HK1062295B - Blocked polyisocyanates - Google Patents

Description

Blocked polyisocyanates

Cross reference to related patent applications

This patent application claims priority from german patent application nos. 10226927.0, 10226931.9, 10226926.2, 10226925.4 and 10226924.6 under the clauses of sections (a) - (d) of 35 u.s.c119, all of which were filed on day 6/17 of 2002.

Technical Field

The invention relates to blocked polyisocyanates, to a process for their preparation and to their use in one-component coatings.

Background

The blocking of polyisocyanates for the temporary protection of the isocyanate groups is a known practice and is described, for example, in Houben Weyl, methods of organic chemistry XIV/2, pages 61 to 70. Curable compositions comprising blocked polyisocyanates have been found to be useful, for example, in Polyurethane (PU) coatings.

The preparation of one-component, storage-stable binders for PU stoving varnishes by blending blocked polyisocyanates with OH-containing polycondensates or polyadducts (polyesters or polyacrylates) is known.

In this one-component coating, the blocking agent plays 2 roles: firstly, premature reaction of the OH component with the NCO groups blocked by the blocking agent is prevented, and secondly, owing to the specific deblocking properties, the blocking agent regulates the curing of the coating within a defined temperature range. However, in addition to these desirable properties, various blocking agents themselves can also impart undesirable properties such as a tendency to crystallize or yellow, uneconomical properties, environmental problems, and serious physiological effects.

This is illustrated by butanone oxime and 3, 5-dimethylpyrazole. These two blocking agents are readily miscible with the polyisocyanates in known coatings and deblock at 130 ℃ and 140 ℃ in about 30 minutes. In respect of side effects, butanone oxime causes yellowing of the stoving coating on heating and the substance itself is toxicologically harmful. The preparation of dimethylpyrazole from acetylacetone and hydrazine hydrate is expensive and this compound gives coatings an unpleasant odour (see for example t.engbert, e.k ö nig, E.J gun, Farbe & rock, cutr. vincentz Verlag, Hanover 97/1996).

In addition, the blocking agent released from the coating film is in a gaseous state, which may cause the coating to blister. If appropriate, the discharged blocking agent is incinerated. For a review of the blocking agents which are suitable in principle, reference may be made, for example, to Progress in Organic Coatings by Wicks et al, 1975,3，73-79；1981，9the sum of the values of, 3-28 and 1999,36，148-172。

for the coil coating art, the blocked polyisocyanate must be capable of crosslinking at a PMT (peak metal temperature) of up to 254 ℃ in a very short time, and the polymer must exhibit minimal, and preferably no, thermal yellowing during the baking operation. The baking temperature required depends primarily on the reactivity of the blocked polyisocyanate and/or the catalyst used in the process.

Disclosure of Invention

It is therefore an object of the present invention to provide novel blocked polyisocyanate systems which do not liberate blocking agents during the reaction, i.e.do not emit emissions, and have a low crosslinking temperature, i.e.a high reactivity. Furthermore, such blocked polyisocyanate systems must be stable on storage at ambient temperatures and, in particular when combined with suitable polyols, must be suitable for the preparation of one-component coatings, in particular stoving varnishes.

The object of the invention is achieved with the polyisocyanates blocked according to the invention and with binders based on such polyisocyanates.

It has been found that CH-acidic compounds having an activated cyclic ketone structure, preferably a cyclopentanone 2-carboxylate structure, are very suitable for blocking polyisocyanates, giving coatings having a low tendency to yellowing without undesirable emission of volatile substances.

The present invention accordingly provides polyisocyanates blocked with activated cyclic ketones, a process for their preparation and one-component coatings obtainable on the basis thereof, in particular stoving varnishes, which are characterized in that the blocked polyisocyanates according to the invention are used as crosslinking components for organic polyhydroxyl compounds.

Detailed Description

The present invention provides a process for preparing PU coatings by adding organic polyisocyanates to the formulations. Such coatings may be single-component PU stoving varnishes. Such coatings may be used to coat a web and may be applied to the web using methods known to those skilled in the art.

Unless specifically stated otherwise, all numerical ranges, amounts, values and percentages used herein, such as those for materials, reaction times and temperatures, ratios of amounts, molecular weight values, and the like in the following description section, are to be read as if prefaced by the word "about", even if the value, amount or range is not specifically stated to be "about".

