Liquid (meth)acrylic syrup, method for impregnating a fibrous substrate with said syrup, and composite material produced after polymerisation of said impregnation syrup

1. A viscous liquid (meth)acrylic syrup comprising:

a) 10 to 60 parts by weight of (meth)acrylic polymer,

b) 40 to 90 parts by weight of (meth)acrylic monomer,

c) 0.1 to 5 parts by weight of initiator to start the polymerization of the (meth)acrylic monomer, said initiator being in the form of a peroxide compound that is liquid in a temperature range of between 0° and 50° C.,

said syrup being characterized in that the initiator is combined with an accelerating system comprising:

d) 0.1 to less than 1 parts by weight of reducing compound,

e) 0.01 to 3 part by weight of metal salt or a mixture of metal salts not comprising any cobalt and

f) 0.1 to less than 1 parts by weight of tertiary amine,

relative to the sum of the (meth)acrylic monomer and of the (meth)acrylic polymer, the two together representing 100 parts by weight.

2. The (meth)acrylic syrup as claimed in claim 1 , wherein the reducing compound d) comprises at least one of the following compounds: ascorbic acid, saccharin, α-hydroxy sulfones, thioureas.

3. The (meth)acrylic syrup as claimed in claim 2 , wherein the reducing compound d) is saccharin.

4. The (meth)acrylic syrup as claimed in claim 1 , wherein the tertiary amine f) is selected from the group consisting of N,N-dimethyl-p-toluidine (DMPT), N,N-dihydroxyethyl-p-toluidine (DHEPT), N,N-diethyl-p-toluidine (DEPT) and para-toluidine ethoxylate (PTE).

5. The (meth)acrylic syrup as claimed in claim 1 , wherein the metal salt or the mixture of metal salts not comprising any cobalt e) is a compound of a transition metal chosen from the fourth period.

6. The (meth)acrylic syrup as claimed in claim 5 , wherein the transition metal is chosen from iron, copper and manganese, or mixtures thereof.

7. The (meth)acrylic syrup as claimed in claim 1 , wherein the liquid peroxide compound c) is an organic peroxide comprising 2 to 30 carbon atoms.

8. The (meth)acrylic syrup as claimed in claim 7 , wherein the peroxide compound is a hydroperoxide chosen from: tert-butyl hydroperoxide, monohydroperoxide, para-methane hydroperoxide, tert-amyl hydroperoxide and cumene hydroperoxide.

9. The (meth)acrylic syrup as claimed in claim 1 , wherein the liquid peroxide compound c) is chosen from methyl ethyl ketone peroxide and methyl isopropyl ketone peroxide.

10. The (meth)acrylic syrup as claimed in claim 1 , wherein the liquid peroxide compound c) is methyl isopropyl ketone peroxide.

11. The (meth)acrylic syrup as claimed in claim 1 , wherein, among the constituent monomers of the syrup, there are between 0 and 5 parts by weight of aromatic vinyl monomer.

12. The (meth)acrylic syrup as claimed in claim 11 , wherein the aromatic vinyl monomer is not styrene.

13. The (meth)acrylic syrup as claimed in claim 1 , wherein, among the constituent monomers of the syrup, there are between 0 and 5 parts by weight of multifunctional monomers.

14. The (meth)acrylic syrup as claimed in claim 1 , further comprising between 0 and 5 parts by weight of oligomers bearing methacrylate functionalities.

15. The (meth)acrylic syrup as claimed in claim 1 , wherein said (meth)acrylic syrup has a dynamic viscosity with a value within the range from 10 mPa·s to 10000 mPa·s.

16. A fibrous substrate impregnated with the (meth)acrylic syrup as claimed in claim 1 , said fibrous substrate consisting of long fibers.

17. A process for polymerizing a viscous liquid (meth)acrylic syrup as claimed in claim 1 , said syrup being a two-component system comprising a first component resulting from the mixing of compounds a), b), d), e) and f) and a second component comprising the initiating compound c), said process consisting of the step of mixing the first and second component of the two-component system less than 10 minutes before injection into a mold or impregnation of a fibrous substrate.

18. An impregnation process for impregnating a fibrous substrate, said fibrous substrate consisting of long fibers, said process comprising the step of impregnating said fibrous substrate with a viscous liquid (meth)acrylic syrup comprising:

a) 10 to 60 parts by weight of a (meth)acrylic polymer,

b) 40 to 90 parts by weight of a (meth)acrylic monomer,

c) 0.1 to 5 parts by weight of an initiator to start the polymerization of the (meth)acrylic monomer, said initiator being in the form of a peroxide compound that is liquid in a temperature range of between 0° and 50° C.,

the initiator being combined with an accelerating system comprising:

d) 0.1 to less than 1 part by weight of a reducing compound,

e) 0.01 to 3 parts by weight of a metal salt or a mixture of metal salts not comprising any cobalt and

f) 0.1 to less than 1 part by weight of a tertiary amine,

relative to the sum of the (meth)acrylic monomer and of the (meth)acrylic polymer, the two together representing 100 parts by weight.

19. A process for manufacturing structured mechanical parts or articles, wherein said manufacturing process comprises the following steps:

a) impregnating a fibrous substrate with a viscous liquid (meth)acrylic syrup as claimed in claim 1 ,

b) polymerizing said viscous liquid (meth)acrylic syrup impregnating said fibrous substrate.

20. The process as claimed in claim 19 , wherein the impregnation of the fibrous substrate in step a) is performed in a closed mold.

21. The process as claimed in claim 19 , wherein step a) of impregnating a fibrous substrate and step b) of polymerization are performed in a closed mold.

22. The process as claimed in claim 19 , wherein said process is chosen from resin transfer molding and infusion.

23. The process as claimed in claim 19 , wherein the temperature of the polymerization in step b) is below 120° C.

24. The process as claimed in claim 19 , wherein the reducing compound d) is saccharin.

25. The process as claimed in claim 19 , wherein the liquid peroxide compound c) is an organic peroxide comprising 2 to 30 carbon atoms.

26. The process as claimed in claim 19 , wherein the liquid peroxide compound c) is methyl isopropyl ketone peroxide.

27. A three-dimensional mechanical or structural part obtained via the manufacturing process as claimed in claim 19 .

28. The part as claimed in claim 27 , wherein said part is a motor vehicle part, boat part, train part, sport article, plane or helicopter part, space ship or rocket part, photovoltaic module part, wind turbine part, furniture part, construction or building part, telephone or cellphone part, computer or television part, or printer or photocopier part.