IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0165915
(2011-06-22)
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등록번호 |
US-8721951
(2014-05-13)
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발명자
/ 주소 |
- Spence, Alvin G.
- Knepper, Jeremy R.
- Grimes, Daniel D.
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출원인 / 주소 |
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
2 인용 특허 :
14 |
초록
▼
A method to form a multiple walled enclosure with low permeation properties and rugged impact resistance useful as a fuel tank or chemical container. The enclosure is made by rotomolding a first charge of thermosetting polymer into an outer layer, then rotomolding a charge of EVOH or other low perme
A method to form a multiple walled enclosure with low permeation properties and rugged impact resistance useful as a fuel tank or chemical container. The enclosure is made by rotomolding a first charge of thermosetting polymer into an outer layer, then rotomolding a charge of EVOH or other low permeation thermoplastic into a second layer, then rotomolding a second charge of thermosetting polymer into a third layer so that the low permeation thermoplastic layer is fully enclosed by layers of thermoset polymer. The preferred thermosetting polymer is crosslinkable polyethylene and the preferred low permeation thermoplastic is EVOH.
대표청구항
▼
1. A method to form a seamless hollow enclosure by rotomolding, including the following steps, in sequence: introducing a first charge of thermosetting polymer resin into an enclosing mold, the thermosetting polymer resin characterized by offgassing during thermal crosslinking;heating the mold, whil
1. A method to form a seamless hollow enclosure by rotomolding, including the following steps, in sequence: introducing a first charge of thermosetting polymer resin into an enclosing mold, the thermosetting polymer resin characterized by offgassing during thermal crosslinking;heating the mold, while rotating the mold about at least two axes, sufficiently to flow the first charge of thermosetting polymer resin but not sufficiently high to thermally crosslink the first charge of thermosetting polymer resin, the first charge of thermosetting polymer resin flowing onto an interior of the enclosing mold and forming a first layer defined by the interior of the enclosing mold;introducing a low permeation thermoplastic resin into the enclosing mold before the first layer has substantially thermally crosslinked;heating the mold sufficiently to flow the low permeation thermoplastic resin onto an internal surface of the first layer while rotating the mold about at least two axes, the low permeation thermoplastic resin forming a second layer;introducing a second charge of thermosetting polymer resin into the mold;heating the mold sufficiently to flow the second thermosetting polymer to form a third layer on an internal surface of the second layer while rotating the mold about at least two axes;continuing to rotate the mold about at least two axes while heating the mold sufficiently to cure each of the first layer and the third layer into crosslinked thermoset polymer layers;cooling the mold while rotating the enclosing mold about at least two axes. 2. The method of claim 1 wherein the first charge of thermosetting polymer resin and the second charge of thermosetting polymer resin are crosslinkable polyethylene resin. 3. The method of claim 1 wherein the low permeation thermoplastic resin is ethylene-vinyl alcohol copolymer resin. 4. The method of claim 1 wherein the low permeation thermoplastic resin is ethylene-vinyl alcohol copolymer resin having a melt flow index greater than 4.2 g/10 minutes at 190° C. under a 2160 g load, andthe first charge of thermosetting polymer resin and the second charge of thermosetting polymer resin are crosslinkable polyethylene resin. 5. The method of claim 1 wherein each of the first thermosetting polymer resin and the second thermosetting polymer resin includes an adhesion promoter. 6. The method of claim 5 wherein the adhesion promoter is selected from the group consisting of maleic anhydride, maleic anhydride grafted polyethylene, anhydride modified ethylene vinyl acetate (EVA), and ethylene methyl acrylate (EMA). 7. The method of claim 4 wherein the low permeation thermoplastic resin includes an adhesion promoter. 8. The method of claim 7 wherein the adhesion promoter is selected from the group consisting of maleic anhydride, maleic anhydride grafted polyethylene, anhydride modified ethylene vinyl acetate (EVA), and ethylene methyl acrylate (EMA). 9. The method of claim 7 wherein the first thermosetting polymer resin is crosslinkable polyethylene having a density of at least 0.935 g/cm3,the low permeation thermoplastic resin is ethylene-vinyl alcohol copolymer having a density of between 1.0 and 1.3 g/cm3,the second thermosetting polymer resin is crosslinkable polyethylene having a density of at least 0.935 g/cm3,the adhesion promoter is selected from the group consisting of maleic anhydride, maleic anhydride grafted polyethylene, anhydride modified ethylene vinyl acetate (EVA), and ethylene methyl acrylate (EMA). 