(METH) acrylic composition, foam material obtained from such composition, method for producing said composition and foam, and use thereof

Abstract

The present invention relates to a (meth) acrylic composition suitable for the preparation of a (meth) acrylic foam, to a method for preparing said (meth) acrylic composition and said (meth) acrylic foam, and to a foam material obtained by polymerization of such a (meth) acrylic composition. In particular, the present invention relates to a (meth) acrylic composition suitable for use in the preparation of a (meth) acrylic foam, said (meth) acrylic composition comprising a liquid polymerizable (meth) acrylic slurry, a blowing agent and an initiation system for initiating the polymerization of said composition, to a method for producing said (meth) acrylic composition and said (meth) acrylic foam, and to a foam material obtained by polymerization of such a (meth) acrylic composition. The invention also relates to a (meth) acrylic composite comprising a cavity filled with a (meth) acrylic foam, to a method for preparing such a (meth) acrylic composite comprising a cavity filled with a (meth) acrylic foam, and an object comprising such a (meth) acrylic composite comprising a cavity filled with a (meth) acrylic foam.

Description

[0001] Field of the Invention The present invention relates to (meth)acrylic acid-based compositions suitable for the preparation of (meth)acrylic acid-based foams, methods for preparing such (meth)acrylic acid-based compositions and such (meth)acrylic acid-based foams, and also to foam materials obtained by the polymerization of such (meth)acrylic acid-based compositions.

[0002] In particular, the present invention relates to (meth)acrylic acid-based compositions suitable for the preparation of (meth)acrylic acid-based foams, said (meth)acrylic acid-based compositions comprising a liquid polymerizable (meth)acrylic acid-based slurry, a blowing agent, and an initiating system for initiating the polymerization of the composition, to methods for preparing such (meth)acrylic acid-based compositions and such (meth)acrylic acid-based foams, and also to foam materials obtained by the polymerization of such (meth)acrylic acid-based compositions.

[0003] The present invention also relates to (meth)acrylic acid-based composite materials comprising cavities filled with (meth)acrylic acid-based foams, to methods for preparing such (meth)acrylic acid-based composite materials comprising cavities filled with (meth)acrylic acid-based foams, and to objects comprising such (meth)acrylic acid-based composite materials comprising cavities filled with (meth)acrylic acid-based foams.

[0004] [Technical Problem] Compared with polymeric bulk materials, foam materials, and especially polymer foams, have many advantages such as low density, good heat insulation, good sound insulation, high specific strength, and corrosion resistance. Foam materials are usually not used alone, but in combination with other materials such as composite materials. For better performance, the foam material should adhere to the composite material.

[0005] A composite material is a macroscopic combination of two or more immiscible materials. A composite material is composed of at least a matrix material forming a continuous phase for the cohesion of the structure and a reinforcing material having various architectures for mechanical properties.

[0006] The goal of using composite materials is to achieve properties by the composite material that cannot be obtained by its individual components when used alone. Therefore, composite materials are widely used in several industrial sectors, such as construction, automotive, nautical or marine, aerospace, transportation, leisure, electronics, and sports, especially due to their better mechanical properties (higher tensile strength, higher tensile modulus, and higher fracture toughness) and their low density compared to homogeneous materials.

[0007] Considering the volume on a commercial industrial scale, the most important category is composite materials with an organic matrix, where the matrix material is usually a polymer. The main matrix or continuous phase of polymer composites is a thermoplastic polymer or a thermosetting polymer.

[0008] One way to prepare polymer composites based on thermoplastic polymers is by using a liquid polymer composition containing monomers, commonly referred to as "syrup". This syrup is used to blend with mineral fillers or to impregnate reinforcing materials, such as fibrous substrates; and then polymerization occurs.

[0009] At the end of the use of an object or article containing a foamed material and a composite material, the object or article should be easily recyclable.

[0010] Compositions that can be converted into polymer foams that can be recycled are needed.

[0011] Polymer foam materials that can be easily attached to thermoplastic composites, especially (meth)acrylic composites, are also needed.

[0012] Compositions that can be converted into polymer foams are also needed.

[0013] Methods for preparing compositions that can be converted into polymer foams are also needed, which have a polymerization reactivity slow enough to have time to transfer the composition, such as filling cavities.

[0014] Another object of the present invention is to provide a method for manufacturing a polymer foam material that can be recycled and attached to a thermoplastic composite material.

[0015] Yet another object of the present invention is to provide a method for manufacturing an object comprising a thermoplastic composite material and a polymer foam material attached to the thermoplastic composite material. Background of the Invention Prior Art Document EP0068439 discloses a method for manufacturing an object made of foamed polymethyl methacrylate. The method includes using a mixture containing methyl methacrylate, a plasticizer, a foaming agent, and a compound that initiates polymerization.

[0017] Document WO 2013 / 056845 relates to a composite material comprising a thermoplastic (meth)acrylic matrix and a reinforcing material formed from a fibrous material, which can have various shapes and sizes and can be of natural or synthetic origin. The thermoplastic (meth)acrylic matrix can be particularly obtained from a viscous liquid composition called "liquid (meth)acrylic syrup", which contains (meth)acrylic monomers, or a mixture of (meth)acrylic monomers and oligomers or polymers dissolved in these monomers.

[0018] Document US2018 / 0079882 discloses the production of fine-pored PMMA foams using a nucleating agent. The nucleating agent is added to the monomer mixture before polymerization.

[0019] Document US2009 / 0233053 discloses an epoxy core with expandable microspheres. A method for manufacturing a molded structure is disclosed, in which the expandable microspheres are mixed with an epoxy resin among other compounds to form a preform. The preform is later wrapped, placed in a mold, and heated to form the structure.

[0020] Document US2020 / 385564 discloses a foamable acrylic composition, particularly for preparing foamed composite parts.

[0021] Document US 6,664,314 discloses a molding composition for producing sanitary ware. The molding composition based on a methyl methacrylate-based slurry with at most 85% filler further contains deformable propellant-filled hollow microspheres.

