WET BONDING OF STORAGE-STABLE 1-COMPONENT SPRAY ADHESIVES BASED ON POLYCHLOROPRENE

Description

[0001] The invention relates to an aqueous formulation comprising a) at least one polychloroprene, b) at least one (meth)acrylic acid ester copolymer, c) at least one microfibrillated cellulose as thickener, and d) optionally further additives, a process for producing the aqueous dispersion according to the invention, a process for producing a wet-on-wet bond of substrates, a process for producing a composite material and the use of the aqueous dispersion according to the invention for bonding.

[0002] Sprayable contact adhesives based on polychloroprene dispersions are known to those skilled in the art and are used in various fields, particularly for foam bonding in the mattress and furniture sectors. The following two processes are particularly well-known: In the 2K (2-component) process, the adhesive formulation and aqueous coagulant are sprayed simultaneously using a spray gun with two nozzles. The two mixtures meet in the spray jet and coagulate there and / or on the substrate surface. See Katsuyuki Hara, Institute of Technology, Osaka, Japan, "Two-part spray mixing water-borne adhesive," World Adhesive Congress, Munich, June 8 to 10, 1988. However, this process is prone to failure and difficult to handle, as both components must be sprayed consistently with a specific mixing behavior.

[0003] In the 1K (1 component) process, an adhesive formulation with limited shear stability is sprayed through a spray gun with a nozzle. It is important to ensure that the formulation is storage-stable and that the viscosity does not change. According to the state of the art, aqueous 1K formulations can contain organic solvents to destabilize the adhesive dispersion and make it tacky when wet (see, for example, EP 0 814 139 A1 or DE 3 028 693 A1). However, due to ecological, economic, occupational safety, and hygiene reasons, there is a growing demand for solvent-free adhesive formulations.

[0004] A further disadvantage of the known aqueous 1K formulations compared to solvent-based systems is the low initial strength immediately after joining due to water trapped in the adhesive.

[0005] EP 0 624 634 A1 and EP 0 470 928 A1 describe solvent-free, aqueous 1-component formulations for the elastic bonding of substrate surfaces. These formulations exhibit higher initial strengths when bonded because they contain a mixture of (meth)acrylic acid ester copolymers and polychloroprene. Further destabilization of the aqueous polymer dispersion (latex) is possible by lowering the pH. The pH is adjusted so that the latex forms a film immediately after application to the substrate and can be pressed or bonded. This is achieved, for example, by adding weak acids, such as boric acid, bicarbonate, acetic acid, glycine, other amino acids, tartaric acid, citric acid, or their alkali and alkaline earth salts. This destabilizes the formulation to the point where it directly forms a film under shear or pressure and can be bonded.These pressure-sensitive dispersions coagulate when they exit the spray gun nozzle.

[0006] In the case of corresponding, destabilized dispersions, the low storage stability, in particular the tendency to coagulation during transport or in the event of temperature fluctuations, is disadvantageous.

[0007] Another method for producing one-component spray adhesives based on polychloroprene is described in DE 10 2009 020497 A1 and involves the addition of phthalates. Many of these phthalates are hazardous to health and are listed as substances requiring authorization, for example, the compound with CAS number 84-69-5. Furthermore, these phthalates can migrate into the adhesive layer. This leads to a significant reduction in adhesive strength, especially in adhesive formulations containing polychloroprene.

[0008] WO 2008 / 034856 A2 describes adhesive formulations containing polychloroprene dispersions, colloidal silicon dioxide, and water-soluble cellulose thickeners. The aim here was to obtain adhesive dispersions with higher heat resistance. No statements are made regarding the storage stability of these formulations.

[0009] EP 3 444 310 A1 describes a process in which the rheological properties of dextrin-containing adhesives for bonding corrugated cardboard are improved by the addition of microfibrillated cellulose. However, the viscosity and storage stability are inadequate, as the viscosity of the formulation increases from 2000 to 5000 mPa*s in 4 days, and the mixture must be stirred at short intervals to prevent sedimentation during storage.

[0010] EP 3 406 140 A1 describes the use of polychloroprene dispersions in combination with colloidal silicon dioxide, white pigments, and microfibrillated cellulose as a protective coating for seedlings or trees. Application is carried out, for example, by spraying. These formulations tend to segregate during storage in the viscosity range suitable for spray applications, with the high-density formulation components, particularly colloidal silicon dioxide or white pigments, settling.

[0011] Furthermore, commercially available anionic polychloroprene dispersions stabilized with resin acids can release significant amounts of HCl over the specified storage time. This additional stress leads to an additional limitation of the storage stability of ready-formulated, reactive 1-component adhesive formulations because the decreasing pH further destabilizes the formulation. This problem, as well as a possible acid attack of the released HCl on possibly pH-sensitive substrates, is usually solved by adding divalent predispersed metal oxides, particularly ZnO, MgO, and / or CaO, sometimes present as nanoparticles, and / or aminic acid scavengers, particularly hydroxylamine, ethanolamine, condensation products, and / or derivatives thereof; see, for example, WO 2004 / 106422 A1.The use of polyvalent metal oxides such as MgO and CaO is undesirable in anionic polychloroprene dispersions stabilized with resin acids, as this destabilizes the latex. Furthermore, concentrations higher than 0.24 wt.% ZnO are subject to labeling requirements in several countries and, due to their amphoteric nature, significantly complicate the production of stable adhesive formulations with a pH value below 9.

[0012] There is therefore still a need for aqueous 1K formulations that do not have the disadvantages described, in particular for 1K formulations that show high initial strength immediately after spraying, can be stored for a long time without coagulation, are viscosity-stable even though the pH of the formulation changes during storage, and are toxicologically safe.

[0013] The object of the present invention is therefore to provide corresponding one-component formulations, in particular ecologically and economically advantageous, aging-, storage-, and shear-stable, aqueous adhesive compositions that exhibit sufficiently high initial strength, i.e., wet strength, after application to the substrate to be bonded, especially immediately after joining. Furthermore, the provided one-component formulations should exhibit excellent pH stability and excellent aging stability despite the omission of potentially environmentally harmful acid scavengers such as ZnO.

