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
  • D21H19/00—Coated paper; Coating material
  • D21H19/36—Coatings with pigments
  • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
  • D21H19/56—Macromolecular organic compounds or oligomers thereof obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H19/58—Polymers or oligomers of diolefins, aromatic vinyl monomers or unsaturated acids or derivatives thereof
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
  • D06M15/00—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment
  • D06M15/19—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment with synthetic macromolecular compounds
  • D06M15/21—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D06M15/285—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds of unsaturated carboxylic acid amides or imides

Definitions

• the present invention is concerned with water-insoluble addition copolymers of ethylenically unsaturated amides and other ethylenically unsaturated monomers in which sufficient amide groups are mono-functionally bonded to a polyaldehyde to render the copolymer thermosettable.
• the copolymer is readily made in the form of a copolymer latex and is useful in processes for the treatment of textile substrates such as binders for nonwoven fabrics and hand or softness modifiers, and in the preparation of papers utilizing binders or coatings.
• Patent 3,100,674 discloses the use of N-methylolamide copolymers for stabilizing protein-containing woven and knitted textile materials against shrinkage.
• U.S. 3,037,963 states at column 7, line 6 "Aldehydes containing two or more aldehyde groups, such as glyoxal, are unsatisfactory and should not be used inasmuch as they cause gel formation when reacted with amide interpolymers."
• U.S. 2,886,557 discloses the reaction of glyoxal with anacrylamide copolymer to produce a crosslinked polymer.
• thermosettable polymer is useful as a self-crosslinking system or, if desired, with external crosslinkers.
• Self-crosslinking polymer systems are particularly useful as: adhesives in soft fiber fabrics;bonding agents, to bond a laminate foam to a fabric or a fabric to another fabric, or in nonwoven fabrics; fabric backing agents; pigment binders, especially for use on paper and to bind pigments to glass fabrics or in pigment printing and dyeing of fabrics; fabric finishing agents, to modify the hand or weight of a fabric; finishes for breatheable waterproof colored fabric; stabilizers for woollen and worsted fabrics and as binders for papers.
• the self-crosslinking nature of the systems produces, upon appropriate curing, products with excellent durability to washing and dry cleaning.
• the addition of external crosslinking agents is not necessary to produce the appropriate crosslinking although in certain instances it is found useful.
• a polymer composition comprising a water-insoluble addition copolymer of (A) monomer which is the product of at least one ethylenically unsaturated unsubstituted amide monomer condensed with one aldehyde group of at least one polyaldehyde, the product having at least one free aldehyde group, and (B) at least one other ethylenically unsaturated monomer; the amide monomer component of (A) and any unsubstituted amide monomer of (B) being up to 50% of the total monomers, by weight.
• the copolymer has sufficient unsubstituted amide groups among the (B) monomers and amide groups mono-functionally bonded to a polyaldehyde, (A), to be thermosettable.
• an external crosslinker is used in the binder composition.
• the invention also relates to processes for producing the polymer and for using the polymer in the manufacture of fabrics and papers. A preferred state in which the polymer is manufactured and used is as a stable polymer latex or polymer emulsion.
• the most important of the other ethylenically unsaturated monomers, other than the amides, are: (1) vinyl esters of an aliphatic acid having 1 to 18 carbon atoms, especially vinyl acetate; (2) acrylic acid esters and methacrylic acid esters of an alcohol having 1 to 18 carbon atoms, and (3) ethylenically unsaturated hydrocarbons such as ethylene, propylene, isobutylene, styrene, alphamethyl styrene and aliphatic dienes such as butadiene, isoprene and chloroprene.
• the ethylenically unsaturated amide of utility in copolymer components (A) and (B) is a polymerizable amide such as acrylamide, methacrylamide and itaconic half ester amide and diamide. Acrylamide and methacrylamide are preferred.
• G lyoxal is an example of the polyaldehyde which is mono-functionally bonded to an amide group to give the following structure: wherein R1, R 2 and R 3 are. independently, hydrogen, a monofunctional organic group or two of them together are a di-functional organic group and A is a single bond, as in glyoxal, or di-functional organic group.
• the polymer is a polyaldehyde-modified, amide-containing, addition copolymer which is used in the manufacture or processing of fabrics or papers.
• the fabrics produced have sufficient resistance to washing and dry cleaning for most practical purposes even without the employment of an external crosslinker, such as an aminoplast or a polyepoxide in conjunction with the polyaldehyde-modified, amide-containing polymer.
