MXPA97007308A - Pressure container: polyolefin mold coating on a poliolef - Google Patents

Abstract

A pressure vessel includes an extruded polyolefin tube, a polyolefin edge molded onto the tube, and a cap coupled to the edge, in the molding coating process, a polyolefin material is molded onto a polyolefin substrate.

Description

PRESSURE CONTAINER: COATING BY MOLDING A POLYOLEFINE ON A POLIOLEFINE FIELD OF LR INVENTION The present invention is directed to a method for manufacturing a pressure vessel using a molding coating process in which the polyolefin is molded onto a polyolefin; and the pressure vessel made by it.

BACKGROUND OF THE INVENTION Pressure vessels with polyolefin housings are known. See, "LIQUI-CEL * Etra-Flow 4" X 28"Membrane Contactor For Proceedings Scale" 1994 Product Bulletin (Contact of Additional Flow Membrane "LIQUI-CEL * of 10.15 cm X 71.12 cm for Processing Scale, 1994, Bulletin However, the housings of these containers must be machined to create the edges to which the lids are to be secured The machining of the housings is cost, a less expensive method is needed for the production of the housings. The molding coating process is known, see: U.S. Patent No. 5,409,655; French No. 2,550,848; and Rohner, M.L. "Injection Ueldable Nylons" ("Nylons Weldable by Injection"), Society of Plastics Engineers, Inc. Rochester, NY, September 15-16, 1993. Typically, in a molding coating process, an elastomer is molded over a substrate (the substrate can be made of metal or rigid plastic). In the patent of E.U.A. No. 5,409,655, KRAYTON *, a thermoplastic elastomer sold by Shell Oil Company of Houston, TX, is molded over NORYLR, a modified nylon material sold by General Electric Company of Fairfield, CT. in French Patent No. 2,550,848, a thermoplastic elastomer (an elastomer based on polypropylene and an ethylene-propylene copolymer) is coated by molding on a polypropylene. In the Rohner article, nylons of injection-solder grade are coated by molding on nylons. Some experts in the plastics industry believe that coating by polyolefin molding (ie, the material coated by molding) on a polyolefin (i.e., the substrate or also referred to as an insert) is not possible because an abutting surface of fusion between the two parts can not be formed without overheating and therefore altering (eg, wrapping or introducing in) the substrate. Accordingly, there is a need for a process by which a polyolefin can be coated by molding on a polyolefin substrate.

BRIEF DESCRIPTION OF THE INVENTION A method for coating a polyolefin on a polyolefin substrate and for making a pressure vessel includes the steps of: providing a polyolefin substrate; place the s? strato in a mold; support the substrate to avoid distortion; injecting an unfilled polyolefin into a mold and onto a substrate surface; and releasing a molded part of the mold. A pressure vessel includes: an extruded polyolefin tube; a polyolefin edge coated by molding on said tube; and a lid coupled to said edge.

