US2229357A - Fibrous product - Google Patents

Description

Patent ed Jan. 21, 1941 2,229,357 I UNITED STATES J PATENT OFFICE rmnons rnonuc'r Gordon E. Wightman, Upper Montclaiig'N. .I., and

Ernest Kritzmacher, Manchester, Conn., assignors, by mesne assignments, to Union Carbide and Carbon Corporation, New York, N. Y., acorporation of New York No Drawing. Application January 25, 1937,

- Serial No. 122,312

3 Claims. (CI. 92-40) This invention relates to the production of sion of about 30% resin content. Generally paper or other fibrous sheet material having a speaking, resinous compositions of the character resinous substance associated therewith for the above described are spoken of as being hydro-philic purpose of increasing the resistance of the mateor water loving in nature, but for the purposes 5 rial to moisture, and is particularly directed to a of this invention, only those resinous composi- 5 new method of producing such material and to tions which will tolerate the addition of substan-' the novel products thereby produced. tially more than an equal amount of water with- One of the purposes of the invention is to proout becoming turbid or cloudy will be designated vide a method of eiiectively associating a resinas hydrophile. It will be seen therefore that the ous substance with the fibers of paper or like hydrophile compositions utilized in the present materialinvention are characterized by containing a It is known to treat paper and like material resinous product capable of holding up to seventy with rosin to impart water resistance thereto. parts of water per thirty parts of the resinous The usual practice is to add to the wet fibrous product, even in neutral condition.

' pulp a rosin soap made by boiling rosin with A further distinguishing feature of these .sodium carbonate. After mixing the rosin soap filterable hydrophile resinous compositions is the with the pulp the rosin is precipitated by the relatively small amount of resinoid migration addition of alum and the pulp is then formed into which occurs in fibrous sheets treated with these a sheet or board and dried. compositions. Thus, when the volatile portion of It has also been proposed to dissolve rosin in a the hydrophile resinous composition is removed, '2 solvent immiscible with water, such as carbon as for example by evaporation,-the resinoid aptetrachloride, and apply the solution to the prepears to remain in the form of adhesive films forme g sheet, after which the solvent is removed upon individual parts of or within the fibers therefrom. themselves, instead of migrating to the exposed The first method entails the disadvantage that surfaces of the fibers, as is so often the case 25 the addition of alum to efiect precipitation of when organic solvent dispersions of comparable the rosin results in the presence of iree acid resinoid concentration are used. which injures the fibers. The second method re- Of particular value in the present invention are quires the drying of the sheet before it can be beat hardenable resinous substances or res- '30 treated with the rosin solution, and a subsequent inoids, especially those substances which change drying operation is required for removing the to a hydrophobe condition upon the application solvents from the sheet. Apparatus for recoverof heat so that, in the final heat treated condiing the solvent is also required. A further distion, they are substantially unaffected by moisadvantage of this method'is that the solvents ture. Especially suitable substances for use in tend to carry the solute to the surface of the sheet the present invention are the liquid masses 010- 05 and concentrate it there upon evaporation. tainable by reacting about equimolecular propor-' These d sadvantages are eliminated by the tions of phenol or cresol with aqueous formaldepresent invention which comprises the treathyde in the presence of a small amount, say 1 ment of the web of paper or other fibrous mate to 2% based on the phenolic constituent, of an rial with resinous substances or compositions in alkaline or other suitable catalyst, stopping the 40 the form of clear aqueous dispersions which are reaction before there is any precipitation or sepad lutable with further'quantities of water. These ration of resinoid.. The resulting relatively clear resinous compositions are apparently not true liquid dispersion will normally contain about aqueous solutions since there is a limit to the 60% resinoid, and will tolerate the addition of amount of water which maybe added without substantially more than an equal amount of causing resin precipitation with attendant cloudwater without becoming cloudy 'or precipitating ing of the dispersion. In general, the most satisthe resinoid. If a drop of the liquid is applied to factory dispersions for use onwet paper pulp have a Wet fibrous surface, it does not remain conbeen found to be those which will tolerate the adcentrated on the area to which it is applied, but

