DE2359538B2 - Powder paints based on solid resins and polyisocyanates - Google Patents

Description

The invention relates to powdery and powder-applied paints which have excellent storage stability and of a solid resin and one containing at least two isocyanate groups Polyisocyanate compound exist. When the solid resin is one reactive with an isocyanate group active hydrogen atom ζ. B. in a hydroxyl group or in a primary or secondary amino group contains, the powder paint obtained is thermosetting at a lower temperature and gives Paint films with excellent surface finish and physical properties.

In recent times various attempts have been made to prevent the evaporation of solvents from Prevent paints into the atmosphere to avoid air pollution. For example a powder spraying process was developed in which a powdery paint that is not volatile Component or contains only a small amount of a volatile component by electrostatic Spraying, or by painting in a fluidized bed. The like. Is applied. As resin components in such Powder paints become vinyl chloride resins, epoxy resins, thermosetting acrylic resins and the like. used. Furthermore, thermosetting polyester resins, thermosetting, acrylic-modified polyester resins, Urethane resins, thermoplastic acrylic resins, thermoplastic polyester resins, thermoplastic acrylic modified ones Polyester resins, etc. are used. When applying -, the powdery paint is heated so that the Resin component contained therein is melted and converted into a thin liquid state, whereby a closed and smooth paint film is formed. The formation of a paint film is thus facilitated by the

κι thermal thin liquid of the resin in powder form Paints strongly influenced, i.e. with a higher thermal thinness of the resin, better Paint films are formed. However, a higher thinness of the resin generally leads to

ι j considerable sticking and excessive caking of the powder particles if they are stored for a long time or at high temperature, so that the use of the resin is practically impossible.
On the other hand, the use of polyurethane resins which are crosslinkable with isocyanates and which have excellent weather resistance, chemical resistance and mechanical properties, is very desirable. Resins of this kind are widely used in solution type paints. Because of the high reactivity of the isocyanate group, it is usually used in a two-pack system, that is, a paint in the form of a solution and a crosslinking agent are mixed immediately before use. Or that

jo isocyanate is used in a one-component system, d. That is, all isocyanate groups are blocked beforehand with a phenol or the like, and after application and after baking, the blocking of the isocyanate groups is lifted, so that the cross-linking

j) completion.

Powder paints containing an isocyanate group crosslinkable urethane resin which is stable at normal temperature can also be prepared in the manner described above, that is, by mixing a completely blocked isocyanate compound with a solid resin containing an active hydrogen atom and grinding the mixture . In order to form a cured paint film from such a powder paint, it must be heated up to the dissociation temperature of the blocking agent. In the case of tolylene diisocyanate blocked with phenol, the dissociation temperature is usually 180 ^° C. or more. In the case of toluene diisocyanate, that with an alcohol

is so blocked, the dissociation temperature is usually 200 ° C or more. To get a sufficient To ensure the degree of crosslinking, it is therefore necessary to bring the paint film to a very high temperature heat. The removal of a blocking agent also usually results in a special odor, which causes environmental pollution and causes discoloration, pore formation and the like in the formed Paint film. The usual heat treatment thus leads to a significant deterioration in the

bo surface quality of the paint films formed and acts to keep the environment clean, which is a desired effect in powder painting processes, opposite.

DT-AS 17 71374, especially in column 1, line 9, DT-OS 19 57 483, especially page I ₁ 2nd paragraph, DT-OS 20 64 098, especially page 1, first and second paragraph, DT-OS 22 15 080, especially p. 1, first, second and third paragraph as well as p. 2, second paragraph, and DT-OS 21 05 777,

In particular, p. 2, second to fourth paragraph, relate to powder paints whose main components contain resins with hydroxyl groups and blocked or blocked isocyanates, in which the isocyanate groups are completely blocked or capped by lactams or other compounds.

DT-OS 20 08 710 relates to a mixture of a polyurethane, which has been produced from a polyisocyanate and a polyol, with another resin. The polyurethane essentially contains no free isocyanate groups, as can be seen from the description of the molar ratios of the polyisocyanate and the polyol in the polyurethane, in particular on page 6, 2nd paragraph, where it says that the polyisocyanate and the polyol in an NCO / OH ratio of 0.8 / 1.2: 1, preferably 1: 1. Are brought to reaction.

