Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G73/00—Macromolecular compounds obtained by reactions forming a linkage containing nitrogen with or without oxygen or carbon in the main chain of the macromolecule, not provided for in groups C08G12/00 - C08G71/00
  • C08G73/02—Polyamines
  • C08G73/028—Polyamidoamines
  • C08G73/0286—Preparatory process from polyamidoamines and epihalohydrins
• • 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
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
• • 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
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
  • D21H17/55—Polyamides; Polyaminoamides; Polyester-amides
• • 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
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/11—Halides
• • 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
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
  • D21H17/56—Polyamines; Polyimines; Polyester-imides
• • 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
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/18—Reinforcing agents
• • 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
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
  • D21H25/005—Mechanical treatment

Definitions

• the invention relates to a process for manufacturing paper using resin systems useful for imparting dry-strength to paper.
• polymers that improve a paper's dry-strength are anionic under normal papermaking conditions, e.g., sodium carboxymethylcellulose, carboxymethyl guar, and copolymers of acrylamide and acrylic acid or sodium acrylate.
• cationic resins are used to improve a paper's dry-strength, including glyoxalated cationic poly(acrylamide)s, high molecular weight cationic polyacrylamides, thermosetting polyamidoamine-epichlorohydrin resins and poly(vinylamines). These resin are sometimes applied with anionic co-factors such as poly(acrylamide-co-acrylic acid) or carboxymethyl cellulose.
• a process for enhancement of paper dry-strength without reducing its softness comprises adding a mixture of an anionic carboxymethyl guar, carboxymethyl bean gum or carboxymethyl hydroxyethyl guar with various cationic additives to a bleached pulp furnish.
• the cationic additive may be a polyamidoamine-epichlorohydrin resin. If the cationic additive is a wet-strength resin, the paper's dry-strength is enhanced without reducing its softness. Additionally, the wet-strength of the paper is increased.
• polyamidoamine-epichlorohydrin resins have been used extensively as wet-strength agents for paper. Typically, these resins are prepared in a two-step process.
• a polyamidoamine prepolymer is prepared from a diacid (e.g. adipic acid).and a polyamine (e.g. diethylenetriamine).
• a diacid e.g. adipic acid
• a polyamine e.g. diethylenetriamine
• the polyamidoamine prepolymer is reacted with epichlorohydrin in an amount equal to or greater than the amount of secondary amine groups in the prepolymer.
• a small amount of epichlorohydrin reacts to effect branching of the prepolymer, accompanied by an increase in molecular weight.
• a majority of the epichlorohydrin reacts with the prepolymer to give reactive functional groups, specifically, either aminochlorohydrin or azetidinium.
• the above-described polyamidoamine-epichlorohydrin resins may be used in combination with anionic acrylamides or anionic cellulose derivatives.
• papers containing these combinations exhibit increased wet-strength as well as increased dry-strength, thereby making papers containing these combinations difficult to repulp.
• a dry-strength system for paper comprising: a cationic component and an anionic component
• the cationic component may comprise a cationic polyamidoamine epihalohydrin polymer.
• an intralinker comprises epihalohydrin.
• the epihalohydrin may be selected from the group consisting of epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin and alkyl-substituted epihalohydrins.
• the epihalohydrin comprises epichlorohydrin
• creping adhesive chemicals are typically sprayed directly onto a surface of a rotating drying cylinder (creping drum) which adheres a paper web as it is passed over the drying cylinder.
• the paper web is removed and creped from the surface of the drying cylinder by the use of a creping blade often called a doctor blade.
• Creping adhesive chemicals which are widely used include polyvinyl alcohols, poly(ethylene vinyl acetate) copolymers, polyvinyl acetate, polyacrylates and thermosetting cationic polyamides which comprise the water-soluble reaction products of an epihalohydrin and a polyamide containing secondary amino groups. These chemicals may be used alone or in combination with each other in order to achieve the desired effect.
• U.S. Pat. No. 5,234,547 to Knight, et al. discloses a method of creping a paper which comprises applying a synthetic anionic polymer to the creping drum prior to the application of the paper web to be creped.
• the polymers used are (meth)acrylate polymers and especially polymers of acrylic or methacrylic acid.
