Fine red iron oxide pigment, and paint or resin composition using the same

A fine red iron oxide pigment of the present invention comprises hematite particles and having a geometrical standard deviation of major axial diameter of not more than 1.5, a geometrical standard deviation of minor axial diameter of not more than 1.3 and an average major axial diameter of 0.005 to 0.1 .mu.m. Such fine red iron oxide pigment is uniform in both major axial diameter and minor axial diameter thereof and exhibits an excellent transparency.

BACKGROUND OF THE INVENTION
 The present invention relates to a fine red iron oxide pigment and a paint
 or a resin composition using the fine red iron oxide pigment. More
 particularly, the present invention relates to a fine red iron oxide
 pigment which is uniform in both major axial diameter and minor axial
 diameter thereof and exhibits an excellent transparency, and a paint or a
 resin composition using the fine red iron oxide pigment, which also
 exhibits an excellent transparency.
 Hematite particles have been widely known as a red iron oxide pigment,
 because these particles can exhibit a red color and have been used in many
 applications such as coloring of paints, printing inks, plastics, films,
 cosmetics or the like.
 Among the hematite particles, by using those particles having a particle
 size of not more than 0.1 .mu.m, the coating film obtained therefrom is
 transparent to visible light and, therefore, such particles are useful as
 a transparent red iron oxide pigment.
 The red iron oxide pigment composed of fine hematite particles having a
 particle size of not more than 0.1 .mu.m (hereinafter referred to merely
 as "fine red iron oxide pigment") are deteriorated in dispersibility in
 vehicles or resin composition due to the reduction of particle size
 thereof. Therefore, a coating film or a resin composition using the fine
 red iron oxide pigment is unsatisfactory in transparency.
 Namely, the fine red iron oxide pigment has a high surface energy and tends
 to be agglomerated due to the reduction of particle size thereof, so that
 it is difficult to disperse the pigment in vehicles or resin compositions.
 Therefore, a coating film obtained from such an insufficient dispersion
 cannot show a sufficient transparency since the fine pigment is
 agglomerated into coarse particles.
 Consequently, it has been demanded to improve not only the dispersibility
 of the fine red iron oxide pigment in vehicles or resin compositions but
 also the transparency of the pigment itself.
 Hitherto, as the method of enhancing the dispersibility of the fine red
 iron oxide pigment, there has been known a method of improving a particle
 size thereof. As such a method, there has been already proposed a method
 of producing fine hematite particles having a uniform particle size by
 first producing fine goethite particles having a uniform particle size in
 an aqueous solution and then heat-dehydrating the obtained fine goethite
 particles while maintaining the uniform particle size of the fine goethite
 particles (Japanese Patent Application Laid-Open (KOKAI) No.
 49-34498(1974), Japanese Patent Publication (KOKOKU) No. 59-48768(1984),
 etc.).
 Especially, in Japanese Patent Application Laid-Open (KOKAI) No.
 49-34498(1974), there are described (1) a process for producing a fine
 iron oxide pigment comprising spindle-shape particles having a uniform
 particle size, a ratio of a major axial diameter to a minor axial diameter
 of not more than 5:1 and an average particle diameter of 5 to 20 nm, which
 process comprises a first step of adding caustic alkali such as sodium
 hydroxide to a solution of a ferrous salt such as ferrous sulfate to
 obtain a ferrous hydroxide colloid solution at a temperature of from room
 temperature to 40.degree. C.; a second step of reacting the obtained
 ferrous hydroxide with bicarbonate such as ammonium bicarbonate to obtain
 a ferrous carbonate colloid solution at a temperature of from room
 temperature to 40.degree. C.; and a third step of passing an
 oxygen-containing gas such as air through said ferrous carbonate colloid
 solution at a temperature of from room temperature to 40.degree. C. to
 transform said ferrous carbonate into ferric oxide hydroxide, and (2) a
 process for producing a fine iron oxide pigment, which process comprises
 (i) producing fine ferric oxide hydroxide comprising spindle-shape
 particles having a uniform particle size, a ratio of a major axial
 diameter to a minor axial diameter of not more than 5:1 and an average
 particle diameter of 5 to 20 nm by conducting a first step of adding
 caustic alkali such as sodium hydroxide to a solution of a ferrous salt
 such as ferrous sulfate to obtain a ferrous hydroxide colloid solution at
 a temperature of from room temperature to 40.degree. C.; a second step of
 reacting the obtained ferrous hydroxide with bicarbonate such as ammonium
 bicarbonate to obtain a ferrous carbonate colloid solution at a
 temperature of from room temperature to 40.degree. C.; and a third step of
 passing an oxygen-containing gas such as air through said ferrous
 carbonate colloid solution at a temperature of from room temperature to
 40.degree. C. to transform said ferrous carbonate into ferric oxide
 hydroxide, (ii) after subjecting said ferric oxide hydroxide as a
 precipitate to washing with water, filtering-out and drying, dehydrating
 said precipitate at a temperature of 250 to 350.degree. C., thereby
 obtaining ferric oxide comprising spindle-shape particles which comprise
 primary particles having a particles diameter of about 5 nm, and have a
 uniform particle size and a ratio of a major axial diameter to a minor
 axial diameter of not more than 5:1.
 In Japanese Patent Publication (KOKOKU) No. 59-48768(1984), there are
 described (1) a process for producing an iron oxide pigment having a
 uniform particle size, which process comprises (i) stirring a ferrous
 carbonate suspension produced by adding an aqueous solution of a ferrous
 salt such as ferrous sulfate to an aqueous solution of carbonate such as
 sodium carbonate, for 2 to 4 hours under a non-oxidation condition, to
 obtain a fine colloid solution, and (ii) while adjusting a pH value of
 said ferrous carbonate colloid solution to 7 to 10, passing an
 oxygen-containing gas such as air through the solution to produce ferric
 oxide hydroxide, and (2) a process for producing an iron oxide pigment
 having a uniform particle size, which process comprises (i) producing a
 fine colloid solution by stirring a ferrous carbonate suspension produced
 by adding an aqueous solution of a ferrous salt such as ferrous sulfate to
 an aqueous solution of carbonate such as sodium carbonate, for 2 to 4
 hours under a non-oxidation condition; (ii) while adjusting a pH value of
 said ferrous carbonate colloid solution to 7 to 10, passing an
 oxygen-containing gas such as air through the solution to produce a
 precipitate of ferric oxide hydroxide; and (iii) after washing with water,
 filtering-out and drying, dehydrating said precipitate of ferric oxide
 hydroxide at a temperature of 250 to 500.degree. C.
 At the present time, it has been most strongly demanded to provide a fine
 red iron oxide pigment having as uniform a particle size as possible in
 order to enhance the dispersibility thereof in vehicles or resin
 compositions. However, such fine red iron oxide pigment which is uniform
 in both major axial diameter and minor axial diameter thereof, cannot be
 obtained yet.
 That is, in the above-mentioned known methods, as shown in Comparative
 Examples hereinafter, the fine goethite particles used as a starting
 material have failed to exhibit a sufficiently uniform particle size,
 especially a uniform minor axial diameter. Further, in the subsequent
 heat-dehydration process, the fine goethite particles tend to be sintered
 together due to the existence of ultrafine goethite particles mingled
 therein, so that the fine red iron oxide pigment obtained by the known
 methods has also failed to exhibit a uniform particle size, especially a
 uniform minor axial diameter.
 On the other hand, in European Patent No. 919522 A, there have been
 proposed acicular hematite particles comprising a geometrical standard
 deviation of major axis diameter of not more than 1.50, a geometrical
 standard deviation of minor axis diameter of not more than 1.35, a BET
 specific surface area of 35.9 to 150 m.sup.2 /g and an average major axis
 diameter of 0.004 to 0.295 .mu.m; and acicular hematite particles
 comprising a geometrical standard deviation of major axis diameter of not
 more than 1.50, a geometrical standard deviation of minor axis diameter of
 not more than 1.35, a BET specific surface area of 35.9 to 150 m.sup.2 /g
 and an average major axis diameter of 0.004 to 0.295 .mu.m. and containing
 aluminum within the particle in an amount of 0.05 to 50% by weight
 (calculated as Al) based on the weight of the acicular hematite particles.
 As a result of the present inventors' earnest studies, it has been found
 that in advance of a heat-dehydrating treatment of fine goethite particles
 at a temperature of 250 to 500.degree. C. to transform the fine goethite
 particles into fine hematite particles, by heat-treating the fine goethite
 particles at a temperature of 100 to 200.degree. C. to make the fine
 goethite particles absorb ultrafine goethite particles, the obtained
 hematite particles having a geometrical standard deviation of major axial
 diameter of not more than 1.5, a geometrical standard deviation of minor
 axial diameter of not more than 1.3 and an average major axial diameter of
 0.005 to 0.1 .mu.m are useful as a fine red iron oxide pigment which is
 excellent in transparency, and a paint or a resin composition obtained by
 using the fine red iron oxide pigment can also show an excellent
 transparency. The present invention has been attained on the basis of the
 finding.
 SUMMARY OF THE INVENTION
 It is an object of the present invention to provide a fine red iron oxide
 pigment which is uniform in both major axial diameter and minor axial
 diameter thereof, and exhibits an excellent transparency.
 It is another object of the present invention to provide a paint or a resin
 composition containing the fine red iron oxide pigment, which is excellent
 in transparency.
 To accomplish the aims, in a first aspect of the present invention, there
 is provided a fine red iron oxide pigment comprising hematite particles,
 and having a geometrical standard deviation of major axial diameter of not
 more than 1.5, a geometrical standard deviation of minor axial diameter of
 not more than 1.3 and an average major axial diameter of 0.005 to 0.1
 .mu.m.