For the process of the present invention, organic polyisocyanates containing at least 2 isocyanate groups are used. In this organic blocked polyisocyanate, the isocyanate groups are blocked with CH-acidic cyclic ketones of the general formula (I)

In the formula:

x represents an electron-withdrawing group,

R¹and R²Independently of one another represent the radical H, C₁-C₂₀Cycloalkyl radical, C₆-C₂₄Aryl radical, C₁-C₂₀Cycloalkyl esters or C₁-C₂₀Cycloalkyl amides, C₆-C₂₄Aryl esters or C₆-C₂₄Arylamides, mixed aliphatic/aromatic radicals containing from 1 to 24 carbon atoms, in which R¹And R²Or may be part of a 4-to 8-membered ring, and

n is an integer of 0 to 5.

The polyisocyanates have a total blocked isocyanate group content (calculated as NCO) of from 0.1 to 25% by weight. Such polyisocyanates are disclosed in the prior application DE-A10132016 of the same applicant.

The blocked isocyanate group content (in NCO) is preferably from 0.1 to 15.6% by weight of the polyisocyanate. The blocked isocyanate group content (in terms of NCO) is more preferably 0.1 to 14% by weight. Where appropriate, partially blocked polyisocyanates may be present and unblocked isocyanate groups may be available for further reaction. Typically, all isocyanate groups are blocked.

The electron withdrawing group X may be any CH-acidic substituent that results in an alpha hydrogen. These substituents may be, for example, ester groups, amide groups, sulfoxide groups, sulfone groups, nitro groups, phosphonate groups, nitrile groups, isonitrile groups, carbonyl groups, polyhaloalkyl groups and halogens, in particular fluorine and chlorine. Preferred are nitrile groups and ester groups, more preferred are methyl carboxylates and ethyl carboxylates.

The rings thereof, where appropriate, also suitable are compounds of the formula (I) which contain heteroatoms such as oxygen, sulfur or nitrogen atoms.

The activated cyclic ketones of formula (I) are preferably 5(n ═ 1) or 6(n ═ 2) membered rings.

Preferred compounds of the general formula (I) are methyl and ethyl cyclopentanone-2-carboxylate, cyclopentanone-2-carbonitrile, methyl and ethyl cyclohexanone-2-carboxylate or cyclopentanone-2-carbonylmethyl. Particular preference is given to methyl cyclopentanone-2-carboxylate and ethyl 2-carboxylate and methyl cyclohexanone-2-carboxylate and ethyl 2-carboxylate. From a technical point of view, cyclopentanone systems are readily obtainable by dieckmann condensation of dimethyl adipate or diethyl adipate. Cyclohexanone-2-carboxylic acid methyl ester can be prepared by hydrogenation of methyl salicylate.

The polyisocyanate used for blocking can be any polyisocyanate suitable for crosslinking compounds containing active hydrogens, i.e., aliphatic, including cycloaliphatic, polyisocyanates containing at least 2 isocyanate groups, aromatic and heterocyclic polyisocyanates, and mixtures thereof.

Typical examples of polyisocyanates are aliphatic isocyanates, for example di-or triisocyanates, such as Butane Diisocyanate (BDI), pentane diisocyanate, Hexane Diisocyanate (HDI), 4-isocyanatomethyl-1, 8-octane diisocyanate (triisocyanatononane, TIN) or cyclic systems, for example 4, 4' -methylenebis (cyclohexyl isocyanate) (Desmodur)^®W, Bayer, Leverkusen), 3, 5, 5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane (IPDI) and omega, omega' -diisocyanato-1, 3-dimethylcyclohexane (H)₆XDI). Examples of aromatic polyisocyanates are 1, 5-naphthylene diisocyanate, diisocyanatodiphenylmethane (MDI) or monomeric MDI, diisocyanatomethylbenzene (TDI), especially the 2, 4-and 2, 6-isomers and technical-grade mixtures of these two isomers, and 1, 3-bis (isocyanatomethyl) benzene (XDI).

Polyisocyanates obtained by reaction of the isocyanate groups of the di-or triisocyanates themselves are likewise very suitable, such as isocyanate dimers (Uretdiones) or carbodiimide compounds, or such as isocyanurates and iminooxadiazinediones formed by reaction of 3 isocyanate groups. Such polyisocyanates may likewise comprise monomeric di-and/or triisocyanates and/or oligomeric polyisocyanates containing biuret, allophanate and acylurea structural units, monomeric di-and/or triisocyanates modified with low monomer contents or proportions, and also the desired mixtures of the polyisocyanates mentioned.

Also very suitable are polyisocyanate prepolymers containing on average more than 1 isocyanate group per molecule. They are initially prepared by reacting a molar excess of a polyisocyanate such as one of the above with an organic compound containing at least 2 active hydrogen atoms per molecule, for example in the form of hydroxyl groups.

