Method for manufacturing plastic bag from recycled plastic bottles

Abstract

The present invention relates to a method of manufacturing a plastic bag comprising preparing a mixture containing about 0.1% to 100% by weight of recycled plastic bottle resin and making the mixture into a plastic bag.

Description

Technical Field

[0001] The present invention generally relates to a method of making plastic bags from recycled plastic bottles, such as recycled plastic milk bottles. Background Art

[0002] Consumers are increasingly concerned about recycling. Single-use plastic bottles are one of the most prevalent and visible forms of plastic use, including plastic waste. Currently, only a small fraction of single-use plastic bottles are recycled. Consequently, there is a strong connection in the public mind between plastic bottles, plastic waste, and the need to increase plastic recycling.

[0003] Single-use plastic bottles are typically made from four types of plastic materials, which are distinguished by plastic resin identification codes, as follows: (1) Plastic bottles used for drinking water and other beverages are typically made from polyethylene terephthalate (PET); (2) High-density polyethylene (HDPE) is used to make rigid plastic bottles such as milk bottles and detergent bottles; (4) Low-density polyethylene (LDPE) is used to make squeeze bottles; and (5) Polypropylene (PP) is used to make medicine bottles.

[0004] Although all plastics used to make plastic bottles can be recycled, in the plastics recycling world, the main focus is on using closed-loop "bottle-to-bottle" recycling processes to make recycled polyethylene terephthalate (rPET) beverage bottles and recycled high-density polyethylene (rHDPE) milk bottles. Bottle-to-bottle recycling typically involves clean "closed stream" recycling involving only one type of recycled plastic - either rPET or rHDPE, and only one color - clear or green rPET, or white or creamy rHDPE.

[0005] There is a technical bias against using mixed-color recycled plastic resins in bottle-to-bottle recycling, due to the presence of black impurities or the blue tint of the blue tamper-evident band on milk bottles being perceived as unclean. There is also a technical bias against using rHDPE from plastic milk bottles in plastic milk bottles, due to the misconception that there is residual odor from previously used plastic milk bottles.

[0006] Concerns about closed-stream, bottle-to-bottle recycling of plastic bottles are a major barrier to using recycled plastic bottles to make other plastic products, such as plastic bags. In addition, there are many technical barriers to using recycled plastic bottles to make plastic bags. Specifically, plastic bags require different functional characteristics, physical properties, physicochemical properties and mechanical properties than plastic bottles and are prepared by different manufacturing processes. Plastic milk bottles are made of hard plastic and must be rigid or semi-rigid, while plastic bags are made of soft plastic and need to have tensile strength, tear strength and ductility. Plastic bottles are typically made using a blow molding process, while plastic bags are typically made using an extrusion process. In addition, food contact plastic bags differ in their chemical composition and regulatory requirements compared to non-food contact plastic bags.

[0007] Furthermore, when two or more types of recycled plastics from plastic bottles are mixed together, they are often incompatible. Mixing different types of recycled plastics often results in a reduction in the quality of the recycled plastic, making it too low a quality to be used in many end uses, such as plastic bags. For example, high-density polyethylene (HDPE) recyclers lose approximately 20% of their revenue due to the low quality of mixed recycled plastics. Compatibilizing additives have been proposed to enable chemically incompatible plastics to be recycled together, but there is no universal compatibilizer that works for all combinations of recycled plastics. In addition, regulatory approval is required when recycled plastics are used in food contact applications, such as food contact plastic bags.

[0008] Another technical barrier to using food-grade recycled plastics to make food contact plastic bags is that complex and expensive cleaning recycling technologies are required to remove contaminants from recycled plastic bottles (such as plastic milk bottles) generated by consumer use and during collection.

[0009] Against this backdrop, there is an unmet need for a method of manufacturing plastic bags from recycled plastic bottles that maintains the necessary functional properties while being cost-effective. Summary of the Invention

[0010] The present invention provides a method for manufacturing a plastic bag, comprising:

[0011] preparing a mixture comprising about 0.1% to 100% by weight of recycled plastic bottle resin;

[0012] The mixture was put into plastic bags.

[0013] The recycled plastic bottle resin may comprise one or more of rPET, rHDPE, rLDPE and rPP.

[0014] The mixture may comprise from about 30% to about 80% by weight recycled plastic bottle resin, with the remainder comprising one or more recycled plastic resins not derived from recycled plastic bottles, virgin plastic resin, recycled plastic fillers, colorants, fragrances, and odor neutralizers.

[0015] Recycled plastic bottle resin can include rHDPE from recycled plastic milk bottles.

[0016] The mixture may contain from about 30% to about 50% by weight rHDPE from recycled plastic milk bottles.

[0017] The recycled plastic resin is not derived from recycled plastic bottles and may comprise recycled linear low density polyethylene (rLLDPE).

[0018] The recycled plastic filler may comprise recycled calcium carbonate (rCaCO3).

[0019] The plastic bag may be a food contact bag and the recycled plastic bottle resin may comprise food grade rHDPE from recycled plastic milk bottles.

