Improved foamability of phenolic resins

Abstract: The invention is a solution of highly advanced phenolic resin with improved inherent foamability that is made from the reaction of phenol, aldehyde, water and alkali the improved foamability being brought about by the incorporation of up to 1.0% by weight, anhydrous basis, lime (calcium hydroxide) into the early stages of the reaction mix. In another embodiment, the invention is a plywood glue composition comprising a solution of lime-­ containing highly advanced phenolic resin, dried animal blood and preferably an aldehyde glue viscosity-lowering agent.

Description: FIELD OF THE INVENTION This invention relates to solutions of advanced phenolic resins with improved foamability that are useful as foamed adhesive binders in the manufacture of plywood. BACKGROUND OF THE INVENTION Phenol-formaldehyde resins are widely used as adhesives and binders in the making of laminated products such as plywood. One process for applying phenol-formaldehyde resins to wood laminates such as plywood is the foam extrusion process. Historically the use of the foam extrusion process to apply solutions of phenol-formaldehyde resin presupposed, of course, that the resin solutions were foamable. At first, it was possible to foam such resin solutions adequately since relatively low molecular weight phenolic resins were used in their manufacture. However, the use of phenolic resins of low molecular weight creates an economic problem in that a relatively long press time is required to cure them in the plywood hot presses. This in turn delays production and increased costs. In an effort to overcome this problem, the plywood industry has turned to the use of more highly advanced (higher molecular weight) resins which cure faster in the press. Presently the high molecular weight resins are supplied to the market in aqueous alkaline solutions containing about 40% by weight resin solids, as opposed to the low molecular weight solutions containing about 50% resin solids that were formerly used extensively. A serious problem attended the use of high molecular weight phenolic resin glues using conventional foaming techniques because they are not foamable at all, or at least with sufficient speed to be useful in the commercial production of plywood using foamed glue. The serious problem of foaming high molecular weight phenolic resin glues was overcome by the addition of various ingredients including a foaming agent such as blood. At the present time, when phenolic glues are applied to wood laminates using the foam extrusion process, the solution of phenolic resin is mixed with water, glyoxal, spray dried blood, wheat flour, sodium hydroxide and surfactant, or various other ingredients, and then pumped through a mechanical foamer where air is introduced. The resulting foam which has a specific gravity of 0.2 or less is then extruded onto the veneer sheets which are consolidated to form panels. The panels are then hot pressed to form a strong exterior bond. In this application, the terms veneer and veneer sheet are used to mean any of the thin layers or plies of wood which are bonded together to form plywood. One key ingredient in foaming solutions of high molecular weight phenolic resins is spray dried blood which acts as a foaming agent and also enhances foam stability. Even though blood contributes much to the phenolic based glue, it is very expensive compared to the other ingredients. Although blood is a good foaming agent, frequently the foam density still varies resulting in skipped spread and poor bonds, which if severe enough can reduce plywood production. Plywood consists of veneer sheets bonded together with grains of alternate layers perpendicular to each other. Veneer is usually made by the rotary lathe method which comprises rotating a log of wood against a knife. Once the rotary peeled veneer is clipped, dried, and graded, it is ready to be made into plywood. The veneer sheets are spread with adhesive, and then consolidated into a package that is conveyed into a prepress that applies 862-1207 kPa (125-175 psi) for about three minutes. After prepressing, the package is conveyed to the hot press. Here the panels are fed into a multiple opening steam press and pressed to cure the phenolic resin. A press temperature of 141°C-182°C (285°F-360°F) and pressure of 862-1380 kPa (125-200 psi) is used. Press time is dictated by panel thickness and particular lay-up. Assembly time ranges anywhere from 10 to 40 minutes with 15-20 minutes being most common. After hot pressing, panels are usually allowed to post cure in the stack for at least two hours before sawing. However, some mills immediately convey them to the saw line where they are trimmed to size. When adhesive is applied to the veneer, several methods can be used such as rubber roll spreading, airless spraying, and curtain coating. However, foam extrusion adhesive application has come into use. Phenolic resin based adhesives are well known in plywood manufacture. As originally