US3109769A

US3109769A - Process for incorporating resins into paper

Info

Publication number: US3109769A
Application number: US127147A
Authority: US
Inventors: Ray C Martin
Original assignee: RAY C MARTIN
Current assignee: RAY C MARTIN
Priority date: 1961-07-27
Filing date: 1961-07-27
Publication date: 1963-11-05
Anticipated expiration: 1980-11-05

Description

Nov. 5, 1963 R. c. MARTIN 3,109,769

PROCESS FOR INCORPORATING RESINS INTO PAPER Filed July 27. 1961 AQUEOUS SLURRY OF BEATEN CELLULOSE FIBER AQUEOUS DISPERSION OF A CHROMIUM COORDINATION COMPLEX OF AN ACYCLIC ACIDO CARBOXYLIC ACID ADDED AND DISPERSED INTO SLURRY TIMING- REACTION RESIN DISPERSION (AND ANY DESIRED FILLERS) ADDED AND DISPERSED INTO SLURRY TIMING- REACTION PAPER FORMED AND DRIED INVENTOR. RAY C. MARTIN ATT'YS.

United States Patent 3,109,769 PROCESS FQR IYCORPORATING RESINS INTO PAPER Ray C. Martin, Freeport, Ill., assignor, by mesne assignments, to Ray C. Martin, Freeport, Ill. Filed July 27, 1951, Ser. No. 127,147 17 Claims. (Cl. 162-464) This invention relates to the art of paper making, and more particularly refers to a novel method of incorporating resins and other additive materials into papermaking pulps at that point of the paper making process generally termed as the wet end, and to the novel products produced thereby.

Unmodified paper and paper board made by conventional methods have many limitations. The products are weak, permeable to water, oil and grease, and lack many of the properties generally desired in a finished paper product. To improve its properties, modifying or reinforcing materials such as resins, pigments, fillers and other related materials are customarily added to the paper.

The majority of processes currently used for incorporating these materials into paper may be characterized as secondary operations, that is, they are methods for treating the paper after the paper itself has been fabricated. Such secondary operations, or applications of the modifying materials made to the basic paper, usually from solvent or hot-melt systems, succeed at best only in applying a film of the modifying material on the paper surface, and to a degree filling the interstices, but do not succeed in enabling the modifying material to penetrate and attach themselves to the fibers since the fibers and additives are electrically repellent to each other. As a result, the full benefit of the modifying materials is not realized. Moreover, the addition of a separate treating step adds to the cost of processing. Even where wet-end processes have been used, complete retention of the additive by the pulp generally has not been achieved, with the result that the excess additive is generally removed in the form of unattached particles, which, together with the fines from the process, frequently cloud the water and render it nonreusable.

It is an object of the present invention to provide a process for the incorporation of resins and other modifying materials in an aqueous medium into papenmaking pulp in the wet-end stage of the paper making process.

It is a further object to provide such a process wherein the resins and other additives are removed from the aqueous medium in which they are applied, and are tenaciously deposited upon the individual pulp fibers.

It is still further an object to provide such a process wherein the coupling agent may he applied without the need for the subsequent addition of insolubilizers.

It is still further an object to provide such a process wherein improved and reinforced papers are produced in which the modifying substance is uniformly dispersed throughout the paper.

It is a further object to provide improved and reinforced paper products which, While incorporating the same modifying materials or additive content, exhibit greatly enhanced properties over products made by other methods.

It is a further object to provide various useful improved 3,169,769 Patented Nov. 5, 1963 and reinforced paper products by the methods of the present invention.

Other objects and advantages of the invention will become apparent from the description which follows, and from the appended claims.

The drawing comprises a flow sheet illustrating the essential process of the invention.

According to the invention, a water-soluble Werner type chromium coordination complex of an acylic acido carboxylic acid in aqueous solution is added and thoroughly mixed into a circulating aqueous suspension of paper-making pulp which has been first beaten in the usual manner. The complex is absorbed by the pulp fibers and functions as a coupling agent for the subsequent attachment of modifying resins and other addit-aments. The modifying materials are preferably of such nature that they may be provided in the form of an aqueous dispersion either as a suspension, colloidal solution, or true solution. Other materials such as inorganic fillers may also be so added. When they are added to the chromium complextreated pulp suspension, the additive materials are attracted and caused to deposit uniformly upon the treated pulp fibers. The pulp furnish so modified may then be processed in the normal manner to produce various finished paper products.

The incorporation of a resin during the paper making process has several attractive potentialities. Because the addition is accomplished during the making of the paper, the additional steps of coating or impregnating of the finished paper and its attendant cost is avoided. Moreover, because the resin is incorporated while the fibers are separated, an extremely uniform dispersion of the resin about the fibers can result.

