DE1921458A1 - Manufacture of nonwovens - Google Patents

Description

Cologne, April 22nd, 1969 AvK / Ax

500 South Main Street, Akron, Ohio 44318 (V.St.A.).

Manufacture of nonwovens

The invention "relates to a process for the production of Nonwovens with improved physical properties, especially with improved internal strength and increased Splitting resistance o

Polymer latices have been used for coating for many years and impregnation of paper and more recently used for the manufacture of nonwovens. This becomes common the paper or fleece is soaked in the latex, whereupon the water is removed and the polymer remains, that binds the fibers in the finished fiber fleece. Regardless of the type of binder used is one of the more important factors that determines the ultimate physical properties associated with a Fiber fleece can be achieved, the amount of binder present in the fleece and also the evenness with which the Binder is dispersed in the fleece. If the fleece as a whole or local areas contain too little binder, are the physical properties of the fiber fleece, in particular the internal bond strength and the Resistance to splitting is very poor, and frequent

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this makes the fleece unsuitable for numerous applications «,

The problem of distributing a sufficient amount of binder evenly throughout the nonwoven material is particularly important when using latex binder systems. In these latex systems, it is often difficult to incorporate sufficient binder to achieve the desired physical properties, that it becomes necessary to impregnate the nonwoven again with the latex a second time after the first binder solution I3T ₀ This is dried, however, a time consuming and costly Treatment and therefore generally undesirable.

Efforts to solve the problem of tempered binder content to solve, led to extensive work primarily in the field of development of improved Latex binder systems ο In general contain the previously developed improved latex binder systems, monomers that, when exposed to heat, chemical reagents or to react catalysts to form crosslinked polymers with improved physical properties capital. However, this approach is not completely satisfactory because the binders are more effective but tend to migrate through the fiber fleece. This migration takes place during drying or hardening of the fleece instead. When removing the water, the polymeric binder reaches the surface of the nonwoven material. This results in an uneven distribution of the binder in the fleece and consequently poor Physical Properties.

The viscosity of the binder latex may G-Ummen and pastes, polyvinyl alcohol and ₉ are the like increases _as before the impregnation of the fiber fleece by the addition of thickening agents such as natural ^. This measure is jedoeüi aar partially effective because it is due to the sefeleohteia penetration ability

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and the difficulty of the order of the thickened laticea it is impossible to achieve a uniform impregnation of the fiber fleece right from the start.

The subject of the invention is a method according to which fiber fleece with significantly improved internal strength (Splitting resistance) can be achieved by covering the fiber fleece with a latex of a carboxylated acrylate or Butadiene polymers impregnated, and then before drying or hardening the action of ammonia or amine vapors is exposed. In order to achieve these improved properties, the fiber fleece or the mat is made with the polymer latex impregnated for the purposes of the invention by interpolymerization of one or more carboxyl-containing Monomer, preferably oc, ß-olefinically unsaturated Carboxylic acid monomer, with an acrylate monomer or butadiene, or by mixing a carboxyl-containing one Polymer or co-polymer latex can be obtained with an acrylate or butadiene polymer latex. Even other polymerizable comonomers can be used in lesser amounts Quantities are interpolymerized to form latiees useful for the purposes of the invention.

The nonwovens treated according to the invention have improved internal strength compared to nonwovens, in the usual way, i.e. without treatment with ammonia or amines. The method according to the invention is applicable to both non-woven fabrics as well as paper. The splitting resistance iet has been increased by up to $ 100 on certain types of paper. The process enables a more even distribution of the polymeric binder to be achieved in the finished product Fleece as a result of the fact that the latex binder is thickened in situ before drying. This thickening in situ reduces the migration of the polymer to the surface of the material when the water is removed afterwards a uniform impregnation from the outset or

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Impregnation with the unthickened binder latex has been achieved is.

The method according to the invention applies to all nonwovens applicable, i.e. depending on the fiber used to manufacture the fleece and the thickness of the fleece Not "limited in use. This is not to say that certain pastes are suitable for use with the aorylate and butadiene polymers used according to the invention for certain applications the nonwovens are not more suitable than others, but only that in all Cases in which a fiber has the necessary properties to be processed into nonwovens or mats zu. werden, these fleeces and mats can be treated according to the invention.

Natural fibers, e.g. cotton, wool, silk, sisal, cäntala (Fibers from the leaves of the agave cantale), henequen, hemp, jute, kenaf, sunn and ramie, can as well as synthetic ones Fibers or threads are used for the production of the nonwovens "or mats. As synthetic Fibers are, for example, rayon (viscose), cellulose esters, e.g. cellulose acetate and cellulose triacetate, Protein fibers, for example from casein, polyamides (nylon), e.g. the duroh condensation of adipic acid and hexamethylenediamine or self-condensation of nylon types made from Caprolaotam, polyester such as polyethylene glycol terephthalate, Acrylic fibers that contain at least about $ 85 acrylonitrile with vinyl chloride, vinyl acetate, vinyl pyridine, methacrylonitrile ο the like. contain, and the so-called modaoryl fibers, the contain small amounts of acrylonitrile, fibers of copolymers of vinyl chloride with vinyl acetate or vinylidene chloride, fibers obtained from the formal derivatives of polyvinyl alcohol and polyolefin fibers, e.g. from polyethylene and polypropylene.

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The fibrous webs or mats can be prepared _e paper by conventional methods, "for example, is produced on a moving fine wire screen from an aqueous suspension of the fibers. When other fibers are to be yerarbeitet to nonwovens, the production of the nonwoven fabric, depending on the particular fiber or fiber blend may , oriented or random deposition, thickness of the fleece etc. by carding, garnishing, deposition from an air stream, from solutions, from a melt, wet laying or the like. "

The method according to the invention is particularly advantageous for special papers that require special binders, to change the structural properties of the paper · Papers made from. bleached or unbleached Fabric as well as unbleached sulphide pulp, bleached sulphide pulp, unbleached sulphate pulp (Kraft paper), semi-bleached and bleached sulfate pulps can be used. Papers, made exclusively from synthetic fibers, and papers made from blends of natural fibers Cellulosic and synthetic fibers can also be used.

