METHOD OF ATTAINING LOW FORMALDEHYDE EMISSION FROM SURFACE COATED OBJECTS

Abstract: A method giving low formaldehyde emission from objects surface coated with clear and/or pigmented lacquers in which the binder wholly or in part consist of one or several amino formaldehyde resisns, and which lacquers also can contain other components usually present in lacquers and paints such as resins, solvents, pigments, fillers, additives, etc, and in which to the lacquer is added from 5 to 70 percent of an unsaturated organic compound (A) and from 0.1 to 2 percent of a peroxide (B) based on the weight of the lacquer, before application on the object to be coated. A lacquer containing said components is also described.

Description: METHOD OF ATTAINING LOW FORMALDEHYDE EMISSION FROM SURFACE COATED OBJECTS The present invention refers to a method of attaining low formaldehyde emission from objects surface treated with clear and/or pigmented lacquers, the vehicles of which consist of wholly or in part one or several amino formaldehyde resins and which also may contain other components, commonly used in lacquers and paints, such as binders, solvents, pigments, fillers, additives, hardeners etc. By surface coating of e.g. wood objects, as furniture, panels, fittings etc. with lacquers or paints containing amino resins e.g. urea-formaldehyde or melamine-formaldehyde resins, a certain emission of formaldehyde to the surrounding atmosphere will appear during and after different phases of the surface treatment process. This may, under unfavourable conditions cause irritation on sensitive persons. It is true that the emission of formaldehyde from the finished object e.g. a piece of furniture, decreases with the time, and eventually practically ceases, but when conditions are unfavourable trouble may arise for several months after the surface coating process. Different ways have been suggested to solve the problem with such formaldehyde emission. Thus, the producers of amino resins have introduced special brands of resins with a low content of so called free formaldehyde, thus giving a lower emission, but also with these resins an embarrassing formaldehyde emission may arise. The Swedish patent application 8106537-7 (Tikkurilan Varitehtaat Oy) describes a method of decreasing formaldehyde emission from particle boards by surface coating with a composition containing cyclic urea. This method however, does not solve the problem of decreasing the emission from a lacquered surface. The European patent publication 43036 (Vianova) describes a process to decrease formaldehyde emission from acid curing alkyd-urea resin lacquers by addition of ethylene urea. However, the effect received by this method does not last very long. Furthermore, the addition of ethylene urea acts inhibiting on the curing process and will impair the properties of the ultimate film. The purpose of the present invention is to provide a permanent decrease of formaldehyde emission from objects surface coated with compositions containing amino resins. The effect of decreasing the formaldehyde emission according to the present invention, depends on a reaction between an unsaturated compound, preferably a binder component e.g. an alkyd such as tall oil alkyd, DCO-alkyd or soya oil alkyd, and formaldehyde, which reaction is catalyzed by a peroxide e.g. benzoyl peroxide. The appropriate composition of the surface coating composition comprises 5-70 percent by weight, preferably 10-40 percent of the unsaturated compound and 0.1-2 percent by weight, preferably 0.2-0.5 percent of the peroxide. The use of such a surface coating composition will provide an essentially decreased formaldehyde emission. Surface coating according to the present invention will also give improved film properties of the coated objects regarding surface resistance towards various liquids. See Table 2. The present invention is