Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/41—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups
  • D21H17/42—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds containing ionic groups anionic
  • D21H17/43—Carboxyl groups or derivatives thereof
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/27—Web or sheet containing structurally defined element or component, the element or component having a specified weight per unit area [e.g., gms/sq cm, lbs/sq ft, etc.]

Definitions

• the present invention is concerned with wet-strength papers and a new and improved process for the production of papers having improved wet-strengths.
• the salts are those of monovalent metals, such as the alkali metals, ammonia, and watersoluble mono-amines, such as diethylamine, triethylamine, diethanolamine, triethanolamine, and morpholine.
• the ammonium salts are preferred because of the volatility of the ammonia on drying of the impregnated papers and low cost. Since maleic acid and aconitic acid are polycarboxylic acids, neutralization with ammonia and amines can produce salts of partial amides, such as the salt of maleamic acid. Such salts are included herein.
• the types of papers with which the present process is concerned are those having a basis weight between 10 and 65 lbs. for a 500 sheet ream in which the sheets are 24" x 36".
• the cellulose fibers (wood pulps) from which the papers are made must also be highly beaten so that they have Canadian freeness values in the range of 260 to 455 cc. They may be sized papers and particularly those sized with rosin in conventional manner using alums such. as the conventional papermakers alum.
• the amount of rosin sizing may be that which is customary, namely from 0.2% to 2% by weight of the rosin based on the weight of fibers in the paper.
• Such papers may comprise, for example, from 5% to 95% of one or more of the artificial fibers mentioned in admixture with 95% to 5% respectively of well-beaten wood pulp fibers (Canadian freeness between 260 and 455 cc.).
• the papers obtained by the process of the present invention are adapted when finished to be employed as wrapping papers (when prepared from sized stock) or as tissue papers including toilet tissue, toweling, creped or atent 3,017,291 Patented Jan. 16, 1962 ice not, diapers, and for other moisture-absorbent uses (when prepared from unsized stock).
• the impregnated papers of the present invention are also adapted to be subjected to subsequent treatments with aqueous media, as in saturation or impregnation with aqueous dispersions or suspensions of other gums, resins, pigments, fillers, and the like, since-the products of the present invention have excellent wet strength which helps them to withstand the forces normally encountered during such wet treatments.
• the copolymer is largely formed of polymerized units of acrylonitrile or esters of acrylic or methacrylic acid.
• the polymer may contain 90 to 97% by weight of an ester of acrylic acid with a lower alcohol having from 1 to 4 carbon atoms, such as methyl acrylate, ethyl acrylate, or butyl acrylate.
• the copolymer may contain units of higher alcohol esters of acrylic acid such as cyclohexyl acrylate, n-hexyl acrylate, amyl acrylate, 2-ethyl-hexyl acrylate, t-octyl acrylate, decyl acrylate, dodecyl acrylate, hexadecyl acrylate, or octadecyl acrylate.
• higher alcohol esters of acrylic acid such as cyclohexyl acrylate, n-hexyl acrylate, amyl acrylate, 2-ethyl-hexyl acrylate, t-octyl acrylate, decyl acrylate, dodecyl acrylate, hexadecyl acrylate, or octadecyl acrylate.
• the copolymer may contain units of acrylonitrile or of lower alkyl esters of methacrylic acid, such as methyl methacrylate, ethyl methacrylate, or butyl methacrylate, or even higher alkyl esters of methacrylic acid such as the cyclohexyl and other alkyl methacrylates corresponding to the higher alkyl esters of acrylic acid mentioned hereinabove.
• the copolymer may also comprise up to 60% by weight of vinyltoluene (the ortho, meta, or para isomers or any mixture thereof), the balance being made up of the acid (or salt) units and acrylonitrile or acrylic acid or methacrylic acid ester units.
• the copolymer may have any molecular weight from about ten thousand up to as high as about ten million.
• the copolymers preferably have molecular weights of about 500,000 (viscosity average) up to as high as several million.
• the emulsion procedure is employed, the emulsifier being used in a proportion of about /2% to 6% based on the weight of monomers (total).
• Conventional aqueous emulsion polymerization techniques are employed.
• Water-soluble initiators may be used such as the alkali metal or ammonium persulfates in amounts from 0.10% to 3% on the weight of the monomers.
