US 2745744 A
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United States Patent TREATING AGENTS INCORPORATION Charles Leslie Weidner and Isaac Richard Dunlap, Cranbury, N. J., assignors to Permacel Tape Corporation, a corporation of New Jersey No Drawing. Application February 9, 1951,
Serial No. 210,281
Claims priority, application Canada February 17, 1950 19 Claims. (11. 92-21 This invention concerns improvements in the art of incorporating polymeric or rubber-like materials into cellulosic and other fibers prior to formation of paper, fiberboard, or similar webs of cellulosic and other fibrous material.
'Re'sinous polymers are used widely in paper treatment since the presence of some resinous materials even in minor amounts, e. g. of the order of one-half of one per cent by weight of the paper, adds materially to the strength of the paper when wet. No entirely satisfactory method of incorporating soft, non-resinous polymers, for instance rubber or other rubber-like synthetic polymers into paper during manufacture was known prior to this invention, although some procedures for the incorporation of such materials were known.
The usual practice of resin addition to paper during manufacture consists of the addition of a colloidal dispersion of the polymer in water to the paper pulp suspension prior to sheet formation, and precipitation of the resin from said colloid onto the pulp fibers by the addition of acid, or of salts yielding an acid solution, such as aluminum sulfate. These acid precipitation processes have three main disadvantages. Briefly:
("1) Operation under acid conditions necessitates the expense of quantities of acid or acid producing materials for addition to adjust the hydrogen ion concentration of the pulp.
(2) Addition of acid involves process control expense; and
(3) Papers made under acid conditions react with certain paper coating materials and aifec-t their properties deleteriously.
One acid precipitation process for the incorporation of rubber-like polymers into paper depends upon sensitizing of a latex of the polymer to precipitation and subsequent precipitation of the polymer phase by means of papermakers alum onto the pulp fibers prior to sheet formation. Another depends upon pretreatment of the pulp by a product known as acid melamine-formaldehyde colloid to increase the receptivity of the pulp to the latex particles. Still another acid precipitation process depends upon similar treatment of the pulp by means of cationic p'olyalkylene polyamine-halohydrin resins with or without alum as an aid in flocculation of the latex. In some of these processes aging of the pulp suspension in contact with the precipitating or flocculating agent is required. When many of the previously known procedures are used for 2,745,744 Patented May 15-, 1956 'ice incorporation of small amounts of resin as wet-strength additives in paper, the products are difiicult if not impossible to saturate with polymer dispersions, such as the commercially available synthetic rubber latices In accordance with this invention N-basic organicpol'ymer salts that arewater soluble may be used as agents to cause particles. of colloidally dispersed solid material to adhere to cellulose and other fibers in a water suspension. Surprisingly, this property of fiocculating polymer particles is not greatly influenced by change in the hydrogen ion concentration of the water system which contains the pulp fibers and the polymer dispersion. This invention, for the first time, permits the addition of wet strength additives to paper pulp under alkaline or neutral conditions and with little or no adjustment of hydrogen ion concentration. While it is preferred to operate under sub- This invention concerns a process for the production of paper of improved wet strength and high receptivity to saturation by water and aqueous media.
The process permits continuous treatment of the pulp suspended in water prior to sheet formation in the manner described in the following steps:
(a) Mixing of a colloidal dispersion of a hydrophobic polymer with the paper pulp suspension in water (said dispersion being substantially free from protective colloid materials). 1
(b) Mixing with the dispersion of paper stock a water solution of a .poly N-basic organic compound comprising- -an amount of dry polymeric ionic material equal to at least 10% by weight of the dispersed phase added in step (a).
(c) Carrying out the paper making procedure in the usual manner.
The objectives of the invention are most advantageously attained when the steps are carried out in theorder given within the shortest possible time interval provided a' laps of at least five seconds transpires after the additions-before the pulp is drained on the wire of the paper machinei' However, steps (a) and (b) maybe effected simultaneously. Mixing during or after each addition is obv'i ously advantageous.
DEFINITION OF TERMS the water-soluble reaction products of'formaldehyd witlt such materials as guanidine and biuret and their substi-'- tut-ion products as well as water-soluble salts of polymeric nitrogen heterocyclic compounds, including their sula's'titution productsand; the corresponding quaternary nium salts. j Y
The term colloidally dispersed solid material as used herein includes dispersions of resinous and rubber-like polymers such as pure, i. e. deproteinized rubber latex, reclaim dispersions, or synthetic rubber latex and vinyl and acrylic polymers and other materials that are available as stable colloidal dispersions in water. Such materials as natural rubber latex, butyl rubber latex, butadiene-styrene latex of any ratio of butadiene to styrene, butadiene-acrylonitrile copolymer latices and neoprene latices made from 2-chloro butadiene, 1,3 and its copolymers (usually predominantly Z-chloro butadiene) are included. Latices of vinyl chloride copolymers, alkyl acrylate polymers and copolymers such as polyethyl acrylate and other soft and elastic or semi-elastic polymers such as Thiokol, polyethylene, polyvinyl methyl ketone, polystyrene or polytetrafluroethylene are amenable to the process described in this invention.
The term sizing is used to include treatment of paper with 0.25 to of resin or rubbery material to improve its properties of strength, tear resistance, fold resistance or resistance to spreading of inks. Saturated papers are commonly understood to include fibrous webs containing from ten to one hundred fifty per cent of their weight of wax, rubber or synthetic rubbers or resins based on the weight of the paper.
By salts we mean such ionizable compounds as are formed between especially guanidine and also between other organic nitrogen bases and equivalent molar proportions of acids such as hydrochloric, sulphuric, nitric, phosphoric, etc. and such organic acids as acetic, formic, propionic, lactic, etc.
However, in our preferred process using guanidine carbonate we obtain basic conditions for the preparation by the alkaline nature of water solutions of the guanidine compound used. Salts of guanidine such as the chloride which yield acid solutions may be processed by the addition of a suitable base to the solution of guanidine salt.