adopted, phenolic adhesives were applied between confronting plies in liquid or droplet form. With the advent of a process for extrusion of foamed glue, phenolic resin based adhesives have been adapted for foam extrusion application. Phenolic adhesives are typically foamed and then applied by a foam extruder. Foaming usually increases the volume of the adhesive about five times. The foam is extruded in flexible coherent parallel rods on the surface of veneer to be bonded, as it travels under an extrusion head. In the preparation of foamed adhesive, as a first step, unfoamed adhesive travels through a defoamer where it is brought to a uniform density of about 930 kg/m³ (0.93 grams/cc). After defoaming, the adhesive may be stored in a feed tank until it is to be foamed. From the feed tank it is metered into a foamer which rapidly converts unfoamed adhesive to foamed adhesive. The foamed adhesive is then directed through the extrusion head onto the surface to be bonded. After extrusion of the rods of foamed adhesive onto the top surface of a veneer sheet, a second layer is placed over the adhesive and the layers are roller pre-pressed. Pre-pressing spreads the rods of foamed adhesive into a uniform mat which wets the adjacent surface and insures good contact between the layers. In the foam extrusion process, if the phenolic resin base is a high molecular weight resin, a foaming agent such as dried blood must be added to the resin to improve its foamability. The Cone et al patent, U.S. 3,905,921, describes a plywood glue in which blood is used to improve the foamability of a high molecular weight phenolic resin. The phenolic resin used by Cone et al was a resin of commerce produced by Borden, Inc., the assignee of this invention. JP-A-56127675 discloses adhesive compositions comprising a ketone-modified urea resin solution, water-insoluble protein and an oxide, hydroxide or basic salt of an alkali metal or an alkaline earth metal. The compositions may be used for bonding wood or inorganic materials. For the purposes of this invention, a solution of high molecular weight phenolic resin solution is defined as a solution which is the condensation product of a phenol, an aldehyde, water and alkali and which has a resin solids content of from 35% to 45% by weight of resinous condensation product and a degree of advancement such as to impart to the aqueous resin solution a viscosity of from 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM and has an alkali content of from 5.5% to 7.6%. The term alkali as used herein, is defined as any of the hydroxides or soluble salts of alkali metals. The term alkalinity of a resin solution as used herein is defined as a measure of the basic properties provided by alkali compounds and alkaline earth compounds in the resin solution. The term "alkali content" of a resin solution as used herein is defined as a calculated figure of the amount of anhydrous sodium hydroxide by weight, based on the total weight of resin solution, that would provide the same degree of alkalinity that is provided by the alkali and alkali earth compounds that are actually in the resin solution. One of the major problems that occurs with foam extrusion glue application is that intermittently small portions of the glue will not foam. When this happens, glue foam density increases and extrusion beads break, causing areas of the ply surface to be void of glue. As one would expect, this produces poor quality plywood. Poor glue foamability is due to a variety of factors that are very subtle, hard to define and control. The phenolic resins made according to this invention inherently foam better than comparable phenolic resins of the prior art and use of the resins of this invention should overcome some of these subtle problems. SUMMARY OF THE INVENTION The invention in one preferred embodiment is a foamable glue composition comprising a solution of high molecular weight phenolic resin, wherein said solution is the reaction product of a reaction mixture comprising phenol, aldehyde, water, alkali and not more than 1.0% of a soluble alkaline earth hydroxide and wherein said solution has a resin solids content of from 35% to 45% by weight, a viscosity of 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM and an alkali content of from 5.5% to 7.6%. In another embodiment, the invention provides a process for making a foamable glue composition comprising dried animal blood having a water solubility of not more than 90% by weight, water, high molecular weight phenolic resin solution, and optionally aldehyde glue viscosity lowering agent, wherein said solution of phenolic resin is the reaction product of a reaction mixture comprising a phenol, an aldehyde, water, alkali metal hydroxide, and not more than 1.0% of an alkaline earth hydroxide added at an early stage of the reaction and said solution has a resin solids content of 35%-45%, a viscosity of 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM and an alkali content of from 5.5% to 7.6%. In another