CHEMICALLY BONDED NONWOVEN SUBSTRATES

Field of the invention

The present invention relates to chemically bonded nonwoven substrates and to polyester binders for chemically bonding nonwoven fibers of a nonwoven substrate.

Technical background

Nonwoven substrates relate to fabric-like materials made from fibers or filaments arranged into a web. The web may be formed by a dry-laid or wet-laid process. The web is then consolidated by bonding the fibers, in other words by forming attachment points between the fibers. Chemical bonding is a consolidation method involving the use of an aqueous dispersion of polymer particles (also referred to as a latex) to bond the fibers. Nonwoven substrates are therefore distinct from knitted substrates or woven substrates in that the substrate is formed by directly bonding the fibers to one another without any interlacing or stitching step.

In the field of disposable nonwovens, the main technologies used for chemically bonding the fibers of nonwoven substrates are based on ethylene-vinyl acetate (EVA) and acrylic (ACR) polymeric dispersions.

In the field of durable (i.e. reusable) nonwovens, such as technical nonwovens or composite materials, other polymers may be used as binders. For example, acrylic modified polymeric dispersions, such as vinyl acrylic dispersions, as well as SBR latexes and vinyl acetate homo-polymers can be used.

These polymers are often self-crosslinking with the disadvantage, however, of comprising formaldehyde-releasing functionalities, such as N-methylol- acrylamide (N-MA). This is undesirable, especially if the nonwovens are to be used in personal care products, food products or clothing.

With the aim of preventing the release of toxic formaldehyde, US patent number 4,455,342 discloses an aqueous dispersion of an acrylic resin, which is suitable for the reinforcement of fibrous articles, such as nonwovens, while being free of formaldehyde or formaldehyde-releasing substances.

Acrylic binders are mostly made from petroleum-based materials. Also, acrylic dispersions are prone to the development of bacteria and require the use of antimicrobial substances. Among the different applicative characteristics required for the polymers used for the chemical bonding of nonwovens, the mechanical properties in dry and wet conditions are a key parameter. The nonwoven producers are still interested in new polymers having formaldehyde free crosslinking functionalities, good mechanical applicative properties but also exhibiting a high bio-sourced content.

Accordingly, there is still a need for alternative binders that may be used to obtain chemically bonded nonwoven substrates with one or more of the following properties: good dry tensile strength, good wet tensile strength, liquid absorptive capacity, softness, biodegradability, high content of bio-sourced components, absence of yellowing and low VOC content (in particular formaldehyde-free).

Summary of the invention

The present invention follows from the unexpected finding by the inventors, that a polyester resin can be used as a non-formaldehyde-releasing binder for chemically bonding nonwoven fibers to provide nonwoven substrates with good water absorbency and good mechanical properties, in particular the wet tensile strength.

Advantageously, the alkyd resin according to the invention can be biosourced and optionally biodegradable.

The present invention thus relates to a chemically bonded nonwoven substrate comprising nonwoven fibers bonded by a binder comprising a polyester resin.

The present invention also relates to a method for chemically bonding fibers of a nonwoven substrate comprising: i) contacting a binder comprising a polyester resin with nonwoven fibers; ii) curing the binder, thereby bonding the nonwoven fibers together to form a chemically bonded nonwoven substrate.

The present invention also relates to a use of a polyester resin for chemically bonding nonwoven fibers.

Description of the invention

As intended herein, the word “comprising” is synonymous to “include” or “contain”. When a subject-matter is said to comprise one or several features, it is meant that other features than those mentioned can be comprised in the subjectmatter. When a subject-matter is said to consist of one or several features, it is meant that no other features than those mentioned are comprised in the subject-matter. When a subject-matter is said to consist essentially of one or several features, it is meant that other features than those mentioned may be comprised in the subjectmatter in minor proportion (for example a composition consisting essentially of Z means a composition comprising more than 90%, more than 95%, more than 98%, more than 99%, more than 99.5%, more than 99.9% or even 100%, by weight of Z based on the weight of the composition).

Nonwoven fibers

Nonwoven fibers according to the invention relate to any fiber suitable to prepare nonwoven substrates. In particular, the nonwoven fibers may be selected from natural fibers, modified natural fibers, synthetic fibers, inorganic fibers and mixtures thereof.

Natural fibers are bio-sourced fibers derived from plants or animals. Animal fibers are fibers made of proteins, which can be obtained from the hair, fur, wool or silk of animals, such as sheep, alpaca, rabbits, goats, horses, llamas, minks or camels. Plant fibers, also referred to as cellulosic fibers, are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood, stem, leaves, flowers or fruits of plants, such as cotton, flax, jute, hemp, sisal, kenaf, nettle, ramie or abaca. In addition to cellulose, the fibers may also contain hemicellulose and lignin, with different percentages of these components altering the mechanical properties of the fibers.

Modified natural fibers, also referred to as artificial fibers, are natural fibers that have been modified by one or more chemical treatments, such as enzymatic treatment, maleinization, epoxidation, esterification, anhydridation or alkoxylation, and/or physical treatments, such as heating or applying steam. Examples of suitable modified natural fibers include viscose, modal, and lyocell.

Synthetic fibers are fibers made by humans through polymerization, mainly of petroleum-based raw materials. Synthetic fibers may be created by extruding fiber-forming materials through spinnerets. Examples of suitable synthetic fibers include polyester, polyamide, acrylic, aramid or olefin (such as polyethylene, or polypropylene).

Inorganic fibers are fibers made of inorganic material. Inorganic fibers can be obtained from inorganic substances such as rock, slag, clay or glass, or from organic material such as pitch, tar or synthetic fibers. Examples of suitable inorganic fibers include mineral wool, glass fibers, basalt fibers, carbon fibers, ceramic fibers or metal fibers.

In one embodiment, the nonwoven fibers may be natural fibers, in particular cellulosic fibers.

Preferably, the nonwoven fibers have a diameter of from about 500 nm to about 100 m, more preferably of about 1 pm to about 50 pm, most preferably of about 1 pm to about 10 pm.

Polyester resin

Polyester resins are well known to the person of skill in the art. Polyester resins are polymers comprising repeating units containing one or more ester bonds (-C(=O)-O or -O-C(=O)-). A polyester resin may be obtained by polycondensation of one or more polyacids and one or more polyols.

The polyester resin according to the invention may be based on: a) a polyol component, b) a polyacid component, and c) optionally one or more additional components such as a fatty component and/or a rosin component.

