AU4623199A

AU4623199A - Composition for filling and sealing electric connectors

Info

Publication number: AU4623199A
Application number: AU46231/99A
Authority: AU
Inventors: Evelyne Bonnet; Maxime Deroch; David Meslet
Original assignee: Atofina SA
Current assignee: Arkema France SA
Priority date: 1998-07-06
Filing date: 1999-07-05
Publication date: 2000-01-24
Also published as: WO2000001751A1; ES2195579T3; ATE234878T1; EP1095084B1; JP2002519488A; DE69906081T2; CA2337142A1; KR20010074673A; DE69906081D1; EP1095084A1

Abstract

The invention concerns a composition comprising a polyisocyanate, a hydroxylated polydiene and a thixotropic agent, said composition being thixotropic before cross-linking and having a pot life of at least two hours at 25 DEG C. Said composition is useful for filling electric connectors and sealing them.

Description

Wo 00/01751 PCT/FR99/01618 COMPOSITION FOR FILLING AND SEALING ELECTRICAL CONNECTORS The present invention relates to a composition 5 for filling and sealing electrical connectors and more particularly to a composition based on a polyurethane formed by the reaction between a polyisocyanate and a hydroxylated polydiene. In the automobile connector field, suppliers 10 work on a "just in time" basis. Thus, the automobile wiring harnesses are manufactured for a given type of vehicle (with certain options) just before factory fitting it into the vehicle. The manufacture of the electrical wires and of 15 the caps (connectors) is automated but the final assembly of the complete electrical harness is very complicated and still requires human intervention. In the assembly zone are the harness being fitted, the caps, the electrical wires which will have 20 to be fitted onto the harness, and an operator who carries out the fitting operation. According to the various controls on vehicles (each vehicle having its options), an order arrives from the automobile manufacturer and the corresponding 25 harness is assembled. The operator assembles the wires in the male or female connectors and closes the caps. Thereafter, or during production, the harness moves into another zone in which the filling of the 30 caps, with a hotmelt, is carried out in order to seal them. This operation is complex and expensive since it is done in real time and requires specific manipulations, and therefore work-in-process. In addition, the hotmelt is put in hot (the term "hotmelt" 35 is understood to mean a thermoplastic composition which is, in general, solid below 100 or 130*C and which is a viscous liquid above it). One object of the invention is to provide a composition of suitable rheology so that: -2 - it can be put into the open caps before the electrical wires are inserted thereinto and so that it cannot then flow when the caps are being manipulated; - it has an open time (or pot-life) that can be 5 delayed by storage at low temperature, that is to say it does not crosslink too quickly so that the operator has the time to insert the electrical wires into it and close the cap, thus fastening the electrical wires and sealing them by the adhesion of the composition to the 10 cap and to the wires. Another object of the invention is to provide a composition having: - a final hardness (after crosslinking) sufficient to damp vibrations and to withstand tearing; 15 - dielectric (insulating) properties; - a temperature withstand according to the automobile standards T2/T3 corresponding to 10 days' aging at 125*C (T2) or 155 0 C (T3); - optionally, good fire resistance. 20 The present invention therefore relates to a composition comprising a polyisocyanate, a hydroxylated polydiene and a thixotropic agent, this composition being thixotropic during the open time. The prior art has not described such 25 compositions. US 4 355 130 describes blends of polyurethanes and polyalphaolefins for insulating electrical devices; US 4 666 968 and US 4 060 583 describe pourable polyurethane gels which crosslink in 24 h at 25 0 C. There is no mention of thixotropy. 30 The composition of the invention is prepared by mixing two parts, one containing the polyisocyanate and the other containing the hydroxylated polydiene. The thixotropic agent and the optional other additives are divided between the parts depending on their reactivity 35 and their compatibility. A catalyst may be present in one of the two parts or may be added separately. It is quite clear that the open time is counted from the mixing of all the ingredients, that is to say the two parts and the optional catalyst.