 In a second aspect of the present invention, there is provided a fine red
 iron oxide pigment comprising hematite particles which contain aluminum
 inside of each particle of said pigment in an amount of 0.05 to 50% by
 weight, calculated as Al, based on the weight of said pigment, and having
 a geometrical standard deviation of major axial diameter of not more than
 1.5, a geometrical standard deviation of minor axial diameter of not more
 than 1.3 and an average major axial diameter of 0.005 to 0.1 .mu.m.
 In a third aspect of the present invention, there is provided a fine red
 iron oxide pigment comprising hematite particles which have at least one
 surface-coating material selected from the group consisting of a hydroxide
 of aluminum, an oxide of aluminum, a hydroxide of silicon and an oxide of
 silicon, on at least a part of the surface of each said pigment particle,
 and having a geometrical standard deviation of major axial diameter of not
 more than 1.5, a geometrical standard deviation of minor axial diameter of
 not more than 1.3 and an average major axial diameter of 0.005 to 0.1
 .mu.m.
 In a fourth aspect of the present invention, there is provided a process
 for producing a fine red iron oxide pigment, comprising:
 (i) heat-treating fine goethite particles at a temperature of 100 to
 200.degree. C. to allow ultrafine goethite particles to be absorbed into
 said fine goethite particles; and
 (ii) then heat-dehydrating said fine goethite particles at a temperature of
 250 to 500.degree. C. to transform said fine goethite particles into fine
 hematite particles.
 In a fifth aspect of the present invention, there is provided a process for
 producing a fine red iron oxide pigment, comprising:
 (i) heat-treating fine goethite particles containing aluminum inside
 thereof in an amount of 0.05 to 50% by weight, calculated as Al, based on
 the weight of the fine goethite particles, at a temperature of 100 to
 200.degree. C. to allow ultrafine goethite particles to be absorbed into
 said fine goethite particles; and
 (ii) then heat-dehydrating said fine goethite particles at a temperature of
 250 to 500.degree. C. to transform said fine goethite particles into fine
 hematite particles.
 In a sixth aspect of the present invention, there is provided a process for
 producing a fine red iron oxide pigment, comprising:
 (i) heat-treating fine goethite particles at a temperature of 100 to
 200.degree. C. to allow ultrafine goethite particles to be absorbed into
 said fine goethite particles;
 (ii) then heat-dehydrating said fine goethite particles at a temperature of
 250 to 500.degree. C. to transform said fine goethite particles into fine
 hematite particles; and
 (iii) treating the thus-obtained fine hematite particles with an aqueous
 solution containing an aluminum compound, a silicon compound or both an
 aluminum compound and a silicon compound, thereby coating the surfaces of
 the said hematite particles with an aluminum oxide, a silicon oxide, an
 aluminum hydroxide, a silicon hydroxide, or a mixture thereof.
 In a seventh aspect of the present invention, there is provided a paint
 comprising a paint base material and the fine red iron oxide pigment as
 set forth in any one of the first to third aspects.
 In an eighth aspect of the present invention, there is provided a rubber or
 resin composition comprising a rubber or resin base material and the fine
 red iron oxide pigment as set forth in any one of the first to third
 aspects.
 DETAILED DESCRIPTION OF THE INVENTION
 The present invention will now be described in detail below.
 First, the fine red iron oxide pigment according to the present invention
 is explained.
 The fine red iron oxide pigment according to the present invention,
 comprises fine hematite particles having a geometrical standard deviation
 of major axial diameter of not more than 1.5, a geometrical standard
 deviation of minor axial diameter of not more than 1.3 and an average
 major axial diameter of 0.005 to 0.1 .mu.m.
 When the geometrical standard deviation value of major axial diameter
 exceeds 1.5 and the geometrical standard deviation value of minor axial
 diameter exceeds 1.3, it may become difficult to uniformly disperse the
 fine red iron oxide pigment in vehicles or resin compositions because
 coarse particles are present in the dispersion. As a result, a coating
 film and a resin composition obtained by using the pigment may fail to
 show a sufficient transparency. In the consideration of the dispersibility
 in vehicles or resin compositions and the transparency of the obtained
 coating film or resin compositions, the geometrical standard deviation
 value of major axial diameter is preferably not more than 1.48, more
 preferably not more than 1.43, and the geometrical standard deviation
 value of minor axial diameter is preferably not more than 1.28, more
 preferably not more than 1.25. Under the consideration of the industrial
 productivity, the lower limit of the geometrical standard deviation value
 of major axial diameter and geometrical standard deviation value of minor
 axial diameter are 1.01, respectively.
 When the average major axial diameter of the fine red iron oxide pigment
 particles is less than 0.005 .mu.m, since an intermolecular force between
 the particles is increased due to the reduction of particle size thereof,
 it may become difficult to uniformly disperse the pigment in vehicles or
 resin compositions. As a result, a coating film or a resin composition
 obtained by using the fine red iron oxide pigment may fail to show a
 sufficient transparency. On the other hand, when the average major axial
 diameter is more than 0.1 .mu.m, although the dispersibility in vehicles
 or resin compositions is good, the pigment particles may be too coarse, so
 that a tinting strength of the pigment may be considerably increased. As a
 result, the coating film or the resin composition obtained by using the
 pigment no longer may show a sufficient transparency.
 In the consideration of the dispersibility in vehicles or resin
 compositions and the transparency of the obtained coating film or resin
 composition, the average major axial diameter of the fine red iron oxide
 pigment according to the present invention, is preferably 0.01 to 0.09
 .mu.m, more preferably 0.01 to 0.08 .mu.m.
 The average minor axial diameter of the fine red iron oxide pigment
 particles according to the present invention is preferably 0.0025 to 0.05
 .mu.m, more preferably 0.005 to 0.045 .mu.m, still more preferably 0.05 to
 0.04 .mu.m.
 When the average minor axial diameter of the fine red iron oxide pigment
 particles is less than 0.0025 .mu.m, since an intermolecular force between
 the particles is increased due to the reduction of particle size thereof,
 it may become difficult to uniformly disperse the pigment in vehicles or
 resin compositions. As a result, a coating film or a resin composition
 obtained by using the fine red iron oxide pigment may fail to show a
 sufficient transparency.
 The fine red iron oxide pigment according to the present invention, further
 has an aspect ratio (average major axial diameter/average minor axial
 diameter) of preferably not more than 20:1, more preferably not more than
 15:1, still more preferably not more than 10:1; and a BET specific surface
 area of preferably 40 to 250 m.sup.2 /g, more preferably 50 to 220 m.sup.2
 /g, still more preferably 70 to 200 m.sup.2 /g. The lower limit of the
 aspect ratio is preferably 2:1.
 When the aspect ratio is more than 20:1, the pigment particles may be
 entangled or intertwined with each other, so that the dispersibility of
 the pigment in vehicles or resin compositions tends to be deteriorated and
 the viscosity of the pigment tends to be increased. As a result, the
 obtained coating film or resin composition may fail to show a sufficient
 transparency.
 When the BET specific surface area of the fine red iron oxide pigment
 particles is more than 250 m.sup.2 /g, since an intermolecular force
 between the particles is increased due to the reduction of particle size
 thereof, it becomes difficult to uniformly disperse the pigment in
 vehicles or resin compositions. As a result, a coating film or a resin
 composition obtained by using the fine red iron oxide pigment may fail to
 show a sufficient transparency. On the other hand, when the BET specific
 surface area is less than 40 m.sup.2 /g, the pigment particles are too
 coarse. As a result, the coating film or the resin composition obtained by
 using the pigment no longer shows a sufficient transparency.
 The fine red iron oxide pigment particle according to the present invention
 may contain aluminum inside of each particle in an amount of 0.05 to 50%
 by weight (calculated as Al). The aluminum-containing fine red iron oxide
 pigment are more excellent in transparency of particles themselves, as
 compared to those containing no aluminum inside thereof, and a resin
 composition obtained by using such an aluminum-containing fine red iron
 oxide pigment can exhibit an improved aging resistance.
 When the amount of aluminum contained inside of each pigment particle is
 less than 0.05% by weight based on the weight of the fine red iron oxide
 pigment, the effects of improving the transparency and the aging
 resistance may not be obtained. On the other hand, when the amount of
 aluminum contained inside is more than 50% by weight, the obtained fine
 red iron oxide pigment can show a sufficient transparency and a sufficient
 aging resistance. However, since the aimed effects of the present
 invention are already saturated, the use of such a large amount of
 aluminum is unnecessary and meaningless. In the consideration of the above
 effects of improving the transparency and the aging resistance of the
 obtained fine red iron oxide pigment as well as the productivity thereof,
 the amount of aluminum contained inside of each particle of the fine red
 iron oxide pigment is preferably 0.1 to 40% by weight (calculated as Al)
 based on the weight of the fine red iron oxide pigment.
 It is preferred that the aluminum contained inside of the fine red iron
 oxide pigment, be substantially homogeneously distributed from a central
 portion to a surface of each pigment particle.
 The fine red iron oxide pigment particles containing aluminum inside
 thereof according to the present invention, may be substantially the same
 in particle size, geometrical standard deviation of major axis diameter,
 geometrical standard deviation of minor axis diameter, aspect ratio and
 BET specific surface area as those of the fine red iron oxide pigment
 containing no aluminum inside thereof according to the present invention.
 At least a part of the surface of the fine red iron oxide pigment particle
 according to the present invention, may be coated with at least one
 surface-coating material selected from the group consisting of a hydroxide
 of aluminum, an oxide of aluminum, a hydroxide of silicon and an oxide of
 silicon. The fine red iron oxide pigment particle coated with the
 surface-coating material, can be further enhanced in dispersibility in
 vehicles or resin compositions as compared to that of the fine red iron
 oxide pigment which is not coated with the surface-coating material. In
 addition, the resin composition obtained by using such a fine red iron
 oxide pigment coated with the surface-coating material is more excellent
 in aging resistance, as compared to that of the resin composition obtained
 by using the fine red iron oxide pigment which is not coated with the
 surface-coating material.