In contrast, the present invention relates to powdery paints in which the polyisocyanate compound as one of the two essential compounds, at least two free isocyanate groups must have per molecule. The disadvantages are clearly evident from the statements made above the above-described, known from the prior art powder paints with masked or end-blocked isocyanate groups.

In an effort to address the incompatibility of thermal Thin liquid and the storage stability and when using a completely blocked To eliminate isocyanate compound as a crosslinking agent disadvantage, it has been found that Powder particles obtained by dispersing a polyisoc; anat connection, containing an isocyanate group are obtained in a solid resin hardly stick together or stick together if stored for a long time or at high temperature. It was further found that this polyisocyanate compound, even when dispersed in solid resins, has a contain active hydrogen atom is so stable that no substantial deterioration in physical Properties of the paint films formed with these paints gives. Since the inventively used Polyisocyanate compound has an extremely low vapor pressure, it reacts so hard with the one active hydrogen atom-containing solid resin that the paint formed is stable to storage and the Properties of the paints formed are not significantly influenced by this. Furthermore, this has Polyisocyanate compound has a significantly lower toxicity, so that undoubtedly a great technical advantage is achieved with it. Also, it is not necessary to use paints that have an active hydrogen atom containing solid resin and containing this polyisocyanate compound at a temperature as high as that of common paints that contain a completely blocked isocyanate compound as a crosslinking agent, to heat to dissociate the blocking agent. This advantage has the result that a sufficient Degree of crosslinking achievable at a lower temperature and further in that no blocking agent is released, no pollution of the environment occurs and the physical properties of the paint films formed are not deteriorated. The invention are based on the above findings.

The invention relates to powdered paints based on solid resins and Polyisocyanates consisting of at least one solid resin with a glass transition temperature of not less than about 5 ° C and at least one polyisocyanate compound which is solid at room temperature, the contains on average at least two isocyanate groups in the molecule, the weight ratio of ι solid resin to polyisocyanate compound in the range from 99: 1 to 30:70.

The powder paints according to the invention contain (A) a solid resin and (B) one Polyisocyanate compound that averages two

ι contains Ii or more free isocyanate groups in the molecule

The solid resins (A) in (C) can be solid resins having an active hydrogen atom, for example, in a Hydroxyl group or a primary or secondary amino group containing isocyanate groups

ι -, is reactive, and (D) solid resins that are not active Containing hydrogen atoms, are divided.

To have good storage stability of the solid resin (A) and the polyisocyanate compound (B) containing powder paint without deterioration

2 (i ensure that the thin liquid is exposed to heat, components (A) and (B) are preferably used in a weight ratio of 99: 1 to 30:70 used. If the amount of component (B) is less than 1% by weight, the influence on the storage stability

j-, speed is much lower. When the amount of the component (B) is more than 70% by weight, it is Thin fluidity under the action of heat is less, and a smooth paint film is obtained using the one obtained Difficult to achieve paint.

in When the solid resin (C) is partially or entirely is used as component (A), components (B) and (C) are preferably used in one The quantitative ratio used is 0.2 to 2 moles of the isocyanate group in the former to 1 mole of the active

ji corresponds to hydrogen in the latter.

Examples of suitable components (A) are acrylic resins, polyester resins, acrylic-modified polyester resins, Epoxy resins, polyether resins, amino resins, polyvinyl chloride resins, polyamide resins, polybutadiene

-in and petroleum resins. Resins are preferred with a Freezing temperature of not less than about 5 ° C, especially from about 5 to 150 ° C (the freezing temperature is measured according to the balance method).

j As components (C) those with a number average molecular weight of about 400 to 30,000 and a glass transition temperature of about 5 to 80 ° C are preferred.

The powder paints according to the invention show good storage stability. If you on Substrates are applied and baked in, they have good thermal fluidity. if component (A) consists partly or wholly of component (C), are stoved Paint films formed with excellent properties.

