WO1999037714A1

WO1999037714A1 - Propoxylated phenols and/or propoxylated aromatic alcohols as plasticisers for epoxy resins and aminic epoxy resin hardeners

Info

Publication number: WO1999037714A1
Application number: PCT/EP1999/000280
Authority: WO
Inventors: Wolfgang Scherzer; Jörg Volle
Original assignee: CIba Spezialitaetenchemie Bergkamen GmbH
Current assignee: CIba Spezialitaetenchemie Bergkamen GmbH
Priority date: 1998-01-27
Filing date: 1999-01-19
Publication date: 1999-07-29
Anticipated expiration: 2000-07-27

Abstract

The invention relates to solvent-free, curable mixtures based on epoxy resins and aminic hardeners, which contain as plasticiser/diluent at least one compound of general formula (I), wherein R1, R3, R5 are each independently of one another H or an unbranched or branched alkyl radical containing 1 to 12 carbon atoms, and R2, R4 is H, where m = 1 to 10 and n = 0 to 3.

Description

- 1-

Propoxylated phenols and/or propoxylated aromatic alcohols as plasticisers for epoxy resins and aminic epoxy resin hardeners

The present invention relates to novel plasticisers for epoxy resins and aminic epoxy resin hardeners as well as to curable mixtures in which said plasticisers are used.

Curable mixtures based on aminic hardeners and epoxy resins are widely used in the industry for coating and improving metallic and mineral substrates.

The epoxy resins used are mainly glycidyl compounds based on bisphenol A (4,4'-dihydroxy- diphenylpropane-2,2), bisphenol F (4,4'-dihydroxydiphenylmethane) or novolaks. However, the viscosity of these glycidyl compounds is very high and is usually from 6.000 to 16.000 mPa»s. It is very difficult, however, to process epoxy resins of such high viscosity as it is virtually impossible to homogeneously mix them with the aminic hardeners designated therefor, in particular at low temperatures. For this reason, so-called reactive thinners are used, such as monoglycidyl ethers of phenols or glycidyl ethers based on mono- or difunctio- nal aliphatic or cycloaliphatic alcohols.

The aminic hardeners used are in particular aliphatic, cycloaliphatic, araliphatic or aromatic amines, and polyaminoamides which optionally contain imidazoline groups.

However, after being cured with the epoxy resin under normal environmental conditions and, especially, at low temperatures, these compounds exhibit sticky surfaces and greasy films as well as insufficient flow properties or incomplete hardening.

These disadvantages are eliminated by letting the amine component react with specific epoxy resins to so-called prepolymers. However, depending on the degree of adduction these prepolymers are highly viscous, partly solid and can for this reason hardly be processed in practice. Readily volatile solvents of low viscosity, such as xylene, are often used to reduce the viscosity. These solvents, however, are problematical when used in thick-layer systems since they cannot evaporate as in the case of thin-layer solvent-containing systems. Solvent residues in coatings can result in blistering, especially when heated, e.g. through solar radiation. Another disadvantage is the environmental pollution resulting from the evaporation of the solvent. Such coatings are moreover more or less distinctly brittle. In practice, a certain flexibility is desirable to prevent tearing of the coatings at increased mechanical stress.

For these reasons, so-called diluents or plasticisers are used. These must be compatible with the epoxy resin and the aminic hardener, should impart a certain flexibility to the brittle epoxy resin/hardener system and should remain homogeneous in the coating after curing.

Phthalates such as dioctyl phthalate, alkyl phenols such as nonylphenols and, especially, benzyl alcohol are usually used to this purpose.

Phthalates are, however, not very suitable, as amide formation may take place with strongly basic amines, the hardener thus being rendered useless. Benzyl alcohol affords stable end products and effects a fast curing rate of the applied coating. A fast curing rate, especially also at low temperatures, is desirable in practice in order to make it possible to pass over or recoat the coating within the briefest time possible. Using benzyl alcohol, however, in many cases also shortens the gel time after the epoxy resin and epoxy resin hardener are mixed, so that practice-oriented processing is hardly possible any longer. The same applies to the use of alkylphenols. The alkylphenols furthermore usually have a fairly high viscosity and therefore have no, or only a minor, viscosity-reducing effect on the epoxy resin/hardener system.

Owing to their toxicological properties, alkylphenols and benzyl alcohols have the additional disadvantage that they can be used only to a limited degree in the drinking water and food sector.

Accordingly, it is the object of this invention to overcome the cited disadvantages and to provide diluents/plasticisers which have, on the one hand, a sufficiently long gel time after the epoxy resin and hardener are mixed and which effect, on the other hand, a rapid curing rate of the applied coating.

