JPS6245905B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to metal foil pigments and their use in printing inks and coatings. In particular, the present invention relates to a continuous process for producing metal foil pigments with a thin luster.

Although the use of metal films in decorative items began thousands of years ago, metal pigments did not become commercially important until several hundred years ago. Historically, the value of a surface coated with gold or other metals lies not only in its beautiful shiny metallic finish, but also in the fact that this surface coating makes the object more resistant to age and weather than any other surface coating available. Ta. The high cost of gold or other metals made it difficult to produce suitable thin foils, and the use of metal films was limited to jewelry, ceramics, and other works of art.

In order to make thin metal foils or membranes a few thousandths of an inch thick, it was necessary to begin with pliable metal that had already been rolled into extremely thin sheets. This sheet was sandwiched between animal hides and pounded again to form a thin enough foil for use. During this operation, the edges of the thin foil broke off and became small particles. It has been discovered that by mixing these pieces with a drying oil, a finish very similar to continuous metal sheet can be obtained. The engineers who created this type of finish produced this metallic pigment by rubbing thinly beaten and rolled metal against a fine wire mesh.

In the mid-1800s, Bethsemer devised the first practical and economical method for producing metal flake pigments. In this method, a metal plate with a suitable luster was pounded or hammered, and then the plate was made into thin flakes, and the pieces were collected to a uniform size.

In 1866, Charles Hall and Paul Harlout independently invented a practical aluminum smelting process that allowed aluminum to be used in commercial quantities. Although aluminum could technically be applied to the Bethsemer process,
It had the disadvantage of producing explosive mixtures over a wide range of air and metal-air ratios.

In 1925, Everett Hall was issued a number of patents for producing safe aluminum flake pigments.
Hall's method was based on a wet ball mill to reduce the size of aluminum in the presence of a paint thinner solution containing a lubricant. Lubricating oil was used to prevent thermal adhesion of the particles, and the type of particles produced was determined by the choice of lubricant. This method minimized the possibility of explosion due to fine aluminum powder, and a large-scale industrial process was developed. An example of the result of this patent is the paint used in 1931 to paint the entire structure of the George Washington Bridge in New York City.

Metal films are currently made using ordinary aluminum flakes and powdered pigments dispersed in ink and then used for printing. Metallic pigments are formed by adhesion of metal vapor,
Electroplating, obtained by direct vacuum sputtering or modified by using foil strips. Films using common aluminum pigments are gray or at best very poorly reflective films. Membranes are generally expensive and the process is difficult to control, making the process unsuitable for large continuous coatings. Examples of metal film compositions and methods for making metal pigments include U.S. Pat. No. 2,941,894 and U.S. Pat.
There is number 4116710.

Diagrams showing the currently used aluminum pigment manufacturing process can be found in Pigment Handbook, Volume 1, Page 799, Figure 16 and Alcoa Aluminum Pigment Product Data, 799, 1976, published by J. Wiley & Saiz, New York.
Monthly Powder and Pigment FA2C - Section 1, page 5, Figure 5.

Aluminum pigments prepared as described above have been used for several years in paints, enamels, lacquers and other coating compositions and processes. The fineness grades of common aluminum pigments range from relatively coarse particle sizes such as 250 microns (60 mesh) to about 44 microns (325 mesh).

A drawback of the common aluminum and metal pigments currently produced is their bulk shape. Different particle sizes and concentrations as high as 30% by weight are common in composition formulations containing conventionally shaped aluminum pigments. Because of the geometry of the aluminum pigment particles, they tend to protrude from the surface of the ink or paint excipient after drying, resulting in a phenomenon called "dusting," and when the dried film is rubbed, this phenomenon occurs and some metal particles are removed. break away. Furthermore, since the pigment particles are not flat and are randomly distributed, the surface of the coating is usually uneven and requires repeated coating. A further disadvantage is the crushing associated with the particle size reduction operation, which removes the original luster of the metal and renders it gray.

