Water-based adhesive with reduced polychloroprene content

Abstract

The present invention relates to a water-based adhesive (1) consisting of one or more a) polychloroprene latex, b) polymer latex, c) tackifier, d) optional auxiliary components, and water, wherein the one or more - polymer latex b) is free of chlorinated compounds and comprises at least one polymerized (meth)acrylate monomer, styrene and / or diene monomer, wherein the polymer latex b) has a glass transition temperature Tg of between -50°C and +50°C, - tackifier c) is in the form of an aqueous dispersion and based on terpene phenolic resin, rosin, rosin ester, or any combination thereof, and - optional auxiliary components d) which are selected from a specific group. Claimed also is a process to manufacture the adhesive (1), a process to bond two substrates (2) with the adhesive (1), a bonded article (3) comprising a first and second substrate (2) being bonded together with the adhesive (1).

Description

[0001] Water-based adhesive with reduced polychloroprene content.

[0002] The present invention relates to a water-based adhesive consisting of one or more a) polychloroprene latex, b) polymer latex, c) tackifier, d) optional auxiliary components, and water, a process to manufacture the adhesive, a process to bond two substrates with the adhesive, a bonded article comprising a first substrate being bonded to a second substrate with the adhesive, as well as the use of the adhesive.

[0003] Water-based, one-component adhesives, i.e., single-component or 1 K adhesives, are state-of-the-art to bond foamed substrates, e.g., in foam-to- foam mattress applications, or foam-to-wood for sofa applications. While the adhesives are typically sprayed or roll coated onto at least one substrate, followed by bonding two substrates together, the adhesives are high demanding formulations with respect to the spray behavior, required bond strengths, and setting time. In addition, the adhesive need to provide a sufficient wet tack.

[0004] It is known that water-based adhesives, which are based on chloroprene latices, provide a good overall performance as they have a high capacity to coagulate at pH lower than 9 and due to the crystallization capability of the chloroprene polymer to maintain a sufficient bonding during and after drying.

[0005] There are, however, a number of disadvantages of this technology based on polychloroprene, including issues relating to industrial hygiene reasons due to the high pH of the adhesive and strong ammonia emissions during application of the adhesive. In addition, this technology has some hazardous concerns due to the chlorine content. The stability of the adhesives is quite limited within a small, highly alkaline pH window. Furthermore, the crystallization of the polychloroprene polymer can occur quickly and when done, it is irreversible. Additionally, these types of adhesives have a low heat resistance. And - in case of a fire - the chlorine release from the polychloroprene polymer is a distinct drawback, and not inline with the present industry efforts to increase the environmental friendliness of the products.

[0006] Therefore, people have undertaken big attempts to reduce the chlorine content in such adhesives. In practice, however, various attempts resulted in a reduction of about 10% of the polychloroprene latex, i.e., the chlorine content of 1 -K adhesives could be reduced only marginally without compromising on the various, high demanding performance levels.

[0007] Hence, it is the objective of the present invention to provide a 1 K adhesive with a distinct reduced, e.g., at least 25% or more, chlorine content. This adhesive needs to be suitable for mattress and sofa applications and thus to bond a foamed substrate to another, e.g., foamed, substrate. This adhesive shall be suitable for spray and roll coating applications. Despite the targeted higher level of chlorine substitution, the adhesive shall still provide - or even surpass - the same demanding application performance - when compared to the state-of-the-art high chlorine reference adhesive.

[0008] This high demanding problem could be solved with a water-based adhesive (1 ), wherein the water-based adhesive (1 ) consists of one or more a) polychloroprene latex, b) polymer latex, c) tackifier, d) optional auxiliary components, and water, wherein the one or more

[0009] - polymer latex b) is free of chlorinated compounds and comprises at least one polymerized (meth)acrylate monomer, styrene and / or diene monomer, wherein the polymer latex b) has a glass transition temperature Tg of between -50°C and +50°C, - tackifier c) is in the form of an aqueous dispersion and based on terpene phenolic resin, rosin, rosin ester, or any combination thereof, and

[0010] - optional auxiliary components d) are selected from the group of fillers, surfactants, pH-regulators, water-soluble polymers, colloids, thickeners, rheology modifying agents, wetting agents, defoamers, dispersing agents, coalescing agents, crosslinking agents, and plasticizers, wherein the surfactants include anionic, and / or nonionic surfactants, wherein the anionic surfactants are selected from the group of C6 - C20 alkyl sulfates, C6 - C20 alkyl sulfonates, C6 - C40 alkyl mono ester of sulfo succinates, C6 - C40 ethoxylated alkyl mono ester of sulfo succinates, C6 - C40 alkyl di ester of sulfo succinates, alkoxy-2-hydroxyalkyl sulfonate, N-(1 ,2-dicarboxy ethyl)- N-octadecylsulfosuccinamate, C6 - C40 N-alkyl sulfosuccinamates, C6 - C40 N-alkyl ether sulfosuccinamates, and their salts, such as N-octadecylsulfosuccinamate, and alkyl amido poly-ethoxy sulfosuccinate. Preferably, the surfactants are - if present - added in an amount of up to 10 wt.%, preferably up to 5 wt.%, in particular up to 3 wt.%.

