EP4103641A1

EP4103641A1 - Methacrylate copolymers, and uses thereof for manufacturing polyurethane foam

Info

Publication number: EP4103641A1
Application number: EP20704045.2A
Authority: EP
Inventors: Guillaume De Combarieu; Laetitia DEWOLF; Florian CLOUP; Nicolas BIA; Alain GRAILLOT
Original assignee: Gaztransport et Technigaz SA
Current assignee: Gaztransport et Technigaz SA
Priority date: 2019-02-18
Filing date: 2020-02-14
Publication date: 2022-12-21
Also published as: CN113423773A; FR3092837B1; WO2020169482A1; CN113423773B; FR3092837A1; KR20210132653A

Abstract

The invention relates to methacrylate-based copolymers and the uses thereof for manufacturing a polyurethane foam. The invention also relates to polyurethane foams comprising said methacrylate copolymers, to a process for manufacturing same, and to the use thereof as insulation material for liquefied gas transport tanks and in particular tanks on methane carriers.

Description

METHACRYLATE COPOLYMERS, AND THEIR USES FOR THE PREPARATION OF POLYURETHANE FOAM

The present invention relates to methacrylate-based copolymers, their uses for the preparation of a polyurethane foam. The present invention also relates to polyurethane foams comprising said methacrylate copolymers, their manufacturing process and their use as insulating material for liquefied gas transport tanks and particularly LNG tankers.

We know, in particular from European patents No. 248,721 and No. 573,327, insulating elements for liquefied gas transport tanks, used in LNG carriers, made up of plywood boxes filled with an insulating material such as foam polyurethane. The insulation elements are divided into two insulation barriers called primary and secondary insulation layers. These insulation elements provide satisfactory thermal insulation but however require a significant installation time because the boxes constituting each primary and secondary layer must not only be fixed to the tank but also joined together in order to constitute the various thermal insulation layers. .

Furthermore, many rigid polyurethane (PUR) foams have been developed for use as an insulation material. This type of material has satisfactory thermal insulation characteristics for such use and remains easy to handle and install. However, PUR foams cannot, without being incorporated into plywood boxes, be suitable for thermal insulation of LNG tankers, because they do not have sufficient mechanical strength characteristics, in particular of the compressive strength type, both at room temperature and cold, to withstand the pressure of the liquefied gas moving in the tank and sudden temperature variations. Patent FR 2 882 756 describes a polyurethane-polyisocyanurate foam reinforced with glass fibers. However, the compressive strength, both at room temperature and cold, of such a foam remains insufficient. It is conventionally known to compensate for weaknesses in mechanical properties such as compression to increase density to obtain a better level of performance. However, the expected effect is not always obtained at room temperature and cold.

The object of the invention is to provide a foam which avoids the aforementioned drawbacks and which exhibits both good thermal insulation characteristics and mechanical characteristics of the Z type compressive strength (that is to say in the direction of foam thickness) hot (about 20 ° C) and cold (about -170 ° C) improved, these characteristics allowing it in particular to be used as a thermal insulation material for LNG tankers when the foam is fiber-reinforced, or for other applications without fiber with relatively cold temperatures (around -30 ° C).

The foam thus exhibits, thanks to the use of a methacrylate copolymer of the invention as defined below, both satisfactory thermal insulation characteristics and, surprisingly, mechanical characteristics of resistance to hot compression. and cold particularly advantageous, thus allowing it to be optionally used as an insulating material for an LNG tanker.

Thus, according to a first aspect, the invention relates to the use of a copolymer prepared from a fluorinated methacrylate (a), a methacrylate (b) containing at least one oxyalkylene group and a methacrylate of alkyl (c) for the preparation of a polyurethane foam. Without wishing to be limited to any one theory, the copolymer of the invention is capable of promoting the solubilization of a swelling agent, of stabilizing the cells formed during the preparation of the polyurethane foam and of promoting nucleation.

According to a particular embodiment, the invention relates to the use of the copolymer as defined above or below, in the presence of a blowing agent and optionally of a catalyst, for the preparation of a polyurethane foam, in particular at starting from an isocyanate compound and at least one polyol compound, the swelling agent, the catalyst, the isocyanate compound and the at least one polyol compound being in particular as defined below.

According to a particular embodiment, the fluorinated methacrylate (a) comprises a carbon chain consisting of an alkyl chain extended by a fluorinated chain, in particular perfluorinated, or of a polyoxyfluoroalkylene chain extended by a fluorinated chain, in particular perfluorinated. According to a more particular embodiment, the fluorinated methacrylate (a) is of the following formula (la), or is a mixture of methacrylates of the following formula (la):

in which :

q is a number between 1 and 3, q being in particular equal to 2;

r is a number between 1 and 7 or between 3 and 7, in particular between 6 and 7, r being in particular equal to

6.

r can be an integer, and / or q can be an integer. r and / or q can also be rational numbers. The methacrylate (a) is then a mixture of methacrylates of formula (la), in which, for each methacrylate of formula (la) of the mixture, q is independently an integer between 1 and 3, q being in particular equal to 2, and r is independently an integer between 3 and 7, r being in particular equal to 6. Thus, the r value of the mixture corresponds to the average of the r values of each methacrylate of formula (la) of the mixture, weighted by the respective proportions of each, and the same for q

According to a more particular embodiment, the fluorinated methacrylate (a) is of the following formula (la ’), or is a mixture of methacrylates of the following formula (la’):

in which :

A is C1-C5 fluoroalkylene, in particular C1-C3 perfluoroalkylene, or C1-C5 alkylene;

q ’is a number between 1 and 100, q’ being in particular between 1 and 3;

r is a number between 1 and 7 or between 3 and 7, r being in particular equal to 3, 4, 5 or 6.

r can be an integer, and / or q ’can be an integer.

r and / or q ’can also be rational numbers. The methacrylate (a) is then a mixture of methacrylates of formula (la '), in which, for each methacrylate of formula (la') of the mixture, q 'is independently an integer between 1 and 100, q' being in particular between 1 and 3, and r is independently an integer between 3 and 7, r being in particular equal to 3, 4, 5 or 6. Thus, the r value of the mixture corresponds to the average of the r values of each methacrylate of formula (la ') of the mixture, weighted by the respective proportions of each, and the same for q'. According to a particular embodiment, the methacrylate (b) containing at least one oxyalkylene group contains at least one oxyethylene group and at least one oxypropylene group.

