UV-Cured PSA Coating for Thermally Sensitive Polymer Substrates

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Solution Overview

Problem

Thermally sensitive substrates, particularly those made of soft PVC, cannot be directly coated with UV-curable hot melt pressure-sensitive adhesives (PSAs) without thermal damage due to high temperatures required for coating and cross-linking, leading to issues like burning when using medium pressure UV mercury lamps.

Innovation Solution

A process involving a UV-cured hot melt PSA applied to thermoplastic polymer substrates with a Vicat A50 softening point up to 170°C, using a low pressure mercury lamp for UV-C radiation to cure the adhesive at a temperature below 120°C, minimizing thermal damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional hot melt PSA coating is applied to thermally sensitive polymer substrates, then adhesive bonding is achieved, but the substrate suffers thermal damage and burning

Engineering Contradiction:

Improveadhesive bondingVSAvoidthermal damage

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent replaces thermal curing with UV light curing. Instead of using conventional hot melt PSA that requires high temperature (160-180°C) for activation and cross-linking, the invention uses UV-curable hot melt PSA that can be cured at much lower temperatures through UV irradiation. This substitution of the curing mechanism eliminates the thermal damage to thermally sensitive substrates while maintaining strong adhesive bonding.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the curing temperature parameter from conventional high temperatures (160-180°C) to low temperatures (below the Vicat softening point of the substrate). By using UV-curable hot melt PSA with glass transition temperatures of -50°C to 50°C and curing it through UV irradiation rather than thermal processing, the substrate temperature remains below its softening point, preventing thermal damage while achieving adequate adhesive strength.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If UV-curable hot melt PSA is used with medium pressure UV mercury lamp, then cross-linking is achieved, but carbon black pigmented films burn off due to infrared absorption

Engineering Contradiction:

Improvecross-linkingVSAvoidheat evolution

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The patent replaces medium pressure UV mercury lamps with low pressure UV mercury lamps. Medium pressure lamps generate significant infrared radiation that is absorbed by carbon black, causing heat evolution and burning. Low pressure lamps emit primarily in the UV range with minimal infrared content, enabling successful cross-linking of UV-curable hot melt PSA on carbon black pigmented substrates without thermal damage or burning.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If thermally sensitive substrates like soft PVC are used, then desired substrate properties are achieved, but conventional coating temperatures cause substrate softening and damage

Engineering Contradiction:

Improvesubstrate propertiesVSAvoidcoating temperature

Core Design Contradiction:

Adaptability or versatilityVSTemperature

Solution Approach 1:

The patent replaces thermal coating and curing processes with UV light-based processes. Conventional hot melt PSA requires heating to 160-180°C for coating and activation, which exceeds the Vicat softening point of soft PVC (100-150°C) and causes substrate damage. UV-curable hot melt PSA can be applied at lower temperatures and cured through UV irradiation, maintaining substrate integrity while achieving the desired adhesive properties.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 process allows for the production of adhesive-coated substrates with minimal thermal damage, enabling the use of thermally sensitive materials like soft PVC without burning, and providing high inner cohesion and resistance to plasticizer migration.

Implementation Method 1

the adhesive composition (b) is a UV-curable or UV-cured hot melt pressure sensitive adhesive

Methodology Applied

Scientific EffectUV curing: Photopolymerisation

Implementation Method 2

using a low-pressure mercury lamp for cross-linking

Methodology Applied

Scientific EffectUV radiation emission: Light

Implementation Method 3

the films are burning off because of the infrared absorption of carbon black and the strong evolution of heat

Methodology Applied

Scientific EffectInfrared absorption: Absorption (EM radiation)

Data Source

PatentEP3114183B1Adhesive-coated thermally sensitive polymer substrate, process for its manufacture and use thereof

Publication Date: 2026.05.06 HENKEL KGAA

AI summary

The invention relates to an adhesive-coated polymer substrate comprising (a) a polymer substrate containing or consisting of a thermoplastic polymer with a Vicat A50 softening point according to DIN EN ISO 306 of up to 220°C, and (b) an adhesive composition coated directly on at least one side of the polymer substrate, wherein the adhesive composition (b) is a UV-curable or UV-cured hot melt pressure sensitive adhesive (PSA). The invention relates moreover to a process for the manufacture of the adhesive-coated polymer substrate as well as to the use thereof.