MXPA96003157A - Method for supplying the brightness control of latex films, and used compositions in this met - Google Patents

Abstract

A method for providing a brightness control in a dry film of an aqueous coating and compositions useful for the brightness control is disclosed. A specific level of gloss is affected by the addition of hard particles of a latex polymer to the soft particles of a latex polymer, which form films. By adjusting the parameters of the hard particles, the relative particle size and size, the desired film brightness can be achieved, while optimizing the other performance characteristics is allowed.

Description

METHOD TO SUPPLY THE BRIGHTNESS CONTROL OF LATEX FILMS, AND THE COMPOSITIONS USED IN THIS METHOD The present invention relates to a method for providing control of the brightness of a film, formed of a coating composition, aqueous or latex, and aqueous coating compositions suitable for use in this method. The brightness of a dry polymer film is a key parameter of appearance and the ability to control such gloss is important in coating applications, such as paints, varnishes and floor polishers.

U.A. Patent No. 4,734,295 discloses a method useful in providing glare control of a reflective-transmissive surface, such as an electronic vision screen. The method of the '295 patent involves applying a coating composition, having organic polymeric particles and a tarnish agent to the surface of the screen, and then allowing this composition to dry. This procedure results in surface irregularities in the dry film, which scatter light, producing an anti-glare effect. This anti-glare effect is controlled by a second stage, which involves the addition of an inert fluid to the dry film, partially covering some of the surface irregularities and thus reducing the anti-glare effect. Glare control, in the '295 patent, is similar to the control of brightness in a film, since both involve surface irregularities created by the particles in a dry polymer film, this film is useful in reducing the reflectance of light from a surface. U.A. Patent No. 3,398,018 discloses a composition for producing matte or low gloss finished films by the addition of large plastic spheres to the latex polymer that forms the film. These hard, large, plastic spheres create a surface roughness that scatters light, thus reducing the brightness of the dry film. The problem with the previous methods and compositions, to control the brightness, is that they do not provide a control, of a stage, that can be predicted, over the wide margin of the desired brightness. The method disclosed in the '295 patent has the disadvantages implied by a two-step process and control is through the addition or subtraction, by trial and error, of a second inert coating, until the desired level is achieved of the reflectance of light. The composition disclosed in the '018 patent is useful only in the low gloss supply, where the measurement of brightness at 60 degrees is less than the value 16. The composition of the' 018 patent also has the disadvantage of producing an inconvenient rough surface, due to the use of very large plastic spheres, larger than 3 microns.

We have found that a specific or predetermined degree of film gloss can be obtained by mixing hard particles of latex polymers, of a selected relative size and quantity, with soft particles of latex polymers, which form films, in an aqueous composition of covering. This simple mixing of the hard and soft particles produces a full range of brightness levels, from a high gloss to a low gloss, in a dry film, formed from the coating composition.

The present invention provides the additional advantage of producing a dry film, without noticeable surface roughness. The present invention also provides flexibility in the formulation of an aqueous coating composition, having any desired level of gloss.

In the first aspect of the present invention, a method is provided for providing a specific gloss level of a dry film of an aqueous coating composition, which comprises mixing from 1 to 60 percent, by weight of the polymer solids, of hard polymer particles, with soft particles of the polymer, both the hard particles and the soft particles have sizes in the range of 30 to 1,000 nanometers, the hard particles have a glass transition temperature in the range of 35 to 160 ° C, and where the glass transition temperature of the hard particles is higher than the glass transition temperature of the soft particles.