The latex binders used for the process according to the invention are aqueous latexes of carboxyl-containing acrylate or butadiene polymers. The required carboxyl groups can either be chemically bonded, ie one or more α, β-olefinically unsaturated carboxylic acid monomers are polymerized with the acrylate or butadiene monomers and optionally with other comonomers, or a carboxyl-containing polymer (thickener) is mixed with the acrylate or butadiene polymer latex. In each case, the latex present in the carboxyl groups constitute about 0.05 to 25 wt -. ⁰ Jo of the total polymer made.

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The alkyl acrylate polymer latices used are produced by polymerization of esters of α, ß-olefinically unsaturated carboxylic acids of the general formula

CH ₂ = C-CuOR ₁ R

in which R represents hydrogen, a methyl radical or Äüiylrest and R .. represents a hydrocarbon radical with 1 to 12 carbon atoms. Representative monomers of the type mentioned above are methyl acrylate, ethyl acrylate, the propyl acrylates, butyl acrylates, amyl acrylates, hydroxyl acrylates, cyclohexyl acrylate, phenyl acrylate, 2-methylhexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethylhexyl methacrylate, and methyl methacrylate, ethyl methodacrylate, nacrylate, and octyl methacrylate. The lower alkyl esters of acrylic and methacrylic acid with 4 ¹ Ms 10 carbon atoms are particularly preferred. The polymeric acrylic atTbinder can contain one or more other polymerizable comonomers, preferably of the vinylidene type (ΟΗρ = Ο ^) interpolymerized with the lower alkyl acrylate monomers. This polymeriaierbaren comonomers to about 49.95 percent -. ⁰ Yes

Make up 20 of the polymer.

The butadiene polymer latices suitable for the purposes of the invention are through polyaerization "on about 29.5 to 95.5% by weight butadiene, preferably up to about 70% by weight Styrene or up to about 50 wt .- ^ acrylonitrile produced. In addition to these monomers, up to about 40 wt or more other polymerizable comonomers therewith be interpolymerized.

The polymerizable comonomers used belong to the vinylidene type (CH ₂ = C ^). Suitable polymerizable comonomers for the purposes of the invention are, for example, conjugated dienes such as isoprene, a-Olefiae me ethylene, propylene and isobutylene, vinyl halides such as Yinyl-

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Chloride, vinyl bromide, vinyl fluoride, vinylidene chloride and vinylidene fluoride, Vinylester as vinyl acetate, alkyl vinyl ether as Hethylvinyläther, Iaopropylvinylather, n-Butylvinylather and Isopropylvinyläther, a _t beta olefinisoh un- · saturated amides, such as acrylamide, N-methyl acrylamide, N-tert, butylacrylamide, N-cyclohexyl acrylamide, biacetona ylamide, methacrylamide and li-ethy! Methacrylamide, α, ß-olefinically unsaturated H-alkylolamides of the general formula

0 H
OH ₂ -OCN- (0H ₂ ) _x -0H

in which R is a hydrogen atom or an alkyl radical with 1 to 4 carbon atoms and χ is a number from 1 "to 4, e.g. N-methylolacrylamide, H-ethanol acrylamide, K-propanol acrylamide, N-methyl o! Methacrylamide and N-ethylol methaorylamide, polyfunctional Compounds such as methylene-bis-acrylamide, Ethylene glycol dimethaorylate, diethylene glycol diacrylate, Ally! Pentaerythritol and divinylbenzene. The latices on Acrylate-based polymers can also contain small amounts of interpolymerized butadiene, while the Butadiene polymer latices are low as comonomers Quantities of esters of α, β-olefinically unsaturated carboxylic acids such as methyl acrylate, xethyl acrylate, propyl aorylate, Butyl acrylate, amyl acrylate, cyclohexyl aorylate, 2-methylhexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, Ethyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, Contain methyl ethacrylate and ethyl ethacrylate can"

When the carboxyl groups necessary for the process according to the invention are chemically bonded in the polymer latices are, they are made by polymerizing one or more α, β-olefinically unsaturated carboxylic acid monomers, containing 3 to 10 carbon atoms with the

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Acrylate or butadiene and introduced with the other coraonomers that may be present. Suitable monomeric acids of this type are, for example, acrylic acid, methacrylic acid, ethacrylic acid, α-chloroacrylic acid, α-cyanoacrylic acid, crotonic acid, ß-acryloxypropionic acid, hydrosorbic acid, sorbic acid, ce-chlorosorbic acid, cinnamic acid, ß-styryl acrylic acid, itaconic acid, citraconic acid, citraconic acid, itaconic acid, citraconic acid , Glutaconic acid and aoonitic acid. Preferred monomeric carboxylic acids are the α, β-monoolefinically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid. If appropriate, mixtures of one or more of the abovementioned carboxylic acids can also be used. The carboxyl containing monomers can be achieved by Interpolymersation content that includes the tTberpolymtPisation, graft or block polymerization o "AEGL _e, be chemically bonded to the butadiene polymer, necessary for the purposes of the invention. In general, the butadiene polymers contain about 0.5 to 20% by weight of interpolnerlsrt © α, β-alefinically unsaturated carboxylic acids. A particularly advantageous polymer latex for the purposes of the invention contains about 50 to 70% by weight of butadiene, 20 to 45% by weight -fC styrene or acrylonitrile, 1 to 5 $ acrylic acid or methacrylic acid and up to about 20% by weight of other polymerized, interpolymerized comonomers. Styrene and acrylonitrile can be present individually or in combination in the butadiene latices. Good nonwovens were obtained when the butadiene latex contained approximately equal parts of styrene and acrylonitrile interpolymerized. The preferred polyacrylate binders for the purposes of the invention contain about 70 to 95% by weight of the acrylic acid ester, about 0.1 to 10% by weight of the carboxyl- containing monomers and about 5 to 29% by weight of other polymerizable comonomers.

