EP1713855A1

EP1713855A1 - Expanded polystyrene solubilisation method

Info

Publication number: EP1713855A1
Application number: EP04817619A
Authority: EP
Inventors: Franck Poutch; Pierre Dalet; José Alcorta
Original assignee: Eska Co
Current assignee: Eska Co
Priority date: 2003-12-31
Filing date: 2004-12-30
Publication date: 2006-10-25
Also published as: US20110021647A1; FR2864544B1; CN1922250A; JP2007518851A; US8546455B2; FR2864544A1; WO2005073303A1

Abstract

The invention relates to a method of solubilising expanded polystyrene (EPS), in which the EPS is brought into contact with at least one initial solvent, enabling the transition of the EPS from an expanded solid state to the gel state. The aforementioned gel is subsequently treated with at least one complementary solvent that is different from the initial solvent, enabling the solubilisation thereof such as to produce a true solution. The invention also relates to the product thus obtained and to the use of said product.

Description

METHOD FOR SOULUB ISATION OF EXPANDED PO YSTRYRENE

The present invention relates to a method for dissolving expanded polystyrene (EPS), allowing the recycling of waste based on this material. This process calls for the use of two types of solvents: a so-called initial solvent, making it possible to destructure the polymer and a so-called complementary solvent, making it possible to obtain said polymer in the form of a true solution. The invention also relates to a true EPS-based solution, capable of being obtained by said method, and which can be used in various applications such as the formulation of adhesive, mastic, varnish sealant, resins, paint or lacquer. International application WO 99/07776 describes a process for recycling and recovering waste of expanded polymer, in particular of expanded styrenic polymer of the polystyrene type and of expanded styrenic copolymers. In this process, the waste of an expanded polymer is incorporated into a mixture of solvents and non-solvents, to obtain a pasty gel, called magma, and characterized by a large dry extract. More particularly, the magma is obtained by treating EPS with the aid of a treatment solution comprising a major proportion of a solvent such as acetone, a minor proportion of a non-fatty lubricant, such as glycerol, which gives a non-sticky surface finish, and, if necessary, alcohol in sufficient quantity to bind the solvent and the lubricant. The magma thus formed has a reduced volume compared to the treated EPS and a non-sticky consistency making it easy to transport and handle. The process for obtaining magma described in international application WO 99/07776 is simple and effective. The magma obtained according to this process can be used in conventional injection, extrusion or molding processes in the plastics industry, as a semi-finished material pasty. However, this magma tends to dissociate into two phases: the first, on the surface, is a mixture, generally transparent, of liquids, called supernatant; and the second, below the surface, is a mass of condensed, opaque and undissolved material whose microscopic appearance is similar to a gel of high viscosity and whose physical properties are characteristic of a heterogeneous system. The term “gel” is understood here to mean a molecular structure in which the molecules form a three-dimensional network by strong electrostatic interactions (ionic or Van der Walls bond) or by crosslinking, and which results from the coagulation of a colloidal solution. . These different phases are, in general, hardly miscible, even if mechanical mixing work is carried out. The gel, which contains polystyrene and represents the recoverable part of the magma, assumes an inhomogeneous appearance due to the state of constant equilibrium which exists between the solvent and the gelled polystyrene. This inhomogeneity can make its industrial transformation difficult into products such as adhesives, paints, varnishes or lacquers. Indeed, to prepare these products, it is important to be able to fractionate the magma as many times as necessary without observing any variation in its composition or in that of the products formed. The inventors have sought to solve this problem in order to provide a product for recycling EPS, which remains homogeneous over time and which can be used to prepare products such as adhesives, paints, varnishes or lacquers. According to a first subject of the invention, this relates to a process for dissolving the EPS, characterized in that: i) the EPS is brought into contact with at least one initial solvent making it possible to pass the EPS from a solid state expanded to that of a gel; and ii) contacting said gel with at least one additional solvent, distinct from the initial solvent, allowing the solubilization of said gel so as to obtain a true solution. The initial solvent and the additional solvent can, depending on the invention intervene in the process in the order indicated or simultaneously. By true solution is meant a homogeneous dispersion of molecules in a solvent. The true solution is not colloidal, unlike gel, which is a type of colloid in which a liquid contains a solid forming a fine network, extending continuously. Depending on the balance that is established between the solvent and the solid, one of the phases of the other may come in excess. In the case of a true solution, on the contrary, the solid phase disappears and is found diluted when an excess of solvent is added. The solubility of polystyrene in a solvent is explained by the neutralization of the association forces between the macromolecular chains which ensure the cohesion of the polymer. A solvent can thus be characterized by its solubility parameter, which is a measure of its internal energy density of cohesion allowing it to maintain in cohesion molecules in the liquid phase. The solubility parameters of the solvents are determined from the heat of vaporization and the molar volumes of the said solvents by the formula of HILDEBRAND, according to the following equation: or :