-3 According to the present invention, the polyisocyanate used may be an aromatic, aliphatic or cycloaliphatic polyisocyanate having at least two isocyanate functional groups in its molecule. 5 By way of illustration of aromatic polyisocyanates, mention may be made of 4,4'-diphenyl methane diisocyanate (MDI), liquid modified MDIs, polymeric MDIs, 2,4- and 2,6-toluylene diisocyanate (TDI) and a mixture thereof, xylylene diisocyanate 10 (XDI), triphenylmethane triisocyanate, tetramethyl xylylene diisocyanate (TMXDI), paraphenylene diisocyanate (PPDI) and naphthalene diisocyanate (NDI). Among aromatic polyisocyanates, the invention preferably relates to 4,4'-diphenylmethane diisocyanate 15 (MDI) and polymeric MDI (PMDI) . The term "polymeric MDI" is understood to mean a product of formula:

NCO-C

6

H

4

CH

2 -6 H4 CH2~ C6H4 inI NCO NCO 20 (CAS (Chemical Abstracts Service) Registration No.: 9016-87-9) By way of illustration of aliphatic 25 polyisocyanates, mention may be made of hexamethylene diisocyanate (HDI) and its derivatives and trimethyl hexamethylene diisocyanate. By way of illustration of cycloaliphatic polyisocyanates, mention may be made of isophorone 30 diisocyanate (IPDI) and its derivatives, 4,4'-dicyclo hexylmethane diisocyanate and cyclohexyl diisocyanate (CHDI). It would not be outside the scope of the invention if one were to use isocyanate prepolymers 35 obtained by the reaction of an abovementioned polyisocyanate with a polyol, such as especially a -4 polyether-polyol, a polyester-polyol and a polydiene polyol, or with a polyamine. Advantageously, the isocyanates are used in amounts such that the NCO/OH molar ratio is between 0.3 5 and 2 and preferably close to 1. The NCO/OH molar ratio must be calculated taking into account the presence of the functional groups that react with the isocyanate functional groups, such as the hydroxyl and/or amine functional 10 groups, and of the optional chain extender. Polymeric MDI is preferred, this having many advantages: - it gives the final product useful mechanical properties; 15 - its toxicity is low (substance harmful when inhaled). By way of illustration of polydiene-polyols that can be used according to the present invention, mention may be made of hydroxytelechelic conjugated 20 diene oligomers which can be obtained by various processes, such as the radical polymerization of a conjugated diene having from 4 to 20 carbon atoms in the presence of a polymerization initiator, such as hydrogen peroxide or an azo compound, such as azobi 25 2,2'-[2-methyl-N- (2-hydroxyethyl)propionamide], or the anionic polymerization of a conjugated diene having from 4 to 20 carbon atoms in the presence of a catalyst, such as dilithium naphthalene. According to the present invention, the 30 conjugated diene of the polydiene-polyol is chosen from the group comprising butadiene, isoprene, chloroprene, 1,3-pentadiene and cyclopentadiene. The number-average molar mass of the polyols that can be used may vary from 500 to 15 000 and preferably from 1 000 to 3 000. 35 According to the present invention, a butadiene-based polydiene-polyol will preferably be used. Advantageously, the polydiene glycol comprises 70 to 85 mol%, preferably 80 mol%, of formula -(-CH 2 -CH = -5

CH-CH

2 -)- units and 15 to 30 mol%, preferably 20 mol%, of units of formula: -4CH 2 - CH] 5