embodiment, the invention is a process for the production of laminate by bonding together with a foamed adhesive binder that is curable under heat and pressure, at least two plies having a layer of the foamed adhesive binder between them, comprising (1) applying to at least one surface of at least one lamina a foamed adhesive binder that is curable upon the application of heat, said adhesive binder comprising in admixture: (a) a solution of high molecular weight phenolic resin, said solution being the reaction product of a reaction mixture comprising phenol, aldehyde, water, alkali metal hydroxide and not more than 1.0% of an alkaline earth hydroxide said solution having a resin solids content of from 35%-45% by weight, a viscosity of from 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM and an alkali content of from 5.5% to 7.6%; (b) dried animal blood; and optionally (c) aldehyde glue viscosity lowering agent; (2) juxtaposing the lamina to which the adhesive binder has been applied with another lamina, and then (3) subjecting said juxtaposed laminae to heat and pressure to cure the resin and unite the laminae to form a laminate. In another embodiment the invention is a cured laminate of at least two cellulosic plies comprising a first ply, a second ply, and a cured phenolic glue interposed between said plies and bonding them together said glue comprising a bonding layer formed by interposing a layer of foamed glue between said plies and applying heat and pressure to cure the glue, wherein said foamed glue comprises a foamed mixture of (a) a solution of high molecular weight phenolic resin, said solution being the reaction product of a reaction mixture comprising phenol, aldehyde, water, alkali metal hydroxide and not more than 1.0% of an alkaline earth hydroxide wherein said solution has a solids content of from 35%-45% by weight, a viscosity of from 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM and an alkali content of from 5.5% to 7.6%; (b) dried animal blood having a water solubility of not more than 90% by weight; and optionally, (c) an aldehyde glue viscosity lowering agent. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph in which the foam density of whipped glue mix in g/cm³ (grams/cc) is plotted versus the time period in minutes during which the glue mix was whipped. The foam density is measured immediately after being whipped. The glue mixtures on which the graph is based were made from the lime-modified phenolic resin solutions and the control resin of Example 1, as described below. This figure shows the following for each of the two glue formulations. A glue mix made with lime-modified phenolic resin solution had greater foamability (i.e., lower foam density) than the control mix which was made with phenolic resin solution that was not lime-modified. Glue mix made with phenolic resin solution modified with 0.50% lime had greater foamability than the comparable glue mix made with phenolic resin solution modified with 0.25% lime. Figure 2 is a graph in which the foam density of whipped glue mix in g/cm³ (grams/cc) is plotted versus the time period during which the glue mix was whipped. The glue mixes on which the graph is based were made from the lime-modified phenolic resin solutions and the control resin of Example 2. This figure shows the following for each of the two glue formulations. A glue mix made with lime-modified phenolic resin solution had greater foamability (i.e., lower foam density) than the control mix which was made with phenolic resin solution that was not lime-modified. Glue mix made with phenolic resin solution modified with 0.50% lime had greater foamability than the comparable glue mix made with phenolic resin solution modified with 0.25% lime. DETAILED DESCRIPTION OF THE INVENTION The invention in one preferred embodiment is an aqueous alkaline solution of a lime-containing high molecular weight resin. The high molecular weight phenolic resins of commerce that are used for formulating adhesives for bonding wood laminates are generally made by the condensation reaction of phenol, aldehyde, water and sodium hydroxide. Cone et al, in the patent referred to above, used a higher molecular weight resin of commerce, sold under the trade mark "Borden W-166S". The improved high molecular weight phenolic resin solution of this invention is made by adding lime in an early stage of the condensation reaction of a reaction mixture of phenol, aldehyde, water, and sodium hydroxide. The resinous condensation product of a phenol and an aldehyde may comprise any of those resinous condensation products suitable for use in the production of plywood-type glues. Typical phenols that may be used comprise phenol itself (benzenol), the cresols, and resorcinol. Typical aldehydes include formaldehyde, acetaldehyde, and furfural. The commonest of such products, and the one that is used in the examples of the invention, is the resinous condensation product of phenol (benzenol) and formaldehyde. The high molecular weight phenolic resin