TABLE OF CONTENTS

Page

TABLE OF CONTENTS.......................................................................................................................................................... i

EXECUTIVE SUMMARY........................................................................................................................................................ 1

1.0 PROJECT OVERVIEW................................................................................................................................................. 2

1.1 PROJECT OBJECTIVES............................................................................................................................................. 3

2.0 PULP MOLDED STRUCTURES.................................................................................................................................. 3

2.1 EXISTING PRODUCTS............................................................................................................................................. 3

2.2 REGULATORY GUIDELINES.................................................................................................................................. 4

2.3 STRUCTURAL PROPERTIES.................................................................................................................................. 4

3.0 RESIDUAL FIBER STRUCTURES.............................................................................................................................. 8

3.1 GENERAL PROPERTIES.......................................................................................................................................... 8

3.2 PHYSICAL CHARACTERISTICS........................................................................................................................... 9

4.0 FURNISH SPECIFICATIONS..................................................................................................................................... 12

4.1 MOLDING PROCESS............................................................................................................................................. 12

4.2 BENCH-TOP TESTING.......................................................................................................................................... 12

4.2.1 DRAINAGE RATE....................................................................................................................................... 13

4.2.2 ASH CONTENT............................................................................................................................................ 14

4.3 FIBER PROCESSING.............................................................................................................................................. 15

5.0 MANUFACTURING TEST STRUCTURES.............................................................................................................. 19

5.1 MOLDING PROCESS............................................................................................................................................. 19

5.2 RESIDUAL FIBER TEST STRUCTURES............................................................................................................ 19

6.0 TEST STRUCTURE EVALUATIONS........................................................................................................................ 22

6.1 END USER EVALUATIONS................................................................................................................................. 22

7.0 FURNISH RECOMMENDATIONS............................................................................................................................ 24

7.1 GENERAL PROPERTIES....................................................................................................................................... 24

7.2 RECOMMENDATIONS........................................................................................................................................ 25

7.3 AREAS FOR FURTHER STUDY.......................................................................................................................... 26

8.0 CONCLUSION.............................................................................................................................................................. 27

9.0 ACKNOWLEDGMENTS............................................................................................................................................. 29

10.0 REFERENCES............................................................................................................................................................... 30

LIST OF FIGURES

Figure 1 - Fiber Length Distributions for Control Structures and Residual Fibers....................................................... 11

Figure 2 - Freeness Values for Control Structures and Residual Fibers......................................................................... 11

Figure 3 - Residual Fiber Freeness Values.......................................................................................................................... 17

Figure 4 - Residual Fiber Length Distributions ................................................................................................................. 18

Figure 5 - Residual Fiber Ash Contents.............................................................................................................................. 18

LIST OF TABLES

Table 1 - Physical and Mechanical Characteristics of Molded Structures...................................................................... 7

Table 2 - Physical Characteristics of Residual Fibers......................................................................................................... 9

Table 3 - Inorganic Concentrations in Residual Fibers..................................................................................................... 10

Table 4 - Effect of Polymers on Drainage Rate................................................................................................................... 14

Table 5 - Ash Content in Screened Residual Fibers.......................................................................................................... 15

Table 6 - Comparisons of Physical Characteristics........................................................................................................... 16

Table 7 - Key for Figures Three, Four and Five................................................................................................................. 17

Table 8 - Physical and Mechanical Characteristics of Test Structures.......................................................................... 21

Table 9 - Specifications for Residual Fiber Furnish........................................................................................................... 25

APPENDICES

Appendix A - Testing Description

Appendix B - Fiber Length Weighted Distribution for Control Structures

Appendix C - Fiber Length Weighted Distribution for Virgin, ONP and OCC Residual Fibers

Appendix D - Bench-Top Testing

Appendix E - Fiber Length Weighted Distribution for Virgin, ONP and OCC Residual Fibers

Appendix F - Flow Diagram Pulp Molding Process

Appendix G- Description of Residual Fiber Types

EXECUTIVE SUMMARY

Pulp and paper mill residual fiber is a major post-industrial waste problem in Washington State. Molded products may provide a market for mill-based residual fibers, may reduce the demand for fossil fuels, increase the beneficial reuse of higher-value pulp feedstocks and increase the use of biodegradable end products. Molded pulp products have the potential to replace many plastic packaging products, particularly expanded polystyrene and corrugated containers.

Absorption Corporation tested and evaluated pulp and paper mill residual fibers as furnished in the manufacture of molded pulp products. The scope of the project was to:

· Develop specifications for pulp suitable for a range of molded products;

· Classify typical mill residual fibers from a minimum of three fiber sources and a minimum of two fiber types;

· Process a range of residual fibers to meet required specifications;

· Run a pilot plant molding operation to prove technical feasibility; and

· Introduce products to end users for validation of viability and acceptability.

Three residual fiber types obtained from five distinct mill sources were tested as potential furnishes for molded pulp technology. Virgin fiber from non-recycled residual (virgin), deink fiber from recycled newsprint residual (ONP) and old corrugated container residual fiber (OCC) was repulped, slurried, screened, thickened and dewatered into suitable fiber furnishes. Furnishes were tested individually and combined during pulp molding trials in the manufacture of various test structures. These test structures included egg trays, perforated berry boxes, mushroom boxes and chick boxes.

Findings indicate that virgin and ONP residual fibers are best suited for molding into structures that are lightweight, rigid and can support their own weight. These fiber types contain TMP, range from 242 ml to less than 785 ml CSF, range from 2.09 mm to 2.64 mm in fiber length, contain an ash content of less than 16%, and contain fewer than 31% rejects in the finer fraction.

One hundred percent ONP residual fiber makes the best furnish for molded structures. The ONP can be added to virgin and OCC fiber furnishes to improve performance in molding equipment and impart structural strength properties. Based on these results, it is concluded that mill-based virgin, ONP and OCC residual fibers can be processed into furnish for use in molded pulp technology

1.0 PROJECT OVERVIEW

The Clean Washington Center (CWC), in association with the Absorption Corporation, tested and evaluated the potential of using pulp and paper mill residual fiber as furnish in molded pulp technology.