[0011] Claimed also is the process to manufacture the water-based adhesive (1 ) according to the invention, wherein the pH of the one or more polymer latex b) is adjusted to pH 6.5 or higher, mixed with the one or more polychloroprene latex a), the one or more tackifier c) and the optional auxiliary components d), followed by adjusting the pH of the obtained mixture to a pH between 8.0 and 11 .5, preferably between 8.3 and 10.0, in particular between 8.5 and 9.5, by adding a pH-regulator such as glycine, in particular an aqueous glycine solution.

[0012] Claimed also is the process to bond two substrates (2) with the adhesive (1 ) according to the invention, wherein the adhesive (1 ) is spray or roll coated on a surface of at least one, preferably on both, substrates (2), and bond said substrates (2) to one another, to result in a bonded article (3).

[0013] Claimed is also a bonded article (3) comprising a first substrate (2) and a second substrate (2), wherein the first substrate (2) is bonded to the second substrate (2) with the adhesive (1 ), wherein the first and the second substrates (2) are the same or different.

[0014] Furthermore, claimed is also the use of the adhesive (1 ) to bond a first substrate (2) to a second substrate (2), wherein the first substrate (2) is a foamed substrate (2).

[0015] Surprisingly, it was found that the content of the polychloroprene latex, i.e. , the chlorine level, in the adhesive (1 ) according to the invention can be reduced in the adhesive (1 ) by 55 wt.% or even more, while the bonding strengths of the adhesive after an open time of 30 sec. as well as after 5 min. are significantly higher, compared to the high chlorine state-of-the-art reference. Furthermore, preliminary results indicate that the other adhesive properties, such as the rheological behavior, the storage stability, as well as the behavior of the adhesive in spray and roll coating are comparable to the reference adhesive. In addition, the adhesive (1 ) surprisingly exhibits an improved wet tack, i.e., the formation of an immediate bond, thus allowing after its application on the substrate - during a very short drying time - to stick the two substrates together, i.e., to provide both, adhesion and cohesion within a very short time of e.g., 30 seconds, and thus maintaining the different substrates, e.g., foams, together. Hence, the quick drying time and thus the fast bonding of the substrates is maintained, which allows to move the assembled articles (3) immediate after bonding to the next steps of the manufacturing process. Despite the distinct improved properties, the adhesive (1 ) is the form of a one- component adhesives, i.e., a single-component or 1 K adhesives. Accordingly, the adhesive (1 ) is ready for use and does not require the addition of another component before or during application. As such, it is highly applicator friendly. Furthermore, the adhesive (1 ) is ecofriendly. Hence, problematic issues with respect to industrial hygiene reasons can be reduced significantly, e.g., due to a pH of e.g., between 8.5 and 10, and a distinct lower ammonia content.

[0016] The making of the adhesive (1 ), i.e., its manufacturing, according to the invention can be made easily in existing vessels. The process is surprisingly less sensitive to pH-adjustments and there is no need for taking an extra effort in any step for making the adhesive.

[0017] The process to bond two substrates according to the invention with the adhesive of the invention is surprisingly similar, straight forward and can be performed with the same type of equipment and the same or similar setting parameters. Hence, the processors of the adhesive do not need to invest in new equipment. Furthermore, the adhesive (1 ) is sufficiently stable during the coating process and allows on open time of 5 minutes or even more.

[0018] The bonded articles (3) according to the invention provide the same good physical properties as the high-performance reference. In addition, the higher heat resistance of the adhesive (1 ) results advantageously in a higher heat resistance of the articles (3), such as sofas or mattresses. And due to better application performance of the adhesive (1 ) according to the invention, the amount of adhesive (1 ) can even be reduced while maintaining the same performance. Hence, the efficiency of the adhesive (1 ) is improved.

[0019] The adhesive (1 ) according to the invention can surprisingly be use with the well-established application techniques, i.e., with both, spray and roll coating, and on the known substrates without amending the parameter settings, e.g., for mattresses and sofa applications.

[0020] The water-based adhesive (1 )

[0021] The water-based adhesive (1 ) according to the invention consists of one or more a) polychloroprene latex, b) polymer latex, c) tackifier, d) optional auxiliary components, and water. Accordingly, no organic solvents are added to the adhesive (1 ).

[0022] In a preferred embodiment, the adhesive (1 ) consists of

[0023] - 10 to 90 wt.%, preferably 25 to 85 wt.%, in particular 40 to 80 wt.%, of one or more polychloroprene latex a),

[0024] - 5 to 89 wt.%, preferably 5 to 70 wt.%, in particular 5 to 55 wt.%, of one or more polymer latex b),

[0025] - 1 to 50 wt.%, preferably 5 to 40 wt.%, in particular 5 to 30 wt.%, of one or more tackifier c), and

[0026] - 0 wt.% to 40 wt.%, preferably 0 to 30 wt.%, in particular 0 to 25 wt.%, of auxiliary components d), wherein the amount of surfactant is 0 wt.% to 5 wt.%, preferably 0 to 3 wt.%, in particular 0 to 2.5 wt.%, wherein the weight portions (wt.%) of the components a), b), c) and d) are based on their solid content, relative to the solid content of the adhesive (1 ). In case the solid content of a component d) cannot be determined due to e.g., its volatility, the content of active ingredients, e.g., the amount of the active content of surfactants present, is used.

[0027] Preferably, the one or more polychloroprene latex a) is a chloroprene emulsion polymerizate which may comprise up to 70 wt.%, preferably up to 50 wt.%, of other monomers such as butadiene and / or isoprene, which are copolymerized with the chloroprene monomer. Suitable polychloroprene latices a) are commercially available and well known to the skilled person in the art.