* HV is the latent heat of vaporization (cal),

* R is the constant of ideal gases (1, 986),

* T is the temperature in ° K, and

* V is the molecular volume (in cm ³ ) Its unit of measurement is usually expressed in (cal / cm ³ ) ^1/2 . Each solvent is characterized by a specific value of δ, which may vary slightly depending on the experimental data from which it is calculated. The values mentioned below are taken from the following work: Engineering techniques, treated plastics and composites (1997), polymers in solution, Perrin, P. and Hourdet, D. An initial solvent and a complementary solvent according to l The invention have different solubility parameters. An initial solvent according to the invention is a solvent whose parameter solubility is greater than the PES solubility parameter. Generally the initial solvent has a solubility parameter greater than 9.5 (cal / cm ³ ) ^1/2 . More generally, the solubility parameter of the initial solvent is in the range 9.6 to 11.0. Such a solvent is also called a latent solvent or diluent; it alone does not allow the PSE to be completely dissolved. The solvents used are preferably organic solvents resulting from the refining / recycling of petroleum products or products of plant origin, or else produced by biotechnological processes. The solvents reported in Table 1 below can be used as the initial solvent within the meaning of the invention. Table 1

The preferred initial solvents are butyronitrile, isophorone, n-butyl lactate, methylisobutylcarbinol, chloroethylene, ethyl-2-hexanol, methylene chloride, cyclohexanone and, more particularly, acetone. An initial solvent of the invention is preferably miscible with water. The inventors have observed that the effectiveness of the process according to the invention is conditioned by the amount of residual water present on the surface of the EPS or absorbed by the EPS. It is estimated that the EPS has the capacity to absorb from 5 to 50 g of water per m ² of contact surface. This absorption is all the more important as the particle size of the unitary beads is low and as the surface of the EPS is altered by tears or grinding of the waste. Water absorption takes place at the surface and by capillarity. This results in a water concentration gradient on the peripheral parts of the EPS which limits the kinetics of densification. The residual water has the drawback of locally inhibiting the effectiveness of the initial solvent. The densification rate, that is to say the kinetics of transformation of the EPS by the initial solvent is, for example, reduced by 50% when the initial solvent contains 1% by mass of water. However, in general, the treatment of soiled EPS waste requires a washing step by water jet to get rid of organic impurities and other encrustations. This step can be followed by thermal drying of the EPS, however this step consumes energy and must be controlled closely to avoid local heating which could degrade the EPS. In order to propose a process that can be implemented in a small enclosure such as, for example, a van that can go from one collection point to another, the inventors have provided various practical solutions to get rid of the residual water. Thus, according to a preferred embodiment of the invention, the method for dissolving the EPS described above comprises a prior step according to which the EPS is washed with an initial solvent solution containing water, for example, an acetone solution. , ethanol or propanol or any other initial solvent of the invention. This solution makes it possible to eliminate the residual surface water or absorbed in the EPS, without modification of the EPS before treatment. An initial solvent of the invention is therefore preferably a water-miscible solvent making it possible to prepare an aqueous solution of said solvent for washing the EPS, such as acetone. The preliminary washing solution of the EPS is preferably an acetone solution containing from 5 to 40% water, more preferably 10 to 30%. An initial solvent such as acetone (δ = 9.8 (cal / cm ³ ) ^1/2 ), makes it possible subsequently to obtain a true solution at low cost since the volume of initial solvent used is generally greater than the volume of additional solvent (ratio greater than 1). Such a true solution has many advantages, among which one can cite a lower flammability, a low toxicity and a physicochemical stability of at least two years in suitable barrels. In addition, the use of such a solvent allows the instruments used to handle the gel obtained from the EPS, to be washed with water. When the EPS is treated with acetone or another preferred initial solvent, the gel obtained can be kept exposed to the weather without the product losing its qualities or presenting a risk to the environment. According to another preferred embodiment of the invention, step i) of the solubilization process consisting in bringing the EPS into contact with at least one initial solvent, is carried out in the presence of an anhydrous salt making it possible to trap the absorbed residual water by the PES or present on the surface of the PSE. Preferably, the anhydrous salt is of the calcium sulphate type. The anhydrous salt can be immersed directly in the solvent in order to dehydrate it, especially when a solution of solvent and water has been previously used for washing the EPS, or it can be contained in cartridges through which have circulates the solvent used. This second possibility allows the recycling of the solvent, but also that of the anhydrous salt contained in the cartridge, because the cartridge can be changed and the salt that it contains dehydrated. In general, 1 to 10% of anhydrous salt is added to the solvent, preferably 5 to 10%. The amount of water collected is of the order of 0.1 to 0.4 g of water per gram of anhydrous salt. When the additional solvent is used after the initial solvent, its addition can take place immediately after the gel has formed or only later, for example after transporting the gel to another industrial processing site. A complementary solvent suitable for the present invention preferably lies in the range of δ varying from 8.5 (cal / cm ³ ) ^{1 2} to 9.5 (cal / cm ³ ) ^{1 2} , more preferably between 8.7 (ca ! / cm ³ ) ^1/2 and 9.3 (cal / cm ³ ) ^1/2 . The additional solvent is preferably chosen from ketones comprising at least 3 carbon atoms, such as methyl ethyl ketone (EK), halogenated aliphatic compounds, such as trichloroethane, organic esters, such as ethyl acetate, or aromatic alcohols, such as phenylcarbinol. Table 2 below gives, for information only, a list of solvents which can be used as additional solvents.