ADVANTAGES OF INVENTION The invention allows ease and simplicity of operation under wide range of hydrogen ion concentration, hence saving on chemical and control cost, permits use of inexpensive resins and rubbers not usable under the prior art, and makes available desirable qualities of saturability and neutrality of product that cannot be obtained by any other known method.
Products made according to the process of this invention in which minor amounts of dispersed polymers are added in order to increase the wet strength of the paper are of great utility in the manufacture of:
saturating papers Toweling Napkins Curtains Cheap molded pulp articles Tea bag paper Kraft bag paper Map paper Wrapping and packaging paper Spinning stocks With the incorporation of larger amounts of resinous or rubbery polymers extremely soft, strong, tear resistant papers are formed which previously could not be economically produced. Such stocks are used in the manufacture of:
Masking tape backings Gaskets Shoe covers Wrapping materials for precision machine parts Pulp preforms for molding.
Shoe midsoles and innersoles Book covers Many of the technical difficulties involved in production of the above materials are circumvented by the ease and simplicity of the invention.
We have found that rubber and resinous or rubber-like synthetic polymers, including many which could not be used under the prior art, may be advantageously incorporated into paper, or similar fibers before sheet formation by the use of minor amounts of the salts of N-basic polymers which are water soluble. As little as two and one-half parts per million of the preferred N-basic material in the water in which the pulp was suspended, yielded in a production trial on a paper machine, complete retention of one-half per cent on the weight of paper of a synthetic rubber polymer. The process permits almost instantaneous precipitation of rubber onto pulp fibers. One hundred per cent retention of one-half per cent by weight of the pulp of synthetic rubber-like polymer was obtained with approximately forty-five seconds treatment time during which the pulp suspension flowed continuously from the pulp screens to the wire of the paper machine. The freeness of the pulp subjected to the treatment is virtually unimpaired both as to drainage time on the wire and in saturability of the paper formed from such treated pulp. The rate of wet strength development in paper made from pulp treated by our process is such that machine broke may be repulped without the use of steam or chemicals in the broke beater, yet wetstrength development is as rapid as with the presently used wet-strength treatments. The invention also has marked economic advantages over the prior art in that it permits for the first time application of wet-strength pulp to acidic environment.
The greatest utility of the invention lies in its simplification of incorporation of minor amounts of resinous and rubbery polymers for imparting wet strength to paper, offering better and more inexpensive wet strength 1 paper for the countless uses for this type of product.
However, it may also be used to incorporate relatively large amounts of resinous or rubber-like polymers into pulp prior to sheet formation, offering advantages over the present art in the production of beater impregnated stocks for the shoe trade, for pulp preforms and the many other uses of impregnated paper.
DETAILS OF THE INVENTION Minor amounts only of N-basic polymer precipitating agents need be used according to the invention, preferably from about 0.01 to about 0.2 per cent of the weight of pulp. Such quantities were found highly satisfactory and perfectly sufiicient to yield good retention of many synthetic polymers in amounts necessary to yield a paper of good wet strength. Some beneficial effects may be obtained using as little as one part per million or as much as two thousand parts per million of cationic N-basic polymeric precipitating agent on the water in which the pulp is dispersed. Substantially equal retention of such synthetic polymers dispersed with anionic, non-ionic, or no dispersing agent was obtained under parallel conditions of sheet making using our preferred precipitating agents. Commercial trials were made on a paper machine using threequarters of one per cent of the weight of the pulp of a synthetic rubber in the sheet at a pH of 6.9 and a treat ment time of about forty-five seconds. Precipitation was effected during flow of stock from screens to headb ox by a concentration in the white water of about six and onehalf parts per million (0.15% by weight of dry pulp), of one of our cationic N-basic polymer fiocculating agents. Substantially one hundred per cent retention was obtained in the sheet.
Some of the N-basic polymers which were used to advantage in the practice of this invention precipitate the most commonly used dispersing agents for latices, soaps and sodium salts of sulfonated organic compounds. The flocculating action of such polymers on some latices and dispersions may be due to removal of some or all of the dispersing agent in this manner. However, as will be shown in subsequent examples, equivalent precipitation of flocculation at levels of resin treatment sufiicient for wet strength paper was obtained in latices made with non-ionic dispersing agents (with which our polymers show no such reaction), and of a latex made with no dispersing agent.
Extensive laboratory trials indicate that there is a gradual loss of efiiciency in precipitation of the dispersed polymeric phase onto the pulp fibers as hydrogen ion concentration, temperature and concentration of solids are raised.
Precipitation etficiency varies somewhat with concentration of the dispersed polymeric phase, but only very slightly with temperature. The time required for complete retention of a polymeric dispersed phase by a pulp is not a linear function of the quantity of polymer it is desired to fix onto a pulp, i. e., to bind to the pulp with sufiicient firmness that it is retained in the sheet formed. For example, one-half per cent and one and three-quarter per cent by weight of pulp of a butadiene-acrylonitrile polymer was fixed with one hundred percent etficiency in less than forty-five seconds, but two to three minutes were required to precipitate one hundred percent of the same polymer onto the same pulp.
The process works best with water dispersions of polymers of relatively low water absorption, such as synthetic rubber latices and polyvinyl chloride, and is of least utility with water dispersions of polymers of relatively high water absorption, such as proteins. It shows little or no fiocculating action on water solutions of polyvinyl alcohol, which has hydrophilic properties, but shows excellent flocculating power for deproteinized rubber latex and synthetic rubber latices.
Since the primary object of the invention is to produce wet strength paper of characteristics not available under the present art, limits of study of conditions were largely confined to the range of conditions under which a paper machine could be economically operated. Flocculation of dispersed phases at solids contents of the order of magnitude of fifty p. p. m. solid polymer were carried out in the range of pH values from 4.3 to 8.5 with little detectable difference in time or amount of precipitating material required for flocculation.
