blown film workbook draft

Higher Institute for Plastics Fabrication

WORKBOOKfor

Blown Film Extrusion Practical Course

Prepared by

Blown Film Extrusion Department 1st Edition 2009Page 1

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs e

ACKNOWLEDGEMENT

In its program to continuously improve the quality of instructions at the Higher Institute for Plastics Fabrication, the Curriculum Steering Committee initiated the creation of the workbooks for all practical courses being offered in the Institute. The Committee is headed by Dr. Khaled Al-Ghefaili, and the members are Dr. Ahmad Al-Ghamdi, Mr. Hiroshi Takeshita, Engr. Issa AlKhormi, Mr. Sumio Iwase, Mr. Kazuhiko Sawada, Mr. Sanjay Rawat, Mr. Zakaria Musa, and Mr. Virgilio Calpe.

This is the HIPF Workbook for Injection Molding for Practical Course. The contents of this workbook were compiled through the efforts of the members of the Blown Film Department, namely, Raul R. Clave (Head of the Department), Isagani Aldover, Philip Floyd Yumul, Jovanny Quilala, Jovef Pangue, Alfred Bacosa, Kirankumar Daraji (Senior Instructors) and Mr. Sumio Iwase and Mr. Takuma Nakashima (Blown Film Expert Advisers). Editing, formatting and design by Virgilio Calpe.

February 2009

Page 2


TABLE OF CONTENTSIntroduction . Course Objectives . General Safety Guidelines ... Grades Summary Sheet ... Workshop Activities Activity 1Basic Theory of Blown Film Extrusion .. Activity 2Polyethylene Films Activity 3Emergency Stop and Safety Devices . Activity 4Blown Film Die Activity 5Blown Film Air Cooling Ring .. Activity 6Blown Film Width and Thickness .. Activity 7Corona Treatment . Activity 8Flexographic Printing Activity 9Bag Making . Activity 10Polyethylene Film Recycling . Activity 11Practice Plant Operations (LDPE) . .. Activity 12Practice Plant Operations (LLDPE) . . Activity 13Practice Plant Operations (HDPE) . .. Formulas Glossary . References ... 8 14 19 26 31 37 42 48 55 64 73 81 85 89 92 110Page 3

4 5 6 7


INTRODUCTIONBlown film extrusion is one of the most commonly used thin-gauge fabrication processes in the world. The majority of the commodity films such as grocery bags, agricultural films and other flexible packaging films used by consumers are produced by this method. The process of producing film by extruding molten resin into a continuous tube is simple. Yet, in fact the system is one of the most complex and sensitive of all the plastics fabricating technologies and it presents many inherent difficulties. A simple blown film line consists of an extruder, die, air ring, iris or bubble cage, collapsing frame, and a winder.

Page 4


COURSE OBJECTIVESThe purpose of this workbook is to enable the trainees to understand and carry out important activities being done in a blown film extrusion process. Focus will be on the most important functions of the machine and the terminologies used in the enterprise. Upon successful completion of this course, the trainee will be able to:

Know the main components of film extruders and their purposes. Describe blown film extrusion process. Identify common polyethylene films. Perform emergency stop using emergency switches. Know the operation of an air ring, die, nip rolls and gusseting equipment. Know the operation of a simple flexographic in-line printer. Know the basic operation of a recycling machine.

Page 5


GENERAL SAFETY PRECAUTIONSInstead of starting operations carelessly, all trainees should discuss the following before starting any activity: (1.) What types of activities are we going to do? (2.) What kind of risks are hidden behind those types of activities? (3.) What should we do to avoid those risks? Here are some safety reminders to always keep in mind:

Keep the work area clean at all times. Use proper hand gloves. Avoid using loose hand gloves. Use the appropriate tool and wear protective dry gloves when you throw away purged resin. Do not lean against the cage guard of the ladder when you work. Pay attention to where your hands are to ensure that your hands are not pinched between rollers and other rotating equipment. Do not run the machine without the protective covers on rotating parts. Avoid clothing or accessories that could easily be pinched or caught in machines. Specifically, do not wear items that hang far from your neck such as long necklaces and IDs. Do not wear rings or loose bracelets. Do not wear clothing that is pleated, sags or has strings. Make sure that you button or fasten your shirt and jacket cuffs, pant cuffs and jacket hem. Do not stand in front of the die.

Page 6


GRADES SUMMARY SHEET Trainee Name: _________________________ Group: ________Semester ___ School Year ___________

ACTIVITIES Activity 1Basic Theory of Blown Film Extrusion Activity 2Polyethylene Films Activity 3Emergency Stop and Safety Devices Activity 4Blown Film Die Activity 5Blown Film Air Cooling Ring Activity 6Blown Film Width and Thickness Activity 7Corona Treatment Activity 8Flexographic Printing Activity 9Bag Making Activity 10Polyethylene Film Recycling Activity 11Practice Plant Operations (LDPE) Activity 12Practice Plant Operations (LLDPE) Activity 13Practice Plant Operations (HDPE) AVERAGE GRADE

GRADE

Page 7


WORKSHOP ACTIVITY #1

Basic Theory of Blown Film ExtrusionTHEORETICAL BACKGROUNDBlown films are created by feeding plastics pellets into an extruder where they are melted and homogenised before they are pumped through a circular blown film die. The melted plastics form a continuous tube which is drawn from the die. It is inflated and simultaneously cooled by rapidly moving air. The tube, also called a bubble, is then flattened as it passes the collapsing frames and drawn through nip rolls and over idler rolls to a winder which pulls and winds the finished rolls of film. A typical film blown film machine consists of the following five major units: Extruder unitconverts the solid pellets into hot melt. Die unitforms the hot melt into tube. Cooling unitcools down and solidifies the hot melt. Take-off unitpulls and flattens the tube at constant speed. Winding unitwinds-up the flattened tube into finish rolls.

Page 8

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #1Basic Theory of Blown Film Extrusion

OBJECTIVES OF THE ACTIVITY1. To learn the basics of operating a blown film machine 2. To identify the parts of the five major units of a blown film and their elements

PROCEDUREPART IThe Basic Operations of Blown Film Machine 1. Go to the Workshop floor and observe any of the blown film machine that is being run by your Instructor. 2. Using data sheet on the following pages, list down accordingly the steps of the blown film process you have observed. Example: Step 1. Put material in the hopper. Step 2. etc PART IIThe Five Major Units of a Blown Film Machine 1. Using the drawing of Blown Film Machine in your data sheet, label the following: a. name of the part/s of each major units. b. name the other elements needed in the process.

Page 9

Report Form - Page 1 of 4Cut Report Form and Submit to Instructor

DATA S H E E TACTIVITY #1Basic Theory of Blown Film ExtrusionTRAINEE NAME GROUP NO.

PART IThe Basic Operations of Blown Film Machine Steps in Blown Film Operations Step No. Description of the Step

Page 10


DATA S H E E TACTIVITY #1Basic Theory of Blown Film ExtrusionTRAINEE NAME GROUP NO.