• EP-A-0 063 301 relates to water-soluble polymers obtainable by reacting an optionally modified polyamidoamine and/or polyureaamine with a bifunctional dihaloalkylene derivative. This document further discloses the use of said polymers as creping additives in the manufacture of creped paper.
• the creping additives are preferably applied on the paper sheet prior to the contact with the heated surface of the creping drum.
• EP-A-0 739 709 discloses a composition for creping fibrous web comprising a polyamine/epihalohydrin resin creping adhesive and a creping release agent that is a plasticizer for the polyamine/epihalohydrin resin.
• creping adhesive chemicals and particularly those polyamides become crosslinked by the input of thermal energy and dehydration which occur on the surface of the drying cylinder.
• EP 0 856 083 B1 discloses a method of creping a paper which comprises applying directly to the surface of the creping drum a water-soluble, non-thermosetting polyamidoamine or modified polyamidoamine which is crosslinked with an epihalohydrin.
• the invention relates to a process for manufacturing paper having dry strength comprising the following steps: forming an aqueous suspension of cellulose fibers; adding a non-thermosetting crosslinked polyamidoamine-epihalohydrin resin to the aqueous suspension of cellulose fibers; and sheeting and drying the aqueous suspension of cellulose fibers to form paper.
• the non-thermosetting crosslinked polyamidoamine-epihalohydrin resin comprises a reaction product of a polyamidoamine and an epihalohydrin and wherein the epihalohydrin to amine is in a ratio of less than 0.10:1 on a molar basis, preferably, the epihalohydrin to amine is in a ratio in the range of about 0.01:1 to less than about 0.10:1 on a molar basis.
• the polyamidoamine has a molecular weight as measured by its reduced specific viscosity (RSV) of greater than 0.13 dL/g prior to reaction with the epihalohydrin.
• the polyamidoamine of use in forming the non-thermosetting crosslinked polyamidoamine-epihalohydrin resins comprises a polyalkylene polyamine having at least two primary amine groups and also at least one secondary and/or at least one tertiary amine group.
• the polyamidoamine may be selected from the group consisting of diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), iminobispropylamine (IBPA), N-methyl-bis-(aminopropyl)amine (MBAPA), bis-hexamethylenetriamine (BHMT) and mixtures thereof.
• the polyamidoamine is diethylenetriamine (DETA).
• the epihalohydrin of use in forming the non-thermosetting crosslinked polyamidoamine-epihalohydrin resins comprises a epihalohydrin selected from the group consisting of epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin and alkyl-substituted epihalohydrins.
• the epihalohydirn is epichlorohydrin.
• This invention pertains to a method for providing dry-strength to paper while not substantially increasing the paper's wet-strength and comprises a non-thermosetting crosslinked polyamidoamine-epihalohydrin resin.
• the non-thermosetting crosslinked polyamidoamine-epihalohydrin resin comprises a reaction product of an epihalohydrin with a water-soluble polyamidoamine comprised of a dicarboxylic acid and a polyamine containing secondary and/or tertiary amines.
• the epihalohydrin and amine are reacted with one another in a ratio. This ratio expressed on a molar basis of less than 0.10:1 on a molar basis of epihalohydrin to amine.
• the amines of the reaction product may be either secondary or tertiary amines.
• the ratio of epihalohydrin to amine is in the range of about 0.01:1 to less than about 0.10:1 on a m
• One aspect of the invention pertains to dry-strength systems in which a water-soluble polyamidoamine's molecular weight, as measured by the polyamidoamine's RSV, is of greater than 0.13 dL/g prior to reaction with the epihalohydrin.
• a water-soluble polyamidoamine's molecular weight as measured by the polyamidoamine's RSV, is of greater than 0.13 dL/g prior to reaction with the epihalohydrin.
• the polyamidoamine's RSV is greater than 0.13 dL/g but less than 0.19 dL/g prior to reaction with the epihalohydrin. More preferably, the polyamidoamine's RSV is greater than 0.15 dL/g but less than 0.18 dL/g prior to reaction with the epihalohydrin.
• the non-thermosetting crosslinked polyamidoamine-epihalohydrin resin may be a crosslinked polyamidoamine epihalohydrin polymer where the epihalohydrin is selected from the group consisting of epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin and alkyl-substituted epihalohydrins.