Although the exact nature of the reaction or mechanism responsible for the present phenomenon is not fully known, it is believed that a functional group of the chromium complex reacts with a functional group of the cellulose molecule to form a bond in the nature of that of an addition compound. So complete is the reaction, that when the additive material is dispersed in the reacted pulp suspension, it is completely removed from the aqueous phase, and the remaining Water becomes perfectly clear. The presence of the chromium complex then changes the electrical charge surrounding the cellulose fiber. As a result, when a resin dispersion is subsequently added, the resin is attracted to the treated fibers.

The compositions which are useful in the present invention may be presented by the general structural formula:

CrClr This formula represents a Werner type chromium complex, wherein R is an aliphatic hydrocarbon grouping. R may be either saturated or unsaturated, substituted or unsubstituted, and may contain additional functional elements or groups, such as -SO -N, etc.

A commercial composition falling within the above empirical structure and which may be used in practicing the invention is marketed under the designation FC-'805 by Minnesota Mining and Manufacturing Company. The preparation of coupling agents of this class is generally disclosed in US. Patent No. 2,662,835 issued to Reed, and comprises reacting chromyl chloride with saturated perfiuoromonocarboxylic acids having from four to twelve carbon atoms in the molecule, such as perfluoro-octanoic acid, in an inert anhydrous or solvent vehicle and in the presence of an alcohol reducing agent or a hydrolyzed ammoniatedderivative thereof. The particular compound PC4305 is a chromium salt of a fatty acid in which some of the hydrogen has been replaced with fluorine, such as perfiuorocaprylic acid. Other complexes of this type such as disclose the US. Patents No. 2,662,835, No. 2,642,416, No. 2,713,593 and No. 2,934,450.

Another Werner type complex which may be used in the process according to the invention is marketed as Quilon by E. I. du Pontde Nemours 8: Company. This composition as disclosed in US. Patent 2,273,040 (February '17, 1942) is prepared by reacting chromyl chloride with a fatty acid such as stearic or palmitic acid in the presence of a reducing agent such as ethyl alcohol. The

formula of the complex may be represented as follows:

CuHss 'pulp is beaten to the desired freeness in order to open up and expose the fibrillae to the necessary degree.

After the pulp has been sufliciently beaten, and the desired pulp freeness has been attained, the beater roll is raised and the beater itself allowed to circulate, and stock is diluted and brought to a consistency of between 1.5-

2.0%. The diluted chromium complex in the desired amount is then added to the circulating pulp. To insure good circulation, the point of addition should preferably be before the raised beater roll. The chromium complex reacts immediately with the beaten cellulose. The complex appears to be absorbed on the surfaces of the fibrillae in the form of a molecular layer.

The time required for reacting the beaten pulp with the chromium complex varies with the fiber consistency and the degree of circulation of the suspension or slurry maintained during the treatment.

When water-soluble addition materials are used, some means should be provided for insolubilizing them after they have been deposited on the fibers, so that when the finised paper product is subjected to water, or water-vapor, the addition materials will not be removed. Where the modifying resin used is thermosetting, such as a phenolic resin, it'may be added directly after the reaction of the coupling agent with the pulp. When urea formaldehyde or melamine formaldehyde resins are used, it has been found. to be very advantageous to include a water dispersiprocess.

chest, machine chest, or other similar points in advance of niques.

lble resin accelerator or catalyst such as NH, salts, amine salts or inorganic non-ammoniacal salts, and to subject the finished paper product to a sufiiciently elevated temperature curing cycle to cause the resin to become crosslinked. When thermoplastic resins are employed, it has been found to be advantageous to include additionally a minor amount of a thermosetting resin, such as urea or melamine formaldehyde, and a Water dispersible accelerator, and to subject the ultimate paper products to a temperature-curing cycle on the dry end of the paper machine to effect cross-linking and insolubilization of the resin.

The amount of chromium complex which need be used varies according to the amount of modifying materials to be added and the type of product to be fabricated. For example, it has been found that about 0.05 of chromium complex solids, based on bone-dry fiber solids, will sufficiently condition pulp to'allow small quantities of resin to be thoroughly and completely incorporated. It has additional-ly been found that an amount of about 0.25% of chromium complex solids, based on bone-dry fiber solids, is sufiicient to-incorporate parts of a resin with 100 parts of cellulose fibers. When larger quantities of chromium complex is utilized, the pulp exhibits a greater freeness, but the green color of the chromium complex becomes apparent in the final product. At 5% chromium complex solids addition, based on bone-dry fiber solids, it has been found that the freeness of the treated furnish has increased and the water drains rapidly upon the deposition of this treated furnish in the coaching box. Although amounts greater than 5% may be used, benefits from such increased addition fall off somewhat, and the end products take on a green color to an appreciable degree.

