Paper bag machine production technology and adhesive selection: the balance between firmness and cost

Release time：2025-08-13 Classification：Knowledge

In the modern packaging industry, paper bags are the core carrier of environmentally friendly packaging. The quality of their sealing (sealing) directly affects packaging efficiency and end-product performance. The sealing process must ensure the structural integrity of the paper bag during transportation and loading, while also balancing production costs and environmental requirements. This has become a key technical challenge in paper bag machine manufacturing.

1. Living technology: analysis of the core technology of modern paper bag machines

Modern packaging equipment has evolved from traditional manual operations to highly integrated automated systems. Taking a typical multi-layer paper bag packaging machine as an example, its workflow includes six precision mechanisms working together:

The dual-sided synchronous conveying system utilizes a chain with a needle plate and a flat belt, with width adjustment via a double-threaded screw mechanism, ensuring precise positioning and transport of bag tubes of varying sizes. The needle plate mechanism, under the pressure of a torsion spring, securely clamps both ends of the bag tube, while an external guide rail guides the bag opening to the subsequent processing area.
Cutting and layering mechanism : Precise cuts are made at the bottom of the bag. Synchronously rotating upper and lower blades, equipped with serrated blades and rubber pads, create slits of specific lengths at the front and back of the bag opening. Layering is accomplished using rectangular bristle brushes, multiple sets of negative pressure suction nozzles, and a spreading and rolling assembly. The nozzles, controlled by double-sided convex blocks, separate the paper layers one by one. Spreading claws then penetrate the gaps to open the bag opening, and rolling rollers create triangular folds, laying the foundation for subsequent folding.
Crease and reinforcement mechanism : Upper and lower folding grooves fold the multi-layered paper base of the bag opening 90° toward the center, and the front and rear crease rollers complete the shaping. The enhanced end paper system is fed from a reel, and the cutting and pressing rollers complete the cutting and gluing of the end paper. The pressure rollers are equipped with vacuum suction holes on their surface to ensure precise positioning of the end paper. The cutting rollers are equipped with serrated blades to achieve fixed-length cutting.
The multi-layer coating and pressing system , the core of the process, consists of multiple coating and pressing rollers with built-in adhesive chambers. Glue holes are located on the roller surface, and the gluing pressure is controlled by a spring-loaded sliding frame. Folding rods are arranged alternately in a figure-eight pattern, executing a cycle of "folding inward - pressing - folding back - gluing" to overlap the front and side panels layer by layer.

Qingdao Huachi's HK-702 production line has expanded its production process to over 20 stations, integrating printing, valve insertion, and drying processes to achieve a high-speed output of 600 bags per minute. This fully automated system significantly reduces the breakage rate of traditional sewn bags and reduces glue consumption by over 30% through precise glue application.

2. Adhesive selection: the game between performance parameters and costs

Adhesives are the "hidden skeleton" of life quality, and their selection requires comprehensive consideration of equipment compatibility, substrate characteristics, and cost constraints. Currently, the mainstream adhesive types present three technical routes:

1. Hot melt adhesive: the first choice for efficiency

Ultra-fast curing properties : Viscosity range is 600–3000 mPa·s at 180°C, forming a strong and tough film within seconds after coating, with production line speeds reaching 150 m/min.
Structural adaptability : RH series handle rope adhesive is specially used for bonding bag handle ropes, forming a flexible connecting layer between kraft paper and cotton rope. In the peel test, the paper fiber is destroyed rather than the adhesive layer detaching.
Cost control points : A precise temperature control system is required (recommended <200°C) to avoid high-temperature carbonization; the principle of "melting as much as needed" is followed to reduce the scrap rate, and the glue supply parameters need to be adjusted when the temperature changes seasonally.

2. Water-based adhesives: a sustainable solution

Outstanding environmental advantages : FY-301 box glue is a representative example. It uses water as solvent, does not contain triphenyls, and has close to zero VOC emissions.
Technological breakthrough : The vinyl acrylic copolymer formula has strong permeability to UV glazed paper and coated paper, with initial adhesion strength reaching paper fiber destruction within 30 minutes and a temperature resistance range spanning -40°C to 70°C.
Application limitations : Drying speed restricts high-speed production lines and must be used in conjunction with a drying unit (such as the closed drying system of the HY-350 paper bag machine).

3. Double-sided tape: Supplementary for specific scenarios

Convenience value : Eliminate the coating process and shorten the equipment debugging time in simple bag production.
Performance shortcomings : When humidity is >70% or temperature is <5°C, the viscosity declines significantly, and the adhesive layer is prone to migration during long-term storage.