Preferred polyisocyanates are those containing isocyanate dimer, isocyanurate, iminooxadiazinedione, acylurea biuret or allophanate structures, e.g.based on Butane Diisocyanate (BDI), pentane diisocyanate, Hexane Diisocyanate (HDI), 4-isocyanatomethyl-1, 8-octane diisocyanate (triisocyanatononane, TIN) or cyclic systems such as 4, 4' -methylenebis (cyclohexyl isocyanate) (Desmodur)^®W, Bayer, Leverkusen), 3, 5, 5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane (IPDI) and omega, omega' -diisocyanato-1, 3-dimethylcyclohexane (H)₆XDI). Examples of preferred aromatic polyisocyanates are 1, 5-naphthylene diisocyanate, diisocyanatodiphenylmethane (MDI) or monomeric MDI, diisocyanatomethylbenzene (TDI), especially the 2, 4-and 2, 6-isomers and technical-grade mixtures of these two isomers, and 1, 3-bis (isocyanatomethyl) benzene (XDI).

More preferred polyisocyanates are those based on Hexane Diisocyanate (HDI), 4' -methylenebis (cyclohexyl isocyanate) and 3, 5, 5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane (IPDI).

Described below is a process for preparing blocked organic polyisocyanates according to the invention, which is characterized in that polyisocyanates are reacted with CH-acidic cyclic ketones of the general formula (I) in the presence of catalysts:

in the formula:

x represents an electron-withdrawing group,

R¹and R²Independently of one another represent the radical H, C₁-C₂₀Cycloalkyl radical, C₆-C₂₄Aryl radical, C₁-C₂₀Cycloalkyl esters or C₁-C₂₀Cycloalkyl amides, C₆-C₂₄Aryl esters or C₆-C₂₄Arylamides, mixed aliphatic/aromatic radicals containing from 1 to 24 carbon atoms, in which R¹And R²Or may be part of a 4-to 8-membered ring, and

n is an integer of 0 to 5.

Wherein the cyclic ketone of formula (I) is used in an amount of 0.8 to 1.2mol per equivalent of isocyanate group of the polyisocyanate used for blocking.

Preferably, 1 isocyanate group equivalent of the polyisocyanate component used for blocking is reacted with 1 equivalent of the blocking agent.

Suitable catalysts are alkali and alkaline earth metal bases, for example powdered sodium carbonate (soda). Depending on the cyclic ketone used, it is also possible to use trisodium phosphate or bases of the amine type, for example DABCO (1, 4-diazabicyclo [2.2.2] octane). Also suitable are carbonates of metals of the second transition group. Preferably, sodium or potassium carbonate is used. Alternatively, the reaction of the cyclic ketone with the isocyanate may be carried out in the presence of a zinc salt catalyst. More preferred is a reaction using zinc 2-ethylhexanoate. Mixtures of catalysts may also be used.

In the process of the invention, the catalyst is added in an amount of from 0.05 to 10% by weight, preferably from 0.07 to 3% by weight, based on the polyisocyanate used. More preferably, 0.1 to 1 wt% of the catalyst is used.

The reaction can be carried out at 0 ℃ to 140 ℃. The preferred temperature range is from 15 ℃ to 90 ℃.

The blocking can be carried out without solvent or in the presence of a suitable solvent. Suitable solvents are the customary coating solvents, such as butyl acetate, methoxypropyl acetate or the solvent naphtha, used in the supplied form, for example aromatic-containing solvents supplied by Exxon chemical company, and also mixtures of the stated solvents. Preference is given to carrying out the blocking in the solvent, in which case the solids content is generally set to 10 to 90%.

In addition to the cyclic ketones of the general formula (I) used according to the invention, it is also possible to use any desired mixtures of blocking agents in the process of the invention in order to achieve the particular coating properties required, but with a proportion of compounds of the formula (I) of at least 30% by weight, preferably at least 50% by weight, more preferably 100% by weight.

The invention also provides a process for preparing one-component stoving varnishes, which is characterised in that the organic polyisocyanates according to the invention are used as a crosslinker component for organic polyhydroxyl compounds.

One feature of the blocked polyisocyanates to be used according to the invention is that they cure in the presence of suitable catalysts in not more than 2 minutes, preferably in a baking time of from 5 up to 60 to 80 seconds, more preferably in a baking time of from 5 up to 35 seconds, when they are mixed with suitable organic polyhydroxyl compounds. Here the furnace temperature is 300-. The baking conditions depend, of course, on the material used and on the thickness of the metal coil to be coated. The furnace temperature is generally set at a temperature not lower than 180 ℃ but not higher than 260 ℃ PMT. The preferred temperature range is 210 ℃ to 245 ℃ PMT. A more preferred range is 216 ℃ to 241 ℃ PMT. The technical properties of the coating film after baking, such as resistance to MEK (methyl ethyl ketone) solvents, hardness and elasticity, at a given baking temperature and a given baking time depend, inter alia, on the amount of catalyst used. Preferably, the baking is carried out at 232 ℃ for 38 seconds. Temperatures of 216 ℃ are also possible. The baking time in the case of an aluminum substrate was 33 seconds. The specific optimal conditions are determined by methods well known to those skilled in the art, i.e. by experiments seeking predetermined ranges, and the temperature in the coil coating oven is monitored with a sensor strip during application.