• a redox system in which the persulfate or like initiator is used in conjunction with a reducing agent such as sodium metabisulfite in about the same proportion as the initiator.
• a promoter such as small proportions of metal ions such as copper, iron, or the like, may be used.
• the polymerization may be effected as a batch system or by continuous addition of the monomers to the aqueous solution containing initiator, reducing agent, and promoter. Generally, it is unnecessary to heat the polymerization system, and in many cases it may be desirable to cool the system to control the temperature and maintain it between room temperature and C. Agitation during the polymerization is generally desirable but may be omitted.
• the amount of water may be selected at the beginning of the polymerization procedure with reference to the amount of comonomers to be copolymerized so that any desired concentration on the order of 25% to 50% or more of copolymer is obtained in dispersed condition in the reaction vessel.
• copolymers of lower molecular weight are desired, there is used in the polymerization medium about 0.2 to 5% of a chain-transfer agent, such as a compound of the following group: long-chain alkyl mercaptans, e.g., t-dodecyl mercaptan, isopropanol, isobutanol, long-chain alcohols, e.g., laurylalcohol, t0ctyl alcohol, CCI C Cl and CBrCl
• a chain-transfer agent such as a compound of the following group: long-chain alkyl mercaptans, e.g., t-dodecyl mercaptan, isopropanol, isobutanol, long-chain alcohols, e.g., laurylalcohol, t0ctyl alcohol, CCI C Cl and CBrCl
• the copolymer dispersion may be applied in the acid or salt
• a neutral or alkaline pH between about 7 and 8.5 is used as this has the advantage of causing less corrosion of the equipment used for application to the paper.
• the copolymer dispersion is originally prepared or diluted to a concentration of about 0.5% to 32%, preferably about 2 to by weight of the copolymer for application.
• the aqueous dispersion of the copolymer is applied to the paper by simply dipping or immersing the paper therein while the dispersion is at a temperature of 70 to 140 F.
• the paper may proceed continuously through such aqueous copolymer dispersion. For example, it may be passed through such a dispersion in a size press immediately following the normal paper drying drums. Of course, the paper proceeds from the size box into a final drier.
• the wet pickup is generally about to 50% cold or up to 80% if heated so that the concentrationof the copolymer dispersion employed with sized papers should be at least about 2 to 4%.
• the paper may be formed from a wide variety of materials. Thus, it may be a kraft pulp, rag pulp, soda, sulfate, groundwood, sulfite pulp, or alpha pulp. Besides employing the normal wood pulp fibers, the paper may be formed of cotton linters and, if desired, the wood or cotton fibers may be used in admixture with fibers from other sources such as jute, hemp, sisal, rags, strings, chopped canvas, and so on.
• the finished paper products may be employedas filter papers, disposable diaper fillers, toilet tissue, paper toweling, bibs, and various wrapping materials.
• the normal drying equipment employed in conventional papermaking machinery is adequate for drying the paper after impregnation with the copolymer dispersion.
• the process can be employed as an on-machine size press coating operation.
• the paper may be treated in an offmachine converting process by passing the paper through asaturating bath (size tub) and then dried and/ or creped on a. drum drier or other drying equipment.
• the copolymers When the copolymers are prepared with relatively little emulsifier present and it is applied in the acid form or in the form ofv an ammonium or volatile amine salt, the application of the copolymer actually serves not only to improve wetstrength but also sizes the paper when unsized paper is the initial starting material.
• the copoly mer especially when in the form of an ammonium or volatile amine salt, after drying down to the insoluble form on the impregnated sheet reduces the penetration of water and/or ink.
• wet-strength resins conventionally employed require either a high temperature cure (in excess of the temperature available in the con ventional paper-drying machinery) or require ageing for as much as one month in order to develop a full wetstrength obtainable therefrom.
• Such wet-strength resins of thermosetting aminoplast type also need a low pH on the acid side to facilitate the cure or development of the wet-strength on ageing.
• the copolymer dispersions of the present invention can be applied at a pH of about 7 to 10 where less likelihood of corrosion on the machinery is encountered.