[0022] None of the cited prior arts disclose a liquid (meth)acrylic-based slurry containing one or more (meth)acrylic polymers, one or more (meth)acrylic monomers, and a blowing agent, especially a molded part containing a (meth)acrylic composite material having cavities filled with (meth)acrylic foam made from such a liquid (meth)acrylic-based slurry. [Summary of the Invention] It has surprisingly been found that a (meth)acrylic composition MC1 can provide a composition for preparing (meth)acrylic polymer foams, which has good adhesion and produces recyclable foams once polymerized. The (meth)acrylic composition MC1 comprises: (a) 100 parts by weight of a liquid (meth)acrylic-based slurry, which comprises: (a 1 ) 1% to 50% by weight of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 containing only one (meth)acrylic functional group per monomer, (b) 0.5 to 25 parts by weight of a blowing agent, (c) Optionally 0.01 to 5 parts by weight of a polymerization initiator (d) Optionally a promoter in the range of 100 ppm to 10,000 ppm.

[0024] It has also surprisingly been found that a (meth)acrylic composition MC1 can provide a composition for preparing a (meth)acrylic polymer foam, which polymerizes and foams at low temperatures, has good adhesion to (meth)acrylic composites, and produces a recyclable polymer foam once polymerized. The (meth)acrylic composition MC1 comprises: (a) 100 parts by weight of a liquid (meth)acrylic slurry, which comprises: (a 1 ) 1% to 50% by weight of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 containing only one (meth)acrylic functionality per monomer, (b) 0.5 to 25 parts by weight of a foaming agent, (c) 0.01 to 5 parts by weight of a polymerization initiator (d) A promoter in the range of 100 ppm to 10,000 ppm.

[0025] It has also surprisingly been found that a (meth)acrylic composition MC1 can be used to prepare a (meth)acrylic polymer foam having good adhesion to (meth)acrylic composites and can be used to prepare a recyclable polymer foam. The (meth)acrylic composition MC1 comprises: (a) 100 parts by weight of a liquid (meth)acrylic slurry, which comprises: (a 1 ) 1% to 50% by weight of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 containing only one (meth)acrylic functionality per monomer, (b) 0.5 to 25 parts by weight of a foaming agent, (c) 0.01 to 5 parts by weight of a polymerization initiator (d) A promoter in the range of 100 ppm to 10,000 ppm.

[0026] It has surprisingly been found that a method for preparing a molded part MP1 comprising a (meth)acrylic composite MCM1 and a (meth)acrylic foam MF1, which produces a molded part having good adhesion between the (meth)acrylic composite MCM1 and the (meth)acrylic foam MF1 and a recyclable molded part, the method comprising the following steps: (i) Provide a (meth)acrylic composite material MCM1 including a cavity. (ii) Provide a (meth)acrylic composition MC1, which comprises: (a) 100 parts by weight of a liquid (meth)acrylic slurry, which comprises: (a 1 ) 1% to 50% by weight of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 containing only one (meth)acrylic functional group per monomer, (b) 0.5 to 25 parts by weight of a foaming agent, (c) 0.01 to 5 parts by weight of a polymerization initiator (d) An accelerator in the range of 100 ppm to 10,000 ppm ； (iii) Transfer the (meth)acrylic composition MC1 into the cavity of the (meth)acrylic composite material. (iv) Polymerize the (meth)acrylic composition MC1. [Brief Description of the Drawings] Figure 1 shows a (meth)acrylic composite material MCM1 (20) in the form of a short tube (10) including a cavity (30).

[0028] Figure 1a ) shows a top view of the short tube (10) made of the (meth)acrylic composite material MCM1 (20) including a cavity (30).

[0029] Figure 1b ) shows the tube (10) along Figure 1a ) the axis A - A' of the side view.

[0030] Figure 1c shows a perspective view of the short tube (10) including a cavity (30).

[0031] Figure 2 shows a molded part MP1 in the form of a short tube (10), which comprises a (meth)acrylic composite material MCM1 (20) having a cavity filled with a (meth)acrylic foam MF1 (40).

[0032] Figure 2a ) shows a top view, Figure 2b ) shows the tube (10) along Figure 2a ) the axis A - A' of the side view, and Figure 2c ) shows a perspective view.

[0033] Figure 3a Showing a surfboard (15) made of a (meth)acrylic composite material MCM1 (20) including a cavity (30), the cavity (30) not shown Figure 3a therein.

[0034] Figure 3b is a side view along Figure 3a axis A - A’ thereof, showing a cavity (30) formed by a first part (20a) and a second part (20b) of a (meth)acrylic composite material MCM1 (20) joined together at a contact line (50). [DETAILED DESCRIPTION OF THE INVENTION] According to a first aspect, the present invention relates to a (meth)acrylic composition MC1, said (meth)acrylic composition MC1 comprising: (a) 100 parts by weight of a liquid (meth)acrylic slurry, which comprises: (a 1 ) 1% to 50% by weight of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 comprising only one (meth)acrylic functionality per monomer, (b) 0.5 to 25 parts by weight of a foaming agent, (c) Optionally 0.01 to 5 parts by weight of a polymerization initiator (d) Optionally a promoter in the range of 100 ppm to 10,000 ppm.

[0036] According to a second aspect, the present invention relates to a (meth)acrylic composition MC1, said (meth)acrylic composition MC1 comprising: (a) 100 parts by weight of a liquid (meth)acrylic slurry, which comprises: (a 1 ) 1% to 50% by weight of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 comprising only one (meth)acrylic functionality per monomer, (b) 0.5 to 25 parts by weight of a foaming agent, (c) 0.01 to 5 parts by weight of a polymerization initiator (d) A promoter in the range of 100 ppm to 10,000 ppm.

[0037] According to a third aspect, the present invention relates to a method for preparing a (meth)acrylic composition MC1, which comprises the following steps: (i) providing component (a) a liquid (meth)acrylic slurry, which comprises: (a 1 ) 1% to 50% by weight of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 containing only one (meth)acrylic functional group per monomer, (ii) for 100 parts of (a), adding component (b) 0.5 to 25 parts by weight of a foaming agent, optionally component (c) 0.01 to 5 parts by weight of a polymerization initiator, and optionally component (d) a promoter in the range of 100 ppm to 10,000 ppm, (iii) mixing components (a) to (b) or (a) to (d).

