example was dehydrated to less than 3% water by weight and at 50-60°C for a sufficient time to give the desired viscosity as measured using a Burckfield viscometer model HBT. It thickened.
Since the change in viscosity due to temperature is significant, a Bruckfield thermocell was used for the resol in the Examples described later. The thermocell consists of a thermal vessel with an SCR controller type HT-64, an SC4-27 spindle and an HT-2 sample vessel. Measurements were performed at 25°C. All listed viscosities were obtained by this technique. The burst pressure of a particular foam cell was determined by measuring the closed cell content of a foam sample, then placing the sample in a pressure tube and applying small increments of isotropic pressure. After applying the above pressure for 5 minutes, the closed cell content was measured again. The sample was then replaced in the tube and pressurized at slightly higher isotropic pressure for 5 minutes before the closed cell content was measured again. This procedure was repeated at higher pressures and the closed cell content was plotted and graphed against pressure. At characteristic isotropic pressures for each foam, the closed cell content was found to drop dramatically by at least 10% and continue to drop thereafter. This pressure is called the "bursting pressure." Example 1 This example illustrates the very high burst pressure of foams according to the invention. The following ingredients were mixed together using a short residence time, high shear pin type mixer supplied by Oaks Machinery Company and commonly referred to as an "Oaks mixer." Resole A (1) F/P ratio 1.89:1 96 parts by weight Viscosity at 25℃ 100000 cps Blowing agent Freon 114 (2) 16.5 parts by weight Surfactant DC-193 (3) 4 〃 Blowing catalyst (4) 2.24 〃 (Note) )(1) RI-5100 (a Monsanto product), a resol containing oxalate dispersed as a result of neutralizing a calcium hydroxide catalyst with oxalic acid. (2) Fluorocarbon (1,2-dichloro-
tetrafluoroethane). (3) Silicone-based surfactants available from Dow Corning under the trade names listed above. (4) A 2:1 (by weight) mixture of diethylene glycol and Ultra TX acid (a toluene sulfonic acid/xylene sulfonic acid mixture available from Witco Chemical Company under the above trade name), expressed by acid component content. The blowing agent was pneumatically fed and the resulting formulation was passed directly through an extrusion head in the form of a nozzle fitted with a torpedo valve to control the rate of expansion of the foamable mixture from the head. The temperature of the mixture in the extrusion head was 40-42°C and the pressure at the valve was maintained at 3.74-4.42 atmospheres. The extrusion head was reciprocated so that a continuous ribbon of foamed mixture was deposited on the moving sheet of kraft paper. The mixture was deposited in essentially parallel lines of 40 cm length so that as foaming occurred, the lines solidified to form a continuous sheet. About 10 minutes to fully cure the foam in that time.
It was left at 60°C for minutes and cut into convenient sizes using a saw. The sections were then stored at 60°C for 18 hours. Samples 1-A to 1-G were taken from different parts of the foam sheet produced by the above method and the density, closed cell content, initial thermal conductivity (k ₁ )
and thermal conductivity (k ₁₀₀ ) after 100 days. The results are listed in Table 1.

EXAMPLE 2 This example illustrates the use of a resol with an F/P ratio of 1.6:1 to produce a foam according to the invention. The resol was the same type of dispersed salt resol used in Example 1, but made at a lower F/P ratio. The resol was dehydrated and thickened to a viscosity of 106,000 cps as described above. The surfactant, blowing agent and catalyst used were as described in Example 1 and the weight proportions were as follows. Resole 96 parts Blowing agent 16.5 parts Surfactant 4 parts Blowing catalyst 1.54 parts
(Value converted to acidic component of catalyst) The above components were mixed as described in Example 1 except that the viscosity of the resol was 106000 cps at 25°C and the temperature in the extrusion head was 49.2°C; Foamed and cured. When evaluated in the same manner as the foam produced in Example 1, the foam had a density of 39.4 Kg/ ^m3 ;
Initial closed cell content of 91.6%, isotropic burst pressure of 2.46Kg/ ^cm2 , _k1 of 0.0181 Watts/m℃ and 0.187
It was found to have a k ₁₀₀ of Watts/m°C. This is 0.13×10 ^-3 for the formula k ₁₀₀ −k ₁ /lnt ₁₀₀ −lnt ₁
gives the k retention value of . Examples 3-10 Examples 3-10 illustrate the sensitivity of the method to changes in ingredients and conditions. In the examples, resols with a nominal F/P ratio of 2:1 were used that were dehydrated to different degrees to give different viscosities. The surfactant and blowing catalyst were the same, but the surfactant and catalyst (Ultra
The amount of (expressed as the amount of TX acid component) was varied. Additives intended to enhance the flexibility of the foam (based on the total weight of the foamable composition) were used as described. For Examples 6, 7, 8 and 9 alone, the form from the extrusion head was 25.4
The mixture was poured into aluminum foil trays measuring 30.5 x 4.8 cm and then placed in a batch furnace at 40-45°C for 18 hours.
Other differences from Example 1 are listed in Table 2.

