US3355407A - Method of producing aqueous emulsions of resins of the phenolformaldehyde type including a softener for impregnating fibrous materials - Google Patents

Description

United States Patent 3,355,407 METHOD OF PRODUCING AQUEOUS EMULSIONS OF RESINS OF THE PHENOLFORMALDEHYDE TYPE INCLUDING A SOFTENER FOR IMPREG- NATING FIBROUS MATERIALS Rinse Dijkstra, Emmasingel, Eindhoven, Netherlands, as-

signor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 14, 1964, Ser. No. 403,906 Claims priority, application Netherlands, Oct. 21, 1963, 299,534 4 Claims. (Ci. 260-293) ABSTRACT OF THE DISCLOSURE Produce aqueous emulsion of a thermo-hardening low molecular weight phenol-formaldehyde resin by reacting monohydroxy benzene with excess of formaldehyde in the presence of oleamide. This abstract is not intended to be a description of the invention defined by the. claims.

The invention relatesto a method of producing an aqueous emulsion of a thermo-hardening, low-molecular reaction product of a monohydrobenzene compound or of a mixture of monohydroxybenzene compounds and formaldehyde by reacting, in water, in the presence of an alkaline reacting substance, a monohydroxybenzene compound or a mixture of monohydroxybenzene compounds with a molecular excess quantity of formaldehyde at a temperature lying between room temperature and the boiling point of the reaction mixture until a low-molecular reaction product is obtained which is suitable for impregnating fibrous materials for example paper.

From sheets of paper impregnated with such an emulsion there can be manufactured the supporting material for printed wirings. To this end a number of paper sheets is impregnated, dried, the resin contained in the paper is precondensed and subsequently, if desired together with a metal foil, the sheets are compressed at a higher temperature to form a unit. A supporting material intended for said use must fulfill high electrical requirements and it must permit of being provided with holes by punching at room temperature or at a slightly higher temperature. It is common practice to provide the printed wiring panel .with holes in order to facilitate mounting of electrical parts on the panel and, as the case may be, to establish electrical connections between printed wirings on either side of the panel.

By punching the panel may be damaged in various Ways so that its electrical and mechanical properties are adversely alfected. The most frequent damage of the panel is formed by cracks. These cracks may extend not only from hole to hole, more or less at right angles to the panel surface but also between the sheets of paper of the panel from a hole in a direction parallel to the panel surface. The latter can be seen from a light-coloured ring around the hole. In both cases moisture and water vapour may penetrate into the sheet material and have a harmful effect on the electrical properties thereof.

It, prior to the punching operation, the sheet material is heated the damage described occurs to a considerably ice lesser extent or it does not appear at all during the punching operation.

Usually the sheet material is 'heated, prior to punching, at a temperature lying between about C. and C. in accordance with the composition. This heating brings about an irreversible, usually small change of the dimensions of the sheet material, but this small change may be suflicient for the electrical properties of the printed wiring on the panel to be varied to an undesirable extent. In order to improve the ease of punching of the sheet material softening groups are sometimes added to the impregnating resins or softeners are added to the emulsions, for example stearylamide (C H COHN However, stearyl amide cannot be used in large quantities (for example more than 10% by weight of the solid resin). With percentages exceeding 10% such impregnating emulsions are in the state of a gel at room temperature and in this case impregnation is only possible at a higher temperature. Moreover, during the production of hard paper from impregnated paper sheets stearylamide is squeezed out so that a layer of stearylamide is formed on the surface of punching the hard paper at normal temperature.

The method according to the invention consists in employing a softener in impregnating emulsions, which softener is bound in the resin molecule so that it is not squeezed out of the materials impregnated in the emulsions under the action of heat and pressure during the manufacture of sheet material. The method according to the invention has furthermore for its object to provide impregnating emulsions that can be employed at room temperature owing to a suitable choice of the softener, in spite of the high percentage thereof.

It has been found that this requirement can be satisfied by adding oleamide (C H CH=CHC- H CONH to the reaction mixture during the production of the emulsion. The oleamide is chemically bound in the resin molecule and is not squeezed out during the manufacture of sheet material, even if it is added in quantities five times the maximum permissible quantity of stearylamide. This may be due to the double bond in the oleamide, which is capable of forming a stable chromane ring with orthomethylene compounds of monohydroxybenzene compounds such as phenol. This reaction is not reversible. The amide bond which can appear only in stearylamide is apparently indeed reversible.

A practical suitability for punching of the hard paper is obtained by adding at least 10 g. of oleamide per grammolecule of the monohydroxybenzene compound during the preparation of the reaction mixture. If more than 35 g. of oleamide per grammol of monohydroxybenzene compound is added to the impregnating liquid during the production, emulsions are, in general, obtained which are lacking in stability by nature. By adding emulsifiers, however, suitable emulsions may be obtained when larger quantities than 35 g. per grammol of monohydroxybenzene compound are added. These greater quantities are usually not required for obtaining a satisfactory suitability for punching; a suitable quantity is for example 30 g. of oleamide per grammol of the monohydroxybenzene compound. If the punched pattern comprises a comparatively great number of small apertures per unit of surface, a quantity of for example 18 g. of oleamide per grammol of the monohydroxybenzene compound is preferred.