• a crosslinked polyamidoamine comprises epichlorohydrin polymer where the epihalohydrin is epichlorohydrin.
• the non-thermosetting crosslinked polyamidoamine-epihalohydrin is a reaction product of a water soluble polyamidoamine comprised of a dicarboxylic acid and a polyamine with secondary and/or tertiary amines present in the polyamidoamine, and an epihalohydrin.
• the RSV of the water soluble polyamidoamine is greater than 0.13 dL/g prior to reaction with the epihalohydrin.
• the non-thermosetting crosslinked polyamidoamine-epihalohydrin resin comprises poly(adipic acid-co-diethylenetriamine) reacted with epichlorohydrin at a mole ratio of less than 0.10 moles of epihalohydrin per mole of amine, preferably at a mole ratio of less than 0.08 moles of epihalohydrin per mole of amine, alternatively at a mole ratio of less than about 0.07 moles of epihalohydrin per mole of amine.
• the polyamidoamine is poly(adipic acid-co-diethylenetriamine).
• the polyamidoamine's molecular weight is controlled by regulating the amount of condensation water removed during the reaction of the dibasic acid and the polyamine.
• the non-thermosetting crosslinked polyamidoamine-epihalohydrin is synthesized by first producing a polyamidoamine and subsequently alkylating and crosslinking the polyamidoamine with epihalohydrin, preferably epichlorohydrin.
• the polyamidoamines useful in the method of the present invention are prepared by the condensation of aliphatic, cycloaliphatic, araliphatic or heterocyclic (preferably aliphatic) polyamines containing at least two amino groups, at least one of which must be a primary amino group, with a saturated or unsaturated aliphatic or aromatic (preferably aliphatic) dicarboxylic acid having from 2 to 12 carbon atoms or their functional equivalents, preferably having from 3 to 10 carbon atoms or their functional equilivalents.
• the dicarboxylic acids and dicarboxylic acid derivatives of use in producing the polyamidoamine comprise two amidization reactive carboxyl (i.e., —COOH) groups.
• Suitable dicarboxylic acids for use in producing the polyamidoamine include the C 2 -C 12 dicarboxylic acids.
• Particular dicarboxylic acids which are suitable include oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, maleic, fumaric, itaconic, phthalic, isophthalic, and terephthalic acids.
• Suitable dicarboxylic acid derivatives for producing the polyamidoamine include dicarboxylic acid esters and dicarboxylic acid halides. Preferred derivatives are the esters.
• Dicarboxylic acid esters which may be used include esters of the C 2 -C 12 dicarboxylic acids, and especially the C 1 -C 3 diesters of these acids.
• Particular diesters which are suitable include dimethyl adipate, dimethyl malonate, diethyl malonate, dimethyl succinate, and dimethyl glutarate.
• the preferred dicarboxylic acid is adipic acid.
• Examples of functional equivalents of dicarboxylic acids include dicarboxylic acid halides.
• Appropriate dicarboxylic acid halides include adipoyl chloride, glutaryl chloride, and sebacoyl chloride.
• a corresponding diester may be used instead of the above mentioned dicarboxylic acids in the formation of the polyamidoamine.
• prepolymerization can be conducted at a lower temperature, specifically, about 110° C. and at atmospheric pressure.
• the byproduct is an alcohol with the type of alcohol dependent upon the identity of the diester. For instance, where a dimethyl ester is employed the alcohol byproduct will be methanol, while ethanol will be the byproduct obtained from a diethyl ester.
• the polyamine comprising a polyalkylenepolyamine may be selected from the group consisting of diethylenetriamine (DETA), triethylenetetraamine (TETA), and tetraethylenepentamine (TEPA), Iminobispropylamine (IBPA), N-methyl-bis-(aminopropyl)amine (MBAPA), bis-hexamethylenetriamine (BHMT) and mixtures thereof.
• DETA diethylenetriamine
• TETA triethylenetetraamine
• TEPA tetraethylenepentamine
• IBPA Iminobispropylamine
• MBAPA N-methyl-bis-(aminopropyl)amine
• BHMT bis-hexamethylenetriamine
• the temperature of the reactants is then raised to about 170° C. and an amount of water contained in the reactants is driven off.
