Patent Application
20240253880
The present application relates to the field of packaging materials for packaging products, in particular packaging materials suitable as alternatives to plastic shrink wrap.
Plastic shrink wrap is a type of plastic film that is used to cover and seal products. The most common uses for plastic shrink wrap are for packaging products such as food, beverages, and consumer goods, and for industrial packaging, such as for palletized goods. Environmental concerns of plastic shrink wrap are significant. It is not easy to recycle when shrink film is crosslinked or when it has multiple layers of various polymers. Plastic shrink wrap can be harmful to the environment if not properly disposed of. Typical plastic shrink wrap is not biodegradable and can take hundreds of years to degrade. When not properly disposed of, plastic shrink wrap can end up in oceans and other bodies of water, where it can harm marine life. Additionally, it is not easy to recycle plastic shrink wrap, and it is difficult to reprocess.
Accordingly, there is a need to replace plastic shrink wrap with a more sustainable packaging material. Biodegradable shrink wrap is an alternative to plastic shrink wrap that is more environmentally friendly. Biodegradable shrink wrap is a type of plastic shrink wrap that is made from biodegradable materials. While biodegradable shrink wrap may be a more environmentally friendly option than traditional plastic shrink wrap, biodegradable shrink wrap is typically more expensive than traditional plastic shrink wrap. Additionally, biodegradable shrink wraps may require a specific environment to break down, such as a commercial composting facility.
Accordingly, those skilled in the art continue with research and development in the field of packaging materials suitable as alternatives to plastic shrink wrap.
Disclosed are stretchable barrier wraps.
In one example, the disclosed stretchable barrier wrap includes an extensible cellulosic substrate having a stretchability of at least 5% and an aqueous polyolefin dispersion barrier layer on the extensible cellulosic substrate.
Also disclosed are methods for manufacturing stretchable barrier wraps.
In one example, the disclosed method for manufacturing a stretchable barrier wrap includes the steps of providing an extensible cellulosic substrate having a stretchability of at least 5% and coating an aqueous polyolefin dispersion barrier layer on the extensible cellulosic substrate.
Other examples of the disclosed stretchable barrier wraps and methods for manufacturing stretchable barrier wraps will become apparent from the following detailed description, the accompanying drawings and the appended claims.
A cellulosic substrate, such as a paper substrate, is a material that is made from cellulose, which is a natural polymer that is the main component of plant cell walls. Cellulosic substrates are often used in the paper and pulp industry, as well as in other applications such as textiles, food packaging, and biomaterials. The most common cellulosic substrates are papers, paperboard, cardboards, etc. Typically, the cellulosic substrates may be made by breaking down wood or another natural cellulose-based material, into fibers, which are then mixed with water to form a pulp. The pulp is then formed into sheets, which are pressed and dried to make paper. Cellulosic substrates can also be derived from other plant-based materials such as cotton, hemp, or flax. The extensible cellulosic substrate may comprise a web of cellulosic fibers. In an aspect, the extensible cellulosic substrate is made up of at least 50% fibers by weight. In another aspect, the extensible cellulosic substrate is made up of at least 60% fibers by weight. In another aspect, the extensible cellulosic substrate is made up of at least 70% fibers by weight. In another aspect, the extensible cellulosic substrate is made up of at least 80% fibers by weight. In another aspect, the extensible cellulosic substrate is made up of at least 90% fibers by weight.
The cellulosic fibers used to form the extensible cellulosic substrate can be selected to provide the stretchable barrier wrap with desired properties. The web of cellulosic fibers can comprise different types of cellulosic fibers. Exemplary cellulosic fibers that can be used include wood fibers and non-wood fibers. Wood fibers can include hardwood fibers, softwood fibers, or a blend of hardwood and softwood fibers. Wood fibers can be, for example, from northern hardwood, northern softwood, southern hardwood, or southern softwood. In a specific example, the wood fibers can be a blend of northern hardwood and northern softwood. The fibers can also be bleached or unbleached. Wood fibers can include virgin fibers, recycled fibers or a combination thereof. Wood fibers used in the invention can be extracted with various pulping techniques. Chemical pulping can be used incorporating kraft, sulfite, and soda processing. In a specific example, wood fibers are kraft fibers extracted using kraft processing. In an aspect, the exemplary cellulosic substrate may include a high content of lignin. For example, the lignin content may be preferably at least 8%, by weight percent, more preferably at least 9%, more preferably at least 10%, more preferably at least 11%, more preferably at least 12%, more preferably at least 13%, more preferably at least 14%, more preferably at least 15%, more preferably at least 16%, more preferably at least 17%, more preferably at least 18%, more preferably at least 20%. A desired lignin content may be achieved by, for example, selecting a suitable cellulosic material and a suitable pulping process. A preferred cellulosic material having high lignin content and having high fiber length cellulosic fibers includes softwood. A desired lignin content may also be achieved by blending hardwood and softwood and by blending virgin and recycled cellulosic fibers. The cellulosic substrate may take the form of a multi-wall cellulosic substrate, such as a two-ply pasted cellulosic substrate. Such a multi-wall cellulosic substrate may provide for improved burst and puncture resistance.
