WO2013050579A1

WO2013050579A1 - Controlled-healing polysiloxanes, process for their preparation and use of said polysiloxanes

Info

Publication number: WO2013050579A1
Application number: PCT/EP2012/069803
Authority: WO
Inventors: Etienne DELEBECQ; François GANACHAUD
Original assignee: Centre National de la Recherche Scientifique CNRS; Universite de Montpellier; Delphi Connection Systems Holding France SAS
Current assignee: Centre National de la Recherche Scientifique CNRS; Universite de Montpellier; Delphi Connection Systems Holding France SAS
Priority date: 2011-10-06
Filing date: 2012-10-05
Publication date: 2013-04-11
Anticipated expiration: 2014-04-06

Abstract

The present invention relates to a silicone polymer with protected isocyanate group having the following general formula (I) wherein A is an alkanediyl group in C₁-C₁₀; B is a protecting group which can be released at a temperature ranging from. 50 to 200° C; each X represents independently hydrogen or a C₁-C₄-alkyl group; p is an integer ranging from 2 to 850; n is an integer higher than 1; to the process for its preparation and to the use of said polysiloxanes.

Description

CONTROLLED-HEALING POLYS ILOXA ES , PROCESS FOR THEIR

PREPARATION AND USE OF SAID POLYSILOXANES FIELD OF THE INVENTION

The instant invention relates to controlied-healing po 1 ys i loxar.es intended notably to be used as additives for sealing oints . The invention relates also to a process for their preparation and to the use of said polymers.

BACKGROUND OF THE INVENTION

Connectors are notably used for connecting an electrical, optical or electro-optical apparatus to another, and can be found in any kind of electrical, optical or electro-optical devices. Such connectors can , for example, be of the type comprising an electrically insulative housing in which electrical wires or optical fibres are inserted. In this document, an electrical connector is taken as an example, but the person skilled in the art will easily transpose this example into connectors for optical or electro-optical applications.

Since it is undesirable that foreign bodies , such as dust and liquids , penetrate the inside of the connectors, it is preferable to seal the connectors against such foreign bodies or liquids. A given class of connectors therefore comprises a so-called mat sealing joint disposed between a housing body (main part of the housing) and a rear grid (rear part of the housing) . Sealing is performed peripherally, for example by the sealing joint being compressed on the housing . Further, the mat sealing j oint is also designed to provide sealing on each cable.

In use, during the cable connector assembly process, force has to be applied to insert the cable through the passageways formed in the sealing joint. However, due to the fact that it is necessary to ensure efficient cable sealing, the passageways have to be 9

dimensioned in such a way that their inner diameter is slightly smaller than that of the cable. As a consequence, high insertion force is required to insert the cable through the mat sealing joint. In addition, cable assembly is performed with a cable which has already been connected to a terminal member (e.g. by crimping or welding) and which presents aggressive contours (sharp edges).

One can therefore understand that the cable insertion step is an aggressive step for the mat sealing joint, which may cause damages to the sealing joint, whereby the sealing efficiency of the sealing joint can be highly affected after several cable insertion/removal operations .

Besides, conventional mat sealing joints often comprise silicone, which is an expensive material. If said material is impaired, the performance of the mat sealing joint decreases. Thus, there exists a need to allow sealing joints to be repaired in situ.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a controlled-healing polysiloxane . Said controlled-healing polysiloxane is intended to be used on at least a part of the surface of sealing joint for improving sealing efficiency. Under controlled conditions, such as moisture and temperature, said polymer is capable to cross-link, thereby ensuring a "self repairing" of the damaged sealing j oint .

To this aim, it is provided a controlled-healing polysiloxane which is a silicone polymer with a protected isocyanate having the general formula (I) according to claim 1.

DETAILED DESCRIPTION

The invention relates to polysiloxanes with a protected isocyanate having the following general formula (I) :

wherein :

A is an alkanediyi group in Ci-Cio, possibly substituted, preferably an alkanediyi group in C1-C , even more preferably a propanediyl group;

B is a protecting group which can be released at a temperature ranging from 50 to 200 °C, preferably from

80 to 15G°C, even more preferably from 90 to 120 °C; each X represents independently hydrogen or a C1-C4- alkyl group, preferably a methyl or ethyl group;

p is an integer ranging from 2 to 850 preferably from

5 to 450 and even more preferably from 10 to 200;

n is an integer higher than 1, preferably higher than

2, and even more preferably from 3 to 25.

In order to avoid any bodying or complete gelation, the molecular mass should preferentially not be above around 60000g/mol . If p is above 850, too important bodying up can occur.