【table】

TABLE The foams produced according to Examples 3-10 had characteristics similar to those of Example 1 and the results are listed in Table 3.

[Table] Examples 1 and 2 above and Examples below
12 and 13 indicate the materials and conditions found for manufacturing the foams of the invention. Variations in various materials and conditions from those used in Example 1 to produce the foam lead to unsatisfactory results as evidenced by the results in Table 3 above. The relationship between these variables is complex and not easily understood at this time. When one variable is changed, the other variable should be considered and changes made as required to obtain the form of the invention. Those skilled in the art will recognize the interplay of these variables after reading this specification. EXAMPLE 11 A sample of a closed cell resol foam of unknown formulation and cure history but with clearly superior performance compared to commercially available phenolic foams was obtained from a third party and tested in 1978. 8
It started on the 15th of May. The preliminary samples were tested by the technique described in Example 1. The results were as follows. Density 35.2Kg/m ³ Closed cell content 97% Thermal conductivity (at the time of acquisition) 0.0132 Watts/m℃ Thermal conductivity (after 100 days) 0.0176 Watts/m℃ △k/△lnt 0.96×10 ^-3 In Example 1 The samples were tested for burst pressure on January 13, 1981 after being heated for 18 hours at 60° C. to undergo at least as good a cure as described. The result obtained was a burst pressure of 1.55 Kg/cm ² . According to the above results, the foam retains its low initial thermal conductivity considerably after 100 days, which is not consistent with that of the present invention or as measured by the k retention value, for example as listed in Table 1. It can be seen that the loss ratio is not as low as that of the foam of the present invention in Example 1. Furthermore, since the foam can withstand high curing temperatures, this retention is not a sufficient indicator of usefulness. The low isotropic burst pressure of the foam indicates that the foam cannot withstand curing without cell collapse. In fact, a foam sample from the same source obtained one month later and untreated
When heated at 120° C. for 1 hour, the closed cell content decreased from 92.2% to 17.5% after 10 minutes in the pycnometer. Therefore, it is believed that this foam does not have sufficient strength to withstand curing operations or thermal cycling so that it can be installed on conventional asphalt waterproof roofs. As a comparison, when the foam produced by the conditions described in Example 1 was subjected to an additional 2 hours at 120°C, the closed cell content decreased only from 95.5% to 94.4%. Example 12 This example illustrates the use of salt-free resols to make foams of the present invention. The resol used was made using the same proportions and ingredients used to make the resol used in Example 1. However, carbon dioxide was used instead of calcium oxide in the resol to neutralize it. The calcium carbonate was precipitated out and the salt-free resol was dehydrated to the appropriate viscosity and mixed with the blowing agent, surfactant and catalyst described in Example 1. Two forms were obtained from two different experiments and the methods and proportions used in these experiments are shown in Table 4 below.
It was the same as described in Example 1 except as indicated in .

【table】

TABLE These two foams were evaluated in the same manner as the foam of Example 1 and the results are listed in Table 5.