This object is achieved according to this invention with curable mixtures based on epoxy resins and aminic hardeners and containing as plasticisers propoxylated phenols and/or propoxylated aromatic alcohols of the general formula (I): (CH₂)_n-O-[CH₂-ςH-θ]_m-H (I) CH.

The novel plasticisers/diluents are obtainable by generally known processes by reacting the phenols/alcohols with propylene oxide in the presence of predominantly basic catalysts. These processes are described, inter alia, in "Ullmann's Enzyklopadie der technischen Chemie", Verlag Chemie GmbH, Weinheim, 4^th edition, Vol. 19, pages 31-38.

The molecular-weight distribution is dependent on the degree of propoxylation. Thus, propoxylation of the phenol and an average degree of propoxylation of 3 mol of propylene oxide (PO) per mol of phenol results in a mixture of different propoxylates where m = 1 to 8. Propoxylation of benzyl alcohol results already at an average degree of propoxylation of 1 mol of PO per mol of benzyl alcohol in a molecular-weight distribution of m = 1 to 4.

The compounds of the general formula (I) which are additionally used in the mixture according to this invention are the technical products having the molecular-weight distributions contingent on the process, which compounds may possibly also contain minor amounts of educt. If this is undesirable, then the reaction products may also be purified by distillation or may be split up into the individual fractionation steps. To adjust the curable and/or cured mixtures to particular technical properties, it is also possible to use mixtures of the compounds.

Surprisingly, it has been found that, in comparison to benzyl alcohol and alkylphenols, the novel plasticisers/diluents in the inventive curable mixtures bring about a markedly longer gel time while effecting, also at low temperatures, a comparable rapid development of the hardness.

The novel diluents are very compatible with the aminic hardeners and with the epoxy resins and impart high flexibility to the cured coating without reducing the chemical resistance, and - 4-

owing to the very low vapour pressure they remain homogeneously distributed in the product. The toxicity of these products is generally very low so that they can also be used in the food and drinking water sector. After application to the substrates, the novel curable mixtures have, also at low temperatures, comparable high initial strengths, making early passability or recoatability of the coatings possible.

Accordingly, this invention relates to curable mixtures based on epoxy resins and aminic hardeners, optionally additionally using colourants, pigments, fillers, UV stabilisers, flow con- trol/plasticising agents, wherein the plasticiser/diluent used is at least one compound of the general formula (I):

(CH₂)_n-O-[CH₂-qH-O]_m-H (I) CH

wherein

Ri , R3, R5 are each independently of one another H or an unbranched or branched alkyl radical containing 1 to 12 carbon atoms, and

R2, R4 are H, where m = 1 to 10, preferably 1 to 5, and n = 0 to 3, preferably 0 to 1.

Preferred curable mixtures are those wherein the components of formula (I) are the propo- xylates of phenol, cresol or benzyl alcohol.

This invention also relates to curable mixtures consisting of

A) an epoxy resin,

B) an aminic hardener,

C) customary assistants, colourants, pigments, fillers, and

D) at least one compound of the general formula (I). - 5-

The novel curable mixtures usefully contain 1 to 40 parts by weight, preferably 5 to 25 parts by weight, based on the sum of the mixture components (A), (B), (C) and (D), of at least one compound of the general formula (I). The diluents/plasticisers used according to this invention can be added, singly or in admixture, both to the epoxy resin and to the aminic hardener. According to this invention, addition to the aminic hardener is preferred.

Examples of aminic hardeners (B) are: polyethylenepolyamines, for example diethylenetriamine, triethylenetetramine, tetraethylene- pentamine etc.; polypropylenepolyamines, for example dipropylenetriamine, tripropylenetetramine and the polyamines obtained by cyanoethylation of polyamines, in particular of ethylenediamine, and subsequent complete or partial hydration; aliphatic amines, for example diaminoethane, diaminopropane, neopentanediamine, diami- nobutane, hexamethylenediamine, 2,2,4(2₎4,4)-trimethylhexamethylenediamine-1 ,6; cycloaliphatic polyamines, for example isophoronediamine, diaminocyclohexane, norbornanediamine, 3(4),8(9)-bis(aminomethyl)tricyclo[5,2,1,0]decane, (TCD-diamine), 1,3- bis(aminomethyl)cyclohexane, bis(aminomethylcyclohexyl)methane; heterocyclic polyamines, for example N-aminoethylpiperazine, 1 ,4-bis(aminopropyl)pipera- zine; araliphatic amines, for example xylylenediamine; polyether amines, for example 1 ,12-diamino-4,8-dioxadodecane; aromatic amines, for example diaminodiphenylmethane; polyaminoamides optionally containing imidazoline, for example condensates of mono- or dimeric fatty acids with polyethylenepolyamines. Preferred examples of aminic hardeners (B) are: xylylenediamine, norbornanediamine, 1 ,3-bisaminomethylcyclohexane, 2,2,4(2,4,4)-trime- thylhexamethylenediamine-1 ,6, isophoronediamine and/or polyaminoamides which optionally contain imidazoline and which are obtainable by condensation of fatty acids with polyethylenepolyamines. The prepolymers preferred according to this invention are the above amine components.

