NO142917B - MATT PAINTING, INCLUDING NON-MOVING POLYMER PEARLS, CHOOSED FROM TWO SIZE AREAS - Google Patents

Description

Matt paints have for many years been produced by exploiting the fact that relatively coarse, inorganic filler particles break the surface of the dry paint film and thus produce a low surface gloss. Although many products of this type have been used successfully, it is accepted that they have limitations when it comes to such properties as surface roughness and the resulting difficulties in connection with cleaning, as well as low resistance to shear forces. It has also been observed that when the surface of such a paint film is sanded, exposed fragments of brittle filler particles break off and leave disturbing, whitish streaks or even shiny spots in the sanded areas.

A proposed method to overcome these difficulties is to replace the inorganic filler particles with polymer beads of similar diameter. Such a method is described, for example, in British patent no. 1 256 784. Paints of this type are free of most of the shortcomings of conventional matt paints, and if the polymer beads used contain a primary pigment such as e.g. titanium dioxide, dispersed in it, they can exhibit an unusually high opacity. However, we have observed that the color range for paints of this type is limited by their tendency, especially if they have low reflectance, to show streaking or slight variations in color in the dry film, depending on the method used to apply the paint .

We have now found that this problem can be solved by using polymer beads that fall within two specific size ranges, the first with diameters from 2 to 10 µm, and the second from 10 to 40 µm.

The object of the present invention is thus

a matte paint, comprising a liquid paint base in which is dispersed pigment and non-film-forming polymer beads whose diameter is 2-40 ym, the beads will make up 55-90% by volume of a dry film of the paint, and the paint is characterized by the fact that the bead material is composed of two parts, each constituting 45-55% of

the total volume, the particle size for the first part being essentially in the range 2-10 ym, and in the second part in the range 10-40 ym, and the particle size within each part varying in accordance with the usual distribution curve for suspension polymerised beads, so that the distribution curve for the collected pearl material will have two maxima, as the two parts of the pearl material can consist of a) only white and/or opaque pearls, whereby it is achieved that the dry paint film has a reflection of over 65%, b) white and/or opaque beads in the first part and clear beads in the second part, whereby the dry film gets a reflection on

30-65%, or,

c) only clear beads, whereby the dry film has a reflection of less than 30%.

What is stated here in the introductory part of the patent claim, as belonging to the state of the art, is known from the above-mentioned British patent document.

The volume of pearls must therefore not amount to more than 90% of the total non-volatile content in the paint. If this limit is exceeded, the resistance to scratching will begin to decrease significantly.

A particularly useful feature of some of these preparations is that they have an unusually high resistance to scratching, for which purpose the large beads must be compact, i.e. free of voids, and should preferably consist of polymers with maximum elongation in the event of a breach of 40%.

The matte paints according to the invention are conventional in the sense that they consist of liquid dispersions of opacifying, coloring and/or film-modifying pigments in a paint base. Dry films of the paint have a matte appearance. We use the term "paint base" (or "paint base") in the broad sense known in the art to denote liquid, film-forming mixtures which in turn can consist of solutions or dispersions of a film-forming polymer (the binder) in volatile liquids. In accordance with established practice, we refer to the components of the liquid paint mixture that remain in a dry film as the non-volatile content of the paint. Of course, the paint base must not dissolve or chemically attack the polymer beads. The only limitation in the choice of paint base is that it must be inert to the beads to be used. The paint may also contain an inorganic filler, but to achieve the best possible result we prefer to leave out such fillers.

By "reflectance" for a paint film we mean "standard green reflectance", measured with a tristimulus differential colorimeter and designated "G" in the American Society for Testing and Materials Method D2244-68. The green filter reflection is used regardless of the color tone of the paint, due to its close correlation with human vision. (Gardner-Sward "Paint Testing Manual", 13th edition page 31) .

It is particularly necessary to avoid color variations in the so-called color bases, i.e. paints of standard color strength to which calculated amounts of liquid dye (reactive dyes) are added in order to achieve a series of standard shades. In order to avoid the unwanted appearance and composition compromises described above, we have found it desirable, when developing a so-called "universal-sal color system", to use three color bases. In the first of these, all pearls are white and opaque. In the second, the beads from the smallest size range (as defined above) are white and opaque, but the largest beads are not, and in the third none of the beads are opaque.

