CA1109619A - Method of making lightweight, rigid thermoplastic pipe - Google Patents
Method of making lightweight, rigid thermoplastic pipeInfo
- Publication number
- CA1109619A CA1109619A CA302,380A CA302380A CA1109619A CA 1109619 A CA1109619 A CA 1109619A CA 302380 A CA302380 A CA 302380A CA 1109619 A CA1109619 A CA 1109619A
- Authority
- CA
- Canada
- Prior art keywords
- pipe
- thermoplastic material
- interior
- thermoplastic
- extruder
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/20—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length
- B29C44/22—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles for articles of indefinite length consisting of at least two parts of chemically or physically different materials, e.g. having different densities
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
- B29C48/09—Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
- B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
- B29C48/21—Articles comprising two or more components, e.g. co-extruded layers the components being layers the layers being joined at their surfaces
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/30—Extrusion nozzles or dies
- B29C48/32—Extrusion nozzles or dies with annular openings, e.g. for forming tubular articles
- B29C48/335—Multiple annular extrusion nozzles in coaxial arrangement, e.g. for making multi-layered tubular articles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
- B29C48/25—Component parts, details or accessories; Auxiliary operations
- B29C48/30—Extrusion nozzles or dies
- B29C48/32—Extrusion nozzles or dies with annular openings, e.g. for forming tubular articles
- B29C48/335—Multiple annular extrusion nozzles in coaxial arrangement, e.g. for making multi-layered tubular articles
- B29C48/337—Multiple annular extrusion nozzles in coaxial arrangement, e.g. for making multi-layered tubular articles the components merging at a common location
- B29C48/338—Multiple annular extrusion nozzles in coaxial arrangement, e.g. for making multi-layered tubular articles the components merging at a common location using a die with concentric parts, e.g. rings, cylinders
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- F16L9/00—Rigid pipes
- F16L9/12—Rigid pipes of plastics with or without reinforcement
- F16L9/121—Rigid pipes of plastics with or without reinforcement with three layers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- General Engineering & Computer Science (AREA)
- Extrusion Moulding Of Plastics Or The Like (AREA)
- Molding Of Porous Articles (AREA)
Abstract
ABSTRACT
Disclosed is a method of making a lightweight, rigid thermoplastic pipe having solid interior and exterior surfaces and a foamed interior, comprising heating a first thermoplastic material in a first extruder, heating a second thermoplastic material containing a heat decomposable chemical foaming agent in a second extruder to a temperature of about at least 400°F, feeding said first thermoplastic material and said second thermoplastic material simultaneously and respectively to multiple and separate passages of a pipe shaping tool, dividing said first thermoplastic material into two streams to form the interior and exterior surfaces of the pipe, the chemical foaming agent of said second thermo-plastic material decomposing as a result of said heating step but said second thermoplastic material remaining in a foam-able but unfoamed state due to pressures within said second extruder and the pipe shaping tool until the pressure is reduced as the second thermoplastic material leaves said tool, whereby the solid interior and exterior surfaces of the pipe and the foamed interior thereof are formed simultaneously.
Exemplified is the manufacture of graft ABS pipe having solid interior and exterior surfaces and a foamed interior.
Disclosed is a method of making a lightweight, rigid thermoplastic pipe having solid interior and exterior surfaces and a foamed interior, comprising heating a first thermoplastic material in a first extruder, heating a second thermoplastic material containing a heat decomposable chemical foaming agent in a second extruder to a temperature of about at least 400°F, feeding said first thermoplastic material and said second thermoplastic material simultaneously and respectively to multiple and separate passages of a pipe shaping tool, dividing said first thermoplastic material into two streams to form the interior and exterior surfaces of the pipe, the chemical foaming agent of said second thermo-plastic material decomposing as a result of said heating step but said second thermoplastic material remaining in a foam-able but unfoamed state due to pressures within said second extruder and the pipe shaping tool until the pressure is reduced as the second thermoplastic material leaves said tool, whereby the solid interior and exterior surfaces of the pipe and the foamed interior thereof are formed simultaneously.
Exemplified is the manufacture of graft ABS pipe having solid interior and exterior surfaces and a foamed interior.