[0014] These objects are achieved according to the invention by an aqueous formulation containing a) at least one polychloroprene, b) at least one (meth)acrylic acid ester copolymer, c) at least one microfibrillated cellulose as thickener, and d) optionally further additives, where that a) the at least one polychloroprene at least 65% by weight, b) the at least one (meth)acrylic acid ester copolymer at 12 to 35% by weight, c) the at least one microfibrillated cellulose at 0.05 to 5% by weight, and d) the optionally present additives at 0.1 to 30% by weight, in each case based on the total weight of the non-volatile components of the formulation, and the sum of the components present in each case amounts to 100% by weight, wherein the microfibrillated cellulose has fibrils with a diameter of 10 to 100 nm, determined using a scanning electron microscope.

[0015] The essential and optional components of the aqueous dispersion according to the invention are described in detail below. a) Polychloroprene:

[0016] According to the invention, the terms "dispersion" and "formulation" are used synonymously. According to the invention, an aqueous formulation is preferably present that contains both dispersed and dissolved components.

[0017] The aqueous formulation according to the invention contains at least one polychloroprene as component a).

[0018] The polychloroprene present in the dispersion according to the invention can be prepared by processes known to those skilled in the art, for example by emulsion polymerization in an alkaline, aqueous medium, as described, for example, in "Ullmanns Encyclopädie der technischen Chemie", Volume 9, p. 366, Verlag Urban und Schwarzenberg, Munich-Berlin 1957, "Encyclopedia of Polymer Science and Technology", Vol. 3, pp. 705 to 730, John Wiley, New York 1965, or "Methoden der Organischen Chemie" (Houben-Weyl) XIV / 1, pages 738 ff. Georg Thieme Verlag Stuttgart 1961.

[0019] According to the invention, at least one polychloroprene homopolymer or at least one polychloroprene copolymer can be used as component a) of the dispersion according to the invention. Suitable polychloroprene copolymers are obtained, for example, by polymerizing chloroprene and 0 to 20 wt. % of at least one ethylenically unsaturated monomer copolymerizable with chloroprene, preferably in an alkaline medium.

[0020] Suitable copolymerizable monomers are described in "Methoden der Organischen Chemie" (Houben-Weyl) XIV / 1, 738 ff., Georg Thieme Verlag Stuttgart 1961. Compounds with 3 to 12 carbon atoms and 1 or 2 copolymerizable carbon–carbon double bonds per molecule are preferred. Examples of preferred copolymerizable monomers are 2,3-dichlorobutadiene and 1-chlorobutadiene. Sulfur can also be used as an inorganic copolymerizable monomer in dispersion form.

[0021] The at least one polychloroprene used as component a) is preferably used as a polychloroprene dispersion. The polychloroprene dispersions preferably used according to the invention are prepared, for example, by emulsion polymerization at 0 to 70 °C, preferably 5 to 45 °C, and a pH of 10 to 14, preferably 11 to 13. Activation is carried out using the usual activators or activator systems. The polychloroprene dispersion used according to the invention can be prepared both continuously and discontinuously, with continuous polymerization being preferred.

[0022] Polychloroprene dispersions which are particularly suitable according to the invention are prepared by emulsion polymerization of chloroprene and optionally an ethylenically unsaturated monomer which is copolymerizable with chloroprene in an alkaline medium, as disclosed, for example, in WO-A 02 / 24825, DE-A 30 02 734, US-A 5,773,544 or WO 2009 / 027013 A. Particular preference is given to polychloroprene dispersions which are prepared by continuous polymerization, as described, for example, in WO 02 / 24825 A, in particular Example 2, and DE 3 002 734, in particular Example 6, wherein the regulator content can be varied between 0.01% and 0.3%.

[0023] In the formulation according to the invention, the at least one polychloroprene is preferably present in particles having an average particle size of 30 to 400 nm, preferably 50 to 300 nm, particularly preferably 60 to 220 nm, each determined by the method according to DIN ISO 13321 -2004, and more preferably has a residual monomer content of less than 100 ppm, preferably less than 50 ppm and particularly preferably less than 20 ppm and most preferably less than 10 ppm.

[0024] To adjust the molecular weight or molecular weight distribution of the polymer used according to the invention, conventional chain transfer agents, for example mercaptans, described in DE 3 002 711 A, GB 1 048 235 A, FR 2 073 106 A, or xanthogen disulfides, described in DE 1 186 215 A, DE 2 156 453 A, DE 2 306 610 A and DE 3 044 811 A, in EP 0 053 319 A, GB 512 458 A, GB 952 156 A and US 2 321 693 A and US 2 567 117 A, can be used.

[0025] The polymerization to produce polychloroprene is typically terminated at a monomer conversion of 50 to 95%, preferably 60 to 80%. Phenothiazine, tert-butylcatechol, and / or diethylhydroxylamine, for example, can be used as an inhibitor. After polymerization, the remaining chloroprene monomer is preferably removed to a residual concentration of less than 100 ppm, preferably less than 50 ppm, for example by steam distillation and / or column degassing. The removal is carried out as described, for example, in W. Obrecht in Houben-Weyl: Methods of Organic Chemistry, Vol. 20, Part 3, Macromolecular Substances, (1987), p. 852 ff.

[0026] The polychloroprene is preferably stored at a temperature of 50 to 110 °C, preferably 60 to 100 °C, particularly preferably 70 to 90 °C, wherein the fraction insoluble in organic solvents (gel fraction) increases by at least 10 wt.% to 1 to 60 wt.%, preferably to 5 to 30 wt.%, particularly preferably to 10 to 20 wt.%.

[0027] Alternatively, the gel content can be achieved by reducing the regulator concentration and / or increasing the monomer conversion. The polychloroprenes mentioned above with different gel contents can differ in their polymer properties, such as heat resistance (softening point).

[0028] In a further step, the solids content of the dispersion can be increased by a creaming process. This creaming is achieved, for example, by adding alginates, as described in "Neoprene Latices, John C. Carl, EI Du Pont 1964, p. 13."

[0029] Suitable polychloroprene dispersions a) according to the present invention are commercially available, for example, under the trade name Dispercoll ®< C from Covestro Deutschland AG.

[0030] In a preferred embodiment, the at least one polychloroprene is present in an amount of at least 70% by weight, based on the total weight of the non-volatile components of the formulation. b) (Meth)acrylic acid ester copolymers:

[0031] According to the invention, the term (meth)acrylic acid ester can mean methacrylic acid, acrylic acid, methacrylic acid ester, acrylic acid ester, or a mixture of two or more thereof.