The man skilled in the art can modified the final mechanical properties of the cross-linked polymer by varying the number of xsocyanate groups, i.e., the n value.

In a specific embodiment, B is selected from the group comprising N-alkyl-aniline , ketone oximes such as 2- butanone oxime, methyl n-amyl ketone oxime, methyl isoamyl ketone oxime, cyclohexanone oxime, methyl isopropyl ketone oxiine , methyl isobutyl ketone oxime, di i sobutyl ketone oxime, methyl tert -butyl ketone oxime, diisopropyl ketone oxime, 2,2,6, 6- Letramethylcyclohexanonc oxime or tetramethylcyclobutanedxone monooxime ; thiols such as thiophenol or 2-mercaptopyridine; CH-azidic compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate , ethyl cyanoacetate, methyl cyanoacetate, or acetylacetone ; amines such as methylphenylamine , diphenylamine , naphthylphenylamine , diisopropylamine, dicyclohexylamine, ethy l isopropy 1 amine, benzy1- ert: -buty 1 a i ne , tert-butylmethylamine , tert- butyliso-propylamine or 2, 2, 6, 6-tetramethylpiperidine ; or heterocyclic compounds such as imidazole, 2 -isopropy] - imidazole, 3, 5-d i methy 1 pyrazole, and b-methy1-2 , 3- dihydropyrazol-3-one; lactams such as [epsilon] - caprolactam, [gamma] -lactam, [delta] -lactam; acetamides such as N-methyl-ace tamide , N-ethylacetamide, N- propylacetamide and N-isopropylacetamide ; phenolic compounds such as phenol, thiophenol, chlorophenol , methylthiophenol, nit ophenol , alkyl phenols, e.g. ethyl phenol , tertiary butyl phenol, cresol, xylenol and resorcinol; and mixtures thereof.

Particularly preferred B groups are mono-or di-alkyl- substituted pyrazole, di-a i. kyl-ketoxyrne ; and mixtures thereof.

In particular, B is selected from the group comprising dimethylpyrazole , methylethylketoxyme , and mixtures thereof.

In a specific embodiment, the polysiloxane according to the invention has the following formulas ( la) or (lb) :

More particular polymers according to the invention are 3, 5-dimethylpyrazole-blocked isocyanatopropyltriethoxysilane having the following formula (l ' ) or methylethylketoxime-blocked

'):

Said polymers are prepared by a two-steps process . In the first step the isocyanate group of a si lane monomer is blocked and in the second step the blocked monomer is linked to a macromolecular structure, e.g. a polysiloxane . . Blocking reaction

2, Po!ycondensation

X, A, B , n and p are such as mentioned above.

When 3, 5-dimethylpyrazole is used for blocking the isocyanate group, the reaction is carried out as follows:

1. Bloc

2. Polycondensation

When methylethylketoxime is used for blocking the isocyanate group, the reaction is as follows;

Blocking reaction

The poiycon.densaLion step is carried out in the presence of a catalyst. Any product capable of catalyzing the a 1 koxy- silanoi reaction can e used. Examples of catalysts can be zirconium and aluminium derivatives, such as those described in GB2144758 and FR2856694; tin catalysts, such as those described in GB841825, GB1097379, FR2557582, EP0235049, US 3862919 and BE842305; calcium and magnesium catalysts, such as those described in US 6818721; titane, as described in US4111890, US5698653, US3689454 and US4722967 ; or basic catalysts, such as alkali metal hydroxide or amine. The amount of catalyst will depend on the type of catalyst used. Generally, said amount will be from 0.01 to 1.5 mo1% , preferably from 0.1 to 0.8 mol% with respect to the silanol content.

In a specific embodiment, the catalyst is tin C<-

Ci2-alkanoate, preferably tin hexanoate, tin heptanoate or tin octanoate.

The temperature of the polycondensation will be between 0 and 80°C, preferably from 20 to 50°C.

The polycondensation is stopped when the desired molecular weight is obtained. The man skilled in the art can use any method for stopping the polycondensation reaction. However, according to a specific embodiment, the catalyst activity can be quenched, for example using a ether crown, tetraglyme, phosphine, tertiary amine, phosphazene, carbene. Examples of phosphines and ether crown can be found in WO2011/018161, in particular, it can e mentioned 12-crown- , 15-crown-5, 18-crown-6, dibenzo 18 -crown- 6, mono- or di-hyd ogen phosphine, tri- (C1-C12- aikyl ) -phosphines such as tri-ethyl phosphine, tri-methyl phosphine, tri-isopropyl phosphine, tri-hexyl phosphine, tri-cyclohexyl phosphine; arylphosphines such as triphenyl phosphine, tritolylphosphine .