In the second aspect of the present invention, an aqueous coating composition is provided comprising hard polymer particles and soft polymer particles, where these hard and soft particles are in the range of 30 to 1,000 nanometers in size; where the hard particles are present from 1 to 60 weight percent of polymer solids; they do not form films and have a Tg in the range of 35 to 1602C; where the soft particles are present in the 40 to 99 weight percent of the polymer solids do form films and have a Tg in the range of -30 to + 75SC, provided that the Tg of the hard particles is greater than the Tg of the soft particles. In a third aspect of the present invention, a surface carrying a dry film of an aqueous coating composition is provided, wherein this aqueous coating composition comprises hard particles of polymer e-ro and soft polymer particles, in which the hard particles and smooth are in the range of 30 to 1,000 nanometers in size; where the hard particles are present from 1 to 60 percent, by weight of the polymer solids, they do not form films and have a Tg in the range of 35 to 160SC; where the soft particles are present from 40 to 90 percent, by weight of the polymer solids, they form films and have a Tg in the range of -30 to + 75se, provided that the Tg of the hard particles is greater than the Tg of the soft particles. By "gloss" is meant in the present invention the relative and natural amount of mirror, or specular, type of reflection of a dry film, formed of an aqueous coating composition, as measured at an angle of incidence of 20 to 60 degrees. By "hard particles", it is meant here latex polymer particles with a glass transition temperature (Tg) greater than the minimum temperature for the coating composition to form a film, here referred to as the "Minimum Formation Temperature". of Movie "or" MFT ". The hard particles of this invention have a Tg between 35 and 160 ° C and are above the MFT. The Tg of the hard polymer used in the invention is greater than the Tg of the soft polymer.

By "soft particles" is meant here the particles of the latex polymer, which form films, which are capable of forming a continuous film with other soft particles on drying. The film-forming particles are those with an MFT at or below room temperature. The MFT of a polymer can be decreased by the use of coalescents. Coalescents are volatile organic solvents that decrease the MFT of the polymer, thus allowing the coating to form a useful film at a temperature below the Tg of the polymer. Preferably, the polymer forming the film contains at least one polymeric component with a Tg between -30 and + 75sc. More preferably, the Tg of the polymer that forms the film is in the range of +10 to + 352C. Drying is preferred under ambient conditions. By "matt finish" is meant herein a dry coating surface, which exhibits little or no gloss, when viewed at any angle. The hard and soft particles in this invention may be homopolymers or copolymers, single or multi-stage, or mixtures of such polymers. Latex particles can be synthesized by conventional polymerization techniques are well known in the art. By "latex" is meant here a stable dispersion of the polymer particles in an essentially aqueous medium. The particles of the latex polymer can be obtained in an aqueous medium or can be obtained in another medium and then dispersed in an aqueous medium. A preferred method of polymerization is by conventional emulsion polymerization. The polymers useful in the invention are not limited to any particular chemistry or physical configuration and may be mixtures of such polymers.

The hard and soft particles of this invention can be prepared by the polymerization of at least one ethylenically unsaturated monomer, such as, for example, the esters of (meth) acrylic acid, vinyl esters, styrene, butadiene and vinyl monomers, such such as vinyl chloride, vinylidene chloride, N-vinyl pyrrolidone; acrylonitrile or methacrylonitrile and ethylene. Polar monomers, such as (meth) acrylic acid, itaconic acid, acrylonitrile, dimethylaminoethyl (meth) acrylate and hydroxyethyl ethyl (meth) acrylate, can also be incorporated in the polymer in an amount of 0 to 12 percent of the total monomer.

The particles, both hard and soft, of this invention have a particle size with diameters in the range of 30 to 1,000 nanometers. A preferred particle size is 50 to 750 nanometers. The hard particles are in the range of thirty times greater than thirty times smaller than the soft particles. A preferred size of the hard particles is six times greater than six times smaller than the size of the soft particles. An increase in the brightness level of a dry polymer film of an aqueous coating composition can be effected in a predictable manner by mixing small hard particles with large soft particles. The gloss of the film is increased by the amount of the hard particles in the coating compositions, increased from 1 to 15 percent by weight of the polymer solids. Hard particles are two to thirty times smaller in size than soft particles. Preferably, the hard particles are two to six times smaller than the soft particles. These hard particles are in the range of 30 to 250 nanometers and the soft particles are in the range of 150 to 1,000 nanometers in size.