PART IIThe Five Major Units of a Blown Film Machine

Properly label the Blown Film Process Diagram

Page 11



QUESTIONS & EXERCISESA. Choose the correct answer. 1. What is the most common material used for blown films? (a.) PVC (c.) Nylon (b.) PET (d.) PE 2. What is the common type of blown film used all over the world? (a.) Downward BF (c.) Upward BF (b.) Horizontal BF (d.) None of the above 3. What part of the blown film machine makes the screw rotates? (a.) blower (c.) haul-off (b.) main motor (d.) winder 4. What is the process of feeding a single die with two or more different polymer melt streams? (a.) blower (c.) haul-off (b.) main motor (d.) none of the above

B. How does blown film differs from other plastics fabrications? Check ( ) if applicable, and cross out ( ) if not applicable. PROCESS Blown Film Extrusion Blow Molding Pipe Extrusion Injection Molding Die Mould Screw and Haul-off / Barrel Take-off Winder

Page 12



CONCLUSION & RECOMMENDATIONS

___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________ ___________________________________________________________________________________ DATE: __________________ TRAINEES SIGNATURE

INSTRUCTORS COMMENTS

TRAINEES GRADE FOR THIS ACTIVITY

________________________ DATE: __________________ INSTRUCTORS SIGNATUREPage 13



Polyethylene FilmsTHEORETICAL BACKGROUND

The ethylene polymer is available in three main grades, low, medium and high density film. Polyethylene, PE, film is slightly opaque, the opacity increasing with density. PE film is waxy to the touch, and is a good moisture barrier. Low and medium density PE films are flexible even when cold. PE is readily heat sealed. High density PE film is suitable for boil-in-the-bag packs, whereas low and medium density films are not. PE film that has a lower MFR means a higher molecular weight and better mechanical strength.

Page 14

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #2Polyethylene Films

OBJECTIVES OF THE ACTIVITY1. To learn the physical properties of Polyethylene (PE) films 2. To compare the differences among the three common types of PE films used in blown film packaging

PROCEDUREPART IPhysical Characteristics of PE Films 1. Collect three samples for each type of the PE films from the plant

LDPE @ 400mm & 30microns LLDPE @ 400mm & 30microns HDPE @ 400mm & 30microns

2. Correctly label the different films. 3. Each film sample should have the same thickness, length and width. 4. Try to stretch each film and write your observation in your data sheet. PART IIProcess Parameters for PE Films 1. Try to find the Melt Temperature and Pressure for processing each type of PE films. 2. Write your data in the table provided in your data sheet. 3. Compare MFR, Density, Melt Temperature, and Pressure for each type of PE films. 4. Which materials do you think is the easiest to process?

Page 15


DATA S H E E TACTIVITY #2Polyethylene FilmsTRAINEE NAME GROUP NO.

PART IPhysical Characteristics of PE Films Stretch the plastics samples: PE Sample LDPE (400mm, 30microns) LLDPE (400mm, 30microns) HDPE (400mm, 30microns) Observations

PART IIProcess Parameters for PE Films PE Sample LDPE LLDPE HDPE MFR 0.2 to 5 0.5 to 2 Density 0.912 to 0.925 0.912 to 0.925 Extruder Melt Temperature Extruder Melt Pressure

0.03 to 0.1 0.945 to 0.955

Based on the above data, which materials is easy to process?

Why?

Page 16



QUESTIONS & EXERCISESChoose the correct answer and mark ( ) the correct ones.

1. Which of these films has a better clarity? a. LDPE b. LLDPE c. HDPE 2. Which is the toughest among these polyethylene films? a. HDPE b. LDPE c. LLDPE 3. Which blown film bag is suitable for carrying more weight? a. LLDPE b. LDPE c. HDPE 4. Choose the correct application of LDPE film. a. food packaging b. shopping bag c. garments packaging d. floor covering 5. Which of these films can be stretch more? a. HDPE b. LDPE c. LLDPE

Page 17










Emergency Stop and Safety DevicesTHEORETICAL BACKGROUNDMACHINE SAFETY GUARDS & DEVICES Safety devices in facilities, machinery and equipment are an essential means of ensuring worker safety. Foolproof devices, failsafe devices and others are used to ensure intrinsic (essential) safety. These devices are usually built into facilities, machinery and equipment so that workers cannot easily remove them. The foolproof function is a safety mechanism designed with a focus on human factors. On the other hand, the failsafe function is a safety mechanism designed with a focus on the protection of facilities, machinery and equipment. Types of safety devices typically used in blown film machine:

Mechanical Interlock Electrical Interlock

All Dangerous spots of the blown film line must be secured by suitable protective devices. If proper guards cannot be mounted due to the conditions at hand, these areas are secured by Emergency devices. Guarding and Barriers The purpose of machine guarding and barrier is to protect the machine operator and other employees in the work area from hazards created by moving parts, rotating parts, flying chips & sparks. Some examples of this are barrier guards, safety gates, etc.

Page 19

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #3Emergency Stop and Safety Devices

THEORETICAL BACKGROUND continuedWARNING SIGN WARNING SIGN

SAFETY COVER

GUARD RAILS

EMERGENCY STOPPush

EMERGENCY STOP

Pull-Down

SAFETY SWITCH

SAFETY GATESafety Interlock Switch

Electrical Interlock

Page 20


OBJECTIVES OF THE ACTIVITY1. To know the purposes of each of the safety devices installed in a blown film machine 2. To learn how to pause or stop the blown film machine in emergency cases 3. To develop awareness of the dangers of blown film machine if safety devices are tampered or by-passed

PROCEDURETypes of Safety Devices Typically Used in Blown Film Machines Walk around the blown film machine assigned to you by your Instructor and try to locate all the safety devices and the emergency stop buttons. PART ISafety Devices and their Functions 1. In your data sheet, write down the names of the safety devices and their functions and answer the questions. PART IIEmergency Stops 1. In your data sheet, indicate all the emergency stop buttons of the blown film machine available in WS02 and answer all the questions.

Page 21


DATA S H E E TACTIVITY #3Emergency Stop and Safety DevicesTRAINEE NAME GROUP NO.

PART ISafety Devices and their Functions Safety Devices of Blown Film Machine, where are they?

SAFETY DEVICES of BLOWN FILM MACHINE1. 2. 3. 4. 5.

1. Do these safety devices really help by reminding you of the danger if YES NO they are not activated? 2. How?

Page 22


DATA S H E E TACTIVITY #3Emergency Stop and Safety DevicesTRAINEE NAME GROUP NO.

PART IIEmergency Stops Emergency stop buttons of Blown Film Machine, where are they?

1. When are we going to use the emergency stop buttons, is it during scheduled shutdown?YES NO

2. Why?

3. If something happens to the machine or to the operator and we need to stop immediately, are we going to use the emergency stop?YES NO

4. Why?

Page 23



QUESTIONS & EXERCISESChoose the correct answer. 1. What type of emergency device is installed above and across the width of the winding station? (a.) emergency stop button (c.) emergency stop cord (b.) warning alarm (d.) none of the above 2. What warning sign is available in the machine indicating danger of being burn? (a.) (b.)

(c.)

(d.)

3. What will you do to stop the machine in case of emergency? (a.) switch off the main switch (b.) leave the machine (c.) press the Emergency Stop push button (d.) follow the shutdown procedure 4. Which mandatory safety sign that informs operator to wear hand protection? (a.) (b.)

(c.)

(d.)

