Polypropylene inner liner of bulk bags and process for producing said polypropylene inner liner

Abstract

A polypropylene inner liner for bulk bags and the process for producing such polypropylene inner liner. The polypropylene inner liner comprises a three- layer film structure overlapping each other, including an outer film layer, a middle film layer, and an inner film layer. Ingredients used to produce polypropylene inner liner comprise polypropylene, propylene elastomer, processing aid, antiblock masterbatch and slip masterbatch and can further comprising colored plastic pellets that has a production process consisting of mixing all ingredients, blow molding the polypropylene inner liner with a plastic bag blowing machine, cutting and thermal sealing the inner liner to acquire polypropylene inner liner of the desired sizes and lengths.

Description

[0001] POLYPROPYLENE INNER LINER OF BULK BAGS AND PROCESS FOR PRODUCING SAID POLYPROPYLENE INNER LINER

[0002] TECHICAL FIELD

[0003] This invention relates to the development of packaging, particularly to the polypropylene inner liner of bulk bags and the process for producing the same.

[0004] BACKGROUND ART

[0005] Plastic is one of the most popular materials used in many industries. Bulk bags are also made from plastic. A bulk bag consists of an outer polypropylene woven bag and an inner liner attached to the inside of the outer polypropylene woven bag. At present, the outer polypropylene woven bag is usually a woven plastic bag made from polypropylene (PP) plastic and the inner liner is made from polyethylene (PE) plastic. The inner liner is characterized as a large plastic film with a width of at least 100 centimeters and a length of 100 centimeters or more. Therefore, the inner liner is generally not made from polypropylene (PP) plastic because polypropylene plastic cannot be blown into large films as required. If polypropylene plastic is used to make a large plastic film, it will cause the film to have holes, creases, wrinkles or flow back and forth, making it impossible to form and actually use. Therefore, nowadays the plastic used to make outer polypropylene woven bag and inner liner are different types of plastic.

[0006] At present, consumers worldwide are becoming increasingly concerned about the environment. The principle of the Circular Economy has therefore been introduced as a practice guideline for the entire chain, from raw materials manufacturers, product manufacturers and product users to the final management of products after use.

[0007] Based on the market’s need to respond to the circular economy by recycling used plastic packaging with maximum efficiency, the production of Mono Material packaging is one option to address this problem. The principle of Mono Material packaging is to select and use all the same types of plastic materials to produce the packaging. It is important to maintain functional properties equivalent to those of the original packaging. Therefore, the problem caused to the bulk bag industry is that the plastics used to make the outer polypropylene woven bag and inner liner are different types of plastics, making them difficult to recycle for re-use because the inner liner must be separated from the outer polypropylene woven bag before being recycled, separated by type of plastic. This wastes time, increases steps and makes the quality of the product after recycling not as good as the original packaging.

[0008] This invention attempts to reduce the aforementioned problems by inventing, developing and improving to produce polypropylene inner liner of bulk bags, which are made from the same type of plastic as the outer polypropylene woven bag. The production formula enables the formation of a large film similar to polyethylene plastic and also helps the inner liner withstand heat better. This is because polypropylene plastic is much more resistant to high temperatures than polyethylene plastic. Polypropylene plastic can withstand heat as high as 150 degrees Celsius, while polyethylene plastic can only withstand a lower temperature, which is 100 degrees Celsius.

[0009] SUMMARY OF THE INVENTION

[0010] This invention relates to polypropylene inner liner of bulk bags and the process for producing said polypropylene inner liner. The polypropylene inner liner comprises a three-layer film structure overlapping each other, including an outer film layer, a middle film layer and an inner film layer. The ingredients used to produce the polypropylene inner liner comprise polypropylene, propylene elastomer, processing aid, antiblock masterbatch and slip masterbatch and can further comprising colored plastic pellets. The production process comprises mixing all ingredients, blow molding the polypropylene inner liner with a plastic bag blowing machine. The plastic bag blowing machine will melt all ingredients into a homogeneous content. The molten ingredients are pressed through the template under pressure. The template serves to form the shape of a thin plastic tube. This thin plastic tube will be blown with air to expand and become thinner as the thin plastic tube with a desired size. The workpiece will be a large, thin plastic tube, which is then passed through smooth rollers to flatten the thin plastic tube. The resulting workpiece is flat and rolled and the inner liner is cut and sealed within the same process with a cutting and sealing machine. The rolls of thin plastic tubes are passed through a cutting and sealing machine with heat to acquire polypropy lene inner liner of the desired sizes and lengths. The polypropylene inner liner obtained according to this invention consist of ingredients that can form large films and also help the polypropylene inner liner to be strong and resistant to tearing, providing better heat resistance.