• the amide-containing polymers when cured as by heating at an elevated temperature, impart resistance to normal laundering operations, such as may be performed with modern detergents, as well as resistance to dry cleaning, which may be performed by chlorinated hydrocarbons.
• the copolymers of the present invention are water-insoluble linear addition copolymers preferably prepared by emulsion copolymerization.
• the copolymers are prepared using up to 50 percent of amide monomers and the remainder other ethylenically unsaturated monomers.
• Amide groups of the polymer are predominantly condensed with one aldehyde group of a polyaldehyde, as indicated by the absence of gelation, and free aldehyde groups remain on the polyaldehyde, as shown by the curability of the polymer.
• the polymer comprises unreacted aldehyde groups and in the self-curing embodiment, unreacted amide groups.
• the polymer also comprises acid groups.
• the preferred polymers of this invention are those in which the polyaldehyde is glyoxal.
• a preferred method for preparing the polymers is by emulsion polymerization of the monomers in the presence of the polyaldehyde, under conditions such that the reaction of the polyaldehyde and the amide occurs, in a one step process producing a polymer which is still thermosettable.
• the thermosettable nature of the product indicates that there, are unreacted aldehyde groups available for crosslinking to other groups reactable with the aldehyde such as other amide groups.
• the latex so produced is used in the manufacture of paper or fabric products following the art-known procedures used for monoaldehyde-amide containing copolymers.
• the fabric or paper containing the polymer is cured at an elevated temperature for a suitable length of time.
• the cured material is water resistant and solvent resistant. It is presumed that the improvement in both strength and resistance properties obtained on curing is due to further coreaction of the aldehyde and amide groups which had been pendant on the polymer to produce a crosslinked polymer.
• the polymer composition of this invention is preferably prepared in latex form as a water-insoluble addition copolymer of an ethylenically unsaturated amide and at least one other ethylenically unsaturated monomer.
• the polymerization is carried out in the presence of a polyaldehyde which bonds to the polymer via the amide groups on the polymer so as to render the copolymer thermosettable.
• the copolymer is little, if any, crosslinked by the polyaldehyde during the polymerization. It is believed that the polyaldehyde is preponderantly mono-functionally bonded to the copolymer.
• the copolymer is not crosslinked but is still crosslinkable at the end of the polymerization step.
• the latex is stable and does not gel when stored at room temperature for months or even longer.
• Preferably all the polyaldehyde in the latex is bonded to the polymer.
• the latex, in a formulation if desired, is applied to the appropriate substrate and the polymer is crosslinked, by curing via heating, using art-known steps for the given use.
• the.polyaldehyde be at least slightly water soluble such as gluteraldehyde or 2-imidazolidone-l,3- bis(2,2-dimethylpropanol) or more preferably, water soluble such as glyoxal.
• polyaldehyde what is meant in this specification is a non-polymeric organic molecule with more than one J roup.
• Aldehydes often form homopolymers or copolymers with water that are not the polyaldehydes referred to in this specification.
• the preferred polyaldehyde of this invention is glyoxal, ordinarily depicted by the structure: Glyoxal is most commonly available commercially as a 40% aqueous solution.
• glyoxal has no appreciable vapor pressure and is not, under atmospheric or vacuum stripping conditions, distillable from water. Aqueous solutions of glyoxal are nonexplosive and nonflammable.
• _Glyoxal in its hydrated form (II) is believed to exist in equilibrium with (IIa) and (IIb):
• the ethylenically unsaturated unsubstituted amide monomers of this invention include acrylamide, methacrylamide, itaconic diamide, crotonamide, acryloxypropionamide, maleic, fumaric and itaconic half amides and so forth.
• the preferred amides are methacrylamide and especially acylamide.
• An unsubstituted amide is an amide having two hydrogens on the amide nitrogen, i.e. the amide group -CONH 2 .
• vinyl esters of an aliphatic acid having 1 to 8 carbon atoms such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl versitate.
• vinyl acetate particularly when used with one or more of the following: vinyl chloride, vinylidene chloride, styrene, vinyl toluene, acrylonitrile, methacrylonitrile, and acrylate or methacrylate esters.
• the acrylate and methacrylate esters of alkyl and cycloalkyl alcohols having 1 to 18 carbon atoms form useful polymers, with C 1 to C 8 alcohols being preferred, particularly mixtures of these and also in mixtures with the following monomers: vinyl acetate, vinyl chloride, vinylidene chloride, styrene, a-methyl styrene, vinyl toluene, acrylonitrile and methacrylonitrile.
