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Kraft Paper Laminated Woven bags Production Process

Kraft paper laminated woven bags represent a harmonious blend of strength, durability, and aesthetic appeal, making them a preferred choice across diverse industries. Understanding the intricate production process behind these versatile bags is crucial for manufacturers aiming to deliver quality products. In this comprehensive guide, we delve into the step-by-step process of crafting kraft paper laminated woven bags, exploring each stage in detail.

1. Material Selection:
The production journey begins with meticulous selection of raw materials. For the woven component, high-density polyethylene (HDPE) or polypropylene (PP) are commonly chosen due to their exceptional tensile strength and tear resistance. These materials undergo weaving processes to create robust woven fabric sheets.

Simultaneously, kraft paper, renowned for its natural look and moisture resistance, is carefully sourced. The paper is typically made from wood pulp through a chemical pulping process, ensuring optimal quality and consistency. Manufacturers may opt for different grades of kraft paper depending on specific bag requirements, ranging from standard to heavy-duty variants.

2. Lamination Process:
The heart of the production process lies in laminating the woven fabric with kraft paper to create a cohesive composite material. This is achieved through a multi-step lamination process, ensuring strong adhesion and uniformity.

Initially, the kraft paper undergoes surface treatment to enhance its bondability with the woven fabric. This treatment may involve applying primers or coatings to the paper surface, optimizing its compatibility with adhesives.

Subsequently, the treated kraft paper is precisely aligned with the woven fabric sheets on a laminating machine. Adhesive layers, typically based on thermoplastic polymers like polyethylene or polyurethane, are applied between the kraft paper and woven fabric to facilitate bonding.

The laminating machine utilizes heat and pressure to activate the adhesive, securely fusing the kraft paper to the woven fabric. This process ensures a strong and durable bond while minimizing the risk of delamination or separation during bag usage.

3. Printing and Design:
Once the lamination process is complete, the composite material is ready for printing and design customization. Manufacturers employ various printing techniques, including flexography, gravure, or digital printing, to apply logos, branding elements, product information, and decorative designs onto the bag surface.

Advanced printing technologies allow for high-resolution graphics and vibrant colors, enhancing the visual appeal of the bags. Additionally, manufacturers may offer customization options such as matte or glossy finishes to cater to diverse aesthetic preferences.

4. Cutting and Stitching:
After printing, the laminated material is precision-cut into individual bag panels according to predetermined dimensions. Automated cutting machines ensure accuracy and consistency, minimizing material wastage.

Subsequently, the cut panels are fed into stitching machines, where skilled operators stitch them together to form complete bags. High-strength sewing threads, selected for their durability and resistance to abrasion, are used to create robust seams that withstand the rigors of handling and transportation.

5. Quality Control:
Quality control checkpoints are strategically integrated throughout the production process to uphold stringent standards and ensure the integrity of the final product. These checkpoints encompass visual inspections, dimensional measurements, and mechanical testing.

Skilled quality assurance personnel meticulously examine each batch of bags for defects such as uneven lamination, printing errors, stitching irregularities, or structural weaknesses. Advanced testing equipment may also be employed to assess factors like tensile strength, tear resistance, and moisture barrier properties.

6. Packaging and Distribution:
Upon passing rigorous quality checks, the finished kraft paper laminated woven bags are carefully packaged to protect them during transit and storage. Manufacturers may utilize shrink wrapping, palletization, or bundling techniques to optimize space utilization and minimize handling damage.

Efficient logistics and distribution networks ensure timely delivery of the bags to customers across domestic and international markets. Collaborative partnerships with logistics providers facilitate seamless supply chain management, enhancing customer satisfaction and loyalty.

Conclusion:
The production process of kraft paper laminated woven bags is a testament to precision engineering, innovative technology, and meticulous craftsmanship. From material selection to final packaging, every stage is orchestrated with utmost care to deliver superior quality products that meet the diverse needs of industries worldwide. By understanding and optimizing each aspect of the production process, manufacturers can elevate their offerings and drive sustained growth in a competitive market landscape.