As used herein a “polyester resin based on component X” or “a polyester resin comprising component X” means a polyester resin obtained by polymerization of a composition comprising component X, in other words a polyester resin comprising units derived from the polymerization of component X.

Preferably, the polyester resin according to the invention is at least partially bio-sourced. In particular, the polyester resin according to the invention may be based on at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, at least 97%, at least 98%, at least 99% or even 100%, by weight of bio-sourced components based on the total weight of the polyester resin.

As intended herein, the polyester resin according to the invention, or components thereof, are said to be “bio-sourced” when they originate from plants or animals, optionally after chemical modifications, such as hydrogenation, hydroxylation, maleinization, epoxidation, esterification, anhydridation or alkoxylation, or after physical treatments, such as heating. Examples of suitable bio-sourced components include rosin, glycerol, naturally occurring oils and fats (i.e. triglycerides extracted from plants, animals or milk), naturally occurring fatty acids, mono- or di-glycerides of naturally occurring fatty acids, naturally occurring polyacids, as well as dimers or trimers thereof and alkyl esters thereof.

Fatty component

The polyester resin may be based on a fatty component.

When the polyester resin is based on a fatty component, the polyester resin may be referred to as an alkyd resin or an oil-modified polyester resin. Accordingly, an alkyd resin may correspond to a polyester resin based on: a) a polyol component, b) a polyacid component and c) an additional component comprising a fatty component and optionally a rosin component.

Alternatively, when the polyester resin is based on a fatty polyacid (such as a dimer or trimer of a fatty acid), said fatty polyacid component may partially or totally replace the polyacid component b). Accordingly, an alkyd resin may correspond to a polyester resin based on: a) a polyol component, b) a fatty polyacid component, and c) optionally one or more additional components, such as an additional fatty component and/or an additional polyacid component and/or a rosin component.

As used herein, the term “fatty component” means a component comprising at least one fatty acid or a derivative thereof.

As used herein, the term “fatty acid” means a compound of formula R-COOH wherein R is an aliphatic hydrocarbon chain bearing from 7 to 36 carbon atoms, preferably 16 to 24 carbon atoms, which may optionally be substituted by one or more substituents such as methyl or hydroxyl. A fatty acid may be saturated or unsaturated. When a fatty acid is unsaturated it may comprise one or more carbon-carbon double bonds. An unsaturated fatty acid may also be referred to as an oxidizable fatty acid as the unsaturations may be oxidized in the presence of air, optionally in the presence of a drier catalyst, to provide crosslinked structures during curing of the alkyd resin. As used herein, the term “fatty acid derivative” means a fatty acid that has been modified, for example by one or more of the following reactions: esterification with an alkanol to provide a fatty acid alkyl ester (FAAE); partial or total esterification of glycerol to provide a mono-, di- or triglyceride; hydrogenation of a carbon-carbon double bond to provide a hydrogenated fatty acid; epoxidation of a carbon-carbon double bond to provide an epoxidized fatty acid; hydroxylation of a carbon-carbon double bond to provide an hydroxylated fatty acid; dehydration of a hydroxylated fatty acid to provide an unsaturated fatty acid; maleinization with maleic anhydride, to provide a maleated fatty acid; dimerization or trimerization of unsaturated fatty acids to provide a fatty acid dimer or trimer oligomerization/standolization of unsaturated fatty acid at high temperature (> 200°C) to provide stand oils of fatty acid, also referred to as standolies.

In particular, the fatty component may comprise at least one fatty acid selected from caprylic acid (8:0), capric acid (10:0), lauric acid (12:0), myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), 12-hydroxystearic acid (18:0), arachidic acid (20:0), behenic acid (22:0), lignoceric acid (24:0), cerotic acid (26:0), myristoleic acid (14:1 ), palmitoleic acid (16:1 ), sapienic acid (16:1 ), oleic acid (18:1 ), elaidic acid (18:1 ), vaccenic acid (18:1 ), linoleic acid (18:2), linoelaidic acid, (18:2), alpha-linolenic acid (18:3), arachidonic acid (20:4), eicosapentaenoic acid (20:5), erucic acid (22:1 ), docosahexaenoic acid (22:6), derivatives thereof and mixtures thereof. In the aforementioned list of fatty acids, the first number in parenthesis indicates the total number of carbon atoms of the fatty acid and the second number indicates the total number of carbon-carbon double of the fatty acid.

In particular, the fatty component may comprise a mixture of fatty acids or derivatives thereof, for example a mixture of monoacids derived from plants or animals, preferably plants. Examples of such mixtures include soybean oil fatty acids (SOFA), sunflower oil fatty acids, tall oil fatty acids (TOFA), castor oil fatty acids (COFA), dehydrated castor oil fatty acids (DCOFA), linseed oil fatty acids (LOFA), rapeseed oil fatty acids, palm oil fatty acids, palm kernel oil fatty acids, coconut oil fatty acids, safflower oil fatty acids, derivatives thereof and mixtures thereof.

Preferably, the fatty acid component has an average iodine value of from 100 to 200 mg of iodine per gram of fatty acid component.

Preferably, the weight ratio between unsaturated fatty acids and total fatty acid of the fatty component according to the invention is of 0, of 1 , or of from 0 to 1 , from 0 to 0.5, or from 0.5 to 1 .

Preferably, the polyester resin according to the invention has an oil length of from 5% to 40%, in particular of from 10% to 35%, more particularly of from 15% to 30% by weight based on the total weight of the polyester resin.

As intended herein, the “oil length” of the polyester resin according to the invention relates to the weight percentage of the fatty component, relative to the total weight of the resin. If the polyester resin is based on a rosin component comprising tail-oil fatty acids, said tail-oil fatty acids are included in the weight percentage of the fatty component. If the polyester resin is based on a polyacid component comprising a fatty acid dimer or trimer, said fatty acid dimer or trimer is included in the weight percentage of the fatty component. If the polyester resin does not comprise a fatty component, then the oil length of the polyester resin is 0%. Such a polyester may also be referred to as an oil-free polyester.

Preferably, the polyester resin according to the invention has an oxidizable unsaturation content of from 0 mmol to 0.25 mmol, in particular of from 0 mmol to 0.15 mmol, more particularly of from 0 mmol to 0.05 mmol, of oxidizable unsaturations per g of dry resin.

As intended herein the “oxidizable unsaturation content” relates to the amount of C=C double bonds in mmol that can be crosslinked per gram of dry resin.

Rosin component

The polyester resin may be based on a rosin component. Suitable rosin-based polyester resins according to the invention are notably described in International publication WO 2012/042153 which is incorporated herein by reference.

