Coating installation of an industrial mass production coating line including non-aqueous solvent composition as barrier liquid

Abstract

Coating installations are provided that include storage tanks for an aqueous base component and a non-aqueous hardener component, circulation lines for the components from the respective storage tanks, a mixer and an entrance to the mixer with a connection between each circulating line and the entrance to the mixer, and a release valve for the non-aqueous hardener component. The coating installation downstream of the non-aqueous hardener release valve is filled with a non-aqueous solvent composition comprising 0 to 10 wt. % of N-alkyl pyrrolidone, 0 to 5 wt. % of dimethyl sulfoxide, 10 to 50 wt. % of γ-butyrolactone, 10 to 50 wt. % of at least one monoalcohol, 10 to 60 wt. % of at least one organic solvent inert towards isocyanate groups, other than γ-butyrolactone, other than N-alkyl pyrrolidone, and consisting of carbon, hydrogen, oxygen and, optionally, nitrogen, and 0 to 10 wt. % of at least one additive.

Claims

1. A coating installation of an industrial mass production coating line for the application of a water-borne two-component polyurethane coating comprising: storage tanks for an aqueous base component and a non-aqueous hardener component; circulation lines for the components from the respective storage tanks, a mixer for receiving the aqueous base component and the non-aqueous hardener component to form a water-borne two-component polyurethane coating composition and an entrance to the mixer with a connection between each circulating line and the entrance to the mixer; a release valve for the non-aqueous hardener component in the connection between the circulating line for the non-aqueous hardener component and the entrance to the mixer; a spray-application device for spraying the water-borne two-component polyurethane coating composition to form the water-borne two-component polyurethane coating and connecting pipework downstream of the release valve for the non-aqueous hardener; wherein the coating installation downstream of the non-aqueous hardener release valve including the mixer, the spray-application devices, and connecting pipework is filled with a non-aqueous solvent composition comprising: 0 to 10 wt. % of N-alkyl pyrrolidone, 0 to 5 wt. % of dimethyl sulfoxide, 10 to 50 wt. % of γ-butyrolactone, 10 to 50 wt. % of at least one monoalcohol, 10 to 60 wt. % of at least one organic solvent inert towards isocyanate groups, other than γ-butyrolactone, other than N-alkyl pyrrolidone, and consisting of carbon, hydrogen, and oxygen and, optionally, nitrogen, and 0 to 10 wt. % of at least one additive.

2. The coating installation of claim 1, wherein the non-aqueous solvent composition consists of: 0 to 5 wt. % of dimethyl sulfoxide, 10 to 50 wt. % of γ-butyrolactone, 10 to 50 wt. % of at least one monoalcohol, 10 to 60 wt. % of at least one organic solvent inert towards isocyanate groups, other than γ-butyrolactone, other than N-alkyl pyrrolidone, and consisting of carbon, hydrogen, and oxygen, and 0 to 10 wt. % of at least one additive selected from the group consisting of defoamers, wetting agents, and surfactants; wherein the sum of the wt. % totals 100 wt. %.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) The applicant has found an improved barrier liquid in the form of the non-aqueous solvent composition disclosed in the preceding paragraph. The barrier liquid comprises γ-butyrolactone and, if any, at best a small amount of N-alkyl pyrrolidone. The above mentioned risk of an urea lump formation during downtimes of an industrial mass production coating line for the application of water-borne two-component polyurethane coatings can be reduced by using the improved barrier liquid. While not wishing to be bound by any theory, it is surmised that polyisocyanate getting accidentally into contact with traces of water (humidity originating from the pulse air, water originating from the aqueous base component and/or water originating from the aqueous cleansing composition) within the installation downstream of the non-aqueous hardener component release valve could react under formation of urea lumps or incrustations in said downstream installation. Apparently, but unexpectedly, the reactivity of the polyisocyanate towards water is less in the presence of γ-butyrolactone compared to its reactivity in the presence of N-alkyl pyrrolidone.

(2) The term “organic solvent” is used herein. It means organic solvents in general and, in particular, such organic solvents as are conventionally used in paint and coatings. Such organic solvents include low-molecular compounds as well as oligomeric compounds but not polymers. The molar mass (in case of low-molecular compounds) or, respectively, the number-average molar mass (in case of an oligomer) of such organic solvents is preferably below 500.

(3) The number-average molar mass data stated herein are number-average molar masses determined or to be determined by gel permeation chromatography (GPC; divinylbenzene-cross-linked polystyrene as the immobile phase, tetrahydrofuran as the liquid phase, polystyrene standards).