]]> https://queen-plast.com/index.php/2024/08/14/kraft-paper-laminated-woven-bags-production-process-in-new-york/feed/ 0 Are Plastic Bags Waterproof ? https://queen-plast.com/index.php/2024/08/14/are-plastic-bags-waterproof/ https://queen-plast.com/index.php/2024/08/14/are-plastic-bags-waterproof/#respond Wed, 14 Aug 2024 22:22:29 +0000 https://queen-plast.com/?p=819

Are Plastic Bags Waterproof ?

Are pp woven bags waterproof? As far as the woven bag itself is concerned, because the woven bag is made of warp and weft tapes, there is only overlap between the tapes, which does not have sealing property. Therefore, the liquid will be left through the gap between the tapes, so the woven bag itself is not waterproof.

However, due to the special requirements of chemical industry, cement, chemical fertilizer, sugar and other industries for packaging, a considerable number of plastic woven bags must have the function of waterproof and sealing. At present, there are mainly two types of waterproof and sealed woven bags produced and applied in the market: one is the ordinary separate combined packaging bag with outer woven bag and inside liner inserted or stitched bag. The other is the composite woven bag coated with a layer of plastic film on the PP woven cloth, which will include two types also, either polypropylene coated woven bag or pp woven laminated bag.

The production equipment and process of the first kind of separated inner lining membrane woven bag are relatively simple, the equipment investment is low, and the application is very wide. The inner and outer bags are separated. The inner bag is blown film bag, which can be divided into LDPE and HDPE. The outer bag is ordinary PP woven bag, and the length and width of the inner bag are slightly larger than the outer bag. When loading materials, the inner and outer bags are uneven and easy to be damaged. In the early years, the inner and outer bags of the inner lining membrane bag and the outer bag need to be set together manually, and the inner and outer bags at the mouth of the bag need to be aligned and sewed, so the production efficiency is low, the waste of manpower is large, and the continuous and efficient production cannot be carried out. A skilled operator can only complete about 1000 bags by hand every day, and only about 300 bags can be sewn by hinge sewing machine every day. Nowadays, with the improvement of all-in-one machine, there are many machinery manufacturers in China that can produce all-in-one machines for bag cutting, sewing and lining. The technology has been widely used and tends to be mature, greatly improving the production efficiency.

Another kind of Coated plastic woven bag production must go through the coating process, using the extrusion coating machine to coat a layer of plastic film with a thickness of about 0.02 ~ 0.04mm on the outside of the woven pp cloth. Or at the same time, to use the coating material as the bonding medium, and then composite a layer of BOPP film on the surface, can achieve better waterproof effect, it was named BOPP
pp woven laminated bag. When doing coating, the temperature of the extruded film is about 300 ℃, and the newly extruded film is combined with the braid by a pair of cooling rollers. However, such high temperature reduces the strength of the cloth surface, reduces the elasticity, increases the brittleness of the bag surface, and makes the bag easier to be damaged in the falling tests.

]]> https://queen-plast.com/index.php/2024/08/14/are-plastic-bags-waterproof/feed/ 0 Production Process of Polypropylene Woven Bags in California https://queen-plast.com/index.php/2024/08/14/production-process-of-polypropylene-woven-bags-in-california/ https://queen-plast.com/index.php/2024/08/14/production-process-of-polypropylene-woven-bags-in-california/#respond Wed, 14 Aug 2024 22:22:24 +0000 https://queen-plast.com/?p=818

Production Process of Polypropylene Woven Bags

Production process of Woven polypropylene bags contains knowlege about plastic industry, textile weaving, and even chemistry. This article is going to introduce the complete production process of how the polypropylene resin becomes a finished woven polypropylene sack step by step.

Sumarize of Woven polypropylene bags production process.

