US2083929A - Process of making a beater furnish - Google Patents

Description

J1 Patented June 1 5, 193 v I PATENT OFFICE success or MAKING A BEATER. roamsn Earl P. Stevenson, Newton, and Howard J. Billings, South Acton, Mesa, assignors, by mesne assignments, to The Richardson Company, Lockland, Ohio, a corporation of Ohio No Drawing. Application February 20, 1933, Se-

rial No. 657,670

' 11 Claims. (01. 92-21) This invention relates to a process of making a beater furnish to wit, a stock suitable for charging a paper mill beater and the product thereof,and more particularlyto making a furnish 5 comprising a fibrous mass containing resin in a high state of dispersion. As will be set forth hereinbelow the resin is made synthetically in the presence of the fibre and forms therewith a product readily reducible to a pulp by the addition of water without the removal of a material amount of the resin.

Articles made from stock which includes resinous material have achieved considerable industrial importance because of their great strength,

durability, resistance to moisture, dielectric strength and other properties and various processes of preparing such stock have been proposed:

One such process comprises the use of laminated sheets impregnated with resinous material and moulded under heat and pressure whereby the sheets are united and the resinous material is converted into a heat infusible body. This process has 'been found relatively expensive since it involves the preparation of a partially polymerized resin, its solution in alcohol, its application by surface coating to relatively thin paperof a specialized type and the waste incident to the loss of solvent and thescrap due to trimming the sheets. Other processes avoid much of this ex pense by introducing into the fibrous mass from erably oi'the phenolic class, in a high state of dispersion. The best of these processes is set forth in United States Patent No. 1,771,150, dated 35 July 22, 1930, in accordance with the teachings of which the resin is associated with the fibrous material prior to the dispersion of the fibres in water to form a pulp. The formation of a pulp already containing the incompletely polymerized 40 resin renders it possible to produce the sheets in greater thickness than was heretofore practically feasible where the sheets were impregnated with synthetic resin varnish. In practice, however, it has been found that such resins particularly those 45 made from various fractions of commercial cresylic acid, contain an appreciable percentage of water soluble bodies which are lost in the process of paper making. Thus, While the retention of the resin by the pulp, as it is formed in 50 the paper or board machine, is remarkably high,

there is still room for improvement. The paper delivered from the machine is of a lower resin content than the pulp originally fed into the beater, which apparently is due fundamentally 55 to solubility of certain resin ingredients which may also, in part at least, affect the attachment .of smaller resin masses to the fibres.

The primary objects of the process embodied in this invention are to introduce the resin ineo gredieiit into the furnish at a lower cost; to imwhich the sheets are made, synthetic resin, prefprove the behavior of the resin under the conditions of pulping, forminginto sheets and drying; to obtain a finer and more uniform distribution of the resin and the fibrous ingredients; in short to produce a beater furnish in which the resin is not only more intimately associated with the fibres but is also substantially insoluble so that the resin content of the finished paper or board is more nearly that of the pulp.

It has been found that these and other advantages can be realized in a simple and economical way by forming. the resin in the presence of the fiber and that, under proper conditions, a product can \be so formed that it is readily reducible to a pulp by the absorption of water. The

water so added is preferably cool relative to the mix, at room temperature, for example. By adding the individual resin-making materials directly to a disintegrated mass of fibrous material, such as sulfite, sulfate, or soda pulp, rag stock, etc., a very thorough distribution canbe secured. On raising the temperature the resin formation takes place directly upon, and in the most intimate contact with, the fibers. This thorough distribution permits the reactions in volved in the polymerization of bodies of the phenolic type with compounds containing an active methyl group (such as formaldehyde) to proceed smoothly in the presence of a suitable catalyst, such as ammonia, and apparently to an extraordinarily uniform degree, so that substantially all the final resin is advanced beyond the water-soluble stage while remaining in the heat fusible stage and is closely bonded to the fibres, the resin being so associated with the fibres as to be retained in the web'which is formed by depositing the fibres upon the screen of a paper machine.

