| Petropol No. 1158 liquid | Petropol No. 2138 liquid
-----------------+--------------------------+-------------------------
Gravity | 15.5-18.5 | 10-11 A. P. I.
Flash | 175° F. minimum. | 230° F. minimum.
Fire | 215° F. minimum. | 280° F. minimum.
Viscosity | 200-225 at 212° F. | 225-300 at 210° F.
Pour | 0° F. maximum. | 45° F. approximate.
Iodine No. | 195 minimum. | 200 minimum.
Molecular weight | 300 approximate. | 425 approximate.
Percent solids | 60-65. | 80-85.
-----------------+--------------------------+-------------------------
Miscible in all proportions with petroleum solvents.
Petropol No. 1158 is used by core oil makers to replace such vegetable
oils as linseed, tung, and perilla. It is used also as a binder and
waterproofing agent on rock wool insulation, replacing rosin and mineral
oil. For spraying coal to minimize dusting, it has the advantage over
calcium chloride of increasing the B. t. u. content of the fuel.
Petropol No. 2138 is a surface coating material which dries by
polymerization. A low cost paint is obtained by combining a pigment and
a plasticizer with the resin. Such paint dries in about one-fourth the
time of linseed oil paints, adheres better to metal, and has greater
resistance to water, acids, and alkalies. In varnishes and enamels it
replaces 12 to 15 percent of tar-acid resin, minimizes skinning, and
gives a higher luster and better flow. Another use of this Petropol is as
a binder in brake linings, replacing certain tar-acid resins.
These two Petropol resins are among the lowest priced synthetics, selling
at present (1938), in tank carlots, for 2 to 5 cents per pound.
The Santoresins are clear, hard, neutral products, melting at 100° C.
They are soluble in drying oils, accelerate the gelatination of tung
oil, are nonreactive with pigments, do not yellow on outdoor exposure,
and are resistant to alkalies, acids, alcohol, and water. Applications
are in protective coatings for wood, metal, paper, leather, cement,
plaster, and other materials, in printing inks, plastic tile, linoleum,
and fiber packages. Being odorless and tasteless they may be used to line
food containers. Their high resiliency and purity recommend their use
as a base for chewing gum. Other uses are as an agent for wetting and
dispersing pigments in rubber and in surface coatings, to replace ester
gum or modified tar-acid resins.
At present the Santoresins are offered at 15 cents per pound in lots of
20,000 pounds or more. Their approximate specifications are:
Appearance A clear hard resin.
Melting point 110° to 120° C. A. S. T. M. (Ring & Ball).
Acid value 0 to 1.
Iodine value 125 to 135.
Specific gravity (at 20° C.) 1.02 or 8.5 lbs. per gallon.
Color (50 percent solution
by weight in toluol) 13 to 15 Gardner Holt standard.
Odor slight when cold, sweet and aromatic when melted. Soluble in
aromatic hydrocarbons, petroleum thinners, turpentine, and varnish oils.
Insoluble in alcohols, esters, ketones, and not completely compatible
with nitrocellulose.
Production.
In the United States two makers of petroleum resins are producing in
commercial quantities and several others are carrying on extensive
research. Production was small in 1935, but increased in 1936 and in
1937. The development and expansion of these resins over the past 2 years
indicate that they will become important.
Imports into and exports from the United States.
There has been no importation of petroleum resins into the United States.
Exports have been confined to samples and experimental quantities.
9. POLYSTYRENE RESINS
The polystyrene resins are thermoplastic products discovered about
100 years ago and are therefore the oldest synthetic resins known.
Their practical application has been greatly retarded by the lack
of inexpensive raw materials of high purity and by the difficulties
experienced in their manufacture.
Ethylene, from petroleum or natural gas, is combined with benzene, from
byproduct coke-oven operations, to form ethyl benzene, which is cracked
to vinyl benzene or styrene. This monomer is polymerized by heat at
100°-150° C. The resin may be extremely tough or very brittle, depending
on the conditions of polymerization. Products having different properties
are obtained by (_a_) low temperature polymerization, (_b_) high
temperature polymerization, and (_c_) catalytic polymerization.
The low-temperature polymers, sometimes designated as alpha-metastyrol,
are produced by polymerizations of vinyl benzene at temperatures under
175° C. A transparent resin, colorless to light yellow, is produced which
is remarkably tough, has excellent tensile strength, unusually good
dielectric properties, and is resistant to most chemicals.
