Organosolv Lignin-Modified Phenolic Resins - ACS Publications

Chapter 24

Organosolv Lignin-Modified Phenolic Resins Phillip M . Cook and Terry Sellers, Jr. 1

Downloaded by UNIV OF CALIFORNIA IRVINE on October 17, 2014 | http://pubs.acs.org Publication Date: July 31, 1989 | doi: 10.1021/bk-1989-0397.ch024

1

2

Eastman Kodak Company, Eastman Chemicals Division, P.O. Box 1972, Kingsport, TN 37662 Forest Products Utilization Laboratory, P.O. Drawer FΡ, Mississippi State, MS 39762 2

An adhesive system for structural wood panels is demon strated in which at least 35% of the resin solids of a phenol-formaldehyde resin are successfully replaced with organosolv hardwood lignin. The bulk properties of the lignin were characterized before and after its purifica tion with aqueous sodium bicarbonate solution. Phenolic resins are described that have been prepared from both purified and non-purified (crude) lignin. The nature of residues removed from the lignin during purification and their effects on resin adhesive properties are also briefly described. Evaluations of the lignin-modified phenolic resins were carried out on a small scale by measuring the lap-shear strength of parallel laminated maple blocks, and on a large scale by performing strength and dimen sional tests on southern pine flake boards (waferboard or strandboard types). Flake board tests included internal bond, static bending (modulus of rupture, M O R ) , water absorption, and thickness swelling. The M O R was mea sured on both dry specimens and specimens subjected to accelerated aging wet-dry cycles. Both maple block and flakeboard evaluations included available commer cial phenolic resins as controls. L i g n i n makes u p a b o u t one-quarter o f the weight o f d r y w o o d a n d is sec o n d o n l y t o cellulose as t h e most a b u n d a n t n a t u r a l l y o c c u r r i n g p o l y m e r . P u l p i n g m e t h o d s w h i c h use o r g a n i c solvents are p a r t i c u l a r l y well-suited t o solubilize the lignins for l i g n i n isolation a n d are r e a d i l y c o u p l e d w i t h solvent recovery (1). D e s p i t e these facts, there are n o large v o l u m e o r g a n o s o l v p u l p i n g processes or c o m m e r c i a l p r o d u c t s based u p o n organosolv l i g n i n ( O S L ) i n the U n i t e d States. 0097-6156/89/0397-0324$06.00/0 © 1989 American Chemical Society

In Lignin; Glasser, W., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1989.


