Method for impregnating a fibrous substrate with a methacrylic mixture comprising a flame-retardant substance
The present invention relates to a (meth)acrylic mixture for impregnating a fibrous substrate, characterized in that it comprises: a) a first dispersion comprising at least one (meth)acrylic polymer obtained by emulsion polymerization of one or more (meth)acrylic monomers, b) a second dispersion comprising at least one flame retardant. The invention also relates to a method for impregnating a fibrous substrate with a (meth)acrylic mixture of this kind, and to a method for manufacturing mechanical parts or structured elements, or articles, from the (meth)acrylic mixture. Another objective of the invention is a mechanical part or a structured element or an article made of composite material, obtained by the implementation of the manufacturing method.
1. A (meth)acrylic mixture for impregnating a fibrous substrate, comprising: a) a first aqueous dispersion comprising at least one (meth)acrylic polymer obtained by emulsion polymerization of one or more (meth)acrylic monomers, and b) a second stable aqueous dispersion comprising at least one flame retardant, combined with a dispersant, wherein the mass percentage of the dispersant in the second stable aqueous dispersion is between 0.01% and 5%, and wherein in the second stable aqueous dispersion, the at least one flame retardant is in the form of particles having a mean diameter D 50 of between 0.5 and 10 μm.
2. The (meth)acrylic mixture as claimed in claim 1 , wherein the at least one (meth)acrylic polymer of the first aqueous dispersion is selected from the group consisting of polyalkyl methacrylates and polyalkyl acrylates.
3. The (meth)acrylic mixture as claimed in claim 1 , wherein the one or more (meth)acrylic monomers of the first aqueous dispersion are selected from the group consisting of acrylic acid, methacrylic acid, acrylic alkyl monomers, methacrylic alkyl monomers and mixtures thereof.
4. The (meth)acrylic mixture as claimed in claim 1 , wherein the one or more (meth)acrylic monomers of the first aqueous dispersion are selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, methacrylic acid, acrylic acid, n-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, isobornyl methacrylate and mixtures thereof.
5. The (meth)acrylic mixture as claimed in claim 1 , wherein the at least one flame retardant of the second stable aqueous dispersion is selected from the group consisting of: phosphorus derivative additives, phosphinates, diphosphinates, phosphonates, phosphates, red phosphorus, ammonium polyphosphates, and mixtures thereof, “ hydrated inorganic fillers, and metal hydroxides.
6. The (meth)acrylic mixture as claimed in claim 5 , wherein the phosphorus derivative additives are selected from the group consisting of phosphinates and diphosphinates having the formulae (I) or (II) below:
in which:
R 1 and R2 denote linear or branched C 1 -C 6 alkyl groups, and/or aryl groups;
R 3 denotes a linear or branched C 1 -C 10 alkylene group, C 6 -C 10 to arylene group, or alkylarylene or arylalkylene group;
M denotes Mg, Ca, Al, Sb, Sn, Ge, Ti, Zn, Fe, Zr, Ce, Bi, Sr, Mn, Li, Na, K;
m is the number of positive charges and is an integer between 1 and 4;
n is an integer between 1 and 4;
x is an integer between and 4.
7. The meth(acrylic) mixture as claimed in claim 5 , wherein the phosphorus derivative additives have one of the formulae (III) or (IV) below:
8. The (meth)acrylic mixture as claimed in claim 1 , wherein the second stable aqueous dispersion comprises between 30% by weight and 70% by weight of the at least one flame retardant, relative to the total weight of the second stable aqueous dispersion.