Additions of such materials as pigments or inert fillers should be made to the beaten and reacted pulp at suitable points along the wet-end portion of the paper making Such suitable addition points are at the beater themachine headbox. This results in thorough and uniform incorporation. The additive materials, such as inerts are formed into a water slurry. Prior to their incorporation with resin they may themselves be treated with the chromium complex. Preferably, resins or related materials such as plasticizers and barrier inducing materials should be incorporated together with the pigment or filling material. Regardless of the treatment to which the filler materials are subjected, they should preferably be added 'to the reacted pulp as a homogenous mixture, since this accomplishes the wetting of the solid particles prior to the addition, and aids in the subsequent reaction by which the particles become attached to the cellulose fibers.

' Among the filler materials which may be used are barium sulfate, calcium carbonate, clay, diatomaceous silica, talc, titanium pigments, and zinc sulfide. Various dye stuffs and opacifying pigments, both natural and synthetic, serving as colorants, may be also added by the same tech- They may be first treated with the chromium complex and combined with any other solids constituting the chemical addition. Upon reaction of the fillers and the otheradditives with the treated pulp, the water becomes clear.

The resinous materials which are suitable for use in the present invention are those which can be readily dispersed in water by one of several means. Even when they are not soluble many resins may be conditioned by techniques Well known to the art, such as by the addition of wetting agents, dispersing agents, or emulsifying agents. Most of the resins commonly used for modification and reinforcement in paper-making may be rendered compatible by means of one of the methods discussed.

The addition of the resin must be made after the pulp has been sufficiently beaten, and after it has been treated with the chromium complex. The reason for this is that fibrillation of the pulp fibers is promoted by the beating processes. The subsequent treatment of the fibers With the chromium complex makes available a large charged surface area for attaching the desired quantity of the resin. Where pigments or inert fillers are to be used in the system, they should preferably be added as a water slurry and thoroughly mixed with the resin and thereby combined with the chromium complex treated pulp. Alternatively they may be added as a water slurry immediately after the addition of resin. The resin, in the form of an aqueous solution, suspension or an emulsion, is added at a low solids content, such as about 2% to 5% total solids. High solids resin-containing varnishes, such as are used in the production of electrical board or postforming board stock, may not tolerate dilution to this extent. Where this situation exists, the resin viscosity may be reduced with water to a point just short of the production of a cloudy condition. The diluted resin is subsequently added in small increments, rather than in the form of a steady stream.

A large variety of resinous materials may be employed, the choice being dictated by the characteristic properties desired in the paper end product. For example, thermoplastic elastomeric latex resins may be used for flexibility, while less flexible resins may be used for barrier properties and grease-proofness. Thermosetting resins such as phenolics may be used for rigidity and for electrical properties.

Among the synthetic fibers which may be used as modifying materials are: polyacrylic fibers (Orlon), polyester fibers (Dacron), or polyamide fibers (nylon). The fibers add strength to the final product and may be used to produce dimensionally stable papers, paper boards, pulp-moldings, and stereotype mats. Where polyester fibers such as Dacron are used, they contribute both excellent dimensional stability and dielectric properties to the final product. Because of the hydrophobic nature of most synthetic fibers, it has been found desirable to soak them for a period of about sixty minutes prior to their incorporation into the treated pulp. Soaking may be accomplished by placing the fiber in an aqueous acidic solution, or in a solution of one of the chromium complexes.

Other inorganic fibers, such as asbestos and ceramic fibers or metallic flakes and powders, may also be incorporated as modifiers for the purpose of strengthening the paper product, or for obtaining other properties such as heat or electrical conduction or insulation. Asbestos or ceramic fibers may be pretreated by immersing them in a chromium complex solution for a period of about 60 minutes prior to incorporation with cellulose fibers. They are then added to the reacted pulp and blended prior to the addition of the resin.

The formulation to be used depends to a large extent upon the properties desired in the end product. For example, long-fibered pulps are effectively used in producing iost-forming board and electrical board, whereas shorterfibered pulps are used for fine papers. Synthetic fibers or inorganic fibers may be used to modify long-fibered stock in order to produce dimensionally stable papers and stereotype mats. For the production of packaging and barrier papers, it has been found desirable to incorporate thermoplastic resins into the pulp. These may be used alone or may be modified with thermosetting resins, or plasticizers to effect such properties as heat sealing, waterproofness, greaseproofness, low moisture-vapor-transmission, and others. Thermosetting resins are generally used to produce post-forming boards which may be subsequently cured to the infusible insoluble stage, and for the production of electrical boards. Particular chemicals may also be employed as additives where particular properties are desired in the end product.