Description
~ 076091-M
\
~1~6~9 The present invention relates to a method of making lightweight, rigid thermoplastic pipe and tubing and the product made thereby. Thermoplastic pipe made of solid plastics such as polyvinyl chloride (PVC) and graft acrylonitrile-butadiene-styrene (ABS) is sold in huge quantities for use in water supply, sanitary and storm pipes, as well as many other applications. One great advantage of the thermoplastic pipe is that it i5 lighter in weight than the pipe it usually replaces or displaces; another advantage is its ease of fabrication into fluid systems. Its structural integrity is good for many applications, but improvement is desired in other applications.
During the past twenty (20) years, thermoplastics containing a foaming agent have found acceptance in many industries, but the use of foamable thermoplastics for many pipe applications is limited due the fluid leakage problem with foamed thermoplastic pipe, or by costly and inefficient methods of making the pipe resistant to leakage. ~;
For many applications a desirable pipe is a smooth surfaced, fluid impervious pipe of a thickness to give it good structural integrity but light enoush to have the light-weight and ease of fabrication advantages of plastic pipe.
A simple, inexpensive and novel method of making such a ; pipe and the pipe made by such method is the subject matter of this invention.
' - . .
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The present inven~ion provides a method of making a lightweight, rigid thermoplastic pipe having solid interior and exterior surfaces and a foamed interior layer comprising heating a first thermoplastic material in a first extruder, heating a second thermoplastic material containing a heat decomposable chemical foaming agent in a second extruder to a temperature of about at least 400 F, feeding said first ; thermoplastic material and said second thermoplastic material simultaneously and respectively to multiple and separate .
passages of a pipe shaping tool, dividing said first thermo-plastic material into two streams to form the interior and exterior surfaces of the pipe, the chemical foaming agent ; of said second thermoplastic material decomposing as a result of said heating step but said second thermoplastic material ~ -remaining in a foamable but unfoamed state due to pressures within said second extruder and the pipe shaping tool until the pressure is reduced as the second thermoplastic material ~-leaves said tool, whereby the solid interior and exterior surfaces of the pipe and the foamed interior thereof are formed simultaneously.
The pipe made in accordance with the method of the pre~sent invention is alightweight, rigid pipe having solid thermoplastic exterior and interior surfaces and a foamed thermoplastic interior. The exterior and interior surfaces and the foamed interior are preferably of the same thermoplastic material. The foamed interior may, however, be of a different plastic provided it is compatible with the plastic used for the exterior and interior surfaces.
The pipe is made by extruding multiple layers of the thermoplastic material. The extruded outer and inner layers are made of solid plastic and comprise the exterior and interior of the pipe, and the extruded center layer is . ~ .
6 ~ ~
made of a foamable plastic, preferably the same as the outer and inner layers.
The thermoplastic utilized in making the pipe may be ABS, PVC, phenylene oxide polymer, polycarbonate, polyethylene, polypropylene, polystyrene, polybutylene or combinations thereof. The center layer of foamable thermoplastic contains a chemical foaming or blowing agent which is incorporated into the plastic prior to charging the plastic to the extruder. Suitable foaming agents are bicarbonate of soda and citric acid, azo-dicarbonamide and the N-nitroso compounds. Modern Plastics Encyclopedia, 1975-1976, at pages 127-129, discloses other ; chemical foaming agents which can be utilized in making foamed ~;~ thermoplastic materials.
The apparatus employed by carrying out the method of the present invention comprises a plurality of extruders, preferably two, connected to a single die having multiple passages for receiving and forming the plastic discharged by the extruders.
Brief Description of the Drawin~s ,~ .
- 20 A better understanding of the novel method of manufacturing the above-described pipe is disclosed in the drawings wherein:
FIGURE 1 is a sectional view of an extrusion die used in making the pipe; and FIGURE 2 is a cross-sectional view taken on the line 2-2 of FIGURE 1.
Disclosed in FIGURE 1 is a tool or die utilized for carrying out the method of the present invention and designated generally by the reference numeral 10. The tool 10 comprises an adapter member 11, a die plate 22 and a forming die 13. The adapter member 11 comprises a housing 11' having openings 14 and 15 which are attached respectively to the discharge end of two sd/ ~ -3~
screw extruders (not shown). An inlet plate 16 is provided in the housing 11' and contains an opening 17 and a diverter plug or mandrel 18. A plurality of passageways 19 are in communication with the openings 17 and 14.