EXAMPLE 13 This example illustrates the production of foams of the present invention using a resol having a nominal F/P ratio of 2:1. All parts are by weight. Continuous mixer model 4MHA with jacket available from Oaks Machinery with the following ingredients:
mixed together using Resole F/P ratio 1.93:1(1) 96 parts Viscosity at 25℃ 263000 cps Blowing agent Freon 114(2) 15 parts Surfactant DC-193(3) 4 parts Blowing catalyst (4) 2.2 parts (Note) (1) The liquid resol contained dispersed oxalate as a result of neutralizing the calcium hydroxide catalyst using oxalic acid. The F/P ratio was obtained by nuclear magnetic resonance (NMR) analysis as described above. (2) Fluorocarbon (1,2-dichloro-
tetrafluoroethane). (3) Silicone-based surfactants available from Dow Corning under the trade names listed above. (4) Diethylene glycol and Witco
A 2:1 weight ratio mixture with Ultra TX acid (based on acid component content), a toluene sulfonic acid/xylene sulfonic acid mixture available from Chemical Company. The blowing agent was held in a bomb-type container and saturated with air by blowing about 15 atmospheres of air into it for about 4-6 hours. This was done to promote uniform nucleation of the blowing agent upon pressure reduction during the subsequent foaming process. The resol, which had been stored at about 5°C to minimize progression, was first brought to room temperature (25°C) and experiments for reactivity were performed. This test was performed at three different acid concentrations (eg, 1, 1.5 and 1.8% as described in (4) above and based on resole weight) to determine the sensitivity of resol reactivity to acid concentration.
150 g of resol and 3 g of DC-193 surfactant were placed in a pint paper cup and mixed for 1 minute with a high speed mixer (720 rpm). Then 22.5
g of Freon 113 blowing agent was added and the contents were mixed for an additional minute. Next, the acidic catalyst solution of toluenesulfonic acid and diethylene glycol was added and mixed for an additional 30 seconds. Approximately 5.7 cm tall with a thermocouple connected to a recorder with 100 g of mixed formulation
cm and into a cylindrical container with a diameter of 20.3 cm. The capped container was placed in an oven set at 60°C, and the peak temperature and time to reach it were noted. The reactivity value, defined as the rate of temperature rise between the furnace temperature and the peak temperature reached by the foamed composition, was expressed in °C/min and was calculated to be 3.2 °C/min. This value is a resol characteristic value such as F/
It varies widely because it depends on the P ratio, water content, molecular weight, etc. A resol having a reactivity value of about 2 to about 12, preferably 3 to 7 at an acid catalyst concentration of 1.5% was used. If the reactivity value is too high, water is added to a particular resol to reduce it, but if the reverse is true, the acid concentration is adjusted upward. The resol and surfactant were first mixed together at about 25-40°C in a jacketed paddle mixer for about 30 minutes under 5 mm of mercury absolute to avoid air entrainment. The resol, surfactant, blowing catalyst and blowing agent were fed continuously into the Oaks mixer in the above ratios through a suitable flow metering device. A turbine meter obtained from Flow Technology, Inc. was used for the Freon and an oval gear meter obtained from Emerson Electric Co., Brux Instrument Division was used for the resol-surfactant-acid catalyst stream. Oaks mixer approximately 93rpm
and water was run through the jacket at about 40°C. Hot water was supplied to the resol supply line at approximately the same temperature. Blowing agent and catalyst were metered into a mixer at 25°C. The temperature of the foam composition entering the mixer was about 30-40°C, while exiting the mixer was about 45-50°C. Temperature rise in high shear mixers should be minimized to limit reactions that would otherwise render the mixer inoperable. Similarly, the mixer pressure should be above the vapor pressure of the blowing agent to avoid premature foaming, and for Freon 114 in this example, the pressure should be maintained at about 3.4 to 6.8 atmospheres. The resulting formulation is 91cm long x diameter from the mixer.
It was fed through a length of insulated transfer tube consisting of 1.27 cm pipe (where foaming begins) to an extrusion head in the form of a 0.64 cm diameter nozzle. Upstream of the extrusion head was a blender with a torpedo control valve (tube-automatic valve B-310208, available from Shrinker Fluid Power Company). This pneumatic control valve controlled the back pressure in the mixer and feed lines and the expansion rate of the foamable mixture exiting the head. The flow rate of the foam composition through the apparatus was approximately 430-440 g/min. The temperature of the mixture at the nozzle was 49°C, while the pressure there was 0.68 atm. The pressure at the inlet leading to the control valve was 3.9 atm, and the temperature at the inlet was 50.9°C. Thickness 0.254mm, progressing at a speed of approximately 24.4cm/min.
The extrusion head was moved back and forth approximately 55.9 cm in 2-4 seconds to deposit a continuous ribbon of foam mixture on a sheet of natural kraft paper weighing 205 Kg/1000 m ^<2> . The distance of the nozzle from the moving paper was kept to minimize air entrainment. The mixture was deposited in essentially parallel lines so that as foaming occurred, it solidified to form a continuous sheet. In this regard, the nature of the foam deposited on the moving paper web is a function of the pressure drop across the control valve. If the pressure upstream of the valve is too high, a mushy deposit will be obtained, which will cause visible stitch lines as the ribbon-like molding exits the head, and will eventually result in undesirable stitch lines having such stitch lines. Generates large bubbles. On the other hand, if such pressure is too low, foam shear will occur in the control valve and supply pipe, which means that the bubbles will collapse and the blowing agent will escape. The stream exiting the nozzle should have a foam consistency such that rapid expansion occurs without air entrapment as the composition is deposited onto the paper substrate. Immediately downstream of the extrusion nozzle, a kraft paper protective cover was applied to the top of the moving foam sheet. Such a cover (having the same properties as the paper substrate) was passed around a stationary roller approximately 30.5 cm from the nozzle in contact with the rising foam sheet. The diameter of the foam then placed across the path of the foam moving the covered foam sheet.
A series of six 3.8 cm closely spaced free-floating steel rolls are forced into compressive engagement to accommodate foam surface irregularities and promote good wetting by the foam of the top layer of protective paper. These rollers served to develop a constant pressure on the moving foam and were positioned vertically to contact the 0.64 cm thick top layer. This is important. This is because the foam product may warp if it does not adhere well to the upper and lower paper layers brought about by contact with the compression rolls. The foam sheet, whose top and bottom surfaces are covered with kraft paper, is then transferred to a 25-foot Air Film Principle Foam Container conveyor.
The mixture was passed through a hot air curing tunnel in the form of a furnace obtained from the Kornylak company listed as Conveyor. This tunnel furnace had a series of five pairs of perforated platens (one in each pair above and below the moving form, each approximately 1.5 m long) arranged vertically 15.2 cm apart. It consisted of a cross section approximately 7.6m long. A film of hot air controlled at 53°C exited the first pair of platens closest to the extrusion nozzle opposite the paper covered top and bottom sides of the foam. Also, the diameter is approximately 3.8cm
A series of mutually approaching floating rollers were present in the oven below the first platen for contacting the covered top portion of the foam sheet. The air flowing out of the remaining platen is approximately 45-55
The temperature was maintained in the range of °C. The residence time of the foam in such an oven was about 31 minutes, at which time it had hardened sufficiently to be cut into convenient shapes with a saw. These sections were then stored at 60°C for 18 hours. Periodically (approximately once every 30 minutes), a thermocouple was inserted into the foam adjacent to the extrusion nozzle and moved down the tunnel to measure the internal temperature of the foam formulation. The peak exotherm temperature was maintained at about 60-65°C and controlled by adjusting the hot air temperature in the curing oven and/or the concentration of acid curing catalyst in the mixture. Samples 5-1 to 5-5 were taken from different parts of the foam sheet produced by the above method and the density, closed cell content, initial thermal conductivity (k ₁ ) and Thermal conductivity (k ₁₀₀ ) was tested after 100 days. The results are listed in Table 6.