 The amount of the surface-coating material on the surface of the fine red
 iron oxide pigment particle is preferably 0.01 to 20% by weight
 (calculated as Al, SiO.sub.2 or both Al and SiO.sub.2) based on the weight
 of the fine red iron oxide pigment. When the amount of the surface-coating
 material is less than 0.01% by weight, the effects of improving the
 dispersibility and the aging resistance may not be obtained. On the other
 hand, when the amount of the surface-coating material is more than 20% by
 weight, although sufficient effects of improving the dispersibility and
 the aging resistance can be obtained, the effects are already saturated
 and, therefore, the use of such a large amount of the surface-coating
 material is unnecessary and meaningless. In the consideration of the
 effects of improving the dispersibility of the obtained fine red iron
 oxide pigment and the aging resistance of the resin composition obtained
 by using such a pigment as well as the productivity of the fine red iron
 oxide pigment, the amount of the surface-coating material is more
 preferably 0.05 to 15% by weight (calculated as Al, SiO.sub.2 or both Al
 and SiO.sub.2) based on the weight of the fine red iron oxide pigment.
 The fine red iron oxide pigment particles coated with the surface-coating
 material according to the present invention, are substantially the same in
 particle size, geometrical standard deviation of major axis diameter,
 geometrical standard deviation of minor axis diameter, aspect ratio and
 BET specific surface area, as those of the fine red iron oxide pigment
 according to the present invention which are not coated with the
 surface-coating material.
 Next, the process for producing the fine red iron oxide pigment particles
 according to the present invention is described.
 That is, fine goethite particles produced by passing an oxygen-containing
 gas such as air through a suspension containing an iron-containing
 precipitate obtained by reacting a ferrous salt with either an aqueous
 alkali hydroxide solution, an aqueous alkali carbonate solution, or an
 aqueous alkali hydroxide and alkali carbonate solution, are previously
 heat-treated at a temperature of usually 100 to 200.degree. C., and then
 are heat-dehydrated at a temperature of usually 250 to 500.degree. C.,
 thereby producing the fine red iron oxide pigment.
 The fine goethite particles used as a starting material in the present
 invention, usually have a geometrical standard deviation of major axial
 diameter of usually not more than 1.8, a geometrical standard deviation of
 minor axial diameter of usually not more than 1.7, an average major axial
 diameter of usually 0.005 to 0.1 .mu.m and an average minor axial diameter
 of usually 0.0025 to 0.05 .mu.m.
 When the heat-treating temperature is less than 100.degree. C., it may be
 difficult to make the fine goethite particles sufficiently absorb
 ultrafine goethite particles (average particle size: usually not more than
 0.001 .mu.m), especially it may be difficult to obtain particles having a
 uniform minor axial diameter. On the other hand, when the heat-treating
 temperature is more than 200.degree. C., the dehydration of the fine
 goethite particles is initiated even under such a condition that the
 ultrafine goethite particles are still remains therein. For this reason,
 the sintering between particles tend to be caused, so that it may be
 difficult to obtain particles having a uniform particle size, especially a
 uniform minor axial diameter. The heat-treating temperature is preferably
 in the range of 120 to 200.degree. C.
 The heat-treating time is preferably 5 to 60 minutes.
 The fine goethite particles obtained by heat-treating at a temperature of
 usually 100 to 200.degree. C., can show a geometrical standard deviation
 of major axial diameter of usually not more than 1.5, a geometrical
 standard deviation of minor axial diameter of usually not more than 1.3,
 an average major axial diameter of usually 0.005 to 0.1 pm and an average
 minor axial diameter of usually 0.0025 to 0.05 pm.
 When the heat-dehydrating temperature is less than 250.degree. C., the
 dehydration reaction may require a long period of time. On the other hand,
 when the heat-dehydrating temperature is more than 500.degree. C., the
 dehydration reaction too rapidly proceeds, so that the obtained particles
 tend to show a broken or inappropriate particle shape, or the sintering
 between particles tends to be caused.
 Meanwhile, the fine red iron oxide pigment containing aluminum inside
 thereof according to the present invention may be produced as follows.
 That is, in the production reaction of the fine goethite particles, an
 aluminum compound is caused to exist in the reaction system in advance of
 passing the oxygen-containing gas such as air therethrough, thereby
 obtaining fine goethite particles containing aluminum inside thereof in a
 substantially homogeneous state. Successively, the thus obtained fine
 goethite particles homogeneously containing aluminum inside thereof are
 heat-treated at a temperature of usually 100 to 200.degree. C. and then
 heat-dehydrated at a temperature of usually 250 to 500.degree. C., thereby
 producing the aimed fine red iron oxide pigment containing aluminum inside
 thereof.
 The aluminum compound may be added to either the aqueous ferrous salt
 solution, any of the aqueous alkali solutions, or the water suspension
 containing the iron- containing precipitate before passing the
 oxygen-containing gas such as air therethrough. Among them, it is
 preferred that the aluminum compound be added to the aqueous ferrous salt
 solution.
 As the aluminum compounds added, there may be exemplified alkali aluminates
 such as sodium aluminate; aluminum salts such as aluminum sulfate,
 aluminum chloride, aluminum acetate, aluminum nitrate, or the like.
 The amount of the aluminum compound added is preferably 0.5 to 350 mol %
 (calculated as Al) based on Fe contained in the aqueous ferrous salt
 solution. When the amount of the aluminum compound added is less than 0.5
 mol %, the aimed effects of the present invention, i.e., the effects of
 improving the transparency and the aging resistance may not be obtained.
 On the other hand, when the amount of the aluminum compound added is more
 than 350 mol %, the aimed effects of the present invention are already
 almost saturated and, therefore, the addition of such a large amount of
 the aluminum compound is unnecessary and meaningless.
 In accordance with the present invention, as described above, at least a
 part of the surface of the fine red iron oxide pigment particle may be
 coated with at least one surface-coating material selected from the group
 consisting of a hydroxide of aluminum, an oxide of aluminum, a hydroxide
 of silicon and an oxide of silicon.
 In this case, the amount of an aluminum compound added is usually 0.01 to
 20% by weight (calculated as Al) based on the weight of the fine red iron
 oxide pigment. When the amount of the aluminum compound added is less than
 0.01% by weight, it may be difficult to coat the surface of the fine red
 iron oxide pigment with the hydroxide of aluminum or oxide of aluminum in
 an amount sufficient to obtain the effects of improving the dispersibility
 and the aging resistance. On the other hand, when the amount of the
 aluminum compound added is more than 20% by weight, since the coating
 effects are already saturated, it is unnecessary and meaningless to add
 such a large amount of the aluminum compound.
 The amount of a silicon compound added is usually 0.01 to 20% by weight
 (calculated as SiO.sub.2) based on the weight of the fine red iron oxide
 pigment. When the amount of the silicon compound added is less than 0.01%
 by weight, it may be difficult to cover the surface of the fine red iron
 oxide pigment with the hydroxide of silicon or oxide of silicon in an
 amount sufficient to obtain the effects of improving the dispersibility
 and the aging resistance. On the other hand, when the amount of the
 silicon compound added is more than 20% by weight, since the coating
 effects are already saturated, it is unnecessary and meaningless to add
 such a large amount of the silicon compound.
 In the case where both the aluminum compound and the silicon compound are
 used, the total amount of these compounds added is preferably 0.01 to 20%
 by weight (calculated as Al and SiO.sub.2) based on the weight of the fine
 red iron oxide pigment.
 Next, the paint using the fine red iron oxide pigment according to the
 present invention, will now be described in detail.
 The solvent-based paint using the fine red iron oxide pigment according to
 the present invention, has a gloss of usually not less than 80%,
 preferably not less than 85%, still more preferably 90 to 150%, when
 formed into a coating film. As to the transparency of the coating film,
 the linear absorption thereof is usually not more than 0.1 .mu.m.sup.-1,
 preferably not more than 0.09 .mu.m.sup.-1, still more preferably 0.01 to
 0.085 .mu.m.sup.-1.
 The water-based paint using the fine red iron oxide pigment according to
 the present invention, has a gloss of usually not less than 75%,
 preferably not less than 80%, still more preferably 85 to 150%, when
 formed into a coating film. As to the transparency of the coating film,
 the linear absorption thereof is usually not more than 0.15 .mu.m.sup.-1,
 preferably not more than 0.1 .mu.m.sup.-1, still more preferably 0.01 to
 0.09 .mu.m.sup.-1.
 As to the blending ratio of the fine red iron oxide pigment according to
 the present invention to a paint base material, the fine red iron oxide
 pigment may be used in an amount of usually 0.5 to 100 parts by weight
 based on 100 parts by weight of the paint base material. In the
 consideration of handling property of the paint, the amount of the fine
 red iron oxide pigment blended is preferably 1.0 to 80 parts by weight,
 more preferably 1.0 to 50 parts by weight based on 100 parts by weight of
 the paint base material.
 The paint base material is composed of a resin and a solvent, and may
 further contain, a defoamer, an extender pigment, a drying agent, a
 surfactant, a hardner, an auxiliary agent and the like.
 Examples of the resins may include those ordinarily used for solvent-based
 paints such as acrylic resins, alkyd resins, polyester resins,
 polyurethane resins, epoxy resins, phenol resins, melamine resins, amino
 resins or the like.
