Handbook of antiblocking, release, and slip additives

338 Pages·2014·6.75 MB·English

by  George Wypych

Handbook of
Antiblocking, Release,
and Slip Additives
3rd Edition
George Wypych
Toronto 2014
Published by ChemTec Publishing
38 Earswick Drive, Toronto, Ontario M1E 1C6, Canada
© ChemTec Publishing, 2005, 2012, 2014
ISBN 978-1-895198-83-6
Cover design: Anita Wypych
All rights reserved. No part of this publication may be repro-
duced, stored or transmitted in any form or by any means without
written permission of copyright owner. No responsibility is
assumed by the Author and the Publisher for any injury or/and
damage to persons or properties as a matter of products liability,
negligence, use, or operation of any methods, product ideas, or
instructions published or suggested in this book.
Library and Archives Canada Cataloguing in Publication
Wypych, George
Handbook of antiblocking, release, and slip additives / George Wypych. -- 3rd
ed.
Includes bibliographical references and index.
ISBN 978-1-895198-83-6
1. Polymers--Additives--Handbooks, manuals, etc. 2. Polymers--Additives--
Health aspects--Handbooks, manuals, etc. I. Title.
TP1142.W95 2014 668.9 C2014-905001-1
Printed in Australia, United States, and United Kingdom by Lightning
Source
1
Introduction
1.1 HISTORICAL DEVELOPMENTS
Surface blocking was a technological hurdle for as long as humans began to pro-
cess materials. In ancient times natural products were used to improve technologi-
cal output and quality. These included beeswax, plant waxes, natural resins, oils,
etc. They were used advantageously in cosmetics (e.g., creams used by Cleopatra
in Egypt), plasters (e.g., wall plasters in Pompei, Italy), molds, etc.
The priority of application of modern additives is not documented in research
publications but the use of antiblocking, release, and slip agents is a rather recent
advancement of technological processes. This is easy to predict, knowing the ori-
gin of several materials involved in their production. Stearic acid is the oldest syn-
thetic material used in material processing. It was first obtained by the French
chemist Chevreul who began studies of soaps and isolated the most common fatty
acids. In 1825, together with Gay-Lussac, Chevreul patented the use of stearic
acid in candle manufacturing. It took about a century to apply stearic acid in poly-
mer processing. Calcium stearate was first used for commercial purposes by Har-
rison in 1924.1
Crambe abyssinica, which is a cool-season oilseed containing large concen-
trations of erucic acid, was introduced in the United States of America in 1940 by
the Connecticut Agricultural Experiment Station.2 About 39% of high-erucic-acid
oils are now used for production of erucamide, which is a common slip agent.2
The first major paper on mold release was published in 1946 by Ziegler.3 It
contained a thorough analysis of the influence of mold material on release proper-
ties. Even more important, the paper3 contained a proposal for a new method of
mold release testing, which gave the fundamental tool for rational analysis of the
problem. More than twenty of the so-called “mold lubricants” were tested by the
newly developed pull-out force method. In addition, the effect of “lubricant” on
product clarity was observed − both results being considered in the final selection.
In the best cases, the decrease of up to 80% of pull-out force was obtained with
these tested “lubricants”. Plasticizers and pigments were also found to facilitate
mold release properties in combination with mold release agents.
Film wrapping and handling characteristics were of major concern for film
producers and these prompted studies of slip agents. The first major paper on the
2 1.2 Expectations from commercial additives
improvement of the friction coefficient of polypropylene film was published in
19664 but in the 1950s, studies and inventions were already reported on the sub-
ject. Polymer selection, concentration of fatty acid amide, and its migration to the
film surface were compared with the coefficient of friction of the resultant film.4
Also, in the same period of time, the quality and output of blown film suf-
fered, which led to the first major study on elimination of blocking during produc-
tion of blown film. The study was published in 1967 but some patents had already
been issued in the 1950s.5-7 In this first broader study, various fatty acids were
tested to establish their performance in solving processing problems. In addition
to blocking, the effect of bubble gas (ammonia or air) and the effect of antiblock-
ing agent on film clarity were considered.5
The above shows that the modern machinery gradually being introduced after
the Second World War influenced a search for additives which may contribute to
more efficient production and better quality of materials. Antiblocking, release,
and slip agents are very recent additions to formulations of plastics but very
important for today’s technology.
1.2 EXPECTATIONS FROM COMMERCIAL ADDITIVES
Some literature sources8-15 generalize expectations from these three types of addi-
tive groups. It is interesting to evaluate the list of these expectations as well as to
compare them between the groups to form a base for selection of required prod-
ucts, definition of the groups, and classification of their members. All three
groups affect many similar properties. Their direct comparison will better point to
their differences (Table 1.1).
