Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1989-01-27
1990-09-25
Marquis, Melvyn I.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525105, 525106, C08F 800
Patent
active
049594133
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to crosslinkable organic polymers and to a process for preparing such polymers. More particularly the present invention is concerned with crosslinkable organic polymers comprising hydrolysable silane groups, which polymers can be thermoformed into shaped articles, for example cable insulation or pipe, and subsequently crosslinked by contacting the articles with water or steam in the presence of a so-called "silanol condensation catalyst". The invention further relates to a process for extruding articles from the crosslinkable polymers or from compositions based thereon.
It is known that organic polymers containing hydrolysable silane groups can be crosslinked by the action of water, preferably in the presence of a silanol condensation catalyst. A number of methods are known for producing such crosslinkable organic polymers. One method comprises copolymerising unsaturated organic monomers, for example, ethylenically unsaturated or vinyl monomers, with unsaturated silane compounds containing hydrolysable groups. Examples of this method are described in GB-A-No. 2028831 and GB-A-No. 2039513 which disclose the preparation of crosslinkable copolymers of ethylene and an ethylenically unsaturated silane compound by copolymerising the monomers at relatively high temperatures and pressures in the presence of a radical polymerisation initiator.
It is also well-known that polymers crosslinkable by the action of water and a silanol condensation catalyst can be prepared by grafting an unsaturated silane compound on to a preformed polymeric material. Grafting processes of this type can be carried out by heating together a base polymer, for example polyethylene, an unsaturated silane compound bearing one or more hydrolysable groups, a grafting initiator and optionally a silenol condensation catalyst, under conditions such that the unsaturated silane compound is grafted on to the base polymer. Examples of this method are disclosed in GB-A-No. 1357549, GB-A-No. 1234034 and GB-A-No. 1286460. An example of a commercial process which employs a grafting reaction of this type is the SIOPLAS (RTM) process. In this process, the base polymer is heated with the unsaturated silane in the presence of a grafting initiator and the product is extruded and pellated to produce a pellated silane-grafted thermoplastic polymer. The pellated polymer can then be fed with a silanol condensation catalyst to a thermoforming process for fabricating shaped products. These shaped products are then crosslinked by exposure to water or steam.
It is also known that water curable polymers can be prepared by reacting a polymer with an azidosilane. European patent application EP-A-No. 150 773 discloses a water curable Polymer of a hydrolysable, azide sulphonylsilane and a substantially linear, low pressure ethylene polymer having a density of about 0.85 to about 0.97. European patent application EP-A-No. 150774 discloses a water curable polymer of a hydrolysable, azide sulphonyl silane and an alkylene alkyl acrylate copolymer. British Pat. No. 1 377 737 discloses a process for preparing a crosslinked polyolefin which comprises exposing a polyolefin in contact with an organosilicon compound having an azidoformate group to ultra violet radiation and/or a temperature above 130.degree. C. and thereafter contacting the product with water in the presence of a metal carboxylate, a titanium ester or a titanium chelate.
A problem with water curable polymers produced using azide sulphonyl silane or an organosilicon compound having an azidoformate group is that the azidosulphonyl groups and azidoformate groups can undergo hydrolysis, splitting the hydrolysabls silane groups from the polymer backbone. Also, hydrolysable azido sulphonyl silanes are highly explosive and are therefore difficult to handle and to react with the polymer.
The present invention relates to crosslinkable polymers prepared by reacting a polymer with an azido silane which is free from azido sulphonyl groups and azido formate groups and overcomes or at least mitigates
REFERENCES:
patent: 3775386 (1973-11-01), Citron
patent: 4812519 (1989-03-01), Gillette
BP Chemicals Limited
Marquis Melvyn I.
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