FR3068037A1 - PROCESS FOR SYNTHESIZING SLICONE / POLYURETHANE MATERIAL - Google Patents

Abstract

A process for synthesizing a silicone / polyurethane material by polyaddition between a pluri-carbonate and a pluri-amine, comprising: - a mixing step in which the pluri-carbonate and the pluri-amine are mixed at a first temperature of mixture T1 during a mixing time t1, - a heating step during which the mixture is heated during a first heating time t2 to a first heating temperature T2 followed by a second heating time t3 to a second temperature T3 wherein at least one of the pluri-carbonates and plurifamines comprises silicone segments.

Description

Process for the synthesis of a Silicone / Polyurethane material

The invention relates to a process for the synthesis of a Silicone / Polyurethane material by polyaddition, in particular intended for the encapsulation of electronic components.

The encapsulation of electronic components generally aims at techniques which consist in protecting electronic components, by covering them, enveloping them, or coating them with a suitable material, with a view to their good long-term operation under the conditions of their use, whether it is an individual electronic component or, a fortiori, a set of components integrated into an electronic module.

To do this, the use of polymeric materials is appropriate by the simplicity of their implementation, which implies in-situ hardening of the material, by polymerization of the constituents of a monomer composition previously applied to cover the products to be protected.

In order for the materials obtained to be of suitable quality for encapsulating electronic components, they are asked to be resistant to operating conditions in terms of temperature and stability over time. The operating temperatures to be supported are in the temperature range above 150 ° C.

Other qualitative requirements for these products relate to resistance to chemical agents, resistance to water and humidity, thermal and electrical insulation capacity.

Polyurethane resins have the required mechanical properties, but their moisture uptake may be too high for an application as an encapsulant. In addition, their thermal stability is lower than that of silicone resins. As for the latter, they are highly hydrophobic and have very good chemical and thermal stabilities. However, they are less impact resistant than polyurethane resins.

Crosslinked materials combining Silicone and Polyurethane have already been synthesized in order to combine the properties of these two polymers while overcoming their defects. The synthetic route explored by Ebdon et al. (Ebdon, JR, Hourston, DJ & Klein, PG Polyurethanepolysiloxane interpenetrating polymer networks: 1. A polyether urethanepoly (dimethylsiloxane) System. Polymer (Guildf). 25, 1633-1639 (1984)) is the development of network architecture interpenetrated polymers (RIP) associating a silicone network obtained from a, cû-dihydroxy-poly (dimethylsiloxane) crosslinked with tetraethoxysilane (TEOS) (polycondensation reaction giving rise to an ethanol release not desired for the application) and a polyurethane network.

However, the immiscibility of the precursors does not allow homogeneous materials to be obtained, since significant phase separation is observed.

Other interpenetrating networks of polymers have been synthesized using a poly (phenylmethylsiloxane) (Klein, PG, Ebdon, JR & Hourstont, DJ Polyurethanepolysiloxane interpenetrating networks: 3. Polyetherurethane-poly (phenylmethylsiloxane) Systems. Polymer (Guildf). 29, 1079-1085 (1988)) in place of a poly (dimethylsiloxane) (PDMS). In this case, the phase separation between the polyurethane and the polysiloxane is reduced, and more homogeneous materials have been obtained.

These syntheses however require the use of solvent.

Interpenetrating networks of polymers combining a Polyurethane network (PUMA) and a Silicone network (Si) have also been synthesized by Vuillequez et al. (Vuillequez, a., Moreau, J., Garda, MR, Youssef, B. & Saiter, JM Polyurethane methacrylate / silicone interpenetrating polymer networks synthesis, thermal and mechanical properties. J. Polym. Res. 15, 89-96 (2008 )). The PUMA network is obtained by radical polymerization initiated by UV radiation of a pluri-methacrylate in the presence of precursors of the silicone network. The silicone network is synthesized by polycondensation between 1’α, ωdihydroxypolydimethylsiloxane and Γω-methacryloxypropyl trimethoxy silane (crosslinking agent). Due to the presence of the methacrylate functions on the crosslinking agent, the two networks are then linked to each other.