[0028] The one or more polymer latex b) of the adhesive (1 ) is free of chlorinated compounds and comprises at least one polymerized (meth)acrylate monomer, styrene and / or diene monomer, wherein the polymer latex b) has a glass transition temperature Tg of between -50°C and +50°C, preferably between -45°C and +35°C.

[0029] If more than one polymer latex b), or a core-shell polymer latex b), is employed, each polymer latex b) or each polymer phase shall preferably have a glass transition temperature Tg within said range, as long as the content of the polymer latex or the polymer phase is 20 wt.% or more, based on the solids content of the adhesive (1 ). According to the invention, the glass transition temperature (Tg) is determined according to DIN 51007 using a heating rate of 10°C / min., wherein the midpoint of the segment of the midtangent between the extrapolated baselines is reported.

[0030] Suitable polymer latices b) are commercially available and well known to the skilled person in the art. The term “free of chlorinated compounds” means that the polymer latex b) contains less than 1 wt.%, preferably less than 0.1 wt.%, in particular 0 wt.%, of a chlorinated compound

[0031] Preferably, the one or more polymer latex b) is a styrene-butadiene latex, styrene-acrylic latex, vinyl-acrylic latex, and / or an all-acrylic latex, or comprises at least one polymerized (meth)acrylate monomer, optionally copolymerized with styrene, vinyl acetate, vinyl C5- to C12- alkanoate, and / or butadiene, wherein the (meth)acrylate monomer is a C1 - to C40-alkyl (meth)acrylate monomer, and vinyl C5- to C12- alkanoate is preferably a branched vinyl C5- to C12- alkanoate, such as vinyl neodecanoate, e.g., VeoVa™ 10. The term vinyl-acrylic latex stands for a copolymer of vinyl acetate and one or more (meth)acrylate monomer, in particular butyl acrylate, and optionally one or more vinyl C5- to C12- alkanoates. A preferred vinylacrylic is a copolymer of vinyl acetate and butylacrylate. The term all-acrylic latex stands for a latex based essentially on (meth)acrylic monomers only.

[0032] In a particular preferred embodiment, the one or more polymer latex b) comprises an all-acrylic latex having a Tg of between -50°C and +10°C, and a styrene-acrylic and / or a styrene-butadiene latex, preferably having a Tg of between -10°C and +30°C.

[0033] In another preferred embodiment, the one or more polymer latex b) further comprises one or more auxiliary monomer, wherein the auxiliary monomer preferably comprises a carboxyl group, such as carboxylic acid monomers, e.g., (meth)acrylic acid, itaconic acid and / or fumaric acid; a hydroxyl group, such as hydroxy alkyl(meth-)acrylates; an amide group, such as (meth-) acrylamide and N-methylol (meth)acrylamide; a nitrile group, such as (methacrylonitrile; an amine group, such as dimethylaminoethyl acrylate, and / or a sulfonate group, such as 2-Acrylamido-2-methylpropane sulfonic acid and its alkali salts.

[0034] The one or more tackifier c) of the adhesive (1 ) is in the form of an aqueous dispersion, and based on terpene phenolic resin, rosin, rosin ester, or any combination thereof. According to the invention, the term “aqueous dispersion” includes aqueous emulsions. The term “rosin”, i.e., colophony, does not include metal salts of rosin acid. Suitable tackifiers c) are commercially available and well known to the skilled person in the art.

[0035] Preferably, the one or more tackifier c) has

[0036] - a softening point between -20°C and 120°C, preferably between 0°C and 110°C, in particular between 25°C and 100°C, determined according to ASTM E28, - a Brookfield LVT-viscosity of 4000 mPas or lower, preferably of 2000 mPas or lower, measured at 50 rpm and 25°C,

[0037] - a solids content of 10 to 75 wt.%, preferably of 30 to 67 wt.%, in particular 40 to 65 wt.%, determined gravimetrically in an oven at 130°C for 1 hr., and / or

[0038] - a particle size between 10 nm and 1 pm, preferably between 50 and 500 nm, determined by dynamic light scattering, and recorded as volume mean of the particle size (MV).

[0039] The optional auxiliary components d) of the adhesive (1 ) are selected from the group of fillers, surfactants, pH-regulators, water-soluble polymers, colloids, thickeners, rheology modifying agents, wetting agents, defoamers, dispersing agents, coalescing agents, crosslinking agents, and plasticizers, wherein the surfactants include anionic, and / or nonionic surfactants, wherein the anionic surfactants are selected from the group of C6 - C20 alkyl sulfates, C6 - C20 alkyl sulfonates, C6 - C40 alkyl mono ester of sulfo succinates, C6 - C40 ethoxylated alkyl mono ester of sulfo succinates, C6 - C40 alkyl di ester of sulfo succinates, alkoxy-2-hydroxyalkyl sulfonate, N-(1 ,2-dicarboxy ethyl)-N-octadecylsulfosuccinamate, C6 - C40 N-alkyl sulfosuccinamates, such as N-octadecylsulfosuccinamate, C6 - C40 N-alkyl ether sulfosuccinamates, such as alkyl amido poly-ethoxy sulfosuccinate, and their salts. Suitable nonionic surfactants include ethoxylated fatty alcohols with a degree of ethoxylation (EO) of from 7 to 80; fatty alcohol ethoxylate, i.e. , ethoxylated fatty alcohol with a degree of ethoxylation (EO) of from 10 to 80; C10 to C14 - oxo alcohol ethoxylate with a degree of ethoxylation (EO) of from 10 to 80, such as Emulan® TO 4070), C10 to C14 - oxo alcohol ethoxylate with a degree of ethoxylation (EO) of from 10 to 80 (such as Emulan® TO 2080). Suitable components d) are commercially available and well known to the skilled person in the art. The surfactant or surfactants, if present, serve to optimize the rheological and / or wetting properties of the adhesive (1 ), but with such low amounts of preferably 3 wt.% or lower they do not improve the bonding strength of the adhesive (1 ).

