WO1995004641A1 - Thermoplastic core and method of using - Google Patents
Thermoplastic core and method of using Download PDFInfo
- Publication number
- WO1995004641A1 WO1995004641A1 PCT/US1993/007291 US9307291W WO9504641A1 WO 1995004641 A1 WO1995004641 A1 WO 1995004641A1 US 9307291 W US9307291 W US 9307291W WO 9504641 A1 WO9504641 A1 WO 9504641A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- core
- thermoplastic
- magnetic
- plastic
- decoring
- 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.)
- Ceased
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
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
- B29C33/52—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles soluble or fusible
-
- 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
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/76—Cores
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2901/00—Use of unspecified macromolecular compounds as mould material
- B29K2901/12—Thermoplastic materials
Definitions
- Fusible core materials for producing a hollow plastic part must be strong, flowable, and light.
- the development work of synthetic plastic core has so far been unsuccessful because of the difficulty of decoring,i.e. , the plastic core material does not melt away easily and cleanly.
- the plastic materials are light but they flow under a shear force due to the high viscosity of polymer phase.
- the present invention intends to overcome the preceding decoring problem by generating a shear force via magnetic force such that a clean melt-out without any residual polymer materials on the inside wall surface can be achieved.
- the weight of fusible core materials is reduced by using thermoplastics as a matrix phase and, for the purpose of decoring or melt-out, magnetic materials selected from the group consisting of shots, particles, and short fibers are employed as reinforcing agent.
- the thermoplastic core is coated with a mold-release film prior to thermoset molding to improve the incompatibility between the thermoplastic core and thermoset mold.
- the thermoplastic core in the thermoset part is decored by heating, preferably by induction coil for efficiency. When a magnet is near the embedded core, magnetic reinforcing agents are pulled out of the hollow internal space by a magnetic force and flowable thermoplastic matrix resin is decored by shear force generated by reinforcing agents.
- Preferred magentic reinforcing agents are iron, steel, nickel, cobalt, their base alloys, ferrites, garnets, permalloy, mumetal, rare earth magnets, and any magnetic materials including any magnetic materials either coated or filled with magnetic materials.
- the method of magnetic decoring can be applied to fusible core alloys reinforced with magnetic shots, particles, or fibers.
- the weight reduction of fusible core materials is achieved by using plastics and strength is provided by reinforcing agents consisting of shots, particles, or fibers.
- the melting point of reinforcing agent must be higher than the thermoplastic matrix phase and the reinforcing material must be bondable to the polymer matrix phase.
- the reinforcing agent can be any strong magnetic materials,i.e. » metals, ceramics, polymers, or composites.
- the preferred magnetic materials are iron, steel, nickel, cobalt, their base magnetic alloys, ferrites, garnets, Alnico TM, platinum- cobalt, samarium-cobalt.
- Alnico is a magnetic alloy consisting of aluminum, nickel, and cobalt.
- Permalloy is a magnetic alloy consisting of nickel and iron.
- Supermalloy consists of nickel, molybdenum, iron, and manganese.
- Mumetal designates a magnetic alloy consisting of nickel, iron, copper, chromium, and manganese.
- strong plastics, metals, or ceramics can be coated with a magnetic film or filled with magnetic materials.
- thermoplastics are used as core and thermosets are preferably molded around the thermoplastic core .
- the decoring is done by heating the molded part with the core embedded and when the temperature reaches high enough for thermoplastics to be flowable , the elctromagnet is energized to magnetic reinforcing agents together with thermoplastics . Assistance can be given by hot air , fluids and/or vacuum.
- the decoring temperature is quite critical since it controls the polymer viscosity .
- the size of shots/particles is limited by the geometrical complexity of the desired parts,i.e., the finer the details, the smaller the size.
- the viscosity or flowability increases with the decrease of size and the strength rises with the shot/particle size decrease.
- there is an optimum size of shots, particles, or fibers considering viscosity, strength, and decoring behavior.
- thermosets are preferred as a molded part, although high melting/softening point thermoplastics can be used as a molding materials for final part as long as they are stable at decoring temperatures.
- the molded thermoplastic core surface is given a mold-release coating to enhance the clean decoring behavior.