The latices of the carboxyl-containing polymers can according to any conventional emulsion polymerization process

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getting produced. The aqueous medium can be emulsifier-free or contain an emulsifier. When using an emulsifier to produce the binder latioes, its Amount "up to about 6% by weight or more, based on the total monomers, be. The emulsifier can be used at the beginning of the Polymerization or added portionwise or metered in during the entire polymerization. Any Customary anion-active, cation-active or nonionic emulsifiers can be used, but the get best results when using anionic emulsifiers. Typical anionic emulsifiers that can be used are the alkali or ammonium salts of the sulfates of alcohols with 8 to 18 carbon atoms, e.g. sodium lauryl sulfate, ethanolamine lauryl sulfate and Ethylamine lauryl sulfate, alkali and ammonium salts of sulfonated petroleum fractions or paraffin oils, sodium salts of aromatic sulfonic acids such as dodeoan-1-sulfonic acid and ootadiene-1-sulfonic acid, aralkyl sulfonates such as Sodium isopropylbenzenesulfonate and sodium dodecylbenzenesulfonate, Alkali and ammonium salts of sulfonated dicarboxylic acid esters such as sodium dioctyl sulfosuccinate and Disodium N-ootadecylsulfosuccinamate, alkali or ammonium salts the free acids of complex organic mono- and diphosphate esters and the like as cationic emulsifiers the salts of strong inorganic acids and organic bases with long hydrocarbon chains are suitable, e.g. laurylamine hydrochloride, diethylaminoethyldecylamine, Decylamine hydrochloride, trimethyloetylammonium bromide and dodecyltrimethylammonium bromide. As niohtionogenic Emulsifiers are, for example, ootyl or nonylphenyl polyethoxyethanol and the like in embossing. The alkali metal salts of aromatic sulfonic acids are preferred as emulsifiers and the sodium salts of aralkyl sulfonates. It can be expedient and advantageous, in addition to the abovementioned emulsifiers, post-polymerization emulsifiers add polymeric latex binders to maintain latex stability

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su improve if the latex a long time before use should be stored. As post-polymerization emulsifiers The same or different emulsifiers can be used as are used for carrying out the polymerization to be needed.

Free radical-forming catalysts are used to initiate the polymerization. Using this Catalysts are not absolutely necessary in certain systems, but these catalysts ensure a more uniform and controllable polymerisation and a good polymerisation rate * The usual ones Free radical initiators can be used, such as the various peroxygen compounds such as persulfates, benzoyl peroxide, tert-butyl hydroperoxide, 1-hydroxycyolohexyl hydroperoxide and azo compounds such as azodiisobutyronitrile and dirnethylazodiisobutyrate. Particularly advantageous as polymerization initiators are the water-soluble peroxygen compounds, e.g. hydrogen peroxide, and the sodium, potassium and

20 ammonium persulfates.

The alkali metal and ammonium persulfates used as catalysts can be used as such or in activated redox systems be used. Typical redox systems are the persulfates in combination with a reducing substance, e.g., a polyhydroxyphenol, and an oxidizable sulfur compound, e.g., sodium sulfite or sodium bisulf it, a reducing sugar, a diazomeroapto compound, a ferricyanide compound, dimethylamino «· pcopionitril and similar heavy metal ions, e.g. silver, Copper (l), bis-iron, cobalt, nickel ions, and others Ions can also be used to activate persulfate catalyzed polymerizations. In general the amount of free radical initiator is about 0.1 to 5 $, based on the G-ev / icht de-r

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Total isomers. The initiator is generally at the beginning added to the polymerization all at once, but the initiator is often added or metered in in portions desirable during the entire polymerization «

When carrying out the polymerizations, the monomers are usually added to the polymerization reactor, which already contains the water and the emulsifier. The reactor and its contents are then heated, followed by the addition of the polymerization initiator. The lemperatür, wherein the polymerization is carried out is not critical importance and may be between about -30 ° and 100 ⁰ O or above. Excellent results were obtained, however, when the Polyiaerisationstemperatur between 0 ° and 90 ⁰ O held wurfi © _c Ds rp ^ value is generally maintained throughout the Poi ^ ^ IEJ iaation below. Polymerization-modifying Μϊΐϋΐ '- .. j - «Β · primary, secondary and tertiary mercaptans, Püffen electrolytes and the like can also be included in the polymerization approach«

Except for latices based on acrylate and butadiene, which Contain interpolymerized carboxyl groups, the process is also applicable if the acrylate or butadiene polymer latices themselves do not contain carboxyl groups or an insufficient amount of carboxyl groups so that they as such would be ineffective for the method according to the invention. However, these latter latices are suitable when a water-soluble salt of an Oopolymer, which by polymerization of an α, β-olefinically unsaturated Carboxylic acid such as acrylic acid, methacrylic acid, itaconic acid and the like with one or more esters of an a, ß-

., - ^ _,, ....., received .w.orden ,. olefinically unsaturated carboxylic acid / or a copolymer an a, ß-olefinisoh unsaturated carboxylic acid with a polyalkenyl polyether of a polyhydric alcohol is added.