The extensible cellulosic substrate is characterized by its ability to stretch. The extensible cellulosic substrate may have a stretchability of at least 5%, preferably at least 6%, more preferably at least 7%. In specific examples, the extensible cellulosic substrate may have a stretchability of in a range of from 5% to 12%, or in a range of from 6% to 11%, or in a range of from 7% to 10%. Stretchability is measured in accordance with the TAPPI standard Test Method TAPPI/ANSI T 494 om-22 for measuring the tensile properties of paper and paperboard, using constant rate of elongation apparatus. This is a standard test method that is used to determine the stretchability of paper or cellulosic substrate. The test method involves measuring the amount of elongation of a strip of paper. The test involves clamping a sample of paper at a specific distance apart and then applying a force to the sample until it breaks. The elongation of the sample is measured, and the percent stretchability of the paper is calculated based on this measurement. The TAPPI/ANSI T 494 test is widely used in the paper industry to determine the stretchability of paper. The stretchability of the cellulosic substrate may be provided by the formation of crepes, which may formed into the cellulosic substrate during the manufacture of the cellulosic substrate or in a secondary process after manufacture of the cellulosic substrate, to impart the desired stretchability to the cellulosic substrate. A type of kraft paper known as “extensible kraft paper” can be used due to its high elasticity and high tear resistance properties. A preferred extensible kraft paper is FibreShield® available from Westrock Company.
The extensible cellulosic substrate may have a basis weight selected according to the intended application. In an aspect, the extensible cellulosic substrate may have a basis weight in a range of from 30 to 120 lb/3000 sq ft. In another aspect, the extensible cellulosic substrate may have a basis weight in a range of from 35 to 100 lb/3000 sq ft. In another aspect, the extensible cellulosic substrate may have a basis weight in a range of from 40 to 80 lb/3000 sq ft. In another aspect, the extensible cellulosic substrate may have a basis weight in a range of from 45 to 55 lb/3000 sq ft. The extensible cellulosic substrate may have a caliper thickness selected according to the intended application. In an aspect, the extensible cellulosic substrate may have a caliper thickness in a range of from 3 to 10 points.
The extensible cellulosic substrate may have a tensile strength selected according to the intended application. In an aspect, the extensible cellulosic substrate may have a tensile strength in a range of from 10 to 90 lbf/in. In another aspect, the extensible cellulosic substrate may have a tensile strength in a range of from 15 to 70 lbf/in. In another aspect, the extensible cellulosic substrate may have a tensile strength in a range of from 20 to 40 lbf/in. The tensile strength is measured in accordance with the TAPPI/ANSI T 494 tensile test for measuring the tensile properties of paper and paperboard, using constant rate of elongation apparatus. This is a standard test method used to measure the tensile strength and elongation of paper and board. This test method is based on the tensile test, which measures the maximum force required to break a strip of paper and the elongation at that point. The test is performed by clamping the sample at a specific distance apart and then applying a tensile load to the sample until it breaks. The maximum force required to break the sample, as well as the elongation at that point, are recorded and used to calculate the tensile strength and elongation of the paper.
The extensible cellulosic substrate may have a tensile energy absorption (TEA) selected according to the intended application. In an aspect, the extensible cellulosic substrate may have a TEA in a range of from 5 to 100 ft. lbs./ft2 In another aspect, the extensible cellulosic substrate may have a TEA in a range of from 10 to 50 ft. lbs./ft2. In another aspect, the extensible cellulosic substrate may have a TEA in a range of from 15 to 25 ft. lbs./ft2. The TEA is measured in accordance with the TAPPI/ANSI T 494. Tensile energy absorption is determined by mechanical testing that determines the amount of energy a material can absorb before it breaks under tensile stress. The test involves applying a tensile load to a specimen of the material and measuring the amount of energy absorbed by the specimen as it stretches and eventually breaks. The test results is typically used to evaluate the material's strength and ductility, and to compare the energy absorption capabilities of different materials.
Referring to
The aqueous polyolefin dispersion barrier layer may include, for example, polyethylene or polypropylene.