5. Which of the following is an example of safeguarding devices? (a.) printing gear cover (b.) railings (b.) winder gates (c.) all of the above

Page 24










Blown Film DieTHEORETICAL BACKGROUNDIn various kinds of plastics fabrication processes, molten resin that leaves the extruder is forced through an orifice (opening, slit) called a die. By this die the molten resin is given its final shape appropriate for the end product. A die used for blown film extrusion has an annular (ring-shaped) outlet (called a lip) through which the molten resin passes. Such a die is called a circular die. The size of a die is expressed by the lip diameter. The lip diameter ranges from a small diameter of about 30 mm to a large diameter of about 1,500 mm.

The Two Types of Die Lip Gap Adjustments:Figure 4.1Upper Die Tightening the bolt

A

Upper Die Goes that way

Upper Die Tightening the bolt Upper Die Goes that way

B

Page 26

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #4Blown Film Die

OBJECTIVES OF THE ACTIVITY1. To learn the basic principles of die mechanisms 2. To understand the die mechanisms and how to adjust the lip gap

PROCEDUREImportant! Before you adjust the gap, you should know which type of adjustable die ring is used for the die available. You should also understand that the adjustable die ring just moves horizontally as a whole by rotating the adjusting bolt. PART IDie Lip Adjustment 1. Prepare the half die head available in the Workshop. 2. Examine carefully what type of die lip gap adjustment the die has. 3. Confirm the movement of the die lip. Confirm whether it is A- or B-type lip gap adjustment. 4. When making adjustment, loosen the bolt on the other side first. Refer to Figure 4.1: For A type, tightening the bolt will widen the gap. For this type, when the die ring is screwed in, the ring is moved in a way that pulls the ring with the bolt to widen the lip gap (see Figure 4.1). For B type, tightening the bolt will narrow the gap. For this other type, when the die ring is screwed in, the ring is moved in a way that pushes the ring with the bolt to narrow the lip gap (see Figure 4.1). 5. Try turning the bolts of your die and observe the outer lip movement of the die. Answer all the questions in your data sheet. PART IIParts of the Die 1. Properly label the parts of the die using the drawing found in your data sheet.

Page 27


DATA S H E E TACTIVITY #4Blown Film DieTRAINEE NAME GROUP NO.

PART IDie Lip Adjustment 1. Referring to the Figure 4.1, what type of die do we have in Workshop 02 Blown Film? A-Type B-Type 2. What happens when you tighten the bolt of this type?

3. In your own opinion, if you widen the die lip gap, does this makes the corresponding blown film wall thicker? YES NO 4. Why?

PART IIParts of the Die

Page 28



QUESTIONS & EXERCISES1. It is the part of the Blown Film machine where the molten resin is forced through its round opening slit and forms a tube. a. screw and barrel b. adapter c. die d. none of these 2. Describe briefly how the material flows as it enters the spiral and outside the spiral. _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ 4. When the die is not properly centered, why is a thinner film produced from the wider die gap and a thicker film from the narrower gap? _______________________________________________________________ _______________________________________________________________ _______________________________________________________________

Page 29










Blown Film Air Cooling RingTHEORETICAL BACKGROUNDBlown film air rings are used primarily to stabilize the bubble and secondarily to cool the melt. In plastics forming, a circular manifold distributes an even flow of cool air into a hollow tubular form passing through the manifold. An air ring is installed just above the die in an upward air cooling blown film machine. The air outlet called a lip (or slit) has an annular shape that surrounds the molten resin extruded from the die. Air is introduced into the ring by the blower, and the air is turned into a uniform flow inside the air ring. Then the air is blown through the lip against the molten resin for cooling. If the flow of air blown out of the lip is not uniform, it leads to nonuniform cooling. As a result, film thickness will be uneven. To prevent this, the air ring is designed to ensure uniform air flow over the entire lip. As the molten resin is cooled, it becomes frosty, or less clear (transparent), and a solidification border appears. This borderline is called a frost line.

Page 31

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #5Blown Film Air Cooling Ring

PARTS OF A SINGLE LIP BLOWN FILM AIR RING

Page 32


OBJECTIVES OF THE ACTIVITY1. To know the importance of air ring to blown film extrusion 2. To understand the construction of an air ring and how to adjust it

PROCEDURE1. Run the blown film line assigned to you by your Instructor. 2. With the supervision of your Instructor, set the parameters to produce a 30microns by 300mm lay flat width film. 3. Once the process has stabilized (as checked by your Instructor), adjust the threaded adjusting ring of the air ring by the doing the following trials:

Trial 1Turn the adjusting ring one-fourth ( ) down Trial 2Turn the adjusting ring another one-fourth ( ) down Trial 3Turn the adjusting ring still another one-fourth ( ) down Trial 4Turn the adjusting ring one-fourth ( ) upward Trial 5Turn the adjusting ring another one-fourth ( ) upward

4. Allow 5minutes intervals for each trial and ensure that the bubble is stable each time. 5. For each trial, observe what will happen to the bubble and take note of what happens to the height of the frost line. 6. Write all your observations on the table provided in your data sheet, and answer all the questions.

Page 33


DATA S H E E TACTIVITY #5Blown Film Air Cooling RingTRAINEE NAME GROUP NO.

OBSERVATIONS Trial No. 1 2 3 4 5 Number of Turns and Direction turn down another turn down another turn down turn upward another turn upward Pressure Reading Bubble Observations

1. When the threaded adjustable ring is adjusted downwards, what happens to the frost line height? goes up or down?goes up goes down

2. What type of air ring does workshop 02 blown film has, Is it single lip or dual lip?single lip dual lip

3. How did you know that it is a _____________lip?

4. If the inside of the air ring is dirty and causing obstruction, will you have an even flow of air in the bubble, yes or no?yes no

5. Does this obstruction cause uneven thickness of the film, yes or no?yes no

Page 34



QUESTIONS & EXERCISES1. _______________________is the part of the Blown Film machine that uniformly cools and then evenly solidifies (make solid) the molten resin extruded from the die. 2. The blowing angle should be appropriately set depending on the type of resin is used, the type of product being made, and other factors. True or False? 3. In the given drawing below, the air ring is called a dual lip because it has _______________, _________________, and ____________________.

4. In the given drawing below, which of these two air rings is used for LLDPE and which is for HDPE? _________ is for LDPE _________ is for HDPE

Page 35










Blown Film Width and ThicknessTHEORETICAL BACKGROUNDThe width (lay-flat width) and thickness of the film to be made are always specified in blown film extrusion. The operators need to set the width and thickness to the specified values correctly and maintain them within the target level during the processing. Once the process is started, first adjust the lay-flat width to the specified value. The screw rotation speed shall be set to the predetermined speed and the amount of air to be introduced into the bubble shall be adjusted. Then the film thickness shall be next step. In blown film extrusion, there are various kinds of operation requirements that directly influence on the shape of the bubble. Examples of these requirements are extruder take-off speed and the amount of air that enters the bubble. In particular, they affect the bubble size and vary the film thickness and lay-flat width.

t

Wt = thickness of film W= width of film

DRolled Film

Page 37

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #6Blown Film Width and Thickness

OBJECTIVES OF THE ACTIVITY1. To learn how to adjust the width and thickness of a blown film bubble

PROCEDURE1. Run the blown film line assigned to you by your Instructor. 2. With the supervision of your Instructor, set the parameters to produce a 30microns by 300mm lay flat width film. 3. Once the process has stabilized (as checked by your Instructor), record the take-off speed and winder tension on the table in your data sheet under Trial 0. 4. Then do the following trials, each time observing what will happen to the film thickness and film width. Record the new thickness and width on the table in your data sheet. TRIAL No. Trial No.1 ACTION Increase the take-off speed by 2m/min. Slightly add tension on winder to adjust the film tension. Open the air valve and let air enter the bubble for at least 2 minutes. Wait for another 3minutes. Let your instructor stabilize the bubble. Observe what will happen to the bubble. Increase the take-off speed by 2m/min. Slightly add tension to winder to adjust the film tension. Observe again what will happen to the thickness of the film. Open the air valve and let air enter the bubble for at least 2minutes. Wait for another 3minutes. Try to stabilize the bubble by yourself while the instructor guides you. Observe what will happen to the bubble.