Pulp and paper mill residual fiber is a major post-industrial waste problem. As of 1989, six hundred mills in the United States produce pulp, paper, paperboard, or related products; 200 of these mills make use of waste paper for their raw material supply and another 300 utilize up to 50% of the waste paper in the manufacturing process (1).[1] Nineteen of these mills are located in Washington State.

Molded pulp product use in this country is nearly 450,000 metric tons per year (500,000 short tons per year), primarily from old newspapers (ONP), with a projected use of 810,000 metric tons per year (900,000 short tons per year) by the year 2000 (1). Alternative non-paper uses for recovered paper will continue to increase into the next century and the greatest use by weight may be in molded pulp products (2).

Molded pulp products have the potential to replace many plastic packaging products, such as expanded polystyrene and corrugated containers. Manufacturing mill-based residual fiber into molded products may reduce the demand for virgin fiber or other valuable raw materials used in packaging and increase the use of biodegradable end products.

Manufacturing molded pulp products from mill residual fibers can provide pulp and paper mills with higher value-added applications than current practices, such as incineration, composting, landfill capping, and soil reclamation. Other advantages include creating new market development opportunities; reducing the demand placed on higher value pulp furnish materials like old corrugated containers (OCC) and old newspaper (ONP); and providing a lower-cost furnish feedstock to molded pulp manufacturers.

This study used pulp and paper mill residual fibers obtained from the gravity or flotation thickening of organic and inorganic materials contained in untreated mill wastewater. The residual fiber was repulped and dewatered in accordance with process patents 5,358,607 and 5,091,245. These processes are used in the manufacture of industrial absorbents, small animal litter, and high performance beddings.

1.1 PROJECT OBJECTIVES

This report summarizes the technical information regarding mill-based residual fiber used as furnish in pulp molded products. Objectives of the report were to:

· Develop specifications for pulp suitable for a range of molded products;

· Characterize typical mill residual fibers from a minimum of three fiber sources and a minimum of two fiber types;

· Process a range of residual fibers to meet required specifications;

· Run a pilot plant molding operation to prove technical feasibility; and

· Introduce products for evaluation by end users for validation of viability and acceptability.

2.0 PULP MOLDED STRUCTURES

2.1 EXISTING PRODUCTS

Molded pulp products can be comprised of pulp from old newspapers (ONP), mixed waste paper (MWP), old corrugated containers (OCC), or from ground wood or chemical pulps. Virgin pulps are required for certain grades of food board and OCC is used in products requiring greater strength properties, such as in cushioning heavy items (3). Pine or fir wood chips with optimum dimensions may also be processed to provide suitable pulp for molded products (3).[2]

Numerous custom design and general use molded pulp structures are manufactured for specialty and non-specialty use markets. Consumer items, nursery containers, food packaging, deliveries, electronics, hardware, and medical equipment are the major categories of molded pulp products on the market (2, 4).

In this study, nursery containers, food packaging, delivery, and electronics were selected as molded products to be evaluated. Cellular phone packaging, berry boxes, apple and egg trays, four-cup beverage trays and toner endcap cushioning were selected as controls to represent these categories. These items were readily available and represented structures available to the pilot plant molding operation.

2.2 REGULATORY GUIDELINES

Pulp from reclaimed fiber is approved for use by the FDA as a component of articles used in producing, manufacturing, packing, processing, preparing, treating, packaging, transporting or holding food (5). The Food and Drug Administration (FDA) approves materials added to wet pulp during stock preparation for use (6,7). Pulp is listed as an indirect human food substance affirmed as generally recognized as safe (GRAS) (8). However, a FDA exemption requires single-service milk container guidelines to use virgin pulp (9).

In addition, the Food Safety and Inspection Service/US Department of Agriculture (FSIS/USDA) identifies regulations that pertain to meat and poultry packaging materials. Edible products may not be packaged in a container composed in whole or in part of any poisonous or deleterious substance, which may render the contents adulterated or injurious to health (10). The temporary tolerance level for unavoidable poisonous or deleterious substances of paper food-packaging materials containing polychlorinated biphenyls (PCBs) is set at 10 part per million (ppm); this does not apply to paper food-packaging material which is separated from food by a functional barrier considered to be impermeable to the migration of PCBs (11).

2.3 STRUCTURAL PROPERTIES

Molded pulp products are manufactured to meet packaging and cushioning performance characteristics for numerous applications. In general, molded packaging or cushioning must be lightweight, non-clingy, rigid, foldable as necessary, support weight during shipping, and offer custom shapes and sizes.

No physical, mechanical and chemical specifications are readily available for determining optimum pulp fiber furnishes for molded structures. For this project, the specification recommendations from a die manufacturer were adopted in the development of suitable residual fiber furnishes.

There are no specific standard methods available for testing molded fiber structures. This project adopted ASTM and TAPPI test standards for the development of protocol for testing molded fiber structures. These standards provided the best available and repeatable methods of measurement of the ten test parameters. The testing methodology is explained in Appendix A.

The physical and mechanical properties of the six molded controls and residual fiber test structures were measured for ten physical properties: caliper, color, internal tear, presence of thermomechanical pulp (TMP), fiber length, freeness, folding endurance, tensile strength, puncture resistance, and density.

These parameters were chosen to describe the physical characteristics of the molded structures:

· Caliper: A general measurement of structure thickness; expressed in millimeters.

· Color: A description of structure pigment color. The pantone matching system (PMS) for defining color can be described using general terms for each structure: apple (2725u) light purple; berry (2725u) deep purple; beverage (4745u) pinkish-tan; consumer (cool gray2u) light gray; egg (400u) light gray; and endcap (467u) paperbag brown.

· Internal tear: A description of pulp stock characteristics; generally varies inversely with density. A greater tear resistance may indicate longer fiber lengths (3); expressed as the force per distance (g/cm).

· Presence of TMP: Determining the presence of thermomechanical pulp is a general indicator of fiber types in pulp; expressed as the depth of the color reaction obtained when fiber is stained with phloroglucinol, a red acid (3).