Tertiary amines can also be used as quenching agents. Examples of suitable tertiary amines are tris [2- ( dimethylamino ) ethyl ] amine ; Ν,Ν,Ν' ,Ν' ' ,Ν' ' - pentamethyldiethylenetriamine; 1,1,4,7,10, 10- hexamethyltriethylenetetramine; N, N ' -diethyl-N, N ' - dimethylethylenediamine ; N, -diethyl-N ' , N ' - dimethylethylenediamine ; N , , N ' , ' - tetraethylethylenediamine .

Ethers which can be used as quenching agents for example diethylene glycol dimethyl ether; tetraethylene glycol dimethyl ether; triethylene glycol dimethyl ether; l-tert-butoxy-2-methoxyethane ; ethylene glycol diethyl ether; diethylene glycol diethyl ether.

Said quenching agents can be used alone or in combination with each others.

The amount of quenching agent depends on its nature. For examples, when Ν,Ν,Ν',Ν' ',Ν' ' - pentamethyldiethylenetriamine is used as a quenching agent, it is used within a range from 50% to 500% by weight with respect to the catalyst weight/ tetraethylene glycol dimethyl ether is used in an amount ranging from 50% to 500% by weight with respect to the catalyst weight.

Preferably, the poiycondensation reaction is carried out with an alkoxylated polydimethylsiloxane, preferably an ethoxylated polydimethylsiloxane, to enhance the poiycondensation.

Said alkoxylated polydimethylsiloxane is obtained according to the following reaction scheme:

Each X' representing independently a Ci-C₄-alkyl group, preferably a methyl or ethyl group.

Without being linked by any theory, the inventors believe that the use of an alkoxylated po1ydίme I.hy1s iioxane allows avoiding the competition between the silanol-siianol reaction and the silanol-aikoxyl reaction, the reaction is thus controlled in a better way.

Furthermore, after polycondensation, a capping reaction can be carried out. Without being linked by any theory, the inventors believe that the capping reaction allows stabilizing the polysiloxane by avoiding a condensation of molecules of polysiloxane on other molecules of polysiloxane. The product is thus more stable.

Said capping reaction is as follows:

X and X¹ being as defined above, preferably, X and X' are methyl or ethyl.

When used, the blocked isocyanate groups of the siloxane polymer are de-blocked by temperature rise and then the siloxane polymers are able to cross-link with formation of carbon dioxide. In fact, the de-blocked isocyanate group of a polymer chain reacts with an amine radical of the same polymer chain or of another polymer chain forming bridges between the polymer chains, according to the following reactio : I. Deblocking reaction

Said reaction is carried out in- the. presence of moisture and at a temperature ranging from 50 to 200 °C, preferably from. 80 to 150 °C, and even more preferably from .90 to 120°C.

Said reaction only releases carbon dioxide .

Further to the above mentioned reaction, a part of the deblocked isocyanate groups can react with the terminal Si -OH groups of the polysiloxane polymer (in which X-=H) according to the following reaction:

terminal Si-OH groups

Of course, said reaction is avoided when using an alkoxylated polydimethylsiloxane and/or the capping reaction .

The invention also relates to composition comprising the silicone polymer with a protected isocyanate group having the following general formula (I) as disclosed above with additives and/or solvent.

Examples of additives which can be used in the composition according to the invention are colors, inks, plasticizers , etc.

Examples of solvent are alkanes (for instance pentane, hexane, heptanes), ethers (such as diethyl ether, tetrahydro uran) , and aromatic solvent (toluene, xylene) .

The composition or the polymer according to the invention can be applied on silicone surfaces and cross- linked in-situ by heating in presence of moisture.

In particular, it can be applied on the surface of a silicone mat seal joint, which has been damaged (e.g. cracks) . The polymer will enter in said cracks and after cross-linking, will heal the cracks.

Such an application is very interesting for mat sealing joints used in the electrical connector industry. Indeed, this type of sealing joint can be damaged during the insertion of the cables through the mat sealing joint. The polymer or composition according to the invention can be applied on the surface of the mat sealing joint and, after insertion of the cable, the sealing joint can be submitted to a controlled cross-linking process during which the polymer cross-links so as to intimately link the sealing joint material to the cable and then to ensure an additional sealing effect.