[0038] According to a fourth aspect, the present invention relates to a method for preparing a (meth)acrylic composition MC1, the method comprising the following steps: (i) providing component (a) a liquid (meth)acrylic slurry, which comprises: (a 1 ) 1% to 50% by weight of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 containing only one (meth)acrylic functional group per monomer, (ii) for 100 parts of (a), adding component (b) 0.5 to 25 parts by weight of a foaming agent, component (c) 0.01 to 5 parts by weight of a polymerization initiator, and component (d) a promoter in the range of 100 ppm to 10,000 ppm, (iii) mixing components (a) to (d).

[0039] According to a fifth aspect, the present invention relates to the use of a (meth)acrylic composition MC1 for preparing a foam or a foamed material, the (meth)acrylic composition MC1 comprising: (a) 100 parts by weight of a liquid (meth)acrylic slurry, which comprises: (a 1 ) 1% to 50% by weight of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 containing only one (meth)acrylic functionality per monomer, (b) 0.5 to 25 parts by weight of a blowing agent, (c) 0.01 to 5 parts by weight of a polymerization initiator (d) A promoter in the range of 100 ppm to 10,000 ppm.

[0040] According to a sixth aspect, the present invention relates to a (meth)acrylic foam MF1 prepared by polymerization of the (meth)acrylic composition MC1.

[0041] According to a seventh aspect, the present invention relates to a method for preparing a (meth)acrylic foam MF1, the method comprising the following steps: (i) Providing a (meth)acrylic composition MC1 according to the first or second aspect, (ii) Optionally filling or pouring the (meth)acrylic composition MC1 into a cavity (30), (iii) Polymerizing the (meth)acrylic composition MC1.

[0042] According to an eighth aspect, the present invention relates to a molded part MP1 comprising a (meth)acrylic composite material MCM1 having a cavity (30) filled with the (meth)acrylic foam MF1.

[0043] According to a ninth aspect, the present invention relates to a method for preparing a molded part MP1 according to the eighth aspect, the method comprising the following steps: (i) Providing a (meth)acrylic composite material MCM1 comprising a cavity (30), (ii) Providing the (meth)acrylic composition MC1, (iii) Transferring the (meth)acrylic composition MC1 into the cavity (30) of the (meth)acrylic composite material MC1, (iv) Polymerizing the (meth)acrylic composition MC1.

[0044] The term “(meth)acrylic monomer” encompasses acrylic monomers and methacrylic monomers. Similarly, the term “(meth)acrylic polymer” encompasses not only acrylic homopolymers, but also methacrylic homopolymers, acrylic copolymers, and methacrylic copolymers.

[0045] The term "PMMA" as used herein refers to homopolymers and copolymers of methyl methacrylate (MMA). For copolymers of MMA, the weight ratio of MMA in PMMA is at least 50% by weight.

[0046] The term "initiator" as used herein refers to a chemical class that forms a compound or intermediate compound that initiates the polymerization of a monomer capable of being successively linked to a large number of other monomers to form a polymeric compound.

[0047] The term "polymer composite" as used herein refers to a multi-component material comprising a plurality of different phase domains, wherein at least one type of phase domain is a continuous phase and wherein at least one component is a polymer.

[0048] The term "thermoplastic" as used herein refers to a polymer that, when heated, transforms into a liquid or becomes more liquid or has a lower viscosity and can assume a new shape by the application of heat and optionally pressure. This also applies to slightly crosslinked thermoplastic polymers that can be thermoformed when heated above the softening temperature.

[0049] The term "cavity" as used herein refers to an empty space within a solid object. The solid object can be, for example, a hollow profile, a hollow tube, the space between at least two sheets (flat or otherwise, with the distance between the sheets varying or constant), or any type of mold or die type having an upper and a lower part that together form a cavity.

[0050] The mention of a range from x to y in the present invention is intended to include the upper and lower limits of the range, equivalent to at least x and at most y.

[0051] The mention of a range between x and y in the present invention is intended to exclude the upper and lower limits of the range, equivalent to greater than x and less than y.

[0052] The liquid (meth)acrylic slurry (a) of the composition according to the present invention comprises (a 1 ) a (meth)acrylic polymer P1 and (a 2 ) a (meth)acrylic monomer M1.

[0053] The liquid (meth)acrylic acid-based slurry (a) of the (meth)acrylic acid-based composition MC1 according to the present invention comprises a (meth)acrylic acid-based polymer P1 between 1% and 50% by weight and a (meth)acrylic acid-based monomer M1 between 50% and 99% by weight. Preferably, the liquid (meth)acrylic acid-based slurry comprises a (meth)acrylic acid-based polymer P1 between 2% and 50% by weight and a (meth)acrylic acid-based monomer M1 between 50% and 98% by weight, more preferably a (meth)acrylic acid-based polymer P1 between 2% and 40% by weight and a (meth)acrylic acid-based monomer M1 between 60% and 98% by weight, still more preferably a (meth)acrylic acid-based polymer P1 between 3% and 40% by weight and a (meth)acrylic acid-based monomer M1 between 60% and 97% by weight, advantageously a (meth)acrylic acid-based polymer P1 between 3% and 35% by weight and a (meth)acrylic acid-based monomer M1 between 65% and 97% by weight, and more advantageously a (meth)acrylic acid-based polymer P1 between 3% and 30% by weight and a (meth)acrylic acid-based monomer M1 between 70% and 97% by weight.

[0054] The dynamic viscosity of the liquid (meth)acrylic acid-based slurry is in the range of 10 mPa*s to 10000 mPa*s, preferably 20 mPa*s to 7000 mPa*s, and advantageously 20 mPa*s to 5000 mPa*s, and more advantageously 20 mPa*s to 2000 mPa*s, and even more advantageously between 20 mPa*s and 1000 mPa*s. The viscosity of the slurry can be easily measured with a rheometer or a viscometer. The dynamic viscosity is measured at 25 °C. If the liquid (meth)acrylic acid-based slurry has Newtonian behavior, meaning no shear thinning, then the dynamic viscosity is independent of the shear in the rheometer or the moving speed in the viscometer. If the liquid composition has non-Newtonian behavior, meaning shear thinning, then the dynamic viscosity is measured at a shear rate of 1 s -1 at 25 °C.

