US3463699A - Process of forming cellulosic fiber products containing a resinous lignocellulose derivative - Google Patents

Description

United States Patent 3,463,699 PROCESS OF FORMING CELLULOSIC FIBER PRODUCTS CONTAINING A RESINOUS LIGNOCELLULOSE DERIVATIVE Ronald L. Broadhead, Bulfalo Grove, and William R. Dunlop, Maywood, Ill., assignors to The Richardson Company, a corporation of Ohio No Drawing. Continuation-impart of application Ser. No. 429,627, Feb. 1, 1965. This application Feb. 26, 1968, Ser. No. 707,974

The portion of the term of the patent subsequent to Oct. 8, 1985, has been disclaimed Int. Cl. D21h 3/02 US. Cl. 162-163 4 Claims ABSTRACT OF THE DISCLOSURE A cellulose fiber composition with improved wet strength and prepared from cellulose pulp and a resinous lignocellulose derivative from the action of steam on a mixture of lignocellulose and a phenolic agent and containing a minimum of about twenty percent curable resin. The derivative is water dispersable by the use of an alkaline agent.

CROSS-REFERENCES This is a continuation-in-part of our copending application S.N. 429,627 filed Feb. 1, 1965 and now-abandoned.

BACKGROUND OF THE INVENTION The present invention is concerned with forming improved cellulose fiber compositions by incorporating with the fibers a high resin-containing lignocellulose derivative.

One exemplary cellulose fiber composition is that employed to form paper. In general, much of the paper available is composed of cellulose fibers which have been separated from the lignin of a lignocellulose raw material, such as wood chips or the like. After the lignin has been removed from the cellulose fibers, the fibers are normally suspended in water and subjected to a beating and refining step. The beating process, for the most part, consists of subjecting the fibers, while in water suspension, to mechanical action whereby the characteristics of the fibers are modified to the extent required for a particular paper type product. Typical modifications obtainable in a beater are shortening, fibrallation and reduction in stiffness. After the fibers have been beaten they may be further refined by mechanical working to additionally modify their characteristics. Following this preliminary working of the fibers in water suspension the fibers are then passed to the felting machine where the water is removed and the fibers closely packed to form a sheet. A more detailed description of fiber treatment and paper making processes may be found in Pulp and Paper, volumes 1 and 11, Casey, 1952.

As a result of the wide variety of applications for paper type products, it is generally necessary to incorporate with the fibers inorganic fillers, to modify opacity, color and similar characteristics. Frequently, other agents are also incorporated to improve the water repellant characteristics of paper, the addition of such agents being referred to as sizing.

In many instances fillers and sizing agents are added at the beater or refining stage and, hence, are intimately bound into the paper fibers. When so added it is frequently necessary to also include a precipitating agent such as alum (aluminum sulphate) whereby the sizing compound, in particular, is precipitated onto the fibers and, hence, is not washed away upon removal of the 3,463,699 Patented Aug. 26, 1969 ice SUMMARY It has now been discovered that the resinous lignocellulose derivative products disclosed and claimed in our copending applications Ser. No. 408,350 filed Nov. 2, 1964 now US. Patent 3,405,053 and Ser. No. 408,351 filed Nov. 2, 1964 (which are hereby incorporated herein by reference) have special utility as additives for paper compositions. In particular, these resinous lignocellulose derivatives have been found to impart to cellulosic paper compositions improved wet and bursting strength and also fold endurance. Such improved properties are believed due to several particular characteristics of the new lignocellulose derivatives.

The lignocellulose derivatives, as disclosed in our aforementioned pending patent applications, are made by subjecting raw lignocellulose to steam treatment in a confined atmosphere for a predetermined period and in the presence of phenolic agents. Accordingly, we have provided a process of improving the wet strength of cellulose fiber products by dispersing in a water slurry of a cellulose pulp a resinous lignocellulose derivative formed from the action of steam on a mixture of lignocellulose and a phenolic agent, which derivative contains a high content of curable resin. We have also provided fibrous products utilizing the above derivative.