· Fiber length: A common pulp measurement used when describing paper properties. The Kajaani fiber length method (FS-200 unit) evaluates fiber-length distributions of cellulosic fibers. The results may be reported as the weighted average fiber length, by weight of the whole pulp. Fiber length (by weight values) is characterized as long fibers (>1.5 mm), medium fibers (0.5 - 1.5 mm), and short fibers (up to 0.5 mm) in the papermaking industry.

· Freeness: Ability of a pulp and water mixture to release or retain water on drainage (3). Pulps having greater freeness values are characterized by the papermaking industry as being faster draining, coarser pulps. Freeness values are defined as coarse (160 - 250 CSF), medium (85 - 95 CSF), and fine (60 - 80 CSF).

· Folding Endurance: Structural bending characteristics; the amount of bending a structure will endure before its tensile strength falls below a standard value of 1 kg (3).

· Tensile Strength: The resistance of material to direct tension; the force required to break a strip of material; expressed as force per unit area (kg/sq cm).

· Puncture Resistance: Ability of a structure surface to withstand puncture by force and energy; reported as force per unit area (kg/sq cm).

· Density: Related to porosity, rigidity and strength; a basic property for comparing strength in pulps (3). Reported as volume per unit area (g/cm).

The Department of Paper Science and Engineering at Miami University, Ohio, analyzed for fiber length, freeness, and presence of thermomechanical pulp (TMP) (12). The contractor evaluated all other characteristics.

Physical and mechanical characteristics of six molded controls are described in Table 1. Fiber length distributions are graphed and shown in Appendix B.

3.0 RESIDUAL FIBER STRUCTURES

3.1 GENERAL PROPERTIES

Residual fiber from pulp and paper production contains a high content of cellulose that has settled out during the primary treatment of mill wastewater. Waste fiber comes from the clarifier at approximately 4% solids and is dewatered to about 25% solids. Similar organic and inorganic constituents are usually found in virgin and recycled primary wastewaters. Organic wastewater constituents contain polysaccharides (cellulose, hemicellulose and starch), lignin, and extractives (polyphenols, resins, fatty acids and pitch). The nonwater fraction typically contains wood fibers.

Inorganic wastewater constituents may contain lime, clays, alum, other paper additives, trace elements and residual chemicals added during processing (13). The nonwater fraction may consist of clay, calcium carbonate, titanium dioxide, inert solids rejected during chemical recovery processes, and other material used in pulp and paper production (14).

Effluents from mills that repulp and deink recovered paper differ from those using virgin fiber. These effluents have lower effluent biochemical oxygen demand (BOD₅) loadings and flows, and greater inorganic contents. The inorganic content results from the pulping and deinking of recovered paper, deinking chemicals, printing inks and coating and filler materials (15, 16). The printing ink fraction contains traceable levels of zinc, chromium, lead, and copper.[3](16)

Printing inks used by related industries are changing and influencing the composition of elements in the inorganic fraction. Ink markets are replacing solvent-based inks with water-based inks and some forms of soy-based ink is estimated to be used in at least one half of the daily newspapers in the United States. The packaging industry is increasing its use of water-based inks (17).

There is a distinction between inks and pigments found in newsprint grade paper residual and those found in other types of deink paper grades, such as mixed office waste (OMP). This distinction includes issues relating to polychlorinated PCBs contamination of the matrix. Prior to June 1971, PCBs were used in the manufacture of carbonless copy paper, an OMP paper grade. Products made from grades of recovered paper containing carbonless paper were contaminated with PCBs. From 1969 to 1980, concentrations of PCBs detected in recovered paper steadily dropped to 96% of original concentrations, and levels detected in finished products decreased even more between 1982 and 1987 (15). The deink residual fiber selected for use in this study is from newsprint grade paper.[4]

Residual fiber types selected as potential pulp molding furnish originated from three distinct paper grades. These paper grades included virgin fiber from non-recycled residual type (virgin), deink fiber from recycled ONP, and OCC residual fiber. These fiber types are generated from the sulphite (calcium base), flotation deinking, and kraft pulp processes, respectively. The mill sources for ONP and OCC waste fiber types changed during this project. The testing results identify each fiber type analyzed and the differences between fiber sources.

3.2 PHYSICAL CHARACTERISTICS

The three fiber types were initially tested for fiber length, freeness, presence of TMP, and ash content. These measurements provided baseline data for comparing the values reported for the six molded controls and residual fiber test structures. Table 2 details the testing results for these physical characteristics. The inorganic residue after combustion is reported as percent ash. During ashing, the volatile fraction is typically comprised of the cellulose fibers. Fiber length is reported by Kajaani weighted average fiber length by weight.

Graphs of the fiber lengths for the virgin, ONP, and OCC residual fibers are presented in Appendix C.

Table 2 Physical Characteristics of Residual Fibers

Mill Source	Sample	TMP Fiber Test	Fiber Length, Avg.	Freeness (CSF)	Ash (%)
Virgin, mill-1	Virgin fiber	Very light pink;trace TMP	2.34 mm	135 ml	5.7
OCC, mill-1	OCC fiber	Dark pink; some TMP	2.78 mm	684 ml	8.7
ONP, mill-1	ONP fiber	Deep purple; large TMP	2.09 mm	110 ml	32

The inorganic fraction in residual fibers varies widely between major fiber types and mills having the same type of residual fiber. One set of analytical data for each fiber type is reported in Table 3. The data describes typical concentrations of inorganic compounds detected in these types of residual fibers.

Table 3 Inorganic Concentrations in Residual Fibers in Parts Per Million (ppm)

(Reported on Dry Weight Basis)

	Fiber Type
Constituent	Virgin (ppm)	ONP (ppm)	OCC (ppm)
Al	3600	10,300	840
Ag	<2.2	<1.5	<2
As	<6.5	0.25	0.15
B	<22	17.0	2.0
Ba	29.0	83.1	34.0
Be	<1.1	<1	<1
Ca	3900	15,800	6,800
Cd	<0.44	<2.5	<0.25
Co	<0.65	1.1	<1
Cr	9.20	11.3	4.0
Cu	110.0	174.0	82.0
Fe	1600.0	690.0	56.0
Hg	<1.9	<0.001	0.03
Na	470	2,080	2,020
Ni	3.80	3.0	<2
Mg	1400.0	357.0	280.0
Mn	56.0	30.7	68.0
P	890.0	575.0
Pb	8.6	8.1	2.0
Se	<6.5	<0.1	<0.5
Sn	<4.4	10.0	6.0
Sr	13.0	27.0	12.0
Ti	65.0	31.0	13.0
V	2.0	8.1	4.0
Zn	120.0	88.7	51.0
PCBs	<MDL*	<MDL*	<MDL*
*MDL = method detection limit

The fiber length and freeness values of the control samples listed in Table 1 are compared in Figures 1 and 2 against those of the residual fibers listed in Table 2.