Trial No.2

Trial No.3

Trial No.4

5. Answer all questions relating to each trial.

Page 38


DATA S H E E TACTIVITY #6Blown Film Width and ThicknessTRAINEE NAME GROUP NO.

DATA & OBSERVATIONS Trial # 0 1 2 3 4 1. When the haul-off speed is increased in Trial No.1, did the thickness also increased, yes or no?yes no

Take-off Speed, Film Thickness, m/min m 30 microns

Winder Tension, N

Width, mm 300mm

2. When you add some more compressed air in Trial No.2, did the width of the film increased, yes or no?yes no

3. What happened to the bubble when you increased again the haul-off speed in Trial No.3?

4. What happened to the width when you add more compressed air in Trial No.4?

Page 39



QUESTIONS & EXERCISESA. Choose the correct answer. 1. What happens to the lay-flat width if more air is introduced into the bubble? (a.) no change (c.) increase (b.) decrease (d.) none of the above 2. If the extruder screw speed is increased, what happens to the film average thickness? (a.) no change (c.) increase (b.) decrease (d.) none of the above 3. What happens to the film average thickness if the take-off speed increased? (a.) no change (c.) increase (b.) decrease (d.) none of the above 4. If the extruder screw speed is decreased, what happens to the film average thickness? (a.) no change (c.) increase (b.) decrease (d.) none of the above 5. What happens to the film average thickness if the take-off speed decreased? (a.) no change (c.) increase (b.) decrease (d.) none of the above B. How do you decrease the width of lay flat tube?

C. How do you increase the thickness of the film?

Page 40










Corona TreatmentTHEORETICAL BACKGROUND

If a corona discharge is generated in air, ozone (O3) is created from the oxygen (O2) in the air. Ozone is a powerful oxidizing gas. This ozone oxidizes the surface of plastics film to make it easier for the ink to stick to the film. This method of treating a plastics film surface is called corona discharge treatment. The corona discharge treatment equipment is made up of a high frequency generator, an electrode, and a treater roll. The wetting tension of PE film and PP film that have not been surface treated is around 30 to 35 mN/m. The tension appropriate for printing on these kinds of film is said to be normally around 40 to 45 mN/m. So, what is wetting tension? Treated film surface can be checked by measuring the wetting tension of the film surface. The wetting tension is an indication of the wettability of a solid surface. Normally, wetting tension of a film that is not surface treated is around 30 to 35 mN/m compared to a treated film which has 40 to 45mN/m.

Page 42

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #7Corona Treatment

Theoretical background continued

This activity will explain how wettability works with the polyethylene film. Below is the schematic drawing of a corona discharge machine (corona treater).

WETTING TENSION MEASUREMENT

The approximate wetting tension of a film can measured by using wetting ink supplied by Polyrema. The ink is used to write on the surface of the film and the ink value where there is no run-off corresponds to the wetting tension of the film.

Page 43


OBJECTIVES OF THE ACTIVITY1. To know the importance of corona treater in blown film printing 2. To know how corona treater affects the film quality during secondary processes

PROCEDURE1. Run a blown film line. 2. Produce a 30microns by 300mm lay flat width LLDPE film. Make sure film passes the corona discharge machine. 3. Once the blown film is stabilized and checked by your instructor, get film samples without the corona treatment, and then with corona treatments at different corona treatment settings. 4. Properly label each sample. 5. Check the wettability of each sample using the wetting ink supplied by POLYREMA. 6. Follow the following settings for the trials: TRIAL NO. CORONA TREATER SETTING 1 2 3 4 0% treater setting (no corona treatment) 40% treater setting 70% treater setting 90% treater setting

7. Your Instructor will demonstrate how the wetting ink is used. Start from the lowest wetting ink value to the highest, and record the trial results in your data sheet for each of the sample. 8. Record whether run-off occurs or not when the sample is tested with each wetting ink values. 9. Answer all questions regarding your observations.

Page 44


DATA S H E E TACTIVITY #7Corona TreatmentTRAINEE NAME GROUP NO.

RUN-OFF OBSERVATIONSTrial No. Treater Setting Did the line run-off? Wetting Ink 42yes yes yes yes no no no no

Wetting Ink 44yes yes yes yes no no no no

Wetting Ink 46yes yes yes yes no no no no

1 2 3 4

0% 40% 70% 90%

1. What happened to the wetting ink applied on the first film sample? Did the liquid line run-off? What does this broken line shows?

2. For the 2nd sample (Trial #2) how did the wetting ink behave in the film? Did it run-off too? What does this mean?

4. For the 3rd sample (Trial #3), do you think the value of the corona discharge is very good for printing? Why?

4. For the 4th sample (Trial #4), do you think the value of the corona discharge is very good for printing? Why?

5. What about sealing this film from Trial #4, do you think that the seal will be very good?

Page 45



QUESTIONS & EXERCISES

1.

The method of treating film surface is called a. gusseting b. sealing c. corona discharge treatment.

2. What is the normal surface tension for untreated PE films? a. 20-30 mN/mtr b. 30-35 mN/mtr c. 40-45mN/mtr

3. Using the wetting liquid application and marking a line on the film, if the line breaks-off or runs-off this means the film is a. untreated b. treated

4. Write down the three major parts of a corona discharge machine. a. ______________________________ b. ______________________________ c. ______________________________

Page 46










Flexographic PrintingTHEORETICAL BACKGROUNDRotary Printingis a printing technique in which the impressions are carved on a rubber plate and stuck on a cylinder, or carved on the cylinder itself, so that the printing can be done on long continuous rolls of paper, cardboard, plastic, or a large number of other substrate. Often Used Printing Processes for Blown Film: Flexographic Printing Rotogravure Printing

FLEXOGRAPHIC PRINTING Flexographic printing has an advantage over rotogravure in that it can use a wider range of inks, water-based rather than oil-based inks, and is good at printing on a variety of different materials like plastics, foils, acetate films, brown paper, and other materials used in packaging. Typical products printed using flexography includes flexible packaging, including retail and shopping bags, food and hygiene bag, etc. A flexographic print is made by creating a positive mirrored master of the required image as a 3D relief in a rubber or polymer material. Flexographic plates can be created with analog and digital plate-making processes. The image areas are raised above the non-image areas on the rubber or polymer plate. The ink is transferred from the ink roll which is partially immerged in the ink tank. Then it transfers to the anilox roll (or meter roll) whose texture holds a specific amount of ink since it is covered with thousands of small wells or cups that enable it to meter ink to the printing plate in a uniform thickness evenly and quickly.