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Suitable copolymer additives of the first type are, for example, copolymers which are about. Contain / "methacrylic acid with about 30 to 85 percent by _e - - 15 to 70 percent, interpolymerized $> an ester of an α, β-olefinically unsaturated carboxylic acid" preferably contain these copolymers about 35 to 65 $ of methacrylic acid and about 40 to 65 $ of an aoryl acid ester. Acrylic esters derived from alcohols with 1 to 8 carbon atoms such as methanol, ethanol, propanol, isopropanol, n-butanol, secondary butanol, tertiary butanol, hexanol, cyclohexanol and octanol are suitable for the production of these copolymers. Esters of one of the alcohols mentioned above with acrylic acid or methacrylic acid are preferably used. If ethyl acrylate is used as the acrylic acid ester, the copolymer generally contains about 40 to 55% methacrylic acid. When using methyl acrylate as the acrylic acid ester, about 35 to 50% by weight of methacrylic acid should be present in the copolymer.If necessary, mixtures of one or more acrylic acid esters can be used to produce these copolymer additives.Ethylacrylate in combination with methyl methacrylate is particularly preferred. The above copolymers are particularly effective when they contain about 0.1 to 0.8 percent by weight of a crosslinking monomer such as methylene-bis-acrylamide, ethylene glycol dimethacrylate, diethylene glycol diacrylate, allyl pentaerythritol and divinylbenzene.

Polymeric thickeners are also suitable as additives for use with the acrylate or butadiene binder latioes, the polymerization of an a, ß-olefinically unsaturated carboxylic acid such as acrylic acid, itaconic acid, Maleic acid and fumaric acid are obtained with a polyalkenyl polyether a polyhydric alcohol, the polyhydric alcohol having about 4 carbon atoms and at least 3 hydroxyl groups and the polyether more than one Contains alkenyl radical per molecule. These thickeners

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are detailed in U.S. Patent 2,798,053 described

The polymeric thickeners for the purposes of the invention are prior to the impregnation of the nonwoven with mixed with the acrylate or butadiene binder latices. Dependent on varies on the carboxyl content of the polymer additive and the desired carboxyl group content in the latex binder the amount of these additives within wide limits »In general, make the above-described external copolymer thickeners about 0.1 to 10 Gewe-A preferably about 0.5 to 4% by weight of the total polymer content of the Binder latex.

Carboxyl-containing polyacrylate latices which contain about 0.1 to 10 wt. The base polymers generally contain about 50 to 99.9% by weight (based on the total monomers) of an ester of an α, β-olefinically unsaturated carboxylic acid and about 0 to 49% by weight of one or more other polymerizable comonomers, preferably about 0 , 5 to 15 wt -. ^a / o of an α, ß-olefinically unsaturated N-alkylol amide, or 0.5 to 35 percent by _e - # of acrylamides or nitriles such as acrylamide, methacrylamide, acrylonitrile or methacrylonitrile.

These preferred and extremely effective latexes of overpolymerized Polyacrylate are made with little modification of the conventional polymerization processes described above obtain. The acrylate base polymer is produced according to these usual processes «,

Certain changes must be made in carrying out the overpolymerization. In general it can

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carboxyl-containing monomers as such can be overpolymerized, or other polymerizable monomers can be used with the carboxyl-containing monomers are combined. Custom ^ bar polymers are obtained when the other polymerizable monomers are vinylidene monomers in such Amounts are used that the weight ratio of the vinylidene comonomer to the monomeric acid is less than about 5: 1 ο excellent overpolymerizations are achieved, when the weight ratio of the vinylidene comonomer to the monomeric acid is kept at 1s1 or below will.

The same monomers that make up the base acrylate polymer are interpolymerized, also serve as advantageous comonomers with the monomeric acid in the Overpolymerization. Small amounts of alkyl acrylates such as Ethyl acrylate and methyl acrylate proved to be particularly advantageous comonomers, which overpolymerized with the acid monomers can be. In addition to the usual vinylidene comonomers, the overpolymerization batch can also be used small amounts of polyfunctional compounds such as methylenebisacrylamide, Ethylene glycol dimethacrylate, diethylene glycol diacrylate, Allyl pentaerythritol and divinylbenzene included will. By including these vinylidene monomers and polyfunctional compounds that interact with the Crosslink acid monomers during overpolymerization

latices are obtained which have excellent stability and can develop extremely high viscosities and when used as a binder for nonwovens in the process according to the invention result in products which have a have significantly improved internal strength or resistance to splitting.

The over-polymerization or grafting of the acid monomers begins when the polymerization of the base polymer is complete or substantially complete. It is be ~ especially useful to start with after one

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Conversion of about 5Ο ^ ό of the basic monomers has been achieved. Preferably, the overpolymerization is delayed "until the monomers making up the basic polymer have polymerized to about Τ0" / ί> or more. The process of combining other monomers with the carboxylic acid monomer is particularly advantageous for achieving stable overpolymerizations and latices if the overpolymerization is delayed until high conversions of the basic monomers are reached.

The method according to the invention consists in that ammonia or amine vapors on the nonwoven fabric with has been impregnated with one of the aforementioned carboxyl-containing polymeric latex binders. By This exposure will thicken the latex binder in situ, causing migration of the polymeric binder from the interior Areas of the fiber fleece to the surface in the removal of the water during drying is prevented. In this way, the polymeric binder is distributed more evenly within the fiber fleece than before was possible. The sheer result of this treatment is a marked improvement in physical properties of the fiber fleece. The internal strength or the resistance to splitting and in general the tensile strength, in particular the wet strength of the fiber webs are improved by using the method according to the invention.

Thus, the greatest possible advantage of the invention is achieved, the _pH value must be kept of the Latioes oarboxylhaltigen polymer during the impregnation or impregnation below certain limits. This achieves complete penetration and uniformity of the binder latex in the entire fiber fleece. This is essential to achieve the improved physical properties. The required _pH value is indeed different from a latex to another, depending on the monomers used and the carboxyl group, but should

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for perfect impregnation, preferably lie on the acidic side. With a neutral or light basic latex, however, acceptable results will be obtained in most cases. In general, the ρττ value of the carboxyl-containing butadiene polymer latex about 7.5 or below, preferably between about 6.5 and 2.5. Excellent results are obtained if latices are acidified at the higher p ^ boundaries prior to impregnation, to a more advantageous one PjT value and a more advantageous viscosity.

