Charles R. FrihartForest Products Laboratory

June 21, 2011

Support from United Soybean Board and Ashland Hercules Water Technologies

Introduction Protein-based adhesives are the oldest forms of

wood glues 20th century – fossil fuel-based adhesives invented

and generally replaced protein adhesives High water resistance Easy to change for individual applications

Disadvantages of synthetic adhesives Urea formaldehyde emits formaldehyde Nonrenewable resources

•Soy history and commercial status

•Prior thoughts

•Proteins

•Current experiments

Motivation For Soy Protein Adhesives Advantages

Reduce formaldehyde emissions Renewable resource with plentiful supply that is not

used for human consumption May have favorable future cost trend vs. fossil fuels

Disadvantages Difficult to make an adhesive out of soy because of its

complex composition Polymer properties are difficult to influence

Soy adhesive formulations Solvent is generally water, although co-solvents can

reduce steam pressures in heated presses Denaturants can modify the protein globules to

improve adhesion and curing Viscosity reducer can allow higher solids Curing agent for improved moisture resistance

Aldehdyes: formaldehyde, glutaraldehyde, glyoxal, etc Phenol-formaldehyde Polyamidoamine-epichlorohydrin (PAE) resin

PAE – Polyamidoamine-epichlorohydrin Kaichang Li of Oregon State developed PAE curing of

soy Important for soy

adhesive wet strength

Presidential GreenChemistry Challenge by ACS to Li, ColumbiaForest Products, andHercules in 2007

Espy, H. 1994. Alkaline-curing polymeric amine-epichlorohydrin resins”, In Wet Strength Resins and Their Application,. TAPPI Press, Atlanta GA, p 17

Soy Flour + PAE Curing Resin

Process and Performance Additives

Soyad ® Adhes ive Technology

CURED ADHESIVE

Soyad Timeline

Commercial successes Makes wood products well below all current

formaldehyde emission standards Soy adhesives used in more than 50 percent of

decorative plywood in the United States Also used commercially in engineered wood flooring

particleboard, and medium density fiberboard

Soy reaction with PAE

Treat more like a standard polymer

Protein Denaturation

Amino Acids

14

Amino Acid Composition of Soy FlourAmino acid % Amino acid %

Aspartic/Asparagine* 5.99 Alanine 2.11Glutamic/Glutamine* 8.86 Proline 2.90Serine 2.76 Valine 2.33Threonine 2.04 Tryptophan 0.06Cysteine 0.73 Isoleucine 2.23Methionine 0.71 Leucine 3.98Lysine 3.32 Phenylalanine 2.53Arginine 3.72 Glycine 2.17Tyrosine 1.72Histidine 1.42Total of reactive: 31.27 Total of unreactive: 18.32

*Approx. 53% of Asp + Glu is actually Asn or GlnFrom Cargill

-COOH

-OH

-SH

Amine

Less like standard extended polymers More like colloids

Protein AssociationSecondary

Crystallite Formation

Primary

Original Polymer Chain

α - helix

β – sheet

Hydrophobic Collapse

Tertiary

Polar and Covalent Bond FormationSubunit Association

Quaternary

Proteins vs. other polymersMost polymers

Often homopolymers Limited types of

functional groups Interchain polar

interactions, crystallites, and entanglements

Limited mobility of chains

Proteins ~ 20 aminoacids Many types of functional

groups Mainly intrachain

interactions Changes in external

environment causes changes in tertiary structure

Aggregates (colloid)

Changes in thought Proteins stay as coiled polymers Hydrophobic attraction and electrostatic repulsion Need to understand colloidal properties Few functional groups are available for reaction Need to understand effect of carbohydrates

Last year reported soy flours did not make much difference despite difference in dispersibilityNow look at soys with different protein content

Soybean products Whole Soybeans

≈ 16-17¢/lb, 36% protein, 18% oil, 36% carbohydrates, 10% moisture Defatted Meal

≈ 15¢/lb, 48% protein, 0% oil, 44% carbohydrates, <10% moisture Soy Flour

≈ 18-25¢/lb, 50% protein, 0% oil, 40% carbohydrates, <10% moisture

High (90%) to low (20%) PDI (dispersible protein) Soy Protein Concentrate

≈ 50-90¢/lb, 65+% protein, 0% oil, up to 35% carbohydrates Soy Protein Isolate

≈ $1.50-2.00+/lb, 90+% protein, 0% oil, up to 10% carbohydrates

Performance of soy proteins Do studies with soy protein isolate help to

understand adhesive performance of soy flour adhesives?

Thus, how does the performance of soy flour compare to concentrate and isolate?

Test different concentrations of each with 5% PAE based upon soy solids for bond strength (wet and dry). Flour – 20, 25, 30, 35 Concentrate – 20, 25, 30 Isolate – 10, 15, 20

Soy Performance - ABES shear, MPaCuring Agent => Without PAE With PAESoy Product Dry Wet Dry Wet

Flour30% 90 PDI

5.0 ± 1.2 0.3 ± 0.2 6.6 ± 1.3 2.2 ± 0.2

Concentrate20%

6.2 ± 0.4 0.4 ± 0.1 7.2 ± 1.0 3.4 ± 0.3

Isolate15%

7.2 ± 1.3 3.0 ± 0.4 7.6 ± 0.8 5.0 ± 0.3

With nearly equal protein content, we observed•Only isolate gave good wet strength without PAE•PAE improved strength of all soy products, but biggest improvement was with the concentrate

Conclusions (Soy Products) With about equal protein content

All gave good bonds under dry conditions, with higher shear strength with increasing protein content

Without PAE under wet conditions, the flour and concentrate gave poor bond strengths

With PAE, all strengths increased with greatest being the concentrate under wet conditions

This led to the model that the protein-protein adhesion was important for bond strength, with the carbohydrates interfering with these bonds, especially under wet conditions.

Isolate

Concentrate

Flour

Protein globule with hydrophobic attraction and electrostatic repulsion

Soluble carbohydrate

Insoluble carbohydrateCONFIDENTIAL

Acknowledgements Forest Products Laboratory Ashland – Hercules and Heartland Resource

Technologies collaborations United Soybean Board, Support Grant 0458