DETAILED DESCRIPTION In one process described in the above identified c0- pending applications, the lignocellulose products are obtained by subjecting sawdust, wood chips or similar raw, unmodified lignocellulose in combination with a phenolic agent, such as phenol, a cresol or a xylenol, initially to the action of substantially dry steam for from 1 to 10 minutes, reducing the pressure within the reaction mass to below p.s.i., and then again subjecting the mass to the action of the substantially dry steam for a second period of from 1 to 10 minutes. Temperature of the steam ranges between 400 F. to 470 F. In this process the lignins and possibly certain hemicellulosic components are chemically modified and converted into an unusually high percentage of resinous material not believed heretofore achieved by similar processes. The amount of such resin thus obtained is generally a minimum of about twenty percent of the final product and may range up to about thirty percent.

In the second process an even higher amount of resinous component is obtainable by incorporating with the lignocellulose and phenolic agent an acid catalyst soluble in the phenolic agent. With this second process a resin content of forty percent or more is possible.

The resinous product from the two processes is somewhat similar to novolak resins obtained by the condensation of phenol and formaldehyde. In particular, the resins are normally thermoplastic and may be cured to a hard thermoset state by heat and pressure in the presence of a methylene-donating agent such as formaldehyde and hexamethylene.

Thus the above lignocellulose product is derived from the reaction of steam on a mixture of a phenolic agent and lignocellulose wherein theproduct has a density of between about 0.8 to 1.2, a maximum of about 12 percent residual lignin and a minimum of about 20 percent of an integral curable resin. Of special interest is the fact that 3 it has been discovered that both of the resinous lignocellulose products obtainable from the foregoing processes can be readily dispersed in water by means of an alkaline agent, particularly ammonia, or a lower alkyl amine, such as methyl or ethyl amine, in the amount of about 3 to percent based on the weight of the lignocellulose derivative. An easily flowable water solution consisting of up to about thirty percent of the resinous lignocellulose derivative can be thus prepared. This property greatly enhances the utility of the lignocellulose derivatives over similar products heretofore derived from raw lignocellulose materials. Such a property readily permits the lignocellulose derivative to be dispersed in the water present in a paper beater or refiner for purposes of incorporating the lignocellulose derivative into the finished paper.

A further advantage is the fact that the resinous lignocellulose derivatives contain primarily cellulose as the remaining component which is readily compatible with the cellulose fibers of the paper slurry.

An additional advantage lies in the possibility of making a formaldehyde reaction product of the resinous lignocellulose derivatives contemplated. As indicated, a methylene-donating agent such as formaldehyde may be reacted with the resinous product to form a thermosetting composition. Broadly analogous thermosetting phenolformaldehyde type resins have been added to paper for improving its strength and for other purposes. However, in general, such resins have not found wide utility except for applications wherein the product is intended to be subjected to pressure at temperatures about 205-212 F the latter temperatures being those normally used on paper making machines.

Paper making processes usually include subjecting the paper after felting to a drying action at a temperature within the above range of 205-212 F. As thistemperature range is below the general curing temperature for the usual phenolic resins employed, it is necessary to provide a further heat treatment to obtain a cure of the phenolic resins when used. However, unlike the usual phenolformaldehyde resin sizes, the corresponding formaldehyde derivatives of the resinous lignocellulose products contemplated by this invention, due to their tack-free nature and molecular weight, can be at least partially cured at a temperature within the above drying temperature range referred to for paper, thereby eliminating the need for additional heat treatment.

By way of illustrating the principles of the invention the following examples are presented.

Example I A resinous lignocellulose product is obtained by twostep cooking of a blend of 80 mesh woodflour and a solution of paratoluenesulfonic acid in cresylic acids (0.74% p-toluenesulfonic acid and 14.7% cresylic acids based on the total charge) in the presence of live steam at 320 p.s.i. for an initial period of six minutes followed by releasing the pressure essentially to the atmospheric level and then returning the pressure to 320 psi. for six minutes. The resulting product containing approximately 40 percent resinous component is dispersed in aqueous castic. The resulting dispersion containing 200 grams of the lignocellulose resin, 500 grams of water and 14 grams of sodium hydroxide, has a pH of 8.1. To this dispersion is then added 160 grams of 37 percent aqueous formaldehyde solution. The resulting mixture is heated with stirring for six hours at 68-85 F.