[0011] The objective of this invention is to provide polypropylene inner liner for bulk bags with improved heat resistance.

[0012] Another objective of this invention is to provide a polypropylene inner liner for bulk bags that is made of the same type of plastic as the outer polypropylene woven bag to facilitate the ease of recycling. This reduces the use of new materials and decreases the creation of plastic waste in the environment.

[0013] DETAILED DESCRIPTION OF THE INVENTION

[0014] This invention relates to polypropylene inner liner of bulk bags and the process for producing such polypropylene inner liner. The polypropylene inner liner comprising a three-layer film structure overlapping each other: an outer film layer, a middle film layer and an inner film layer.

[0015] The outer film is the layer that sticks to the outer polypropylene woven bag.

[0016] Considering the ingredient of polypropylene inner liner, it accounts for 100%, the ingredient composition of the outer film accounts for 25% of the total ingredient. The middle film layer accounts for 50% of the total ingredients and the inner film layer accounts for 25% of the total ingredients.

[0017] The polypropylene inner liner comprises ingredients calculated in percentage by weight as follows:

[0018] The ingredients used to produce polypropylene inner liner are as follows:

[0019] Polypropylene 61.00 - 83.00 % by weight

[0020] Propylene Elastomer 15.00 - 40.00 % by weight

[0021] Processing Aid 0.20 - 1.50 % by weight

[0022] Antiblock Masterbatch 0.90 - 2.50 % by weight

[0023] Slip Masterbatch 0.08 - 0.60 % by weight

[0024] In the production process, the plastic bag blowing machine with 3 extruders is used to acquire a 3-layer film structure, including an outer film, middle film layer and inner film layer. The outer film accounts for 25% of the total ingredients, the middle film layer accounts for 50% of the total ingredients and the inner film layer accounts for 25% of the total ingredients.

[0025] The ingredients of each layer of the film structure are as follows:

[0026] The ingredients of the outer film layer are as follows:

[0027] Polypropylene 19.00 - 24.50 % by weight of the total ingredients used to produce the polypropylene inner liner;

[0028] Polypropylene Polymer 1.00 - 6.50 % by weight of the total ingredients used to produce the polypropylene inner liner;

[0029] Processing Aid 0.05 - 0.50 % by weight of the total ingredients used to produce the polypropylene inner liner.

[0030] The ingredients of the outer film layer account for 25% of the total ingredients used to produce polypropylene inner liner.

[0031] The ingredients of the middle film layer are as follows:

[0032] Polypropylene 42.00 - 46.50 % by weight of the total ingredients used to produce the polypropylene inner liner;

[0033] Propylene Elastomer 4.00 - 8.50 % by weight of the total ingredients used to produce the polypropylene inner liner;

[0034] Processing Aid 0.12 - 0.75 % by weight of the total ingredients used to produce the polypropylene inner liner.

[0035] The ingredients of the middle film layer account for 50% of the total ingredients used to produce the polypropylene inner liner.

[0036] The ingredients of the inner film layer are as follows:

[0037] Polypropylene 0 - 12.00 % by weight of the total ingredients used to produce the polypropylene inner liner;

[0038] Propylene Elastomer 10.00 - 25.00 % by weight of the total ingredients used to produce the polypropylene inner liner;

[0039] Processing Aid 0.03 - 0.25 % by weight of the total ingredients used to produce the polypropylene inner liner;

[0040] Antiblock Masterbatch 0.90 - 2.50% by weight of the total ingredients used to produce the polypropylene inner liner;

[0041] Slip Masterbatch 0.08 - 0.60 % by weight of the total ingredients used to produce the polypropylene inner liner. The ingredients of the inner film layer account for 25% of the total ingredients used to produce the polypropylene inner liner.

[0042] The preferable polypropylene according to this invention, can be selected from polypropylene for blowing film, preferably Moplen EP310D from HMC Polymer.