 Examples of the resins may include those ordinarily used for water-based
 paints such as water-soluble alkyd resins, water-soluble melamine resins,
 water-soluble acrylic resins, water-soluble urethane resins, water-soluble
 epoxy resins, acrylic emulsion resin, urethane emulsion resins, acrylic
 styrene emulsion resins, epoxy emulsion resins, vinyl acetate emulsion
 resins or the like.
 Examples of the solvents may include those ordinarily used for
 solvent-based paints such as toluene, xylene, butyl acetate, methyl
 acetate, methyl isobutyl ketone, butyl cellosolve, ethyl cellosolve, butyl
 alcohol, aliphatic hydrocarbons or the like.
 Examples of the solvents may include those ordinarily used for water-based
 paints water and butyl cellosolve, ethyl cellosolve, propylene glycol
 monomethyl ether, methyl cellosolve acetate, butoxyethyl acetate,
 ethoxyethanol, hexoxyethanol, methyl ethyl ketone, phenyl glycol ether,
 ethanol, butyl alcohol, butoxyethanol, propanol, propoxypropanol or the
 like.
 As the defoamers, there may be used commercially available products such as
 NOPCO 8034 (tradename), SN-DEFOAMER 477 (tradename), SN-DEFOAMER 5013
 (tradename), SN-DEFOAMER 382 (tradename) or SN-DEFOAMER 247 (tradename)
 (all produced by San-Nopco Co., Ltd.); ANTIFOAM 08 (tradename) or EMULGEN
 903 (tradename) (all produced by Kao Co., Ltd.); or the like.
 The paint according to the present invention can be produced by blending
 the fine red iron oxide pigment according to the present invention and the
 above-mentioned paint base material in specific weight ratios by a
 commonly used mixer such as ball mill, roll mill, homomixer, shaker,
 attritor or sand grinder.
 Next, the resin composition using the fine red iron oxide pigment according
 to the present invention, is described.
 As to the transparency of the resin composition using the fine red iron
 oxide pigment according to the present invention, the linear absorption
 thereof is usually not more than 0.15 .mu.m.sup.-1, preferably not more
 than 0.10 .mu.m.sub.-1, more preferably 0.03 to 0.095 .mu.m.sup.-1. In
 addition, the resin composition has a dispersing condition of usually not
 less than 3, preferably not less than 4, more preferably 5 when evaluated
 by such a method as defined in Examples hereinafter.
 Further, the resin composition using the fine red iron oxide pigment
 particles containing aluminum inside thereof and the fine red iron oxide
 pigment particles whose at least a part of the particle surface is coated
 with the surface-coating material according to the present invention, can
 exhibit such a transparency that the linear absorption thereof is usually
 not more than 0.1 .mu.m.sup.-1, preferably not more than 0.095
 .mu.m.sup.-1, more preferably 0.03 to 0.093 .mu.m.sup.-1 and a dispersion
 condition of not less than 4, preferably 5, when evaluated by such a
 method as defined in Examples hereinafter.
 In addition, as to the aging resistance, the resin composition using the
 fine red iron oxide pigment particles according to the present invention,
 shows S.sub.A (%) (=S/S.sub.0.times.100; a percentage of discolored area
 (S) to total area (S.sub.0) of colored resin plate, when evaluated by such
 a method as defined in Examples hereinafter) of usually more than 10% when
 heated for 10 minutes. Whereas, the aging resistance of the resin
 composition using the fine red iron oxide pigment particles containing
 aluminum inside thereof and the fine red iron oxide pigment particles
 whose at least a part of the particle surface is coated with the
 surface-coating material according to the present invention, can be
 increased up S.sub.A (%) (=S/S.sub.0 =100; a percentage of discolored area
 (S) to total area (S.sub.0) of colored resin plate, when evaluated by such
 a method as defined in Examples hereinafter) of usually not more than 10%
 even after heated for 90 minutes.
 The amount of the fine red iron oxide pigment blended in the resin
 composition according to the present invention is usually 0.01 to 50 parts
 by weight based on 100 parts by weight of resins. In the consideration of
 handling property of the resin composition, the amount of the fine red
 iron oxide pigment blended is preferably 0.05 to 45 parts by weight, more
 preferably 0.1 to 40 parts by weight based on 100 parts by weight of
 resins.
 As the resins used in the resin composition, there may be exemplified
 natural rubbers, synthetic rubbers, thermoplastic resins such as polyvinyl
 chloride, polyolefins such as polyethylene, polypropylene or the like,
 styrene polymers, polyamides, or the like. The resin composition may
 contain, additives such as a lubricant, a plasticizer, an anti-oxidizing
 agent, an ultraviolet light absorber or various other stabilizers.
 The additives may be added in an amount of usually not more than 50% by
 weight based on the total weight of the fine red iron oxide pigment and
 the resins. When the amount of the additives added is more than 50% by
 weight, the resin composition is deteriorated in moldability.
 The resin composition according to the present invention may be produced by
 intimately mixing a resin and the fine red iron oxide pigment together in
 advance and then applying-a strong shear force to the resultant mixture by
 a kneader or an extruder while heating, in order to deaggregate aggregates
 of the fine red iron oxide pigment and uniformly disperse the fine red
 iron oxide pigment in the resin composition. The thus obtained resin
 composition may be formed into an appropriate shape upon use according to
 the applications thereof.
 The feature of the present invention lies in such a fact that when fine
 goethite particles are previously heat-treated at a temperature of usually
 100 to 200.degree. C., it is possible to obtain fine goethite particles
 having not only a uniform major axial diameter but also a uniform minor
 axial diameter.
 The reason why the fine red iron oxide pigment having a uniform particle
 size can be obtained according to the present invention, is considered as
 follows. That is, since ultrafine goethite particles are absorbed into the
 fine goethite particles, the amount of ultrafine goethite particles is
 considerably reduced. Further, since the obtained fine goethite particles
 show not only a uniform major axial diameter but also a uniform minor
 axial diameter as well as less content of ultrafine goethite particles,
 the sintering between the particles during the subsequent heat-dehydration
 treatment due to the existence of ultrafine goethite particles can be
 effectively prevented. As a result, it is possible to obtain fine hematite
 particles which can sufficiently retain or inherit the uniform particle
 size of the fine goethite particles.
 The fine red iron oxide pigment composed of fine hematite particles having
 a geometrical standard deviation of major axial diameter of usually not
 more than 1.5 and a geometrical standard deviation of minor axial diameter
 usually of not more than 1.3, can show not only a uniform major axial
 diameter but also a uniform minor axial diameter, resulting in enhancement
 of dispersibility in vehicles or resin compositions. Further, the coating
 film and the resin composition obtained by using such a fine red iron
 oxide pigment are excellent in dispersibility and transparency.
 The reason why the fine red iron oxide pigment according to the present
 invention can show an improved dispersibility, is considered as follows.
 That is, since the obtained fine hematite particles having a geometrical
 standard deviation of major axial diameter of usually not more than 1.5
 and a geometrical standard deviation of minor axial diameter of usually
 not more than 1.3, are uniform particles containing less amounts of coarse
 particles and ultrafine particles, it is considered that the fine red iron
 oxide pigment composed of such fine hematite particles can show an
 improved dispersibility in vehicles or resin compositions.
 The reason why the paint and the resin composition obtained by using the
 fine red iron oxide pigment according to the present invention can show an
 improved transparency, is considered as follows. That is, the fine red
 iron oxide pigment can show an excellent dispersibility in vehicles or
 resin compositions since the pigment is composed of particles having an
 excellent dispersibility. For this reason, it is considered that the
 coating film or the resin composition obtained by using the fine red iron
 oxide pigment is free from aggregated particles and coarse particles.
 The reason why the resin composition obtained by using the fine red iron
 oxide pigment containing aluminum inside of each pigment particle
 according to the present invention can show an excellent aging resistance,
 is considered as follows. That is, the catalytic effect of hematite
 particles by which the resin composition tends to be aged or deteriorated,
 can be suppressed by the aluminum contained inside of each pigment
 particle. Further, since the fine red iron oxide pigment containing
 aluminum inside of each particle thereof is highly dispersed and mixed in
 the resin composition due to the excellent dispersibility thereof, the
 pigment can exhibit an excellent light- or heat-insulating effect. For
 this reason, the obtained resin composition can be effectively prevented
 from being adversely affected by light or heat.
 The fine red iron oxide pigment according to the present invention, has not
 only a uniform major axial diameter but also a uniform minor axial
 diameter and, therefore, are excellent in transparency. Accordingly, the
 fine red iron oxide pigment according to the present invention is suitable
 as a transparent red pigment.
 Further, the paint or the resin composition obtained by using the fine red
 iron oxide pigment according to the present invention can also show an
 excellent transparency due to the uniformity in particle size and the
 excellent transparency of the pigment.

EXAMPLES
 The present invention will now be described in more detail with reference
 to the following examples and comparative examples, but the present
 invention is not restricted to those examples and various modifications
 are possible within the scope of the invention.
 The properties in the examples were measured by the following methods.
 (1) The average major axial diameter and average minor axial diameter of
 particles are respectively expressed by the average values obtained by
 measuring major axial diameters and minor axial diameters of about 350
 particles which were sampled from a micrograph obtained by magnifying an
 electron micrograph (.times.30,000) four times in each of the longitudinal
 and transverse directions.
 (2) The aspect ratio of particles is a ratio of the average major axial
 diameter to the average minor axial diameter thereof.
