GB2148344A - Wood pulp incorporating melamine or ammeline - Google Patents

Abstract

Melamine or ammeline is added to wood or wood pulp so that paper produced therefrom has wet and dry strength, ink and pigment retention, improved color and brightness, soil and grease resistance, and electrical properties. The melamine may be added during bleaching of pulp, or during refining in a thermomechanical pulping process, or during beating of a pulp, which may be derived from waste paper. Salts thereof may also be used.

Description

SPECIFICATION Improved process for producing wood pulp utilizing and s-triazine additive, and an improved wood pulp and paper containing an-triazine This invention is directed to paper and paper products, and particularly to improved processes for producing wood pulp for utilization in paper manufacture, to an improved wood pulp, and to the ultimate paper product obtained. More specifically, the present invention is directed to the utilization of a select s-triazine additive, such as melamine, in the production of wood pulp for use in the manufacture of paper products; to the wood pulp containing the additive, and to an improved paper made with the s-triazine containing wood pulp.

The art of papermaking, including the processes of producing paper pulp, is a well-established art. Thus, there are well known processes for producing wood pulp from trees by either thermomechanical, chemical, or semi-chemical treatments. These treatments are extensively described in the literature, such as in Pulp and Paper, Chemistry and Chemical Technology, by James P. Casey, Editor; Third Edition, 1980-1983, published in four volumes by John Wiley & Sons, Inc., New York, incorporated herein by reference.

Conventionally, wood logs obtained from growing trees are first cut into small sections and then into chips in the first stage of the pulping process. The chips are then digested in a semi-chemical, or a chemical operation to separate the lignin, which holds the wood fibers together, from the cellulose or hemi-cellulose.

The lignin is discarded, and the cellulosic material is further treated for use in making paper.

In the thermomechanical process (TMP), pulping is accomplished by preheating of the wood chips, preferably under pressure, to soften the lignin contained in the wood to permit the separation of the constituent fibers. Thereafter the lignin is partially separated from the cellulosic products in bleaching operations. In a chemical process the wood chips are cooked, normally in a closed digester tank, in the presence of a suitable chemical reagent. In the sulfite process, the chemical reagent is a bisulfite salt, i.e., the sulfite process. In the sulfate or kraft process, the chemical reagent is caustic soda or sodium sulfide, i.e, the sulfate process. In the soda process, caustic soda is used as the chemical reagent. All of the chemical processes are similar in the sense that the chemical reagent is used to digest the lignin which holds the cellulose or hemi-cellulosic fibers together.The pulps resulting from the chemical processes are known as chemical pulps.

Typically, after the initial pulping stage, whether in a thermomechanical, a semi-chemical, or a chemical process, the pulps are subjected to a number of subsequent operations. In one such operation the wood pulp is bleached with a bleaching agent such as chlorine or an oxygen-containing material, such as hydrogen peroxide, gaseous oxygen or ozone, to bleach the wood pulp, followed by various washing steps. In another post-pulping operation the pulp is mechanically manipulated or beaten to fibrillate and fiberize the wood fibers so that bonding of the fibers in a subsequent papermaking process can take place.The purpose of such post-pulping operations is to provide wood pulps suitable for subsequent papermaking, with the paper which is ultimately produced having the desired characteristics for a given application such as proper color, brightness, ink receptivity, pigment receptivity, and various other properties such as wet and dry strength, grease resistance, and/or electrical characteristics depending upon the end application.

In the various post-pulping operations it has been recognized that additives can be added to enhance the operation. For example, in the refining step the use of dye additives such as congo red are known to accelerate the beating process and reduce the energy requirements of the process. Although congo red dye is advantageous, the use of the dye causes a red coloration of the wood pulp and, unless the coloration is removed, the coloration will carry over into the paper product made from the pulp.

Accordingly, although wood pulps are known which have excellent characteristics, there is a recognized need for improvements in the preparation of wood pulps for use in paper-making both from the economic standpoint and from the stand-point of obtaining ultimate paper products having the desired characteristics for a particular application.

Accordingly, it is a primary object of the present invention to provide an improved additive for use in papermaking, and particularly for use in the production of wood pulp, including recycled pulp, which is subsequently used in papermaking.

It is another object of the present invention to provide an additive for use in papermaking, and particularly in the production of wood pulp which is relatively inexpensive and which will provide improved economics in the wood pulping process.

