DESC:Field of Invention:
The present invention relates to an extrusion blow moulding process for forming a strengthened container. More particularly, the present invention covers an extrusion blow moulding process for forming strengthened container having ribs/pattern on inside surface of the wall of the container.

Background of Invention:
Ribbing is a popular design feature that has been applied for a long time to many food, personal care, and homecare containers. Ribs are a feature in plastic injection moulded parts. They are thin extensions that run perpendicular from a wall or plane. They are commonly used to provide additional support and strength to a part. Further, by addition of ribs there is difference in the shrinkage due to variation in the thickness in the wall distribution. However, generally, ribs are formed through the outside wall of the bottle by engraving cavities, thereby making the outer surface of the bottle uneven. The unevenness of the surface makes it difficult for applying labels or printing with good aesthetic appeal.

The option which was proposed was to introduce the ribs on the inner surface of the container. This concept of disposing ribs on the inner surface of the wall of the container and leaving the outer wall plain was proposed in US4151249, currently assigned to Graham Packaging Plastic Products, Inc. US4151249 proposes use of two different materials having different elasticity modules as a result of which on blowing, the material with lower elasticity modules expands more quickly as compared to material having higher elasticity module. This difference in elasticity modules leads to formation of ribs on the inner surface of the wall of the plastic container. The use of two materials with differing elasticity moduli increases the overall cost and complexity of the process. It further, necessitates a change from most existing specifications for packaging, which typically include only one type or grade of material.

Further, containers with ribs disposed on the inner surface are also disclosed in WO 2000/035759. Accordingly, the containers as disclosed in WO ‘759 have ribs disposed on the inner surface of the container. According to WO ‘759, the ribs extend throughout the inner surface of the container, including the neck. However, presence of ribs in the neck might lead to leakage of the contents.

Therefore, it is an intent of current inventors to provide a simpler and more economical method for fabricating containers with internal ribs using ribbed parisons which demonstrate improved aesthetic appeal, increased strength and minimal chances of leakage.

Summary of Invention:
In an aspect, the present invention provides an extrusion blow moulding process for forming strengthen containers, with ribs disposed on the inner surface of a container, and the container thereof, whereby the ribs in the neck of the container are flattened during blow moulding.

In another aspect, the invention provides a process for forming the ribs which are disposed on the inner surface of the wall of the parison, preferably on the drain zone and the parison thereof.

In yet another aspect, the invention provides a mandrel designed to dispose the ribs on the inner surface of the wall of the parison, whereby the ribs are inscribed on the drain zone and the process for forming a container using ribbed parison, such that, the ribs are formed on the inside surface of the wall of the container.

Brief Description of Drawings:
Fig. 1 illustrates the outer surface of the bottle manufactured by the process of the invention and demonstrates that outer surface is similar to that of the container without ribs shown on left.

Fig. 2 illustrates the internal ribs formed by the process of the invention with the ribbed container being on right and non-ribbed container being on the left.

Fig. 3A illustrates inscriptions present on the drain zone of a convergent mandrel as per invention of this patent.

Fig. 4A illustrates inscriptions present on the drain zone of a divergent mandrel as per invention of this patent.

Detailed Description of Invention:
The present invention describes an extrusion blow moulding process for forming the container which has ribs disposed on the inner surface of wall of the container. The container is formed using ribbed parison. The ribs are introduced by using a mandrel which is designed to allow formation of said ribs on the inner surface of wall of the parison which is then blown in the mould using compressed air to form the strengthened container with ribs on the inside wall of the container.

The change in profile of the parison program is made to incorporate the modified mandrel design and for light weighting of the container. Corresponding change in parison profile in conjunction with the modified mandrel is critical to the performance of the bottle, that is, strengthening of the bottle. The change in processing conditions, such as, increase in processing temperatures also results in better formation of ribs on the inner wall of the container.

In an embodiment, the process of current invention comprises of extruding the plastic resin through a die-mandrel to form a parison. The parison is than blown into a cold metal mould to form the container.

In accordance with above embodiment, the mandrel is partially inscribed with grooves or other patterns which form ribs or other patterns on the inner surface of the wall of a parison, preferably, the mandrel is inscribed only on the drain zone. The inscription on the drain zone leads to formation of ribs on the inner surface of wall of the parison.