[0040] Preferably, the fillers include a mineral filler, such as calcium carbonate, talcum, zinc oxide and / or clay; the pH-regulators include glycine, and / or boric acid; the water-soluble polymers include polyethers, polyalcohols, polysaccharides, and / or polyamines; and / or the rheology modifying agents include alkali swellable emulsions (ASE), hydrophobically modified alkali swellable emulsions (HASE), hydrophobically modified polyurethanes (HELIR), hydrophobically modified polyethers (HMPE), and / or inorganic rheology modifiers such as attapulgites. Suitable colloids, thickeners, rheology modifying agents, wetting agents, defoamers, dispersing agents, coalescing agents, crosslinking agents and plasticizers, such as e.g., TOU, i.e., 2,5,7, 10-tetraoxaundecane, and 1 ,3-dioxolanes, are known to the skilled person in the art, wherein zinc oxide may act also as coalescing agent and as crosslinking agent. The person skilled in the art can well make the suitable selection of the specific type and amount of added auxiliary components d) - optimized to the specific application.

[0041] In a preferred embodiment, the optional auxiliary components d) are not halogenated, i.e., free of a e.g., chlorinated polyolefin resin, or having multiple, e.g., 5 or more, halogen atoms, such as Cl or Br, which are bonded covalently to a carbon atom. Furthermore, the components d) do not include crosslinking molecules, such as epoxy resins.

[0042] Preferably, the solids content of the adhesive (1 ) is between 30 and 75 wt.%, in particular between 35 and 70 wt.%, and most preferably between 40 and 65 wt.%, determined gravimetrically in an oven at 130°C for 1 hr. In addition, or alternatively, the pH of the adhesive (1 ) is between 8.0 and 11 .5, preferably between 8.3 and 10.0, in particular between 8.5 and 9.5. Furthermore, for air spraying perspectives, the adhesive (1 ) has preferably a viscosity of between 300 to 2000 mPas, when measured by a rheometer with a 50 mm cone plate at a shear rate of 7 per seconds and a temperature of 22°C.

[0043] The process to manufacture the adhesive (1 )

[0044] The process according to the invention to manufacture the water-based adhesive (1 ) includes that the pH of the one or more polymer latex b) mixed the one or more tackifier c), is adjusted to pH 6.5 or higher, e.g., by addition of caustic Soda, then mixed with the one or more polychloroprene latex a), and the optional auxiliary components d), followed by adjusting the pH of the obtained mixture to a pH between 8.0 and 11.5, preferably between 8.3 and 10.0, in particular between 8.5 and 9.5, by adding a pH-regulator such as glycine, in particular in the form of e.g., a 10 wt.% aqueous solution, and / or hydrochloric acid, preferably diluted hydrochloric acid solution, such as 1 N, or 0.1 N, HCI-solution. This process is surprisingly robust and results in a stable adhesive (1 ) without flocculation and / or sedimentation of the adhesive.

[0045] Process to bond two substrates (2) with the adhesive (1 )

[0046] The Process according to the invention to bond two substrates (2) with the adhesive (1 ) includes that the latter is spray or roll coated on a surface of at least one, preferably on both, substrate (2), to result in a bonded article (3).

[0047] In the process to bond two substrate (2) to one another, the adhesive (1 ) can - due to the desired rheological behavior - be applied to the substrates (2), e.g., by roll or spray coating. This can be done with the same apparatus and setting parameters. The adhesive allows - when applied onto the substrate (2) - a very short drying time and sufficiently sticking the two substrates (2) together and still proved sufficient adhesion and cohesion after, e.g., 30 seconds. As a conclusion thereof, the assembled articles (3) can be moved to the next manufacturing step after the bonding step.

[0048] Preferably, the substrates (2) to bond the two substrates (2), are a polymeric foam, polymer felt, i.e., a woven and / or non-woven fabric based on polymer fibers, wood, metal, and / or solid plastic, wherein preferably at least one substrate (2) is a polymeric foam, i.e., a polymer foam or foamed polymer. When the substrate (2) is a polymeric foam, the substrate (2) is a foamed substrate (2). The term “polymeric foam”, i.e., foamed substrate (2), is most typically an easy and reversibly compressible and bendable polymeric foam. Hence, suitable polymeric foams - in particular for mattrass and sofa applications - are preferably elastomeric polymeric foams and have a density of 10 to 100 kg / m3, preferably of 20 to 70 kg / m3, in particular 25 to 50kg / m3.