- a silicon-based mold-release agent is useful in enhancing the incompatibility between thermosets and thermoplastic core. Any mold-release agent such as fluorocarbon-based or carbon-based one can be used if it improves the incompatibility between thermosets and thermoplastic core.
- the spherical shot is not the only geometry but also included are particles, short fibers, cubes, or any aggregates of random geometry.
- the reinforcing phase can even consist of a mixture of shots, particles, short fibers, cubes, and other aggregates. It may also consist of some of the above reinforcing agents.
- the amount of nonspherical reinforcing agents is desired to be small enough to maintain the good flowability and surface smoothness.
- the reinforcing agents are often given a special size coating to make them bondable to specific thermoplastic matrix phases.
- the amount of reinforcing agent is greater than about 10 % by volume for strength improvement and less than about 70 % by volume for moldability/flowability. For the purpose of decoring a large amount of magnetic reinforcing agent is desirable.
- the technique of magnetic decoring can be applied also to shot or particle-reinforced fusible alloys when the reinforcing shots, particles, or short fibers are magnetic such as steel, iron, nickel, cobalt, their base magnetic alloys, ferrite, garnets, ferrosilicon, alnico, mumetal. permalloy, or any other magnetic materials.
- an electromagnet is energized to attract magnetic shots/particles/fibers while the tin-based or bismuth-based matrix alloys are fused out in oil , for example.
- thermoplastic resins reinforced with 10 to 60 volume % steel shots or particles are molded as a core and then thermoset phenol resin or thermoset polyester is molded around the thermoplastic core.
- the decoring is done by heating the thermoplastic core by induction coil heating or comparable heating systems and a magnet is used to remove the softened/melted core.
- thermo ⁇ plastic resins are:
- Glass fiber-reinforced polyetheretherketone is molded around the shot-reinforced polyester thermoplastic core and then decored by a magnet at high temperatures below the softening point of polyetheretherketone but above the softening point of polyester.
- the shot content is 10 to 60 % by volume and the shot material is steel.
- Tin-based tin-bismuth alloy for example 90 wt.% tin-10 wt.% bismuth, reinforced with 30 wt.% steel shots is used as a core and thermoset is molded around this alloy core.
- the decoring is performed in oil using a magnet at about 200 to 230 degree C.
- Eutectic tin-bismuth alloy reinforced with 30 wt.% steel shots is used as a core and then a thermoplastic resin in molded around this core.
- the decoring is done in oil using a magnet at about 140 to 155 degree C.
- Tin-based tin-lead-antimony alloy reinforced with steel shots is also used as a core for thermoset molding and decored by a magnet.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
Thermoplastic solid or hollow cores reinforced with strong magnetic shots or/and particles are molded, and then thermosets are molded around such a thermoplastic core. The thermoplastic core is decored by a magnet at a high temperature above the softening point of thermoplastic matrix to produce a hollow curved internal space.
Description
Thermoplastic Core and Method of Using
Background Information
Fusible core materials for producing a hollow plastic part must be strong, flowable, and light. The development work of synthetic plastic core has so far been unsuccessful because of the difficulty of decoring,i.e. , the plastic core material does not melt away easily and cleanly. Generally the plastic materials are light but they flow under a shear force due to the high viscosity of polymer phase. The present invention intends to overcome the preceding decoring problem by generating a shear force via magnetic force such that a clean melt-out without any residual polymer materials on the inside wall surface can be achieved.
SUBSTITUTESHEET
Summary
The weight of fusible core materials is reduced by using thermoplastics as a matrix phase and, for the purpose of decoring or melt-out, magnetic materials selected from the group consisting of shots, particles, and short fibers are employed as reinforcing agent. The thermoplastic core is coated with a mold-release film prior to thermoset molding to improve the incompatibility between the thermoplastic core and thermoset mold. The thermoplastic core in the thermoset part is decored by heating, preferably by induction coil for efficiency. When a magnet is near the embedded core, magnetic reinforcing agents are pulled out of the hollow internal space by a magnetic force and flowable thermoplastic matrix resin is decored by shear force generated by reinforcing agents. Preferred magentic reinforcing agents are iron, steel, nickel, cobalt, their base alloys, ferrites, garnets, permalloy, mumetal, rare earth magnets, and any magnetic materials including any magnetic materials either coated or filled with magnetic materials. The method of magnetic decoring can be applied to fusible core alloys reinforced with magnetic shots, particles, or fibers.