When the parison is blown between the moulds using compressed air to give shape to it, the ribs or other patterns are formed only on the inner surface of the wall of a container, while, outer surface of the wall of the container remains smooth. Further, the ribs in the neck of the container are flattened after blow moulding. The flattening of ribs in neck lead to reduction in leakage of the contents of a container.

By virtue of this modification, the consumer is unaware of any changes to the packaging and there is no impact on ability to label or print on the surface of the bottle as seen in Fig 1. The ribs can only be observed under light as shown in Fig 2.

In accordance with the current embodiment, the mandrel inscribed with ribs or other pattern could be convergent mandrel or divergent mandrel, as shown in Fig. 3 and Fig. 4 respectively. Further, it has been shown that the optimum results are obtained when inscriptions are made at the drain or oblique discharge zone, as shown in Fig 3 and Fig 4, respectively. and not along the entire profile of the mandrel.
In accordance with the above embodiment, the moulding temperature for parison is maintained between 130 – 350°C. However, the best results are obtained, when the moulding temperature is maintained between 180 – 270°C. Further, in accordance with above embodiment, the maintained blow air pressure is maintained between 3 – 14 bar. preferably, the blow air pressure is maintained between 5 – 10 bar.

In accordance with the above embodiment, any number of ribs may be added on the mandrel. Preferably, number of said ribs/patterns ranges from 2 to 96. Most preferably, the number of said ribs/patterns ranges from 16 to 64.

In a preferred embodiment, the ribs / pattern has width ranging from 0.1 mm to 10 mm and have depth of 0.1 mm to 10 mm.

In a preferred embodiment, the distance between ribs / patterns is from 0.1 mm to 100 mm, depending upon the size of the container. However, in a most preferred embodiment, the distance between ribs / patterns is from 0.2 mm to 10 mm.

In accordance with the above embodiment, the parison is made from materials selected from High Density Poly Ethylene (HDPE), Low Density Poly Ethylene (LDPE), Linear Low Density Poly Ethylene (LLDPE), Polypropylene (PP), their blends and such, which may be virgin or recyclable material. The parison could also be made of multi-materials including above materials with barrier materials and tie layers to produce barrier multi-layer containers.

In one of the embodiments, the process of the invention can be used for manufacturing ribbed or other patterned containers from recycled plastic. This is significant as it allows for incorporating recycled plastic from 0% to 100% in the bottle which is critical to sustainability targets of major FMCG companies. Further, in accordance with above embodiment, the ribs present in the neck portion of the container are flattened during blow moulding process, such that the flattened neck portion which prevents leakage of the contents.

It was observed that, the containers manufactured by the process of the invention demonstrate improved hoop strength and compression strength.

In an embodiment, the process of the invention can also be used for forming parisons and containers having “composite wall”, whereby multitude of plastic resins, including barrier resins and tie layers, can be passed through the die-mandrel simultaneously to form a composite wall or multi-layer container consisting of multiple layers of plastic, preferably from 1 to 10 layers. However, the plastics used in the process of the invention need not have different elasticity modules for forming ribs on the surface of the wall of the parison.

Furthermore, the process of the invention can be applied at scale from a simple 1 head machine (1 die/mandrel) which produces 1 bottle per cycle on a single station Extrusion blow moulding machine or 2 bottles per cycle on a double station Extrusion blow moulding machine up to a 40 head machine (40 dies/mandrels) producing 40 bottles per cycle on a single station Extrusion blow moulding machine or 80 bottles per cycle on a double station Extrusion blow moulding machine. Also, the cycle time for production of ribbed containers is the same as that of containers without ribs. The ability to apply this process at a scale is an essential development of this invention allowing economical commercial production.

Further, the process of the invention can be used for forming containers having volume in range of 50ml to 1000L. Furthermore, the process of the invention can be used for manufacturing barrels, oil tanks etc. which require high hoop and compression strength using minimum plastic material. Further, the ribbed container can be used to pack liquid as well as non-liquid products.

Furthermore, the process of the invention can also be used for manufacturing covers or fuel tanks used by the automotive industries for light weighting of their products manufactured by Extrusion Blow Moulding. By addition of these ribs, there was no impact on the cycle time of the machine thereby giving the same productivity.

