Classifications

• • D—TEXTILES; PAPER
  • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
  • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
  • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
  • D04H1/40—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
  • D04H1/58—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives
  • D04H1/587—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties by applying, incorporating or activating chemical or thermoplastic bonding agents, e.g. adhesives characterised by the bonding agents used

Definitions

• This invention relates to formaldehyde-free binding compositions useful in the preparation of formaldehyde-free nonwoven fabrics. More particularly, it refers to formaldehyde-free binding compositions comprising methacryl- ­or acryl-amidoglycolic acid alkyl ethers, alkyl esters and alkyl ester-alkyl ethers.
• Nonwoven fabrics comprise loosely assembled webs or masses of fibers bound together with an adhesive binder.
• Nonwoven fabrics are produced by bonding together a loosely assembled fibrous web with a polymeric binder.
• Self-­crosslinking polymer latices have been used as the binder to impart strength, particularly wet strength, to the product so that the web does not rupture or disintegrate into individual fibers under a wet condition.
• the typical bonding process involves, first, the addition of the latex to the fibrous web while the latex is in the uncured condition and then the curing process when the latex develops crosslinking bonds between polymer molecules.
• the ability to develop a strong crosslinking bond after curing is believed to be essential to obtain good wet strength.
• Adequately bonded nonwoven fabrics have advantages over woven fabrics for a large variety of uses. It is known to form bonded nonwoven fabrics by impregnating, printing or otherwise depositing an adhesive bonding composition on a base web predominantly comprising relatively long fibers, including those of textile length of from about 1 ⁇ 2 inch (1.27 cm) to about 21 ⁇ 2 inch (6.35 cm), or more. These fibers may be of cellulosic or polymeric materials such as polyesters, polyamides, polyacrylates and the like.
• the base web of nonwoven fibers, to which the binder is applied can be produced by carding, garnetting, airlaying, papermaking procedures, or other known operations.
• the operation of bonding fibers in place is much less expensive than conventional spinning and weaving.
• the bonded nonwoven fabrics can be made in a much greater range of thicknesses per unit weight, with more homogeneous structures, no unravelling tendency, and with greater water absorbancy, porosity and resiliency, when required.
• Such fabrics are preferable to woven fabrics in a large number of applications such as facings or top sheets in diapers, incontinent pads, bed pads, sanitary napkins, hospital gowns, and the like. In such applications, it is desirable that the nonwoven fabric simulate the drape, flexibility and softness of a woven fabric to as great a degree as possible.
• binder used in the formation of such nonwoven fabrics will influence the properties of the final product especially with respect to its wet and dry tensile strength, tear strength, absorbency and resilience.
• binder compositions will influence the properties desired in the final product. This may consist of modifying the composition of the binding composition to combine the properties of different latices.
• the latex forming the adhesive binder can be self-­crosslinkable or use a separate crosslinking agent.
• Conventional self-crosslinkable latices comprise all acrylate polymers, such as methacrylate and acrylate homo- ­and copolymers; vinyl acetate-acrylates, ethylene-vinyl acetate or styrene acrylate copolymers and N-methylol acrylamide or N-methylol methylacrylamide as crosslinking agent.
• acrylate polymers such as methacrylate and acrylate homo- ­and copolymers
• vinyl acetate-acrylates vinyl acetate-acrylates, ethylene-vinyl acetate or styrene acrylate copolymers and N-methylol acrylamide or N-methylol methylacrylamide as crosslinking agent.
• the curing is effected at elevated temperatures and low pH whereby the N-methylol moieties condense to form bisacrylamide crosslinks and formal
• U.S. Patent 4,454,301 to Cady et al discloses coating compositions comprising MAGME which upon curing release alcohol byproducts of lower toxicity than the formaldehyde released by the binding composition of the prior art.
• U.S. Patent 4,436,280 also to Cady et al discloses the use of a vinyl polymer containing MAGME residues as a coating composition, and utilizes a separate "amine-terminated triazine resin" as the crosslinking agent.
• the present invention relates to substantially formaldehyde-free nonwoven fabrics prepared by using a binder composition comprising a methacryl- or acryl- ­ acrylamidoglycolic acid ester, ether or ester-ether.
• substantially formaldehyde-free nonwoven fabrics can be prepared with a binder composition comprising at least one methacryl- or acryl-amidoglycolic acid alkyl ether, alkyl ester or alkyl ester-alkyl ether or homo- or co-polymers thereof.
• substantially formaldehyde-free is meant that the residual content of free formaldehyde in the nonwoven fabric after cure varies from about 0 to about 1 ppm. This is in contrast to free formaldehyde content on the order of about 50 to 60 ppm or more in nonwoven fiber products cured with N-methylol acrylamide containing emulsions commonly used in the art.