Among the paper making pulps which may be used in practicing the invention are the following: alpha cellulose, cotton linters, rag, recovered broke, semi-chemical, sulfate, sulfite, soda, or mechanical. Any other papermaking pulp may also be employed.

The resins used as additive materials may be modified the properties desired in the finished product.

by the addition of plasticizers of the conventional type which are compatible With the particular resin used, and which are capable of modifying the resins in the desired manner, as for example phthalates, adipates, sabacates, dibenzoates, stearates, and polymeric materials. Other materials such as water soluble glycerides and glycols may aiso be used.

Among the pigments and inerts which may be added for particular properties are titanium dioxide, various sulfates, clays, zinc sulfide, carbonates, silicates, dyestuffs, talc, and opacifying pigments, both natural and synthetic.

For water barrier type products various Waxes may be incorporated, such as paraffin, microcrystalline wax, polyethelene, and other natural or synthetic waxes.

A large variety of resins may be used as modifying agents according to the present invention. As previously stated, in order to incorporate the resins it is necessary that they be dispersible in Water, since the paper making process is primarily a water process. Thermoplastics such as various vinyl derivatives, ethylenic resins, rosin and related compounds, natural resins, chlorinated diphenols, cellulose esters and ethers, natural and synthetic rubbers, phenolic resins in the novalac stage, and many others may be advantageously utilized. Where finished products are desired which may be cured to the insoluble, infusible state, thermosetting resins such as phenolics, ureas, melamines, alkyds, polyesters, epoxies, silicones, and many others may be used. Water soluble materials such as proteins, starches, carboxymethyl cellulose, glues, resins, caseins, etc., may also be employed.

For particular functional properties, specialized chemicals may be incorporated among which are mold-resistant chemicals, bacteria-resistant chemicals, insect-resistant chemicals, rodent-resistant chemicals, or flame-resistant chemicals.

The amount of chromium complex that may be incorporated is not critical, and will generally depend upon By using less than 5% of the complex to condition the pulp, it is possible to incorporate a resin such as a phenolic in an amount equal to the weight of the dry pulp.

Amounts of the complex in the range of 0.05% to 5.0%, based on dry weight of pulp, have been found effective. Amounts greater than 5% may be used where the increased color intensity is not detrimental.

A large number of various types of products may be formed by the processes included Within the scope of the invention. These products may be classified in three main groups: products comprised of cellulose fibers modified by resin, products comprised of cellulose fibers modified by the addition of a resin together with other fibers, and products comprised of cellulose fibers modified by the addition of a resin together with various filler materials other than fibers.

Among the important products of the first group are: post-forming fibrous board stock, electrical board, wet strength papers, barrier papers, battery separators, and laminated structures.

Post-forming boards may be produced according to the present invention by treating the beaten pulp with the chromium complex, and subsequently adding a suit able resin and treating by time-reacting in the aqueous stage. Among the resins which may be used are Waterdispersible phenolformaldehyde resins, polyester resins, or epoxy resins. Thermosetting or heat-reactive resins are preferred as they may be molded and cured subsequently to the formation of the board by heating to temperatures in excess of 300 F., under molding pressure.

A preferred resin for the production of electrical board is a phenol-formaldehyde resole, or A stage resin, that is, one which is not yet advanced to the intermediate condensation state. The formed material is subjected to temperatures of below 250 F. to drive off the water and is then ready for further processing.

' ness of 350 ml.

resin to the infusible and insoluble state.

High wet strength papers may be prepared in a manner similar to that described above by treatment with the chromium complex and subsequently the desired resin. The formed paper must then be heated to remove the moisture and cross-link and insolubilize the chromium complex and resin combination. Various resins such as acrylics, elastomers, vinyl polymers and copolymers, urea or melamine thermosetting resins, or combinations of resins may be used.

Various fillers other than fibers may be used. Aluminum powder is such an example. When the pulp is first beaten and then treated with the chromium complex, the treated aluminum flakes will be taken out of solution and deposited on the reacted pulp fibers when they are subsequently incorporated with the resin into the pulp suspension.

Other additive fillers such as cork, sawdust, lignin, and other related products may be deposited on the pulp fibers by first treating with the chromium complex, as

described above. a

In order to test the prepared paper boards for resistance to peanut oil, an oil-wicking test is used in the following manner. Specimens of the board are first freshly cut to size 4" long x 1" wide. Freshly cut sharp edges are needed as observation points to observe oil movement. On each specimen a line is drawn 1" from the bottom,

and four additional lines apart are drawn above the 1" line. The strip is immersed in peanut oil in a glass beaker, the oil being filled until it reaches the one inch or bottom line. The time is recorded and movement of the oil is noted over a period of time. Upward wicking of the oil is indicated by a darkening of the board.