As used herein, the term “rosin component” means a component comprising rosin or a derivative thereof.

As is well known by one skilled in the art, rosin, also referred to as colophony, is a natural resin derived from resinous trees, in particular conifers, such as pines, cedars, firs, hemlocks, larches, spruces. Rosin may be produced by heating conifer oleoresin (i.e. gum tapped from living conifers) to eliminate the volatile liquid terpene components, also referred to as turpentine. Rosin produced with this process may be referred to as gum rosin. Gum rosin generally comprises resin acids and is substantially exempt of fatty acids. Alternatively, rosin may be produced from the distillation of crude fall-oil (CTO). Rosin produced with this process may be referred to as tail-oil rosin (TOR) or tail-oil pitch and is referenced under CAS No. [8016-81-7]. Crude fall-oil is a by-product resulting from the manufacture of paper pulp by the Kraft process. When conifer wood shavings are treated with a mixture of sodium hydroxide and sodium sulfide under hot conditions, the lignin and the hemicellulose degrade and dissolve in the liquor, whereas the cellulose can be recovered in the form of pulp and then washed. The liquor, which also contains resin acids and fatty acids in the form of sodium carboxylates, may be recovered and concentrated. The foam which forms at the surface of the concentrated liquor, also referred to as kraft soap or resin soap, may be recovered and acidified under hot conditions with sulfuric acid so as to provide crude tail-oil. Crude tail-oil may then be distilled at reduced pressure to provide tail-oil rosin as the residual non-volatile fraction. Tail-oil rosin generally comprises resin acids and tail-oil fatty acids (mainly palmitic acid, oleic acid and linoleic acid).

The term “rosin” encompasses gum rosin and tail-oil rosin. The composition of rosin varies depending on the resinous tree used and where it comes from. The term “rosin derivative” means a rosin that has been modified, for example by one or more of the reactions described above for the modification of a fatty acid.

In particular, the rosin component may comprise at least one resin acid or a derivative thereof. The rosin component of the polyester resin may comprise a mixture of resin acids or derivatives thereof.

As intended herein, a “resin acid”, also called a “resinous acid” or “rosin acid”, refers to a polycyclic compound, in particular a terpenoid, bearing one carboxylic acid group which can be derived from resinous trees, in particular conifers. The term “resin acid derivative” means a resin acid that has been modified, for example by one or more of the reactions described above for the modification of a fatty acid.

Preferably, the rosin component comprises at least one resin acid represented by one of the following formulae (I) and (II), or a derivative thereof: wherein the hashed bonds may independently be selected from single C-C bonds and double C=C bonds.

More preferably, the rosin component comprises at least one resin acid selected from the group consisting of abietic acid, pimaric acid, levopimaric acid, dihydroabietic acid, tetrahydroabietic acid, dehydroabietic acid, palustric acid, neoabietic acid, isopimaric acid, sandaracopimaric acid, derivatives thereof and mixtures thereof.

The polyester resin according to the invention may be based on from 20% to 85%, in particular from 25% to 80%, more particularly from 30% to 75%, even more particularly from 35% to 70%, by weight of resin acid or derivative thereof, based on the total weight of the polyester resin.

Polyacid component

The polyester resin may be based on a polyacid component.

As used herein, the term “polyacid component” means a component comprising a polyacid or a derivative thereof. The polyacid component may comprise a mixture of polyacid or derivatives thereof.

As used herein, a polyacid is a compound bearing at least two -COOH groups, in particular from 2 to 3 -COOH groups. The term “polyacid derivative” is a compound capable of yielding a polyacid in situ, for example by hydrolysis or ring opening. Examples of suitable polyacid derivatives include alkyl esters of a polyacid and cyclic anhydrides. The polyacid may preferably be an aromatic polyacid or an aliphatic polyacid (i.e. a non-aromatic polyacid). Examples of suitable polyacids include phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, adipic acid, azelaic acid, glutaric acid, 3,3-diethylglutaric acid, malonic acid, pimelic acid, sebacic acid, suberic acid, succinic acid, 2,2- dimethylsuccinic acid, 2-methylsuccinic acid, dodecenylsuccinic, acid, dodecanedioic acid, citric acid, a fatty acid dimer, a fatty acid trimer, itaconic acid, fumaric acid, maleic acid, citraconic acid, trimellitic acid, derivatives thereof and mixtures thereof.

The polyester resin according to the invention may be based on 10% to 55%, in particular from 15% to 50%, more particularly from 20% to 45%, even more particularly from 25% to 40%, by weight of polyacid or derivative thereof, based on the total weight of the polyester resin.

Polyol component

The polyester resin may be based on a polyol component.

As used herein, the term “polyol component” means a component comprising a polyol or a derivative thereof. The polyol component may comprise a mixture of polyols.

As intended herein, the term “polyol” means a compound bearing at least two hydroxyl (OH) groups.

A polyol may have an OH functionality ranging from 2 to 10, preferably from 3 to 6. In other words, the polyol may bear from 2 to 10, preferably from 3 to 6 OH groups. In one embodiment, the polyol component may comprise a polyol having an OH functionality of at least 3.

More preferably, the polyol component according to the invention comprises at least one polyol selected from the group consisting of ethylene glycol, polyethylene glycol (preferably with a number-average molecular mass Mn ranging from 300 to 6,000 g/mol), propylene glycol (1 ,2-propanediol), 1 ,3- propanediol, dipropylene glycol, triethylene glycol, glycerol, diglycerol, trimethylolpropane, di(trimethylolpropane), trimethylolethane, pentaerythritol, dipentaerythritol, sorbitol, mannitol, methyl glucoside, polyglycerol (in particular glycerol oligomers, such as Polyglycerol-3 and decaglycerol) as well as the alkoxylated (i.e. ethoxylated and/or propoxylated derivatives thereof) and mixtures thereof.

As intended herein “polyglycerol-3” is a mixture of glycerol oligomers, i.e. glycerol oligomerized in the presence of oligomers containing 30% to 55% by weight of glycerol trimer constituting the predominant oligomer.

Most preferably, the polyol component comprises, or consists of, polyglycerol-3, in particular with a -OH functionality ranging from 5 to 6. Preferably, the polyester resin according to the invention has an acid number of 2 to 15, preferably from 5 to 12 mg KOH/g.

Preferably, the polyester resin according to the invention has a hydroxyl number of 30 to 120, preferably from 40 to 100 mg KOH/g.

Preferably, the polyester resin according to the invention has a numberaverage molecular mass Mn, measured by GPC as polystyrene equivalents in THF, of from 1000 to 10 000, in particular of from 1 100 to 5000, more particularly of from 1200 to 3500.