SUBSTITUTE SHEET
Detailed Description of Preferred Embodiments
The weight reduction of fusible core materials is achieved by using plastics and strength is provided by reinforcing agents consisting of shots, particles, or fibers. The melting point of reinforcing agent must be higher than the thermoplastic matrix phase and the reinforcing material must be bondable to the polymer matrix phase. The reinforcing agent can be any strong magnetic materials,i.e. » metals, ceramics, polymers, or composites.
The preferred magnetic materials are iron, steel, nickel, cobalt, their base magnetic alloys, ferrites, garnets, Alnico TM, platinum- cobalt, samarium-cobalt. Permalloy TM, MumetalTM, SupermalloyTM, rare earth magnets, ferrosilicon, or any other magnetic materials.
The trademark Alnico is a magnetic alloy consisting of aluminum, nickel, and cobalt. Permalloy is a magnetic alloy consisting of nickel and iron. Supermalloy consists of nickel, molybdenum, iron, and manganese. Mumetal designates a magnetic alloy consisting of nickel, iron, copper, chromium, and manganese.
For instance, strong plastics, metals, or ceramics can be coated with a magnetic film or filled with magnetic materials.
SUBSTITUTESHEET
Since the core must be f usible , thermoplastics are used as core and thermosets are preferably molded around the thermoplastic core . The decoring is done by heating the molded part with the core embedded and when the temperature reaches high enough for thermoplastics to be flowable , the elctromagnet is energized to magnetic reinforcing agents together with thermoplastics . Assistance can be given by hot air , fluids and/or vacuum. The decoring temperature is quite critical since it controls the polymer viscosity . When shots, particles, or fibers are pulled by a magnet , a shear force is exerted on the softened/flowable polymer phase via shots , particles, or fibers.
SUBSTITUTE SHEET
A clean decoring having no residual polymer materials on the inside hollow wall surface requires a fairly high viscosity but not too high to impede the flowability through curved and complex geometry. Therefore, for each polymer type, there is an optimum decoring temperature range in terms of flowability and clean decoring.
The size of shots/particles is limited by the geometrical complexity of the desired parts,i.e., the finer the details, the smaller the size. The viscosity or flowability increases with the decrease of size and the strength rises with the shot/particle size decrease. Hence, there is an optimum size of shots, particles, or fibers considering viscosity, strength, and decoring behavior.
As the molded plastic part must be stable at decoring temperatures, thermosets are preferred as a molded part, although high melting/softening point thermoplastics can be used as a molding materials for final part as long as they are stable at decoring temperatures.
The molded thermoplastic core surface is given a mold-release coating to enhance the clean decoring behavior. For example, a silicon-based mold-release agent is useful in enhancing the incompatibility between thermosets and thermoplastic core. Any mold-release agent such as fluorocarbon-based or carbon-based one can be used if it improves the incompatibility between
SUBSTITUTE SHEET
thermoset mold and thermoplastic core.
As reinforcement, the spherical shot is not the only geometry but also included are particles, short fibers, cubes, or any aggregates of random geometry. The reinforcing phase can even consist of a mixture of shots, particles, short fibers, cubes, and other aggregates. It may also consist of some of the above reinforcing agents. The amount of nonspherical reinforcing agents is desired to be small enough to maintain the good flowability and surface smoothness. The reinforcing agents are often given a special size coating to make them bondable to specific thermoplastic matrix phases.
The amount of reinforcing agent is greater than about 10 % by volume for strength improvement and less than about 70 % by volume for moldability/flowability. For the purpose of decoring a large amount of magnetic reinforcing agent is desirable.
The technique of magnetic decoring can be applied also to shot or particle-reinforced fusible alloys when the reinforcing shots, particles, or short fibers are magnetic such as steel, iron, nickel, cobalt, their base magnetic alloys, ferrite, garnets, ferrosilicon, alnico, mumetal. permalloy, or any other magnetic materials. When the fusible alloys are melted, an electromagnet is energized to attract magnetic shots/particles/fibers while the tin-based or bismuth-based matrix alloys are fused out in oil , for example.