10. The method of claim 1 wherein the low permeation thermoplastic resin comprises a polymer from the group consisting of polyamide 6, polyamide 66, polyamide 12, acetal, polyoxymethylene, polyvinylidene fluoride, polyetheretherketone, ethyl vinyl alcohol copolymer, and polyethylene terephthalate. 11. The method of claim 7 wherein the adhesion promoter is selected from the group consisting of maleic anhydride, maleic anhydride grafted polyethylene, anhydride modified ethylene vinyl acetate (EVA), and ethylene methyl acrylate (EMA). 12. A method to form a multiple layer seamless hollow enclosure by rotomolding, including the following steps, in sequence: introducing both a low permeation thermoplastic resin and a first quantity of thermosetting polymer resin into an enclosing mold at the same time;heating the mold sufficiently to flow both the low permeation thermoplastic resin and the first quantity of thermosetting polymer resin while rotating the mold about at least two axes;controlling the mold temperature and speed of rotation of the mold to allow the low permeation thermoplastic resin to separate from the first quantity of thermosetting polymer resin, the first quantity of thermosetting polymer resin forming a first layer of thermosetting polymer resin on an internal surface of the mold, the low permeation thermoplastic resin forming a second layer on all internal surfaces of the first layer;introducing a second quantity of thermosetting polymer resin into the mold;heating the mold sufficiently to flow the second quantity of thermosetting polymer resin while rotating the mold about at least two axes, the second quantity of thermosetting polymer resin forming a third layer on all internal surfaces of the second layer;continuing to rotate the mold about at least two axes while heating the mold sufficiently to cure the first and second thermosetting polymer resins into crosslinked thermoset polymer layers;cooling the mold while rotating the mold about at least two axes. 13. The method of claim 12 wherein the first quantity of thermosetting polymer resin is crosslinkable polyethylene;the low permeation thermoplastic resin is ethylene-vinyl alcohol copolymer;the second thermosetting polymer resin is crosslinkable polyethylene. 14. The method of claim 12 wherein the first quantity of thermosetting polymer resin is of particle size less than 500 microns;the low permeation thermoplastic resin is of particle size greater than 500 microns. 15. The method of claim 13 further characterized by placing the second quantity of crosslinkable polyethylene in a thermally degradable container and introducing the container into the mold at the same time as the low permeation thermoplastic resin and the first quantity of thermosetting polymer resin are introduced into the mold. 16. A method to form a multiple layer seamless hollow enclosure by rotational molding, including the following steps in sequence: introducing a first thermosetting polymer resin into an enclosing mold;heating the mold sufficiently to raise an internal mold temperature sufficiently to flow the first thermosetting polymer resin without thermally crosslinking the first thermosetting polymer resin into crosslinked polyethylene, the heating occurring while rotating the mold about at least two axes, the first thermosetting resin forming a first layer on an inside of the enclosing mold;introducing a first charge of adhesive agent into the mold before the first thermosetting polymer resin has thermally crosslinked;heating the mold sufficiently to melt the first charge of adhesive agent while rotating the mold about at least two axes, the first charge of adhesive agent forming a second layer on an inside of the first layer;introducing a low permeation thermoplastic resin into the enclosing mold before the first thermosetting polymer resin has thermally crosslinked;heating the mold sufficiently to melt the low permeation thermoplastic resin while rotating the mold about at least two axes, the low permeation thermoplastic resin forming a third layer on an inside of the second layer;introducing a second charge of adhesive agent into the mold;heating the mold sufficiently to melt the second charge of adhesive agent while rotating the mold about at least two axes, the second charge of adhesive agent forming a fourth layer on an inside of the third layer;introducing a second charge of thermosetting polymer resin into the mold;heating the mold sufficiently to melt the second charge of thermosetting polymer resin while rotating the mold about at least two axes, the second charge of thermosetting polymer resin forming a fifth layer on an inside of the fourth layer;continuing to rotate the mold about at least two axes while further heating the mold to raise the internal mold temperature sufficiently to ensure thermal crosslinking of the first and second thermosetting polymer resins into crosslinked thermoset polymer layers;cooling the mold while rotating the mold about at least two axes. 17. The method of claim 16 wherein the low permeation resin is ethylene-vinyl alcohol copolymer. 18. The method of claim 16 wherein the adhesive agent is from the group consisting of maleic anhydride, maleic anhydride grafted polyethylene, anhydride modified ethylene vinyl acetate (EVA), and ethylene methyl acrylate (EMA);the first thermosetting polymer resin is crosslinkable polyethylene;the low permeation thermoplastic resin is ethylene-vinyl alcohol copolymer;the second thermosetting polymer resin is crosslinkable polyethylene. 