The color base from which any desired hue can be obtained by adding dye is selected as follows: For hues with a reflectance above 65%, a color base is selected in which all pearls are white and opaque. For hues with a reflectance between 30 and 65%, a color base is used in which only the smallest pearls are white and opaque, and for hues with a reflectance below 30%, a color base must be used in which all pearls are clear.

The bead diameter can be measured microscopically, but we have found it more appropriate to use an instrument such as a Coulter Counter for this purpose. It is accepted, in each individual batch of beads, that a smaller part of them may lie outside these size ranges, and such normal variation can be tolerated in the execution of the invention.

Suitable polymer beads can, for example, be produced by polymerisation of a water emulsion of a syrup, containing polymerisable elements which can be converted into solid polymer, for example a solution of an unsaturated polyester in styrene. Other polymers that can be produced in the form of beads by such a technique are urea/formaldehyde condensates and methacrylic polymers.

White, opaque beads can be produced by similar methods after first having dispersed a base pigment, e.g. titanium dioxide, in the syrup before it is emulsified in water. At least 1% by weight of white pigment is usually required to provide opacity to the beads.

The opaque nature of a pearl can be easily determined by examining it microscopically using translucent light.

Alternatively, opacity can be imparted to the beads by forming a bluish structure in them. The blisters may in turn include some pigment particles. By a vesicular particle we mean a particle that contains several separate air sacs or vesicles enclosed in a shell of essentially non-porous polymer. Particles of this type are, for example, described in Australian patent no.

439 432 and in Norwegian patents no. 116 992, 131 428 and 139 224 (pigment containing).

Certain materials used in the examples below are: hydroxyethyl cellulose "Natrosol 250 H.R." or

corresponding types

polyvinyl alcohol "Gelvatol 20/90" or similar types

unsaturated polyester resin "Crystic C/96" or equivalent bactericide "Proxel T.L." or equivalent styrene/maleic anhydride - "S.M.A. 1440"

copolymer

"Natrosol", "Gelvatol", "Crystic" and "Proxel" are trademarks.

Slurry of clear beads, 10-40 micrometers

The slurry was prepared as follows:

To a solution of 0.33 parts of hydroxyethyl cellulose in 49.11 parts of water, 11.17 parts of a 7.5% aqueous solution of an 80% hydrolyzed polyvinyl alcohol were added and stirred.

A solution of 30.83 parts of an unsaturated polyester resin and 1.12 parts of a 50% benzoyl peroxide paste in 5.10 parts of styrene was added to the above aqueous solution and mixed at high speed until the largest emulsion particles were visible under a microscopy, had a diameter of 40 ym.

The emulsion was stirred slowly and 0.18 parts of diethylaniline was added. The slow stirring was continued

3 hours, while polymerization of the emulsion particles took place.

When the polymerization was finished, the pH of the emulsion was adjusted to 9 with approximately 0.15 part of a 28% ammonia solution.

0.05 part of a bactericide and 1.96 parts of an aqueous ammonia solution (pH 9) containing 35% of a styrene/maleic anhydride copolymer were added. The size range for the thus produced polymer beads was estimated at 10-40 ym.

Slurry of clear beads, 2-10 micrometres

The slurry was prepared as follows:

To a solution of 0.33 parts of hydroxyethyl cellulose in 351.11 parts of water, 11.17 parts of a 7.5% aqueous solution of an 80% hydrolyzed polyvinyl alcohol were added and stirred.

A solution of 30.83 parts unsaturated polyester resin and

1.12 parts of a 50% benzoyl peroxide paste in 5.10 parts styrene was added to the above aqueous solution and mixed at high speed until the largest particles of the emulsion visible under a microscope were 10 µm in diameter.

The emulsion was stirred slowly, and 14 parts water and

0.18 part diethylaniline was added. The slow stirring was continued for 3 hours while the polymerization of the emulsion particles took place.

When the polymerization was finished, the pH of the emulsion was adjusted to 9 with approximately 0.15 part of a 28% ammonia solution.

0.05 part of a bactericide and 1.96 parts of an aqueous ammonia-alkaline solution (pH 9.0) containing 35% of a styrene/maleic acid hydride copolymer were added.

The size range for the thus produced polymer beads was estimated at 2-10 ym.