[0032] The formulation according to the invention further contains at least one (meth)acrylic acid ester copolymer b). According to the invention, preference is given to using copolymers containing at least (meth)acrylic acid, at least one (meth)acrylic acid ester, and / or at least one further monomer, for example styrene. Particular preference is given to using acrylic acid ester copolymers containing at least one acrylic acid ester and at least one further monomer, in particular styrene.

[0033] Suitable (meth)acrylic acid ester copolymers, especially styrene-(meth)acrylic acid ester copolymers, especially aqueous dispersions thereof, and processes for their preparation are known to the person skilled in the art. They are described, for example, in Irving Skeist's Handbook of Adhesives, 2nd Edition 1977, page 528 et seq., "Acrylic adhesives and sealants, K. Eisenträger, W. Druschke."

[0034] The at least one (meth)acrylic acid ester copolymer is present in an amount of 12 to 35 wt.%, preferably 15 to 30 wt.%, particularly preferably 18 to 28 wt.%, based on the total weight of the non-volatile components of the formulation.

[0035] The (meth)acrylic acid ester copolymers which can be used according to the invention preferably contain 50 to 80% by weight of styrene and 20 to 50% by weight of one or more (meth)acrylic acid esters of alcohols having 1 to 18 C atoms, preferably methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, optionally in a mixture with methacrylic acid esters such as methyl methacrylate, and 0 to 10% by weight of one or more ethylenically unsaturated, functional comonomers, the data in % by weight each adding up to 100% by weight.

[0036] A comparison of the compatibilities between polychloroprene and (meth)acrylic acid ester copolymers shows that styrene-(meth)acrylic acid ester copolymers are particularly compatible with polychloroprene and are therefore preferred. Furthermore, the viscosity of the styrene-(meth)acrylic acid ester copolymers and their glass transition temperature (Tg) can influence the adhesive strength in polychloroprene-based adhesive formulations. Therefore, according to the invention, preference is given to styrene-(meth)acrylic acid ester copolymers with low viscosities, in particular in the range <400 mPa*s, measured at 250 l / s, 23°C according to DIN EN ISO 3219-1994, and more preferably with a Tg <0°C. They increase the adhesive strength in the formulations and are therefore preferred.

[0037] The at least one (meth)acrylic acid ester copolymer is preferably present in the aqueous formulation according to the invention in an amount of 15 to 30 wt.%, very particularly preferably 18 to 28 wt.%, in each case based on non-volatile components of the aqueous formulation.

[0038] Suitable styrene-(meth)acrylic acid ester copolymers b) according to the present invention are, for example, commercially available, e.g. under the trade name Acronal ®<, from BASF Deutschland AG. c) microfibrillated cellulose as thickener:

[0039] The aqueous formulation according to the invention further contains at least one microfibrillated cellulose as a thickener.

[0040] Microfibrillated cellulose is known per se to those skilled in the art. It is generally a natural cellulose in which the cellulose fibers have been disrupted and shredded by repeated passage through a homogenizer to form fibrils and microfibrils. Microfibrillated cellulose is characterized by a very high water retention value, a high degree of chemical accessibility, and the ability to form stable gels in water or other polar solvents. Suitable microfibrillated cellulose can be obtained, for example, as disclosed in EP 0 120 471 A2, WO 2015 / 180844 A1, EP 2 196 579 A1, or WO 2011 / 095335 A1. Possible applications of microfibrillated cellulose are mentioned, for example, in US Pat. Nos. 4,341,807 and 4,378,381.

[0041] Microfibrillated cellulose suitable according to the invention is, for example, commercially available under the trade name Exilva ®< from Borregaard, in particular microfibrillated celluloses with the trade names Exilva ®< P01-V and Exilva ®< F01-V.

[0042] The at least one microfibrillated cellulose is preferably contained in the aqueous formulation according to the invention in an amount of particularly preferably 0.2 to 3 wt.%, in each case based on the non-volatile components of the aqueous formulation.

[0043] The microfibrillated cellulose used in the invention has fibrils with a diameter of 10 to 100 nm. Measurement is performed using a scanning electron microscope (SEM).

[0044] In addition to the microfibrillated cellulose, other thickeners may optionally be present. Additional thickeners suitable for use according to the present invention are described, for example, in W. Heilen et al., "Additive für Gewässerlacksysteme," Vincentz-Verlag Hannover, ISBN 978-3-86630-845-9, page 61 ff. Suitable thickeners are present, for example, in amounts of 0.01 to 15 wt. %, preferably 0.3 to 5.0 wt. %, based in each case on the non-volatile components of the aqueous composition. Suitable thickeners are preferably selected from the group consisting of polyacrylic acids, water-soluble polyurethanes, silicas, cellulose derivatives such as polycarboxylated cellulose ethers, nonionic cellulose ethers, alginates, xanthans, polyvinyl alcohols, and mixtures thereof.

[0045] By optionally including additional thickeners in the aqueous composition according to the invention, several technical advantages can be achieved. For example, the viscosity is increased, resulting in more precise dosing and less dripping of the aqueous composition. Furthermore, a more consistent layer thickness is achieved after application of the aqueous composition to the substrate compared to compositions that do not contain thickeners. d) any other additives present:

[0046] The aqueous composition according to the invention may optionally contain additives in an amount of 0.1 to 30% by weight, based on non-volatile components of the aqueous composition.

[0047] For example, wetting agents, in particular polyphosphates such as sodium hexametaphosphate, naphthalenesulfonic acid, ammonium or sodium polyacrylic acid salts, can be added.

[0048] Also suitable are salts of polyacrylic acids, especially sodium salts of polyacrylic acids, such as those commercially available under the trade name Dispex N40 from BASF SE. They are preferably added in an amount of 0.2 to 0.6 wt. %, all figures based on the non-volatile components of the aqueous composition.

[0049] Flame retardants can also be added to the aqueous composition to increase the fire safety of the molded articles produced therefrom. Examples of flame retardants include organic phosphorus and nitrogen compounds, organochlorine and organobromine compounds, and inorganic flame retardants such as antimony trioxide, aluminum hydroxide or aluminum oxide. In the context of the present invention, preference is given to using aluminum hydroxide as the flame retardant in the aqueous composition, with particular preference being given to using aluminum hydroxide with an average particle size d(50) in the range from 1.0 to 3.9, in particular 1.7 - 2.1 µm. Flame retardants are used in amounts known to the person skilled in the art, for example up to 30% by weight, preferably 0.1 to 30% by weight, particularly preferably 1.5 to 15% by weight.