Overall, though the production process of woven pp sacks requires multiple equipments, it’s still an industry with simple process flow, easy control of process parameters, easy equipments operation, high production efficiency. Actually it’s mostly benefited from its stable and reliable equipments with safe operation and low maintenance rates. Specific manufacturing process steps of woven polypropylene (PP) bags will be as follows,

Polypropylene tapes drawing.
Circular weaving.
Coating and lamination.
Printing.
Cutting and sewing.
Baling.

Production process of Woven polypropylene bags specific steps.

Step 1 , Polypropylene Tapes Drawing

1. Raw material

Raw material of woven polypropylene ( PP ) bags are divided to powder polypropylene and particle polypropylene. For different pp woven bag applications, manufacturers are taking different types of polypropylene materials and added with different additives. In the early stage of this industry, almost all the manufacturers were using 100% particle polypropylene material. With development of technology, more and more manufacturers awared that to add a certain percentage of modifying material ( mainly Caco3 ) could not only increase the stability of materials but also could greatly reduce material costs, the percentage is commonly controlled within the range of 20%-40%.

2. Manufacturing process of polypropylene tapes drawing

After raw material of Polypropylene and additives were put into the extruder, it is heated at 190-250 ℃ and sheared by the screw and barrel. After plasticization process, the material is extruded at constant pressure and velocity. After formed by the tooling die, materials enter into the cooling water in shape of melted film. After cooling, the film is slit into narrow embryo yarns by the blades. Then the embryo yarn is being stretched in the oven with high temperature until it comes out in shape of flat tapes. Then the flat tapes are heat set on the hot rollers, and shrink at low traction speed. Finally, the flat tapes are rewinded by the disk differential tension winding system. It becomes the base structure of pp woven fabric and woven polypropylene sacks.

3.Technological indexes of polypropylene tapes drawing.

The technological indexes of polypropylene tapes manufacturing are mainly divided into four categories:

Physical and chemical modification index. It mainly includes blending modification, blending ratio, adding ratio of functional additives and blending ratio of recycled materials.
Physical property and rheological index. It mainly includes draft ratio, inflation ratio and retraction ratio.
Mechanical performance index. It mainly includes breaking force, relative breaking force, and elongation at break, linear velocity and linear density deviation;
Dimension tolerance index. It mainly includes the thickness and width of flat tapes (yarn).

Step 2. Circular Weaving.

1.Circular knitting process

First of all, the warp tape is drawn out from the bottom of each row of spindles on the warp frame. Through the porcelain hole on the warp frame, to the first vertical plate, to the yarn pressing roller, to the yarn feeding roller, to the yarn guiding roller, to the second vertical plate, to the yarn guiding roller,to the magnetic hole, to the tension rod, to the round steel buckle, to the warp fixing ring and reach the reserved cloth base. Meanwhile, the weft tapes are loaded into the shed, when the circular looms starts to run, shuttles move in circling running. With close cooperation of the warp tape supplying system and the shuttle pushing device, warp tapes and weft tapes are knnited as tubular woven polypropylene fabric. Traction device was equiped on the top of the loom which would guides tubular fabric to a press roller and then goes to rewinding device behind the warp frame. Common type 4 shuttles circular looms could knit around 2300meters of Woven polypropylene fabric rolls every 24hours.

2. Main manufacturing index of polypropylene circular knitting process

Weaving density.

Weaving density refers to the number of warp and weft tapes in a 100 mm × 100 mm area. Different applications of woven polypropylene bags require different weaving density. A case in point, bags for flour packing will requires more tighter weaving to avoid leakage of flours. The density of commonly used woven fabric is 36 × 36 pieces / 10cm, 40 × 40 pieces/10 cm, 48 × 48 / 10 cm. (Some countries are using mesh density per square inch, like 7×7, 10×10, 14×14 etc.)

Tensile strength of woven fabric.

Tensile strength is also called tensile capacity, tensile force. For pp woven fabric, it bears tensile strength in warp and weft directions, so it is called warp tensile strength or weft tensile strength also. It’s the most important index of woven fabric which decides how heavy or capacity could a polybag carries. Unit of Tensile strength Newton/5cm.

