WO2013050580A1

WO2013050580A1 - Controlled-healing polysiloxane for sealing joints

Info

Publication number: WO2013050580A1
Application number: PCT/EP2012/069804
Authority: WO
Inventors: Etienne DELEBECQ; François GANACHAUD; Alain Flers
Original assignee: Delphi Connection Systems Holding France; Centre National De La Recherche Scientifique - Cnrs; Universite Montpellier Ii Sciences Et Techniques
Priority date: 2011-10-06
Filing date: 2012-10-05
Publication date: 2013-04-11

Abstract

The present invention relates to a sealing joint for connectors comprising a controlled-healing polysiloxane, to the process for applying said controlled- healing polysiloxane to a sealing jointr to the process for cross-linking said controlled-healing polysiloxane and to its use as a repairing additive for a mat sealing joint.

Description

CONTROLLED-HEALING POLYSILOXANE FOR SEALING JOINTS

FIELD OF THE INVENTION

The instant invention relates to self-healing sealing joints for connectors , for instance electrical , optical or electro-optical connectors.

BACKGROUND OF THE INVENTION

Connectors are notably used for connecting an electrical, optical or electro-optical apparatus to a complementary apparatus, 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 and to this end a sealing joint is implemented in the connector. A given class of cable connectors 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 periphericall , for example by compression of the sealing joint against the housing via the rear grid. Further, the mat sealing joint is designed to provide sealing on each cable so as to ensure sealing at the level of the cable. Sealing joint is generally made of a cross- linked polysiloxane material.

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 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) . The f ont leading end of the terminal member, which is usually manufactured by stamping and folding a sheet of metal, is intended to be inserted through the sealing joint. A schematic representation of a terminal member is represented in Fig. 1, where it can be seen that the front leading end 1 of the terminal member 2 comprises sharp edges 3.

One can therefore understand that the cable insert ion 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.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved sealing joint exhibiting a high sealing efficiency even after several wire insertion/removal operations.

To this aim, it is provided a mat sealing joint for a connector comprising a controlled-healing polys i 1 oxane according to claim 1.

According to a specific embodiment, the mat sealing joint for a connector is at least partially coated with a controlled-healing polysiloxane layer.

The mat sealing joint of the present invention can comprise a central portion provided with a plurality of passageways, particularly six passageways arranged in one row, said central portion being coated with a controlled- healing polysiloxane. The sealing efficiency of the wire, is further improved by providing at least the passageways with a control 1 ed-heaii rig polysiloxane.

For economic reason, only the passageways are provided with the controlled-healing polysiloxane i.e. the controlled-healing polysiloxane is applied only within the area where the wires will be inserted.

The controlled-healing polysiloxane which is comprised in the mat sealing joint according to the invention comprises an isocyanate-protected polysiloxane .

Such an isocyanate-protected polysiloxane is disclosed in the pending patent, filed on October 6^th 2011 by the same applicants, whose title is "CONTROLLED-HEALING POLYSILOXANES, PROCESS FOR THEIR PREPARATION AND USE OF SAID POLYSILOXANES". The isocyanate-protected polysiloxane is defined by the following general formula (I) :

wherei :

A is an alkanediyl group in Ci-Cio, possibly substituted, preferably an alkanediyl group in Ci-C₄, 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 150 ° C , even more preferably from 90 to 120 °C; each X represents independently hydrogen or a Ci-C,-- 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 from 2, and even more preferably from 3 to 25.

The polysiloxane comprises an isocyanate group which is protected by a chemical moiety selected from the group comprising N- lkyl-ani line , ketone oximes such as 2- butanone oxime, methyl n-amyl ketone oxime, methyl isoamyl ketone oxime, cyclohexanone oxime, methyl isopropyl ketone oxime, methyl isobutyl ketone oxime, diisobutyl ketone oxime, methyl tert-bulyl ketone oxime, diisopropyl ketone oxime, 2 , 2 , 6 , 6-tetramethylcyclohexanone oxime or tetramethylcyclobutanedione 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, ethylisopropylamine , ben y1-tc rt -bufy1amine, tert-butylmethylamine , tert- butyliso-propylamine or 2,2, 6, 6-t.et ramethyipiperi dine; o heterocyclic compounds such as imidazole, 2-isopropyl·- imidazole, 3, 5-dimethylpyrazole, and 5-methyl-2 , 3- dihydropyrazol-3-one ; lactams such as [epsilon] - capro I actam, [gamma] -lactam, [delta] -lactam, and acetamides such as N-methyl-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 .

