Paint Technology and Tests

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Title: Paint Technology and Tests

Author: Henry A. Gardner

Release Date: September 13, 2011 [EBook #37420]

Language: English

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PAINT TECHNOLOGY AND TESTS

PAINT TECHNOLOGY

AND TESTS.

BY

HENRY A. GARDNER

Assistant Director, The Institute of Industrial Research, Washington, D. C.

Director, Scientific Section, Paint Manufacturers’ Association of the United States, etc.

McGRAW-HILL BOOK COMPANY

239 WEST 39TH STREET, NEW YORK

6 BOUVERIE STREET, LONDON, E.C.

1911

Copyright, 1911, by the

McGraw-Hill Book Company

THE·PLIMPTON·PRESS·NORWOOD·MASS·U·S·A

TO

MY MOTHER

PREFACE

A few years ago the producer and consumer of paints possessed comparatively little knowledge of the relative durability of various pigments and oils. There existed in some cases a prejudice for a few standard products, that often held the user in bondage, discouraging investigation and exciting suspicion whenever discoveries were made, that brought forth new materials. Such conditions indicated to the more progressive, the need of positive information regarding the value of various painting materials, and the advisability of having the questions at issue determined in a practical manner.

The desire that such work should be instituted, resulted in the creation of a Scientific Section, the scope of which was to make investigations to determine the relative merits of different types of paint, and to enlighten the industry on various technical problems. Paint exposure tests of an extensive nature were started in various sections of the country where climatic conditions vary. This field work was supplemented in the laboratory by a series of important researches into the properties of pigments, oils, and other raw products entering into the manufacture of protective coatings. The results of the work were published in bulletin form and given wide distribution. The demand for these bulletins early exhausted the original impress, and a general summary therefore forms a part of this volume.

The purpose of the book is primarily to serve as a reference work for grinders, painters, engineers, and students; matter of an important nature to each being presented. Without repetition of the matter found in other books, two chapters on raw products have been included, and they present in condensed form a summary of information that will prove of aid to one who desires to become conversant with painting materials with a view to continuing tests such as are outlined herein. In other chapters there has been compiled considerable matter from lectures and technical articles presented by the writer before various colleges, engineering societies, and painters’ associations.

The writer wishes to gratefully acknowledge the untiring efforts of the members of the Educational Bureau of the Paint Manufacturers’ Association, whose early endeavors made possible many of the tests described in this volume. Kind acknowledgment is also made to members of the International Association of Master House Painters and Decorators of the United States and Canada, who stood always ready to aid in investigations which promised to bring new light into their art and craft.

HENRY A. GARDNER.

Washington

, October, 1911.

CONTENTS

PAINT TECHNOLOGY

CHAPTER I

PAINT OILS AND THINNERS

Constants and Characteristics of Oils and Their Effect upon Drying. An attempt has been made to give in this chapter a brief summary of the most important characteristics of those oils finding application in the paint and varnish industry. For methods of oil analysis, the reader is referred to standard works on this subject; the analytical constants herein being given only for comparative purposes.

It is well known that one of the most desirable features of a paint oil is the ability to set up in a short period to a hard surface that will not take dust. This drying property is dependent upon the chemical nature of the oil. If it is an unsaturated compound, like linseed oil, rapid absorption of oxygen will cause the film to dry rapidly and become hard. If the oil be of a fully satisfied nature, like mineral oil, oxygen cannot be taken up to any great extent and drying will not take place. The various animal and vegetable oils differ in their power of oxygen absorption to a lesser or greater extent. This difference is referred to by the chemist in terms of the iodine value. The iodine value of linseed oil is approximately 190, meaning that one gram of the oil will take up 190 centigrams of iodine. Oils with high iodine values have good drying powers, while those with low iodine values are, as a rule, very slow drying in nature.

For a description of the working and drying properties of various oils used in paints, see Chapter XIV. The oxygen absorption of various oils and mixtures is shown in Chapter II.