Slurry of white beads, 10-40 micrometers

The slurry was prepared as follows:

A solution of 8.51 parts of a 2.5% hydroxyethyl cellulose solution and 8.51 parts of a 7.5% solution of an 80% hydrolyzed polyvinyl alcohol in 35.70 parts water was formed. 16.20 parts of a titanium dioxide pigment (rutile) was dispersed by high speed stirring to a fineness of less than 2 µm Hegmann in a solution of 23.50 parts of an unsaturated polyester in 3.70 parts of styrene. A mixture of 0.85 parts of a 50% benzoyl peroxide paste and 1.02 parts of divinylbenzene was added to the above dispersion. The resulting mixture was added to the above aqueous solution and mixed at high speed until the largest emulsion particles visible under a microscope were 40 µm.

The emulsion was then stirred slowly, and 0.22 part of diethylaniline was added. The slow stirring was continued for 1 hour while the polymerization of the emulsion particles took place.

When the polymerization was complete, the pH of the emulsion was adjusted to 9 with approximately 0.12 part of a 28% ammonia solution.

0.04 part of a bactericide and 1.58 parts of an aqueous ammonia solution (pH 9.0) containing 35% of a styrene/maleic anhydride copolymer were added.

The size range for the thus produced polymer beads was estimated at 10-40 ym.

Slurry of white beads, 2-10 micrometres

A solution of 9.20 parts of a 2.5% hydroxyethyl cellulose solution and 13.80 parts of a 7.5% solution of an 80% hydrolyzed polyvinyl alcohol in 18.50 parts water was formed.

14.80 parts of a titanium dioxide pigment (rutile) was dispersed by stirring at high speed to a fineness of less than 2 ym Hegmann in a solution of 21.30 parts of an unsaturated polyester resin in 3.40 parts of styrene. 0.75 part of a 50% benzoyl peroxide paste was added to this dispersion. The resulting mixture was added to the above water solution and mixed at high speed until the largest particles visible under the microscope were 10 µm.

The emulsion was then stirred slowly, and 15.70 parts of water and 0.18 parts of diethylaniline were added. The slow stirring was continued for 1 hour while the polymerization of the emulsion particles took place.

When the polymerization was finished, the pH of the emulsion was adjusted to 9 with approximately 0.90 part of a 28% ammonia solution.

0.03 part of a bactericide and 1.44 parts of an aqueous ammonia solution (pH 9.0) containing 35% of a styrene/maleic anhydride copolymer were added.

The size range for the thus produced polymer beads was estimated at 2-10 ym.

The invention is illustrated by the following examples where all parts are parts by weight.

EXAMPLE 1

A paint according to the invention to be used as a color base was produced using high speed dispersing equipment with the following composition:

EXAMPLE 2

A paint according to the invention for use as a color base was prepared using high speed dispersing equipment with the following composition:

The example was repeated replacing the acrylic latex with a latex of a vinyl acetate polymer, consisting of a copolymer of vinyl acetate and 2-ethylhexyl acrylate in the weight ratio 85/15.

EXAMPLE 3

A paint according to the invention for use as a color base was produced using equipment for d-dispersion at high speed with the following composition:

EXAMPLE 4

Colored paints were produced from the color base according to example 1, and these were applied to a test plate with a brush. The dried films were examined for color uniformity and degree of coverage.

By adding a pitch color consisting of a dispersion of phthalocyanine blue (pigment) in a miscible medium, blue paints were produced with a G-reflection (as defined above) of less than 60%. They showed an unacceptable degree of unevenness in the colour, visible both as streaks in the direction of the brush and so-called "flips and flops" (colour changes). However, all the colored paints had good coverage.

When a pitch color consisting of a corresponding dispersion of a red iron oxide pigment was added, the pink paints with a G-reflectance of less than 60% showed an unacceptable degree of color shift. Paints with greater reflectivity were acceptable in this respect. All paints had good coverage. When a pitch color consisting of an equivalent dispersion of a carbon black pigment was added, the gray paints with a G-reflectance of less than 66% showed an unacceptable degree of color shift. Paints with greater reflectivity were acceptable in this respect. All paints had good coverage.

EXAMPLE 5

Colored paints were produced from the color base from example 2, and these were brushed onto a test plate with a brush. The

the dried films were examined for color change and opacity.

Using a phthalocyanine pitch dye, blue paints with a G-reflectance of less than 29% showed unacceptable color shift. The coverage was judged to be unacceptably low for paints with G-reflection greater than 65%. However, paints with G-reflection in the range 29-6 5% were acceptable with regard to both color change and covering ability.