A decrease in the brightness level of a dry polymer film of an aqueous coating composition can be effected in a predictable manner by: 1) mixing small hard particles with large soft particles, between 15 and 40 percent of the hard particles by weight; 2) mix the hard particles with the soft particles of approximately the same size (unimodal) between 15 and 60 percent of the hard particles by weight, and 3) mix large hard particles with small soft particles, between 1 and 60 percent hard particles by weight. In an aqueous coating composition, which has small hard particles and large soft particles, the brightness of the dry film decreases as the amount of the small hard particles in the coating composition is increased between 15 and 40 weight percent. the solids of the polymer. The hard particles are in the range of 30 to 250 nanometers in size. The hard particles are in the range of 30 to 250 nanometers in size. The soft particles are in the range of 150 to 1,000 nanometers in size. Preferably, the size of the soft particles is between 200 and 750 nanometers. Hard particles are two to thirty times smaller than soft particles. Preferably, the hard particles are two to six times smaller than the soft particles. In an aqueous coating composition, having hard particles and soft particles of approximately the same size, or unimodal, the brightness of the dry film decreases as the amount of the hard particles in the coating composition is increased from 15 to 60 percent by weight of the polymer solids. By unimodal it is understood here that the hard particles are between half and twice the size of the soft particles. Preferably, the hard and soft particles are approximately equal in size. The particle size, both hard and soft, is in the range of 50 to 750 nanometers. Preferably, both hard and soft particles are between 75 and 500 nanometers in size.

In aqueous coating compositions, having large hard particles and small soft particles, the brightness of the dry film decreases as the large hard particles in the coating composition is increased from 1 to 60 weight percent of the solids in the coating composition. polymer. The hard particles are in the range of 150 to 1,000 nanometers in size. Preferably, the size of the hard particles is between 200 and 750 nanometers. The soft particles are in the range of 30 to 250 nanometers in size. Large hard particles are two to thirty times larger than soft particles. Preferably, the hard particles are two to six times larger than the soft particles.

The aqueous coating compositions of this invention are typically prepared by conventional techniques, which are well known in the art of coating. First, adjuvants, such as, for example, defoamers, pigments and cosolvents, are well dispersed in water.

Next, the polymers are mixed in the aqueous composition, with low-cut agitation, together with other coating adjuvants, as desired. The polymers of this invention can be added in any order to the formulation. The aqueous coating composition may contain, in addition to the polymers, conventional additives, such as, for example, pigments, coalescing agents, diluents, emulsifiers, thickeners, humectants, plasticizers, fillers, curing agents, soaking agents, biocides. , anti-foaming agents, dyes, waxes and antioxidants. The aqueous coating composition of this invention can be used to formulate a variety of coatings, including, for example, latex paints for architectural and industrial applications, caulks, sealants, varnishes, inks, paper coatings, coatings for fibers woven and non-woven, coatings for leather and floor polishers or sealers for floor coverings. One example is the use of the aqueous coating composition as a matt floor polish.

The flexibility in the formulation of an aqueous coating of a specific gloss level is provided by the selection of the hard particles in a certain amount and with a relative particle size.

The coatings of this invention can be applied to the surface of a wide variety of substrates, such as, for example, wood, paper, fibers, glass, ceramics, plaster, stucco, asphalt, vinyl slabs, plastics, leather and concrete.

Test Methods: The brightness of a dry film of a coating composition was determined by measuring the specular gloss, as described below. The measured brightness is a relative specular reflectance of the coating surface compared to that of a standard (according to ASTM D 523, an optically smooth black gloss, with a refractive index n = 1,567) was used with the angled reflectances of incidence of 20 and 60 degrees, using the equation: brightness = reflectance of the coating / reflectance of the standard x 100 Brightness Measurement: A test sample was laid on a black glass, with a hollow sheet of 0.254 cm. , and dried at 252C and 50% relative humidity, for 24 hours. The specular brightness was measured using a GLOSSGARD II gloss meter (Hunter Associates Laboratory, Inc.) according to ASTM-D 523-89, with reflectance angles of 20 and 60 degrees.