The preferred fiocculating agent is produced by reacting formaldehyde with guanidine carbonate at a molar ratio at least one to one, although at least two to one is preferred. The chemical structure of the desired product is not fully understood, but the action of the material in flocculating particles of polymer onto pulp fiber is believed to be due to the presence of a multiplicity of positively charged amino groups linked together into a polymeric electrolyte so that each polymer molecule has many positive charges distributed along its length. Also effective in carrying out the invention is the polymeric electrolyte made by the treatment of polyvinyl pyridine with any lower alkyl halide having an alkyl group of from one to eight carbon atoms, e. g. (Fuoss-Iour. Poly. Sci. 3, 246-63 (1948)). The structure of this material is well known.
All other compounds tested are much less efiective in carrying out the invention, although many are useful and it is believed that the explanation is to be found:
(a) In the large chain length of the above compounds, as effectiveness appears to increase with chain length.
(b) Their high degree of ionization, perhaps influenced by chain length, as effectiveness appears to increase with an increase in the degree of ionization.
In addition to the preferred reagents we have found useful in specialized applications, such N-basic compounds as polyfunctional amine salts including diethylene triamine salts and particularly substituted polyfunctional amine salts. Salts of its higher homologs (e. g. triethylene tetramine and tetraethylene pentamine) are of increasing efliciency as the molecular weight of the compound and its functionality increase. Water soluble polyvinyl amine salts, including substituted polyvinyl amine salts, and the corresponding quaternary ammonium compounds are included in this invention. Also included are water-soluble amino derivatives of cellulose, starch and related materials. Guanidine derivatives of the type of amino guanidine and including substituted guanidine's reacted with formaldehyde to yield water-soluble polymeric salts are effective in this invention, but more costly than our preferred precipitating agent. Quaternary ammonium salts obtained by the reaction of alkyl halides and polymeric amines can be made in great variety. Useful in this invention are those which are water soluble,- particularly those made from polyvinyl pyridine and its copolymers which are readily accessible. Salts of the polymer obtained from reaction of ethylene imine and substituted ethylene imines, with itself are of significant effectiveness, increasing in precipitating power as the molecular weight of the polymer increases. Similar polymers may be formed by a corresponding condensation of trimethylene imine and its substitution products. These are also useful in the invention. Salts of polyfunctional aliphatic amines, such as tetraethylene pentamine, may be used advantageously for the incorporation of polymers dispersed by means of anionic dispersing agents. Such amine salts do not have significant flocculating power for polymers dispersed by means of non-ionic or no dispersing agents.
The polyalkylene amine halohydrin resins are neither useful nor eflicient in the operation of the invention, re quiring fifteen to twenty minutes treatment time to yield retention comparable to that obtained in less than one minute with our preferred precipitating agent.
The exact nature of the reaction product of guanidine carbonate and formaldehyde which is our preferred precipitating or fiocculating agent, is not known. Its polymeric nature is apparent from the appearance of the dried solid, the viscosity of water solutions of the reaction product and the established chemical technology relating to the reaction of guanidine and formaldehyde.
The increase in flocculating power with increase in chain length of guanidine carbonate-formaldehyde with reaction time is shown in the following table and. compared with other less effective reagents:
Cubic Gentig gf ne tii ti to Required to Flo culate 10 Flocculate 10 Precipitant Aqueous Solution cc 0.2% cc. 0.2%5050 0% Solids Acrylonitrile lgggi i' copoly-mer Copolymer Fused 1 Dispersed Xamp 3 with 5% Soap Sodium Chloride 5 5 Ethylene Diamine 1. 2 1.0 Triethylene Tetramine Acetate 0.6 0.5 Tetra Ethylene Pentamine Acetate.-. 0.15 0.1 Guanidine Carbonate-Formaldehyde,
freshly made up 2. 4 5 Heated 30 minutes on steam bath 0. 5 0. 3 Heated 45 minutes on steam bath O. 4 O. 2 Standing 16 hours room temperature 0. 3 0; 4 Heated 10 hours 98-101" 0 0.05 0.05 I
The essential improvement in flocculating efficiency as chain length of the ion bearing molecule increases is shown.
MODIFICATIONS Modifications with regard to resinous or rubber-like materialswhich may be incorporated into cellulosic fibers by means of the invention are easily made. As will be shown later in examples, the sole requirement is that the polymer be in colloidal dispersion in water. The invention is operable with water dispersions made by means of anionic, non-ionic, or no dispersing agent, but operates most efficiently with colloidal dispersions made with anionic dispersing agents.
In imparting increased wet strength to paper, the invention may be most advantageously used with such materials as synthetic rubber polymers which are available as soap-dispersed latices of polymer content of about forty percent by weight. The use of these materials without antioxidant in paper yields a paper with a wet strength development time permitting easy repulping of machine broke without the use of heat or chemicals. The use of other synthetic copolymers in paper is equally effective, but the time for wet strength development of papers containing such materials is not as favorable for most economical operation as that of similar papers containing butadiene-acrylonitrile copolymer without antioxidant. With a normal amount of a typical commercial antioxidant wet strength development of a sheet of paper containing 2% of a copolymer of sixty percent butadiene and forty percent acrylonitrile required almost a year under ordinary conditions of storage, without antioxidant full wet strength was developed in less than six weeks under similar conditions of storage.
METHODS OF OPERATION The most advantageous use of the invention is in the preparation of wet strength paper. This may be carried out by simple addition of the polymer latex and the fiocculating agent (as a water-solution) at conveniently accessible points in the system supplying stock to the paper machine. The above method of operation requires little or no adjustment of the pH of the stock, since pulp bleaching operations are normally alkaline and the only acid pulp produced in large quantity, sulfite, is usually bleached before use. With unbleached kraft, the cooking being alkaline, normal washing of the pulp will yield a stock of acceptable hydrogen ion concentration with little or no chemical addition.