Linseed Oil. The seed of the flax plant which is extensively grown in North Dakota, Argentine Republic and Russia, contains approximately 36% of oil which may be obtained by grinding, heating, and expression. Ripe native seed generally produces a pale oil of little odor; the oil from Argentine seed often having a greenish tint and an odor resembling sorghum. While filtering, pressing and ageing will remove considerable of the (foots) mucilaginous matter, phosphates, silica, etc., from the oil, the better grades which are intended for varnish making are often refined with sulphuric acid. A light colored oil which may be heated without breaking results from this treatment, but such oils are apt to contain considerable free fatty acid, unless they are washed with alkali subsequent to the sulphuric acid treatment. On account of its rapid drying properties and general adaptability for all classes of paints and varnishes, linseed oil has never been supplanted by any other oil. Chemically it consists of the glycerides of linoleic, oleic, and isolinoleic acid, its constitution being responsible for its very high iodine value.

Field of Flax in bloom in North Dakota

Boiled linseed oil, a heavier and darker product, is made by heating the raw oil in open kettles to high temperatures, generally with the addition of metallic driers such as litharge, and black manganese. The resinates of lead and manganese are often added to oil heated at a lower temperature, to obtain a boiled oil of lighter color.

New type of Flax Harvester which pulls plant up by the roots, thus preventing infection of soil

Modern Concrete Elevators for storing Flaxseed

View of Linseed Oil Factory showing hydraulic press, tanks, etc.

Photographs courtesy of Spencer Kellogg Sons

Flaxseed Crushers

Filter Presses for removing extraneous matter from linseed oil

Linseed Cake from Oil Press

Glycine Hispida

Mammoth soya bean plants

Photographs courtesy of David Fairchild, Plant Explorer, U. S. Dept. of Agriculture

Glycine Hispida

Soya bean plants under cultivation at Arlington, Va.

By blowing air through linseed oil that has been heated to approximately 200 degrees Fahrenheit, either with or without drier, heavy bodied oils are obtained, which find special application in varnishes and technical paints. As the viscosity of these oils increase, the iodine values decrease, and a slight rise in saponification value and specific gravity is observed. The following analyses of various types of linseed oil were recently made by the writer:

Soya Bean Oil. The soya plant which is extensively cultivated in Asia produces a seed bearing up to 22% and over of a golden colored oil having a peculiar leguminous odor. The oil, which probably consists of the glycerides of oleic, linoleic, and palmitic acids, is secured by crushing, steaming and pressing the seed. There are several varieties of the plant, and they are said to be the best annual legume for forage, the straw and fruit being rich in nitrogen and very fattening as a cattle food. Soya may be grown in nearly any country and is a great carrier of nitrogen to land deficient in this element. Although the oil has been used abroad for many years for soap-making purposes, its use as a drying oil is comparatively recent; being introduced into the paint industry of the United States during the year 1909, when linseed oil started on its phenomenal rise in price.

Glycine Hispida

Mammoth soya bean plant

Glycine Hispida

Soya bean plant, showing nitrogen gathering tubercles on roots

The oil has given fair service in some paints when mixed with upwards of 75% of pure linseed oil. It is of a semi-drying nature, but may be made to dry rapidly when mixed with manganese and lead linoleate driers. By compounding it under heat with tung oil and rosin, a substitute for linseed oil is produced, which some claim to be quite valuable.

Table I gives the constants of several samples of soya oil examined by the writer. Table II shows the iodine value of mixtures of soya and linseed oils. Table III shows the results of drying experiments on soya oils containing different percentages of lead and manganese driers.

TABLE I

Chemical Characteristics of Soya Bean Oil

TABLE II

Iodine Values of Linseed Oil and Mixed Oils

TABLE III

Soya Bean Oil and Lead Drier

Soya Bean Oil and Manganese Drier

Soya Bean Oil, Manganese and Lead Drier

Tung Oil. There are grown in China and Japan many varieties of the "aleurites cordata," popularly known as the tung tree. This tree bears great quantities of large sized nuts containing as high as 40% of an oil which yields itself in a viscous yellow form upon heating and crushing of the fruit. The raw oil, which chemically consists of the glycerides of oleic, oleo-margaric, and probably isomeric acids, is distinguished by its rapid drying properties. When spread in a thin layer it produces a hard film with an opaque frosted surface, often showing a tendency to wrinkle. Treated tung oil will dry to a clear, water-shedding, elastic film. This oil is made by heating the raw tung oil at a comparatively low temperature with other oils and a metallic drier such as litharge.

