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Questions and Answers
What distinguishes integrated plants from independent plants in the corrugated industry?
What distinguishes integrated plants from independent plants in the corrugated industry?
Which type of corrugating plant specifically converts sheets into boxes?
Which type of corrugating plant specifically converts sheets into boxes?
What is the primary material used for the fluting medium in corrugated board manufacturing?
What is the primary material used for the fluting medium in corrugated board manufacturing?
What role does the starch-based adhesive play in the corrugated board manufacturing process?
What role does the starch-based adhesive play in the corrugated board manufacturing process?
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In the manufacturing process of corrugated board, what happens immediately after the fluting medium is plasticized?
In the manufacturing process of corrugated board, what happens immediately after the fluting medium is plasticized?
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What characterizes the smallest flute profile in corrugated board?
What characterizes the smallest flute profile in corrugated board?
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Which of the following statements about adhesives in corrugated board is true?
Which of the following statements about adhesives in corrugated board is true?
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What is the primary benefit of larger flute profiles in corrugated boxes?
What is the primary benefit of larger flute profiles in corrugated boxes?
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What role does the preconditioning process play in the production of corrugated boards?
What role does the preconditioning process play in the production of corrugated boards?
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In the context of board specifications, what does 'Mullen burst' refer to?
In the context of board specifications, what does 'Mullen burst' refer to?
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Why are pre-printed liners significant in the production of double facers?
Why are pre-printed liners significant in the production of double facers?
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Which quality does not contribute to the performance properties of corrugated boards?
Which quality does not contribute to the performance properties of corrugated boards?
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Which coating is commonly used to provide moisture resistance in corrugated boards?
Which coating is commonly used to provide moisture resistance in corrugated boards?
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What is the primary purpose of adhesive in box construction?
What is the primary purpose of adhesive in box construction?
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Which type of box is known for providing extra protection due to its fully overlapping flaps?
Which type of box is known for providing extra protection due to its fully overlapping flaps?
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What does the scoring allowance refer to in box dimensioning?
What does the scoring allowance refer to in box dimensioning?
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In the manufacturing process, which stage combines printing, slotting, folding, and gluing for high output?
In the manufacturing process, which stage combines printing, slotting, folding, and gluing for high output?
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Which printing technique is best for producing high-quality graphics on small flutes?
Which printing technique is best for producing high-quality graphics on small flutes?
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What effect does high humidity have on corrugated box strength?
What effect does high humidity have on corrugated box strength?
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Which type of joint is the least expensive method for constructing boxes?
Which type of joint is the least expensive method for constructing boxes?
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What is the main disadvantage of using a taped joint?
What is the main disadvantage of using a taped joint?
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Which box style features no top flaps?
Which box style features no top flaps?
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What does the Box Compression Test (BCT) formula help determine?
What does the Box Compression Test (BCT) formula help determine?
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What is the purpose of a SKU (stock keeping unit) in packaging?
What is the purpose of a SKU (stock keeping unit) in packaging?
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Which property is primarily assessed by the Elmendorf test?
Which property is primarily assessed by the Elmendorf test?
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What does the moisture content of paper primarily affect?
What does the moisture content of paper primarily affect?
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Which of the following is NOT a factor considered in paper characterization?
Which of the following is NOT a factor considered in paper characterization?
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What type of paper is made from sulfate pulp and is often unbleached?
What type of paper is made from sulfate pulp and is often unbleached?
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What does the 'basis weight' of paper refer to?
What does the 'basis weight' of paper refer to?
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Which paper property relates directly to its performance in storage and packaging lines?
Which paper property relates directly to its performance in storage and packaging lines?
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Which testing standard is NOT commonly associated with paper and packaging?
Which testing standard is NOT commonly associated with paper and packaging?
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What is the primary use of molded pulp in packaging?
What is the primary use of molded pulp in packaging?
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What material is commonly used in extrusion coated papers for better performance in wet conditions?
What material is commonly used in extrusion coated papers for better performance in wet conditions?
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What type of paper is characterized by being greaseproof and highly refined?
What type of paper is characterized by being greaseproof and highly refined?
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Which of the following properties is NOT influenced by the optical characteristics of paper?
Which of the following properties is NOT influenced by the optical characteristics of paper?
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What is the main advantage of using metallized paper in packaging?
What is the main advantage of using metallized paper in packaging?
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Study Notes
Corrugated Industry
- Integrated plants source at least 50% of materials from affiliated mills.
- Independent plants source more than 50% of materials from external suppliers.
Types of Corrugating Plants
- Sheet feeder plants manufacture corrugated board in sheet form for converters.
- Sheet plants purchase sheets from sheet feeders and convert them into boxes.
