MXPA00007464A - Aqueous coating and its use in lacquers - Google Patents

Abstract

Cellulose material-containing coating oil-in-water emulsion comprises 5-50 wt.%cellulosic material, 5-50 wt.%hydroxyl-containing varnish resin(s), 0.1-10 wt.%polyisocyanate(s) with free NCO group(s), 10-65 wt.%water, 0.5-30 wt.%plasticizer, 0-20 wt.%emulsifier and 0-45 wt.%organic solvent(s). The ratio of OH:NCO is 1:0.01-1.

Description

AN AGUOUS COATING AGENT AND ITS USE IN LACQUER Field of the Invention Combined nitrocellulose lacquers prepared by nitrocellulose (NC) solution, an alkyl resin, a plasticizer and possibly optional lacquer additives in organic solvents are known. These lacquers can be used on lacquered surfaces such as, for example, wood, metal, paper, leather, plastics, etc. The disadvantage of these is the high solvent content of 60 to 80%.

BACKGROUND OF THE INVENTION EP 0 076 443 describes the preparation, inter alia, of emulsions of aqueous NC / alkyd resins in which the solvent is completely or partially replaced by water. If the surfaces, for example wood, are bonded with these aqueous emulsions and the chemical resistance is determined in accordance with DIN 68 861, part 1, 1 B, then the resistances to water, ethanol and acetone are not sufficient.

REF.:122111 Two-component aqueous polyurethane coating agents, chemically crosslinked with free polyisocyanates as hardeners for the binder are described in EP 0 358 979. According to such document, polyhydroxyacrylates as binding components are capable of emulsifying certain polyisocyanates with groups of free isocyanates, these are also called lacquer polyisocyanates. The aqueous two-component system produced in this medium cures to give cross-linked films. The lacquer polyisocyanates are biuret, urethane, uretdione and / or oligomeric derivatives containing an isocyanate group of readily available monomeric or simple diisocyanates, in particular hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) and / or bis (isocyanatocyclohexyl) methane (HMDI). Lacquer polyisocyanates used in accordance with EP 0 358 979 have a viscosity at 23 ° C up to 1000 mPa.s and have an average NCO functionality of 2.2 to 5.

DE-OS-A 4 226 243 discloses an aqueous two-component coating agent based on polyisocyanates and modified polyesters of self-and ulsifying fatty acids and polyurethanes. European patent application EP-A 0 496 205 also discloses combinations of aqueous binders based on self-emulsifying polyisocyanates and urethane, polyester resins containing a carboxyl and hydroxyl group. German Patent DE 3 122 030 discloses coating compositions consisting of polyisocyanates and water-dilutable alkyd, melamine and acrylic resins, which also contain water miscible solvents.

The disadvantage of these water-dilutable two-component binders described above is the low solids content in which they can be achieved, the short shelf life and the long drying / curing times. In addition, the moisture in the wood, the initial hardness and the formation of sands are unsatisfactory.

Description of the Invention Now, the object of the invention comprises improving the resistance of lacquer resin emulsions NC, in this way, the good resistances according to DIN 68 861, part 1, B 1, are achieved with these systems of individual aqueous components.

The invention relates to an aqueous emulsion, the process of its preparation causes the addition of a cellulosic substance to the reaction products or to a mixture of a polyisocyanate with a lacquer resin containing at least one hydroxyl group. A single-component lacquer emulsion is obtained by the addition of at least one plasticizer and water and optionally at least one emulsifier and one organic solvent.

Lacquer emulsions comprise a product prepared from: a) 5 - 50% by weight of cellulosic substance. b) 5 - 50% of one or more hydroxyl groups containing resins of. laccases c) 0.1-10% by weight of polyisocyanates with more than one free isocyanate group d) 0.5-30% by weight of the plasticizer e) 0.0-20% by weight of the emulsifier f) 0.0-45% by weight of at least an organic solvent g) 10-65% by weight of water wherein the sum of a) ag) is always 100%, characterized in that the weight ratio of the cellulose substance to the lacquer resin containing the OH group is 1: 5 to 5: 1 and the proportion in equivalents of OH groups (from lacquer resin) to NCO groups is 1: 0.01-1.0.

