USRE23347E - Art of making phenol-aldehyde re - Google Patents

Description

Reissued Mar. 20, 1951 ART OF IVIAKING PHENOL-AIJDEHYDE RE"-- ACTION PRODUCTS AND THE PRODUCT THEREOF Donald V. Redfern, Seattle, Wash., assignor to American-Marietta Company, Adhesive, Resin and Chemical Division, Seattle, Wash, a cor-- poration of Illinois NoDrawing, Original No. 2,457,493, dated December 28, 1948, Serial No. 772,016, September. 3, 1947. Application for reissue January 3, 1950,

Serial No. 136,652

15 Claims.

The presentv invention relates to the art of making phenol aldehyde reaction products and the products thereof and, in more particular, to a phenol-aldehyde resulting from, and the reaction using, an alkali as a catalyst, viscosity reducer and solubilizer, and adding such alkali stepwise to limit the Cannizzaro reaction and to increase the degree of condensation while still maintain..- ingwater solubility- The application is a. continuatiomin-part. of application Serial No. 722,975, filed January 18, 1947, the latter application being a. continuationin-part of application Serial No. 510,269, filed November 13, 1943, both of said applications now being abandoned.

The material formed by the present process finds particular application as an impregnator for paper and cloth, a, binder for plywood, and .as a molding material o a binder in a molded product.- In fact, the product finds a new use wherever a fast-setting high molecular weight resin is needed.

In the prior art of producing phenol formaldehyde resins, when using an alkali asv a catalyst, the setting-up time from the soluble stage to the insoluble-infusible stage has been long; long, at least, as compared with. thetime of the .present invention. v

The concept of the present rocess is that of prolonging, expanding, or widening the condensation reaction in the water-soluble phase, with the consequent shortening and moving along of the final reaction, i. e., setting into an insolubleinfusible product, with a resulting improvement of the final product as to insolubility and infusi- 5 'bility. Considering the reaction as a multiplication or increasing of the chemical linkages of the material under reaction, the longer this multiplication on linkages is continued before a final setting into infusibility and insolubility, the better will be the final product. It would seem ohvious that this multiplication of linkages would be at a greater rate, would be more uniform, would be more stable, and would result in longer Matter enclosed in heavy brackets 1 appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

and more cross chains of linkages if the reaction were to be carried, out in the liquid or solution stage, instead of the. solid or semi-solid phase.

In speaking of his product as soluble in water, applicant isv speaking of the salt of the resin the water-soluble stage.

as found in an alkaline solution. If the solution is neutralized, then the neutral resin is, for all practical purposes, insoluble both in water and ethyl mcohol, ethanol.

In the prior. art, it has always been considered that the end of the soluble stage, just before the final act of setting into the insoluble-infusible stage, has been reached. when the. viscosity curve began to. rise sharply, Processing, except for the final setting and possible mixing with other com pounds, was then. terminated. The final, setting usually consisted of placing the material in its final iorm or location and then applying the heat and/or a catalyst to. effect solidification. In the prior art this setting into the insoluble-infusible stage has been a relatively long time.

The group of compounds. referred to as. a phenol are those potentially reactive phenols, such as phenol, cresylic acid, [resorcinol] xylenol, and other monohydric [and dihydric] phenols known in the art. The expression av phenol as herein used. is. to be given arecognized meaning in the. art and. includes [both] monohydric [and] [dihydric]v phenols in which one [or two]. hydroxyl group is [groups areIattached to the carbon ring. As examples of the ald'ehydes that may be used in. the. performance of the present invention, there are cited: formaldehyde, acetaldehyde, iurfural, and benzald'ehyde. This, condensation reaction is generic. to aldehydesand poly-functional. aldehydes. In carrying out the presentv invention the aldehydes used may comprise any oi; the. prior art. aldehydes, used in producing phenol-aldehyde condensation products.

In the prior art, it was considered necessary to further the reaction in the water-soluble stage by a careful control of the temperature with respect to time, and the art has several. interesting examples of temperature-time curves for It is obvious that controls of this type are a hindrance to rapid production of the resin. Also, in the present invention lower phenol-aldehyde ratios may be used to increase the water solubility without a reduction in time, as the control of the reaction rate by the stepwise addition of alkali allows the reaction in the presence of large amounts of formaldehyde to be carried on rapidly at high. temperatures.

Having in mind the above. it is an object of the present invention to produce a water-soluble f Another object is the carrying out 3 phenol-aldehyde reaction product that has had a maximum possible reaction prior to setting into the insoluble-infusible stage.

A further object of the present invention is the production of a phenol-aldehyde reaction resin by a process having a wide range of time-term, perature relations.

Yet another object of the present invention is the prolongation of the water-soluble stage reaction and a shortening of the settin time of the final product.

Another object of the present invention is the production of a. phenol-aldehyde reaction product that is no longer soluble after slight heating for a short period of time.

It is also an object of the present invention to form a final-set phenolealdehyde resin that is insoluble in water, alcohol, acid, or alkali.

It is also an object of the present invention to produce a product which, upon addition of alkali in the later reaction stages, will produce solubility and some slight reaction, but which reaction and solubility zone is narrow, so that a short final reaction, that is, setting period, usually brought about by heating, will give an infusible and insoluble material which cannot be readily solubilized by further additions of alkali.

A further object of the present invention is the formation of a process for, "and the productionof, a liquid resin which is soluble in water in all proportions, but is substantially insoluble methyl alcohol, ethanol.

Another object is the provision of a liquid phenolic resin which is highly stable during long storage.

of the phenolaldehyde reaction, by the stepwise addition of alkali to limit the Cannizzaro reaction.

: A further object of the present invention is the formation of phenol-aldehyde resins by a process that allows a much wider variation in the phenol-formaldehyde ratios and the formaldehyde-alkali ratio than was possible in the prior "art.