[0050] In further, but not preferred, embodiments, fungicides can also be added for preservation. These are preferably used in amounts of up to 1% by weight, preferably 0.02 to 1% by weight, based on non-volatile components, of the aqueous composition. Suitable fungicides include, for example, phenol and cresol derivatives or organotin compounds.

[0051] Optionally, tackifying resins, such as unmodified or modified natural resins such as rosin esters, hydrocarbon resins, or synthetic resins such as phthalate resins, can also be added to the formulation according to the invention in dispersed form (see, for example, "Klebharze" (Adhesive Resins) by R. Jordan and R. Hinterwaldner, pages 75 to 115, Hinterwaldner Verlag, Munich, 1994). Alkylphenol resin and terpenephenol resin dispersions with softening points greater than 70°C, particularly preferably greater than 110°C, are preferred.

[0052] It is also possible to use organic solvents such as toluene, xylene, butyl acetate, methyl ethyl ketone, ethyl acetate, dioxane or mixtures thereof or plasticizers such as those based on adipate, phthalate or phosphate, in each case in amounts of preferably 0.5 to 10 parts by weight, based on non-volatile components of the aqueous composition.

[0053] The aqueous composition of the present invention may also contain up to 30 wt.%, preferably 0.1 to 30 wt.%, particularly preferably 1.5 to 15 wt.%, of at least one pigment, preferably selected from white pigments, more preferably selected from the group consisting of chalk, TiO 2 , ZnO, MgO, Al(OH) 3 Al 2 O 3 or mixtures thereof.

[0054] Zinc oxide or magnesium oxide can preferably be used as an acceptor for small amounts of hydrogen chloride, which can be released from the chloroprene polymers, and are therefore additionally included in preferred embodiments. These are preferably added in amounts of up to 10 wt. %, preferably 0.1 to 10 wt. %, particularly preferably 1 to 5 wt. %, based in each case on the non-volatile components of the aqueous composition, and can partially hydrolyze in the presence of the polychloroprene dispersions or contain hydrolyzable components. The added MgO and / or ZnO are preferably present as predispersed formulations or pastes. In this way, the viscosity of the formulation can be increased and adjusted to a desired level.

[0055] However, other stabilizers, such as litharge, or additives that hydrolyze dispersions in the presence of alkaline polychloroprene, can also be added. If a higher viscosity of the aqueous composition according to the invention is not desired, ZnO or MgO additives can be omitted without negatively affecting the storage stability of the product.

[0056] In preferred embodiments, the optionally present at least one additive is selected from pigments, flame retardants, antioxidants, dispersing aids, emulsifiers, wetting agents, adhesion promoters and defoamers.

[0057] The aqueous formulation according to the invention can further contain, as additives, conventional ageing, oxidation and / or UV protection agents, preferably based on oligofunctional secondary aromatic amines or oligofunctional substituted phenols, such as products of the type 6-PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, for example Vulkanox ®< from Lanxess Deutschland GmbH, DTPD, DDA, BPH, BHT or compounds based on HALS (hindered amine light stabilizers), benzotriazoles, oxalanilides, hydroxybenzophenones and / or hydroxyphenyl-S-triazines. Rhenofit ®< DDA 50 EM, a diphenylamine derivative from Rhein Chemie, is particularly effective.

[0058] Typically, corresponding aging, oxidation, and / or UV protection agents are introduced in emulsified form as an aqueous dispersion. According to the invention, aging, oxidation, and / or UV protection agents can be present in an amount of up to 5 parts by weight, preferably 0.1 to 5% by weight, particularly preferably 1 to 3 parts by weight, particularly preferably 1.5 to 2.5 parts by weight, in each case based on the amount of polychloroprene present.

[0059] The present invention therefore preferably relates to the aqueous formulation according to the invention, wherein a) the at least one polychloroprene at least 70 wt.%, b) the at least one (meth)acrylic acid ester copolymer at 15 to 30 wt.%, preferably 18 to 28 wt.%, c) the at least one microfibrillated cellulose at 0.2 to 3 wt.%, and d) the optionally present additives at 0.1 to 30 wt.%, each based on the total weight of the non-volatile components of the formulation, and the sum of the components present amounts to 100% by weight.

[0060] The aqueous formulation according to the invention is preferably characterized by specific rheological properties, in particular by the fact that in the so-called "low-shear" range of 10 / s to 100 / s, the viscosity changes only slightly with respect to the shear rate, i.e., it behaves essentially proportionally to the shear rate. In the context of the present invention, a slight change means that in the so-called "low-shear" range of 10 / s to 100 / s, the viscosity changes by less than 4.5 times.

[0061] This preferred behavior of the aqueous formulation according to the invention leads to easier application of the formulation by brush, roller or doctor blade, reduces the mixing time in the preparation of the formulation and facilitates the flow of the formulation according to the invention in the lines of the spray equipment.

[0062] The aqueous formulation according to the invention preferably has a pH of 8.2 to 9.8, preferably 8.5 to 9.5. The pH of the aqueous formulation according to the invention can be adjusted using inorganic acids and / or organic acids and / or amino acids and / or their buffer systems known to the person skilled in the art, in particular containing corresponding sodium and potassium salts. Glycine is preferably used.

[0063] The aqueous formulation according to the invention preferably has a viscosity of 500 to 7,000 mPa*s, particularly preferably 1,500 to 6,000 mPa*s, in each case determined according to DIN ISO 2555 using a Brookfield rotational viscometer.

[0064] In the aqueous formulation according to the invention, the mixing ratio of at least one (meth)acrylic acid ester copolymer to the at least one microfibrillated cellulose is preferably 2:1 to 8:1, preferably 3:1 to 5:1, optimally 4:1. In this embodiment, the viscosity and storage stability, for example after 12 months, are particularly advantageous.

[0065] The aqueous formulation according to the invention preferably has a solids content of 50 to 60 wt.%, particularly preferably 52 to 57 wt.%, in each case based on the total formulation.

[0066] The present invention also relates to the process for preparing the aqueous formulation according to the invention, comprising at least the steps: (A) providing components a), b), c), optionally d) and water in the appropriate amounts, and (B) mixing the components provided in step (A) to obtain the aqueous formulation.