Table 2

The additional solvents make it possible to obtain good homogeneity and satisfactory physical stability of the true solution according to the invention. The physicochemical characteristics of the solvents used in the context of the process of the invention are chosen so as to comply with regulatory or legislative, health and safety requirements. Thus, they do not present any toxicity or harmfulness incompatible with the technical applications envisaged. The most suitable additional solvents are: cyclohexamine, ethyl acetate, butyric acid, chloroform, mesityl oxide, methyl ethyl ketone, 1-chlorobutane, amyl acetate, l n-butyl acetate, methylal, methylisoamyl ketone, methyl isobutyl ketone, propyl acetate, diethyl ketone, ethylbenzene and xylene. Among these solvents, ethyl acetate is preferred. The initial solvent generally represents between 10% and 70%, of preferably between 30% and 70% of the volume of the final true solution, and the amount of additional solvent represents between 10% and 70%, preferably between 10% and 50% of the volume of said final true solution. In general, the proportion of additional solvent represents between 1% and 30%, preferably between 15% and 30% of the volume of the initial solvent; more generally, the volume ratio between initial solvent (s) and complementary solvent (s) is greater than 1. The amount of EPS used for the invention is usually between approximately 0.2 and 1 kg per liter of initial solvent, and preferably between 0.5 and 1 kg. Typically, the process of the invention involves acetone as the initial solvent and ethyl acetate as the additional solvent. It can also involve acetone and methyl ethyl ketone (MEK), as well as any combination of at least one initial solvent chosen from the list appearing in table 1 with at least one complementary solvent taken from the list appearing in table 2 , but not limited to these solvents only. The use of a non-fatty lubricant, such as glycerol, which was prescribed in the previous patent application WO 99/07776, is not necessary for the implementation of the method of the present invention. Indeed, such a lubricant has the drawback of considerably limiting the action of the additional solvent and therefore the formation of a true solution. In the absence of glycerol, the process is more efficient and consumes less additional solvent, which, economically, among other things, makes the process more advantageous. The present invention also relates to a composition allowing the solubilization of the EPS, capable of being implemented for the purposes of the process of the invention. This composition comprises: an initial solvent enabling the EPS to pass from an expanded solid state to that of a gel; at least one complementary solvent distinct from the initial solvent, allowing the complete solubilization of said gel so as to obtain a true solution. The nature, quantities and proportions of each of the components present in this composition are as defined above for the purposes of carrying out the method according to the invention. The invention also consists of a true solution capable of being obtained by the method of the invention. This true solution is characterized in that it contains: polystyrene; an initial solvent enabling the EPS to pass from an expanded solid state to that of a gel; at least one complementary solvent distinct from the initial solvent, allowing the complete solubilization of said gel so as to obtain a true solution. It is considered that 1 kg of true solution preferably comprises between 0.2 and 0.8 kg of PSE, more preferably, between 0.3 and 0.6 kg of PSE. The true solution may comprise additives, in particular a plasticizer such as those mentioned below, preferably in a proportion of between 5% and 20% by volume relative to the total volume and more preferably between 10% and 15% by volume per compared to the total volume. The true solution may also contain a tackifying agent, such as rosin, in a proportion which preferably varies between 10% and 20% by volume relative to the total volume. A true solution according to the invention can be used to prepare different products, which constitute another object of the invention. These products may consist of paint, sealant, sealant, varnish, resin, paint or lacquer or an adhesive. To prepare such products, the true solution of the invention is used, to which one or more additives such as a dye, a pigment, a tackifying agent such as rosin, a cohesive agent, such as a alcohol such as ethanol, a filler to increase the volume or a plasticizer, which may be required to impart the desired flexibility. The preferred plasticizers belong to the following product classes: dialkylphthalates, diarylphthalates, dialkylarylphthalates, triaryl- phosphates, triarylalkylphosphat.es and trialkylphosphates. Examples of products of these classes which may be suitable are mentioned in Table 3 below: Table 3

