US3044895A - Process for treating paper - Google Patents

Description

United States Patent Ofiice 3,044,895 PRCES FGR TREATING PAPER Larry Z. lsaacson, Cincinnati, Ohio, assignor to Formica Corporation, Cincinnati, ()hio, a corporation of Delaware No Drawin Filed Dec. 9, 1957, Ser. No. 701,319 2% Claims. (Cl. 117-=-6) This invention relates to a process for treating paper Webs with phenolic resins and to the product prepared thereby. More particularly, this invention relates to a method for producing phenolic resin impregnated paper particularly for use as core sheets in the manufacture of laminates. Still further, this invention relates to the method of treating paper with water until said paper is wetted and introducing said wetted paper into a homogeneous mixture of a water-soluble phenolic resin and a water-insoluble fusion phenolic resin dispersed in an inert mutual solvent for the two resins and drying the paper web.

One of the objects of the present invention is to produce paper impregnated with phenolic resins to be used as the core sheets of laminated articles. A further object of the present invention is to produce phenolic resin impregnated paper having the required electrical properties by use of an expedient and economic process. These and other objects of the present invention will be discussed in greater detail hereinbelow.

The use of phenolic resin impregnated paper as core sheets for laminates has long been known in the art. Various methods for impregnation of these paper Webs with the electrical grade phenolic resin have been tried and although many of these processes have been successful in the production of a desirable product, the processes of the prior art have in many instances left a great deal to be desired, either because of the multiplicity of steps involved, the time factor and/or the economic factor of cost of production. I have discovered that by preparing a homogeneous dispersion of a water-soluble phenolformaldehyde resin and a water-insoluble fusible phenolform-aldehyde resin dispersed in a common inert mutual solvent I can treat the paper in a satisfactory, expedient and economical process which avoids a number of the steps of the prior art and yet produces a completely satisfactory product. This is accomplished by wetting the paper web prior to its introduction into the mixed resin dispersion. This Wetting of the paper web can be accomplished in a plurality of ways, for instance, the paper Web can be'passed through a water bath or the paper Web can be sprayed on both faces with water or the paper web can be exposed to live steam or passed through a pair of wetted rollers or a plurality of the same. The most practical method, particularly from the standpoint of uniform wettings is the spraying technique and this is preferred. The paper as normally received will contain 5% of moisture although seemingly in a dry state. The addition of as small an amount as 1% of additional moisture will enhancevthe penetration of the water-soluble phenolic component into the fibers. Much larger additions of moisture are needed, however, in order to develop maximum penetration. A total of about of added Water over and beyond the original water content, i.e. a final water content of is necessary in order to assure maximum penetration. Larger quantities of water may be added such as water up to about 40% over and beyond the original moisture content, but it is to be noted that after a total of 15% of Water has been added to the paper web, no significant further improvement is achieved. As a consequence, for practical purposes assuming that the original paper web contains approximately 5% of moisture, there is added water in an amount to approximate 10% to 25% of added moisture.