To facilitate impregnation of the nonwoven fabric, the total solids content of the latex binder is generally used kept under about $ 50. Excellent results will be Get with latices that are about $ 15 to $ 35 total solids

15 included «

A critically important feature of the invention is the action of ammonia or amine vapors on the impregnated Non-woven fabric. In general, ammonia is preferred because it is readily available and gaseous and is excellent Solubility in the binder latioes in the applied Temperatures, however, can also use primary, secondary or tertiary aliphatic monoamines with excellent Results are used. Typical amines that are suitable can contain up to 12 carbon atoms, however amines with up to 6 carbon atoms are generally preferred. Excellent results are with gaseous Amines such as methylamine, ethylamine, dimethylamine and trimethylamine have been obtained. The higher molecular weight amines, which are liquid under normal conditions at room temperature are, for example, primary amines with 3 to 11 carbon atoms and the lower secondary and tertiary amines, which are normally exert significant vapor pressure at room temperature or slightly above and are readily soluble in water, can also be used. In general, those suitable for the process according to the invention have amines

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Boiling points below about 15O ⁰ C, preferably below about 100 ⁰ G. The easy solubility of ammonia and amines in water ensures that they act evenly on the binder latices even in the innermost areas of the fiber fleece and thereby cause a thickening of the latex in situ and a Eliminate subsequent migration of the binder to a large extent. »Ammonia and amines have the ability to be absorbed instantaneously or essentially instantaneously by the impregnated fiber fleece, and come into contact with both the inner and the superficial areas with the same effect, whereby the method according to of the invention is so advantageous and the development of superior physical properties in the fiber treated according to the invention

15 nonwovens possible.

Attempts to achieve this uniform treatment of impregnated nonwovens by other methods have been unsuccessful. Either, in cases where the binder latex was thickened prior to impregnation, the binder could does not penetrate evenly into the fiber fleece, or the attempt to subsequently thicken the binder latex not to do with ammonia or amines according to the invention, but with other means, led to such a thing strong and rapid initial thickening on the surface of the nonwoven fabric, which thereby further penetration of the thickener was prevented into the inner areas of the fiber fleece, so that these inner Areas of migration of the binding agent during irooknen subject »

The treatment of the impregnated fiber fleece with ammonia or amine vapors depends on the one used Different latex binders and thickeners. The contact times are generally shorter than about 80 minutes and are preferably between about 2 seconds and 5 minutes »When using ammonia and

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more volatile amines have worked successfully with contact times between 5 seconds and 1 minute it was found that maximum properties were imparted to the cured nonwoven fabric. When the maximum thickening the binder latex is reached once, results from a further treatment with ammonia or amines no further improvement in the properties of the fleece, but longer exposure to the Ammonia or amine vapors also have no adverse effects.

The treatment with ammonia or amine is expediently carried out in a chamber which is kept at room temperature or above, for example in an oven with material feed due to gravity, in which there is a sufficient concentration of ammonia or amine vapors for the treatment of the impregnated fiber fleece can be maintained. The treatment ovens can "be kept at elevated temperatures, but these temperatures should generally ^{not exceed 100 °} C., especially when long treatment times are used. Due to the short contact times which are possible in the process according to the invention, the impregnated Nonwoven fabric, through which ammonia or amine vapors are continuously passed to facilitate treatment, such a continuous process is highly desirable for large-scale operations.

After treatment and thickening with ammonia or amine, the fleece is dried and cured. Drying is typically accomplished by passing the nonwoven material through one or more heating chambers maintained at a temperature between about 93 and 149 ° C. The preferred drying temperature is in the range between about 107 and 135 ⁰ C. The heating chambers can be maintained * in order to facilitate the removal of 'the water, the dried, optionally under reduced pressure.

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Web is then generally performed by one or more heating chambers, the "be maintained at higher temperatures, to cure the binder used and the ultimate physical properties of the nonwoven Removing · zubilden. These heating chambers are at temperatures between about 121 and 163 ⁰ C. preferably maintained from 135 to 149 ⁰ C. In each drying cycle of the hardness level, the nonwoven material may be once or as often be performed as required by the heating chamber. depending on the temperature exforderlich for the particular binder used latex, drying and curing must not be carried out in two separate stages »

In the following examples, the amounts given relate to based on weight, unless otherwise stated.

example 1

To illustrate the method according to the invention, developed a butadiene polymer latex containing interpolymerized carboxyl groups for use as a binder The latex was produced by emulsion polymerization of 52 parts of butadiene, 45 parts of styrene and about 1.5 parts each of acrylic acid and methacrylic acid in 95 parts of water, which is 3 parts of an alkylbenzenesulfonate contained as an emulsifier. The polymerization was carried out with 0.15 parts of potassium persulfate as a catalyst

triggered. The reaction mixture was kept at about 50 ^° C. until essentially complete conversion was achieved. The butadiene copolymer latex obtained contained about total solids.

An impregnation bath was made by diluting the latex to 25% total solids with distilled water became. Uncoated flat paper 0.25 mm thick (Patterson Parchment Company) with minimal contact of Paser to fiber was wrapped in a dacron marquisette

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given and then impregnated by placing the paper in the Latex bath was dipped. The excess binder latex was then removed by placing the paper between nip rollers, which were kept under a pressure of about 9 kg, was passed through «The impregnated paper was then taken out of the marquisette cover «,

The impregnated in the manner described paper was then treated for 3 minutes with Amrnoniakdämpfen by being placed in a warm (60-80 ⁰ C) oven, the ammonia vapors contained. The ammonia atmosphere was created by placing a fresh 20% ammonium hydroxide solution in a dish on the bottom of the oven before inserting the paper. Immediately after the action of the ammonia, the paper was dried and ^{cured for 5 minutes in an oven kept at 135 °} C. with ventilation.