Dioctyl phthalate (DOP) is a preferred plasticizer. The present invention also relates to the use of the true solution according to the invention for the preparation of a solid, pasty or liquid composite article. These articles prepared from the true solution can consist of pasty or liquid products such as adhesives, in particular for wood and paper, varnishes, coatings, seals, paints and lacquers as well as solid products consisting in particular of agglomerated particle boards. The liquid or pasty article may consist of a peelable product for the temporary protection of windows, hydrophobic varnishes for roofing tiles, temporary flexible joints for buildings, new adhesives. An adhesive according to the invention may comprise a mixture of several true solutions obtained according to the method of the invention, or a true solution with an appropriate additional organic solvent. An adhesive according to the invention can also contain anti-UV agents. The true solution can also be used to regenerate or synthesize a polymer or copolymer based on styrene in an expanded or unexpanded form. The examples presented below illustrate the invention.

EXAMPLE 1 Preparation of the EPS for its chemical treatment Used cases of EPS which have been used for the refrigerated transport of foodstuffs (ex: fish) were recovered with a view to their transformation by the solubilization process of the invention. The boxes have been stripped of heterogeneous elements that may surround them such as paper, fasteners or plastic packaging, then passed with a water jet so as to remove organic impurities and other encrustations. As mentioned in the description, the residual water on the surface of the EPS or absorbed by the EPS locally makes the action of the initial solvent ineffective during the chemical transformation of the EPS. It was undertaken, as shown in Table 4 below, washing tests and rinsing of the boxes prepared above with an acetone solution in which the percentage of water was varied. This experiment was carried out in order to determine the influence of the water content of the washing solution on the rate of densification, that is to say of solubilization, of the EPS. L, I, H: Length, Width, Height of the volume of EPS treated

When the EPS is clean and dry (control) and the initial solvent used is acetone, the densification time is around 18 seconds. When the EPS is washed in water for 30 seconds, the densification time increases to 64 seconds. If rinsed, this same EPS washed with hard water with an acetone solution containing 5% water, the densification time is reduced to 29 seconds. It therefore appears that a preliminary washing step with an acetone solution containing water makes it possible to treat wet or soiled recovery EPS, without significantly hampering the solubilization procedure which will follow.

EXAMPLE 2: transformation of the gel into yray solution

1 / Formulations and properties of the gel

The true solutions described below were obtained by first dissolving 1.33 kg of EPS, previously washed and dried by forced air circulation at room temperature in 1 kg of a solution comprising 98.7% of acetone and 1.3% ethanol (% V / V). A gel is thus obtained having a dry extract of 57%, the physical and mechanical properties of which are summarized below:

- Physical properties The gel is in the form of a two-phase body characterized by the existence of a first phase consisting of a transparent mixture of liquids, called supernatant, and a second phase consisting of an opaque condensed material , without real cohesion.

- Adhesive properties Comparative tests were carried out to assess the mechanical performance of the gel as an adhesive. For this, mechanical failure tests were carried out using assemblies of "standard" plywood substrates, brought into contact with the adhesive to be tested, which is subjected to increasingly strong gradual stresses. At rupture, the relative displacement of the assembled parts is measured at the time of rupture. The gel was used to make such an assembly with two different grammages: 150 g / m ² or 300 g / m ² . For comparison, the same protocol was applied to a joint made with a conventional neoprene adhesive sold under the BOSTIK ^®. The results obtained for the two types of adhesives are reported in Table 5, below.