The opening 15 in the housing 11' is in communication with a passageway 21 which in turn is in communication with passageways 22 and 23. The passageways 23 communicate with a manifold 24 which further communicates with passageways 2S pro- -~
vided in a flow restrictor 26. Passageway 22 is formed by a `10 bore in the housing 11' and a bore in a noz~le element 22'. A
restriction 26' is formed by the interior surface of the flow restrictor 26 and the exterior surface of the nozzle 22'.
The die plate 12 contains a mandrel or spreader 27 and a die orifice 28. The forming die contains a tubular passageway 29 and is heated and/or cooled by fluid passages 31 which are connected to a conventional heat exchanger (not shown).
In the utilization of the tool 10 to carry out the present invention to form the pipe 32 of FIGURE 2, which pipe has solid interior and exterior layers or surfaces 33, 34 and a foamed interior 35, thermoplastic material, which has been heated to its melt temperature in an extruder (not shown), enters the opening 15 and passes through the passageway 21 and to the passageways 22 and 23. A portion of the thermoplastic material passes through passageway 23 to the manifold 2~, thence through the passageways 25, through the restriction 25', the die orifice 28 and through the tubular passageway 29 of the forming die 29 to form the exterior surface of a pipe 32. At the same time, another portion of the thermoplastic material flows from passage-way 21 through passageway 22, by spreader 27, through the die orifice 28 and the passageway 29 of the forming die 13 to form the interior surface of a pipe.
Simultaneously, a foamable thermoplastic material is ~ ,.
~; `,~ ' :- ~
sd/ ~ - 4 -discharged from an extruder into the opening 14 and passes through the opening 17, past the diverter plug 18, through the passageways 19, through the restriction 26' and thence through the center of the die orifice 28 and the passageway 29 of the forming die 13, to form the internal core of the pipe 32.
Preferred Embodiment The preferred embodiment of the present invention is the manufacture of the pipe 32 made of a graft polymer of acry-lonitrile-butadiene-styrene (ABS) having interior and exterior solid layers or surfaces 33, 34 of ABS and an expanded ABS
interior 35. Molten ABS containing no foaming agent and at a temperature of 400F enters the opening 15 under pressure from an extruder and passes through the passageways 22 and 23 and their communicating passageways, through the die orifice 28 and forming orifice 29 to form the inner and outer surfaces 33, 34, respectively, of the pipe 32. The ABS is in pellet form and is a product prepared by polymerizing 25 parts by weight acryloni-trile and 45 parts by weight styrene in the presence of 30 parts by weight~of polybutadiene. A batch of the same ABS was made into a foamable compound by compounding therein 0.3 parts per hundred of azodicarbonamide at a temperature below the decomposition temperature (about 385F to about 400F) of the azodicarbonamide. The compounded, foamable ABS composition ;~
was then pelletized and charged to an extruder wherein it was heated progressively to a temperature of 400F. At this temperature, the composition was molten and the azodicarbonamide ~` had decomposed. The composition, however, had not completely "foamed" due to the inherent pressures in the extruder. The molten and foamable ABS enters the opening 14 of the adapter member 11 and passes, still under pressure, through the opening 17, the openings 19, the restriction 2~' and the center of the die orifice 28 to form the interior layer 35 of the pipe 32.
, "
", ,~
~ sd/ ~r5 -5-As the coextruded solid and foamable ABS leaves the die orifice 28, it enters the passageway 29 of the forming die where the interior layer of foamable ABS expands due to a reduction in pressure, thus forming the pipe 32 with its solid interior and exterior surfaces 33, 34 and its foamed interior 35.
While the preferred embodiment of the present invention has been described with respect to the manufacture of ABS pipe ; having a foamed interior, the invention is applicable to other thermoplastic materials such as PVC, phenylene oxide polymers, polycarbonates, polyethylenes, polypropylene, polystyrene and p~lybutylene. It is also contemplated that the foamed interior can be made of one thermoplastic material and the interior ~
and exterior surfaces of another thermoplastic material. -Azodicarbonamide was used in the preferred embodiment for foaming the interior ABS layer of the pipe. However, it is contemplated that other chemical foaming agents can be employed. Modern Plastics Encyclopedia, 1975-1976, at pages 127-129, discloses the use of azodicarbonamide as a foaming agent as well as many other chemical foaming agents suitable for use in carrying out the present invention.