[0055] Regarding the liquid (meth)acrylic acid-based slurry (a), it comprises (a 1 )(meth)acrylic acid-based monomer M1 and (a 2 )(meth)acrylic acid-based polymer P1. Once the (meth)acrylic acid-based composition MC1 has been polymerized, the (meth)acrylic acid-based monomer M1 copolymerizes with the (meth)acrylic acid-based monomer M2 and is converted into a (meth)acrylic acid-based polymer P2 comprising monomer units of the (meth)acrylic acid-based monomer M1 and other possible comonomers.

[0056] The liquid (meth)acrylic acid-based slurry of the (meth)acrylic acid-based composition MC1 according to the present invention may contain only one (meth)acrylic acid-based polymer P1, but may also contain a mixture of two, three or even more (meth)acrylic acid-based polymers P1. If there is a mixture of different (meth)acrylic acid-based polymers P1, the difference is the composition of each (meth)acrylic acid-based polymer P1 or the molecular weight of each (meth)acrylic acid-based polymer P1 or both.

[0057] The said or each (meth)acrylic acid-based polymer P1 comprised in the liquid (meth)acrylic acid-based slurry may be particularly selected from: · polyalkyl acrylates comprising alkyl acrylate homopolymers and alkyl acrylate copolymers, and · polymethylalkyl acrylates comprising methylalkyl acrylate homopolymers and methylalkyl acrylate copolymers.

[0058] According to a preferred embodiment, the said or each (meth)acrylic acid-based polymer P1 is polymethyl methacrylate (PMMA), it being understood that, as shown above, polymethyl methacrylate (PMMA) may mean a methyl methacrylate (MMA) homopolymer or an MMA copolymer.

[0059] In particular, in the case where the liquid (meth)acrylic acid-based slurry contains a mixture of two or more polymethyl methacrylates P1, this mixture may be formed by mixing at least two MMA homopolymers having different molecular weights, by mixing at least two MMA copolymers having the same monomer composition and different molecular weights, by mixing at least two MMA copolymers having different monomer compositions or by mixing at least one MMA homopolymer and at least one MMA copolymer.

[0060] According to a first preferred embodiment, the (meth)acrylic acid-based polymer P1 is selected from methyl methacrylate homopolymers or methyl methacrylate copolymers or mixtures thereof, methyl methacrylate advantageously constituting at least 50% by weight of the said or each (meth)acrylic acid-based polymer P1.

[0061] According to an embodiment of the present invention, methyl methacrylate constitutes at least 55% by weight of the said or each (meth)acrylic acid-based polymer P1.

[0062] According to another specific embodiment, the said or each (meth)acrylic acid-based polymer P1 contains at least 70% by weight, advantageously at least 80% by weight, preferably at least 90% by weight, and more preferably at least 95% by weight of methyl methacrylate.

[0063] When the (meth)acrylic polymer P1 is a methyl methacrylate (MMA) copolymer, it may contain at least one comonomer containing at least one ethylenically unsaturated bond and capable of copolymerizing with methyl methacrylate. Among these comonomers, acrylic acid, methacrylic acid, and (meth)acrylic acid alkyl esters in which the alkyl group contains 1 to 12 carbon atoms may be particularly mentioned. (Meth)acrylic acid alkyl esters refer to alkyl esters of acrylic acid or methacrylic acid. As examples of comonomers, methyl acrylate and (meth)ethyl acrylate, (meth)butyl acrylate, or 2-ethylhexyl (meth)acrylate may be mentioned.

[0064] Advantageously, the (meth)acrylic polymer P1 is a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate and an acrylic acid alkyl ester or a methacrylic acid alkyl ester in which the alkyl group contains 1 to 12 carbon atoms, advantageously 1 to 6 carbon atoms, and preferably 1 to 4 carbon atoms.

[0065] According to a first preferred embodiment, when the (meth)acrylic polymer P1 is a methyl methacrylate (MMA) copolymer, this methyl methacrylate (MMA) copolymer contains 70% to 99.9% by weight, advantageously 80% to 99.9% by weight, preferably 90% to 99.9% by weight, and more preferably 95% to 99.9% by weight of methyl methacrylate and 0.1% to 30% by weight, advantageously 0.1% to 20% by weight, preferably 0.1% to 10% by weight, and more preferably 0.1% to 5% by weight of at least one comonomer containing at least one ethylenically unsaturated bond copolymerizable with methyl methacrylate. Preferably, each of the comonomers is selected from methyl acrylate and ethyl acrylate.

[0066] In an advantageous variant of the first preferred embodiment, when the (meth)acrylic polymer P1 is a methyl methacrylate (MMA) copolymer, the (meth)acrylic polymer P1 is a copolymer of methyl methacrylate and an acrylic acid alkyl ester.

[0067] In a preferred variant of the first preferred embodiment, when the (meth)acrylic polymer P1 is a methyl methacrylate (MMA) copolymer, the (meth)acrylic polymer P1 is a copolymer of methyl methacrylate and methyl acrylate or ethyl acrylate.

[0068] According to a second preferred embodiment, when the said or each (meth)acrylic polymer P1 is a methyl methacrylate (MMA) copolymer, this methyl methacrylate (MMA) copolymer comprises from 50% to 99.9% by weight, advantageously from 52% to 99.9% by weight, preferably from 53% to 99.9% by weight, and more preferably from 55% to 99.9% by weight of methyl methacrylate and from 0.1% to 50% by weight, advantageously from 0.1% to 48% by weight, preferably from 0.1% to 47% by weight, and more preferably from 0.1% to 45% by weight of at least one comonomer containing at least one ethylenic unsaturation copolymerizable with methyl methacrylate. Preferably, the said or each comonomer is selected from methyl acrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate or butyl methacrylate.

[0069] The weight-average molecular weight (designated as M w w) of the said or each (meth)acrylic polymer P1 is generally relatively high and can thus be greater than 40 000 g / mol, advantageously greater than 45 000 g / mol, and preferably greater than 50 000 g / mol. The weight-average molecular weight can be measured by size exclusion chromatography (SEC).

[0070] If not crosslinked, the (meth)acrylic polymer P1 generally has a melt mass-flow rate (MFR) ISO 1133-2:2011 (230 °C / 3.8 kg) between 0.1 g / 10 min and 20 g / 10 min, or a melt mass-flow rate between 0.2 g / 10 min and 18 g / 10 min, or between 0.3 g / 10 min and 16 g / 10 min or between 0.4 g / 10 min and 13 g / 10 min.