 (3) The geometrical standard deviation values of major axial diameter and
 minor axial diameter of particles are respectively expressed by the values
 obtained by the following method. That is, the major axial diameter and
 minor axial diameter of the particles were respectively measured from the
 above magnified electron micrograph. The actual major axial diameter and
 minor axial diameter and the number of the particles were respectively
 calculated from the measured values. On a logarithmic normal probability
 paper, the major axial diameter and minor axial diameter were respectively
 plotted at regular intervals on the abscissa-axis and the accumulative
 number (under integration sieve) of particles belonging to each interval
 of the major axial diameter and minor axial diameter were respectively
 plotted by percentage on the ordinate-axis by a statistical technique. The
 values of the major axial diameter and minor axial diameter corresponding
 to the accumulative number of particles of 50% and 84.13%, respectively,
 were read from the graph, and the geometrical standard deviation was
 calculated from the following formula:
 Geometrical standard deviation=
 {major axial diameter or minor axial diameter corresponding to 84.13% under
 integration sieve}/{major axial diameter or minor axial diameter
 (geometrical average diameter) corresponding to 50% under integration
 sieve}
 The closer to 1 the geometrical standard deviation value, the more
 excellent the particle size distribution of the particles.
 (4) The specific surface area is expressed by the value measured by a BET
 method.
 (5) The amounts of Al and Si contained in particles were measured by a
 fluorescent X-ray spectroscopy device "3063M Model" (manufactured by
 Rigaku Denki Kogyo Co., Ltd.) according to JIS K0119 "General rule of
 fluorescent X-ray analysis".
 (6) The transparency of a coating film or a resin composition using the
 fine red iron oxide pigment, is expressed by a linear absorption
 coefficient calculated from a measured light transmittance of a coating
 film obtained by coating a 100 gm-thick clear base film with a paint
 prepared by the method described hereinafter, or a measured light
 transmittance of a resin plate having the below-mentioned composition,
 according to the following formula. The respective light transmittances
 were measured by a self-recording photoelectric spectrophotometer
 "IIU-2100" (manufactured by Simazu Seisakusho Co., Ltd.).
 Linear absorption coefficient (.mu.m.sup.-1)=ln(1/t)/FT
 wherein t represents a light transmittance (-) at.lambda.=900 nm.
 The smaller the linear absorption coefficient, the more easily the light
 transmits through the coating film or the resin composition, i.e., the
 higher the transparency.
 (7) The aging resistance (S.sub.A (%)) is determined by the following
 method. That is, a colored resin plate (1.5 cm in length.times.1.5 cm in
 width.times.1 mm in thickness) having the below-mentioned composition in
 which the fine red iron oxide pigment was kneaded, was heated at
 190.degree. C., and the S.sub.A (%) was obtained at intervals of 5% from
 the following formula.
EQU S.sub.A (%)=(S/S.sub.0).times.100
 Wherein S represents an area where the resin was discolored and
 deteriorated after heating, S.sub.0 represents a whole area (1.5
 cm.times.1.5 cm=2.25 cm.sup.2) of the colored resin plate before heating.
 Namely, the condition that the S.sub.A (%) is 0%, denotes that the colored
 resin plate suffers from no deterioration, while the condition that the
 S.sub.A (%) is 100%, denotes that the colored resin plate is completely
 deteriorated.
 (8) The dispersibility in vehicle was determined by measuring the gloss on
 a coating surface of a coating film obtained by using a paint prepared by
 the below-mentioned method.
 More specifically, the gloss was obtained by measuring the 20.degree. C.
 gloss using a glossmeter UGV-5D (manufactured by Suga Shikenki Co., Ltd.).
 The higher the gloss, the more excellent the dispersibility of the fine
 red iron oxide pigment particles in vehicle.
 (9) The paint viscosity is expressed by the value obtained by measuring the
 viscosity (at 25.degree. C.) of a paint preparing by the below-mentioned
 method, at a shear rate (D) of 1.92 sec.sup.-1 using an E-type viscometer
 (cone plate-type viscometer) EMD-R (manufactured by Tokyo Keiki Co.,
 Ltd.).
 (10) The dispersibility in resin composition was evaluated by visually
 counting the number of undispersed aggregate particles on the surface of
 the obtained resin composition, and classifying the results into the
 following five ranks. The 5th rank represents the most excellent
 dispersing condition.
 Rank 5: No undispersed aggregate particles were recognized;
 Rank 4: 4 undispersed aggregate particles per 1 cm.sup.2 were recognized;
 Rank 3: 9 undispersed aggregate particles per 1 cm.sup.2 were recognized;
 Rank 2: 10 to 49 unidispersed aggregate particles per 1 cm.sup.2 were
 recognized; and
 Rank 1: not less than 50 undispersed aggregate particles per 1 cm.sup.2
 were recognized.
 Example 1
 &lt;Production of Fine Red Iron Oxide Pigment&gt;
 A slurry of acicular fine goethite particles obtained by using an aqueous
 ferrous sulfate solution and an aqueous sodium carbonate solution, was
 filtered using a filter press, and then the obtained filter cake was
 sufficiently washed with water while passing water therethrough.
 The obtained wet cake was dried at 120.degree. C. for 24 hours, and then
 pulverized by a free crusher (M-2 model, manufactured by Nara KikeLi
 Seisakusho Co., Ltd.), thereby obtaining fine goethite particles. The
 obtained fine goethite particles had an average major axial diameter of
 0.0688 .mu.m, a geometrical standard deviation value of major axial
 diameter of 1.33, an average minor axial diameter of 0.0101 .mu.m, a
 geometrical standard deviation value of minor axial diameter of 1.28, an
 aspect ratio of 6.8:1 and a BET specific surface area value of 165.3
 m.sup.2 /g.
 The obtained fine goethite particles were charged into a metallic
 heat-treatment furnace, and heat-treated therein at 150.degree. C. for 30
 minutes, thereby allowing ultrafine goethite particles to be absorbed into
 the fine goethite particles.
 Successively, the obtained fine goethite particles were charged again into
 the metallic heat-treatment furnace, and then heat-dehydrated therein at
 340.degree. C. for 30 minutes, thereby obtaining a fine red iron oxide
 pigment. The obtained fine red iron oxide pigment had an average major
 axial diameter of 0.0620 .mu.m, a geometrical standard deviation value of
 major axial diameter of 1.33, an average minor axial diameter of 0.0108
 .mu.m, a geometrical standard deviation value of minor axial diameter of
 1.15, an aspect ratio of 5.7:1 and a BET specific surface area value of
 143.8 m.sup.2 /g.
 Example 2
 &lt;Production of Solvent-Based Paint Using Fine Red Iron Oxide Pigment&gt;
 5.0 g of the fine red iron oxide pigment obtained in Example 1, and other
 paint components shown below were charged into a 250-ml glass bottle.
 These components were intimately mixed and dispersed together with 160 g
 of 3 mm.phi. glass beads by a paint shaker for 120 minutes, thereby
 preparing a mill base.
 Composition of Solvent-Based Paint:

Fine red iron oxide pigment 9.9 parts by weight
 Melamine resin (SUPER-PECKAMINE 19.8 parts by weight
 J-820-60 (tradename) produced by
 Dai-Nippon Ink Kagaku Kogyo Co.,
 Ltd.)
 Alkyd resin (BEKKOSOL 1307-60EL 39.6 parts by weight
 (tradename) produced by Dai-Nippon
 Ink Kagaku Kogyo Co., Ltd.)
 Xylene 29.7 parts by weight
 Butanol 1.0 part by weight
 The viscosity of the obtained solvent-based paint was 2,304 cP.
 The thus obtained paint was applied onto a transparent glass plate (having
 a size of 0.8 mm (thickness).times.70 mm (width).times.150 mm (length))
 and then dried, thereby obtaining a coating film thereon. The obtained
 coating film had a gloss of 93% and a linear absorption of 0.0528
 .mu.m.sup.-1.
 Examples 3
 &lt;Production of Water-Based Paint Using Fine Red Iron Oxide Pigment&gt;
 5.0 g of the fine red iron oxide pigment particles obtained in Example 1
 were mixed with a water-soluble alkyd resin, etc., at the below-specified
 ratio. The mixture was added along with 160 g of 3 mm.phi. glass beads
 into a 250-ml glass bottle, and intimately mixed and dispersed together
 with by a paint shaker for 90 minutes, thereby producing a mill base.
 Composition of Mill Base:

Fine red iron oxide pigment 9.9 parts by weight
 particles
 Water-soluble alkyd resin 19.8 parts by weight
 (Tradename: S-118 produced
 by Dai-Nippon Ink Kagaku
 Co., Ltd.)
 Defoamer (Tradename: NOPCO 8034 0.5 part by weight
 produced by San-Nopco
 Co., Ltd.)
 Water 7.3 parts by weight
 Butyl Cellosolve 6.2 parts by weight
 The thus obtained mill base and other components shown below were blended
 together at the below-specified ratio, and further intimately mixed and
 dispersed together by a paint shaker for 15 minutes, thereby producing a
 water-based paint.
 Composition of Water-Based Paint:

Mill base 43.7 parts by weight
 Water-soluble alkyd resin 28.6 parts by weight
 (Tradename: S-118 produced
 by Dai-Nippon Ink Kagaku
 Co., Ltd.)
 Water-soluble melamine 11.0 parts by weight
 resin (Tradename: S-695
 produced by Dai-Nippon
 Ink Kagaku Co., Ltd.)
 Defoamer (Tradename: NOPCO 0.5 part by weight
 8034 produced by
 San-Nopco Co., Ltd.)
 Water 13.8 parts by weight
 Butyl Cellosolve 2.4 parts by weight
 The thus obtained water-based paint had a viscosity of 2,048 cP.
 Next, the water-based paint was applied onto a transparent glass plate
 (having a size of 0.8 mm.times.70 mm.times.150 mm) and then dried, thereby
 obtaining a coating film thereon. The obtained coating film had a gloss of
 88% and a linear absorption of 0.0852 .mu.m.sup.-1.