SUBSTITUTESHEET
Example 1
Thermoplastic resins reinforced with 10 to 60 volume % steel shots or particles are molded as a core and then thermoset phenol resin or thermoset polyester is molded around the thermoplastic core. The decoring is done by heating the thermoplastic core by induction coil heating or comparable heating systems and a magnet is used to remove the softened/melted core. The kinds of thermo¬ plastic resins are:
(1 ) Polycarbonate
(2) Polypropylene
(3) High density polyethylene
(4) Thermoplastic polyester
(5) ABS
(6) Acetal
(7) Nylon
(8) Polystyrene
Example 2
Glass fiber-reinforced polyetheretherketone is molded around the shot-reinforced polyester thermoplastic core and then decored by a magnet at high temperatures below the softening point of polyetheretherketone but above the softening point of polyester. The shot content is 10 to 60 % by volume and the shot material is steel.
SUBSTITUTE SHEET
Example 3
Tin-based tin-bismuth alloy, for example 90 wt.% tin-10 wt.% bismuth, reinforced with 30 wt.% steel shots is used as a core and thermoset is molded around this alloy core. The decoring is performed in oil using a magnet at about 200 to 230 degree C. Eutectic tin-bismuth alloy reinforced with 30 wt.% steel shots is used as a core and then a thermoplastic resin in molded around this core. The decoring is done in oil using a magnet at about 140 to 155 degree C. Tin-based tin-lead-antimony alloy reinforced with steel shots is also used as a core for thermoset molding and decored by a magnet.
SUBSTITUTESHEET
Claims
1. A method of molding an internally hollow plastic article using a thermoplastic core, said method comprising the steps of: molding a thermoplastic core to produce a hollow internal space in a plastic molded part, said core consisting essentially of a thermoplastic matrix phase and reinforcing magnetic agents, overmolding a plastic around said core, and decoring said thermoplastic core by a magnet at temperatures higher than the softening point of said thermoplastic core.
2. A method according to claim 1, wherein said reinforcing magnetic agents are selected from the group consisting of iron, steel, nickel, cobalt, their base magnetic alloys, ferrites, garnets, rare earth magnets, ceramics coated or filled with magnetic materials, plastics coated or filled with magnetic materials, metals coated or filled with magnetic materials, and composites coated or filled with magnetic materials.
3. A method according to claim 1, wherein the content of said magnetic agents is less than about 70 volume % for flowability and greater than about 10 volume % for strength improvement.
4. A method according to claim 1, wherein the geometry of said magnetic agents is spherical.
5. A method according to claim 1, which comprises heating the overmolded plastic to the softening temperature of the core and using an electromagnet or a permanent magnet to pull the core out of the overmolded plastic wherein said overmolded plastic is a thermoset or thermoplastic.
SUBSTITUTESHEET
6. A method according to claim 1, wherein said thermoplastic core.is given a mold-release coating enhancing the incompatibility between the overmolded part and the thermoplastic core, said mold- release coating being selected from the group consisting of silicon -based, fluorocarbon-based, and zinc stearate-based materials.
7. A thermoplastic core capable of producing a hollow internal space in a plastic body molded around said core, said core being capable of being melted out or decored at temperatures which do not damage said body.
8. The core of claim 7 in which the decoring or melt-out of the core is assisted by magnetic means acting on magnetic reinforcing particles bonded in said core.
9. The core of claim 7 in which the decoring or melt-out of the core is assisted by electromagnetic induction heating or thermal heating of core during decoring.
10. A method according to claim 1, wherein the geometry of said magnetic agents is nonspherical.
11. A method according to claim 1 , wherein said magnetic agents consist of a major amount of spherical shots and a minor amount of nonspherical agents selected from the group comprised of particles, short fibers, platelets, cubes, and irregular shape aggregates.
12. A fusible thermoplastic core for use with lost core plastic molding technology, said core consisting essentially of a thermoplastic matrix phase and reinforcing magnetic shots of spherical shape, said core being overmolded with a thermoset or a thermoplastic, and said core is capable of being decored by a
SUBSTITUTESHEET magnet at temperatures higher than the softening point of said thermoplastic core.