• the binder composition used in the preparation of formaldehyde-free nonwoven fabrics comprises at least one alkyl acrylamidoglycolate alkyl ether or acrylamidoglycoamide alkyl ether having repeating units of the following general structures: wherein R is hydrogen or methyl, R′ is selected from alkyls of 1-6 carbon atoms and cycloalkyls of 5-6 carbon atoms, R2 is selected from alkyls of 1-6 carbon atoms and cycloalkyls of 5-6 carbon atoms, each of which is optionally substituted with oxygen or nitrogen heteroatoms, and R3 and R4 are selected from hydrogen, alkyls or cycloaliphatic alkyls of 1 to 20 carbons optionally modified with nitrogen or oxygen moieties.
• alkyl acrylamidoglycolate alkyl ether or acrylamidoglycoamide alkyl ether is polymerized with comonomers such as acrylic and methacrylic acid and their methyl, ethyl, propyl, butyl and 2-ethyl hexyl esters; styrene, methylstyrene, styrene-butadiene and ethylstyrene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate; vinyl versatate, itaconic acid and its mono or diethyl propyl and butyl esters, fumaric acid and its mono or di-propyl, butyl and ethyl esters; acryl- and methacrylamides and their alkylates, olefins such as ethylene, propylene, butadiene and the like, nitriles such as acrylonitrile, methacrylonitrile,
• the latex binder can also contain a reactive function selected from hydroxy, carboxy and amido groups or combinations thereof.
• a preferred binder composition is one in which the polymer containing the alkyl acrylamidoglycolate alkyl ether or an acrylamidoglycoamide alkyl ether also contains a comonomer providing a sufficient quantity of hydroxy, carboxy, and/or amido groups.
• the binder composition can be readily cured at a temperature of about 300°F or higher for adequate time periods, usually at least about 2 to 5 minutes. Curing will, of course, depend upon temperature, composition, time, presence or absence of an accelerator and the like. Curing can be accelerated, if desired, by addition to the composition prior to coating of an acid curing accelerator such as oxalic acid or p-toluene-sulfonic acid, or a transesterification catalyst such as a tin salt.
• an acid curing accelerator such as oxalic acid or p-toluene-sulfonic acid
• a transesterification catalyst such as a tin salt.
• Preferred monomer mixtures for preparing the solutions or latices comprise about 1 to 20 parts by weight of an alkyl acrylamidoglycolate alkyl ether or an acrylamidoglycoamide alkyl ether and about 85-99 total parts by weight of the comonomers, and most preferably, about 2-10 parts by weight of an alkyl acrylamidoglycolate alkyl ether or an acrylamidoglycoamide alkyl ether and about 90-98 parts by weight of the comonomer.
• the polymer solutions of the present invention are prepared by known emulsion polymerization methods to yield an aqueous latex.
• the latices of the present invention can be prepared in aqueous media, by conventional emulsion polymerization techniques using methods known in the art, such as batch or semi-batch polymerization processes.
• the semi-batch process is operated with a minor portion of the monomers charged initially to the reactor, with the remaining monomers gradually added over the course of the reaction until completed.
• Various free-radical forming catalysts can be used in carrying out the polymerization of the monomers, such as persulfates including sodium, potassium and ammonium persulfates; peroxides such as benzoyl and hydrogen peroxides; hydroperoxides such as t-butyl and cumyl hydroperoxides; and azo compounds such as azobis(isobutyronitrile).
• Combination type catalysts employing both reducing agents and oxidizing agents can also be used.
• the use of this type of combined catalyst is generally referred to in the art as "redox polymerization” or "redox system”.
• the reducing agent is also often referred to as an activator and the oxidizing agent as an initiator.
• Suitable reducing agents or activators include bisulfites, sulfoxylates, or other compounds having reducing properties such as ferrous salts, and tertiary aromatic amines, e.g., N,N-dimethylaniline.
• the oxidizing agents or initiators include hydrogen peroxide, organic peroxides such as benzoyl peroxide, t-­butyl hydroperoxide, cumyl hydroperoxide and the like, persulfates, such as ammonium or potassium persulfate, perborates, and the like.
• combination type catalysts or redox systems which can be used include hydrogen peroxide, ammonium persulfate, or potassium persulfate, with sodium metabisulfite, sodium bisulfite, ferrous sulfate or dimethylaniline.
• Other types of catalysts that are well known in the art and which do not contain formaldehyde can also be used to polymerize the monomers.
• the catalyst is employed in an amount of 0.01 to 5%, preferably 0.25 to 0.75% based on the weight of monomer introduced into the system.
• the activator is ordinarily added in aqueous solution and the amount of activator is generally 0.25 to 1 times the amount of catalyst.
• Emulsifiers including anionic, nonionic and cationic surface active compounds can be used.
• Suitable anionic emulsifiers include alkyl and alkylaryl sulfonates, alkyl and hydroxyalkanol sulfates, alkyl and alkylaryl disulfonates, sulfonated fatty acids, sulfates and phosphates of polyethoxylated alkanols and alkylphenols and esters of sulfosuccinic acids.