• copolymer dispersions of the present invention are the fact that they need not be applied at higher temperature than 140 F. or even above 70 F. (normal room temperature) to provide good impregnation and pickup, whereas the customary thermosetting aminoplast resins generally have to be at a temperature of 180 F. at the point of impregnation in order to provide efficient pickup by the paper. Also, the copolymer dispersions are of relatively low viscosity so that thorough, uniform impregnation of the paper is readily obtained.
• the copolymers of the present invention provide an improvement in wet-strength immediately on drying which is from 50 to greater than the wet-strength obtained with conventionally employed thermosetting aminoplast resins even after 28 days of ageing required for the substantially full development of wet-strength with such aminoplast resins.
• thermosetting aminoplast resins are applied at about 14% solids at about C. at an acid pH of about 4.5 with alum or hydrochloric acid. They have a tendency to gel at this temperature and must be promptly used. Batchesof as much as 200 gallons are made up at a time and any left over after a batch wetstrength paper run must be thrown out.
• the aqueous copolymer, dispersions of'the present invention are stable and can be stored indefinitely so that they can be saved for the next wet-strength batch con. version operation.
• thermosetting aminoplast types of. wet-strength resins when applied to sized papers either reduce or destroy the sizing effects.
• the compositions of the present invention either have no efiect on thesize of the sized paper or, when a low proportion of emulsifier is employed for producing the copolymer dispersion, the sizing is increased.
• the tensile strengths are in pounds per inch width of the paper as determined by a conventional Scott IP4 tester. The wet strengths were measured. after a one-hour soak in water at room temperature. The percentwet strengthisthe ratio, expressed as a percentage, of the wet strength to the dry strength.
• EXAMPLE 1 An aqueous dispersion containing 0.5% of a copolymer of 9.0% by weight of ethyl acrylate and 10% of aconitic acid was applied at 70. F. to a bleached sulfite paper obtained from a pulp having a Canadian freeness of 450 ml. by passing the paper through the dispersion and then through rubber squeeze rolls. The impregnated paper picked up 0.5% of copolymer (on fiber) and was dried at.300 F. for 10 minutes. Similarly a solution of the same copolymer was applied at 2.5%, 5%, and 10% concentration providing 2.3%, 4.6%, and 8.9%v of copolymer on the fiber weight of the dried sheet. of the dispersions were in the range 2.53.2.' The results are given in the following Table I:
• EA represents ethyl acrylate
• AcA represents aconitic acid
• MalA represents maleic anhydride.
• the pH values of the dispersions were adjusted with ammonium hydroxide, except in run number 2.
• Example 3 A mixture of equal parts of polyethylene glycol terephthalate fibers (Dacron: 3 denier per filament, A inch) and bleached sulfite fibers (455 cc. Canadian freeness) was formed into paper sheets by the method described in Example 3 above.
• the Dacron fibers were not subjected to any heating but simply mixed with the beaten bleached sulfite pulp before sheet formation.
• the papers were saturated by the technique of Example 1 with aqueous dispersions (about l% to 5.5% concentrations) of the polymers listed in Table IV in which BA represents butyl acrylate, then dried and heated as in Example 3.
• Bleached kraft pulp beaten to a Canadian freeness of 270 cc. was formed into 60 lb. basis weight (3000 sq. feet) paper sheets, treated by the technique of Example 1 with aqueous dispersions (about 2.5% to 5.5% concentrations) of the polymer saturants of Table V, dried, and heated as in Example 3.
• Example 5 (270 cc. Canadian freeness) was formed into sheets of 40 lb. basis weight (3000 sq. feet) and treated by the technique of Example 1 with the aqueous dispersions (about 1% to 12% concentrations) of the polymer saturants of Table VI. This series illustrates the effect of pH of the dispersion. The pH adjustments were made with ammonium hydroxide. It is clearly shown that the levels of wet strength realized by this process are substantially unaffected by pH over the range 2.4 to 8.9. Drying and heating were carried out exactly as in Example 3.
• a method for producing a Wet-strength paper which comprises impregnating throughout its mass a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of 10 to 65 lbs.
• aqueous dispersion containing 2 to 32% by weight of a water-insoluble copolymer of 3 to 10% by weight of units of a member selected from the group consisting of maleic acid, aconitic acid, and salts and anhydrides thereof, and at least one other comonomer selected from the group consisting of acrylonitrile, vinyltolnene, esters of acrylic acid, and esters of methacrylic acid, said dispersion being of low viscosity, having a total solids content not over about 36% by weight, and the amount of copolymer therein being at least about by weight of the total solids content of the dispersion, drying the impregnated paper and heating the impregnated paper at a temperature of 240 F. to 450 F. for a period ranging from about 2 to 5 minutes at the higher temperature to about 30 minutes at the lower temperature.