amount of water without initiating clouding or sheet. Neither does it require a; neutralizin precipitation of the resinoid. In other words, a acidifying agent to deposit the resinoid. resin dispersion containing about 60% of res- A-reaction product of the phenolic typ can be lnoid will .tcleraie an additional quantity of water made dilutable with water under operating con- 55 sufficient to give a clear unclouded resin disperditions differing from the above, such as using a 55 v0 dition of substantially more than an equal immediately disappears into the mass of the smaller amount of alkaline catalyst and reacting for a longer period of time, or until the reaction mixture separates into two layers, and then adds ing up to 540% more of caustic based on phenol 5 to obtain an aqueous solution, or a large amount of alkaline catalyst, say about 540% sodium hydroxide based on phenol, may be used in the initial reaction when a liquid mass results which can be diluted with water as desired. However, as the i amount of caustic used is increased beyond 1 or 2% the mass appears to take on more and more the characteristicsof a resinoid soap in solution, and at 4% or more, to exhibit the properties of true salt solutions to the extent of requiring l5 precipitation or neutralization by known means such as alum to remove caustic present in excess of 4%, and preferably caustic in excess of 2% either before or after applying the resinous composition to the fibrous sheet.

In accordance with the present invention,

therefore, it has been found that to avoid removal of caustic present in excess of 2% without resorting to precipitation or neutralization it is necessary to use not in excess of 2% of an alkaline catalyst during resin condensation, and

moreover, that the condensation should be in- -terrupted before there is any precipitation or separation of the resinoid.

It has been found, furthermore, that the aque- 80 ous mass need not be of an alkaline character.

Instead the alkaline catalyst may be completely neutralized by suiiicient acid and the neutralized solution may be used. or a small amount of an organic .acid such as phenol, tannic acid, citric 88 acid, lactic acid, etc., can be added to give an acid reaction, and stable aqueous masses arethereby obtained which can be diluted with substantially more than an equal amount of water without clouding or precipitating the resinoid.

40. ypical examples for the preparation of hydrophile resinoids suitable for the purposes of this application are the following:

Example 1 100 parts of phenol and 80 parts of aqueous formaldehyde (40% solution) are reacted in the presence of 0.8 part sodium hydroxide for about 30 minutes. At the end of the reaction period, the liquid mass is still clear and no precipitation has occurred. It is dehydrated preferably in vacuo until the resinoid content formed constitutes about of the total mass. The viscosity of the finished dispersion will be about 80-100 55 cp. If the liquid mass is diluted with an equal weight of water or until the resinoid content is about 30% it still remains clear and suitable for use with alpha cellulose fibers, pulp or ground wood. a 69 When cresols or other higher phenols are used as a component of the resinoid, or when a more extended dilution with water is desirable, it is generally advantageous to include a volatile water-soluble organic solvent, such as alcohol, in 55 the liquid mass to avoid precipitation of the resinoid. For example, if alcohol is present in an amount of about 10% of the water the composition may be diluted to a resinoid content of as little as 5% of the total mass. However, evenv 70 without the inclusion of an organic solvent the mass is not rendered unusable even by dilution until clouding occurs for the hydrophile property ofidistributing in water or spreading and disappearing when applied to a wet fibrous surface is still manifested,

tannic acid, rendering the liquid mass slightly Example 2 100 parts of cresol and 87.5 parts of aqueous formaldehyde (40% solution) and 5.3 parts ammonium hydroxide (28% solution of ammonia 5 in water) are reacted 30 minutes at C. The reaction mass is then dehydrated preferably in vacuum until a test portion of the resinv is hard and brittle when dropped into water at 2 C. 73.7 parts of denatured alcohol are added to give 10 a spirit varnish containing about 60% resinoid. Such a dispersion-will have a viscosity of about 80-100 op. 50 parts of this dispersion blended with 50 parts of the hydrophile resin described in Example 1 may be diluted with parts of 15 water to give a water-alcohol-resin dispersion which is slightly opalescent but suitable for treating a web of paper or other fibrous material.

