What is the knowledge of kraft paper?

Paper or paperboard produced from chemical pulp produced in the kraft process

"Craft paper" redirects here. Not to be confused with paper craft

Kraft paper or kraft[1] is paper or paperboard (cardboard) produced from chemical pulp produced in the kraft process.

Sack kraft paper (or just sack paper) is a porous kraft paper with high elasticity and high tear resistance, designed for packaging products with high demands for strength and durability.[2]

Pulp produced by the kraft process is stronger than that made by other pulping processes; acidic sulfite processes degrade cellulose more, leading to weaker fibers, and mechanical pulping processes leave most of the lignin with the fibers, whereas kraft pulping removes most of the lignin present originally in the wood. Low lignin is important to the resulting strength of the paper, as the hydrophobic nature of lignin interferes with the formation of the hydrogen bonds between cellulose (and hemicellulose) in the fibers.[3]

Kraft pulp is darker than other wood pulps, but it can be bleached to make very white pulp. Fully bleached kraft pulp is used to make high quality paper where strength, whiteness, and resistance to yellowing are important.

Manufacture

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Wood pulp for sack paper is made from softwood by the kraft process. The long fibers provide the paper its strength and wet strength chemicals are added to even further improve the strength. Both white and brown grades are made. Sack paper is then produced on a paper machine from the wood pulp. The paper is microcrepped to give porosity and elasticity. Microcrepping is done by drying with loose draws allowing it to shrink. This causes the paper to elongate 4% in the machine direction and 10% in the cross direction without breaking.[2] Machine direction elongation can be further improved by pressing between very elastic cylinders causing more microcrepping.[2] The paper may be coated with polyethylene (PE) to ensure an effective barrier against moisture, grease and bacteria, although recyclability is hindered. Zein coatings are also water resistant but allow better recyclability.[4]

A paper sack can be made of several layers of sack paper depending on the toughness needed.

Kraft paper is produced on paper machines with moderate machine speeds. The raw material is normally softwood pulp from the kraft process.

Maintaining a high effective sulfur ratio or sulfidity is important for the highest possible strength using the kraft process.

The kraft process can use a wider range of fiber sources than most other pulping processes. All types of wood, including very resinous types like southern pine,[5] and non-wood species like bamboo and kenaf can be used in the kraft process.

Qualities

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• Normal kraft paper is strong and relatively coarse. It has high tensile strength. The grammage is normally 40–135 g/m2.
• Sack kraft paper, or just sack paper, is a porous kraft paper with high elasticity and high tear resistance, designed for packaging products with high demands for strength and durability.
• Absorbent kraft paper is made with controlled absorbency (i.e. a high degree of porosity). It is made of clean low kappa hardwood kraft and has to have a good uniformity and formation.
• Spinning kraft paper is an especially strong type of kraft paper with relatively low grammage (40 g/m2). This paper requires the best possible machine direction strength and cross machine elongation. This is done by high fiber orientation on the paper machine.
• Hunting cartridge paper is a kraft paper used in shotgun shells. This paper needs a high tensile strength in the machine direction, which is the axial direction of the cartridges. In the cross direction, the cartridge is supported by the gun-pipe, but a sufficient elongation is needed. The body of the cartridge is wound of a kraft paper of 80–120 g/m2, which is further covered by an outer sheet of 60–80 g/m2 with colour and printing.
• Candy wrapping paper and twisting paper are thin 30–40 g/m2 kraft papers and are mostly flexo or offset printed. These papers require a good strength, with highly oriented fibers. Twisting paper is mostly opaque and often supercalendered.

Applications

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See also

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References

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• Yam, K. L., Encyclopedia of Packaging Technology, John Wiley & Sons, 2009, ISBN 978-0-470-08704-6

• Kraft paper at Wikimedia Commons

Kraft paper, renowned for its enduring strength and versatility, stands out as a favored packaging option in various sectors. Its widespread use spans industries, commerce, and personal applications alike. Whether you’re curious about its applications or have common questions regarding this reliable packaging material, our guide aims to provide you with a more in-depth understanding. Explore the numerous uses of kraft paper and gain insights into its enduring popularity in the world of packaging.

What is Kraft Paper?

Kraft paper, made from a blend of new and recycled chemical pulp, is robust and tear-resistant. Its eco-friendly and fully recyclable nature, coupled with high elasticity, burst resistance, and wet strength, makes it perfect for a variety of uses. Discover it in natural brown or pure paper rolls available at Continual Solutions.

What is Kraft paper used for?

Due to its strong tear-resistance, wet strength, and overall durability, Kraft paper is utilized in numerous industrial and commercial applications. It serves various purposes, including:

Heavy-duty industrial packaging
Gift wrapping
Void filling
Tray lining
Protective wrapping

Kraft paper uses

Kraft paper, created through the Kraft process using chemical pulp, is recognized for its strength, durability, and versatility. These qualities make it a widely chosen option for diverse packaging needs. Below are some typical applications of Kraft paper in packaging:

1. Corrugated Boxes:
Kraft paper is often used to make corrugated boxes, providing strength and sturdiness to packaging materials. Corrugated boxes are widely used in shipping and transportation due to their durability and protective qualities.

2. Wrapping and Cushioning:

Kraft paper is used as a wrapping material for items that require protection during shipping or storage. It can also be crumpled and used as cushioning material to protect fragile items.

3. Bags and Sacks:
Kraft paper is used to manufacture paper bags and sacks, commonly used in the packaging of groceries, cement, chemicals, and other bulk materials. These bags are favored for their strength and eco-friendly nature.

4. Envelopes:
Kraft paper envelopes are commonly used for mailing documents and other flat items. The durability of Kraft paper provides protection to the contents during transit.

5. Food Packaging:
Kraft paper offers a delightful touch to food presentation, especially for deli-style sandwiches or fresh bakery items. Its authentic deli feel and traditional bakery-style packaging make it a preferred choice. With high tear-resistance and the ability to withstand grease and liquid, Kraft paper prevents messy situations in case of leakages, making it a popular, recyclable, and cost-effective option for point-of-purchase food wrapping.

6. Labels and Tags:
Kraft paper is used to make labels and tags for various products. Its natural appearance and texture make it an aesthetically pleasing choice for labeling.

8. Book Covers:
Kraft paper is sometimes used as book covers, providing a protective layer for books and adding a rustic or natural aesthetic.

9. Industrial Packaging:
In industrial settings, Kraft paper is used for packaging heavy-duty items, machinery parts, and other industrial products. Its strength and tear resistance make it suitable for such applications.

10. Void Fill and Filler Material:
Kraft paper adds a remarkable touch to deliveries, playing a significant role beyond simple void filler or shopping box fill. It contributes to the ‘wow’ factor in package presentation, enhancing the overall unboxing experience and adding a unique element to deliveries.

Kraft paper’s versatility, strength, and eco-friendly properties make it a popular choice across various industries for packaging solutions. Its use aligns well with the growing emphasis on sustainable and environmentally friendly packaging options.

Feel free to reach out to Continual Solutions today for top-notch Kraft paper solutions. Whether you’re aiming to showcase, package, or protect your products, our premium selection of natural Kraft paper is precisely what you need.