Another benefit to the automotive connector industry for implementing the present silicone polymer is that this polymer ca be chosen for cross-linking in the condition of use of the motorized vehicle. For instance, the polymer will be formulated such that it is able to cross-link at the temperature in the vehicle engine compartment when the vehicle is running. Thus even if a default of the sealing j oint of the connector has not been detected during the car assembly, the risk of malfunction of the connector (due to short circuit caused by the presence of humidity in the connector) is highly limited since the sealing j oint is capable to "self-heal" as soon as the vehicle engine is started.

EXAMPLES :

EXAMPLE !: Synthesis of DMP-blocked IPTES

The synthesis was carried out according to the following reaction :

I PTES DMP DMP-blocked IPTES

A 100 ml two-necked flask equipped with magnetic stirrer, argon inlet, condenser was charged with 8.55 g (89 mraol ) of

3, 5-dimethylpyrazole (DMP) and heptane (35 ml). The reactants were heated to reflux with a silicone oil bath. At 100°C, DMP is solubilized and 20 g (81 mmol) of isocyanatopropyl triethoxysilane (IPTES) was added dropwise to the reaction mixture. The reaction was carried out until no NCO peak (2273 cm^"1) could be detected in the IR spectrum.

The IR spectrum of the obtained DMP-blocked IPTES is represented in Figure 1.

The solvent was then removed with rotary evaporator. The conversion and the purity were checked by ¹R NMR. The 5.8ppm signal of free DMP shifts to 5.9 ppm when DMP blocks the isocyanate functions. The chemical shifts observed by ¹H NMR spectrum are represented in Figure 2.

The reaction conversion (94%) has been calculated from signal intensities ratio as follows; C=I₅.g _ppm/ (I5.9 _ppm +I5.B _ppm) based on the shift value of the 5.8 ppm signal. No significant by-product was detected and the solution contained slightly more than 10% of free DMP.

Example 2 : Synthesis of MEKO-blocked IPTES

The synthesis was carried out according to the following reaction :

IPTES MEKO MEKO-blocked IPTES A 100 ml two-necked flask equipped with magnetic stirrer, argon inlet, condenser was charged with 3,87 g (44 mmol) of methylethyl ketoxime (MEKO) . The reactants were heated to 3 ° C and 10 g (40 mmol) of isocyanatopropyl triethoxysilane (IPTES) was dropwise added to the reaction mixture. The reaction was carried out until no NCO peak (2273 cm^"1) could be detected in the IR spectrum.

The IR spectrum of the obtained MEKO-blocked IPTES is represented in Figure 3.

The conversion and the purity were checked by ¹H NMR: the isocyanate functions are blocked by MEKO. The 8.9 ppm signal of free MEKO shifted to 6.4 ppm when MEKO blocked the isocyanate functions. The chemical shifts observed by ¹H NMR are represented in Figure 4.

The reaction conversion (90%) was calculated from signal intensities ratio as follows; C=Ig.4 _ppBs/ (Ie.4 ppm + e.9 ppm) based on the shift value of the NH signal. No significant side product was detected and the solution contained slightly more than 10% of free MEKO.

Example 3 : Polycondensation of DMP-blocked IPTES

38.12 g (0,11 mol) of DMP-blocked IPTES and 250.03 g (0.25 mol ) of silanol terminated polydimethylsiloxane (Mw = 1300 g/mol, Ip-1.6 ) were charged in a 250 ml two-necked flask equipped with mechanic stirrer. The mixture is heated to 50 °C and 1.25 g (3.09 mmol) of tin octoate is added.

After 6h, the reaction was stopped by adding tetraglyme (33.35 g) in the mixture and cooling down the reactor.

Molecular weights were determined through Steric Exclusion Chromatography (SEC) equipped with RI (refractive index) and UV detectors, both of them show one peak of polymer at 890s with similar weight distribution. The DMP-blocked IPTES was detected in RI and UV at 1110s and tetraglyme was only detected with RI detector at 1140s. Steric Exclusion Chromatography (SEC) analyses were performed using a Spectra-Physics apparatus, equipped with a set of PL gel (5 mm) MIXED-C columns, from Polymer Laboratories and two detectors, refractive index and UV absorption. The eluent was tetrahydrof ran at a flow rate of 1 mL.min^"1. The calibration curve was established using Polystyrene standards from Polymer Laboratories and toluene as flowmarker.

The RI detection is represented in Figure 5.

The polymer peak (890s) analysis was as follows:

mass at the peak maximum

Mw= (∑i i x i²) / (∑iNi x Mi)

Mz- ( iNi x M,³) / (∑iNi x Mi²)

Mz+1= (∑i₊iN_i+1 x M_i+i³) / (∑_i+iN_i+1 x M_i+1 ²)

Mv— viscosimetrie mean mass

D ^■ (∑ii x N_x) / (∑i i)

with

i: polymerization degree,

M : molar mass

i : the number of polymeric chains of molar mass Mi.