Preferably, the polyester resin according to the invention has a Tg, measured by DSC, ranging from -40°C to 50°C and more preferably from -20°C to 35°C.

A particularly preferred polyester resin is a rosin-based alkyd resin marketed under trade name SYNAQUA® 4856 by Arkema.

The preparation of the polyester resin according to the invention, in particular the alkyd resin according to the invention, can be performed by polycondensation reaction under inert atmosphere at a temperature of between 180°C and 300°C, preferably between 250°C and 270°C, preferentially with removal of the water formed during condensation. A vacuum (reduced pressure) of moderate level ranging from 50 to 250 mmHg may be applied at the end of the polycondensation in order to reduce the reaction times. It is possible, in order to prevent and/or further reduce the coloration and oxidation of rosin during the synthesis, to use additives, in particular antioxidants, as employed in the preparation of rosin esters used in particular for adhesives: phenol sulfites, paraformaldehyde, hypophosphorous acid, trialkyl or triphenyl phosphites. A more exhaustive list of additives that may be used for this purpose is described in US patent number 4,744,925, column 2, lines 50-62, which list is incorporated herein by reference.

In a preferred embodiment, the polyester resin is subsequently emulsified to provide an aqueous emulsion of polyester resin.

The emulsion may be obtained by phase inversion in the presence of one or more surfactants or by self-emulsification without any surfactant, preferably by phase inversion in the presence of one or more surfactants.

In the phase inversion process, the emulsification may be carried out at a temperature of from 30 to 90°C and preferably from 50 to 85°C. The emulsification may be carried out in a reactor stirred via a dual-flow stirring system. The resin may be emulsified, at neutral or slightly alkaline pH. The resin may be emulsified in the presence of a surfactant or a mixture of surfactants. The presence of a surfactant improves the stability of the dispersion, thus preventing sedimentation and/or coalescence during the emulsification and storage/use of the product. A selection criterion for a nonionic surfactant is the HLB index (hydrophilic-lipophilic balance) representing the ratio of hydrophilic and hydrophobic characters in the surfactant.

The surfactant may comprise a surfactant selected from an ionic surfactant (preferably anionic surfactant), a nonionic surfactant, a hybrid surfactant of mixed structure and combinations thereof.

Among the anionic surfactants that are suitable for this invention, mention may be made of sodium, lithium, potassium, ammonium or magnesium salts of alkyl ether sulfates (in particular with alkyl ranging from Cs to Cis or C12), alkyl benzene sulfates, alkyl sulfates, alkyl phosphates, dialkyl sulfosuccinate esters or even soaps obtained from the corresponding fatty acids. The anionic surfactant is preferably used in combination with at least one nonionic surfactant.

According to the present invention, a hybrid surfactant of mixed structure is a surfactant which comprises both a nonionic structure, such as a polyoxyalkylene segment (more particularly oxyethylene and/or oxypropylene units) and an anionic structure (for instance a sulfonate or sulfate or phosphate or phosphonate group) on the same molecule or molecular chain. For example, the hybrid surfactant of mixed structure may be a sulfonate, sulfate, phosphate or phosphonate ester of a polyether alcohol or of an alkoxylated fatty alcohol. Another example of a hybrid mixed surfactant is an alkoxylated alkyl phenol sulfonate or phosphonate.

As preferred examples of suitable nonionic surfactants, mention may be made of: ethoxylated C12-C18 fatty alcohols (6 to 50 OE), ethoxylated iso-Cio fatty alcohols (6 to 50 OE), ethoxylated mono-branched C10-C18 fatty alcohols (6 to 50 OE), sorbitol fatty esters, ethoxylated sorbitol esters (5-50 OE), alkyl polyglucosides, glucamides, glycerol, diglycerol or polyglycerol fatty esters, ethoxylated fatty acids (7-100 OE), ethoxylated castor oil (hydrogenated or non-hydrogenated) (30-40 OE), glycol or polyethylene glycol fatty acids, nonionic polymers and other block copolymers, for instance poly (propylene glycol)-poly(ethylene glycol) block copolymer. The nonionic surfactant is preferably combined with an anionic surfactant.

Preferably, a combination of a nonionic surfactant and of an anionic surfactant is used. The weight ratio of the ionic surfactant to nonionic surfactant may be from 25/75 to 50/50. Such a combinations advantageously provides stable emulsions with a small particle size, preferably less than 300 nm.

The total amount of surfactant may be from 2% to 15%, preferably from 5% to 10%, by weight based on the weight of the polyester resin.

The pH of the medium is preferably adjusted as a function of the acidity of the resin. This is why a basic aqueous solution, of from 1% to 50% and preferably from 10% to 20% by weight of base, may be introduced after the addition of the surfactants, at the emulsification temperature. To this end, basic (alkaline) aqueous solutions may be used, such as aqueous LiOH, NaOH or KOH solutions, aqueous ammonia or amines, preferably tertiary or hindered amines, such as diethanolamine, triethanolamine, aminomethylpropane or triethylamine.

The aqueous dispersion of the resin may also be obtained by selfemulsification of the resin without any surfactant after at least partial neutralization of the carboxylic functions of the resin.

Binder

The binder according to the invention comprises at least one polyester resin according to the invention.

The binder according to the invention may be contacted with the nonwoven fibers in an uncured (i.e. liquid) state. The binder may be in a cured state forming a cured (i.e. solid) polymer matrix interconnecting the nonwoven fibers. The term “binder” may thus indifferently refer to an uncured binder (prior to curing) or to a cured binder (after curing). The cured binder may be obtained by curing the uncured binder.

Preferably, the uncured binder may be in the form of an aqueous emulsion of the polyester resin as defined above, preferably an oil-in water emulsion of the polyester resin. Accordingly, the uncured binder may comprise polyester resin droplets dispersed in an aqueous phase. During curing, the aqueous phase of the emulsion may be removed and the polyester resin droplets may coalesce to form a continuous polymer matrix.

The aqueous emulsion may have a solids content relative to the weight of the aqueous emulsion ranging from 30% (w/w) to 70% (w/w) and preferably from 40% (w/w) to 60% (w/w). Preferably, the mean particle size of the polymer droplets of the aqueous emulsion according to the invention ranges from 100 to 500 nm. The aqueous emulsion according to the invention may be free of any organic solvent, this meaning a corresponding content of volatile organic compounds (VOC) in said emulsion of less than 2000 ppm, preferably less than 1000 ppm and more preferentially less than 500 ppm.