According to an alternative embodiment, the methacrylate (b) containing at least one oxyalkylene group is of the following formula (Ib), or is a mixture of methacrylates of the following formula (Ib):

in which :

B is a hydrogen atom, or a linear or branched C1 to C ₄ alkyl, in particular methyl, or an alkyl acetate group of the formula -C (= 0) -D, where D is linear alkyl or branched in C 1 to C ₄ , in particular methyl,

on the scale of the mixture, v and w are molar proportions between 0 and 1, such that v + w = l, with w ¹ 0, and optionally v ¹0,

p is an integer such that:

v * p, the number of propylene glycol units (-0-ϋ¾-ϋί (ϋ¾) -) in the methacrylate (b) is between 0 and 7, in particular between 3 and 7, and preferably between 4 and 6,

w * p, the number of ethylene glycol (-O-CH2-CH2) -) units in the methacrylate (b), is between 38 and 54.

In particular, v * p is a rational number. The methacrylate (b) is then a mixture of methacrylates of formula (Ib), in which, for each methacrylate of formula (Ib) of the mixture, v * p is independently an integer between 0 and 7, in particular between 3 and 7 , and w * p is independently an integer between 38 and 54. Thus, the v * p value of the mixture corresponds to the average of the v * p values of each methacrylate of formula (Ib) of the mixture, weighted by the respective proportions of each, and the same for w * p. Still in this case, v * p is in particular a rational number between 5 and 5.3, and / or w * p is in particular a rational number between 38 and 54.

v * p can optionally be an integer, in particular equal to 5, and / or w * p can be an integer, in particular between 38 and 54, w * p being more particularly equal to 42. On the scale of a molecule, the propylene glycol and ethylene glycol groups have a block or random type distribution.

According to an even more particular embodiment, the methacrylate (b) containing at least one oxyalkylene group is of the following formula (Ib), or is a mixture of methacrylates of the following formula (Ib):

in which v, w, p and D are as defined above, D being in particular methyl. According to a particular embodiment, the alkyl methacrylate (c) is of the following formula (le), or is a mixture of methacrylates of the following formula (le):

in which s is an integer between 0 and 12 or between 2 and 12, s being in particular equal to 3 or 4.

s can be an integer.

s can also be a rational number. The methacrylate (c) is then a mixture of methacrylates of formula (le), in which, for each methacrylate of formula (le) of the mixture, s is independently an integer between 2 and 12, q 'being in particular equal to 3 or 4. Thus, the value s of the mixture corresponds to the average of the values of each methacrylate of formula (le) of the mixture, weighted by the respective proportions of each. According to a particular embodiment, the invention relates to the use of a copolymer of a fluorinated methacrylate (a) comprising a carbon chain consisting of an alkyl chain extended by a fluorinated chain, in particular perfluorinated, of a methacrylate (b ) containing at least one oxyethylene group and at least one oxypropylene group, and an alkyl methacrylate (c) for the preparation of a polyurethane foam.

According to a more particular embodiment, the invention relates to the use of a copolymer of a fluorinated methacrylate (a) of formula (la), of a methacrylate (b) of formula (Ib) and of a methacrylate of alkyl (c) of formula (Ie) for the preparation of a polyurethane foam. According to a particular embodiment, the content by weight of monomer (a) is from 12 to 40% relative to said copolymer, and / or the content by weight of monomer (b) is from 20 to 65% relative to said copolymer, and / or the weight content of monomer (c) is from 10 to 65% relative to said copolymer.

According to a particular embodiment, the number-average molar mass is between 6000 and 15000 g / mol.

According to a more particular embodiment, the content by weight of monomer (a) is approximately 36% relative to said copolymer, the content by weight of monomer (b) is approximately 52% relative to said copolymer, and the content by weight in monomer (c) is approximately 12% relative to said copolymer, the number-average molar mass of the copolymer being in particular approximately 7400 g / mol.

According to another more particular embodiment, the content by weight of monomer (a) is approximately 15% relative to said copolymer, the content by weight of monomer (b) is approximately 36% relative to said copolymer, and the content weight of monomer (c) is of approximately 50% relative to said copolymer, the number-average molar mass of the copolymer being in particular approximately 9500 g / mol.

According to another more particular embodiment, the content by weight of monomer (a) is approximately 27% relative to said copolymer, the content by weight of monomer (b) is approximately 62% relative to said copolymer, and the content weight of monomer (c) is approximately 11% relative to said copolymer, the number-average molar mass of the copolymer being in particular approximately 12,700 g / mol.

According to another more particular embodiment, the content by weight of monomer (a) is approximately 15% relative to said copolymer, the content by weight of monomer (b) is approximately 22% relative to said copolymer, and the content weight of monomer (c) is approximately 63% relative to said copolymer, the number-average molar mass of the copolymer being in particular approximately 14,500 g / mol.

According to another more particular embodiment, the content by weight of monomer (a) is approximately 15% relative to said copolymer, the content by weight of monomer (b) is approximately 26% relative to said copolymer, and the content weight of monomer (c) is approximately 59% relative to said copolymer, the number-average molar mass of the copolymer being in particular approximately 10,400 g / mol.

According to a particular embodiment, the copolymer has the following formula (II):

in which, independently of the pattern repeated n times:

x, y and z are respectively the molar proportions of monomer (a), (b) and (c) in the copolymer, between 0 and 1, with x + y + z = 1, provided that x ¹0, y ¹0 and z ¹0; n, the degree of polymerization in number DPn of the copolymer of formula (II), is an integer between 1 and 1000, DPn preferably being between 10 and 100, and very preferably between 10 and 80; and in which, independently of the pattern repeated n times:

on the scale of the mixture, v and w are molar proportions between 0 and 1, such that v + w = l, with w 7 0, and optionally v ¹0,

p is an integer such that:

v * p, the number of propylene glycol units (-0-CH ₂ -CH (CH ₃ ) -) in the methacrylate (b) is between 0 and 7, in particular between 3 and 7, and preferably between 4 and 6,

q is an integer between 1 and 3, q being in particular equal to 2;

r is an integer between 1 and 7 or between 3 and 7, in particular between 6 and 7, r being in particular equal to 6;

s is an integer between 0 and 6 or between 2 and 12, s being in particular equal to 3 or 4.

The monomers (a), (b) and (c) correspond respectively to the units present x, y, and z times. Thus, the values v, w, p, q, r and s are chosen as indicated above, regardless of the repeating unit repeated n times. They can thus vary within the ranges defined above from one repetition to another of said unit.

On the scale of the mixture, the values x, y, z, q, r, s, v, w and p and n can be rational numbers.

According to a more particular embodiment, the copolymer has the following formula (Ha):

x, y, z, v, w, p, r and n being as defined above, q being as defined above, and being in particular equal to 2.

According to an advantageous embodiment, v * p is from 4 to 6, w * p is a number between 38 and 54, r equal 6 or 7, r being in particular equal to 7, and DPn is an integer preferably between 10 and 100, and very preferably from 10 to 80.