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325

L i g n i n s are p h e n o l i c - l i k e p o l y m e r s t h a t f r o m t i m e t o t i m e have been considered for use as a p h e n o l replacement i n p h e n o l - f o r m a l d e h y d e ( P F ) resins. T o d a y , however, very l i t t l e l i g n i n is used i n p h e n o l i c resins. P u r i f i e d k r a f t l i g n i n s have been suggested as a p h e n o l s u b s t i t u t e , b u t the price o f such l i g n i n s has been s t r u c t u r e d to be e q u a l to t h a t of p h e n o l , a n d resin adhesive suppliers have resisted i t s use. V e r y l i t t l e has been p u b l i s h e d o n the use of O S L i n phenolic adhesives despite the fact t h a t these l i g n i n s are generally f o u n d to have a higher p u r i t y a n d r e a c t i v i t y t h a n l i g n i n s f r o m conventional p u l p i n g methods. T h e most p r o m i n e n t w o o d adhesives used over the last q u a r t e r of a c e n t u r y have been a m i n o p l a s t a n d p o l y p h e n o l i c types (2). I n the U n i t e d States, p o l y p h e n o l i c adhesives continue t o be p r e d o m i n a n t l y used for p r o d u c t i o n of weather-resistant w o o d p r o d u c t s , such as s t r u c t u r a l p l y w o o d s and flake boards (3). P h e n o l i c r e s i n prices have increased over the past decade, generally p a r a l l e l i n g p h e n o l prices. T h i s increase has o c c u r r e d i n p a r t due to a c o n t i n u i n g erosion of U n i t e d States p h e n o l m a n u f a c t u r i n g c a p a c i t y a n d the c o r r e s p o n d i n g increase i n a v a i l a b i l i t y o f p h e n o l f r o m other countries. A n y significant increase i n the price of o i l (the source of phenol) itself or i n t e r r u p t i o n i n s u p p l y w i l l o n l y c o m p o u n d the p r o b l e m a n d raise p h e n o l prices even higher. T h e o b j e c t i v e o f t h i s w o r k was to d e m o n s t r a t e the u t i l i t y o f organosolv red oak l i g n i n (a projected cheaper p o l y p h e n o l t h a n phenol) i n p h e n o l i c adhesives for w o o d composites. T h i s w o r k i n v o l v e d three stages: 1. A n a l y t i c a l c h a r a c t e r i z a t i o n of red oak O S L . 2. R e s i n synthesis of O S L - m o d i f i e d p h e n o l - f o r m a l d e h y d e resins. 3. E v a l u a t i o n of l i g n i n - m o d i f i e d resins used to b o n d m a p l e blocks a n d s o u t h e r n p i n e flake boards. Results and Discussion Analytical Characterization. A s expected, red oak O S L c o n t a i n s m u c h less sulfur a n d ash b u t more c a r b o h y d r a t e s t h a n k r a f t l i g n i n ( T a b l e I) (kraft l i g n i n i n c l u d e d for c o m p a r i s o n ) . T h e m o l e c u l a r weight a n d p o l y d i s p e r s i t y ( T a b l e II) are less for red oak O S L t h a n for k r a f t l i g n i n ( I n d u l i n A T , W e s t vaco, C h a r l e s t o n , S C ) , a n d O S L has g o o d s o l u b i l i t y i n o r g a n i c solvents ( T a b l e I). S o l u b i l i t y i n r e f l u x i n g methylene chloride was s u r p r i s i n g l y h i g h . P u r i f i c a t i o n of the O S L b y aqueous r e s l u r r y i n 1 0 % s o d i u m b i c a r b o n a t e s o l u t i o n increases the softening t e m p e r a t u r e ( T a b l e II). T h e r m o g r a v i m e t r i c weight loss for the O S L is s i m i l a r to t h a t of k r a f t l i g n i n . E x c e p t for a s l i g h t l y elevated m e t h o x y l content, the N M R a n d d e g r a d a t i o n results i n T a b l e II are w i t h i n the expected range for a h a r d w o o d lignin. OSL Impurities. It was also of interest to d e t e r m i n e the i m p u r i t i e s removed f r o m crude O S L b y r e s l u r r y i n aqueous s o d i u m b i c a r b o n a t e , w h i c h was done to i m p r o v e its usefulness i n p h e n o l i c resins ( C o o k , P . M . , E a s t m a n K o d a k at K i n g s p o r t , T N , p e r s o n a l c o m m u n i c a t i o n s , 1987). E x t r a c t i o n a n d acetyl a t i o n procedures, i n v o l v i n g methylene c h l o r i d e , acetic a n h y d r i d e p y r i d i n e


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T a b l e I. L i g n i n c h a r a c t e r i z a t i o n ( b u l k a n d soi l u b i l i t y properties) Amount Kraft Lignin

Crude OSL

% %

97

97

97

A s h , 775°C

1.94

1.13

3.48

Carbohydrates: (Extraction-HPLC)

%

3.0

1.1

0.7

Combustion: C H Ν S

% % % %

59.85 5.87 0.27 0.24

60.94 5.63 Trace 0.04

61.99 5.65 0.52 1.68

E x t r a c t i o n (weight loss): E t h e r , reflux H e p t a n e , reflux M e t h y l e n e chloride, reflux Water, 25°C Water, 60°C W a t e r , 100°C

% % % % % %

6 < 1 50 5 12 5*

Non-volatiles


Purified OSL

Basis

A n a l y t i c a l Text

* S a m p l e agglomerates S o l u b i l i t y (25° C ) : Methanol Ethanol n-Propanol 2-Propanol Acetic A c i d Acetone 2-Butanone Acetonitrile E t h y l Acetate