It is another object of the present invention to provide an additive for use in papermaking, and particularly in the production of wood pulp for subsequent use in paper which, when retained in the pulp, provides an improved wood pulp.

It is still another object of the present invention to provide an improved additive for use in the production of wood pulp for use in papermaking which, when retained in the wood pulp, provides improved characteristics such as increased strength, ink receptivity, brightness, decreased static charge accumulation, and pigment compatibility and retention in the paper produced with the wood pulp.

The above and other objects will be apparent from the following general description and the preferred embodiments.

The aforesaid objects are accomplished according to the present invention by adding at a suitable stage in the wood pulping process an s-triazine additive, such as melamine. It was initially discovered that melamine when added to wood pulp before subjecting the wood pulp to conventional bleaching methods, such as chlorine or oxygen bleaching, not only functioned as a viscosity protector or stabilizer during the course of the bleaching process, but also provided improved color, brightness, and strength to the bleached wood pulp. It was subsequently found that the presence of melamine in the refining stage of the pulping process reduced the time and energy requirements of the beating process and provided a wood pulp having improved fiber characteristics, including flexibiiity, thereby providing improved bonding of the fibers when the pulp was used in paper.

It has now been discovered that the wood pulp will retain the s-triazine additive after the wood pulping process, and that the retained s-triazine-cellulose-lignin composition provides a paper having superior characteristics regardless of whether the pulp is made using a thermomechanical, chemical, or semi-chemical operation. The paper made from the wood pulp containing the s-triazine composition provides a paper having excellent pigment compatibility and retention; improved ink receptivity; greatly increased mechanical strength including burst, tensile and tear strengths, and increased electrical conductivity. The s-triazine composition also permits rapid and compiete de-inking of the paper during a paper recycling process.Thus, it has been found that the s-triazine functions to enhance the processing of wood into wood pulp suitable for papermaking, and that when retained in the wood pulp at the time of making paper the s-triazine composition provides a finished paper having improved characteristics. The discovery of the present invention, therefore, not only eliminates the need to remove the wood pulping additive before converting the pulp to paper, but also provides an improved paper product. "Paper" as used herein means a sheet, blanket, or mat of individual fibers of cellulose derived from wood.The fibers may be woven ornon-woven, and normally are not woven. "Pulp" as used herein means a mass of cellulose fibers in bulkform and from which paper or other pulp products are manufactured. "Wood pulping" as used herein means the process of converting wood chips to a slurry of cellulose fibers in an aqueous medium.

The additives which can be utilized according to the present invention are select s-triazine compounds containing at least two NH2 groups and having the formula

wherein Xis an NH2 or OH group, or a salt thereof. The preferred compound is melamine wherein X is an NH2 group, or a salt thereof such as melamine sulfamate, melamine sulfite, melamine chloride, melamine sulfate, melamine phosphate, melamine hypochlorite, melamine chlorate, melamine chlorite, melamine perchlorate, melamine nitrate, melamine peracetate, and melamine hydrogen sulfite. It has also been found that melamine made in accordance with the process as set forth in Thomas and Best, U.S.Patent Application Serial No. 568,408 filed January 5, 1984 entitled "Anhydrous High-Pressure Melamine Synthesis," assigned to the assignee of the present application and incorporated herein by reference, can be effectively utilized.

The product of the process defined in the aforesaid Thomas et al application will contain up to about 4% of substituents not melamine, including melam, C6HgN11; melem, C6H5N10; ammeline, C3N50H5, ammelide, C3N402H4, and urea. The product of the aforesaid application is commonly called Melamine II, a trademark of Melamine Chemicals, Inc., Donaldsonville, Louisiana. The salts of Melamine II as set forth above in defining the salts of melamine have also been found to be effective additives. Another select s-triazine additive which can be utilized according to the present invention include ammeline having the formula

which is basic in character.

The select s-triazine additives can be used to improve the pulping of wood which, when subjected to a digester operation to remove lignin or other resinous material, will provide a cellulosic or hemi-cellulosic product in fiberized form. The most common and preferred materials are the hardwood and softwood trees such as the various types of pine, fir, spruce, poplar, oak, maple, mahogany, ash, and the like. The additives can also be effectively used when paper and pulp are recycled to form a new paper or pulp material. "Wood" as used herein means a mixture of lignin and cellulose fibers derived from trees or similar plants as commonly found in the forests. The phrase "s-triazine additive" as used herein means the s-triazine as it is added in the wood processing.The phrase "s-triazine composition" as used herein means the composition of the s-triazone additive interacted with the cellulose and lignin.