Unit Weight per square meter of pp woven fabric.

The weight per unit area of woven fabric is expressed by gram weight per square meter, which is an important technical index of woven fabric. Gram weight per square meter mainly depends on the density of warp and weft and the thickness of flat yarn. Gram weight per square meter affects the tensile strength and load capacity of woven fabric. PP woven bags manufacturers control their costs of material by adjusting the g/m2 of the pp woven fabric what they are using. In some countries, Denier is also used to express the thickness of woven polypropylene fabric, as to how to cover denier to gsm please visit our article How to Convert Denier of PP Woven Fabric to GSM.

Width.

The width of woven fabric directly affects the bag making process. For tubular fabric, the width is expressed by half of the circumference. Width also involves the shrinkage rate. After cutting, printing and sewing, the width of the bag will be slightly smaller than that of the cloth width which just been woven, which we call it width retraction.

Step 3. Coating and lamination.

1.Manufacturing process of coating and lamination.

Working principle of coating and lamination are exactly same which is to compound the melted polypropylene and Polyethylene onto pp woven fabric. The difference is when we saying lamination, we are using BOPP film or kraft paper to compound with woven polypropylene fabric while doing coating. Coating and lamination could be made on one side or both sides of woven pp fabric. For different materials lamination, differnent ratio of resins are taken as lamination material. For instance, for Bopp to pp woven fabric lamination, perfect ratio is 3PP:1PE, but for Kraft paper to PP woven fabric lamination, the perfect ratio will goes to 3PE:1PP. Temperature setting on extrusion dies needs to be adjusted accordingly as well.

2.Main manufacturing index of coating and lamination.

Main manufacturing index of coating and lamination is the controlling skill on temperature setting, coating pressure setting, and coated material peeling off strength.

Step 4. Printing

There are two typical types of printing method for pp woven sacks.

Flexographic Printing. Please visit our article”Can PP Woven Bags Be Printed” for detailed information about flexographic printing.
Rotogravure Printing.Please visit our article”Gravure Printing for Woven Bags” for detailed information about Rotogravure printing.

Step 5. Cutting and Sewing

In the initial development stage of woven bag production industry, bag cutting and sewing are divided into two separate steps. With the development and updating of technology and production equipment, the cutting and sewing processes of woven bags have gradually merged into two different units on a machine.

1.Cutting

The woven bag cutting is divided into heat cutting and cold cutting.

Heat cutting. For those woven bags that are not been laminated, a high-temperature blade should be used to cut the bag while ironing the cut tapes to avoid scattering.
Cold cutting. that is to cut bags with a blade at room temperature, is only for those woven bags that have been coated. The cold cutting process does not require heating blades, so the power consumption is less.

2.Sewing

The sewing thread is polyester threads now which was made by cotton. Different thickness of the sewing thread, needle pitch would affects the strength of the sealing. Customer could choose to use single stitch or double stitch on the bottom of the bags.

The sewing and cutting machine is a type of all-in-one machine, it may intergrated with functions of sewing,cutting,gusseting,liner inserting, handle punching or even top hemming. Among the complete manufacturing process of pp woven bags, sewing and cutting machines offers functional options for different bags’ applications.

Step 6. Baling

Packing volumetric directly decides how much freight would be the freight cost for shipping, different type of baling machines offers diffrent pressures on packed pp woven bags, the more pressure it offers, the less volumetric could get. This logic makes Hydraulic type of baling machines popular in current markets.

After baling, the complete manufacturing process of pp woven bags has been done and it’s been ready for shipping.

For the readers of this article, if you are interested in set up an factory for pp woven bags manufacturing, we would like to recommend you to start from importing pp woven fabric and do sewing and cutting at your side, that would be more simple and cost-effective to start with.

For any question about PP woven bags manufacturing, welcome to contact us for further discussion.

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