The binder according to the invention may further comprise at least one moisture-retaining additive, such as a glycol, in particular a polyethylene glycol (PEG).

The binder according to the invention may also comprise at least one surfactant or a mixture of surfactants as described above.

The binder of the invention may comprise a second resin which is distinct from the polyester resin as defined above. Preferably, the binder according to the invention comprises at least one ethylenically unsaturated resin, more preferably an aqueous dispersion of an ethylenically unsaturated resin.

In one embodiment, the ethylenically unsaturated resin may be simply admixed with the polyester resin, i.e. the ethylenically unsaturated resin and the polyester resins are prepared separately and are mixed together after they have been polymerized. In other words, the ethylenically unsaturated resin and the polyester resin may not be in a co-polymerized form. The binder may thus be an aqueous composition comprising emulsified droplets of polyester resin and ethylenically unsaturated resin particles which are distinct from one another. In particular, the ethylenically unsaturated resin and the polyester resin may not be bonded to one another by chemical covalent bonds or strong physical intermolecular interactions such as hydrogen bonding or electrostatic interactions.

In another embodiment, the ethylenically unsaturated resin and the polyester resins may be co-polymerized or form a hybrid polymer. For example, a multistage polymerization process can be used wherein a first resin is prepared in a first step and, in a subsequent step, one or more monomers of a second resin are added and polymerized in the presence of the first resin. Alternatively, the polyester resin and the ethylenically unsaturated resin may be prepared separately and subsequently bonded to one another by chemical covalent bonds or strong physical intermolecular interactions. For example if the ethylenically unsaturated resin comprises carboxylic acid groups, they can react with the hydroxyl groups of the polyester resin by heating. The binder may thus be an aqueous dispersion of particles comprising both the ethylenically unsaturated resin and the polyester resin. Advantageously, the presence of at least one ethylenically unsaturated resin in the binder improves the mechanical properties of the resulting chemically bonded nonwoven substrates.

The ethylenically unsaturated resin may be selected from a (meth)acrylic resin, a vinylic resin, a styrenic resin, an olefinic resin and mixtures thereof.

As used herein, a (meth)acrylic resin is a polymer comprising monomeric units derived from the polymerization of one or more (meth)acrylic monomers, such as alkyl (meth)acrylates (in particular methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, tert-butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate), hydroxyalkyl (meth)acrylates (in particular 2-hydroxyethyl (meth)acrylate), (meth)acrylic acid, (meth)acrylamide, (meth)acrylonitrile or mixtures thereof; and optionally one or more ethylenically unsaturated co-monomers, such as vinyl aromatic monomers (in particular styrene), vinyl monomers, unsaturated polyacids, unsaturated polyacid derivatives, or mixtures thereof. When the (meth)acrylic resin comprises monomeric units derived from vinyl co-monomers as described below, the resin may be referred to as a vinyl-(meth)acrylic resin. When the (meth)acrylic resin comprises monomeric units derived from vinyl aromatic co-monomers as described below, the resin may be referred to as a styrene-(meth)acrylic resin.

As used herein, a vinylic resin is a polymer comprising monomeric units derived from the polymerization of one or more vinyl monomers, such as vinyl halides (in particular vinyl chloride), vinyl esters (in particular vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl pentanoate, vinyl hexanoate, vinyl octanoate, vinyl 2-ethylhexa noate, vinyl pelargonate, vinyl laurate, vinyl stearate, and vinyl versatate, i.e. esters of branched monocarboxylic acids having 6, 9, 10 or 1 1 carbon atoms, available under references VeoVa® EH, VeoVa® 9, VeoVa® 10 or VeoVa® 1 1 from Hexion), vinyl ethers (in particular methyl-, ethyl-, butyl- or iso-butyl vinyl ether) or mixtures thereof; and optionally one or more ethylenically unsaturated co-monomers, such as olefins, (meth)acrylic monomers, unsaturated polyacids, unsaturated polyacid derivatives, or mixtures thereof. When the vinylic resin is a vinyl ester resin that comprises monomeric units derived from (meth)acrylic co-monomers as described above, the resin may be referred to as a vinyl ester-(meth)acrylic resin. When the vinylic resin is a vinyl ester resin (in particular a vinyl acetate resin) that comprises monomeric units derived from an ethylene co-monomer, the resin may be referred to as an ethylenevinyl ester resin (in particular an ethylene-vinyl acetate resin (EVA)). As used herein, a styrenic resin is a polymer comprising monomeric units derived from the polymerization of one or more vinyl aromatic monomers, such as styrene, alpha-methylstyrene, tert-butylstyrene, ortho-, meta- or paramethylstyrene, ortho-, meta- or para-ethylstyrene, o-methyl-p-isopropylstyrene, p- chlorostyrene, p-bromostyrene, o,p-dichlorostyrene, o,p-dibromostyrene, ortho-, meta- or para -meth oxystyrene, optionally substituted indenes, optionally substituted vinylnaphthalenes, acenaphthylene, diphenylethylene, vinyl anthracene or mixtures thereof; and optionally one or more ethylenically unsaturated co-monomers such as butadiene, (meth)acrylic monomers, vinyl monomers, unsaturated polyacids, unsaturated polyacid derivatives, or mixtures thereof. When the styrenic resin comprises monomeric units derived from (meth)acrylic co-monomers as described above, the resin may be referred to as a styrene-(meth)acrylic resin. When the styrenic resin comprises monomeric units derived from a butadiene co-monomer, the resin may be referred to as a styrenebutadiene resin (SBR).

As used herein, an olefinic resin is a polymer comprising monomeric units derived from the polymerization of one or more olefin monomers, such as ethylene, propene, 1 -butene, isobutylene, diisobutylene, 1 -nonene, 1 -decene or mixtures thereof; and optionally one or more ethylenically unsaturated co-monomers such as (meth)acrylic monomers, vinyl esters, unsaturated polyacids, unsaturated polyacid derivatives, or mixtures thereof.

Preferably, the ethylenically unsaturated resin according to the invention is selected from a (meth)acrylic resin, a styrene-(meth)acrylic resin, a vinyl ester- (meth)acrylic resin, an ethylene-vinyl ester resin, a vinyl ester resin, a styrenebutadiene resin and combinations thereof. More preferably, the ethylenically unsaturated resin is a (meth)acrylic resin, a styrene-(meth)acrylic resin or a vinyl ester-(meth)acrylic resin.