The amount of additive which is to be utilized in combination with the wood or wood pulp will vary depending upon the stage of the addition and the function of the additive. Thus, if the selected s-triazine additive is to be added in the wood pulping process, the amount employed should preferably be from about 0.05 to 20 parts to each 100 parts of wood. The addition of the selected s-triazine additive to a sulfide or sulfite process will preferably be in the range of from about 0.5 to 10 parts per 100 parts of wood. The addition of the selected s-triazine additive to a thermomechanical or chemical-mechanical wood pulping process should preferably be in the range of from about .05 to 5 parts per 100 parts of wood.Normally some of the s-triazine additive will be lost during the wood processing conditions, and it may be desirable to add additional additive in steady-state recycle operation. The composition of s-triazone additive-cellulose-lignin will have beneficial effects on further pulp processing consistent with the pulping conditions and the resultant composition retained on the pulp. If the s-triazine additive is to be added during the bleaching process, the amount employed should be from about 0.05 to 3 parts to each 100 parts of wood pulp.

Normally some of the additive will be lost during the bleaching and subsequent washing steps; and, accordingly, it may be desirable to add additional additive upon completion of the bleaching process in order to have an effective amount of the additive in a subsequent processing step, for example in the refining step in a thermomechanical process or in the beating process of a chemical orthermomechanical process.

Further, it has been found that the final paper or pulp, if the amount of the select s-triazine composition is maintained above about 0.05 parts per 100 parts in the wood pulp, the paper made from the pulp will have increased strength characteristics; ink and pigment retention; soil and grease resistance, and electrical properties. It is particularly desirable if the paper is to be effective in reprography (which requires that the paper accept electrical deposits of ink) that the amount of additive be present at the upper end of the above range. Based on the above guides as well as the presently preferred embodiments set forth hereinafter, one skilled in the art will be able to select an effective amount of the s-triazine additive in order to accomplish the desired objectives.

At the present time it is not certain how or why the s-triazine additive provides the beneficial effect in the different stages of the pulping process. It is believed, however, that the s-triazine additive during the pulping process and the beating process interacts with the wood cellular structure to cause the fiber bundles to separate into cellulose fibers and lignaceous components to provide a pulp containing the s-triazine composition. It is believed in the bleaching or recycling process wherein the fibers have already been isolated that the s-triazine additive interacts with the lignin or lignin-coated cellulose through hydrogen bonding or co-valent bonding to the separated fibers.In any event, the melamine or melamine derivative need not be removed from the treated cellulose fibers, thus providing an enhanced physical property effect not obtainable with an additive which is merely physically blended with cellulosic fibers.

Having described the invention in general terms, the following examples set forth the presently preferred embodiments of this invention. Examples 1 through 3 illustrate the addition of the select s-triazine additive during the bleaching stage of the pulp preparation. Examples 4 and 5 illustrate the addition of the s-triazine additive during the refining step of a thermomechanical pulping process. Example 6 illustrates the addition of the s-triazine additive in a post-pulping beating stage. Example 7 illustrates the addition of the s-triazine in a recycling process. Example 8 illustrates a trial done in a commercial papermaking mill.In the following examples the various tests are measured according to standard TAPPI (Technical Association of the Pulp and Paper Industry, Atlanta, Georgia) methods, with the tests utilized being designated as follows: Tests and TAPPI Standards TAPPI Standard (1) Laboratory Processing of Pulp (Beater) T200 - os-70 (PFI Mill) T248 pm-74 (2) Canadian Standard Freeness T 227 - os-58 (3) Forming handsheets for physical testing T 205 - om-80 T205 - om-81 (4) Brightness T452 - os-72 T452 - os-77 (5) Scattering coefficient T425 - om-81 (6) Fiber classification (Bauer-McNett) T233 - os-75 (7) Physical testing of handsheets Calipher T220 - os-71 Burst Index T220 - os-71 Tensile Index T220 - os-71 Tear Index T220 - os-71 Folding Endurance T220 - os-71 (8) Kappa Number T236 - os-76 (9) Viscosity (Cp) T230 - os-76 (10) Freeness T227 - os-58 (11) SommervilleShives TAPPI 57(6),87 (1974) Example 1 MelamineAsA Viscosity Stabilizer In the Bleaching Stage of Pulp Preparation Unbleached kraft process pulp having a kappa number of 38.7 was treated with sulfamic acid, urea, or melamine at various percentages on pulp according to the following bleaching procedure. The single capital letters, C, E, D are used to describe particular bleaching stages as described in Pulp and Paper, Chemistry and Chemical Technology, by James P. Casey, Editor; Third Edition, Vol. 1, 1980, page 669, John Wiley & BR< Sons, Inc., New York. The removal of lignin during the bleaching stage is expressed as a reduction in the Kappa number.