The polymers in Examples 1 to 3 were prepared by the standard emulsion polymerization. The particle sizes of the polymer were measured by light scattering, using a Broo haven BI-90 Partiole Sizer particle measuring device. Glass transition temperatures were measured by differential scanning calorimetry (DSC) and are provided as the midpoint of the transition, or calculated from the Fox equation: 1 Tg (copolymer) = 1 Tg (monomer A) + 1 / Tg (monomer B) + 1 / Tg (monomer n), etc. The emulsions of the hard and soft polymers were mixed in the indicated percentages and stirred to produce a homogeneous mixture.

Example 1 Example 1 shows the effect on the brightness of the film in the mixture of small hard particles with large soft particles. The hard particles were synthesized by the emulsion polymerization of a monomer composition of 46% butyl methacrylate, 3% methacrylic acid and 51% methyl methacrylate. The hard particles were 100 nanometers in size, with a Tg of 60ac. The emulsion was 44.7% solids.

The soft polymer particles were synthesized from a monomer composition of 52% butyl acrylate, 46% methyl methacrylate and 2% methacrylic acid. The particles of the polymer that forms the smooth film were 394 nanometers in size, with a Tg of 2SC. The emulsion contained 44.5% solids. The polymer emulsions, hard and soft, were mixed as indicated and the gloss was measured on the films produced from the mixture. TABLE 1 Mixture of Small / Mild Large Hard Particles The results show that the brightness increases as hard particles are added, between 1 and 10 weight percent, reaching a maximum in brightness between 10 and 20 weight percent of small hard particles. The gloss decreases by small hard extra particles, between 20 and 40 weight percent.

Example 2 Example 2 shows the effect on the gloss of the film of the mixture of hard particles and smooth particles of equal size (unimodal) in a coating composition. The hard particles were synthesized from a monomer composition of 27% butyl acrylate, 72% methyl methacrylate and 2% methacrylic acid. The hard particles had a size of 122 nanometers and a Tg of 422C. The emulsion had 45.2% solids. Emulsions of hard and soft polymers were mixed as indicated and the gloss was measured on the films produced from the mixture.

The soft particles were synthesized from a monomer composition of 65% butyl acrylate, 33% methyl methacrylate and 2% methacrylic acid. The soft particles had a size of 118 nanometers and a Tg of -172C. The emulsion was 44.9% solids.

TABLE 2 Unimodal Mix of Hard / Soft Particles The results show a decrease in gloss as the percentages of the hard polymer particles increase between 0 and 60% by weight of these hard particles. Example 3 Example 3 shows the effect on the brightness of the film of the mixture of large hard particles with small soft particles. The hard particles were synthesized from a monomer composition of 3% butyl acrylate, 95% methyl methacrylate and 2% methacrylic acid. The hard particles had a size of 497 nanometers with a Tg of 80 ° C. The emulsion had 44.8% solids. The soft polymer particles were synthesized from a monomer composition of 46% butyl methacrylate, 3% methacrylic acid and 51% methyl methacrylate. The emulsion had 44.7% solids. The soft particles had a size of 100 nanometers with a Tg of 60ac, in coalescence with 15% by weight, based on the polymer solids, of Dowanol PPH (Dow Chemicals). The emulsions of the hard and soft polymers were mixed as before and the gloss was measured on the films produced from this mixture.