The epoxy compounds used for prepolymerising the cited polyamines are the known and commercially available products comprising at least one epoxy group per molecule. According to this invention it is preferred to use glycidyl ethers based on mono- or polyvalent phenols, for example phenol, cresol, bisphenol A, bisphenol F, novolaks, mono- or polyvalent aliphatic alcohols containing 4 to 18 carbon atoms, for example butanol, butanediol, hexanol, hexanediol, fatty alcohols having a chain length of 8 to 18 carbon atoms, polyoxyal- kylene glycols, for example diethylene glycol, dipropylene glycol, polyoxypropylene glycol, diethylene glycol monobutyl ether.

The degree of adduction can be varied within wide limits and is influenced by the kind of amine compound and glycidyl compound and can furthermore be adjusted to the respective field in which the curable mixture is used.

Positive results are generally achieved whenever 0.1 to 1 mol of the glycidyl compound is used per mol of the amine compound so that there are on average more than 2 free active hydrogens bound to amino nitrogen atoms in the adduct.

These amine adducts are usually prepared by placing the amine component in a vessel and homogenising it with the diluent/plasticiser. The glycidyl compound is added at 60 to 80°C. The mixture is stirred for about 30 min until adduction is complete. It is also possible to add the plasticiser after the adduction.

So-called "isolated adducts" can also be used, which are prepared with an excess of the amine component, excess amine being removed by distillation after the adduction. In this case the plasticiser is added after the distillation step.

In accordance with this invention it is preferred to use prepolymers with xylylenediamine, norbornanediamine, 1 ,3-bisaminomethylcyclohexane, 2,2,4(2₎4,4)-trimethylhexamethylene- diamine-1 ,6, isophoronediamine and also polyaminoamides. The epoxy resins (A) used according to this invention are commercially available products containing at least one epoxy group per molecule and are derived from mono- and or polyvalent and/or polynuclear phenols, in particular bisphenols and novolaks, for example diglycidyl ethers of bisphenol A and bisphenol F. An extensive enummeration of these epoxy compounds may be found in the compendium "Epoxidverbindungen und Epoxidharze" by A. M Paquin, Springer Verlag Berlin, 1958, chapter IV, and in Lee & Neville, "Handbook of Epoxy Resins", 1967, chapter 2.

It is also possible to use mixtures of two or more epoxy resins. - 7-

According to this invention it is preferred to use mixtures of glycidyl ethers based on bisphenol A, bisphenol F or novolaks with so-called reactive diluents, for example monoglycidyl ethers of phenols or glycidyl ethers based on mono- or polyvalent aliphatic or cycloaliphatic alcohols. Examples of such reactive diluents are phenyl glycidyl ether, cresyl glycidyl ether, p-tertiary-butylphenyl glycidyl ether, butyl glycidyl ether, C₁₂-C_ualcohol glycidyl ether, butane diglycidyl ether, hexane diglycidyl ether, cyclohexanedimethyl diglycidyl ether or glycidyl ethers based on polyethylene glycols or polypropylene glycols. By adding these reactive diluents it is possible to reduce the viscosity of the epoxy resins to a practice-oriented viscosity of <1000 mPa»s.

It is also possible to add the standard additives (C) to the novel curable mixtures, for example fillers, such as pebbles, sands, silicates, graphite, silicium dioxide, talcum, mica etc. in the grain size distributions customarily used in this field, pigments, colourants, accelerators, stabilisers, flow control/plasticising agents, non-reactive extender resins and other plasticisers and diluents.

Analytical methods

Tecam value

Value for the gel time, measured using the Gelation Timer GT3, of Techne, Cambridge, GB, at 23°C and at 50% relative humidity.

Sample mixtures of resin and hardener = 100 g.