The delignification/bleaching stages were accomplished as follows: Protective agents were added at the indicated percentages on pulp and chlorination with chlorine water (C stage) was at 9.66% chlorine on pulp at room temperature for one hour at 3% pulp consistency.

Caustic extraction with sodium hydroxide (E stage) was done at 4% NaOH on pulp at 70"C for one hour at 12% pulp consistency. Chlorine dioxide bleaching with C102 (D stage) was at 1.5% C102 on pulp at 70"C for 2.5 hours at 12% pulp consistency.

Table I presents the pulp properties after the C and E stages and after C, E and D stages when the various protective agents were added to kraft process pulp. About 0.25% melamine on pulp is as effective after C and E stages as 0.50% sulfamic acid. Continuing the bleaching through the chlorine dioxide stage (stage D), the data of the table indicates that in the two experiments where the viscosity was measured (28.6 and 29.2), the viscosity is significantly higher than the base case of 17.1 when no melamine was used.

TABLE I EFFECT OF CELLULOSE PROTECTORS IN CHLORINE DELIGNIFICATION Pulp Properties C-E Stage C-E-D Protective on Kappa Viscosity Brightness Viscosity Agents pulp Number (cup) % lCpJ None .. 8.6, 9.0 24.5, 23.7 72, 71.3 17.1 Sulfamic Acid 0.5 9.5 35.8 71.3 23.7 Urea 1.0 8.2 33.8 71.0 22.0 Melamine 0.10 8.8,9.1 27,27.2 71.5,72.5 - 0.15 9.6 29.9 72.0 -0.20 8.6 32.8 73.0 -0.26 9.0 37.7 70.5 -0.30 10.3 38.0 71.5 -0.50 10.4 40.0 71.8 28.6 0.80 9.7 41.0 71.7 -1.20 9.7 41.6 71.8 -1.43 9.7,9.4 41.6,42,41.2 72,71.5 29.2 Example 2 Melamine As A Viscosity Stabilizer When UsedAt Various Temperatures In The Chlorination Stage Unbleached kraft process spruce pulp having a kappa number of 38.7 was bleached in C-E-D sequences with and without the use of melamine and sulfamic acid in the chlorination stage at different temperatures.

Table II contains a summary of the comparative pulp properties after C-E stages, and Table Ill summarizes the comparative properties after C-E-D stages. It can be seen from these figures that melamine at a reduced level (0.25%) is as effective as sulfamic acid (0.5%) even at higher temperatures of chlorination.

TABLE II Effect Of Melamine At Different Temperatures Of Chlorination (Pulp Properties After C-E Stages) Protective Agent None SulfamicAcid Melamine Properties (Control) (0.5% On Pulp) (0.25% On Pulp) Temp. 30"C Kappa Number 8.5 7.7 7.5 Viscosity (Cp) 23.8 36.7 34.7 Temp. 400C Kappa Number 8.2 8.7 6.2 Viscosity (Cp) 23.2 34.2 34.0 Temp. 50"C Kappa Number 8.6 7.7 6.5 Viscosity (Cp) 22.2 32.5 32.8 Conclusions: At all temperatures the Kappa Number achieved is lowest with melamine. Viscosity values obtained with melamine are comparable to those achieved by using a higher percentage of sulfamic acid.

