Creping The crepe blade is the point at which the final sheet appearance is created. The geometry of the blade and its application are critical in establishing the best possible end product. Specifically designed for tissue applications, the crepe blade, along with the Yankee against which it operates, is the heart of the process. The doctor holder uses a special pneumatic loading arrangement to load the blade against the Yankee cylinder and has a “flexible finger” type backing. The mechanical lock prevents collision of the holder with the cylinder when there is no blade in place. For certain applications and upon request, a stiff holder can be substituted. Angle adjustment The doctor assembly is adjustable for different applications and end product properties. The entire assembly can be rotated on the assembly journal by means of a jacking bolt that changes the position of the assembly relative to the loading cylinder stroke. At a glance Flexible holder ensures even application of the creping load. Adjustable angular position allows flexibility for different products and properties.

1. •Introduction
•Definition of Creping
•Types of Creping
•Types of Crepe
Creping
•Hardware Geometry
•Theoretical Model
•Process Variables
•Sheet Properties
•Coatings

2. Yankee Dryer
Wet PressReel Doctor
Blade
Crepe
Structure
Formed
Creping

3. Yankee Dryer
Uncreped
Sheet
Creped
Sheet
Blade Holder

4. Creping Changes the Sheet
From
To

5. Hood
Yankee
Dryer
Former
Felt
Reel
Creping Blade
Typical Dry-Crepe Machine

6. •Introduction
•Theoretical Model
- Macroscopic Model
- Microscopic Model
•Hardware Geometry
•Process Variables
•Sheet Properties
•Coatings
Creping

7. Yankee Dryer
Coating
Adhesive Uncreped
Sheet
Creped
Sheet
Grind
Angle
Blade Holder
Blade
Wear
Angle
Pocket
Angle
Blade
Extension

8. YANKEE
DRYER
Mechanism of Creping
YANKEE
DRYER
Microfold
(Primary Crepe)
Macrofolds
(Secondary Crepe)
Microfold
(Primary Crepe)
Macrofold
(Secondary Crepe)
Yankee
Dryer
Doctor Blade

9. Creping Analogy
6 m
90E
Pocket
Angle
MG SHEET CREPING
BLADE
95 km/hr

10. Failure Mechanisms in Compression
P
Shear
Zone
Lateral
Supports
P
(a) Shear-slip-plane
mode (brittle)
(b) Bending mode (c) Bulging mode
(internal rupture)
PP
P
Lateral
Supports
We want this
kind of failure
P

11. Crepe
Wavelength
Crepe
Amplitude
Folding
Radius
Crepe Structure Measurement

12. Creped Sheet
100X Actual Size

13. •Introduction
•Theoretical Model
•Hardware Geometry
•Angle Definition
•Inter-Relationships
•Measuring Blade Angles
•Process Variables
•Sheet Properties
•Coatings
Creping

14. Creping Geometry
Yankee Tangent Line
Yankee Tangent
Creping Blade
Yankee
Dryer

15. Creping Geometry
Blade Wear Angle
Yankee Tangent
Creping Blade
Yankee
Dryer
Blade Wear
Angle

16. Creping Geometry
Blade Grind Angle
Yankee
Dryer
Blade
Grind
Angle
Yankee Tangent
Creping
Blade

17. Creping Geometry
Creping Pocket Angle
Blade
Yankee
Dryer
Creping
Pocket
Yankee Tangent
Creping

18. POCKET = 90 - WEAR+ GRIND
Creping Geometry
Creping Angle Summary
Yankee
Dryer
Blade
Grind
Angle
Yankee Tangent
Creping
Blade

19. Creping Geometry
Sheet Take-Off Angle
Creped
Sheet
Creping
Blade
Yankee
Dryer
Yankee
Tangent
Sheet
Take-Off
Angle
SHEET-TO-BLADE + TAKE-OFF = POCKET

20. Creping Geometry
Sheet to Blade Angle
Sheet-to-
Blade Angle
Creping
Blade
Yankee
Dryer
Yankee
Tangent
Creped
Sheet
SHEET-TO-BLADE + TAKE-OFF = POCKET

21. Effect of Creping Pocket Angle
Crepe Amplitude vs Creping Pocket Angle
PRIMARY
SECONDARY
Creping Pocket Angle, degrees
0.6
0.5
0.4
70
0.3
0.1
0
0.2
75 80 85 9065
Yankee
Dryer CREPING
POCKET
Yankee Tangent
Creping
Blade
CrepeAmplitudes,mm