According to the invention, a release coating is applied continuously on at least one side of the carrier sheet. The metal vapor is deposited in a thin film 350 to 450 Angstroms thick on at least one side of the release film. The carrier sheet with the release film and the thin metal film thereon is passed through a solvent system, the solvent dissolves the release film, and most of the metal film is peeled from the carrier sheet into the solvent. The remaining metal film is then wiped from the carrier sheet into a non-reactive liquid medium where it is dispersed into finely divided pigments by vigorous stirring or ultrasound. The metal pigment flakes can be collected and formulated into coating and printing compositions.

The present invention relates to a method for producing metal pigments, which method comprises: (a) applying a release film on at least one side of a carrier sheet; (b) depositing a thin film of metal directly on the release film; and (c) depositing a thin film of metal directly on the release film. (d) separating the metal film from the carrier sheet into particles to form a material substantially free of the release film; The method comprises the steps of producing a metal pigment, collecting the metal pigment in a non-reactive solvent, and (e) concentrating and comminuting the metal pigment into particles having a diameter of 25 to 50 microns.

FIG. 1 is a process diagram of the metal pigment manufacturing method of the present invention.

FIG. 2 is a schematic diagram of the method of the invention.

FIG. 3 is an enlarged view of an embodiment of the stripping device of the present invention.

Now, in FIG. 2, the carrier sheet 11 is the roller 1
The solution is continuously supplied from 2 and enters a container 13 where a release film 1 is applied on at least one side of the carrier sheet 11.
4 can be added. Then the applied carrier sheet 1
5 passes through a metallizing vacuum evaporator 16 where a thin metal film is deposited on at least one side of the coated carrier sheet. The carrier sheet 17 provided with the metal film passes through a stripper 18 containing a solvent, where the release film is dissolved. The flaked metal particles or pigments are collected in a solvent in the stripper 18 and then sent by a pump 29 to settling tanks 24, 24'. The carrier sheet with the metal film on which the release film has been dissolved and has exited the stripper 18 is then transferred to a roller 19.
through a suitable wiper 20 in a chamber 21 containing a solvent 22. The wiper 20 helps ensure that the metal film is completely removed in flakes and the clean carrier sheet is rolled up. The metal flakes or pigments collected in the solvent 22 can be sent by means of a pump 23 to settling tanks 24, 24'. Another embodiment, a stripping bath 25, is shown in FIG. The metallized carrier sheet passes through wiper 20' and around roller 26. The metal pigment is collected at the bottom of tank 25 and sent by pump 27 to a settling tank.

The carrier sheet 11 may be a polyester film, for example a polyethylene terephthalate sheet such as Mylar, or other suitable sheet such as cellophane or polypropylene.

Suitable release films are materials that are easily dissolved and on which a metal film can be deposited. Examples of this release film include polyvinyl chloride, polystyrene, chlorinated rubber, acrylonitrile-butadiene-styrene copolymer, nitrocellulose, methyl methacrylate, acrylic copolymer, fatty acids, waxes, rubbers, There are polymers such as gels and mixtures thereof. Application of the release film can be accomplished by dissolving the coating material in a suitable solvent and applying a uniform thin film on both sides using a standard continuous roller coater at commercially acceptable speeds of 500 to 1000 feet per minute. The coated carrier sheet may be dried until the solvent is removed. Suitable machines include a two-point rotogravure coating machine manufactured by Interroto of Richmond, Virginia, and a general purpose rotogravure coating machine with a roller-to-roller rewind-winding device such as a drying tunnel. Good results are obtained with 0.75 to 1.50 pounds of release membrane per ream, preferably about 1.0 pound (3000 square feet). It is important not to apply more than 1.50 pounds of release film per ream. Also, membranes with less than 0.25 pounds per ream have insufficient release properties.

The coated carrier sheet 15 passes through a metallizing vacuum evaporator 16 to deposit a metal film on one or both sides of the release film. The thickness of the deposited metal film is 350-450 angstroms, controlled by the power required for the fabric speed and evaporation rate. Suitable bright metals for deposition include aluminum, chromium,
There is copper, steel, silver and gold. Metal is approx. per square
Evaporated at a rate of 3.50 ohms (resistance reading). This corresponds to 350 angstroms on one side of the membrane or 7.0 ohms or 700 angstroms on both sides.