The synthesized materials contain no more than 6% silicone.

The reaction of formation of the silicone network leads to the evolution of alcohol during the synthesis. In addition, their synthesis is long (24h at 150 ° C).

Another way to combine Silicone and Polyurethane within a crosslinked material, is the synthesis of semi-interpenetrating polymer networks (semi-RIP). Byczynski et al. (Byczyhski, L ·., Dutkiewicz, M. & Maciejewski, H. Thermal degradation kinetics of semiinterpenetrating polymer network based on polyurethane and siloxane. Thermochim. Acta 560, 55-62 (2013)) thus immobilized a linear polyurethane in a material crosslinked siloxane by reaction between a telechelic epoxide PDMS and a diamine. Materials with greater thermal stability than polyurethane have been obtained.

It is important to note that in all these works, the syntheses are carried out in the presence of solvent, which greatly facilitates the miscibility of the precursors. However, in the case of encapsulation of electronic components, it is preferable not to use a solvent as this may damage the components to be encapsulated.

Finally, lately, Byczynski et al. (Byczyhski, L ·., Dutkiewicz, M. & Maciejewski, H. Thermal degradation studies of poly (urethane-siloxane) thermosets based on copoly (dimethyl) (methyl, hydroxypolyoxyethylenepropyl) siloxane. Thermochim. Acta 589, 252-261 (2014 )) have developed a material combining silicone and polyurethane, without using a solvent. Beforehand, the co-poly (dimethyl) (methyl, hydroxypolyoxyethylenepropyl) siloxane (PSPEG) copolymer is prepared by a hydrosilylation reaction between a polyoxyethylene allyl ether terminated with hydroxyl functions and a co-poly (dimethyl) (methyl, hydroxypolyoxyethylene- propyl) siloxane. The material combining silicone and polyurethane is finally obtained by reacting PSPEG with different diisocyanate compounds. The material ultimately contains only 26% silicone.

However, these materials contain polyethylene oxide grafts which promote water uptake. In addition, their thermal degradation noted at 5% mass loss is only 215 ° C. The properties of this material therefore do not allow its use as an encapsulant for electronic compounds.

The object of the present invention is to provide a synthesis process requiring neither solvent nor catalyst of a silicone / polyurethane material which can be used as an encapsulant for electronic compounds.

The invention thus provides a process for the synthesis of a Silicone / Polyurethane material by polyaddition between a pluri-carbonate and a pluri-amine, comprising:

a mixing step, E1, during which the pluri-carbonate and the pluri-amine are mixed at a first mixing temperature Tl during a mixing time tl,

a heating step, E3, during which the mixture is heated during a first heating time t2 to a first heating temperature T2 followed by a second heating time t3 to a second heating temperature T3, in which at at least one of the pluri-carbonates and pluri-amines comprises silicone segments.

Advantageously, the synthesis process according to the invention is simple, can be carried out directly in contact with the components to be encapsulated without solvent or catalyst and makes it possible to obtain a silicone / polyurethane material whose physicochemical properties make it a good encapsulant.

The method according to the invention can also include one or more of the characteristics below, considered individually or according to all technically possible combinations:

the pluri-carbonate is a pluri-cyclocarbonate; and / or the cyclocarbonates of the pluri-cyclocarbonate have between 5 and 8 bonds; and / or the carbonates of the pluri-carbonate are linked to each other by a poly-siloxane or hydrocarbon chain; and / or the carbonates of the pluri-carbonate are linked to each other by a chain of formula (I):

R1

Si-O

R3

R2

-Sin |

R4 with n greater than or equal to 1 and less than or equal to 50 and R1 to R4 of the hydrocarbon groups; and / or the hydrocarbon chain of the pluri-carbonate is an alkyl chain containing a number of carbon atoms greater than or equal to 1 and less than or equal to 50; and / or the pluri-amine comprises at least two primary amine functions linked together by a poly-siloxane or hydrocarbon chain; and / or the amine functions of the pluri-amine are linked together by a chain of formula (I):