Board which is completely impermeable to oil will, of course, exhibit no wicking over a long period such as '48 hours. However, for certain purposes board in which wicking advances di in two and one half hours is acceptable.

Example A charge of 1000 grams of bleached pulps, on an airdry basis, constituting pine sulfate and 50% sulfite was introduced into a cycle beater containing 12 gallons water. The pulp mixture was beaten to a Canadian free- One-half of the beater charge was retained and sufficient water added to develop a consistency of 1.55%. Thereafter, a iluorochemical chromium com plex, identified as FC805, in an amount equal to 0.25% by weight of FC805 solids in relation to pulp solids, was added as a dilute aqueous dispersion to the moving pulp suspension in the beater. The beater was used as a mixer with the beater roll raised. The FC-805 was added at the propeller shaft as a point of good agitation. A timingreaction cycle of 15 minutes, under circulation, proved sufficient to complete the reaction. Completion of the reaction was determined by taking a sample of the reacted pulp and adding it to water in a beaker. In a short time the reacted pulp solids separated and the water was observed to be crystal clear. The pH of the solution was 7.0.

Resinous additions were separately prepared constituting a total of 3% resin solids based on pulp solids. The resin addition comprised equal parts of polyethylene, polyvinylidene chloride, and melamine formaldehyde (80% solids). The first two resins were combined in the form of emulsions and diluted with water to a nonvolatile solids content of about 5%. The melamine formaldehyde was weighed separately and diluted with water. An insolubilizing salts, diammonium phosphate, in an amount equal to 30% by weight of the melamine formaldehyde, was Weighed and dispesred in water, and thereafter added and thoroughly incorporated with the melamine resin. The accelerated melamine formaldehyde dispersion was then incorporated with the blended emulsions. The entire resin addition was then incorporated with the previously reacted pulp stock maintained under circulation. Reaction between the resins and the treated pulp was immediate. An additional 15 minutes stirring period was utilized to complete the reaction. The pH of the water remained at 7.0 and a sample exhibited a tight complex structure with a crystal clear water layer.

The consistency of the resinmodified pulp stock was determined and the volume measured which would give 50 grams by weight of dry solids. The stock was further reduced with water and placed in a couching box for board-making. Drainage was rapid and formation was very good. The wet sheet was transferred to a press, and, after two pressings, the sheet was supported between blotter stock and transferred to a sheet dryer. After one minute of drying on each side the sheet was placed on chip board and given a smoothing operation by passing it through the nip of the steel rolls of a calender. The sheet was again placed on a dryer and each si e again contasted for minute. A pass through tightened smoothing rolls resulted in a sheet having a very smooth surface. The sheet was placed on a dryer and dried to a constant weight. After the sheet had been weighed, a caliper measurement was taken, and the sheet was air-dried overnight at room temperature. It was subsequently conditioned for 72 hours under standard air and humidity conditions.

An oil impermeability test as described above was performed by cutting strips from the sheet and immersing the strips in a vertical position in a container of peanut oil to determine edge-wicking resistance. The strips exhibited complete resistance to edge-wicking action over a 48 hour period. A board exhibiting such high resistance to oil wicking is suitable for use as top liner in carton construction of packaging cake mix.

Example 2 One hundred grams, air-dry basis, of pulp furnish as prepared in Example 1 were added to a bell jar containing 5000 cc. water. The diluted pulp stock was well circulated by a power driven agitator. FC-805, in an amount constituting 0.25% chromium complex solids based on pulp solids, was dispersed in water and added to the pulp stock. Circulation was continued for seven minutes to permit adequate mixing. A resin mixture was then prepared consisting of equal parts by weight of polyethylene, polyvinylidene chloride, and melamine formaldehyde. The first two resins were combined in the form of emulsions and diluted to a solids content of about 5%. The melamine formaldehyde was weighed separately and diluted with water. An insolubilizing salt, diammonium phosphate, in an amount equal to 30% by weight of the melamine formaldehyde was dispersed in water and incorporated with the melamine. A clay filler in an amount of 50% based on pulp solids was separately water-slurried and then combined with 6% non volatile solids of the resinous addition mixture, prior to incorporation with the treated pulp. The entire addition component was then incorporated into the diluted pulp stock at moderate speed circulation. Reaction began immediately and circulation was continued for five minutes. The pH of the solution at this point was 7.0. A sulfuric acid/ alum solution was added in an amount sutlicient to bring the pH to 5.0. The aqueous phase at first showed cloudiness, but upon standing for four hours cleared completely. A board having a 0.15 inch caliper, prepared as in Example I, appeared to be well filled and exhibited an exceptionally smooth printing surface, qualifying it as suitable as top liner material for carton containers.