• polymerization to polyamidoamine is essentially complete.
• the aqueous polyamidoamine solution is to have an RSV of greater than 0.13 dL/g at this stage of the process.
• An amount of water is added to the reactor, and the resultant polyamidoamine is stirred until it dissolves in the water.
• the amount of water added to the reactor is not critical to the process.
• An amount of the aqueous polyamidoamine solution is charged into a reaction vessel and diluted with water.
• the total aqueous polyamidoamine solution is not critical.
• An amount of an epihalohydrin, preferably epichlorohydrin, is charged into the reaction vessel to provide a reaction solution having a concentration of about 30% by weight total solids (polyamidoamine+epihalohydrin).
• the temperature of the reactants is raised to about 45° C. to about 70° C., preferably about 52° C. to about 62° C., more preferably about 57 to about 58° C.
• the viscosity of the solution is monitored.
• the reaction is stopped by diluting the polymer with cold water.
• the reaction can be stopped through the adjustment of the pH of the solution with a mineral acid to a pH of about 3.5.
• the final solids of the resultant crosslinked solution is from about 5% to about 30% by weight, preferably about 10% to 25% by weight, more preferably about 15% to about 18% by weight.
• the polyamidoamines or modified polyamidoamines are preferred to react with a substoichiometric amount of epihalohydrin.
• a substoichiometric amount it is ensured that the epihalohydrin completely reacts with the polyamidoamine or the modified polyamidoamine so that no further crosslinking can take place under elevated temperature conditions.
• the epihalohydrin to amine is in a ratio in the range of about 0.01:1 to less than 0.10:1 on a molar basis, preferably in a ratio in the range of about 0.03:1 to about 0.08:1 on a molar basis, more preferably in a ratio in the range of about 0.05:1 to about 0.07:1 on a molar basis.
• any functional groups which remain after crosslinking and can result in further crosslinking under the elevated temperature conditions can be “neutralized” by reacting the crosslinked polyamidoamine or modified polyamidoamine with suitable agents. Any remaining free epoxy functionality of the epihalohydrin, which could lead to further crosslinking, can e.g. be removed by reacting the crosslinked polyamidoamine or modified polyamidoamine with an amine or ammonia.
• the polyamidoamines useful in the method of the present invention are obtained by the condensation of a dicarboxylic acid and an amine containing two primary amino groups and at least one secondary amino group, e.g., diethylenetriamine.
• the condensation results in polyamidoamines which contain about ten dicarboxylic acid derived units and the corresponding amount of amine derived units.
• the condensation product is reacted with an epihalohydrin, preferably epichlorohydrin.
• the epihalohydrin is used in substoichiometric amounts to make sure that no free reactive functionality is included in the crosslinked polyamidoamine which would make it crosslinkable and thus thermosetting.
• thermosetting polyamidoamines useful as wet strength agents or non-thermossetting polyamidoamines useful as retention aids or as adhesion-improving agents for paper creping are described. All of these modified polyamidoamines are also useful in the method of the present invention as long as they are non-thermosetting, i.e. crosslinking of the polyamidoamines has been effected by the use of substoichiometric amounts of epihalohydrin or any functional crosslinkable groups remaining after crosslinking have been “neutralized” (see above). Examples for modifications of polyamidoamines are disclosed in U.S. Pat.
• modified polyamido amines are disclosed in DE-A-34 21 557. These are polyamidoaminepolyamines formed by transamidation of polyamidoamines with polyamines which are obtainable by reacting under substantially anhydrous conditions and at elevated temperatures of at least 150° C.
• Gelling and thermosetting of polyamidoamine resins result from the presence of reactive epihalohydrin functionality. Both gelling and thermosetting entail the formation of intermolecular connections between discrete resin molecules. Gelling and thermosetting are caused by reaction between reactive epihalohydrin functionality and epihalohydrin reactive amine groups of different resin molecules; the reactive epihalohydrin functionality crosslinks the different molecules, and these molecules accordingly form an interconnected structure which is insoluble.
• thermosetting resin the act of heating and/or drying the resin hardens it, as well as rendering it insoluble.
• resin solutions are acid stabilized, so that heating will not gel or thermoset the resin.