13. The core of claim 7 which has its melt out improved by a coating of mold release which has been applied to said core before said plastic body is molded around said core.
14. The core of claim 7, wherein the core itself is hollow.
SUBSTITUTE SHEET
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/435,621 US5244747A (en) | 1989-11-13 | 1989-11-13 | Thermoplastic core and method of using |
| PCT/US1993/007291 WO1995004641A1 (en) | 1989-11-13 | 1993-08-04 | Thermoplastic core and method of using |
| AU48004/93A AU4800493A (en) | 1989-11-13 | 1993-08-04 | Thermoplastic core and method of using |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/435,621 US5244747A (en) | 1989-11-13 | 1989-11-13 | Thermoplastic core and method of using |
| PCT/US1993/007291 WO1995004641A1 (en) | 1989-11-13 | 1993-08-04 | Thermoplastic core and method of using |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1995004641A1 true WO1995004641A1 (en) | 1995-02-16 |
Family
ID=26786931
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US1993/007291 Ceased WO1995004641A1 (en) | 1989-11-13 | 1993-08-04 | Thermoplastic core and method of using |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO1995004641A1 (en) |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1604528A1 (en) * | 1966-06-16 | 1970-11-12 | Bayer Ag | Mold core for the production of all types of hollow bodies |
| DE2417691A1 (en) * | 1974-04-11 | 1975-10-23 | Phoenix Gummiwerke Ag | MOLD FOR MANUFACTURING TIRES |
| US4464324A (en) * | 1981-09-21 | 1984-08-07 | Ozen | Apparatus and method for injection moulding of plastic parts of irregular shape, hollow or undercut form |
| WO1989011551A1 (en) * | 1988-05-23 | 1989-11-30 | Yoon Technology | Fabrication of fusible core alloy composites for plastics molding |
| JPH0262207A (en) * | 1988-08-30 | 1990-03-02 | Ube Ind Ltd | Resin molding method using core |
| JPH02301408A (en) * | 1989-05-17 | 1990-12-13 | Nissan Motor Co Ltd | Removing method for metal core |
| WO1992003895A1 (en) * | 1988-11-08 | 1992-03-05 | Electrovert Ltd. | Flux control for induction heating of melt-out cores |
| JPH04282207A (en) * | 1991-03-08 | 1992-10-07 | Calsonic Corp | Manufacture of hollow body of synthetic resin |
-
1993
- 1993-08-04 WO PCT/US1993/007291 patent/WO1995004641A1/en not_active Ceased
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1604528A1 (en) * | 1966-06-16 | 1970-11-12 | Bayer Ag | Mold core for the production of all types of hollow bodies |
| DE2417691A1 (en) * | 1974-04-11 | 1975-10-23 | Phoenix Gummiwerke Ag | MOLD FOR MANUFACTURING TIRES |
| US4464324A (en) * | 1981-09-21 | 1984-08-07 | Ozen | Apparatus and method for injection moulding of plastic parts of irregular shape, hollow or undercut form |
| WO1989011551A1 (en) * | 1988-05-23 | 1989-11-30 | Yoon Technology | Fabrication of fusible core alloy composites for plastics molding |
| JPH0262207A (en) * | 1988-08-30 | 1990-03-02 | Ube Ind Ltd | Resin molding method using core |
| WO1992003895A1 (en) * | 1988-11-08 | 1992-03-05 | Electrovert Ltd. | Flux control for induction heating of melt-out cores |
| JPH02301408A (en) * | 1989-05-17 | 1990-12-13 | Nissan Motor Co Ltd | Removing method for metal core |
| JPH04282207A (en) * | 1991-03-08 | 1992-10-07 | Calsonic Corp | Manufacture of hollow body of synthetic resin |
Non-Patent Citations (3)
| Title |
|---|
| DATABASE WPI Week 9247, Derwent World Patents Index; AN 92-384830 * |
| PATENT ABSTRACTS OF JAPAN vol. 14, no. 235 (M - 975)<4178> 18 May 1990 (1990-05-18) * |
| PATENT ABSTRACTS OF JAPAN vol. 15, no. 81 (M - 1086) 25 February 1990 (1990-02-25) * |
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