In the preparation of the resin impregnating bath, one prepares separately two different phenolic resins; a watersoiuble phenolic resin and a separately prepared waterinsoluble phenolic resin. This latterclass of resins is frequently identified as a spirit-soluble phenolic resin or an electrical grade phenolic resin. In the preparation of the water-soluble phenolic resin, one may use phenol and formaldehyde as the starting ingredients in a mol ratio varying between about 1:1 and 1:3, respectively, but preferably 121.2 to 1:25 phenol to formaldehyde, respectively. In order to achieve water solubility in this class of resins, a number of factors must be kept in mind, for instance, the number of methylol groups should be kept high while the degree of condensation is kept low. The amount of free formaldehyde should be kept at a minimum in order to avoid loss in yield, odor and toxicity. These phenol-formaldehyde resins may be reacted on either the alkaline or the acid side of the pH range. Since difiiculty in control of the reaction on the acid side is sometimes experienced, it is preferred that the reaction be carried out on the alkaline side for better Water solubility characteristics. To accomplish this, one may use an alkaline material such as the alkali metal hydroxides and alkaline earth metal hydroxides, their oxides, carbonates and the like. Additionally, one may use ammonium hydroxide or the organic primary amines such as methyl amine, ethyl amine, propyl amine and the like. For best results, sodium hydroxide, triethyl amine and the like should be used. The temperature at which the reaction is carried out is not critical and may be varied between about 40 C. and 100 C. but preferably between 60 and C. ,When lower temperatures are used such as 40 C., the reaction time is lengthened prior to reaching a low fre e' formaldehyde content and for this reason the middle temperatures are preferred. At 40 C. it may well take as long as 16 hours'to achieve the desired free formaldehyde content. At 60 to 80 C. the reaction time is between about 1 and 2 hours. The use of higher temperatures such as 100 C. will ordinarily be avoided because of the risk of producing too much 18% by weight of water-soluble phenolic resin solids based on the total Weight of resin solids. The waterinsoluble phenolic resin will be present in a corresponding amount, namelscbetween about to about 78% by weight of insoluble resin solids based on the total weight of resin solids. Preferably, the insoluble resin solids will be present in an amount varying between 89% and 82% by weight of insoluble resin solids based on the total weight of resin solids. v

The water-insoluble phenolic resin may be prepared by reacting formaldehyde with a phenol. Among the phenols which may be used in the practice of the processof the present invention to prepare the water-insoluble phenolforrnaldehyde resin are phenol per se, or one of the.

cresols, such as meta-cresol, para-cresol, and ortho-cresol, xylenol, or mixtures of these phenols coreacted with formaldehyde. The meta-cresol is preferred. Frequently, it is desirable to make use of a mixture of phenols in making the water-insoluble phenolic resin such as a mix Patented July 17, 1962 ture of meta-cresol and xylenol-formaldehyde resins or cresol-aniline-formaldehyde resins and the like. A considerable number of these resinous materials and their method ofpreparation are well known in the art. Among the xylenols which may be used in the resins of the present invention are 2,3-dimethyl phenol, 3,4-dimethyl phenol, 3,5-dimethyl phenol, 2,6-dimethyl phenol, 2,4- dimethyl phenol, 2,5-dimethyl phenol and the like.

Among the mutual inert solvents for the two separately prepared phenolic resins used in the present invention are those organic materials having a boiling point not greater than about 150 C. that are normally liquid such as the monohydric alcohols including methanol, ethanol, or the ketones such as acetone, methylethyl ketone, diethyl ketone, ethylpropyl ketone, dipropyl ketone, and the like. It is sometimes desired to use a miscible blend of one of the above-recited solvents with an aromatic solvent such as benzene, toluene, xylene, and the like. Ethanol alone provides a very desirable solvent mutually inert to each of the resinous components. Equal portions of ethanol and toluene also make a desirable solvent. Still further, equal portions of ethanol, toluene and methyl ethyl ketone make a desirable solvent mixture. For most purposes, a polar-type solvent or mixture thereof is to be chosen.

The paper treated in accordance with the process of the present invention may be a cellulosic type paper, of which many are conventionally known in the art, including kraft paper. After the paper to be treated has been wetted with the water and passed through the resin impregnating bath, the paper is passed through a drier heated at a temperature between about 110 and 160 C. in order to drive off the volatiles only in the paper Web. The residence time in the drier will be determined by the temperature of the drier. Longer residence times will be required at the lower temperatures and shorter residence at the higher temperatures. After the paper has evolved from the drier, it is then rolled and stored or it may be used at once.

The amount of total resin solids present in the impregnating bath may be varied over a fairly substantial range such as between about solids to about 80% solids. Preferably, for optimum results, the total percent of resin solids should be between and 60% by weight based on the total Weight of resin solids and the dispersing medium.

