introduction to psa technology - levera

©2006 LEVERA Pte Ltd

Introduction toIntroduction to

Pressure Sensitive Adhesive Pressure Sensitive Adhesive

Technology Technology

Process Engineering Technical Training Series

CC Lee

Principal Consultant


Definition of PSADefinition of PSA(Pressure Sensitive Adhesives)

A special class of adhesive that is:

• Permanently tacky at Room Temperature

• Spontaneously adhere on contact or with little pressure

• Require no activation by water, solvent or heat to form a strong bond


PSA Polymers Life CyclePSA Polymers Life Cycle

InfancyInfancy

GrowthGrowth

MaturityMaturity

AgeAge

Hot Melts of

• UV radiation cured Acrylic

Emulsions of

• Acrylic copolymers

• SB copolymers

Hot Melts of

• SIS/SBS block

Copolymers

Solvent Solutions of

• Rubber/Resin

• Acrylic


Common PSA ClassificationCommon PSA Classification

NoneNoneNoneHigh

TemperatureSilicone

EmergingCommonFewFewRubber

EmergingDevelopmentalMost CommonSpecialty

Acrylic

UV Hot MeltHot MeltEmulsionSolvent


Typical PSA Polymer Performance Typical PSA Polymer Performance

0

10

20

30

40

50

60

70

80

90

100

Heat R

esist

ance

Chem

ical R

esist

ance

UV Res

istan

ceAdh

esive

Clea

rity

Apolar

Adh

esion

Wat

er R

esist

ance

UV Acrylic

EmulsionAcrylic

Hot MeltSBS/SIS


Common PSA coating methodsCommon PSA coating methods


Capabilities / Limitations of Common Coating MethodsCapabilities / Limitations of Common Coating Methods

Emulsion, hot melt100-500220-50050,000-125,000Curtain

Emulsion, hot melt, 100% solids

100-300220-700400-

200,000Slot die

Emulsion, hot melt, 100% solids

300-700515-750.400-

500,000. Extrusion die

Solution, emulsion100-70022-5015-1500Gravure

Solution, emulsion100-700525-250300-50,000Reverse roll

Solution, emulsion,100% solids

100-4001025-7504,000-50,000

Knife over roll

Solution, emulsion100-1501015-100100-1,000Wire rod

Type of AdhesivesCommonly Used

Coating Speed,m/min

CoatingAccuracy,

+/- %

Coating Weight,gm/m 2

Viscosity,> cps

Coating Method


Variation of Adhesion with Coat WeightVariation of Adhesion with Coat Weight

0

2

4

6

8

10

12

2 6 10 14 18 22 26 30

Adhesive Coat Weight (gsm)

Adh

esio

n (N

/25m

m)


Typical Emulsion PSA Materials Typical Emulsion PSA Materials

Manufacturing ProcessManufacturing Process


Emulsion PSA Label Manufacturing Process

5 Rollers Silicone Coater

Vario Gravure Adhesive Coater

Laminator

Corona Discharge

Adhesive OvenUV Radiation

Facestock Unwind

Product Rewind

Liner Unwind

Face-stock

Adhesive

Silicone Release

Liner

Corona Discharge


Emulsion Emulsion VarioVario Gravure CoaterGravure Coater

Gravure roll

Application roll

Backing roll

Feed box Pressure Range: 0.2 -0.6 bar Above Atmospheric Pressure

Speed Ratio Application roll / Line Speed Ratio Range: 1.1 -1.3


Reverse Gravue Coat Weight Chart

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Speed Ratio

Wet

Coa

t Weigh

t (gs

m) 25

28

30

45

55

65

90


Relative Effects of Parameters on the Evaporation Time of Relative Effects of Parameters on the Evaporation Time of

Polymer Polymer --Water MixturesWater Mixtures

10.2Other

<0.160-100Water content, %

1.610-30Air speed, l/min

20.220-40Temperature, °C

60.210-90Relative humidity, %

Effect on Evaporation Rate% Range Investigated Parameter

The combination of hot air and infrared radiation are well suited for the accelerated drying of waterborne adhesives and coatings. This is probably the most effective variation in formulation or production to gain a large improvement in speed. The hot air primarily affects the coating surface while the IR radiation, depending on the wavelength can penetrate into the deeper layers of the coating. With the IR method, favored evaporation of water can be achieved through irradiation in the OH band region


Adhesive Drying Chart

50

60

70

80

90

100

110

120

130

140

150

160

170

60 70 80 90 100 110 120 130 140 150 160 170

Line Speed

Ove

n T

empe

ratu

re o

C10

12

14

16

18

20

21

22

23

24

25

26

27

28

Water Content gsm


Formulation of Emulsion PSAFormulation of Emulsion PSA

Ammonia

Thickener/

Water

Wetting Agents

Defoamers

Plasticizer

Base

DispersionTackifiers

Mixer

PumpFilter

Storage

Tank

QC:

•Solid Content

•pH

•Viscosity

•Wetting

•Foam


Ad

hesio

n/T

ack

CohesionLow High

Low

High

Heat

Resistant

Removable

General Purpose

Permanent

High Tack & Adhesion

Cold

Temperature

Classification of Adhesive by Classification of Adhesive by

Common FunctionsCommon Functions


Quality Control after Coating ProcessQuality Control after Coating Process

Quantitative Criteria:

1. Adhesion

2. Initial Tack

3. Cohesion

4. Coat Weight

Qualitative Criteria:

1. Adhesive Voids

2. Air Bubbles

3. Foreign Particles

4. Clarity

introduction to psa technology - levera

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