Examples of catalysts suitable for crosslinking are DBTL (dibutyltin dilaurate), titanium 2-ethylhexanoate, titanium tetraisopropoxide and other customary titanium (IV) compounds, zirconium 2-ethylhexanoate and other customary zirconium (IV) compounds, aluminum triethoxide, strontium triflate, iridium 2-ethylhexanoate, iridium triflate, lanthanum 2-ethylhexanoate, lanthanum triflate, cobalt 2-ethylhexanoate, copper 2-ethylhexanoate, indium triflate, gallium acetylacetonate, nickel acetylacetonate, lithium 2-ethylhexanoate, lithium triflate, sodium 2-ethylhexanoate, sodium acetate, sodium triflate, magnesium 2-ethylhexanoate, magnesium triflate, calcium 2-ethylhexanoate, calcium triflate, zinc 2-ethylhexanoate, zinc dithiocarbamates, zinc acetylacetonate, Zinc tetramethylheptanedioate, zinc salicylate, zinc chloride and other commonly used zinc (II) compounds, bismuth 2-ethylhexanoate and bismuth acetate. Preferred catalysts are compounds of zinc and bismuth, more preferred are zinc 2-ethylhexanoate and bismuth 2-ethylhexanoate.

Suitable polyhydroxyl compounds for this end use and further details regarding the preparation and use of stoving varnishes of this type are known from the literature, for example from DE-A19738497 or EP-A0159117. A more preferred use of the product of the invention is its use as a crosslinking agent in the field of coil coatings.

Polyols that can be used in the coil coating process are listed in the table below. Polyester polyols, polycarbonate polyols and polyacrylate polyols may all be used. In principle, any binder having a sufficiently high OH content can be used.

Trade name/brand	Type (B)	Form of supply
			Alkynol 1665 SN/1B	Oil-free, branched, saturated polyesters	65％SN100/IB
Alkynol VP LS 2013	Oil-free, branched polyesters	70％SN100
			Alkynol VP LS 2326	Oil-free, branched, saturated polyesters	60％SN100
Desmophen 651 MPA	Branched polyesters	67％MPA
			Desmophen 670	Polyesters with low degree of branching	Contains no solvent
Desmophen 690 MPA	Branched polyesters	70％MPA
			Desmophen 1200	Polyesters with low degree of branching	Contains no solvent
Desmophen 1652	Oil-free, linear polyesters	Contains no solvent
			Desmophen C 200	Linear polycarbonate-polyesters	Contains no solvent

Using the blocked polyisocyanates according to the invention, high-quality, emission-free coatings are obtained which generally have a low yellowing level.

In addition to the components mentioned, the binders according to the invention may further comprise stabilizers, for example HALS amines or solvents, and up to 5% by weight, based on the solids of the finished coating, of OH-functional hydrazide compounds. Further suitable additives include, for example, CAB (acetyl cellulose butyrate) and, for example, Acronal^®4F (leveling agent and defoaming agent).

As the stabilizer component against thermal yellowing, use may be made of the addition reaction product of hydrazine hydrate with 2mol of propylene carbonate mentioned in EP-A0829500, of the formula:

(molecular weight 236)

Raw materials: blocked polyisocyanates

Preparation of polyisocyanates blocked with alpha-acidic cyclic ketones

Blocked polyisocyanate a:

to 193.5g (1 eq) Desmodur^®N3300 to a solution (70% total concentration) of 14g of methoxypropyl acetate (8 parts) and 29.9g of xylene (17 parts) was added 0.17g of 2-zinc ethylhexanoate (0.05% by weight) of the catalyst. The following reaction takes place in a nitrogen atmosphere. After the mixture was stirred together to homogeneity, 156.2g (1 eq) of cyclopentanone 2-carboxylic acid ethyl ester (distilled) were carefully added dropwise. The reaction temperature during the dropwise addition should not be higher than 40 ℃. After the addition of the ester had been completed, stirring was continued at 40 ℃ until the NCO value had reached zero (after about 6 hours). The theoretical blocked NCO content is 8.3%. The desired viscosity was then set with 7% solids 2-butanone. In addition, Tinuvin (2.5% of solids) (8.7g) was added^®770 DF (bis (2, 2, 6, 6-tetramethyl-4-piperidyl) sebacate). The polyisocyanate used was an HDI polyisocyanate having an isocyanurate structure, an NCO content of 21.8% and a viscosity of 3000mPas (Desmodur)^®N3300, bayer, Leverkusen).