With reference to the following examples the method according to the invention will be described more fully.

For producing the resins the following method was employed.

Starting from a monohydroxybenzene compound or a mixture of monohydroxybenzene compounds and a molecular excess quantity of formaldehyde, if desired in the form of paraformaldehyde, amounting preferably to a maximum of 1.5 grammol per grammol of the monohydroxybenzene compound, a reaction product is prepared in a basic medium (pH 7.0 to 8.5) in water in which per grammol of hydroxybenzene compound at least 1.2 grammol of formaldehyde is bound. The pH value of 7.0 to 8.5 of the reaction medium is obtained by means of a basically reacting substance which is not incorporated in the resin molecule. Then the acid content of the reaction mixture is adjusted to a value lying between pH 2.5 and by means of an acid-reacting substance which is incorporated in the resin molecule and forms with the basically reacting substance a salt which is not dissociated or substantially not dissociated or which is insoluble.

Suitable hydroxybenzene compounds are in the first place monohydroxybenzene compounds, phenol and cresols, but also other hydroxybenzene compounds such as xynols may be employed.

Suitable basically reacting substances are for example earth-alkaline compounds soluble in phenol-containing water such as Ca(OH) Ba(OH) and aliphatic tertiary amines and quaternary ammonium bases such as (C H N, (CH hN-OH. Acidically reacting compounds incorporated in the resin molecule are for example boric acid, metacresotinic acid, aminosulphonic acids and their ammonium salts.

After the production the resin content may be adjusted by distilling off water from the resin emulsion or by adding water thereto. In, general, emulsions containing 20 to 40 mls. of water per initially available grammolecule of monohydroxybenzene compounds yield satisfactory results. With this method the first step in the basic medium provides a low-molecular, hydrophilic resin. By using the said acids, the resin becomes hydrophobic subsequent to impregnation and hardening so that the dielectric properties are improved.

It has been found that, when using greater quantitie of oleamide and when using phenols substituted with alkyl groups it is advisable to employ tertiary amines as basically reacting substances and to add the formaldehyde wholly or partly in the form of paraformaldehyde to the reaction mixture.

It has furthermore been found that when great quantities of oleamide are employed it is advisable to add phenol to the reaction mixture subsequent to acidification. It is found that the dielectric properties of the materials produced by means of such a resin are improved in this way. Theoretically this might be accounted for by the fact that by the addition of phenols the hydrophilic methylol groups sterically hindered by the long carbon chains of the oleamide are converted into hydrophobic groups; also substituted phenols such as nonylphenol may be employed. They are capable of partly replacing the oleamide. It was found to be advantageous to use quantities up to- 0.1 mol of phenol per grammol of monohydroxybenzene.

flux cooler sealed from the air by means of a soda lime tube a mixture of: 733.6 g. of water-con ai ing phenol,

.content of about 80% 7 mol. of phenol, 332.9 g. of synthite 9.8 mol of formaldehyde, 7.0 g. of triethylamine=0.07 mol and 96.0 g. of water is caused to boil, while stirring, boiling being continued for 50 minutes. Then 210 g. of oleamide (oleylamide) of technical quality is added to the reaction mixture and boiling is continued for 5 to 10 minutes. Then the mixture is cooled to C. and at this temperature 20 g. (0.105 mol) of ammonium salt of sulfanilic acid is added, after which cooling is performed, while stirring, to 20 C. The reaction mixture obtained has a pH value of about 4.3 at 20 C. and can be employed without further steps as an impregnating resin.

Example 2 In a reaction flask comprising an agitator and a reflux cooler, sealed from the air by means of a soda lime tube a mixture of 733.6 g. of aqueous phenol-:7 mol of phenol, 364.9 g. of synthite containing 10.5 mol of formaldehyde, 7.0 g. of triethylamine=0.07 mol and 85.0 g. of

water is caused to boil and boiling is continued for 50' minutes, while stirring. Then 195 g. of oleamide (oleylamide) of technical quality is added to the reaction mixture and boiling is continued for 10 minutes. Subsequently, the mixture is cooled to 70 C. and at this temperature 0.07 mol=6.8 g. of aminosulphonic acid (sulphaminic acid) in 60 g. of water is added while stirring. After the homogenisation 73.4 grns. of aqueous phenol (0.7 mol of phenol) is added, while constantly stirring and the mixture is further cooled to room temperature. The reaction mixture obtained has a pH value of about 4.4 and may be employed as an impregnating resin without the need for further steps.