• the non-thermosetting crosslinked polyamidoamine-epihalohydrin resin of the present invention is non-gelling. With substantially all of the epihalohydrin already reacted to link polyamidoamines, the dearth of reactive epihalohydrin functionality precludes, or at least greatly limits, reaction between the discrete resin molecules.
• the non-thermosetting crosslinked polyamidoamine-epihalohydrin resin can accordingly be redissolved after drying and/or heating.
• the process for manufacturing paper comprises three principal steps: (1) forming an aqueous suspension of cellulose fibers; (2) adding a strengthening additive; and (3) sheeting and drying the fibers to form paper.
• the step of forming an aqueous suspension of cellulosic fibers is performed by conventional means, such as known mechanical, chemical and semi-chemical, etc., pulping processes.
• a suspension may be formed by repulping paper or paperboard.
• the pulp may be washed to remove residual pulping chemicals and solubilized wood components.
• the step of adding the strengthening additive e.g. a non-thermosetting crosslinked polyamidoamine-epihalohydrin resin is carried out according to conventional means through direct addition to the papermaking system.
• a non-thermosetting crosslinked polyamidoamine-epihalohydrin resin is carried out according to conventional means through direct addition to the papermaking system.
• resins having similar chemistries as the non-thermosetting crosslinked polyamidoamine-epihalohydrin resins of use in the present invention had been applied directly to the surface of a creping drum rather than to the wet end of the papermaking system.
• the step of sheeting and drying of the fibers to form paper is carried out according to conventional means, such as those described in Casey, Pulp and Paper, cited above.
• the preferable level of addition of the non-thermosetting crosslinked polyamidoamine-epihalohydrin resin is about 0.1 to 2% based on the dry-weight of the pulp.
• the process for manufacturing paper having dry strength may also comprise use of additives, such as a crosslinked starch.
• the crosslinked starch may be added at a level of about 0.1 5% to about 2.0% by weight of the paper, preferably about 0.25% to about 1.5% by weight of the paper, more preferably about 0.5% to about 1.25% by weight of the paper.
• the crosslinked starch may be any crosslinked starch used in the paper-making process.
• the crosslinked starch may be selected form the group consisting of potato starch, tapioca starch, wheat starch, corn starch and other crosslinked starches derived from waxy maize. Crosslinked starches of use in the instant invention are described in U.S. Pat. No. 4,643,801 incorporated herein by reference in its entirety.
• the process for manufacturing paper having dry strength of the invention may also comprise use of a wet-strength resin.
• the wet-strength resin may be added at such levels to the paper so as not to significantly increase the paper's wet-strength.
• the process for manufacturing paper having dry strength of this invention may also be used to enhance the dry-strength of wet-strengthened papers.
• a wet-strength resin can then be added to at such levels to provide only the needed amount of wet-strength, and the non-thermosetting crosslinked polyamidoamine-epihalohydrin resin used in this invention can be used to increase the dry-strength without further increasing the wet-strength.
• wet-strength resins available from Hercules Incorporated are Kymene®557H resin, Kymene®736 resin, Kymene®450 resin, Kymene®557LX resin and Kymene® Plus resin.
• the wet-strength resin may be added at a level of about 0.025% to about 1.5% by weight of the paper, preferably about 0.05% to about 1.0% by weight of the paper, more preferably about 0.075% to about 0.75% by weight of the paper.
• Polyamidoamine epichlorohydrin (“PAE”) resins are the most preferred wet-strength resins.
• Kymene®557H resin in which adipic acid is reacted with diethylenetriamine (DETA) to form a polyamidoamine that is alkylated and crosslinked with epichlorohydrin to form a PAE resin, namely, adipic acid-DETA polyamidoamine epichlorohydrin.
• the wet-strength resin may comprise an aldehyde-functionalized starch or a glyoxal-modified polyacrylamide resin.
• the process for manufacturing paper having dry strength of the invention may also comprise use of a retention aid.
• the retention aid may be a high molecular weight polyacrylamide or a high molecular weight flocculent.
• the retention aid may be poly(ethyleneoxide).
• the retention aid may be a microparticulate retention aid.
• the microparticulate retention aid may be selected from the group consisting of bentonite and colloidal silica.