Blocked polyisocyanate B:

3 eq (580.5g) Desmodur^®n3300 and 1eq (353g) Desmodur^®Z4470, an aliphatic polyisocyanate based on Isophorone Diisocyanate (IDPI) and dissolved in Aromatic 100 and n-butyl acetate (2: 1), was dissolved in 415g of xylene under nitrogen (70% strength mixture after reaction). To this mixture was added 1.45g (0.1 wt%) of zinc 2-ethylhexanoate catalyst. After the mixture was stirred together to homogeneity, 4eq (624.8g) of cyclopentanone 2-carboxylic acid ethyl ester were carefully added dropwise. The reaction temperature during the dropwise addition should not be higher than 40 ℃. After the addition of the ester was complete, stirring was continued at 40 ℃ until the NCO value was close to zero (about 12 hours). The blocked NCO content was 8.1%. After the reaction was completed, 101.7g of 2-butanone (7% by solid) and 29g of Tinuvin (2% by solid) were added^®770 DF. The polyisocyanate used was one having an isocyanurate structure, an NCO content of 21.8%, and a viscosity of 3000mPas (Desmodur^®N3300, Bayer Corp., Leverkusen) and a polyisocyanate based on IPDI having an isocyanurate structure (NCO content 11.9%, viscosity 2000mPas, Desmodur)^®Z4470, bayer, Leverkusen).

Blocked polyisocyanate C:

0.9eq (174.2g) Desmodur^®n3300 and 0.1eq (29g) Desmodur^®W (bis (4-isocyanatocyclohexyl) methane) trimer was dissolved in 141.6g of xylene under nitrogen (70% strength mixture after reaction). To this mixture was added 0.351g (0.1 wt%) of zinc 2-ethylhexanoate catalyst. After the mixture was stirred together to homogeneity, 1eq (156.2g) of cyclopentanone 2-carboxylic acid ethyl ester was carefully added dropwise. The reaction temperature during the dropwise addition should not be higher than 40 ℃. After the addition of the ester was complete, stirring was continued at 40 ℃ until the NCO value was close to zero (about 12 hours). The blocked NCO content was 8.16%. After the reaction was complete, 7g (2% solids) of Tinuvin was added^®770 DF. The polyisocyanate used was one having an isocyanurate structure, an NCO content of 21.8% and a viscosity of 3000mPas (Desmodur)^®N3300, Bayer corporation, Leverkusen) and a polyisocyanate based on Desmodur with isocyanurate structure^®Polyisocyanate mixture of W (13.5% Desmodur)^®N3300, degree of trimerization 20%, NCO content 14.5%, 65% solids (solution in xylene/methoxypropyl acetate).

The blocking agent cyclopentanone 2-carboxylic acid ethyl ester used was obtained from the Fluka company.

Blocked polyisocyanates for comparison:

BL 3175 (Bayer corporation), a crosslinked polyurethane bakeable resin based on hexamethylene diisocyanate, in a 75% strength solution in solvent naphtha 100, has a viscosity of about 3300mPas, an NCO content (after blocking) of about 11.1% and a blocking agent of butanone oxime.

BL 3370 (Bayer), an aliphatic crosslinked polyurethane bakeable resin, in a solution of about 70% concentration in 1-methoxyisopropyl acetate (MPA), having a viscosity of about 3500-1200mPas, an NCO content (after blocking) of about 8.9%, the blocking agent being diisopropylamine.

The polyols used were: see table below.

Preparation of the polyurethane coating of the invention

The preparation of the coating according to the invention is described after the preparation of the blocked isocyanate component has been illustrated.