[0071] The liquid (meth)acrylic slurry of the (meth)acrylic composition MC1 according to the invention may comprise only one (meth)acrylic monomer M1, but may equally well comprise a mixture of two, three or even more (meth)acrylic monomers M1. These will be (meth)acrylic monomer M1a, (meth)acrylic monomer M1b, (meth)acrylic monomer M1c and so on.

[0072] Whether the liquid (meth)acrylic slurry comprises one or more (meth)acrylic monomers M1, the said or each (meth)acrylic monomer M1 comprises only one (meth)acrylic functionality per monomer.

[0073] Regarding the (meth)acrylic monomer (M1), the monomer is selected from alkyl acrylic monomers, alkyl methacrylic monomers, hydroxyalkyl acrylic monomers, hydroxyalkyl methacrylic monomers, and mixtures thereof. The alkyl acrylic monomer or alkyl methacrylic monomer refers to an alkyl ester of acrylic acid or methacrylic acid.

[0074] Preferably, the (meth)acrylic monomer (M1) is selected from hydroxyalkyl acrylic monomers, hydroxyalkyl methacrylic monomers, alkyl acrylic monomers, alkyl methacrylic monomers, and mixtures thereof, wherein the alkyl contains 1 to 22 straight-chain, branched-chain, or cyclic carbons; the alkyl preferably contains 1 to 12 straight-chain, branched-chain, or cyclic carbons.

[0075] Advantageously, the (meth)acrylic monomer (M1) is selected from methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and mixtures thereof.

[0076] According to a preferred embodiment, at least 50% by weight, and preferably at least 60% by weight of the (meth)acrylic monomer (M1) is methyl methacrylate.

[0077] According to a first more preferred embodiment, at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, advantageously at least 80% by weight, and even more advantageously 90% by weight of the monomer (M1) is a mixture of methyl methacrylate and optionally at least one other monomer.

[0078] In a first variant of the present invention, the liquid (meth)acrylic slurry comprises: (a 1 ) 3% to 45% by weight, and preferably 3% to 40% by weight of the (one or more) (meth)acrylic polymer P1, and (a 2 ) 55% to 97% by weight, and preferably 60% to 97% by weight of the (one or more) (meth)acrylic monomer M1.

[0079] In a second variant of the present invention, the liquid (meth)acrylic slurry comprises: (a 1 ) 3% to 25% by weight, preferably 4% to 25% by weight, more preferably 5% to 25% by weight, and even more preferably 5% to 24% by weight of the (one or more) (meth)acrylic polymer P1, and (a 2 ) from 75% to 97% by weight, preferably from 75% to 96% by weight, more preferably from 75% to 95% by weight, and even more preferably from 76% to 95% by weight of one or more (meth)acrylic monomers M1.

[0080] In an advantageous variant, the or each (meth)acrylic polymer P1 and the or each (meth)acrylic monomer M1 of the liquid (meth)acrylic slurry comprise at least one identical (meth)acrylic unit, such a variant allowing the solubility of the (meth)acrylic polymer(s) P1 in the (meth)acrylic monomer(s) M1 to be optimized.

[0081] Preferably, the or each (meth)acrylic polymer P1 is selected from homopolymers of methyl methacrylate or copolymers of methyl methacrylate and methyl acrylate and copolymers of methyl methacrylate and ethyl acrylate or copolymers of methyl methacrylate and butyl acrylate or copolymers of methyl methacrylate and butyl methacrylate, each comonomer being present in the copolymer at most at 45% by weight.

[0082] Preferably, the (meth)acrylic monomer M1 is methyl methacrylate.

[0083] In a first advantageous variant, the liquid (meth)acrylic slurry comprises a (meth)acrylic polymer P1 and not a mixture of (meth)acrylic polymers P1.

[0084] In a second advantageous variant, the liquid (meth)acrylic slurry comprises a mixture of two (meth)acrylic polymers P1.

[0085] In another advantageous variant, the liquid (meth)acrylic slurry comprises a (meth)acrylic monomer M1 and not a mixture of (meth)acrylic monomers M1.

[0086] A stabilizer or reaction inhibitor may also be present in the liquid (meth)acrylic slurry to prevent the spontaneous polymerization of the (meth)acrylic monomer(s) M1.

[0087] These stabilizers may in particular be selected from hydroquinone (HQ), hydroquinone monomethyl ether (HQME), 2,6 - di - tert - butyl - 4 - methylphenol (BHT), 2,6 - di - tert - butyl - 4 - methoxyphenol (Topanol O) and 2,4 - dimethyl - 6 - tert - butylphenol (Topanol A).

[0088] These stabilizers may be present in the liquid (meth)acrylic acid-based slurry in a proportion of not more than 5 parts by weight, advantageously not more than 4 parts by weight, and preferably between 0.3 and 3 parts by weight, based on the total of 100 parts by weight of the (meth)acrylic acid-based polymer P1 and the (meth)acrylic acid-based monomer M1 (one or more).

[0089] Regarding the blowing agent, it may be selected from physical blowing agents, chemical blowing agents, expandable beads or pre-expanded beads.

[0090] In a first preferred embodiment, the blowing agent is selected from physical blowing agents.

[0091] In a second preferred embodiment, the blowing agent is selected from chemical blowing agents.

[0092] In a third preferred embodiment, the blowing agent is selected from expandable beads.

[0093] In a fourth preferred embodiment, the blowing agent is selected from expandable polymer beads.

[0094] In a fifth preferred embodiment, the blowing agent is selected from expandable polymer beads including an outer layer containing an inorganic compound.

[0095] In a sixth preferred embodiment, the blowing agent is selected from pre-expanded beads.

[0096] In a seventh preferred embodiment, the blowing agent is selected from pre-expanded polymer beads.

[0097] In an eighth preferred embodiment, the blowing agent is selected from pre-expanded polymer beads including an outer layer containing an inorganic compound.

[0098] In a ninth preferred embodiment, the blowing agent is selected from a mixture of at least two of any of the beads from the foregoing embodiments.

[0099] In a tenth preferred embodiment, the blowing agent is selected from a mixture of at least one expandable bead from the foregoing embodiments and at least one pre-expanded bead from the foregoing embodiments.

[0100] If the blowing agent is beads, it generally has a volume average particle diameter between 1 µm and 500 µm.