In order to impart desirable wet strength properties to paper by means of the invention, only minor amounts of rubber or synthetic rubber polymers need be used, i. e., quantities of the order of two percent or less by weight. In the use of quantities of polymer of this order of magnitude, if it is desired to preserve the moisture absorption qualities of the sheet, as would be necessary for paper towel stock, the polymer dispersion should be added to the suspension of paper fibers before the fiocculating agent; if such absorption is undesirable the flocculating agent should be added first. However, the utility of the invention is not confined to the addition of such small amounts of polymers to paper stock, since equally good retention of resin by cellulosic fibers may be obtained with amounts of polymer and of pulp of substantially equal weight. Acceptable conditions for fixing relatively large quantities of polymer, fifty to one hundred percent of the weight of pulp, are that the pulp dispersion containing the colloidally dispersed polymer be at approximately one-half percent consistently in the pH range of from about 6.3 to 7.5 and that at least one part of our preferred precipitating agent be used for each fifteen parts dispersed polymer. The optimum results as to reaction time and retention of polymer were obtained at room temperature at a pH of 7.3 with a synthetic rubber polymer dispersed with an anionic dispersing agent.
One of the most important uses of the invention is concerned primarily with the addition of small amounts of resinous or rubber-like materials from colloidal dispersion to paper-making fibers in order to provide wet strength for the finished paper product, while at the same time providing a product which will be receptive to saturation with aqueous polymeric dispersions (especially natural rubber or synthetic rubber-like polymers). In addition, however, the process may be used with minor variations to incorporate relatively large amounts of resinous or rubber-like materials even in amounts substantially equal to the Weight of the fibrous base.
The following examples are furnished by way of further explanation of the invention only and are not to be taken as limiting its scope.
Example I The following example illustrates the basic concept of the invention, the application of several polymers from different dispersions to kraft pulp using three different dispersing agents. In all cases two percent polymer solids in the dry weight of the pulp was used. Obviously some of the polymers used had greater inherent qualities of imparting wet strength to the paper than did certain others. In all cases the White water was as clear as when a control sheet was similarly made up using no polymer dispersion.
The presence of the polymers in the sheets was further confirmed by microscopic examination.
The procedure used for making the hand sheets was as follows: Semi-bleached kraft pulp was beaten to a Schopper-Reigler freeness of seven hundred and fifty cubic centimeters in a one pound Valley beater. The hydrogen ion concentration of the beaten stock was adjusted to a pH of 6.7-6.9 with acetic acid and portions of the stock sutficient to make one thirty-pound sheet (24 36" 480"=30 lbs.) in the hand sheet mold were removed and diluted to 0.08 percent consistency with tap water. The tap water used for dilution had a pH (colorimetric) of 6.8-6.9.
To the portions of diluted stock was added a diluted latex of the polymer to be tested containing two percent of the weight of the dry pulp of the dry polymer. After mixing the latex with the pulp dispersion the precipitating agent in a water solution was added in the amount indicated, the pulp system stirred and a sheet made and dried in the usual manner.
In the table given below G. C. F. indicates the reaction product of guanidine carbonate and formaldehyde as described in Example XII, G. C. F. 11 the reaction product of the same materials as described in Example XIII, PvPyBBr indicates the reaction product of polyvinyl pyridine and n-butyl bromide as described by Fuoss, Jour. Poly. Sci. 2 248-63, (1948), and TEPAAc the product obtained by neutralizing tetraethylene pentanine with acetic acid. The concentration of these flocculating agents in the water from which the sheet was formed is given in the table.
The table lists the results obtained in wet tensile strength of the hand sheets and on control sheets, made in the same way except for the omission of the polymer. G. C. F. was used in the water dispersion of pulp from which the control sheets were formed.
The latices used are described at the end of the table listing results.
All sheets tested contained two percent dry polymer on the semi-bleached kraft pulp.
Kraft Pulp Semi-Bleached Wet Latex Precip; Agent and Gone. Tgg/rsile, Remarks 0.3 2.7 1 yr. after ma g. 0.8 Y
05 C A 1 p. 1. 24 A. 0.99 A 0. 76 A" 0.9 B 0.53 B 0. 35' C l-. 00 G 0.77 D .34 D p. 0.85 D- p. .46 D p. 0. 44 E; p. 1. 22 Do. E 1 p. p. m .33 Do. E TEPAAc, 56 p. p. m. .67 Do. F O. F., 21 p. p. m 1. 52 Do. I PvPyBBr, 1 p. p. m. 0'. 43 Do. F TEPAAc, 56 p. p. m. 0.91 Do. G G C. F., 21 p. p. m 1.17 Do. G PvPyBBr, 1 p. p. m 0.33 Do. G TEPAAc, 56 p. p. m 0. 81 Do. H PvPyBBr, 1 p. p. m 0. 76 Do. A (pH of sys- G. O. F., 21 p. p. m 1.69 Do.
tem 8.5).- A (8 sec. reac- G. C. F 21 p. p. m 1. 36 Do.
tion time of precipitant) No'1'E.The polymer contained monobeuzylether of hydroquinone.
The la-tices used are listed below A-Copolyn1er sixty percent butadiene, forty percent acrylonitrile by weight, five percent on the weight of the polymer, of commercial soap as dispersing agent.
BPolyethylacrylate dispersed by means of five percent sulfonated alcohol, sodium salt.
CCopolymer seventy-four percent butadiene, twenty six percent styrene (both by weight) dispersed by means of five percent commercial soap.
D'High styrene, eighty-five percent, butadiene, fifteen percent copolymer dispensed by means of commercial soap.
EPolyethylacrylate dispersed by means of a polyether alcohol. (Other water-insoluble acrylates having at least 10 rtzaibgn) atoms in the saturated alkyl chain may be substi- F' A copolymer of largely vinylchloride and also vinylidine chloride dispersed by means of commercial soap.