22. Reflective Wear Angle Gauge
Flashlight Angle Finder
Sighting Tube
Micarta Block
Doctor Blade
Base
Magnet

23. Typical Dry Creping Geometry
12 - 24
2.6 kN/m (15 pli)
Blade Wear Angle
Loading Pressure
O
0 - 15
82 - 88
52 - 68
12 - 30
12 - 19 mm
0.65- 1.25 mm
Blade Grind Angle
Creping Pocket Angle
Sheet Take-Off Angle
Sheet-To-Blade Angle
Blade Extension
Blade Thickness
O
O
O
O

24. Creping Mechanism
Effect of Pocket Angle
Pocket Angle < 80
Pocket Angle > 80
Primary Crepe Only
Primary & Secondary Crepe

25. Creping Mechanism
TISSUE CROSS SECTIONS
Creping Pocket Angle = 65
Creping Pocket Angle = 80
O
O

26. •Introduction
•Theoretical Model
•Hardware Geometry
•Process Variables
•Pocket Angle
•Adhesion
•Basis Weight
•Uncreped Sheet Properties
•Sheet Properties
•Coatings
Creping

27. Creping Mechanism
Effect of Adhesion Level
LOW ADHESION
HIGH ADHESION
Fine, Uniform Crepe
Coarse, Skippy Crepe

28. Creping Mechanism
TISSUE CROSS SECTIONS
Dryer Adhesion = 2.3 gram per inch
Dryer Adhesion = 12.2 gram per inch

29. Effect of Adhesion on Crepe Amplitude
2 4 146 8 10 12 16
Sheet-To-Dryer Adhesion (g/in)
0.13
0.15
0.11
0.09
0.07
0.05

30. Creping Mechanism
UNCREPED
SECTIONS
High Adhesion, Pocket < 80
High Adhesion, Pocket > 80
PRIMARY
CREPE
ONLY
PRIMARY &
SECONDARY
CREPING
Low Adhesion, Pocket < 80
#1
#2
#3
o
o
o

31. Effect of Basis Wt on Crepe Amplitude
8 10 20
Basis Weight (gsm)
0.11
0.09
0.07
0.05
0.03
12 14 16 18

32. •Introduction
•Theoretical Model
•Hardware Geometry
•Process Variables
•Sheet Properties
•Creping Moisture
•Strength
•Debonding
•Crepe ratio
•Coatings
Creping

33. 200X
Sheet Debonding

34. 0
4 8 12 16 200
20
40
60
80
100
Debonding In Creping Process
Effect of Adhesion and Blade Geometry
Adhesion To Dryer (g/in)
80 Pocket
70 Pocket
60 Pocket
o
o
o

35. 50 60 70 80 90 100
Dryer Adhesion vs Sheet Dryness
Sheet Dryness, %
FT 94
TAPPI

36. Strength - Softness Curve
Facial Tissue
Invariant Tensile Strength (g/ 3” sheet)
0
2
4
6
8
10
12
0 200 400 600 800 1,000 1,200 1,400
QALSoftness

37. Strength - Softness Curve
Facial Panel Softness
Invariant Tensile Strength (g/3”)
0 400 800 1,200 1,600 2,000
0
2
4
6
8
10
12

38. Historical Line
Closed Pocket Angle
Open Pocket Angle
Very Open Pocket
8
600
6
4
2
0
1,000 1,400 1,800 2,200
Overall Strength (g)
10
Softness

39. Facial Tissue Brand /
Structural Comparison
Sheet Debonding
vs. Stiffness
% Debonding/
Length
Sensory Panel
Stiffness
15.0Marcal 7.4
30.0 6.0
5.0
5.8
4.5
3.6
30.0
37.5
45.0
55.0
Secondary Fiber Kleenex
Virgin Fiber Kleenex
Regular Puffs
Kleenex Softique
New Puffs
Panel Stiffness

40. Reel Doctor
Blade
Crepe Ratio
Crepe Ratio = V2 / V1
where:
V2is Reel surface speed
V1is Yankee Dryer surface speed

41. Bulk Development in Creped Wadding
1 2 3 4 5
0.2
0.4
0.6
0.8
0
Crepe Ratio
90 Pocket
80 Pocket
O
O
O

42. Debonding In Creping
Weak Points
KOTEX ® TYPE WADDING
Closed Pocket, High Adhesion
Uniformly Debonded, No Weak Points
KLEENEX ® FACIAL WADDING
Open Pocket, High Adhesion

43. •Introduction
•Theoretical Model
•Hardware Geometry
•Process Variables
•Sheet Properties
•Coatings
•Definition
•Inorganic Coatings
•Organic Coatings
•Application Systems
Creping