R1

Si-O

R3

R2

-Sin |

R4 with n greater than or equal to 1 and less than or equal to 50 and R1 to R4 of the hydrocarbon groups; and / or the hydrocarbon chain of the pluri-amine is an alkyl chain containing a number of carbon atoms greater than or equal to 1 and less than or equal to 50; and / or during the mixing step, the pluri-carbonate and the pluri-amine are mixed with a ratio of molar concentration in amine function and in carbonate function greater than or equal to 0.5 and less than or equal to 1.5 ; and / or the mixing time tl is greater than or equal to 1 min and less than or equal to 2 hours; and / or the first mixing temperature T1 is greater than or equal to 10 ° C and less than or equal to 45 ° C; and / or the mixing step is carried out under dynamic vacuum; and / or the first heating temperature T2 is higher than the first mixing temperature T1 and is less than or equal to 75 ° C; and / or the second heating temperature T3 is higher than the first mixing temperature T1 and the first heating temperature and is less than or equal to 125 ° C; and / or the first heating time, t2, is greater than or equal to 10 minutes and less than or equal to 30 minutes; and / or the second heating time, t3, is greater than or equal to 5 minutes and less than or equal to 60 minutes; and / or the method comprises a second heating step E4 during which the product resulting from the heating step E3 is heated for a third heating time t4 to a third heating temperature T4, with t4 greater than or equal to 1 day and less than or equal to 12 days and T4 greater than or equal to 125 ° C and less than or equal to 175 ° C; and / or the mixing and heating steps are carried out without solvent; and / or the mixing and heating stages are carried out without catalyst; and / or the mixture is poured into a housing comprising electronic components and associated connection circuits before the heating step.

The invention also relates to a Silicone / Polyurethane material, in particular intended for the encapsulation of electronic compounds, obtained by the process according to the invention.

The Silicone / Polyurethane material can include one or more of the characteristics below, considered individually or in all possible combinations:

- a calculated soluble fraction, for example after 72 hours of hot extraction with chloroform, greater than or equal to 1% by mass and less than or equal to 50% by mass; and or

- a hardness expressed in Shore A less than or equal to 70; and or

- a water uptake expressed according to ISO 62 standard less than or equal to 25%.

The invention finally relates to an electronic module obtained according to the process according to which the mixture is poured into a housing comprising electronic components and associated connection circuits before undergoing the thermal program. Such an electronic module is, for example, a power module which combines transistors, for example of the MOSFET type, to form a rectifier or an inverter, as can be found in motor vehicle alternator-starters.

The present invention will be better understood in the light of the following description which is given only for information and which is not intended to limit said invention, accompanied by the following figures.

Figure 1 is a representation of the different stages of the synthesis process according to the invention, and Figures 2 to 4 show the loss of mass of different materials according to the invention exposed to a constant temperature of 150 ° C in air.

The synthesis process according to the invention does not require the use of solvent or catalyst and makes it possible to obtain materials combining silicone and polyurethane.

The reaction between a pluri-carbonate and a pluri-amine is a step polymerization, more particularly a polyaddition. The synthesis process consists in creating the polyurethane groups during the synthesis of materials from the polyaddition between a pluri-carbonate containing carbonate functions and a pluri-amine comprising amine functions.

As illustrated in FIG. 1, polyaddition is a simple synthesis which may include a mixing step E1 and a heating step E3 during which the mixture undergoes a thermal program.

During the mixing step, a pluri-carbonate and a pluri-amine are mixed at a first mixing temperature T1 during a mixing time tl.

At least one of the pluri-carbonates and pluri-amines comprises silicone segments.

According to a preferred embodiment of the invention, the pluri-carbonate is a pluricyclocarbonate.

Advantageously, this makes it possible to avoid the formation of secondary product during the polyaddition reaction.

For example, the cyclocarbonates of the pluri-cyclocarbonate have between 5 and 8 bonds. Preferably all the cyclocarbonates of the pluri-cyclocarbonate have the same number of bonds.

The carbonate functions of the pluri-carbonate are typically linked together by a poly-siloxane or hydrocarbon chain comprising or not heteroatoms.