Page 48

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #8Flexographic Printing

Theoretical Background continued

PARTS OF A FLEXOGRAPHIC PRINTER

Plate Cylinder Impression Cylinder

Anilox Roller

Fountain Roller

Page 49


OBJECTIVES OF THE ACTIVITY1. To learn the basic operation of a flexographic printing machine for blown film 2. To know the parts and functions of a flexographic printing machine

PROCEDURE1. Pre-heat a blown film machine that has in-line flexographic printing machine. 2. Prepare a rubber clich for flexographic film print run and the schematic drawing of a flexographic printing machine. 3. Mount the rubber plate on the plate cylinder. Make sure of the alignment by following the groove etched on the cylinder surface. See the drawing.

4. Move gear 1 (for Roll 1) towards gear 2 (for Roll 2) and mesh their teeth by about 3mm by turning knob C clockwise. 5. Pour ink in the ink pan. Ink level at least a few millimetre of the fountain roller lower portion. 6. Switch-on the printing drive.

Page 50


Procedure continued 7. Move the fountain roller 3 towards the anilox roller 4 by turning knob A clockwise. Observe the ink between these rollers. Putting more pressure between roller 3 and 4 means reducing the ink on the anilox concave surface and lesser ink will be transferred to the rubber plate. 8. Move carriage of 3 & 4 towards 1 by turning the knob B until ink from the anilox is transferred to the rubber plate. 9. Activate the pneumatic cylinder for the carriage D and observe the printing on the film. 10. If print does not appear yet, turn knob C slower clockwise until print appears. Note: Each of the specific knobs has to be adjusted to attain a good ink tone balance and better quality print. 10. When you feel you have attained the best print, take a sample printed film and cut the printed portion. 11. Attach the printed film in your data sheet.

Page 51


DATA S H E E TACTIVITY #8Flexographic PrintingTRAINEE NAME GROUP NO.

1. When you pressed the fountain roller with the anilox roller, does this mean we are reducing the ink being transferred to the printing plate?YES NO

2. What is the function of knob A?

3. When you pressed carriage 3 & 4 to roller 1, did the image appear on the film?YES NO

4. What is the function of knob B?

FLEXOGRAPHIC PRINTED FILM

ATTACH YOUR PRINTED FILM HERE!Page 52



QUESTIONS & EXERCISESChoose correct answer. 1. Which type of printing is done on polyethylene blown film? a. Screen printing b. Rotogravure printing c. Laser printing d. Flexographic printing Which process is done before printing the polyethylene film? a. Heat treatment b. Chemical treatment c. Corona treatment d. Laser treatment Why do plastics surfaces require pre-treatment for printing? a. To make plastic thicker b. To make plastic stronger c. To make plastic more decorative d. To make strong ink bonding on surface What type of chemical (thinner) is used to make printing ink thin and dryable during flexographic printing? a. Acid b. Kerosene c. Petrol d. Alcohol What is that rubber-like material we use in flexographic in making a printing plate? a. PVC b. Photopolymer c. Polyethylene d. None of these

2.

3.

4.

5.

Page 53










Bag MakingTHEORETICAL BACKGROUNDEvery day, our lives are touched by plastics packaging products. Polyethylene bag is one of the best applications of packaging products. Polyethylene bag is used for various purposes like shopping, grocery, laundry, food packaging, garments, textiles, agriculture, industrial products packaging, garbage, waste management, etc. There are mainly two types of methods to make polyethylene bags.

Bottom sealed bag Top and bottom sealed bag

Examples of Bottom Sealed Bag Products

Examples of Top and Bottom Sealed Bag Products

Page 55

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #9Bag Making

Theoretical Background continued BOTTOM SEALING DIAGRAM

BOTTOM SEALING PROCESS FLOW

Page 56


Theoretical Background continued DOUBLE SEALING DIAGRAM

DOUBLE SEALING PROCESS FLOW

Page 57


Theoretical Background continued TYPES OF BAGS

EXAMPLES OF BAG MAKING PRODUCTS

Page 58


OBJECTIVES OF THE ACTIVITY1. 2. 3. To learn making polyethylene poly bags for various applications To learn the proper adjustment of sealing temperature to come up with acceptable product To determine the effect of product type on the production output rate

PROCEDUREPART ISealing Temperature for LDPE and HDPE Bags 1. Familiarize yourself with the bag making machine assigned to you by your Instructor. 2. Determine the effect of changing the sealing temperature to final product by changing the temperature setting. 3. Make 5 trials with 5 different temperatures using LDPE film. 4. Each time you change the temperature, record the bag cutting speed and inspect the product if acceptable or not. 5. Record all your data in your data sheet. 6. Do the same for HDPE film.

PART IIProduction Output 1. Run five (5) different bag products (different sizes and materials) at constant speed using the machine assigned to you by your Instructor. 2. For each run, record the bag cutting speed and the production output (bags/min). 3. Record all your data in your data sheet.

Page 59


DATA S H E E TACTIVITY #9Bag MakingTRAINEE NAME GROUP NO.

PART ISealing Temperature for LDPE and HDPE Bags SEALING TEMPERATURE FOR LDPE BAGS Trial No. 1 2 3 4 5 SEALING TEMPERATURE FOR HDPE BAGS Trial No. 1 2 3 4 5 Sealing Temperature Bag Cutting Speed Sealing Qualityaccepted rejected

Sealing Temperature

Bag Cutting Speed

Sealing Qualityaccepted rejected

accepted

rejected

accepted

rejected

accepted

rejected

accepted

rejected

accepted

rejected

accepted

rejected

accepted

rejected

accepted

rejected

Page 60


DATA S H E E TACTIVITY #9Bag MakingTRAINEE NAME GROUP NO.

PART IIProduction Output Trial No. Bag Size (length) Bag Cutting Speed Product Rate (bags/min)

Material

1

2

3

4

5

Page 61



QUESTIONS & EXERCISES1. Which of these three are the bottom seal and the top & bottom seal bag? ____________ is the bottom seal bag. ____________ is the top & bottom seal bag.

2. In the given drawing, why did they call this a top and bottom sealing? Explain briefly. ___________________________ ___________________________ ___________________________ ___________________________ ___________________________ ___________________________ ___________________________ ___________________________ 3. Give at least two applications of this top & bottom sealed bags. Clue: bags that can be found in a market. Applications: _______________________________ _______________________________

Page 62










Polyethylene Film RecyclingTHEORETICAL BACKGROUNDRecycling Procedure for Polyethylene Film 1. Start machine heat-up. Set the temperature according to the required setting for the type of material to be recycled.Scrap Material Temperature Settings C LDPE 180 - 200 LLDPE 190 - 210 HDPE 195 - 220

2. Check the cooling water supply in/out and ensure that it is ON.OUT IN

3. Set the shredder temperature at 60C initially, then increase up to 100C, as temperature increases after shredder start.Shredder Temperature

4. Start feeding scraps in shredder drum, ensuring that no metal or foreign matter is present. Set shredder speed to 45rpm maximum. The load must not exceed 22amps.Speed Control

Page 64

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #10Polyethylene Film Recycling

Theoretical Background continued 5. After reaching to the set barrel temperature, clean the screen or change if required and check breaker plate also.

Screen Change Controls Up/Down

Screen Cleaning

6. Connect conveyor to the shredder and after ensuring metal detector is functioning, put conveyor in auto mode. Also connect the cooling water chamber to die-face cutter and tighten the screw properly.

7. When shedder drum temperature reaches 90C, and barrel temperature, 185C to 220C, start oil pump, water pump, vibrator, blowers, and centrifuge.