Table: polyol for coil coating process

Trade name/brand	Type (B)	Form of supply	Viscosity [ mPa. multidot.s ]]	Acid value	OH fraction [% ]]	Equivalent weight
							Alkynol 1665 SN/IB	Oil-free, branched, saturated polyesters	65％SN100/IB	2700±300	≤5.5	About 1.7	1000
Alkynol VP LS 2013	Oil-free, branched polyesters	70％SN100	4000±200	5.0±1.0	About 2.0	850
							AlkynolVP LS 2326	Oil-free, branched, saturated polyesters	60％SN100	About 1500	About 2.2	About 0.6	2830
Desmophen 651 MPA	Branched polyesters	67％MPA	14500±3500	≤3.0	5.5±0.4	309
							Desmophen 670	Polyesters with low degree of branching	Contains no solvent	＞200000	≤2.5	4.3±0.4	395
Desmophen 690 MPA	Branched polyesters	70％MPA	10000±3500	≤6.0	1.4±0.2	1214
							Desmophen 1200	Polyesters with low degree of branching	Contains no solvent	300 + -100 (70% in MPA)	≤4.0	About 5.0	340
Desmophen 1652	Oil-free, linear polyesters	Contains no solvent	11000±2000	≤4.0	1.6±0.2	1063
							Desmophen C 200	Linear polycarbonate-polyesters	Contains no solvent	1050±25075℃	≤0.1	1.7±0.2	1000

One-component polyurethane roll-coating finish, white, polyol component Alkynol^® 1665

A ═ polyisocyanate a, B ═ polyisocyanate B, C ═ polyisocyanate C

	1	2	3	4	5
						Ball milling formula (granularity < 5 mu m)	BL 3175	BL 3370	A	B	C
Alkynol 1665, 65% in solvent naphtha 100 and isobutanol (31.5: 3.5)	9.8	9.8	9.8	9.8	9.8
						Kronos 2160	29.3	29.3	29.3	29.3	29.3
Solvesso 200 S (SN 200 S)	7.8	7.8	7.8	7.8	7.8
						Supplement
Alkynol 1665，65％supply form	21.5	20.0	19.3	19.1	19.2
						Desmodur BL 3175, 75% in solvent naphtha 100	11.9
Desmodur BL 3370, 70% in 1-methoxyisopropyl acetate		14.1
						A, 70% in xylene/MPA 17: 8			14.8
B, 70% in xylene				15.0
						C, 70% in xylene					14.9
Zinc 2-ethylhexanoate, 10% in SN 200S			0.7	0.7	0.7
						DBTL, 10% in SN 200S (3)	0.7	0.7
Acronal 4F，50％，SN 200 S(4)	1.5	1.5	1.5	1.5	1.5
						CAB 531-1, 10%, SN 200S/butanediol 2: 1(5)	7.3	7.3	7.3	7.3	7.3
SN 200 S	10.3	9.6	9.6	9.6	9.6
							100.0	100.0	100.0	100.0	100.0
	Comparative example			The invention

Remarks (4+5) CAB and Acronal^®The combination of 4F provides devolatilization

Action and leveling action.

Supplier (1) Kronos International INC, Leverkusen

(2)Deutsche Exxon，Cologne

(3)Brenntag，Mülheim/Ruhr

(4)BASF AG，Ludwigshafen

(5)Krahn Chemie，Hamburg

The raw materials used

Alkynol^®1665: oil-free saturated polyesters based on isophthalic acid/adipic acid/NPG/propylene glycol, bayer, Leverkusen, OH content: 1.7%, based on 65% in the solvent naphtha 100/isobutanol (31.5: 3.5).

CAB (cellulose acetylbutyrate): the supplier: hamburger Krahn chemical company, manufacturer: kingsport eastman, usa; CAB 531-1 (about 53% butyryl content, hydroxyl content 1.7% -not included in the calculation).

Acronal^®4F: the manufacturer: ludwigshafen basf corporation, butyl acrylate based polymers (leveling and defoaming agents).

Solvesso^®200S: the manufacturer: Esso/Exxon, 99% aromatics in solvent, evaporation number (ether 1) to 1000.

Whiteness index measurement

ASTM E313, whiteness index

Commercial Berger (Berger) whiteness (No DIN)

Whiteness ═ R_y+3(R_z-R_x)。

The yellowness index G according to DIN 6167 is calculated using the following formula:

x, Y + Z-the tristimulus value according to DIN 5033,

a red/green axis^*

b-blue/yellow axis^**

Positive values * are more red, negative values * are more green,

positive values * are more yellow, negative values * are more blue,

MEK (acetone) tolerance assay

Method description (according to ECCA-T11 and DIN EN ISO 2812-1 and DIN EN 12720):

the MEK rub test is a rapid method of verifying final cure of the coating film. The cotton pad soaked with acetone was reciprocated over the film at constant pressure.

Instrumentation/auxiliary equipment: balance (Bizerba brand), weights 100g, 1kg and 2 kg.

The procedure is as follows:

1kg of back pressure is used for film thickness of 20 μm or less, and 2kg of back pressure is used for film thickness of 20 μm or more.

The metal test plate was fixed to the weighing plate of the balance with a membrane clamp and an anti-slip membrane. The balance was adjusted with a 100g weight and a dead weight compensator. The acetone soaked cotton pad was reciprocated over the coating film at the selected test pressure until the coating film was broken.