Photographs courtesy of David Fairchild

Aleurites Cordata (Chinese Wood Oil) Barrel Factory at Cooperage Shop

Photographs courtesy of David Fairchild

Aleurites Fordii (Chinese Wood Oil)

Fruit from trees at the end of fourth year

The affinity of tung oil for rosin has resulted in the production of a series of moderate-priced varnishes most suitable for use in floor and deck paints or wherever great hardness is required. These varnishes are also finding application in the manufacture of concrete, steel, and flat wall paints; being especially suitable for the above purposes when compounded with kauri gum japan.

Aleurites Fordii

Wood Oil tree, thirty feet high and three feet in diameter, on banks of Yangtse River, Western Szechuan, China. Opium Poppy in the foreground

Aleurites Cordata

Flowering specimen of the Chinese Wood Oil tree at Riverside, California, planted in 1907. Photograph taken in 1910, when tree had borne fifty fruits

During the boiling of raw tung oil the temperature must not exceed much over 400 degrees Fahrenheit. Otherwise a peculiar hamming will take place, the whole mass becoming solid and of no further value as a varnish or paint vehicle. Some peculiar internal disturbance or rearrangement of the molecules is evidently effected by heat, and although the reaction is not clearly understood, it has been ascribed to auto-polymerization. Scott has stated that the phenomenon of gelatinization is due to the exposure of the surface of the oil to the air, and that boiling in vacuo obviates such results. The lusterless surface produced when tung oil varnishes are dried in vitiated air would tend to confirm the conclusion that the oil is very subject to atmospheric influences.

Lumbang Oil, which is obtained from a tropical species of Tung, is very similar in appearance and properties to Linseed Oil.

Constants of Tung Oils

Photographs courtesy Alpin I. Dunn

Menhaden Net drying in the Sun

Transporting Menhaden from net to deck of boat, in swinging basket

A big catch of Menhaden made off Narragansett Bay

Menhaden Oil. Of all the marine-animal oils, such as seal, herring, sardine, whale, and menhaden, the latter is the most valuable. It is produced by steam digestion and pressure of the menhaden or piogey fish, which are caught in great quantities off the Atlantic Coast. Prompt cooking and treatment of the fish results in a light-colored oil having very little odor, the residue left in the presses being of great value as a fertilizer. Although several grades of oil termed crude, brown, light, etc., are produced, the most satisfactory for use in paint is that grade termed light winter pressed. This oil is of a pale straw color and has a high iodine number which is responsible for its rapid drying value. It contains less of the stearates that precipitate from crude oil, but sufficient to render its film water-shedding and elastic. The presence of too great a quantity of stearates is apt to result in a very soft film, and the use of hard driers, such as the metallic tungates, is therefore advisable with menhaden oil. When mixed with linseed oil paints the odor of menhaden oil is sometimes noticeable, but it disappears entirely after such paints are applied. Its use with linseed oil in technical paints exposed to the salty air of the Coast has given good results, often preventing checking and chalking.

The following constants were determined on samples of menhaden oil received in the writer’s laboratory:

Whale Oil. While ordinary whale oil is too dark and odorous to ever come into extensive use as a paint oil, it is probable that the refined oil will be utilized in the manufacture of certain technical paints. Whale oil is boiled from chopped whale blubber, the first trying being the lightest in color, while the later tryings, as well as the product made from bones, are of darker color and of very bad odor. Oil of mirbane is often used to mask this odor. The oil contains large quantities of stearin and palmitin, as well as wax-like constituents which are apt to be thrown out of solution in very cold weather, or when the oil is mixed with other oils. The refined oil, when ground with lead and zinc pigments and mixed with equal parts of linseed oil and treated tung oil, dries to an elastic and soft film. Experiments are being made to utilize whale