Adhesive test data comparison table

type Peel strength Drying time Temperature range Environmental certification
hot melt adhesive Paper fiber damage 3-8 seconds -20~60℃ REACH halogen-free
Water-based box glue 30 minutes paper fiber destruction 15-30 minutes -40~70℃ FDA benzene-free certification
Double-sided tape Interface separation risk immediate 5~40℃ Some contain solvents

type	Peel strength	Drying time	Temperature range	Environmental certification
hot melt adhesive	Paper fiber damage	3-8 seconds	-20~60℃	REACH halogen-free
Water-based box glue	30 minutes paper fiber destruction	15-30 minutes	-40~70℃	FDA benzene-free certification
Double-sided tape	Interface separation risk	immediate	5~40℃	Some contain solvents

3. Dynamic balance strategy between firmness and cost

Material level optimization

Substrate adaptation : For 30-120g kraft paper, it is recommended to use high-solid content hot melt adhesive; for new environmentally friendly materials such as embedded yarn paper and water-soluble yarn composite paper, water-based adhesive is preferred to avoid high-temperature melt adhesive damaging the fiber structure.
Precise glue quantity control : Through the perforated glue coating roller and servo quantitative system (such as SZN-650 paper bag machine), the coating accuracy is controlled within ±0.1g/bag to avoid "insufficient glue or glue opening" or "over-glueing".

Process innovation

Local reinforcement design : hot melt adhesive is used only in stress concentration areas (such as the valve bag check pipe interface and the handbag rope anchor point) for reinforcement, and water-based adhesive is used for the main body of the bag to reduce overall costs.
Gradient curing technology : The Shenzhien 650 machine combines infrared pre-curing with delayed compaction by a pressure roller, allowing the hot melt adhesive to harden the surface within 3 seconds while ensuring deep-layer colloid leveling.

Equipment selection logic

High-speed scenarios : Fully automatic lines (such as the Jiansheng HY-350) prefer to use a hot melt adhesive system, combined with a 380V 25kW adhesive supply unit, to achieve a production capacity of 600 bags/minute.
Medium-sized production line : Qingdao Huachi HK-702 is compatible with both water-based and hot-melt systems, and can switch glue types through modular gluing stations to adapt to the production of multiple categories.

IV. Industry Innovation Trends: Green and Intelligent Dual-Track Evolution

Application of bio-based materials

Starch-modified hot-melt adhesives are beginning to replace petroleum-based products, increasing biochar content to over 40% while maintaining viscosity at 180°C. Protein cross-linking technology is emerging in the water-based adhesive field, significantly improving water resistance.

Intelligent glue control system

The next-generation glue machines, launched in 2025, will integrate AI-powered visual inspection units to analyze glue line width and penetration in real time, dynamically adjusting glue temperature, pressure, and coating weight. For example, the closed-loop control system in Kaixiang's grape bag machine has reduced the debonding rate from 2.1% to 0.3%.

Multifunctional integrated equipment

Jiansheng HY-350 and other models realize the integration of "printing-lamination-living". The flexographic printing unit and the living mechanism share the servo control system, with a registration error of ≤±1mm, eliminating the secondary handling loss of the coil in the traditional process.

5. Practical Selection Guide: Technology Decisions in Three Scenarios

Cement/chemical heavy-duty bags
are preferably made of a four-layer gluing machine + high-viscosity hot melt adhesive (viscosity ≥ 2500mPa·s at 180℃), with additional gluing paper in the side and bottom reinforcement areas, and the tile-shaped concave baffle pressing process of patent CN92226927 is used.
Food-grade valve bags
use a check tube forming mechanism (with an L-shaped pedal and electromagnetic pusher). The adhesive must comply with FDA standards. Water-based adhesive or bio-based hot melt adhesive is recommended.
The shopping bags
are equipped with a handle string gluing station, which uses RH series low-temperature hot melt adhesive (softening point 80-115°C) to avoid discoloration of coated paper due to high temperature.

As the packaging industry transitions toward a circular economy, the evolution of sustainable technologies is essentially a cross-fertilization of materials science, mechanical engineering, and cost control . Future breakthroughs will focus on: low-temperature rapid curing of biodegradable adhesives, AI-driven dynamic optimization algorithms for adhesive quantity, and micro-coating technology suitable for ultra-thin, high-strength paper substrates. Only by embracing the inseparable "iron triangle" of durability, efficiency, and environmental friendliness can companies achieve lasting competitiveness in the green packaging trend.