1

3 < 1 11 2 6 3*

severely. g/L g/L g/L g/L g/L g/L g/L g/L g/L

-

105 53 35 15 108 104 96 86 59

-

-

-

-

I n d u l i n A T b y Westvaco, C h a r l e s t o n , S C ; a purified pine l i g n i n . a n d water, were followed w h i c h p r o d u c e d three residues f r o m the i m p u r i ties a n d each was s u b m i t t e d for G C / M S a n d H N M R analyses. R e s i d u e 1 proved to be nearly a l l l i g n i n - r e l a t e d p r o d u c t s . Residues 2 a n d 3 were f o u n d p r i n c i p a l l y to c o n t a i n f u l l y acetylated m o n o m e r i c C5 a n d Ce sugars w h i c h were also C i alcoholic glycosides. R e s u l t s of G C / M S investigations of the residues i n d i c a t e d t h a t the l o w - m o l e c u l a r - w e i g h t i m p u r i t i e s (e.g., m o n o - f u n c t i o n a l l i g n i n - r e l a t e d species, waxes, a n d c a r b o h y d r a t e s ) s h o u l d be removed to i m p r o v e the O S L r e a c t i v i t y . T h e extent of i m p u r i t y r e m o v a l can be a p p r o x i m a t e d by m e a s u r i n g gelation t i m e (i.e., the higher the i m p u r i t y content, the longer the gel t i m e ) . F o r e x a m p l e , the g e l a t i o n t i m e (using 1


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T a b l e II. P h y s i c a l a n d c h e m i c a l c h a r a c t e r i z a t i o n of l i g n i n Amount

Basis

Crude OSL

Purified OSL

Kraft Lignin

softening-initial: (TMA)

°C

89

124

124

softening-final : (TMA)

°C

111

138

169

% % % % % %

1 3 5 18 44 55

0 1 2 10 38 49

1 3 6 12 26 51

2227 906 2.46

2030 925 2.19

2479 523 4.32

22.04 (1.55) 1.33

-

13.70 (0.81) < 1

0.60-0.65 0.55-0.60 1.90-1.95 3.60-3.70 1.15-1.25

-

0.57-0.62 0.70-0.72 2.50-2.55 4.25-4.30 1.35-1.40

A n a l y t i c a l Test T


T

T G A (weight loss): 50°C 100°C 200°C 300°C 400°C 500°C

G P C m o l e c u l a r properties: (CH C1 /HFIP, Styragel Col.) M 2

1

2

W

M

N

M /M W

N M R analysis: OCH

%

3

Syringyl/guaiacyl Bonds: OH (Phenolic) O H (Aliphatic) H (Aromatic) H (Aliphatic) H (Hydroxyl)

N

(bonds/Cg unit) ratio per per per per per

C9 C9 C9 C9 C9

unit unit unit unit unit

Source: G l a s s e r , W . G . R e p o r t to P . M . C o o k . L o c a t e d at E a s t m a n C h e m i c a l D i v i s i o n , Research L a b o r a t o r y , P . O . B o x 1972, K i n g s p o r t , T N 27662 (1984). 1

I n d u l i n A T b y Westvaco, C h a r l e s t o n , S C ; a purified pine l i g n i n .

a S u n s h i n e G e l Tester) at 100°C (212°F) was 21 minutes for a P F resin sol u t i o n , 26 minutes for a purified O S L / P F resin b l e n d , a n d 53 m i n u t e s for an u n p u r i f i e d O S L / P F resin b l e n d . T h e procedure involves b l e n d i n g d r y l i g n i n solids w i t h a P F resin s o l u t i o n to a 2 3 % l i g n i n c o n c e n t r a t i o n a n d a d j u s t i n g w i t h water a n d 5 0 % s o d i u m h y d r o x i d e to the p H (e.g., 1 1 . 1 ± ) a n d viscosity (e.g., 500 ± 50 c P ) of the P F resin. Block Lap-Shear Results. F o r l a m i n a t e d m a p l e w o o d , this w o r k i n d i c a t e d a m a x i m u m of 4 0 % of the P F resin solids can be replaced w i t h O S L w i t h o u t