Table 5: Mechanical characteristics of BOSTIK ^® gel and glue

When a weight of 150 g / m ² gel, strain at break is evaluated at approximately 1, 5 MPa (N / mm ²⁾ against 0.3 MPa for the similar joints made with glue BOSTIK ^®. The gel is therefore more resistant than BOSTIK ^® glue (stress levels significantly higher at break). He is very cohesive. However, the BOSTIK ^® adhesive has a deformation at break approximately 2 times greater than that of the gel. Compared to BOSTIK ^® , the gel is therefore much less flexible. The film obtained with the gel is therefore cohesive but fragile, which constitutes a handicap in the event of reception of non-axial stresses (peeling, stretching, etc.) and / or harmonics (shock, vibrations, etc.). 2 / Obtaining a true solution A true solution was prepared in accordance with the invention using the gel formed in point 1 / above, to which was added either methyl ethyl ketone (MEK) or acetate d ethyl in proportions such that a homogeneous solution is obtained. The true solutions obtained are used in the examples below.

3 / Analysis of the true solution by measuring the open time and the ease of coating: The open time (or open assembly time) designates the maximum duration after coating during which the gluing is effective. The ease of coating is dependent on the fluidity and the homogeneity of the adhesive. In adhesives in organic solution, the open limit time corresponds to the disappearance by evaporation of a percentage of solvent such that the film loses its tackifying properties (tackiness), which means that it no longer develops any interaction with the substrate. that it should stick. During the formulation tests, ethyl acetate and MEK were incorporated into the gel as described above, as an additional solvent, at a rate of 0% to 25% of the volume of the gel. Tables 6 and 7 below summarize the open time and the ease of coating obtained for each of the formulations.

Table 6: Effect of ethyl acetate

Table 7: Effect of MEK.

As acetone is a very volatile solvent, its disappearance by evaporation when it is deposited in a thin layer is very rapid. The gel therefore has an open time which is low. The results reported in Tables 6 and 7 show that when an increasing percentage of ethyl acetate (Table 6) or MEK (Table 7) is added to acetone, in both cases, a significant increase in the duration of open time. The addition of additional solvent therefore makes it possible to obtain an open time approximately 4 times greater than that obtained for the gel. It is found that ethyl acetate makes it possible to substantially improve the coating from a concentration of ethyl acetate of 5%, and leads to a perfect coating with a concentration of 10%.

4 / Measurement of viscosity - compatibility of solvents The compatibility of an additional solvent with the gel can be evaluated by measuring the viscosity of the true solution. The more compatible the solvent and the gel, the more fluid the true solution obtained, with an equivalent dry extract. Viscosity measurements were carried out using additional solvents MEK, ethyl acetate and trichloroethane. The measurements were carried out with a BROOKFIELD DV II + viscometer, with mobile S64. The test was carried out at room temperature and at a speed of 6 revolutions / minute. The results obtained with different volumes of solvents are reported in Table 8, below:

Table 8: Effect of additional solvents on viscosity (in mPa.s.)

The results obtained show that at relatively low volumes of ethyl acetate, it is possible to obtain a true solution whose viscosity is compatible with the manufacture of adhesive. The quantities of MEK and trichloroethane must be much greater to obtain a viscosity equivalent.

EXAMPLE 3 Mechanical properties of the yray solution A true solution obtained from the gel of Example 1, to which 15% of ethyl acetate was added, was tested in order to determine its resistance to mechanical stress, stronger, as well as its deformation at break. A simple shear test of two pine test pieces of dimension 100 x 24 x 5 mm was carried out for a bonding surface of 25 x 24 mm ² , or 6 cm ² for a grammage in simple gluing (coating on one side) 300 mg.m ^"2. The same test was carried out using a vinyl adhesive marketed under the brand RAKOLL ^® 6XL-3 / F-Neu. The results of these two tensile tests at 1 mm / min ^{" 1} on a test piece in pine are shown in Table 9.

Table 9: Mechanical performance of the true solution

For the two types of adhesive, true solution and RAKOLL, a cohesive rupture in the adhesive is observed. This rupture occurs for a maximum stress value situated in both cases around 2.5 MPa. The test results show that the strain at break is considerably improved when ethyl acetate is added to the gel. The addition of 15% ethyl acetate makes it possible to go from a deformation of 1.4% in the case of the gel alone (see example 2, that is to say without solvent 2.8% in the case where the additional solvent is added.

