Wood Adhesives: Chemistry and Technology, Volume 2

437 Pages·2018·19.78 MB·English

by  Pizzi

WOOD ADHESIVES
CHEMISTRY AND TECHNOLOGY
Volume 2
edited by
A, Pizzi
Division of Processing and
Chemical Manufacturing Technology
Council for Scientific and Industrial Research
Pretoria, South Africa
CRC Press
Taylor & Francis Croup
Boca Raton London New York
CRC Press is an imprint of the
Taylor & Francis Group, an informa business
Library of Congress Cataloging in Publication Data
Main entry under title:
(Revised for vol. 2)
Wood adhesives.
Includes bibliographical references and indexes.
1. Adhesives. 2, Wood-Bonding. I. Pizzi,
A, (Antonio)
TP968.W66 1983 568*3 83-20870
ISBN 0-8247-1579-9 (v.l)
ISBN 0-8247-8052-3 (v.2)
This book is printed on acid-free paper.
Copyright © 1989 by MARCEL DEKKER All Rights Reserved
Neither this book nor any part may be reproduced or transmitted in
any form or by any means, electronic or mechanical, including photo­
copying , microfilming, and recording, or by any information storage
and retrieval system, without permission in writing from the publisher.
MARCELDEKKER,INC.
270 Madison Avenue, New York, New York 10016
Current printing (last digit) :
10 9 8 7 6 5 4 3 2
PRINTED IN THE UNITED STATES OF AMERICA
Preface
Wood Adhesives: Chemistry and Technology, Volume 1 was written
as a basic textbook for adhesives chemists and wood technologists
training in a fascinating, important, and sometimes obscure—but
never dull—field. Volume 2 is a natural follow-up. It contains a
host of interesting and important concepts and information that
could not be included or expanded upon in the previous volume.
It is by no means exhaustive, since some breakthroughs and con­
cepts, such as in carbohydrates-based adhesives for wood, are
still in such rapid flux that a report on them now would be incomplete
and perhaps misleading.
The material presented, however, is of such interest that no
self-respecting wood technologist or chemist in this field can afford
to be unaware of it. The various chapter authors are considered
specialists in their particular fields or have participated in and
been greatly involved in the history of the reported developments.
The book could be divided broadly into two sections, concepts and
adhesives, but by necessity, the borders of such a division are
fictitious; the two are often intertwined and meld into each other.
In the preface to the first volume, protein adhesives were
described as a dying line. They are included in this volume because
they are still used extensively in some countries and have resisted
the onslaught of synthetic resins in the last half a century, indicating
an unusually resilient product. Possibilities definitely exist for
their modification, upgrading, and use in countries where synthetic
adhesives are not produced. Hence, in this field, the accumulated
knowledge of perhaps centuries must not be allowed to be forgotten.
They are masterfully described in the chapter by Alan L. Lambuth.
In another chapter, William E. Johns describes the exciting develop -
ment and intriguing concept of ”gluing without glue," of which he
was so much at the forefront during its recent development. Lawrence
Gollob^s chapter on structure/property relationships in phenol-
formaldehyde adhesives is a clear indication of things to come,
of the direction in which adhesive technologists must go and are
bound to go in the future. Kenneth R. Geddes fills the vacuum
on the chemistry of polyvinyl-acetate that was so obvious in the
first volume. He also describes the development of the continuous
IV Preface
recycle reactor, in the commercialization of which he played such
a major role—a few are already in operation in several countries.
Rainer Marutzky’s chapter on formaldehyde emission makes the point
once again with his usual sharpness and incisiveness on this very
important topic of recent times.
My own contribution consists of chapters covering three topics
that have, or are likely to have, some impact on wood adhesives.
The first, "honeymoon” fast-set adhesives for glulam and finger­
jointing, is a concept born in North America less than two decades
ago that matured to extensive modifications and commercialization
in Africa. It is a true success story, both technically and commer­
cially. The second, the approach to phenolformaldehyde cellulose
adhesion forces by conformational analysis, a theoretical technique
borrowed from the research on the spatial structure of macromolecules,
is of interest because so many other similar problems in wood adhe­
sives could possibly be approached fruitfully by the same technique.
The third, the "blue glue," is a success story in the making. A
vast step forward in phenol/resorcinol/ formaldehyde resins, it already
indicates what the impact of true resin engineering on the adhesives
world is likely to be.
The other South African writers are less well known in the
wood adhesives world, but judging from the topics addressed, it
is quite likely that some of their developments will be known better
in a few years. Of particular mention is the work of Gerrit H.
van der Klashorst on bagasse lignin-formaldehyde reactions. I have