328

d e t r i m e n t a l l y affecting adhesive properties ( T a b l e III) ( C o o k , P . M . , E a s t m a n K o d a k at K i n g s p o r t , T N , p e r s o n a l c o m m u n i c a t i o n s , 1987). O r g a n o solv l i g n i n - P F resins were at least equivalent t o the c o m m e r c i a l (control) resin a n d o u t - p e r f o r m e d k r a f t l i g n i n - b a s e d P F resins at the 3 5 % a n d 4 0 % solids replacement levels ( T a b l e I I I ) . P u r i f i e d O S L generally y i e l d e d better results t h a n u n p u r i f i e d . A d i s t r a c t i n g q u a l i t y of k r a f t l i g n i n resins is the s u l f u r - l i k e odor p r o d u c e d d u r i n g resin p r e p a r a t i o n a n d p a n e l hot pressing. Use o f O S L alleviates t h i s p r o b l e m . T h e reasons w h y O S L o u t - p e r f o r m e d k r a f t l i g n i n i n t h i s w o r k are not clear, b u t are likely r e l a t e d to the m o l e c u l a r weight characteristics of the O S L a n d its ease of s o l u b i l i z a t i o n . B a s e d u p o n the p r o p o s e d s t r u c t u r e s of h a r d w o o d a n d softwood l i g n i n s , the c o n t r a r y w o u l d have been p r e d i c t e d (i.e., the higher s y r i n g y l / g u a i a c y l r a t i o s of h a r d w o o d w o u l d be expected to be more d e t r i m e n t a l to b o n d i n g ) . T a b l e I I I . Selected m a p l e b l o c k test results Dry Bond

4-Hour Boil

Strength Lignin Shear Wood Shear Wood Retention Replacement Strength Failure Strength Failure ( D r y / W e t ) (%) (MPa) (%) (MPa) (%) (%)

Resin T y p e

1

Control P F OSL-PF (crude l i g n i n )

0

5.18

80

3.08

0

60

24

4.99

100

2.54

30

51

OSL-PF (CH C1 extracted)

34

5.35

100

3.02

40

57

Kraft L - P F (Indulin A T )

35

4.25

90

1.83

0

43

OSL-PF (NaHC0 washed)

40

5.60

60

3.37

30

60

40

4.14

40

1.90

10

46

45

2.68

20

1.00

0

37

2

2

2

3

Kraft L - P F (Indulin A T ) OSL-PF (crude l i g n i n ) 1

2

2

M u l t i p l y M P a b y a factor of 145 to convert to p s i . T h i s resin also contained 1% m e l a m i n e .

Flake Board Test Results. R e s u l t s f r o m i n i t i a l screening tests l o o k e d p r o m i s i n g for the use of k r a f t pine l i g n i n a n d organosolv h a r d w o o d l i g n i n at 2 5 % s u b s t i t u t i o n for p h e n o l i n P F resins used to b o n d flake boards. Therefore, t h i s s t u d y was designed to concentrate o n i m p r o v i n g the O S L - P F cook p r o cedure, increase the p h e n o l s u b s t i t u t i o n to 3 5 % , a n d measure these effects b y e x p a n d i n g the b o a r d test c r i t e r i a (4). I n general, the p u r i f i e d O S L - P F


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24.


329

resins as well as the u n p u r i f i e d O S L - P F resins p e r f o r m e d e q u a l t o , or b e t ter t h a n , the c o n t r o l c o m m e r c i a l resins a n d the c o n t r o l resins c o n t a i n i n g c o m p a r a b l e s u b s t i t u t i o n a m o u n t s of p e c a n shell flour (vs. O S L ) i n a l l test p a n e l properties e x a m i n e d (Table I V ) .


T a b l e I V . Selected test results of flake boards

Physical Property

L a b o r a t o r y Test R e s u l t s Sampling of F o u r Control Resin Β 35% O S L USA Mills 100% P F 3 5 % P S Purified Crude (1986)

Units

Density

avg.

kg/m

1

3

650-700

(average o f boards was 753)

Internal bond M o d u l u s of rupture

avg.

kPa

340-460

510

386

717

538

avg.