Evaluation:

the test report recorded the number of times the cotton pad was reciprocated on the coating film (the number of double strokes) until the coating film was broken, and the number of double strokes was 100 times at most. After 100 double strokes (if any), the film was evaluated for changes (dull, soft).

Determination of T bending test

According to ECCA T7 (ECCA: European coil coating Association)

Description of the method:

the range is as follows:

the method describes the determination of the crack resistance of an organic coating when bent through 180 °.

The principle is as follows:

in this test, the sample is bent 180 ° parallel to the winding direction for 1-2 seconds with the coating facing outwards. To ensure a consistent bend 2 a tight contact between the metal sheets is necessary. The minimum bend radius that the sample can achieve without cracking determines the bend resistance of the sample at 180 ° bend. The adhesion was tested with adhesive tape after each bending operation.

Equipment:

the apparatus that can be used to carry out the method comprises a vise and a protective chuck.

Preparation work:

the samples were stored under laboratory temperature and laboratory air humidity conditions for at least 24 hours. The measurement was performed under the same conditions.

If more precise conditions are specified or in case of controversy, attention should be paid to the details specified in ISO3270-1984, namely a temperature of 23. + -. 2 ℃ and a relative humidity of 50. + -. 5%.

The method comprises the following steps:

a thin sheet metal strip approximately 2cm wide was cut in the direction of winding. The strip was bent parallel to the winding direction for 1-2 seconds with the coating facing outwards. The metal strip is then compressed tightly on the vise.

The crack of the bent edge was inspected with a magnifying glass of magnification 20. The tape was then pulled under pressure 3 times to determine its adhesion.

This 0T bend test measures cracks when conducted with R and adhesion when conducted with H, on a scale of 0 to 5, with 0 being the highest score and 5 being the worst score.

The metal is bent around itself until cracking and adhesion reach 0 points.

The test ended no later than 3.0T.

Resistance to subsequent cracking

The modified T-bend strip was exposed to 100 ℃ for 30 minutes and then re-tested for cracking.

Preparing the coating:

the tests were carried out in a white coil top coating according to the standard formulation (formulation guide RR 6830). For this purpose, a millbase is first prepared from an oil-free saturated polyester according to the following ball milling formulation:

9.8 parts of oil-free polyester Alkynol^®1665, 65% of the available forms,

7.8 parts of solvent Solvesso^® 200S

22.3 parts of white pigment Kronos 2330

The millbase was dispersed with 2mm Siliqurtz beads. Dispersed in Skandex^®In the mixer for 1 hour. (Note: the same formulation can be used in a ball mill and Skandex)^®In a mixer (shaker). Using Skandex^®The mixer has the advantages that: many samples can be dispersed simultaneously and ground in a closed container. The beads were then removed by sieving in a fume hood. )

The millbase is separated from the glass beads by sieving.

The remaining components of the coating were added with stirring.

21.5 parts of oil-free polyester Alkynol^®1665, 65% of the available forms,

11.9 parts of blocked polyisocyanate^*)

0.7 part of DBTL, 10% in Solvesso^®In the 200S of the process, the first step of the process,

7.3 parts of cellulose acetylbutyrate CAB 531-1, 10% in a ratio of 2: 1

Solvesso^®In the ratio of 200S to butanediol,

1.5 parts of Acrynol^®4F, 50% in Solvesso^®In 200S

x parts of Solvesso^®200S (when BL 3175 is used as the closed type polyisocyan

10.3 parts when acid ester is used

Amount of blocked PIC added depends on the equivalent weight of the PIC (Desmodur in this case)^®BL 3175-for comparison). The polyol and blocked polyisocyanate are mixed in equal equivalents, i.e. if there are fewer blocked NCO groups, the proportion of blocked PIC must be increased. The equivalent weights are given in the data table.

By Solvesso^®The coating is adjusted to a processing viscosity of about 70 seconds DIN 4/23 ℃ by 200S.

The coating was applied to a chromized (Chromated) aluminum sheet (1mm thick) by a knife coating method.

Immediately after the coating was applied, the aluminum sheet was baked on a rotating plate in an Aalborg oven.

The furnace temperature of PMT at 210 ℃ and 350 ℃ is 30 seconds

The furnace temperature of PMT is 216 ℃, 350 ℃ and 33 seconds

The furnace temperature of PMT is 224 ℃ and 350 ℃ for 35 seconds

PMT 232 ℃ 350 ℃ furnace temperature 38 seconds

The furnace temperature of PMT is more than 254 ℃ and 350 ℃ for 50 seconds

The dry film thickness is 20-22 μm.

