CS218400B1 - Paints based on unsaturated polyesters - Google Patents

Abstract

The invention relates to coatings based on unsaturated polyesters intended primarily for the surface treatment of wooden surfaces, especially furniture. The essence of the invention lies in the fact that the materials consist of a mixture of two types of unsaturated polyesters with different specified degrees of saturation, reactive solvents (mainly styrene), a specified mixture of inert solvents, paraffin, hydroquinone, colloidal silicon dioxide, and/or fillers and/or pigments.

Description

The invention relates to coatings based on unsaturated polyesters, reactive and inert solvents, additives and optionally fillers or pigments. The compositions are intended mainly for surface protection of wooden substrates, especially furniture. The cured coatings have good adhesion to the substrates, excellent mechanical and optical properties and can be sanded and polished.

Paints based on unsaturated polyesters dissolved in reactive solvents, usually styrene, are now commonly used, especially in the furniture industry. Not only varnishes and enamels based on this are used here, but also putties containing a significant amount of filler. Paints made from unsaturated polyester varnishes are characterized by high gloss, emphasis on the structure of wood, resistance to local overheating, hot water and a wide range of solvents. Therefore, they have proven themselves particularly well where high demands are placed on the surface finish in terms of appearance, such as in the case of visible surfaces of furniture, musical instruments, television cabinets, etc. The issue of the correct selection of varnishes, requirements for the quality of substrates, methods and conditions of application has already been addressed in a number of professional works, which concern both the composition of the varnishes themselves and the initiators and accelerators used for their curing (for example, J. Mleziva et al.: Polyestery, jejich výroba a zpračavaných, SNTL, Prague 1978, pp. 458 to 464). Unsaturated polyester coatings are also covered by some Czechoslovak patents and AO, for example No. 121,759, 137,821, 142141, 159,569,, 171,360, 178,452, 178,500, 178,803.

Recently, the method of applying unsaturated polyester varnishes in multiple layers (the so-called DUP system) has been increasingly used. This is a surface treatment using two different types of polyester varnishes with different viscoelastic properties of the cured paint films (Czech Patent Office No. 182 860).

This results in an improvement in the viscoelastic properties of the entire coating system while maintaining high surface quality. The adhesion of coating layers to porous cellulose substrates (wood, cellulose decorative foils, etc.) is usually quite satisfactory, but if necessary it can be increased, for example according to Czechoslovak Administrative Procedure Code No. 189 437. However, the varnishes used for these purposes so far and applied in the above-mentioned way have some shortcomings, which are manifested mainly when applying thick layers to porous substrates, i.e. in quantities of 500 to 600 g/m ² . Under these conditions, there is often a slowed escape of air bubbles from the wetted substrate and a deterioration in the quality of the paraffin layer formed on the surface, which has an adverse effect on the quality of the surfaces obtained by the final surface treatment of the hardened coatings.

These shortcomings are not present in coatings based on unsaturated polyesters, reactive and inert solvents, additives and possibly fillers and/or pigments, which are the subject of this invention. Its essence lies in the fact that the said coatings consist of 48 to 72 parts by weight of a mixture of unsaturated polyesters containing 11 to 23% by weight of polyesters with a degree of saturation of 0.7 to 1.0 and 77 to 89% by weight of polyesters with a degree of saturation of 1.7 to 2.3, of 35 to 52 parts by weight of styrene with an optional content of up to 5% by weight of acrylic and/or methacrylic acid and/or their alkyl esters with the number of carbon atoms in the alkyl group of 2 to 8, of 0.5 to 7 parts by weight of a mixture of inert solvents containing 6.5 to 20% by weight of dialkyl ketones with the number of carbon atoms in the alkyl groups of 1 to 4, preferably methyl ethyl ketone, optionally up to 25% by weight of extraction gasoline, up to 45% by weight of monohydric alcohols with the number of carbon atoms of 2 to 3 and up to 45% by weight of ethyl acetate, further from 0.04 to 0.15 parts by weight of paraffins with a softening point of 48 to 60 °C, preferably 52 to 54 °C, 0.01 to 0.04 parts by weight of hydroquinone, 0.05 to 0.8 parts by weight of colloidal silicon dioxide, preferably with a specific surface area of 250 to 380 m ² /g, and optionally up to 30 parts by weight of fillers and/or pigments.

Unsaturated polyesters for coatings according to the invention are prepared by polyesterification of phosphite, maleic and fumaric acids with ethylene glycol, propylene glycol and optionally cyclohexanol or methylcyclohexanol. They are defined by the degree of saturation, which is the mutual weight ratio of saturated and unsaturated dicarboxylic acids used in their preparation. This ratio is easily controlled, for example, by determining the content of unsaturated acids by polarography or infrared spectrometry and is not dependent on the dry matter of the varnishes.