EXAMPLE 4 Addition of plasticizing agents and tackifying resins to the yray solution The dioctylphthalate (DOP) was tested as an additive for a true solution obtained from a gel according to Example 2 to which added 12% ethyl acetate. DOP is in the form of a liquid, the boiling point of which is 365 ° C and the solidification point of which is -50 ° C. The percentage of DOP in the true solution was varied. The procedure for testing the mechanical properties of the adhesive obtained is the same as that set out in Example 3. The mechanical parameters obtained for the different formulations comprising a variable% of DOP, are given in Table 10, below. .

Table 10: Effect of DOP on the mechanical properties of the true solution

Tensile test at 1 mm. min, on pine specimens, grammage of 300g. m, by simple gluing.

The results show that the addition of DOP up to 13% by volume of the final solution allows a gain in flexibility (less clear cohesive rupture) for this type of formulation. Likewise, it appeared that the addition of an increasing amount of crude rosin as an additive to the true solution obtained according to Example 2 by adding 24% of ethyl acetate (Table 11), made it possible to reduce the mechanical strength of the adhesive obtained. This indicates that rosin, to some extent, also plasticizes the true solution while increasing its adhesive power.

Table 11: Effect of rosin on the properties of the true solution

Tensile tests at 1 mm. min, on pine specimens, weight of 300 g. m by simple gluing.

EXAMPLE 5 Influence of glycerol on the production of the yarie solution. In application WO 99/07776, it is indicated that a non-fatty lubricant such as glycerol makes it possible to obtain a pasty magma having a non-sticky surface state, which is advantageous with regard to the handling of said magma and its transport. . To evaluate the impact of glycerol on obtaining in direct mode (the initial solvent and the complementary solvent are used simultaneously) of the true solution, PSE was treated on the one hand with a composition A comprising 15% of ethyl acetate, 80% acetone and 5% water and on the other hand a composition B comprising 15% ethyl acetate, 80% acetone and 5% glycerol. Each composition was placed under stirring in a 5-liter beaker. Quite unexpectedly, at equal viscosity, it was found that the amount of PSE dissolved using composition A was much greater than the amount of PSE dissolved using solution B comprising glycerol. We therefore observe here a negative impact of glycerol on the effectiveness of the treatment of the gel with ethyl acetate.

EXAMPLE 6: formulations of products made from yray solution. The true solution used to prepare the products described below comprises 85% by volume of gel as defined in Example 2 and 15% by volume of MEK.

a) hydrophobic varnish for roof tiles The varnish for roof tiles obtained by mixing: 20% of true solution;

- 78% of MEK;

- 1.5% of DOP; and 0.5% Tinuvin® (antioxidant).

b) Putty A putty is obtained by mixing: 30% of true solution;

- 27% of Hexolit® AP 422 (Clariant); 21% charge (ex: talc or chalk);

- 14% of DOP; 4% tackifier (ex: rosin ester); 3% white dye (ex: titanium oxide); and 1% color (commercial dye for oil paint).

c) Flexible polymers suitable for molding and which incorporate different natures of charges 30% of true solution; 52% of fillers (ex: talc, chalk, fibers, etc.)

- 14% of DOP; 3% white dye (ex: titanium oxide); and 1% color (commercial dye for oil paint).

d) halogen-free flame retardant particle board A particle board is obtained by mixing: 13% of true solution; 36% wood particles;

- 9% of MEK;

- 40% of Hexolit® APP 750 (Clariant); and

- 2% of an SBS solution comprising 70% MEK and 30% Evoprène® 027.

e) M1 flame retardant particle board with 40% halogen hexabromocyclododecane 36% wood particles; 21.6% true solution

- 2.4% of an SBS solution comprising 70% of MEK and 30% of Evoprène® 027.

f) peelable protection for windows Peelable protection for windows is obtained by mixing 54% of true solution;

- 27% of MEK;

- 14% of DOP; 5% turpentine.