According to one embodiment of the invention, the poly-siloxane chain connecting the carbonate functions of the pluri-carbonate can be of formula (I):

R1

Si-O

R3

R2

-If ⁿ I

R4 with n greater than or equal to 1 and less than or equal to 50 and RI to R4 of the hydrocarbon groups.

For example, the groups R1 to R4 can be alkyl groups, such as for example methyl and / or phenyl groups. Preferably, the groups R1 to R4 are all identical.

Alternatively, the carbonate functions of the pluri-carbonate can be linked together by an alkyl chain containing a number of carbon atoms greater than or equal to 1 and less than or equal to 50.

The primary amine functions of the pluri-amine are typically linked to each other by a poly-siloxane or hydrocarbon chain.

According to one embodiment of the invention, the poly-siloxane chain linking the amine functions of the pluri-amine is of formula (I):

R1

Si-O

R3

R2

-Sin |

R4 with n greater than or equal to 1 and less than or equal to 50 and RI to R4 of the hydrocarbon groups.

For example, the groups R1 to R4 can be alkyl groups, such as for example methyl and / or phenyl groups. Preferably, the groups R1 to R4 are all identical.

Alternatively, the primary amine functions can be linked to one another by an alkyl chain containing a number of carbon atoms greater than or equal to 1 and less than or equal to 50.

During the mixing stage, the pluri-carbonate and the pluri-amine are mixed with a molar concentration ratio in amine function and in carbonate function greater than or equal to 0.5, for example greater than or equal to 0.8 and less than or equal to 1.5, for example less than or equal to 1.2.

The mixing is preferably carried out under dynamic vacuum, with magnetic stirring for example, in order to facilitate the homogenization of the mixture.

The mixing step is carried out at a first mixing temperature T1 greater than or equal to 10 ° C and less than or equal to 45 ° C. Typically, the mixing step is carried out at room temperature.

The duration of the mixture influences the homogeneity of the silicone / polyurethane material obtained. The homogeneity of the material is important for its use as an encapsulant for electronic components. The time t1 is therefore important with regard to the physical properties of the material obtained.

The mixing time tl can be greater than or equal to 1 min and less than or equal to 2 hours.

The heating of the mixture during the heating stage is an important factor in obtaining the silicone / polyurethane material. Indeed, the yield of the poly addition depends on the temperature conditions.

Preferably the first heating temperature T2 is higher than the first mixing temperature T1 and is less than or equal to 75 ° C. Typically, the first heating temperature T2 is greater than or equal to 40 ° C and less than or equal to 50 ° C.

The first heating time is preferably greater than or equal to 10 minutes, for example greater than or equal to 15 minutes, and less than or equal to 30 minutes, for example less than or equal to 25 minutes.

According to one embodiment of the invention, the second heating temperature T3 is higher than the first heating temperature T2 and is less than or equal to 125 ° C. Typically, the second temperature is greater than or equal to 90 ° C and less than or equal to 110 ° C.

Preferably, the second heating time is greater than or equal to 5 minutes, for example greater than or equal to 15 minutes, and less than or equal to 60 minutes, for example less than or equal to 30 minutes.

As illustrated in FIG. 1, the method according to the invention can also include, after the mixing step E1 and before the heating step E3, a step E2 during which the mixture obtained after the mixing step is cast in a housing comprising electronic components and associated connection circuits before being heated according to the heating step E3. The encapsulation of the electronic components and the polymerization of the material are then carried out simultaneously.

The method according to the invention may also include a second heating step E4 during which the silicone / polyurethane material obtained after the heating step E3 is heated during a third heating time t4 to a third heating temperature T4.

Typically, the third heating time t4 is greater than or equal to 1 day, for example greater than or equal to 6 days, and less than or equal to 12 days, for example less than or equal to 10 days.

The third heating temperature T4 is preferably greater than or equal to 125 ° C and less than or equal to 175 ° C.

The second heating step makes it possible to synthesize a new silicone / polyurethane material also comprising urea functions without the use of isocyanate, catalyst or solvent.