DESCRIPTION OF THE DRAWINGS For the purposes of illustration of the invention, the drawings are in the form that is currently preferred; however, it should be understood that this invention is not limited to the precise provisions and instrumentalities shown. Figure 1 is a plan view of a pressure vessel with detached parts. Figure 2 is a plan view of the extruded tube of which the container housing is formed with detached parts. Figure 3 is a cross section of the molding coating section that forms part of the container housing. Figure 4 is a vieta on the floor of the housing with detached parts.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, in which similar numbers indicate similar elements, a pressure vessel 10 is shown in Figure 1. The pressure vessel 10 includes a housing 12., an end cap 14 and a clamp 16. The housing 12 comprises a molding-coated section 18 having an edge 20 and an extruded tube 24. The pressure vessel 10 (ie, housing 12 and preferably lid). 14) is made of polyolefin material. The clamp 16 can be made of a metal or plastic material. The section molding 18 is welded to the extruded tube 24 along a weld line 22. The welding of the section recieved by molding 18 to the extruded tube 24 is achieved by a molding coating process (which is described here below). Pressure vessel, as used herein, represents a cover capable of withstanding pressures up to 8,486 kg / cm * gauge. These pressure vessels can be used in hollow fiber membrane contacts described in US Patents. Nos. 5,264,171 and 5,352,361, which are incorporated herein by reference. Polyolefin, as used herein, refers to a class or group name for thermoplastic polymers derived from simple olefins; these olefins specifically exclude elastomers. The polyolefins will be described in detail below. Referring to Figure 2, the housing 12 is shown. The housing is formed in part of an extruded tube 24. Each end of the extruded tube 24 has a machined section 26. The machined section is formed with a surface which facilitates the forming a welding line between the machined section 26 and the molding-coated section 18. The machined section 26 is preferably formed by cutting, as in a lathe, but could be molded instead. The extruded tube 24 is made of an unfilled (or net) polyolefin material. Unfilled, as used herein, refers to the lack or substantial lack of a material that acts as a mold release agent or a polymer flow agent or an internal polymer lubricant. The polymer material may be either an extrusion grade polymer or an injection moldable grade polymer, but preferably it is an extrusion grade polymer. The polyolefin material shall have a melt flow index (ASTM D1238) of less than 5 and a relative density (ASTM D792A.2) of approximately 0.8 or greater (the relative density being indicative of the strength of the materials) . Preferably, the polyolefin material has a molten bath flow index of less than 1 and a relative density of about 0.9 or greater. The polyolefin material can be any thermoplastic polymer, e.g., polypropylene, and perhaps either a homopolymer or a copolymer. Suitable polyolefin materials include PRO-FAX 6523 or 7823 polypropylene resins available from Montell USA of Ulilmington, De. Referring to Figure 3, a section recieved by molding 18 is illustrated. The molding section 18 comprises a edge 20, a neck section 28, and a female co-incidental section. The female matching section 30 is adapted to be sealed by sealing (e.g., welding) with a machined section 26 of extruded tube 24 through the welding line 22. The molding section 18 is formed in a mold during the molding coating process. The mold is described in more detail later. The molding-coated section 18 is made of an unfilled (or net) polyolefin material. Unfilled, as used herein, refers to the lack or substantial lack of a material that acts as the mold-releasing agent or polymer flow agent or an internal polymer lubricant. The polyolefin material can be either an extrusion grade polymer or an injection moldable grade polymer, but preferably it is an extrusion grade polymer. The polyolefin material should have a melt flow index (ASTM D1238) of less than 5 and a relative density (ASTM 792A-2) of about 0.8 or greater (the relative density being indicative of the strength of the materials). Preferably, the polyolefin material has a melt flow rate of less than 1 and a relative density of about 0.9 or greater. The polyolefin material may be any thermoplastic polymer, e.g., polypropylene, and may be either a homopolymer or a copolymer. Suitable polyolefin materials include PRO-FAX 6523 or 7823 polypropylene resins available from Montell E.U.A. of Wil ington, DE. Referring to Figure 4, the molding-coated section 18 is shown in engagement with the extruded tube 24 through a welding line 22. During manufacture, the extruded tube 24 is preferably machined to form machined sections 26. The tube machined extruded 24 of inserted in a mold. The mold (not shown) is adapted to receive the machined section 26 of the extruded tube 24 and support the internal surface thereof. The mold is also adapted to form the section coated by molding 18 through an injection technique. The manufacture of this multi-part mold is within the scope of the art. With the mold of multiple parts in place, polyolefin material is injected, at the suggested use temperature for the resin, in the mold, and the molding-coated section 18 is formed by it. At the same time, the molding-coated section 18 is welded to the machined section 26 of the extruded tube 24. Subsequently, the housing 12 (ie, the tube 24 with the molding section 18 integrally formed) is released from the mold . The present invention can be modalized in other specific forms without departing from the spirit or essential attributes thereof and therefore reference should be made to the appended claims, rather than to the previous descriptive memory, as indicated by the scope of its invention.

Claims (13)

NOVELTY OF THE INVENTION CLAIMS

1. A pressure vessel comprising: an extruded polyolefin tube; a polyolefin edge coated by molding on said tube; and a lid coupled to said edge.

2. A pressure vessel according to claim 1, further characterized in that said edge is made of an unfilled polyolefin.

3. The pressure vessel according to claim 1, further characterized in that said polyolefin is polypropylene.

4. A method for making a pressure vessel by molding a polyolefin onto a polyolefin substrate comprising the steps of: providing a polyolefin substrate; place the substrate in a mold, support the substrate to avoid distortion; injecting an unfilled polyolefin into the mold and onto a surface of the substrate; and releasing a molded part of the mold.

5. The method according to claim 4, further characterized in that said substrate is made of an unfilled polyolefin.

6. The method according to claim 4, further characterized in that said polyolefin is a polypropylene.

7. - The method according to claim 4, further characterized in that said polyolefin has a molten bath flow index of less than 5 and a relative density of about 0.8 or greater.

8. The method according to claim 7, further characterized in that said polyolefin has a molten bath flow index of less than 1 and a relative density of about 0.9 or greater.

9. A method for molding a polyolefin on a polyolefin substrate comprising the steps of: providing a polyolefin substrate; place the substrate in a mold, support the substrate to avoid distortion; injecting an unfilled polyolefin into the mold and onto a surface of the substrate; and releasing a molded part of the mold.

10. The method according to claim 9, further characterized in that said substrate is made of an unfilled polyolefin.

11. The method according to claim 9, further characterized in that said polyolefin is a polypropylene.

12. The method according to claim 4, further characterized in that said polyolefin has a melt flow index of less than 5 and a relative density of about 0.8 or greater.

13. The method according to claim 12, further characterized in that said polyolefin has a molten bath flow index of less than 1 and a relative density of about 0.9 or greater.