Process for the injection moulding of multi-layered articles

• US 5,188,787 A
• Filed: 07/17/1992
• Issued: 02/23/1993
• Est. Priority Date: 01/25/1988
• Status: Expired due to Term

• Current Assignee: Liqui-Box Canada Incorporated (Corteva, Inc.)
• Original Assignee: Du Pont Taiwan Limited (Corteva, Inc.)
• Inventors: Lillis, Rupert M., White, George, King, David C.
• Primary Examiner(s): Thurlow, Jeffery
• Assistant Examiner(s): VARGOT, MATHIEU D
• Application Number:
  US07/913,961
• Time in Patent Office: 221 Days
• Field of Search: 264/163, 264/153, 264/246, 264/229, 264/255, 264/268, 264/265, 264/291, 264/292, 264/269, 264/511, 264/550, 264/259, 264/553, 264/554, 264/513, 264/544, 264/549, 264/257 , 264/258, 264/157, 264/296, 264/328.1, 264/328.11, 264/328.14, 264/294, 264/DIG. 50, 425/111, 425/125, 425/127, 425/398, 425/388, 425/553, 425/292, 220/415
• US Class Current: 264/153
• CPC Class Codes: B29C 2045/14188 trimming the article in the mould
• CPC Class Codes: B29C 2045/14213 deforming by gas or fluid pressure in the mould cavity
• CPC Class Codes: B29C 45/1418 the inserts being deformed or preformed, e.g. by the injection pressure
• CPC Class Codes: B29C 45/14778 the article consisting of a material with particular properties, e.g. porous, brittle
• CPC Class Codes: B29C 51/04 Combined thermoforming and prestretching, e.g. biaxial stretching
• CPC Class Codes: Y10S 264/50 Use of fluid pressure in molding

Abstract

This invention relates to an injection moulding process for the manufacture of multi-layered articles, especially articles having barrier properties. The process includes clamping a thermoplastic film over the cavity of a mould of an injection moulding process, the film being capable of being stretched. The film is then stretched within the mould by inserting the core of the mould, preferably using a core in which a central part enters the mould and partially stretches the film prior to the remainder of the core entering the mould. The mould is then closed, excess film is trimmed off and polymer is injected into the mould cavity. The resultant article is a multi-layered injection moulded article which, depending on the characteristics of the film and injected polymer, may have barrier properties to oxygen, liquids or the like that are superior to articles moulded from only the polymer. The process is particularly useful in the moulding of containers having a depth:width ratio of at least 0.5.

Claims

1. A process for the injection moulding of a multi-layered container having barrier properties using injection moulding apparatus, said container having a depth:

width ratio of at least 0.75;

1, said apparatus having a mould block with a core that is adapted to be inserted into a cavity of the mould block in a spaced-apart relationship related to the thickness and shape of the container to be moulded, said core having a tip that is comprised of an outer core and a centrally located plunger that moves independently of the outer core, the surfaces of the outer core and of the plunger forming the surface of the core when the core is located within the mould block, comprising the steps of;

(a) clamping a self-supporting thermoplastic film over the cavity of the mould block said film being selected from (1) PVDC-coated polyethylene, (2) laminates of polyethylene/PVDC/polyethylene, (3) laminates of polyethylene/ethylene-vinyl alcohol/polyethylene, (4) laminates of polyethylene/polyvinyl alcohol/polyethylene, (5) laminates of polyethylene/PVDC/ethylene-vinyl acetate copolymer, (6) laminates of polyethylene/polyvinyl alcohol/ethylene-vinyl acetate copolymer, and (7) laminates of polyethylene/ethylene-vinyl alcohol/ethylene-vinyl acetate copolymer and further being capable of being stretched to conform to the shape of the core that is to be inserted into the mould block.

(b) substantially uniformly stretching the film by sequentially stretching the film in two stages within the mould block using the core, with the plunger preceding the outer core into the mould block, such that (i) the plunger stretches the thermoplastic film, and (ii) the outer core further stretches the film, the plunger retracting into the outer core as the outer core enters the cavity of the mould block, thereby forming the surface of the core in the mould block;

(c) closing the mould block and core, with excess film, being trimmed off substantially simultaneously therewith using a serrated blade, the serrated blade located on the core and entering a recess in the mold block upon closure;

(d) injecting molten thermoplastic polyolefin into the mould between the film and the surface of the mould cavity, said polyolefin being bonded to the film such that the container is formed with polyolefin on its outer surface thereof and the polyethylene of the film on its inner surface thereof;

(e) allowing the container so moulded to cool to below the heat distortion temperature of the moulded container; and

(f) opening the mould block and core and removing the moulded container;

said film having different barrier properties than the thermoplastic polyolefin with respect to at least one of oxygen, hydrocarbon liquids, and water.

2. The process of claim 1 in which the polyolefin is polyethylene.

3. The process of claim 2 in which the container has a ratio of depth:

width of at least 0.90;

1.