Figure 1 Fiber Length Distributions for Control Structures and Residual Fibers

Figure 2 Freeness Values for Control Structures and Residual Fibers

4.0 FURNISH SPECIFICATIONS

4.1 MOLDING PROCESS

Furnish recipes are formulated to meet the performance requirements of the molding equipment, dies, and product use requirements. These specifications are the proprietary information of the manufacturers of the individual products. In this project, the pilot plant molding operation recommended that the residual fiber furnish meet typical pulp fiber furnish specifications (18). Suitable pulp fiber furnishes generally have:

· target freeness value of 260 ml CSF;

· inorganic content of less than 15%;

· fiber length range having minimal finer and coarser fractions; and

· no contaminants.

These specifications were adopted and used as a guideline in establishing furnish specifications for the residual fiber materials.

Pulp molding equipment operates at high speeds, therefore the pulp furnish must drain at a target rate of greater than 260 ml CSF. Using higher molecular weight polymers is one practice recommended to increase freeness values or drainage rates in certain stocks (19).

Residual fiber materials typically contain clay particles which affects the inorganic content of the fiber furnish. Frequent cleaning of molding equipment may be required when fiber furnishes contain more than 15% inorganic content. Some pulp cleaning/thickening equipment may remove a percentage of the incoming inorganic constituents and/or reduce the finer fiber fraction. These fiber modifications may lower ash content while increasing freeness values (20).

The fiber length requirement for moldability is nominal. Molding equipment screens are designed to capture the finer fraction (18). One possible method to increase pulp yield may be to remove a percentage of the finer and/or coarser fraction present in the mill waste fiber stream during the fiber preparation phase. (This was initially tested during this project.)

4.2 BENCH-TOP TESTING

Bench-top testing was used to determine a feasible method to process the residual fibers to meet furnish specifications. This method was applied to measure the potential effects from fiber screening and the use of high/low molecular weight polymers on waste fiber furnishes. The testing measured the effects on:

· drainage rate (ml/5 minutes);

· ash content (percentage by weight); and

· coarser fraction (percentage by weight).

The pilot plant testing center of Black Clawson recommended the following fiber cleaning methods to prepare the residual fibers for use as furnish:

1. screen for the finer and/or coarser fractions (fractionating or pressure screens);

2. reverse flow cleaners (centrifical cleaners); or

3. apply high speed washer/thickener.[5]

Evaluations made prior to bench-top testing indicate that the OCC residual fiber type had an average fiber length of 2.78 mm (weight weighted average); a freeness value of 684 ml CSF; and an ash content of 8.7% (as shown in Table 2 and in Figure 1).

The average fiber length of the OCC residual fiber type closely matches that of the berry carton control (Table 1), 2.78 mm and 2.75 mm, respectively. The freeness value exceeds the recommended minimum value of 260 CSF and is within 15% of the maximum value for freeness (800 CSF). The ash content is approximately 40% less than the recommended maximum of 15%.

The results indicated that criteria was met for the fiber to be considered suitable furnish for pulp molded products. Based on the initial tests, the OCC residual fiber type was not included in the bench-top analysis.

4.2.1 Drainage Rate

One anionic and three cationic polymers were added to slurries of virgin and ONP residual fibers at 3% consistencies to determine drainage rates. A cationic polymer with a low molecular weight increased the drainage rate of one virgin fiber subsample (virgin-4). Drainage rates are listed in Table 4.

Table 4 Effect of Polymers on Drainage Rate

Sample Identifier	Polymer Type	(ml/5 min.)
virgin-1	No polymer	70
virgin-2	No polymer	37
virgin-3	No polymer	107
virgin-4	Cationic-1	108
virgin-5	Cationic-2	83
virgin-6	Cationic-3	78
virgin-7	Cationic-1a	39
virgin-8	Anionic-1	42
ONP-1	No polymer	55
ONP-2	Cationic-1	55
ONP-3	Cationic-1	40
ONP-4	Cationic-2	19
Descriptions
Cationic-1: relatively low molecular weight; 10ml (25 ppm)
Cationic-1a: dilute Cationic-1; 5 ml (12.5 ppm) Cationic-2: relatively medium molecular weight; 10 ml.
Cationic-3: relatively high molecular weight.; 5 ml (12.5 ppm)
Anionic-1: 10 ml.

4.2.2. Ash Content

Slurries of virgin and ONP fibers were hand-screened, oven-dried and ashed to determine effects on inorganic content. Fiber slurries of 1.5% were used in the screening analysis. Fiber samples were evaluated four times using four different screening methods. As previously reported in Section 3.2, the virgin fiber material had the lowest ash content of all fiber types. The virgin fiber was hand-screened to contrast and compare the results with data obtained from screening the ONP fiber.

After the initial screening, ash content in the virgin fiber slurry was reduced by 7%, and the ash content of the ONP slurry was reduced by 25%. Screening did lower ash content in both fiber types. The virgin fiber was not included in subsequent screenings. A description of the bench-top screening method is detailed in Appendix D.

Pre-screening and post-screening comparisons are presented in Table 5. For comparative purposes, the OCC fiber type was not included in the bench-top analysis but is included in the table. The screening and ash analysis is divided into four evaluations. Lot 1 includes virgin and ONP fiber samples and Lots 2 through 4 include only ONP fiber.