CH=CH

2 Also suitable are copolymers of conjugated dienes and of vinyl and acrylic monomers, such as 10 styrene and acrylonitrile. It would not be outside the scope of the invention if one were to use in-chain epoxidized hydroxytelechelic butadiene oligomers or else hydrogenated hydroxytelechelic oligomers of conjugated 15 dienes. According to the present invention, the polydiene-polyols may have number-average molecular masses at most equal to 7 000 and preferably between 1 000 and 3 000. 20 The OH number expressed in meq/g is between 0.5 and 5 and their viscosity is between 1 000 and 10 000 mPa.s. By way of illustration of polydiene-polyols, mention may be made of the hydroxyl-terminated 25 polybutadienes sold by Elf Atochem S.A. under the names PolyBd*R45 HT and PolyBd"R20 LM. Mixtures of the abovementioned compounds may be used, such as, for example, mixtures of polyether polyols and of polydiene-polyols. 30 Advantageously, hydroxylated polybutadiene is used. It provides: - good hydrophobicity of the system (resistance to moisture, to water, to acids and to bases); - low-temperature flexibility (Tg at least 35 -60 0 C), the product having to remain flexible and to withstand vibrations even at -40*C; - a good high-temperature thermal withstand (125 0 C in a confined enclosure in the absence of oxygen); -6 - good dielectric properties; - good adhesion; - elastomeric elongation and hardness properties over a wide temperature range. 5 The role of the thixotropic agent is to give the composition, before crosslinking, a thixotropic nature (that is to say the viscosity decreases with shear rate) . The term "thixotropy" is advantageously understood to mean that the composition can be poured 10 into a 100 cm 3 beaker to mid-height, which can then be turned upside down without the composition leaving the beaker. Thus, the product: - does not flow when it is deposited in the cap. A paste or mastic is obtained. This avoids having 15 to handle liquid products, which would be incompatible with the application. The cap must be able to be closed without the product flowing. On the other hand, the viscosity falls during shearing, which allows: 20 - easier in-machine processing (the product becomes more liquid and therefore mixes more easily); - better distribution of the product when the cap is closed (under this shear, the product again becomes more fluid and this allows it to fill the empty 25 spaces) . By way of example of a thixotropic agent, mention may be made of pyrogenic silica. The amount of thixotropic agent depends on the rheological properties of the polyisocyanate and of the 30 hydroxylated polydiene and on the presence of other fillers; a person skilled in the art may easily determine this amount. With regard to the pyrogenic silica, from 2 to 10 parts and preferably from 3 to 6 parts of this are sufficient per 100 parts of 35 hydroxylated polydiene if the composition also contains mineral fillers such as calcium carbonate (see below). Advantageously, the composition comprises a chain extender. This makes it possible, inter alia: -7 - to adjust the final mechanical properties, such as the tear strength and the hardness; and - to adjust the ratio of the hydroxylated polydiene/polyisocyanate mixture to the other 5 ingredients of the composition in order to be compatible with in-machine processing of the compound. The term "chain extender" is understood to mean here compounds carrying at least two functional groups that react with the isocyanate functional groups. 10 As examples of such reactive functional groups, mention may be made of hydroxyl functional groups and amine functional groups. According to the invention, the chain extender may be chosen from polyols. The molecular mass may be 15 between 62 and 500. By way of illustration of such compounds, mention may be made of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, hexylene glycol, 20 2-ethyl-1,3-hexanediol, N,N-bis (2-hydroxypropyl) aniline, 3-methyl-1,5-pentanediol and mixtures of at least two of the aforementioned compounds. It is also possible to use polyamines as chain extenders. Their molecular mass may be between 60 and 25 500. By way of illustration of such polyamines, mention may be made of ethylenediamine, diphenyl methanediamine, isophoronediamine, hexamethylenediamine and diethyltoluenediamine. 30 At least one part by weight, and preferably 5 to 30 parts by weight, of one or more of the afore mentioned chain extenders will be used per 100 parts by weight of polyol employed. It is also possible to add a catalyst which may 35 be chosen from the group comprising tertiary amines, imidazoles and organometallic compounds. By way of illustration of a tertiary amine, mention may be made of diaza-1, 4-bicyclo[2.2.2]octane

(DABCO).