Example II A second dispersion of the lignocellulose resin is prepared by stirring a 100 gram portion of the original lignocellulose resin in 444 grams of an aqueous solution containing 7 grams of sodium hydroxide.

i Example III The basic aqueous dispersion of methylolated lignocellulose resin of Example I was added to a slurry of cellulose pulp (solids content 5%) in a Waring blendor. The resulting slurry was mixed for 15 minutes and then an aqueous alum solution was added to bring the pH of the charge to 4 in accordance with commercial paper making. The pulp was drained off on a screen and the mixture was passed through a squeeze roll to form a sheet which was dried at 212 F. Sheets were made at methylolated resin levels of 1, 3, 6, 10 and 20 parts per parts of dry cellulose pulp. In all cases, the cellulosic fibers were evenly coated by resin by this technique.

Example IV The same procedure was used to form a cellulose pulp containing the aqueous caustic solution of the untreated lignocellulose resin of Example II and to prepare sheets from the resulting resin coated cellulosic fibers. Again levels of 1, 3, 6, 10 and 20' percent of resin were used based on the pulp.

Example V Similar resin-coated cellulose pulps were prepared from the basic dispersion of the methylolated lignocellulose resin except that the alum addition was omitted. The pH of the pulp was about 8 under these conditions.

Example VI Example V was repeated except that the basic solution of the untreated resin obtained from Example II was used.

Control tests were run in which the cellulosic pulp was passed through the same sequence of steps but without the lignocellulose resin. In other control tests starch and phenolic formaldehyde additives were included in the sequence without the addition of the lignocellulose resin.

In all cases, the sheets prepared from the lignocellulose derivative treated pulps, even at the 1% level of both the modified and unmodified lignocellulose, were markedly tougher than all of the controls. Toughness was manitested in an increased resistance to rupture of the sheet on folding through an angle of 270360. The controls all ruptured after three such folds or less. The sheets containing the lignocellulose derivative resinous product only ruptured after 8 to 40 such folds depending on the resin content.

In general, it is contemplated that the lignocellulose derivative can be combined with substantially pure or refined cellulose pulp within the range of between about 5 to 20 percent. It will be appreciated that, for equivalent results, the derivative made using phenol soluble acid catalyst and containing upwards of 40 percent resin can be used in lesser amounts than the corresponding derivative made without the acid catalyst and containing up to about 30 percent resin. Further, it will also be understood that the present lignocellulose derivatives can be incorporated in all pulp mixtures for manufacture of not only various types of paper but also box board, building materials and similar sheet type applications wherein such products are derived from cellulose pulp in an aqueous slurry. Also contemplated are laminated structures involving two or more sheets containing the lignocellulose derivatives dispersed therein which may be laminated together by heat and pressure to provide a boardlike structure of varying properties, depending upon the amount of resinous derivative present, number of laminations, etc.

Of additional interest is the fact that a pulp composition in sheet form containing the lignocellulose derivatives in suitable percentages can be hot rolled to provide a hard and more glossy finish to the end product, depending upon the amount of derivative used and its resin content. At levels of 5 percent derivative and above the calendered product will also show improved stiffness. Such a process has particular application when using the methylolated derivative wherein the heat of the rolling is sutficient to advance the cure of the methylolated resinous component to an infusible state.

Frequently, articles of one type or another are molded from cellulosic pulp slurries, such as egg cartons. It is contemplated that similar applications can also be served by use of the resinous lignocellulosic products as a binder for the pulp.

We claim:

1. A process of improving the wet strength of cellulose fiber products which comprises dispersing in a water slurry of a cellulose pulp a resinous lignocellulose derivative formed from the action of steam on a mixture of lignocellulose and a phenolic agent, the derivative containing a minimum of about twenty percent curable resin, and forming the cellulose pulp and derivative into the product.

2. The process of claim 1 which includes producing a methylolated form of said derivative and dispersing said methylolated form in said water slurry.

3. The process of claim 2 wherein the forming step includes removing water from the slurry to form a fibrous sheet and drying the sheet, and wherein the dried sheet is subjected to elevated temperature suflicient to advance the methylolated derivative to a substantially infusible state.

4. A sheet-like product of claim 1.

References Cited UNITED STATES PATENTS S. LEON BASHORE, Primary Examiner US. Cl. X.R.