. he present invention in one of its forms is directed'to'a'process for producing a thermosetting phenol-aldehyde resin condensation product comprising forming an aqueous mixture of a; phenol selected from the group consisting of phenol, cresol,'and xylenol [resorcin] and an ale 'dehyde in which the aldehyde group is the sole reactive group, and an alkaline catalyst accel -eratingthe formation of the resin reaction-prod- ?uct on heating, the amount of catalyst used to 'catalyzethe reaction is that amount which is capable of producing an alkalinity equivalent to the alkalinity produced by sodium hydroxide in an amount not over of the total mixed constituents. The molar ratio, of the aldehyde to the phenol varies from 121' to 3:1. The resulting mix "is heat-reacted to produce a water soluble phenol-aldehyde reaction-product, the viscosity of ,the latter increasing during this initial reaction period and being indicative of the advancement of the water soluble reaction-product toward the stage where the water soluble state terminates, said aldehyde retainin its reactivity during the formation of the water soluble phenol-aldehyde reaction-product. The increased viscosity of the 'water soluble reactionproduct and its tendency to progress to a water insoluble reaction-product is reduced by adding additional alkaline material and further "condensing the" water soluble resin to a' stage where the aqueous solution of the mix shows a precipitate upon the addition of ethanol,

said condensation product remaining water soluble and having a pH range varying between 9.5 and 14. This alternate step of adding an alkaline material and condensing may be repeated a number of times as hereinafter more fully set forth.

It has been found that the phenol-aldehyde reaction for a resin may be carried out by adding quantities of alkali and heating to a point where there is a sharp rise in the viscosity (this bein well known in the art) to produce a water-soluble initial phenol-aldehyde reaction product and then adding further quantities of alkali to reduce the viscosity and then further heatin until the viscosity again begins to rise rapidly. The reaction may be carried out as a continuous operation of adding alkali and heat, that is, a continuous control of the reaction by the stepwise addi- 7 "limits of the other ingredients.

" tion of alkali'and the continuous control of temperature. If carried to the limit, these stepwise acts of adding alkali to reduce viscosity and heating to further the reaction can be carrieclon until theaddition of further amounts of alkali will not decrease the viscosity. Further heating for a short time, for example, thirty seconds to ten minutes, at temperatures from 285 F. to R, will then give an insoluble-infusible stage product,

This adding of alkali in small quantities while progresing the reaction is important, as it helps curb side reactions, such as the Cannizzaro reaction. As shown by Roger Adams in his book, Or anic Reactions, vol. II, 3d edition, published by John Wiley & sons, Inc., New York, N. Y., 1944, pages 98 and 99, the Cannizzaro reaction is particularly liable to take place when the concentration of alkali'is greater than 10% in the presence of free aldehyde, this is a'2.95 normal alkaline solution. If the alkali is added in large amounts at high temperatures, it will react with the formaldehyde to convert it to methyl alcohol and formic acid, thus preventing the phenol-formaldehyde condensation. This reaction has been the main stumbling block which has prevented the prior art from progressing the reaction to the stage obtainable by the present process. Applicant has limited the Cannizzaro reaction by the stepwise addition of alkali. This reduces the alkali present while there is a large amount of free formaldehyde present, controls the reaction rate, r-esolubilizes the product,-and allows the resinification of the phenol and formaldehyde to continue. I g

This control of viscosity by the stepwise addi tion of an alkali is for the purpose of continuing the Water soluble stage reaction to a greater degree of condensation than has heretofore been considered possible. The rising viscosity which threatens to terminate the water-soluble stage reaction, is continually reduced, or knocked down,

by the addition of alkali. This high degree of The amount of alkali added at each step and the number of steps are determined by the desired control over the progression of the reaction, as evidenced by the viscosity and solubility and extent of the Cannizzaro reaction. The amount of alkali that maybe added under variouscondi:

tions is exemplified in the various specific examples. The general description and discussion preceding the specific examples gives an outline of the limits of alkali. additions, as well as the L; H. Baekeland, in his article The syntheses.

8 constitution and uses of. Bakelite, published in "The Journal of Industrial. and Engineering Chemistry, vol. 1, No.3, March, 1909, pages 149 The aqueous solution of the Redfern water soluble resin reaction-product shows a precipitate upon the addition of ethanol.

155, defines the three stages of a phenolic resin, as follows:

A-stage, initial condensation product At ordinary temperatures, may be liquid, or viscous or pasty or solid. It is soluble in alcohol, acetone, phenol, glycerine and similar solvents; is soluble in NaOH. Solid A is brittle and. melts if heated. All varieties of A, heated long enough under suitable conditionsv will change first into B, then finally into C.

B-stage, intermediate condensation product Is solid at all temperatures. Brittle, but slightly harder than solid A, at ordinary temperatures; insoluble in all solvents but may swell in acetone, phenol, or terpineol without entering into complete solution. If heated, it. does not melt, but softens decidedly and becomes elastic and somewhat rubber-like, but on cooling, becomes hard again and brittle. Further heating under suitable conditions changes it into C. Although B is infusible,it can be molded under pressure in a hot mold to a homogeneous, coherent mass, and the latter can be further changed into C by the proper application of heat.

and still maintain them in an alkaline solution phase. This stage, that of a resin advanced so that it is no longer soluble except in a high alkaline solution, is very close to the final C-stage and I have designated it as the incipent C-stage, in order to distinguish it from the A-stage, the B-stage, and the C-stage, as defined by Baekeland and to distinguish it from other prior art resins.

The difference between my resin in the incipient C-stage and other resins is clearly shown in the following table by the comparison between the Redfern resin, made according to the present process, the Van Epps resin, made in accordance with the disclosure of Clarence F. Van Epps, Patent No. 2,360,376, of October 1'7, 1944, and the Nevin resin, made in accordance with the disclosure of J. V. Nevin, Patent No. 2,150,698, of March 14, 1939.