According to an advantageous embodiment, x is equal to approximately 0.4, and y is equal to approximately 0.1. According to another advantageous embodiment, x is equal to approximately 0.08, and y is equal to approximately

0.02.

According to another advantageous embodiment, x is equal to approximately 0.37, and y is equal to approximately 0.16.

According to another advantageous embodiment, x is equal to approximately 0.07, and y is equal to approximately

0.02.

According to another advantageous embodiment, x is equal to approximately 0.077, and y is equal to approximately 0.025.

According to another aspect, the invention relates to a process for preparing polyurethane foam comprising the steps of:

(i) bringing an isocyanate compound into contact with at least one polyol compound, in the presence:

of a catalyst chosen from tin salts, potassium carboxylates and optionally tertiary amines,

a physical and / or chemical blowing agent,

a copolymer of a fluorinated methacrylate (a), a methacrylate (b) containing at least one oxyalkylene group and an alkyl methacrylate (c), as described above, and

possibly a flame retardant, and

(ii) allow the mixture obtained in step (i) to solidify, after expansion, so as to form a polyurethane foam.

According to one embodiment, the copolymer and the blowing agent as defined above are mixed together prior to step (i), in particular to form an emulsion.

According to the present invention, the polyurethane foam is formed by the reaction of the isocyanate compound and the at least one polyol compound. Without wishing to be limited to any theory, the reaction between these different compounds is likely to take place according to the following four reactions:

The first reaction is the reaction in which the water molecules react with the NCO groups of the isocyanate compound to form amine groups and CO2 molecules. The release of CO2 involves the swelling of the foam.

In the second reaction, the amine groups resulting from the second reaction react with the NCO groups to form urea groups.

At the same time, during the third reaction, the hydroxyl groups of the polyol compound react with the NCO groups to form urethane groups.

Finally, during the fourth reaction, called trimerization, the excess NCO groups combine in threes to form isocyanurate groups.

The first and second reactions (the second reaction being linked to the first), compete with the third and fourth reactions as described above.

In particular, the fourth reaction is very minor in the context of the present invention. The occurrence, or not, of this reaction can in particular be linked to the value of the isocyanate index, in base 100, as defined below. These reactions are manifested on a macroscopic scale by a general swelling of the foam induced by the internal release of CO2 and / or the evaporation of the physical swelling agent, mainly linked to the exotherm of reactions 1 to 3.

According to a particular embodiment, the amount of copolymer is from 0.1 to 10% by mass relative to the at least one polyol compound, in particular from 0.5 to 2% by mass, more particularly around 1.5%. en masse.

According to a particular embodiment, the isocyanate compound is such that its content by mass of isocyanate function is from 100 to 130, and / or its viscosity at 25 ° C is from 200 to 600 mPa.s, and / or its functionality average is 2.5 to 3.5, preferably 2.7 to 3.1. The average functionality is defined by the number of average NCO groups present in each molecule of isocyanate compound.

The percentage of NCO groups, defined by the mass ratio of the NCO groups / 100 grams of isocyanate component, is advantageously between 28 and 32%. According to a particular embodiment, the isocyanate compound is chosen from diphenylmethylene diisocyanates (MDI), in particular diphenylmethylene 2,2'-diisocyanate (2,2'-MDI), diphenylmethylene 4,4'-diisocyanate ( 4,4'-MDI) and 2,4'-diphenylmethylene diisocyanate (2,4'-MDI); toluene diisocyanates (TDI), in particular toluene 2,6-diisocyanate (2,6-TDI) and toluene 2,4-diisocyanate (2,4-TDI); 4,4'-dibenzyl diisocyanate (4,4'-DBDI); m-xylylene diisocyanate (m-XDI); 2,4'-dibenzyl diisocyanate (2,4'-DBDI), methylene bis (4-cyclohexylisocyanate) (H12MDI); isophorone diisocyanate (IPDI); hexamethylene diisocyanate (HDI); 1,5-naphthalene diisocyanate, bitolylene diisocyanate; and polyisocyanates, especially poly-diphenylmethylene diisocyanate (PMDI); the isocyanate compound being in particular a diphenylmethylene diisocyanate or a poly-diphenylmethylene diisocyanate.

Undistilled or crude methylene diphenyl poly-diisocyanate can be commonly used. This product is commonly available in the market under the brand name Suprasec marketed by Hunstman.

According to a particular embodiment, the at least one polyol compound is such that its hydroxyl group value is from 200 to 500 mg KOH / g, and / or its viscosity at 25 ° C is from 200 to 6000 mPa.s , preferably between 1000 and 3000 mPa.s, and / or its average functionality is between 2 and 6.

The hydroxyl number (OH number) of polyols is defined by the weight ratio of dosage in mg KOH per g of polyol compounds.

The determination of the OH number makes it possible to assess the crosslinking capacity of the polyol (s). According to a particular embodiment, the at least one polyol compound is chosen from polyesters, sorbitol and its derivatives, polyethers, glycerol and its derivatives, sucrose and its isomers and / or derivatives, and their mixtures, the compound polyol being in particular an aromatic polyester.

The term "derivative" of a given polyol is understood to mean in particular said polyol, substituted by at least one poly (alkylene oxide) chain, in particular a poly (ethylene oxide and / or propylene oxide) chain.

This polyol or this mixture of polyols can also be a polyetherpolyol, obtained by polyaddition of propylene oxide (PO) and / or ethylene oxide (EO) to at least one of the polyols as defined above. , according to one of the methods well known in the state of the art.

Representative examples of polyols derived from sorbitol are, for example, the polyols of the brand Daltolac from Huntsman. The OH number is within a range of 150 to 600, preferably between 300 and 600, for example 500 for the polyol of the type derived from sorbitol.

Representative examples of polyether type polyols are, for example, products derived from glycerol whose side chains are extended by propylene oxide, such as for example those marketed by Shell Chemicals under the brand Caradol, by Dow under the brand name. Voranol, by Carpenter under the Carpol brand or by Coim under the Isoter brand. The OH number is within a range of 150 to 600, preferably between 300 and 600, for example 250 for the second polyol.

Representative examples of polyester-type polyols are aliphatic polyester polyols or preferably aromatic polyester polyols such as phthalic anhydride derivatives. In the context of the present invention, the derivatives of diethylene glycol ortho-phthalate, for example the products marketed by Stepan under the brand StepanPol are preferably used. The OH index is for example 250 for the third polyol.

According to a particular embodiment, the isocyanate index, that is to say the molar ratio of NCO functions to OH functions is greater than or equal to 1, in particular greater than 1.

When the isocyanate index, based on 100, is approximately between 95 and 150, the foam resulting from this formulation is of the polyurethane (PUR) type and ideally between 105 and 130. When the isocyanate index is greater than 200-250, that is to say when there is an excess of NCO groups, the foam resulting from this formulation is of the polyisocyanurate (PIR) type.