The component (B) must be so depending on the kind and the glass transition temperature of the component (A) be chosen that they melt with the

bo component (A) is well tolerated and the Powder paint containing component (A) does not impart tackiness. When the freezing temperature of component (A) is below about 5 ° C, the raised paints are often sticky and with

Difficult to grind at room temperature. When the component (A) is partially or exclusively composed of the component (C), lead components (C) with an egg ^r - ^r iertemperatur above about 80 ° C to poor

thermal flow properties under normal stoving conditions, so that smooth paint films are not formed.

Specific examples of suitable acrylic resins that can be used as component (A) are the polymers obtained by polymerizing one or more of the monomers mentioned below: unsaturated monomers containing hydroxyl groups (e.g. 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and 2-hydroxyethyl acrylate), unsaturated acid amide monomers (e.g. acrylamide, N-methylolacrylamide and methacrylamide), unsaturated monomeric carboxylic acids (e.g. acrylic acid, methacrylic acid, itaconic acid and crotonic acid), unsaturated monomeric acid anhydrides (e.g. itaconic anhydride> and maleic anhydride), unsaturated glycidyl monomers (e.g. glycidyl acrylate and glycidyl methacrylate), acrylic acid esters (e.g. ethyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate), methacrylic acid esters (e.g. methyl methacrylate, n-lauryl methacrylate and isobutyl methacrylate) B. dibutyl maleate and diethyl maleate), fumaric acid esters (e.g. dibutyl fumarate and dieth yl fumarate), styrene and its derivatives (e.g. B. a-methylstyrene, 0-chlorostyrene, -bromostyrene and p-bromostyrene) and nitriles (z. B. Acrylonitrile, Methacrylni- y> tril and ethyl acrylonitrile).

Acrylic resins which have a number average molecular weight of about 1000 to 30,000 and about 1 χ ΙΟ " ⁴ to 30 χ 10" ⁴ mol active hydrogen atoms / g are preferred. When the number average molecular weight less than about 1000 or the content of active hydrogen atoms below about 1 χ 10 ~ ⁴ mol / g is, finds no sufficient crosslinking takes in the paint film which has been formed from a such an acrylic resin-containing paint. Furthermore, this paint film does not have good physical properties. When the number average molecular weight is over about 30,000, the thermal flow properties of the paint films become poor. At a content of active hydrogen atoms of more than about 30 IO χ ⁴ mol / g, the crosslinking proceeds excessively fast, so that the surface condition of the coating film is greatly deteriorated.

As specific examples of suitable polyester resins, the reaction products are one or more kinds of Polycarboxylic acids such as saturated aliphatic carboxylic acids (e.g. oxalic acid, succinic acid, glutaric acid, Adipic acid, pimelic acid, suberic acid, sebacic acid and isosebacic acid) and aromatic carboxylic acids (e.g. phthalic acid, isophthalic acid and terephthalic acid) and their anhydrides with one or more of the the following polyhydric alcohols mentioned as examples:

Ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol,

Triethylene glycol, 1,4-butanediol,

2,3-butanediol, 1,5-pentanediol,

1,4-pentanediol, 1,6-hexanediol, 1,5-hexanediol,

1,4-hexanediol, 1,3-hexanediol, 2,3-hexanediol, 2,4-hexanediol, 2,5-hexanediol, 3,4-hexanediol,

1,7-heptanediol, 1,6-heptanediol,

1,5-heptanediol, 1,4-heptanediol,

1,3-heptanediol, 2,3-heptanediol,

2,4-heptanediol, 2,5-heptanediol, b ^r >

2,2-dimethyl-1,3-propanediol (neopentyl glycol),

2,2-diethyl-1,3-propanediol,

2-ethyl-2-butyl-1,3-propanediol,

2,4-cyclohexanedimethylol,
Trimethylolpropane and
Glycerin.

The polyester resins can optionally be modified with customary modifying agents. Suitable modifying agents are, for example, unsaturated aliphatic carboxylic acids (e.g. maleic acid, Fumaric acid, itaconic acid, citraconic acid and linoleic acid) or their anhydrides (e.g. maleic anhydride), higher unsaturated aliphatic carboxylic acids, natural oils and fats (e.g. linseed oil, sardine oil, dehydrated castor oil, safflower oil, soybean oil, cottonseed oil, castor oil and palm oil), synthetic oils or fats and fatty acids obtained from the hydrolysates of these oils and fats.

