Bookbinding Adhesive Viscosity and Hardness Control
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Solution Overview
Problem
Conventional bookbinding adhesives, such as EVA and moisture-curing polyurethane hot-melt adhesives, face challenges in achieving high-speed application properties, cutting properties, and book opening properties while maintaining sufficient bookbinding strength.
Innovation Solution
A bookbinding adhesive with specific properties, including a melt viscosity of 1,000 to 10,000 mPa·s at 120°C, JIS A hardness of 20 or more initially and 95 or less after one week, and an upper yield stress of 7 MPa or less, which can be achieved using a moisture-curing polyurethane hot-melt adhesive with specific polyol and polyisocyanate components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If EVA adhesive is used to achieve satisfactory bond strength, then bookbinding strength is improved, but the adhesive film thickness must be increased which deteriorates book opening properties
Solution Approach 1:
The patent changes the viscosity parameter of the adhesive from conventional high viscosity to specifically 1,000 to 10,000 mPa·s at 120°C, and controls the cured film hardness to 95 JIS A or less. These parameter changes enable achieving satisfactory bond strength with a thinner adhesive film (50-200 μm), thus improving book opening properties while maintaining bookbinding strength.
2Ease of operation
If moisture-curing polyurethane hot-melt adhesive has high viscosity, then application is easier, but the adhesive overflows or scatters during high-speed application
Solution Approach 1:
The patent optimizes the viscosity parameter to 1,000 to 10,000 mPa·s at 120°C, which is lower than conventional adhesives. This parameter change prevents overflow and scattering during high-speed application while maintaining ease of application, thereby improving productivity without sacrificing operational ease.
3Productivity
If moisture-curing polyurethane hot-melt adhesive has low viscosity, then high-speed application is improved, but the adhesive becomes too hard after curing
Solution Approach 1:
The patent carefully balances two parameters: viscosity at 120°C (1,000 to 10,000 mPa·s) for high-speed application, and cured film hardness (95 JIS A or less) for book opening properties. This balanced parameter control allows the adhesive to have low enough viscosity for high-speed application while remaining soft enough after curing to enable easy book opening.
Solution Approach 2:
The patent uses a composite adhesive formulation containing polyol, polyisocyanate, and optional additives. This composite material approach allows independent optimization of processing properties (viscosity) and final properties (hardness), resolving the contradiction between high-speed application and book opening properties.
4Ease of operation
If adhesive viscosity is increased to improve application properties, then ease of application is improved, but cutting properties deteriorate
Solution Approach 1:
The patent optimizes viscosity to 1,000 to 10,000 mPa·s at 120°C, which is lower than conventional adhesives. This parameter change improves cutting properties by preventing excessive adhesion to cutting tools while maintaining ease of application through controlled flow characteristics.
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 exhibits excellent high-speed application, cutting, and book opening properties, along with strong bookbinding strength, making it suitable for various bonding applications, including bookbinding, fiber bonding, and optical member lamination.
Implementation Method 1
moisture-curing polyurethane hot-melt adhesive
Implementation Method 2
melt viscosity at 120°C
Data Source
AI summary
An object to be achieved by the present invention is to provide a bookbinding adhesive which is excellent in high-speed application properties, cutting properties, book opening properties, and bookbinding strength. The present invention is directed to a bookbinding adhesive characterized by having a melt viscosity in the range of from 1,000 to 10,000 mPa·s, as measured at 120° C. by means of a cone plate viscometer, exhibiting a JIS A hardness of 20 or more, as measured with respect to the adhesive which is applied and allowed to stand for 30 minutes, in an atmosphere at 23° C., and exhibiting a JIS A hardness of 95 or less, as measured with respect to the adhesive which is applied and allowed to stand for 30 minutes, in an atmosphere at 23° C., and is then allowed to stand in an atmosphere at 23° C. and at a humidity of 50% for one week, wherein a cured film of the adhesive has an upper yield stress of 7 MPa or less. The bookbinding adhesive is preferably a moisture-curing polyurethane hot-melt adhesive containing an urethane prepolymer having an isocyanate group which is obtained by reacting a polyol (A), which contains a crystalline polyester polyol (a-1) and a polyether polyol (a-2), with a polyisocyanate (B).