According to a particular embodiment, the chemical blowing agent is water.

According to a particular embodiment, the amount of chemical blowing agent is from 0.05 to 5% by mass relative to at least one polyol compound, in particular from 0.05 to 1% by mass, more particularly approximately 0, 2-0.3% by mass. According to a particular embodiment, the physical swelling agent is chosen from hydrochlorofluorocarbons (HCFC), hydrofluorocarbons (HFC), hydrocarbons (HC) in particular chosen from cyclopentane, n-pentane, iso-pentane and l 'iso-butane, 1,1,1,3,3-pentafluoropropane, trans-1-chloro-3,3,3-trifluoropropene, 1,1,1,3,3-pentafluorobutane, 1,1 , 1,2,3,3,3-heptafluoropropane and their mixtures, in particular mixtures 1,1,1, 3, 3-pentafluorobutane / l, 1, 1, 2,3, 3, 3-heptafluoropropane.

The physical blowing agents preferentially used are the non-chlorinated pentafluorobutane compounds and in particular 1,1,1,3,3-pentafluorobutane also known under the name of HFC-365mfc in particular of the Solkane 365 brand marketed by Solvay and HFC -245fc of the Enovate 3000 brand marketed by Honeywell, as well as trans-1-chloro-3,3,3-trifluoropropene also known under the name Solstice Liquid Blowing Agent marketed by Honeywell.

The preferred amount of physical blowing agent is calculated based on the density of the desired PU foam.

According to one embodiment, the amount of physical blowing agent is from 0.1 to 30% by mass relative to the at least one polyol compound, in particular from 5 to 10% by mass, or is approximately 15% by mass. mass. According to a particular embodiment, the amount of preferred physical blowing agent is from 0.1 to 30% by mass relative to at least one polyol compound, in particular from 5 to 10% by mass, in particular for bulk foams. volume between 150 and 110 kg / m ³ , or approximately 15%, in particular for a foam of approximately 50 kg / m ³ with the addition of approximately 2% of chemical blowing agent.

According to another particular embodiment, the amount of physical swelling agent, when it is a pentane derivative as defined in particular above, is from 0.1 to 20% by mass relative to at least one polyol compound, in particular for foams with a density of between 50 to 150 kg / m ³ .

According to an advantageous embodiment, the physical blowing agent is combined with a chemical blowing agent, in particular water, as a blowing agent.

The catalyst can be a gelation, expansion, hardening, or even trimerization catalyst, commonly used in the preparation of polyurethane foams.

As regards the catalyst chosen from tin and bismuth salts, potassium carboxylates and optionally tertiary amines, particularly advantageous catalysts in the context of the present invention are for example tin IV carboxylates, in particular. dibutyltin dilaurate (DBTL) or tin octanoate; and potassium carboxylates such as potassium octanoate. Advantageously, catalysts based on tin and / or of potassium octanoate type are used simultaneously in the absence of catalysts of amine type.

The tin-based catalysts are for example those of the DBTL type marketed by Evonik under the KOSMOS brand (formerly Air Products under the Dabco brand) and are advantageously used in a proportion of between 0.01 and 1% by mass of the mass. total of the polyols (i.e. of the polyol compound).

The potassium octanoate type catalysts are for example those marketed by Air Products also under the Dabco brand and are advantageously used in a proportion of between 0.01 and 2% by weight of the total weight of the polyols and preferably between 0.02 and 0.2. %.

The catalysts of amine type are in particular of alkyl amine type, in particular chosen from bis (2-dimethylaminoethyl) ether, N, N-dimethylaminopropylamine, N, N-dimethylcyclohexylamine, N, N, N ', N', N ”-pentamethyldiethylene -triamine, triethylenediamine, or of the ethanol amine type, in particular chosen from diethanolamine, 2 (2-dimethylamino-ethoxy) ethanol, N- [2- (dimethylamino) ethyl] -N-methylethanolamine, dimethylethanolamine.

Amine-type catalysts are for example those marketed by Evonik under the trademark Polycat or by Huntsman under the trademark JELLCAT (for example DMCHA or PMDETA) and are advantageously used in a proportion of between 0.01 and 1% by mass of the mass. total polyols.

According to a particular embodiment, the catalyst is chosen from triethylenediamine, pentamethyldiethylenetriamine, dimethylcyclohexylamine, 1,4-diazabicyclo (2,2,2) - octane, and dibutyltin dilaurate, the catalyst being in particular dilaurate of dibutyltin.

The catalysts are used to accelerate one or more of the various reaction steps mentioned above. For example, the tin catalysts and the tertiary amines act preferentially on stages 1 to 3, while the catalysts based on potassium octanoate preferentially act on the trimerization reaction (stage 4).

According to a particular embodiment, a surfactant can be used in the context of the present invention in addition to the copolymer as defined above.

Examples of the surfactant are siloxane-oxyalkylene copolymers and other organopolysiloxanes. Alkoxylation products of fatty alcohols, oxoalcohols, lipophilic amines, alkylphenols, dialkylphenols, alkyl cresols, alkylresorcinol, naphthol, alkylnaphthol, naphthol, naphthylamine, aniline , alkylaniline, toluidine, bisphenol A, alkylated bisphenol A, polyvinyl alcohol, but also the alkoxylation products of condensation products of formaldehyde and alkylphenols, formaldehyde and dialkylphenols, formaldehyde and alkyl cresorcinol, formaldehyde and alkylresorcinol , formaldehyde and aniline, formaldehyde and toluidine, formaldehyde and naphthol, formaldehyde and alkylnaphthol, but also deformaldehyde and bisphenol A, can also be used. Mixtures of two or more of these surfactants can also be used. The surfactant is for example the copolymer Tegostab B 8404 (Evonik), or DC 193 (Dabco).

A flame retardant can be used within the scope of the present invention to further limit the flammability of the foam.

The flame retardants known from the prior art can generally be used. Flame retardants are, for example, brominated ethers (Ixol B 251), brominated alcohols such as dibromoneopentyl alcohol, tribromoneopentyl alcohol and PHT-4-diol, as well as chlorinated phosphates such as tris ( 2-chloroethyl) phosphate, tris (2-chloroisopropyl) phosphate (TCPP), tris (l, 3-dichloroisopropyl) phosphate, tris (2,3-dibromopropyl) phosphate and tetrakis (2-chloroethyl) ethylenediphosphate, or their mixtures.

In addition to the aforementioned halogenated phosphates, it is also possible to use inorganic flame retardants such as red phosphorus, preparations comprising red phosphorus, expandable graphite, aluminum oxide hydrate, aluminum trioxide, antimony, arsenic oxide, ammonium polyphosphate and calcium sulphate or cyanuric acid derivatives such as melamine or mixtures of two or more flame retardants such as ammonium polyphosphates and melamine.