Page 65


Theoretical Background continued 8. Start die face cutter and set speed to 1500 initially. Increase die face cutter speed in order to maintain pellet size of 2mm. Monitor the size of pellets and adjust the speed when needed.

Variable Speed Control

9. Start extruder at 25 rpm initially, then increase gradually up to 45 rpm. Observe the ampere meter to control motor load (max 40 amps).

Extruder Speed Setting

Extruder Amps Meter

10. Observe smooth operation.

Page 66


OBJECTIVES OF THE ACTIVITY1. To learn recycling machine operation

PROCEDURE.Observe the recycling machine start up procedure and write start-up steps in the given work sheet.(worksheet#9.1) Write your observations and fill data in process parameter sheet ( work sheet #9.2) PART IRecycling Machine Startup Procedure 1. Observe the startup procedure for the recycling machine as performed by your Instructor. 2. In your data sheet, write down the steps on the table provided. PART IIRecycling Machine Process Parameters 1. Observe the actual recycling run for different plastics materials. 2. Use the Process Monitoring Sheet provided in your data sheet to record your data on the actual machine run.

Page 67


DATA S H E E TACTIVITY #10Polyethylene Film RecyclingTRAINEE NAME GROUP NO.

PART IRecycling Machine Startup Procedure START PROCEDURE STEP OBSERVED1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

Page 68


DATA S H E E TACTIVITY #10Polyethylene Film RecyclingTRAINEE NAME GROUP NO.

PART IIRecycling Machine Process Parameters Process Monitoring SheetRecycling MachineSCRAP MATERIALS PROCESS PARAMETERS LLDPE LDPE HDPE

Cylinder 1 Cylinder 2 Barrel Temperature Cylinder 3 Cylinder 4 Joint Filter Die Shredder Temperature Shredder Speed Shredder Motor Load (Amps) Extruder Speed Extruder Motor Load (Amps) Cutting SpeedPage 69



QUESTIONS & EXERCISESChoose correct answer. 1. What are the advantages of recycling plastics? a. By recycling we can make more plastics b. Making plastics cheaper c. Recycling machinery business can grow up d. Reduce the consumption of energy and less pollution 2. What is the STANDARD MARKING CODE for HDPE? a. b. c. d.

3. Why are STANDARD MARKING CODES developed? a. To identify the strength of each plastics b. To identify the cost of each plastics c. To understand the number of times the plastics can be recycled d. To help consumers identify and sort the main types of plastic 4. What is the consumption of plastics in packaging industries? a. 35% b. 25% c. 30% d. 15%

5. What is the importance of oil circulation in the gear box of the extruder? a. To provide lubrication and reduce friction b. To increase the speed of an extruder c. To save power consumption of machine d. For cooling the gear box 6. Select the barrel temperature (C ) range for HDPE scrap material a. 195, 200, 205, 210, 215, 220, 225 b. 165, 170, 175, 180, 185, 190, 195 c. 175, 180, 185, 190, 195, 200, 205 d. 170, 180, 180, 187, 190, 190, 195 7. Why is a metal detector provided on the conveyor? a. To sense metal and allow it to go into the shredder and extruder b. To sense metal and save the extruder from damage c. To measure the weight of plastics fed into the shredder d. To avoid dust to go inside 8. How do you increase or decrease the size of plastics pallets? a. By adding or reducing material to the shredder b. By increasing or decreasing the barrel temperature c. By increasing or decreasing the speed of die face cutter d. By increasing or decreasing cooling temperaturePage 70









WORKSHOP ACTIVITY #11-13

Practice Plant OperationsPRACTICE YOUR OPERATIONS SKILLS!1. Now that you have learned the basics of the Blown Film Extrusion process, it is time to practice your skills in running the plant and producing acceptable products. Strictly follow the Standard Operating Procedures (SOP) for each plant operations that you are going to perform. Use the worksheet tables and forms in the next pages to record your data. After each practice operations, write your general comment on the how well you have done your practice in the Conclusion & Recommendations page. Write down what you have done well, and what you should improve for the next practice. Enjoy practicing while being safe!

2. 3. 4.

5. 6.

Page 72

Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #11-13Practice Plant Operations

STANDARD OPERATING PROCEDURES (SOP) PART ASOP for Plant Run Preparations1. 2. 3. Read and understand carefully the JOB INSTRUCTIONS given by your instructor. (See Job Instruction #1). Switch on main power and pre-heat the blown film machine according to the temperature listed in the Job Instruction. Check the condition of the following:

Chilled water for barrel and reduction gear cooling (optional). Air supply for downstream equipments like nip rolls, winder and pressure roll.

4. 5.

Prepare the materials to be used according to the Job Instruction. Prepare the following tools and equipments:

Dial thickness gauge Tape measure Cutting knife for film Silicon spray Cotton rags for die cleaning Guide twine or flat rope

Allen wrench for die adjustment Cotton Gloves Brass or copper spatula Scouring paste Scouring pad

6. 7.

Prepare bobbins according to the width of the roll to be produced. Set the bobbin to the shafts of the winder and wrap around adhesive tape with the sticky surface exposed. Two turns are enough just to stick the film during change roll. Have at least five bobbins for replacements during roll change. Prepare the guide twine to the web path from the die to winder. Fill the hopper with the required materials. Change the screen in the screen changer if necessary.

8. 9. 10.

Page 73


Standard Operating Procedures continued 11. Check the following blown film major parts conditions:

Sizing basket up and down movement Haul-off unit roll rotation and air pressure and functions Collapsing device functional adjustments Corona treater if flexo printing will run Printing unit functional adjustments and rolls rotations Winder air pressure required for pressure roll and test for roll change

11.

Wait for 1.5 hours till the ready indicator light lights up and verify again the temperature settings if the actual display temperatures correspond to the set temperatures. If yes, machine is ready to run. If not, check settings. If actual temperature is low, extend preheating time.

PART BSOP Startup1. 2. 3. 4. 5. 6. 7. 8. Open the shutter of the hopper. Switch-on the main motor and adjust the screw rpm to 10. Caution: Avoid facing the die during this stage. Melt material may spurt-out. Remove the initial extruded melt. This contains air trap in a material that should be removed. Increase screw speed to 30 rpm and remove the molten materials in the die. Wait until the high melt pressure drops. Do item 5 for 50, 75, and 100 rpm and back to 0. Clean the die and the die lip using scouring pad and scouring paste. Check die gap alignment. Align if off-centered by loosening and tightening centering screws. Use Allen wrench for adjusting the screws.

Page 74


Standard Operating Procedures continued 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. Open the blower damper at 30 degrees. Minimal air blown at the film for initial start. Open compressed air supply for inflating the bubble at minimum only. Make a loop on the film guide twine and have it ready. Switch-on again the main motor and set the screw speed to 25 rpm. Switch-on the haul-off nip and set the nip roll speed to 6-8 rpm. As the melt comes out let it cool to solidify and tie the film guide twine loop on that cooled lump. Pull gently the melt as it continue forming into a bubble. After the solid lump passes between the nip rolls, close the nip roll and let it do the pulling of the bubble. Temporarily closed the compressed air. Just pull the flat tube gently till it reaches the printing unit. Using the cutting knife, cut diagonally the film to make a pointed end. Insert this pointed end between the plate and impression roller of the printer. Pass the film between the open pressure roll and winder roll. Close the pressure roll pinching the film. Immediately, start the winder. Set minimum winding tension. Insert the film in between the rotating winder roller and bobbin with caution and start winding the film. Increase screw rpm gradually to the target rpm. (See Job Instruction.) Increase bubble diameter to its required lay-flat tube width. (See Job Instruction.) Increase nip roll speed according to the required film thickness. (See Job Instruction.) Switch-on corona treater if printing unit will run.