In particular, the chemical moiety is selected from the group comprising mono-or d I -alkyl -substituted pyrazole, di-alkyl-ketoxyme ; N-alkyl-aniline and mixtures thereof. In a preferred embodiment, the chemical moiety is selected from the group comprising dimethylpyrazole, methylethylketoxyme and mixtures thereof.

Due to its viscosity and its structure, the controlled-healing polysiloxane forms a layer which adheres on the mat sealing j oint . When said mat sealing joint is submitted to moisture and heating, the controlled-healing polysiloxane is able to crosslink and can no longer be peeled off.

Said cross-linking is preferably made after insertion of the wire.

Another obj ect of the invention also relates to the sealing joint comprising a controlled-healing polysiloxane which is able to cross-link.

The invention relates also to a process for applying a controlled-healing polysiloxane to a sealing j oint . Said application can be made only on a part of the surface of the sealing j oint .

The controlled-healing polysiloxane can be applied alone or a composition comprising the controlled-healing polysiloxane with additive and/or solvent can be applied. The use of a solvent can allow a decrease of the viscosity and thus facilitates the application and minimizes the amount of po 1 ysiloxane applied. Additives such as colors , extenders, plasticizers can be used as well.

The controlled-healing polysiloxane or the composition comprising the controlled-healing polysiloxane is applied by a method selected in the group comprising spraying, injecting, dipping, brushing and mixtures thereof.

The invention also relates to a process for cross- linking the controlled-healing polysiloxane. Said cross- linking is carried out in the presence of moisture and under heating. The temperature necessary for cross-linking is within a range of 50 to 200 °C, preferably from 80°C to 120 °C . Under 50 °C, there is a risk that the crosslinking does not occur and above 120 °C the rate of cross-linking is not further improved.

The duration of the crosslinking will depend on various parameters such as the amount of polysiloxane, moisture degree, temperature, etc. In general cross-linking is achieved after 1 to 24 hours.

Another subject of the invention is the use of a controlled-healing polysiloxane as a repairing additive for a sealing joint. The controlled-healing polysiloxane is applied on the surface of a mat sealing joint, then the wires are inserted in the passageways and the mat sealing joint can be used. Due to the insertion of the wire, the silicone surrounding the passageways can be impaired or even torn. However, due to the presence of the controlled- healing polysiloxane, as soon as the mat sealing joint is submitted to moisture and heat, a cross-linking will occur with a release of carbon dioxide. Said cross-linking will result in a healing or repairing of the impaired areas and filling of the torn parts . The tightness is thus enhanced .

Other characteristics and advantages of the invention will readily appear from the following non- limitative examples. EXAMPLES

Example 1 : preparation of the controlled-healing polysiloxane .

The synthesis was carried out according to the following reaction :

IPTES DMP BMP-blocked IPTES

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

3 , 5-dimethylpyrazole (DMP) and heptane (35 ml). The reactants were heated to reflux via a silicone oil bath. At 1Q0°C, DMP is soiubil i zed and 20 g (81 mmol) of isocyanatopropyl triethoxysilane (IPTES) was added dropwise to the reaction mixture. The reaction was carried cut 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 2.

The solvent was then removed with a rotary evaporator. The conversion and the purity were checked by ¹H NMR. The 5.8 ppm signal of free DMP shifts to 5.9 ppm when DMP blocks the isocyanate functions. The chemical shifts observed by ½ NMR are represented in Figure 3.

The reaction conversion (94%) was calculated from signal intensities ratio as follows; C=I₅.g _PPm/ (I5.9 _PPm +I5.8 ppm) based on said 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.

38.12 g (0.11 mol) of the obtained 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 was heated to 50 °C and 1.25 g (3.09 mmol) of tin octoate was added.