Polyester resins are preferred having a number average molecular weight of about 500 to 5,000 and a hydroxyl group to 45 χ χ 3 of about IO ⁴ IO ⁴ mol / g. In a number average molecular weight below about 500, or a hydroxyl group content below about 3 χ 10 ^-4 mol / g, the crosslinking of the paint film is insufficient, and physical properties are poor. If the number average molecular weight is more than about 5000, the thermal flow behavior is poor. When a hydroxyl group content greater than about 45 ΙΟ- χ ⁴ mol / g the paint films have a poor surface finish.

Suitable acrylic-modified polyester resins are resins which are obtained by grafting an ethylenically unsaturated monomer and / or an acrylic resin onto the polyester resin in a conventional manner by polymerization, condensation, addition, chain transfer reactions and / or the like. Acrylic-modified polyester resins of this type which have a number average molecular weight of about 500 to about 20 000 IO 3 ⁴ χ χ to 45 IO ⁴ moles of active hydrogen atoms / g are preferably included. When the number average molecular weight and active hydrogen atom content are within these ranges, the formation of well crosslinked paint films with good physical properties is ensured.

Suitable epoxy resins are, for example, polyfunctional polycondensates of bisphenol A and epichlorohydrin Epoxy compounds obtained by condensation of novolaks with epichlorohydrin Polyether chain epoxy compounds and alicyclic epoxy compounds. Examples of suitable amino resins are the urea resins, melamine resins and guanamine resins. As polyether resins, for example, are suitable Addition products of alkylene oxides, e.g. B. ethylene oxide and propylene oxide, with low molecular weight poly oils, z. B. ethylene glycol, glycerin, trimethylolpropar and pentaerythritol. For advantageous production before Resin compositions crosslinkable with isocyanates are expediently epoxy resins with a number average of Molecular weight from about 400 to 4000 or polyether resins having a number average molecular weight from about 500 to 3000 used. These resins are used in such an amount that the Sum of the number of hydroxyl groups in one molecule of the resin and the number of free isocyanate groups is not less than 5 in one molecule of the polyisocyanate compound. In the case of the amino resins are advantageously those with a number average molecular weight of about 400 to 2000 in one

such amount is used that the sum of the numbers of primary and secondary amino groups and hydroxyl groups in one molecule of the resin and the number of free isocyanate groups in one molecule of the polyisocyanate compound is not less than 5.

As the component (B) preferably polyisocyanate compounds are used, the (z. B. 5 ⁰ C to 3O) at room temperature are set to cause a reaction between the free isocyanate groups and the active hydrogens to prevent as used as component (A) solid resin .

These polyisocyanate compounds can be prepared by converting polyisocyanates, e.g. B. Diisocyanates or triisocyanates

(e.g. hexamethylene diisocyanate,

Ethylene diisocyanate, propylene diisocyanate,

Tetramethylene diisocyanate,

Decamethylene diisocyanate,

Triphenyl methane triisocyanate,

4,4'-ethylene biscyclohexyl isocyanate,

4,4'-methylenebiscyclohexyl isocyanate,

o.cü'-diisocyanate-l.S-dimethylbenzene,

Phenylene diisocyanate,

Lysine diisocyanate methyl ester,

I sophorone diisocyanate,

Trimethylhexamethylene diisocyanate,

Diphenylmethane 'M' diisocyanate,

S.S'-dimethyldiphenylmethane-'M'-diisocyanate)

into a biuret structure or an allophanate structure. The polyisocyanate compounds can also be prepared are made by reacting one or more of the polyisocyanates mentioned and / or those mentioned Polyisocyanate compounds with a biuret or allophanate structure with one or more chain extenders with the formation of polyisocyanate compounds with an average of two or more free isocyanate groups in the molecule. Examples of suitable chain extenders include: polyhydric alcohols and Polycarboxylic acids used in the manufacture of the above polyester resins, substituted and unsubstituted diamines

(e.g. ethylenediamine, tetramethylenediamine,
Pentamethylenediamine, hexamethylenediamine,
Octamethylenediamine, decamethylenediamine,
p-xylylenediamine,

Ν, Ν'-diisobutylhexamethylenediamine,
Ν, Ν'-diethylene hexamethylene diamine,
N-isobutylhexamethylenediamine and
N-benzylhexamethylenediamine),

Water and amino alcohols.