(4) The non-aqueous solvent composition comprises 0 to 10 wt. %, preferably 0 wt. % of N-alkyl pyrrolidone. Examples of N-alkylpyrrolidones include N-methylpyrrolidone and N-ethylpyrrolidone.

(5) The non-aqueous solvent composition comprises 0 to 5 wt. %, preferably 0 wt. % of dimethyl sulfoxide.

(6) The non-aqueous solvent composition comprises 10 to 50 wt. %, preferably 25 to 35 wt. % of γ-butyrolactone.

(7) The non-aqueous solvent composition comprises 10 to 50 wt. %, preferably 25 to 35 wt. % of at least one monoalcohol, especially C3-C8 monoalcohol, more especially saturated C3-C8 monoalcohol. Examples of saturated C3-C8 monoalcohols can include the isomers of propanol, the isomers of butanol, the isomers of pentanol, the isomers of hexanol, the isomers of heptanol, the isomers of octanol, cycloaliphatic monoalcohols such as cyclohexanol, alkyl-substituted derivatives of cyclohexanol with no more than 8 carbon atoms, and the like. Preferred saturated C3-C8 monoalcohols can include the isomers of propanol, the isomers of butanol and the isomers of pentanol.

(8) The non-aqueous solvent composition comprises 10 to 60 wt. %, preferably 30 to 50 wt. % of at least one organic solvent inert towards isocyanate groups, other than γ-butyrolactone, other than N-alkyl pyrrolidone, and consisting of carbon, hydrogen, oxygen and nitrogen, or consisting of carbon, hydrogen and oxygen. The organic solvents inert towards isocyanate groups, other than γ-butyrolactone and consisting of carbon, hydrogen and oxygen are preferred.

(9) Examples of such organic solvents consisting of carbon, hydrogen, oxygen and nitrogen can include acyclic amides like 3-methoxy-N,N-dimethylpropionamide and 3-butoxy-N,N-dimethylpropionamide. 3-methoxy-N,N-dimethylpropionamide and 3-butoxy-N,N-dimethylpropionamide are available as Equamide M 100 and Equamide B 100, both from Idemitsu Kosan Co. Ltd., Tokyo.

(10) Examples of such organic solvents consisting of carbon, hydrogen and oxygen can include ethers, for example, ethylene glycol di-C1-C6-alkyl ethers, propylene glycol di-C1-C6-alkyl ethers, diethylene glycol di-C1-C6-alkyl ethers, dipropylene glycol di-C1-C6-alkyl ethers and tetrahydrofuran; ketones, for example, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl isoamyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone, isophorone, 2,4-pentanedione and methoxy hexanone; esters, for example, ethyl ethoxypropionate, methyl glycol acetate, ethyl glycol acetate, butyl glycol acetate, butyl diglycol acetate, methoxypropyl acetate, ethoxypropyl acetate, methoxybutyl acetate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, the pentyl acetate isomers, hexyl actetate, heptyl acetate, ethylhexyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, butyl butyrate, diethyl malonate, dimethyl adipate, dimethyl glutarate, dimethyl succinate, ethylene glycol diacetate and propylene glycol diacetate; lactones other than γ-butyrolactone, for example, ε-caprolactone; and carbonates, for example, dimethyl carbonate, dibutyl carbonate and propylene carbonate.

(11) The non-aqueous solvent composition comprises 0 to 10 wt. %, preferably 0 wt. % of at least one additive. Examples of additives may include defoamers, wetting agents and surfactants.

(12) In some embodiments, the non-aqueous solvent composition consists of

(13) 0 to 10 wt. %, preferably 0 wt. % of N-alkyl pyrrolidone,

(14) 0 to 5 wt. %, preferably 0 wt. % of dimethyl sulfoxide,

(15) 10 to 50 wt. %, preferably 25 to 35 wt. % of γ-butyrolactone,

(16) 10 to 50 wt. %, preferably 25 to 35 wt. % of at least one monoalcohol, especially C3-C8 monoalcohol, more especially saturated C3-C8 monoalcohol,

(17) 10 to 60 wt. %, preferably 30 to 50 wt. % of at least one organic solvent inert towards isocyanate groups, other than γ-butyrolactone, other than N-alkyl pyrrolidone, and consisting of carbon, hydrogen, oxygen and, optionally, nitrogen, and

(18) 0 to 10 wt. %, preferably 0 wt. % of at least one additive,

(19) wherein the sum of the wt. % totals 100 wt. %.