【table】

[Table] The above results demonstrate that the density is between 30 and 70 Kg/ ^m3 , the closed cell content is at least 85%, the thermal conductivity after 100 days is less than 0.020 Watts/m℃, the k retention value is less than 0.5× ^10-3 and Figure 2 shows a partially cured foam of the present invention having an isotropic burst pressure greater than 1.75 Kg/ ^cm2 . The reason for the high k ₁₀₀ and k retention values for samples 5-1 and 5-2 is unknown.

Claims (1)

[Claims] 1. A method for continuously producing a partially cured phenolic foam, characterized by comprising the following steps (a) and (b): (a) a molar ratio of formaldehyde to phenol;
a phenolic resol having a ratio of 1.2:1 to 2.5:1, a surfactant in an amount of 0.5 to 6% by weight of the resol;
and depositing on a conveyor a partially expanded phenolic froth foam containing at least one blowing agent that readily evaporates under atmospheric pressure; (b) further expanding and curing the froth foam; 2. A partially cured phenolic foam core having two main surfaces characterized by having the following steps (a), (b) and (c) and a surface finishing material provided on at least one main surface thereof. A method of manufacturing an insulation board having: (a) transporting the surface finishing material along the production line, and (b) ensuring that the molar ratio of formaldehyde and phenol is
a phenolic resol having a ratio of 1.2:1 to 2.5:1, a surfactant in an amount of 0.5 to 6% by weight of the resol;
and depositing on the surfacing a partially expanded phenolic froth foam containing at least one blowing agent that readily evaporates under atmospheric pressure; (c) contacting the froth foam with the surfacing. In this state, it is further expanded and hardened.