Neutral resins were prepared by neutralizing the resin solutions to a pH of 7.0, filtering the precipitated resins and washing with distilled water until free of sodium. The washed resins were air dried for 48 hours, then the solubility in ethanol was determined. Moisture contents of the air-dried resins were determined and all values corrected for this.

oftentimes in actual practice it is difficult to bring the water-soluble stage along to the maximum possible reaction with an intervening storage time of several days or weeks before the final setting. For this reason, the commercial prodnet is usually stopped short of the maximum so as to minimize the possibility of setting before the desired time. However, even when stopping short of the maximum water-soluble stage reaction by the present process, as was done in the above comparison, the reaction has been carried so much further than the prior art reactions, that the setting time to the insoluble-infusible stage is much shorter than the prior art setting times. As an example of this rapid setting time, using a resin of the present invention, two three-ply panels were glued together and pressed in a hot press at 200 p. s. i. and 260 F. in 5.5 minutes.

Many, if not all, of the bases of the alkali metals, and the alkaline salts of the alkali metals may be used for solublizing and for catalyzing during the reaction period. Applicant has found that the most desirable range for the end of the water-soluble stage is a pH above 9.5. the Weaker bases and salts may be used for raising the pH in the lower ranges and the stronger reagents used in the upper ranges, the main criteria being that of raising the pH to increase solubility, although, as stated above, the optimum seems to lie above 9.5 pH.

By use of the term alkaline materia as herein set forth, it is intended to include chemicals such as those enumerated herein, and other alkaline material, that will have the desired cfiect of raising the pH of the material to the level which will give solubility, further the reaction, and/or catalyze the reaction.

[Some of the bases of the alkali metals and the alkaline salts of the alkali metals that may be used are the carbonates and hydroxides of: sodium, potassium, lithium, barium, calcium, and magnesium. Ammonium hydroxide and ammonium carbonate may also be used] Some of the bases of the alkali metals that may be used as solublieers are the hydroxides of sodium, potassium and lithium.

It has also been found that such compounds as sodium phenate may be used, that is, the initial Physical appearance and solubility of resins alkali y v been combined with the phenol Alkaline Resin Rediern Van Epps Nevin Percent water soluble W lgggi: h

Percent ethanol soluble 8.8%.

Some of the resin to form a water-soluble product.

prior to the beginning of the reaction. The desideratum is that the alkali, such as those listed above, should be present in a form which insures its availability for combination with the reaction product during the water-soluble stage, that is, any salt of a phenol which will release an element that will form an alkaline solution.

In the measurements of his pH, applicant has used a Beckman pH meter with a calomel electrode and a lithium glass electrode and standardized at pH to compensate for the alkali metal ion efiect.

In the prior art, alkalies (sodium hydroxide being generally used) have been used as catalytic agents only. In the present reaction, the alkalies are also being used to solubilize the product. This is probably done by the alkali combining with During the setting period, portions of the alkali are freed. It is probable that this freed alkali will then act as a catalytic agent to speed the setting and to shorten the setting time. This is considered to be important, as it has been found that many of the prior art products may be treated by the addition of an alkali just prior to the setting not only to solubilize but to speed up the final reaction and to'produce a superior product.

There have been set forth above oertainphenols, aldehydes, and alkalies, as being specific materials that may be used in the performance of the present invention; however, these materials and others, are the ones generally recognized in the art for the making of resins of this gen= eral type.

In the prior art, it has been necessary to carefully control the temperature, because once the viscosity begins to increase sharply, the reaction must be stopped if an immediate conversion to the insoluble-infusible stage is to be prevented. In the present process, the control of the to nperature is of far less importance, as the viscosity may be reduced by additions of further alkali.

Another factor entering into reactions of the in its oWn' plant, performs a final blending or mix: ing oft he resin with other ingredients, such. as

type mentioned herein, is that of the molar ratio stability of the product. Applicant has found animal blood, fillers, water, etc., to effect the de? sired glue or bonding material for spreading on the veneer sheets prior to the pressing and heating of the plywood to effect the final setting into the insoluble-infusible stage of the resin.

Herebelow and preceding the examples is a general description and discussion thereof. In those examples using phenol, such has a 40 C. freezing point about ten parts of the water are used for premixing the phenol. All during the initial addition of phenol and aldehyde, and following the first adding of alkali, called the mix period, until the initial temperature is raised, and during the following heating and additions of alkali, called the cook period, the mixture of materials is agitated. The ratios given are molar ratios of aldehyde to caustic to phenol. poises at 25 C., and such is indicated by the symbol (eta). When, as in Example 1, there is found the expression 8.9 parts of NaOI-I, 5.5-8.81 the meaning is that the addition of the alkali will give the stated viscosity. If it is stated, Hold C. for 40 min. to 6.00-l0.00 the meaning is that the stated viscosity is controlling, and the time may vary, as it is only of secondary importance. When the reaction is indicated as be ing carried to insolubility, fto insol. this is insolubility at 25C. 1 The limits of the molar ratios of the ingredients to phenol are: water, zero to 26.1; formaldehyde, 1 to 3; and sodium hydroxide, 0.22 to 2.5. As above noted, the phenolused in the examples is stated as 40' C. freezing-point phenol. Thisis a reduction of the examples to a"'uniform basis, as other freezing-point phenols have been used. In all ingredients, the molar value is controlling and not the particular concentration or chemical. The amount of phenol is given in all examples as parts by weight. The actual weight used is determined by the processing facilities. The actual weight will in some measure determine the 1 various time periods, due to the time required to that progression of the reaction as herein set forthenables him to obtain greater variation in the aldehyde-phenol ratio than was possible ,in the prior art.

The theoretical limits for the formaldehydephenol ratio are 1:1 and 3:1. The prior art has not been able to obtain a satisfactory resin with I a smaller ratio than 2.5:1. Applicant has found that he can obtain a very satisfactory resin throughout the range of 1.1 to 3: 1. He attributes this to the completeness of the reaction, the GX-r tent of the linear chains and cross chains obtainable by the present process. In the smallerratios every link is important. In the larger ratios, curtailment of the Cannizzaro reaction is important. The condensation is promoted in both the larger and smaller ratios by the present process.