19. A method to form a seamless hollow enclosure by rotomolding, including the following steps in sequence: introducing a first charge of thermoplastic polymer resin into an enclosing mold, the thermoplastic polymer resin being one or more of the group consisting of polyethylene, grafted polyethylene, plasma treated polyethylene, and ethylene vinyl acetate;heating the mold sufficiently to flow the first thermoplastic polymer resin onto an interior of the enclosing mold while rotating the mold about at least two axes, the first thermoplastic polymer resin forming a first layer defined by the interior of the enclosing mold;introducing a low permeation thermoplastic resin into the enclosing mold, the low permeation thermoplastic resin being ethylene vinyl alcohol copolymer resin;heating the mold sufficiently to flow the low permeation thermoplastic resin onto an internal surface of the first layer while rotating the mold about at least two axes, the low permeation thermoplastic resin forming a second layer;introducing a charge of crosslinkable polyethylene resin into the mold;heating the mold sufficiently to flow the crosslinkable polyethylene resin while rotating the mold about at least two axes, the crosslinkable polyethylene resin forming a third layer on an internal surface of the second layer;continuing to rotate the mold about at least two axes while heating the mold sufficiently to ensure thermal crosslinking of the third layer into a crosslinked polyethylene layer;cooling the mold while rotating the enclosing mold about at least two axes. 20. The method of claim 19 wherein the ethylene-vinyl alcohol copolymer resin has a melt flow index greater than 4.2 g/10 minutes at 190° C. under a 2160 g load. 21. A method to form a seamless hollow enclosure by rotomolding, including the following steps in sequence: introducing a charge of thermosetting polymer resin into an enclosing mold, the first charge of thermosetting polymer resin comprising crosslinkable polyethylene;heating the mold sufficiently to flow the thermosetting polymer resin onto an interior of the enclosing mold while rotating the mold about at least two axes, the thermosetting polymer resin forming a first layer defined by the interior of the enclosing mold, the first layer not having crosslinked;introducing a charge of ethylene-vinyl alcohol copolymer resin into the enclosing mold before the first charge of thermosetting polymer resin has thermally crosslinked;heating the mold sufficiently to flow the ethylene-vinyl alcohol copolymer resin onto an internal surface of the first layer while rotating the mold about at least two axes, the ethylene-vinyl alcohol copolymer resin forming a second layer;continuing to rotate the mold about at least two axes while heating the mold sufficiently to ensure thermal crosslinking of the first layer into a crosslinked thermoset polymer layer;cooling the mold while rotating the enclosing mold about at least two axes. 22. A method to form a seamless hollow fuel tank by rotomolding, including the following steps, in sequence: introducing a first charge of crosslinkable polyethylene resin into an enclosing mold;heating the mold, while rotating the mold about at least two axes, to a sufficiently high internal mold temperature to flow the first charge of crosslinkable polyethylene resin but not high enough to thermally crosslink the first charge of crosslinkable polyethylene resin, the first charge of crosslinkable polyethylene resin flowing onto an interior of the enclosing mold and forming a first layer defined by the interior of the enclosing mold;introducing ethylene-vinyl alcohol copolymer resin of low viscosity into the enclosing mold before the first layer is thermally crosslinked, the ethylene vinyl alcohol copolymer resin having a melt flow index of greater than 4.2 g/10 minutes, at 190° C. using a 2160 g load;heating the mold sufficiently to flow the ethylene-vinyl alcohol copolymer resin onto an internal surface of the first layer while rotating the mold about at least two axes, the ethylene vinyl alcohol copolymer resin forming a second layer;introducing a second charge of crosslinkable polyethylene resin into the mold;heating the mold sufficiently, while rotating the mold about at least two axes, to flow the second charge of crosslinkable polyethylene resin, the second charge of crosslinkable polyethylene resin forming a third layer on an internal surface of the second layer;continuing to rotate the mold about at least two axes while heating the mold sufficiently to thermally crosslink the third layer and to ensure thermal crosslinking of the first layer;cooling the mold while rotating the enclosing mold about at least two axes. 23. The method of claim 22 wherein the ethyl vinyl alcohol copolymer forms a uniform homogeneous layer of less than 1 mm thickness,each of the first and third layers have a density of between 0.92 and 0.96 g/cm3,the ethyl vinyl alcohol copolymer resin having a density of about 1.0 to 1.3 g/cm3,the ethyl vinyl alcohol copolymer resin is of particle size of about 35 mesh. 24. The method of claim 22 wherein the mold is first