A copolymer of seventy-five percent butadiene. twentyfive percent acrylonitrile dispersed by means of the dispersing potwer6 0315 the acrylonitrile-pH of twenty-eight percent solids HPol'ychloroprene latex soap dispersed.
Example 11 In the following table the wet tensile strength of thirty pound sheets on the same basis of a highly bleached sulfite pulp beaten to seven hundred and fifty cc. Schopper R'cigler freeness containing two percent of the polymers indicated is given. The sheet making conditions, the precipitating'agents used, and the pH of the system were the same as in the preceding example.
two percent by weight Wet Ten- Latex sile; #lln'.
Precip. Agent and Cone.
The latices used in these experiments and: the abbreviat'ions used in the above table for the latices and the precipitating agent are as described and explained in the preceding example.
Example III Hand sheets were made as described in preceding exam ples under the same conditions previously used, but substituting a bleached ground wood pulp for the kraft and sulfite previously used. This ground wood pulp had a 10 freeness of five hundred and ninety cubic centimeters Schopper R'eigler. The latices and precipitating agents and the abbreviations used therefor are described in Example I In all cases, as in preceding examples, twopercent of the polymer by weight of the dry pulp was used;
Latex Precip. Agent and Gone. m a 9 G. G. F., 21 p. p. m 0.1 G. C. F., 21 p p. m. 1.15 PvPyBBr, 1 p. p. m. 0.99 TEPAAc, 56 p. p. m. 0.77 G. O. F., 21 p. p: m 0.82 PvPyB r, 1 p. p. m. 0 'IEPAAc, 56 p. p. m 0. 72 G. O. F., 21 p. p. m 1-. 27 PvPyB r, 1 p. p. m. 0.91
Example IV The following example illustrates the formation of sheets containing equal weights of synthetic rubber and pulp.
To a dispersion of 8.9 grams of semi-bleached kraft pulp of seven hundred and fifty Schopper Reigler cubic centimeters freen'ess' in 1.8 liters of water was added twenty three cubic centimeters, sixty percent butadiene, fifty percent a'crylonitrile' copo'lymer latex at a solids content of 38.8%. After mixing the latex with the pulp slurry sixty cubic centimeters of a thirty percent solution of guanidine carbonate-forr'naldehyde' polymer precipitating agent was added and stirred gently with a spatula. The resulting mixed dispersion was allowed to stand for five minutes, diluted to about one-quarter per centconcentration and formed in a sheet seventeen inches square in a sheet mold. The white water from the sheet was clear and the drainage time of the sheet was not noticeably longer than that of a sheet of similar weight 17.8' gm. containing no resin.
Example V To 8.9 grams of a semi-Bleached kraft pulp of a freeness of six hundred and twenty-five cubic centimeters (Schopp'er Reigler) dispersed in 1.8 liters of water was added twenty-six cubic centimeters of an aqueous dis persion of'p'olysty'rene containing thirty-four percent by weight of polystyrene dispersed by means of commercial soap in an amount equivalent to three percent by weight of the dry weight of the dispersed polystyrene. After mixing the latex and the pulp suspension, the resulting slurry was added to' a sheet mold seventeen inches square containing approximately 1.8 liters of water above the wire. Precipitation was brought about by the addition of 1.8 grams ofguanidine carbonate-formaldehyde condensation' polymer dissolved in two hundred cubic centimeters of water. The precipitating agent solution was mixed with the slurry and after about thirty seconds of mixing the" sheet was formed. Drainage was slower and formation' ofthe sheet was not as even as in previously made sheets containing a much lower amount of added resin or rubbery material. Retention of the polystyrene'was almost" complete. The resulting sheet was dried, folded several times and pressed for ten minutes between polished sheets of stainless steel at approximately three hundred and fi ft'y' pounds per square inch at a temperature of one hundred and fifty degrees centigrade. It was cooled under pressure and when removed from the press had formed a dense, hard, somewhat brittle laminate.
Example VI This illustrates the sizing of paper with resin under basic conditions. Two grams of semi-bleached kraft pulp at a Schopper Reigler freeness of eight hundred and thirty cubic centimeters Was dispersed in eight hundred cubic centimeters of water. and a water dispersion of rosin size comprising one tenth of a gram solids was added and mixed with the pulp sus ension. The hydrogen ion concentration of the pulp rosin soap dispersion corresponded to a pH of 8.7. Precipitation at any lower hydrogen ion concentration at which the rosin sizes are normally stable is, of course, possible. To this dispersion was added three cubic centimeters of an aqueous solution of the condensation product of guanidine carbonate and formaldehyde comprising two tenths of one percent solids. The pulp dispersion was stirred moderately, allowed to stand for five minutes and a sheet formed, couched and dried. Examination of this sheet showed that good sizing of the sheet had been obtained in the method described above; it had the feel and rattle of sized paper and no significant ink spread when written on. The rosin size in the above example was a complex mixture obtained by treating rosin with sodium carbonate. However, sodium carbonate is only the preferred member of the group of alkaline materials which react with rosin to yield water-soluble or water-dispersible compounds, for instance potassium carbonate or sodium hydroxide.
Example VII On a paper machine trial the process for imparting wet strength was carried out as follows:
Semi-bleached ltraft pulp of brightness of forty-two to O forty-three percent and beaten to a Green freeness of four hundred and thirty cubic centimeters comprised the furnish. The rubbery copolymer was that identified as A in Example I and was added to the pulp suspension at the consistency regulator box at a solids content of the latex of 3.8 percent and at ratios of three-quarter and one and one-half percent of dry rubbery copolymer to dry pulp. The pulp suspension had been adjusted to a hydrogen ion concentration equivalent to a pH of 6.8-7. The guanidine carbonate-formaldehyde condensate was added at a concentration of three tenths of one percent solids in water solution to the stock just after the screens and was allowed to carry out its precipitating action on the rubbery copolymer during the approximately forty-five seconds required for any portion of the stock to flow from the screen to the slice of the paper machine. The hydrogen ion concentration of the white water corresponded to a pH of 6.8 to 7.2 during the course of the run. The calculated concentration of the precipitating agent in the stock as it flowed to the paper machine was about 6.5 parts per million, since the stock consistency ranged during the run from twenty one to twentysix hundreds of one percent.