TABLE 3 Mixture of Hard Large / Soft Small Particles The results show a decrease in gloss as the percentage of large hard particles increases from 1 to 60 weight percent of the polymer solids. Example 4 Mixtures of polymers of large hard particles and small soft particles were formulated in floor polishing compositions. Polymer A is an emulsion polymer with 40% solids, synthesized from 95% methyl methacrylate, 3% butyl acrylate and 2% acrylic acid. The polymer had a particle size of 580 nanometers and a Tg of 80ac. Polymer B is a 38% emulsion polymer, synthesized from 45% methyl methacrylate, 45% n-butyl methacrylate and 10% methacrylic acid. The polymer had a particle size of 90 nanometers and a Tg of 69ac.

Preparation of polishing compositions for floors: The following materials were mixed with a low-cut mixture by means of a magnetic stir bar, for 5 minutes.

The following ingredients were added to these mixtures, with continuous agitation: The mixtures were stirred for one hour, before application. Each mixture was applied to a black vinyl slab at a rate of 4 milliliters per 930 square centimeters, with a Mohair applicator. The slab was cured overnight at 25ac and 50% relative humidity. A visual measurement of each slab was made.

Results: The results show that the brightness of a floor polisher can be controlled by the addition of large hard particles to small soft particles. The gloss decreased (increased matte finish), as the percentage of large hard particles in the polishing of floors is increased in relation to the small soft particles.

Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as property: CLAIMS 1. A method for supplying a specific brightness level in a dry film of a composition aqueous coating, which comprises mixing from 1 to 60 percent of hard polymer particles, by weight of the polymer solids, with particles of a mild polymer; both polymer particles, hard and soft, have sizes in the range of 30 to 1,000 nanometers; the hard polymer particles have a glass transition temperature in the range of 35 to 160ac; and wherein the glass transition temperature of the hard polymer particles is greater than the glass transition temperature of the soft polymer particles.
2. 2. The method according to claim 1, for providing an increased level of brightness, in which the hard particles are: present from 1 to 15 weight percent of the polymer solids; from two times smaller to thirty times smaller than soft particles, and have a size of 30 to 250 nanometers.
3. 3. The method according to claim 2, wherein the hard particles are two to six times smaller than the soft particles.
4. The method, according to claim 1, for providing a decreased level of brightness, in which the hard particles are: present from 15 to 60 weight percent of the polymer solids; twice as much as thirty times smaller than soft particles; and they have a size of 30 to 750 nanometers.
5. 5. The method according to claim 1, wherein the hard particles are: present from 15 to 40 weight percent of the polymer solids; of twice less than thirty times smaller than the soft particles; and they have a size of 30 to 250 nanometers.
6. 6. The method according to claim 1, for providing a decreased gloss level, in which the hard particles are twice as large as up to thirty times larger than the soft particles and have a size in the range of 150 to 1000 nanometers.
7. 7. The method according to claim 6, wherein the hard particles are two to six times larger than the soft particles.
8. 8. An aqueous coating composition, comprising particles of a hard polymer and particles of a soft polymer; where the hard and soft particles have a size in the range of 30 to 1,000 nanometers; wherein the hard particles are present from 1 to 60 weight percent of the polymer solids; they do not form films and have a Tg in the range of 35 to 1602C; where the soft particles are present from 40 to 99 weight percent of the polymer solids; yes they make movies; and where the Tg of the hard particles is greater than the Tg of the soft particles.
9. 9. A surface carrying a dry film of an aqueous coating composition, this aqueous coating composition comprises particles of a hard polymer and particles of a soft polymer; where the hard and soft particles have a size in the range of 30 to 1,000 nanometers; where the hard particles are present from 1 to 60 weight percent polymer solids, do not form films and have a Tg in the range of 35 to 160ac; where the soft particles are present from 40 to 99 weight percent of the polymer solids and do form films; and where the Tg of the hard particles is greater than the Tg of the soft particles.
10. 10. The surface that carries a dry film, according to claim 9, wherein this dry film is a polish for floors of matte finish, in which the hard particles are two to thirty times larger than the soft particles and have a larger size. of 150 nanometers.