Also, while a particular tool 10 has been described as one means for carrying out the present method, other tools as well as other feed means to the openings 14 and 15 can be ; employed.
X
s~ -6-
\
~1~6~9 The present invention relates to a method of making lightweight, rigid thermoplastic pipe and tubing and the product made thereby. Thermoplastic pipe made of solid plastics such as polyvinyl chloride (PVC) and graft acrylonitrile-butadiene-styrene (ABS) is sold in huge quantities for use in water supply, sanitary and storm pipes, as well as many other applications. One great advantage of the thermoplastic pipe is that it i5 lighter in weight than the pipe it usually replaces or displaces; another advantage is its ease of fabrication into fluid systems. Its structural integrity is good for many applications, but improvement is desired in other applications.
During the past twenty (20) years, thermoplastics containing a foaming agent have found acceptance in many industries, but the use of foamable thermoplastics for many pipe applications is limited due the fluid leakage problem with foamed thermoplastic pipe, or by costly and inefficient methods of making the pipe resistant to leakage. ~;
For many applications a desirable pipe is a smooth surfaced, fluid impervious pipe of a thickness to give it good structural integrity but light enoush to have the light-weight and ease of fabrication advantages of plastic pipe.
A simple, inexpensive and novel method of making such a ; pipe and the pipe made by such method is the subject matter of this invention.
' - . .
~i~9$~
The present inven~ion provides a method of making a lightweight, rigid thermoplastic pipe having solid interior and exterior surfaces and a foamed interior layer comprising heating a first thermoplastic material in a first extruder, heating a second thermoplastic material containing a heat decomposable chemical foaming agent in a second extruder to a temperature of about at least 400 F, feeding said first ; thermoplastic material and said second thermoplastic material simultaneously and respectively to multiple and separate .
passages of a pipe shaping tool, dividing said first thermo-plastic material into two streams to form the interior and exterior surfaces of the pipe, the chemical foaming agent ; of said second thermoplastic material decomposing as a result of said heating step but said second thermoplastic material ~ -remaining in a foamable but unfoamed state due to pressures within said second extruder and the pipe shaping tool until the pressure is reduced as the second thermoplastic material ~-leaves said tool, whereby the solid interior and exterior surfaces of the pipe and the foamed interior thereof are formed simultaneously.
The pipe made in accordance with the method of the pre~sent invention is alightweight, rigid pipe having solid thermoplastic exterior and interior surfaces and a foamed thermoplastic interior. The exterior and interior surfaces and the foamed interior are preferably of the same thermoplastic material. The foamed interior may, however, be of a different plastic provided it is compatible with the plastic used for the exterior and interior surfaces.
The pipe is made by extruding multiple layers of the thermoplastic material. The extruded outer and inner layers are made of solid plastic and comprise the exterior and interior of the pipe, and the extruded center layer is . ~ .
6 ~ ~
made of a foamable plastic, preferably the same as the outer and inner layers.
The thermoplastic utilized in making the pipe may be ABS, PVC, phenylene oxide polymer, polycarbonate, polyethylene, polypropylene, polystyrene, polybutylene or combinations thereof. The center layer of foamable thermoplastic contains a chemical foaming or blowing agent which is incorporated into the plastic prior to charging the plastic to the extruder. Suitable foaming agents are bicarbonate of soda and citric acid, azo-dicarbonamide and the N-nitroso compounds. Modern Plastics Encyclopedia, 1975-1976, at pages 127-129, discloses other ; chemical foaming agents which can be utilized in making foamed ~;~ thermoplastic materials.
The apparatus employed by carrying out the method of the present invention comprises a plurality of extruders, preferably two, connected to a single die having multiple passages for receiving and forming the plastic discharged by the extruders.
Brief Description of the Drawin~s ,~ .
- 20 A better understanding of the novel method of manufacturing the above-described pipe is disclosed in the drawings wherein:
FIGURE 1 is a sectional view of an extrusion die used in making the pipe; and FIGURE 2 is a cross-sectional view taken on the line 2-2 of FIGURE 1.
