What is valve bag?

Valve bag is one of the most commonly used packaging solution especially for those products in powder form, flours, activated carbon, plastic particles and cement, to name a few. One of the most significant features of valve bag is the small opening or valve on the corner through which it is filled. The valve is made with an inner flap which functions as a self-closing check valve after filling. It is available with a plain valve or with an extended inner sleeve of paper or film. If an extended "tuck-in sleeve" is used, the sleeve is manually folded down and back into the pocket under the sleeve for positive closure against sifting. Simply put, when the filling is complete, the pressure of the content inside the bag will automatically seal the valve mouth and achieve the self-sealing function.

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What is a Pinch-Bottom?

As the name suggests, this is a form of bag design on the bottom of the bag. simply speaking, when the material is filled inside the bag, the special gusseted bottom flattens out, allowing the bag to stand up on its own. Thera are many merits on this feature, one of the most practical one is that during transportation, instead of laid flat, standing up bags will save considerable storage space and operation times by which increase efficiency and economic benefits. In addition, the pinch-bottom is also a strengthening of the bottom by extruding layers of kraft paper, or plastic films together to provide extra intensity. Hence, this kind of bag are commonly used to carry medium and heavy materials from 25kg to 50kg depending on the requirements.

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How does valve bag work?

Valve bag doesn’t work on its own, they have to work in coordinate with the machine. Valve bagging is when a bag is filled using a specialized machine. The machine uses a spout placed in or near the opening of the bag. A measured amount is placed in each bag. This can be done in a fully automated or semi-automated manner. This ensures consistency in quantity and minimizes lost product. In addition, the details of the valve mouth can be readily changed in accordance with the machine since different industries have different types of filling machines. This kind of automation has allowed much higher efficiency in comparison to manual operations. Meanwhile, it decreases the risks of contamination to the working environment as well as protecting the well-being of the workers.By and large, there are two major types of valve bags made from kraft paper, and plastic. Occasionally, according to the storage requirements of concrete materials, multiple layers of films will be extruded together to produce a multiwall valve bag.

High Speed Filling

Efficiency is the dominating feature for many industries. The common industrial filling using normal packaging bag has its own limitations. It will cost a considerable amount of wastage because the machine and the design of bag doesn’t match. For the same reason, the wastage of raw materials will contaminate the working environment by which threatening the well-beings of workers involved in the production line. The application of valve bag has prevented wastage from happening meanwhile protect workers from being exposed to possible contamination. Hence, the design of valve bag as well as the invention of filling machines have solved such problems once and for all and contributes to the construction of a clean working environment.

Different types of valve bags

By and large, there are two major types of valve bags made from kraft paper, and plastic. Occasionally, according to the storage requirements of concrete materials, multiple layers of films will be extruded together to produce a multiwall valve bag.

PE valve bag

Polyethylene or polythene (abbreviated PE) is the most common plastic in use nowadays. It is a polymer, primarily used for packaging (plastic bags, plastic films, etc.). As of 2017, over 100 million tonnes of polyethylene resins are being produced annually, accounting for 34% of the total plastics market. It is a transparent plastic bag that can be used for packaging of clothing, bags, and electronic products.

PE film itself has many advantages. It has low strength and hardness, but is very ductile and has good impact strength; it will stretch rather than break. Moreover, Polyethylene has a melting point range of 120 to 180 degrees Celsius for medium to high density and 105 to 115 degrees Celsius for low-density polyethylene. The good heat resistant properties enable it to be used in high and low temperatures. The most prominent feature of PE films is its excellent rigidity which maintains a firm protective structure and exhibits excellent moisture resistant properties.

PP valve bag

Compared to PE film, PP film has its own area of expertise. The nature of woven fabrics of has allowed the bag to retain its shape even when its fully loaded. Unlike PE film which is an entirety, the woven fabric has given it extra tear resistance in terms of puncture and weight. In addition, pp woven film has better air permeability that prevent bulging of bag from happening. However, this advantage could also be considered as disadvantage, meaning that exterior contamination is more likely to enter into the PP bag than other forms of bags. The problem can be easily resolved by adding an inner layer of protective film.

Some also say that pp woven bag can be put in the washing machine and being reused multiple times given its superior bag strength.

Paper valve bag

As the name implies, the valve mouth on the side of the bag allows high-speed filling as well as avoiding spillage especially for powdered products such as flours and cement.

Paper valve bag is made of porous kraft paper with high elasticity and high tear resistance, designed for packaging products with high demands for strength and durability because they are laminated in several layers of films. They are often used as shipping containers for bulk materials such as fertilizer, animal feed, sand, dry chemicals, flour and cement. Many have several layers of sack papers, printed external layer and inner plies. Some paper sacks have a plastic film, foil, or polyethylene coated paper layer in between as a water-repellent, insect resistant, or rodent barrier.

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Open-Mouth Bag or Valve Bag?

Compared to valve bag, open mouth bags are bags used in the packaging industry that are factory closed on one side of the tube, and closed by sewing or sealing on the other side. Open mouth bag still holds great market share while valve bag is also rapidly growing to be the predominating packaging solution in many industries.

According to the researchandmarket.com, amid the COVID-19 crisis, the global market for Bag On Valve Technology estimated at US$391.1 Million in the year 2020, is projected to reach a revised size of US$520.9 Million by 2027, growing at a CAGR of 4.2% over the analysis period 2020-2027. Aerosol B.O.V, one of the segments analysed in the report, is projected to record a 4.6% CAGR and reach US$260.1 Million by the end of the analysis period. After an early analysis of the business implications of the pandemic and its induced economic crisis, growth in the Standard B.O.V segment is readjusted to a revised 4.2% CAGR for the next 7-year period.

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Hence, it is predictable that the consumption of valve bag will continue to grow in a stable way given its safer filling machine. Less importantly, the gradual advancement of filling machine will to a certain degree contribute to the growth of valve bag consumption as bulging problems will be solved in order to ensure a safer and stable production line.

In technical terms, valve bag creates less dust and guaranteed a clean production environment whereas in the case of open mouth bag, a considerable amount of wastage and dust will threaten the safety of the workers in the production line. However, in the case of sealing, the sealing for open-mouth bags, whether made of paper or woven polypropylene, is tight and may be reproduced even at high throughput while valve bag has a self-sealing function which is not always tightly sealed.

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Concluding Remarks

No matter what kind of packaging solution you are about to choose, make sure that your priority is to create a safe production environment upon which efficiency, price can be considered. Taking professional advice is also important when you are hesitating about what kind of packaging solution is best for you, choosing the packaging solution that most fits your products by consulting with your packaging manufacturer. If you need any professional advice, we are here to help. Contact us here at SHU Packaging today so that we can discuss the details of your premier customised packaging solution.