Table 5 Ash Content in Screened Residual Fibers (averages)

Mill Source	Sample	Description	Pre-screen	Lot 1	Lot 2	Lot 3	Lot 4
OCC, mill-1	1	OCC	8.7	-	-	-	-
Virgin, mill-1	2	Virgin	5.7	5.3	-	-	-
ONP, mill-1	3	ONP	32	24	22.8	16.6	18.5

The ash content in virgin and ONP residual fiber types were reduced to within 10% of the recommended value for pulp molding furnish. The greatest reduction in ONP inorganic content is seen in Lot 3, possibly due to the screening technique. Lot 3 was blended for a longer time period.

Drainage rate and ash content results may vary for pilot plant operations processing fiber in trials using full scale, high speed washing and thickening equipment.

4.3 FIBER PROCESSING

This project evaluated OCC residual fiber from two mill sources. The first OCC fiber type

(mill-1, OCC) was evaluated for fiber length, freeness, and presence of TMP. Results indicated that unprocessed OCC waste fiber material from this mill source exceeded the recommended minimum physical values for use in pulp molding equipment. Thus, OCC fiber type was not scheduled for inclusion in the subsequent fiber preparation processes.

The pilot plant misplaced the first OCC fiber type just prior to testing all fiber types in the pulp molding operation. A second OCC residual fiber type replaced the first OCC fiber type, due to unavailability for more of the first OCC residual fiber.

The ONP residual fiber source changed after the initial phase of physical characteristics testing (initial ONP residual fiber source -- mill-1, ONP). ONP residual fiber from a second mill source was included in subsequent testing (cited as mill-2, ONP). The mill source for the virgin residual fiber remained constant throughout all phases of testing (mill-1, virgin). The first set of dewatered OCC fiber and partially dried virgin and ONP fiber types were sent to a pilot plant molding operation to determine pulp furnish potential.

The material was repulped (hydropulper), slurried (1%), screened for coarser fraction, thickened and dewatered. [6] Both fiber types were partially dried to approximately 85% dryness. Samples were collected from all three fiber types and evaluated for freeness and fiber length characteristics, before and after processing.

All fiber samples were screened according to the Somerville screening technique to determine the percentage of rejects in the finer fractions, and to determine the affect of the finer fraction on drainage rate. The Somerville screening results for both processed (p) and unprocessed (un) fiber materials are shown in Table 6. Column five shows the freeness values after screening for rejects.

Table 6 Comparisons of Physical Characteristics (12)

Mill Source	Sample	Freeness (ml)	% Rejects	Freeness (ml)	Fiber Length (mm)
ONP, mill-2	p-ONP	549	16.59	590	2.53
Virgin, mill-1	p-Virgin	510	26.88	695	2.43
OCC, mill-1	un-OCC	785	31.13	753	2.64
ONP, mill-2	un-ONP	780	60.05	763	2.20
Virgin, mill-1	un-Virgin	252	25.98	650	2.41

The freeness, fiber length and ash content of all the residual fiber samples are compared in Figures 3, 4, and 5. The data is presented according to fiber type by mill source; coarser fraction screened and thickened (processed); and finer screened fraction (Somerville-screened). The Sommerville screen has a plate with 756 slits each 4.5 cm long and 0.15 mm wide, also described in TAPPI Useful Method 242 (21). Table 7 provides a key for the letter abbreviations appearing in these figures. Fiber length distribution graphs are shown in Appendix E.

Table 7 Key for Figures Three, Four and Five

Figure 3	Figure 4	Figure 5	Mill Source	Processed	Screened
A	A	B	ONP, mill-2	Yes	No
B		A	ONP, mill-2	Yes	Yes
C	B		ONP, mill-2	No	No
D			ONP, mill-2	No	Yes
E	C	C	ONP, mill-1	No	No
F	D	D	Virgin, mill-1	Yes	No
G		E	Virgin, mill-1	Yes	Yes
H	E		Virgin, mill-1	No	No
I			Virgin, mill-1	No	Yes
J	F	F	Virgin, mill-1	No	No
K	G	G	OCC, mill-2	No	No
L			OCC, mill-2	No	Yes
M	H	H	OCC, mill-1	No	No

Figure 3 Freeness Values between Fiber Types

Figure 4 Fiber Length Distributions between Fiber Types

Figure 5 Ash Contents between Fiber Types

5.0 MANUFACTURING TEST STRUCTURES

5.1 MOLDING PROCESS

A high-speed pulp molding process is comprised of nine steps:

1) Stock preparation by blending the pulp and water in a pulper;

2) Pulp is advanced to the molder vat containing forming dies;

3) Forms are molded by pressing against the forming dies;

4) A transfer mechanism matches transfer dies with the formed fiber products and deposits them onto moving dryer conveyor trays (a trolley beam and hoist allows quick die changes out);

5) Forms are dried and fiber products exit the drying section into the discharge section;

6) Fiber products are to be transferred across a synchronized shuttle plate by a pusher conveyor;

7) Discharge conveyors align and send sorted products into stackers;

8) Stackers orient, count and stack designated quantities of products into bundles; and

9) Bundles are loaded onto pallets and moved into storage (18).

A flow diagram of the pulp molding process is presented in Appendix F.

The pulp is thickened to yield 4% consistency during stock preparation. Materials added to the wet pulp may include a wet strength resin, a sizing agent, polymers to aid retention and drainage, a slimicide or colorant. These additions comprise about 2% of the solids content in the final pulp stock (18). Rosin and wax sizing agents range from 1% to 3% rosin size, or 2% wax size plus ½% rosin size. Finished molded products may be treated with wax, saturated with asphalt, or treated otherwise for water and oil resistance properties (1).

5.2 RESIDUAL FIBER TEST STRUCTURES

A perforated berry box, two mushroom boxes, two chick boxes, and three egg trays were molded from the three residual fiber types. The structures and corresponding fiber types are described as:

· perforated berry box consists of 100% ONP (berry-A);

· one mushroom box made from 50% ONP and 50% virgin (berry-B);

· one mushroom box made from 50% ONP and 50% OCC (berry-C);

· one chick box from 100% ONP (chick box-A);

· one chick box from 50% ONP and 50% OCC (chick box-B); and

· each of the egg trays from 100% ONP (egg-A), 100% virgin (egg-B) and

100% OCC (egg-C).