 Example 4
 &lt;Production of Resin Composition Using Red Iron Oxide Pigment&gt;
 0.5 g of the fine red iron oxide pigment obtained in Example 1 and 49.5 g
 of polyvinyl chloride resin particles (103EP8D (tradename), produced by
 Nippon Zeon Co., Ltd.) were weighed, charged into a 100 ml beaker and
 intimately mixed together by a spatula, thereby obtaining mixed particles.
 The thus obtained mixed particles were mixed with 1.0 g of calcium
 stearate. The mixture was then gradually fed to hot rolls which were
 heated at 160.degree. C. and whose clearance was set to 0.2 mm, and
 continuously kneaded together until a uniform resin composition was
 obtained. Thereafter, the obtained resin composition was separated from
 the hot rolls, and used as a raw material for a colored resin plate.
 Successively, the resin composition was interposed between surface-polished
 stainless steel plates, placed in a hot press heated to 180.degree. C.,
 and pressure-molded therein while applying a pressing force of 1
 ton/cm.sup.2 thereto, thereby producing a colored resin plate having a
 thickness of 1 mm. The obtained colored resin plate had a linear
 absorption of 0.0853 .mu.m.sup.-1 and a dispersing condition of 4.
 &lt;Fine Goethite Particles 1 to 5&gt;
 As fine goethite particles as a starting material, there were prepared fine
 goethite particles 1 to 5 as shown in Table 1.
 Incidentally, fine goethite particles containing aluminum inside thereof
 were produced by using aluminum compounds shown in Table 1.
 &lt;Fine Goethite Particles 6 to 13 and Fine Hematite Particles 1&gt;
 The same heat-treating procedure as defined in Example 1 was conducted
 except that kind of fine goethite particles to be treated, heat-treating
 temperature and heat-treating time were changed variously.
 The main production conditions and various properties of the obtained
 heat-treated fine goethite particles and fine hematite particles are shown
 in Table 2.
 Examples 5 to 10
 The same procedure as defined in Example 1 was conducted except that kind
 of the fine goethite particles to be heat-treated, heat-dehydration
 temperature and heat-dehydration time were changed variously, thereby
 obtaining a fine red iron oxide pigment.
 The main production conditions and various properties of the obtained fine
 red iron oxide pigment are shown in Table 3.
 Comparative Example 1
 The same procedure as defined in Example 1 was conducted except that the
 fine goethite particles 1 were heat-dehydrated at 370.degree. C. for 60
 minutes without the preceding heat-treatment of the fine goethite
 particles, thereby obtaining a red iron oxide pigment.
 The production conditions and various properties of the obtained red iron
 oxide pigment are shown in Table 3.
 Comparative Example 2
 The same procedure as defined in Example 1 was conducted except that the
 fine goethite particles 12 were heat-treated at 80.degree. C. for 60
 minutes, and then heat-dehydrated at 340.degree. C. for 45 minutes.
 The production conditions and various properties of the obtained red iron
 oxide pigment are shown in Table 3.
 Comparative Example 3
 The same procedure as defined in Example 1 was conducted except that the
 fine goethite particles were successively heat-dehydrated at 310.degree.
 C. for 60 minutes and then at 340.degree. C. for 45 minutes without the
 preceding heat-treatment of the fine goethite particles.
 The production conditions and various properties of the obtained red iron
 oxide pigment are shown in Table 3.
 Comparative Example 4
 The same procedure as defined in Example 1 was conducted except that the
 fine goethite particles 13 were heat-treated at 180C for 30 minutes, and
 then heat-dehydrated at 680.degree. C. for 60 minutes.
 The production conditions and various properties of the obtained red iron
 oxide pigment are shown in Table 3.
 Comparative Example 5
 (Red Iron Oxide Pigment Obtained by the Method Described in Example 1 of
 Japanese Patent Application Laid-Open (KOKAI) No. 49-34498(1974))
 4.1 liters of a 6.49 N-sodium hydroxide solution was added to 10 liters of
 a 1.3 mol-ferrous sulfate solution. The obtained solution was further
 mixed with water, thereby obtaining a mixed solution having a total volume
 of 27.5 liters. While minimizing the amount of oxygen admixed into the
 solution and while stirring, the obtained mixed solution was maintained at
 33.degree. C. and subjected to the production reaction of ferrous
 hydroxide for 10 minutes. Thereafter, while minimizing the amount of
 oxygen admixed into the solution and while stirring, the obtained ferrous
 hydroxide colloid solution was mixed with 22.5 liters of a 0.63
 mol-ammonium bicarbonate solution, thereby obtaining a solution having a
 total volume of 50 liters. The obtained solution was maintained at
 33.degree. C. and subjected to the production reaction of ferrous
 carbonate for 30 minutes. The obtained ferrous carbonate colloid solution
 was maintained at 33.degree. C., and air was passed therethrough at a feed
 rate of 140 liters per minute. After air was passed through the ferrous
 carbonate colloid solution for 50 minutes, a precipitate composed of
 yellow iron oxide hydroxide particles was obtained from the solution. The
 obtained precipitate of yellow iron oxide hydroxide particles were washed
 with water, filtered out and then dried at 100.degree. C., thereby
 obtaining yellow iron oxide hydroxide particles.
 The obtained yellow iron oxide hydroxide particles were spindle-shaped
 particles, and had an average major axial diameter of 0.01 .mu.m, a
 geometrical standard deviation value of major axial diameter of 1.81, an
 average minor axial diameter of 0.0033 .mu.m, a geometrical standard
 deviation value of minor axial diameter of 1.55, an aspect ratio of 3.0:1
 and a BET specific surface area value of 256.1 m.sup.2 /g.
 Next, the yellow iron oxide hydroxide particles was allowed to stand in air
 at 300.degree. C. for 60 minutes, thereby obtaining red iron oxide
 particles.
 Various properties of the obtained red iron oxide particles are shown in
 Table 3.
 Comparative Example 6
 (Red Iron Oxide Particles Obtained by the Method Described in Example 1 of
 Japanese Patent Publication (KOKOKU) No. 59-48768(1984))
 6.8 liters of a 0.56 mol-sodium carbonate solution was charged into a
 cylindrical reactor. While blowing a nitrogen gas into the reactor, 5.2
 liters of a 0.69 mol-ferrous sulfate solution was gradually added
 thereinto. The obtained ferrous carbonate-containing suspension had a pH
 value of 8.3. The suspension was stirred at room temperature for 2 hours
 while blowing a nitrogen gas thereinto. Thereafter, the nitrogen gas was
 replaced with air, and the air was passed through the suspension at a feed
 rate of 5.0 liters per minute. After air was passed through the suspension
 for 25 minutes, the oxidation reaction was completed, thereby obtaining a
 precipitate composed of yellow iron oxide hydroxide particles. The
 obtained precipitate was washed with water, filtered out and then dried at
 100.degree. C., thereby obtaining yellow iron oxide hydroxide particles.
 The obtained yellow iron oxide hydroxide particles had an average major
 axial diameter of 0.038 .mu.m, a geometrical standard deviation value of
 major axial diameter of 1.70, an average minor axial diameter of 0.0095
 .mu.m, a geometrical standard deviation value of minor axial diameter of
 1.48, an aspect ratio of 4.0:1 and a BET specific surface area value of
 216.5 m.sup.2 /g.
 Next, the obtained yellow iron oxide hydroxide particles was allowed to
 stand in air at 280.degree. C. for 180 minutes, thereby obtaining red iron
 oxide particles.
 Various properties of the obtained red iron oxide particles are shown in
 Table 3.
 Example 11
 450 g of the fine red iron oxide pigment obtained in Example 5 was
 deaggregated in 10 liters of pure water using a stirrer, and further
 passed though a Homomic Line Mill (manufactured by Tokushu Kika Kogyo Co.,
 Ltd.) three times, thereby obtaining a slurry containing the fine red iron
 oxide particles.
 The concentration of the obtained slurry containing the fine red iron oxide
 particles was adjusted to 45 g/liter, and 10 liters of the slurry was
 sampled. The slurry was heated to 60.degree. C. while stirring, and the pH
 value of the slurry was adjusted to 4.0.
 Next, 167 ml of a 1 mol/liter-aluminum acetate solution (equivalent to 1.0%
 by weight (calculated as Al) based on the weight of the fine red iron
 oxide particles) was added to the slurry, and then the slurry was allowed
 to stand for 30 minutes. Thereafter, the pH value of the slurry was
 adjusted to 7.0 by adding an aqueous sodium hydroxide solution thereto,
 and the slurry was further allowed to stand for 30 minutes. Next, the
 slurry was successively subjected to filtration, washing with water,
 drying and pulverization, thereby obtaining a fine red iron oxide pigment
 whose particle surface was coated with a hydroxide of Al.
 Examples 12 to 16
 The same procedure as defined in Example 11 was conducted except that kind
 of the fine red iron oxide pigment, kind of the surface-coating material,
 pH value before adding the Al and/or Si compounds, amounts of the Al
 and/or Si compounds added and final pH value were changed variously,
 thereby obtaining a fine red iron oxide pigment whose particle surface was
 coated with the surface-coating material.
 The main production conditions are shown in Table 4 and various properties
 of the obtained fine red iron oxide pigment are shown in Table 5.
 Examples 17 to 28
 &lt;Paint Using Fine Red Iron Oxide Pigment&gt;
 The same procedure as defined in Example 2 was conducted except that kind
 of the fine red iron oxide pigment was changed variously, thereby
 obtaining a paint.
 The main production conditions and various properties of the obtained paint
 are shown in Table 6.
 Comparative Examples 7 to 12
 The same procedure as defined in Example 2 was conducted except that kind
 of the fine red iron oxide pigment was changed variously, thereby
 obtaining a paint.
 The main production conditions and various properties of the obtained paint
 are shown in Table 7.
