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Corrugated Là Gì

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Most items at your favorite supermarket, discount store, or shopping mall were safely delivered in boxes made of corrugated cardboard, and many are displayed in the same boxes, which were manufactured so they could be opened and used for this purpose. Other items may arrive in their own corrugated or uncorrugated paperboard boxes. Because corrugated cardboard is such a versatile packaging material, millions of tons are used each year to protect and display products. During 1992, more than 25 million tons of corrugated cardboard were produced in the United States. Another 6 million tons of uncorrugated boxboard or paperboard were also produced for use in folding cartons.Bạn đang xem: Corrugated là gì

Corrugated cardboard is a stiff, strong, and light-weight material made up of three layers of brown kraft paper. In 1884, Swedish chemist, Carl F. Dahl, developed a process for pulping wood chips into a strong paper that resists tearing, splitting, and bursting. He named it the kraft process because it produces a strong paper that resists tearing, splitting, and bursting.

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From the paper mill, rolls of kraft paper are transported to a corrugating, or converting, plant. At the plant, layers of kraft paper are crimped and glued to form corrugated cardboard, which is then cut, printed, folded, and glued to make boxes. At the beginning of this process, kraft rolls from the paper mill are loaded into a huge machine called a corrugator. A typical corrugator is as long as a football field—300 feet (91.44 meters). Some rolls of kraft paper are used as the corrugating medium, and others are used as liners, the layers of kraft paper glued on each side of the medium. After the corrugator has heated, glued, and pressed the kraft paper to form corrugated cardboard, the continuous sheet of cardboard is cut into wide box blanks that then go to other machines for printing, cutting, and gluing. Finally, batches of finished boxes are banded together for shipping to the food processor, toy maker, automobile parts distributor, or any of the thousands of businesses that depend on corrugated cardboard packaging.

Raw Materials

Fast-growing pine trees provide the primary raw material used to make corrugated cardboard. The largest packaging companies own thousands of acres of land where trees are matured, harvested, and replaced with seedlings. After the trees are harvested, they are stripped of their limbs; only the trunks will be shipped by truck to a pulp mill. The largest packaging companies also own the mills where trees are converted to kraft paper. At the mill, the harvested tree trunks are subjected to the kraft process, also known as the sulfate process because of the chemicals used to break down wood chips into fibrous pulp. After pulping and other processing, the fibers are sent directly to the paper machine where they are formed, pressed, dried, and rolled into the wide, heavy rolls of kraft paper sent to corrugating plants to be made into cardboard.

At the corrugating plant, only a few other raw materials are needed to make a finished box. Com starch glue is used to bond the corrugated medium to the liner sheets. Because so much glue is used, rail cars or large tanker trucks deliver it as a dry powder that will be stored in huge silos at the corrugating plant until it is needed. Drawn from the silo, the dry com starch is mixed with water and other chemicals and pumped into the corrugator to be spread on the corrugated medium as the layers of liner are added. Other raw materials are used to finish the corrugated cardboard after production. Waxes made from paraffin or vegetable oils can be applied to make a water- or grease-resistant container for food products. Brightly colored inks are also applied to create bold graphic designs for self-supporting displays featuring product name, information, and company name and logo. Teams of salespeople and designers work together to create the manufacturing and printing patterns, called dies, that are used to cut and print a specific box design. The dies are created in a pattern shop and transferred to the rotary die-cutting equipment and printers that finish the box blanks.

Design

Kraft paper has been manufactured since 1906. Since then, pulp processing, paper making, and corrugating operations have been developed to a high state of efficiency and productivity. Today, in the corrugated cardboard industry, designers are creating innovative containers that require four-color printing and complex die-cutting. These innovative containers are designed with sophisticated software such as computer- aided design (CAD) programs, allowing a packaging designer to brainstorm different package designs before manufacturing begins. A designer using a CAD program can call up and modify different designs that have been stored in a computer design library. Thus, existing packages can generate new designs. Many retail stores use such light, strong, and colorful containers directly, as point-of-purchase displays.

The Manufacturing Process

Pulping the pine chips

1 Manufacturing a corrugated cardboard box begins with the pulping of wood chips in the kraft (sulfate) process. First, tree trunks are stripped of bark and torn into small chips. Next, these chips are placed in a large, high-pressure tank called a batch digester, where they are cooked in a solution, or liquor, made of sodium hydroxide (NaOH) and several other ionic compounds such as sulfates, sulfides, and sulfites. These strongly alkaline chemicals dissolve the lignin, the glue-like substance that holds the individual wood fibers together in a tree trunk.

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2 When the pressure is released after several hours, the wood chips explode like popcorn into fluffy masses of fiber.

Making kraft paper

3 After additional cleaning and refining steps, a consistent slurry of wood pulp is pumped to the paper-making machine, also known as a Fourdrinier machine. Gigantic, square structures up to 600 feet long (182.88 meters), these machines contain a wire mesh in which the paper is initially formed. Next, the paper is fed into massive, steam-heated rollers and wide felt blankets that remove the water. At the end, the finished medium, or liner, is rolled for shipment.

Shipping and storing the kraft paper

4 Rolls of kraft paper for corrugating are available in many sizes to fit the production equipment at different corrugating plants. The most common roll sizes are 67 inches (170.18 centimeters) wide and 87 inches (220.98 centimeters) wide. An 87- inch roll of heavier paper can weigh up to 6,0 pounds (2, 724 kilograms). As many as 22 rolls of 87-inch paper can be loaded into one railroad boxcar for shipment to a corrugating plant.

5 At the plant, the kraft paper is separated into different grades, which will be used for the medium and the liner. These different grades of corrugated cardboard can be made by combining different grades of kraft paper. A knowledgeable packaging specialist works with a customer to determine the strength required for the corrugated cardboard container being planned. Then, when a plant receives an order for containers, a product engineer specifies the combination of medium and liner to produce a cardboard to match the customer’s requirement.

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Corrugating the cardboard

6 Using powerful fork-lifts, skilled equipment operators select, move, and load rolls of kraft paper at one end of the corrugator.

Chuyên mục: Chia Sẻ

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