Sulphur products for adding a polythiol on a norbornene...

Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Polymerizing – cross-linking – or curing

Reexamination Certificate

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C522S146000, C522S162000, C522S180000, C526S286000, C526S289000, C528S376000

Reexamination Certificate

active

06447708

ABSTRACT:

The present invention relates to novel sulphur products from the addition of at least one polythiol to at least one norbornene derivative comprising an exocyclic ethylenic unsaturation, to a process of manufacture of these sulphur products, to a composition which can be crosslinked by the radical route comprising such a sulphur product in the crosslinkable state, and to the resulting crosslinked products and their manufacture.
The invention is targeted at broadening the range of these sulphur products which are of advantage in various fields: optical materials, coatings and adhesives, and for which the mechanical properties can be varied as a function of the polythiol.
In particular, it is desired to produce, for optical applications, products which can be crosslinked by the radical route, in particular by the photochemical route, to give crosslinked materials with a high refractive index, by more specifically targeting, in this case, products having the highest possible sulphur content in order to further improve the refractive index of these materials.
Reaction products of polythiols and of unsaturated alicylic compounds having at least two unsaturations per molecule, at least one of them being a cyclic unsaturation, have been generally disclosed.
However, experiments carried out by the Applicant Company have allowed it to be found that:
the direct crosslinking of a mixture of polythiol and of vinylnorbornene is not always possible: the mixture of tri- or tetrathiols tested with vinylnorbornene was a two-phase mixture; the dithiols tested gave a homogeneous mixture with vinylnorbornene but the addition of a photoinitiator did not make possible crosslinking under UV;
the reaction by the thermal route of a polythiol and of dicyclopentadiene with one thiol group per mole of dicyclopentadiene results in a product which does not crosslink under UV with a polythiol as crosslinking agent.
It is under these circumstances that the Applicant Company has discovered that, surprisingly, a specific family of compounds, namely substituted norbornenes comprising an exocyclic unsaturation, gives with polythiols, under stoichiometric conditions of one or of approximately one thiol group per one mole of the norbornene in question, addition products which can subsequently be crosslinked under UV and generally by the radical route in the presence of at least one polythiol.
It is thus possible to prepare materials with a high sulphur content, corresponding to the targeted objectives, by first preparing a liquid crosslinkable sulphur product (P) which will constitute the starting material for the formulation of a product (P) or of a composition which can be crosslinked in the desired form: film or moulded item. The said sulphur product (P) does not exhibit the disadvantages of the polythiols and of the norbornene derivatives from which it is obtained, which products are volatile, have an unpleasant smell and are toxic. The formulator of the product (P′) or of the crosslinkable composition will then handle products which are nontoxic and odourless or with a very slight smell.
A first subject-matter of the present invention is therefore a sulphur product obtained by the addition reaction of at least one polythiol (I)
(A) with at least one compound of formula (II):
in which R
1
represents a linear or branched aliphatic residue comprising an ethylenic unsaturation double bond, it being possible for the latter to be that by which R
1
is connected to the norbornene ring, it also being possible for the said ring to comprise other substituents chosen from C
1
-C
3
alkyl groups, in proportions corresponding or substantially corresponding to one thiol group of the polythiol or polythiols (I) per mole of the compound or compounds (II), the thiol groups of the compound or compounds (I) adding predominantly to the cyclic double bond of the compound or compounds (II) and, on average, one ethylenic unsaturation of a compound (II) of the two which it carries remaining free; or