• the unsaturated hydrocarbons such as ethylene, isobutylene and styrene are particularly useful when used in conjunction with one or more esters, nitriles or amides of acrylic acid or of methacrylic acid or with vinyl esters, vinyl chloride or vinylidene chloride.
• esters, nitriles or amides of acrylic acid or of methacrylic acid or with vinyl esters, vinyl chloride or vinylidene chloride In all of these systems, it is quite common and indeed useful to include a small amount such as a 1/2 percent to about 2 1/2 percent, 4%, or perhaps 8% or more, of an ethylenically unsaturated carboxylic acid monomer in the monomer mixture used for making the copolymers.
• Acids used include acrylic, methacrylic, itaconic, aconitic, citra- conic, crotonic, maleic, fumaric the dimer of methacrylic acid and so forth.
• the use of the acids often aids in the curing of the polymer.
• Esters of these acids with C I to C 18 alcohols may be used.
• the preferred esters of methacrylic acid in these copolymers are methyl, ethyl, propyl and butyl with methyl being most preferred.
• the preferred esters of acrylic acid are the methyl, ethyl, n-propyl, isopropyl, n-butyl, secondary butyl, isobutyl and 2-ethylhexyl esters.
• a copolymer composition containing at least about 60% by weight of esters of acrylic or methacrylic acid or a mixture of these is especially useful.
• the preferred copolymers of the present invention are water-insoluble, linear addition copolymers obtained by emulsion copolymerization of unsubstituted amide monomers with other monomers; the copolymerization being carried out in the presence of a polyaldehyde.
• the upper limit of the concentration of amide monomer is determined by the solubility of the copolymer formed; there is to be less amide monomer than the amount sufficient to render the copolymer water soluble. Although 50% or 25% may be employed, it is found that 12% by weight of amide monomer, on copolymer, normally suffices and 0.5% is a usual lower limit for effective crosslinking.
• the amide monomer content is between 2% and 10% with 3% to 6% being most preferred.
• One embodiment of this invention provides self-crosslinking polymer when the amount of polyaldehyde used is such that there is sufficient for the polymer to be capable of effective crosslinking but not so much in relation to the amount of amide present that substantially all of the amide groups are reacted with.polyaldehyde during the polymerization. These desiderata are achieved when there are about 0.2 to about 0.8 of a mole of polyaldehyde per mole of amide groups.
• the latex is prepared and applied to the fabric or paper for the curing or second stage reaction if there is 0.2 mole of polyaldehyde per mole of amide there is 0.8 mole of amide groups available for the crosslinking reaction.
• crosslinking is achieved by use of an external aminoplast crosslinking agent such as a polyamide or a compound containing amide-like NH 2 groups, such as urea and melamine, or aldehyde-substituted amide groups including dihydroxy ethylene urea.
• an external aminoplast crosslinking agent such as a polyamide or a compound containing amide-like NH 2 groups, such as urea and melamine, or aldehyde-substituted amide groups including dihydroxy ethylene urea.
• Use of the formaldehyde adducts would defeat the purpose of the invention so formaldehyde-free aminoplasts are preferred.
• polystyrene resin preferred polystyrene resin
• preferred polyamides those of oxalic, malonic, adipic, pinelic, suberic, azelaic, sebacic, isophthalic, terephthalic and the like acids.
• amides of dimer and trimer acids and mixtures thereof these acids are prepared by the polymerization of C 18 fatty acids.
• the external crosslinking agent is used in an amount up to about 25% of the copolymer, up to 11% being preferred, and up to 7% being most preferred.
• Formulations in which the polyaldehyde to amide ratio is high usefully embody 0.5% or more, preferably over 2% of external crosslinker.
• the glass transition temperature of the copolymer, before curing, is preferably below 35°C, more preferably below 20 0 c and most preferably below 0°C.
• the weight average molecular weight of the polymer, aside from any small amounts which may be gelled, is preferably from 100,000 to 10,000,000 with from 300,000 to 3,000,000 being preferred.
• a polyaldehyde such as glyoxal, admixed but not coreacted with an amide copolymer, such as a copolymer of acrylamide or methacrylamide, may be applied to a substrate and cured to produce a fabric or paper.
• the fabric or paper so produced is found to be less resistant to water, laundering and dry cleaning than fabric or paper employing the copolymers of this invention, other conditions being the same.
• high proportions of the crosslinking moieties taken together, that is, of amide and aldehyde tend to give products which are excessively stiff. Of course, in certain applications, the stiffness is desirable. Low levels of amide or aldehyde lead to a loss of the resistance properties.