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

Molecular weights were determined through SEC equipped with RI (refractive index) and UV de ectors , both of them showed one peak of polymer at 890 s with similar weight distribution. The DMP-blocked IPTES was detected in RI and UV at 1110 s and tetraglyme was only detected with RI detector at 1140 s.

Steric Exclusion Chromatography (SEC) analyses were performed using a Spectra-Physics apparatus, equipped with a set of PL gel (5 mm) MIX D-C columns, from Polymer Laboratories and two detectors, refractive index and UV absorption. The eluent was tetrahydrofuran 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 4.

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

mass at the peak (890s)

(∑iNi x Mi) / ∑iNi

(∑_x i x Mi²) / (∑iNi x Mi )

Mz= (∑iNi x Mi³) / (∑; | x Mi²)

Mz+1= (∑_i+iN_i+i x M_i+1 ³) / (∑_i+iN_i+1 x M_i+1 ²)

Mv= viscosinet io mean mass

DP= {∑ii x Ni) / (∑iNi)

with

i: polymerization degree,

Mi: molar mass

Ni : the number o polymeric chains of molar mass Mi . The UV detection is represented in Figure 5.

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

Example 2 :

10 g of the polymer obtained in example 1 was added with 10 pL of a blue color agent.

Said composition was applied with a brush on a mat sealing j oint as represented in Figure 6. The blue film 6 on the surface of the mat sealing joint 4 was visible. The coated joint mat sealing was then placed in an oven at 90% moisture under 80 °C during 2 hours.

Then the mat sealing joint 4 was transversally cut along the array represented on Fig 6a, and a photo of said section was taken (see fig. 7) . As it can be seen on figure 6b, the passageways 5 are filled up with the controlled- healing polymer. The material is completely solid, i.e., it is not flowable . An homogeneous film was present on the mat sealing joint, which could not be peeled off even when compressed air was injected in a direction opposite to the direction of insertion of the wires, along arrow A on figure 6b.

A slight blowing appears after the cross-linking, which is due to the release of the carbon dioxide.

Example 3 :

Two strips of silicone of 10cmx2cmx 2mm were used (see Fig 8a) . The polymer obtained in example 1 was applied on half a surface of one strip. The other strip was applied on the top of the polymer layer (see fig.8b) . Said assembly was placed in an oven during 2 hours at 80 °C at 90% moisture. Afterwards, both strips were fi mly attached to each others, they could not be peeled off (see fig.8c).

Claims

1. Λ sealing j oint for connectors comprising a controlled-healing polysiloxane.

2. The sealing joint according to claim 1, which is at least partially coated with a controlled-healing polysiloxane layer.

3. The sealing joint according to claim 1 or 2, wherein the controlled-healing polysiloxane layer comprises isocyanate-protected polysiloxane .

4. The sealing joint according to claim 3, wherein the isocyanate-protected polysiloxane presents the following general formula (I) :

wherein :

A is an alkanediyl group in Ci-Cio, possibly substituted, preferably an alkanediyl group in Ci-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 150°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;

5. The sealing joint according to claim 3 or 4, wherein the isocyanate is protected by a chemical moiety selected from the group comprising mono-or di-alkyl- substituted pyrazole, di-alkyl -ket:.oxyme; N-al kyl-anil ine and mixtures thereof.

6. The sealing joint according to anyone of claims 1 to 5, wherein the controlled-healing polysiloxane is crosslinkable in the presence of moisture and heat.

7. The sealing joint according to anyone of claims 1 to 6, which is made of a cross-linked polysiloxane material .

8. A process for applying a controlled-healing polysiloxane, to a sealing joint, wherein a control 1 ed- healing polysiloxane layer is applied on at least a part of a surface of a sealing joint.

9. A process according to claim 8, wherein the controlled-healing polysiloxane is applied by a method selected in the group comprising spraying, injecting, dipping, brushing and mixtures thereof.

10. A process for cross-linking the control 1 ed- healing polysiloxane, wherein the co rolled-healing polysiloxane is cross-linked in the presence of moisture and under heating.

11. Use of a cont. oll ed-healing polysiloxane, as a repairing additive for a mat sealing joint.

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