The use of, or the presence of, an alkali insures the stability of the alkaline resin solution at room temperature. This is especially important because in the industry the preparation of the water-soluble stage material is usually performed by a separate organization from that which sets the resin into its final insoluble-infusible stage.

purchases its resin from outside sources and then.

go from one temperature level to the next. The first column of the examples gives the parts by weight. The temperatures given are indegrees centrigrade. A small amount of water, about ten parts, is premixed with the phenol to facilitate the handling thereof. When the-phenol is in the kettle, Water is added from zero to about 26 mole, de pending upon the percentage of solids in the final resin required, and to give the desired reaction control. With resins of a low total solids, it is desirable to add some of the water later in the reaction, in fact, the total water may be added in small amounts during the whole of the process. The above aqueous solution is maintained between 15 C. and 40 C. To thissolution is added the aldehyde. ,molarratio changes the properties of the final resin with regard to flow and setting characteristics. However, all the ratios used permit the advancement of the resin into the B-stage and then the incipient C-stage, which incipient C'- stage is defined as a characteristic of the resins of this invention. After the aldehyde has been thoroughly mixed with the above constituents, and while the temperature is still'maintained betw'een'15? 'C."'ahd 40 C., the reaction periodisstar-te'd by .the gear tion of initial alkali solution, with con tant agita} All viscosities are given in Varying the formaldehyde-phenol or otherwise. this point or its molecular equivalent in other the phenol and formaldehyde.

and type of kettle, or reactor.

tion of the mix. The alkali solutions may be varied from 10% to saturated aqueous solut ons, The'so'dium hydroxide added at alkalies is used as a catalyst for the reaction of The effect of Varying the amount of catalyst is reflected primarily in the rate of reaction.

The initial alkali expressed as sodium hydroxide should not be over 10% of the total initial mix, which is a 2.95 normal alkaline solution. Example 8 in ra. sho s an initial caustic of 5.25% and Example 9, infra, 0.7%. As previously stated, throughout the process, the alkali may be continuously added.

' When the initial alkali has been added and thoroughly mixed in, the mix period is closed and the cook period initiated by raising. the temperature above C. and up to boiling, around 100 C. The time taken to raise the mix to cook temperature may vary greatly, from five minutes to four hours or more, dependin upon the size and heat transfer ratios of the mix and. equipment. This'cook temp rature is determined by the time which may be allowed for thisstep and by the size The temperature is, in many cases, brought to the boiling point and the materials refluxed, as such speeds the reaction to the greatest possible extent. The refluxing temperature is broadly from 95 to 105 34 0., depending upon the reaction mix and the size and type of reactor vessel. 1

The cook is continued at theabove temperature .until the viscosity of the mix reaches a pre-determined value indicating the approach of the endpoint of a cook for prior art Water-soluble resins.

When a large mix is involved, it is well to drop the temperature before reaching the end-point sothat the reaction will be slowed and the endpoint not passed over. In certain ratios of formaldehyde, caustic, and phenol, the resinadvances to'an alkaline insoluble stage. In such certain resins, this insoluble point, instead of viscosity, is used'as the determining point for the addition of more caustic to maintain solubility of the resin.

The reaction is a function of the time-temperature ratio.

alkaline solution, which is a function of the advancement of the reaction. Ihe viscosities stated may be varied over a wide range, depending upon the proportion of aldehyde to phenol and the time temperature ratio variations.

At this stage, as insolubility, or the C'-stage, approaches, a. further amount or amounts of alkali are added, in order that the reaction may be continued and progressed beyond that found in the prior art. This further amount of alkali solubilizes the resin and decreases the viscosity.

inafter illustrate this technique and give particular amounts.

The final viscosity may vary from 0.5 to 2001 This value is more or less arbitrary, depending upon the type of product desired. In all cases, when thedesired viscosity is obtained, the mix The important controlling point is the solubility or viscosity of the resin when in the "Example 1 Phenol 100 Water 93.6 37% formaldehyde 177.5 50% NaOH n 37.9

Mix and bring to 100 C. in 100 minutes Reflux to 0.501;, cool to 72 C. in 140 minutes 50% NaOH, 5.5-8.81 8.9 Hold 75C. for 40 minutes to 6.040.001; 50% NaOH, 2.75-3;00n 19.3 Hold at 80 C. for fifl 'minutes Cool below 40C., 4.30-5.00

Final: 43-5001 pH 12.68, 42% solids. Ratio: 2.04:0.79:1.0.

Example 2 Phenol 100 Water .109 37% formaldehyde 147 50% NaOH 18.5 Mix and bring to 100 C. .in 100 minutes Reflux for 290 minutes, 27.001; -50% NaOH 12519 C001 to C. in 50 minutes, 6.501; 50% NaOH 17.4 Cool to below 40 C., 3.001;

Final: 3.00 1, PH 10.50, 42% solids. Ratio: 1.70:0.61:1.

Example 3 U. S. P. cresol 100 Water 81.3 37% formaldehydenu 142.2 50% NaOH 33.0 Mix and brin to 35 C. in 100 minutes Hold for 80 minutes, 10.001; 0001 to C. Hold for 67 minutes, 46.001 50% NaOH 7.9 Hold at 65 C. for 13 minutes, 10.709 50% NaOH 17:.6

Raise to C. and hold for 86 minutes, 3.301; Cool below 40C.

Final: 3.301 pH 13.02, 42% solids. Ratio: 1.9:

Ratio: 1.9:

11 Example Phenol 100 -Water -1 350.9

Furfural 193.9 50% NaOH 37.9 .Mix and bring to 98 C. in 100 minutes 50% NaOH 9.0 Reflux for 5 minutes to insolubility 50% NaOH 6.8 Reflux for 87 minutes to insolubility 50% NaOH 2.1 Refluxfor 13 minutes to insolubility 50% NaOH1L; 1 2.9 {Cool to 90 C. in 56 minutes to in'solubility 50% NaOH, coolbelow 40 (1., 3.101 8.5

Final: 3.107;, pH 11.70, 42% solids. Ratio: 1.9 :0. 79:1.-0.'