Preference is given to polyisocyanate compounds which are obtained by reacting the abovementioned reactants in an equivalent ratio of the free isocyanate groups to the active hydrogen atoms in the chain extender of more than 1 (expediently not less than 1.5 and not more than 10) in the presence or absence of an inert solvent (e.g. B. butyl acetate, toluene and methyl ethyl ketone) with or without a suitable basic catalyst or metal catalyst [e.g. B. triethylamine, N-methylmorpholine, dibutyltin dilaurate and tin (II) chloride] at a temperature of room temperature to 200 ⁰ C are made (suitably from 50 to 16O ⁰ C). If the chain extender contains impurities in a large amount, by-products are generated and the physical properties of the paint films produced are considerably deteriorated. For this reason, the chain extender is expediently beforehand in the usual manner, for. B. purified by distillation, extraction or adsorption.

j The reaction product obtained in this way can in certain cases contain unreacted polyisocyanates and / or oligomers and as such or after Removal of the unreacted polyisocyanates and the oligomers in the usual way, for. B. by distillation, Extraction or adsorption.

After purification in the manner described, the product obtained can be used alone or in combination be used.

The powder paints of the present invention containing components (A) and (B) are special advantageous as a powder coating. They can be used for this purpose alone or in combination with an or Several additives can be used that are commonly used in the painting field

2 »become. Examples of such additives are: reactive compounds (e.g. aromatic polyamines, aliphatic polyamines, polycarboxylic acids and their anhydrides, polycarboxylic acid hydrazides, dicyandiamide, BF3 amine complex compounds, completely blocked cyanate compounds), pigments (e.g. TiO ₂ , FeO, silicon dioxide , CaCO ₃ , BaSO ₄ , carbon black and phthalocyanine blue), plasticizers (e.g. dibutyl phthalate and dioctyl phthalate), cellulose derivatives (e.g. cellulose acetobutyrate, methoxy cellulose and ethoxy cellulose),

jo anion-active surfactants (e.g. fatty acid salts and higher Alcohol sulfates), non-ionic surface-active compounds (e.g. polyoxyethylene alkyl ethers), cation-active Surfactants (e.g. alkylamine salts and quaternary ammonium salts), leveling agents (e.g. silicone resins and Acrylic resins) and crosslinking catalysts for curing at low temperatures (e.g. triethylamine and Dibutyltin dilaurate).

The powder paints according to the invention can be prepared by uniformly mixing the ingredients in the usual way, e.g. B. in the dry or semi-dry state or as a melt, with the formation of a uniform dispersion can be produced. This uniform dispersion is then formed with the Ground powder paint.

The powder paint can be applied to the surfaces to be coated by conventional application methods, e.g. B. by electrostatic powder spraying or by application in a fluidized bed and subsequent baking, this generally at a temperature of 140 to

so 240 ⁰ C takes place for a time of 5 to 60 minutes, can be applied with the formation of good paint films. In resin compositions which can be crosslinked with isocyanate groups, for example, be obtained by baking at relatively low temperatures of below 200 ⁰ C urethane resins having excellent surface finish. Since no blocking agent is released during baking, the use of the mixtures according to the invention as paints does not result in any pollution of the environment.

Practical and presently preferred embodiments of the invention are illustrated in the following examples in which the parts and percentages are by weight.

example 1
^b 1-1) Preparation of the polyisocyanate compound

In a flask equipped with a reflux condenser, thermometer, nitrogen inlet and stirrer

444.4 parts of isophorone diisocyanate and 62 parts of ethylene glycol were added. After displacing the air with nitrogen, the reaction is carried out at 90 to 100 ° C. for 24 hours. The product is colorless, transparent and solid at room temperature and contains 39.5 χ 10- ⁴ mole of 5 free isocyanate groups per gram.