Hardness according to Shore D

Measured using the apparatus type 38009, of Carl Frank GmbH, on samples 70mm in diameter and 6mm thick, after 1 , 2 and 5 days. The final hardness is measured after further curing of the samples at 60°C (48 hour (h)) and subsequent cooling to room temperature. - 8-

Examples

Example 1

38.5 g of xylylenediamine and 46.5 g of phenolpropoxylate having an average degree of propoxylation of 1 mol of propylene oxide (PO) per mol of phenol are placed in a reaction vessel. This mixture is heated to about 60°C and, with stirring, 15 g of a diglycidyl ether of bisphenol A having an epoxy value of 0.535 are added over about 60 min such that the temperature does not rise above 80°C. The reaction product is then stirred for 30 min.

This gives an adduct hardener having an NH equivalent of 95 g/equivalent.

50 Parts by weight of this hardener adduct are stirred together with 100 parts by weight of an epoxy resin (epoxy resin based on bisphenol A/bisphenol F, diluted with a glycidyl ether based on a monofunctional fatty alcohol, epoxy equivalent: -190 g/equivalent, viscosity: 950 mPa«s/25°C) at room temperature (23°C). The gel time is determined at room temperature. The samples for the determination of the hardness according to Shore D are stored at 23°C and at 10°C. The hardness according to Shore D is determined after 1 day, 2 and 5 days and after further hardening at 60°C (48 h). The results are compiled in Table 1.

Example 2

The preparation of the hardener component and its subsequent processing is carried out as in Example 1 , but using a phenolpropoxylate having an average degree of propoxylation of 3 mol of PO per mol of phenol as plasticiser/diluent.

Example 3

The preparation of the hardener component and its subsequent processing is carried out as in Example 1 , but using a benzyl alcohol propoxylate having an average degree of propoxylation of 1 mol of PO per mol of benzyl alcohol as plasticiser/diluent.

Example 4

The preparation of the hardener component and its subsequent processing is carried out as in Example 1 , but using a nonylphenolpropoxylate having an average degree of propoxylation of 1 mol of PO per mol of nonylphenol as plasticiser/diluent. Comparison Example 5

The mixture of the hardener component and its subsequent processing is carried out as in

Example 1 , but using benzyl alcohol as plasticiser/diluent.

Example 6

43.5 g of norbornanediamine, 15 g of epoxy resin according to Example 1 and 41.5 g of phenolpropoxylate having an average degree of propoxylation of 1 mol of PO per mol of phenol are reacted in accordance with Example 1 :

NH equivalent: 95 g/equivalent. The subsequent processing is carried out as described in Example 1.

Example 7

A hardener is prepared in analogy to Example 6, but using a phenolpropoxylate having an average degree of propoxylation of 3 mol of PO per mol of phenol as plasticiser/diluent. The subsequent processing is carried out as described in Example 1.

Example 8

A hardener is prepared in analogy to Example 6, but using a nonylphenolpropoxylate having an average degree of propoxylation of 1 mol of PO per mol of nonylphenol as plasticiser/diluent. The subsequent processing is carried out as described in Example 1.

Example 9

A hardener is prepared in analogy to Example 6, but using a benzyl alcohol propoxylate having an average degree of propoxylation of 1 mol of PO per mol of benzyl alcohol as plasticiser/diluent. The subsequent processing is carried out as described in Example 1.

Comparison Example 10

A hardener is prepared in analogy to Example 6, but using benzyl alcohol as plasticiser/diluent. The subsequent processing is carried out as described in Example 1. - 10-

Example 11

44.6 g of 2,2,4(2,4,4)-trimethylhexamethylenediamine-1 ,6, 15 g of epoxy resin according to Example 1 and 40.4 g of phenolpropoxylate having an average degree of propoxylation of 1 mol of PO per mol of phenol as plasticiser/diluent are reacted in accordance with Example 1.

Example 12

A hardener is prepared in analogy to Example 11 , but using a para-tertiary-butylphenolpro- poxylate having an average degree of propoxylation of 1 mol of PO per mol of para-tertiary- butylphenol as plasticiser/diluent.

The subsequent processing is carried out as described in Example 1.

Comparison Example 13

A hardener is prepared in analogy to Example 11 , but using benzyl alcohol as plasticiser/diluent. The subsequent processing is carried out as described in Example 1.

Example 14

40 g of 1 ,3-bisaminomethylcyclohexane, 15 g of epoxy resin according to Example 1 and 45 g of phenolpropoxylate having an average degree of propoxylation of 1 mol of PO per mol of phenol are reacted in accordance with Example 1.