[0101] For 100 parts by weight of the liquid (meth)acrylic acid-based slurry, the blowing agent is present in the (meth)acrylic acid-based composition MC1 in an amount of 0.5 parts by weight to 25 parts by weight.

[0102] Preferably, for 100 parts by weight of the liquid (meth)acrylic acid-based slurry, the blowing agent is present in an amount of 1 part by weight to 25 parts by weight, and more preferably 1 part by weight to 20 parts by weight.

[0103] Most preferably, for 100 parts by weight of the liquid (meth)acrylic acid-based slurry, the foaming agent is present in an amount of 1 to 15 parts by weight.

[0104] The (meth)acrylic acid-based composition MC1 according to one aspect of the present invention further comprises a polymerization initiator, the function of which is to ensure the start of the polymerization of the (meth)acrylic acid-based monomer M1.

[0105] The polymerization initiator may be selected from organic peroxides, peroxy esters, peroxyacetals and azo compounds.

[0106] The polymerization initiator may particularly be selected from diacyl peroxides, peroxy esters, peroxy dicarbonates, dialkyl peroxides, peroxyacetals, hydroperoxides or peroxyketals.

[0107] In one embodiment, the polymerization initiator is selected from benzoyl peroxide.

[0108] In another embodiment, the polymerization initiator is selected from diisobutyryl peroxide, cumyl peroxyneodecanoate, bis(3-methoxybutyl) peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, cumyl peroxyneoheptanoate, dipropyl peroxydicarbonate, t-amyl peroxyneodecanoate, di-sec-butyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-tert-butylcyclohexyl) peroxydicarbonate, bis(2-ethylhexyl) peroxydicarbonate, t-amyl peroxyneodecanoate, t-butyl peroxyneodecanoate, dibutyl peroxydicarbonate, dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxypivalate, t-butyl peroxyneoheptanoate, t-amyl peroxypivalate, t-butyl peroxypivalate, di-(3,5,5-trimethylhexanoyl)-peroxide, dilauroyl peroxide, didecanoyl peroxide, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, t-amyl peroxy-2-ethylhexanoate, benzoyl peroxide, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxy diethylacetate, t-butyl peroxyisobutyrate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, t-amyl peroxy-2-ethylhexyl carbonate, t-amyl peroxyacetate, t-butyl peroxy-3,5,5-trimethylhexanoate, 2,2-bis(tert-butylperoxy)butane, t-butyl peroxyisopropyl carbonate, t-butyl peroxy-2-ethylhexyl carbonate, t-amyl peroxybenzoate, t-butyl peroxyacetate, 4,4-bis(tert-butylperoxy)butyl valerate, t-butyl peroxybenzoate, di-tert-amyl peroxide, dicumyl peroxide, di-(2-tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hex-3-yne, di-tert-butyl peroxide, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile), azodiisobutyramide, 2,2'-azobis(2,4-dimethylvaleronitrile), 1,1'-azobis(hexahydrobenzonitrile) or 4,4'-azobis(4-cyanovaleric acid).

[0109] The (meth)acrylic composition MC1 according to the present invention may contain 0.01 to 5 parts by weight of a polymerization initiator.

[0110] According to a particular embodiment, per 100 parts by weight of the liquid (meth)acrylic acid-based slurry, the (meth)acrylic acid-based composition MC1 according to the invention comprises from 0.02 to 4 parts by weight, and advantageously from 0.03 to 3 parts by weight, of a polymerization initiator.

[0111] What has just been described for the polymerization initiator applies fully to an initiator system which consists of a polymerization initiator and a polymerization activator or promoter.

[0112] The (meth)acrylic acid-based composition MC1 according to the invention may also advantageously further comprise a polymerization activator or promoter according to certain aspects.

[0113] According to a particular embodiment, per 100 parts by weight of the (meth)acrylic acid-based slurry, the (meth)acrylic acid-based composition according to the invention comprises between 100 ppm and 10,000 ppm, advantageously between 100 ppm and 7,000 ppm, and preferably between 200 ppm and 5,000 ppm, of a polymerization activator or promoter.

[0114] The invention also relates to a process for preparing the (meth)acrylic acid-based composition MC1.

[0115] According to the invention, the process comprises the steps of: i) providing components a) to b) or a) to d), ii) adding component b) or b) to d) to a), and iii) mixing components a) to b) or a) to d).

[0116] Step iii) of the process for preparation according to the invention is carried out by mixing all the components comprised in the (meth)acrylic acid-based composition MC1, taking care to first prepare the liquid (meth)acrylic acid-based slurry, then to introduce into this (meth)acrylic acid-based slurry a blowing agent and, where appropriate, a polymerization activator or promoter, and finally to introduce the polymerization initiator.

[0117] This mixing may be manual or may be carried out using a mixing device.

[0118] Optionally, the mixing is carried out by stirring and for a time between 1 minute and 6 hours, advantageously between 2 minutes and 2 hours, more advantageously between 3 minutes and 1 hour, and preferably between 4 minutes and 1 hour.

[0119] The manufacturing process according to the invention is thus a process which is particularly simple to implement and which can be easily implemented in existing installations dedicated to the manufacture of (meth)acrylic acid-based compositions.

[0120] The viscosity of the (meth)acrylic composition MC1 comprising compounds a) to d) or a) to e) is between 50 mPa*s and 10,000 Pa*s at 23 °C.

[0121] Preferably, the viscosity of the (meth)acrylic composition MC1 comprising compounds a) to d) or a) to e) is in the range of 50 mPa*s to 100 Pa*s, more preferably 50 mPa*s to 50 Pa*s, even more preferably 50 mPa*s to 25 Pa*s, even still more preferably 50 mPa*s to 20 Pa*s at 23 °C, even still more preferably between 50 mPa*s and 15 Pa*s, advantageously between 50 mPa*s and 10,000 mPa*s, and more advantageously between 50 mPa*s and 5,000 mPa*s.

[0122] The (meth)acrylic composition MC1 according to the invention can also be used for the preparation of foams or foamed materials.

[0123] One aspect of the invention is a (meth)acrylic foam MF1 prepared by polymerization of the (meth)acrylic composition MC1.

[0124] Another aspect of the invention is the use of the (meth)acrylic foam MF1 for filling a cavity (30).

[0125] A further aspect of the invention is a method for preparing the (meth)acrylic foam MF1.

