GB2084165A

GB2084165A - Improvements in oxidisable alkyd resins

Info

Publication number: GB2084165A
Application number: GB8129185A
Authority: GB
Original assignee: Vianova Resins AG
Current assignee: Allnex Austria GmbH
Priority date: 1980-09-29
Filing date: 1981-09-28
Publication date: 1982-04-07
Also published as: DE3130960A1; AT372097B; FR2491081B1; ATA484680A; DE3130960C2; FR2491081A1; GB2084165B

Abstract

Polyethylene glycol-modified oxidisable alkyd resins may be produced by esterifying (i) 70-85% by weight of a low molecular weight alkyd resin intermediate or mixture of such intermediates, the said intermediate or mixture containing 15-45% by weight of drying fatty acids and having an intrinsic viscosity (measured in chloroform at 20 DEG C) of 4.5 to 8.5, an acid value of below 10, a hydroxyl value of 80 to 200 mg KOH/g and a polyethylene glycol content (introduced by esterification) of 4 to 8% by weight, and (ii) 15-30% by weight of a polymer formed by copolymerisation of from 10 to 25% by weight of methacrylic acid with 30 to 55% by weight of unsaturated fatty acids and 30 to 60% by weight of vinyl- or vinylidene compounds carrying no functional groups besides the double bond until an acid value of 10 to 25 mg KOH/g and an intrinsic viscosity (measured in chloroform at 20 DEG C) of 8-15 ml/g is attained. The modified alkyd resin thus obtained may be emulsified in water with neutralisation of the acidic groups with ammonia or organic amine(s). With the addition of solvents and conventional additives the emulsions may be used in the preparation of paints and enamels.

Description

SPECIFICATION Improvements in oxidisable alkyd resins This invention relates to oxidisable alkyd resins, aqueous emulsions containing them and paints and enamels based on such aqueous emulsions.

A great number of patent specifications describe the preparation of water emulsifiable alkyd resins modified with polyethylene glycol (PEG); see for example U.S. Patent Specifications Nos.

2,634,245; 2,853,459; 3,133,032; 3,223,659; 3,379,548; 3,437,615; 3,437,618; 3,442,835; 3,457,206; 3,639,315; German Offenlegungsschrift No. 14 95 032 or British Patent Specifications Nos. 1,038,696 and 1,044,821.

The emulsifying capacity of these resins is partly due to their amphipatic nature. The major part of the resin molecule is hydrophobic, while the added PEG chains and the C00H groups neutralised with amines are hydrophilic. Furthermore, the negative charges of the -COOO groups prevent coagulation of the emulsion droplets owing to electrostatic repulsion. With sufficient concentration of PEG and C00H groups alkyd resins form which can be emulsified spontaneously upon addition of water, i.e. without the use of high shear rates. Transparent "microemulsions" are formed, which are in thermodynamic equilibrium and thus stable.

Nevertheless, so far alkyd resin emulsions have shown insufficient storage stability. The reason for this is the insufficient stability of the alkyd resin molecules in the presence of water.

Alkyd resins are polyesters and as such can be decomposed by hydrolysis. Hydrolysis starts where resin and water make contact, that is at the surface envelope of the emulsion droplets. In this envelope are the hydrophilic PEG-chains and the carboxylate groups. The links between these groups and the main chain of the alkyd resin molecule are thus particularly at risk.

In the cited patent specifications the PEG is introduced through direct or indirect esterification or reesterification. The acid groups essentially stem from ophthalic semiester groups. In these cases the ester linkages of the system are in the direct vicinity of the hydrated envelope of the hydrophilic group and thus are very susceptible to hydrolysis. To the extent they are hydrolysed the amphipatic character of the molecules and the negative charge of the emulsion droplets are reduced leading ultimately to coagulation.

Therefore attempts have been made to reduce the rate of hydrolysis by introducing hydrophobic unsaponifiable groups between the hydrophilic group and the adjacent ester linkage. According to Austrian Patent Specification No. 356 227 (= European Patent No.