Suitable cellulosic substances are preferably cellulose esters, in particular nitrocellulose of any viscosity level or pious mixtures thereof or mixtures thereof. Nitrocellulose, for example in conventional industrial nucellellulose grades, ie cellulose nitrates with a nitrogen content of 10.7 to 12.6% by weight, are very particularly suitable.

Other cellulose substances which may be used are cellulose acetobutyrate and cellulose acetopropionate in varying viscosity and substitution states.

The conventional lacquer resins can be used as lacquer resins if they contain reactive groups of isocyanates such as, for example, -OH, COOH, -NH2, -CONH2. Conventional lacquer resins are, for example, alkyd, maleic acid, phenol, formaldehyde, xylene formaldehyde, ketone, sulfonamide, aldehyde, amine, epoxy, carbamate, coumaron / indene resins, sucrose esters and vinyl or acrylate resins and copolymers of these.

It is advantageous if the lacquer resins containing a hydroxyl group have an OH value between 20 and 200 mg KOH / g.

The plasticizers which can be used are conventional plasticizers such as, for example, the esters of aliphatic monocarboxylic acids, preferably with 2 to 18 carbon atoms such as cetyl acetate, glycol diacetate, stearates, acetate. ricinoleic, dicarboxylic acids such as, for example, dioctyl adipate, dimethylcyclohexylmethyladipate, dibutyl sebacate; aromatic dicarboxylic acids such as, for example, dibutyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, aliphatic tricarboxylic acids, preferably with 8 carbon atoms, of aromatic dicarboxylic acids and of monohydric alcohols with 2 to 10 carbon atoms, of dihydric alcohols with 2 to 6 carbon atoms and trihydric alcohols with 3 carbon atoms of the esters of inorganic acids such as, for example, tributyl phosphate, triphenyl phosphates; esters of citric acids with alcohols having 1 to 5 carbon atoms, which can also be reacted with monocarboxylic acids having 1 to 4 carbon atoms; and also sulfonamides, oils such as castor oil and linseed oil and the alkoxylation products of the mentioned compounds such as, for example, ethoxylated castor oil and soybean oil, stearates and phosphates.

Emulsifiers used are optionally anionic emulsifiers, for example, long chain alkylaryl sulfonates such as dodecylbenzene sulfonate or butylaphthalene sulfonate, alkyl sulfates such as stearyl or lauryl alcohol sulfates, sulfosuccinates such as dioctyl succinate disodium, or non-emulsifying emulsifiers. ionics, emulsifiers such as octyl or nonylphenol-oxyethylates.

The disodium salts of the sulfosuccinic acid derivatives of ethoxylated nonylphenols can also be mentioned as anionic emulsifiers.

Conventional organic solvents can be used as solvents to provide the cellulosic substance and the lacquer resin soluble therein.

The polyisocyanates are any organic polyisocyanates with free isocyanate groups, aliphatically, cycloaliphatically, araliphatically and / or aromatically bound, which are liquid at room temperature. Particularly preferred polyisocyanates are polyisocyanates or mixtures of polyisocyanates with isocyanate groups exclusively aliphatically and / or cycloaliphatically linked, with an NCO functionality (average) of between 1.8 and 5.0.

If required, the polyisocyanates can be used mixed with small amounts of inert solvents to lower the viscosity to a value within the mentioned range.

Suitable products are, for example, "lacquer polyisocyanates" based on hexamethylene diisocyanates or l-isocyanate-3, 3, 5-trimethyl-5-isocyanatomethyl-cyclohexane (IPDI) and / or bis- (isocyanatocyclohexyl) -methane, in particular, those which are based exclusively on hexamethylene diisocyanates. The "lacquer polyisocyanates" based on these diisocyanates are understood to be biurets, urethane, uretdione and / or derivatives containing an isocyanate group known per se from these diisocyanates.