Example 3 Paperboard suitable for use as carton stock for dairy products was prepared utilizing the basic process described in Example 1. The pulp was first beaten to the desired freeness. To the beaten pulp was then added 0.25 by weight of FC-805 based on pulp solids. After the materials were thoroughly reacted, 9% resins solids based on pulp solids were added.

The resin solids had the following composition:

Polyethylene 33.33

Microcrystalline wax 33.33

Polyvinylidene chloride 16.67%

Melamine formaldehyde 16.67% (containing diammonium phosphate as an accelerator).

Sufficient sulfuric acid/ alum solution was then added to adjust the pH of the solution to 4.5. Cyrstal clear white water was observed in the finished stock upon standing for four hours. The pulp was then formed in the couching box as in Example 1 and processed into finished board.

Example 4 A pulp furnish of 1000 grams of pulp (air dry basis) comprised of 80% combined news print, patent coated liner scrap and kraft cuttings, and 20% beaten unbleached kraft was placed in a cycle beater. One hundred grams of the pulp combination (air-dry basis) were then placed in a bell jar containing 500 cc. water. Five percent Quilon solids were added to the mixture in the bell jar. This relatively large amount of chromium complex coupling agent was used because of the high percentage of short fiber stock" contained in the news furnish. Mixing was carried on for a period of 30 minutes to react the Quilon with the pulp.

A resinous addition utilizing the same resin mixture described in Example 1, in an amount of 6% solids based on pulp solids was added. The reaction began immediatedly. An addition of alum solution was made until a pH of 5.0 was attained. When the reaction was complete, the water became crystal clear.

A board was prepared as in the previous examples and, after drying and aging, was subjected to a peanut oil wicking test as described above. Vertical wicking was limited to inch in 2 /2 hours, indicating that the board was suitable for use as a mid-filler material for carton container stock.

Example This example illustrates the use of larger amounts of the coupling agent than the previous examples. A beaten pulp stock was prepared as in Example 1 and subsequently treated with 1% by weight of Quilon, based on dry pulp solids. One half of the Quilon addition was directly made to the pulp, and the other half was incorporated with the subsequent resin addition, to act as an insolubilizer for the resin. The resin addition totalled 12% resin solids based on dry pulp and had the following composition:

Percent Polyvinyl acetate 50 Polyvinylidene chloride 33.3 Melamine formaldehyde 16.7

When the resin components were added to the reacted pulp, further reaction began immediately, and was furthere promoted by the addition of acid to attain a pH of 4.5 in the slurry. The water phase became crystal clear.

Paper barrier board was formed from the pulp as in Example 1 and exhibited a green-grey cast as the result of the high Quilon content. This product is suitable for use where the color is not objectionable.

Example 6 Utilizing the process of Example 1, beaten pulp was treated with 0.25% FC-805 based on dry pulp weight.

A resin mixture comprised of one third melamine formaldehyde containing diammonium phosphate as an accelerator in an amount equal to 30% by weight of the melamine formaldehyde, and two thirds polyvinyl acetate was prepared. An amount of the resin combination calculated as 10% by weight solids based on the weight of dry pulp was separately prepared. Ten percent cork dust and 0.50% Quilon solids by weight based on cork solids were then separately combined in a water slurry, allowed to react, and combined with the resin. This mixture was then added to the moving pulp stock and after complexing was followed by the addition of suiiicient acid and alum mixture to bring the pH of the solution to 5.0.

The treated pulp exhibited great freeness in couching, fast drainage and good formation. Paper board was formed as in the examples above having good properties.

Example 7 Using the method of the examples above, bleached pulps were treated with 0.25% Quilon based on dry pulp solids. An amount equal to 6.25% of an emulsified nitrocellulose lacquer based on dry pulp Weight, containing 32% nitrocellulose, 28% resin, 20% plasticizer, and 20% polyvinyl alcohol was then complexed with the reacted pulp. Sullicient alum was added to adjust the water to a pH of 5.0. The water subsequently became crystal clear. The treated pulp was formed into a barrier paper board as in the examples above.

Example 8 Beaten pulp stock prepared as in Example 7 was treated with 0.375% Quilon by weight based on dry pulp. A 7.5% mixture of resins containing 83.30% nitrocellulose lacquer emulsion and 16.70% acrylonitrite rubber emulsion was added and completely incorporated into the pulp stock. A barrier paperboard was produced from the treated pulp by the method described above.