Claims

CLAIMS 1. Process for the solubilization of expanded polystyrene (PSE), characterized in that: i) the PSE is brought into contact with at least one initial solvent enabling the PSE to pass from an expanded solid state to that of a gel ; and ii) contacting said gel with at least one additional solvent, distinct from the initial solvent, allowing the solubilization of said gel so as to obtain a true solution. 2. Method according to claim 1, characterized in that steps i) and ii) are carried out successively in this order or simultaneously. 3. Method according to claims 1 and 2, characterized in that it does not involve the use of a non-fatty lubricant, such as glycerol. 4. Method according to any one of claims 1 to 3, characterized in that the amount of initial solvent represents between 10% and 70%, preferably between 30% and 70% of the volume of the true solution obtained, and the amount of additional solvent represents between 10% and 70%, preferably between 10% and 50% of the volume of the true solution obtained. 5. Method according to any one of claims 1 to 4, characterized in that the proportion of additional solvent represents between 1% and 30%, preferably between 15% and 30% of the volume of initial solvent. 6. Method according to any one of claims 1 to 5, characterized in that the initial solvent has a solubility parameter greater than 9.5 (cal / cm ³ ) ^1/2 . 7. Method according to any one of claims 1 to 6, characterized in that the initial solvent is chosen from acetone, butyronitrile, isophorone, π-butyl lactate, methylisobutylcarbinol, chloroethylene, ethyl-2-hexanol, methylene chloride, and cyclohexanone. 8. Method according to any one of claims 1 to 7, characterized in that the initial solvent is acetone. 9. Method according to any one of claims 1 to 8, characterized in that the additional solvent has a solubility parameter of between 8.5 (cal / cm ³ ) ⁷² and 9.5 (cal / cm ³ ) ^1/2 , preferably between 8.7 (cal / cm ³ ) ¹⁷² and 9.3 (cal / cm ³ ) ^1/2 . 10. Method according to any one of claims 1 to 9 characterized in that the additional solvent is chosen from cyclohexamine, ethyl acetate, butyric acid, chloroform, mesityl oxide, methylethylketone, 1-chlorobutane, amyl acetate, π-butyl acetate, methylal, methylisoamyl ketone, methyl isobutyl ketone, propyl acetate, diethyl ketone, ethylbenzene and xylene. 11. Method according to any one of claims 1 to 10, characterized in that the additional solvent is ethyl acetate or methylethylketone (MEK), or a mixture of ethyl acetate and methylethylketone. 12. Method according to any one of claims 1 to 11, characterized in that the initial solvent is acetone and the additional solvent is ethyl acetate. 13. Method according to any one of claims 1 to 12, characterized in that the initial solvent is acetone and the additional solvent is methylethylketone. 14. Method according to any one of claims 1 to 13, characterized in that said method comprises a prior step according to which the EPS is washed with an initial solvent solution containing water. 15. Method according to any one of claims 1 to 14, characterized in that step i) is carried out in the presence of an anhydrous salt making it possible to trap the residual water absorbed by the PSE or present on the surface of the PSE . 16. The method of claim 15, wherein the anhydrous salt is of the calcium sulfate type. 17. Method according to any one of claims 14 to 16, in which the initial solvent solution for washing the EPS beforehand is an acetone solution containing from 5 to 40% of water, preferably 10 to 30%. 18. Composition allowing the solubilization of PSE comprising an initial solvent enabling the EPS to pass from an expanded solid state to a gel; and at least one complementary solvent distinct from the initial solvent, allowing complete solubilization of said gel so as to obtain a true solution. 19. True solution capable of being obtained by the method according to any one of claims 1 to 17. 20. True solution according to claim 19, characterized in that it comprises an amount of PSE per liter of final solution between 0.2 and 0.8 kg, preferably between 0.3 and 0.6 kg. 21. True solution according to one of claims 19 and 20, characterized in that it further comprises at least one additive chosen from: a modifying agent to improve the mechanical properties of the solution; a tackifying agent; a cohesion agent, such as alcohol; and a charge to increase the volume. 22. True solution according to claim 21, in which the modifying agent is a plasticizer, such as DOP, in a proportion of between 5% and 20%, preferably between 10% and 15% by volume relative to the total volume of the solution. 23. True solution according to claim 21, in which the tackifying agent is rosin, used in a proportion of between 10% and 20% by volume relative to the total volume of the solution. 24. Use of a true solution according to any one of claims 15 to 19, as an adhesive. 25. Use of a solution according to any one of claims 19 to 23, for the manufacture of particle boards, putty, seal, paint, varnish, peelable protection for windows or resin. 26. Use of a true solution according to any one of claims 19 to 23, for the regeneration or the synthesis of a styrene-based polymer or copolymer.