(B) with at least one crosslinkable product (P), such as obtained in accordance with point (A) above, the double bonds of the said product (P) having been completely or substantially completely consumed, the product (P′) obtained being a crosslinked product.
The polythiol or polythiols (I) which have been used to form the crosslinked product (P′) are not necessarily the same as those which have been used to form the crosslinkable product (P).
The crosslinked product (P′) is obtained with a polythiol (I) with an SH functionality of at least 2 in the case where the crosslinkable product (P) has a functionality of ethylenic unsaturations of at least 3 and with a polythiol (I) with an SH functionality of at least 3 in the case where the crosslinkable product (P) has a functionality of ethylenic unsaturations of at least 2. In the case where mixtures of polythiols are used for the crosslinking, their mean SH functionality will be at least 2.
The compound of formula (II) is in particular 5-vinyl-2-norbornene (5-vinylbicyclo[2.2.1]hept-2-ene) or 5-ethylidene-2-norbornene (5-ethylidenebicyclo[2.2.1]hept-2-ene).
The polythiols (I) are chosen in particular from the compounds of formula R
2
—[—SH]
n
, in which:
R
2
is an n-valent aliphatic, aromatic or heterocyclic radical or an n-valent radical comprising a combination of these, it being possible for R
2
to comprise substituents, it being possible for the backbone or the substituents to be interrupted by at least one heteroatom chosen from —O— or —S— and/or one group chosen from
n is an integer from 2 to 6.
The polythiols (I) can be polythiols obtained by addition of a polythiol of formula R
2
—[—SH]
n
, in which R
2
and n are as defined above, to a compound of formula (II) as defined above, with an excess of thiol and under addition conditions which prevent crosslinking, on the basis of the Makosco-Miller relationship (Macromolecules, 1976, volume 9, pages 199-211).
Examples of polythiols comprise:
(1) aliphatic polythiols, such as methanedithiol, 1,2-ethanedithiol, 1,1-propanedithiol, 1,3-propanedithiol, 2,2-propanedithiol, 1,6-hexanedithiol, 1,2,3-propanetrithiol, 1,1-cyclohexanedithiol, 1,2-cyclohexanedithiol, 2,2-dimethylpropane-1,3-dithiol, 3,4-dimethoxybutene-1,2-dithiol, bicyclo[2.2.1]-heptane-exo-cis-2,3-dithiol, 1,1-bis(mercaptomethyl)cyclohexane, thiomalic acid bis(2-mercaptoethyl ester), 2,3-dimercaptosuccinic acid 2-mercaptoethyl ester, 2,3-dimercapto-1-propanol 2-mercaptoacetate, 2,3-dimercapto-1-propanol 3-mercaptopropionate, diethylene glycol bis(2-mercaptoacetate), diethylene glycol bis(3-mercaptopropionate), 1,2-dimercaptopropyl methyl ether, 2,3-dimercaptopropyl methyl ether, 2,2-bis(mercaptomethyl)-1,3-propanedithiol, bis(2-mercaptoethyl) ether, ethylene glycol bis(2-mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), trimethylolpropane tris(3-mercaptopropionate), trimethylolpropane tris(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), polyethylene glycol dimercaptoacetates and polyethylene glycol di(mercaptopropionates), and these same compounds substituted by halogen, such as chlorine and bromine;
(2) aromatic polythiols, such as 1,2-dimercaptobenzene, 4-t-butyl-1,2-benzenedithiol, 1,3-dimercaptobenzene, 1,4-dimercaptobenzene, 1,2-bis(mercaptomethyl)benzene, 1,3-bis(mercaptomethyl)benzene, 1,4-bis(mercaptomethyl)benzene, 1,2-bis(mercaptoethyl)benzene, 1,3-bis(mercaptoethyl)benzene, 1,4-bis(mercaptoethyl)benzene, 1,2-bis(mercaptomethyleneoxy)benzene, 1,3-bis(mercaptomethyleneoxy)benzene, 1,4-bis(mercaptomethyleneoxy)benzene, 1,2-bis(mercaptoethyleneoxy)benzene, 1,3-bis(mercaptoethyleneoxy)benzene, 1,4-bis(mercaptoethyleneoxy)benzene, 1,2,3-trimercaptobenzene, 1,2,4-trimercaptobenzene, 1,3,5-trimercaptobenzene, 1,2,3-tris(mercaptomethyl)benzene, 1,2,4-tris(mercaptomethyl)benzene, 1,3,5-tris(mercaptomethyl)benzene, 1,2,3-tris(mercaptoethyl)benzene, 1,2,4-tris(mercaptoethyl)benzene, 1,3,5-tris(mercaptoethyl)benzene, 1,2,3-tris(me

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