Also suitable within the invention, but less preferred, are aromatic polyisocyanates, in particular "lacquer polyisocyanates" based on 2,4-diisocyanatotoluene or technical grade mixtures thereof with 2,6-diisocyanatotoluene or based on '4,4 -diisocyanatodiphenylmethane or mixtures of these with their isomers and / or higher homologs. These types of aromatic lacquer polyisocyanates are, for example, isocyanates containing a urethane group, such as are obtained by reacting amounts in excess of 2, -diisocyanatotoluenes with polyhydric alcohols such as trimethylolpropane. Additional aromatic lacquer polyisocyanates are, for example, trimers of the monomeric diisocyanates mentioned by way of example, that is, the corresponding isocyanatoisocyanurates.

Basically, the use of unmodified polyisocyanates of the type mentioned by way of the example is obviously also possible.

The polyisocyanate component can generally consist of any mixture of all the polyisocyanates mentioned by way of the example.

The hydrophilized polyisocyanates of the above-mentioned basic products, which can be easily emulsified in water, are also suitable.

The resin emulsion in lacquer / cellulose substance is prepared in accordance with EP 0 076 443.

The reaction, for example, of the alkyd resin containing the OH group, dissolved in eg butyl acetate, with a polyisocyanate, is carried out at room temperature up to a maximum of 80 ° C, preferably up to 60 ° C, where the OH: NCO ratio has to be adjusted, so that the resin does not gel, but is still effectively film-forming. The NCO groups have not reacted completely with the OH groups in the lacquer resin.

The cellulose, plasticizer, optionally emulsifying substance, optionally organic solvents, are added to the alkyd resin modified in this way and stirred until the fibers of the cellulosic substance can not be observed longer. The material is then passed through a highly viscous state. An oil-in-water emulsion (a one-component system) is produced by the addition of water. It is also possible to add additional hydrophilic polyisocyanates to this emulsion by then obtaining a "two component system".

The invention also provides the use of a coating agent according to the invention in lacquers for the treatment of wood, metal, plastics, paper, leather or glass surfaces.

Depending on the application area (for example, wood, metal, plastics, paper, leather, glass and lacquered films), other known organic solvents may also be added to the emulsion, wherein a solvent concentration of 30% with respect to The final lacquer formulation should not be exceeded.

The viscosity can be adjusted for use in the desired application, either with water or by the addition of water-soluble thickeners based for example on polyurethanes, cellulose, guar, starch and the like.

In addition, the substances, which improve the processing or application properties such as, for example, lubricants, agents that improve shine, anti-foam agents, agents that improve the formation of sand, flow control agents, stabilizers, stabilizers, light and dyes, pigments and conventional lacquer additives can also be added to the emulsion, preferably in the aqueous phase.

The emulsions of aqueous coating agents prepared according to the invention have very good flow characteristics, high gloss, and good resistance to water, ethanol and acetone, in accordance with DIN 68 861 part 1, 1B Examples In a stirred 2 liter container, the polyisocyanate was added to the alkyd resin containing a hydroxyl group, with stirring (100 rpm) at 20 ° C. After the addition of dibutyltin dilaurate, the mixture was heated to 60 ° C and stirring was continued for 2 hours. After the addition of the emulsifier, dibutyl phthalate and methoxypropyl acetate, standard type E 24 nitrocellulose (content N2 = 12.1% by weight) wet with 35% by weight of water, was added and the mixture was homogenized for 1 hour at 60 ° C and 50 rpm. Then, the water was added and the stirring speed was increased to 900 rpm, while the mixture was cooled simultaneously to room temperature. 1! The alkyd resin containing a hydroxyl group "Halweftal B 32", obtained from Hüttenes-Alberts Lackrohstoff Gmb, was used as 62.4% by weight of the solid alkyd resin dissolved in butyl acetate (sample value OH = 152 mg KOH / g).