[0049] In another preferred embodiment, the polymeric foam is a polyurethane foam, a polyethylene foam, a polyester foam, a polyether foam, a polyamide foam, and / or a polypropylene foam; the metal is preferably aluminum, iron, stainless steel, cupper, brass, or an alloy; the solid plastic may be a composite, and / or a fiber-reinforced plastic. Hence, the process according to the invention includes to bond a polymeric foam as a first substrate (2) to another polymeric foam being a second substrate (2), wherein the substrates (2) may be of the same or of different type of polymeric foam. Alternatively, the second substrate (2) may be different to a polymeric foam. Thus, the process includes to bond a polymeric foam to e.g., wood, a metal or solid plastic, wherein the latter substrates may be covered with a paint and / or a varnish.

[0050] Bonded article (3) Bonded article (3) comprising a first substrate (2) and a second substrate (2), wherein the first substrate (2) is bonded to the second substrate (2) with the adhesive (1 ) of the invention, wherein the first and the second substrates (2) are the same or different. Hence, the bonded article (3) according to the invention includes a polymeric foam as the first substrate (2) bonded to another polymeric foam being the second substrate (2), wherein the polymeric foams may be the same or of different type. Alternatively, the polymeric foam as first substrate (2) may be bonded with the adhesive (1 ) to e.g., wood, a metal or solid plastic.

[0051] Use of the adhesive (1 )

[0052] The claimed use of the adhesive (1 ) according to the invention is to bond a first substrate (2) to a second substrate (2), wherein the first substrate (2) is a foamed substrate (2).

[0053] The foamed substrate (2) is most typically a polymeric foam, preferably a polyurethane foam, a polyethylene foam, a polyester foam, a polyether foam, a polyamide foam, and / or a polypropylene foam. Advantageously, the polymeric foam has a density of 10 to 100 kg / m3, preferably of 20 to 70 kg / m3, in particular 25 to 50 kg / m3.

[0054] Preferably, said use includes that the second substrate (2) is another foamed substrate (2) or wood, metal, and / or solid plastic, and / or the adhesive (1 ) is sprayed, or roll coated onto the surface of the substrates (2).

[0055] Examples Raw Materials used

[0056] As polychloroprene (PC) latex a) was Dispercoll® C84 from Covestro AG employed, which had a solids content of 55 wt.%, a Brookfield viscosity of about 100 mPas (LV / Sp2 / 60 rpm / 25°C), a pH of 13, and an MFFT of 5°C.

[0057] As polymer latex b) was

[0058] - as styrene-butadiene polymer latex (SB) the commercial Ligos™ A3603 from Trinseo employed. The latex had a solids content of 52 wt.%, a pH of 7.5, and a glass transition temperature Tg of 0°C;

[0059] - as styrene-acrylic polymer latex (SA1 ) the commercial Ligos™ C9001 from Trinseo employed, which had a solids content of 49 wt.%, a pH of 8.5, and glass transition temperature Tg of +20°C;

[0060] - as styrene-acrylic polymer latex (SA2) the commercial Ligos™ C9031 from Trinseo employed, which had a solids content around 50 wt.%, a pH of 8, and glass transition temperature Tg of +20°C;

[0061] - as all-acrylic polymer latex (AA1 ) the commercial Ligos™ C9190 from Trinseo employed, which had a solids content of 62.5 wt.%, a pH of 6.0, and glass transition temperature Tg of -25°C; and

[0062] - as all-acrylic polymer latex (AA2) the commercial Ligos™ C9187 from Trinseo employed, which had a solids content of 62.5 wt.%, a pH of 6.0, and glass transition temperature Tg of -42°C.

[0063] Employed tackifiers c) were

[0064] - Dermulsene RE1513® from DRT (T1 ), which is an aqueous dispersion, i.e. , emulsion, based on a rosin ester having a softening point of 76 °C and a solid content of 54 wt.%; and

[0065] - Dermulsene 222® from DRT (T2), which is an aqueous emulsion based on a mixture of a rosin ester and a terpene resin having a softening point of 45 °C and a solid content of 56 wt.%. Preparation of the water-based adhesive (1)

[0066] For our reference formula containing only the polychloroprene latex: The polychloroprene latex a) was first, while stirring, adjusted to pH 9.2 by adding an aqueous 10% wt.% glycine solution while stirring.

[0067] For our references formula containing the formulation according to the invention:

[0068] The polymer latices b) were, while stirring, mixed first with one or more tackifier c), followed by adjusting to pH 7 or higher by adding an aqueous 10 wt.% NaOH solution.

[0069] To obtain the adhesive (1 ), the one or more polychloroprene latex a) was added to the obtained mixture of the one or more polymer latex b) and the one or more tackifier c). If required, the pH was again adjusted to pH 8.5 to 9.2 using an aqueous 10 wt.% glycine.

[0070] Application tests

[0071] The obtained adhesive (1 ) was sprayed, using a commercial spray gun for spraying water-based adhesives with compressed air for coat weights of 50 to 90 g / cm2, on the same side of the two extremities of a polyurethane foam (Seebauer Living Foam Pad Medium RG35 / 40). The dimensions of the Pll foam were 20 x 3.5 x 5 cm (length x width x thickness) with a density of 35 / 40 kg / m3and the dimensions of the sprayed surfaces were each 3.5 x 3.5 cm (length x width). The wet coat weight per surface was adjusted to 50 to 90 g / cm2 After a drying time, i.e. , an open time (OT) of the adhesive (1 ) of i) 30 sec., and ii) 5 min., respectively, the two extremities of the same sample were bonded together by bending the PU-foam and pressing the sprayed surfaces onto each other with a weight of 1 .5 kg for 15 sec.