1-2) Preparation of the paint

To a mixture of 350 parts of an acrylic resin (composed of methyl methacrylate, styrene, isobutyl methacrylate, n-butyl methacrylate, glycidyl methacrylate and 2-hydroxyethyl methacrylate; Glycidylgruppengehalt 10.6 χ ΙΟ- ⁴ mol / g; hydroxyl χ 2 10- ⁴ Moug; number average molecular weight 6000; glass transition temperature of 50 ⁰ C), 37.5 parts of sebacic acid, 100 parts of titanium dioxide (rutile), and 5 parts of a leveling agent (appearance: pale yellow, viscous liquid; Color: 2 [G ardner]; viscosity 5000 SUS [1,150 centistokes] at 98 , 9 ° C; specific weight: 1.00 [15.6 / 15.6 ⁰ C]; refractive index: 1.4130-1.4190 at 25 ° C [40% 2,2,4-trimethylpentane solution]; Solubility: soluble in benzene, toluene, xylene, petroleum ether, carbon tetrachloride and mineral oil, soluble in isopropanol to about 2-3% by weight, insoluble in water; flash point [COC]: 182.2 ° C; use: the leveling agent is used as Agents used to improve the flow properties of non-aqueous paints and adhesives et By incorporating it into a paint in the appropriate concentration, the flow properties of the paint are greatly increased, and a jo

Table 1

A smooth surface of the coating produced with it is achieved. The leveling agent is an acrylic ester polymer with a low glass transition temperature and a relatively low degree of polymerization.) 25 parts of the in Section 1-1 given polyisocyanate compounds prepared. The mixture is a melt in one Extruder mixed, ground and passed through a sieve with a mesh size of 149 μ, using a powder paint (hereinafter referred to as "1-A") is obtained.

For comparison, a mixture of the same acrylic resin with sebacic acid, rutile and leveling agent is shown in treated in the same manner to obtain powder paint hereinafter referred to as "1-B" will.

1-3) test

The powder paint "1-A" and "1-B" are applied with an electrostatic spray device iron panels and baked 30 minutes at 200 ⁰ C. The results of the tests on the paint films are shown in Table 1. After storage for 7 days at 40 ⁰ C service and bakes the powder paint "1-B" together strong and then for practical use unusable while the powder paint remains "1-A" unchanged and can be used to produce paint films have essentially the same properties as the paint films made with the paint before storage.

Powder paints
1-A

Remarks

1-B

Test time immediately after Her

position

Gloss 89%

Smoothness good

Impact resistance 20 cm

Hardness 35

immediately after manufacture

90% good 20 cm

34

Example 2

2-1) Making a
blocked polyisocyanate compound

253.2 parts of the polyisocyanate compound prepared according to Example 1 and 94 parts of phenol are reacted for 3 to 8 hours at 130 to 14O ⁰ C. After the free isocyanate groups have been blocked completely, the temperature is lowered. A yellowish brown, transparent product which is solid at room temperature is obtained.

50

55

2-2) Preparation of a paint

W)

A mixture of 155 parts according to Example 2-1) and polyisocyanate compound produced 345 parts of a polyester resin (consisting of isophthalic acid, 5 _b neopentyl glycol and glycerin; hydroxyl group content 17.7 χ ΙΟ- / g mole ^4; number-average molecular weight 1200; glass transition temperature 50 ⁰ C) becomes 60 ° due to mirror reflection

DuPont impact test;
Height of fall of the falling weight
(500 g, 12.7 mm)

Sward swing value; Glass plate 58; Polymethyl methacrylate plate 23

Mixing in the molten state made in an extruder and ground. The powder is through a Sieve with a mesh size of 149 μ, using a powder paint (hereinafter referred to as »2-A«) is obtained.

Separately from this, 200 parts of titanium dioxide (rutile) are added to the above mixture. The ingredients are melt mixed and ground, using a powder paint (hereinafter referred to as "2-B").

For comparison, a mixture of 190 parts of the blocked polyisocyanate compound prepared according to Example 2-1) is used and 310 parts of the aforesaid polyester resin in the same manner a powder coating (hereinafter referred to as "2-C") processed.