MPa

22-38

33

33

34

34

Accelerated aging

%of dry M O R

50-70

76

75

77

70

Water absorption

%

25-34

33

35

25

19

Thickness swell

%

12-15

16

25

15

11

R e s i n solids applied

%

3-5

5

3.25

5

5

These panels were b o n d e d w i t h a r e s i n s o l u t i o n c o n t a i n i n g 6 5 % P F and 3 5 % p e c a n shell ( P S ) flour, d e l i v e r i n g 3.25% resin solids to the furnish. N o t e : T o convert m e t r i c to E n g l i s h u n i t s — k g / m to l b / f t , m u l t i p l y b y a factor of 0.0624; k P a to p s i , m u l t i p l y b y a factor of 0.145; M P a to p s i , m u l t i p l y b y a factor of 145.

1

3

3

Use of p o w d e r e d l i g n i n s as a n extender at 2 5 % to 3 5 % replacement of P F solids i n l i q u i d c o m m e r c i a l resins is i m p r a c t i c a l because of p r o b l e m s of d i s p e r s i o n , viscosity, a n d s t a b i l i t y w h i c h h i n d e r subsequent u n i f o r m resin s p r a y a p p l i c a t i o n . However, s u b s t i t u t i o n of l i g n i n for p h e n o l at levels of 35 weight percent, or higher, i n cooked l i g n i n - p h e n o l - f o r m a l d e h y d e c o p o l y m e r s is p r a c t i c a l . W h i l e i m p u r e (crude) O S L cooked into a P F resin a n d used to b o n d flake boards y i e l d e d s i m i l a r b o a r d properties to cooked p u r i f i e d O S L i n P F resins, the i m p u r e l i g n i n was troublesome d u r i n g the cook procedures, f o r m i n g gels u p o n l o n g m e t h y l o l - l i g n i n c o n d e n s a t i o n . I m p u r e l i g n i n was m o r e g r i t t y t h a n purified l i g n i n a n d some extraneous m a t e r i a l m a y have settled r a t h e r t h a n dissolve or suspend i n the cooked resins. I m p u r e l i g n i n required a n a d j u s t m e n t i n the water i n b o t h steps of the cook t o y i e l d a satisfactory n o n - v o l a t i l e solids content. If a n y coarse l i g n i n settled i n the cooked resin, t h i s m a y p a r t i a l l y e x p l a i n the lower percent n o n - v o l a t i l e solids p h e n o m e n o n w i t h resins i n c o r p o r a t i n g i m p u r e l i g n i n .



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Conclusions It has been d e m o n s t r a t e d t h a t red oak O S L c o u l d be used t o replace 3 5 % to 4 0 % o f the p h e n o l (or phenolic resin solids) i n p h e n o l - f o r m a l d e h y d e resins used t o l a m i n a t e m a p l e w o o d a n d t o b o n d s o u t h e r n p i n e flake b o a r d s (waferb o a r d a n d / o r s t r a n d b o a r d ) w i t h o u t adversely affecting the p h y s i c a l b o n d p r o p e r t i e s . W h i l e t h i s p u l p i n g process a n d b y - p r o d u c t l i g n i n do not c o m m e r c i a l l y exist at t h i s t i m e i n the U n i t e d States, lignins f r o m such processes are projected to cost 4 0 % to 5 0 % less t h a n p h e n o l as a p o l y m e r r a w m a t e rial. It is r e c o m m e n d e d t h a t a r e s l u r r y of crude O S L i n a n organic s o l vent or 1 0 % aqueous salt (e.g., N a H C O a ) s o l u t i o n be p e r f o r m e d to remove l o w - m o l e c u l a r - w e i g h t (mono-functional) species, waxes, a n d c a r b o h y d r a t e s . T h i s p u r i f i c a t i o n leads to a n i m p r o v e m e n t i n O S L r e a c t i v i t y a n d c o n t r i b u t e s to the usefulness of O S L as a P F resin extender or P F c o p o l y m e r r a w m a t e r i a l . It is presumed t h a t extraneous removed m a t e r i a l s i n the crude l i g n i n react w i t h f o r m a l d e h y d e b u t do not lead to p r o d u c t i v e c r o s s - l i n k i n g p o l y mer f o r m a t i o n . T h e success o b t a i n e d i n t h i s s t u d y o n b o n d i n g flake b o a r d a n d m a p l e blocks s u p p o r t s the p o s s i b i l i t y of u s i n g O S L i n resins for b o n d i n g crosswise l a m i n a t e s (i.e., p l y w o o d ) . Subsequent research conducted at the M i s s i s s i p p i Forest P r o d u c t s U t i l i z a t i o n L a b o r a t o r y o n O S L - P F resins for b o n d i n g p l y w o o d has been e q u a l l y successful.