Example 6 Phenofl' r Y 100 a 'Acetal'de'hyde"' 89 50% NaOH -l. 37.9

Mix and bring to 100 C. in 100 minutes 50% NaOH added in small increments dur' ing reflux, insolubility control 73.6

Total reflux time, 905 minutes "(2001 below 40 C.

-:- .Final: 42% solids. Ratio:.1.9:1.33:1.0.

. Example 7 ,,I

Phenol 100 Water 364.3

Benzaldehyde 214.3

50% NaOH 37.9

Mix and bring to 100 C. in 100 minutes Reflux 50% NaOH added in small increments during reflux, insolubility control 178.6 Total reflux time, 1,120 minutes Cool below 40 C. Final: 60% solids. Ratio: 1.9:2.55:1.0.

Example 8 Phenol 100 Water 189 Formaldehyde 216 50% NaOH- 59.3 Mix and bring to 100 C. in 100 minutes Reflux for 140 minutes, 1481;

Cool to 75 C. in minutes 50% NaOH 149.0 Hold 75 C. for minutes Cool below 40 C., 631

Hold for 30 minutes Cool .to 40 C., 4.75-5.00

Final: 475-5001;. pH 10.25, 38% solids. Ratio:

. Example 10 Phenol 10.0

Water I 106.3 37% formaldehyde 1 172.2 50% NaOH 40.25 Mix and bring to 95 C. in 120 minutes Reflux for 100 minutes Cool to 60 C., 1.481; 50% NaOH 9.53 Cool below 40 C., 46.31

Final: 46.31;, pH 10.5, 42% solids. Ratio:

Example 1, above,'will be given hereinbelovvdn more detail for an easier understanding of,thi's and the other examples. The details of this and the other examples are details. which on the whole are not given in the general discussion above of all the examples. i'

' In Example 1, the phenol is premixed with 1.1 parts of water to facilitate handling and is placed in an agitated, jacketed reaction kettle. All during the addition of the reagents and dure ing the reaction the materials are agitated, ln this example 82.6 parts of water is the preferred amount added at this point. To the above aqueous solution, which is maintained, preferably at 20 0., aqueous commercial, or C. 1 .37% formaldehyde solution, which may contain up to 15% methanol, is added. The amount is 1775 parts or 2.04 mols of formaldehydeto one mol of phenol. x

After the formaldehyde has been thoroughly mixed with the above constituents and while the temperature is still maintained at 20 C., a 50% aqueous sodium hydroxide solution is added. The 50% concentration is used because of its availability and ease of handling. For this ex ample, the 50% caustic solution is 37.9 parts, which is a ratio of 0.44 mol of the'caustic per molof phenol.

After the caustic is added, the reaction mixture is heated with constant agitation to a point where the mixture begins to boil and is refluxed. The time taken to raise the reaction mixture to the boiling temperature is from 80 to 120 minutes for this example. I

The reaction mix is refluxed until the alkaline solution has reached a predetermined viscosity of 0.501;. This viscosity can be varied, dependin upon the composition of the reaction mixture and the properties of the desired resin. In

. this example, the reaction is then gradually cooled to to 73 C. over a period of from 60 p to 140 minutes and held until a preferred viscosity of 32 to 631 is obtained, with a maximum variation between 22 and 100 poises.

At this point the neutralized resin is in the B-stage and is from to water insoluble. The time and temperatures stated here are preeferred for this example, but longer times may be used at temperatures as low as 40 C. and shorter times at temperatures as high as C.

At this stage, which is the normal end-point for. water soluble resins of the prior art, 8.9 parts of 50% aqueous caustic solution or its equivalent in other alkalies is added in order that the reaction may be continued. This caustic addito solubilize the reaction products. Without this caustic addition, continuation of the heating of the resin will advance it quickly into the C-stage. The reaction is continuedat 70 to.80 C. for minutes or the equivalent time-temperature ratio, to obtain a. Viscosity of 6 to 10v] and a neutralized resin which is 87.5 to 92.5% water insoluble but will still flow under pressure.

At this stage, 19.3 parts of caustic are added to reduce the viscosity of" the reaction mix from 6 to 10 poises to 2.75 to 3.00 poises. Broadly, this caustic may again var from this stated amount depending upon the original ratio of the reacting constituents and the time-temperature ratio employed in the reaction. In all cases, the

amount required is determined by the desired reduction in viscosity or increase in solubility.

The specific reaction is continued at to 85 C. until a final preferred viscosity of 4.3 to 5.91115 reached. The final pH is 12.60 to 12.80.

In actual usage, and particularly in making plywood, there are iive variable factors used in the evaluation of a phenolic resin adhesive. These factors are cured rate, adhesion of the cured product, assembly time, storage life, and spreadability. tor.

The resins of all the examples give adhesives with nearly perfect adhesion. The resins of =Examples -1 and 8 are very satisfactory when so evaluated. They have a fast curing time in the press, perfect adhesion, and long storage life. The spreadability is good, and the assembly time is rather :short. These two examples illustrate the wide variation in caustic that may be had and yet the resins havesimilar use characteristics.

Generally, a reduction in storage life means a faster setting resin. This is true of Examples 6, 7, and 10. Also, these three examples show Wide variations in caustic.

Examples 3, -4, 5, 6., and 7 illustrate to some extent the wide variety of ingredients that may be used in the practice of the present invention.

Examples 8 and 9 illustrate the wide variation in the molar ratio of aldehyde that may take place under the present invention. These two examples further illustrate the wide variation in caustic that may be used. Generally, more caustie is used with an increase in the aldehyde, but this is not necessarily true, as the various examples indicate.