[0067] To prepare the aqueous formulation according to the invention, the proportions of the individual components are selected such that the resulting formulation according to the invention contains components a), b), c) and optionally d) in the amounts stated above.

[0068] In a preferred embodiment of the present invention, the aqueous formulation according to the invention is prepared by mixing a dispersion containing at least one polychloroprene with at least one (meth)acrylic acid ester copolymer and at least one microfibrillated cellulose and optionally further additives, in particular the above-mentioned adhesive auxiliaries and additives.

[0069] More preferably, the at least one polychloroprene is used as an aqueous dispersion, the at least one (meth)acrylic acid ester copolymer is used as an aqueous dispersion, the adhesive auxiliaries and additives are used as an aqueous dispersion, and the at least one microfibrillated cellulose is used as a suspension which is predispersed in the aqueous dispersion of the at least one aqueous (meth)acrylic acid ester dispersion.

[0070] In a further preferred embodiment of the present invention, the aqueous formulation according to the invention is prepared by initially introducing a dispersion containing at least one polychloroprene and adding a mixture of at least one microfibrillated cellulose and at least one (meth)acrylic acid ester copolymer. Further additives, in particular the above-mentioned adhesive auxiliaries and additives, can then be added if desired.

[0071] The mixture of at least one microfibrillated cellulose and at least one (meth)acrylic acid ester copolymer is preferably obtained by mixing the aforementioned components under shear forces of 4 to 66 m / s, particularly preferably 28 to 35 m / s, in particular using a static mixer and / or a dynamic mixer. The resulting mixture can then be mixed into the dispersion containing at least one polychloroprene, optionally adding further additives.

[0072] By means of this particularly preferred process for producing the mixture comprising at least one microfibrillated cellulose and at least one (meth)acrylic acid ester copolymer, a similar mixture viscosity of the aqueous formulation according to the invention is achieved in the production of the aqueous formulation according to the invention with a preferably smaller amount of at least one microfibrillated cellulose.

[0073] The preparation of the aqueous formulation according to the invention, in particular the preparation of the individual mixtures or dispersions, can generally be carried out under any conditions deemed suitable by the person skilled in the art, for example at a temperature of 18 to 28°C, ideally at room temperature (23°C), more preferably in equipment known to the person skilled in the art, for example in stainless steel, glass, or enameled process equipment. Rust formation and soluble metal alloys, including aluminum containers, must be avoided during adhesive production.

[0074] The present invention also relates to an adhesive composition comprising at least the aqueous formulation according to the invention and, optionally, further additives known to those skilled in the art, for example organic acids, in particular glycine, for example for adjusting the pH. Urea may also be present, in particular to improve cold stability.

[0075] The present invention further relates to the process according to the invention for producing a wet-on-wet bond between substrates, wherein an adhesive composition comprising the aqueous formulation according to the invention is applied to a substrate and after at most 5 minutes, preferably at most 2 minutes, particularly preferably at most 1 minute, a wet bond is formed before film formation.

[0076] The aqueous formulation according to the invention can generally be applied to the substrates using all common application methods, in particular by brushing, rolling, spraying, and / or atomizing, in particular by spray application, brush application, or roller application. The adhesives according to the invention are preferably applied by spray application.

[0077] Substrates suitable according to the invention are, for example, wood, paper, thermoplastics, elastomeric plastics, thermoplastic-elastomeric plastics, vulcanizates, textile fabrics, knitted fabrics, braids, leather, metals, ceramics, asbestos cement, stoneware, concrete, foams, in each case with each other and / or to porous substrates, preferably with a density of less than 1 kg / liter.

[0078] In particular, the present invention relates to the process according to the invention for producing a wet-on-wet bond, wherein an adhesive composition according to the invention comprising the aqueous formulation according to the invention is applied to a foam substrate, for example by means of spray application, roller application or brush application, and after a flash-off time of < 5 min, preferably < 2 min, particularly preferably ≤ 1 min, a wet bond is produced before film formation.

[0079] The present invention further relates to the process according to the invention for producing a composite material by bonding the individual joining parts of the composite material, wherein the aqueous formulation according to the invention is used.

[0080] The present invention also relates to the use of the aqueous formulation according to the invention for bonding wood, paper, thermoplastics, elastomeric plastics, thermoplastic-elastomeric plastics, vulcanizates, textile fabrics, knitted fabrics, braids, leather, metals, ceramics, asbestos cement, stoneware, concrete, foams, in each case to one another and / or to porous substrates, preferably with a density of less than 1 kg / liter, in particular for bonding foams in mattress, furniture and / or upholstery bonding.

[0081] The present invention is further illustrated by the following examples: Examples

[0082] Table 1 shows the ingredients used in the examples according to the invention and / or comparative examples: Table 1: Components used type Trade name Properties / Structure used form Polychloroprene Dispercoll ®< C 84 Aqueous colloidal dispersion of a 2-chlorobutadiene polymer with a high degree of crystallization aqueous dispersion, 55 wt.% solids Acrylic acid ester-styrene copolymer Acronal ®< 3710 Copolymer of styrene and (meth)acrylic acid ester, viscosity 500 to 1200 mPa*s, Tg 16°C aqueous dispersion, 47 to 49 wt.% solids Acrylic acid ester-styrene copolymer Acronal ®< 5400 Copolymer of styrene and (meth)acrylic acid ester, viscosity 50 to 350 mPa*s, Tg -10°C aqueous dispersion, 57 wt.% solids Silica sol Dispercoll ®< S 4510 Aqueous anionic colloidal disperse solution of amorphous silicon dioxide, average particle size approx. 30 nm aqueous dispersion, 45 wt.% solids microfibrillated cellulose Exilva ®< P01-V average hydrodynamic length approx. 70 µm, average fiber length 1 to 1000 µm aqueous suspension, 10 wt.% solid Methylcellulose Culminal ®< 2000 S nonionic cellulose ether solid Anti-aging agents Rhenofit ®< DDA-EM 50 50% diphenylamine derivative aqueous dispersion, 50 wt.% solids Thickener Borchi ®< Gel A LA anionically neutralized polyacrylate with low shear range, APEO and organotin free, non-volatile content 9 to 11 wt.%, diluted to an aqueous dispersion aqueous dispersion, 5 wt.% solids pH regulator Glycine Aminoacetic acid solid Methods / measurement methods:

[0083] The following methods or measurement methods were used in the examples according to the invention and / or comparative examples.

