WO1997021748A1

WO1997021748A1 - Long-term hydrolysis-stable polyurethanes containing ester groups

Info

Publication number: WO1997021748A1
Application number: PCT/EP1996/005337
Authority: WO
Inventors: Roland Grützmacher; Andreas Heidbreder; Bernd Beuer; Peter Döbrich
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1995-12-11
Filing date: 1996-12-02
Publication date: 1997-06-19
Also published as: DE19546116A1

Abstract

The invention relates to long-term hydrolysis-constant polyurethanes which contain ester groups and can be obtained by reacting ring opening products of epoxidized fatty acid esters obtained from fatty acids and/or mixtures of fatty acids with 16 to 20 C-atoms and monofunctional alcohols with 1 to 8 C-atoms with at least trifunctional alcohols with corresponding polyisocyanates. The proportion of bi-unsaturated or poly-unsaturated fatty acids is in total at least approximately 40 % by weight and the proportion of mono-unsaturated fatty acids is on average less than 35 % by weight.

Description

_» Long-term hydrolysis-stable polyurethanes containing ester groups"

Field of the Invention

The invention relates to the use of ring opening products of epoxidized fatty acid esters, obtainable from fatty acids and / or fatty acid mixtures with 16 to 20 carbon atoms and monofunctional alcohols with 1 to 8 carbon atoms, the proportion of two or more unsaturated fatty acids totaling at least about 40% by weight. -% and the proportion of monounsaturated fatty acids is on average less than 35 wt .-%, with at least trifunctional alcohols, for the production of polyurethanes. The materials can be used as foams, casting resins and / or coatings for the production of moldings, coatings and composite materials and the like.

State of the art

Polyester polyols are ideal for the production of polyurethanes. The polyether polyols used up to now, when processed correctly, led to polyurethanes with satisfactory material properties, but the high polarity of the polyether groups did already when the polyol component was water-absorbed, which resulted in blistery, foamy materials. For this reason, the hydrophilicity of the polyether polyols made it impossible to work on moist or water-based substrates.

The use of polyester polyols as a polyol component for the production of polyurethane materials brought about a significant reduction in these phenomena. However, the person skilled in the art is aware of the problems which the ester bond brings with regard to the hydrolysis stability of the materials produced therefrom. Due to the release of carboxyl groups associated with the hydrolysis and the change in polarity caused thereby, the material absorbs water in an aqueous environment, which leads to softening and possibly complete destruction of the material. So far, it has been possible to make polyurethane materials containing ester groups largely hydrophobic, so that at least the formation of bubbles during processing and the brief hydrolysis under aqueous conditions have been minimized. Nevertheless, the stability to hydrolysis over a period of several months left something to be desired in all of these cases. The continuous release of acid groups by the ester cleavage led to increased water absorption, softening and ultimately loss of the desired properties of the material. In the case of the casting resins in particular, which are used, for example, as cable casting compounds for stabilizing and isolating current-carrying parts, such long-term behavior is problematic in the long term, in particular when used in a damp or wet environment. Similar problems naturally arise in all other areas of application of polyurethane materials, such as foams or coatings, where long-term stability of the materials is important in environments which favor hydrolysis. Although the destruction of the material can be slowed down by increasing the crosslinking density in the polyurethane, the hydrolysis nevertheless continues and leads to a loss of function. In this context, of course, the drastic change in the material properties, which goes hand in hand with a higher crosslinking density, must also be taken into account. In particular, the glass transition temperature is determined by the additionally restricted mobility of the molecular segments is restricted, so that as a rule the material becomes hard and brittle with increasing crosslinking density and thus loses some of the elasticity desired, for example to compensate for density fluctuations associated with temperature changes.

Casting resins are known to be liquid synthetic resins or those which can be liquefied by moderate heating, which are poured into open molds and harden there. Casting resins also include isocyanate casting resins. According to DIN 55958, this means synthetic resins that are based on aliphatic, cycloaliphatic or aromatic isocyanates and still contain free isocyanate end groups. They can be cured under various conditions. For example, a one-component casting resin made of a polyurethane prepolymer with terminal free or blocked isocyanate groups which cure on exposure to moisture, whereby heating can take place, e.g. accelerate the reaction or increase the strength. A two-component casting resin is based e.g. on polyhydroxy compounds based on branched polyesters or polyethers as the first component and on polyisocyanate as the second component. After the two components have been mixed, they harden at room temperature or at a slightly elevated temperature.