[0072] The Initial bonding strength was assessed as following: After the pressing time of 15 sec., the weight was removed and the strength was felt immediately afterwards by hand by trying to open the bonded foam right after pressing (graded from 0 = no strength, to 5 = foam will break).

[0073] For assessing the 15min bonding strength, the same test as described above, but on a different sample, was carried out 15 min. after pressing. The bonding strength was graded as following:

[0074] 0 = no strength, foam opens

[0075] 1 = very light strength foam maintained by itself

[0076] 2 = light strength foam maintained by itself

[0077] 3 = medium strength foam maintained by itself

[0078] 4 = good strength foam maintained by itself

[0079] 5 = strong strength foam maintained by itself

[0080] For assessing the 24 hrs. bonding strength, a different sample was prepared. After storing the sample for 24 hrs. at ambient conditions (23°C + / - 2°C and 50% + / - 10% RH) the samples were debonded manually and the foam failure was graded as following:

[0081] 0 = no strength, 0 to 9 % cohesion failure of bonded surface

[0082] 1 = 10% to 30% cohesion failure of bonded surface

[0083] 2 = 31 % to 50% cohesion failure of bonded surface

[0084] 3 = 51 % to 70% cohesion failure of bonded surface

[0085] 4 = 71 % to 90% cohesion failure of bonded surface

[0086] 5 = 91 % to 100% complete foam break Table 1 : Bonding strengths (BS) of various adhesive (1 ) compositions comprising the styrene-butadiene (SB) polymer latex b) were assessed having an open time (OT) of 5 min. All formulated adhesives (1 ; SB1 to SB3) show no sedimentation nor gel formation after 30 days stored at room temperature, and they have a shear thinning rheology profile. All applied adhesives have a viscosity of between 300 to 2000 mPas, when measured by a rheometer with a 50 mm cone plate at a shear rate of 7 per seconds and a temperature of 22°C.

[0087] 1 ) PC stands for the polychloroprene latex a), i.e. , Dispercoll® C84.

[0088] 2) SB stands for the styrene butadiene (SB) polymer latex b).

[0089] 3) The tackifier c) was either Dermulsene RE1513® (T1 ) or Dermulsene 222® (T2).

[0090] 4) The Bonding strength (BS) of the adhesive (1 ) compositions was assessed for samples which were bonded after an open time (OT) of 5 min.

[0091] 5) As reference was the pH-adjusted polychloroprene (PC) latex a), i.e., Dispercoll® C84, used. The results of Table 1 show impressively that the content of the polychloroprene latex a) can - when using the styrene butadiene (SB) polymer latex a) - be reduced by 25% (SB1 and SB2), and 40% (SB3), respectively, without compromising the performance of the various bond strengths. To the contrary, the latter are even better after a bond time of 15 min. and 24 hrs., respectively.

[0092] Table 2: Bonding strengths (BS) of various adhesive (1 ) compositions comprising a styrene-acrylic (SA) latex polymer latex b) was assessed having an open time (OT) of 30 sec. and 5 min. All formulated adhesives (1 ; SA1 to SA4) show no sedimentation nor gel formation after 30 days stored at room temperature, and they have a shear thinning rheology profile. All applied adhesives have a viscosity of between 300 to 2000 mPas, when measured by a rheometer with a 50 mm cone plate at a shear rate of 7 per seconds and a temperature of 22°C.

[0093] 1 ) See Table 1 above. 2) SA stands for Ligos™ C9001 as polymer latex b).

[0094] 3) See Table 1 above.

[0095] 4) See Table 1 above.

[0096] 5) The Bonding strength (BS) of the adhesive (1 ) compositions was assessed for samples which were bonded after an open time (OT) of 30 sec.

[0097] 6) As reference was the pH-adjusted polychloroprene (PC) latex a) used, i.e., Dispercoll® C84.

[0098] The results of Table 2 show impressively that the content of the polychloroprene latex a) can - when using the styrene-acrylic (SA) polymer latex b) - be reduced by 40% (SA1 ) to even 55% (SA4), respectively, without compromising the performance of the various bond strengths. To the contrary, in particular the samples SA2 and SA3 provide a superior bonding strength after both, 30 sec. open time as well as the 5 min. open time (OT) samples. It needs to be emphasized that after a bonding time of 24 hrs., the samples SA2, SA3 and SA4 result in most cases in a 100% cohesion failure within the foam substrate, while the reference sample results - after a 5 min. open time (OT) - mainly in an adhesion failure. The insufficient bonding strength of example SA1 with 30 sec. open time indicate that this specific formulation is not optimized. It is believed that with a different ratio of polymer latex b) to tackifier c), and e.g., with another type of tackifier c), bonding strengths with 30 sec. OT may be improved significantly, while maintaining the favorable 5 min. OT results.

[0099] Table 3: Bonding strengths (BS) of various adhesive (1 ) compositions comprising as the one or more polymer latex b) a mixture of an allacrylic (AA) polymer latex and a styrene-acrylic (SA) polymer latex. The performance of the adhesive (1 ) compositions was assessed having an open time (OT) of 30 sec. and 5 min. All formulated adhesives (1 ; AA1 , AA2 and AA3) show no sedimentation nor gel formation after 30 days stored at room temperature, and they have a shear thinning rheology profile. All applied adhesives have a viscosity of between 300 to 2000 mPas, when measured by a rheometer with a 50 mm cone plate at a shear rate of 7 per seconds and a temperature of 22°C.