The physical properties of the hardened paper were then determined and compared with the properties of the same impregnated paper, but which had not been treated with ammonia. The tensile strength (breaking strength) of the nonwoven materials was determined according to ASTM D 1117-63 (strip method). Samples used to determine dimensional stability were kept in water for 16 hours at room temperature immediately before the test. The splitting resistance for the fibers and the internal strength of the paper were determined as follows: A fleece sample of 25.4 × 152 mm was placed between two pieces of adhesive tape (Bondez T ~ 7) ″ of 38 × 152 mm. The layer structure was held for 30 seconds glued to a hot plate with the weight of an iron at 135 ° O. The adhesive strips were then pulled apart at a speed of 30.5 cm / minute.

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Papers impregnated with the butadiene binder latex described above and dried in the usual way and had been cured had a barrel strength of 953 g / 2.54 cm wide and an internal strength of 408 g / 2.54 cm wide. Same paper samples that were made after the Impregnation and treated with ammonia vapors according to the invention prior to drying and curing a wet strength of 1.4 kg / 2.54 cm width and a splitting resistance of 468 g / 2.54 cm width.

When the butadiene latex described above is impregnated used by nonwovens other than paper, similar improved properties are obtained. Likewise, the properties of both paper and textile nonwovens are carboxylated with them Butadiene latices are impregnated if the treatment time is shorter than 3 minutes. Treatment times down to 10 seconds are effective. Through treatment with diethylamine instead of ammonia a comparable improvement in wet strength and des

20 splitting resistance achieved.

Example 2

The butadiene latex of Example 1 prepared was 25 $ G-esamtfeststoffe diluted, followed by the _pH value _is adjusted by addition of acetic acid 10biger to 3.5.

2.5 parts of a water-soluble salt of an copolymer of about 70% alkyl acrylate and about 30% methacrylic acid were mixed with the latex to increase the total content of carboxyl groups in the resulting butadiene binder latex. Paper, which is impregnated in the manner described in Example 1, treated for 3 minutes with ammonia at 81 ⁰ C and 5 minutes was cured at 135 ⁰ C, had a wet strength of 2 kg / 2.54 cm width and a Aufspalfcwiderstand of 544 g / 2.54 cm wide.

909845/1711

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Examples' j to 5

Latices based on a butadiene polymer with interpolymerized material Styrene and acrylonitrile were produced by a common emulsion polymerization method. the Latices were then impregnated on a 0.254 mm thick flat paper was used, which was then tested for its internal strength and adhesive strength, the Polymers from Examples 3 and 4 did not contain any interpolymerized, carboxyl group-containing monomers, therefore these latices were before use as a binder with 2.5 parts of the carboxylate described in Example 2 Mixed polymers. The test results are given in Table I, the internal strength in g / 2.54 cm Width and wet strength in kg / 2.54 cm width

15 ben is.

909845/171 1

Table I.

Example composition of the polymer

Detected property Mt iis.tex impregnated paper

Paper impregnated with latex + 2.5% copolymers as a thickening agent

none 3 minutes no hand treatment with ITH, lung

(81 ⁰ C) ³

3 minutes treatment with! THt p

Butadiene
Styrene

Wet strength (kg / 2.54 cm width)

Internal strength, 1.18 g / 2.54 cm width

604

2.72

695

Butadiene
Acrylonitrile ■ 3 U-Methylolaorylamide

Wet strength (kg / 2.54 cm 3 width)

Inner strength / 2.54 cm width

t, 11.8

590

11.34

726

Butadiene
Acrylonitrile methylmeth *

acrylate
Methacrylic acid

Wet strength (kg / 2.54 cm width)

Internal strength, g / 2.54 cm width, 1.68

91

2.13

173

7.3

530

6.92 632

192U58

A latex of alkyl acrylate with one überpolymerisierten carLoxylhaltigen monomers was prepared as a binder for fiber webs by an emulsified monomer mixture containing 32 parts Water 88.5 parts of _s ethyl acrylate, 2.7 parts of acrylonitrile, 1.8 parts of acrylamide and 1.8 parts of H -MethyIolacryIamid contained, in 64 parts of water containing 0.26 part of ammonium persulfate and an emulsifier, which was subjected to emulsion polymerization. The polymerization was carried out at 80 ° C., the monomer mixture being metered into the polymerization reactor for about 1 hour. Shortly before the addition was complete, a mixture of 2.6 parts of methacrylic acid, 2.5 parts of ethyl acrylate, 0.8 part of methyl methacrylate and 0.005 part of ethylene-bis-acrylamide was added to the reactor. The polymerization was then ^{carried out further at 80 0} O until essentially complete conversion was achieved. The final latex contained a total of 98 parts of water, 0.3 part of iatric lauryl sulfate as an emulsifier, and about 50% total solids. Paper was impregnated and tested in the manner described in Example 1. The test results are shown in Table II below.

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Table II

Properties of the paper * Duration of treatment with ammonia **

less than 5 seconds. , 1 min, 3 mn. 60 minutes

Dry strength, kg / 2.54 cm width 27 »7

Wet strength, kg / 2.54 cm width 7.26 11 βφ

Tensile strength after hurting with

Q ₅ solvent, kg / 2.54 cm width 16.8 ο

J £ dry elongation, <fc 9 ■ -

ui Internal bond strength, g / 2.54 cm width 567 1190

14.52 13.6

1106

1191

28, 1 14, 06 17, 7th 9

* Average of 3 samples

** The heating chamber v / urde "at 81 ⁰ C held

CJR GD

192.H58

^{Paper which was held at 81 °} C. for 3 minutes before curing, ie was subjected to the same heat treatment as the 3-minute treated samples mentioned in Table I,. had only about half the internal bond strength of samples treated with ammonia. Had been in other words, by the ammonia treatment of Paservliese, the 3 'contained with Aerylatbindetlati ^r e © carboxyl groups treated "could nonwoven materials are obtained, compared to where borrowed impregnated fleeces twice Aufspaltxvider- - had stood.