solutions of commerce as well as those made in the examples of this invention are characterized by having a relatively high degree of advancement so that the resin will set rapidly in a plywood press, i.e., in a matter of several minutes less as compared with the time required when phenolic resins having conventional degree of advancement are used. The degree of advancement of such resins is a difficult property to characterize. However, for present purposes high molecular weight phenolic resin solutions are those which have a resin solids content of from about 35-45% by weight and the resins have a degree of advancement such as to impart to the aqueous alkali resin solutions in which they are contained a viscosity in the range of from 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM. In another embodiment, the invention is rapidly-foamable liquid phenolic glue comprising a solution of lime-modified high molecular weight phenolic resin, dried animal blood, water and preferably an aldehyde glue viscosity lowering agent. By incorporating up to 1.0% anhydrous lime by weight (or equivalent) based on total weight of the reaction mix into the early stage of the reaction of the high molecular weight phenolic resin, it is possible to improve the inherent foamability of the phenolic resin produced and thereby reduce the quantity of dried animal blood needed to make foamed adhesive for bonding wood laminates. A reduction of the quantity of blood needed reduces costs. It is contemplated that the use of these lime-containing resins will allow more freedom in the selection of other resin composition variables such as wheat flour and surfactant. Applicants have discovered that the viscosity stability of adhesive systems which contain lime-modified high molecular weight phenolic resins is enhanced when compared to adhesive systems which contain unmodified high molecular weight phenolic resin. This improvement comes about because smaller amounts of blood are needed to make the adhesive system. It is theorized that the improved foamability of the lime modified phenolic resin solution of this invention comes about because lime is a divalent catalyst. It is contemplated that an improved resin could be made using other alkaline earth hydroxides or mixtures thereof in place of lime. Anhydrous lime was used in the examples of this invention. Anhydrous lime (i.e. anhydrous calcium hydroxide) is a standard item of commerce and is in powdered form. It is contemplated that any alkaline earth metal hydroxides in anhydrous or hydrous form could be used in place of anhydrous lime. The blood used to make the adhesives of the invention may be the dried blood of commerce available in powdered form. This product is manufactured by collecting beef, hog or sheep blood from the slaughter house floor and dehydrating it under controlled conditions to a dry powder form. In one successfully operated commercial process, the blood is sprayed into a cyclone separator containing hot air under carefully controlled conditions of temperature and time to produce a spray dried blood product of desired properties. By controlling the operating variables the degree of water solubility of the dry blood may be varied over a range of from completely soluble to completely insoluble in water. It is preferred to use a dried blood product having a water solubility of from 30%-90% by weight. Blood products having a solubility of less than 30% are not quite as efficient as foaming agents as are those having a greater degree of water solubility. One the other hand, blood products having a water solubility of more than 90% may cause gelation of the compositions. The aldehyde glue viscosity lowering agent that is preferably used to make the adhesives may be any suitable aliphatic or aromatic aldehyde. Typical aldehydes which may be used are the lower aliphatic aldehydes including formaldehyde; the formaldehyde donors, such as paraformaldehyde, sodium sulfite formaldehyde, and onyzolidine; glyoxal; glutaraldehyde; pyruvicaldehyde and the lower molecular weight aromatic aldehydes such as benzaldehyde. These aldehydes may be used singly or in combination with each other. They are used in an amount sufficient to reduce the viscosity of the glue to the desired level. In the experiments which demonstrate the invention, solutions of lime-modified high molecular weight phenolic resins were prepared. These resins were made up into glue formulations comprising resin, blood, water and glyoxal as the viscosity lowering agent. The foamability of each glue formulation was then tested by whipping the glue for an appropriate time and measuring the density of the foamed glue. The experiments showed that an adhesive comprising phenolic resin made from a reaction mix containing up to about 1.0% anhydrous lime by weight based on the total weight of the reaction mix foamed better than an adhesive made with resins containing lesser amounts of lime or no lime. In the examples, the high molecular weight phenolic resin solutions were