There was therefore a need for isocyanate casting resins, foams or coating compositions for the production of moldings, coatings, foams, coatings and / or composite materials which, on the one hand, are insensitive to moisture and chemicals during production, so that bubbles do not form during curing, but, on the other hand, show long-term use of the hardened materials over a very long period of time, hydrolysis stability. In addition, despite the higher stability, the materials should still have sufficient flexibility and thus glass transition temperatures that correspond to those of the polyurethanes used to date. This technical problem has so far only been solved unsatisfactorily by the polyols known from the prior art. For example, DE-Al-43 08 097 describes the production of isocyanate casting resins from polyols with more than 10 carbon atoms and with 2 or more hydroxyl groups. To prepare the polyols, epoxidized fats and oils, or their esters with monofunctional alcohols, are ring-opened with polyfunctional alcohols. The publication mentions the fact that such isocyanate casting resins are insensitive to hydrolysis and are advantageous with regard to the formation of bubbles during processing. However, the publication gives no indication that with a certain selection of polyols an almost ideal hydrolysis behavior can be achieved, in which the water absorption stops completely after a relatively short time when a maximum value is reached and the test specimen maintains a constant weight.

Surprisingly, it has now been found that the use of ring-opening products of epoxidized fatty acid esters or their mixtures containing two or more unsaturated fatty acid esters with 16 to 20 C atoms of a total of at least 40% by weight and monofunctional alcohols with 1 to 8 C atoms, with at least trifunctional alcohols as polyols for the production of polyurethanes leads to materials which have excellent long-term hydrolysis stability and whose water absorption per unit of time after an initial phase becomes negligibly small.

Description of the invention

The invention thus relates to the use of ring-opening products of epoxidized fatty acid esters, obtainable from fatty acids and / or fatty acid mixtures with 16 to 20 C atoms and monofunctional alcohols with 1 to 8 C atoms, the proportion of two or more unsaturated fatty acids totaling at least about 40% by weight .-% and the proportion of monounsaturated fatty acids is on average less than 35 wt .-%, with at least trifunctional alcohols, for the production of polyurethanes. Fatty acid mixtures are preferably used, the proportion of di- or polyunsaturated fatty acids totaling approximately 40 to 85, in particular approximately 50 to 76% by weight. Particularly good results are obtained when using fatty acid mixtures in which this proportion is approximately 50 to 68% by weight.

To prepare polyols suitable according to the invention, the epoxidized fatty acid esters can be subjected to complete ring opening with polyfunctional alcohols or also partial ring opening. The partial ring opening results in modified fatty acid esters with epoxy and hydroxyl and ether groups. The production of such products using the example of triglycerides is the subject of German patent application DE 32 46 612. Thereafter, triglycerides of a fatty acid mixture containing at least partially olefinically unsaturated fatty acids with mono- or polyhydric alcohols in the presence of catalysts for the production of triglyceride reaction products are subjected to partial ring opening, by stopping the reaction by destroying or removing the catalyst and / or the alcohol reactant after a conversion of 20 to 80 mol%, based on epoxy groups.

A particularly important class inventively suitable polyols for two-component casting resins are _j ring opening products of epoxidized Fettsäureestern monofunctional C - to C alcohols, in particular Cp to C ^ alcohols, eg epoxidized

Fatty acid methyl, ethyl, propyl or butyl esters.

Alcohols with a functionality of 3 to 8, preferably 3 to 6, in particular trimethylolethane, trimethylolpropane, glycerol, pentaerythritol or sorbitol, and mixtures of these alcohols are generally used to open the ring. Products of this type can be produced by known epoxidation and ring opening processes. Ring opening products are preferred in which a ratio between epoxidized fatty acid esters and the alcohol used for the reaction is from 1: 0.1 to 1:10, in particular from 1: 0.5 until 1: 4 has been applied. Analogous to the opening products of epoxidized fatty alcohols, 1: 1 or 1: 2 adducts can also be produced here. As a rule, the reaction products of epoxidized fatty acid methyl esters with aliphatic C3- to Co-

Alcohols having the functionality 3 to 6 polyols obtainable according to the invention are preferred.

Fatty acids are understood to mean carboxylic acids with almost exclusively unbranched carbon chains, in particular with an average of more than 12 carbon atoms, preferably with 16 to 20 carbon atoms. According to the invention, those fatty acids or fatty acid mixtures are advantageously used which contain two or more unsaturated fatty acids, e.g. Linoleic and linolenic acid, contained in the quantities required at the beginning. They can advantageously be obtained from fats and oils of natural origin, e.g. from linseed, trans, sunflower, corn, tall, hemp, perilla, poppy, safflower, walnut and soybean oil.

Usually, no pure fatty acid derivatives prepared by distillation fractionation or similar, equivalent purification processes are used for the production of the polyurethanes according to the invention, but rather those derivatives which are obtained from the implementation of suitable fatty acid cuts, such as are obtained in particular in the suitable implementation of naturally occurring fats and oils. Thus, in the sense of the invention, it is entirely expedient to first transesterify the fats and oils mentioned with the suitable monofunctional alcohols, to epoxidize the corresponding alkyl esters and then to subject them to a ring opening with at least trifunctional alcohols.