 Examples 29 to 40
 &lt;Resin Composition Using Fine Red Iron Oxide Pigment&gt;
 The same procedure as defined in Example 4 was conducted except that kind
 of the fine red iron oxide pigment was changed variously, thereby
 obtaining a resin composition.
 The main production conditions and various properties of the obtained resin
 composition are shown in Table 8.
 Comparative Examples 13 to 18
 The same procedure as defined in Example 4 was conducted except that kind
 of the red iron oxide particles was changed variously, thereby obtaining a
 resin composition.
 The main production conditions and various properties of the obtained resin
 composition are shown in Table 9.
 TABLE 1
 Production Properties of fine goethite
 of fine particles
 goethite Geometrical
 particles Average standard
 Kind of major deviation of
 Kind of aluminum axial major axial
 starting compound diameter diameter
 particles added Shape (.mu.m) (-)
 Fine -- Spindle- 0.0472 1.55
 goethite shaped
 particles 1
 Fine Aluminum Spindle- 0.0571 1.55
 goethite sulfate shaped
 particles 2
 Fine Aluminum Acicular 0.0758 1.56
 goethite sulfate
 particles 3
 Fine Aluminum Acicular 0.0312 1.52
 goethite acetate
 particles 4
 Fine Sodium Acicular 0.0916 1.61
 goethite aluminate
 particles 5
 Properties of fine goethite particles
 Geometrical
 standard
 Average deviation of
 Kind of minor axial minor axial
 starting diameter diameter Aspect ratio
 particles (.mu.m) (-) (-)
 Fine 0.0089 1.31 5.3:1
 goethite
 particles 1
 Fine 0.0093 1.33 6.1:1
 goethite
 particles 2
 Fine 0.0114 1.32 6.6:1
 goethite
 particles 3
 Fine 0.0063 1.35 5.0:1
 goethite
 particles 4
 Fine 0.0201 1.38 4.6:1
 goethite
 particles 5
 Kind of Properties of fine goethite particles
 starting BET specific surface Al content
 particles area (m.sup.2 /g) (wt. %)
 Fine 175.5 --
 goethite
 particles 1
 Fine 192.1 2.56
 goethite
 particles 2
 Fine 158.2 1.87
 goethite
 particles 3
 Fine 221.8 0.63
 goethite
 particles 4
 Fine 82.6 9.64
 goethite
 particles 5
 TABLE 2
 Conditions of heat-treatment
 Kind of Kind of Tempera-
 particles to starting ture Time
 be treated particles Atmosphere (.degree. C.) (min)
 Fine Fine goethite air 180 30
 goethite particles
 particles 6 obtained in
 Example 1
 Fine Fine goethite air 150 30
 goethite particles 1
 particles 7
 Fine Fine goethite air 170 30
 goethite particles 2
 particles 8
 Fine Fine goethite air 150 60
 goethite particles 3
 particles 9
 Fine Fine goethite air 150 60
 goethite particles 4
 particles 10
 Fine Fine goethite air 190 30
 goethite particles 5
 particles 11
 Fine Fine goethite air 80 60
 goethite particles 1
 particles 12
 Fine Fine goethite air 310 60
 hematite particles 1
 particles 1
 Fine Fine goethite air 180 30
 goethite particles 1
 particles 13
 Properties of heat-treated fine goethite
 particles
 Geometrical standard
 Kind of Average major deviation of major axial
 particles to axial diameter diameter
 be treated (.mu.m) (-)
 Fine goethite 0.0689 1.33
 particles 6
 Fine goethite 0.0471 1.35
 particles 7
 Fine goethite 0.0572 1.36
 particles 8
 Fine goethite 0.0757 1.36
 particles 9
 Fine goethite 0.0313 1.32
 particles 10
 Fine goethite 0.0917 1.40
 particles 11
 Fine goethite 0.0472 1.55
 particles 12
 Fine hematite 0.0425 1.65
 particles 1
 Fine goethite 0.0471 1.35
 particles 13
 Properties of heat-treated fine goethite
 particles
 Geometrical
 standard
 Average deviation of
 Kind of minor axial minor axial Aspect
 particles to diameter diameter ratio
 be treated (.mu.m) (-) (-)
 Fine goethite 0.0101 1.15 6.8:1
 particles 6
 Fine goethite 0.0090 1.18 5.2:1
 particles 7
 Fine goethite 0.0094 1.13 6.1:1
 particles 8
 Fine goethite 0.0116 1.12 6.5:1
 particles 9
 Fine goethite 0.0065 1.10 4.8:1
 particles 10
 Fine goethite 0.0202 1.16 4.5:1
 particles 11
 Fine goethite 0.0089 1.31 5.3:1
 particles 12
 Fine hematite 0.0121 1.38 3.5:1
 particles 1
 Fine goethite 0.0089 1.19 5.3:1
 particles 13
 Properties of heat-treated fine goethite
 Kind of particles
 particles to be BET specific surface Al content
 treated area (m.sup.2 /g) (wt. %)
 Fine goethite 168.1 --
 particles 6
 Fine goethite 178.5 --
 particles 7
 Fine goethite 189.7 2.56
 particles 8
 Fine goethite 153.1 1.88
 particles 9
 Fine goethite 216.9 0.63
 particles 10
 Fine goethite 83.0 9.65
 particles 11
 Fine goethite 176.9 --
 particles 12
 Fine hematite 131.6 --
 particles 1
 Fine goethite 175.9 --
 particles 13
 TABLE 3
 Conditions of heat-
 Examples and Kind of dehydration treatment
 Comparative particles to Temp. Time
 Examples be treated Atmosphere (.degree. C.) (min)
 Example 5 Fine goethite air 340 30
 particles 6
 Example 6 Fine goethite air 320 30
 particles 7
 Example 7 Fine goethite air 370 20
 particles 8
 Example 8 Fine goethite air 310 60
 particles 9
 Example 9 Fine goethite air 300 45
 particles 10
 Example 10 Fine goethite air 320 60
 particles 11
 Comparative Fine goethite air 370 60
 Example 1 particles 1
 Comparative Fine goethite air 340 45
 Example 2 particles 12
 Comparative Fine hematite air 340 45
 Example 3 particles 1
 Comparative Fine goethite air 680 60
 Example 4 particles 13
 Comparative -- air 300 60
 Example 5
 Comparative -- air 280 180
 Example 6
 Properties of fine red iron oxide pigment
 Geometrical standard
 Examples and Average major deviation of major
 Comparative axial diameter axial diameter
 Examples (.mu.m) (-)
 Example 5 0.0632 1.33
 Example 6 0.0428 1.35
 Example 7 0.0513 1.36
 Example 8 0.0690 1.36
 Example 9 0.0281 1.33
 Example 10 0.0823 1.42
 Comparative 0.0421 1.66
 Example 1
 Comparative 0.0418 1.56
 Example 2
 Comparative 0.0406 1.65
 Example 3
 Comparative 0.0498 1.42
 Example 4
 Comparative 0.0100 1.83
 Example 5
 Comparative 0.0360 1.72
 Example 6
 Properties of fine red iron oxide pigment
 Geometrical
 standard
 Average deviation of
 Examples and minor axial minor axial Aspect
 Comparative diameter diameter ratio
 Examples (.mu.m) (-) (-)
 Example 5 0.0099 1.15 6.4:1
 Example 6 0.0090 1.18 4.8:1
 Example 7 0.0087 1.13 5.9:1
 Example 8 0.0113 1.12 6.1:1
 Example 9 0.0067 1.10 4.2:1
 Example 10 0.0191 1.16 4.3:1
 Comparative 0.0092 1.32 4.6:1
 Example 1
 Comparative 0.0091 1.34 4.6:1
 Example 2
 Comparative 0.0121 1.33 3.4:1
 Example 3
 Comparative 0.0211 1.31 2.4:1
 Example 4
 Comparative 0.0038 1.55 2.6:1
 Example 5
 Comparative 0.0101 1.48 3.6:1
 Example 6
 Properties of fine red iron oxide
 Examples and pigment
 Comparative BET specific surface Al content
 Examples area (m.sup.2 /g) (wt. %)
 Example 5 154.9 --
 Example 6 130.6 --
 Example 7 132.0 2.82
 Example 8 164.1 2.08
 Example 9 222.2 0.70
 Example 10 96.5 10.56
 Comparative 123.4 --
 Example 1
 Comparative 151.3 --
 Example 2
 Comparative 131.6 --
 Example 3
 Comparative 54.5 --
 Example 4
 Comparative 231.6 --
 Example 5
 Comparative 196.8 --
 Example 6
 TABLE 4
 Coating with
 aluminum and/or
 silicon compound
 Kind of fine pH value before
 red iron Concentration addition of Al
 oxide of water and/or Si
 pigment suspension compound
 Examples (Example No.) (g/liter) (-)
 Example 11 Example 5 45 4.0
 Example 12 Example 6 45 10.0
 Example 13 Example 7 45 4.0
 Example 14 Example 8 45 10.3
 Example 15 Example 9 45 3.8
 Example 16 Example 10 45 10.5
 Coating with aluminum and/or silicon compound
 Aluminum and/or silicon compound
 Amount of Al or Si
 compound added
 Kind of Al (calculated as Al Final pH
 and/or Si and/or SiO.sub.2) value
 Examples compound added (wt. %) (-)
 Example 11 Aluminum 1.0 7.0
 acetate
 Example 12 Water glass #3 2.0 7.0
 Example 13 Aluminum/ 3.8 7.5
 sulfate
 Example 14 Sodium 9.5 6.5
 aluminate
 Example 15 Colloidal 5.5 6.8
 silica
 Example 16 Sodium 5.0 7.0
 aluminate
 Water glass #3 2.0
 TABLE 5
 Properties of fine red iron oxide pigment
 coated with hydroxide of aluminum and/or oxide
 of silicon
 Geometrical Geometrical
 standard standard
 Average deviation Average deviation
 major of major minor of minor
 axial axial axial axial
 diameter diameter diameter diameter
 Examples (.mu.m) (-) (.mu.m) (-)