[0043] Propylene Elastomer is a substance used to increase viscosity and enhance flexibility, enable the product to be stronger, not brittle and improve film formation, which is appropriate according to this invention, selected from Vistamaxx from ExxonMobil, preferably Vistamaxx3980FL from ExxonMobil.

[0044] Processing Aid is an additive used in the plastics production process to help the process run smoother and more efficiently, coat metal surfaces and screws to reduce adhesion of liquid plastic and prevent pellet burn, reduce the occurrence of melt fracture in film, decrease instability among surfaces in multi-layer films and increase the homogeneity of ingredients in the formula.

[0045] Antiblock Masterbatch is an additive that increases the roughness of the film surface, making the film easier to separate.

[0046] Slip Masterbatch is an additive that reduces friction between film surfaces, making it slippery and easily separated.

[0047] Antiblock Masterbatch and Slip Masterbatch are substances that make the film surface slippery and prevent film adhesion, with the amount of auxiliary substances in the preferable ratio, which will more easily separate the film, resulting in better opening the bag and easier use of the bag.

[0048] The following are some examples of ingredients used to produce polypropylene inner liner that have been tested, but are not limited to these examples, as shown below:

[0049]

[0050] From the example to experiment the mixing of ingredients in various ratios as revealed in Tables 1 - 4, it was found that the ingredient ratios in Example 2 shown in Tables 3 and 4 are the preferable ingredients used to produce polypropylene inner liner.

[0051] The ingredients used to produce polypropylene inner liner can further comprising colored plastic pellets to acquire polypropylene inner liner of various colors as desired, by adding colored plastic pellets to the structure of the outer film layer or middle film layer or both layers in the mixing ratio of colored plastic pellets amounting to 0.1 - 3 % by weight of the total ingredients used to produce polypropylene inner liner.

[0052] The production process for polypropylene inner liner comprises of the following steps:

[0053] 1. Mix the ingredients for each layer of film — outer film layer, middle film layer, and inner film layer — with a plastic pellet mixer according to the proportion of composition by weight of the ingredients used to prepare each layer of film as mentioned above.

[0054] 2. Blow mold all the above ingredients into polypropylene inner liner with a 3- Layer Co-Extrusion Blown Film Machine that has 3 extruders; each extruder is dedicated to the ingredients of each film layer. The extrusion unit serves to feed and melt all ingredients into a homogeneous content by using the screw to rotate and compress the ingredients, moving them along the screw housing, using heat at a temperature of 170-220 degrees Celsius, wherein the preferable temperature is 180-200 degrees Celsius. 3. Then, the molten ingredients are pressed through the template under pressure. The template serves to form the shape of a thin plastic tube. This thin plastic tube will be blown with air to expand and become thinner as the thin plastic tube with a desired size, until acquiring a workpiece with a large, thin plastic tube, which is passed through smooth rollers to flatten the thin plastic tube. The resulting workpiece is flat and rolled into a thin plastic tube roll to wait for further cutting and sealing.

[0055] 4. Cut and seal the inner liner with a cutting and sealing machine. The rolls of thin plastic tube roll are passed through a cutting and sealing machine with heat to acquire polypropylene inner liner of the desired sizes and lengths.

[0056] The polypropylene inner liner according to this invention has a width of at least 100 centimeters.

[0057] The preferable plastic bag blowing machine according to this invention is a 3 -layer co-extrusion blown film machine with 3 extruders.

[0058] Strength Test

[0059] The strength test of polypropylene inner liner compared to the inner liner made from polyethylene, tested by pulling the film content of polypropylene inner liner and pulling the seal of the polypropylene inner liner, compared to the inner liner made from polyethylene, it was found that polypropylene inner liner are stronger and more resistant to tensile forces than the inner liner made from polyethylene.

[0060] Heat Resistance Property Test

[0061] In the heat resistance property test, hot oil boiled at a measured temperature of 140 degrees Celsius is poured into a polypropylene inner liner. According to this invention, the polypropylene inner liner can withstand the heat of oil with temperature at 140 degrees Celsius.

[0062] From the ingredients of the aforementioned polypropylene inner liners, this makes it possible to form large films similar to the use of polyethylene plastic and it also helps the polypropylene inner liner to withstand heat better.