Polymerization at high temperatures (above 175° C.) yields a brittle
resin designated as beta-metastyrol. This type is transparent but usually
dark in color, has low tensile strength and shock resistance.
When vinyl benzene is polymerized in the presence of catalysts, the
resulting resin is similar to resins obtained at high temperatures,
except that it is lighter in color. It is sometimes designated as
gamma-metastyrol. Oxidizing agents are usually the catalysts. Clear,
colorless, vitreous resins are obtained by excluding air during
polymerization.
Properties and uses.
Polystyrene resin is a clear, colorless, highly thermoplastic molding
material with high insulating property, moisture resistance, inertness,
dimensional stability, and impact strength. It can be molded directly
by heat and pressure, and the molded articles are remarkably resistant
to discoloration by light. Polystyrene has a dielectric constant of
2.6, a power factor of 0.02 percent, and is equivalent to fused quartz
as an electrical insulator of low dielectric loss. Films of 0.002 inch
thickness have a dielectric strength of more than 2,000 volts per mil
thickness, which is better than that of any other available synthetic
resin and even better than that of shellac. The tensile strength of
the resin is 5,500 to 7,000 pounds per square inch, and its impact
resistance remains unchanged at temperatures as low as minus 70° C. It
transmits all wave lengths of light down to 3,000 Angstrom units.
Polystyrene is adapted to large scale production of transparent,
translucent, and opaque moldings in a wide variety of colors. It is
easily molded by injection processes, softening at about 150° F. and is
molded at 300° to 375° F., under 3,000 to 30,000 pounds pressure per
square inch. As much as 40 percent filler may be used without seriously
affecting the tensile strength, although the filler does affect the
dielectric properties. Since the resin is thermoplastic there is no waste
in the molding operation; scrap material may be reground and used again.
The unusual properties of these polystyrene resins should give them
widespread applications when the cost is low enough to make them
competitive with other materials. Potentially large volume outlets are
in radio frequency insulation; in dentures because of the strength, low
specific gravity, ease of coloring, and absence of odor and taste of the
material; in electrical parts for submarine and aircraft storage battery
cases and separators; and for the manufacture of glass eyes.
Other possible applications of polystyrene resins are in metal lacquers
and in light colored enamels. Their toughness and light color, together
with their solubility in cheap solvents, suggest their use for these
purposes. Such lacquers are said to be quick-drying, resistant to water,
and moderately so to acids and alkalies.
Production in the United States.
For a number of years, the Naugatuck Chemical Division of the United
States Rubber Co. produced small quantities of polystyrene resins, which
were marketed under the trade name Victron when for general purposes and
under the trade name Marvelyn when for use in dentures. Little progress
was made because of high costs and failure to produce a water-white
product. The sales price was between $1.50 and $2 per pound. Early
in 1937 the Naugatuck Chemical Division transferred its patents on
polystyrene resins to the Carbide and Carbon Chemicals Corporation.
The Dow Chemical Co., Midland, Mich., late in 1937 announced commercial
production of clear, colorless polystyrene in several forms. Styron
is the trade name for the resin from this source. In January 1938,
the Bakelite Corporation announced Bakelite Polystyrene. The plants
manufacturing polystyrene have a capacity in excess of 2,000,000 pounds a
year, and the resin is currently offered at 72 cents per pound.
At least one other domestic firm is doing research on the polystyrenes
and expects to produce commercially in the near future.
Imports into and exports from the United States.
At least two commercial types of polystyrene resins are produced abroad.
Both are made in Germany and marketed under the trade names Resoglas
and Trolitul. Resoglas is a water-white, transparent thermoplastic
resin softening at about 150° C. Its water absorption is low, it is
nonoxidizing, and does not discolor on weathering and baking. Appreciable
quantities are produced in Germany and the sales price there was reported
to have been 40 cents per pound during 1936.
[Illustration: MOLDED POLYSTYRENE RESINS.
Source: Bakelite Corporation, 247 Park Avenue, New York, N. Y.]
Small quantities of Resoglas and Trolitul have been imported from Germany
in recent years. Table 9 shows the quantities imported in recent years.