8 By way of illustration of organometallic compounds, mention may be made of dibutyltin dilaurate and dibutyltin diacetate. The amounts of catalyst may be between 0.01 and 5 5 parts by weight per 100 parts by weight of polyol. Advantageously, the composition of the invention includes a product for absorbing water. Its role is to absorb the water present in the fillers, but also, during production, to prevent the reaction of the 10 isocyanate with moisture, which reaction would generate bubbles. This product is, for example, a molecular sieve. The amount depends on its absorbing power and on the moisture content of the fillers and on the 15 humidity of the ambient environment. Usually, 1 to 5 parts per 100 parts of hydroxylated polydiene are sufficient. The composition of the invention may also include one or more mineral fillers such as calcium 20 carbonate, kaolin, silica, mica, talc, hydrated alumina, etc. The role of the mineral filler is: - to limit the dimensional shrinkage during crosslinking; 25 - to limit the thermal expansion of the product; - to reduce the raw materials cost of the formulation; - to increase the viscosity of the formulation; 30 - to adapt the hardener/resin blend ratio; - to color the resin in order to make it opaque; - to give fire resistance. The amount of mineral filler depends on the 35 desired properties. It may be up to 200 parts, and advantageously from 50 to 100 parts, per 100 parts of hydroxylated polydiene. It is also possible to add to the polyurethane formulation (the composition of the invention), i.e. to -9 the compound of the various ingredients, before or during the polymerization, adhesion promoters such as functional silanes, that is to say products having a trialkoxysilane end group and an organic functional 5 group, such as an amine, epoxy or vinyl functional group, coupling agents such as unsaturated carboxylic acids or acid anhydrides, and inert fillers and various additives such as antioxidants, UV stabilizers, anti corrosion pigments. 10 Preferably, the composition of the invention essentially contains no plasticizer, that is to say at most an amount such that there is neither migration nor exudation. Thus: 15 - the compatibility with the other plastics in contact with the polyurethane, such as the cap, etc., is better (plasticizers often tend to migrate and contaminate the other materials); - the heat-aging is improved (plasticizers tend 20 to leave the system, hence a weight loss and dimensional shrinkage). As explained above, the composition of the invention is obtained by mixing two parts containing the various ingredients at room temperature (or at a 25 temperature such that there is no significant crosslinking - i.e. the composition remains liquid when it is stirred) . In general, it suffices to be below 30 or 40"C. Each of these parts is stable and can be 30 preserved for several months at 25 0 C. The two parts may be mixed in any conventional device. The composition of the invention has a sufficient open time to be able to fill the caps and place the electrical wires therein, that is to say it 35 does not crosslink significantly (it remains liquid when stirred) at least for 30 minutes and preferably between 2 and 4 hours at 25*C. The open time can also be increased by storing the compositions of the - 10 invention at low temperature, for example between -20 and -10*C. Preferably, the open time To (in hours), after storing the composition as soon as it has been 5 prepared, for Ts hours at -13"C is To (in hours) = 3.8 - 0.0585 x T,. The accuracy of this formula is ± 15 minutes. The use of the composition of the invention is particularly advantageous since: 10 - the product can be deposited in the open caps in a parallel operation (i.e. all the caps are filled on a single specific line); - the product does not flow out of the caps (thixotropy); 15 - the open caps filled with product are stored in a freezer, which allows the crosslinking rate to be slowed down sufficiently over a period possibly ranging up to 3 days; - after removing them from the freezer, 20 operators have at least one hour (this being consistent with the time for manufacturing an automobile electrical harness) during which the resin has not gone beyond the open time (pot-life), which allows the wires to be encapsulated and the caps to be closed; the 25 operators take the caps and close them on the wires, simultaneously assembling and sealing them; - the product then normally crosslinks at room temperature, relatively rapidly. The crosslinking is completed in a few hours. 30 Once the cap has been closed, the composition crosslinks during the day, that is to say before being fitted into the vehicle. Thus, it is possible to fill the caps and then store them in a freezer (at a temperature of about 35 -13*C). Keeping the product cold greatly slows down the crosslinking. Thus, if the open time of the resin is about 4 hours just after mixing, it remains more than 1 h 15 minutes after storing them in a freezer for 45 hours, as the above formula shows.