2488) the polyethylene glycol is etherified in a first step with an excess of an alkyd phenol resol and is condensed onto tung oil via the remaining methylol groups with the formation of chromane ring linkages. This modified tung oil is then further processed to give an alkyd resin.

According to German Offenlegungsschrift No. 24 1 6 658 ophthalmic acid is partly replaced by adducts of acrylic or methacrylic acid with unsaturated fatty acids. In both cases, as could be expected, enhanced storage stability of the emulsion was found.

A further important improvement has only been described in European Patent Applications Nos. 80 106.533.5 and 80 106.672.1 of the present applicants, which are not yet published.

According to these applications polyethylene glycol is introduced in the form of etherification products of alkylphenol resols or hydroxyl fatty acid esters and the carboxyl groups are introduced as acidic polymers. The acidic polymers are obtained through copolymerisation of methacrylic acid and unsaturated fatty acids such as linolenic acid and vinyl and/or acrylic monomers carrying no other functional groups besides the -C = C- double bond. The polymers are reacted with low molecular weight, practically carboxyl-free alkyd resin intermediates such that the carboxyl groups of the fatty acids are quantitatively esterified, while the tertiary acid groups of the polymer stemming from methacrylic acid remain substantially unreacted. These acid groups essentially act to stabilise the emulsion after neutralisation with amines.Decomposition by hydrolysis is hindered owing to the existence of iarge hydrophobic molecular segments between the acid group and the ester linkage.

On further development of this idea it has been found that the acidic polymer is the one component having the most influence on the properties of the emulsion. It can be supposed that the polymer segments owing to an increased quantity of carboxyl groups preferably concentrate on the outside of the polymer and as well as stabilising the emulsion electrostatically serve as an unsaponifiable protecting colloid. Thus it has been possible through optimisation of the composition of the acidic polymers and their method of preparation and introduction, to achieve alkyd resin emulsions with superior storage stability containing a quantity of from 3-4% of PEG, calculated on resin solids. Owing to the low PEG-content, these alkyd resin emulsions are also superior to conventional alkyd resin solutions as regards film resistance.

Further it has been found that for specific uses, such as for oxidisable alkyd resin emulsions for force-drying industrial paints, alkyd resin intermediates can be used having the PEG linked by direct esterification. Vis-a-vis the last mentioned methods there is the advantage that one production step can be omitted and thus production costs are reduced. There is a further advantage over the method according to European Patent application 80 106 533.5 in that practically non-yellowing pale alkyd resin finishes can be formulated.

The present invention is thus concerned with oxidisable alkyd resins comprising esterification products of (i) 70-85% by weight of a low molecular weight alkyd resin intermediate or mixture of such intermediates, the said intermediate or mixture containing 15-45% by weight of drying fatty acids and having an intrinsic viscosity (measured in chloroform at 20 C) of 4.5 to 8.5, an acid value of below 10, a hydroxyl value of 80 to 200 mg KOH/g and a polyethylene glycol content (introduced by esterification) of 4 to 8% by weight, and (ii) 15-30% by weight of a polymer formed by copolymerisation of from 10 to 25% by weight of methacrylic acid with 30 to 55% by weight of unsaturated fatty acid and 30 to 60% by weight of vinyl- or vinylidene compounds carrying no functional groups besides the double bond, the said esterification products having an acid value of 10 to 25 mg KOH/g and an intrinsic viscosity (measured in chloroform at 20"C) of 8 1 5 ml/g. Upon neutralisation of the acid groups of the said resins with ammonia or organic amine(s) the resins may be emulsified in water, optionally with the addition of up to 20% of auxiliary organic solvents. The invention accordingly further relates to the aqueous emulsions thus produced.

In a further aspect the invention relates to a process for producing improved PEG-modified oxidisable alkyd resins in which component (i) and component (ii) as hereinbefore defined are esterified until an acid value of 10 to 25mg KOH/g and an intrinsic viscosity (measured in chloroform at 20"C) of 8-1 5 ml/g is attained. The modified alkyd resin thus obtained may be emulsified in water with neutralisation of the acidic groups with ammonia or organic amine(s).

Up to 20% by weight of auxiliary organic solvents may be added.