TABLE III Effect Of Melamine At Different Temperatures Of Chlorination (Pulp Properties After C-E-D Stages) Protective Agent None Sulfamic Acid Melamine Properties (Control) (0.5% On Pulp) (0.25% On Pulp) Temp. 30"C Kappa Number 3.2 2.5 1.8 Viscosity (Cp) 17.5 24.5 24.0 Brightness % 71.0 70.5 71.0 Temp. 40"C Kappa Number 3.1 2.8 2.2 Viscosity (Cp) 16.8 23.7 23.5 Brightness % 70.5 71.0 70.5 Temp. 50"C Kappa Number 2.3 3.2 2.5 Viscosity (Cp) 16.3 21.3 21.5 Brightness % 70.0 70.0 70.5 Conclusions: At each temperature level the effect of melamine on viscosity is comparable to that of sulfamic acid but with a lower dosage level (0.25% melamine against 0.5% sulfamic acid).

Example 3 Melamine As A Viscosity Stabilizer In the Hypochlorite Bleaching Stage Of Pulp Preparation Unbleached kraft process spruce pulp having a Kappa number of 38.7 was bleached in a C-E-H sequence with the use of sulfamic acid (0.5%) or melamine (0.25%) in the hypochlorite stage (H stage) in two separate experiments. A third experiment was done without any additive as a control. The comparative results reported in Table IV show the effect of melamine as a viscosity stabilizer in the hypochlorite stage of bleaching.

TABLE IV Effect Of Melamine In The Hypochlorite Stage Properties After Properties After Protective Agents C-E Stages C-E-H Stages Used In Chlorinationi Kappa Viscosity Kappa Viscosity Brightness Hypochlorite Stage Number (Cp) Number (cup) None/None (Control) 6.0 18.3 1.7 7.5 75.3 None/Sulfamic Acid (0.5%) 6.0 18.3 1.3 9.4 76.5 None/Melamine (0.25%) 6.0 18.3 1.5 9.2 75.1 Conclusions: Results indicate comparable viscosities for melamine in comparison with those obtained for sulfamic acid at higher dosage levels.

Example 4 illustrates the use of melamine in the first pressurized refining stage and in the second atmospheric refining stage of a thermomechanical pulping operation.

Example 4 A pilot plant trial was done using loblolly pine which had been first debarked, chipped, and screened. The material had a specific gravity of 0.461 g/cc and 41.1% moisture content. The chip screen analysis appears in Table V.

TABLE V Chip Screen Analysis Actual Cumulative 1 on 1 " screen 0 2 % on 3/4" screen 7.1 7.1 3 %on5/8"screen 14.7 21.8 4 % on 1/2" screen 20.3 42.1 5 % on 1/4" screen 48.3 90.4 6 %on 1/8" screen 8.4 98.8 7 %through 1/8"screen 1.2 100.0 The chips were presteamed in the digester for three minutes at 30 psi(g) steam and refined in a primary refiner under a pressure of 30 psi(g). The primary refiner was C-E Bauer model 418 Pressurized Double Disk Refiner equipped with 31104/7 R0869 MC plates (C-E Bauer, Springfield, Ohio). In the control run no chemical was added while in the experiment, melamine was added in the form of a solution at the level of 1.4 parts by weight melamine to 100 parts by weight of dry wood at the plug wiper of the primary refiner.

The primary stage pulp was divided into different lots and refined in a secondary stage atmospheric refiner with varying specific energy inputs. The second stage refiner was a C-E Bauer model 401 Atmospheric Double Disk Refiner equipped with 3610X plates.

The resultant pulps were sampled in accordance with standard TAPPI procedures and tested for Canadian Standard Freeness, Somerville Shives, Bauer-McNett classifications, physical and optical properties according to the TAPPI procedures listed above. The data appears in Table VI.

