Label Adhesive Composition Low-Temperature Coating and Die Cutting
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Solution Overview
Problem
Existing hot melt adhesives for labels face challenges in achieving a balance between ease of coating at low temperatures and satisfactory die cutting properties, leading to suboptimal productivity and adhesive performance.
Innovation Solution
An adhesive composition incorporating a (styrene polymer block)-[(styrene-butadiene) random copolymer block] diblock copolymer, polyisoprene, and an asymmetric aromatic vinyl-conjugated diene-aromatic vinyl block copolymer with specific molecular weight ratios and a tackifier resin, which reduces melt viscosity at low temperatures and enhances die cutting properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hot melt adhesives are used, then adhesive performance can be maintained, but die cutting properties deteriorate due to high viscosity and threading issues
Solution Approach 1:
The patent uses a composite adhesive system combining a polyolefin resin base polymer with a specific block copolymer (containing styrene and butadiene blocks) and tackifier resin. This composite formulation reduces viscosity at processing temperatures while maintaining adhesive performance, thereby improving die cutting properties without sacrificing reliability.
Solution Approach 2:
The patent modifies the rheological parameters of the hot melt adhesive by controlling the molecular weight distribution and composition of the block copolymer. The block copolymer with specific glass transition temperatures and tan δ values changes the viscosity-temperature relationship, enabling easier die cutting at lower temperatures while maintaining adhesive strength.
2Productivity
If hot melt adhesive application temperature is reduced, then productivity improves, but coating quality deteriorates due to insufficient melting and application
Solution Approach 1:
The patent changes the thermal-rheological parameters of the adhesive by incorporating a block copolymer with specific glass transition temperatures (-50°C to -100°C) and tan δ values (0.5 to 2.0). This enables the adhesive to maintain appropriate viscosity at lower application temperatures (reducing energy consumption and improving productivity) while still achieving proper coating quality through controlled flow and adhesion.
3Ease of operation
If adhesive viscosity is reduced for easier coating, then application temperature can be lowered, but die cutting properties worsen due to increased threading and adhering to die
Solution Approach 1:
The patent creates a dynamic viscosity profile through the block copolymer addition, where the adhesive exhibits temperature-dependent and shear-rate-dependent viscosity. At application temperature, the adhesive has lower viscosity for easy coating, but at die cutting conditions, the viscosity increases appropriately to prevent threading and adhering to the die, thus resolving the contradiction between ease of coating and die cutting properties.
Solution Approach 2:
The composite formulation combining polyolefin resin, block copolymer, and tackifier resin creates a material with tailored rheological properties. The block copolymer specifically modifies the viscosity behavior to provide easy coating at application temperature while maintaining die cutting performance, preventing both excessive viscosity during application and excessive viscosity during die cutting.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The adhesive composition allows for easy application at low temperatures, improves die cutting properties, and results in labels with excellent holding power and tackiness, thereby enhancing productivity.
Implementation Method 1
the effect of the application temperature and die cutting properties (ease of cutting to a constant size without threading or adhering to the die when the adhesive is cut with a die cutter) of the hot melt adhesive on the productivity of labels has grown extremely large
Implementation Method 2
the incorporation of the styrene-isoprene block copolymer contributes to an increase in the tan δ value at 20°C of the pressure sensitive adhesive, and as a result, the die cutting properties are enhanced
Data Source
AI summary
Provided is an adhesive composition for labels, which can be easily applied at a relatively low temperature and has satisfactory die cutting properties so that the adhesive composition can contribute to an improvement of the productivity of labels, and which is capable of producing labels having excellent holding power and tackiness. There is disclosed an adhesive composition for labels comprising: a block copolymer A represented by the following general formula (A); a polymer C, which is a polymer having a glass transition temperature of -30°C or lower, or a block copolymer that has a polymer block having a glass transition temperature of -30°C or lower at an end of the polymer chain; and a tackifier resin D. Ar1a-Da-Ar22 (A), in the general formula (A), Ar1a represents an aromatic vinyl polymer block having a weight average molecular weight of 6,000 to 20,000; Ar2a represents an aromatic vinyl polymer block having a weight average molecular weight of 22,000 to 400, 000; and Da represents a conjugated diene polymer block having a vinyl bond content of 1 mol% to 20 mol%.