V - 11 Consequently, when the operator starts to manufacture a harness, all that is necessary is for him to take the caps out of the freezer and he will have an open time of more than one hour, allowing him to close the 5 caps. The present invention also relates to the connectors filled with the compositions of the invention. It also relates to a process for manufacturing electrical harnesses whose connectors are 10 filled as explained above. Examples A composition of the invention was prepared by mixing two parts, A and B (the parts are by weight), PART A PolyBd R45 HT 100 Voranol RA 100 8 Silane A 187 2 No air liquide 2 Aerosil R202 4 Siliporite SA 1720 3 Omya 90 T 84.4 PART B NCO/OH 1.00 DESMODUR VL 50 20.34 (%_NCO =_32.5) 15 in which the products have the following meanings: - PolyBd*R45 HT: a hydroxylated polybutadiene of Mn of 2 800 (determined by steric exclusion chromatography), having a hydroxyl number IoH expressed 20 in milliequivalents per gram (meq/g) of about 0.83, a viscosity in mPa.s (cp) at 30*C of 5 000 and a relative density of 0.90; - Voranol RA 100: a polyether polyol having an Mn of 209, a hydroxyl number of 530 mg KOH/g, a 25 viscosity of 900 to 1 500 mPa.s and a relative density of 1.055 at 25 0

C;

- 12 - Silane A 187: a liquid gamma-glucidoxypropyl trimethoxysilane having a relative density of 1.09 at 250*C and a molecular weight of 236; - No air liquide: a degassing agent; 5 - Aerosil R202: a pyrogenic silica (thixotropic agent); - Siliporite SA 1720: a molecular sieve for absorbing water; - Omya 90 T: a calcium carbonate having a 10 particle size (mean diameter) of 1.1 pm; - DESMODUR VL 50: an MDI-type polyisocyanate. The following properties were obtained: Mechanical properties Shore A hardness 61 Tensile strength (MPa) 5.2 (0.5) Modulus G at 100% (MPa) 3.0 (0.1) Elongation at break (%) 331 (46) Tear strength (N/mm) 18.9 (2.6) Open time measured on 100 g at 25 0 C 3 h 15 The values in brackets denote the standard deviations.

Claims

1. A composition comprising a polyisocyanate, a hydroxylated polydiene and a thixotropic agent, this 5 composition being thixotropic during the open time.

2. The composition as claimed in claim 1, characterized in that the hydroxylated polydiene is a hydroxylated polybutadiene.

3. The composition as claimed in any one of the 10 preceding claims, characterized in that the amount of thixotropic agent is from 2 to 10 parts and preferably 3 to 6 parts per 100 parts of hydroxylated polydiene.

4. The composition as claimed in any one of the preceding claims, characterized in that a chain 15 extender is present in an amount of 5 to 30 parts per 100 parts of hydroxylated polydiene.

5. The composition as claimed in any one of the preceding claims, characterized in that a product for absorbing water is present. 20

6. The composition as claimed in any one of the preceding claims, characterized in that a mineral filler is present in an amount up to 150 parts, preferably 50 to 100 parts, per 100 parts of hydroxylated polydiene. 25

7. The composition as claimed in one of the preceding claims, characterized in that the open time To (in hours) after storage at -13 0 C for T. hours, after it has been prepared, is such that To = 3.8 - 0.0585 x T s . 30

8. Electrical connectors filled with the composition of any one of the preceding claims.

9. A process for manufacturing electrical harnesses comprising connectors, characterized in that, during the open time, the connectors are filled with a 35 composition according to any one of claims 1 to 7, then the electrical wires are inserted into them and closed.

10. The process as claimed in claim 9, characterized in that the open time is extended by storing, at low temperature, the connector filled with - 14 the composition before the electrical wires are inserted into it.