According to the invention novel alkyd resin emulsions can be produced which are ideally suited for use in oxidisable industrial paints. The PEG content of these alkyd resins preferably lies between 3.4 and 6% by weight.

Suitable alkyd resin intermediates (component (i)) have an average molecular weight of from 500 to 5000, preferably 1000 to 3000. Preferably the acid value of component (i) is below 5mg KOH/g. The PEG is introduced into the alkyd resins through direct esterification, i.e.

simultaneously with the other components. Normal raw materials for drying alkyd resins can be used, and the preparation of the alkyd intermediates may be effected according to known methods. The methods and raw materials are known to those skilled in the art and need no further comment.

In many cases, to improve the processing characteristics of the emulsion, such as pigment wetting and siccative compatibility, it is appropriate to use not just one alkyd intermediate but mixtures of them, including proportions of PEG-free products. In this case, the percentages quoted in respect of component (i) refer to such a mixture of resins.

According to the present invention, in order to introduce the carboxyl groups necessary for the stabilisation of the emulsion, there are used polymers obtained through free-radical polymerisation of 10-25% by weight of methacrylic acid 30-55% by weight of a drying oil fatty acid preferably with an iodine number of at least 1 25 and 30-60% by weight of one or more vinyl- and/or vinylidene compounds, containing no other functional groups besides the double bond, particularly acrylic compounds.

Suitable drying fatty acids are those containing conjugated double bonds, such as dehydrated castor oil fatty acids or isomerised fatty acids, or those carrying isolated double bonds, like technical grade soya-, safflower or linseed oil fatty acids. Since isolated fatty acids have less reactivity a higher excess has to be used. Unless the fatty acid reacts completely on polymerisation, the rest will be linked during esterification with the alkyd resin.

Suitable vinyl- or vinylidene compounds are styrene, vinyl toluene, and vinyl esters of acetic acid, propionic acid or versatic acid. Available alkyl esters of acrylic and methacrylic acids are preferred. The selection is governed inter alia by the compatibility of the compounds with the alkyd resin intermediate. Normally those polymers with the best compatibility have the best emulsifying effect.

The polymerisation may be carried out in solution at from 80 to 140, preferably 90-110"C, with the addition of an initiator where necessary. Suitable initiators are radical-forming compounds reactive within this temperature range. Dibenzoylperoxide is particularly suitable. For limiting the molecular weight normal chain transfer agents such as tert.dodecylmercaptan may be used. The end point of polymerisation is taken to be attained when the non-volatile content has become constant, which means there has been substantial reduction of the amount of volatile monomers in the reaction mixture.The intrinsic viscosity of the polymer or polymer blend with the unreacted fatty acid lies between 4 and 9 ml/g (measured in dimethylformamide at 20on). Under the cited conditions side reactions such as dimerisation of the fatty acid are substantially suppressed. Thus the fatty acids which are not polymerised remain unchanged and retain their oxidising--cross-linking capacity after their introduction into the alkyd resin.

Alkyd resin and polymer should be combined such that upon complete esterification of the fatty acids at from 1 70 to 200 C an acid value of from 10 to 25 mg KOH/g and an intrinsic viscosity of from 8 to 1 5 ml/g (measured in chloroform at 20"C) results. The resins are generally dissolved with a maximum of 20%, preferably 5 to 15% by weight of auxiliary organic solvents and are emulsified in water containing the quantity of ammonia or organic amines necessary for neutralisation of from 50 to 100% of the acid groups, generally at temperatures of from 40 to 80"C. Suitable auxiliary solvents are for example alcohols or ether alcohols like n-butanol or ethyleneglycolmonobutylether.Suitable amines are for example triethylamine or dimethylethanolamine.

The products of the invention serve as a basis for oxidisable, water dilutable paints which can be applied by any normal method and are mainly suited for industrial application. With adequate siccativation the paints dry at room temperature within from 1.5 to 4 hours, but preferably are force-dried at e.g. 80"C. In the preparation of stoving paints crosslinking components are added in the form of water-compatible amine-formaldehyde resins.