Disclosed in FIGURE 1 is a tool or die utilized for carrying out the method of the present invention and designated generally by the reference numeral 10. The tool 10 comprises an adapter member 11, a die plate 22 and a forming die 13. The adapter member 11 comprises a housing 11' having openings 14 and 15 which are attached respectively to the discharge end of two sd/ ~ -3~
screw extruders (not shown). An inlet plate 16 is provided in the housing 11' and contains an opening 17 and a diverter plug or mandrel 18. A plurality of passageways 19 are in communication with the openings 17 and 14.
The opening 15 in the housing 11' is in communication with a passageway 21 which in turn is in communication with passageways 22 and 23. The passageways 23 communicate with a manifold 24 which further communicates with passageways 2S pro- -~
vided in a flow restrictor 26. Passageway 22 is formed by a `10 bore in the housing 11' and a bore in a noz~le element 22'. A
restriction 26' is formed by the interior surface of the flow restrictor 26 and the exterior surface of the nozzle 22'.
The die plate 12 contains a mandrel or spreader 27 and a die orifice 28. The forming die contains a tubular passageway 29 and is heated and/or cooled by fluid passages 31 which are connected to a conventional heat exchanger (not shown).
In the utilization of the tool 10 to carry out the present invention to form the pipe 32 of FIGURE 2, which pipe has solid interior and exterior layers or surfaces 33, 34 and a foamed interior 35, thermoplastic material, which has been heated to its melt temperature in an extruder (not shown), enters the opening 15 and passes through the passageway 21 and to the passageways 22 and 23. A portion of the thermoplastic material passes through passageway 23 to the manifold 2~, thence through the passageways 25, through the restriction 25', the die orifice 28 and through the tubular passageway 29 of the forming die 29 to form the exterior surface of a pipe 32. At the same time, another portion of the thermoplastic material flows from passage-way 21 through passageway 22, by spreader 27, through the die orifice 28 and the passageway 29 of the forming die 13 to form the interior surface of a pipe.
Simultaneously, a foamable thermoplastic material is ~ ,.
~; `,~ ' :- ~
sd/ ~ - 4 -discharged from an extruder into the opening 14 and passes through the opening 17, past the diverter plug 18, through the passageways 19, through the restriction 26' and thence through the center of the die orifice 28 and the passageway 29 of the forming die 13, to form the internal core of the pipe 32.
Preferred Embodiment The preferred embodiment of the present invention is the manufacture of the pipe 32 made of a graft polymer of acry-lonitrile-butadiene-styrene (ABS) having interior and exterior solid layers or surfaces 33, 34 of ABS and an expanded ABS
interior 35. Molten ABS containing no foaming agent and at a temperature of 400F enters the opening 15 under pressure from an extruder and passes through the passageways 22 and 23 and their communicating passageways, through the die orifice 28 and forming orifice 29 to form the inner and outer surfaces 33, 34, respectively, of the pipe 32. The ABS is in pellet form and is a product prepared by polymerizing 25 parts by weight acryloni-trile and 45 parts by weight styrene in the presence of 30 parts by weight~of polybutadiene. A batch of the same ABS was made into a foamable compound by compounding therein 0.3 parts per hundred of azodicarbonamide at a temperature below the decomposition temperature (about 385F to about 400F) of the azodicarbonamide. The compounded, foamable ABS composition ;~
was then pelletized and charged to an extruder wherein it was heated progressively to a temperature of 400F. At this temperature, the composition was molten and the azodicarbonamide ~` had decomposed. The composition, however, had not completely "foamed" due to the inherent pressures in the extruder. The molten and foamable ABS enters the opening 14 of the adapter member 11 and passes, still under pressure, through the opening 17, the openings 19, the restriction 2~' and the center of the die orifice 28 to form the interior layer 35 of the pipe 32.
, "
", ,~
~ sd/ ~r5 -5-As the coextruded solid and foamable ABS leaves the die orifice 28, it enters the passageway 29 of the forming die where the interior layer of foamable ABS expands due to a reduction in pressure, thus forming the pipe 32 with its solid interior and exterior surfaces 33, 34 and its foamed interior 35.