[0020] Alternatively, the plastic bag may be a non-food contact bag and the mixture may include one or more colorants, flavoring agents, odor neutralizers, and recycled plastic filler.

[0021] The present invention also provides a plastic bag made by the method. DETAILED DESCRIPTION

[0022] According to an embodiment of the present invention, a method for manufacturing a plastic bag may generally begin with preparing a mixture comprising about 0.1% to 100% by weight of recycled plastic bottle resin (i.e., post-consumer or recycled plastic resin from recycled plastic bottles). Next, the mixture may be made into a plastic bag, for example, by melting and extruding it into a film to make a plastic film bag. Such a plastic film bag may be single-layer or multi-layer. The film constituting the plastic film bag may have a thickness of about 6 to 100 microns, for example, about 9 to 25 microns. Alternatively, the mixture may be made into a plastic bag by melting and extruding it through rollers to form a thin nonwoven fabric, thereby manufacturing a nonwoven plastic bag.

[0023] The mixture and the plastic bags made therefrom may comprise from about 30% to about 80% by weight of recycled plastic bottle resin, with the remainder comprising at least one recycled plastic resin not derived from recycled plastic bottles, virgin plastic resin (e.g., virgin PET, virgin HDPE, virgin LDPE, virgin PP, and virgin LLDPE), recycled plastic filler, colorant, fragrance, and odor neutralizer. Optionally, one or more of the colorant, fragrance, and odor neutralizer may also comprise, in whole or in part, recycled material.

[0024] For example, recycled plastic resin that is not derived from recycled plastic bottles may contain rLLDPE. Recycled plastic fillers may contain rCaCO3. For example, rCaCO3 may contain calcium carbonate ore from a quarry that was initially rejected for its intended industrial use and subsequently cleaned and processed to make it suitable for reuse as rCaCO3 in recycled plastic bags, rather than being rejected and sent back to the quarry for dumping.

[0025] The recycled plastic bottle resin may have a mixed color from recycled plastic bottles of different colors, such as gray, black, white, and mixtures thereof. The recycled plastic bottle resin may include one or more rPET, rHDPE, rLDPE, and rPP. When the recycled plastic bottle resin includes a mixture of rPET and rHDPE or rLDPE from mixed recycled plastic bottles, or a mixture of rPP and rHDPE or rLDPE, the mixture may also include a compatibilizer, such as a PE / PP compatibilizer or a PET / PE compatibilizer.

[0026] For example, a recycled plastic bottle resin may include rHDPE derived from recycled plastic milk bottles. In certain embodiments, the mixture may contain from about 30% to about 50% by weight of rHDPE derived from recycled plastic milk bottles. The rHDPE weight percentage may vary within this range, depending on the desired functional properties of the plastic bag and cost considerations.

[0027] These plastic bags may include food contact bags, which may or may not have any type of closure system. For example, these food contact bags may include freezer bags, zipper storage bags, slide storage bags, resealable (or reclosable) bags, fruit and vegetable bags, sandwich bags, side pockets, flat roll bags, vacuum seal bags, barrier bags, pouches, etc. The closure system of food contact bags may include zippers, sliders, etc.

[0028] When the plastic bag is a food contact bag, the recycled plastic bottle resin may contain food-grade rHDPE from recycled plastic milk bottles. Using food-grade rHDPE has advantages in purity and extrusion or blown film because it contains fewer contaminants that disrupt bubbles and stability, and less actual or perceived odor.

[0029] Recycled plastic fillers may not be used in food-grade bag blends unless they are approved for food contact use. Additionally, blends suitable for food contact bags may optionally contain colorants but may not contain flavorings or odor neutralizers.

[0030] When the food contact bag is a resealable bag, if the recycled plastic bottle resin includes high-density polyethylene (HDPE) and / or recycled linear low-density polyethylene (rLLDPE), the closure system can be extruded integrally with the bag body. Alternatively, if the type of recycled plastic bottle resin is not suitable for integral extrusion, the closure system can be laminated to the bag body. For example, the food contact bag can include a thick slide bag with a stand-up base (such as a stand-up bag) as an alternative to a food container, or a resealable bag with a laminated zipper closure system.

[0031] Alternatively, these plastic bags may include non-food contact bags that do not come into contact with food, and may or may not have any type of closure. These non-food contact bags may include organizer bags, trash bags, garbage bags, lawn bags, shopping totes, laundry bags, non-woven plastic bags, and the like. Closure systems for these non-food contact bags may include tie handles, draw tapes, wavetop closures, and the like.

[0032] When the plastic bag is a non-food contact bag, the mixture may include one or more non-food-grade rHDPE, rPET, rLDPE, and rPP, which are derived from different types of recycled plastic bottles. Furthermore, mixtures suitable for non-food contact bags may include one or more colorants, odorants, and odor neutralizers. Furthermore, mixtures suitable for non-food contact bags may also include recycled plastic fillers, such as rCaCO3.