Table 1.1. Performance indicators and their potential effects on
acceptance of antiblocking (A), release (R), and slip (S) additives
Performance characteristics Effect A R S
Surface roughening8 spacing effect S S N
Particle size distribution8 yield and performance S N N
Specific surface area8 friction coefficient and wear S N N
Dusting13 health S N N
Chemical intertness19 S N N
Density8 product weight S N N
Dispersibility13,14 quality and process time S S S
Number of particles on surface14 efficiency S N N
Homogeneity13 handling Y Y Y
Low moisture pick up13 processing cost, quality Y S S
Purity14 degradation, toxicity Y Y Y
Color15 cost of color correction Y Y Y
Introduction 3
Table 1.1. Performance indicators and their potential effects on
acceptance of antiblocking (A), release (R), and slip (S) additives
Performance characteristics Effect A R S
Haze19 increase with concentration Y Y Y
increase
Compatibility14 optical properties S S S
Refractive index15 clarity, haze S N N
Compatibility with polymer8,19 migration to surface S Y L
Low transfer to material in contact12 migration to coextruded layers S Y Y
Inertness to one contact surface10 ease of separation N Y N
Adhesion to hot metal surface9 demolding temperature, distortion N Y N
Surface tension10 wetting, migration to surface S Y Y
Good spreading characteristics11 formation of film on mold N Y S
Improved mold flow18 lubrication S S Y
Oxidation and thermal stability18 oxygen permeability reduced S Y Y
Weathering18 protective layer S Y Y
Non-interference with polymerization11 properties of product S Y Y
Non-interference with peroxide cure18 composition S S S
Interaction (A and S) synergism or inhibition Y N Y
Residue on product9 adhesion, welding S Y Y
Reduced surface tack18 protective film/surface roughness Y P P
Non-staining18 inert layer on surface, low adhesion S Y Y
Build up10 mold cleaning frequency S Y Y
Non-blooming12 product quality S S Y
Toxicity10 health and safety Y Y Y
Handling safety14 health and safety Y S S
Solvent type and concentration11 health and safety S Y Y
Food contact approval10 health and safety Y Y Y
Low volatility10 loss from melt, bubbling N Y Y
High efficiency11 low concentration required Y Y Y
Wrinkled film waste/cost Y N Y
Increased line speed19 cost Y Y Y
Improvement of production rate15 cost Y Y S
Improved mold filling18 adjustment of melt rheology S S S
Hardness15 equipment wear S N N
Reduced coefficient of friction18 surface film S Y Y
Abrasion and scratch resistance18,19 surface modification S Y Y
Water repellency18 hydrophobic properties S Y Y
Improved electrical properties18 some are antistatics S S S
4 1.3 Definitions
Table 1.1. Performance indicators and their potential effects on
acceptance of antiblocking (A), release (R), and slip (S) additives
Performance characteristics Effect A R S
Static charge formation19 difficult dispersion Y N N
Price14 cost Y Y Y
Performance characteristic expected − Y, expected for some additives − S, not expected − N, low −
L, possible − P.
1.3 DEFINITIONS
Merriam-Webster’s Dictionary describes blocking of paper as sticking together
under the influence of heat and pressure. This is quite a precise definition of
blocking, which is an adhesion between materials (usually of the same kind),
which makes it difficult to separate them. The blocking is mostly associated with
polyethylene and polypropylene films, but it may affect any other product.14,16
Antiblocking is an action, usually carried out by reformulation (addition of
antiblocking agent(s)), which aims at reduction of forces of adhesion between the
materials in contact. Other components of formulation and/or physical parameters
are essential and these are considered throughout the entire book.
The meaning of release is defined as a removal of the force or its effect. This
may be related to a material in a flowing form (e.g., melt) or in a solid state. In the
case of liquid form, the release properties are usually balanced by the use of exter-
nal and internal lubricants, which alone or in combination give a proper balance of
release and adhesion as it is suitable for efficient processing. In the solid state,
release properties are usually required to separate a product from the form in
which the product was manufactured. The most likely application of release
agents is in the molding industry, but other processes, such as calendering, extru-
sion, embossing, etc. also require special additives to help in separation of a prod-
uct from the part of the machine on which the material is being formed.17 These
will all be cases of release agents which mostly act by forming a layer which sep-
arates the product and the mold. Sometimes, lowering the coefficient of friction
also helps in separation of the product from the mold and this calls for joint use of
a release agent together with slip agents discussed below.
To slip means to move with a sliding motion, which implies that a slip agent
must address deficiency in the material related to too high a friction between the
two surfaces in contact. The surfaces in contact may be composed of the same or
different materials. The slip agents are used in both processing and use of manu-
factured materials.
The above definitions show the differences and similarities in functions of
the three groups of additives, which frequently overlap to the extent that assigning
their proper functions and designations sometimes becomes ambiguous.
Introduction 5
1.4 CLASSIFICATION
Table 1.2 shows chemical groups of materials that are used as either antiblock,
release, or slip additives.