Preferably, the ethylenically unsaturated resin according to the invention comprises monomeric units derived from the polymerization of at least one unsaturated polyacid or derivative thereof. As intended herein, the term “unsaturated polyacid derivative” means a compound capable of yielding a unsaturated polyacid in situ, for example by hydrolysis or ring opening. Examples of suitable unsaturated polyacid derivatives include alkyl esters of unsaturated polyacids and cyclic anhydrides. Preferably, the unsaturated polyacid or derivative thereof is selected from the group consisting of fumaric acid, maleic acid, itaconic acid, aconitic acid, mesaconic acid, anhydrides thereof and mixtures thereof. More preferably, the unsaturated polyacid is itaconic acid. Advantageously, the presence of an unsaturated polyacid or derivative thereof in the ethylenically unsaturated resin according to the invention provides chemically bonded nonwoven substrates with enhanced wet tensile strength (WTS). Without wishing to be bound by theory, it is believed that this enhancement is obtained by chemical reaction between at least part of the carboxylic groups of the ethylenically unsaturated resin and at least part of the hydroxyl groups of the polyester resin during curing of the binder.

The ethylenically unsaturated resin may have a glass transition temperature Tg of from 25 to 60°C, in particular 30 to 50°, more particularly 35 to 45°C, as measured according to the method described herein.

In one embodiment the ethylenically unsaturated resin is a (meth)acrylic resin, a styrene-(meth)acrylic resin or a vinyl ester-(meth)acrylic resin obtained from a monomeric composition comprising: a) 0 to 70 %, preferably 5 to 60 %, of one or more alkyl (meth)acrylate monomers having a Tg higher than 0°C (such as methyl methacrylate); b) 30 to 70 %, preferably 40 to 60 %, of one or more alkyl (meth)acrylate monomers having a Tg lower than 0°C (such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and mixtures thereof); c) 0 to 50 %, preferably 25 to 35%, of one or more monomers selected from a vinyl aromatic monomer (such as styrene), a nitrile monomer (such as acrylonitrile) and mixtures thereof; d) 1 to 10 %, preferably 3 to 6%, of one or more ethylenically unsaturated acids or derivatives thereof (such as (meth)acrylic acid or itaconic acid); e) 0 to 50%, preferably 0 to 30 %, of one or more vinyl ester monomers (such as a vinyl ester of a C2-C10 carboxylic acid), f) 0 to 30% of one or more monomers different from a), b), c), d) and e) as defined above; g) 0 to 1 .5% of at least one chain transfer agent (such as a thiol); wherein the % are % by weight based on the total weight of monomers a) + b) + c) + d) + e) + f) and the sum of a) + b) + c) + d) + e) + f) is equal to 100%.

In one embodiment, the ethylenically unsaturated resin is a (meth)acrylic resin, a styrene-(meth)acrylic resin or a vinyl ester-(meth)acrylic resin obtained from a monomeric composition comprising: a) 5 to 70 %, preferably 10 to 60 %, of one or more alkyl (meth)acrylate monomers having a Tg higher than 0°C (such as methyl methacrylate); b) 30 to 70 %, preferably 40 to 60 %, of one or more alkyl (meth)acrylate monomers having a Tg lower than 0°C (such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and mixtures thereof); c) 0 to 50 %, preferably 25 to 35%, of one or more monomers selected from a vinyl aromatic monomer (such as styrene), a nitrile monomer (such as acrylonitrile) and mixtures thereof; d) 1 to 10 %, preferably 3 to 6%, of one or more ethylenically unsaturated acids or derivatives thereof (such as (meth)acrylic acid or itaconic acid); e) 0 to 50%, preferably 0 to 30 %, of one or more vinyl ester monomers (such as a vinyl ester of a C2-C10 carboxylic acid), f) 0 to 30% of one or more monomers different from a), b), c), d) and e) as defined above; g) 0 to 1 .5% of at least one chain transfer agent (such as a thiol); wherein the % are % by weight based on the total weight of monomers a) + b) + c) + d) + e) + f) and the sum of a) + b) + c) + d) + e) + f) is equal to 100%.

For example, the ethylenically unsaturated resin may be a (meth)acrylic resin obtained from a monomeric composition comprising: a’) 30 to 70 %, preferably 40 to 60 %, of one or more alkyl (meth)acrylate monomers having a Tg higher than 0°C (such as methyl methacrylate); b’) 30 to 70 %, preferably 40 to 60 %, of one or more alkyl (meth)acrylate monomers having a Tg lower than 0°C (such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and mixtures thereof); c’) 0 % of one or more monomers selected from a vinyl aromatic monomer (such as styrene), a nitrile monomer (such as acrylonitrile) and mixtures thereof; d’) 1 to 10 %, preferably 3 to 6%, of one or more ethylenically unsaturated acids or derivatives thereof (such as (meth)acrylic acid or itaconic acid); e’) 0 % of one or more vinyl ester monomers (such as a vinyl ester of a C2-C10 carboxylic acid), f ’) 0 to 30% of one or more monomers different from a), b), c), d) and e) as defined above; g’) 0 to 1 .5% of at least one chain transfer agent (such as a thiol); wherein the % are % by weight based on the total weight of monomers a’) + b’) + o’) + d’) + e’) + f’) and the sum of a’) + b’) + o’) + d’) + e’) + f’) is equal to 100%.

In another example, the ethylenically unsaturated resin may be a styrene- (meth)acrylic resin obtained from a monomeric composition comprising: a”) 0 to 30 %, preferably 1 to 20 %, of one or more alkyl (meth)acrylate monomers having a Tg higher than 0°C (such as methyl methacrylate); b”) 30 to 70 %, preferably 40 to 60 %, of one or more alkyl (meth)acrylate monomers having a Tg lower than 0°C (such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and mixtures thereof); c”) 30 to 70 %, preferably 40 to 60 %, of one or more monomers selected from a vinyl aromatic monomer (such as styrene), a nitrile monomer (such as acrylonitrile) and mixtures thereof; d”) 1 to 10 %, preferably 3 to 6%, of one or more ethylenically unsaturated acids or derivatives thereof (such as (meth)acrylic acid or itaconic acid); e”) 0 % of one or more vinyl ester monomers (such as a vinyl ester of a C2-C10 carboxylic acid), f”) 0 to 30% of one or more monomers different from a), b), c), d) and e) as defined above; g”) 0 to 1 .5% of at least one chain transfer agent (such as a thiol); wherein the % are % by weight based on the total weight of monomers a”) + b”) + c”) + d”) + e”) + f”) and the sum of a”) + b”) + c”) + d”) + e”) + f”) is equal to 100%.