intended for surface coated objects in general, especially however objects of wood, board. particle board etc. surface coated with clear and/or pigmented lacquers containing one or several amino resins. Examples of such resins are urea-formaldehyde resins, melamine-form- aldehyde resins, phenolic resins, benzoguanamine resins and derivatives of these e.g. methyl or butyl ethers. Examples of other components usually present in such lacquers are binders such as alkyds, polyesters, polyacrylates, catalysts such as p-toluene sulphonic acid, phosphoric acid, ethylphosphoric acid and organic solvents, pigments, fillers, and additives. The formaldehyde decreasing effect of the present invention is demonstrated by the following examples and tables where "Chamber value, mg/m 3 " refers to testing according to the so called chamber method: CEN TC N 76D, 1982. According to this method the object to be tested is placed under well defined conditions in a chamber with a certain air turn-over and then the equilibrium concentration of formaldehyde in air is measured in mg/m 3 . Description of the method can be received from Comite Europeene de Coordination des Normes, c/o Afnor, Tour Europe, CEDEX 7, 92080 Paris. The invention is further illustrated by means of the following examples. Example 1 Comparative example A clear lacquer without any unsaturated compound or peroxide is prepared with the following composition: 57.3 nitrocellulose VF2, 20% in ethanol/ethylacetate 34 Soalkyd 11-628, 75% saturated synthetic fatty acid alkyd 3.4 Soamin M80 butylated mela ine resin 5.3 Soamin 888EB butylated urea resin 60% Soalkyd and Soamin are manufactured by SOAB AB, Mδlndal, S eden. 100 parts by volume of the lacquer are mixed with 5 parts by volume of a curing agent (38% by weight of para- toluene sulphonic acid + 2% of phosphoric acid in ethanol) and applied on glass plate, 100 g/m 2 dry film. The wet film was dried and cured for 1 hour at 50°C. After 26 days the formaldehyde emission was measured to 0.6 mg/m 3 according to the chamber method. Example 2 Same as example 1, but with the addition of 0.5% by weight of benzoylperoxide (BPO) to the wet paint. Chamber value after 26 days = 0.6. Example 3 As example 1, but with Soalkyd 11-704, an unsaturated tall oil alkyd instead of Soalkyd 11-628. Chamber value after 18 days = 0.24. Example 4 As example 3, but with the addition of 0.35% by weight of BPO to the wet paint. Chamber value after 20 days = 0.049. Example 5 On an oak-veneered particle board a lacquer with the following composition was applied. 57,3 nitrocellulose VF2, 20% 34 Soalkyd 11-704 75%, tall oil alkyd 3.4 Luwipal 044 melamine resin 5.3 Plastopal 8736, 60% urea resin 100 Addition of 0.35% BPO Addition of catalyst as in example 1. Application 2 x 100 g/m 2 = 90 g/m 2 dry film, by curtain coater. Drying 1 hour - 50°C each coat. Ttvinner: BuAc/ethanol 1:1 Luwipal 044 is n-butylated monomeric mela in resin from BASF. Plastopal 8736 is i-butylated urea resin, 60% in i-butanol, from BASF. Chamber value after 33 days = 0.045. TABLE 1 EX. Dry Unsaturation Peroxide Time Chamber film g/m 2 days value 1 100 - - 26 0.6 2 100 - BPO 26 0.6 3 100 tall oil alkyd - 18 0.24 4 100 tall oil alkyd BPO 20 0.049 5 90 tall oil alkyd BPO 33 0.045 Table 2 Surface resistance against liquids, SIS 83 91 18, Liguid Time Lacqiαer Ex. 3 Lacquer Ex.3 days + 1% BPO Water 24 4 5 Ethanol 48% 16 3 4 Coffee 16 4 3 Substrate: Dark, stained wood. Assessment of surface defects is made according to a scale 1-5, where 5 is best (no change). Examples 6-11 Various peroxides Formulation: 57,3 NC VF2 20% 34 Soalkyd 11-875, 75% tall oil alkyd 3.4 Luwipal 044 5.3 Plastopal 8736 1.0 Peroxide 50% Table 3 Ex. Peroxide Time Chamber value days mg/m 3 6 (ref.) - 21 0.15 7 BPO 21 0.05 8 MEK 21 0.10 9 MIKP 21 0.13 10 CuHP 21 0.16 11 LP 21 0.06 BPO = benzoylperoxide MEK = methylethylketone peroxide MIKP = methylisobutylketone peroxide CuHP = cumenehydroperoxide LP = laurylperoxide. Examples 12-17 Various unsaturation. Formulation: 57.3 NC VF2 20% 34 unsaturated alkyd, 75' 3.4 Luwipal 044 5.3 Plastopal 8736 1.0 BPO, 50% Table 4 EX. Type Alkyd Time Chamber days value 7 (ref . )Tall oil Soalkyd 11-875 21 0.05 12 DCO Uralac S4682 21 0.07 13 Conjugated soya oil ϋralac S4683 21 0.07 14 Conjugated DCO ϋralac S4684 21 0.06 15 Techn linseed oil ϋralac S4685 21 0.07 16 Linseed/Wood oil 9:1 ϋralac S4686 21 0.06 17 Linseed/Wood oil 75:25 ϋralac S4687 21 0.06 ϋralac are alkyd resins from DSM Resins, Holland. Exa les 18-24 Various concentration of peroxide. Formulation: 57.3 NC VF2 34 Soalkyd 11-875 3.4 Luwipal 044 5.3 Plastopal 8736 Table 5 Ex. % BPO Time Chamber value days mg/m 3 18 0 23 0.15 19 0.05 23 0.13 20 0.15 23 0.10 21 0.25 23 0.07 22 0.5 23 0.06 23 1.0 23 0.06 24 1.5 23 0.06 Examples 25-32 Effect of light and darkness. The storing conditions before measuring the Chamber Value of the surfaces coated according to the invention will incluence the formaldehyde emission. Depending whether stored in light or darkness the following results are obtained: Formulation: 57.3 NC VF2 34 Uralac 3867, 75% tall oil alkyd 3.4 Luwipal 044 5.3 Plastopal 8736 Table 6 Ex. ght/Dark Time Cha b.Val days mg/m 3 25 Light 23 0.08 26 BPO 0.5 Light 25 0.04 27 Dark 19 0.16 28 BPO 0.5 Dark 22 0.09 Formulation white paint: Alkyd: soalkyd 11-875 Melanine resin: Luwipal 044 Urea resin : Plastopal 8736 Pigment: Titaniumdioxide Alkyd: amine resin: 75:25 ϋrea:melamine resin: 50:50 NC: 3.1% VF2 Pigment volume cone (PVC): 17.6 % Solid: 63% weight Solvent: ethanol:BuAc 10:90 Table 7 Ex. Peroxide % Light/Dark Time Chamb.Val days mg/m 3 29 - - Light 19 0.06 30 BPO 0. .5 Light 19 0.05 31 - - Dark 13 0.10 32 BPO 0. .5 Dark 13 0.05

Claims: CLAIMS 1. A method for attaining low formaldehyde emission from objects surface coated with clear and/or pigmented lacquers in which the binders wholly or in part consist of one or several amino formaldehyde resins and which lacquers also can contain other components usually present in lacquers and paints, such as other resins, solvents, pigments, fillers, additives etc. c h a r a c t e r i z e d in that from 5 to 70 percent of an unsaturated organic compound (A) and from 0.1 to 2 percent of a peroxide (B), based on the weight of the lacquer, are added to the clear and/or pigmented lacquer before its application on the object to be coated. 2. A method according to claim 1, wherein to the unsaturated organic compound (A) is a polymer. 3. A method according to claim 2, wherein the polymer is an alkyd . 4. A method according to claim 3, wherein the alkyd is a tall oil alkyd, a DCO alkyd or a soya oil alkyd. 5. A method according to any of the claims 1-4, wherein the peroxide (B) is a benzoyl peroxide. 6. Lacquer with low formaldehyde emission with binders which wholly or in part consist of one or several amino formaldehyde resins and which lacquer also can contain other components usually present in laqcuers and paints such as resins, solvents, pigments, fillers, additives etc., c h a r a c t e r i z e d in that the lacquer contains from 5 to 70 percent of an unsaturated organic compound (A) and from 0.1 to 2 percent of a peroxide (B), based on the weight of the lacquer. 7. Lacquer according to claim 6, wherein the unsaturated organic compound (A) is a polymer. 8. Lacquer according to claim 7, wherein the polymer is an alkyd. 9. Lacquer according to claim 8, wherein the alkyd is a tall oil alkyd, a DCO alkyd or a soya oil alkyd. 10. Lacquer according to any of the claims 6-9, wherein the peroxide (B) is a benzoyl peroxide.

Inventors: FREDRIKSSON LENNART, GOETHE SVEN, OESTROEM OTTO, FREDRIKSSON, LENNART, GOETHE, SVEN, OESTROEM, OTTO
Applicants: BECKER WILHELM AB, AB WILH BECKER
Application year: 1987
Main classification: C09D3
IPC codes: C09D101, C09D167