While the preferred embodiment of the present invention has been described with respect to the manufacture of ABS pipe ; having a foamed interior, the invention is applicable to other thermoplastic materials such as PVC, phenylene oxide polymers, polycarbonates, polyethylenes, polypropylene, polystyrene and p~lybutylene. It is also contemplated that the foamed interior can be made of one thermoplastic material and the interior ~
and exterior surfaces of another thermoplastic material. -Azodicarbonamide was used in the preferred embodiment for foaming the interior ABS layer of the pipe. However, it is contemplated that other chemical foaming agents can be employed. Modern Plastics Encyclopedia, 1975-1976, at pages 127-129, discloses the use of azodicarbonamide as a foaming agent as well as many other chemical foaming agents suitable for use in carrying out the present invention.
Also, while a particular tool 10 has been described as one means for carrying out the present method, other tools as well as other feed means to the openings 14 and 15 can be ; employed.
X
s~ -6-
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of making a lightweight, rigid thermo-plastic pipe having solid interior and exterior surfaces and a foamed interior layer comprising heating a first thermo-plastic material in a first extruder, heating a second thermo-plastic material containing a heat decomposable chemical foaming agent in a second extruder to a temperature of about at least 400°F, feeding said first thermoplastic material and said second thermoplastic material simultaneously and respect-iyely to multiple and separate passages of a pipe shaping tool, dividing said first thermoplastic material into two streams to form the interior and exterior surfaces of the pipe, the chemical foaming agent of said second thermoplastic material decomposing as a result of said heating step but said second thermoplastic material remaining in a foamable but unfoamed state due to pressures within said second extruder and the pipe shaping tool until the pressure is reduced as the second thermoplastic material leaves said tool, whereby the solid interior and exterior surfaces of the pipe and the foamed interior thereof are formed simultaneously.
2. A method in accordance with claim 1 wherein the first thermoplastic material and the second thermoplastic material containing a foaming agent is a graft polymer of acrylonitrile, styrene and butadiene.
3. A thermoplastic pipe made in accordance with the method of claim 1.
4. A thermoplastic pipe made in accordance with the method of claim 2.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US79692177A | 1977-05-16 | 1977-05-16 | |
| US796,921 | 1977-05-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1109619A true CA1109619A (en) | 1981-09-29 |
Family
ID=25169403
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA302,380A Expired CA1109619A (en) | 1977-05-16 | 1978-05-01 | Method of making lightweight, rigid thermoplastic pipe |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS53141367A (en) |
| AU (1) | AU520032B2 (en) |
| CA (1) | CA1109619A (en) |
| DE (1) | DE2821333C2 (en) |
| FR (1) | FR2391058A1 (en) |
| GB (1) | GB1595128A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9963591B2 (en) | 2012-12-18 | 2018-05-08 | Ems-Patent Ag | Polyamide molding material and moldings manufactured from same |
Families Citing this family (21)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2455972A1 (en) * | 1979-05-10 | 1980-12-05 | Sogecan Ste Gle Canalisations | PROCESS AND APPARATUS FOR THE EXTRUSION OF PLASTIC TUBES WITH COMPOSITE WALLS |
| IT1126452B (en) * | 1979-11-30 | 1986-05-21 | Mario Calcagni | EXTRUSION HEAD FOR PROFILES FOR FIXTURES AND SIMILAR, AS WELL AS PROFILE OBTAINED |
| US4465449A (en) * | 1982-12-06 | 1984-08-14 | Borg-Warner Chemicals, Inc. | Coextrusion feedblock for making lightweight, rigid thermoplastic pipe |
| US4507071A (en) * | 1983-05-12 | 1985-03-26 | Cosden Technology, Inc. | Coextrusion apparatus for producing multiple layered thermoplastic pipe |