• a method for producing a wet-strength paper which comprises impregnating throughout its mass a substantially dry paper prepared from cellulose fibers beaten to a Canadian freencss between 260 and 455 cc. and having a basis weight of 10 to 65 lbs. per ream of 500 sheets having a size of 24" x 36" with an aqueous dispersion containing 2 to 15% by weight of an ammonium salt of a copolymer of ethyl acrylate and 3 to 10% by weight of aconitic acid, said dispersion being of low viscosity,
• a method for producing a wet-strength paper which comprises impregnating throughout its mass a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of to 65 lbs.
• aqueous dispersion containing 2 to by weight of a copolymer of a mixture of ethyl acrylate and 3 to 10% by weight of maleic anhydride, said dispersion being of low viscosity, having a total solids content not over about 17% by weight, and the amount of copolymer therein being at least about 85% by weight of the total solids content of the dispersion, and heating the impregnated paper at a temperature of 240 F. to 450 F. for a period ranging from about 2 to 5 minutes at the higher temperature to about 30 :minutes at the lower temperature.
• a method for producing a wet-strength paper which comprises impregnating throughout its mass a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of 10 to 65 lbs.
• a method for producing a wet-strength paper which comprises impregnating throughout its mass a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 45 5 cc. and having a basis weight of 10 to 65 lbs. per ream of 500 sheets having a size of 24" X 36 with an aqueous dispersion containing 2 to 15% by weight of an ammonium salt of a.
• copolymer of butyl acrylate and 3 to 10% by weight of aconitic acid said dispersion being of low viscosity, having a total solids content not over about 17% by weight, and the amount of copolymer therein being at least about 85% by weight of the total solids content of the dispersion, and heating the impregnated paper at a temperature of 240 F. to 450 F. for a period ranging from about 2 to 5 minutes at the higher temperature to about 30 minutes at the lower temperature.
• a method for producing a wet-strength paper which comprises impregnating throughout its mass a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of 10 to 65 lbs.
• aqueous dispersion containing 2 to 15 by weight of a copolymer of a mixture of ethyl acrylate and 3 to 10% by weight of aconitic acid, said dispersion being of low viscosity, having a total solids content not over about 17% by weight, and the amount of copolymer therein being at least about 85% by weight of the total solids content of the dispersion, and heating the impregnated paper at a temperature of 240 F. to 450 F. for a period ranging from about 2 to 5 minutes at the higher temperature to about 30 minutes at the lower temperature.
• a method for producing a wet-strength paper which comprises impregnating throughout its mass a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of 10 to 65 lbs.
• aqueous dispersion containing 2 to 15% by weight of a copolymer of butyl acrylate and 3 to 10% by weight of aconitic acid, said dispersion being of low viscosity, having a total solids content not over about 17% by weight, and the amount of copolymer therein being at least about by weight of the total solids content of the dispersion, and heating the impregnated paper at a temperature of 240 F. to 450 F. for a period ranging from about 2 to 5 minutes at the higher temperature to about 30 minutes at the lower temperature.
• a method for producing a wet-strength paper which comprises impregnating throughout its mass a substantially dry paper prepared from a mixture of fibers consisting of 5 to by Weight of cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and 95 to 5% by weight respectively of artificial fibers, said paper having a basis weight of 10 to 65 lbs.
• aqueous dispersion containing 2 to 32% by weight of a water-insoluble copolymer of 3 to 10% by weight of units of a member selected from the group consisting of maleic acid, aconitic acid, and salts and anhydrides thereof, and at least one other comonomer selected from the group consisting of acrylonitrile, vinyltoluene, esters of acrylic acid, and esters of methacrylic acid, said dispersion being of low viscosity, having a total solids content not over about 36% by weight, and the amount of copolymer therein being at least about 85 by weight of the total solids content of the dispersion, drying the impregnated paper and heating the impregnated paper at a temperature of 240 F. to 450 F. for a period ranging from about 2 to 5 minutes at the higher temperature to about 30 minutes at the lower temperature.