A further advantage of this process is that, while much of the resin is closely bonded to the fibres it is substantially insoluble in water and the fibres themselves are not impregnated and hence will freely absorb the water to form the pulp without impairing the bond of the resin thereto. In this connection it may be noted that an attempt to increase the resin content of a beater furnish by impregnating the fibres with the resin has previously been made. This has, however, proven to be unsatisfactory because in order to impregnate the fibres the resin must be soluble in and carried by a strongly alkaline solution. Consequently, while the furnish has a high resin content the water added to the furnish must of necessity displace the resin solution from the fibres in order that they can absorb the water. The dissolved resin then escapes through the screens of the paper making machine so that the resin content of the finished paper is very low indeed. 4 I

Another obvious advantage of the present procedure is the saving in over-all process costs. By causing the resin to be formed within a mass of fibers there is'less handling of materials; also certain of the steps usually followed in preparing 5 these resins in the kettle are omitted resulting in a saving in power, heat and labor. Moreover, by carrying outthe-reaction in the presence of a relatively small amount of alkali catalyst, preferably less than 5% of the weight of the resin-forming ingredients, there is no. danger of producing soluble resins or of dissolving any of the resins formed in the reaction, and hence the possibility of losing any of the resins in the subsequent steps of felting and/or moulding the pulped fibers is minimized, if not wholly eliminated.

The process in its simplest conception can be carried out in a, rotary digester of conventional paper mill design and using direct steam for heating.

' On account of the large size of paper mill digesters of the ordinary rotary type, batches of several tons must be made at one time so that a slight over-curing or under-curing of the resin in one batch would affect large quantities of the furnish. Furthermore, while the resin made in the rotary digester is satisfactory for some purposes, it does'not possess all of the qualities essential .to a high grade product. This may be atttribued in part to' the lack of sufiicient mixing and kneading during the processing to prevent separation of the various phases during the reaction.

We therefore prefer to work with smaller batches, to use indirect heat, and also to subject the fibrous mass to more drastic working than that in a digester, during the period of condensing the phenolic and methylene bodies of the resin, and thereafter to extend the resin or binder phase so formed more uniformly through the mass. The well-known Werner & Pfleiderer mixer has proven to be entirely suitable to this purpose, when equipped with a vapor-tight cover and a vent pipe through which the mixer may be opened to the atmosphere to prevent building up pressure and to provide means for controlling the distillation of volatile ingredients from the mixer. Other suitable mixing devices may be used.

Our preferred procedure is in part an adaptation of the principle disclosed in the Patent No.

1,771,150 above mentioned. We not only associate the resin with the fibres in the presence of too little water to act as a circulating medium, and prior to a pulping stage, but we also form the resin in the presence of the fibres in this first stage, mix the resin in a sticky condition with the fibres and permit advancement of the resin to continue in the presence of, the fibres in a controlled way, so that at the end of the mixing I stage the resin, while still thermoplastic or heat fusible, is substantially insoluble. Thereby is obtained a fibrous composition which can be readily reduced by assimilation of, and dilution with,

water to a pulp possessing afibre dispersion proper for paper making and wherein the fibre- 7' within the scope of thisinvention. The formula selected for illustration comprises the following materials:

Pounds Unbleached sulphite p'ulp (shredded) 140 Soda ash l 5 Crude cresylic acid (commercial grade comprising chiefly a mixture of meta and para cres0ls) 140 Commercial formalin (containing about.

40% formaldehyde) 106% 10 26 B ammonia 12% When treated in a Werner 8: Pfieiderer mixer the pulp may be, and preferably should be. wet with approximately an equal weight of water. 15 After the pulp is disintegrated by the action of the mixer the soda ash preferably dissolved in water should be added, followed by the other ingredients in the order given. After covering and connecting with the outlet or vent pipe the mixer 20 is heated with indirect steam until the mass reaches a temperature of approximately 212' I". The formation of the resin begins when the temperature approaches 200 F. and takes place very rapidly as the temperature is carried to 212' I". 25 This temperature is maintained for 1 hour, at

. the end of which time cold water is added in suflicient quantity to break up the more or less plastic mass to a condition suitable for charging to a paper mill beater. 30

When treated in a digester the dry pulp is first charged followed as before by the resin ingredients preferably in the order given. The digester is rotated for about one-half an hour to mix the resin ingredients thoroughly with the pulp. Steam is then injected until the temperature reaches approximately 212 F. which temperature is maintained for one hour, and the digester is then dumped.