prepared using standard procedures and equipment. In the examples, the resin glue mixes were made from water, glyoxal, blood and resin solution. The blood used was California Spray Dry beef blood having a solubility of 77% ± 2.5%. It is contemplated that other kinds of dried blood or dried blood blends could be used. The glyoxal used was an aqueous solution containing 40% glyoxal. Unless otherwise stated, the mixing of water, glyoxal, blood and resin was done by hand using a beaker and a spatula. Under commercial conditions in a plywood mill, a mechanical mixer would be used. In the examples, in order to measure the foamability of the mixes, a mechanical foamer was used. The mechanical foamer used consisted of a cylinder (stator) and mixing blade (rotor) that whipped air into the glue. Air pressure was applied to the cylinder and a regulator was used to control air pressure. Glue was poured into the cylinder and sealed; air was loaded to 448 kPa (65 psi) and the agitator (rotor) was turned on. The glue was whipped for the desired time and the foamer was then turned off and air was released. When the air pressure was released the glue foamed up in the cylinder. The foamer was then opened and a sample of the foamed glue was removed and its density was determined. The foam density was determined by filling a foam sample into a cup of known volume so as to completely fill the cup and weighing the filled cup. This weight, tared for the weight of the cup, is divided by the cup-weight of water, tared for the weight of the cup. A glue mix of water, glyoxal, blood and resin which foams to give a foam density of 180 kg/m³ (0.18 grams/cc) or less is considered a good mix to use for the foam gluing of wood laminates. In the examples, when the mechanical foamer was used, 100 ml of glue mix was placed in the cylinder; the rotor was rotated at 650 RPM and the air pressure was maintained at 448 kPa (65 psi). Whipping time was either one, two or three minutes. Two series of tests were run and the results are reported below in Example 1 and Example 2. In each example, a set of three comparable high molecular weight phenolic resins with different amounts of lime were prepared and designated A (control - no lime), B, and C. Subsequently, different glue mixes, designated Mix I and Mix II, were made up. The glue mixes were foamed and the density of each foamed glue was measured. The invention will be demonstrated by the following examples. In these examples and elsewhere throughout the specification, parts and percentages are by weight and temperatures are in degrees Celsius unless expressly indicated otherwise. Weights of ingredients are given on an as is basis unless otherwise indicated. In all of the examples which describe the preparation of the solutions of high molecular weight phenolic resin, the progress of the reaction was measured by a Gardner-Holt viscometer. All Brookfield viscosity values recited hereinabove and in the appended claims are made with reference to an RVF Brookfield Viscometer using a No 2 spindle at 20 RPM and at 25°C unless otherwise specified. EXAMPLE 1 PART 1 - PREPARATION OF SOLUTIONS OF HIGH MOLECULAR WEIGHT PHENOLIC RESINS In Example 1, the resins were made from 4,000 g batches of a mixture of phenol (benzenol), formaldehyde, water, sodium hydroxide and lime. The phenol used was an aqueous solution containing 86.3% phenol; the formaldehyde solution used was a 50% aqueous solution; the sodium hydroxide solution used was a 50% aqueous solution and the lime was powdered anhydrous calcium hydroxide. Three resins were prepared: Resin 1A, (control - no lime); Resin 1B, containing 0.25% lime by weight based on the total weight of the reactants; and Resin 1C, containing 0.50% lime. Preparation of Resin IA (control - no lime) 1034.88 g of phenol, 1281.56 g of formaldehyde solution and 1083.56 g of water were charged into the reaction pot and heated to 50°C. 304 g of sodium hydroxide solution were charged over a period of about 60 minutes with the temperature held at 65°C. The mix was then heated to 96°C and condensed to "B-C" (as measured by Gardner Holt viscometer). 296 g of sodium hydroxide solution were charged over 15 minutes. The mix was condensed to "J" at 96°C and then condensed to "V" at 84°C followed by full cooling. Preparation of Resin 1B (0.25% lime) 1034.88 g of phenol; 1281.56 g of formaldehyde solution and 1073.56 g of water were charged and heated to 50°C. 10 g of anhydrous lime (calcium hydroxide) was charged and the mixture was held for ten minutes to just below 65°C. 304 g of sodium hydroxide solution were charged over 60 minutes holding the temperature at 65°C. The resin was heated to 96°C and condensed to "B-C". 296 g of 50% sodium hydroxide solution was charged over 15 minutes and the mix was condensed to "J" and 96°C and then to "V" at 84°C followed by full cooling. Preparation of Resin 1C (0.50% lime) 1026.8 g of phenol; 1271.4 g of formaldehyde solution and 1081.8 g of water were charged and heated to 50°C. 20 g of anhydrous lime (calcium hydroxide) was charged and held for 10 minutes below 65°C. 304 g of sodium hydroxide solution were charged over 60 minutes holding the temperature at 65°C. The resin was heated to 96°C and condensed to "B-C". 