BR-102012022682-B1 - Aqueous coating composition for treating leather, and a method for providing a low-gloss coating to natural or synthetic leather.

Abstract

AQUEOUS COATING COMPOSITION FOR TREATING LEATHER, AND METHOD FOR PROVIDING A LOW-GLOSS COATING TO NATURAL OR SYNTHETIC LEATHER The present invention relates to aqueous coating compositions having a low gloss for treating natural or synthetic leather. These aqueous coating compositions contain one or more water-soluble poly(ethylene oxide) resins having the general formula [-CH2CH2O]n and one or more polymeric binders.

Inventors

• Theodore Tysak

Assignees

• ROHM AND HAAS COMPANY

Dates

Publication Date

20260317

Application Date

20120906

Priority Date

20110915

Claims (8)

1. 1. Aqueous coating composition for treating leather, comprising: A) 1% to 94.95% by weight of an aqueous solvent comprising water; B) 5% to 80% by weight of a polymeric binder, wherein the polymeric binder has a glass transition temperature of 25 to 90°C; (e) 0.05% to 10% by weight of a water-soluble poly(ethylene oxide) resin having the general formula [-CH2CH2O-]n, wherein n is selected to have a weight-average molecular weight of 100,000 to 1,000,000 g/mol of water-soluble poly(ethylene oxide), characterized in that said water-soluble poly(ethylene oxide) resin comprises polymerized units derived from ethylene oxide and propylene oxide, wherein a coating of the aqueous coating composition has a gloss at 60° of 8.3 to 12 and a luminosity of 66.21 to 75.31, as determined in a two-layer coating on leather.
2. 2. Coating composition according to claim 1, characterized in that it comprises 0.1% to 5% by weight of said water-soluble poly(ethylene oxide).
3. 3. Coating composition according to claim 1, characterized in that it comprises 10% to 60% by weight of said polymeric binder.
4. 4. Coating composition according to claim 1, characterized in that it comprises 75% to 94.95% by weight of said aqueous solvent comprising water.
5. 5. Coating composition according to claim 1, characterized in that said polymeric binder is a polymer comprising polymerized units derived from one or more ethylenically unsaturated monomers.
6. 6. Coating composition according to claim 1, characterized in that it further comprises the following additional components: solvents, preservatives, wetting agents, leveling agents, wax emulsions, defoamers and viscosity modifiers.
7. 7. Coating composition according to claim 1, characterized in that said polymeric binder comprises polymerized units derived from one or more ethylenically unsaturated monomers, an acid-functionalized residue, and a polyvalent metal ion.
8. 8. A method for providing a low-gloss coating to natural or synthetic leather, characterized by comprising applying one or more layers of the coating composition as defined in claim 1 to a leather substrate, and allowing each layer to dry before use or application of another layer.

Description

Field of Invention [001] The present invention relates to low-gloss aqueous coating compositions for application to leather. These aqueous coating compositions contain one or more water-soluble poly(ethylene glycol) resins to reduce gloss. Fundamentals of the Invention [002] Natural and synthetic leathers are used to prepare many useful products such as clothing, footwear, bags, car interiors, upholstery, wallets, eyeglass cases and other items, handbags and belts, to name just a few. It is beneficial to treat leather to protect it against wear, scratching, bending, moisture and cracking. In addition to protection against the aforementioned damage, it is also desirable that such coatings provide a continuous film or coating having good aesthetic and visual properties such as surface smoothness (also known as "soft touch"), non-sticky surface, homogeneous texture and color, and appropriate gloss level. Several methods of treating leather are known. Typically, such treatments consist of applying a coating to the outer or upper surface of the leather substrate with one or more compositions that are selected depending on the specific characteristics for the intended use of the leather. There are also multiple acceptable techniques for applying such compositions to leather substrates, including brushing, rolling, spraying, rubbing, flow coating, and lamination. The application technique is, naturally, selected depending on the nature of the coating composition and the type of leather product to be made from the coated leather. [003] Some leather coating compositions are made from casein, a milk-derived protein, which is cured with formaldehyde or glutaraldehyde, or even first mixed with alkoxy-alkyl-ureas and then cured with an acid catalyst (see, e.g., U.S. Patent No. 4,374,872). Nitrocellulose lacquer is another widely used material for coating leather substrates, but it requires pretreatment with an adhesive layer to bond the leather and typically results in a glossy, non-sticky, hard finish. U.S. Patent No. 3,930,921 describes a two-layer coating for leather substrates having a top layer of nitrocellulose lacquer and a sublayer of cross-linked polyacrylate resin that eliminates the need for adhesive pretreatment. Polyurethane is also commonly used to provide a protective coating to leather substrates. For example, U.S. Patent No. 5,061,517 discloses a composition for painting footwear and other leather products comprising a polyurethane elastomer in toluene and isopropyl alcohol solvent, providing a thin, flexible, wear-resistant coating. U.S. Patent No. 5,872,182 describes one- and two-component water-based sulfonated polyurethane compositions for use as an adhesive, coating, and primer for footwear and other leather products. Generally, from a health, environmental, and safety standpoint, water-based coating compositions are currently preferred over organic solvent-based compositions because they have reduced or even zero emissions of volatile organic compounds (VOCs). [004] Additional components, such as colorants, plasticizers, thickeners, gloss control agents, and plasticizers, among others, are frequently added to leather coating compositions to modify certain characteristics different from those conferred by the coating composition. For example, plasticizers are frequently added to lacquer compositions to make the lacquer coating more flexible, but this sometimes results in surface stickiness over time (see U.S. Patent No. 5,061,517). U.S. Patent No. 5,061,517 recognizes the possibility that additional components may be included in leather coating compositions for various purposes. [005] Depending on the product or intended use of the treated leather, high gloss or low gloss may be preferred. When gloss control is used, it remains important to control or maintain other desirable characteristics such as flexibility, scratch resistance and impact resistance. [006] One way to lower gloss has been the addition of matting agents, which are either inorganic particles, such as, for example, silica or calcium carbonate particles, or organic particles, such as, for example, polyurethane dispersions, which function by roughening the surface of the film, or water-dispersed acrylic dispersants that function to coagulate or prevent film formation. For example, US Patent Number 5,002,584 describes a polishing (top) coating for leather substrates comprising cellulose acetate-butylate or poly(ether-siloxane), and to which matting agents comprising silicon dioxide or aluminum oxide have been added. US Patent Number 7,842,129 discloses a transparent lacquer formulation for coating wood, metals, plastics, and natural and synthetic leathers comprising silicon dioxide matting agents. Although effective in reducing glare, such matting particles often impair film integrity and can lead to the loss of important film properties such as water and abrasion resistance, slip resistance, etc. Furthermore, matting particles tend to