Base material: alkynol 1665 catalyst: 0.2% (calculated as base solids)

The ratio of base materials: equivalent baking conditions: 232 deg.C (PMT)

Pigment: titanium dioxide Kronos 2330 dumbbell test piece: 42

Binder-pigment ratio: 1: 1 matrix: by usingBonder 722Pretreated A1 tablet

Blocked polyisocyanates of interest
							BL 3175	Ex.A	Ex.B	Ex.C	BL 3370
Film thickness [ mu ] m]ECCA-T1(1)	20-22	20-22	20-22	20-22	20-22
						Whiteness Wb ═ Ry +3(Rz-Rx) (Berger)	92.3	91.6	92.2	91.4	91.6
Yellowness index	-3.1	-2.4	-2.6	-2.5	-2.8
						Gardner gloss 60 ° ECCA-T2 (1))	76	67	68	65	69
MEK rub test (PMT 196 ℃ C.)/whiteness	-	-	-	-	95X/92.4
						MEK rub test (PMT 199 ℃ C.)/whiteness	10X/94.1	100X/94.6	65X/94.0	100M/93.9	100X/92.4
MEK rub test (PMT 204 ℃)/whiteness	95X/93.6	100X/94.6	100M/94.3	100X/94.4	100X/92.5
						MEK rub test (PMT 210 ℃)/whiteness	100X/93.6	100X/94.2	100X/94.0	100X/94.1	100X/92.4
MEK rub test (PMT 216 ℃)/whiteness	100X/93.3	100X/93.8	100X/94.0	100X/94.2	100X/92.0
						MEK rub test (PMT 224 ℃ C.)/whiteness	100X/93.1	100X/93.0	100X/92.9	100X/93.2	100X/91.8
MEK wiping test (PMT 232 ℃)	100X	100X	100X	100X	100X

Microhardness HU correction

128.7

55.1

99.8

86.0

140.7

(N/mm2) phi, 3 measurements
						Impact test [ inch/lbs ]]ECCA-T5(1)	80	80	80	80	80
Adhesion 6mm cross-hatch cupping test ECCA-T6(1)	0	0-1	0	0	0
						T-bending test T0.0	R5 H1	R5 H1	R5 H1	R5 H1	R5 H1
R is crack T0.5	R1 H0	R1 H0	R2 H0	R2 H0	R1 H0
						H-adhesion T1.0	R0	R0	R0	R0	R0
Best score T1.5
						Worst score T2.0
Subsequent crack testing 30min.100 deg.C	T1.5+T1.0-	T1.5+T1.0-	T1.5+T1.0+	T1.5+T1.0+	T1.5+T1.0-

(^*1): the method is improved because the measurements are not made in climatic zones. -indicates subsequent cracking and + indicates no subsequent cracking.

Although the present invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims. The scope of the invention is limited only by the claims.

Claims (9)

1. An organic polyisocyanate containing at least 2 isocyanate groups, wherein said isocyanate groups have been blocked with a CH-acidic cyclic ketone of the following general formula (I):

in the formula:

x represents an ester group, and X represents an ester group,

R¹and R²Represents a compound of formula (I) or (II),

n is a number of 1, and n is,

and wherein the organic polyisocyanate has a total blocked isocyanate group content, calculated as NCO, of from 0.1 to 25% by weight.

2. The organic polyisocyanate according to claim 1 wherein the CH-acidic cyclic ketone of formula (I) is cyclopentanone-2-carboxylic acid ethyl ester.

3. A process for the preparation of an organic polyisocyanate according to claim 1 comprising reacting a polyisocyanate with a CH-acidic cyclic ketone of the general formula (I):

in the formula:

x represents an ester group, and X represents an ester group,

R¹and R²Represents a compound of formula (I) or (II),

n is a number of 1, and n is,

wherein the cyclic ketone of formula (I) is used in an amount of 0.8 to 1.2mol per equivalent of isocyanate group of the polyisocyanate used for blocking.

4. A process according to claim 3 wherein the organic polyisocyanate contains one of the following structures: isocyanate dimers, isocyanurates, iminooxadiazinediones, acyl ureas, biurets, and allophanate structures.

5. A process according to claim 3, wherein one of the following is used as catalyst: alkali metal bases, alkaline earth metal bases, zinc salts, trisodium phosphate or bases of the amine type.

6. A process for preparing a polyurethane coating comprising incorporating into the formulation an organic polyisocyanate according to claim 1.

7. The process according to claim 6, wherein the polyurethane coating is a one-component polyurethane baking varnish.

8. Polyurethane coatings comprising organic polyisocyanates according to claim 1.

9. A coil coating process comprising applying to a coil a coating according to claim 8.