Example 3 In a reaction flask provided with an agitator and a reflux cooler sealed from the air by means of a soda lime tube, a mixture of 1048 g. of aqueous phenol (10 mol of phenol), 477.8 of synthite containing 13.75 mol of formaldehyde, 10 g. of triethylamine=0.1 mol and 127 g. of water, is caused to boil, while stirring and boiling is continued for 50 minutes. Then 140.7 g. (0.5 mol) of oleamide (oleylamide) of technical quality is added and boiling is continued for 10 minutes. Subsequently, the mixture is cooled to 70 C. C., after which 0.1 mol .of aminosulphonic acid=9.71 g. dissolved in 78 g. of water is added and then 0.5 mol=110.3 g. of nonylphenol is added. Whilst stirring the mixture is finally cooled to room temperature. The reaction mixture may then be employed as an impregnating resin.

Example 4 A number of sheets of kraft paper having a weight of g./m. is impregnated in the impregnating resins obtained as described in the preceding examples. The measuring results given in the following table are obtained.

It will be obvious that the emulsions obtained by this invention may be employed not only for the manufacture of hard paper but also for impregnating textile tissues and other fibrous materials. 7

The use of oleamide is not restricted to the resin emulsions obtained by the methods described in the preceding examples; also resins of the phenolforrnaldehyde type obtained by other methods may be advantageously softened by means of oleamide.

1 Synthite is the tradename of a low-molecular pnraformaldehyde marketed by Barter Trading Corp. Ltd, Great Britain in the form of a solid white substance having a formaldehyde by weight. The conventional parafornlaldehydes may, however, also be employed.

Basic substances Resin Resin Resin Example 1 Example 2 Example 3 Pressing conditions:

Time, min 30 30 30 Pressure, kg./cm. 60 60 60 Temperature, C 150 160 150 Properties of the hard paper:

Resin content, percent 52 55 54 Thickness, mm 1. 56 1. 08 1. 39

After 24 After 24 After 24 Air dry hours Air dry hours Air dry hours water water water tan 6 at 20 0. x10 and- 100 o.lsec 376 398 205 354 154 188 1,000 c./Sec 315 324 194 258 149 153 2,000 c./sec 315 320 196 248 2 mcJsec 408 403 336 368 386 390 Resistivity at 300 v. and 20 C. in

ohm-cm N 4. 7X10 4. 4x10 3. 7 X10 2. 3X10 4. 3X10 2. 9X10 What is claimed is:

1. A method of producing an aqueous emulsion of a low-molecular Weight phenol formaldehyde resin, said method comprising the steps, reacting, in an alkaline aqueone medium, a mixture of a monohydroxybenzene and a molecular excess of formaldehyde in an amount not greater than about 1.5 grammols of the formaldehyde per grammol of the monohydroxybenzene, adding oleamide to said reaction medium in an amount of about 10 grams to about 35 grams of the oleamide per grammol of the monohydroxybenzene compound, decreasing the pH of the reaction medium to a value between about 2.5 and 5 by the addition of an acidic substance and allowing said reaction to continue until at least about 1.2 grammols of formaldehyde have reacted with each grammol of the monohydroxybenzene.

2. The method of claim 1 wherein the aqueous medium is rendered alkaline by the addition of a tertiary amine.

References Cited UNITED STATES PATENTS 2,869,195 1/ 1959 Cooper et a1. 260-293 SAMUEL H. BLECH, Primary Examiner.

MURRAY TILLMAN, Examiner.

I C. BLEUTGE, Assistant Examiner.

Claims (1)

1. A METHOD OF PRODUCINT AN AQUEOUS EMULSION OF A LOW-MOLECULAR WEIGHT PHENOL FORMALDEHYDE RESIN, SAID METHOD COMPRISING THE STEPS, REACTING, IN AN ALKALINE AQUEOUS MEDIUM, A MIXTURE OF A MONOHYDROXBENZENE AND A MOLECULAR EXCESS OF FORMALDEHYDE IN AN AMOUNT NOT GREATER THAN ABOUT 1.5 GRAMMOLS OF THE FORMALDEHYDE PER GRAMMOL OF THE MONOHYDROXYBENZENE, ADDING OLEMIDE TO SAID REACTION MEDIUM IN AN AMOUNT OF ABOUT 10 GRAMS TO AOUT 35 GRAMS OF THE OLEAMIDE PER GRAMMOL OFTHE MONOHYDROXYBENZENE COMPOUND, DECREASING THE PH OF THE REACTION MEDIUM TO A VALUE BETWEEN ABOUT 2.5 AND 5 BY THE ADDITION OF AN ACIDIC SUBSTANCE AND ALLOWING SAID REACTION TO CONTINUE UNTIL AT LEAST ABOUT 1.2 GRAMMOLS OF FORMALDEHYDE HAVE REACTED WITH EACH GRAMMOL OF THE MONOHYDROXBENZENE.