The alkyd resin containing the hydroxyl group was prepared according to example 1 in the application NL 1 008 777, it was used as 71.1% by weight of the solid alkyd resin in butyl acetate (sample value OH = 145 mg KOH / g). 31 Emulsifier 1): Mixture of polyethoxy tridecyl ether phosphate and tridecyl-poly (ethoxy) -ethanol (commercial product "Rhodafac RS 710" from Rhone Poulenc Chemie).

! Emulsifier 2: triglyceride-ethoxylate (commercial product "Product GN 8403/50" from Zchimmer &Shwa z).

To determine the chemical resistance in accordance with DIN 68 861, part 1, IB, 8 g of butyl glycol acetate, 100 g of the emulsion of example 1 were added, 6 g were added to the emulsion of example 2 and 8 g were added to the emulsion of example 3.

The emulsions were applied as primary lacquers and top coatings to wood, using a 120 μm scraper blade. The primary was dried at 50 ° C, sanded and lacquered with topcoat. In accordance with DIN 68 861, part 1, 1 B, the final coating was dried for 7 days at 50 ° C, then stored for 24 hours at room temperature and then the water, ethanol and acetone resistance was determined.

For comparison, in accordance with EP-B 0 076 443, the NC / alkyd 4 resin emulsion was prepared from the same starting materials as in Example 1 and the emulsion 5 was prepared as in Example 2, but without polyisocyanate and without dibutyltin dilaurate. 6 g of butyl glycol acetate were added to 100 g of each of emulsions 4 and 5, before application to these woods. The resistance to water, ethanol and acetone. respectively, in accordance with DIN 68 861, part 1, IB, are summarized in the following table: It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the foregoing, the following is claimed as property:

Claims (5)

1. A lacquer emulsion characterized in that it comprises the product of a reaction of a) 5-50% by weight of cellulose substance. b) 5 - 50% of one or more hydroxyl groups containing lacquer resins c) 0.1 - 10% by weight of polyisocyanates with more than one free isocyanate group d) 0.5 - 30% by weight of the plasticizer e) 0.0 - 20% by weight of the emulsifier f) 0.0-45% by weight of at least one organic solvent g) 10-65% by weight of water wherein the sum of a) to g) is always 100%, and wherein the weight ratio of the hydroxyl groups of said b) to NCO groups is 1: 0.01 - 1.0.

2. The lacquer emulsion of claim 1, characterized in that the cellulose substance is the cellulose ester.

3. The lacquer resin of claim 1, characterized in that the lacquer resin b) has an OH value of 20 to 200 mg KOH / g.

4. A process for the preparation of the lacquer emulsion of claim 1, characterized in that it comprises: (i) combining said polyisocyanate with said lacquer resin containing a hydroxyl group in the presence of a catalyst to produce a reaction and adding said cellulosic substance during or after the completion of said reaction, to obtain a reaction product and (ii) adding to said reaction product, at least one plasticizer to obtain a mixture, and (iii) homogenizing said mixture, and iv) add this water to obtain an oil-in-water emulsion.

5. A method of using the lacquer emulsion of claim 1, characterized in that it comprises application of said emulsion to at least one surface of a material selected from the group consisting of wood, metal, paper, plastics, leather and glass. AN AGUOUS COATING AGENT AND ITS USE IN LACQUER SUMMARY OF THE INVENTION A lacquer emulsion containing a cellulose substance prepared from a) 5 - 50% by weight of cellulosic substance. b) 5 - 50% of one or more hydroxyl groups containing lacquer resins c) .0.1 - 10% by weight of polyisocyanates with more than one free isocyanate group d) 0.5 - 30% by weight of the plasticizer e) 0.0 - 20 % by weight of the emulsifier f) 0.0-45% by weight of at least one organic solvent g) 10-65% by weight of water wherein the sum of a) to g) is always 100%, characterized in that the weight ratio of the OH groups (from the lacquer resin) to NCO groups is 1: 0.01-1.0.