Example 15

A hardener is prepared in analogy to Example 14, but using a nonylphenolpropoxylate having an average degree of propoxylation of 1 mol of PO per mol of nonylphenol. The subsequent processing is carried out as described in Example 1. - 11-

Comparison Example 16

A hardener is prepared in analogy to Example 14, but using benzyl alcohol as plasticiser/diluent. The subsequent processing is carried out as described in Example 1.

Example 17

48 g of isophoronediamine, 15 g of epoxy resin according to Example 1 and 37 g of phenolpropoxylate having an average degree of propoxylation of 1 mol of PO per mol of phenol are reacted in accordance with Example 1.

Comparison Example 18

A hardener is prepared in analogy to Example 17, but using benzyl alcohol as plasticiser/diluent. The subsequent processing is carried out as described in Example 1.

Example 19

50 g of norbornanediamine and 50 g of a propoxylated nonylphenol having an average degree of propoxylation of 1 mol of PO per mol of nonylphenol are homogenised at room temperature.

NH equivalent: 76 g/equivalent.

40 Parts by weight of this hardener mixture are stirred together with 100 parts by weight of the epoxy resin described in Example 1 at room temperature (23°C).

The subsequent processing is carried out as described in Example 1.

Comparison Example 20

A hardener is prepared in analogy to Example 19, but using nonylphenol as plasticiser/diluent.

The subsequent processing is carried out as described in Example 1. -12-

Table 1

Example (E) Gel time 10 °C 23 °C Final hardness

Comparison tecam value Hardness > ace. to Shore D Hardness ace. to Shore D (5 days/23 °C

Example 23 °C/min day days days day days days +48 h/60°C)

(C1E) 1 2 5 1 2 5

E1 95 54 73 77 70 77 78 78

E2 188 20 67 76 63 72 77 78

E3 127 26 65 71 60 69 73 76

E4 104 70 77 79 77 79 80 82

CE5 48 53 67 72 66 72 73 74

E6 58 67 76 76 77 80 80 81.5

E7 102 54 70 76 74 77 80 81

E8 72 71 77 79 79 80 81 83

E9 70 56 70 77 73 76 78 80

CE10 34 66 75 77 76 78 78 79.5

E11 68 30 60 71 53 67.5 71.5 77.5

E12 77 56 73 78 72 76 80 81

CE13 42 30 53 66.5 44 61 66.5 75.5

E14 64 65 75 78.5 74 79 79 80.5

E15 72 71 76 78 76 80 80 80

CE16 34 65 72.5 76.5 72 76 76.5 78

E17 207 2 58 78.5 42 74 80 82.5

CE18 120 6 63 77.5 52 77 80 80.5

E19 84 77 79 80.5 80 80.5 81 82

CE20 22 79 81 81 81 81 82 82

Claims

- 13-What is claimed is

1. A curable mixture based on an epoxy resin and an aminic hardener, optionally additionally using colourants, pigments, fillers, UV stabilisers, flow control/plasticising agents, wherein the plasticiser/diluent used is at least one compound of the general formula (I):

(CH₂)_n-O-[CH₂-CH-O]_m-H (I)

CH,

wherein

Ri . 3_> R5 are each independently of one another H or an unbranched or branched alkyl radical containing 1 to 12 carbon atoms, and

R2. R4 are H, where m = 1 to 10 and n = 0 to 3.

2. A curable mixture according to claim 1 , which consists of

A) an epoxy resin,

B) an aminic hardener,

C) customary assistants, colourants, pigments, fillers, and

D) at least one compound of the general formula (I).

3. A curable mixture according to claim 1 , wherein the aminic hardener B) is xylylenediamine, norbornanediamine, 1 ,3-bisaminomethylcyclohexane, 2,2_I4(2,4,4)-trimethylhexame- thylenediamine-1 ,6, isophoronediamine and/or polyaminoamides which optionally contain imidazoline and which are obtainable by condensation of fatty acids with polyethylenepolyamines.

4. A curable mixture according to claim 3, which comprises using prepolymers of the aminic hardener B). - 14-

5. A curable mixture according to claim 1 , which comprises adding at least one compound of the general formula (I) to the aminic hardener.

6. A curable mixture according to claim 1 , which comprises adding at least one compound of the general formula (I) to the epoxy resin.

7. A curable mixture according to claim 1 , wherein the component of formula (I) is the propo- xylate of phenol, cresol or benzyl alcohol.

8. A curable mixture according to claim 7, wherein the degree of propoxylation (m) is 1 to 5.