DE2054509A1 - Process for the production of homogeneous mixtures of pigments and thermosetting resins and their use - Google Patents

Description

SOCIETA ¹ ITALIAITA RESIlIE S.ρ.Α.,
Milan, Italy

"Process for the production of homogeneous Ge.r.i_; chen from pigments and thermosetting resins and their uses "

Priority: November 14, 1969, Italy, Mr. 24 411-A / 69

It is known to homogenize thermosetting resins together with pigments, optionally in the presence of various additives. Incomplete homogenization, however, results in an uneven production of the end products, generally pellets Color with tiny spots and craters on the surface. In these circumstances the brightness is the End products not uniform. The mechanical properties can also be adversely affected to a certain extent will.

For the homogenization of highly hardenable resins with pigments are ball mills have heretofore been commonly used. Pigment, resin granulate and necessary additives are added to the mill and grind to a powder that is as homogeneous as possible. That The resulting mixture is then used to produce the end products,

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usually used by prepressing. However, this method has several disadvantages. If, for example, the mixture is heated by condensation to increase the degree of crosslinking of the resin, undesirable fluctuations in the degree of pourability occur, which are also promoted by the relatively long residence time in the ball mill. Another disadvantage of this homogenization is the formation of crusts which adversely affect the mechanical properties of the objects obtainable from the mixtures. Finally, in the case of the mixtures, foreign particles that originate from the grinding devices cannot be removed.

The object was therefore to find a method to eliminate or at least substantially reduce the aforementioned disadvantages.

The method according to the invention solves this problem.

The invention thus relates to a process for the production of homogeneous mixtures of pigments and thermosetting resins by grinding the particles in a grinding device, which is characterized in that the particles of the resin with a diameter of less than 0.6 cm and the organic or inorganic pigments with a diameter of less than 0.5 μ in an amount of 0.02 to 8 parts by weight of pigment per 100 parts by weight of resin in the presence of an inert gas at a pressure of 3 to 8 at a fine grinding device and homogenized therein for 1 to 20 minutes. The mixture is preferably homogenized in such a way that at least about 65 % of the particles have a particle size below 100 μ. .

A fine grinding device is primarily understood to mean a jet mill, in which, as is known, the size of the solid

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Particle is reduced substantially by crushing and rubbing the particles together. When the invention The process is simultaneously firstly a homogenization of the pigment and the resin and secondly a comminution of the Substances achieved into a finely divided powder.

The gases used are preferably nitrogen, air or other gases which are inert to the particles to be homogenized are. One can also use water vapor, preferably from about 7 to 17 atm, but its use is because of the in the Homogenization to be maintained, relatively high Temperatures are not so much desirable if one wants to get a dry end product.

The completely homogeneous mixture in the form of a very fine powder, for example a particle size of 1 to 20 μl, is obtained continuously from the gases leaving the Peinstmahleinrichtung when the homogenization has lasted 1 to 20 minutes. Crosslinking of the resin can be avoided or at least substantially reduced under these conditions. This is achieved by the short dwell time in the Peinstmahlvorrichtung. In addition, no impurities from the grinding devices get into the mixtures, as was previously the case with the pail. Finally, the mixtures obtained can be used to achieve a uniform color and an essentially crater-free and stain-free surface on the pellets formed from the mixtures.

Examples of thermosetting resins are phenolic, epoxy, polyester and amino resins in the form of particles of their diameter is preferably 0.05 to 0.5 cm.

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Examples of pigments are inorganic pigments such as yellow or orange-colored cadmium sulfide, chromium oxide, iron oxide, cobalt blue, titanium dioxide, zinc sulfide or barium sulfate, or organic Pigments, such as phthalocyanine, anthraquinone or monoazo • .colors.

Examples of additives to the thermosetting resins and pigments are inert fillers, plasticizers, lubricants or release agents, Stabilizers or catalysts. Examples of inorganic fillers are silica gel, infusor earth, quartz, asbestos, Mica, glass fibers or calcium carbonate. Examples of Organic fillers are cellulose, wood flour, cotton waste and polyamides. Examples of lubricants or release agents are zinc stearate, fatty acids or soaps, while the catalysts are e.g. zinc sulfate, acid esters or organic bases can be used. Hexamethylenetetramine is particularly advantageous as a stabilizer.

The examples illustrate the invention.

Example 1 Production of the resin granules.