Page 75


Standard Operating Procedures continued

PART CSOP for Shutdown1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. Close the shutter of the hopper. Switch-off corona treater if printing unit is running. Wait till the bubble starts to rattle. It is better to have a little material inside the barrel and die to seal-off the barrel form air getting inside. Gradually bring down the screw speed to 0 rpm. Switch-off the main motor. Bring down nip roll speed to 0 and switch-off. Open the nip roll. Bring down winder speed to 0 and switch-off. Open the pressure roll. Close the chilled water supply valve. Start lowering the temperature for 30 minutes. Switch-off the main power. Bring good rolls to the bag making area. Record the total roll weight produced in the Job Instruction. Bring all scrap to the recycling area. Record the total weight of the scrap in the Job Instruction. Return all tools and equipment to their proper places. Fill-up all the information needed in the Job Instruction. Submit the Job Instruction to your instructor.

Page 76


DATA S H E E TACTIVITY #11Practice Plant Operations (LDPE)TRAINEE NAME GROUP NO.

BLOWN FILM EXTRUSION PRODUCTION REPORTMachine No. Date: Material Specifications No. 1 2 Machine Running Condition Monitoring Lot Number Heater Zone 1.1 Heater Zone 1.2 Heater Zone 1.3 Actual Temperature (oC) Heater Zone 2.1 Heater Zone 2.2 Heater Zone 3.1 Heater Zone 3.2 Heater Zone 3.3 Heater Zone 3.4 Heater Zone 4.1 MT Extruder Screw Speed (rpm) Extruder Melt Pressure (bar) Air Ring Pressure (KPa) Temperature (oC) Haul-off Speed (mpm) Corona Treater Power (%) Printing Unit Motor Load (%) Winder Tension (N) Lay-on Pressure (bar) Contact Pressure (bar)Page 77

Product Description:

Type

Resin Name / Grade

Blending Ratio (%)

1.

2.

3.

4.

5.


DATA S H E E TACTIVITY #11Practice Plant Operations (LDPE)TRAINEE NAME GROUP NO.

BLOWN FILM EXTRUSION PRODUCTION REPORT continuedOutput Monitoring Lot Number Dismount Time Roll Number Length (m) Weight (kg) Total Scrap Weight (kg) Quality Check Monitoring Roll Number Measuring Point 1 Measuring Point 2 Measuring Point 3 Measuring Point 4 Measuring Point 5 Measuring Point 6 Measuring Point 7 Measuring Point 8 Average Thickness (m) Lay Flat Width (mm) Gusseted LFW (mm) Left Gusset Width (mm) Right Gusset Width (mm) Treating Level (OK/NOK) Tape Test (OK/NOK) Print Centering (OK/NOK) Print Repeat Length (mm) Clarity (OK/NOK) Color (OK/NOK) Defects (W/WO) Roll Disposition (Pass / Reject / On-Hold)Page 78

1.

2.

3.

4.

5.

Thickness Profile (m)


Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #11Practice Plant Operations (LDPE)

QUESTIONS & EXERCISES1. If you want to raise the frost line height, what part of the machine are you going to adjust? a. winder tension b. the haul-off c. Air adjusting ring 2. If you want to decrease the film thickness, what control are you going to adjust? a. haul-off speed b. winder speed c. main motor speed 3. How are you going to adjust the speed in question #2? a. increase speed b. decrease speed 4. If you want to reduce the lay-flat width, what are you going to do with the bubble? a. increase air inside b. decrease air inside 5. How are you going to increase or decrease the air inside the bubble? Describe in your own words. ______________________________________________________ ______________________________________________________ 6. Is it necessary to use a film guide twine during start-up? Why? ______________________________________________________ ______________________________________________________ 7. Give at least 3 important speed adjusting controls of the blown film control panel. _________________________________________________ _________________________________________________ _________________________________________________Page 79


Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #11Practice Plant Operations (LDPE)







DATA S H E E TACTIVITY #12Practice Plant Operations (LLDPE)TRAINEE NAME GROUP NO.



Type

Resin Name / Grade

Blending Ratio (%)

1.

2.

3.

4.

5.


DATA S H E E TACTIVITY #12Practice Plant Operations (LLDPE)TRAINEE NAME GROUP NO.

BLOWN FILM EXTRUSION PRODUCTION REPORT continuedOutput Monitoring Lot Number Dismount Time Roll Number Length (m) Weight (kg) Total Waste (kg) Quality Check Monitoring Roll Number Measuring Point 1 Measuring Point 2 Measuring Point 3 Measuring Point 4 Measuring Point 5 Measuring Point 6 Measuring Point 7 Measuring Point 8 Average Thickness (m) Lay Flat Width (mm) Gusseted LFW (mm) Left Gusset Width (mm) Right Gusset Width (mm) Treating Level (OK/NOK) Tape Test (OK/NOK) Print Centering (OK/NOK) Print Repeat Length (mm) Clarity (OK/NOK) Color (OK/NOK) Defects (W/WO) Roll Disposition (Pass / Reject / On-Hold)Page 82

1.

2.

3.

4.

5.



Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #12Practice Plant Operations (LLDPE)

QUESTIONS & EXERCISES1. What does melt pressure indicate? a. The pressure before the screen b. The pressure after the screen 2. What does indicator means if the reading is high (500) _______________________________________________________ _______________________________________________________ 3. What happens to the output if the screen is clogged-up, increase or decrease? Why? _______________________________________________________ _______________________________________________________ 4. If the cooling of the barrel is not working, what do you think will happen to the bubble? _______________________________________________________ _______________________________________________________ _______________________________________________________ 5. If the rolled film in the shaft is hard to removed, what must be the probable cause? _______________________________________________________ _______________________________________________________ 6. How are you going to prevent the problem in #5 from happening during operations? _______________________________________________________ _______________________________________________________ 7. Give at least 2 causes why bubble is pulsating. _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________

Page 83


Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #12Practice Plant Operations (LLDPE)







DATA S H E E TACTIVITY #13Practice Plant Operations (HDPE)TRAINEE NAME GROUP NO.



Type

Resin Name / Grade

Blending Ratio (%)

1.

2.

3.

4.

5.


DATA S H E E TACTIVITY #13Practice Plant Operations (HDPE)TRAINEE NAME GROUP NO.

BLOWN FILM EXTRUSION PRODUCTION REPORT continuedOutput Monitoring Lot Number Dismount Time Roll Number Length (m) Weight (kg) Total Waste (kg) Quality Check Monitoring Roll Number Measuring Point 1 Measuring Point 2 Measuring Point 3 Measuring Point 4 Measuring Point 5 Measuring Point 6 Measuring Point 7 Measuring Point 8 Average Thickness (m) Lay Flat Width (mm) Gusseted LFW (mm) Left Gusset Width (mm) Right Gusset Width (mm) Treating Level (OK/NOK) Tape Test (OK/NOK) Print Centering (OK/NOK) Print Repeat Length (mm) Clarity (OK/NOK) Color (OK/NOK) Defects (W/WO) Roll Disposition (Pass / Reject / On-Hold)Page 86

1.