The following examples illustrate the invention. All cited parts are by weight unless otherwise stated. The listed figures for the intrinsic viscosity were measured in chloroform at 20"C, unless otherwise stated.

Preparation of the alkyd resin intermediates A 1 to A 3 Alkyd Resin A 1: 120 parts ptert.butylbenzoic acid, 50 parts dehydrated castor oil fatty acid, 55 parts linseed oil fatty acid, 80 parts PEG 1500, 50 parts phthalic anhydride and 1 5 parts tetrahydrophthalic anhydride are heated to 160"C in a suitable reaction vessel and held at this temperature for 60 minutes. 110 parts pentaerythritol are then added, the temperature raised to 210"C and the batch esterified under azeotropic distillation with xylene to an acid value of below 3 mg KOH/g.

Alkyd Resin A 2: 120 parts ptert.butylbenzoic acid, 70 parts dehydrated castor oil fatty acid, 35 parts linseed oil fatty acid, 50 parts phthalic anhydride and 110 parts pentaerythritol are heated to 220 C and reacted at this temperature for 60 minutes. 45 parts of tetrahydrophthalic anhydride are then added and esterification is carried on to an acid value of below 5 mg KOH/g under azeotropic distillation with xylene.

Alkyd Resin A 3: 60 parts benzoic acid, 60 parts rosin, 50 parts phthalic anhydride, 110 parts pentaerythritol and 0.4 parts zinc octoate (8% metal content) are heated to 260"C. 60 minutes after this temperature is reached a gentle azeotropic distillation with xylene is commenced and the esterification carried on to an acid value of below 5 mg KOH/g. After the temperature has been reduced to below 220"C 70 parts of linseed oil fatty acid, 35 parts of dehydrated castor oil fatty acid and 45 parts of tetrahydrophthalic acid are added and the batch esterified with distillation to an acid value of below 5 mg KOH/g.

The specifications of the intermediates are listed below.

Table 1: Al A2 A3 Solids content (%) 93.8 97.1 96.2 fatty acids (%)* 23.2 26.2 26.2 PEG 1500 (%)* 17.6 - - acid value (mg KOH/g) 1.5 4.7 4.2 Hydroxyl value (mg KOH/g) 176 129 134 intrinsic viscosity (ml/g) 6.1 6.9 7.3 calculated on 100% resin solids Preparation of the Polymers P 1 to P 3 Table 2 gives the composition of the polymers. To prepare the polymers the raw materials for part 1 are heated to reflux temperature (about 95"C) and parts 2 and 3 are then added together to part 1. At reflux temperature polymerisation is carried on to practically complete conversion (determination of resin solids). If required, one fourth of the peroxide quantity can be added in addition.

The specifications of these polymers are also listed in Table 2.

Table 2: P1 P2 P3 Part 1 xylene 40 40 40 isopropanol 40 40 40 linseed oil fatty acid 60 50 50 isobutyl methacrylate 11 10 1 3 2-ethylhexyl acrylate 1 - vinyltoluene 2 6 2 methacrylic acid 6 4 5 dibenzoyl peroxide 3 3 3 dodecylmercaptan 0.2 0.2 0.2 Part 2 isobutyl methacrylate 44 40 52 2-ethylhexyl acrylate 4 vinyltoluene 8 24 8 methacrylic acid 24 1 6 20 dodecylmercaptan 0.8 0.8 0.8 Part 3 xylene 10 10 10 methylethylketone 10 10 10 linseed oil fatty acid 40 20 dehydrated castor oil fatty acid - - 30 dibenzoyl peroxide 11 11 11 Time of addition (hours) 5 6 5 Constants fatty acid content (%)* 50 41 44.5 methacrylic acid content (%)* 1 5 11.8 1 3.9 solids content (%) 65.5 62.7 64.1 intrinsic viscosity ml/g 4.6 5.4 5.5 measured in dimethylformamide calculated on 100% resin solids Examples 1 to 3: The alkyd resin intermediates and polymers are blended in the ratios listed in Table 3 and are heated to 180"C to distil off the solvents completely, vacuum being employed towards the end of the reaction. Then, at 1 80 to 200"C, the blend is esterified to the acid value and intrinsic viscosity listed in Table 3. In the first stage, the esterification is enhanced by azeotropic distillation with xylene. The xylene is vacuum-stripped just before the final values are attained.