When the latex described above is used for impregnating a polyester nonwoven fabric, and the impregnated fabric was 5 Mi mn en gshärtet at 135 ⁰ C, the polyester had a utibehandelte Aufspaltwiderstand of 595 -g / 2.54 cm width. The polyester sample, which had been treated with ammonia for 3 minutes before curing, had a higher splitting resistance, namely the cohesion within the polyester fleece was greater than the adhesion of the adhesive strip to the impregnated polyester fleece _; , and the fleece could be peeled off the adhesive tape before it split.

Example 7

An acrylate latex binder similar to that according to Example 6 was made after dilution to $ 25 total solids used to impregnate fluffy paper 0.254 mm thick. The impregnation and testing were carried out in the manner described above. The paper was' before the usual hardening carried out at 135 ° C for 5 minutes 3 minutes or 10 minutes with diethylamine vapors from a Treated 10bigen aqueous solution of the amine. The splitting resistance is compared in Table III with the values obtained without treatment with diethylamine and with a non-impregnated comparison paper *

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- 27 -

Table III

Paper sample splitting resistance, g / 2.54 cm width

I-.iclit impregnated matching paper, not treated uit diethyloniin 142

Impregnated prepreg paper, not treated with diethylamine

delt with Diethylamine loading 567 3 minutes
acts with Diethylamine 907 10 mins
treated Example 8 964

Acrylic acid was interpolymerized with ethyl acrylate, acrylonitrile and N-methylolacrylamide in a batch for a customary emulsion polymerization. The resulting polymer contained about 1 part acrylic acid, 94 parts ethyl aylate, and about 5 parts acrylonitrile and N-metholol acrylate oil. When diluted with water to about 257 "total solids, the polymer latex was used as an impregnant for paper samples in the manner described in Example 1. The impregnated untreated Comparison papers were cured 5 minutes at 135 ⁰ C, had a ITaßfestigkeit of 12.25 kg / 2.54 cm width and a Aufspaltwiderstand of 397 g / 2.54 cm width. the paper samples, .the after the impregnation and before the Curing, which had been treated with ammonia for 3 minutes in a heating chamber , showed a "Q"/> higher wet strength and a splitting resistance which was more than 50 $ higher The splitting resistance was 624 g / 2.54 cm width.

Example 9

About 100 parts of the acrylate polymer latex prepared according to Example 8 (25 total solids), which contained about 1 part of interpolymerized acrylic acid, were mixed with

909045/1711 ORIGINAL BATHROOM

_ ₂₈ _ 192H58

2.5 parts of a water-soluble salt of a copolymer of about 70 '/ a alkyl acrylates and about 3Q / ° metharyl acid mixed in order to increase the total content of carboxyl groups in the latex obtained. Treated Hachdein the paper samples for 3 minutes at 81 ⁰ C with ammonia and 5 minutes had been cured at 135 ⁰ C, was the ITaßf estigkeit 15.42 kg / 2.54 cm width and Aufspaltwiderstand 992 g / 2.54 cm width.

Example 10

10% acetic acid was added to 100 parts of the latex described in Example 8 until the latex had a p n value of about 3.4. 1 part of a copolymer of acrylic acid and about 1% by weight of a polyallyl ether of sucrose with an average of about 5.8 allyl groups per sucrose molecule was mixed with the acrylate latex. The latex obtained was used as an impregnating agent for 0.254 mm thick flat paper. After impregnation, the paper was treated with ammonia vapors at 89 ° C. for 3 minutes and then cured in the usual manner. The paper showed a noticeable increase (822 g / 2.54 cm width) in the splitting resistance compared with the impregnated papers described in Example 3.

example 11th

An acrylate polymer latex, which was suitable as a binder for nonwovens and papers, but contained no carboxyl groups, was prepared by emulsion polymerization of 93 parts of ethyl aylate, 4 parts of methyl methacrylate and 3 parts of a mixture of acrylic acid amides.The latex, which contained about 25 # total solids, was made in divided into two parts. The first portion was left unchanged, while the second T _e il was mixed with e INEM water-soluble salt of a copolymer of about 7Ö # alkyl acrylate and about 30 # methacrylic acid (2.5 parts of copolymer / 100 parts of latex). 0.254 mm thick paper

909845 / 1.711

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was impregnated with both latices to get the effect of one Treatment with ammonia lasting 3 minutes before hardening (5 minutes at 135 ° C) to determine the wet strength and the splitting resistance of the paper samples are given in Table IV below.

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Table IV

CD O CO 00

Impregnating agent ÜSi ^ properties of the breading

Ealifestigiceit, kg / 2.54- cm width

Inner binding , g / 2.54 cm wide

Without treatment
with ITK *

Ethyl acrylate-i-ethyl methaorylate-acrylic acid amide copolymer latex

100 'Heal copolymer latex + 2.5 parts water soluble Acrylate-methacrylic acid copolymer

Minutes with
ITH, treated

Without treatment with

Minutes
with case
treated

7.71

369

454

10.89

397

964

192U58

The above examples clearly show the advantages Recognize the invention, oie illustrate that nonwovens , üie rait carboxyl-containing acrylate and butadiene polymer latices are impregnated, which are then treated with ammonia, improved internal bond strength and have improved leak strength. They also show that according to the definition, Vex 'proceed with binder latices which due to the interpolymerization of one or more carboxylic monomers with the acrylate or butadiene monomers Contain chemically bonded carboxyl groups, or with Acrylnt- or Butadienebinderlatices, which to achieve the required carboxyl content with carboxyl-containing Uorolymerlatices are mixed, is feasible.