44. Title of Chart
Title of Chart
"Advanced" Coatings"Natural" Coatings
Organic From
Fibers
Organic From
Fibers
Inorganic
Salts
Inorganic
Salts
Embedded
Fibers
Embedded
Fibers
Synthetic
Additives

45. Title of Chart
Inorganic Salts
•100 ppm Calcium
needed to form good
coatings
•Some must harden
water to achieve
•More than 600 ppm
will cause excessive
scaling elsewhere
Organic From
Fibers
Embedded
Fibers
Inorganic
Salts

46. Creping Adhesive References
Poly-(aminoamides) Winslow.Spicer 1972:Giles.Espy 1975:Oliver
1980:Schoreer et al.1982: Soerens 1985.1987:
Obokata.Takizawa 1990
Polyamides Lazorisak et al. 1977: Pomplu.Grube 1984 : Marzullo
1987:Chen et al. 1989: Soerens 1991
Polyamines Lazorisak et al. 1977: Latimer.Stevens 1983: Soerens
1991
Polyvinyl Alcohol Bates 1975: Grube.Ries 1981: Pomplun.Grube 1984:
Soerens 1985: Pippen 1987; Soerens 1987: Chen et al.
1989:Soerens 1991
Polyvinyl acetate &
copolymers
Grossman1977: Lazorisak et al.1977: Grube.Ries
1981: Pomplun.Grube1984 : Pippen1987: Chen et al
1989
Polyethers & copolymers
polycrylic acid
Pomplu.Grube 1984: Soerens 1991 : Lazorisak et al.
1977:
Animal glue Fuxelius 1967: Sanford.Sisson 1967: Lazorisak et al.
1977: Oliver 1980
Starch Fuxelis 1967: Salvucci. Yannos 1974: Oliver 1980
Cellulose derivatives Grossman 1977: Marzullo 1987

47. Title of Chart
Absorption
Diffusion
Mechanical
Interlocking
Weak
Boundary
Layers
Chemical
Bonding
Acid-Based
Interactions
Electrostatic
Attractions
Components of Adhesion

48. Strong adhesion between materials
is governed by two interactions:
• Intimate molecular contact closer than 9
angstroms (0.0000000009 meters). This is a
necessary condition.
•Maximum attractive force with minimum
potential energy. This is a sufficient condition.
(Chung 1991)

49. Force
Cast Iron
Adhesive
Cotton Cloth
Peel Speed = 30 cm/min
Peel Adhesion Test

50. Adhesion Values
0.0 0.5 2.01.0 1.5 2.5 3.0 3.5 4.0
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
Concentration (% actives)
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
AveragePeelForce(g/25mm)

51. Typical Tensile Stress
Strain
Low Modulus
Weak
Tough
Strain
High Modulus
Strong
Tough
Brittle

52. Coating Requirements
• Must form uniform films
• Provide stable adhesion
• Be stable
• Have some re-wettability
• Have controllable hardness

53. Synthetic Additives
Organics from
Fibers
Inorganic
Salts
Embedded
Fibers
Thermoplastic
(rewettable)
Thermoset
(cross-linking)
Release

54. Kymene
• Good attraction to fibers (cationic)
•Strength increases with heating
•Crosslinking polymer
•Limited wettability
•Provides good dryer protection
•Minimum addition rate for dryer
protection is 0.35 kg/ton

55. PVA
• Nonionic (compatible with kymene)
• Good film former
• High cohesive strength
• Rewettable
• Different grades available
•% Hydrolysis
•Molecular Weight
• Typical application amounts: 0.3-2.5 kg/ton
based on tissue grade

56. Peel Adhesion
PVA / KYMENE MIXTURES
100 20 6030 40 50 10070 80 90
600
800
700
1,000
900
1,100
1,200
% Polyvinyl Alcohol (balance kymene)

57. Releases
• Modify coating
•Provide lubrication for doctor blade
•Examples
Quaternary Amines - Quaker 2008
Emulsified Oils - Cynol, Mulrex, Houghton
Polyglycol Esters - Hercules M-1336
•Quat. Amines and Esters provide less release
action
•Oils are powerful releases and difficult to
control to correct amount

58. What we spray on the dryer -
Water
Polymer A
Polymer B
Release
Inorganic Salts
What is actually in the coating -
Cellulose fiber
Ash?
Polymer A
Polymer B
Inorganic Salts
Release
Water
Dryer Coating Composition
(In order of % of mixture)

59. Coating Application System
Recirculation Line
Chemicals
Water

60. Coating Application System
Hard Water
Chemicals
Mixer
Spray Boom & NozzlesFilters (2)
Yankee
SurfacePressure
Gauges
Booster Pump
Variable Speed Chemical
Metering Pumps (Gear)
Mass
Flowmeters
In-line
VS VS VS
FIC FIC FIC
Check
Valves