Example 9 A barrier board was produced from bleached pulps prepared as above by incorporating 6% Quilon solids based on dry pulp weight. Subsequently 12% resin solids based on dry pulp were added, followed by sufficient alum to lower the pH to 5.0. A board was prepared from the treated pulp which had a green-grey color.

Example 10 A paperboard was prepared in a manner similar to the examples above for the following composition:

Pulp solids parts FC-805 0.25 (based on pulp solids) Hydroxyethyl cellulose dispersion 0.06% solids (based on pulp solids) Resin mixture 11% (based on pulp solids), containing:

Polyvinyl acetate 36.5% Melamine formaldehyde 9% Polyethylene 16.35% Micro-crystalline wax 38.15% Glyoxal 1.1% (insolnbilizer) The pulp was treated at an adjusted pH of 7.5. The treated pulp was then formed into board as above.

Example 11 In order to demonstrate the method of incorporating a filler having a large surface area, a paper board containing metal powder was made as follows.

Paper pulp was beaten and then treated with FC805 as in Example 2. Ten percent by weight aluminum powder, based on pulp solids, was first slurried with a Water dispersion of 0.2% Volan, also based on metal powder solids. The slurry was then combined with a resin dispersion similar to that of Example 2 containing 9% resin solids by Weight based on pulp solids. The entire mixture was added to the pulp suspension and thoroughly mixed. After standing for 4 hours the aqueous phase became clear and colorless. Drainage was rapid l. .5. during the paper making process, and there was no indication of free aluminum powder. After calendering, the

paper sheet was smooth and bright.

Example 12 t A charge of 500 grams of mixed pulps, air dry basis, taken from a production beater, and which pulps had been beaten until a Williams freeness of 315 had been attained, was placed in a cycle heater, and diluted with water to a consistency of 1.75 EC-805, in an amount of 0.25% based on pulp solids was added as a dilute aqueous solution and reacted with the pulp solids under circulation for 20 minutes. Subsequently, a separately prepared aqueous dispersion of phenol formaldehyde resin in a quantity of 1.5% solids based on pulp solids plus 23% inert fillers also based on pulp solids, were homogeneously combined and incorporated into the reacted pulp stock which was then mixed for 15 minutes.

The consistency of the combined stock was then taken to determine the amount required to produce a mat having 75 grams dry weight. The determined quantity of stock was couched off, pressed, and dried.

A stereotype mat was prepared and aged for one da coated with release coating, and tested by contact with molten lead at 600 F. plus. The mat was tested for dimensional stability and found to be satisfactory.

'Example 13 Into a batch of mixed pulps containing 500 grams pulp (dry weight) similar to that of Example 12, after dilution and conditioning with FC-805, as in Example 12, then were further incorporated A inch 9 micron glass fibers in an amount of 4% based on pulp solids. The glass fibers were previously water-wetted in a dispersion containing 0.25% Volan. Separately 23% inert fillers based on pulp solids were water slurried. The glass fibers and slurried fillers were combined and incorporated with the moving stock. After the reaction was complete, the pulp was formed into a stereotype mat and tested as above as in Example 12. It was found to be satisfactory for stereotype mat use. 7

Example 14 A beaten stock containing a combination of bleached pulps was treated with 0.25% FC805 based on pulp solids. Amres 1420, a liquid phenol formaldehyde resin produced by American-Marietta Company was added in an amount equal to 10% resin solids based on pulp solids and circulation continued until all solids were complexed. After 10 minutes stirring the pH solution was brought from pH 10 to pH by the addition of acid/alum solution. The water at this point was crystal clear. Drainage was very good and no sticking was experienced on the press. The resin was well distributed throughout. Hand sheets having a weight of 45 grams were produced from the treated pulp. After a cure of minutes at 325 F., the board was rigid and appeared to be well suitedfor use as post-forming board stock.

Example 15 A pulp stock was beaten and treated with FC-805 as in Example 14. An epoxy-novolac resin was emulsified and a sufficient amount of the resin emulsion was then introduced to incorporate 15% resin solids based on dry pulp. The pH of 9.0 was then reduced with acid/alum solution of a pH 5.0. Observation of a sample of the stock indicated that all ingredients had migrated to the pulp and a crystal clear water separation resulted.

Sheets were prepared as in Example 14 above and exhibited extremely good resin distribution and increased edge tearing resistance.

Invention is claimed as follows:

1. A process for depositing a water-dispersible resin on cellulose pulp fibers comprising first dispersing a coupling agent into an aqueous suspension of said fibers, and subsequently dispersing said resin into said suspension, said coupling agent consisting essentially of a water- 12 soluble chromium coordination complex of an acyclic acido carboxylic acid.