Separately from this, 200 parts of titanium dioxide (rutile) are added to the above mixture. The ingredients are mixed as a melt and ground to obtain a powder paint (hereinafter referred to as "2-D").

2-3) test

The powder paint composition "2-A" and "C-2" are applied with an electrostatic spray device Zinnbleche and 30 minutes at 160 ° C, 180 ° C, 200 ° C and baked 22O ⁰ C. The paint films formed are extracted with acetone in a Soxhlet extractor for 5 hours. The percentages by weight of the insoluble material determined are shown in FIG. 1 as a function of the stoving temperature. Curve 1 shows the results for powder coating "2-A" and curve 2 shows the results for powder coating "2-C". The figure shows

that the paint prepared according to the invention at a lower temperature than the comparative paint can be burned in.

The powder paints "2-B" and "2-D" are applied with an electrostatic spray device Iron sheets applied and 30 minutes at 180 ° C resp. Baked for 30 minutes at 200 ° C. In addition, the powder coating becomes »2-B« after storage for 6 months applied to an iron sheet at room temperature under the same conditions and then baked. The results of the tests on the paint films are shown in Table 2.

Table 2 Powder paints 2-C 2-D Remarks 2 B after storage immediately after immediately after for 6 months Manufacturing assignment Manufacturing 88% 90% 91% no numerous Mirror reflection 60 ° shine no no strong yellowing Pores no 25 cm 25 cm Discoloration 25 cm DuPont impact resistance Impact resistance test; Height of fall 35 35 weight (500 g, 12.7 mm) 36 Sward-Schaukeiwert; hardness Glass plate 58; Polymethyl 92.0 93.5 methacrylate plate 23 95.0 % By weight insoluble Insoluble in acetone material proportion of

As shown in Table 2, the paint according to j-j Table 3 has

Invention good storage stability, and the resulting

Paint films have excellent gloss, resistance to discoloration and no pores.

Example 3
3-1) Preparation of the polyisocyanate compound

212 parts of lysine diisocyanate methyl ester and 114 parts of purified bisphenol A are placed in a flask. The reaction is carried out under the conditions mentioned in Example 1. As a product, a pale yellow, transparent, solid resin at room temperature is obtained, which has a free isocyanate group content of 30.7 χ 10- ⁴ mol / g.

3-2) Preparation of the paint

In the manner described in Example 2, a powder paint of 183.5 parts of the according to Example 3-1) polyisocyanate compound prepared, 316.5 parts of the same polyester resin as in Example 2 and 175 parts of titanium dioxide (rutile).

3-3) test

The according to Example 3-2) powder paint prepared is applied with an electrostatic spray device on an iron plate and baked for 30 minutes at 18O ⁰ C, wherein a non-porous elastic paint film is obtained with excellent gloss. The results of the tests on the paint film are shown in Table 3.

Order immediately
after manufacture

Order after storage
for 3 months

86% 87% no no no no 25 cm 25 cm 34 34 88.0% 87.5%

^w shine

Pores

Discoloration

Impact resistance

hardness
⁴ ^ In acetone

insoluble part

The tests were carried out in the manner described in Example 2.

Example 4
4-1) Preparation of the polyisocyanate compound

250.2 parts of diphenylmethane-4,4'-diisocyanate, 31 parts of purified ethylene glycol and 281.2 parts of butyl acetate are placed in a flask. After displacing the air with nitrogen, the reaction is carried out for 24 hours at 100 to 12O ⁰ C. After removing the

ho butyl acetate from the reaction mixture under reduced pressure a white powdery solid is obtained which has a free isocyanate group content of 35.6 χ 10- ⁴ mol / g.

_Μ 4-2) Preparation of the paint

In the manner described in Example 2, a powder paint of 166.5 parts of the according to Example 4-1) produced polyisocyanate compound,

333.5 parts of the same polyester resin as in Example 2 and 175 parts of titanium dioxide (rutile) were produced.

4-3) test

The according to Example 4-2) Pulveranstrich- ■ prepared -, medium is applied with an electrostatic spray device onto an iron plate and 30 minutes at 180 ° C ^e: ngebrannt, wherein a non-porous elastic paint film is obtained with excellent gloss and color stability. Even after being stored for 3 months at room temperature, the powder paint can be used to produce good paint films.