• An especially useful polymer is a copolymer of, by weight, 20 to 97% ethyl acrylate, 0 to 97% propyl or butyl acrylate or a mixture thereof, O to 25% acrylonitrile, 0 to 50% methyl methacrylate, 3 to 6% acrylamide, O to 2% itaconic acid and 1 to 2% glyoxal. More preferred is a copolymer which consists of 70 to 95% ethyl acrylate, 3 to 5% acrylonitrile, O to 25% butyl acrylate, O to 10% methyl methacrylate, 3 to 4% acrylamide, and 0.5 to 1.5% itaconic acid and 1 to 2% glyoxal, by weight.
• Another embodiment of this invention provides a process for the preparation of substantially un-crosslinked polymer containing aldehyde groups, which comprises reacting predominently one aldehyde group of at least one polyaldehyde with at least one ethylenically unsaturated, unsubstituted amide monomer and, simultaneously and/or subsequently, subjecting the monomer to polymerization conditions in the presence of at least one other ethylenically unsaturated monomer.
• the preferred copolymerization process is a conventional emulsion polymerization procedure with certain modifications.
• "Emulsion Polymerization” is taught in books, so titled, by D. C. Blackley (Wiley, 1975) and by F. A. Bovey et al. (Interscience Publishers, 1965).
• the coreaction of the aldehydes (mono-functionally) with the amide during the polymerization is favored by using a thermal polymerization process, the presence of all of the aldehyde in the kettle charge at the beginning of the polymerization or prior to the polymerization and the presence of part of the amide in the kettle prior to the polymerization.
• the aldehyde-amide reaction need not be completed before the polymerization is begun thus the polymerization is carried out in the presence of any remaining polyaldehyde and of a free radical initiator. At the end of the polymerization substantially all of the glyoxal in the latex is bonded to the copolymer.
• the emulsion polymerization procedures may employ a suitable emulsifier, prefererably an anionic emulsifier and a free radical initiator which may, if desired, although it is not the preferable system, be a component of any of the well known redox initiator systems.
• Preferred emulsifiers are sulfates and sulfonates such as sodium lauryl sulfate, and sodium dodecyl benzene sulfonate. Many others are well known in the emulsion polymerization art.
• the amount of emulsifier is usually between 1/2% and 6% on the weight of monomers with 1% to 3% being preferred.
• Suitable chaser systems are employed to result in a polymer system essentially free of formaldehyde, amide monomer and polyaldehyde.
• the polymerization process may be one which produces graft or block copolymers wherein one or more but not all of the monomers are first polymerized and then one or more other monomers are copolymerized with the first polymer obtained.
• the latex is usually at an acid pH as manufactured, typical values being in the pH range from two to three. Formulation of the latex for a given application may shift the pH, for example incorporation of an acid catalyst usually lowers the pH somewhat, a drop of about a half unit is often found. In preferred formulations the system is stable at room temperature including formulations containing acid catalysts.
• a preferred use of the binders of the present invention is to bind nonwoven webs to form nonwoven fabrics.
• the selection of fibers and the description of the application of a binder is given in U.S. 3,157,562, column 3, line 30 to column 4, line 53, herein incorporated by reference.
• the polyaldehyde reacts with amide groups on the monomer or on the polymer by means of one amide group reacting with one aldehyde group.
• This reaction occurs before, and/or contemporaneous with, the vinyl polymerization reaction which forms the polymer.
• the aldehyde-amide reaction occurs, in the polymerization vessel, subsequent to the polymerization.
• the resulting unit in the aldehyde polymer adduct has the theoretical formula (III).
• the reaction depicted to form crosslinked structure (IV) occurs.
• the following reaction is thought to occur, producing crosslinking by means of structure (V):
• the aldehyde may react with other types of groups containing reactive hydrogen, the groups being those of others of the polymer molecules or of other crosslinking molecules. There may also be some reaction, during curing, between the aldehyde groups of the polymer molecules and reactive groups in the fibers of the paper or fabric, such as the hydroxyl groups of the cellulose fibers. While the precise nature of the reaction and the products thereby obtained are not clearly understood, it is believed that the resistance to laundering and dry cleaning is the result of a reaction between binder polymer molecules to crosslink these molecules and/or a reaction between the binder polymer molecules and the reactive sites of the fiber molecules.
• the polymers of this invention are crosslinked by a curing step which may either be simultaneous with or following the drying of the polymer on the substrate.