Table 1.2. Chemical composition of antiblock, release, and slip
agents
Chemical group Antiblock Release Slip
Alcohol phosphates Y
Calcium carbonate Y
Carbon nanotubes Y
Cellulose acetate in solution Y
Ceramic spheres Y
Diatomaceous earth Y
Fatty acid amides Y Y
Fatty acid esters Y
Fatty acid salts Y Y Y
Fatty acids Y Y
Fluorocompounds Y Y
Graphite Y
Molybdenum sulfide Y
Kaolin Y
Lignosulfonates Y
Limestone Y
Polytetrafluoroethylene Y Y
Polyvinylalcohol in solution Y
Resins in solution Y
Secondary amides Y Y
Silica and silicates Y
Silicones (oils and crosslinked) Y Y Y
Talc Y
Waxes (natural and synthetic) Y Y Y
Zeolites Y
There are some areas of overlap in usage of different chemical groups but
specific compounds frequently differ in each application (fatty acid amides are a
classical example of compounds used in all three applications). One obvious gen-
eral difference is that inorganic materials are only used as antiblocking additives.
Chemical classification is used in the next chapter, which discusses general prop-
erties of antiblocking, release, and slip additives.
6 References
Several other means of classification are also possible as Table 1.3 shows.
Table 1.3. Classification of antiblocking, release, and slip additives
Means of classification Antiblocking Release Slip
State of matter
solid Y N Y
liquid Y Y Y
Chemical composition
organic Y Y Y
inorganic Y N Y
Application form
powder micronized solid Y Y Y
liquid Y Y Y
solution N Y N
emulsion N Y N
suspension N Y N
Method of application
internal Y Y Y
external N Y S
Polymer type
specific cases discussed in Chapters 11, 12, and 13
Product type
Processing method
The details regarding chemical structure, application form, method of appli-
cation, and use of individual products for different polymers, products, and pro-
cessing methods are given in the Database of Antiblocking, Release, and Slip
Agents, which constitutes a separate publication on CD-ROM.18 Various aspects
of these additives are discussed in separate chapters in a generalized form.
REFERENCES
1 Calcium Stearate. Natl. Organic Standards Board Techn. Advisory Panel Review, Sep 4, 2002.
2 Glaser, L. K., Crambe: An Economic Assessment of the Feasibility of Providing Multiple-Peril
Crop Insurance, November. 1996.
3 Ziegler, E. E., India Rubber World, 114, 826-9, 1946.
4 Schael, G. W., J. Appl. Polym. Sci., 10, 653-61, 1966.
5 Dighton, G. L., SPE J., 23, 4, 91-2, 109, 1967.
6 Barker, H. C., US Patent 2,770,608.
7 Symonds, A. E., US Patent 2,770,609.
8 Harper C. A., Ed., Modern Plastics Handbook, McGraw-Hill 2000.
9 Kulshreshtha, A. K.; Awasthi, S. K., Popular Plast. Packaging, 43, 4, 67-76, 1998.
10 Mark, H. F., Encyclopedia of Polymer Science and Engineering, Release Agents,
John Wiley & Sons, 1985.
11 Murphy, J., Additives for Plastics Handbook, Chapter 17: Lubricants, mould release
agents, slip, anti-block, Elsevier, Oxford, 1996.
12 Soutar, A. M., Polym., Laminations & Coat. Conf., Boston, Sept. 8-12, 1996, 319-28, 1996.
13 van Essche, G.; Schmidt, A., TAPPI Polymers, Laminations & Coatings Conference, Atlanta,
Aug. 22-26, 1999, 2, 807-813, 1999.
14 Koromminga, T.; van Esche, G., Plastics Additives Handbook, Zweifel, H, Ed., Hanser, 2001.
Introduction 7
15 Antiblock − “The Basics”, Ampacet.
16 Sobottka R.; Feltham E., Anti-blocking of Polymer Films in Plastics Additives - An A-Z
reference, Ed. Pritchard, G., Kluwer 1998.
17 Pritchard, G., Release Agents in Plastics Additives - An A-Z reference, Kluwer 1998.
18 Wypych, A., Database of antiblocking, release, and slip agents. ChemTec Publishing,
Toronto 2005.
19 Keck-Antoine, K; Lievens, E; Bayer, J; Mara, J; Jung, D-S; Jung, S-L, Multilayer Flexible
Packaging, Marks, S, Ed., Elsevier, 2010, pp 239-48.
2
Generic Types
2.1 INTRODUCTION
Additives are arranged in this section according to their function, such as: anti-
blocking, release, and slip. Some additives may play several roles. For example,
fatty acid amides are used as antiblocking, release, and slip agents. In such cases,
the main function of an additive is used for its assignment (for example, fatty acid
amides are assigned to the slip agents group). Chapters 11 to 13 contain break-
downs of the additives use by polymer, product, and method of processing.
Many commercial additives constitute mixtures of several components or
formulations of unknown composition. These additives are not included in this
discussion. Only generic materials are compared in this chapter. The role of this
chapter is:
• to find commonalities among additives belonging to the same generic
group
• to expose differences between different generic groups to be used as advi-
sory tools in additive selection.
Description of additives within their generic groups falls into one of the fol-
lowing categories:
• general (some examples of commercial additives are given in tables; com-
prehensive treatment of the data on commercial additives can be found in
CDROM database, entitled Database of Antiblocking, Release, and
Slip Additives)28
• physical properties
• health and safety
• ecological effect
• applications.
Using the standardized method of data presentation, typical characteristics of
the groups are presented in tabulated form for easy comparison.