The fiber types were tested in chick box structures for the purpose of evaluating the fiber ability to support larger spans and the strength related to larger span sizes. The results of test data evaluating the physical and mechanical characteristics of the molded residual fiber structures is presented in Table 8.

The ONP residual fiber was the optimum fiber type for use in the molding process and in the resulting structures. During manufacturing, the ONP residual fiber was added as filler to the virgin and OCC residual fibers to increase strength properties in the test structures.

The egg tray was the only structure successfully molded using 100% OCC residual fiber. The OCC residual fiber did not perform well in the dies and the resulting structures did not hold together or support their own weight.

6.0 TEST STRUCTURE EVALUATIONS

The perforated berry box made of 100% ONP, and the egg trays composed of 100% ONP, 100% virgin, and 100% OCC fiber types were evaluated by end-users for validation of viability. With the exception of the OCC egg tray structure, all test samples achieved the minimum criteria for strength, appearance, and size. The samples were not dyed, contained less than 4% wax, and were uniform in shape, size and color. Small slivers appeared infrequently in all structures.

Chick box structures are constructed in dies and meant to support longer span lengths. The test structures were constructed to determine how well the residual fiber types would mold in larger dies, hold together after molding, and support their own weight. Criteria was met for the two chick boxes, one made with 100% ONP and one made with 50% ONP with 50% OCC. The structure was not successfully molded using 100% virgin, 100% OCC, or a combination of these two fibers.

6.1 END-USER EVALUATIONS

Berry Box

Unlike the test structures, berry box end-users currently use large, stiff, dyed structures in retail and wholesale. The cost for perforated berry boxes is approximately $0.04 each. The end-user stated that, although the test structure was not identical to the structures currently used, its strength, size, and lack of dye could be utilized in their wholesale operation as containers within cardboard flats. The structure’s strength and size would be acceptable for this use. No concern was expressed over the appearance of small shives.

Comments from the berry box end-user follow:

Benefits:

· Made from 100% recycled materials.

· Low wax content for a one-time use product may allow alternative disposal or reuse options.

· Potential for cost savings to the end-user; if the cost of the residual fiber structure was priced lower than the structures currently used.

Concerns:

· Performance of the test structure with juicy fruits.

· Potential transfer of flavor from the structure to the fruit because of the low wax content.

· Color of the test structure for use in retail marketability (relating to the lack of dye).

· Strength of the test structure when used individually, without the support of cardboard flats.

Egg Tray

Egg tray end-users currently use a uniformly sized small, stiff, gray structure to hold 30 eggs per tray. The cost per tray is approximately $0.04. The trays must be of optimum size and strength to pass through the automated system and support 30 eggs per tray. To minimize interference with the de-nester apparatus and the transfer of slivers to tray handlers, the molded trays must be moisture-free and contain no large wood fibers. The automated system accepts one size of tray for all sizes of eggs. Tray color is of minor importance.

As a result of the test tray die-size, none of the test structures fit the width dimension of end-users’ tray de-nester apparatus nor did they fit within standard shipping boxes. The test tray die design of the egg nest area also interfered with the test structures ability to hold the eggs deep within the nest area. The structures were compatible with the automated apparatus placing the eggs in the trays and with the conveyor belt system. Only the 100% ONP and the 100% virgin fiber trays provided the level of stiffness necessary to support 30 eggs. The color of the test structures and the appearance of colored specks were deemed unimportant.

Comments by end-users regarding egg tray features:

Benefits:

· The test structures were softer than the rigid structures

· Eggs did not bounce in the test structures.

Concerns:

· The trays would need to be sized to fit the tray denester apparatus and shipping boxes.

· The trays must provide a level of strength to support 30 eggs per tray in a stacked configuration.

· The test trays must hold eggs deep within the nest area, regardless of egg size.

7.0 FURNISH RECOMMENDATIONS

7.1 GENERAL PROPERTIES

Residual fiber furnishes must be suitable for use in molding equipment and meet the requirements suggested for typical pulp-fiber furnishes outlined in Section 4.1. Specifications vary for the use of residual fiber in molded structures and are related to performance characteristics for each structure. This study suggests that a range of preliminary values can be assigned for freeness, fiber length, percentage of rejects and ash content specifications.

Blending and screening actions during bench-top testing noticeably reduced the inorganic fraction of the virgin and ONP residual short fibers. Virgin fiber that was blended for one minute and drained using a 100-mesh screen reduced the matrix ash content by 7%. The ash content of the ONP fiber matrix was reduced by 48% when the matrix was blended for four minutes and drained with the 100-mesh screen. Results of ash analysis in two of the three sub-samples fell within the ideal range for maximum inorganic content of matrices for use in pulp molding equipment.

The physical characteristics of the virgin and ONP residual fiber types generally corresponded to fiber characteristics of the control structures. Characteristics of the OCC fiber type corresponded closely to the endcap control structure, having primarily OCC fibers. All three of the fiber types molded into test structures exceeded the minimum value for freeness and fiber length and met the recommended minimum for ash content.

At the time of molding residual fiber into test structures, the virgin fiber had a freeness value of 510 ml, an average fiber length of 2.43 mm, contained 26.88% finer rejects, and an ash content of 7.9%. Screening out the coarser fiber fraction during furnish processing increased the freeness value by 51% and increased the average fiber length by 1%. The ash content varied in all the screened and unscreened samples and was greatest in the screened material.

The ONP residual fiber furnish had a freeness value of 549 ml, an average fiber length of 2.53 mm, contained 16.59% rejects, and an ash content of 15.7%. Screening out the coarser fiber fraction during furnish processing decreased the freeness value by 30% and increased the average fiber length by 13%. Ash content varied after each screening in bench-top analysis, but was lowest in the processed material at the time of molding the residual fibers into test structures.

The OCC residual fiber furnish had a freeness value of 785 ml CSF, an average fiber length of 2.64 mm, contained 31.13% rejects and an ash content of 7.7%. The OCC fiber was not processed prior to molding into test structures.