296 g of sodium hydroxide solution were charged over 15 minutes and the mix was condensed to "J" at 96°C and then to "V" at 84°C followed by full cooling. The composition of each resin on a weight percent basis is shown in Table 1, below. The specifications of each resin are listed in Table 2. PART 2 - PREPARATION AND FOAMING OF FOAMABLE GLUE MIXES Foamable glue mixes, Mix 1 and Mix 2, were made corresponding to each solution of high molecular weight phenolic resin that was prepared. The formulations for glue mix 1 and glue mix 2 are described in Table 3. The glue mix 1 using resin 1A was made as follows. 20.4 g of water and 0.8 g of 40% glyoxal were mixed together with a spatula in a beaker for a few seconds. 9.8 g of dried blood were added and mixing was continued for one to two minutes. The mixture was left standing for five minutes and then mixed until smooth which took about two minutes. 70.1 g of water was added and mixing was continued for about a half a minute. 348.2 g of resin 1A were added and mixing was continued for about two minutes. The glue mix was now ready for foaming. In order to foam glue mix 1, 100 ml of the mix was placed in the cylinder of the mechanical foamer described above. The rotor of the foamer was then rotated at 650 RPM with an air pressure of 448 kPa (65 psi) for one minute. The pressure was then released and the foam density of the foamed glue mix was measured as described above. The foam density was measured to be 302 kg/m³ (0.302 grams/cc). The above procedures were repeated twice. In one instance glue mix 1 was foamed for two minutes and in the second instance glue mix 1 was foamed for three minutes. The preparation and foaming as described above was repeated for all resins and for all three time periods. The density of each of the prepared foams was measured and all the results are recorded in Table 4. EXAMPLE 2 PART 1 - PREPARATION OF SOLUTIONS OF HIGH MOLECULAR WEIGHT PHENOLIC RESINS In Example 2, the resins were made from 4500 g batches of a mixture of phenol (benzenol), formaldehyde, water, sodium hydroxide solution and lime. The phenol used was an aqueous solution containing 86.3% phenol; the formaldehyde solution used was a 50% aqueous solution; the sodium hydroxide solution used was a 50% aqueous solution and the lime was powdered anhydrous calcium hydroxide. Three resins were prepared: Resin 2B, (control - no lime); Resin 2B containing 0.25% lime, and Resin 2C containing 0.50% lime. Preparation of Resin 2A (control- no lime) 1164.2 g of phenol, 1441.8 g of formaldehyde solution and 1219.0 g of water were charged in the reaction pot and heated to 50°C. 90.0 g of sodium hydroxide solution were charged and the temperature was taken to 97°C and held for 10 minutes. 252.0 g of sodium hydroxide solution were charged over 15 minutes at 97°C. and condensed to "C-D". 333.0 g of sodium hydroxide solution were charged over 18-20 minutes and condensed to "J-K" at 97°C. The resin was cooled to 80-84°C and condense to T/V and then fully cooled. Preparation of Resin 2B (0.25% lime) 1164.2 g of phenol, 1441.8 g of formaldehyde solution and 1207.8 g of water were charged into the reaction pot and heated at 50°C. 11.3 g of anhydrous lime was charged with the temperature held below 65°C for 10 minutes. 90.0 g of sodium hydroxide solution were charged over ten minutes and the batch was then taken to 97°C and held for 10 minutes. 252.0 g of sodium hydroxide solution were charged over 15 minutes and the batch was condensed to "C-D" at 97°C. 333 g of sodium hydroxide solution were charged over 15 minutes and condensed to "J-K" at 97°C. The batch was cooled to 80-84°C and condensed to T/V and then fully cooled. Preparation of Resin 2C (0.50% Lime) 1155.1 g of phenol, 1430.4 g of formaldehyde solution and 1217.0 g of water were charged into the reaction pot and heated to 50°C. 22.5 g of anhydrous lime were charged and the batch was held below 65°C for ten minutes. 90.0 g of sodium hydroxide solution were charged over 10 minutes. The batch was taken to 97°C and held for ten minutes. 