It is therefore preferred in the sense of the invention to subject the epoxidized transesterification products of soybean oil, linseed oil, cottonseed oil and sunflower oil to such a ring opening with monofunctional alcohols.

All previously mentioned alcohol mixtures which can be used as polyols can still be subjected to a chain extension reaction. To this end, they are listed at known conditions implemented with C2 to C ^ epoxides. The preferred is here

Reaction with ethylene oxide. The alcohol mixtures can be reacted with 1 to 40 moles of ethylene oxide per mole of OH groups. The reaction with 5 to 20 mol and in particular with 10 to 15 mol of ethylene oxide is preferred. In addition to ethylene oxide, it is also possible to react with propylene oxide, using up to 40 mol, but preferably 5 to 20 mol, of propylene oxide per mol of OH group. Furthermore, other short-chain epoxides, such as glycidol, can be used. Finally, butene oxide is a suitable reactant. The reaction with ethylene oxide and / or with glycidol leads to a hydrophilization of the hardener, which is desirable for some applications.

The isocyanate component of the casting resins according to the invention is an isocyanate compound with functionality 2 to 4. Both aromatic and aliphatic, monocyclic and polycyclic, polyfunctional isocyanate compounds are suitable here. Thus, according to a first embodiment, tolylene diisocyanate or diphenylmethane diisocyanate can be used as the aromatic isocyanate compound. Technical diphenylmethane diisocyanate with a content of higher functional diisocyanates and a functionality of isocyanate groups greater than 2 is particularly suitable. Another suitable aromatic diisocyanate is xylylene diisocyanate. In addition, a large number of aliphatic isocyanates with functionality 2 and higher can be used. Examples here are isophorone diisocyanate, tris (6-isocyanatohexyl) isocyanurate and

Dicyclohexylmethane diisocyanate as cyclic aliphatic diisocyanates. Further examples are aliphatic, straight-chain diisocyanates, such as those obtained by phosgenation of diamines, for example tetramethylene diisocyanate or hexamethylene diisocyanate. In particular, in the sense of the invention, isophorone diisocyanate, tris (6-isocyanatohexyl) isocyanurate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate (HDI), HDI biuret and / or HDI trimer can be used.

In addition to the polyfunctional isocyanate compounds per se, prepolymers can also be used as the isocyanate component in the two-component casting resins according to the invention become. Prepolymers here are understood to mean the adducts of polyfunctional isocyanates with polyfunctional alcohols, for example the reaction products of one of the aforementioned aromatic or aliphatic diisocyanates with ethylene glycol, propylene glycol, glycerol, trimethylolpropane or pentaerythritol. Reaction products of diisocyanates with polyether polyols, for example polyether polyols based on polyethylene oxide or based on polypropylene oxide, can also be used as prepolymers. Prepolymers whose polyol component consists of building blocks based on o leochemistry are also suitable. For example, the reaction products of hydroxy group-containing triglycerides such as castor oil or the ring opening products of epoxidized triglycerides with mono- or polyhydric alcohols can be used. The ring opening products of soybean oil, rapeseed oil, linseed oil, cottonseed oil and / or sunflower oil should be mentioned in particular. The polyols according to the invention are equally suitable for the production of prepolymers. However, cyclic prepolymers made from diisocyanates can also be used, for example isocyanurates. In particular, those polyurethane prepolymers are used which carry an average of two or more isocyanate groups per molecule, such as isocyanurates, but also adducts of aliphatic or aromatic diisocyanates with diols and / or triols can be used according to the invention.

The two-component casting resins and coating compositions may further contain various auxiliaries, which are preferably mixed into the polyol. Fillers, for example, can be used here. Suitable fillers are inorganic compounds which are not reactive towards isocyanates, such as chalk or gypsum, precipitated silicas, bentonites, ground minerals and other inorganic fillers known to those skilled in the field, such as inorganic fibers. Organic fillers and fibers can also be used, in particular fiber short cuts and others. Fillers are preferred which impart thixotropy to the casting resins. The addition of zeolite as a drying agent can be of particular importance. In this way, particularly homogeneous, bubble-free materials can be obtained. The two-component casting resins or coating compositions according to the invention can also contain accelerators. Suitable are, for example, tertiary bases such as bis (N, N-dimethylamino) diethyl ether, dimethylaminocyclohexane, N, N-dimethylbenzylamine, N-methylmorpholine and the reaction products of dialkyl- (β-hydroxyethyl) amine with monoisocyanates and esterification products of Dialkyl- (ß-hydroxyethyl) amine and dicarboxylic acids. Another important accelerator is the 1,4-diamino-bicyclo- (2.2.2) octane. Non-basic substances can also be used as accelerators. Metal compounds may be mentioned here, for example iron pentacarbonyl, nickel tetracarbonyl, iron acetylacetonate and tin (II) - (2-ethylhexoate), dibutyltin dilaurate or molybdenum glycolate.