B e i s ρ i e 1 5

5-1) Preparation of the paint

In the manner described in Example 1, a powder paint (hereinafter referred to as "5-A") of 126.6 parts of the polyisocyanate compound prepared in Example 1 and 400 parts of acrylic resin (consisting of methyl methacrylate, styrene, n-butyl acrylate and 2-hydroxyethyl methacrylate; Hydroxyl group content 12.5 χ ΙΟ- ⁴ mol / g; number average molecular weight 5000; freezing temperature 55 ° C). 2i

Separately, 131.6 parts of titanium dioxide (rutile) are added to the above mixture. The parts are mixed as a melt. The mixture is ground using a powder paint (hereinafter referred to as "5- B"). jo

For comparison, a powder paint (hereinafter referred to as "5-C") is composed of 173.6 parts of the blocked according to Example 2 (2-1) prepared

Table 4

Polyisocyanate compound and 400 parts of the aforementioned acrylic resin.

Separately, 131.6 parts of tilane dioxide (rutile) are added to the above mixture. the Components are mixed as a melt. The mixture is ground using a powder paint (hereinafter referred to as "5-D") is obtained.

5-2) test

The powder paint "5-A" and "C-5" are applied with an electrostatic spray device Zinnbleche and baked for 30 minutes at 160 ⁰ C ₁ 180 ⁰ C, 200 ° C and 220 ° C. The paint films formed are extracted with acetone in a Soxhlet extractor for 5 hours. The proportions of the insoluble material in% by weight are shown in FIG. 2 as a function of the burn-in time. Curve 3 represents the results for powder paint "5-A" and curve 4 the results for powder paint center / "5-C" , FIG. Figure 2 shows that the paint according to the invention can be baked at a lower temperature than the comparative paint.

The Pulveranstrichrr.lttel "5-B" and "D-5" are applied with an electrostatic spray device aul iron plates and 30 minutes at 180 ⁰ C 30 minutes at 200 ⁰ C baked. Furthermore, after storage for 3 months at room temperature, the powder paint “5-B” is applied to an iron sheet under the same conditions and then baked ^{at 180 ° C. for 30 minutes.} The results of the tests on the paint films are shown in Table 4 below.

Powder paint 5-B 5-C

5-D

assignment

shine
Pores
Discoloration

Impact resistance

Part insoluble in acetone

immediately after

Manufacturing

86%

no

no

20 cm

34

92.1%

after storage immediately after for 3 months Manufacturing 84% 86% no numerous no strength Yellowing 25 cm 20 cm 35 34 92.7% 92.1%

The tests were carried out in the manner described in Example 2.

1 sheet of drawings

Claims (5)

Patent claims: 1. Powder paints based on solid resins and polyisocyanates, consisting of at least one solid resin having a glass transition temperature of not less than about 5 ° C and at least one polyisocyanate compound which is solid at room temperature and an average of at least contains two isocyanate groups in the molecule, the weight ratio of solid resin to Polyisocyanate compound ranges from 99: 1 to 30:70 2. Powdered paint according to claim 1, characterized in that it is used as a polyisocyanate compound an addition product of a diisocyanate or triisocyanate with a chain extender, the contains two or more active hydrogen atoms. 3. Powder paint according to claim 1 and 2, characterized in that it χ as strength resins, acrylic resins having a number average molecular weight of 1000 to 30 000 / or a content of active hydrogen atoms of 1 10- ⁴ to 30 of χ 10 ~ ⁴ mol / gent hold . 4. Powdery paints according to claim 1 to 3, characterized in that they are solid resins polyester resins with a number average molecular weight of 500 to 5000 and / or a content of active hydrogen atoms of 3 χ 10- ⁴ to 45 χ 10- ⁴ mol / g included. 5. Powder paint according to claim 1 to 4, characterized in that it contains as solid resins acryl-modified polyester resins having a number average molecular weight of 500 to 20 000 / or eineim content of active hydrogen atoms of 3 χ 10- ⁴ to 45 χ 10 ^"4 Mol / g included.