Ammonia is generally the. preferred catalyst in 40 preparing phenolic-type resins; in carrying out our process as in the example above cited, we have however found t advantageous to supplement the catalytic action of the ammonia by that of a fixed alkali. As an example of such a fixed 45 alkali, we find soda ash to be suitable. Other substances may be used in suitable proportions as catalysts. more or less supplementing or replacing the ammonia and/or soda ash. These other substances include salts of weak acids and 50 strong alkalies. Strong alkalies such as caustic soda, however, when used as a catalyst'make this process extremely difficult to control, the reaction proceeding so rapidly that the resin goes over to the infuslble state before the reaction 55 can be stopped in the mixer. The reaction with a caustic soda resin can be retarded by using a large excess of caustic soda but this dissolves the resin as it is formed and obviously prevents the formation of the substantially insoluble resin 60 which is one feature of this invention,

The mixing operation should be carried to the point where a product is obtained which is nonadhesive when mixed with cold water. This condition is readily determined, for example, byremoving a small quantity of the material from the mixing or digesting device and manipulating it in the fingers in the presence of cold water. When the material sticks to the fingers, further processing is required, as the reaction of the resin components has not progressed far enough. When the material is no longer sticky, however, the condensation of the resin components has progressedfar enough for the purpose desired,

and should be stopped. This is readily accomplished by the addition of relatively large quantities of cool or cold water, which serves to check further condensation as well as to make a watery feltable pulp, as already described, suitable after beating for sheeting on a paper machine. the composition is thus diluted or quenched too soon, it will stick to the paper-making felts and screens. If it is allowed to condense too far, on the other hand, the resulting sheets or other products become lifeless"-that is, they can be molded only poorly or perhaps not at all,because the resin has advanced too far toward the final infusible stage before the diluting or quenching step.

The pulp as made in both the digester and the mixer as described will contain approximately equal percentages of resin and fiber (calculated on the dry basis). When properly mixed during the resin-forming period, the stock as delivered from either thedigester or the mixer will appear remarkably uniform and free from aggregates or nodules of fibers over-rich in resin. In fact, it will'have the characteristic feel, when suificiently cool, of any ordinary watery pulp; and the resin will not be readily discernible, so thorough is its distribution, though its presence in substantial amount and in more or less adhesive contact with the fibers is apparent under magnification sufficient to resolve the individual fibers.

The presence of water is desirable in the formation of a synthetic resin fibrous product suitable for a beater furnish. In the Werner- Pfieiderer mixing process, part of the water may be added when or shortly after the pulp is added, and more may be added after the reaction is complete. In the digester process, this water is obtained partly from the resin ingredients,- and partly from the condensation of the steam which is injected directly into the stock. Suflicient water must in any event be retained with the pulp during and after its.association with resin and before it is charged into the beater. If it is allowed to dry out, as is done in the manufacture of many resin-bearing fibrous compositions, the composition could not be broken down on addition of further water to form a feltable pulp, but would result in a non-feltable product comprising more or less irregular masses and agglomerates of resin-and-fibre suspended in or separated by the water.