 Example 11 0.0632 1.33 0.0100 1.15
 Example 12 0.0428 1.35 0.0091 1.18
 Example 13 0.0512 1.37 0.0087 1.13
 Example 14 0.0691 1.35 0.0115 1.12
 Example 15 0.0280 1.32 0.0067 1.10
 Example 16 0.0823 1.41 0.0191 1.41
 Properties of fine red iron oxide pigment
 coated with hydroxide of aluminum and/or oxide
 of silicon
 BET specific
 Aspect ratio surface area Al content
 Examples (-) (m.sup.2 /g) (wt. %)
 Example 11 6.3:1 150.4 --
 Example 12 4.7:1 135.3 --
 Example 13 5.9:1 128.6 2.82
 Example 14 6.0:1 171.1 2.08
 Example 15 4.2:1 202.6 0.70
 Example 16 4.3:1 23.6 10.56
 Properties of fine red iron oxide pigment
 coated with hydroxide of aluminum and/or oxide
 of silicon
 Amount of hydroxide of Amount of oxide of
 aluminum covered silicon covered
 (calculated as Al) (calculated as SiO.sub.2)
 Examples (wt. %) (wt. %)
 Example 11 0.99 --
 Example 12 -- 1.93
 Example 13 3.66 --
 Example 14 8.69 --
 Example 15 -- 4.89
 Example 16 4.66 1.83
 TABLE 6
 Production of paint
 Kinds of fine Properties of
 red iron paint
 oxide pigment Kinds of Viscosity
 Examples (Example No.) resins (cP)
 Example 17 Example 5 Amino-alkyd 2,124
 resin
 Example 18 Example 6 Amino-alkyd 2,304
 resin
 Example 19 Example 7 Amino-alkyd 2,099
 resin
 Example 20 Example 8 Amino-alkyd 1,792
 resin
 Example 21 Example 9 Amino-alkyd 2,560
 resin
 Example 22 Example 10 Amino-alkyd 1,690
 resin
 Example 23 Example 11 Amino-alkyd 1,920
 resin
 Example 24 Example 12 Amino-alkyd 1,536
 resin
 Example 25 Example 13 Amino-alkyd 1,766
 resin
 Example 26 Example 14 Amino-alkyd 1,612
 resin
 Example 27 Example 15 Amino-alkyd 2,099
 resin
 Example 28 Example 16 Amino-alkyd 1,894
 resin
 Properties of coating film
 Transparency of
 coating film (linear
 20.degree. Gloss coefficient
 Examples (%) absorption) (.mu.m.sup.-1)
 Example 17 101 0.0648
 Example 18 99 0.0711
 Example 19 112 0.0732
 Example 20 105 0.0832
 Example 21 118 0.0468
 Example 22 98 0.0768
 Example 23 111 0.0526
 Example 24 109 0.0654
 Example 25 118 0.0666
 Example 26 106 0.0762
 Example 27 121 0.0312
 Example 28 96 0.0619
 TABLE 7
 Production of paint
 Kinds of red
 iron oxide Properties of
 pigment paint
 Comparative (Comparative Kinds of Viscosity
 Examples Example No.) resins (cP)
 Comparative Comparative Amino-alkyd 2,304
 Example 7 Example 1 resin
 Comparative Comparative Amino-alkyd 2,560
 Example 8 Example 2 resin
 Comparative Comparative Amino-alkyd 2,688
 Example 9 Example 3 resin
 Comparative Comparative Amino-alkyd 2,432
 Example 10 Example 4 resin
 Comparative Comparative Amino-alkyd 5,632
 Example 11 Example 5 resin
 Comparative Comparative Amino-alkyd 4,096
 Example 12 Example 6 resin
 Properties of coating film
 Transparency of
 Comparative 20.degree. Gloss coating film (linear
 Examples (%) absorption) (.mu.m.sup.-1)
 Comparative 76 0.1632
 Example 7
 Comparative 68 0.1783
 Example 8
 Comparative 76 0.1826
 Example 9
 Comparative 78 0.2120
 Example 10
 Comparative 65 0.1562
 Example 11
 Comparative 58 0.1936
 Example 12
 TABLE 8
 Production of resin composition
 Fine red iron oxide pigment
 Kind Amount
 Examples (Example No.) (part by weight)
 Example 29 Example 5 1.0
 Example 30 Example 6 1.0
 Example 31 Example 7 1.0
 Example 32 Example 8 1.0
 Example 33 Example 9 1.0
 Example 34 Example 10 1.0
 Example 35 Example 11 1.0
 Example 36 Example 12 1.0
 Example 37 Example 13 1.0
 Example 38 Example 14 1.0
 Example 39 Example 15 1.0
 Example 40 Example 16 1.0
 Production of resin composition
 Resin
 Amount
 Examples Kind (part by weight)
 Example 29 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 30 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 31 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 32 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 33 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 34 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 35 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 36 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 37 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 38 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 39 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Example 40 Polyvinyl chloride resin 99.0
 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Production of resin composition
 Additive
 Amount Kneading
 (part by temperature
 Examples Kind weight) (.degree. C.)
 Example 29 Calcium 2.0 160
 stearate
 Example 30 Calcium 2.0 160
 stearate
 Example 31 Calcium 2.0 160
 stearate
 Example 32 Calcium 2.0 160
 stearate
 Example 33 Calcium 2.0 160
 stearate
 Example 34 Calcium 2.0 160
 stearate
 Example 35 Calcium 2.0 160
 stearate
 Example 36 Calcium 2.0 160
 stearate
 Example 37 Calcium 2.0 160
 stearate
 Example 38 Calcium 2.0 160
 stearate
 Example 39 Calcium 2.0 160
 stearate
 Example 40 Calcium 2.0 160
 stearate
 Properties of resin composition
 Transparency of resin
 composition (linear
 Dispersing condition coefficient
 Examples (-) absorption) (.mu.m.sup.-1)
 Example 29 4 0.0823
 Example 30 3 0.0840
 Example 31 4 0.0912
 Example 32 4 0.0816
 Example 33 3 0.0800
 Example 34 5 0.0921
 Example 35 5 0.0832
 Example 36 5 0.0798
 Example 37 5 0.0816
 Example 38 4 0.0726
 Example 39 5 0.0658
 Example 40 5 0.0912
 properties of resin composition
 Percentage of area of portion deteriorated and
 discolored when heated at 190.degree. C.
 {(S/S.sub.0) .times. 100} (%)
 Examples 30 min. 60 min. 90 min.
 Example 29 -- -- --
 Example 30 -- -- --
 Example 31 0 0 5
 Example 32 0 5 5
 Example 33 0 5 10
 Example 34 0 0 5
 Example 35 -- -- --
 Example 36 -- -- --
 Example 37 0 0 0
 Example 38 0 0 5
 Example 39 0 0 5
 Example 40 0 0 0
 TABLE 9
 Production of resin composition
 Red iron oxide pigment
 Comparative Kind Amount
 Examples (Comparative Example No.) (part by weight)
 Comparative Comparative 1.0
 Example 13 Example 1
 Comparative Comparative 1.0
 Example 14 Example 2
 Comparative Comparative 1.0
 Example 15 Example 3
 Comparative Comparative 1.0
 Example 16 Example 4
 Comparative Comparative 1.0
 Example 17 Example 5
 Comparative Comparative 1.0
 Example 18 Example 6
 Production of resin composition
 Resin
 Comparative Amount
 Examples Kind (part by weight)
 Comparative Polyvinyl chloride resin 99.0
 Example 13 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Comparative Polyvinyl chloride resin 99.0
 Example 14 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Comparative Polyvinyl chloride resin 99.0
 Example 15 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Comparative Polyvinyl chloride resin 99.0
 Example 16 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Comparative Polyvinyl chloride resin 99.0
 Example 17 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Comparative Polyvinyl chloride resin 99.0
 Example 18 103EP8D (produced by
 Nippon Zeon Co., Ltd.)
 Production of resin composition
 Additive
 Amount Kneading
 Comparative (part by temperature
 Examples Kind weight) (.degree. C.)
 Comparative Calcium 2.0 160
 Example 13 stearate
 Comparative Calcium 2.0 160
 Example 14 stearate
 Comparative Calcium 2.0 160
 Example 15 stearate
 Comparative Calcium 2.0 160
 Example 16 stearate
 Comparative Calcium 2.0 160
 Example 17 stearate
 Comparative Calcium 2.0 160
 Example 18 stearate
 Properties of resin composition
 Transparency of resin
 composition (linear
 Comparative Dispersing condition coefficient
 Examples (-) absorption) (.mu.m.sup.-1)
 Comparative 1 0.1683
 Example 13
 Comparative 2 0.1821
 Example 14
 Comparative 1 0.2023
 Example 15
 Comparative 1 0.2562
 Example 16
 Comparative 1 0.3652
 Example 17
 Comparative 1 0.2865
 Example 18
 Properties of resin composition
 Percentage of area of portion deteriorated
 and discolored when heated at 190.degree. C.
 Comparative {(S/S.sub.0) .times. 100} (%)
 Examples 30 min. 60 min. 90 min.
 Comparative 10 20 50
 Example 13
 Comparative 20 40 85
 Example 14
 Comparative 15 25 60
 Example 15
 Comparative 20 45 40
 Example 16
 Comparative 20 40 60
 Example 17
 Comparative 15 30 70
 Example 18