Retention of the rubbery copolymer by the sheet of paper formed on the paper machine was substantially one hundred percent, since no evidence of the presence of rubbery copolymer in the white water or on any part of the paper machine could be found after four hours of continuous operation. The saturability of the paper containing rubber copolymer added by means of our process was substantially identical to that of the same sheet made up without any addition of rubber copolymer. A comparison of wet tensile strength and dry tensile strength obtained by the addition of rubbery copolymer and the pickup of latex solids by the papers under identical condition of impregnation with latex as shown in the following table:
- All results are averages of ten tests.
Example VIII The application of the invention to the improvement of the wet strength of paper wherein the operations were 12 carried out on a paper machine under basic conditions is illustrated by the following:
The furnish consisted of kraft pulp of a brightness of fifty-two-fifty-five percent and the pH of the contents of the beaters was not lowered by any addition of chemical. To the stream of pulp slurry as it was removed from the heaters was added rubbery copolymer latex A described in Example I (at a rubbery copolymer content of three percent by weight) at such a rate that the resulting pulp slurry contained about one part of rubbery copolymer by weight to two hundred parts of dry pulp by weight.
After dilution of the resulting pulp slurry containing rubbery copolymer there was added an aqueous solution comprising one percent by weight of the guanidine carbonate-formaldehyde-condensation product described in Example XIII in such an amount that the dry guanidine carbonate-formaldehyde-condensation product contained therein was equal to from twenty to twenty-two percent by weight of the weight of the dry rubbery copolymer contained in the pulp slurry.
The above operations were carried out in the paper machine stock preparation system and any given portion of the stock reached the paper machine in approximately forty-five seconds after the addition of the guanidine carbonate-formaldehyde solution.
The operation of the paper machine was carried out in the normal manner and no deposition of rubbery copolymer except in the paper could be found. The white water showed no rubbery copolymer held in suspension when concentrated to small volume and the raw white water directly from the Wire showed a pH of 7.9 colorimetric. The paper made had a wet tensile of 0.72 pound per inch after heating for one hour in a circulating air oven at one hundred ten degrees centigrade, when tested after conditioning at standard conditions, and a sample of the same paper made without the addition of the rubbery copolymer had a wet tensile of 0.11 pound when similarly tested.
Example IX The conditions, and pulp of Example I (using Latex A) were duplicated with the exception that polyethylene imine hydrochloride in an amount equal to twice the weight of guanidine carbonate used in Example I was employed as precipitating agent. The time required for precipitation was greater than in Example I but otherwise results were substantially the same.
Example X The least advantageous conditions for the application of the invention are illustrated in the following example where in a somewhat hydrophilic material, polyethylacrylate, dispersed by means of a non-ionic dispersing agent (a polyether alcohol) was incorporated into paper pulp. Sheets were made up as outlined in Example I using the same pulp and substituting the polyethylacrylate dispersion for the polymers used in that example. The volume of dispersion used contained a weight of dry polymer equal to the weight of the dry pulp used or 8.9 grams. Sheet making procedure was as outlined in Example I using three different flocculating agents. Although retention was not complete with any of the fiocculating agents, useful products were obtained. The retention obtained as shown by extraction of the dried sheets is shown in the following table:
13 a Example XI Hand sheets of thirty pound basis weight (twenty-four by thirty-six inches, four hundred eighty sheets) were made up of kraft pulp of a brightness of fifty and of seven hundred fifty cubic centimeters Schopper-Reigler freeness.
Hand sheet A was made up as described in Example I.
Hand sheet B was made up as described in Example I except that the order of addition of precipitating agent and latex were reversed, that is, the cationic polymer solution Was added and mixed with the pulp before the addition of the rubbery copolymer.
Hand sheet C was made up as described except that the latex was omitted. Saturation times of these hand sheets were determined by flotation on a water dispersion containing thirty-three percent dry weight of a mixture of synthetic rubber-like copolymers, dispersed by means of commercial soap and one-half of one percent of the weightof rubbery copolymers of a commercial wetting agent consisting la'rgerly of sodium lauryl sulfonate. The saturation times shown in the following table were taken as the time required for penetration through the sheet of the latex mixture from the wire to the felt side.
Saturation Time 1 to 2 seconds. 40 to 50 seconds. Less than 1 second.
Example XII One hundred and twenty-one grams of commercial guanidine carbonate, one hundred grams of commercial thirty-seven percent formaldehyde are'mixed and heated with occasional stirring, on an electric hot plate.
The initial hydrogen ion concentration of the mixture was equivalent to a pH of about 8.5.v At the end of four hours of heating, the reaction vessel contained a viscous (when hot) transparent mass and the-pH had fallen to about 7.5. Water was added and stirred to dissolve the reaction product. All during the heating, there was evolution of carbon dioxide from the reaction, and it was to facilitate the escape of this material that water was added. After additional heating for one and one-half hours at the boiling point of the solution, the pH was about 7.2 as measured with pH paper, andheating was discontinued.
The product obtained was an almost colorless solution containing thirty-seven percent solids. The viscosity of this thirty-seven percent solution was not substantially greater than water. The dry reaction product was a transparent, very slightly colored solid, softening below eighty degrees centigrade.
Heating of the reaction mixture more strongly than A was done in the above example by allowing substantially all the water to evaporate from the reaction components yields a light yellow, somewhat brittle solid with a softening point above one hundred degrees centigrade.