• the curing may be by long subjection to the normal atmosphere in high temperature climates or by heating the articles coated or impregnated with the polymer described herein to a temperature of 80°C to about 400°C or higher for periods of time from a few seconds at the higher temperatures up to an hour or more at the lower temperatures. Temperatures below 80°C may be employed if somewhat longer times are used. Typical schedules for air dried systems are about 15 seconds to about 15 minutes at temperatures in the neighborhood of 150°C.
• the polymer of this invention may be used in combination with other polymers commonly employed in bonding or treating fabrics and paper.
• catalysts are not necessary to obtain the crosslinking desired in the cure step, they may be used.
• Acid catalysts well known in the art, may be employed at levels up to 1% with 0.1% to 0.5% being preferred. Higher levels of catalysts often, but not always, produce undesirable side effects.
• acid catalysts are oxalic acid, boron trifluoride ethyl etherate, salts of hydrochloric acid such as the zinc or magnesium salts, salts of nitric acid such as the zinc or magnesium salts, maleic acid, p-toluene sulfonic acid, butyl acid phosphate and so forth.
• compositions of the present invention may be formulated with pigments, dyes, thickening agents and other conventional components needed to achieve the properties desired for the given end use.
• aqueous dispersions of these polymers may contain water-soluble thickening agents such as tragacanth, water-soluble cellulose ethers, polyvinyl alcohol or partially saponified polyvinyl acetate or polymers or copolymers of acrylic or methacrylic acid soluble in water.
• the proportions of the ingredients in the aqueous systems may be varied widely and are adjusted in any convenient manner so that the dispersion or paste have a consistency suitable for the application by the particular technique to be used for this purpose.
• the drying referred to above may be air drying by simple exposure to the ambient atmosphere or it may be force drying of the coated or impregnated material at temperatures below 80°C. As noted, the air drying or force drying may itself produce a cured product without the need of a subsequent curing step. Of course, usually a cure step is desired.
• the upper limit of temperature and its duration in the curing step should be so selected and correlated as to avoid decomposition or other damage to the coated or impregnated article.
• the curing operation serves to render the polymer insoluble in organic liquids as well as water.
• compositions may be applied to the substrates in any suitable manner such as by spraying, brushing, rollercoating dipping, knife-coating, and so on. Excess of the applied material may be wiped by any suitable squeegeeing operation such as between pressure rollers, by air squeegeeing, or by a knife or doctor blade. Thereafter, the coating may be dried and cured as stated hereinabove. Besides simple air-drying, there may be employed for this purpose heated air as in an oven or tunnel drier, radiation such as by infrared lamps, or electrical induction, either of electromagnetic or electrostatic high frequency induction fields. The baking or curing operation may be accomplished by the use of any suitable heating devices such as infrared lamps or electromagnetic or electrostatic high frequency induction devices.
• the coating compositions are applied to substrates having reactive groups, such as paper or textiles formed of cellulosic or proteinaceous fibers
• the substrate may take part in the reaction during curing and baking so that the copolymer and the substrate are combined chemically, whereby outstanding adhesion, durability, and resistance to water, washing, laundering, and solvents, including those used for dry-cleaning, such as perchloroethylene, carbon tetrachloride, and solvent naphthas, are obtained.
• the present invention provides novel thermoplastic, thermosettable, and/or thermosetting copolymers which combine the qualities of efficiency, economy and being comparatively inert in ecological effects. Even when present at comparatively low levels in the copolymer, the amide-glyoxal system provides highly efficient cures such as cures familiar to those skilled in the art, obtainable by means of formaldehyde or formaldehyde condensate systems.
• the products produced have laundering resistance and dry cleaning resistance typical of the formaldehyde-containing systems as can be determined by testing the bonded or treated fabric or paper for durability in the presence of water or in laundering and in dry cleaning tests.
• the aqueous'latexes of the present invention are sufficiently stable to pose no problems to the formulator or manufacturer using and applying these systems.
• the bonded fibrous products of the present invention are characterized by softness, flexibility, resistance to discoloration on exposure to ultraviolet light, resistance to chlorinated hydrocarbon dry-cleaning fluids, and resistance to laundering. Because of the softness and flexibility and good draping qualities of the products of the present invention, they are particularly well adapted for use in garments where porosity, permeability to moisture vapor, and soft hand and feel, make the products advantageous where contact with the skin of a wearer may be involved. In general, the products are quite stable dimensionally and have good resilience and shape-retention properties. They are adapted for use not only in garments but as padding or cushioning, and moisture- absorbing articles, such as bibs and diapers.