Similar behavior was observed with other vomit colors.

EXAMPLE 6

Colored paints were produced from the color base according to example 3, and these were brushed onto a test plate with a brush. The dried film was examined for color change and opacity.

No colored paints from this color base showed color shifting. However, coverage was only acceptable for paints with G-reflection below 30%.

EXAMPLE 7 (Comparative example)

Demonstration of the effect of reducing the amount of pearls to less than 55% of total solids.

A paint, suitable for use as a color base, was prepared using rapid dispersing equipment with the following composition:

In this color base, the beads comprise 40% by volume of the solids, as opposed to 67% in Example 3. The paint was colored to give a G-reflection of less than 30%, as described in Example 6, and brushed onto a test plate . The paint film exhibited a high degree of translucency and a mottled appearance, caused by glistening spots and streaks. The paint films discussed in Example 6 did not show these defects.

EXAMPLE 8 (Comparative example)

Demonstration of the effect of changing the relative amounts of the large and small beads.

Two color bases, hereinafter referred to as (a) and (b), were prepared according to the same procedure and using the same materials and amounts as used in Example 3, with the exceptions that the amounts of beads used therein were substituted with the following quantities:

These slurries contain the same total volume

of beads as the slurries used in Example 3, but in (a) the large beads make up 35% of the total volume of beads, and in (b) they make up 65% of the total volume. Both of these figures lie outside the required interval of 45-55% (of total pearl volume) in contrast to example 3 where the large pearls make up 50% of total pearl volume.

The two color bases were colored as described in example 6 and then coated on two sample plates. The film of the colored base (a) showed unacceptable translucency, and the base (b) had an acceptable appearance, but was very sensitive to scratching and wear. The colored base in Example 3 did not exhibit any of these defects.

EXAMPLE 9

Preparation of a color base using a non-aqueous film former.

Slurries of white beads from both the 2-10 µm and 10-40 µm ranges were dried, and the dried beads were mixed so that beads from the 10-40 µm range made up 50% by volume of the mixture. 10 parts of titanium dioxide were dispersed in 20 parts of a 40% solution in xylene of a soybean oil/glycerol phthalate alkyd of 50% oil content. 5 parts of the dry beads and 10 parts of xylene were added to this mixture, and the whole was dispersed by sandblasting. The resulting base was then filtered.

The base was stained with a pitch stain consisting of a dispersion of phthalocyanine blue in a xylene-compatible medium. In this way, a series of blue paints was produced, and films of these were brushed onto test plates with a brush. It was found that paints with G-reflectance above 60% showed acceptable color shift, but those with lower G-reflectance were unacceptable.

EXAMPLE 10

Comparison of the colored paints according to the present invention and colored paints comprising beads with a single size distribution.

The paints comprising beads of a single size order were produced using the method according to British patent no. 1 256 784, the paint in question being used being indicated as no. 6 in table 3 (p. 9 in the patent document). Samples of this paint were colored with phthalocyanine blue to reflectances of 20%, 50% and 70%, and these were compared respectively with a colored paint of reflectance 20%, prepared from the color base according to Example 3, a colored paint with reflectance 50%, prepared from the color base according to example 2, and a colored paint with reflectance 70%, prepared from the color base according to example 1, all three being colored with the same phthalocyanine blue. In each case, the paint described in the said British patent document exhibited unacceptable characteristics, e.g. streaking and color changes, or a combination of these defects, while the corresponding paint according to the present invention had a satisfactory appearance.

Claims (1)

Matte paint, comprising a liquid paint base in which is dispersed pigment and non-film-forming polymer beads whose diameter is 2-40 ym, the beads will make up 55-90% by volume of a dry film of the paint, characterized in that the bead material is composed of two parts, each constituting 45-55% of the total volume, the particle size of the first part essentially being in the range of 2-10 ym, and of the second part in the range of 10-40 ym, and the particle size within each part varying in accordance with the usual distribution curve for suspension polymerized beads, so that the distribution curve for the collected bead material will have two maxima, as the two parts of the bead material can consist of a) only white and/or opaque beads, whereby it is achieved that the dry paint film gets a reflection of over 65%, b) white and/or opaque beads in the first part and clear beads in the second part, whereby the dry film gets a reflection of 30-65%, or, c) only clear beads, whereby the dry film has a reflection of less than 30%.