[0126] The method for preparing the (meth)acrylic foam MF1 comprises the following steps: (i) providing a (meth)acrylic composition MC1 as defined above, (ii) optionally filling or pouring the (meth)acrylic composition MC1 into a cavity (30), (iii) polymerizing the (meth)acrylic composition MC1.

[0127] The different embodiments of the provided (meth)acrylic composition MC1 and its various components can be combined in any combination.

[0128] In a first preferred embodiment of the method for preparing the (meth)acrylic foam MF1, the (meth)acrylic composition MC1 is filled or poured into the cavity (30). Polymerization takes place inside the cavity (30). Foaming occurs or at least starts during the polymerization step (iii).

[0129] The polymerization is carried out at a temperature below 140 °C.

[0130] The polymerization is carried out at a temperature above 10 °C.

[0131] The polymerization starts at a temperature above 10 °C and increases during the polymerization process.

[0132] The temperature during the polymerization process is high enough to activate the blowing agent. The temperature during the polymerization process can be raised to above 100 °C or above 80 °C or above 60 °C.

[0133] The polymerization and foaming occur together.

[0134] In one embodiment, the foaming is carried out by the heat released from the polymerization reaction.

[0135] In a second preferred embodiment of the method for preparing the (meth)acrylic foam MF1, the (meth)acrylic composition MC1 is filled or poured into a cavity (30) formed of a thermoplastic composite material. Preferably, the cavity (30) is formed of a (meth)acrylic composite material MCM1 (20). For the second preferred embodiment of the method for preparing the (meth)acrylic foam MF1, the temperature conditions are the same as those of the first preferred embodiment. The polymerization and foaming can also occur together.

[0136] In another aspect, the present invention relates to a molded part MP1, which comprises a (meth)acrylic composite material MCM1 having a cavity filled with a (meth)acrylic foam MF1.

[0137] In the first preferred embodiment, the (meth)acrylic composite material MCM1 is a fiber-reinforced (meth)acrylic composite material.

[0138] In the second preferred embodiment, the (meth)acrylic composite material MCM1 is a particle-reinforced (meth)acrylic composite material.

[0139] According to one embodiment of the present invention, the molded part MP1 is obtained by the polymerization of the (meth)acrylic composition MC1 in the cavity of the (meth)acrylic composite material MCM1.

[0140] The molded part MP1 according to the present invention can be used in many industries, and especially in the housing, motor vehicle, railway, sports, aviation industry, aerospace, photovoltaic or wind power industry, as well as in marine applications and medical applications.

[0141] For example, the following objects or products may include the molded part MP1: wind turbine blades, surfboards, boats, pressure vessels, pipes, tubes, profiles.

[0142] [Method] The weight-average molecular weight can be measured by size-exclusion chromatography (SEC). The chromatographic column is calibrated with PMMA standard samples having molecular weights between 402 g / mol and 1,900,000 g / mol. For the number-average and weight-average molecular weights Mn and Mw respectively, the average molecular weight is expressed in g / mol. For this measurement, the concentration is 1 g / L.

[0143] According to ISO 2555:2018 “Plastics - resins in the liquid state or as emulsions or dispersions - Determination of apparent viscosity using a single-cylinder type rotational viscometer method”, the viscosity of the (meth)acrylic composition containing at least components a1) and a2) is measured at 23 °C using a Brookfield viscometer.

[0144] [Examples] The compounds used to prepare various (meth)acrylic compositions are as follows: - As the (meth)acrylic polymer P1: PMMA formed from a copolymer of methyl methacrylate and ethyl acrylate, obtained from Altuglas under the name Altuglas® BS 520B, - As the (meth)acrylic monomer M1: methyl methacrylate stabilized with hydroquinone monomethyl ether, - As the initiator, benzoyl peroxide (BPO) is used, - As the accelerator, DMPT (N,N-dimethyl-p-toluidine) is used, - As the blowing agent: unexpanded microspheres Dualite® from Chase.

[0145] Slurry S1 is prepared by first dissolving 20 parts by weight of PMMA (BS520, an MMA copolymer containing ethyl acrylate as a comonomer) as P1 in 80 parts by weight of methyl methacrylate stabilized with MEHQ (hydroquinone monomethyl ether) as the (meth)acrylic monomer M1. The viscosity of slurry S1 at 23 °C is 104 m·Pas.

[0146] Slurry S1 is used to prepare the compositions of the examples and comparative examples of the present invention by adding additional compounds.

[0147] Then, 5 parts by weight of Dualite U011-128D unexpanded microspheres are added to 100 parts of slurry S1 as the blowing agent.

[0148] 3 parts of BPO were also added.

[0149] Table 1 – Compositions prepared, phr unless otherwise indicated Quantity / [phr] Example 1 Comparative Example Slurry S1 100 100 Foaming Agent 5 0 Initiator 3 3 Accelerator 1 1 Polymerize the mixture from Table 1.

[0150] The following results summarized in Table 2 were obtained.

[0151] Table 2 – Characteristics of the resulting polymeric compositions Quantity / [phr] Example 1 Comparative Example Density 150 kg / m3 1200 kg / m3 Foam Quality Uniform Bulk Material A uniform foam was obtained with the composition according to the example.

Claims

1. A (meth)acrylic acid composition MC1, comprising: (a) 100 parts by weight of a liquid (meth)acrylic syrup comprising: (a 1 ) 1 to 50 wt. % of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 comprising only one (meth)acrylic function per monomer, (b) 0.5 to 25 parts by weight of a blowing agent, (c) 0.01 to 5 parts by weight of a polymerization initiator (d) optionally between 100 ppm and 10,000 ppm of an accelerator.

2. The (meth)acrylic composition MC1 according to claim 1, Features It contains (c) 0.01 to 5 parts by weight of a polymerization initiator (d) between 100 ppm and 10,000 ppm of accelerator.

3. The (meth)acrylic composition MC1 according to claim 1 or 2, Features The one or more (meth)acrylic polymers P1 comprise a mixture of different (meth)acrylic polymers P1, the difference being the composition of each (meth)acrylic polymer P1 or the molecular weight of each (meth)acrylic polymer P1 or both.