• the microparticulate retention aid may comprise a synthetic polymeric microparticle.
• the process for manufacturing paper having dry strength of the invention may also comprise use in paper which contains a highly crosslinked material for charge control or for fine particle retention.
• the highly crosslinked material for charge control may be selected from the group consisting of alum, polyaluminum chloride, poly(diallyldimethylammonium) chloride, poly(dialkylamine-epichlorohydrin) and polyethyleneimine.
• additives useful in the papermaking process of this invention include sizes, defoamers, fillers, wetting agents, optical brighteners, inorganic salts, etc.
• the process for manufacturing paper having dry strength of the invention is of utility in manufacturing many types of paper.
• the process for manufacturing paper having dry strength of the invention is of particular utility in manufacturing papers selected from the group consisting of bleached board, linerboard, corrugating medium, newsprint, printing and writing paper, tissue and towel.
• the process for manufacturing paper having dry strength of the invention is preferably used in the manufacture of recycled liner board and recycled corrugating medium.
• the reduced viscosity of a 2% solution of polymer in 1 N ammonium chloride is determined at 25.0° C. by means of a Ubbelohde viscometer and a Brinkmann Viscotimer. Flow times of a 2% polymer solution and a pure solvent are measured and the relative viscosity (Nrel) calculated. The reduced viscosity is calculated from the relative viscosity. This method is based on ASTM D446.
• ammonium chloride flow time should be measured once per day that Polymer RV measurements are made. This value should be used in the RV calculation.
• the tensile tests were determined using TAPPI test method T494.
• the Mullen burst was determined using TAPPI test method T807.
• the Ring Crush was determined using TAPPI test method T818, and the Scott Bond was determined using TAPPI Method T569.
• a non-thermosetting crosslinked polyamidoamine was prepared in two steps.
• a mixture of adipic acid, triethylenetetramine (TETA) and diethylene triamine (DETA) was condensed at elevated temperature to a low molecular weight poly(amidoamine) and diluted to a 35% solids solution in water (RSV 0.17 dL/g).
• this polymer was crosslinked using a substoichiometric amount of epichlorohydrin to obtain a non-thermosetting resin as a 24% solids solution in water (RSV 0.39 dL/g) (Resin A1).
• Paper of 115 g/m 2 was made on a model papermaking machine using re-dispersed commercial neutral recycled linerboard furnish, with conductivity controlled at 2000 micro Siemens per centimeter and pH of 7. Resin A1 was added at several addition levels to the furnish. The properties of the dried paper were compared to an untreated control. Properties studied included dry tensile (MD and CD), Ring crush resistance (MD and CD), and Mullen burst strength.
• Table 1 shows Resin A1 provides dry strength improvements at commercially useful addition levels.
• non-thermosetting crosslinked polyamidoamine resin was prepared in two steps.
• a mixture of adipic acid, triethylenetetramine (TETA) and diethylene triamine (DETA) was condensed at elevated temperature to a low molecular weight poly(amidoamine) and diluted to a 35% solids solution in water (RSV 0.17 dL/g).
• this polymer was crosslinked using a substoichiometric amount of epichlorohydrin to obtain a non-thermosetting crosslinked polyamidoamine resin as a 25% solids solution in water (RSV 0.39 dL/g) (Resin A2).
• resins were made based on the use of DETA and a mixture of TEPA (tetraethylenepentamine) and DETA to provide after crosslinking respectively Resin B at 15% solids and Resin C at 24.1% solids.
• TEPA tetraethylenepentamine
• Paper of 115 g/m 2 was made on a model papermaking machine using re-dispersed commercial neutral recycled linerboard furnish, with conductivity controlled at 2000 micro Siemens per centimeter and a pH of 7. Resins A2, B and C were added at several addition levels and the properties of the dried paper were compared to the untreated control. Properties studied included dry tensile (MD and CD), Ring crush resistance (MD and CD), and Mullen burst strength, wet tensile and Scott internal bond.
• MD and CD dry tensile
• MD and CD Ring crush resistance
• Mullen burst strength wet tensile and Scott internal bond.
• Resins A, B and C provide dry strength improvements over the untreated control at a commercially useful addition levels.

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• 2006
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