As other halogen-free liquid flame retardants, it is possible to use diethyl ethanephosphonate (DEEP), triethyl phosphate (TEP), dimethyl propylphosphonate (DMPP), diphenyl cresyl phosphate (DPC).

According to a particular embodiment, the flame retardant is of the non-halogenated type. Thus, unlike a halogen-type flame retardant, the incorporation of this type of flame retardant in a composition has no harmful action for the environment. The flame retardant is preferably used in proportions of approximately 5% to 20% by mass of the total mass of at least the polyol compound.

Other additives such as fillers, crosslinking agents, colorants can advantageously be added to the formulation.

According to a particular embodiment, the foam obtained at the end of step (ii) has a density of between 20 and 250 kg / m 3. According to a particular embodiment, the mixture obtained during step (i) is, prior to step (ii), brought into contact with a stack of mats of glass fibers optionally associated with one another by a binder, in order to obtain a stack of mats of glass fibers impregnated with said mixture obtained during step (i). The expansion and solidification of said mixture leads to the formation of a block of reinforced foam containing the stack of mats of glass fibers.

Preferably, said mats of glass fibers have a basis weight of between 300 to 900 g / m ² , more advantageously, between 300 and 600 g / m ² . The glass fibers preferably constitute from 6 to 13%, preferably from 8 to 12% by mass relative to the total mass of the block of reinforced foam.

Advantageously, the glass fiber mats consist of glass fibers with a linear density of 10 to 60 Tex, preferably 20 to 40 Tex.

All the aforementioned parameters relating to the glass fiber mats and the glass fibers themselves are also favorable for a satisfactory impregnation of the glass mats and have been found to be able to give the foam characteristics of the tensile strength type. (i.e. elongation) satisfactory.

The glass fiber mats preferably used for the present invention consist of continuous strand glass mats in particular sold by Owens Corning under the Unifilo brand or marketed by 3B under the CFM brand.

Depending on the amount of binder and the weight per unit area of the glass fiber mats, and in order to possibly help obtain acceptable mechanical properties, the number of glass fiber mats varies, for example, from 3 to 20.

According to a particular embodiment, the foam obtained at the end of step (ii) is in the form of a block of foam with a thickness of between 10 and 40 cm. Thus, depending on the desired use, for example as an insulation material, a sufficient amount of formulation, optionally of glass fiber mats, and of blowing agent will be defined so as to prepare a block of foam with a desired thickness. The advantage of preparing foam blocks with a thickness of 20 cm is that, after deburring, the foam blocks can directly be used as a secondary insulating layer of an LNG carrier, which usually has a thickness of 18 cm, and / or cut transversely at the level of their half to directly form a layer of primary LNG carrier insulation, which usually has a thickness of 9 cm. Likewise, a block of foam prepared with a thickness of 30 cm, can, after deburring and cutting to a third of its thickness, simultaneously form a primary insulation layer of 9 cm and a secondary insulation layer of 18 cm. Others configurations to form blocks are possible such as the association of a primary insulation layer of 10 cm with a secondary insulation layer of 30 cm, or a primary insulation layer of 10 cm with a layer 38 cm secondary insulation layer, or a 15 cm primary insulation layer with a 25 cm secondary insulation layer. The width and length of the blocks is for example 100 cm by 300 cm.

The process for preparing polyurethane foam advantageously takes place as follows. The different components of the formulation can be mixed in a low pressure rigid foam mixer type mixer.

However, to facilitate the processing, the blowing agent and the various additives are generally introduced into the container comprising the polyol compound (s). Then the mixture comprising the polyol compound (s) and the various additives are then mixed with the isocyanate compound and the formulation resulting from this mixture is poured onto a surface, into a mold, or onto a stack of several mats of glass fibers. The blowing agent and certain additives or catalysts can be added to the composition after mixing the polyol compound (s) and the isocyanate compound.

The deposition rate is calculated according to the knowledge of those skilled in the art as a function of the speed of the conveyor, the height of the block and the desired density.

Then the foam blocks can crosslink for a period of between 5 and 30 min. Alternatively, the foam blocks can crosslink, in particular completely, and cool to room temperature for approximately 48 to 96 hours, before cutting.

Then the upper and lower and possibly side parts of the foam now in the form of a foam block are removed. This deburring step makes it possible to obtain foam blocks of given dimensions, for example from 9 to 10 cm and / or from 18 to 20 cm, and / or from 25 to 30 cm.

This single cutting step from a single block of foam makes it possible to simultaneously obtain a primary layer and a secondary insulation layer, which not only saves material, because less deburring losses are produced, but also a saving of time, because only one step is necessary for the production of the two layers of thermal insulation.

According to another aspect, the invention relates to a polyurethane foam comprising a copolymer of a fluorinated methacrylate (a), of a methacrylate (b) containing at least one oxyalkylene group and of an alkyl methacrylate (c), said copolymer being as described above. According to one embodiment, the polyurethane foam comprises mats of glass fibers. According to another embodiment, the polyurethane foam is devoid of mats of glass fibers. According to another aspect, the invention relates to a composition, in particular an emulsion, comprising a copolymer of a fluorinated methacrylate (a), of a methacrylate (b) containing at least one oxyalkylene group and of an alkyl methacrylate (c ), said copolymer being as described above, and a physical blowing agent, as defined above.

According to another aspect, the invention relates to a polyurethane foam capable of being obtained by the process as defined above.

According to another aspect, the invention relates to the use of a foam as defined above in the thermal insulation of liquefied gas transport tanks, and in particular of LNG tankers.

According to another aspect, the invention relates to a copolymer of a fluorinated methacrylate (a), of a methacrylate (b) containing at least one oxyalkylene group and of an alkyl methacrylate (c), said alkyl being a chain linear or branched or cyclic alkyl having 1 to 12 carbon atoms.

In particular, the invention relates to a copolymer as defined in the embodiments mentioned above.