2. A process according to claim 1 wherein said coupling agent consists essentially of stearato chromic chloride.

3. A process according to claim 1 wherein said coupling agent consists essentially of methacrylato chrornic chloride. 2

4. A process according to claim 1 wherein said coupling agent consists essentially of a Werner-type chromium coordination complex of a perfluorocarboxylic acid.

5. A process according to claim 1 wherein said coupling agent consists essentially of a chromium coordination complex of a saturated perfluorocarboxylic acid having from 4l2 carbon atoms.

6. A process for depositing a resin on beaten cellulose pulp fibers comprising first adding a coupling agent to an aqueous suspension of said fibers and mixing said suspension to deposit said coupling agent on said fibers, and subsequently adding an aqueous dispersion of said resin to said suspension and mixing said suspension until said resin is deposited on said fibers, said coupling agent consisting essentially of a water-soluble chromium coordination complex of an acyclic acido carboxylic acid.

7. A process according to claim 6 wherein said coupling agent consists essentially of stea-rato chromic chloride.

8. A process according to claim 6 wherein said coupling agent consists essentially of methacrylato chromic chloride. 7

9. A process according to claim 6 wherein said coupling agent consists essentially of a Werner-type chromium coordination complex of a perlluorocarboxylic acid.

10. A process according to claim 6 wherein said coupling agent consists essentially of a water-soluble chromium coordination complex of a saturated perfluorocarboxylic acid having from 4-12 carbon atoms.

11. A process for depositing an adherent coating of a water-soluble resin with cellulose pulp fibers comprising the steps sequence of beating an aqueous suspension of said fibers until they have attained a suitable dreeness, adding an aqueous solution of a coupling agent to said suspensicnand continuously circulating said suspension until said coupling agent has been substantially deposited on said fibers, and adding an aqueous dispersion of said resin to said suspension and mixing said suspension until said resin has been substantially deposited on said fibers, said coupling agent consisting essentially of a water-soluble chromium coordination complex of an acyclic aoido carboxylic acid.

'12. A process according to claim 11 wherein said coupling agent consists essentially of stearato chromic chloride.

13. A process according to claim 11 wherein said coupling agent consists essentially of methacrylato chromic chloride.

14. A process according to claim 11 wherein said coupling agent consists essentially of a Werner-type chromium coordination complex of a perfiuorocarboxylic acid.

15. A process according to claim 11 wherein said coupling agent consists essentially of a water-soluble chromium. coordination complex of a saturated perfiuorocarboxylic acid having from 4-12 carbon atoms.

16. A process for the production of resin-modified paper which comprises the steps sequence of dispersing a coupling agent into an aqueous suspension of beaten cellulose pulp fibers, dispersing a water-dispersible resin and an inert filler into said suspension, and forming said pulp fibers into paper on a paper-making machine, said coupling agent consisting essentially of a water-soluble chromium: coordination complex of an acyclic acido carboxylic acid.

17. A modified paper product which may be molded to a permanent shape at elevated temperature and pressure, said paper product having been prepared by the steps in sequence of dispersing a coupling agent into an aqueous suspension of beaten cellulose pulp fibers, dispersing a water-dispersible resin into said suspension, and forming said paper from said pulp fibers on a paper making machine, said coupling agent consisting essentially of a water-soluble chromium coordination complex of an acyclic acido carboxylic acid.

References (IiteaZ in the file of this patent UNITED STATES PATENTS ller Oct. 10, 1944 Pattilloch Nov. 10, 1953 McQuiston Ian. 19, 1954 Cilley et a1 Nov. 27, 1956 Collier July 30, 1957 Hawley et al Apr. 12, 1960 Pattilloch Ian. 9, 1962 Martin May 29, 1962 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,109,769 November 5, 1963 Ray C. Martin It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 13, for "absorbed read adsorbed column 7, line 75, for "salts" read salt column 8, line 2, for "dispesred" read dispersed line 25, before "minute" insert one column 9, line 26, for "500" read 5000 lines 62 and 63, for "furthere" read further column 10, line 67, before "aluminum" insert of Signed and sealed this 21st day of April 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J, BRENNER Attesting Officer Commissioner of Patents

Claims

1. A PROCESS FOR DEPOSITING A WATER-DISPERSIBLE RESIN ON CELLULOSE PULP FIBERS COMPRISING FIRST DISPERSING A COUPLING AGENT INTO AN AQUEOUS SUSPENSION OF SAID FIBERS, AND SUBSEQUENTLY DISPERSING SAID RESIN INTO SAID SUSPENSION, SAID COUPLING AGENT CONSISTING ESSENTIALLY OF A WATERSOLUBLE CHROMIUM COORDINATION COMPLEX OF AN ACYCLIC ACIDO CARBOXYLIC ACID.