Preferably, the weight ratio between the polyester resin according to the invention and the ethylenically unsaturated resin according to the invention is from 1 :10 to 10:1 , in particular from 1 :5 to 5:1 , more particularly from 1 :2 to 2:1 .

The binder of the invention may comprise a catalyst. A catalyst may be used to facilitate curing and to promote cross-linking. Examples of suitable catalysts include metal salts (in particular metal soap carboxylates) or metal complexes (in particular metals complexed with nitrogen-containing ligands) based on cobalt, iron, manganese, vanadium, calcium, zirconium, or barium.

The binder of the invention may comprise a cross-linker. A cross-linker may be used to provide cross-links with the polyester resin to enhance the mechanical properties of the resulting chemically bonded nonwoven substrate. Methods for preparing a binder with an aqueous polyester emulsion according to the invention are notably described in International publication WO 2012/042153 which is herein incorporated by reference.

Chemically bonded nonwoven substrate

As intended herein, a “chemically bonded nonwoven substrate” relates to an interconnected web of nonwoven fibers bonded together by a binder. The binder may create a network of interlocked fibers throughout the nonwoven structure.

A chemically bonded nonwoven substrate according to the invention preferably does not encompass webs of nonwoven fibers bonded solely by means other than chemical bonding, for example mechanical, solvent and/or thermal bonding. However, the web of nonwoven fibers may be subjected to other bonding techniques, for example mechanical bonding, prior to the chemical bonding with the binder of the invention. Mechanical bonding includes needlefelting, stitchbonding, and hydroentangling. Solvent bonding involves softening or partially dissolving fibers with a solvent to provide self-bonding surfaces. Thermal bonding involves the use of heat and often pressure to fuse or weld fibers together at points of intersection or in patterned bond sites.

A chemically bonded nonwoven substrate according to the invention preferably does not encompass webs of nonwoven fibers that are only superficially coated with a layer of cured binder. Accordingly, the binder may not be present only on the surface of the web of nonwoven fibers, i.e. as a finish coating resulting from a chemical finishing treatment, but may at least partially penetrate into the web of nonwoven fibers. For example, the binder may penetrate the web of nonwoven fibers in an amount of at least 50%, at least 60%, or least 70%, at least 80%, at least 90%, at least 95%, at least 99% or even 100% of the thickness of the web of nonwoven fibers.

Preferably, the chemically bonded nonwoven substrate according to the invention is selected from abrasives and sheets for scouring, agricultural coverings, agricultural seed strips, apparel linings, automobile headliners, automobile upholstery, bed linen, bibs, blinds/curtains, cheese wraps, civil engineering fabrics, civil engineering geotextiles, coffee filters, cosmetic removers and applicators, covering and separation material, detergent pouches/fabric softener sheets, diapers, envelopes, filters, flooring, garment bags, household cleaning wipes, house wraps, hygiene products, insulation, labels, laundry aids, laundry bags, medical nonwovens, such as bandages, cast paddings and covers, dressings, packs, sterile overwraps, sterile packaging, surgical drapes, surgical gowns, swabs or under-pads, mops, personal wipes, reusable bags, roofing undercoverings and products, table linen, tags, tea and coffee bags, toilet paper, upholstery, vacuum cleaning bags, wallcoverings, wipes, in particular for household care, floor care, cleaning or pet care.

The chemically bonded nonwoven substrate of the invention may be prepared according to the method described hereinafter.

Method

The invention also relates to a method for chemically bonding fibers of a nonwoven substrate. The method of the invention comprises the following step: i) contacting a binder comprising a polyester resin according to the invention with a web of nonwoven fibers; ii) curing the binder, thereby bonding the nonwoven fibers together to form a chemically bonded nonwoven substrate.

The method of the invention may be carried out as a separate and distinct operation or it may be carried out as a sequential operation in tandem with formation of a web of nonwoven fibers. The web of nonwoven fibers used in step i) may be obtained by an airlaying, wetlaying or drylaying web formation process. The method of the invention may be repeated to enhance physical or chemical properties of the chemically bonded nonwoven substrate.

In step i) the binder can be contacted with/applied to the web of nonwoven fibers by numerous methods well-known to the person skilled in the art, such as spraying, impregnation (also referred to as saturation), padding or foaming. In particular, the nonwoven web may be impregnated with the binder, for example by immersing the web in a binder bath or by flooding the web as it enters the nip point of a set of pressure rolls. Alternatively, the nonwoven web may be sprayed with the binder, i.e. by dispensing the binder in fine droplet form through a system of nozzles. The amount of binder applied on the web may be from 2 to 40%, in particular from 5 to 30%, more particularly from 10 to 25%, by weight of dry binder based on the weight of the dry nonwoven fibers.

The method of the invention may comprise a drying step between steps i) and ii). As used herein, the term “drying” means removing the water or solvent contained in the binder. For example, the web of nonwoven fibers may first be heated at a temperature and for a time sufficient to remove most of the water but not to substantially cure the binder. Other drying methods include removal of water by vacuum or roll pressure. Alternatively, the drying step and curing step may be carried out simultaneously.

As used herein, the term “curing” means chemically altering the binder for example crosslinking through formation of covalent bonds between the various functional groups of the binder, formation of ionic interactions and clusters, and/or formation of hydrogen bonds. Furthermore, the curing can be accompanied by physical changes in the binder, for example phase transitions or phase inversion.

The curing step ii) may be carried out by heating the web of nonwoven fibers at a temperature and/or for a period of time to effect curing (crosslinking).

The binder may be cured at a temperature of at least 80°C, at least 90°C, at least 100°C, at least 1 10°C, at least 120°C, at least 130°C, at least 140°C, at least 150°C, at least 160°C, or at least 170°C.

The binder may be cured at a temperature below 200°C, 190°C, 180°C, 170°C, 160°C, 150°C, 140°C, 130°C, 120°C or 1 10°C.

Preferably, the binder is cured at a temperature of from 140°C to 180°C.

Curing can in particular be carried in a ventilated oven or an industrial drying line.

Curing may be carried out for a period of time of 5 seconds to 2 hours, in particular 1 minute to 20 minutes.

The curing step may be a multistage curing step with at least two curing steps. The curing speed can be promoted by the addition of a cross-linker or catalyst in the binder. EXAMPLES

Material and methods

The polymer-based binders used for the comparative evaluation below are characterized for their bonding properties and softness without further formulation (neat polymer) by applying the polymer on a cellulosic substrate at a dry pick up of indicatively 25% (by weight of dry binder based on the weight of dry fibers).