[0084] Application of adhesive formulation and assessment 1) Spraying method: The adhesive formulation is applied to the test material using a spray gun (Walther PILOT PREMIUM ND, p = approx. 1.5 bar) with a spray nozzle (diameter approx. 1.0 mm). 2) Brush coating: The adhesive formulation is applied to both sides of the PU foam body using a brush. 3) Test specimens PU foam specimens are used as test material as follows: Foam quality: stn / schaumstofftechnik-Nürnberg GmbH, Type: ST 5540, Test specimen dimensions: 101 × 49 × 30 mm, Material basis: PUR, Colour: white, Gross weight (in kg per m²): 40, Net density (in kg per m³, according to ISO-845): 38, Compressive strength (40%, in kPa, according to DIN EN ISO 3386): 5.5 Tensile strength (in kPa, according to DIN EN ISO 1798): > 120, Elongation at break (in %, according to ISO-1798): > 110, Compression set (50% / 70°C / C22h, according to DIN EN ISO-1856): < 4 4) Determination of the initial strength: The following are used as test material (see Fig. 2) Test specimens as described under 3) are used. To assess the initial strength, the test specimens are bent in the middle (4) with a wooden stick (3) (round wood D = 7 mm or square 7 x 7 mm) immediately after the adhesive has been applied to the top side (2) of the foam body (1) using the spray coagulation process (application rate 130 to 150 g / m² wet) and then guided (4) in the middle using the testing device (5) through two steel rollers (6) (diameter 40 mm, length 64 mm), the tangential distance (7) of which was previously set to 10 mm using a threaded spindle (8). The initial strength is sufficient if the test specimen or the adhesive seam (9) does not open despite the restoring forces present in the test specimen. 5) Assessment of the initial strength The expected immediate initial strength is present when the test specimen or the adhesive seam (9) no longer opens despite the restoring forces present in the test specimen.To better quantify the initial strength, it is rated as follows: very good (1): The tension is immediately held after the test specimen is pulled through the gap between the two rollers once. If the foam specimen is pulled apart on both sides after 120 seconds, material will tear out or the foam specimen can only be reopened with very great force. good (2): The tension is immediately held after the test specimen is pulled through the gap between the two rollers once, and the foam specimen can be reopened after 120 seconds when pulled apart on both sides without great force. satisfactory (3): The test specimen opens after the test specimen is pulled through the gap between the two rollers once. The test specimen only remains closed after repeated application or by hand pressure (pressed once for approx. 1 second). poor (4): The tension is not maintained even after repeated application of pressure (roller method and hand pressing).6) Determination of viscosity: The viscosity of the dispersions is determined using a Brookfield viscometer according to DIN ISO 2555. The spindle is carefully immersed in the dispersion to be measured, if possible without the formation of air bubbles. To do this, the sample bottle is placed on a lifting platform and initially raised until the spindle can be attached to the drive shaft without the spindle body emerging from the dispersion. The lifting platform is raised further until the spindle is immersed in the sample up to the immersion groove on the spindle shaft. The motor is switched on. As soon as the LED display of the measured value has stabilized, the measured value is read. Depending on the viscosity range, the following procedure is followed: Viscosity range < 1,000 mPa*s, measurement with spindle LV-2 (62) at 60 rpm. Viscosity range 1,000 to 2,500 mPa*s, measurement with spindle LV-2 (62) at 12 rpm. Viscosity range 2,500 to 10,000 mPa*s, measured with spindle LV-3 (63) at 12 rpm.7) Determination of pH: A single-rod measuring electrode, e.g., a Metrohm pH meter, is immersed in the dispersion or solution to be tested. 8) Dispersing mixtures of fibrillated cellulose and acrylic acid ester copolymer: 250 g of fibrillated cellulose (Exilva ®< P01-V) are weighed into a tin can, followed by 625 g of (meth)acrylic acid ester copolymer (Acronal ®< 5400). Dispersal is carried out using a Dispermat AE 3M and a large dissolver disk at 25 m / s for 15 minutes. The tests were conducted at a speed of 5 to 30 m / s in increments of 5 m / s. 9) Determination of rheological properties: The samples were tested according to DIN EN ISO 3219 using an Anton Paar MCR302 rotational rheometer. The coaxial cylinder system CC27 (steel measuring cylinder with a diameter of 26.6 mm and steel cup with a diameter of 28.9 mm) with the Peltier heater C-PTD200 was used.The measuring cylinder served as the rotor and the beaker as the stator. The flow curve, i.e., the measured viscosity as a function of shear rate, was measured at 23 °C, starting at a shear rate of 0.1 l / s in 33 time steps of 5 s each up to 1000 l / s. Production of adhesive formulations:

[0085] Tests V9 to V15 and V17 were each prepared in a 900 ml polypropylene plastic beaker fitted with a dissolver disk, a stirring speed of 600 rpm (2.2 m / s), and a stirring time of 15 minutes. Dispercoll®< C 84 and Rhenofit®< DDA-EM were mixed with stirring, followed by the addition of Acronal®< 5400 or 3700 and Exilva®< P01-V, either individually or as a pre-mixed mixture. After a stirring time of 15 minutes, the pH and viscosity were measured. Depending on the viscosity, the viscosity was measured as described under point 8 using spindle LV-2 (62) or LV-3 (63) at 12 revolutions per minute. The highest instantaneous value and the viscosity value lasting approximately 15 seconds were recorded in each case. After the pH and viscosity were determined, the dissolver disk was replaced by a propeller stirrer (35 mm) and glycine was added while stirring until a pH of 9.0 was reached.When adjusting the pH with glycine, the stirring speed was 600 rpm. Viscosity at pH 9.0 was measured as described in section 8 using spindle LV-2 (62) or LV-3 (63) at 12 revolutions per minute. The highest instantaneous value and the viscosity value measured for approximately 15 seconds were recorded. Determination of long-term storage stability:

[0086] The viscosity of water-based adhesive formulations used in spray application was typically in the range of 200 to 5000 mPa*s (target viscosity). Table 2: Dispersions Example V1 V2 3 V4 V5 V6 V7 V8 Dispercoll C 84 73,1 72,4 72,6 72,6 75,8 75,3 75,3 75,5 Rhenofit DDA-50 EM 1,5 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Acronal 5400 21,9 21,8 21,8 21,8 19 18,8 18,8 18,8 Exilva P01-V 0 1,5 0,9 0,8 0 1,3 0,9 0,7 Glycine 3,5 2,8 3,2 3,3 3,7 3,1 3,5 3,5 Acronal ®< 5400 / Exilva ®< P01-V - 2,5:1 3,8:1 4,7:1 - 2,5:1 3,8:1 4,4:1 sum 100 100 100 100 100 100 100 100 All data in wt.%, based on the solid V means comparative test Table 3: Viscosities and pH values Example V1 V2 3 V4 V5 V6 V7 V8 Initial pH value 9,1 9,2 9,2 9,1 9,1 9,1 9,2 9,1 Initial viscosity [mPa*s] 124 6880 3690 2570 111 5590 3114 2220 pH value after 12 months coag 8,4 8,6 8,5 coag 8,4 8,4 8,5 Viscosity after 12 months [mPa*s] above nb 9350 5040 7060 nb 9940 7250 6130 center nb 9350 4830 5030 nb 4910 4330 4330 below nb 9350 4780 4830 nb 5780 2940 3420 V means comparative test coag means coagulated nb means not determined Table 4: Comparison of the formulations according to the invention with the prior art Example V9 V10 V11 12 V13 V14 V15 16 V17 Dispercoll ®< C 84 76,3 74,3 73,3 73,2 76,8 75,9 92,9 73,5 74,3 Rhenofit ®< DDA-50 EM 1,5 1,5 1,5 1,5 1,5 1,5 1,9 1,5 1,5 Acronal ®< 3710 19,1 - - - - - - - - Acronal ®< 5400 - 21,2 20,9 20,9 - - - - - Dispercoll ®< S 4510 - - - - 19,2 - - - - Borchigel ®< ALA / water 1:1 - - 1,4 - - - - - - Dispercoll ®< S 4510 / Exilva ®< P01-V - - - - - 19,6 - - - Exilva ®< P01-V - - - 1,5 - - 1,5 - - Exilva ®< P01-V / Acronal ®< 5400 - - - - - - - 22,1 - Acronal ®< 5400 / Culminal ®< MC 2000 S - - - - - - - - 21,2 Glycine 3,1 3,0 2,9 2,9 2,4 3,0 3,7 2,9 3,0 in total 100 100 100 100 100 100 100 100 100 V means comparative test All data in wt.%, based on the solid Table 5: Viscosities and pH values Example V9 V10 V11 12 V13 V14 V15 16 V17 Initial pH value 9,0 9,0 9,0 9,0 9,0 9,0 9,0 9,0 9,0 Initial viscosity [mPa*s] 3370 87 1300 3800 29 3540 3500 2700 4500 Initial strength 2 1 1 1 1 2 1 1 3 pH value after 1 week 8,9 8,9 8,9 9,0 8,9 8,9 8,9 8,9 8,9 Viscosity after 1 week [mPa*s] 3520 90 1650 4250 29 3720 3500 3410 11300 pH value after 3.5 months 8,9 8,8 2 phases 8,8 coag 8,7 8,8 8,8 8,9 Viscosity after 3.5 months [mPa*s] 3420 150 2 phases 4300 coag 4400 specks 3700 2940 coag Initial strength 2 1 - 1 - 2 2 1 nb pH value after 5 months 8,9 coag coag 8,7 coag coag coag 8,7 nb Viscosity after 5 months [mPa*s] 3900 nb nb 4320 nb nb nb 2950 nb Initial strength 2 nb nb 1 nb nb nb 1 nb V means comparative test coag means coagulated nb means not determined Example 9:

[0087] In this standard formulation, thickening is achieved by a high-viscosity (meth)acrylic acid ester copolymer (Acronal®< 3710). Although the viscosity range and storage stability are sufficient, the desired high initial bond strength is not achieved. Example 10:

[0088] Replacing the high-viscosity (meth)acrylic acid ester copolymer (Acronal ®< 3710) with a low-viscosity (meth)acrylic acid ester copolymer (Acronal ®< 5400) significantly improves the initial strength of the bond, but the viscosity is too low and the storage stability is limited (coagulation after 5 months). Example 11:

[0089] The addition of a standard thickener (polyacrylate Borchigel ®< ALA) to the low-viscosity (meth)acrylic acid ester copolymer (Acronal ®< 5400) increases the viscosity of the formulation with good initial bond strength, but storage stability is limited (separation after 3.5 months of storage and subsequent coagulation). Example 12 (according to the invention)

[0090] The addition of Exilva ®< P01-V to the low-viscosity (meth)acrylic acid ester copolymer (Acronal ®< 5400) increases the viscosity of the formulation while maintaining good initial bond strength. Storage stability is excellent, and the viscosity of the formulation remains constant over a 5-month storage period despite a decrease in pH during storage. Example 13:

[0091] Replacing the low-viscosity (meth)acrylic acid ester copolymer (Acronal ®< 5400) with a silica sol (Dispercoll ®< S 4510) results in a low-viscosity, storage-unstable formulation. Example 14:

[0092] Replacing the low-viscosity (meth)acrylic acid ester copolymer (Acronal ®< 5400) with a mixture of silica sol (Dispercoll ®< S 4510) and Exilva ®< P01-V results in an acceptable viscosity with low initial bond strength, but the storage time is limited by speck formation and coagulation. Example 15:

[0093] Replacing the low-viscosity (meth)acrylic acid ester copolymer (Acronal ®< 5400) with Exilva ®< P01-V results in an acceptable viscosity with good initial bond strength, but storage time is limited by coagulation. Example 16 (according to the invention):

[0094] If, according to Example 12, Exilva ®< P01-V and low-viscosity (meth)acrylic acid ester copolymer (Acronal ®< 5400) are mixed under high shear before addition and added as a mixture, the desired viscosity of the formulation is achieved even with a lower proportion of Exilva ®< P01-V. With very good initial bond strength, the storage stability and viscosity of the formulation remain unchanged for over 5 months despite a reduction in the pH value during Example 17:

[0095] Replacing microfibrillated cellulose (Exilva®< P01-V) with a commercially available methylcellulose (Culminal®< 2000 S) resulted in an adhesive mixture that was not stable during storage. Its viscosity increased sharply after one week of storage and even coagulated after 3.5 months. The viscosity remained constant during storage. Determination of rheological properties