ONP residual fiber performed best as furnish in molding equipment, as compared to the virgin and OCC fiber. The ONP fiber was also added to the virgin and OCC fiber types as a binder to enhance moldability in molding equipment and impart strength properties in the test structures.

A set of preliminary specifications for virgin and ONP residual fiber types is suggested in Table 9. These specifications are recommended for use in a wide range of molded structures. Due to the poor performance characteristics of the OCC fiber during molding, it is suggested that this fiber type be blended 50/50 with ONP fiber.

Table 9 Specifications for Residual Fiber Furnish

	TMP	Freeness	Length	Ash	Finer Rejects	Coarser Rejects
Fibers	Presence	ml	mm	%	%	%
Virgin ONP	Yes	242-496	2.09-2.53	<16	<27	<2

7.2 RECOMMENDATIONS

The findings of this project provide general information about the use of residual fiber materials in the manufacture of pulp molded products. It is recommended that additional testing take place before setting standard specifications, since residual fiber types can vary between pulping batches, fiber streams within mills, and mill operations.

The use of polymers in bench-top tests suggests that lower molecular weight polymers may increase the drainage rate in virgin fibers. However, these preliminary findings are inconclusive. It is suggested that polymers of varying molecular weights, and polymers in combination with screening out the finer fiber fraction, be tested with the virgin and ONP residual fibers before recommending their use in pulp furnishes.

The results from testing the physical characteristics of the OCC residual fiber indicate that the fiber met the criteria to be suitable furnish for pulp molded products. The OCC residual furnish did not perform well in the pilot plant molding operation. It is recommended that additional refining may improve the performance of the OCC residual fiber during the pulp molding process.

It is recommended that additional test methods be included in bench-scale testing, which may increase the accuracy for determining effects on fiber furnishes. Additional methods include, screening for the finer fiber fraction; using reverse flow cleaners; or evaluating the effectiveness of using a high speed deink washer. These methods may be useful in determining the effects on fiber furnish by reducing the inorganic fraction and increasing freeness values.

It is also recommended that a complete set of quality assurance/quality control (QA/QC) measures be established prior to the start of fiber processing. Typical QA/QC parameters may include: classifying mill sources according to waste fiber types; establishing concentration limits on organic and inorganic constituents according to residual fiber types; monitoring the fiber furnish regularly; recording typical and atypical process information; and periodically collecting product samples for physical and chemical analysis.

Finally, it is recommended that the use of residual fiber in certain plastic and other molded structures be investigated. Some plastic molded structures are reinforced with pulp, primarily to increase strength properties

7.3 AREAS FOR FURTHER STUDY

The following recommendations propose additional areas of study important for evaluating fiber residuals in molded pulp products.

· Collect and evaluate residual fibers from multiple mill sources to determine suitability as fiber furnish in molded products.

· Evaluate additional physical and chemical characteristics depending upon end-use requirements, such as saturation point for determining wet strength properties, odor, and detectable affects on the flavor of foods by direct or indirect contact with the trays.

· Evaluate additional mechanical properties of residual fiber structures, such as strength of hinge top containers.

· Determine the economic feasibility and viability of manufacturing and marketing new and other existing pulp molded products from residual fibers.

· Investigate compatibility of functional food barrier materials with molded fiber products.

· Investigate the feasibility of reclaiming, recovering and remanufacturing residual fiber structures into recycled molded products.

· Determine if virgin, ONP, or OCC residual fiber types are suitable pulp fillers for use in molded plastics.

· Investigate the potential use of non-virgin residual pulp fiber in certain grades of food board, including ability to meet existing safety guidelines. Specifically focusing on the biological (bacterial) content of the end-product.

8.0 CONCLUSION

Three residual fiber types from five distinct mill sources were tested as potential furnishes in molded fiber products. Certain pulp and paper residual fiber materials can be successfully processed into typical pulp molded structures, meet the regulatory guidelines for pulp in molded structures, and are viable and acceptable.

Virgin fiber from non-recycled residual and deink fiber from ONP residual are suitable for molding into egg trays, perforated berry boxes, mushroom boxes and chick boxes. The test structures are lightweight and rigid, contain perforations, and can support their own weight. These residual fibers contain TMP, range from 242 ml to less than 785 ml in freeness, are between 2.09 mm to 2.64 mm in fiber length, and contain fewer than 31% rejects in the finer fraction. Pulp furnishes can be processed to meet these specifications by screening for the finer and/or coarser fraction and using lower molecular weight polymers to increase drainage rate.

The results from testing the physical characteristics of the OCC residual fiber indicate that the fiber meets necessary criteria to be suitable furnish for molded pulp products. Based on the findings, it is determined that the OCC residual fiber does not need further refining. During the subsequent pilot plant molding operation, the 100% OCC residual furnish did not perform well. The fiber did not form in, or transfer from, the dies and the resulting structures did not hold together.

One hundred percent ONP residual fiber gives the best results as a molded fiber furnish. The ONP fiber can be added to virgin and OCC residual fiber furnishes to improve their performance in the molding equipment and impart structural strength properties.

9.0 ACKNOWLEDGMENTS

Absorption Corp. would like to thank these molded pulp product users for evaluating the residual fiber test structures and offering valuable comments and suggestions:

Mr. Mark Coulter, Dynes’ Broadview Farm, Burlington

Mrs. Charlene Boxx, Boxx’s Berry Farm, Ferndale

CWC is a nonprofit organization providing recycling market development services to both businesses and governments, including tools and technologies to help manufacturers use recycled materials. CWC is the managing partner of the Recycling Technology Assistance Partnership (ReTAP), an affiliate of the national Manufacturing Extension Partnership (MEP) – a program of the US Commerce Department’s National Institute of Standards and Technology. The MEP is a growing nationwide network of extension services to help smaller US manufacturers improve their performance and become more competitive. ReTAP is also sponsored by the US Environmental Protection Agency.

10.0 REFERENCES

1. ASTM Standardization News, Vol. 17, 1989, pp. 46-49.

2. Friberg T. Alternative uses for Recovered Paper. Resource Recycling, Vol. 12, No. 1, 1993, pp. 26-33.

3. Casey J.P. Pulp and Paper Chemistry and Chemical Technology. Interscience Publ., New York, 1961, Vol. III, 2nd ed.

4. Fibercell Corporation. Product Bulletin, Portville, New York, 1996.

5. 21 CFR 176.260. Pulp from Reclaimed Fiber. Food and Drug Administration, 1995.