909845/1711 ORIGINAL BATHROOM

Claims (1)

- 32 claims Process for the production of nonwovens with improved physical properties, in particular with significantly increased splitting resistance, characterized in that the nonwoven fabric with a Aqueous carboxyl-containing dispersion of an acrylate or butadiene polymer impregnated and the impregnated nonwoven fabric before drying or curing with Treated ammonia vapors or vapors of an amine with 1 to C atoms. 2. The method according to claim 1, characterized in that that an aliphatic monoamine with 1 to 6 carbon atoms is used as the amine. j5. Method according to claim 1 and 2, characterized in that ^ that the exposure time of the ammonia to the impregnated fiber fleece is about 2 seconds to 5 minutes and the exposure temperature is less than 100 ° C. 4. The method according to claim 1 to 3, characterized »that the polymer latex has a powert below about 7.5 and the polymer about 0.5 to 2o wt, - $ i of one or more α, ß-olefinically unsaturated carboxylic acid monomers with 3 to Io contains carbon atoms. % Butadiene and containing interpolymerized to about 25 to 45 wt .- # styrene or acrylonitrile - 5. The method according to claim 1 to 4, ^ characterized in that as polymer, a butadiene polymer is used, to about 99.5 wt.. 909845/1711 6. The method according to claim 5, characterized in that that the butadiene polymer to about 4o wt .- ^ one or several vinylidene comonomers from the group consisting of vinyl acetate, methacrylonitrile, acrylamide, methaerylamide, Methylene-bis-acrylamide and α, β-olefinically unsaturated N-alkylolamides of the formula 0 H η ι CH ₂ = CCN (CH _{2) X} -QH, R in which R is a hydrogen atom or an alkyl radical 1 to 4 carbon atoms and χ is a number from 1 to 4, contains interpolymerized. 7. The method according to claim 1 to 4, characterized in that the polymer is an alkyl acrylate polymer is used, which is about 99 »5 wt .- ^ one or several esters of an α, β-olefinically unsaturated one 15 carboxylic acid of the general formula CH ₂ = C-COOR ₁ R in which R is a hydrogen atom, a methyl or ethyl radical and R, a hydrocarbon radical of 1 to 12 C atoms is, contains interpolymerized. 8. The method according to claim 7, characterized in that the alkyl acrylate polymer up to about 49.95 wt .- ^ one or more polymerizable comonomers from the group of butadiene, styrene, vinyl acetate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, methylenebisacrylamide and α, β-olefinically unsaturated N-alkylolamides of the formula & 098-45 / 1.71 1 192H58 O H η ι CH ₀ = CCN- in which R is a hydrogen atom or a methyl radical and χ is a number from 1 to 4, .interpolymerized contains. 9. The method according to claim 4, characterized in that the α, β-olefinically unsaturated carboxylic acid aonomers on an alkyl acrylate base polymer, which is up to about 99.5% w> - $ of the lower alkyl ester of the α, β-olefinically unsaturated carboxylic acid contains interpolymerized, overpolymerized or is grafted. Io. A method according to claim 9, characterized in that the alkyl acrylate to about 49 wt -.% Methylene-bis-acrylamide, one or more polymerizable comonomers selected from the group of butadiene, styrene, vinyl acetate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and α, β- olefinically unsaturated N-alkylolamides of the formula O H tt ι CH ₂ = CCN (CHG) _x -OH, R in which R is a hydrogen atom or a methyl radical and χ is a number from 1 to 4, contains interpolymerized. 11. The method according to claim 1, characterized in that a copolymer obtained by polymerizing an α, β-olefinic unsaturated carboxylic acid with one or more esters of an α, β-olefinically unsaturated carboxylic acid has been obtained, or a copolymer which 90 9845/1711 192H58 by polymerizing a <x, ß-olefinically unsaturated Carboxylic acid with a polyalkenyl ether of a polyhydric alcohol has been obtained with one held at a p ^ of less than about 7.5 Acrylate or butadiene polymer latex blends. 12. The method according to claim 11, characterized in that the acrylate or butadiene polymer latex is none Contains carboxyl groups. That the copolymers from about 15 to Jo by weight 13. The method of claim 12, characterized -.% M & er acrylic acid and about 3o to 85 wt -.% Of an alkyl ester containing an α, ß-olefinically unsaturated carboxylic acid interpolymer ized. 14. The method according to claim I3 characterized in that the copolymer is about 35 to 65 wt -.% Methacrylic acid, about 4o to 65 wt .- ^ an ester of an acrylic acid with a 1 to 8 carbon atoms-containing alcohol and about o, l . contains interpolymerized% of a crosslinking monomer and total polymer is present in an amount of from about o, l to Io by weight 5ί - to 0.8 wt. 15. The method of claim 14, daduroh in that the copolymer of ethyl acrylate with about 4o to 55 wt -% of methacrylic acid containing interpolymerized and. in an amount of about 0.5 to 2.5 wt -.%, based on the total polymer, is present. 16. The method according to claim 14, characterized in that the copolymers of methyl acrylate with from about 35 to 5o weight - contains interpolymerized% methacrylic acid and. 9 O 9 8 U b / 1 7 1 1 192U58 in an amount of about 0.5 to 2.5 wt .- #>, based on the total polymer, is present, 17. The method according to claim 12, characterized in that the copolymer is a cc, ß-olefinisoh unsaturated carboxylic acid from the group acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid with .. one of a polyhydric alcohol with up to 4 carbon atoms and at least contains three hydroxyl groups and one polyether containing more than one alkenyl radical in the molecule, interpolymerized and is present in an amount of about 0.1 to 10% by weight , based on the total polymer. 909845/171 1