TABLE VI Results Derived From Test Results On Loblolly TMP Pulp, Refined With And Without Melamine As An Additive Energy Applied During Secondary Refining Step Cumulative r 1) Calculated Energy BHPDIADT CSF(2) To Reach 200 CSF Shives Control, 82.9 596 117 BHPD/ADT 3.16 No Melamine 90.2 475 117BHPD/ADT 1.46 108.0 226 117 BHPD/ADT 0.48 115.3 210 117 BHPD/ADT 0.80 Melamine,1.4%, 69.9 644 103 BHPD/ADT 3.06 Added to Primary 83.2 413 103 BHPD/ADT 0.79 Refiner Only 99.5 240 103 BHPD/ADT 0.36 123.1 99 103 BHPD/ADT 0.16 Melamine, 1.5%, 77.6 622 109 BHPD/ADT 3.23 Added To Secondary 88.3 475 109 BHPD/ADT 1.32 Refiner Only 108.0 232 109 BHPD/ADT 0.37 111.8 158 109 BHPD/ADT 0.71 Melamine Added To 69.5 630 100 BHPD/ADT 2.66 Primary Refiner, 1.4%, 84.0 455 100 BHPD/ADT 0.72 And To Secondary 100.3 210 100BHPD/ADT 0.35 Refiner, 0.7% 119.7 108 100 BHPD/ADT 0.21 ( 1) - Brake Horsepower Days/Air Dried Ton (2) - Canadian Standard Freeness (mL) According to the Table VI data, refining appeared to proceed better and faster in the presence of melamine.

Lower energy was needed to achieve an equivalent freeness. In this trial, specific energy (BHPD/ADT) was 117 HP to obtain a freeness of 200 without melamine, while it was only 103 HP with the use of melamine as a refining additive to the primary refiner. Fewer shives were produced. Tear, burst, and tensile strength were maintained at the lower specific energy input, this result is significant. There was no effect on the optical properties of the pulps. No noticeable changes in opacity or brightness were observed.

Example 5 The thermomechanical pulps produced according to Example 4 were used in this trial to assess the effect of melamine in a post-treatment such as bleaching.

The pulp samples -- control (without melamine) and experimental (with 1.4 melamine in the plug wiper of primary refiner) -- were bleached in two independent experiments with H202 (1% by weight on pulp) in the presence of sodium silicate (5% on pulp of a 40% silicate solution), magnesium sulfate (0.05 on pulp), and sodium hydroxide (1.25% on pulp). The reaction was allowed to proceed for two hours at 60 t 2"C at 10% pulp consistency. The initial pH of the pulp was 10.0, and at the end of two hours it was 9.6.

The brightness achieved in the case of control pulp was 51.5 with a scattering coefficient of 38.9 m2/kg, while in the case of melamine-treated pulp the corresponding figures were 55.8 and 47.9 m2/kg, respectively.

These figures indicate that the presence of melamine in pulp enhances the bleaching effect of a subsequent treatment.

Example 6 compares various beater additives using the PFI mill. The PFI mill is one of several laboratory instruments used in determining the refining characteristics of wood pulps. In this test the number of revolutions of the beater is recorded and the freeness of pulp attained at that total number of revolutions is measured.

Example 6 Unbleached spruce kraft pulp and bleached spruce kraft pulp were refined in a laboratory pulp beating apparatus (PFI mill, Paperindustriens Forskninginstitutt, Oslo, Norway, TAPPI standard 248 pm-74). The pulps were refined without any additive (control), with 1.7 parts by weight congo red to 100 parts by weight pulp; with 1.5 parts by weight melamine for 100 parts by weight pulp, or with 6.7 parts by weight Procion Yellow M-RS fiber reactive dye (ICI Americas, Inc., Wilmington, Delaware) to 100 parts by weight pulp. The dyeing treatment in the case of the fiber reactive dye was at pH 10.5 and at a high NaCI level, the NaCI used being of equal weight to the pulp. The PFI mill uses 25 grams of pulp made up to 250 grams total weight of the suspension (i.e., 10% consistency).

The effect of the several additives in the PFI mill refining of unbleached spruce kraft pulp on Canadian Standard Freeness, Tensile Index, Burst Index, Tear Index, and MIT Folds is reported in Table VII.

TABLE VII The Effect Of Beating Additives On PFI Mill Refining Of Unbleached Spruce Kraft Pulp Tensile Burst Tear MIT Revolutions Freeness Index Index Index Double In PFl Mill CSFmL Nmig kPam2/g mNm2/g Folds Control 7700 600 52.0 4.74 17.38 412 10000 515 56.9 5.25 17.05 522 12500 450 62.6 5.38 16.90 608 15000 390 62.1 5.54 16.80 425 19000 320 60.9 5.60 16.32 405 Melamine at 1.5% 7500 570 58.8 5.12 19.04 314 10000 495 60.8 5.42 18.48 430 12500 435 63.4 5.54 18.10 535 15000 380 63.2 5.74 17.70 638 18000 310 62.2 5.94 17.36 522 Direct Dye Congo Red at 1.7% 8000 545 54.4 4.91 19.0 397 10000 500 58.4 5.24 18.64 410 12700 440 61.7 5.36 18.40 486 15000 385 62.8 5.52 17.95 542 18000 320 62.1 5.74 17.92 590 Fiber Reactive Dye Procion Yellow M-RS at 6.7% 7500 625 44.8 4.02 13.30 65 10000 540 47.5 4.22 13.15 100 12500 475 52.0 4.29 12.96 122 15000 405 53.1 4.27 12.72 114 18000 330 54.0 4.26 12.64 110 Examination of the CSF Freeness at each total number of revolutions in Table VII shows that when melamine is present, a lower number of revolutions is needed to reach any desired level of freeness whether that level be, for instance, 500, 400, or 300 mL.

