Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
301 words
A method for manufacturing a heat insulating pipe comprising a pipe having a foamed insulating layer around the outer surface of said pipe, said foamed insulating layer having an expansion ratio of at least 4 and comprising three integrally formed sub-layers, said sub-layers including a cellular middle foamed sub-layer which is integral with a cellular inner foamed sub-layer and a cellular outer foamed sub-layer, said inner and outer sub-layer being on opposite sides of said middle sub-layer, said cellular inner foamed sub-layer being the innermost sub-layer with respect to said pipe and surrounding the outer surface of said pipe, the cells of said inner and outer cellular sub-layers being smaller than the cells of said middle cellular sub-layer, the ratio μ 1 /μ 2 of the cell dimensions of said cellular middle sub-layer being between 0.3 and 0.9, wherein μ 1 is the average cell dimension measured in the radial direction of said pipe and μ 2 is the average cell dimension measured in the axial direction of said pipe; the method for producing said 3 sub-layered foamed insulating layer comprising: passing a pipe heated to a temperature of between 60° C. and 120° C. through the nipple of a cross-head die and simultaneously extruding a mixture of a propylene-ethylene block polymer having an ethylene content of between 1 and 20% by weight and a Melt Index of between 0.1 and 4 together with a foaming agent over the outer surface of said pipe to cause said mixture to expand and form said 3 sub-layered foamed insulating layer on said pipe, the relationship between the overall thickness t of the 3 sub-layered foamed insulating layer, the expansion ratio M of the 3 sub-layered foamed insulating layer, and the die-nipple distance d of the cross-head die being ##EQU3## wherein K=0.75 to 0.20.
Claim 2
Independent Claim
301 words
A method for manufacturing a heat insulating pipe comprising a pipe having a foamed insulating layer around the outer surface of said pipe, said foamed insulating layer having an expansion ratio of at least 4 and comprising three integrally formed sub-layers, said sub-layers including a cellular middle foamed sub-layer which is integral with a cellular inner foamed sub-layer and a cellular outer foamed sub-layer, said inner and outer sub-layer being on opposite sides of said middle sub-layer, said cellular inner foamed sub-layer being the innermost sub-layer with respect to said pipe and surrounding the outer surface of said pipe, the cells of said inner and outer cellular sub-layers being smaller than the cells of said middle cellular sub-layer, the ratio μ 1 /μ 2 of the cell dimensions of said cellular middle sub-layer being between 0.3 and 0.9, wherein μ 1 is the average cell dimension measured in the radial direction of said pipe and μ 2 is the average cell dimension measured in the axial direction of said pipe; the method for producing said 3 sub-layered foamed insulating layer comprising: passing a pipe heated to a temperature of between 60° C. and 120° C. through the nipple of a cross-head die and simultaneously extruding a mixture of a propylene-ethylene block polymer having an ethylene content of between 1 and 20% by weight and a Melt Index of between 0.1 and 4 together with a foaming agent over the outer surface of said pipe to cause said mixture to expand and form said 3 sub-layered foamed insulating layer on said pipe, the relationship between the overall thickness t of the 3 sub-layered foamed insulating layer, the expansion ratio M of the 3 sub-layered foamed insulating layer, and the die-nipple distance d of the cross-head die being ##EQU3## wherein K=0.75 to 0.20.
Claim 3
Dependent Claim
9 words
The method of claim 1 wherein K is 0.3-0.4.
Claim 4
Dependent Claim
27 words
The method of claim 1 or 2 wherein said propylene-ethylene block copolymer is a powder having a Melt Index of 0.1-2 and an ethylene content of 7-20%.
Claim 5
Dependent Claim
22 words
The method of claim 3 wherein said propylene-ethylene block copolymer has admixed therewith up to 40% by weight of an ethylene-propylene rubber.
Claim 6
Dependent Claim
24 words
The method of claim 1 or 2 wherein said propylene-ethylene block copolymer has admixed therewith up to 40% by weight of an ethylene-propylene rubber.
Claim 7
Dependent Claim
19 words
The method of claim 1 wherein said foaming agent has a decomposition temperature of between 120° and 170° C.
Claim 8
Dependent Claim
19 words
The method of claim 4 wherein said foaming agent has a decomposition temperature of between 120° and 170° C.
Claim 9
Dependent Claim
20 words
The method of claim 1 or 2 wherein said pipe is a copper pipe which has been precoated with resin.
Claim 10
Dependent Claim
31 words
The method of claim 6 wherein said pipe is a copper pipe which has been precoated with resin applied from an aqueous resin-containing emulsion or an aqueous-containing solution and then baked.
Claim 11
Dependent Claim
20 words
The method of claim 1 wherein said middle sub-layer comprises 40-90% of the total thickness of said formed insulated layer.