6. 21 CFR 176.180. Componenets of Paper and Paperboard in Contact with Dry Food. Food and Drug Administration, 1995.

7. 21 CFR 176.300. Slimicide. Food and Drug Administration, 1995.

8. 21 CFR 186.1673. Pulp. Food and Drug Administration, 1995.

9. Fabrication of Single-Service Containers and Closures for Milk and Milk Products. Public Health Service, Food and Drug Administration, 1991.

10. 9 CFR 317.24. Packaging Materials. FSIS, U.S. Department of Agriculture, 1996.

11. 21 CFR 109.30. Tolerances for Unavoidable Poisonous or Deleterious Substances. Food and Drug Administration, 1995.

12. Miami University. Laboratory Reports, Paper Science and Technology, Oxford, OH, 1996-1997.

13. Henry C.L. Nitrogen Dynamics of Pulp and Paper Sludge Amendments to Forest Soils. University Washington, Seattle, 1989, PhD Dissertation.

14. Gellman I. Alternative Management of Pulp and Paper Industry Solid Wastes. Technical Bulletin 655, National Council of the Paper Industry for Air and Stream Improvement, Inc, New York, 1993.

15. Spangenberg R.J. Secondary Fiber Recycling. Tappi Press, Atlanta, 1993.

16. Makkonen N. The Properties of Deinking Sludge. Paper and Timber, Vol. 74, No. 2, 1992, pp. 132-138.

17. Tollefson C. Shades of Green. Chemical and Marketing Reporter, September 20, 1993.

18. Emery International Developments, Ltd. Product Bulletin, Toronto, ONT., 1996.

19. BetzDearborn; Paper Process Group. Jacksonville, FL., 904-448-4968, 1996.

20. Black Clawson Company; Shartle Division. Middletown, OH., 513-424-7400.

21. Clark J.d’A. Pulp Technology and Treatment for Paper. Miller Freeman Publ., San Francisco, 1985.

[1] U.S. waste paper is characterized having a high virgin, long-fiber content (1).

[1] Wood chip dimensions of 1.25 cm to 1.90 cm by 0.3 cm.

[1] Deink mixed waste residual typically contains less trace metals than municipal solid waste (16).

[1] Newsprint grade paper is primarily groundwood.

[1] DNT™ washers sold by Black Clawson are generally for use on tissue deinking applications to remove ash and fines.

[1] Coarser fraction removed on a Johnson screen; thickened using a Sidehill screen (0.05 mm/0.002 in. nominal sieve opening). Coarser fraction containing rocks, plastics, shives and other reject contaminants.

[1] U.S. waste paper is characterized having a high virgin, long-fiber content (1).

[2] Wood chip dimensions of 1.25 cm to 1.90 cm by 0.3 cm.

[3] Deink mixed waste residual typically contains less trace metals than municipal solid waste (16).

[4] Newsprint grade paper is primarily groundwood.

[5] DNT™ washers sold by Black Clawson are generally for use on tissue deinking applications to remove ash and fines.

[6] Coarser fraction removed on a Johnson screen; thickened using a Sidehill screen (0.05 mm/0.002 in. nominal sieve opening). Coarser fraction containing rocks, plastics, shives and other reject contaminants.

CONTROL SAMPLES
Parameter	Apple	Berry	Beverage	Consumer	Egg	Endcap
Caliper (mm)	1.56	1.56	1.56	1.56	0.78	1.56
Color (PMS)	2725u	2725u	4745u	c.gray2u	400u	467u
Color Description	Light	Deep purple	pinkish-tan	light gray	light gray	paperbag brown
Internal tear (g/cm)	3318.2	2045.5	1409.1	3545.5	2818.2	6136.4
Fiber Type	ONP	ONP	ONP	ONP	ONP	ONP,OCC
Presence of TMP	Yes	Yes	Yes	Yes	Yes	limited presence
Fiber length (mm)	2.39	2.75	2.18	2.09	2. 27	2.13
Freeness (ml)	363	245	297	242	363	496
Fold (kg)	4/1	3/1	1/1	1/1	23/1	8/1
Tensile Strength (kg/sq cm)	20.92	29.31	38.53	44.30	53.22	28.55
Puncture (kg/sq cm)	31.64	77.34	48.65	69.74	33.96	105.46
Density (g/cu cm)	0.32	0.48	0.32	0.32	0.64	0.43

STRUCTURES
	Berry-A	Berry-B	Berry-C	Chickbox –A	Chickbox-B		Egg – A	Egg – B	Egg-C
% OCC			50%		50%				100%
% ONP	100%	50%	50%	100%	50%		100%
% Virgin		50%						100%
PARAMETERS
Caliper (mm)	1.59	1.59	1.59	3.18		3.97	3.18	2.38	3.18
Color (PMS)	40lu	wgray2uu	466u	401u		w.gray2u	400u	482u	872u
Internal tear (g/cm)	1298.7	909.1	1060.6	4772.7		5757.6	1906.8	1452.8	302.7
Fiber length (mm)	2.53	a	a	2.53		a	2.53	2.43	2.64
Freeness (ml)	549	a	a	549		a	549	510	785
Fold (kg)	<1/1	1/1	<1/1	<1/1		<3/1	b	b	b
Tensile Strength (kg/sq cm)	30.3	a	a	20.22		28.19	b	b	b
Puncture (kg/sq cm)	7.80	10.55	12.87	38.07		68.55	5.84	9.67	4.68
Density (g/cu cm)	0.31	0.31	0.34	0.30		0.25	0.29	0.23	0.26

CONTROL SAMPLES

Parameter

Beverage

Egg

Endcap

Figure 2 Freeness Values for Control Structures and Residual Fibers

Lot 2

STRUCTURES

Berry-C

Chickbox-B

Egg – A

Egg – B

Egg-C

PARAMETERS

Berry Box

Egg Tray