TABLE 9.—_Resoglas and Trolitul: United States imports for consumption,
1933-37_
--------+-----------------------------+---------------------------
| Resoglas (polystyrol) | Trolitul
Year +----------+-------+----------+--------+-------+----------
| Quantity | Value |Unit value|Quantity| Value |Unit value
--------+----------+-------+----------+--------+-------+----------
| _Pounds_ | | |_Pounds_| |
1933 | 771 | ([1]) | | 672 | ([1]) |
1934 | 991 | ([1]) | | 200 | ([1]) |
1935 | 110 | $97 | $0.88 | 4,608 |$3,782 | $0.82
1936 | 2,220 | 1,901 | .86 | 4,671 | 3,641 | .78
1937[2] | None | None | | 6,788 | 4,077 | .60
--------+----------+-------+----------+--------+-------+----------
[1] Not available.
[2] Preliminary.
Source: Analyses of invoices of paragraph 28, act of 1930—U. S.
Tariff Commission.
With the more advanced development of polystyrol resins in Germany prior
to 1938, evidenced by larger commercial production, by wider application,
by the marketing of a water-white product at a considerably lower price,
it might be expected that imports into the United States would have been
in considerably larger amount than shown in table 9. That they were small
was probably due to the high rate of duty which made them expensive
as compared with other synthetic resins in the United States and thus
limited their market to uses in which the others were less satisfactory.
Resoglas was reported to have been selling for 40 cents per pound in
Germany. The imported resin is assessed for duty under the provisions of
paragraph 28 of the Tariff Act of 1930 at 45 percent ad valorem based
on American selling price (as a competitive product) and 7 cents per
pound. The American selling price of the resin made in the United States
until late in 1937, as determined by the Bureau of Customs, Treasury
Department, was $1.85 per pound. The duty was therefore 90 cents per
pound. Imports of Trolitul were valued at 75 cents per pound, giving a
cost of $1.75 per pound laid down, duty paid, in domestic markets. With
the present American selling price of 72 cents per pound, the duty would
be approximately 36 cents per pound.
10. VINYL RESINS
Vinyl acetate, vinyl chloride, and to a lesser extent vinyl
chloroacetate, are the raw materials (monomers) for the several vinyl
resins commercially produced in the United States, Canada, and Germany.
These are all esters of the hypothetical vinyl alcohol and are made by
the action of acetic and hydrochloric acids on acetylene.
The spontaneous polymerization of vinyl derivatives has been known for
many years, although its significance and industrial application have
been realized only recently. Vinyl acetate, probably the most important
of the vinyl esters, was discovered in 1912 and first made in Canada in
1917.
Vinyl resins may be classified into (_a_) polyvinyl acetate, (_b_)
copolymers of vinyl acetate and vinyl chloride, (_c_) polyvinyl chloride,
and (_d_) polyvinyl chloroacetate.
Description and uses.
_Polyvinyl acetate resins._—The several commercial types of vinyl acetate
resins are marketed under the trade names Vinyloid A, Alvar, Gelva,
Formvar, and Mowilith. The first of these is a product of Carbide and
Carbon Chemicals Co., New York, the next three are products of Shawinigan
Chemicals Limited, Shawinigan Falls, Canada, and the last is made by
the Interessen Gemeinschaft Industrie A. G., Germany. Vinyloid A and
Gelva represent the simplest series of vinyl acetate resins and are
made by polymerizing the monomer. The softening point and viscosity of
the polyvinyl acetate resins increase with higher polymerization. Such
resins are colorless, tasteless, odorless, thermoplastic products. They
are soluble in coal-tar solvents and are compatible with certain alkyd
resins, tar-acid resins, and natural resins. Films of polyvinyl acetate
resin are not discolored by exposure, and after irradiation they become
opaque to ultraviolet light, are hard and tough, and have good adherence
and endurance. Their dielectric strength is good and they do not show a
carbon track after the passage of an electric arc. Various grades having
softening points from 80° to 200° C. are available.
Polyvinyl acetate resins are used in making transparent papers,
paper to metal laminations, glassine papers for food packaging, as a
substitute for chicle in chewing gum, and as a component of paints,
varnishes, and lacquers. They have the desirable properties of
compatibility, durability, resistance to abrasion, and rust inhibition
in the surface-coating use. Having the same refractive index as pyrex
glass, they leave no line of demarcation when used as a cement for that
material. They have been used to stiffen toe-caps in shoes and articles
made from paper pulp suspensions. Gelvas are not molded as such because
of their tendency to cold flow. They are used, however, as a binder for
ground mineral fillers in advertising signs and for wood flour in molded
artificial wood carvings. In nitrocellulose lacquers they improve the
adhesion, luster, and toughness.