Experimental Wood Pulping and Lignin Purification. T h e w o o d p u l p i n g i n v o l v e d red oak w o o d c h i p s , aqueous organic solvent, a n d a n a c i d c a t a l y s t , w h i c h were p r o cessed at 120 to 140°C. T h e r e s u l t a n t p u l p was washed w i t h more aqueous solvent, w a t e r - s l u r r i e d a n d cooled. T h e l i g n i n was i s o l a t e d by r e m o v i n g the solvent under v a c u u m , replacement of solvent w i t h water, l i g n i n prec i p i t a t i o n , filter cake water w a s h i n g , a n d d r y i n g . T h e l i g n i n was p u r i f i e d b y s l u r r i n g one p a r t of d r y O S L i n five p a r t s of a 1 0 % aqueous s o d i u m b i c a r b o n a t e s o l u t i o n at 6 0 ° C for one h o u r . T h e s l u r r y was cooled to r o o m t e m p e r a t u r e a n d filtered. T h e filter cake was washed w i t h water u n t i l the filtrate was less t h a n 7.5 p H . T h e filter cake was then d r i e d i n a forced-air oven at 50 to 5 5 ° C , w i t h a weight y i e l d of 9 0 % to 9 5 % . T h e r e s u l t a n t d r y and loose l i g n i n was used w i t h o u t further processing such as g r i n d i n g . Analytical Characterization. T h e l i g n i n s were characterized a n a l y t i c a l l y by the f o l l o w i n g m e t h o d s : H N M R s p e c t r a , gel p e r m e a t i o n c h r o m a t o g r a p h y (5), gas c h r o m a t o g r a p h y (6), t h e r m a l measurements, e l e m e n t a l a n a l y s i s , sugar content, e x t r a c t i o n s , s o l u b i l i t y , a n d c o m b u s t i o n properties. 1

Resin Preparation. T w o approaches to resin p r e p a r a t i o n were used w i t h regard t o the i n i t i a l stages of condensation, d e p e n d i n g o n w h e t h e r the resin was i n t e n d e d for l a m i n a t i n g m a p l e blocks or for b o n d i n g s o u t h e r n pine flake boards. F o r m a p l e block resins, the steps i n v o l v e d were as follows: a d d i t i o n of water, s o d i u m h y d r o x i d e ( o p t i o n a l ) a n d l i g n i n , w h i c h were heated a n d


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h e l d u n t i l a homogeneous m i x t u r e was o b t a i n e d ; a d d i t i o n of either 1 0 0 % of the p h e n o l or 1 0 % to 2 0 % of the formaldehyde r e q u i r e d i n the cook a n d heated t o 75 t o 9 0 ° C for 30 to 90 m i n u t e s ; a d d i t i o n of the r e m a i n d e r of the p h e n o l (unless a l l was a d d e d i n i t i a l l y ) , a n d f o r m a l d e h y d e , h o l d i n g at 60 to 7 5 ° C for 30 t o 90 m i n u t e s . F o r m a p l e block b o n d i n g , a series o f cooks were m a d e i n w h i c h 2 4 % to 4 5 % of the resin solids were replaced w i t h O S L or k r a f t l i g n i n . F o r flake b o a r d resins the steps i n c l u d e d the f o l l o w i n g : a p r e p o l y m e r synthesis of m e t h y l o l - l i g n i n condensation for 30 to 90 m i n u t e s , t h e n a sequential m e t h y l o l - l i g n i n , p h e n o l - f o r m a l d e h y d e c o n d e n s a t i o n (resin synthesis) step, w h i c h varied f r o m 3 to 5 hours cook t i m e (4). F o r flake b o a r d resins, cooks were m a d e w i t h 2 5 % a n d 3 5 % of the p h e n o l replaced w i t h p u r i f i e d a n d u n p u r i f i e d O S L . V a r i o u s properties of the resins were d e t e r m i n e d b y s t a n d a r d m e t h o d s , i n c l u d i n g n o n - v o l a t i l e solids, viscosity, p H , free f o r m a l d e h y d e , free p h e n o l , alkalinity, a n d gel t i m e . I n b o t h studies, c o m m e r c i a l resins were o b t a i n e d a n d used as controls. T a b l e V provides t y p i c a l s t o i c h i o m e t r i c d a t a of resin reactants i n v e s t i g a t e d for b o t h resin types. T a b l e V . T y p i c a l s t o i c h i o m e t r i c properties of resin reactants A m o u n t by Resin T y p e Reactant