Heating the reactants in the above proportions on a steam plate yielded, upon heating for about ten hours, a product having a softening point below room temperature which was colorless and transparent.
The reaction products obtained by the methods given above were substantially equivalent in precipitating power when used as described in this disclosure; yet, neither guanidine carbonate nor formaldehyde alone or in combination in an unreacted condition have significant precipitating action unless added in concentrations much greater than is required for their reaction products as described above.
The product we desire to use is a water soluble condensation polymer of guanidine carbonate and formaldehyde. The above examples are based on the use of commercial materials and some variation may be expected due to slight differences in materials or reaction conditions.
Example XII] The precipitating agent used in Examples:V-II and VI-I-I was prepared substantially as described in Example XII except that the ratio of aqueous thirty-seven percent formaldehyde toguanidine carbonate was two to one'by weight and heating was by means of steam at eight pounds gauge pressure in ajacketed kettle for ten hours.
The guanidine carbonate used in all of these examples was a commercial product obtained from American Cyanamid Company and was described by the supplier as being. of the following composition:
Guanidine carbonate "percent--. 96-98 Moisture percent max 0.5 Ash percentmax.. 0.2 Insoluble matter (water) percent max" Q2 This material containe dLtwo to. three percent of 'various triazines, including ammelin'e and ammelide. A maximum of one-quarter of a percent of. sulfate as. S03 was also present.
During the heating process the reaction mixture jelledi However, upon the addition of water, solution was easily regained and cooking continued. Water" was added at two other times during the ten'hours cooking period and heating was continued until one drop of one part by weight of reaction mixture diluted with fifty parts of water would cause immediate. clouding of a' water" dispersion of the latex used in Example I when added to two hundred cubic centimeters of a water dispersion of the rubbery copolymer containing fifty parts per million of solids. The jacketed kettle was open to the air and only intermittent agitation of the reaction mixture was maintained duringthe heating. period. There was some loss of formaldehyde from the reaction mixture during the heating period and much foaming; Therefore, the volume of the reaction vessel should be at least twice that of the cold unreacted materials.
A precipitating agentequival'ent to that described above was prepared from another lot ofv commercial. gua'n'idine carbonate which contained no triazines by' the same method of preparation outlined above.
Example XIV As mentioned earlier, the guanidine carbonate-formaldehyde reaction product of these examples is only one of several possible precipitating agents. It is to be preferred for reasons of precipitation. efficiency, economy and ease of preparation and stability upon storage at ordinary conditions. The substantial equivalency of guani-dine salts other than thecarbonate and of substituted. g-uanidines and of such materials as biuret when reacted with formaldehyde as outlined in. previous examples is illustrated in the following table. Sheet making was carried out as described in Example- 1. using two percent of polymer latex A solids on the weight of dry pulp with thesubstitution of the indicated materialfor the: guanidinc carbonat'e-formaldehyde.
Precipitant- Amount of Preciplt'ant Biuret-HCHO 2.5 cc. 0.4%water solu...
Example XV The test is carried out in the following manner: To 400 ml; of approximately 50 p. p. m. polymer dispersion is added one drop of twenty-five percent water solution of fiocculating agent and the dispersion containing the flocculating agent is stirred gently with a spatula. The time required for opacity or deep opalescence to develop with the dispersion is a measure of the etficiency of the flocculating agent. A readily discernible opalescence is required, the minimum for reasonable retention in the pulp.
The table given immediately below shows the results of tests by the procedure outlined above, for several polymeric latices with poly N-basic flocculating agents of four types.
dispersion, in which said non-fibrous material is incorporated along with said fibers.
2. The product of claim 1.
3. A process as defined in claim 1 in which the N-basic organic polymer comprises an aldehyde reaction product of a guanidine carbonate.
4. A process as defined in claim 1, in which the polymer precipitating agent comprises a substantially neutral reaction product of substantially one mol guanidine salt and at least one mol aldehyde.
5. A process as defined in claim 1, in which the nonfibrous material is a hydrophobic polymer.
6. A process as defined in claim 1, in which the guan- Dispersion Flocoulating Agent Result of Addition Guanidine Carbonate-formaldehyde Polyvinyl amine HCI Tetraethylene pentamine ace Polyvinyl pyridim'um butyl bromide Guanidine Oarbonateformaldehyde...
Polyvinyl pyridinium N-butyl bromi Tetraethylene pentamine acetate..- Guamdine carbonate-formaldehyd Polyvinyl pyridinium butyl bromid XXIX do Tetraethylene pentamine acetate..- XXX Polychlioro butadlene 1.3 (Neoprene) soap dis- Guanidine carbonate-formaldehyde Opaque 5 sec perse XXXI do Polyvinyl pyridinium butylbrornide do 5 sec XXXII do Tetraethylene pentamine acetate do 5 sec. XXXIII Buld.%!)l9 acrylonitrile no dispersing agent (latex Guanidine carbonate-formaldehyde Deep Opalescent see p XXXIV do Polyvinyl pyridinium butyl bromide o 30 sec XXXV -do Polyvinyl amine HGl No action XXXVI do Tetraethylene pentamine acetate do XXXVII. Butaditene Aerylonitrile non-ionic dispersing Guanidine carbonate formaldehyde Deep OpalescenL. 30 see.
agen XXXVIII... do Polyvinyl pyridinium lt 30 sec. XXXIX do Tetraethylene pentamine acetate No action XL do Polyvinylamine HCI do XLL. Carnauba wax triethanolamm oa Guanldine carbonate-formaldehyde Opalescent 30 sec. XLII Parafiin wax sulionated alcohol dispersing agentdo rio 30 sec.
Polyethyl acrylate sulionated detergent -do Opaque 5 see. do Polyvinyl pyridinium salt r do 5 sec. Polyvinyl amine Hm 5 sec. Tetracthylene pentamine -do 5 sec. Guanidine carbonate-formaldehyde. Opalescent 10 sec. Polyvinyl pyridinium butyl bromide. d 10 sec.