4. A composition according to any one of claims 1 to 3, Features The or each (meth)acrylic polymer P1 is chosen from methyl methacrylate homopolymers or methyl methacrylate copolymers or mixtures thereof, methyl methacrylate advantageously constituting at least 50% by weight of the or each (meth)acrylic polymer P1.

5. The composition according to any one of claims 1 to 4, Features The viscosity of the liquid (meth)acrylic syrup at 25° C. is between 10 m*Pas and 10 000 m*Pas.

6. The composition according to any one of claims 1 to 5, Features The (meth)acrylic polymer P1 has a weight average molecular weight M greater than 40 000 g / mol. w .

7. A composition according to any one of claims 1 to 6, Features The (meth)acrylic polymer P1 has a melt mass flow rate (MFR) ISO 1133-2:2011 (230° C. / 3.8 kg) between 0.1 g / 10 min and 20 g / 10 min.

8. A composition according to any one of claims 1 to 7, Features The blowing agent is selected from physical blowing agents.

9. The composition according to any one of claims 1 to 7, Features The blowing agent is selected from chemical blowing agents.

10. The composition according to any one of claims 1 to 7, Features The blowing agent is selected from expandable beads.

11. The composition according to any one of claims 1 to 7, Features The blowing agent is selected from expandable polymer beads.

12. A composition according to any one of claims 1 to 7, Features The blowing agent is selected from expandable polymer beads comprising an outer layer comprising an inorganic compound.

13. A composition according to any one of claims 1 to 7, Features The blowing agent is selected from pre-expanded beads.

14. A composition according to any one of claims 1 to 7, Features The blowing agent is selected from pre-expanded polymer beads.

15. A composition according to any one of claims 1 to 7, Features The blowing agent is selected from pre-expanded polymer beads comprising an outer layer comprising an inorganic compound.

16. A composition according to any one of claims 1 to 7, Features The blowing agent is selected from a mixture of at least two beads from any of claims 10 to 15.

17. A composition according to any one of claims 1 to 7, Features The blowing agent is selected from a mixture of at least one expandable bead and at least one pre-expanded bead.

18. A composition according to any one of claims 10 to 17, Features The beads have a volume average particle size between 1 µm and 500 µm.

19. A composition according to any one of claims 1 to 18, Features The liquid (meth)acrylic syrup comprises: (a 1 ) 3 to 45% by weight, and preferably 3 to 40% by weight, of a (meth)acrylic polymer P1, and (a 2 ) 55 to 97 wt %, and preferably 60 to 97 wt % of the (meth)acrylic monomer M1.

20. A composition according to any one of claims 1 to 18, Features The liquid (meth)acrylic syrup comprises: (a 1 ) 3 to 25 wt %, and preferably 4 to 25 wt %, and more preferably 5 to 25 wt %, and even more preferably 5 to 24 wt % of (meth)acrylic polymer P1, and (a 2 ) 75 to 97 wt %, and preferably 75 to 96 wt %, and more preferably 75 to 95 wt %, and even more preferably 76 to 95 wt % of the (meth)acrylic monomer M1.

21. A method for preparing a (meth)acrylic composition MC1 according to any one of claims 1 to 20, wherein The following steps are involved: (i) providing component (a) a liquid (meth)acrylic acid syrup comprising (a 1 ) 1 to 50 wt. % of one or more (meth)acrylic polymers P1, and (a 2 ) 50% to 99% by weight of one or more (meth)acrylic monomers M1, each monomer M1 comprising only one (meth)acrylic function per monomer, (ii) To 100 parts of (a), add component (b) 0.5 to 25 parts by weight of a blowing agent, optional component (c) 0.01 to 5 parts by weight of a polymerization initiator, and optional component (d) 100 ppm to 10,000 ppm of an accelerator. (iii) Mixing components (a) to (b) or (a) to (d).

22. The method according to claim 21, Features The mixing is carried out by stirring and lasts for a period of between 1 minute and 6 hours.

23. Use of the (meth)acrylic composition MC1 according to any one of claims 1 to 19 for preparing a foam or a foamed material.

24. A (meth)acrylic foam MF1 prepared by polymerization of the (meth)acrylic composition MC1 according to any one of claims 1 to 19.

25. A method for preparing a (meth)acrylic foam MF1, wherein The following steps are involved: (i) providing a (meth)acrylic composition MC1 according to any one of claims 1 to 19, (ii) optionally filling or pouring the (meth)acrylic composition MC1 into the cavity, (iii) polymerizing the (meth)acrylic composition MC1.

26. The method according to claim 25, Features The (meth)acrylic composition MC1 is filled or poured into the cavity (30).

27. The method according to claims 25 and 26, Features The polymerization takes place within the cavity (30).

28. The method according to any one of claims 25 to 27, Features Foaming occurs or at least starts during the polymerisation step (iii).

29. The method according to any one of claims 25 to 28, Features The cavity (30) is formed of a (meth)acrylic composite material MCM1.

30. The method according to any one of claims 25 to 29, Features The temperature was below 140°C during the polymerisation step.

31. The method according to any one of claims 25 to 30, Features The temperature during the polymerization may be elevated to above 100°C or above 80°C or above 60°C.

32. Use of the (meth)acrylic foam MF1 according to claim 24 for filling cavities.

33. A moulded part MP1 comprising a (meth)acrylic composite material MCM1 having a cavity filled with a (meth)acrylic foam MF1 according to claim 24.

34. A method for producing a molded part MP1 according to claim 33, said method The following steps are involved: (i) providing a (meth)acrylic composite material MCM1 including a cavity, (ii) providing a (meth)acrylic composition MC1 according to any one of claims 1 to 19, (iii) transferring the (meth)acrylic composition MC1 into the cavity of the (meth)acrylic composite material MCM1, (iv) polymerizing the (meth)acrylic composition MC1.

35. The method according to claim 34, Features The (meth)acrylic composite material MCM1 is a fiber-reinforced (meth)acrylic composite material.

36. The method according to claim 35, Features The (meth)acrylic composite material MCM1 is a particle-reinforced (meth)acrylic composite material.

37. An object comprising a moulding part MP1 according to claim 33.

38. An object according to claim 37, selected from a wind blade, a surfboard, a boat, a pressure vessel, a tube, a pipe or a profile.

39. An article comprising a (meth)acrylic composite material MCM1 and a (meth)acrylic foam MF1 according to claim 24.

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