252.0 g of sodium hydroxide solution were charged over 15 minutes and condensed to "C-D" at 97°C. 333 g of sodium hydroxide solution were charged over 15 minutes and condensed to "J-K" at 97°C and cooled to 80-84°C and condensed to T/V and fully cooled. The composition of each resin as calculated on a weight percent basis is shown in Table 1. The specifications of each resin are listed in Table 2. PART 2 - PREPARATION AND FOAMING OF FOAMABLE GLUE MIXES The preparation and foaming of glue mixes was done in the same way as described in example one except that in this example Resins 2A, 2B and 2C were used. The density of each of the foams prepared was measured and the measurements are recorded in Table 4. SPECIFICATIONS OF THE RESINS Resin % Solids Content Alkali % Content Viscosity Resin 1A (Control, no lime) 40.6 7.45 1.05 Pa s (1050 cps) Resin 1B (0.25% Lime) 40.14 7.73 9.4 Pa s (940 cps) Resin 1C (0.50% Lime) 40.10 8.10 9.18 Pa s (918 cps) Resin 2A (Control) 39.93 7.46 8.58 Pa s (858 cps) Resin 2B (0.25% Lime) 40.25 7.76 9.22 Pa s (922 cps) Resin 2C (0.50% Lime) 39.90 8.16 8.46 Pa s (846 cps) RESIN FORMULATIONS CALCULATED ON WEIGHT % BASIS Component Resin Formulation Percent by Weight 1A 1B 1C 2A 2B 2C Phenol (100%) basis 22.328 22.328 22.153 22.328 22.328 22.153 Formaldehyde (50% solution; reported on as is basis) 32.039 32.039 31.787 32.039 32.039 31.787 Water 30.633 30.383 30.560 30.633 30.383 30.560 Lime (anhydrous calcium hydroxide) -- 0.250 0.500 -- 0.250 0.500 Sodium Hydroxide (50% solution; reported on as is basis) 7.600 7.600 7.600 2.000 2.000 2.000 Sodium Hydroxide (50% solution; reported on as is basis) 7.400 7.400 7.400 5.600 5.600 5.600 Sodium Hydroxide (50% solution; reported on as is basis) -- --- --- 7.400 7.400 7.400 GLUE MIX COMPOSITIONS Ingredient Mix 1 Mix 2 Weight (Grams) Weight % Weight (Grams) Weight % Water 20.4 20.1 13.9 20.8 Glyoxal, 40% (Reported on as is basis) 0.8 0.2 0.6 0.1 Blood, spray dried (77 ± 2.5% solubility) 9.8 2.2 6.7 1.5 Water 70.1 79.6 Resin (Solution of high molecular weight phenolic resin) 348.9 77.5 349.2 77.6 Total 450.0 100.0 450.0 100.0 FOAM DENSITY DATA Example 1 Mix I (2.17% Blood) Mix II (1.48% Blood) Resin No Whip Time (minutes) Foam Density (x10⁻³ kg/m³) (gram/cc) Whip Time (minutes) Foam Density (x10⁻³ kg/m³) (gram/cc) 1A (0% Lime) 1' 0.302 1' 0.230 2' 0.184 2' 0.140 3' 0.136 3' 0.111 1B (.25% Lime) 1' 0.231 1' 0.172 2' 0.163 2' 0.117 3' 0.114 3' 0.155 1C (.50% Lime) 1' 0.198 1' 0.156 2' 0.136 2' 0.111 3' 0.106 3' 0.107 Example 2 Resin # 2A (0% Lime) 1' 0.321 1' 0.213 2' 0.200 2' 0.144 3' 0.117 3' 0.100 2B (.25% Lime) 1' 0.300 1' 0.238 2' 0.183 2' 0.155 3' 0.120 3' 0.098 2C (.50% Lime) 1' 0.256 1' 0.194 2' 0.174 2' 0.136 3' 0.107 3' 0.091 The data of Table 4 is displayed graphically in Figure 1 and Figure 2. Figure 1 is a graph based on data from Example 1 and Figure 2 is a graph based on data from Example 2. The data in Table 4, that are graphically displayed in Figure 1 and Figure 2, show that when other factors are kept essentially the same, glue mixes made with a solution of lime-containing high molecular weight phenolic resin have greater foamability than glue mixes made with a solution of lime-free high molecular weight phenolic resins. Another way to interpret the data is that lime-containing high molecular weight phenolic resin has a greater inherent foamability than a solution of lime-free high molecular weight phenolic resin because an otherwise comparable glue mix made with a solution of lime-containing high molecular weight phenolic requires less blood as a foaming agent to achieve the same foamability as a glue mix made with a solution of lime-free high molecular weight phenolic resin. The data further demonstrate that a solution of 0.5% lime-containing high molecular weight phenolic resin has greater inherent foamability than a solution of 0.25% lime-containing high molecular weight phenolic resin. This indicates that the inherent foamability of a solution of lime-containing high molecular weight phenolic resin varies directly with the amount of lime used. Applicants have determined that more than 1.0% lime should not be added to a high molecular weight phenolic resin composition because lime will begin to precipitate out and adversely affect the resin.

Claims: A foamable glue composition comprising a solution of high molecular weight phenolic resin, wherein said solution is the reaction product of a reaction mixture comprising phenol, aldehyde, water, alkali, and not more than 1.0% of a soluble alkaline earth hydroxide and wherein said solution has a resin solids content of from 35% to 45% by weight, a viscosity of 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM and an alkali content of from 5.5% to 7.6%. The composition of claim 1, wherein said alkaline earth hydroxide is selected from the group consisting of calcium hydroxide, magnesium hydroxide, barium hydroxide and mixtures thereof and wherein said alkali is sodium hydroxide. The composition of claim 2, wherein said alkaline earth hydroxide is calcium hydroxide and wherein the amount of calcium hydroxide, anhydrous basis, is an amount greater than zero up to 1% by weight, based on the weight of said reaction mixture. The composition of claims 1 to 3, wherein said aldehyde is formaldehyde and said phenol is benzenol. The composition of claims 1 to 4, further comprising, in admixture with the solution of high molecular weight phenolic resin, animal blood and water. The composition of claims 1 to 5, further comprising an aldehyde glue viscosity lowering agent. A process for making a foamable glue composition comprising dried animal blood having a water solubility of not more than 90% by weight, water, high molecular weight phenolic resin solution, and optionally