[0033] The following examples are intended to illustrate the present invention. They are not intended to limit the scope of the present invention.

[0034] Example 1 Plastic dry garbage bag

[0035] A 1 kg mixture was prepared containing 800 g of rHDPE from recycled plastic milk bottles and 200 g of a recycled plastic filler masterbatch. The recycled plastic filler masterbatch contained 160 g of rCaCO3 and 40 g of rHDPE from recycled plastic milk bottles as the filler carrier resin. Thus, 84% of the total weight of the mixture consisted of recycled plastic bottle resin from recycled plastic milk bottles, and overall, the mixture contained 100% recycled material.

[0036] The mixture is heated and extruded into a plastic film to create a plastic trash bag with suitable functional properties and a total recycled content of 100%.

[0037] Example 2 Kitchen Organizing Bag

[0038] Kitchen organizer bags were made from a first blend that comprised, by weight, 30% rHDPE from recycled plastic milk bottles, 15% virgin HDPE, 5% color concentrate, and 50% rHDPE / rLLDPE from non-recycled plastic bottles. The resulting kitchen organizer bags had suitable functional properties and a total recycled content of 80%.

[0039] Kitchen organizers can also be made from a second blend consisting of 30% rHDPE from recycled plastic milk bottles, 7% rCaCO3, 3% color concentrate, 50% rHDPE from non-recycled plastic bottles, and 10% rLLDPE from non-recycled plastic bottles, by weight. This blend provides suitable functional properties and a total recycled content of 97%. It is believed that the 3% color concentrate could be replaced with a suitable recycled colorant to bring the total recycled content of the kitchen organizer to 100%.

[0040] Example 3 Sliding Bag

[0041] The food contact slide bags are made from a blend of 30% food-grade HDPE from recycled plastic milk bottles and 70% virgin HDPE and LLDPE resins. The resulting slide bags have suitable functional properties and a total recycled content of 30%.

[0042] Example 4 Nonwoven plastic bag

[0043] The nonwoven plastic bag is made from a first blend comprising 100% rPET from recycled water bottles. The nonwoven rPET bag thus made has suitable functional properties and a total recycled content of 100%.

[0044] The nonwoven plastic bags were also made from a second blend that contained 100% rPP from recycled water bottles. The resulting nonwoven rPP bags had suitable functional properties and a total recycled content of 100%.

[0045] It is believed that nonwoven plastic bags made from rPP could be more cost-effective because it is cheaper and more readily available than rPET. It is also considered possible to add recycled plastic fillers, such as rCaCO3, to either the first or second blend to reduce costs while retaining the necessary functional properties and achieving a total recycled content of 100%.

[0046] The present invention is not limited to the examples just presented. In other words, those skilled in the art will recognize that they can readily reproduce these examples with similar success by substituting any of the generic or specifically described recycled plastic resins, recycled plastic fillers, process conditions, and sequence of process steps mentioned anywhere in this specification for any of the ones actually used in the preceding examples.

[0047] Embodiments of the present invention provide methods for making plastic bags from recycled plastic bottles that are both generally applicable and specifically applicable.

[0048] Unless the context requires otherwise, the term "comprising" means "including but not limited to," and has the same meaning as the term "comprises."

[0049] Any reference to prior art is not an admission that this prior art is common general knowledge.

[0050] The scope of the present invention supported by the above-described embodiments is defined by the following claims.

Claims

1. A method for manufacturing a plastic bag, comprising: preparing a mixture comprising about 0.1% to 100% by weight of recycled plastic bottle resin; The mixture is put into plastic bags.

2. The method of claim 1, wherein the recycled plastic bottle resin comprises one or more of recycled polyethylene terephthalate (rPET), recycled high-density polyethylene (rHDPE), recycled low-density polyethylene (rLDPE) and recycled polypropylene (rPP).

3. The method of claim 2, wherein the mixture comprises from about 30% to about 80% by weight of recycled plastic bottle resin, with the remainder comprising one or more recycled plastic resins not from recycled plastic bottles, virgin plastic resins, recycled plastic fillers, colorants, fragrances, and odor neutralizers.

4. The method of claim 3, wherein the recycled plastic bottle resin comprises rHDPE from recycled plastic milk bottles.

5. The method of claim 4, wherein the mixture comprises from about 30% to about 50% by weight rHDPE from recycled plastic milk bottles.

6. The method of claim 3, wherein the recycled plastic resin that is not from recycled plastic bottles comprises recycled linear low density polyethylene (rLLDPE).

7. The method of claim 3, wherein the recycled plastic filler comprises recycled calcium carbonate (rCaCO3).

8. The method of claim 4, wherein the plastic bag comprises a food contact bag, wherein the recycled plastic bottle resin comprises food grade rHDPE from recycled plastic milk bottles.

9. The method of claim 3, wherein the plastic bag is a non-food contact bag, wherein the mixture comprises one or more colorants, flavoring agents, odor neutralizers, and recycled plastic fillers.

10. A plastic bag made according to the method of claim 1.