heated sufficiently in an oven to reach a mold internal temperature of approximately 150° C. to flow the first charge of crosslinkable polyethylene onto the interior of the enclosing mold,the mold is removed from the oven while the ethylene vinyl alcohol copolymer resin is introduced into the mold,the mold is returned to the oven and is subsequently heated to raise the mold internal temperature to approximately 190° C. while the ethylene-vinyl alcohol copolymer resin is flowed onto the internal surface of the first layer,the mold is removed from the oven and the mold internal temperature reduces to approximately 100° C. as the second charge of crosslinkable polyethylene is introduced into the mold,the mold is then returned to the oven and reheated to raise the mold internal temperature to approximately 210° C. while the mold is rotated until the second charge of crosslinkable polyethylene is flowed into the third layer on the internal surface of the second layer;thereafter the mold continues to be heated sufficiently while being rotated, to ensure thermal crosslinking of both the first layer and the third layer into cross linked polyethylene layers;finally the mold is cooled to gradually reduce the mold internal temperature to approximately 100° C. while the mold is rotated about two axes and the first layer, the second layer and the third layer solidify. 25. The method of claim 19 wherein the ethylene-vinyl alcohol copolymer resin has a melt flow index greater than 4.2 g/10 minutes at 190° C. under a 2160 g load,one or more of the first thermoplastic polymer resin, the ethylene vinyl alcohol copolymer resin and the crosslinkable polyethylene resin includes an adhesion promoter,the adhesion promoter is selected from the group consisting of maleic anhydride, maleic anhydride grafted polyethylene, anhydride modified ethylene vinyl acetate (EVA), and ethylene methyl acrylate (EMA),the first charge of thermoplastic polymer resin is selected from the group consisting of polyethylene, grafted polyethylene, plasma treated polyethylene, and ethylene vinyl acetate. 26. The method of claim 1 wherein the first charge of thermosetting polymer resin and the second charge of thermosetting polymer resin are crosslinkable polyethylene resin having a melting temperature of approximately 120° C. to 130° C.,the low permeation thermoplastic resin is low viscosity ethylene-vinyl alcohol copolymer resin having a melt flow index greater than 4.2 g/10 minutes at 190° C. under a 2160 g load,the ethyl vinyl alcohol copolymer resin is of particle size of about 35 mesh,the ethylene vinyl alcohol copolymer having a density within the range of about 1.0 to 1.3 g/cm3,the ethylene-vinyl alcohol copolymer resin having a melting temperature within the range of approximately 150° C. to 200° C.,the first charge of crosslinkable polyethylene having a density of between 0.92 and 0.96 g/cm3,the second charge of crosslinkable polyethylene having a density of between 0.92 and 0.96 g/cm3,one or more of the first crosslinkable polyethylene resin, the ethylene vinyl alcohol copolymer and the second charge of crosslinkable polyethylene resin includes an adhesion promoter,the adhesion promoter is selected from the group consisting of maleic anhydride, maleic anhydride grafted polyethylene, anhydride modified ethylene vinyl acetate (EVA), and ethylene methyl acrylate (EMA). 27. A method to form a seamless hollow enclosure by rotomolding, including the following steps in sequence: introducing a charge of crosslinkable polyethylene resin into an enclosing mold;heating the mold, while rotating the mold about at least two axes, to a sufficiently high internal mold temperature to flow the charge of crosslinkable polyethylene resin but not high enough to thermally crosslink the charge of crosslinkable polyethylene resin, the charge of crosslinkable polyethylene resin flowing onto an interior of the enclosing mold and forming a first layer defined by the interior of the enclosing mold;introducing ethylene-vinyl alcohol copolymer resin of low viscosity into the enclosing mold before the first layer is thermally crosslinked, the ethylene vinyl alcohol copolymer resin having a melt flow index of greater than 4.2 g/10 minutes, at 190° C. using a 2160 g load;heating the mold sufficiently to flow the ethylene-vinyl alcohol copolymer resin onto an internal surface of the first layer while rotating the mold about at least two axes, the low permeation thermoplastic resin forming a second layer;introducing a charge of thermoplastic polymer resin into an enclosing mold, the thermoplastic polymer resin being one or more of the group consisting of polyethylene, grafted polyethylene, plasma treated polyethylene, and ethylene vinyl acetate;heating the mold sufficiently to flow the thermoplastic polymer resin onto an internal surface of the second layer while rotating the mold about at least two axes, the first thermoplastic polymer resin forming a third layer;continuing to rotate the mold about at least two axes while heating the mold sufficiently to ensure thermal crosslinking of the first layer into a crosslinked polyethylene layer;cooling the mold while rotating the enclosing mold about at least two axes.
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