Metal evaporation is performed using standard methods such as dielectric, resistive, electron beam and sputtering. The thickness of the deposited metal film is important in obtaining shiny particles.
A very uniform thin film is required to obtain maximum leafing properties. The film thickness that provides the desired continuous reflectivity of the metal particles is 350 to 450 angstroms. When used as a coating composition
At thicknesses above 450 angstroms, the leafing properties of the particles begin to break down. At thicknesses below 350 Angstroms, the metal particles are too fine to separate from the resin solvent stripping system.

If necessary, the carrier sheet with the deposited thin metal film thereon is stretched under tension to about 1 to 2% of its length to create a crack in the metal surface. As shown in Figure 1, this method is called energizing, and the subsequent withdrawal operation is approximately 2
Promote twice as much.

The metallized carrier sheet 17 then passes through a solvent bath 18 containing a solvent in which the release film is dissolved. Suitable solvents for dissolving the peeling film include acetone,
These include chlorinated solvents such as methylene chloride, methyl ethyl ketone, methyl isobutyl ketone, toluene, and butyl acetate.

The metallized carrier sheet passes through a solvent bath 18 over a series of rollers 19 and an air knife 2 for removing unadhered metal particles from the carrier sheet.
0 or an appropriate wiper. The air knife may be in the same chamber 18 as the solvent, but is typically in a separate chamber 21 containing the solvent 22 as shown in FIG. This solvent may or may not be the same solvent as the solvent in vessel 18, but it is important that it is non-reactive with the metal pigment. A suitable air knife can be manufactured with a hollow tube connected to a source of compressed air at approximately 90 PSI. Nozzles or holes are mounted on the machine at evenly spaced transverse lengths to direct air jets perpendicularly to the moving carrier sheet. The air jet removes any residual metal debris that may remain on the membrane. The air knife also serves as a drying mechanism for the wet carrier sheet and thus aids in winding. It is also preferred to use a vapor degreasing process which completely removes both residual metal and release film from the carrier sheet before winding. Vapor degreasing also cleans any residual flakes from residual metal debris. The air may be at ambient temperature, cooled or heated for optimum efficiency.

The solvent in tank 18 can be used until it is full. Furthermore, the solvent can be recovered from the solution containing the membrane material, and the residual membrane material, if properly purified, can be reused in subsequent coating operations.

The pigment dispersed in the solvent is transferred to a stripping tank 18.
or 21 or pump 29 or 23
It can either be transferred to sedimentation tanks 24, 24' or passed through a centrifuge to obtain a concentrated suspension of pale, lustrous metallic pigment. The metal pigment concentration in the solvent is preferably about 0.045%, but in any case the concentration does not exceed 0.2% before centrifugation.

The metal pigment is then crushed into particles, approximately 90% of which are 25-50 microns in diameter. A preferred device for reducing the pigment to the appropriate particle size is a sonorator which operates by ultrasonic action and does not impair the reflective properties of the glossy surface of the pigment particles. A suitable ultrasonic dispersion machine is a Triplex Sonorator unit, Model A HP, Model A, Design 150, manufactured by Sonic Corporation of Stamford, Conn.

The pale lustrous metallic pigment with a diameter of 25-50 microns is then concentrated to 5-15% pigment solids.
The pigment concentrate can then be formulated into a jetting lacquer or printing ink.

However, for example, if the solvent exchange method with methyl cellosorb is first used, then approximately 20% of the metal solids are
It has been discovered that further concentration may be achieved by collecting %. This concentrated liquid has a metal concentration of 1.0-
At 5.0% by weight it is used as a lacquer or printing ink formulation. This formulation is finally passed through equipment that homogenizes it to a final metal particle size of about 10-20 microns. 1 produced by the method of the present invention
A coating composition containing -5% by weight of aluminum pigment was surprisingly found to have excellent covering power and to give a continuous mirror finish.

The metal films obtained by this method resemble the brightness, reflected light and covering power of commercial metal foils. The natural alignment of the single layer leafing pieces covers a large surface area with a very small amount of pigment. For example, 130 grams of the solid aluminum bright leafing pigment of the present invention is converted into one gallon of printing ink to provide approximately 3,000,000 square inches of excellent coverage using a #300 quadrilateral cell rotogravure printing cylinder. The efficacy of the description is due to the ability of the invention to modify the product itself.