Examination of the strength properties reported in Table VII (Tensile Index, Burst Index, Tear Index, and MIT Double Folds or Folding Endurance) shows that at any given refining level the melamine addition results in a greater strength property.

The effect of the several additives in the PFI mill refining of bleached spruce kraft pulp as to Canadian Standard Freeness, Tensile Index, Burst Index, Tear Index, and MIT Double Folds is reported in Table Vlil.

TABLE VIII Effect Of Various Additives On PFI Mill Refining Of Bleached Spruce Kraft Pulp Tensile Burst Tear MIT Revolutions Freeness Index Index Index Double In PFI Mill CSF mL Nmig kPam2/g mNm2/g Folds Control 3000 630 59.7 5.36 20.9 470 5000 550 61.5 5.94 19.66 525 7500 430 63.6 6.20 19.3 665 10000 355 66.1 6.42 18.7 740 12000 330 57.3 6.72 18.4 610 Beating Additive Melamine at 1.5% 3500 615 63.5 5.40 21.64 485 6500 455 65.0 6.10 19.93 690 9500 - - - - 1035 10000 325 68.7 6.56 19.38 980 12000 290 70.8 6.82 19.12 810 Direct Dye Congo Red at 1.7% 3400 610 62.4 5.50 21.0 445 5000 515 62.8 6.04 20.16 560 8000 405 67.8 6.38 - 725 10000 345 68.7 6.52 19.46 770 12000 290 69.6 6.77 19.48 780 Fiber Reactive Dye Procion Yellow M-RS at 6.7% 3000 635 31.7 3.15 17.70 22 5200 535 38.6 3.86 15.16 45 8000 395 46.4 4.30 13.54 80 10000 320 46.3 4.42 13.50 85 12000 255 44.5 4.50 13.35 100 Examination of the CSF Freeness at each total number of revolutions in Table VIII shows that when melamine is present a lower number of revolutions is needed to reach any desired level of freeness whether that level be, for instance, 400, or 300 mL. Examination of the strength properties reported in Table VIII shows that at any given refining level the melamine addition results in a greater strength properties.

Example 7 A previously used paper is recycled. An aqueous slurry of paper pulp is formed using caustic with Melamine II being added as an aqueous slurry of the Melamine II to the pulp. The paper pulp is then beaten in a batch pulping operation using caustic and the melamine additive under conditions that the ink and filler agents are selectively separated from the cellulose pulp fibers. The addition of the melamine additive to the caustic pulp results in a higher quality pulp having less degradation of fiber strength.

Example 8 To demonstrate the feasibility of using the s-triazine additive in a commercial plant, Melamine II was utilized in a commercial plant trial run. In the trial run the Melamine II was added in an amount of 0.25 parts per 100 parts of pulp material during the chlorination bleaching stage. The data obtained from the trial run is set forth in Table IX.

