Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1997-01-30
1998-05-26
Nagumo, Mark
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525197, 525209, 525222, 525227, 525288, C08J 324
Patent
active
057565821
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates, in the silane-crosslinking of polyolefins, a process of silane-crosslinking for producing a silane-crosslinked polyolefin in one step which uses a carrier polymer A containing an organic unsaturated silane and the like in a high concentration and a carrier polymer B containing a silanol condensation catalyst and the like.
BACKGROUND ART
A simple method which has been widely known for crosslinking polyolefins is the so-called silane crosslinking method which comprises grafting an organic unsaturated silane to the polyolefin in the presence of a free radical generating agent to effect silane grafting, and then contacting the resulting silane-grafted polymer with water in the presence of a silanol condensation catalyst to effect crosslinking. This method is disclosed, for example, in JP-B-48-1711 and JP-A-57-49109.
However, this method comprises at least two steps, that is, the silane grafting step and the silanol condensation step. Accordingly, at least two extrusion steps are necessary to obtain the ultimate product, inevitably resulting in economical disadvantage.
An already known one-step process is the monosil process. This process requires a liquid addition apparatus for injecting an organic unsaturated silane in the form of liquid into an extruder, and hence involves the problems of slippage and metering error. Moreover, the process requires an expensive special type extruder with a high L/D ratio to insure uniform dispersion of small amounts of additives, resulting in economical disadvantage. Furthermore, a very high grade technique is necessary in the extrusion.
Another known one-step process is a silane crosslinking method which introduces silane into a solid carrier polymer disclosed in JP-A-3-167229. In this method, however, a porous polymer or EVA is used as the solid carrier polymer and, in addition to silane and a free radical generating agent, such other additives as a silanol condensation catalyst and an antioxidant are introduced to the solid carrier polymer; hence the method involves the problems of low crosslinking efficiency and poor storability caused by oligomerization by condensation of silane or inhibition of crosslinking due to radical capture.
The present invention has been made to overcome the aforesaid problems and has for its object to provide, in the silane-crosslinking of polyolefins, a process of silane-crosslinking for producing a silane-crosslinked polyolefin in one step which uses a carrier polymer A containing an organic unsaturated silane and the like in high concentrations and a carrier polymer B containing a silanol condensation catalyst and the like.
DISCLOSURE OF THE INVENTION
The present invention relates to a process for producing a silane-crosslinked polyolefin which is characterized by melt-blending (i) a polyolefinic base polymer, (ii) a carrier polymer A containing an organic unsaturated silane represented by the formula RR'SiY.sub.2, wherein R is a monovalent olefinic unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R' is a monovalent hydrocarbon group other than aliphatic unsaturated hydrocarbon groups or is the same group as Y, and a free radical generating agent and containing substantially no water and (iii) a carrier polymer B containing a silanol condensation catalyst and an antioxidant, at a temperature higher than the crystal melting point of the base polymer to effect reaction, and then contacting the resulting reaction product with water to effect crosslinking. In this process for producing a silane-crosslinked polyolefin, the base polymer is preferably a polymer selected from the group consisting of polyethylene, polypropylene, copolymer of ethylene and an .alpha.-olefin, ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-vinyl acetate copolymer (EVA), chlorinated polyethylene (CPE), and the mixtures thereof; the carrier polymer A is preferably a polymer selected from the group consisting of ethylene-ethyl acrylate copolymer (EEA),
REFERENCES:
patent: 4707517 (1987-11-01), Bullen et al.
patent: 4783511 (1988-11-01), Schmid
patent: 5112919 (1992-05-01), Furrer et al.
Nagumo Mark
Sumitomo Bakelite Company Limited
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