- Corrugator box plants manufacture boards and convert them into finished products.
Manufacturing Process of Corrugated Board
- Linerboard is typically made from kraft unbleached fourdrinier paper.
- Fluting medium is produced through a semi-chemical process and often contains recycled content.
- Adhesive is starch-based and mixed on-site to ensure optimal bonding.
Manufacturing Process Overview
- Fluting medium is plasticized to become pliable.
- Fluting medium is coated with adhesive.
- First liner is pressed onto the fluted medium.
- Second liner is added to create a double-faced board.
- Board is cured and dried for a strong bond.
- Board is cut into sheets for further processing.
Cutting, Slitting, and Scoring
- Scores correspond to the flaps of the box.
- Cuts correspond to the length needed for a box blank.
Corrugating Board Configurations
- Flute profile is defined by height and pitch, with A (largest) to E (smallest).
- Larger profiles offer cushioning while smaller profiles are better for printing.
Single Facer Key Details
- Liner and fluting medium are preconditioned with heat and steam.
- Adhesive viscosity determines how much adhesive is delivered.
- Pressure between liner and medium is applied.
Double Facer Key Details
- Bridge allows curing time for the bond between medium and liner 1.
- Adhesive is applied to the tips of flutes.
- Pressure is applied to prevent damage to the flute.
- Liner 2 is outside the box.
- Pre-printed liners are always applied to the double facer.
Board Specifications
- Basis weight, sheet size, and board strength are key factors.
- Mullen burst test measures burst strength.
- Edge crush test measures edge crush strength.
- Wet strength is an important performance property.
Coatings
- Water resistance is achieved with polyethylene, wax, or water-based coatings.
- Moisture resistance is achieved with paraffin coatings.
- Oil and grease resistance are achievable.
- Abrasion resistance is achieved to reduce scuffing of graphics and products.
Corrugated Box Design: Materials and Construction
- Linerboard is typically unbleached kraft paperboard, with options for coatings for printability.
- Corrugated medium is made from unbleached semi-chemical hardwood pulp, both virgin and recycled.
- Adhesive bonds together the linerboard and corrugated medium.
- Flutes are oriented parallel to the depth dimension for optimal stacking strength.
Corrugated Box Design: Dimensions and Styles
- Inside dimensions ensure product fit.
- Outside dimensions account for transportation factors.
- L = longest side panel.
- W = shortest side panel.
- D = distance between the top and bottom openings.
- Scoring allowance is the amount of material taken up in the fold.
- Consider shelf space, truck space, conveyor width, fillers, sealers, center of gravity, and inserts.
- Common styles include RSC, HSC, FOL, CSSC, telescope boxes, folders, rigid boxes, and self-erecting boxes.
Corrugated Box Design: Manufacturing Process
- Key stages include printing slotter, folder gluer, and flexo-folder gluer.
- Die cutting is used for unique designs, cutouts, and perforations.
- Types of die cutting include rotary and platen.
Corrugated Box Design: Printing and Finishing
- Direct printing is common for small flutes.
- Preprinting offers high quality and is economical for short runs.
- Litho-labeling glues printed labels onto the board.
- Flexography is fast with fine print and quick setup time.
- Silk screen is low volume but high quality.
- Offset lithography is best for small flutes.
- Digital printing provides good speed and resolution.
Corrugated Box Design: Performance and Techniques
- Strength decreases over time under load.
- High humidity reduces strength.
- Stacking patterns and position impact load distribution.
- Warehouse conditions and transportation modes influence performance.
- Box compression test (BCT) measures compression strength.
- ASTM D 4169 simulates transportation.
- ASTM D 642 measures compression strength.
Corrugated Box Design: Joints
- Glued joints are the least expensive and need flaps.
- Stitched or stapled joints are the strongest and require flaps.
- Taped joints are the weakest and do not require flaps.
Box Converting: Flexo-Folder-Gluer
- Used for creating the simplest boxes - RSC.
- Combines several operations in one machine.
Box Converting: Flexo-Folder-Gluer Steps
- Feed section: Sheets are fed to the machine, slit to the width of the blank, scored across the flutes, cut to the length of the blank, and fed one at a time for printing.
- Flexo section: Blanks are printed using flexography.
- Scoring section: Body scores are made.
- Slotter section: Slots are cut to create top and bottom flaps.
- Folder-gluer section: Folds are made and adhesive is applied.
- Delivery section: Boxes are counted and bundled.
Box Converting: Printing
- Flexography is the most common and cheapest printing method.
- Liners can be pre-printed to improve quality.
- Litholaminations add a printed sheet to the board.
- Commodity boxes have minimal printing.
- High-quality printing serves as advertising.