Blocks (mol)

Flake Board (mol)

W a t e r (sufficient for desired n o n - v o l a t i l e solids) Phenol Formaldehyde Organosolv l i g n i n Sodium hydroxide Urea

1.00 1.8-3.0 0.25-0.80 0.40-0.65 -

1

1

1.00 2.98 0.25 0.64 0.09

A s s u m e a m o l e equivalent u n i t of 200 for organosolv l i g n i n , based o n a t y p i c a l a n a l y z e d C9 l i g n i n u n i t .

Maple Block Screening Method. A series of e x p e r i m e n t a l procedures were p e r f o r m e d o n b o n d i n g m a p l e block w o o d ( C o o k , P . M . , E a s t m a n K o d a k at K i n g s p o r t , T N , p e r s o n a l c o m m u n i c a t i o n s , 1987). T h e procedure a d o p t e d was the A S T M D 905 s t a n d a r d , m o d i f i e d as follows: S u g a r m a p l e (Acer saccharum) w o o d , 76 b y 25 b y 5.7 m m i n size (3 inches l o n g , 1 i n c h w i d e , and 0.25 i n c h t h i c k ) , w i t h 6% m o i s t u r e content was p l a n e d to o b t a i n fresh surfaces for b o n d i n g . T h e desired a m o u n t of resin ( w i t h no m i x additives) was weighed (58.6 g / m , 12 l b / 1 0 0 0 f t , resin solids basis) a n d a p p l i e d t o one block surface a n d t h e n a second clean block was o v e r l a p p e d so t h a t 25 square m m (1 square inch) surface area c o m m o n to each block was coated. T h e resin coated blocks were placed d i r e c t l y i n the hot press (no c l a m p t i m e ) . T h e blocks were hot pressed at 177°C (350°F) for 4 to 6 m i n u t e s at 3.44 M P a (500 p s i ) . A l l b o n d e d blocks were allowed to 2