[0100] 1 ) See Table 1 above. 2) AA (2a)) stands for an all-acrylic polymer latex, i.e., Ligos A9190 or Ligos A9187 (see below), and SA (2b)) stands for a styrene-acrylic polymer latex, i.e., Ligos™ C9001 or Ligos™ C9031 as the one or more polymer latex b).

[0101] 3) See Table 1 above. 4) See Table 1 above.

[0102] 5) The Bonding strength (BS) of the adhesive (1 ) compositions was assessed for samples which were bonded after an open time (OT) of 30 sec.

[0103] 6) As reference was the pH-adjusted polychloroprene (PC) latex a) used, i.e., Dispercoll® C84. 7) As all-acrylic polymer latex was Ligos A9190 employed.

[0104] 8) As all-acrylic polymer latex was Ligos A9187 employed.

[0105] 9) As styrene-acrylic polymer latex was Ligos A9001 employed.

[0106] 10)As styrene-acrylic polymer latex was Ligos A9031 employed.

[0107] The results of Table 3 demonstrate an even further improvement of the performance properties with an increased wet tack, e.g., initial bonding strength, after an open time (OT) of 30 sec., and 5 min. The content of the polychloroprene latex a) could be reduced to as low as 45 wt.%, as demonstrated in experiment No. AA3, by employing a combination of an allacrylic polymer latex b) having a Tg of -25°C and -42°C, respectively, and a styrene-acrylic polymer latex b) having a Tg of +20°C. Furthermore, the content of the tackifier c) remains at 15 wt.%, based on the solid content of the adhesive (1). It is noticed that the presence of the tackifier c) is key to obtain the high-performance levels. And in another formulation, i.e., experiment No. AA4, the performance properties of the initial bonding strength, measured after an open time of 30 sec., as well as after 5 min., increased to the maximum level of 5, i.e., the foam breaks, which refers to a cohesion failure, which represents the maximum strength obtainable. The same applies to the measurements of the bonding strengths after 15 min., and 24 hrs.

[0108] The excellent bond strength (BS) results reported in Table 3 with the adhesive (1) according to the invention comprising as the one or more polymer latex b) an all-acrylic polymer latex and a styrene-acrylic latex, suggest that the polychloroprene latex a) can be reduced even more without reducing - at least significantly - the performance level.

[0109] These experiments emphasize that the amount of polychloroprene latex - and thus the content of chlorine in the adhesive - can be reduced to, e.g., 45% or even more, and still providing significantly better adhesion of the bonded PU-foam samples, when compared to the mere high-performing polychloroprene latex reference.

[0110] In addition, the adhesives (1) exhibit a superior stability, hence a good storage stability, robust properties with respect to pH variations, favorable properties upon spray and roll coating, good initial bond strengths as well after 15 min. and 24 hrs. for both, the 30 sec. and the 5 min. (OT), also between various substrates. In addition, the adhesive (1), and thus the bonded articles (3) have distinct lower chlorine release in case of a fire.

Claims

Claims1. Water-based adhesive (1 ), wherein the water-based adhesive (1 ) consists of one or more a) polychloroprene latex, b) polymer latex, c) tackifier, d) optional auxiliary components, and water, characterized in that the one or more- polymer latex b) is free of chlorinated compounds and comprises at least one polymerized (meth)acrylate monomer, styrene and / or diene monomer, wherein the polymer latex b) has a glass transition temperature Tg of between -50°C and +50°C,- tackifier c) is in the form of an aqueous dispersion and based on terpene phenolic resin, rosin, rosin ester, or any combination thereof, and- optional auxiliary components d) are selected from the group of fillers, surfactants, pH-regulators, water-soluble polymers, colloids, thickeners, rheology modifying agents, wetting agents, defoamers, dispersing agents, coalescing agents, crosslinking agents, and plasticizers, wherein the surfactants include anionic, and / or nonionic surfactants, wherein the anionic surfactants are selected from the group of C6 - C20 alkyl sulfates, C6 - C20 alkyl sulfonates, C6 - C40 alkyl mono ester of sulfo succinates, C6 - C40 ethoxylated alkyl mono ester of sulfo succinates, C6 - C40 alkyl di ester of sulfo succinates, alkoxy-2-hydroxyalkyl sulfonate, N-(1 ,2-dicarboxy ethyl)-N- octadecylsulfosuccinamate, C6 - C40 N-alkyl sulfosuccina- mates, C6 - C40 N-alkyl ether sulfosuccinamates, and their salts.

2. Adhesive (1 ) according to claim 1 , characterized in that the adhesive (1 ) consists of- 10 to 90 wt.%, preferably 25 to 85 wt.%, in particular 40 to 80 wt.%, of one or more polychloroprene latex a),- 5 to 89 wt.%, preferably 5 to 70 wt.%, in particular 5 to 55 wt.%, of one or more polymer latex b),- 1 to 50 wt.%, preferably 5 to 40 wt.%, in particular 5 to 30 wt.%, of one or more tackifier c), and- 0 wt.% to 40 wt.%, preferably 0 to 30 wt.%, in particular 0 to 25 wt.%, of auxiliary components d), wherein the amount of surfactant is 0 wt.% to 5 wt.%, preferably 0 to 3 wt.%, in particular 0 to 2.5 wt.%, wherein the weight portions (wt.%) of the components a), b), c) and d) are based on their solid content, relative to the solid content of the adhesive (1 ), wherein, in case the solid content of a component d) cannot be determined, the content of active ingredients is used.