Box Converting: Printed Elements
- Box maker certificate usually includes the box maker's name, location, and minimum specifications.
- Brand identification highlights the product's brand.
- SKU (stock keeping unit number) is used for inventory management.
Paper Characterization and Properties
- Important factors include moisture content, physical characteristics, strength properties, and optical properties.
- Material tests are conducted by suppliers prior to conversion.
- Packaging tests assess performance and are used by converters and buyers.
Testing Procedures
- Established standards are used for repeatability and reproducibility.
- Repeatability refers to consistent results by one operator in one lab.
- Reproducibility refers to consistent results across labs and equipment.
Moisture Content
- Equilibrium moisture content is reached in a specific humidity and temperature.
- Isotherms indicate how moisture absorption varies with relative humidity.
- Hysteresis is the difference in moisture content between drying and increasing relative humidity.
Effect of Moisture Content on Paper
- Moisture content affects dimensions and flatness.
- Fibers swell and shrink, causing dimensional changes.
- Curling occurs due to uneven fiber swelling.
Physical Properties of Paper
- Basis weight is the paper weight per ream.
- Caliper is the paper thickness.
- Density is the ratio of basis weight to caliper.
- Smoothness, gloss, gas transmission, and curl also impact performance.
Basis Weight / Grammage
- Price is based on $/ton.
- Basis weight relates to strength and stiffness.
- A ream is 3000 ft2 for paper and 1000 ft2 for paperboard.
Mechanical Properties of Paper
- Tensile, tear, fold, and compression tests are used to assess mechanical properties.
- Tensile strength is stronger in the machine direction than the cross direction.
- Coefficient of friction impacts machiniability and storage behavior.
Tear Strength
- Measures the energy needed to propagate a tear.
- Elmendorf test measures tear strength.
Burst Strength
- Widely used test correlated to tensile strength.
- Used for linerboards and combined corrugated boards.
Optical Properties of Paper
- Properties include brightness, opacity, gloss, smoothness, and color.
- Surface roughness, coatings, basis weight, and light interactions influence optical properties.
- Light interactions include reflectance, scattering, transmission, and absorption.
Paper Types
- Kraft paper is strong and often unbleached.
- Sulfite paper is typically bleached.
Paperboard Types
- Solid bleached suflate (SBS) is preferred for high speed packaging.
- Solid unbleached suflate (SUS) is clay coated for printability.
- Chipboard is 100% recycled and low strength.
- Folding boxboard is most common in Europe and uses mechanical pulp in the middle layers.
Containerboard Types
- Linerboard is made from southern pine or douglas fir fibers.
- Corrugating medium is made from hardwood and recycled fiber.
Paper Types - Specific Types
- Tissues are the lightest paper type.
- Greaseproof paper is resistant to oil and grease.
- Glassine paper is smooth, semi-transparent, and resistant to air and oil vapor.
- Parchment paper is strong when wet and highly grease resistant.
- Clay coated papers are coated with clay and pigments for improved graphics and smoother surfaces.
Laminated and Extrusion Coated Papers
- Extrusion coating applies melted plastic to the paper surface for wet conditions and heat sealing.
- Laminations bond layers of plastic film, foil, or paper with a melted adhesive.
- Common plastic types include low-density polyethylene.
Metallized Paper
- Offers the look of foil without lamination.
- Aluminum particles are deposited on the paper surface.
- Cost-effective due to less material usage.
Cellophane
- Made from high-purity wood pulp dissolved and cast onto a drum.
- Plasticized and coated for barrier and heat sealing properties.
- Still used in niche markets where stiffness, a dead fold, and specific color qualities are needed.
Molded Pulp
- Fiber slurry is molded into 3D shapes.
- Plain molding produces thicker parts for cushioning and thinner parts for trays.
- Precision molding produces smooth surface parts using thermoformed fibers.
Equations
- Estimating Cost of a Box
- McKee Equation for BCT: BCT = 5.87 x ECT x combined board caliper x box perimeter.
- Basis Weight Calculation:
Textbook Notes
- Repeatability tests a sample in the same lab.
- Reproducibility tests a sample in different labs.
- TAPPI (Technical Association of the Pulp and Paper Industry), ASTM (American Society for Testing and Materials), and ISO (International Organization for Standardization) are important organizations.
- Material tests evaluate properties like thickness and tensile strength.
- Package tests evaluate properties like compression strength and drop-height survival.
- Caliper is used to measure thickness of paperboard and paper.
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Description
Explore the intricacies of the corrugated industry, focusing on the types of plants involved, from integrated to independent operations. Understand the manufacturing process of corrugated boards, including the materials used and the production steps from fluting medium to finished products.