Also, according to a particular embodiment, the fluorinated methacrylate (a) comprises a carbon chain consisting of an alkyl chain extended by a fluorinated chain, in particular perfluorinated, the fluorinated methacrylate (a) being in particular of formula (Ia) or ( the following '), or is a mixture of methacrylates of the following formula (la) or (la'):

in which :

A is C1-C5 fluoroalkylene, in particular C1-C3 perfluoroalkylene, or C1-C5 alkylene _;

q is a number between 1 and 3, q being in particular equal to 2;

q "is a number between 1 and 100, q" preferably being between 1 and 3;

r is a number between 1 and 7 or between 3 and 7, in particular between 6 and 7, r being in particular equal to 6. According to a particular embodiment, the methacrylate (b) containing at least one oxyalkylene group contains at least one oxyethylene group and at least one oxypropylene group, the methacrylate (b) containing at least one oxyalkylene group being in particular of the following formula (Ib) , or being a mixture of methacrylates of the following formula (Ib):

in which :

B is a hydrogen atom, or a linear or branched C1 to C ₄ alkyl, in particular methyl, or a group -C (= 0) -D, where D is a linear or branched C1 to C ₄ alkyl , in particular methyl,

p is an integer such that:

v * p can optionally be an integer, in particular equal to 5, and / or w * p can be an integer, in particular between 38 and 54, w * p being more particularly equal to 42. According to one mode of particular embodiment, the alkyl methacrylate (c) has the following formula (le):

in which s is an integer between 0 and 12 or between 2 and 6, s being in particular equal to 3 or 4.

in which, independently of the pattern repeated n times:

x, y and z are respectively the molar proportions of monomer (a), (b) and (c) in the copolymer, between 0 and 1, with x + y + z = 1, provided that x ¹0, y ¹0 and z ¹0; n, the degree of polymerization in number DPn of the copolymer of formula (II), is an integer between 1 and 1000, DPn preferably being between 10 and 100, and very preferably between 10 and 80;

and in which, independently of the pattern repeated n times:

p is an integer such that:

w * p, the number of ethylene glycol (-O-CH2-CH2) -) units in the methacrylate (b), is between 38 and 54;

q is an integer between 1 and 3, q being in particular equal to 2;

r is an integer between 1 and 7 or between 3 and 7, in particular between 6 and 7, r being in particular equal to 6; s is an integer between 0 and 6 or between 2 and 12, s being in particular equal to 3 or 4;

the copolymer being in particular of the following formula (Ha):

According to a particular embodiment:

v * p is equal to 5, w * p is equal to 42 and r is equal to 6 or 7, DPn being in particular equal to about 15 or about 45; and or

x is about 0.4, and y is about 0.1, the number average molar mass in particular being about 7,400; or

x is about 0.08, and y is about 0.02, the number-average molar mass in particular being about 9,500.

According to another particular embodiment:

v * p is equal to approximately 5.1, w * p is equal to approximately 46.2 and r is equal to 6, DPn being in particular equal to approximately 20, the number-average molar mass being in particular approximately 12,800; and / or x is about 0.37, and y is about 0.16.

According to another particular embodiment:

v * p is equal to approximately 5.2, w * p is equal to approximately 50 and r is equal to 6, DPn being in particular equal to approximately 69, the number-average molar mass being in particular approximately 14,500; and or

x is about 0.07, and y is about 0.02.

According to another particular embodiment:

v * p is equal to approximately 5.2, w * p is equal to approximately 50 and r is equal to 6, DPn being in particular equal to approximately 46, the number-average molar mass being in particular approximately 10,400; and or

x is about 0.077, and y is about 0.025. Definitions

As used in this specification, the term "about" refers to a range of values of ± 10% of a specific value. For example, the expression "about 20" includes values of 20 ± 10%, or values from 18 to 22.

For the purposes of the present description, the percentages refer to percentages by weight relative to the total weight of the formulation, unless otherwise indicated.

As understood here, ranges of values in the form of "x-y" or "from x to y" or "between x and y" include the x and y bounds as well as the integers between these bounds. By way of example, "1-5", or "from 1 to 5" or "between 1 and 5" denote the integers 1, 2, 3, 4 and 5. Preferred embodiments include each integer taken individually in the range of values, as well as any sub-combinations of these integers. By way of example, preferred values for "1-5" may include the integers 1, 2, 3, 4, 5, 1-2, 1-3, 1-4, 1-5, 2-3, 2 -4, 2-5, etc.

The term “methacrylate” is intended to mean in particular an ester derived from the methacrylate ion of formula CH ₂ = C (CH) COCr.

By “copolymer of a methacrylate (a), of a methacrylate (b) and of a methacrylate (c)” is meant a polymer resulting from the copolymerization of three types of monomer, namely the monomers (a), (b), and (c). This copolymerization can be done from a mixture of monomers comprising the monomers (a), (b), and (c), or from a mixture of monomers consisting of the monomers (a), (b), and (vs).

By "fluorinated methacrylate" is meant in particular an ester derived from the methacrylate ion of formula CH2 = C (CH3) COO, the ester group of which is fluorinated, that is to say substituted by at least one fluorine.

By "methacrylate containing at least one oxyalkylene group" is meant in particular an ester derived from the methacrylate ion of formula CH2 = C (CH3) COO, the ester group of which contains at least one -O-alkyl- residue.

By “at least one polyol compound” is meant a polyol compound or a mixture of polyol compounds. Thus, when a percentage by mass relative to at least one polyol compound is mentioned, this percentage is given relative to the polyol compound when there is only one, or relative to the mixture of polyols when there is one. two or more.

By “independently of the pattern repeated n times”, it is meant that the indices x, y, z, v, w, p, q, r and s may be different from one occurrence to another of the pattern repeated n times. In particular, the indices x, y, z, v, w, p, q, r and s have the same value, for any occurrence of the pattern repeated n times. By "alkyl" is meant, for each occurrence, a linear or branched or cyclic alkyl chain having from 1 to 12 carbon atoms.

By "fluorinated chain" is meant a linear or branched or cyclic alkyl chain having from 1 to 12 carbon atoms of which at least one of the hydrogen atoms is substituted by a fluorine. Likewise, by "fluoroalkylene" is meant an alkylene of which at least one of the hydrogen atoms is substituted by a fluorine.

By "perfluorinated chain" is meant a linear or branched or cyclic alkyl chain having 1 to 12 carbon atoms, all of the hydrogen atoms of which are substituted by fluorine.

By “molar fractions of monomer (a), (b) and (c) in the copolymer”, respectively x, y and z, is meant the ratio between the number of moles of monomer (a), (b) or (c ) respectively, on the total number of moles of monomer (i.e. the number of moles of monomer (a), (b) and (c). Thus, we have ax + y + z = 1.

The term “degree of polymerization DPn of the copolymer of formula (II)” means the total number of monomer units, that is to say the sum of the monomer units corresponding to the monomers (a), (b), and ( vs).

By "on the scale of the mixture, v and w are molar proportions ...", it is meant that v and w relate to the mixture of the monomer corresponding to the propylene glycol unit (-O-CH2- CH (CH3) -) and of the monomer corresponding to the ethylene glycol unit (-O-CH2-CH2) -) capable of making it possible to obtain the methacrylate of formula (Ib) or of the mixture of methacrylates of formula (Ib).