TABLE IX Commercial Plant Trial Chlorination Stage Addition Of Melamine II Properties Control Run Experimental Run C.S. Freeness mL 500 300 500 300 Brown Stock Brown Stock Folding endurance 179 204 166 174 Tensile Index Nm/g 94.0 95.2 95.3 96.3 Tear Index mNm2/g 10.12 9.86 9.93 9.47 Burst Index kPam2/g 7.07 7.31 6.96 7.27 CE Pulp C-E Pulp Without Melamine II With Melamine II Folding endurance 131 161 200 164 (73.2) (78.9) (120.5) (94-3) Tensile Index Nm/g 91.8 92.1 97.7 93.6 (97.7) (96.7) (102.5) (97.2) Tear Index mNm2/g 8.41 8.04 10.11 9.69 (83.1) (81.5) (101.8) (102.3) Burst Index kPam2/g 6.60 7.16 7.20 7.40 (93.4) (97.9) (103.4) (101.8) C-E-H-D Pulp C-E-H-D- Pulp Folding endurance 110 112 127 129 (61.5) (54.9) (76.5) (74.1) Tensile Index Nm/g 89.8 88.6 93.0 96.7 (95.5) (93.1) (97.6) (100.4) Tear Index mNm2/g 7.21 7.34 8.12 7.52 (71.2) (74.4) (81.8) (79.4) Burst Index kPam2/g 6.09 6.15 6.42 6.64 (86.1) (84.1) (91.2) (91.3) 1) The figures in the brackets indicate % of corresponding brown stock properties.

2) The * indicates the averaging of at least 4 data points to establish a statistically significant result.

The data of Table IX establishes that when the melamine additive was utilized, the pulp had increased tensile, tear and burst strengths. Most surprising, the tear and burst strengths were both significantly improved. This is a distinct advantage since it is normally expected that an improved tear strength is gained only as a result of a decrease in the burst strength, or vice versa.

In the aforesaid preferred embodiments, the melamine which was utilized in the examples can be replaced with the melamine and Melamine II salts with substantially the same results. Further, the melamine can be replaced with ammeline. However, the improved results obtained in the treatment of the wood pulp with ammeline may be somewhat less effective than with melamine or Melamine II. Further, the additive can be effectively employed in other wood pulping processes including all types of chemical processing and thermomechanical-chemical processing.

It has been determined that paper products made from the wood pulp containing the s-triazine additives as above defined exhibit improved color and brightness, and have enhanced characteristics with respect to de-inking of paper to be recycled, ink and pigment retention, wet and dry strength, soil and grease resistance, dyeability, and electrical properties permitting the paper to be used for reprography.

As will be apparent to one skilled in the art, various modifications can be made within the scope of the aforesaid description. Such modifications being within the ability of one skilled in the art form a part of the present invention and are embraced by the appended claims.

Claims (11)

1. Process for the treatment of wood and wood pulp comprising the steps of adding an s-triazine compound having the formula

wherein Xis-NH2 or -OH; to said wood or wood pulp during a stage of the treatment of said wood pulp, and thereafter continuing said treatment, said s-triazine being added in an amount effective to improve the pulping of said wood or wood pulp.

2. The process of claim 1 wherein said s-triazine compound is present in an amount effective to improve said pulping of said wood and to provide a wood pulp containing said s-triazine in an amount effective to enhance the characteristics of a paper product made with said pulp.

3. The process of claim 1 wherein said s-triazine compound is added during the bleaching stage of said wood pulp treatment.

4. The process of claim 1 wherein said wood pulp treatment is a thermomechanical pulping operation and said s-triazine compound is added during the refining stage.

5. The process of claim 1 wherein said pulping process is a chemical process.

6. Wood pulp processed to be effective in papermaking and containing in said wood pulp an s-triazine compound the formula

wherein Xis-NH2 or -OH; said s-triazine compound being present in said wood pulp in an amount effective to enhance the characteristics of said wood pulp.

7. A paper product manufactured from a wood pulp containing an s-triazine compound having the formula

wherein Xis-NH2 or -OH; said s-triazine compound being present in said paper product in an amount effective to enhance the characteristics of said paper product.

8. A composition of matter comprising the product formed from the interaction of wood or wood pulp and an s-triazine compound having the formula

wherein Xis-NH2 or -OH.

9. A composition of matter comprising a cellulose-lignin-s-triazine, said s-triazine compound having the formula

wherein X is -NH2 or -OH; said cellulose being present in an amount of from about 70% to 99.9%, said lignin being present in an amount of from about 0.1% to 30%, and said striazine compound being present in an amount of from about 0.025% to 5%.

10. A composition of matter comprising lighinin-s-triazine; said s-triazine having the formula

wherein Xis-NH2 or -OH; said s-triazine being present in an amount of from about 0.1% to 10%.

11. A composition of matter comprising cellulose-s-triazine, said s-triazine having the formula

wherein Xis-NH2 or -OH; said s-triazine being present in an amount of from about .01% to 5%.