In order that the concept of the present invention may be more completely understood, the following examples representing methods for the preparation of the resins used in the present invention are set forth in which all parts are parts by weight unless otherwise indicated. These examples are set forth primarily for the purpose of illustration and any specific enumeration of detail contained therein should not be interpreted as a limitation on the case except as is indicated in the appended claims.

RESIN A A water-soluble phenol-formaldehyde resin is prepared by introducing into a suitable reaction vessel equipped with thermometer and stirrer 940 parts of phenol, 1010 parts of a 37% aqueous solution of formaldehyde and 10 parts of triethyl amine. The charge is heated to about 80 C. and is held at about that temperature to a water tolerance of 1000%. Thereupon, there is added 100 parts of ethyl alcohol and the resin solution is cooled to room temperature. A water tolerance of 1000% means that 10 parts of the resin solution can be diluted with 100 parts of water without any indication of permanent precipitation of resin from solution.

RESIN B A water-insoluble fusible phenolic resin is prepared by introducing into a suitable reaction vessel equipped with a thermometer, stirrer and reflux condenser 1010 parts of a 37% aqueous solution of formaldehyde, 1100 parts of cresylic acid (a mixture of ortho-, meta-, and para-cresols, preponderantly meta-cresol), 165 parts of tung oil and 30 parts of a 28% aqueous solution of ammonia. The charge is heated to the reflux temperature and held at that temperature for about 30 minutes. The reflux condenser is removed and the system is dehydrated by removing about 640 parts of water. Thereupon, there is added 460 parts of toluene, 300 parts of dioctyl phthalate and 920 parts of ethyl alcohol.

Example 1 23 parts of the resin A solution and 145 parts of the resin B solution are blended together and introduced into an impregnating tank. A web of kraft paper is sprayed with water to a water content of about 15% moisture total. Thereupon, the wetted web is introduced into the mixed resin impregnating bath, removed therefrom and passed through a drying oven, heated to a temperature of about 125-135" C. and on removal from the oven, is passed continuously to a roller and wound to form a roll of the resin impregnated paper.

In the preparation of the water-insoluble phenolic resin, one may use the selected phenol to formaldehyde in a mol ratio varying between about 1:1 and 1:2 but preferably about 1:1.25. A preferred catalyst would be ammonia. The condensation should be carried to a well advanced stage so as to provide water-insoluble characteristics but maintain fusibility. It is sometimes desired to modify the water-insoluble phenolic resin with a glyceride oil such as the tung oil shown hereinabove, including linseed oil, soya oil, caster oil, and the like. These oils may be either non-drying, semi-drying or drying oils and may be present in an amount varying between about 5% and 15% by weight based on the total weight of resin solids.

It is sometimes desirable to make use of a plasticizer for the water-insoluble phenolic resin of which a plurality are well known in the art including dibutyl phthalate, diamyl phthalate, dihexyl phthalate, diheptyl phthalate, dioctyl phthalate and the like. Of these, the dioctyl phthalate is preferred. The amount of plasticizer that may be used can be varied between about 10% and 20% by weight based on the total weight of resin solids.

When additives or modifiers are used in the preparation or use of the resinous materials used in the present invention such as the glyceride oils and the plasticizers, these materials are considered to be a part of the total of the resin solids inasmuch as they do not volatilize during the drying step and become a part of the resin impregnated paper web.

I claim:

1. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of Water with water in an amount ranging from about 1% to 40% by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 5% to 22%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about to 78% by weight, based on total resin solids, of a water-insoluble phenolformaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

2. A process for treating paper webs comprising wetting a cellulosic paper web, containing not more than about 5% of water with water in an amount ranging from about 10% to 25% by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 11% to 18%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and corresponding from about 89% to 82% by weight, based on total resin solids, of a water-insoluble phenolformaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

3. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of water by spraying said web with water in an amount ranging from about 1% to 40% by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 5% to 22%, by weight, based on total resin solids, of a Water-soluble phenolformaldehyde resin and correspondinglyfrom about 95% to 78% by weight, based on total resin solids, of a waterinsoluble phenol-formaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

4. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of water by spraying said Web with water in an amount ranging from about to 25% by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 11% to 18%, by weight, based on total resin solids, a water-soluble phenol-formaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a Waterinsoluble phenol-formaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

5. A process tortreating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of water with water in an amount ranging from about 1% to 40% by weight, based on the weight of said web, impregnating the wetted Web with a mixture of from about 5% to 22%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about 95 to 78% by weight, based on total resin solids, of a Water-insoluble cresol-formaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

6. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of water with water in an amount ranging from about 1% to 40% by weight, based on the Weight of said web, impregnating the wetted web with a mixture of from about 5% to 22%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about 95% to 78% by weight, based on total resin solids, of a water-insoluble cresol-xylenolformaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper Web.

7. A process for treating paper webs comprising wetting a cellulosic paper Web containing not more than about 5% of water with water in an amount ranging from about 1% to 40% by weight, based on the weight of said web, impregnating the wetted web with a mixture or from about 5% to 22%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about 95% to 78% by weight, based on total resin solids, of a water-insoluble cresol-aniline-formaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

8. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of water by spraying said web with water in an amount ranging from about 1% to 40% by weight, based on the weight of said Web, impregnating the wetted web with a mixture of from about 5% to 22%, by weight, based on total resin solids, of a Water-soluble phenoltormaldehyde resin and correspondingly from about 95 to 78% by weight, based on total resin solids, of a waterinsoluble cresol-forrnaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

9. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of water by spraying said web with Water in an amount ranging from about 1% to 40% by weight, based on the Weight of said web, impregnating the wetted web with a mixture of from about 5% to 22%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about to 78% by weight, based on total resin solids, of a Waterinsoluble cresol-xylenol-formaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper Web.

10. A process for treating paper Webs comprising wetting a cellulosic paper web containing not more than about 5% of water by spraying said web with water in an amount ranging from about 1% to 40% by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 5% to 22%, by weight, based on total resin solids, of a water-soluble phenolformaldehyde resin and correspondingly from about 95% to 78% by weight, based on total resin solids, of a waterinsoluble cresol-aniline-formaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

11. A process for treating paper webs comprising Wetting a cellulosic paper Web containing not more than about 5% of water by spraying said web with water in an amount ranging from about 10% to 25% by weight, based on the Weight of said Web, impregnating the wetted web with a mixture of from about 11% to 18%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a water-insoluble cresol-formaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

12. A process for treating paper webs comprising Wetting a cellulosic paper Web containing not more than about 5% of water by spraying said web with water in an amount ranging from about 10% to 25 by Weight, based on the Weight of said web, impregnating the wetted web with a mixture of from about 11% 'to 18%, by weight, based on total resin solids, of a Water-soluble phenol-formaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a water-insoluble cresol-xylenol-formaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

13. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of water by spraying said web with water in an amount ranging from about 10% to 25 by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 11% to 18%, by weight, based on total resin solids, of a water-soluble phenolformaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a waterinsoluble cresol-aniline-formaldehyde resin, dispersed in a mutual, inert solvent, and drying the impregnated cellulosic paper web.

14. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of Water by spraying said web with Water in an amount ranging from about 10% to 25 by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 11% to 18%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a Water-insoluble cresol-formaldehyde resin, dispersed in ethanol, and drying the impregnated cellulosic paper web.

15 A process for treating paper Webs comprising Wetting a cellulosic paper Web containing not more than about 5% of water by spraying said web with water in an amount ranging from about 10% to 25% by weight, based on the weight of said web, impregnating the wetted Web with a mixture of from about 11% to 18%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about 89% to 82% by Weight, based on total resin solids, of a water-insoluble cresol-xylenol-forrnaldehyde resin,

7 dispersed in ethanol, and drying the impregnated cellulosic paper web.