Alvars are made by replacing part or all of the acetate groups in
Gelva with acetaldehyde. Their viscosity varies with the degree of
polymerization and their properties vary according to the extent of
replacement of the acetate groups. The Alvar types do not cold flow
when molded, are tougher, harder, and have better adhesion but are less
resistant to weathering than the Gelva types. Other properties are about
the same as those of the Gelvas. Alvars having 70 to 80 percent acetate
group replacement are used chiefly in spirit type varnishes, lacquers,
and enamels that must stand exposure to weather. Another Alvar type
is used in injection and press molding. The high binding power of the
resin permits the use of large percentages of filler without loss of
desirable properties. Such moldings may be machined and polished, and
take inserts, such as the wood core in shoe heels. Flexible phonograph
and transcription records made from the Alvars have gained wide approval.
An 85 percent (acetate replacement) type has better impact strength and
is used in toilet articles. Sheets, rods, and tubes of this resin may be
machined in much the same way as nitrocellulose plastic and used where
noninflammability is an asset.
Formvars are made by replacing part or all of the acetate groups in Gelva
with formaldehyde. These resins are colorless, odorless, tasteless, and
thermoplastic. They have higher softening points and greater tensile and
impact strength than the Alvars. They are resistant to alcohols, coal-tar
solvents, fats, oils, or water. Moisture transmission rate through a film
of this resin is about one-tenth that through regenerated cellulose and
one-fourth that through cellulose acetate.
The grades of the Formvars available are designated by the extent of
replacement of the acetate group. The 75-percent replacement type has
excellent mechanical strength and flexibility and is unaffected by
sunlight. Formvars of 95 percent acetate displacement have a tensile
strength as high as 10,000 pounds per square inch and offer possibilities
in the manufacture of artificial silk and photographic film.
The vinyl resins have made possible a new type of safety glass superior
to any heretofore marketed. By condensing butylaldehyde with vinyl
acetate, a polymer is obtained which is used as the inner layer between
two sheets of glass. Heat and pressure secure complete adhesion and yield
a sheet with greater resistance to breakage at low temperatures than the
types now in general use.
Although safety glass was invented in 1905, and many substitutes for the
original nitrocellulose inner layer have been proposed, only two reached
commercial importance before the development of the vinyl resins. These
are cellulose acetate and the acrylate resins. Safety glass used in
automobile windshields up to about 1930 discolored after a year or two
of service. This discoloration was due to the action of the actinic rays
of the sun on the nitrocellulose layer. Since 1930 this difficulty has
been largely overcome by using an actinic ray filter glass (a special
glass with a high iron content) in front of the nitrocellulose sheet, or
by using cellulose acetate, which is not discolored to the same extent
by light, as a substitute for nitrocellulose. Both cellulose nitrate
and cellulose acetate, however, have a tendency to lose toughness and
strength at low temperatures, to absorb moisture, and to separate from
the glass around the edge unless sealed, and to lose their plasticizer
and shrink.
Although a vast improvement over ordinary plate glass, laminated glass
made with cellulose nitrate or acetate has the serious defect of being
brittle at low temperatures, such as prevail in the winters of northern
States. It is easily shattered at zero Fahrenheit, while at 60° F.
and above it is quite strong. This shortcoming led to the development
of the vinyl resin sheet for safety glass with a remarkable degree of
toughness. At normal temperatures it has rubberlike toughness which,
although decreased at low temperatures, is not punctured by the impact
of a half-pound steel ball falling from a 30-foot height at minus 10°
F., whereas nitrocellulose or acetate laminated glass withstands the
impact of a fall from not greater than one-tenth this height. A further
advantage of the vinyl sheet is that it is water resistant, making the
sealing of the edges of the glass unnecessary and thus reducing costs.
Exposure to ultraviolet light in Florida sunlight for more than 2 years
did not discolor it.
The many desirable properties of the vinyl resins, as outlined above,
indicate their widespread use in laminated safety glass when it is
available in sufficient quantities. It is estimated that our annual
output of safety glass interlayer sheets exceeds 17,000,000 pounds, of
which 25 to 30 percent are for windshields, and 70 to 75 percent for side
and back windows of automobiles.