also participated extensively enough in this area of adhesives poly­
merization, formulation, and application to judge its importance
in this, as well as in other fields. The lignin-based cold-set reported
is a world first, and both the thermosets and the cold-sets are now
on the verge of commercial exploitation.
My sincere thanks go to the authors who have contributed these
very provocative and stimulating chapters.
A. Pizzi
Contributors
F. A. Cameron ** Division of Processing and Chemical Manufacturing
Technology, Council for Scientific and Industrial Research, Pretoria,
South Africa
Gerard Elbez Centre Technique du Bois et de L’Ameublement,
Paris, France
Kenneth R. Geddest Research Department, Crown Decorative
Products Ltd., Darwen, Lancashire, England
Lawrence Gollob Chemical Division, Georgia-Pacific Resins, Inc.,
Decatur, Georgia
William E. Johns Department of Mechanical and Materials Engineering,
Washington State University, Pullman Washington
Alan L. Lambuth Timber and Wood Products Group, Boise Cascade
Corporation, Boise, Idaho
Rainer Marutzky Fraunhofer-Institute for Wood Research, Braun­
schweig, Federal Republic of Germany
A, Pizzi Division of Processing and Chemical Manufacturing Tech­
nology, Council for Scientific and Industrial Research, Pretoria,
South Africa
Neville E. Quixleyi Expandite (PTY) Ltd., Isando, South Africa
Present affiliations:
* Industrial Laminates (PTY) Ltd., Alrode, South Africa
tCrown Berger Licensing Group, Crown Berger Europe Limited,
Darwen, Lancashire, England
iT. A.C. National (PTY) Ltd., Benoni South, South Africa
VI Contributors
R. Smit* Division of Processing and Chemical Manufacturing Tech­
nology, Council for Scientific and Industrial Research, Pretoria,
South Africa
Gerrit H. van der Klashorst Division of Processing and Chemical
Manufacturing Technology, Council for Scientific and Industrial
Research, Pretoria, South Africa
^Present affiliation: Department of Chemistry, Rand Afrikanse
Universiteit, Johannesburg, South Africa.
Contents
PREFACE 111
CONTRIBUTORS V
1. PROTEIN ADHESIVES FOR WOOD
Alan L. Lambuth
lo Introduction 1
IL Soybean Adhesives 2
III. Blood Glues 13
IV. Casein Glues 22
V. Other Proteins 26
References 27
THE CHEMISTRY OF PVA 31
Kenneth R. Geddes
I. Introduction 31
IL Process Outline 31
III. Vinyl Acetate Monomer 33
IV. Internal Plasticization and Copolymerization 33
V. Water 36
VL Initiators 36
VII, Surface-Active Agents 38
VIII. Colloids : Polyvinyl Alcohol 41
IX. Other Colloids 42
X. Buffers and pH Adjusters 43
XL External Plasticizers, Coalescents, Tackifiers
and Crosslinking Agents 43
XIL Fillers and Pigments 44
XIII. Fungicides and Preservatives 44
XIV. Polymerization Reactions and Kinetics 45
XV. Copolymerization Kinetics 49
XVI. Glass Transition Temperature of Copolymers 51
XVII. Emulsion Polymerization by the Batch Process
in the Presence of Surfactant 51
vili Contents
XVIII. Emulsion Polymerization of Vinyl Acetate
Stabilized by Polyvinyl Alcohol Alone 54
XIX. Continuous Emulsion Polymerization 55
XX. High Pressure Polymerization 60
XXI. Practical Aspects of Production of PVA
Adhesives 62
XXII. Film Formation and Film Properties 65
References 66
3. THE CHEMICAL BONDING OF WOOD 75
William E. Johns
I. Introduction 75
II. Varieties of Chemical Bonding 77
III. Discussion 87
IV. Summary 92
References 92
4. PHENOL-FORMALDEHYDE STRUCTURES IN
RELATION TO THEIR ADHESION TO WOOD CELLULOSE 97
A. Pizzi and R. Smit
I. Introduction 97
II. The Structure of Some Phenol-Formaldehyde
Condensates for Wood Adhesives 98
112
III. Adhesion to Wood Cellulose
IV. Conclusions 118
References 119
5. THE CORRELATION BETWEEN PREPARATION
121
AND PROPERTIES IN PHENOLIC RESINS
Lawrence Gollob
121
I. Introduction
II. Concepts of Synthesis/Structure/Property
Relationships 123
III. Outlook 150
References 150
LIGNIN FORMALDEHYDE WOOD ADHESIVES 155
Gerrit H, van der Klashorst
I. Introduction 155
II. Polymerization Reactions for Alkali Lignin 157
Contents ix
III. The Utilization of Alkali Lignin in Phenol-
Formaldehyde Wood Adhesives 160
IV. Industrial Soda Bagasse Lignin-Based Cold-
Setting Wood Adhesives 164
V. Lignin-Based ”Honeymoon" Adhesives 166
VI. Soda Bagasse Thermosetting Wood Adhesives 166
VII. Meta-Modified Lignin-Based Wood Adhesives 173
vili. Reaction of Industrial Lignin with Formalde­
hyde at the Meta Positions 181
IX. Preparation of Cold-Setting Wood Adhesive
Based on the Metamodification of Industrial
Pine Kraft Lignin 184
X. Conclusion 186
Reference 187
7. LOW-■RESORCINOL PRF COLD-SET ADHESIVES-
THE BRANCHING PRINCIPLE 191
A. Pizzi
I. Introduction 191
II. Chemistry of PRF Resins and Branching 193
III. Different Branching Molecules 195
IV. Branched PRF Characteristics 201
V. Base- and Acid-Catalyzed Formulations;
Pot-Life and Shelf-Life 205
VL Formulation 208
VII. Conclusion 209
References 210
8. HOTMELTS FOR WOOD PRODUCTS 211
Neville E. Quixley
I. Introduction 211
II. Background 211
III. How Do Hotmelts Work? 212
IV. Application Areas 212
V. Ethylene-Vinyl Acetate Hotmelts for Edging 215
VI. Polyamide Hotmelts for Edging 219
VII. Edge-Bonding Techniques 220
vili.
Health and Safety 227