The resins are diluted to a solids content of 85% with ethylene glycol monobutylether and at 50 to 70"C are emulsified in deionized water containing a 4:1 mixture of triethylamine and dimethylethanolamine. The quantity of amine and water are chosen such that the emulsion has a pH-value between 9 and 10 and a viscosity of 50 to 100 Pa.s with a solids content of about 45 to 50% (measured at 20"C with a BROOKFIELD rotation viscometer, spindle 7.4 U/min.).

The emulsions are transparent and have pronounced structured viscosity.

Table 3: Composition and constants (Quantities refer to resin solids) Examplel 2 3 alkyd resin A 1 25 24 26 alkyd resin A 2 55 52 alkyd resin A 3 - - 54 polymer P 1 20 - polymer P 2 - - 30 polymer P 3 - 24 Constants of the resin combination PEG-content (%) in the resin blend 5.5 5.56 6.53 in the end product 4.4 4.24 4.58 acid value (mg KOH/g) 16.4 15.8 17.0 intrinsic viscosity (ml/g) 9.2 9.5 9.1 resin solids (%) 85 85 85 Constants of the emulsions resin solids (%) 45.4 44.8 47.1 viscosity (Pa.s, 20"C) 54 65 91 pH-value 9.6 9.3 9.7 Comparison examples In order to demonstrate the technical progress over the state of the art one emulsion was prepared according to Austrian Patent Specification No. 356 227 = European Patent No. 2488 and German Offenlegungsschrift No. 24 16 658.

Comparison example A: The emulsion prepared according to Example 1 of Austrian Patent Specification No. 356 227 has a solids content of 37% and a viscosity of 97 Pa.s.

Comparison example B: The emulsion was prepared according to Example 2 of German Offenlegungsschrift No. 24 1 6 658. Although this is not in conformity with the instructions in the specification, the resin was diluted with ethylene glycol monobutyl ether to 90% prior to emulsifying in order to create comparable conditions for all examples, emulsification being enhanced by the addition of the ether.

The emulsion has a solids content of 48% and a viscosity of 52 Pa.s.

Evaluation of storage stability of the emulsion at elevated temperature Storage of the emulsions at 80"C showed the values listed in Table 4.

Table 4 Example Storage time at 80'hours 1 2 3 A B 8 i.O. i.O. i.O. LV LV 16 i.O. i.O. i.O. BK SV 24 i.O. i.0. i.O. A BK 32 LV i.O. LV - BK 48 LV LV LV - A i.O. no change LV slight reduction in viscosity SV strong reduction in viscosity BK coagulation starts (emulsion becomes flaky) A emulsion sediments Evaluation of pigmented paints The emulsions were pigmented with titanium dioxide (pigment/binder ratio 1:1) and were combined with 3% (on resin solids) of a water tolerant siccative blend (1.2% Co, 7.2% Ba, 3.2% Zn), 1% of an anti-skinning agent and 0.5% of a slip aid.They were diluted to application viscosity with deionised water.

Evaluation of film properties 24 hours after preparation, the paints were applied to glass plates in a dry film thickness of about 30 tm and after a flash-off of 30 minutes force-dried (30 min/80 C). Pendulum hardness and water resistance were tested 24 hours after application.

The results of the evaluation are given in Table 5.

Table 5: Example 1 2 3 A B storage stability (4 weeks/40 C) i.O. i.O. i.O. SV;B LV;B pendulum hardness (DIN 53 157) 54 62 60 59 41 water resistance (24 hours, water at 205C) - - LE- SE softening BLISTERING (DIN 53 209) - - mo/go - ml/gl regeneration - - REG - RB GA paint strongly yellowed i.O. . no essential change LV, SV: light or strong reduction in viscosity B . precipitation LE, SE: light or strong softening REG regenerates after 8 hours (room temperature) RB wrinkling GA reduction in gloss