At least one of the series of Mowiliths made in Germany is polymerized
vinyl acetate. It is recommended as an ingredient of water-white
lacquers. It is compatible with nitrocellulose and is extremely durable
and not disintegrated or discolored on exposure to weather.
_Copolymers of vinyl acetate and vinyl chloride._—The simultaneous
polymerization of mixtures of vinyl acetate and vinyl chloride yields
resins with the desirable properties of the two reactants. The extent
of plasticity is largely controlled by varying the ratio of the vinyl
derivatives. Resins high in vinyl chloride content are better suited to
molding, and those high in vinyl acetate are better lacquer ingredients.
These resins are marketed as Vinylites by the Carbide and Carbon
Chemicals Co., New York. They are thermoplastic, odorless, tasteless, and
practically nonflammable. Their outstanding properties are resistance
to water, soap, acids, alkalies, and alcohol, and their strength and
good dielectric properties. Their stability to light is improved by
the addition of ultraviolet absorbing compounds and their stability to
heat by the addition of lead oleate, calcium stearate, or other bases.
Water absorption and compatibility with other resins is increased as the
chloride content increases.
The principal types of copolymers are:
Vinylite VYN, high molecular weight. This resin is used in dentures
where good fatigue resistance, impact strength, and tensile strength are
required. It contains 85 to 88 percent vinyl chloride.
Vinylite VYN, medium molecular weight. This resin is used in general
molding and extending applications including sheets, rods, and tubes. Its
vinyl chloride content averages 85 to 88 percent.
Vinylite VYN, low molecular weight. This resin is used in moldings,
coated paper, lacquers, floor tile, phonograph records, and felt
impregnation. It contains 85 to 88 percent vinyl chloride.
Vinylite VYC. This resin of low molecular weight is compatible with
nitrocellulose and is used in lacquers and finishes for industrial
applications. Lacquers from the Vinylites are called Vinyloids.
The Vinylites for molding are thermoplastic and shrink very little,
making them applicable to large moldings. They may be used in extension
processes such as tooth-brush preforms, pipe lining, and wall trim.
Fillers and pigments may be added, although pigments containing iron and
zinc have harmful effects on the stability of the resin. The fillers
used are wood flour, mica, talc, and alpha cellulose. Fillers reduce the
mechanical strength of the resin and lessen its resistance to water.
Plasticizers, such as dibutyl phthalate or tricresyl phosphate, give a
softer, more flexible resin. Resins from the copolymers resemble the
cellulose derivatives in their molding characteristics, mechanical
strength, and appearance.
In lacquers the Vinylites offer high resistance to water, oils, and
chemicals. The drying of such lacquers is by evaporation rather than
by oxidation. They are suitable for lining food containers, coating
concrete, coating paper for bottle cap liners, and as a stiffener for
box toes of shoes. Their most successful application at present is as an
inside coating for beer cans. Floor tile containing these resins mixed
with slate flour or other filler has good possibilities.
_Polyvinyl chloride resins._—Vinyl chloride may be polymerized to give
nonflammable resins of varying solubilities. The completely polymerized
resin is practically insoluble at ordinary temperatures and is used as a
rubber substitute. It is marketed as Koroseal by B. F. Goodrich Rubber
Co., Akron, O. Compared with natural rubber, it has greater resistance to
acids, alkalies, oils, and alcohol, more flexing life, better resistance
to sunlight, water, and oxidation. Solutions of this resin marketed as
Korolac are used in special types of varnishes.
_Polyvinyl chloroacetate resins._—These resins known as Mowiliths are
made in Germany. Application is largely for surface coating. Practically
no information on this type is available.
_Divinyl acetylene and synthetic rubber._—Two products closely related
to those described above but probably not synthetic resins as defined
for this discussion are divinyl acetylene, a synthetic drying oil, and
Neoprene, a synthetic rubber.
Acetylene, when passed into a solution of copper chloride and ammonium
chloride, combines with itself. When two molecules of acetylene react
monovinyl acetylene is formed, and when three molecules of acetylene
react divinyl acetylene is formed. Monovinyl acetylene reacts with
hydrochloric acid to give chloroprene, which is polymerized to synthetic
rubber or Neoprene.