2.

3.

4.

5.



Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #13Practice Plant Operations (HDPE)

QUESTIONS & EXERCISES1. Give at least 2 causes of die lines. _______________________________________________________ _______________________________________________________ 2. Give at least 2 causes of uneven film thickness. _______________________________________________________ _______________________________________________________ 3. What are you going to do with the die if the film wall at the right side is thicker than the left side? _______________________________________________________ _______________________________________________________ _______________________________________________________ _______________________________________________________ 4. Give at least 2 causes of film blocking. _______________________________________________________ _______________________________________________________ 5. Give at least 3 common problems of blown film process. _______________________________________________________ _______________________________________________________ _______________________________________________________

Good Luck!!!!!

Page 87


Wo r k b o o k fo r Bl ow n F i lm P r a c t ic a l C o u rs eWORKSHOP ACTIVITY #13Practice Plant Operations (HDPE)







Formulas for Blown Film ComputationsBlow Up Ratio (BUR)

BUR =

Bubble Diameter, D 2 Die Diameter, D1

D2 = LFW

2

D2

D1

D 2 = 0.637 LFWwhere: LFW = Lay Flat Width, cm D1 = the die diameter, cm D2 = the bubble diameter, cm

Die

Theoretical Bag Film Weightt =thickness, cm

Wbag = w L t 2 where: Wbag = theoretical bag film weight in grams w = width of the bag, cm L = cut length of the bag, cm t = thickness of the film, cm = material density, gm/cm Film Bag L

W

Page 89


Formulas for Blown Film ComputationsTheoretical Roll Weightw

Wbag = w L t 2 where: Wbag = theoretical bag film weight in grams w = width of the bag, cm L = cut length of the bag, cm t = thickness of the film, cm = material density, gm/cm

t

Rolled Film

Theoretical Output

Computing for Output Rate per RPM of a Given Output:

Output Rate per RPM =

Output Rate, kg per hour Screw Speed, RPM

Output Rate = ___________ kg/hr/RPM

Getting the Needed Output of a Desired Screw RPMTarget Output = Desired Screw Speed, RPM Output Rate per RPM

Target Output = __________ kg/hr

Page 90


Formulas for Blown Film ComputationsTheoretical Take-off Speed

Theoretical Take - off Speed =

Output Rate LayFlatWidth 2 Thickness Density

Theoretica l Take - off Speed (cm/min) =

Output Rate (g/min) LFW (cm) 2 t (cm) (g/cm 3 )

Page 91


Glossary of technical terms for Blown FilmAir-ring A circular component of a blown film system that directs cool air up the sides of a tubular blown film bubble to cool and solidify the melt. Plastics made by mechanically blending two or more different polymers. Substance compounded into a resin to modify its characteristics (i.e., antistatics, stabilizers, plasticizers, flame retardants, etc.). The process of exposing the film to a controlled environment for an interval of time.

Alloy Additive Aging

Ambient conditions The existing conditions of temperature and humidity in any building or room. Amorphous A polymer is said to be amorphous when its molecules are in long random or coiled chains. Amorphous plastics tend to be transparent, and are more soluble than crystalline plastics. Having no crystalline structure. Mechanically or laser-engraved roll for transfer of ink to printing plate. Specifications are in lines per inch and cell volume (ex. 800-line anilox will transfer a thinner film of ink than a 300-line anilox). An additive used in plastic, generally at 1 or 2% that roughens the film surface from adhering to each other. The most common antiblocks are based on clay by-products. Additives that prevent oxygen from causing molecular breakdown in polymers.

Anilox Roll

Antiblock

Antioxidant

Anti-static agent A substance that can be applied to the surface of a plastic article, or incorporated in the plastics from which the article is to be made. Its function is to render the surface of the plastic article less susceptible to accumulation of electrostatic charges which attract and hold fine dirt or dust on the surface of the plastic article. Auxiliary equipment The types of equipment used to enhance, support or add to the precision and efficiency of injection, extrusion or other primary processing machinery.(Continued on page 93)

Page 92


(Continued from page 92)

Arc Band heater

A luminous glow by the flow of electric current through ionized air, gas or vapor between two separated electrodes or contacts. Electrical heating units fitted to extruder barrels, adaptors, dies, nozzles, etc., utilized for heating the polymer to a desired temperature. A metal tube that houses a rotating screw, or sometimes a ram, in which plastic is heated before extrusion or moulding. A layer of material in film, sheet or a blow molded container that prevents the passage of moisture, flavors or certain gases.

Barrel Barrier layer

Biaxial Orientation The process of stretching a hot plastic in two directions under conditions resulting in molecular orientation in two directions. Bleed (1) To give up color when in contact with water or a solvent. (2) Undesired movement of certain materials in a plastic (e.g., plasticizers in vinyl) to the surface of the finished article or into an adjacent material; also called migration. (3) An escape passage at the parting line of a mold, like a vent but deeper, that allows material to escape or bleed out. Substrate sticking to itself after being printed and rewound. Image often transfers to back-side of other label. (1) A non-continuous surface coating on plastic products that comes from ingredients such as plasticizers, lubricants, antistatic agents, etc., which are incorporated into the plastic resin. It is not always visible. Bloom is the result of ingredients coming out of solution in the plastic and migrating to its surface. Migration of additives to the surface of the film Film made by extruding molten plastic through a circular die, and forming an inflated, tubular bubble that moves through a cage as it cools, to be sliced open, collapsed and formed into rolls.

Blocking Bloom

Blooming Blown film

Breaker plate A metal plate installed across the flow of the stock between the end of an extruder screw and the die, with openings through it such as holes or slots. It usually is used to support a screen pack. Bubble In blown film referred to as the inflated molten tube.(Continued on page 94)

Page 93


(Continued from page 93)

Cage, blown film A structure, usually with rollers or roller beads, through which a bubble of blown film passes at it is extruded and cooled. Calcium carbonate (CaCO3) A filler and extender used in thermoplastics. It occurs naturally in the form of minerals such as calcite, chalk, limestone, marble, and whiting. Calendering The making of sheet or film with high-quality surface characteristics by passing molten plastic from a kneader over a series of rollers that flatten and/or emboss it. The thickness of the substrate usually measured in thousandths of an inch (mils). "Microns" (metric) are specified for some substrates.

Caliper

Cartridge heater Cylindrical electrical heater used to heat nozzles, hot runners and moulds in injection and compression molding. Cast film Chiller A film process, used where good cosmetics are needed, in which molten plastic flows over a chilled roll or through a quench bath. A self-contained system comprised of a refrigeration unit and a coolant circulation mechanism consisting of a reservoir and a pump. Chillers maintain the optimum heat balance in thermoplastic processing by constantly re-circulating chilled cooling fluids to molds, machines, etc.

Coefficient of friction, COF A measure of how slippery a film is. Coefficient of friction is a number that expresses, for a given surface, the ratio of the force required to slide an object over a frictionless surface to the force required to slide the same object over the actual surface. The COF, or slip properties, of film are important in determining how that film will perform on conversion equipment and in final form such as in open ability or stacking. This test determines the ability of film to slide over itself and is used to determine the effectiveness of slip additives incorporated into resins. Both static (starting) and kinetic (sliding) friction are measured. Coextrusion A process whereby two or more plastics are extruded through one die, to produce a material combining their properties.

Collapsing frame A pair of