• They are also useful as heat- and sound-insulating materials and as filtration media, both for liquids and gases. They can be laminated with paper, textile fabrics, or leather to modify one or both surfaces of the latter materials. They may be adhered to films of cellophane, polyethylene, saran, poly- ethyhlene glycol terepththalate (Mylar) or metallic foils, such as of aluminum, to improve the tear strength of such films and foils, to make the latter more amenable to stitching, and to modify other characteristics including strength, toughness, stiffness, appearance, and handle.
• Mylar poly- ethyhlene glycol terepththalate
• metallic foils such as of aluminum
• binder may be preferentially applied, if desired, to portions of the fibrous product, such as one or both of the faces or parts thereof, it is characteristic of the binder of the present invention that, if such preferential treatment is not desired, substantially uniform distribution may be obtained because of the reduced tendency of the binder after initial distribution throughout the body of the fibrous product to migrate to the surfaces thereof during drying.
• the temperature is maintained at ca. 83°C. Fifteen minutes after the addition, the batch is cooled to 55°C. and chased with:
• the same chaser charge is added after thirty minutes and again after sixty minutes. Fifteen or more minutes after the last chaser 50 g. of 35% aqueous hydrogen peroxide is added.
• the polymerization procedure is the same as Example 1 except that the composition of the monomer emulsion is:
• the polymerization procedure is the same as Example 1 except that 80 g. of a 40% glyoxal solution is in the kettle and the composition of the monomer emulsion is:
• the polymers of Examples 1, 2 and 3 and that of a typical acrylate latex based on methylolated acrylamide crosslinking are padded onto a light weight ( 0 . 0 17 kgm-2) ( 0 . 5 oz ./y d . 2 ) rayon nonwoven web to give a fiber/binder ratio of 80/20.
• the methylolated acrylamide polymer is catalyzed with 0.5% ammonium nitrate in the bath but the glyoxal polymers are uncatalyzed.
• the webs are air dried and then cured for two minutes at 150°C. Tensile values are measured on 25.4 mm x 101.6 mm (1 in.
• the typical latex employing the formaldehyde chemistry is polymerized by a redox procedure. It is prepared at 45% polymer in water and from the following monomers: 1.7% acrylamide, 2.4% N-methylolacrylamide and 95.9% ethyl acrylate.
• Example 5 In the preparation of the redox latex (Example 5), a process similar to that of Example 1 is used except that the initiator consists of ammonium persulfate and sodium bisulfite with a trace of a ferrous salt and the temperature is about 65°C.
• the latices of Examples 6 and 7 are prepared by the process of Example 1.
• the bonded webs were tested as in Example 4 with the results given in the table below.
• the web bonded with the polymer containing the highest glyoxal level, Example 11, has less wash durability than the others.
• Example 2 Using the thermal process, as in Example 1, polymers were prepared in which the acrylamide to glyoxal molar ratio was held at 3 and the acrylamide level was varied as given in the following table. Bonded webs were prepared and tested as in Example 4, with the results given in the following table. a A pp l i ed at 15 % polymer bath solids with 0.5% NH 4 NO 3 catalyst. Webs were air-dried and cured at 149°C (3000F)/2 min.
• Example 2 Using the procedure of Example 1, polymers were made incorporating itaconic acid at three levels and acrylamide at two levels also utilizing two values of the acrylamide glyoxal ratio. One polymer was also made by a redox polymerization process. The preparation of the bonded webs and the testing was as in Example 4 with the results being given in the table below.
• a polymer of the composition of Example 2, omitting the glyoxal, is prepared by the process of Example 5, and divided into three aliquots.
• the aliquot is used as is; in Example 24, glyoxal is post added at the level of 1/2 mole per mole of acrylamide; and in Example 25, glyoxal is post added at the same level in addition to which the latex is heat aged at 60°C (140°F) for 70 hours.
• Each aliquot is then used to bond a nonwoven rayon web and tested by the procedure outlined in Example 4.
• the heat age sample was heat aged before the addition of the ammonium nitrate catalyst.
• the results show that post addition of glyoxal has comparatively little effect on the properties of the bonded fiber, however, heat aging after post adding the glyoxal does produce a marked improvement in the properties of the bonded fiber although not to the level achieved with the coreacted glyoxal in Example 2. It is recognized that in all three of these examples, there may have been a limited amount of crosslinking by mechanisms not involving the amide or the glyoxal.

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