It suitably characterizes the reactivity of unsaturated polyesters and their mixtures, which increases with decreasing value of this ratio. In general, polyesters with a degree of saturation of 1.7 to 2.3 are of medium reactive types, while a degree of saturation of 0.7 to 1.0 is characteristic of highly reactive types. Their miscibility with a reactive solvent, i.e. styrene, is usually in the range of 60 to 80% by weight, but can theoretically reach up to 100% by weight. For the preparation of coatings according to the invention, unsaturated polyesters are best used in the form of 6- to 70% solutions in styrene. The most advantageous properties of coatings, especially in terms of sandability of coatings and final surface quality, are achieved by using unsaturated polyesters with low hydroxyl number and acid number. The optimum lies in the range of 20 to 30 milligrams of KOH/g.

The combination of Inert Solvents is governed by

Theological and other properties of coatings in terms of requirements for their application. For example, when applying using screen coating devices in quantities above 400 g/m ^2, it is necessary that the coatings do not flow below the edge of the leading edge of the poured substrate. This requirement is met only by coatings according to the invention with a consistency of at least 45 s/20 °C, measured with a spout cup with a hole of 4 mm in diameter (ČSN 67 3013). The containers of the screen coating device are filled in such a way that the first coating head applies the coating with a curing initiator, i.e. with a solution of ketone peroxides, and the second coating head applies the coating with an accelerator, i.e. with a solution of cobalt naphthenate or cobalt octoate. By combining inert solvents, for example extraction gasoline and propyl alcohol, good wetting of substrates and a reduction in the sensitivity of the coating to residual moisture can be successfully achieved. At the same time, the escape of air displaced from the substrate in the form of small bubbles is accelerated and the quality of the surface paraffin layer is increased, making the surfaces easier to work with.

Example 1

Unsaturated polyester varnish for pouring

Unsaturated polyester with a degree of saturation of 0.6 based on propylene glycol, phthalic acid and fumaric acid 10.5 wt. d.

Unsaturated polyester with a degree of saturation of 1.96 based on ethylene glycol, violet acid, fumaric acid

and methylcyclohexanol 47.5 wt. d. Styrene 42.0 wt. d. Isopropyl alcohol 1.5 wt. d. Ethyl acetate 1.5 wt. d. Methyl ethyl ketone 1.5 wt. d. Paraffin (softening point 52/54 ^B C) 0.05 wt. d.

Hydroquinone 0.02 wt. d.

Colloidal silicon dioxide (specific surface area 380 m ² /g) 0.28 wt. d.

Paint consistency at 20 °C 50 s

Properties of the cured coating:

Grindability level 2 Resistance to temperature changes (ČSN 67 3098 B) 28 cycles Resistance to failure during subcooling -50 °C

Example 2

Unsaturated polyester enamel white

Unsaturated polyester with a degree of saturation of 0.8 based on propylene glycol, phthalic acid and fumaric acid 10.0 wt. d.

Unsaturated polyester with a degree of saturation of 1.8 based on ethylene glycol, propylene glycol, fumaric acid,

violet and cyclohexanol 40.0 mass d. Styrene 49.0 mass d. Methacrylic acid 1.0 mass d. n-propyl alcohol 1.0 mass d. Ethyl acetate 1.7 mass d. Methyl ethyl ketone 0.8 mass d. Extraction gasoline 0.5 mass d. Paraffin (softening point 52/54 °C) 0.1 mass d.

Hydroquinone

0.03 wt. d.

Colloidal silicon dioxide (specific surface area 200 m ² /g) 0.3 wt. d.

Titanium white rutile

6.0 wt. d.

Claims (1)

SUBJECT Paints based on unsaturated polyesters, reactive and inert solvents, additives and optionally fillers and / or pigments, characterized in that they consist of 48 to 72 parts by weight of an unsaturated polyester mixture containing 11 to 23% by weight of polyesters having a degree of saturation of 0.7 to 1.0 and 77 to 89% by weight of polyesters having a degree of saturation of 1.7 to 2.3, of 35 to 52 parts by weight of styrene with an optional content of up to 5% by weight of acrylic and / or methacrylic acid and / or their alkyl esters having carbon numbers in an alkyl group of 2 to 8, from 0.5 to 7 parts by weight of an inert solvent mixture containing 6.5 to 20% by weight of the invention of dialkyl ketones having a number of carbon atoms in alkyl groups of 1 to 4, preferably methyl ethyl ketone, or up to 25% by weight of naphtha up to 45% by weight of monovalent alcohols having a carbon number of 2 to 3 and up to 45 ° / oh % of ethyl acetate, furthermore from 0.04 to 0.15 parts by weight of paraffin with a softening point of 48 to 60 ° C, preferably from 52 to 54 ° C, from 0.01 to 0.04 parts by weight of hydroquinone, from 0.05 to 0.8 % by weight of colloidal silica, preferably having a specific surface area of 250 to 380 m ² / g, and optionally up to 30 parts by weight of fillers and / or pigments.