The amount of water present should not generally be less than approximately the dry weight of the fibre. Lesser amounts of water, though usable, do not always give satisfactory results. The water need not bepresent with the fibres when they are first charged into the mixing device. However, it is desirable to add water either before or during the mixing of the fibre with the resin-forming ingredients, in order that the process may proceed satisfactorily. When using the digester, such water-addition ordinarily takes place by condensation of steam, as already pointed out. In-the Werner-Pfieiderer, it is generally best and easiest to add the water at some convenient time before the resin-forming materials are added.

example, punching stockit may be desirable to add a plasticizer during the mixing. Well- .known plasticizers, such as dibutyl phthalate are suitable. The degree of moisture-proofness of the final molded or sheeted product depends to a great extent upon the thoroughness with which the fibres and resin are incorporated during the mixing operation. The strength of the final product varieswith the strength of the pulp usedthus, kraft pulp gives a much stronger product than bleached sulfite pulp. for example.

A furnish formed as above-described is in condition for charging into a beater without further processing. Only a'moderate period of beating is required to condition the pulp for delivery to the paper machine. If the resin has been properly advanced no difficulty is experienced from sticking on the screen, felts or dryers, and the sheet can be dried without curing the resin to its final state. In the case of those resins which comprise chiefly the condensation products of phenol, greater precautions must be exercised in drying them than in the case of the so-called cresylic resins. With the former, it may on occasion be necessary to resort to either vacuum or relatively low temperature air-drying.

Papers and boards made from the new and improved resinous beater furnish are in every way suitable for use in the manufacture, of laminated products such as sheets used for punching out small mechanical parts or electrical insulators;

for the manufacture of shaped and drawnarticles such as trays; in the fabrication of decorated panels used for table tops, interior trim, and imitation wood paneling.

The fibrous materials used herein may'not only be those 'most commonly used in paper-making, such as those hereinbefore mentioned, but may also be other fibres such as asbestos, textile fibres, etc., either separately or mixed in varying proportions with other fibres. The use of asbestos as the greater or total amount of fibre in the product permits the manufacture of sheets or molded products having a considerable degree of resistance to heat.

The phenolic-type resins herein mentioned include those of'that name commonly known and used in resin-making. Thus, the phenols and the cresols are included, either separately or in suitable mixtures. Also, other types of heat-reactiveresinsmaybe used inplace ofp'artorall of the phenolic-type resins herein mentioned. These other types may be used-in accordance with this invention, and are suitable for extending the utility of this new method into fields beyond those here enumerated. It will be understood however that any resins suitable for this process must be capable of being advanced to a water insoluble state while still remaining in heat fusible condition.

We claim:

1. The process of manufacturing a paper-making furnish containing alkali condensed phenolic resins which comprises the steps of saturating a mass of shredded pulp with a solution of formal dehyde and a suitable phenolic body, adding thereto an ammonia catalyst, heating the saturated mass to a temperature sufficient to cause the reaction of the added ingredients to form resin particles substantially-insolublein water dispersed throughout themassunder conditions for controlling the distillation therefrom of volatile ingredients by such heating, while maintaining, the fibres in a water moistened condition to facilitate their ready assimilation of water and, when the temperature below that at whichfurtherad- I vancement will occur.

2. The process of manufacturing a paper-making furnish containing alkali condensed phenolic,-

resins, which comprises the steps of rendering a mass of shredded pulp alkaline, saturating such alkaline mass with a solution of formaldehyde and a suitable phenolic body, adding thereto an ammonia catalyst, heating the saturated mass to a temperature sumcient to cause the reaction of the added ingredients to form resin particles substantially insoluble in. water dispersed throughout the mass, the fibres being maintained in a water moistened condition to facilitate their ready assimilation of water and when the desired state of resin advancement hasbeen reached, quenching with water to lower rapidly the temperature below that at which further advancement will occur.

3. The process of manufactm'ing a paper-making. furnish containing heat-reactive resinous material, which comprises adding to a mass of shredded pulp a small amount of alkali suflicient only to render the mass alkaline, saturating the alkaline mass with a solution of formaldehyde and a phenolic body, adding thereto an alkaline catalyst including ammonia present in an amount less than five per cent'of the reactive formaldehyde and phenolic ingredients, heating the saturated mass to' a temperature sufilcient to cause the reaction of the ingredients to form a substantially water-insoluble resin dispersed throughout the mass, and when the desired state of resin advancement has been reached, rapidly lowering the temperature to a point sufllcient to arrest further advancement.