Example 3 145 parts of phenol, 145 parts formalin and 1 p'art sodium carbonate are reacted 1 hour under reflux. 0.75 part of concentrated sulfuric acid are added to the clear liquid and then 1 part of acid to rosolic acid. It remained clear and could 'be diluted with an equal weight of water without clouding or precipitating the resin. Such a solution may be used in the treatment of cellulose products. 0 Example 4 108 parts cresol, parts formalin, 160 parts water and 3 parts ammonia sp. g. .897 were heated to boiling under a reflux condenser for 30 minutes, after which time the reaction mix- 35 ture was still a clear liquid. It was then dehydrated until about parts of a viscous resin was obtained still containing about 18% water. This was dissolved in 43 parts of alcohol containing 2 parts lime. The resulting dispersion was clear and could be diluted with at least an equal quantity of water. It could be used with advantage for the treatment of cellulosic materials.

Other resins or resinoids which have, or can 45 be given, a hydrophile character, such as rosin and other natural resins, such as shellac, ureaformaldehyde resinoids, resins of the alkyd type and the like may also be advantageously used in practicing the invention. 50

Example 5 60 parts urea and 160. parts aqueous formaldehyde 40% solution and 1 part hexamethyiene tetramine were boiled under a reflux condenser for 15 minutes. The reaction mixture was a clear liquid at the end ofthe reaction .period. 50 parts denatured alcohol were added and 2 parts of citric acid which was suii'icient acid to render the liquid resinous mass, just faintly acid 0 to litmus. This liquid resinous mass could be diluted with an equal quantity of water without initiating clouding, if used within three hours after completion of the reaction, and was suitable for use with cellulosic compositions. On 65 standing more than three hours, however, the liquid resinous mass tolerated less and less water.

The hydrophile resinous substances are preferably applied by passing the dried or undried sheet through a. bath of the resinous composition 70 or by spraying the resinous composition upon the surface of the dried or undried fibrous; sheet.

It is particularly advantageous to apply the resinous composition to the undried. sheet as in this case one-drying operation is eliminated. 75

For example, the liquid resinous composition may be applied to the paper web as it comes from the wire of a Fourdrinier machine or analogous device. In this case the sheet has typically a water content of about 60% and the liquid resinoid composition immediately penetrates and disappears into the sheet.

When a sheet or a stack of sheets treated as just described is dried and subjected to hot pressing or calendering a most marked and unexpected resistance to moisture absorption is brought about as well as a greatly improved surface appearance.

After treatment of the fibrous sheet with liquid resinoid composition, it is dried. If the composition comprises a resinoid of the heathardenable type the drying operation is preferably so carried out that the moisture content is removed without materially advancing the stage of polymerization of the resinoid.

If a laminated product is desired the drying operation is advantageously conducted as follows: The web of treated fibrous material is rolled on a cylinder or similar device until the desired thickness of board is obtained. The board is then cut from the cylinder and dried, preferably by hanging in lofts. After the boards are dried they are subjected to combined heat and pres sure between heated platens, whereby well bonded laminated structures of high moisture resistance are produced.

This method provides an eifective and eco-- nomical way of producing laminated structures as it obviates the necessity of coating and superposing a number of separate sheets.

When aqueous resinous compositions containing an organic solvent are used, the proportion of such solvent is preferably limited to such an amount, depending on the particular solvent, that after application of the composition to a fibrous surface and evaporation of the solvent,

sufiicient water remains to insure proper distribution of the hydrophile resinous content. Enough water should remain after removal of the solvent to prevent undue concentration and agglomeration of the resin. When a wateralcohol mixture is used the alcohol may constitute as much as of the mixture without disturbance of the hydrophile action when it-is evaporated. When the residual water is thereafter removed, the resinous substance remains associated with the fiber, apparently in the form of extended films.