• Nonionic emulsifiers include polyoxyethylene condensates (usually 5 to 70 moles of ethylene oxide per mole) of alkylphenols, fatty alcohols, fatty acids, amides or mercaptans and block copolymers of propylene oxide and ethylene oxide.
• Cationic emulsifiers include alkyl quaternary ammonium and alkyl quaternary phosphonium salts.
• nonionic and/or anionic emulsifiers are preferred and used in amounts of about 1 to 10% by weight of the monomers.
• a nonwoven fabric comprising a web or mass of fibers in contact with, such as by impregnation, any of the aforesaid latex compositions and cured.
• Curing of the web emulsion composition can be effected by means known to the art, including heating at elevated temperatures, low pH, and use of free radicals.
• the fibers useful in the practice of the invention include: cellulose and its derivatives such as esters, for example, cellulose acetate, propionate and butyrate, and mixed esters such as the acetate-butyrate and acetate-­propionate; polyesters such as poly(ethylene terephthalate) and poly(ethylene tere-co-isophthalate); polyamides such as nylon 6 and nylon 6,6; and poly(acrylates) or poly(methacrylates) such as poly(methyl methacrylate); and mixtures thereof.
• esters for example, cellulose acetate, propionate and butyrate, and mixed esters such as the acetate-butyrate and acetate-­propionate
• polyesters such as poly(ethylene terephthalate) and poly(ethylene tere-co-isophthalate)
• polyamides such as nylon 6 and nylon 6,6
• poly(acrylates) or poly(methacrylates) such as poly(methyl methacrylate); and mixtures thereof.
• the nonwoven fabric product is characterized by substantially no free-formaldehyde content after drying and curing at a binder add-on which is sufficient to bond the fiber web together.
• a sufficient amount of binder add-on can be at least about 3% by weight on a dry basis, and preferably about 10 to 100 weight % binder add-on, on a dry basis.
• the dried and cured nonwoven product will have a free-formaldehyde content of less than about 5 parts per million (ppm) and preferably, below about 1 ppm. Such levels are feasible at about 50 weight % binder add-on, on a dry basis. Levels of free formaldehyde of about 1 ppm or less are considered almost formaldehyde-free and are obtainable by this invention.
• the proportion of MAGME monomers to the comonomers can vary from about 1 to about 20, and preferably from about 2 to about 10.
• a monomer composition consisting of 42 parts of butyl acrylate, 52 parts of styrene, 1 part of acrylic acid, and 5 parts of methyl acrylamido glycolate methyl ether (MAGME) was dispersed in 40.5 parts of water containing 3.8 parts of poly(oxyethylene) octyl phenyl ether (30 moles ethylene oxide), 0.5 parts of sodium dodecyldiphenyloxide to form a pre-emulsion.
• the temperature was allowed to reach 60-62°C and held for 10 minutes. Subsequently, the remainder of the pre-emulsion was continuously added to the reaction vessel over 4 hours while the reaction temperature was kept at 60-62°C. Upon completion of the pre-emulsion addition, the reaction mixture was kept at 60-62°C for another 30 minutes and then two streams of aqueous solutions of 0.1 part of tert-butyl hydroperoxide in 0.7 parts of water and 0.1 part of sodium hydrosulfite in 0.7 parts of water were added to the reaction vessel over 30 minutes. This produced a latex having a total solids content of 50.2%, a Brookfield viscosity (spindle 3, 50 rpm) of 330 centipoise and a pH of 2.2.
• Example 1 was repeated except that the following were substituted for the monomer mixture:
• the resulting latex had a total solids content of 50.9%, a Brookfield viscosity (spindle 3, 50 rpm) of 400 centipoise and a pH of 2.14.
• Example 1 was repeated except that the following were substituted for the monomer mixture:
• the resulting latex has a total solids content of 50.1%, a Brookfield viscosity (spindle 3, 50 rpm) of 70 centipoise and a pH of 2.14.
• the resulting latex had a total solid content of 52.8%, a Brookfield viscosity (spindle 3, 50 rpm) of 780 centipoise and a pH of 4.5.
• the resulting latex had a total solid content of 52.9%, a Brookfield viscosity (spindle 3, 50 rpm) of 610 centipoise and a pH of 4.5.
• Saturation baths were prepared by diluting 98 grams of the latices from Examples 1 to 4 with 575 grams of an aqueous solution containing 0.5 grams of oxalic acid. Sheets of Whatman #4 Chromatography paper (9" x 7.5") were immersed in the saturation bath, squeezed through a laboratory wringer, dried at room temperature, and cured for 5 minutes at 300°F in a forced draft oven. The dry pick-up of binder in paper was 10% by weight. The sheets were then tested for dry and wet tensile strength. Tensile strengths of 1 inch x 6 inch strips were evaluated with an Instron Tester.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Nonwoven Fabrics (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Adhesives Or Adhesive Processes (AREA)

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Cited By (14)

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• 1988
  • 1988-06-24 EP EP88305840A patent/EP0302588A3/fr not_active Withdrawn
  • 1988-07-11 AU AU18922/88A patent/AU1892288A/en not_active Abandoned
  • 1988-07-30 JP JP63192000A patent/JPS6443589A/ja active Pending

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