4. The process of manufacturing a paper-making furnish containing heat-reactive phenolic aldehyde resins, which comprises the steps of preparing a. mass of fibre containing an amount of water sufficient to assure a water dispersible end product but insumcient to act as a circulating medium, distributing throughout said mass the resin-forming ingredients, and applying heat to cause said ingredients to react in the presence of said fibers and form particles of thermo-plastic resin substantially insoluble in the reacting medium.

5. The process of manufacturing a papermaking furnish comprising 'a mass of pulped fibre and phenolic aldehyde resin, the resin being formed insitu in the fibre mass, which process includes the steps of mechanically mixing a wetted mass of fibre, adding the resin formingingredients thereto, continuing the mechanical mixing while effecting by heat the formation of a thermoplastic resin substantially insoluble in the reacting medium advanced to the stage where, in its association with the fibre, it is nonadhesive toward paper making instrumentalities when the mass is reduced to a watery pulp such as is'usedin paper making.

6. The process of manufacturing a papermaking furnish containing fibre and heat reactive phenolic aldehyde resin, which comprises the steps of preparing a mass of fibre containing an amount of water suificlent to assure a water dispersible end product but insufiicient to act as acirculating medium mechanically mixing the mass of fibre, adding the resin forming ingredients thereto, continuing the mechanical mixing in the presence of heat until the resin is advanced to the stage where it is substantially insoluble in the reacting medium and where, on

diluting with water and cooling to a temperature within the range of the water employed in paper making, it is non-tacky and thermoplastic insoluble in the reacting medium while thermoplastic;

7. The process of manufacturing a papermaking furnish containing fibre and heat reactive phenolic aldehyde resin which comprises the steps of preparing a mass of fibre containconcomitantly with the mechanical mixing, and continuing such mixing until the resin has been advanced to the stage where, while remaining heat fusible, it is insoluble in the reacting medium and, in its association with the fibre, is

non-adhesive to paper making instrumentalities, the resulting mixture being characterized by the property of readily assimilating water.

8. The process of manufacturing a papermaking furnish containing heat-reactive resins,

which consists in mixing dry fibre with cresylio acid, formaldehyde, and an alkaline catalyst in the presence of water, and heating the resulting mixture to form a synthetic resin which, while remaining heat fusible, is insoluble in the reacting medium and non-tacky, the resulting fibreresin mixture being characterized by the property of readily assimilating water and the reduction thereby to a watery pump'suchas is used in 35 water and cooling to a temperature within the range of the water employed in paper-making, it

is non-tacky and thermoplastic.

10. The prdce'ss of manufacturing a papermaking furnish containing heat reactive resins, which consists in mixing fibre with cresylic acid, formaldehyde-and an alkaline catalyst comprising a mixture of ammonia and a fixed alkali in the presence of water, andheating the resulting mixture to form asynthetic resin, which, while remaining heat fusible, is insoluble in the reacting medium and non-tacky, the resulting fibre-resin mixture being characterized by the,

property of readily assirnilating water and the reduction thereby to a watery pulp such as is used in paper-making.

11. The processor manufacturing a papermaking furnish containing heat reactive resins, which consists in mixing fibre with cresylic acid formaldehyde and an ammonia catalyst in the presence of water, and heating the resulting mixture to form a synthetic resin which, while remaining heat fusible is non-tacky, the resulting fibre-resin mixture being characterized by the property of readily assimilating water and the reduction thereby to a watery pulp such as is used in paper-making.

EARL P. STEVENSON. HOWARD J. BILLINGS.

CERTIFICATE or CORRECTION.

Patent No; 2,083, 929.

EARL P. sTEvENsoN, ET AL:

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 4, second column, lines 5 and 6, claim 6, strike out the words ".insoluble in the reacting medium while thermoplastic"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 31st day of August, A. D. 1937.

Leslie Frazer (seal) Acting Commissioner or Patents.

June 15, 1957.