A mixture of 30.3 percent by weight of beechwood cellulose, 1.9 percent by weight of hexamethylenetetramine, 1.2 percent by weight of stearic acid, 1.4 percent by weight of zinc sulfate and 65.2 percent by weight of a urea-formaldehyde resin is comminuted in a hammer mill. In particular, the resin used contains formaldehyde and urea in a molar ratio of 1.45 ; 1 and has the following characteristics : Dry content 73 5 * 1 Flow rate at 25 ° C: 80 to 90 seconds. Treatment will

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continued until the mixture has the following particle size distribution owns:

0 percent by weight over 1000 ^ u

1 percent by weight over 500 p. 7 percent by weight over 250 y.

10 percent by weight over 150 μ 14 percent by weight over 100 p. and 68 percent by weight below 100 u.

Be ispiel 2

(Comparative example)

100 parts by weight of the mixture from Example 1 are mixed with 0.2 parts by weight of zinc stearate, 0.7 parts by weight of zinc sulfide, 0.03 part by weight of yellow cadmium sulfide, 0.03 part by weight

/ added / share orange-colored cadmium oxide and 0.1 part cobalt blue /

Geraisch obtained is in a steatite ball mill up to one

Ground weight of 2.5 g / cm. In the ball mill, the balls take 34 % and the mixture 43 % of the volume, while 23 % free volume remains. Samples are taken after each 2 and after 4 hours of milling and are examined in accordance with the information in Example 4.

Example 3

A mixture like the starting mixture in Example 2 is passed continuously through a ^{jet mixer which is commercially available under the name "Micronette 11} " from Societa Gusero. Air is passed tangentially through nozzles at a pressure of 7.7 atm

pressed into the jet mixer. First the homogenization time is 4 minutes and then 7 1/2 minutes. The two

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The samples obtained are examined as described in Example 4 ".

Example 4 , study of the final products.

50 g each of the samples obtained by the methods of Examples 2 and 3 are placed in a ⁰ to 155 C, heated to 150 circular press and then 60 seconds at a. Pressure of 200 at pressed. The disks obtained (3 of each sample) with a diameter of 2 30 to 240 mm and a thickness of 0.5 to 0.6 mm are tested for the number of resin spots and pigment spots and for the surface brightness. In particular, the resin stains are checked for transparency. The table below shows the results. The number of resin spots and pigment spots for each sample indicate the maximum and minimum values for the respective 3 samples.

Tabel

at Time, Particle size distribution above above above above , % number the Bright game Min. above 500 250 150 100 under Resin- Pig- speed 1000 P. P. V P. 100 flek-! ment P. 0.3 4.5 *
5 6th P. ken flek-
ken 2 120 0 0.1 4th 4th 7th 84.2 30th 60-1Ot) Well 240 0 0.5 1 . 1.5 2.5 85 3-7 4-10 Well 3 4 · 0 94.5 3-7 2-3 out drawing 0.5 1 1 1 net 8th 0 96.5 3-7 1 out drawing net

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Claims (1)

• - 7 - Claims /l.J Process for the production of homogeneous mixtures from pigments and thermosetting resins by grinding the particles in a grinding device, characterized in that the Particles of the resin with a diameter of less than 0.6 cm and the organic or inorganic pigments with a diameter of less than 0.5 microns in an amount of 0.02 to 8 parts by weight of pigment fed to 100 parts by weight of resin in the presence of an inert gas at a pressure of 3 to 8 atm and homogenized therein for 1 to 20 minutes. 2. The method according to claim 1, characterized in that one the Peinstmahleinrichtung additional inert fillers, plasticizers, Feeds lubricants or release agents, stabilizers and / or catalysts. 3. The method according to claims 1 or 2, characterized in that that the inert gas is water vapor at a pressure of 7 to 17 at used. 4. Process according to Claims 1 to 3> characterized in that the resins used are amino, phenolic, epoxy or polyester resins . 5. Process according to Claims 1 to 4, characterized in that the resins are used in the form of particles with a diameter of 0.05 to 0.5 cm . : 109829 / 101G ■ - 8 - 6. The method according to claims 1 to 5 »characterized in that that the pigments used are yellow and / or orange-red cadmium sulfide, chromium oxide, iron oxide, cobalt blue, titanium dioxide, zinc sulfide and / or Barlum sulfate used. 7. Process according to Claims 1 to 6, characterized in that that phthalocyanine, anthraquinone and / or monoazo dyes are used as pigments. 8. The method according to claims 1 to 7, characterized in that the homogenization is carried out in such a way that at least 65% of the particles have a particle size below 100 μ. 9 · Use of the mixtures according to claims 1 to 8 for Production of pellets. ^ß AD ORIGINAL 109829/1016