1 Acrysol G. S. is said to be a sodium salt of polyacrylic acid.
The above description of the invention shows its essential features and its application to the incorporation of resins into fibrous webs prior to formation of sheets. The essential improvement in flocculating efiiciency as chain length of the ion bearing molecule increases is shown.
The purpose of the invention as outlined above to improvethe art of incorporating polymeric materials into paper prior to sheet formation by means of polymeric cationic materials which are water-soluble has been described and illustrated. The invention includes in its spirit many embodiments not specifically listed above and is limited only by the prior art.
The claims are:
1. A process for making felted fibrous webs composed of fibrous and non-fibrous material comprising the steps of: a. Mixing an aqueous anionic colloidal dispersion of non-fibrous material, with a water dispersion of fiber comprising from about one-fifth of one per cent to about one hundred percent hydrophobic material based on the weight of said fiber; and in the presence of said material b. Adding as the essential precipitating agent from about one part to about two thousand parts per million parts of dispersion and added non-fibrous material of a precipitating agent comprising an aqueous solution of a water-soluble poly-N-basic polymer salt of a strong base and not surface active each molecular unit having at least three basic nitrogen groups recurring along the polymeric chain, said solution of poly-N-basic salt having a pH above about 4.3, thereby precipitating said dispersion; and c. Forming a web from said precipitated Tetraethylene pentamine acetate No action idine salt is a guanidine aldehyde condensation product salt.
7. In a paper making process wherein an emulsion is added to the furnish and subsequently coagulated on the individual fibers comprising the furnish, the improved method comprising, coagulating the emulsion with guanidine formaldehyde condensate as the essential precipitating agent. I I
8. A method of paper manufacture comprising the steps of, first adding an emulsion to the fibrous beaten pulp suspension and then incorporating in the thus-treated suspension as the essential precipitating agent guanidine formaldehyde condensate in an amount suflicient to coagulate the emulsion on the beaten fibers of the pulp.
9. A method of paper manufacture comprising, at the beater, beating the fibrous pulp suspension to a workable consistency, adding an emulsion to the beaten pulp suspension, agitating the mixture to produce a homogeneous mixture, and coagulating the emulsion on the fibers with guanidine formaldehyde condensate as the essential precipitating agent.
10. The method of producing emulsion-treated paper products comprising, beating the fibrous pulp suspension to a workable consistency, adding emulsion to the beaten pulp suspension, adding as the essential precipitating agent guanidine formaldehyde condensate to the mixture in an amount sufiicient to coagulate the emulsion, and sheeting the emulsion-treated pulp on a paper machine.
ll. The method of producing emulsion-treated paper products comprising the steps of beating the fibrous pulp suspension to a workable consistency, maintaining the pH of the pulp suspension at or slightly above seven, subsequently adding an emulsion to the beaten pulp suspension, adding as the essential precipitating agent guanidine formaldehyde condensate to the mixture in an amount sutficient to precipitate the emulsion on the beaten fibers, and then sheeting the pulp on a paper machine.
12. A paper making process comprising the steps of producing a pulp suspension of the desired consistency, incorporating in the pulp suspension an emulsion to be coagulated on the pulp fibers, and incorporating as the essential precipitating agent guanidine formaldehyde condensate in the pulp suspension to coagulate the emulsion on the pulp fibers.
13. A paper making process comprising the steps of producing a pulp suspension of the desired consistency, incorporating in the pulp suspension an emulsion to be coagulated on the pulp fibers, and incorporating in the pulp suspension as the essential precipitating agent the reaction product of formaldehyde and a compound of the group consisting of guanidine carbonate and guanidine nitrate to coagulate the emulsion on the pulp fibers.
14. A paper making process comprising the steps of producing a pulp suspension of the desired consistency, incorporating in the pulp suspension an emulsion to be coagulated on the pulp fibers, and incorporating in the pulp suspension as the essential precipitating agent the reaction product of formaldehyde and a compound producing guanidine ions in solution to coagulate the emulsion on the pulp fibers.
15. A paper making process comprising the steps of producing a pulp suspension of the desired consistency, incorporating in the pulp suspension an emulsion to be coagulated on the pulp fibers, and incorporating in the pulp suspension as the essential precipitating agent the reaction product of formaldehyde and a compound of the group consisting of guanidine carbonate, guanidine chloride, guanidine sulphate, guanidine phosphate, guanidine acetate, guanidine formate, guanidine propionate, guanidine lactate and guanidine nitrate to coagulate the emulsion on the pulp fibers.
16. A process as defined in claim 1 in which the N-basic organic polymer comprises a Water-soluble quaternary ammonium salt of a polyvinyl amine.
17. A process as defined in claim 1, in which the N-basic polymer comprises a water-soluble aldehyde reaction product of a substituted polyvinyl amine wherein there are from one to two substitution groups, each comprising from one to two carbon chains.
18. A process as defined in claim 1, in which the cationic N-basic organic polymer comprises a water-soluble salt of a polyvinyl amine.
19. A process as defined in claim 1, in which the cationic N-basic polymer is a Water soluble ammonium salt reaction product of a vinyl pyridine polymer and a lower alkyl halide.
References Cited in the file of this patent UNITED STATES PATENTS 1,992,589 Tucker Feb. 26, 1935 2,330,084 Scott Sept. 21, 1943 2,343,090 Smith Feb. 29, 1944 2,343,095 Smith Feb. 29, 1944 2,375,245 Pretzel May 8, 1945 2,488,515 Sherman et al Nov. 15, 1949 2,492,702 Neubert et a1. Dec. 27, 1949 2,563,897 Wilson et al Aug. 14, 1951 2,601,597 Daniel et a1 June 24, 1952 2,601,598 Daniel et al June 24, 1952 2,601,671 Wilson et al June 24, 1952 2,668,111 Lindquist Feb. 21, 1954