The following examples demonstrate the practice of the invention.

Example 1 An aluminum pigment was produced by the following method. A release film containing 10% nitrocellulose in toluene was coated onto a 1/2 mil thick Mylar carrier sheet using a 200-line square rotogravure roller of a commercially available roller coater, dried, and the nitrocellulose was coated on the carrier sheet. A glossy film was applied. The coated carrier sheet was then coated with a CVC manufactured by CVC Products, Lochiester, New York.
Metalized on a roller-type vacuum evaporator called a vacuum roll coater.
A 400±50 angstrom aluminum film was attached. This coated and metallized carrier sheet is passed through a stripping machine to produce approximately 0.1% by weight aluminum flakes.
A concentrated aluminum flake suspension was collected. The solvent used for the stripping operation consisted of 50% toluene and 50% methyl ethyl ketone (MEK). The aluminum flake-containing suspension was allowed to settle and further thicken to approximately 6% solids.

Example 2 A 10% nitrocellulose solution was applied to a 1/2 mil thick Mylar carrier sheet in a commercial roller coater using a 100 line rotogravure roller. A second film of chlorinated rubber was then applied over the nitrocellulose. The coated carrier sheet is 400±50
After metallization with angstrom aluminum, the metallized carrier sheet was mixed with 25% acetone and toluene.
25%, MEK25% and butyl acetate 25%
The aluminum was removed by treatment in a bath consisting of: The metal particles were then concentrated to 6% solid aluminum.

Example 3 A toluene solution of an acrylic copolymer was applied to a 1/2 mil thick cellophane carrier sheet at a concentration of about 10 polymers per ream.
Applied in the amount of lbs. Apply coating sheet to 400±
50% toluene, 40% MEK and 10% acetone after metallization with 50 angstroms of aluminum
The aluminum was removed by treatment with a solution consisting of:
The aluminum piece peeled off easily and had a shiny appearance.

Example 4 A release film consisting of a mixture of methyl methacrylate resin and acrylic copolymer dispersed in a solution of 50% MEK and 50% toluene was coated on a 1/2 mil thick polyester carrier sheet, one layer per side, on a commercial machine. Hit
Applied in an amount of 1.0 lb. The coated sheet was metallized with copper to a thickness of approximately 400 angstroms. The peeled film was dissolved with methylene chloride and the faint, shiny copper particles were collected.

Example 5 Nitrocellulose dispersed in toluene was coated on both sides of a 1/2 mil thick polyethylene terephthalate carrier sheet at an amount of about 1.25 pounds per ream. The coated carrier sheet was metallized on both sides with aluminum 400±50 angstroms thick. Release film MEK45%, toluene 45% and acetone 10%
The metallized carrier sheet was peeled off by dissolving it in a solvent consisting of: The thin aluminum particles were collected in the solvent mixture.

Example 6 A 1/2 mil thick Mylar carrier sheet was coated with about 1.0 pounds of nitrocellulose per ream per side on a commercial machine and then metallized with about 400±50 angstroms of chromium. MEK50% and toluene 50%
% solution to dissolve the nitrocellulose release membrane and remove the chromium pieces from the carrier sheet.

Example 7 The products obtained in Examples 1 to 6 were placed in a centrifuge and spun at 13,000 to 16,000 rpm for 5 minutes. The supernatant liquid was removed to obtain a pigment concentrate containing about 10 to 20% by weight of pigment.

Example 8 The metal pigments of Examples 1 to 6 obtained from the procedure of Example 7 were passed through a sonorator using a 21 gap orifice. An examination of the particles revealed that at least 90% of them had a diameter dimension of 25 to about 50 microns. Of course, the particle thickness remained approximately 400±50 angstroms. These metal pigments were further concentrated to about 10% and passed through an ultrasonic dispersion machine.
The pigment was uniformly subdivided into optimal pigment sizes ranging from 20 to 20 microns.