The binder used in Example 1 according to the invention is a bio-sourced alkyd emulsion (Synaqua® 4856, Arkema).

The (meth)acrylic dispersion used in Comparative Example 2 is a formaldehyde-free (meth)acrylic dispersion (ENCOR 1 130 S from Arkema).

The (meth)acrylic dispersion used in Comparative Example 3 is a selfcrosslinking (meth)acrylic dispersion containing monomeric units derived from the polymerization of itaconic acid (Acrylic EXP1 ). It is prepared according to the process detailed below.

The binder used in Example 2 according to the invention is a mixture of biosourced alkyd emulsion Synaqua® 4856 and Acrylic EXP1 in a 1 :1 dry/dry weight ratio.The substrate is a mechanically bonded mono-layer cellulosic nonwoven.

The measurements used for the evaluation are the Dry Tensile Strength (DTS), the Wet Tensile Strength (WTS) as well as the Liquid absorptive capacity (LAC), the glass transition temperature (Tg) and the softness.

Preparation of Acrylic EXP1 (self-crosslinking (meth)acrylic dispersion containing monomeric units derived from the polymerization of itaconic acid)

1038.4 g of deionized water, 20.9 g of DISPONIL® FES 32 (available from BASF) and 10.1 g of sodium carbonate were added to a glass reactor fitted with a condenser, a stirrer, a temperature control system and inlets for nitrogen, the initiator solutions and the pre-emulsion feed, respectively. A monomer pre-emulsion composed of 1873.4 g of deionized water, 95.7 g of a 31 wt% solution of DISPONIL® FES 32, 1487.1 g of ethyl acrylate, 1651.6 g of methyl methacrylate, 177.0 g of styrene and 192.1 g of itaconic acid was prepared in another container fitted with a stirrer (pre-emulsifier).

When the contents of the reactor reached a temperature of 60°C, 252.6 g of the monomer pre-emulsion and 27.0 g of 1 1 wt% aqueous solution of sodium persulfate, 0,01 g of Iron sulfate heptahydrate and 1.2 g of sodium metabisulfite dissolved in 12.0 g of water were added into the reactor. About one minute after the addition of the initiators, the remaining portion of the monomer pre-emulsion, 272.4 g of 5 wt% aqueous solution of sodium persulfate and 2.9 g of sodium metabisulfite dissolved in 103.6 g of water were fed at constant rate into the reactor over a period of 3 hours. The contents of the reactor were kept at a temperature of 64-66°C throughout the introduction. Then, the reaction medium was maintained at 64-66°C for a further 45 minutes. After that, 75.0 g of a 13 wt% aqueous solution of tert-butyl hydroperoxide and 96,4 g of a 12 wt% aqueous solution of Bruggolite® FF6 were fed separately into the reactor at 60°C over a period of 90 minutes at constant rate. Fifteen minutes after the end of the above addition, the resulting mixture was cooled to 35°C and subsequently filtered through a 36 mesh screen. The pH and solids content were respectively adjusted with ammonia to be between 5.0 and 6.0 and demineralized water to about 45 wt% of solids.

Dry Tensile Strength (PTS)

The test was carried out according to the procedure described in standard ISO 9073-3:1989. Prior to the application of the binder, the nonwoven substrate was conditioned in a climatic chamber at 23°C and 50% of Relative Humidity (RH), and then weighed. The application of the binder was carried out in a foulard by applying the binder at 25% of solids on the cellulosic substrate (21 x 29 cm) which was first dried in a ventilated oven at 130°C for 5 minutes and then cured by increasing the temperature of the oven up to 160°C for 90 seconds. After drying, the finished nonwoven was weighed for the measure of the applicative “dry pickup” and further conditioned for 24 hours before proceeding with the mechanical tests. The DTS was measured at 23°C and the specimens (5 x 15 cm) were pulled with a dynamometer in the cross direction of the nonwoven taken from the previously prepared substrate. Results were reported in N/m.

Wet Tensile Strength (WTS)

The test was carried out following the procedure described in standard ISO 9073-3:1989 using a tearing speed of 100 mm/min. Specimens for measuring WTS were prepared as indicated above for DTS with the difference that, before measurement, the specimens were soaked for 10 minutes in deionized water at 23°C. Results were reported in N/m. Liquid absorptive capacity (LAC)

This test was carried out following the procedure described in standard ISO 9073-6:2000. Specimens for measuring LAC were prepared as indicated above for DTS. Specimens (10 x 10 cm) were weighed (dry weight), attached to a metallic mesh and placed into deionized water at 23°C for 1 minute. The specimens were removed from water, placed in a conditioned room for 2 minutes and weighed (wet weight). Liquid absorptive capacity (LAC) was determined as:

LAC = 100 x (wet weight - dry weight)/dry weight

Glass transition temperature (Ta)

The aqueous polymer dispersion was applied on a PTFE plate, and dried for 7 days at 23°C and 50% relative humidity. The Tg was determined by Differential Scanning Calorimetry (DSC). The DSC was carried out with a temperature increase of -100 to 100°C with a rate of 20°C/min. Two runs were carried out with a cooling rate of 40°C/min between the runs. The Tg corresponds to the temperature of the midpoint point of the DSC curve of the second run.

Softness (Subjective)

The impregnated and dried specimens were conditioned in a climatic chamber at 23°C and 50% of RH for 24 H. The softness is determined qualitatively, the operator gives a personal judgement of the softness and the flexibility of the nonwoven material. The test starts with a preliminary assessment, attributing to the hardest and the softest specimen a grade of respectively 0 and 5. The other specimens are then evaluated accordingly. The operator then values from 0 to 5 in agreement with the personal feeling when the non-woven is crumpled in the hands.

Results

The results are shown in the table below:

The nonwoven substrate chemically bonded with the bio-sourced alkyd emulsion of Example 1 according to the invention had higher DTS and LAC and similar WTS compared to those of the nonwoven substrate bonded with the acrylic dispersion of Comparative example 2. Both chemically bonded nonwoven substrates had good hand softness and flexibility (determined qualitatively by touching the nonwoven substrate).

The nonwoven substrate chemically bonded with the acrylic binder of Comparative example s had excellent mechanical properties but was very stiff. The nonwoven substrate chemically bonded with a mixture of polyester binder and acrylic binder of Example 2 according to the invention had the best balance between mechanical properties and softness.

Advantageously, the nonwoven substrates chemically bonded with the bio- sourced alkyd emulsions of the invention may be at least partly biodegradable and can be marketed as a bio-sourced product.