3. Adhesive (1 ) according to claim 1 or 2, characterized in that the one or more polychloroprene latex a) is a chloroprene emulsion polymerizate which may comprise up to 70 wt.% other monomers.

4. Adhesive (1 ) according to any one of claims 1 to 3, characterized in that the one or more polymer latex b) is a styrene-butadiene latex, styrene- acrylic latex, vinyl-acrylic latex, and / or an all-acrylic latex, or comprises at least one polymerized (meth)acrylate monomer, optionally copolymerized with styrene, vinyl acetate, vinyl C5- to C12- alkanoate, and / or butadiene, wherein the (meth)acrylate monomer is a C1 - to C40- alkyl (meth)acrylate monomer, and vinyl versatate is a vinyl C5- to C12- alkylester.

5. Adhesive (1 ) according to any one of claims 1 to 4, characterized in that the one or more polymer latex b) further comprises one or more auxiliary monomer, wherein the auxiliary monomer preferably comprises acarboxyl group, such as carboxylic acid monomers, e.g., (meth)acrylic acid, itaconic acid and / or fumaric acid; a hydroxyl group, such as hydroxy alkyl(meth-)acrylates; an amide group, such as (methacrylamide and N-methylol (meth)acrylamide; a nitrile group, such as (meth-)acrylnitrile; an amine group, such as dimethylaminoethyl acrylate, and / or a sulfonate group, such as 2-Acrylamido-2-methyl- propane sulfonic acid and its alkali salts.

6. Adhesive (1 ) according to any one of claims 1 to 5, characterized in that the one or more tackifier c) has- a softening point between -20°C and 120°C, preferably between 0°C and 110°C, in particular between 25°C and 100°C, determined according to ASTM E28,- a Brookfield LVT-viscosity of 4000 mPas or lower, preferably of 2000 mPas or lower, measured at 50 rpm and 25°C,- a solids content of 10 to 75 wt.%, preferably of 30 to 67 wt.%, in particular 40 to 65 wt.%, and / or- a particle size between 10 nm and 1 pm, preferably between 50 and 500 nm, determined by dynamic light scattering.

7. Adhesive (1 ) according to any one of claims 1 to 6, characterized in that the fillers include a mineral filler, such as calcium carbonate, talcum, zinc oxide, and / or clay; the pH-regulators include glycine and / or boric acid; the water-soluble polymers include polyethers, polyalcohols, polysaccharides, and / or polyamines; and / or the rheology modifying agents include alkali swellable emulsions (ASE), hydrophobically modified alkali swellable emulsions (HASE), hydrophobically modified polyurethanes (HELIR), hydrophobically modified polyethers (HMPE), and / or inorganic rheology modifiers such as attapulgites.

8. Adhesive (1 ) according to any one of claims 1 to 8, characterized in that- the solids content of the adhesive (1 ) is between 30 and 75 wt.%, preferably between 35 and 70 wt.%, and in particular between 40 and 65 wt.%, and / or- the pH of the adhesive (1 ) is between 8.0 and 11 .5, preferably between 8.3 and 10.0, in particular between 8.5 and 9.5.

9. Process to manufacture the water-based adhesive (1 ) according to any one of claims 1 to 8, characterized in that the pH of the one or more polymer latex b) mixed with the one or more tackifier c) is adjusted to pH of 6.5 or higher, then mixed with the one or more polychloroprene latex a), and the optional auxiliary components d), followed by adjusting the pH of the obtained mixture to a pH between 8.0 and 11.5, preferably between 8.3 and 10.0, in particular between 8.5 and 9.5, by adding a pH-regulator such as glycine, and / or hydrochloric acid.

10. Process to bond two substrates (2) with the adhesive (1 ) of any one of the claims 1 to 8, wherein the adhesive (1 ) is spray or roll coated on a surface of at least one, preferably on both, substrates (2), and bond said substrates (2) to one another, to result in a bonded article (3).11 . Process according to claim 10, characterized in that the substrates (2) are a polymeric foam, polymer felt, wood, metal, and / or solid plastic, wherein preferably at least one substrate is a polymeric foam.

12. Process according to claim 11 , characterized in that the polymeric foam is preferably a polyurethane foam, a polyethylene foam, a polyester foam, a polyether foam, a polyamide foam, and / or a polypropylene foam; the metal is preferably aluminum, iron, stainless steel, cupper, brass, or an alloy; the solid plastic may be a composite, and / or a fiber- reinforced plastic.

13. Bonded article (3) comprising a first substrate (2) and a second substrate (2), wherein the first substrate (2) is bonded to the second substrate (2) with the adhesive (1 ) of any one of claims 1 to 8, wherein the first and the second substrates (2) are the same or different.

14. Use of the adhesive (1 ) according to any one of claims 1 to 8 to bond a first substrate (2) to a second substrate (2), wherein the first substrate (2) is a foamed substrate (2).

15. Use according to claim 14, wherein the second substrate (2) is another foamed substrate (2) or wood, metal, and / or solid plastic, and / or the adhesive (1) is sprayed, or roll coated onto the surface of the substrates (2).

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