16. A process for treating paper webs comprising wetting a ccllulosic paper web containing not more than about of water by spraying said web with water in an amount ranging from about to by weight, based on the weight of said Web, impregnating the wetted web with a mixture of from about 11% to 18%, by weight, based on total resin solids, of a watersoluble phenol-formaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a water-insoluble cresol-aniline-formaldehyde resin, dispersed in ethanol, and drying the impregnated cellulosic paper web.

17. A process for treating paper webs comprising Wetting a cellulosic paper web containing not more than about 5% of water by spraying said web with Water in an amount ranging from about 10% to 25% by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 11% to 18%, by Weight, based on total resin solids, of a Water-soluble phenol-formaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a waterinsolub1e cresol-formaldehyde resin, dispersed in a mixture of ethanol and toluene, and drying the impregnated cellulosic paper web.

18. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of water by spraying said web with water in an amount ranging from about 10% to 25 by weight,

based on the weight of said web, impregnating the wetted web with a mixture of from about 11% to 18%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a water-insoluble cresol-xylenol-formaldehyde resin, dispersed in a mixture of ethanol and toluene, and drying the impregnated cellulosic paper Web.

19. A process for treating paper webs comprising wetting a cellulosic paper Web containing not more than about 5% of water by spraying said web with water in 8 an amount ranging from about 10% to 25 by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 11% to 18%, by weight, based on total resin solids, of a water-soluble phenol-formaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a water-insoluble cresol aniline-formaldehyde resin, dispersed in a mixture of ethanol and toluene, and drying the impregnated cellulosic paper web.

20. A process for treating paper webs comprising wetting a cellulosic paper web containing not more than about 5% of water by spraying said web with water in an amount ranging from about 10% to 25 by weight, based on the weight of said web, impregnating the wetted web with a mixture of from about 11% to 18%, by weight, based on total resin solids, of a water-soluble phenolformaldehyde resin and correspondingly from about 89% to 82% by weight, based on total resin solids, of a water-insoluble cresol-formaldehyde resin, dispersed in a mixture of ethanol, toluene and methylethyl ketone, and drying the impregnated cellulosic paper web.

References Cited in the file of this patent UNITED STATES PATENTS 1,966,458 Novak July 17, 1934 2,343,095 Smith Feb. 29, 1944 2,554,128 Spokes May 22, 1951 2,702,758 Uhlig ,Feb. 22, 1955 2,708,645 Norman May 17, 1955 2,721,815 Mullen Oct. 25, 1955 2,732,295 Hollenberg Jan. 24, 1956 2,739,908 Marsh Mar. 27, 1956 2,758,101 Shappell Aug. 7, 1956 2,801,198 Morris et a1 July 30, 1957 2,825,706 Sanders Mar. 4, 1958 OTHER REFERENCES Bauer: Method for Combining Phenolic Resins and Paper, TAPPI Section, pages 28-30, Paper Trade Journal, vol. 125, N0. 3, pages -52.

Claims (1)

1. A PROCESS OF TREATING PAPER WEBS COMPRISING WETTING A CELLULOSIC PAPER WEB CONTAINING NOT MORE THAN ABOUT 5% OF WATER WITH WATER IN AN AMOUNT RANGING FROM ABOUT 1% TO 40% BY WEIGHT, BASED ON THE WEIGHT OF SAID WEB, IMPREGNATING THE WETTED WEB WITH A MIXTURE OF FROM ABOUT 5% TO 22%, BY WEIGHT, BASED ON TOTAL RESIN SOLIDS, OF A WATER-SOLUBLE PHENOL-FORMALDEHYDE RESIN AND CORRESPONDINGLY FROM ABOUT 95% TO 78% BY WEIGHT, BASED ON TOTAL RESIN SOLIDS, OF A WATER-INSOLUBLE PHENOLFORMALDEHYDE RESIN, DISPERSED IN NUTUAL, INERT SOLVENT, AND DRYING THE IMPREGNATED CELLULOSIC PAPER WEB.