Advantageously, the addition of ribs on the inner wall of container helps in reducing the use of plastic to perform the same functional properties for a similar product without ribs, thereby reducing the carbon footprint and helping the environment in sustainability.

In another advantageous embodiment, it was observed that the compression strength of shoulder of the containers has also improved.

Examples:
Example 1:
The data presented in this example demonstrates increased top load strength as compared to state-of-the-art container, even when the weight of the present container is reduced. The volume was kept the same.
Volume (ml) Weight (g) Top Load Strength (N) Process Temp (C) Process Pressure (bar) Cycle Time (sec)
State of art 600 45 350 235 8.5 14
Present Invention 600 40.5 355 235 8.5 14
Invention 2 - stronger 600 45 500 235 8.5 14

The said example demonstrates increased top load strength for the containers produced by the method described in this specification with the same production rate.

The above description is merely illustrative, which is not intended to limit the scope of the invention to the described embodiment. The description covers alternatives, modifications of the embodiments described above. Number of alternatives, modification, changes, integration in terms of material used and method employed may be envisaged within the scope of the invention. The various features and advantages above are demonstrated with reference to the various embodiments in accordance with the present invention.
,CLAIMS:
1. An extrusion blow moulding process for forming a container, wherein the process comprises:
a. extruding the plastic resin through a die-mandrel to form a parison;
b. blowing the parison of Step (a) into a cold metal mould to form the container, and
c. flattening the ribs present in the neck potion of the container of step (b),
wherein, the mandrel is inscribed with grooves or patterns on the drain zone of the mandrel which form ribs or other patterns on the inner surface of the wall of a parison.

2. The process as claimed in Claim 2, wherein the mandrel is a convergent mandrel.

3. The process as claimed in Claim 2, wherein the mandrel is a divergent mandrel.

4. The process as claimed in Claim 2, wherein ribs / pattern have width of 0.1 mm to 30 mm.

5. The process as claimed in Claim 5, wherein ribs / pattern have depth of 0.1 mm to 10 mm.

6. The process as claimed in Claim 2, wherein the distance between ribs / patterns is from 0.1 mm to 100 mm depending upon the size of the container

7. The process as claimed in Claim 7, wherein the distance between ribs / patterns is from 0.2 mm to 30 mm.

8. The process as claimed in Claim 2, wherein a number of said ribs/patterns ranges from 2 to 96.

9. The process as claimed in Claim 9, wherein a number of said ribs/patterns ranges from 16 to 64.

10. The process as claimed in Claim 1, wherein the parison is made from materials selected from High Density Poly Ethylene (HDPE), Low Density Poly Ethylene (LDPE), Linear Low Density Poly Ethylene (LLDPE), Polypropylene (PP), their blends and such.

11. The process as claimed in Claim 1, wherein multitude of plastic resins can be passed through the die-mandrel simultaneously to form a composite wall or a multi-layered container.

12. The process as claimed in Claim 1, wherein the container demonstrates improved hoop strength and compression strength.

13. The process as claimed in Claim 1, wherein blow moulding temperature is maintained between 130 – 350 °C.

14. The process as claimed in Claim 14, wherein blow moulding temperature is preferably maintained between 180 – 250 °C.

15. The process as claimed in Claim 1, wherein the blow air pressure is maintained between 3 – 14 bar.

16. The process as claimed in Claim 16, wherein the blow air pressure is preferably maintained between 5 – 10 bar.

17. The process as claimed in Claim 1, wherein the container includes recycled resin from 0 – 100%.

18. The process as claimed in Claim 1, wherein, the container has a volume in range of 50ml to 1000L.

19. A container manufactured by the process as claimed in Claim 1, wherein the container comprising an orifice, a neck, a shoulder, a body, a heal and a base, wherein the container is provided with ribs or other patterns on the inner surface of the wall of a container and wherein the ribs in the neck portion of the container are flattened during blow moulding.

20. The container as claimed in Claim 19, wherein the container has a volume in range of 50ml to 1000L.

21. The container as claimed in Claim 19, wherein the walls of the container are multi-layered to form a composite wall.

22. The container as claimed in Claim 19, wherein the container demonstrates improved hoop strength and compression strength.