Preparation of the copolymers of the invention

The copolymers of the present invention can be synthesized by a process of polymerization in solution, or in emulsion, or in suspension. They can be in the form of random polymers, gradient polymers, block polymers. They can be obtained by conventional radical polymerization, controlled radical polymerization (RAFT, ATRP, NMP, RITP, etc.), or group transfer polymerization.

FIGURES

Figure 1 illustrates the compressive strength at 23 ° C, as a function of density, of foams as mentioned in the examples.

Figure 2 illustrates the compressive strength at -170 ° C, as a function of density, of foams as mentioned in the examples. FIG. 3 is a photograph of the polyurethane foam E1 as defined in Example 2, which enabled the measurements relating to the E1 foam recorded in Table 3 of said Example 2.

Figure 4 is a photograph of the polyurethane foam E2 as defined in Example 2, which allowed the measurements relating to the E2 foam recorded in Table 3 of said Example 2.

Figure 5 is a photograph of the E3 polyurethane foam as defined in Example 2, which allowed the measurements relating to the E3 foam recorded in Table 3 of said Example 2.

Examples

Example 1: synthesis of the copolymers

Fluorinated methacrylate (a), in particular of formula (la), methacrylate (b) containing at least one oxyalkylene group, in particular of formula (Ib), and alkyl methacrylate (c), in particular of formula ( le), are diluted in 2-butanone as solvent (dry extract - 20%). The radical initiator used to initiate the polymerization is GAIBN (Azobisisobutyronitrile - 2.5 to 3% by mass). The reaction medium is placed under an inert atmosphere by bubbling argon for 30 min. The polymerization reaction takes place at 70 ° C until complete conversion. After polymerization, the methacrylic polymer is obtained by precipitation in pentane and evaporation of the solvents under industrial vacuum.

The fluorinated methacrylate (a) is in particular tridecafluorooctyl methacrylate ([2144-53-8]). The alkyl methacrylate (c) is in particular butyl methacrylate.

The methacrylate (b), before acylation, is in particular a Polyglykol compound sold by Clariant, in particular Polyglycol MA 350, MA 750, MA 1000 M70, MA 2000 M55, MA 3000, or MA 50000 M50; or the compound Visiomer MPEG 2005 MA W (Evonik). When in the methacrylate of formula (Ib), B is of formula -C (= 0) -D as defined above, this methacrylate is obtained from a methacrylate of formula (Ib), with B = - OH, by reaction with an acyl chloride, in particular acetyl chloride (1.1 eq. per alcohol function) in the presence of triethylamine in dichloromethane.

Particular copolymers are obtained by using the molar fractions of monomer of formula (la), (Ib), with B = -C (= 0) -Me and (le), in the copolymer, respectively x, y and z (such as as defined previously), as indicated in the following table:

Example 2: synthesis of polyurethane foams

The different elements of component 1 of Table 2 are mixed uniformly. Components 3 and then 2 are then added to component 1. The formulations thus obtained are cast on a glass fiber mat so that the reinforced polyurethane foam has a fiber content of 9% and a density of 130 kg / m. ³ . In these tests, the weight per unit area, the rate of binder and the number of mats of glass fibers are respectively 450 g / m ² , 0.8% and 8.

Three polyurethane foams, named El, E2 and E3, are obtained using the copolymers of the invention, S 1 / S2 and S3, respectively, and a commercial copolymer not object of the invention.

After stabilization, hot and cold Z compressive strength tests are carried out on a laboratory scale on each of the 3 previous polyurethane foams.

The polyurethane foams of the invention can be obtained by any process well known to those skilled in the art from the formulations indicated in Table 2. In particular, they can be obtained by a continuous process. In this case, for example:

the raw materials are stored, liquid, in large stainless steel tanks. These tanks are equipped with agitators to keep the materials fluid. A metering device is attached to the reservoirs so that the appropriate amount of reactive material can be pumped. The relationship between the different components is strictly controlled;

the various compounds are passed through a heat exchanger as they are pumped through the pipes. The exchanger adjusts the temperature to the reaction temperature. At the end of the pipes is a polymer distribution head where the chemical reactions mentioned above start;

the distribution head is hung above the treatment line. For the production of rigid polyurethane foam insulation, a roll of kraft paper is wound up at the start of the processing line. This paper is moved along a conveyor and brought under the distribution head; As the paper passes, polyurethane is deposited on it. Polyurethane increases in volume thanks to blowing agents;

After the expansion reaction begins, a second, upper layer of paper can be applied to the polyurethane foam. Additionally, side papers can also be rolled in the process. The rigid foam is passed through a series of panels which control the width and height of the foam. When they pass through this section of the production line, they are usually dried;

at the end of the production line, the foam insulation is cut with an automatic saw to the desired length.

The cell size of the foams obtained is given in the following table.

Thus, it appears that the modification of the parameters x, y and z as defined above makes it possible to easily vary the size of the cells of the polyurethane foam obtained.

Example 3: Compressive strength tests

This example illustrates the results of tests in Z compression (that is to say in the thickness of the reinforced foam), hot and cold, which simulate the pressure at the side walls of the tanks, generated by the movement of liquefied gas within the tank of an LNG carrier, for example.

When the Z compression tests are carried out hot, they take place at room temperature. When these tests take place cold, they take place in a cryostat in which the temperature is -170 ° C (by using liquid nitrogen).

These tests are carried out on the first block of foam obtained during casting (L) or on the second block of casting (L2).

Z-compression tests are carried out according to standard M3007: ISO 844 (or equivalent). The compressive strength is evaluated by measuring the pressure applied vertically to the surface of each of the samples, as a function of the displacement of the surface from its initial position in the direction of the thickness of each sample. These measurements are plotted on a so-called compressive strength curve (not shown). The maximum pressure applied before rupture of the structure of the reinforced foam (maximum of said curve) corresponds to the maximum compressive strength which is referred to here as Z compression.

The results obtained are illustrated in Figures 1 and 2.

It appears that the foams of the invention are more resistant to compression, both at room temperature and in cold conditions, than current foams, in particular E3 foam.

Claims

1. Polyurethane foam comprising a copolymer of a fluorinated methacrylate (a), a methacrylate (b) containing at least one oxyalkylene group and an alkyl methacrylate (c).

2. Foam according to claim 1, in which the fluorinated methacrylate (a) comprises a carbon chain consisting of an alkyl chain extended by a fluorinated chain, in particular perfluorinated, the fluorinated methacrylate (a) being in particular of formula (Ia) or (la ') following, or a mixture of methacrylates of formula (la) or (la') below:

in which :

q is a number between 1 and 3, q being in particular equal to 2;

q ’is a number between 1 and 100, q’ being in particular between 1 and 3;

r is a number between 1 and 7, r being in particular equal to 3, 4, 5 or 6.