2


332



s t a n d (post cure) at a m b i e n t temperatures for 24 hours p r i o r to t e s t i n g . T e n b o n d e d b l o c k s were tested d r y a n d ten were tested after a n acceler ated a g i n g regimen (4 h b o i l i n water, cool, a n d test wet) for each r e s i n . T h e lap-tension-shear s t r e n g t h of the test specimens was measured u s i n g a n I n s t r o n m a c h i n e , a n d s u b j e c t i v e estimates of the percent w o o d failure (or b o n d failure) were observed a n d recorded. T h e d a t a were subjected to s t a t i s t i c a l analysis. Flake Board Screening Method. T h i s phase of the s t u d y has been p r e v i o u s l y r e p o r t e d i n more d e t a i l b y Sellers et al. (4) b u t c a n be s u m m a r i z e d as follows. D i s c - c u t s o u t h e r n pine flakes (wafers a n d / o r strands) were o b t a i n e d f r o m c o m m e r c i a l flake b o a r d plants i n the S o u t h e r n U n i t e d States. T h e flakes were a p p r o x i m a t e l y 76 m m (3 i n . ) l o n g , 19 to 38 m m (0.75 to 1.5 i n . ) w i d e , a n d 0.5 to 0.8 m m (0.020 to 0.030 i n . ) t h i c k a n d adjusted to 2 . 5 % m o i s t u r e content at the t i m e of use. E a c h resin t y p e was a p p l i e d at 5 % a n d 7% resin solids rates. T h e m a t c o n f i g u r a t i o n was homogeneous a n d h a n d felted i n sufficient size to o b t a i n a t r i m m e d p a n e l m e a s u r i n g 560 b y 610 b y 12.5 m m (22 b y 24 by 0.5 i n . ) . T h e m a t s were hot pressed at 205°C ( 4 0 0 ° F ) for 6 minutes w i t h a dual-pressure regimen ( 5 . 5 1 / 2 . 7 5 M P a , 8 0 0 / 4 0 0 p s i ) . T h e i n i t i a l h i g h pressure was d r o p p e d after one m i n u t e i n t o the cycle a n d the panels were pressed to 1 2 . 7 - m m (0.5-in.) m e t a l stops i n the hot press. T h e target density was 745 k g / m (46 l b / f t ) . T h r e e panels per resin t y p e a n d a p p l i c a t i o n rate were m a d e . R e s i n types i n c l u d e d the c o n t r o l c o m m e r c i a l resins (no l i g n i n content), l i g n i n - m o d i f i e d P F resins, a n d c o n t r o l P F resins c o n t a i n i n g a n inert filler (pecan shell flour) at the same loads as the l i g n i n s u b s t i t u t e d resins. Screening tests for p a n e l perfor m a n c e i n c l u d e d i n t e r n a l b o n d ( I B ) , d r y s t a t i c b e n d i n g ( m o d u l u s of r u p t u r e , M O R ) , accelerated a g i n g M O R (strength r e t e n t i o n after a n A m e r i c a n P l y w o o d A s s o c i a t i o n performance 6-cycle test), a n d d i m e n s i o n a l tests [water a b s o r p t i o n ( W A ) a n d thickness swell ( T S ) ] . T h e s t a t i s t i c a l a n a l y s i s was a two-factor e x p e r i m e n t (resin type-resin a p p l i c a t i o n level), u s i n g a n a n a l ysis of variance a n d Τ tests ( L S D ) for g r o u p i n g for the various p h y s i c a l properties tested. 3

3

Product Disclaimer T h e use of t r a d e , firm, or c o r p o r a t i o n names i n this p u b l i c a t i o n is for the i n f o r m a t i o n a n d convenience of the reader. S u c h use does not c o n s t i t u t e an official endorsement or a p p r o v a l b y the M i s s i s s i p p i Forest P r o d u c t s U t i l i z a t i o n L a b o r a t o r y ( M F P U L ) , M i s s i s s i p p i S t a t e U n i v e r s i t y , or the E a s t m a n K o d a k C o m p a n y of any p r o d u c t or service to the e x c l u s i o n of others w h i c h m a y be s u i t a b l e . A cknowledgment s A p p r e c i a t i o n is expressed to the following M F P U L employees: D r . A . L . W o o t e n (retired) for resin synthesis; G a r y S t o v a l l a n d George M i l l e r for resin a n d flake b o a r d s a m p l e p r e p a r a t i o n a n d t e s t i n g ; a n d L y n n P r e w i t t for G F C work. M a t e r i a l s were d o n a t e d i n s u p p o r t of t h i s project b y B o r d e n


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Incorporated, Chembond Corporation, E a s t m a n K o d a k Company, Georgia P a c i f i c C o r p o r a t i o n , L o u i s i a n a Pacific C o r p o r a t i o n , a n d S o u t h e a s t e r n R e d u c t i o n C o m p a n y . T h i s w o r k was s u p p o r t e d by t w o research grants f r o m Eastman Kodak Company.


Literature

Cited

1. Chemical Week 1984, 134(1), 26, 28. 2. Conner, A . H.; Lorenz, L . F . J. Wood Chem. Technol. 1986, 6(4), 591613. 3. Sellers, T . , Jr. Plywood and Adhesive Technology, Marcel Dekker: New York, 1985; pp. 349-373. 4. Sellers, T . , Jr.; Wooten, A . L . ; Cook, P. M . Proc. Structural Wood Composites: New Technologies for Expanding Markets; Forest Products Research Society, Madison, WI, 1988, Proc. No. 47359, 43-50. 5. Glasser, W . G . ; Glasser, H . R.; Morohoshi, N. Macromol. 1981, 14(2), 252-262. 6. Glasser, W . G . ; Barnett, C . Α.; Sano, Y . J. Appl. Polym. Sci., Appl. Polym. Symp. 1983, 37, 441-460. RECEIVED February 27,1989


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