The evaluation of Example 2 is not quite the same as Example 1. The curing rate of Exam- Waterproofness is not a variable facple 2 is slower, but the assembly time is longer.

The other factors are similar to Example 1. Examples 1, 2, 3, 4, 5, and 10 give good general usage adhesives. The other examples indicate the extent of variation in ingredients that may behad and still obtain .a desirable resin. 'In many instances such variations find particular application, such as impregnators and for uses requiring fast setting.

As a binder for plywood, 500 parts of the'liqu-id resin is mixed with 100 parts of water and 75 the present invention in papeumakingirem 0.5

T4 of Commerce specification for Douglas fir 'plywood, CS 45-45, tested a minimum of 90% wood failure instead of the required 60%.

In the prior art it has not been possible to use water soluble phenolic compounds to improve the fiber in soft-boards, hard-boards, or webs, so that such products are stronger, smoother, more waterproof, orharder. This failure of the prior art to use water soluble phenolic compounds for fiber and board improvement been due to a lack of resin retention by the fibers and the inability of the prior art resins to advance to the insoluble stage under operating conditions. Applicantfs resins obviate these prior art defects and are usable for fiber board an web improvement because they are advanced to the incipient C-stage, further than the prior art resins. This allows them to be almost completely precipitated and to of the resin added to the slurry isire tained on and in the fibers and the resin is set to the C-stage under operating conditions possible in board and paper manufacturing plants.

In the use of thep-resent resin in fiber improvement, the h rein set forth water soluble phenolaldehyde resin is added to and evenly dispersed in the fiber slurry or Web and the resin is acidified to a pH of about 5.9 to 4:3 to precipitate the resin on and in the fibers. The fiber, board, or web has excess water removed, usually by suction and the fibers are heated to set the resin to the final insoluble stage. In thecase of various fiber boards,- this heating ma take place in a press or drying oven. In p-apermaking, this heating may be done on the calendering rolls.

In the making of pulp and paper board, and the use therein or any resin, there is formed a slurry of water and waste wood broken down under various mechanical or semi-chemical means or methods in which the fibers are individually separated. The pH of this slurry is adjusted to approximately 7 and the resin added thereto in amounts from 10 to 50% of the dry weight of the pulp; This slurry is then agitated until auniform resin fiber dispersion is obtained.

After obtaining a uniform dispersion of the resin in the fiber slurry, the resin is precipitated on and in the fiber by reducing the pH of the slurry to 4.5 plus or minus about 1. Acetic acid, hydrochioric acid, sulfuric acid, alum, or other acid or acid salt may be used to obtain this reduction in pH, the criteria being that of an acid or acid salt capable of obtaining this desired reduction in pH.

The fiber slurry containing the precipitated resin is then formed on a screen and the excess water removed by suction. This water may be returned and reused in the process. The pulp mass is then pressed and dried in the manner now common in the formation of pulp board. and paper board. Insofar as possible, without detriment to the fibers, it is desirable that the temperature be raised high enough and maintained high long enough to permanently set the resin into the C-stage.

By using the highly condensed resin of my invention, a high resin retention 0f at least 85% to on the fiber is obtained by acid precipitation. This precipitated resin is then converted toan infusible, water-insoluble, solvent-resistant compound under heat, or heat and pressure.

In the making of paper, the resins of the present invention may be used with a resulting improvement in many of the physical characteristics ofthe finished product. In the practice of desired in the finished web.

to 50% resin, based on the dry weight of the paper pulp, is added to the paper slurry prior to the sheet formation, preferably in the beater chest. The paper, resin, and slurry mixture is then thoroughly agitated and is acidified bythe addition of the same or similar acids orv acid salts mentioned in connection with the processing of paper board above, to a pH of approx. 6 to 4. The acidified pape slurry is diluted to the desired concentration, usually about 0.3 by weight of pulp, and the paper sheet is then formed in the conventional manner of passing the aper slurry'upon a screen and removing the excess water by suction, and then carrying the formed sheet over a series of heated rolls. These heated rolls dry and calender the paper and: will set the resin to the final C-stage. i By' the use of. a highly advanced phenol aldee hyde resin of my invention; and its acid precipitation on and in the fibers of the paper, 85% to 99% 01' the resin added to the paper slurry is re tained in the finished web. i The resins of my invention may also be used to impregnate a web or sheet of paper, cloth, or other fibrous material already formed. Previously formed web may be impregnated, either by a batch-process or by a continuous operation along the sheet or web.

In the continuous process of impregnating a fibrous sheet or web of material, the material to beimpregnated is run through an aqueous solutionof the resin in a concentrationdependent uponthe percent of resin desired in the finished sheet. After the fibrous material has been com- .pletely saturated, it is run from the resin bath through a set of squeegee rolls or doctor blades to remove excess resin solution. The web is then run through an acidifying bath adjusted to a pH of approximately 4.5 plus or minus 1. This acid bath may contain any of the acids previously mentioned for acidifying and precipitating the.

" passed over and between heat and pressure rolls to set the resin and obtain the desired finish for the web.

If it is desired, a web may be impregnated with the resins of my present invention by a batch treatment. In such treatment, the web is placed ina solution of resin which solution is at a concentration depending upon the amount of resin When the web has been thoroughly impregnated with the resin by mechanical agitation or other desirable means,

the batch is acidified by adding acid of the nature previously disclosed above to precipitate the resin in and on the fibers of the web. After precipitation of the resin in the fibers of the web, the sheet or web is removed from the batch and .then treated with heat and pressure to set the resin and obtain the desired finish for the web.