61. Metering Pumps
Advantages
Disadvantages
• Inexpensive
•Uneven flow, possible
hammering in lines
•Pulsation dampers
needed
•More Accurate
•Infinite speed
adjustment
• Expensive

62. •Reduces nozzle plugging from:
•Water source
•Undissolved PVA
•Bacteria "slugs"
•Should be placed close to
application
•Progressively finer screens as
you move down steam
Filters

63. •Must be safe and convenient for operator
•Should have:
•Gauge cocks to isolate tips
•Separate cross bars w/individual bodies for each tip
•Removable booms
•Typical set-up: 15 cm apart, 12-20 cm away from yankee,
700 900 kPa supply pressure

64. •K-C uses Spraying Systems Unijet® nozzles
•Spray angles range from 65 - 110
•Flowrates range from .025 - .100 gpm
•Nozzle part number tells flowrate and spray
angle at 275 kPa
Example:
8001
80 Spray Angle .100 gpm Flowrate
650050
65 Spray angle .050 gpm Flowrate
Spray Nozzles
O O
O
O

65. "W"
"H"
Spray Nozzle Geometry
O/2 O/2

66. 20 40 60 10080 120 140 160 200180
50
60
70
40
100
80
90
Spraying Systems Uni Jet Nozzles
8001
6501
6501
650025
Nozzle Pressure (PSI)
650025

67. Spraying Systems Vee Jet Nozzles
0.3
0.2
0.1
0 20 40 60 10080 120 140 160 200180
650025
650033
650050
650067
6501
0
Pressure (PSI)

68. 50
Volumetric Distribution of Spray Nozzle
For A New Nozzle
0
3 5 7 9 11 13 15 17 19 21 23 25 27 29 311
10
20
30
40
Spray Pattern

69. Spray Pattern
313 5 7 9 11 13 15 17 19 21 23 25 27 291
0
10
20
50
30
40
Volumetric Distribution of a Spray Nozzle
For a worn nozzle

70. Volumetric Distribution of Spray Nozzle
Double Coverage - New Nozzles
0
3 5 7 9 11 13 15 17 19 21 23 25 27 29 311
10
20
50
30
40
Spray Pattern

71. 50
Volumetric Distribution of Spray Nozzle
Double Coverage - Worn Nozzles
0
3 5 7 9 11 13 15 17 19 21 23 25 27 29 311
10
20
30
40
Spray Pattern

72. Volumetric Distribution Spray Coverage
Triple Coverage - New Nozzles
Spray Pattern
30
40
20
0 1
10
95 13 17 21 25 29

73. Volumetric Distribution Spray Coverage
Triple Coverage - Worn Nozzles
50
40
30
20
0
10
1 5 9 13 17 21 25 29
Spray Pattern

74. Drying Load
(for coating application)
Nozzle
Size
Spray
Pressure
Spray
Spacing
Nozzle
Coverage
X's
Total
Flow
Flow
per
Nozzle
Number of
Nozzles
Steam
Consumption
% of Total
Steam Flow
(kg/cm2
) (cm) (LPM) (LPM) (KG/HR)
6501
650050
8001
650067
8.4
8.4
2.8
8.4
15
15
23
10
2
2
2
3
19.5
9.8
7.6
20.1
0.65
0.33
0.38
0.45
30
30
20
45
656
328
254
674
13.4%
6.3%
4.8%
13.9%

75. Spray System
Recommendations
Spray Tips - 650050
Coverage - Double Overlap / 5 Offset
Boom - Easily Changeable Tips/Booms
Filters - 70 to 100 Microns
Pumps - Gear Pumps
Mixing - Direct Injection
Water - 100+ ppm Calcium and Alkalinity
Temperature- As is (non heated)
Flow Meters - Micromotion (Mass Flowmeters)
Chemicals - PVA/Kymene/Release
O

76. Adhesive Type Comments
poly (aminoamides) Commercial materials
crosslinked
with epichlorohydrin 48-70
polyamides polyacrylamide 165
ployvinyl pyrrolidone 126-174
polyamines commercial ethylene dichloride
alkylamine type -18-20
polyvinyl alcohols commercial 68-75
polyvinyl acetate 28
polyethers polyethylene oxide (PEO) -67
polypropylene oxide (PPO) -75
poly (acrylic acid) 106
cellulose derivatives methyl cellulose 150
ethyl cellulose 43
hemicellulose various types 150-220
Glass Transition Temperatures of Common
Dryer Coating Chemicals
T (C)g