Indeed, at 150 ° C., the depolymerization of part of the urethane functions takes place, which generates cyclocarbonate and amine functions, the latter being able to react with the urethane functions still present to form urea functions.

The formation of these urea functions makes it possible to create a new silicone network with polyurethane and urea crosslinking nodes. The urea functions increase the thermal stability of the material.

The invention also relates to a Silicone / Polyurethane material, in particular intended for the encapsulation of electronic compounds, for example obtained by the process according to the invention.

The soluble fraction of said silicone / polyurethane material calculated, for example after 72 hours of hot extraction with chloroform can be greater than or equal to 1% by mass and less than or equal to 50% by mass.

The hardness of the Silicone / Polyurethane material expressed in Shore A can be greater than or equal to 5 and less than or equal to 70, for example less than or equal to 60.

The water uptake of the Silicone / Polyurethane material expressed according to ISO standard 62 may be less than or equal to 25%, for example less than or equal to 10%.

The degradation temperature of the silicone / polyurethane material in air expressed at 5% mass loss can be greater than or equal to 250 ° C. and less than or equal to 350 ° C.

The physicochemical properties of this material make it a suitable material for the encapsulation of electronic components.

Advantageously, the synthesis process according to the invention can be carried out directly in contact with the components to be encapsulated.

The present invention also relates to the electronic module thus obtained.

The following examples of the synthesis of a silicone / polyurethane material are only given for information and do not constitute a limitation.

In the following examples, the pluri-carbonate and the pluri-amine are according to the following formulas:

ch ₃ • CHj-O-CHj-CHj-CHt-Sî-OCH *

CH:

If- OCH:

çh ₃

Si-OL-OL-OL-O-CH: I ‘‘ ‘, CH <

PDMS bis cydocarbonate

Η ₂ Ν ^{/ ΧζΝχ / Χ} ΝΗ ₂

Tris (2-arTi noetty l) arri ne

Example 1:

During the mixing step, 0.300 g (0.0059 mol of amine functions) of tris (2 aminoethyl) amine (purity: 96%, Mn = 146.23 g / mol) and 2.823 g (0.0059 mol of functions cyclocarbonate) of PDMS bis cyclocarbonate (Mn = 955 g / mol, Icarbonate = 2.093 meq / g) are placed in a pill box and stirred under dynamic vacuum using a magnetic stirrer.

The mixture is then poured into aluminum cups placed in an oven for 20 min at 50 ° C and then 20 min at 100 ° C. After the heating step, a yellow translucent material is obtained.

The material thus obtained is then characterized according to its physicochemical properties.

The soluble fraction of the material, calculated after 72 hours of hot extraction with chloroform for example, is 5% by mass.

The hardness of the material expressed in Shore A is 50.5 ± 2.4.

The material's water uptake, expressed according to ISO 62, is 5%, measured by TGA under air flow at 20 ° C / min heating rate.

The water contact angle is 85 ° ± 2.

The material's degradation temperature in air, expressed at 5% mass loss, is 289 ° C with an air flow at 20 ° C / min heating rate.

The loss of mass of the material during its time of exposure to a constant temperature of 150 ° C in air is illustrated in Figure 2.

Example 2:

During the mixing stage, 0.425 g (0.0084 mol of amine functions) of tris (2 aminoethyl) amine (purity: 96%, Mn = 146.23 g / mol) and 2,000 g (0.0084 mol of functions cyclocarbonate) of PDMS bis cyclocarbonate (Mn = 474 g / mol, Icarbonate = 4.19 meq / g) are placed in a pill box and stirred under dynamic vacuum using a magnetic stirrer.

The mixture is then poured into aluminum cups placed in an oven for 20 min at 50 ° C and then 20 min at 100 ° C. After the heating step, a yellow translucent material is obtained.

The material thus obtained is then characterized according to its physicochemical properties.

The soluble fraction of the material, calculated after 72 hours of hot extraction with chloroform, is 2% by mass.

The hardness of the material expressed in Shore A is 50.6 ± 1.0.

The water uptake of the material, expressed according to ISO standard 62, is 11%, measured by TGA under air flow at 20 ° C / min heating rate.