In the "impregnating of previously formed fibrous webs, as contrasted to the treatment of loose fibers in *a's lurry, it is not as necessary to jfpr'ecipitate the'resin on the fibers by an acid {treatment as it is when the fibers are loose in a doesnot give as good impregnation and bonding .g t e resin h fibe The h'e'rein Jm'ethod of producing a thrmo= setting phenol-aldehyde condensation product comprising forming a water soluble phenolaldehyde condensation product, and reacting the latter until the condensation product advances to a stage where it becomes insoluble in an aqueous alkaline solution and then resolubilizing the insoluble resin in its aqueous alkaline solution by adding thereto an alkaline medium, is claimed in copending application Serial No. 58,373, filed November 4, 1948.

The herein described method of forming a cellulose fiber product bonded with an insoluble infusible phenol-aldehyde resin is claimed in co-' pending application Serial No.- 58372, filed No vember 4, 1948.

Having thus described my invention, I claim: 1. The process of producing a thermosetting phenol-aldehyde resin condensation product com prising forming an aqueous mixture of a phenol selected from the group consisting of phenoL-cresol, and xylenol, [resorcinol,] an aldehyde in which the aldehyde group is the sole reactive group, and an inorganic alkaline catalyst accelerating the formation of the resin reaction-product on heating, said catalyst expressed as sodium hydroxide being present in an amount equivalent to not over 10% of the total mix constituentsthe molar ratio of the aldehyde to the phenol varying from 1:1 to 3:1, heat-reacting said mix and producing a water-soluble phenol-aldehyde reaction product, the viscosity of the latter increasing during this initial reaction period and being indicative of the advancement of the water-soluble reaction-product towards a stage where the watersolub1e state terminates, said aldehyde retaining its activity during the formation of the We.- ter-soluble phenol-aldehyde reaction-product, reducing the viscosity of the Water-soluble reaction-product and its tendency to progress to a water-insoluble reaction-product by adding thereto an alkali metal hydroxide, [additional] [inorganic alkaline material,] and further [condensing] heating the water-soluble resin to a stage where an aqueous solution of the mass shows a precipitate upon the addition of ethanol, said condensation reaction-product remaining water-soluble, said alkali metal hydroxide [alkaline material] increasing the pH of the finally condensed product to between 9.5 and 14 inclus1ve.

2. The process of producing a thermosetting phenol-aldehyde resin condensation product comprising forming an aqueous mixture of a phenol selected from the group consisting of phenol, cresol, and xylenol, [and resorcinol,] an aldehyde in which the aldehyde group is the sole reactive group, and an inorganic alkaline catalyst ac,- celerating the formation of the resin reactionproduct on heat, said catalyst being present in an amount equivalent to not over 10% of the total mix constituents expressed as sodium hydroxide, the molar ratio of the aldehyde to the phenol varying from 1:1 to 3:1, heat-reacting said mix and producing a water-soluble phenolaldehyde reaction-product, the viscosity of the latter increasing during this initial reaction period and being indicative of the advancement of the water-soluble reaction-product towards a stage where the water-soluble state terminates, said aldehyde retaining its activity during the formation of the water-soluble phenol-aldehyde,

alternately adding to said initial resin condensa- 'g-anicf! alkali[ne materiallm'tal hydroxide and then after each additionof' the alkali[ne material] 'met'a'l' hydroxide heati'ng- [condensing] the so [alkaline-Zitreated resinr'ea'ctiomproduct, each time the alkali metal-hydroxide [alkaline materiallis added'there being a reduction of the viscosity of the water-soluble resin reactionpro'duct and'the tendency-ofthe water-soluble :version of the resin reaction mass to a waterinsoluble state, said additions oialkali being terminated while the resin reactiongproduct' is in a water-soluble stage, the aqueous solution of the water-soluble resin reaction-product showing a precipitate upon the additionof' ethanol, said alkali[ne material] metal hydroxide increasing the pH' of the finally condensed product to'between 95' and 14 inclusive 3; The process of producing a thermosetting phenol-aldehyde resin condensation product comprising forming an aqueous mixture of phenol, an aldehyde in which the aldehyde group is the sole reactive group, and an inorganic: alkaline catalyst accelerating the formation of the resin reaction-product on heating, said catalyst being present in an amount equivalentto not over 10% of the total mix constituents expressed as sodium hydroxide, the molar ratio of the aldehyd'e to the phenolv-aryi'ng' from "1 :1 to S 1, heatreacting said mix and producing'a' water-soluble phenol-aldehyde reactiomproduct, the viscosity of the latter increasing during this initial reaction period and being indicative of the advancement of the water-soluble reaction-product towards a. stage: where th"WatBII+S011Xb1f-) stage terminates, said aldehyde retaining its activity during the formation of the water-soluble phenolaldehyde reaction-product, reducing the viscosity of the: water-soluble reaction-product and its tendency to progress to a water-insoluble reaction-product by adding thereto [additional] an [inorganic] alkali[ne material] metal hydroxide and further heating [condensing] the water-soluble resin to a stage where an aqueous solution of. the mass shows aprecipitate upon the addition of ethanol, said alkali[ne material] metal hydroxide increasing: the pH of the finally condensed product to between 9.5 and 14 inclusive.

4. The process of producingathermosetting phenolaldehyde resin condensation product comprising forming an aqueous mixture of phenol, an aldehyde in which the aldehyde group is the sole reactive group, and an inorganic alkaline catalyst accelerating the formation of the resin reaction-product on heating, said catalyst being present in an amount equivalent to not ove 10% of the total mix constituents expressed as sodium hydroxide, the molar ratio of the aldehyde to the phenol Varying from 1:1 to 3:1, heat reacting said mix and producing a water soluble phenol-aldehyde reaction-product, the viscosity of the latter increasing during this initial reaction period and being indicative of the advancement of the water-soluble reaction-product towards a stage where the water-soluble state terminates, said aldehyde retaining its activity during the formation of the water-soluble phenolaldehyde reaction-product alternately adding to said initial resin condensation product [a further amount of] an [inorganic] alkali[ne material] metal hydroxide and then after each addition of the alkali[ne material] metal hydroxide heating [condensing] the so [alkaline] treated resin reaction-product, each time the alkali[nem'aterial] metal hydroxide is added therebeinga reduction of the viscosity of the water-soluble resin reactionproduct and a tendency of thewater-soluble resin reaction-product to progress towards a waterinsoluble stage thereby permitting a further condensation of the-resin reaction mass without conversion of the" resin reaction mass to a water-insoluble state, said additions of alkali being terminated while the resin reaction-product is in a Water-soluble stage, the aqueous solution of the water-soluble resin reaction product showing a precipitate upon the addition of ethanol,

said alkali[ne material] metal hydroxide increasing the pH of the finally condensed product to between 9.5 andll4 inclusive.