Example 9 The aluminum pigment of Example 7 treated according to Example 8 was formulated into a printing ink with the following composition: Aluminum leafing pigment (solid basis)
5g Nitrocellulose 1g Stearic acid 5g Methyl/Ethyl Cellosorb 60%/40%
A printing ink of this formulation using a 93.5 g 300 line mesh roller and then pressing with a polished steel roller gave an effect similar to applying hot stamping oil or aluminum foil to a laminate.

Example 10 An aluminum pigment produced according to the invention was formulated into a jet lacquer with the following composition: Aluminum pigment 1 g Acrylic binder 0.5 g Wetting agent 0.1 g Methyl/ethyl cellosorb 60%/40%
98.4g 100.0g One gallon of Lacquer of this composition has been found to be sufficient to produce a spray area of about 350,000 to 400,000 square inches using a conventional injector.

Small particles are usually required to obtain highly reflective coatings for maximum coating effectiveness and compatibility with printing, coating, lacquer and paint products, while larger particles are needed for other purposes. Metal foil can be used. The resulting materials, which can reduce or eliminate ultrasonic dispersion and achieve a flashing effect at low concentrations of pigment, are suitable for certain applications.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of the metal pigment manufacturing method of the present invention.
FIG. 2 is a schematic diagram of the method of the invention. FIG. 3 is an enlarged view of the stripping apparatus during the method of the invention. Number in the figure, 11...Carrier sheet, 12, 19, 2
6... Roller, 13... Solution container, 15... Coated carrier sheet, 16... Vacuum evaporator for metallizing, 17... Carrier sheet with metal film attached, 18... Stripper, 20, 20'... Wiper, 24, 2
4'...Sedimentation tank.

Claims (1)

[Scope of Claims] 1 (a) A release film is attached to at least one side of a carrier sheet, (b) a metal is deposited directly on the release film as a thin film, and (c) the release film with the deposited metal is attached. (d) The metal film is separated from the carrier sheet into particles to form a metal pigment that is substantially free of the release film and is non-reactive. 1. A method for producing a metallic pigment, comprising the steps of: collecting the metallic pigment in a neutral solvent; and (e) concentrating and subdividing the metallic pigment into particles having a diameter of 25 to 50 microns. 2. The method of claim 1, wherein the metal is deposited by evaporating the metal and depositing it on the release membrane as a 350 to 450 angstrom thick film. 3. The method according to claim 1 or 2, wherein the metal is aluminum, chromium, copper, steel, silver or gold. 4 0.75 to 1 ream per side of carrier sheet
4. A method according to any one of claims 1 to 3, wherein the release film is applied in an amount of 1.50 lbs. 5 The release film is made of polyvinyl chloride, polystyrene, chlorinated rubber, acrylonitrile-butadiene-styrene copolymer, nitrocellulose, cellophane,
The method according to any one of claims 1 to 4, which is methyl methacrylate, acrylic copolymers, fatty acids, waxes, rubbers, gels, or mixtures thereof. 6. A method as claimed in any one of claims 1 to 5, in which the carrier sheet is stretched by 1 to 2% of its length before separating the metal membrane. 7. The method according to any one of claims 1 to 6, wherein the metal membrane separation step is performed using an air knife. 8. The method according to any one of claims 1 to 7, wherein the release film dissolving solvent and the non-reactive solvent are the same. 9. The method according to claim 8, wherein the solvent for dissolving the release film and the non-reactive solvent are both contained in the solvent bath. 10 The above-mentioned peeling film dissolving solvent and non-reactive solvent are placed in the first tank and the second tank, respectively, and the second tank is
10. A method as claimed in any one of claims 1 to 9, wherein the reservoir is located at a convenient preselected position relative to the first reservoir. 11. The method according to any one of claims 1 to 10, wherein the carrier sheet is made of polyethylene terephthalate. 12 Claim 1 in which the operation is continuous
The method according to any one of paragraphs to paragraph 11. 13. A method according to claim 1, in which the metal pigment is concentrated to a solids content of 5 to 15% and subdivided into pieces with a diameter of 10 to 20 microns. 14. The method according to claim 1 or 13, wherein the fragmentation step is performed using ultrasound.