The application of hydrophile resinous compositions is not limited to the procedures described above. The compositions can, for example, be sprayed or dripped onto the web Just prior to its passage under the making roll or onto the sheet as it winds upon the making roll. Another alternative method comprises spraying a partially dried sheet while it is passing through the paper drier, or to apply the resinous composition thereto by means of a contact roller. It is not essential that the paper be in a wet condition, as the resinous composition may be applied to the paper when dry or partially dried; obvious-1y, however, it is usually advantageous to make the application to the sheet while in the wet condition to avoid a second drying.

The present invention has been found to be of particular advantage when applied to fibrous sheet material which has had a binding agent,

such as a phenolic resinoid, a resin or other binder, associated therewith in the process of manufacture. An example of such fibrous sheet material which has given particularly desirable results in the present invention are resinoidcontaining fibrous sheets produced by the Socalled wet process. In a typical form of this process a solid phenolic resinoid in powdered or sludge form is added to the fiber pulp in a beater and thoroughly mixed. The pulp is made into a sheet in the usual manner and dried. If, before drying such sheets, they are treated with a liquid hydrophile resinous composition, for example a phenolic resinoid composition, in the manner described above, laminated structures made by superposingthe dried sheets and subjecting the stack to heat and pressure, are found to have greatly reduced water absorption, even when the added resinoid is as low as 0.5% of the sheet. The water absorption is normally reduced to onetenth or less of its original value by-the treatment of the invention, although the added resinoid amounts to only one-third to one twentyfifth'of the resinoid originally present.

Not only is there the marked and unexpected decrease in water absorption of the finished product, due to the application of a hydrophile resinous substance to a resin-containing sheet, but the material produced in accordance with the invention also exhibits a substantial improvement in the surface appearance after molding or hotpressing into laminated or board stock. An increased uniformity of resin distribution in the body of the material is also obtained. As a result of this improvement hot-pressed laminated structures and other articles produced by the method of the invention can, for example, be sanded without the formation of a striated surface effectsuch as results from the sanding of laminatiad material made by the usual method of coating and impregnating sheets with alcoholic or other solutions of resinoids, and removing the solvent.

This application is a continuation-in-part of our application Serial No. 727,582, filed May 25, 1934. 7

We claim:

l. Fibrous composition having incorporated therewith a binder and in'addition having uniformly associated with the fibers thereof a hyd drophile heat-hardened phenolic resinoid capable of admixture with up to 70 parts of water per 30 parts of the resinoid in neutral condition without clouding or precipitation.

2. Fibrous composition having incorporated therewith a phenolic resinoid binder and in addi tion having uniformly associated with the fibers thereof a hydrophile heat-hardenable phenolic resinoid capable of admixture with up to 70 parts of water per 30 parts of the resinoid in neutral condition without clouding or precipitation.

3. Fibrous composition having incorporated therewith from 15 to 50% of 'a phenolic resinoid binder and in addition having uniformly associated with the fibers thereof from 0.5 to 10% of a hydrophile heat-hardenable phenolic resinoid capable of admixture with up to 70 parts of water per 30 parts of the resinoid in neutral condition without clouding or precipitation.

GORDON E. WIGHTMAN. ERNEST KRITZMACHER.

CERTIFICATE or commoner. .Patent No. 2,229,557. I January 21,- 1911.1. combo: E. WIGHTMAN, ET AL.

It is hereby c of the above numbered patent requiring correction as follows: Page}, secline 51, claim 1, for "heat-hardened" reqd --heat-hardenab1e--;

Patent should be read with this correction therein 0nd column,

and that the said Letters that the same may conform to the record of the casein the. Patent Offi Signedand sealed this 18th day of February, A. D. 1914.1.

Henry Van Arsdele (Seal) ertified that error appears in the printed specification Acting Commissioner of Patents.