Claims

CLAIMS1. A polypropylene inner liner comprises a three-layer film structure, an outer film layer, a middle film layer and an inner film layer, wherein the polypropylene inner liner comprises ingredients calculated in percentage by weight as follows:Polypropylene 61.00 - 83.00 % by weightPropylene Elastomer 15.00 - 40.00 % by weightProcessing Aid 0.20 - 1.50 % by weightAntiblock Masterbatch 0.90 - 2.50 % by weightSlip Masterbatch 0.08 - 0.60 % by weight2. The polypropylene inner liner according to claim 1, wherein the outer film layer accounts for 25% of the total ingredients used to produce polypropylene inner liner, the middle film layer accounts for 50% of the total ingredients used to produce polypropylene inner liner and the inner film layer accounts for 25% of the total ingredients used to produce polypropylene inner liner.

3. The polypropylene inner liner according to claim 1, wherein the ingredients of the outer film layer are as follows:Polypropylene 19.00 - 24.50 % by weight of the total ingredients used to produce the polypropylene inner liner;Polypropylene Polymer 1.00 - 6.50 % by weight of the total ingredients used to produce the polypropylene inner liner;Processing Aid 0.05 - 0.50 % by weight of the total ingredients used to produce the polypropylene inner liner, the ingredients of the middle film layer are as follows:Polypropylene 42.00 - 46.50 % by weight of the total ingredients used to produce the polypropylene inner liner;Propylene Elastomer 4.00 - 8.50 % by weight of the total ingredients used to produce the polypropylene inner liner;Processing Aid 0.12 - 0.75 % by weight of the total ingredients used to produce polypropylene inner liner, the ingredients of the inner film layer are as follows:Polypropylene 0 - 12.00 % by weight of the total ingredients used to produce the polypropylene inner liner;Propylene Elastomer 10.00 - 25.00 % by weight of the total ingredients used to produce the polypropylene inner liner;Processing Aid 0.03 - 0.25 % by weight of the total ingredients used to produce the polypropylene inner liner;Antiblock Masterbatch 0.90 - 2.50% by weight of the total ingredients used to produce the polypropylene inner liner;Slip Masterbatch 0.08 - 0.60 % by weight of the total ingredients used to produce the polypropylene inner liner.

4. The polypropylene inner liner according to claim 1, wherein the polypropylene inner liner further comprising additional ingredients of colored plastic pellets with the ratio of 0.1 - 3 % by weight of the total ingredients used to produce the polypropylene inner liner.

5. The polypropylene inner liner according to claim 4, wherein the colored plastic pellets are ingredients of the structure of the outer film or the middle film layer or both layers.

6. The polypropylene inner liner according to claim 1, wherein polypropylene can be selected from polypropylene for film blowing, preferably Moplen EP310D from HMC Polymer.

7. The polypropylene inner liner according to claim 1, wherein propylene elastomer can be selected from Vistamaxx from ExxonMobil, preferably Vistamaxx3980FL from ExxonMobil.

8. The production process of the polypropylene inner liner according to any one of claims 1-7, comprising: mixing the ingredients for each layer of film — outer film layer, middle film layer and inner film layer — with a plastic pellet mixer according to the proportion of composition by weight of the ingredients used to prepare each layer of film; blow molding all the above ingredients into polypropylene inner liner with a 3 -Layer Co-Extrusion Blown Film Machine that has 3 extruders, eachextruder is dedicated to the ingredients of each film layer, wherein the extrusion unit serves to feed and melt all ingredients into a homogeneous content by using the screw to rotate and compress the ingredients, moving them along the screw housing, using heat at a temperature of 170-220 degrees Celsius, wherein the preferable temperature is 180-200 degrees Celsius; then, pressing the molten ingredients through the template under pressure, wherein the template serves to form the shape of a thin plastic tube, in which the thin plastic tube will be blown with air to expand and become thinner as the thin plastic tube with a desired size, until acquiring a workpiece with a large, thin plastic tube, which is passed through smooth rollers to flatten the thin plastic tube and result in a workpiece that is flat and rolled into a thin plastic tube roll; cutting and sealing the inner liner with a cutting and sealing machine, wherein the rolls of thin plastic tube are passed through a cutting and sealing machine to acquire polypropylene inner liner of the desired sizes and lengths.

9. The production process of polypropylene inner liner according to claim 8, wherein the preferable temperature used in melting all ingredients into a homogeneous content is 180 -200 degrees Celsius.

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