The UV detection is represented in Figure 6.

The polymer peak (890s analysis was as follows;

Example : Confirmation of cross-linking

The polymer obtained in example 3 was applied on the surface of a first si 1 i cone film with a brush thus forming a polymer layer. Then, a second silicone film was applied on said polymer layer.

Immediately after the application, the two films could be peeled_* Then the assembly was placed in an oven during 2 hours at 80°C at 90% moisture.

Afterwards, both films were firmly attached to each other, they could not be peeled off, indicating that the cross- linking reaction has occurred.

Claims

1. A silicone polymer with protected isocyanate having the following general formula (I):

wherein :

A is an alkanediyl group in Ci-Cio, possibly substituted, preferably a alkanediyl group in C1-C4, even more preferably a propanediyl group;

80 to 150°C, even more preferably from 90 to 120 °C; each X represents independently hydrogen or a C1-C4- alkyl group, preferab ! y a methyl or ethyl group;

p is an integer ranging from 2 to 850 preferably from

5 to 450 and even more preferably from 10 to 200;

n is an integer higher than 1 , preferably higher than

2, and even more preferably from 3 to 25.

2. The silicone polymer according to claim 1, wherein B is selected from the group comprising N-alkyl- aniline, ketone o ro.es such as 2-butanone oxime , methyl n- amyl ketone oxime, methyl isoamyl ketone oxime, cyclohexanone oxime, methyl isopropyl ketone oxime, methyl isobuty1. ketone oxime, diiscbufyi ketone oxime, methyl tert-butyl ketone oxime, diisopropyl ketone oxl me , 2,2,6,6- tetraraethylcyclohexanone oxime or tetramethyicye Lobutanedi one monooxime; thiols such as thiophenol or 2-mercaptopyridine; CH-azidic compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, ethyl cyanoacetate, methyl cyanoacetate, or acetylace one ; amines such as methy1 phenyiaminc , dipheny Lanine , naphthylphenylamine, diisopropylamine, dicyclohexylamine , ethylisopropylamine , benzyl-tert-butylamine, tert-butylmethylamine, tert- butyliso-propylamine or 2, 2, 6, 6-tetramethylpiperidine; or heterocyclic compounds such as imidazole, 2-isopropyl- imidazole, 3, 5-dimethylpyrazole, and 5-meLhy1- , 3- dihydropyrazol-3-one ; lactams such as [epsilon] - caprolactam, [gamma] -lactam, [delta] -lactam, or acetamides such as N-methy1-acetamide , N-ethylacetamide, N- propylacetamide, N-isopropylacetamide ; phenolic compounds such as phenol , thiophenol , chlorophenol , methylthiophenol, nitrophenol, alkyl phenols, e.g. ethyl phenol, tertiary butyl phenol, cresol, xylenol and resorcinol; and mixtures thereof .

3. The silicone polymer according to claim 1, wherein B is selected in the group comprising dimethylpyrazole, methylethylketoxyme and mixtures thereof.

4. The silicone polymer according to anyone of claims 1 to 3, which is a 3 , 5-dimethylpyrazole-blocked polyisocyanatoalkoxysiloxane of formula (la) or a methylethylketoxime-blocked po i yisocyanatoa I koxysiioxane of formula (lb) :

wherein X, n, p and A are as defined in claim 1

5. The silicone polymer according to anyone of claims 1 to 4, which is the 3, 5-dimethylpyrazole-blocked isocyanatopropyltriethoxysilane having the following formula (la') or the methylethylketoxime-blocked isocyanatopropyltriethoxysilane having the formula (lb'):

6. A process for preparing a silicone polymer with a protected isocyanate group according to anyone of claims 1 to 5, comprising protecting an isocyanate-derived silicon monomer and reacting said protected monome with a siloxane polymer .

7 , The process according to claim 6, wherein the reaction is as follows:

I , Blocking reaction

.2. Polycondensation

8, Cross-linking process of a silicone polymer with protected isocyanate group according to anyone of claims 1 to 5 , wherein the protected isocyanate is released by heating in the presence of moisture and wherein the deprotected isocyanate groups react with each other for forming a cross-linked polymer; 1 , Deblocking reaction

C(¾

2,

9, Composition comprising the protected isocyanate- silicone polymer with additive and/or a solvent.

10. Use of the polymer or composition as additive for a siloxane rubber.