According to an aspect of the present description, the aqueous polyolefin dispersion barrier layer may include a pigment. The pigment may include, for example, a clay and or a calcium carbonate. Other pigments, such as plastic pigments, titanium dioxide pigment, zinc oxide pigment, mica, silicas, bentonite, montmorillonite clays, hollow sphere pigments, talc pigment and the like, may be used without departing from the scope of the present disclosure. The ratio of the binder to the pigment is preferably at least 1 to 2. In an aspect, the pigment is primarily clay, preferably at least 50 percent by weight to the total pigment weight, more preferably at least 60 percent by weight, more preferably at least 70 percent by weight, more preferably at least 80 percent by weight, more preferably at least 90 percent by weight, more preferably at least 95 percent by weight, more preferably at least 98 percent by weight, more preferably at least 99 percent by weight. The aqueous polyolefin dispersion barrier layer may preferably have a coat weight, on a dry basis, of at least 0.5 lb/3000 ft2, such as in a range from 0.5 lb/3000 ft2 to 20 lb/3000 ft2, preferably ranging from 1 lb/3000 ft2 to 12 lb/3000 ft2, more preferably ranging from 2 lb/3000 ft2 to 10 lb/3000 ft2. The aqueous polyolefin dispersion barrier layer provides a barrier property, particularly a moisture barrier property, to the extensible cellulosic substrate, without creating a problem with the blocking of the resulting stretchable barrier wrap.
Referring to
Referring to
The extensible cellulosic substrate may further include a printed ink on the printable coating to display information relating to the contents of a container formed therefrom. The extensible cellulosic substrate may be printed with indicia, such as high-quality advertising text and graphics, by a printing operation. The printing operation may include any apparatus or system capable of marking the extensible cellulosic substrate with indicia. For example, the printing operation may include a printing press capable of printing high quality text and/or graphics (e.g., advertising text and graphics) onto the extensible cellulosic substrate. Specific examples of printing techniques include offset printing, gravure printing, flexographic printing and digital printing.
The present description provides for a stretchable barrier wrap that offers good repulpability and recyclability. The combination of a mechanically strong and stretchable cellulosic substrate with moisture barrier properties enables for an environmentally sustainable stretchable barrier wrap suitable for plastic shrink wrap replacement.
The following paper substrate was used in the examples: Kraft Paper FibreShield® Porous, manufactured at Longview mill, WestRock, basis weight 49.2 lb/3000 F2. Raw materials that can be used in the barrier coating formulations are shown in Table 1.
One side or both sides of the paper was/were coated on a blade coater using the Polyolefin Barrier Dispersion (POD-1) for the examples listed in Table 2.
The coat weight values (lb/3000 ft2) and the test results of the coated extensible paper are shown in Tables 2 and 3.
Water barrier property of the coated paper was evaluated by water Cobb (TAPPI Standard T441 om-04) in g/m2 per 2 minutes or 15 minutes, using 23° C. water. In other words, the Cobb test determines how much water is absorbed after 2 minutes or 15 minutes.
Gurley Porosity of the samples was tested according to the TAPPI standard Test Method T 460 om-21 (Air resistance of paper—Gurley method). The test is performed by measuring the time it takes for a known volume of air to pass through a sample of the paper or board at a known pressure. The test result is reported as the Gurley number, which is the time, measured in seconds, for a specified volume of air to pass through a sample of the paper or board. The lower the Gurley number, the more porous the paper or board is considered to be.
Coefficient of Friction (COF) testing was conducted on a Hanatek Advanced Friction Tester according to TAPPI standard T-549. Top samples were cut to 2.5 inch by 2.5 inch to mirror the sled dimensions and bottom samples were cut to 4 inch by 8.5 inch. They were tested along machine-direction (MD) and cross-direction (CD), respectively, with the print (the second) side against the print (the second) side of the coated substrate. The Static COF and Dynamic COF of both MD and CD were recorded. High COF can help to avoid anti-skid property when packages are stacked on a pallet.
Mullen Burst Strength (or Bursting Strength) of the samples were tested on a Mullen burst tester according to the TAPPI standard Test Method TAPPI/ANSI T 403 om-22 (Bursting strength of paper). Test samples were conditioned under TAPPI (23° C., 50% RH) or Tropical (38° ° C., 90% RH) environment for overnight before testing.
Four tensile breaking properties of the samples, including Tensile Strength, Modulus (tensile stiffness), Stretch, and TEA (tensile energy absorption), were tested according to the TAPPI standard Test Method TAPPI/ANSI T 494 om-22 (Tensile Properties of Paper And Paperboard, Using Constant Rate Of Elongation Apparatus). Test samples were conditioned under Tappi (23° C., 50% RH) or Tropical (38° C., 90% RH) environment for overnight before testing.
The following paper substrate was used in the next set of examples: Kraft Paper FibreShield® Porous, manufactured at Longview mill, WestRock, basis weight 55.3 lb/3000 ft2. The barrier coatings with formulations as shown in Table 5 were applied on one side of the substrate on a pilot blade coater. Raw materials that can be used in the barrier coating formulations are shown in Table 1.
The coat weight values (lb/3000 ft2) and the test results of the coated extensible paper are shown in Tables 6 and 7 and 8.
Further, the disclosure comprises examples according to the following clauses:
Although various examples of the disclosed stretchable barrier wraps and methods for manufacturing stretchable barrier wraps have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications and is limited only by the scope of the claims.
This application claims priority from U.S. Ser. No. 63/481,867 filed on Jan. 27, 2023, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63481867 | Jan 2023 | US |