(20) Preferred non-aqueous solvent compositions according to the invention consist of 25 to 35 wt. % of γ-butyrolactone, 25 to 35 wt. % of at least one monoalcohol, especially C3-C8 monoalcohol, more especially saturated C3-C8 monoalcohol, and 30 to 50 wt. % of at least one organic solvent inert towards isocyanate groups, other than γ-butyrolactone, and consisting of carbon, hydrogen and oxygen, wherein the sum of the wt. % totals 100 wt. %.

(21) The non-aqueous solvent composition of the invention can be used as barrier liquid within a coating installation of an industrial mass production coating line for the application of water-borne two-component polyurethane coatings. The invention relates therefore also to the use of the non-aqueous solvent composition as barrier liquid within a coating installation of an industrial mass production coating line for the application of water-borne two-component polyurethane coatings. With regard to the coating installation of an industrial mass production coating line for the application of water-borne two-component polyurethane coatings, reference is made to the above section “Background of the Invention”. As already disclosed there, it is typical that such a coating installation comprises, among others, a release valve for a non-aqueous hardener component, typically a non-aqueous polyisocyanate hardener. The non-aqueous solvent composition of the invention can in particular be used as barrier liquid within the installation downstream of such non-aqueous hardener component release valve of such coating installation of an industrial mass production coating line for the spray-application of water-borne two-component polyurethane coatings. The non-aqueous solvent composition may be filled into the downstream installation so as to entirely fill the downstream installation or to fill at least some space directly downstream of the non-aqueous hardener component release valve, for example, the connection between said valve and the entrance of the mixer.

EXAMPLES

Reference Example 1 (Production of a Polyisocyanate Composition 1)

(22) 30 pbw (parts by weight) of N-ethylpyrrolidone, 46 pbw of a hydrophilic aliphatic polyisocyanate based on hexamethylene diisocyanate with an NCO value of 17.4 and 24 pbw of DESMODUR® N 3600 from Bayer (trimerized hexamethylene diisocyanate with an NCO value of 23) were mixed.

Reference Example 2 (Production of a Polyisocyanate Composition 2)

(23) 29.5 pbw of γ-butyrolactone, 46 pbw of a hydrophilic aliphatic polyisocyanate based on hexamethylene diisocyanate with an NCO value of 17.4 and 24.5 pbw of DESMODUR® N 3600 from Bayer were mixed.

Example 3 (Production of a Solvent Composition)

(24) 29.5 pbw of γ-butyrolactone, 32.1 pbw of n-butanol and 38.4 pbw of butyl glycol acetate were mixed.

Reference Example 4 (Production of a Solvent Composition)

(25) 29.5 pbw of N-ethylpyrrolidone, 32.1 pbw of n-butanol and 38.4 pbw of butyl glycol acetate were mixed.

Reference Example 5

(26) 2 pbw of the polyisocyanate composition of reference example 1 were mixed with 1 pbw of the solvent composition of example 3 to form a first solvated polyisocyanate composition. In a separate operation, 2 pbw of the polyisocyanate composition of reference example 2 were mixed with 1 pbw of the solvent composition of example 3 to form a second solvated polyisocyanate composition. In a further separate operation, 2 pbw of the polyisocyanate composition of reference example 1 were mixed with 1 pbw of the solvent composition of reference example 4 to form a third solvated polyisocyanate composition.

(27) 98 pbw of each of the solvated polyisocyanate compositions were manually mixed with 2 pbw of deionized water making use of a spatula. In a separate operation, 99 pbw of each of the solvated polyisocyanate compositions were manually mixed with 1 pbw of deionized water making use of a spatula. The viscosity change of each mixture over time at 20° C. was qualitatively determined. The results are summarized in the following table 1.

(28) TABLE-US-00001 TABLE 1 Mixtures of example compositions 1 + 3, 2 + 3 and 1 + 4 with water: 1 + 4 1 + 3 2 + 3 1 + 4 1 + 3 2 + 3 with with with with with with 1 wt. % 1 wt. % 1 wt. % 2 wt. % 2 wt. % 2 wt. % of of of of of of water water water water water water Ini- liquid, liquid, liquid, liquid, liquid, liquid, tially low low low low low low viscos- viscosity viscosity viscosity viscos- viscos- ity ity ity after liquid, liquid, liquid, increased liquid, liquid, 24 low low low viscosity low low hours viscos- viscosity viscosity viscos- viscos- ity ity ity after solid- increased liquid, solidified solid- solid- 72 ified viscosity low ified ified hours viscosity after solidified increased 96 viscosity hours after solidified 120 hours