3. Foam according to any one of the preceding claims, in which the methacrylate (b) containing at least one oxyalkylene group contains at least one oxyethylene group and at least one oxypropylene group, or the methacrylate (b) containing at least one oxyalkylene group is of formula (Ib) below, or a mixture of methacrylates of formula (Ib) below:

in which : B is a hydrogen atom, or a linear or branched C1 to C4 alkyl, in particular methyl, or a group -C (= 0) -D, where D is a linear or branched C1 to C4 alkyl, in especially methyl,

on the scale of the mixture, v and w are molar proportions between 0 and 1, such that v + w = l, with w 4 0, and optionally v ¹0,

p is an integer such that:

4. Foam according to any one of the preceding claims wherein the alkyl methacrylate (c) is of the following formula (le), or a mixture of methacrylates of the following formula (le):

in which s is a number between 0 and 12, s being in particular equal to 3 or 4.

5. Foam according to any one of the preceding claims wherein the number-average molar mass is between 6000 and 15000 g / mol.

6. Foam according to any one of the preceding claims, in which the copolymer is of the following formula (II):

in which, independently of the pattern repeated n times:

and in which, independently of the pattern repeated n times:

p is an integer such that:

q is an integer between 1 and 3, q being in particular equal to 2;

r is an integer between 1 and 7, in particular between 6 and 7, r being in particular equal to 6; s is an integer between 0 and 6, s being in particular equal to 3 or 4; the copolymer being in particular of the following formula (Ha):

7. Foam according to claim 6 in which:

v * p is equal to 5, about 5.1 or about 5.2, w * p is equal to 42, about 46 or about 50, and r is equal to 6 or 7, DPn being in particular equal to about 45; and or x is about 0.4, and y is about 0.1; or

x is about 0.08, and y is about 0.02; or

x is about 0.37, and y is about 0.16; or

x is about 0.07, and y is about 0.02; or

x is about 0.077, and y is about 0.025.

8. Use of a copolymer of a fluorinated methacrylate (a), of a methacrylate (b) containing at least one oxyalkylene group and of an alkyl methacrylate (c) as defined in any one of the claims. 1 to 7 for the preparation of a polyurethane foam.

9. A process for preparing polyurethane foam comprising the steps of:

a physical and / or chemical blowing agent,

of a copolymer of a fluorinated methacrylate (a), of a methacrylate (b) containing at least one oxyalkylene group and of an alkyl methacrylate (c), as described in any one of claims 1 to 7, and

possibly a flame retardant, and

10. Preparation process according to claim 9, wherein the amount of copolymer is from 0.1 to 10% by mass relative to at least one polyol compound, in particular from 0.5 to 2% by mass, more particularly about 1.5% by mass.

11. Preparation process according to any one of claims 9 to 10, wherein the isocyanate compound is such that its content by weight of isocyanate function is between 100 and 130, and / or its viscosity at 25 ° C is between 200. at 600 mPa.s, and / or its functionality average is from 2.5 to 3.5, preferably between 2.9 and 3.1, and / or is chosen from diphenylmethylene diisocyanates (MDI), in particular diphenylmethylene 2,2'-diisocyanate (2, 2'-MDI), diphenylmethylene 4,4'-diisocyanate (4,4'-MDI) and diphenylmethylene 2,4'-diisocyanate (2,4'-MDI); toluene diisocyanates (TDI), in particular toluene 2,6-diisocyanate (2,6-TDI) and toluene 2,4-diisocyanate (2,4-TDI); 4,4'-dibenzyl diisocyanate (4,4'-DBDI); m-xylylene diisocyanate (m-XDI); 2,4'-dibenzyl diisocyanate (2,4'-DBDI), methylene bis (4-cyclohexylisocyanate) (H12MDI); isophorone diisocyanate (IPDI); hexamethylene diisocyanate (HDI); 1,5-naphthalene diisocyanate, bitolylene diisocyanate; and polyisocyanates, especially poly-diphenylmethylene diisocyanate (PMDI); the isocyanate compound being in particular a diphenylmethylene diisocyanate or a poly-diphenylmethylene diisocyanate.

12. Preparation process according to any one of claims 9 to 11, wherein the at least one polyol compound is such that its hydroxyl group value is from 200 to 500 mg KOH / g, and / or its viscosity at 25. ° C is between 200 and 6000 mPa.s, and / or its average functionality is between 2 and 6, and / or is chosen from polyesters, sorbitol, polyethers, glycerol and their mixtures, the polyol compound being in particular an aromatic polyester.

13. Preparation process according to any one of claims 9 to 12, wherein the isocyanate index, that is to say the molar ratio of NCO functions to OH functions is greater than or equal to 1, in particular greater than 1. .

14. Preparation process according to any one of claims 9 to 13, wherein

- the chemical blowing agent is water, and / or

- the amount of chemical blowing agent is from 0.05 to 5% by mass relative to at least one polyol compound, in particular from 0.05 to 1% by mass, more particularly approximately 0.2-0.3% en masse.

15. Preparation process according to any one of claims 9 to 14, in which: the physical swelling agent is chosen from hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), hydrocarbons (HC) in particular chosen from cyclopentane , u-pentane, /. so-pentane and /. so-butane, the physical swelling agent being chosen in particular from 1,1,1,3,3, -pentafluoropropane, trans-1- chloro-3,3,3- trifluoropropene, 1, 1, 1, 3,3-pcntafluorobutanc, 1,1,1,2,3,3,3-heptafluoropropane and mixtures thereof, and / or

the amount of physical blowing agent is from 0.1 to 30% by mass relative to the at least one polyol compound, in particular from 5 to 10% by mass, or is about 15% by mass.

16. Preparation process according to any one of claims 9 to 15, wherein the catalyst is chosen from triethylenediamine, pentamethyldiethylenetriamine, dimethylcyclohexylamine, 1,4-diazabicyclo (2,2,2) -octane, and dibutyltin dilaurate, the catalyst being in particular dibutyltin dilaurate.

17. Preparation process according to any one of claims 9 to 16, in which the foam obtained at the end of step (ii) has a density of between 20 and 250 kg / m ³ .

18. Use of the foam according to any one of claims 1 to 7 in the thermal insulation of liquefied gas transport tanks, and in particular of LNG tankers.

19. Copolymer of a fluorinated methacrylate (a), of a methacrylate (b) containing at least one oxyalkylene group and of an alkyl methacrylate (c), said alkyl being a linear or branched or cyclic alkyl chain having 1 to 12 carbon atoms.

20. A composition comprising a copolymer of a fluorinated methacrylate (a), a methacrylate (b) containing at least one oxyalkylene group and an alkyl methacrylate (c), and a physical blowing agent.