aldehyde glue viscosity lowering agent, wherein said solution of phenolic resin is the reaction product of a reaction mixture comprising a phenol, an aldehyde, water, alkali metal hydroxide, and not more than 1.0% of an alkaline earth hydroxide added at an early stage of the reaction and said solution has a resin solids content of 35%-45%, a viscosity of 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM and an alkali content of from 5.5% to 7.6%. The process of claim 7, wherein said alkaline earth hydroxide is selected from the group consisting of lime, calcium hydroxide, magnesium hydroxide, barium hydroxide and mixtures thereof. The process of claim 8, wherein said alkaline earth hydroxide is calcium hydroxide and wherein the amount of said alkaline earth oxide, anhydrous basis, is from an amount greater than zero up to one percent by weight, based on the weight of said reaction mixture. The process of claim 9, wherein said aldehyde is formaldehyde and said phenol is benzenol. A process for the production of laminate by bonding together with a foamed adhesive binder that is curable under heat and pressure, at least two plies having a layer of the foamed adhesive binder between them, comprising (1) applying to at least one surface of at least one lamina a foamed adhesive binder that is curable upon the application of heat, said adhesive binder comprising in admixture: (a) a solution of high molecular weight phenolic resin, said solution being the reaction product of a reaction mixture, comprising phenol, aldehyde, water, alkali metal hydroxide and not more than 1.0% of an alkaline earth hydroxide said solution having a resin solids content of from 35%-45% by weight, a viscosity of from 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM and an alkali content of from 5.5% to 7.6%; (b) dried animal blood; and optionally (c) aldehyde glue viscosity lowering agent; (2) juxtaposing the lamina to which the adhesive binder has been applied with another lamina, and then (3) subjecting said juxtaposed laminae to heat and pressure to cure the resin and unite the laminae to form a laminate. The process of claim 11, wherein said alkaline earth hydroxide is selected from the group consisting of lime, calcium hydroxide, magnesium hydroxide, barium hydroxide and mixtures thereof and wherein said alkali metal hydroxide is sodium hydroxide. The process of claim 12, wherein said alkaline earth hydroxide is calcium hydroxide and wherein the amount of said alkaline earth hydroxide, anhydrous basis, is greater than zero and less than one percent by weight based on the weight of said reaction mixture. The process of claim 13, wherein said aldehyde is formaldehyde and said phenol is benzenol. The process of claims 11 to 14, wherein the laminate is a laminated cellulosic product, the binder is applied to at least one of any two abutting surfaces of the laminae and the binder further comprises water. The process of claim 15, wherein said laminated cellulosic product is plywood. A cured laminate of at least two cellulosic plies comprising a first ply, a second ply, and a cured phenolic glue interposed between said plies and bonding them together said glue comprising a bonding layer formed by interposing a layer of foamed glue between said plies and applying heat and pressure to cure the glue, wherein said foamed glue comprises a foamed mixture of (a) a solution of high molecular weight phenolic resin, said solution being the reaction product of a reaction mixture comprising phenol, aldehyde, water, alkali metal hydroxide and not more than 1.0% of an alkaline earth hydroxide wherein said solution has a solids content of from 35%-45% by weight and a viscosity of from 0.3 Pa s (300 cps) to 1.5 Pa s (1500 cps) as measured on a Brookfield RVF viscometer at 25°C with a No 2 spindle at 20 RPM and an alkali content of from 5.5% to 7.6%; (b) dried animal blood having a water solubility of not more than 90% by weight; and optionally, (c) an aldehyde glue viscosity lowering agent. The cured laminate of claim 17, wherein the said alkaline earth hydroxide is calcium hydroxide and wherein the amount of said alkaline earth hydroxide, anhydrous basis, is from an amount greater than zero up to one percent by weight, based on the weight of said reaction mixture. The cured laminate of claim 17, wherein said alkaline earth hydroxide is selected from the group consisting of lime, calcium hydroxide, magnesium hydroxide, barium hydroxide and mixtures thereof. The cured laminate of claims 17 to 19, wherein said aldehyde is formaldehyde and said phenol is benzenol. The cured laminate of claims 17 to 20, wherein the foam density of said foamed glue at the time of application was 180 kg/m³ (0.18 gm/cc) or less.

Inventors: CREEL LEWIS DALE, DETLEFSEN WILLIAM DAVID, JOHNSON LEE ROY, CREEL, LEWIS, DALE, DETLEFSEN, WILLIAM, DAVID, JOHNSON, LEE ROY
Applicants: BORDEN INC, BORDEN, INC.
Application year: 1989
Main classification: C08J9
IPC codes: C08G8, C08L61, C09J5, C08J9, B32B7, C09J189, C09J161