• a method for producing a wet-strength paper which comprises impregnating throughout its mass a substantially dry paper prepared from a mixture of fibers consisting of 5 to 95% by weight of cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and 95 to 5% by weight respectively of artificial fibers selected from the group consisting of regenerated cellulose, cellulose acetate, nylon, polyethylene glycol terephthalate, vinyl resin, and acrylic resin fibers, said paper having a basis Weight of 10 to 65 lbs.
• aqueous dispersion containing 2 to 32% by weight of a water-insoluble copolymer of 3 to 10% by Weight of units of a member selected from the group consisting of maleic acid, aconitic acid, and salts and anhydrides thereof, and at least one other comonomer selected from the group consisting of acrylonitrile, vinyltoluene, esters of acrylic acid, and esters of methacrylic acid, said dispersion being of low viscosity, having a total solids content not over about 36% by weight and the amount of copolymer therein being at least about 85% by weight of the total solids content of the dispersion, drying the impregnated paper and heating the impregnated paper at a temperature of 240 F. to 450 F. for a period ranging from about 2 to 5 minutes at the higher temperature to about 30 minutes at the lower temperature.
• a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of 10 to 65 lbs. per ream of 500 sheets having a size of 24" x 36" impregnated throughout its mass with 0.5 to 32% by weight, based on the dry weight of the fibers, of a dry, insoluble material consisting essentially of a copolymer of 3 to 10% by weight of units of a member selected from the group consisting of maleic acid, aconitic acid, and salts and anhydrides thereof, and at least one other comonomer selected from the group consisting of acrylonitrile, vinyltoluene, esters of acrylic acid, and esters of methacrylic acid.
• a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of to 65 lbs. per ream of 500 sheets having a size of 24" x 36" impregnated throughout its mass with 0.5 to 32% by weight, based on the dry weight of the fibers, of a dry, insoluble material consisting essentially of a copolymer of ethyl acrylate with 3 to 10% by weight of aconitic acid.
• a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of 10 to 65 lbs. per ream of 500 sheets having a size of 2 x 36" impregnated throughout its mass with 0.5 to 32% by weight, based on the dry weight of the fibers, of a dry, insoluble material consisting essentially of a copolymer of ethyl acrylate with 3 to 10% by weight of maleic anhydride.
• a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of 10 to 65 lbs. per ream of 500 sheets having a size of 24" x 36" impregnated throughout its mass with 0.5 to 32% by weight, based on the dry weight of the fibers, of a dry, insoluble material consisting essentially of an ammonium salt of a copolymer of ethyl acrylate with 3 to 10% by weight of aconitic acid.
• a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 and 455 cc. and having a basis weight of 10 to 65 lbs. per ream of 500 sheets having a size of 24" x 36" impregnated throughout its mass with 0.5 to 32% by weight, based on the dry weight of the fibers, of a dry, insoluble material consisting essentially of an ammonium salt of a copolymer of ethyl acrylate with 3 to 10% by weight of maleic anhydride.
• a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 to 455 cc. and having a basis weight of 10 to lbs. per ream of 500 sheets having a size of 24" x 36 impregnated throughout its mass with 0.5 to 32% by weight, based on the dry weight of the fibers, of a dry, insoluble material consisting essentially of an ammonium salt of a copolymer of butyl acrylate with 3 to 10% by weight of aconitic acid.
• a substantially dry paper prepared from cellulose fibers beaten to a Canadian freeness between 260 to 455 cc. and having a basis weight of 10 to 65 lbs. per ream of 500 sheets having a size of 24" x 36" impregnated throughout its mass with 0.5 to 32% by weight, based on the dry weight of the fibers, of a dry, insoluble material consisting essentially of a copolymer of butyl acrylate with 3 to 10% by weight of aconitic acid.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Paper (AREA)

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Cited By (10)

Citations (6)

• 0
  • BE BE586294D patent/BE586294A/xx unknown
• 1959
  • 1959-01-06 US US785128A patent/US3017291A/en not_active Expired - Lifetime
  • 1959-12-31 GB GB44423/59A patent/GB937934A/en not_active Expired
• 1960
  • 1960-01-06 FR FR814988A patent/FR1244284A/fr not_active Expired

Patent Citations (6)

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