Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1985-05-22
1986-05-27
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
264 53, 521 82, 521 86, 521 88, 521 92, 521 93, 521 96, 521143, 521154, 521910, C08J 912
Patent
active
045916063
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a cross-linked polyolefin foam which has been foamed with water and cross-linked by hydrolysing and condensing silyl groups on the polyolefin.
Cross-linked polyolefin foam is presently produced by using chemical foaming agents, such as azodiacarbonamide, which decompose on being heated and generate gaseous nitrogen. The cross-linking is usually achieved by the aid of a radical former, such as dicumylperoxide. The cross-linking reaction is also achieved with the aid of heat. Cross-linked polyethylene foam manufacturing processes have also been developed, but in their case cross-linking is accomplished with the aid of irradiation. The above-mentioned products have very low densities, for which reason no applications requiring strength and rigidity can be contemplated. When an organic peroxide is used as a cross-linking agent, control of the process is difficult because foaming and cross-linking process, are both temperature-dependent. Endeavours are, as a rule, to proceed so that when being foamed the polyethylene is partly cross-linked because in this way a more uniform foam is obtained. The above-mentioned processes require extra apparatus after the extruder for cross-linking and foaming.
Polyethylene is also cross-linked by grafting to it an unsaturated alkoxysilane and by hydrolysing and condensing silyl groups by treating the end product with hot water or steam, with the aid of a condensing catalyst. Nowadays, polyethylene that is cross-linkable in this way is available in the form of two mix components, one of them containing grafted alkoxysilane and the other containing condensation catalyst. These granulates are mixed prior to extrusion and the end product is cross-linked with hot water or steam in a separate process step. Also other silane cross-linking processes exist, which differ somewhat from the process just described. In one process, all raw materials are supplied directly into the extruder at the step in which the end product is being manufactured. A separate cross-linking step is required in this case too.
It is true that foam cross-linked with silane is being produced to some extent, but all these processes use azodicarbonamide as foaming agent, and cross-linking takes place by treating the end product with hot water or steam.
SUMMARY OF THE INVENTION
The invention concerns foamed polyolefin foam cross-linked with silane for which no cross-linking step performed afterwards is necessary. The silane-cross-linked polyolefin foam of the invention is characterised in that it contains 60-99.9% polyolefin, 0.1-10% chemically bound hydrolysed silane, 0-5% condensation catalyst, 0.1-5% water, and 0-20% water carrier substance.
The invention also concerns a new procedure for manufacturing foamed, silane-cross-linked polyolefin foam. The procedure of the invention is characterized in that for polyolefin to be extruded, polyethylene is used which contains, as foaming agent, 0.1-5% water, and 0-20% water carrier substance.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The polyolefin according to the invention to be foamed and cross-linked may be any polyolefin (LDPE, LLDPE, HDPE, PP, etc., or their copolymers or mixtures), and the foaming agent may be any water-containing substance which is miscible with and dispersible in molten polyolefin (a compound containing crystal water, such as CaSO.sub.4.H.sub.2 O, CaSO.sub.4.1/2H.sub.2 O and Al.sub.2 O.sub.3.3H.sub.2 O, or water-absorbing compound, such as CaCl.sub.2 and artificial silica, or a water-solving substance miscible with the polyolefin, such as ethylene glycol, propylene glycol, polyethylene glycol and polypropylene glycol). For silane any unsaturated hydrolysable silane which can be grafted to the polyolefin chain or copolymerised with the polyolefin by a radical reaction (by organic peroxide, electron irradiation or other means) may be used. Silyl peroxides may also be used towards this end.
The aim is, independent of the mode of adding foaming agent, silane or organic peroxide, that the
REFERENCES:
patent: 4160072 (1979-07-01), Shinkai et al.
patent: 4252906 (1981-02-01), Hosokawa et al.
patent: 4333898 (1982-06-01), Schmidtchen
patent: 4413066 (1983-11-01), Isaka et al.
patent: 4456704 (1984-06-01), Fukumura et al.
Chemical Abstracts, vol. 93 (1980), No. 240,562y, JP 8094940.
Foelak Morton
Neste Oy
LandOfFree
Polyolefin foam foamed with water and cross-linked with silane, does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyolefin foam foamed with water and cross-linked with silane, , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyolefin foam foamed with water and cross-linked with silane, will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1571305