[0096] In a Dispermat CD dissolver, Exilva ®< P01-V is placed in a stainless steel beaker (height 180 mm, diameter 120 mm) fitted with a dispersing disc (diameter 80 mm), and then Acronal ®< 5400 is added. The ratio of Acronal ®< 5400 to Exilva ®< P is 80 to 20 in the mixture. The two individual components were mixed for 15 minutes at different shear rates. Table 6: Determination of rheological properties Example V18 V19 V20 V21 V22 V23 24 Dispercoll ®< C 84 76,5 76,5 76,5 76,5 76,5 76,5 76,5 Rhenofit ®< DDA-50 EM 1,5 1,5 1,5 1,5 1,5 1,5 1,5 Exilva ®< P01-V / Acronal ®< 5400 19,8 19,8 19,8 19,8 19,8 19,8 19,8 Preparation of the mixture under shear (m / s) 4,4 5 10 15 20 25 30 Glycine 2,2 2,2 2,2 2,2 2,2 2,2 2,2 pH value after addition of glycine 9,0 9,0 9,0 9,0 9,0 9,0 9,0 pH value after 7 days 9,0 9,0 9,1 9,0 9,0 9,0 9,1 Initial viscosity [mPa*s] 2070 1890 2040 1950 2170 2400 2420 Viscosity after 7 days [mPa*s] 1580 2400 2590 2220 2500 2740 2440 Viscosity after 21 days [mPa*s] 1420 1940 2400 2100 2350 3510 2330

[0097] All formulations, regardless of pretreatment, are within the same viscosity range and are storage-stable. All formulations exhibit pseudoplastic behavior, except for the "low shear" range of 10 / s to 100 / s, where the viscosity changes only slightly with the shear rate.

[0098] In Figure 1The viscosity is plotted in mPa*s on the y-axis and the shear rate in 1 / s on the x-axis. Figure 1 As shown by way of example using the formulation according to Example 24, the shear stress changes only slightly compared to the shear rate in the inventive Example 24 in this range. This behavior of the inventive dispersion leads to easier application of the formulation by brush, roller, or doctor blade, reduces dripping and sagging of the applied formulation, reduces the mixing time during preparation of the formulation, and facilitates the flow of the inventive formulation in the lines of the spray equipment.

Claims

1. Aqueous formulation comprising a) at least one polychloroprene, b) at least one (meth)acrylic ester copolymer, c) at least one microfibrillated cellulose as thickener, and d) optionally further additives, wherein a) the at least one polychloroprene is present at at least 65 wt%, b) the at least one (meth)acrylic ester copolymer is present at 12 to 35 wt%, c) the at least one microfibrillated cellulose is present at 0.05 to 5 wt%, and d) the additives optionally present are present at 0.1 to 30 wt%, based in each case on the total weight of the non-volatile fractions of the formulation, and the sum total of the components present makes 100 wt% in each case, wherein the microfibrillated cellulose has fibrils with a diameter of 10 to 100 nm, determined with a scanning electron microscope.

2. Formulation according to Claim 1, characterized in that the at least one polychloroprene is present in particles with a mean particle size of 30 to 500 nm and preferably has a residual monomer content of less than 100 ppm.

3. Formulation according to Claim 1 or 2, characterized in that the at least one (meth)acrylic ester copolymer is at least one styrene-(meth)acrylic ester copolymer.

4. Formulation according to any of Claims 1 to 3, characterized in that a) the at least one polychloroprene is present at at least 70 wt%, b) the at least one (meth)acrylic ester copolymer is present at 15 to 30 wt%, preferably 18 to 28 wt%, c) the at least one microfibrillated cellulose is present at 0.2 to 3 wt%, and d) the additives optionally present are present at 0.1 to 30 wt%, based in each case on the total weight of the non-volatile fractions of the formulation, and the sum of the components present makes 100 wt% in each case.

5. Formulation according to any of Claims 1 to 4, characterized in that the at least one polychloroprene has up to 10 wt%, based on the total weight of the at least one polychloroprene, of 2,3-dichlorobutadiene as comonomer.

6. Formulation according to any of Claims 1 to 5, characterized in that the at least one (meth)acrylic ester copolymer has a viscosity of ≤ 400 mPas, measured at 250 1 / s, 23°C according to DIN EN ISO 3219-1994.

7. Formulation according to any of Claims 1 to 6, characterized in that the fibrils of the at least one microfibrillated cellulose have a diameter of 10 to 100 nm.

8. Formulation according to any of Claims 1 to 7, characterized in that it has a viscosity of 500 to 7000 mPa*s, preferably 1500 to 6000 mPa*s, determined in each case according to DIN ISO 2555 by means of a Brookfield rotational viscometer.

9. Method for producing an aqueous formulation according to any of Claims 1 to 8, comprising at least the steps of: (A) providing the components a), b), c), optionally d) and water in the corresponding amounts, and (B) mixing the components provided in step (A) to give the aqueous formulation.

10. Method according to Claim 9, characterized in that a dispersion comprising at least one polychloroprene is introduced and a mixture of at least one microfibrillated cellulose and at least one (meth)acrylic ester copolymer is added.

11. Method according to Claim 10, characterized in that the mixture of at least one microfibrillated cellulose and at least one (meth)acrylic ester copolymer is obtained by mixing the stated components under shearing forces of 4 to 66 m / s, preferably 28 to 35 m / s, in particular with a static mixer and / or dynamic mixer.

12. Method according to any of Claims 9 to 11, characterized in that production takes place in a continuous method or in a discontinuous method.

13. Method for producing a wet-on-wet bond between substrates, characterized in that an adhesive composition comprising the aqueous formulation according to any of Claims 1 to 8 is applied to a substrate and after at most 5 min, preferably at most 2 min, more preferably at most 1 min, wet bonding takes place before film formation.

14. Method for producing a composite material, by bonding the individual adherends of the composite material, characterized in that the aqueous formulation according to any of Claims 1 to 8 is used.

15. Use of the aqueous formulation according to any of Claims 1 to 8 for bonding wood, paper, thermoplastics, elastomeric plastics, thermoplastic-elastomeric plastics, vulcanizates, textile woven, knitted and / or braided fabrics, leather, metals, ceramic, asbestos cement, stoneware, concrete, foams, in each case to one another and / or to porous substrates, preferably with a density of less than 1 kg / litre, more particularly for bonding foams in mattress, furniture and / or upholstery bonding.