| US4499041A (en) * | 1983-05-23 | 1985-02-12 | Cosden Technology, Inc. | Coextrusion process for producing multiple layered thermoplastic pipe |
| FR2564375B1 (en) * | 1984-05-18 | 1987-03-06 | Eternit Financiere | PROCESS FOR THE MANUFACTURE OF LIGHTWEIGHT, RIGID TUBES IN THERMOPLASTIC MATERIAL |
| JPS6228222A (en) * | 1985-07-30 | 1987-02-06 | Sumitomo Chem Co Ltd | Manufacture of polypropylene-based resin expanded pipe |
| KR950005495Y1 (en) * | 1992-10-01 | 1995-07-12 | 신용구 | Double-walled pipe |
| DE9409077U1 (en) * | 1994-06-03 | 1994-08-11 | Augst, Reiner, 02689 Wehrsdorf | Floatable, swirlable carrier material for biotechnological processes |
| GB9505789D0 (en) * | 1995-03-22 | 1995-05-10 | Glynwed Steel Tubes Ltd | Plastics-coated tube |
| FI100130B (en) | 1995-12-12 | 1997-09-30 | Uponor Innovation Ab | Multilayer plastic pipe |
| US6073657A (en) | 1995-12-12 | 2000-06-13 | Uponor Innovation Ab | Method for producing homogeneous material with an extruder, an extruder, and a multilayer plastic pipe |
| DE29712989U1 (en) * | 1996-07-29 | 1997-10-02 | Poloplast Kunststoffwerk Gmbh & Co Kg, Leonding | Multi-layer pipe |
| NL1005371C2 (en) * | 1997-02-25 | 1998-08-26 | Wavin Bv | Multilayered pipe used in water disposal |
| US6183673B1 (en) * | 1998-04-24 | 2001-02-06 | Industrial Thermo Ploymers Limited | Method for forming extruded foam with surface coating |
| DE19920916A1 (en) | 1999-05-06 | 2000-11-16 | Basf Ag | Laminated sheet or film for refrigerators |
| DE202009007494U1 (en) | 2009-05-26 | 2009-09-17 | Dow Global Technologies, Inc., Midland | Multilayer thermoplastic sheet materials and thermoformed articles made therefrom |
| EP2499932B1 (en) * | 2011-03-17 | 2016-05-11 | EMS-Patent AG | Casing body |
| EP2666803B1 (en) | 2012-05-23 | 2018-09-05 | Ems-Patent Ag | Scratch-proof, transparent and ductile copolyamide moulding materials, moulded parts produced from same and use of same |
| EP2778190B1 (en) | 2013-03-15 | 2015-07-15 | Ems-Patent Ag | Polyamide moulding material and moulded body produced from the same |
| DE102013105749B4 (en) | 2013-06-04 | 2015-09-03 | W. Müller GmbH | Extrusion hose head for discontinuous foaming |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE600533A (en) * | 1960-02-24 | 1900-01-01 | ||
| US3561493A (en) * | 1965-04-21 | 1971-02-09 | Paul Maillard | Composite tubes and method of manufacturing same |
| DE6602679U (en) * | 1966-05-18 | 1969-06-26 | Ruetgerswerke Und Teerverwertung Ag | HEAT-INSULATED PIPES AND PIPE PARTS MADE OF PLASTICS |
| AT325299B (en) * | 1967-02-27 | 1975-10-10 | Hegler Wilhelm | DEVICE FOR MANUFACTURING TUBES FROM THERMOPLASTIC PLASTIC |
| GB1211860A (en) * | 1967-10-03 | 1970-11-11 | Ici Ltd | A process for the production of pipe |
| US3855376A (en) * | 1971-04-15 | 1974-12-17 | Mitsubishi Rayon Co | Process for making structural material having a foamed inner layer |
| DE2236375A1 (en) * | 1972-07-25 | 1974-02-07 | Technoform Caprano U Brunnhofe | Plastic pipes for hot water - with polyolefin inner layer and polyamide outer layer |
-
1978
- 1978-05-01 CA CA302,380A patent/CA1109619A/en not_active Expired
- 1978-05-04 AU AU35752/78A patent/AU520032B2/en not_active Expired
- 1978-05-11 FR FR7814036A patent/FR2391058A1/en active Granted
- 1978-05-15 JP JP5747278A patent/JPS53141367A/en active Granted
- 1978-05-16 DE DE2821333A patent/DE2821333C2/en not_active Expired
- 1978-05-16 GB GB19919/78A patent/GB1595128A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9963591B2 (en) | 2012-12-18 | 2018-05-08 | Ems-Patent Ag | Polyamide molding material and moldings manufactured from same |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6130892B2 (en) | 1986-07-16 |
| FR2391058B1 (en) | 1981-07-24 |
| FR2391058A1 (en) | 1978-12-15 |
| AU3575278A (en) | 1979-11-08 |
| JPS53141367A (en) | 1978-12-09 |
| DE2821333A1 (en) | 1978-11-30 |
| DE2821333C2 (en) | 1984-08-23 |
| GB1595128A (en) | 1981-08-05 |
| AU520032B2 (en) | 1982-01-14 |
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