The water contact angle is 87 ° ± 2.

The material's degradation temperature in air, expressed at 5% mass loss, is 272 ° C with an air flow at 20 ° C / min heating rate.

The loss of mass of the material during its time of exposure to a constant temperature of 150 ° C in air is illustrated in Figure 3.

Example 3:

During the mixing step, 0.300 g (0.0059 mol of amine functions) of tris (2 aminoethyl) amine (purity: 96%, Mn = 146.23 g / mol) and 2.823 g (0.0059 mol of functions cyclocarbonate) of PDMS bis cyclocarbonate (Mn = 955 g / mol, Icarbonate = 2.093 meq / g) are placed in a pill box and stirred under dynamic vacuum using a magnetic stirrer.

The mixture is then poured into aluminum cups placed in an oven for 20 min at 50 ° C and then 20 min at 100 ° C.

The yellow translucent material is obtained is heated at 150 ° C for 8 days.

The material thus obtained is then characterized according to its physicochemical properties.

The soluble fraction of the material, calculated after 72 hours of hot extraction with chloroform, is 16% by mass.

The water uptake of the material, expressed according to ISO standard 62, is 20%, measured by TGA under air flow at 20 ° C / min heating rate.

The material's degradation temperature in air, expressed at 5% mass loss, is 320 ° C with an air flow at 20 ° C / min heating rate.

The loss of mass of the material during its time of exposure to a constant temperature of 150 ° C. in air is illustrated in FIG. 4.

The invention has been described above with the help of embodiments without limitation of the general inventive concept.

Many other modifications and variations suggest themselves to a person skilled in the art, after reflection on the different embodiments illustrated in this application.

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Claims (11)

1. Process for the synthesis of a Silicone / Polyurethane material by polyaddition between a pluricarbonate and a pluri-amine, comprising: a mixing step, El, during which the pluri-carbonate and the pluri-amine are mixed at a first mixing temperature Tl during a mixing time tl, a heating step, E3, during which the mixture is heated during a first heating time t2 to a first heating temperature T2 followed by a second heating time t3 to a second heating temperature T3, characterized in that that at least one of the pluri-carbonates and pluri-amines comprises silicone segments. 2. Synthesis process according to claim 1, in which the pluri-carbonate is a cyclic pluricarbonate. 3. Synthesis process according to one of the preceding claims, in which the carbonates of the pluri-carbonate are linked to one another by a poly-siloxane or hydrocarbon chain. 4. Synthesis process according to one of the preceding claims, in which the pluri-carbonate carbonates are linked together by a chain of formula (I): R1 I R2 I I i Si-0- 1 -Yes- | ^{J n} 1 R3 R4 with n greater than or equal to 1 and less than or equal to 50 and R1 to R4 of the hydrocarbon groups. 5. Synthesis process according to one of the preceding claims, in which the pluri-amine comprises at least two primary amine functions linked together by a polysiloxane or hydrocarbon chain. 6. Synthesis method according to one of the preceding claims in which during the mixing step the pluri-carbonate and the pluri-amine are mixed with a molar concentration ratio in amine function and in carbonate function greater than or equal to 0.5 and less than or equal to 1.5. 7. Synthesis process according to one of the preceding claims, in which the first heating temperature T2 is higher than the first mixing temperature T1 and is less than or equal to 75 ° C. 8. Synthesis process according to one of the preceding claims, in which the second heating temperature is higher than the first mixing temperature and the first 10 heating temperature and is less than or equal to 125 ° C. 9. Synthesis method according to one of the preceding claims, comprising a second heating step E4 during which the product from the heating step E3 is heated for a third heating time t4 to a third heating temperature 15 T4, with t4 greater than or equal to 1 day and less than or equal to 12 days and T4 greater than or equal to 125 ° C and less than or equal to 175 ° C. 10. Electronic module obtained by the method according to one of the preceding claims in which the mixture is poured into a housing comprising electronic components and 20 of the associated connection circuits before the heating step, E3. 11. Silicone / Polyurethane material obtained by the process according to one of claims 1 to