Claims

1. An oxidisable alkyd resin comprising an esterification product of (i) 70-85% by weight of a low molecular weight alkyd resin intermediate or mixture of such intermediates, the said intermediate or mixture containing 15-45% by weight of drying fatty acids and having an intrinsic viscosity (measured in chloroform at 20"C) of 4.5 to 8.5, an acid value of below 10, a hydroxyl value of 80 to 200 mg KOH/g and a polyethylene glycol content (introduced by esterification) of 4 to 8% by weight, and (ii) 15-30% by weight of a polymer formed by copolymerisation of from 10 to 25% by weight of methacrylic acid with 30 to 55% by weight of unsaturated fatty acid and 30 to 60% by weight of vinyl- or vinylidene compounds carrying no functional groups besides the double bond, the said resin having an acid value of from 10 to 25 mg KOH/g and an intrinsic viscosity (measured in chloroform at 20"C) of 8-1 5 ml/g.

2. An oxidisable alkyd resin according to claim 1, in which the acid value of component (i) is less than 5 mg KOH/g.

3. An oxidisable alkyd resin according to claim 1 or claim 2 having a polyethylene glycol content of 3.4 to 6% by weight.

4. An oxidisable alkyd resin according to any of the preceding claims wherein polyethylene glycols with molecular weights between 500 and 5000 are employed in the preparation of component (i).

5. An oxidisable alkyd resin as claimed in claim 4 in which polyethylene glycols with molecular weights between 1000 and 3000 are employed in the preparation of component (i).

6. An oxidisable alkyd resin according to any of the preceding claims in which component (i) comprises a mixture of alkyd resin intermediates containing polyethylene glycol and alkyd resin intermediates free from polyethylene glycol.

7. An oxidisable alkyd resin according to any of the preceding claims in which the polymers used as component (ii) contain free fatty acids.

8. An oxidisable alkyd resin according to claim 7 in which the products used as component (ii) have an intrinsic viscosity from 4 to

9 ml/g, measured at 20"C in dimethylformamide.

.9. An oxidisable alkyd resin substantially as described in any one of Examples 1 to 3.

10. An aqueous emulsion comprising an oxidisable alkyd resin according to any of the preceding claims in which the acidic groups of the oxidisable alkyd resin are neutralised with ammonia and/or organic amines.

11. An aqueous emulsion according to claim 10 having a polyethylene glycol content of 3 to 4% by weight.

1 2. An aqueous emulsion according to either of claims 10 and 11 additionally comprising up to 20% by weight of organic solvents.

1 3. An aqueous emulsion substantially as described in any one of Examples 1 to 3.

14. A paint or enamel comprising an aqueous emulsion according to any of claims 1 to 11.

1 5. A paint or enamel according to claim 14 additionally comprising one or more pigments, antiskinning agents, slip aids and/or other conventional additives.

1 6. A process for producing oxidisable alkyd resins in which process: (i) 70-85% by weight of a low molecular weight alkyd resin intermediate or mixture of such intermediates, the said intermediate or mixture containing 15-45% by weight of drying fatty acids and having an intrinsic viscosity (measured in chloroform at 20"C) of 4.5 to 8.5, and acid value of below 10, a hydroxyl value of 80 to 200 mg KOH/g and a polyethylene glycol content (introduced by esterification) of 4 to 8% by weight, and (ii) 15-30% by weight of a polymer formed by copolymerisation of from 10 to 25% by weight of methacrylic acid with 30 to 55% by weight of unsaturated fatty acid and 30 to 60% by weight of vinyl- or vinylidene compounds carrying no functional groups besides the double bond are esterified until an acid value of 10 to 25 mg KOH/g and an intrinsic viscosity (measured in chloroform at 20"C) of 8-15 ml/g is attained.

1 7. A process for producing an oxidisable alkyd resin substantially or described in any one of Examples 1 to 3.

1 8. A process for producing an aqueous emulsion which comprises emulsifying in water an oxidisable alkyd resin as claimed in any of claims 1 to 9 with neutralisation of the acidic groups of the oxidisable alkyd resin with ammonia and/or organic amine(s).

1 9. A process for producing an aqueous emulsion substantially as described in any one of Examples 1 to 3.