5. The. method of claim 1-- in which the aldehyde is formaldehyde.

6'. The product of the method of claim 5.

7.. The method of claim 2 in which the aldehyde is formaldehyde;

8. The product of the method of claim-l.

' [9. The. method of claim. 1 in which the alkalilfne material] metal hydroxide: is a caustic alkali] [102 The methode'of claim 2 in whichthe alkaliljne material] metal hydroxide is a caustic alkali] [11. The method of claim 4 in which the alka1i[ne material] metal hydroxide is a: caustic alkali-.1

12.. The productof the method of claim 1.

13.; The'method ofclaim 3 in. which the aldehyd'e'is formaldehyde.

'14. The'method 0 claim 4 in whichihe-aldehycleis formaldehyde.

1-5. The process" of producing a thermosetting phenol-aldehyde resin condensation product comprising forming an aqueous mixture of phenol, an aldehyde whiehthealdehyde' group is the sole reactive group, and an inorganic alkaline catalyst accelerating the formation of the resin reaction-product on heating, said catalyst being present in an amount equiualentto not over'10 of the total mix constituents expressedas sodium hydroxide, the molar-ratio of the aldehyde to the phenol varying from 1:1 to 3:1, heat-reacting said mix and producing a water soluble phenolaldeh'yde reaction-product, the viscosity of the latter increasing during this initial reaction period and being indicative of the advancement of the water-soluble reaction-product towards a stage where the water-soluble state terminates, said aldehyde retaining its activity during the formation of the water-Soluble phenol-aldehyde reaction-product, alternately adding to said initial resin condensation-product an alkali metal hydroxide and then, after each addition of the alkali metal hydroxide, heating the so-treated resin reaction-product, each time the alkali metal hydroxide is added there being a reduction of the viscosity of the water-soluble resin reaction-product and a tendency of the watersoluble resin reaction-product to progress towards a water-insoluble stage thereby permitting a further condensation of the resin reaction mass without conversion of the resin reaction mass to a water-insoluble state, said additions of alkali being terminated while the resin reactionproduct is in a water-soluble stage, the aqueous solution of the water-soluble resin reaction product showing a precipitate upon the addition of ethanol, said alkali metal hydroxide increasing 19 the pH of the finally condensed product to between 9.5 and 14 inclusive.

16'. The process of producing a thermosetting phenol-aldehyde resin condensation product comprising forming an aqueous mixture of phenol selected from the group consisting of phenol, cresol, and xylenol, an aldehyde in which the aldehyde group is the sole reactive group, and

an inorganic alkaline catalyst accelerating the formation of the resin reaction-product on heatthe water-soluble resin reaction-product begins to rapidly rise, repeating said steps of adding an alkali metal hydroxide and heating, terminating said additions of alkali metal hydroxide and heating while the resin reaction-product is in a water soluble stage and while the aqueous solution of the water soluble reaction product shows a precipitate upon the addition of ethanol, said alkaline material increasing the pH of the finally condensed product to between 9.5 and 14 inclusive.

17. The process of producing a thermosetting phenol-aldehyde resin condensation product comprising forming an aqueous mixture of phenol, an aldehyde in which the aldehyde group is the sole reactive group, and an inorganic alkaline catalyst accelerating the formation of the resin reaction-product on heating, said catalyst being present in an amount equivalent to not over of the total mix constituents expressed as sodium hydroxide, the molar ratio of the aldehyde to the phenol varying from 1:1 to 3:1, heat-reacting said mix until there is a sharp rise in the viscosity of the water-soluble reaction-product, adding a further amount of an alkali metal hydroxide to reduce the viscosity, then heating until the viscosity of the water soluble phenol-aldehyde reaction product begins to rapidly rise, repeating said steps of adding an alkali metal hydroxide and heating, terminating said additions of alkali metal hydroxide and heating while the resin reaction-product is in a water soluble stage and while the aqueous solution of the water solu- -ble reaction product shows a precipitate upon the addition of ethanol, said alkaline material increasing the pH of the finally condensed prodact to between 9.5 and 14 inclusive.

18. The process of producing a thermosetting phenol-aldehyde resin condensation product comprising forming an aqueous mixture of a phenol selected from the group consisting of phenol, cresol, and xylenol, an aldehyde in which the aldehyde group is the sole reactive group, and an inorganic alkaline catalyst accelerating the formation of the resin reaction-product on heating, said catalyst expressed as sodium hydroxide being present in an amount equivalent to not over 10% of the total mix constituents, the molar ratio of the aldehyde to the phenol varying from 1:1 to 3:1, heat-reacting said mix and producing a water-soluble phenol-aldehyde reaction product, continuing heat-reacting the reaction mass until the viscosity thereof approaches but does not attain the water insoluble stage, reducing the viscosity of the resulting water soluble reaction mass and its tendency to progress towards a water insoluble reaction product by adding an alkali metal hydroxide, and further heating the water soluble resin to a stage where an aqueous solution of the reaction mass shows a precipitate upon the addition of ethanol, said condensation reaction product remaining, water soluble, said alkali hydroxide increasing the pH of the finally condensed product to between 9.5 and 14 inclusive. DONALD V. REDFERN.

REFERENCES CITED The following references are of record in the file of this patent or the original patent:

UNITED STATES PATENTS