In addition to the compounds mentioned, the casting resins or coating compositions may also contain other auxiliaries. Solvents should be mentioned here. Solvents which in turn do not react with isocyanate groups are suitable, for example halogenated hydrocarbons, esters, ketones, aromatic hydrocarbons and others. Plasticizers, flame retardants, retarders, dyes, stabilizers and anti-aging agents, as are known in corresponding casting resins, can also be included.

The polyols used according to the invention can be replaced by other polyols to an extent of up to 80%. However, they are preferably used unmixed.

The isocyanate casting resins or coating compositions are stored in two components until they are used, that is to say up to this point in time the polyol and isocyanate compound are stored separately. For use, these two compounds are mixed with one another and the mixture is applied to the substrates to be coated. With regard to the mixing ratio and measures to influence the pot life, reference is made to the general specialist knowledge of the person skilled in the art. This is, for example, in the monograph by Saunders and Frisch "Polyurethanes, Chemistry and Technology ", Volume XVI of the series High Polymers" Interscience Publishers "New York - London, Part I (1962) and Part II (1964). To find the right mixture ratio, the skilled worker will generally find an equivalence of isocyanate and OH- For this purpose, the OH number of the alcohol mixtures and the isocyanate number of the isocyanate compounds can be determined in preliminary tests, from which the number of moles of reactive groups per gram can then be calculated, particularly suitable polyols according to the invention have OH numbers between 120 and 500, preferably between 150 and 380. Depending on the chemical structure, however, compounds with a lower or higher OH number, for example with OH numbers between 60 and 120 or between 240 and 700, are suitable, provided their functionality is not less than two OH groups per molecule is.

The casting resins or coating compositions prepared according to the invention are largely inert to moisture and even to water. So it is possible to use them for damp surfaces e.g. Use wood or textiles. In addition, they are also resistant to aggressive media such as salt solutions, inorganic or organic acids - e.g. Acetic acid, alkali, organic solvents and organic ester oils, e.g. synthetic esters such as rapeseed oil methyl esters and lubricant esters. The resins and compositions are therefore suitable for use in the chemical industry, in the electrical and mineral oil industry and e.g. in bathrooms, for model making and for facades, in particular for concrete renovation and painting as well as for corrosion protection. Tough, impact-resistant, flexible coatings can be produced.

Another object of the invention is the use of the polyurethanes according to the invention in composite materials and / or blends, blends being understood as meaning homogeneous, micro- or else macro-separated mixtures with other plastics. For this purpose, the polyurethanes can be processed in different mixing ratios with one or more additional components together to form a material with improved and / or new properties. In contrast to the fillers, which mainly have a cost-reducing function, they take over in the following addressed additives a functional, mainly associated with an improvement in the physical properties of the material in the material. To produce composite materials, the polyurethanes according to the invention are processed together, for example, with natural or synthetic fibers, fiber short cuts, fabrics or the like. Suitable materials are, for example, the natural fibers such as silk, cotton, wool, jute, hemp, flax, sisal, straw or the like, but the secondary products of these fibers in their processed form, for example as fabrics, are also suitable. The fibers can be incorporated into the polyurethanes according to the invention both in untreated and in treated form. For example, sizes based on siloxane or polyester, as are known to those skilled in the art for such surface treatments, have proven to be suitable agents for surface treatment. In many cases, the resulting composite materials have excellent stability, tear resistance, abrasion resistance and toughness, as is required for many applications in areas subject to hydrolysis.

In addition to natural fibers, synthetic fibers such as polyamides, polyesters, polyethers or carbon, but also inorganic fibers such as glass fibers and glass fiber mats can also be incorporated.

The invention is explained in detail using the following examples:

Examples

To compare the properties of the polyurethanes based on the polyols according to the invention and those corresponding to the known prior art, comparative tests were carried out with the following polyols.

According to the invention:

Polyol El: polyester / ether, OHZ 390 (soy fatty acid methyl ester epoxide / TMP)

Comparative examples:

Polyol VI polyether, OHZ 530 (TMP x PO) polyol V2 polyether, OHZ 390 (TMP x PO) polyol V3 polyester / ether, OHZ 310 (oleic acid methyl ester epoxide / TMP) polyol V4 polyester, OHZ 160 (castor oil)

Examples of resistance to hydrolysis

Water absorption of PUR test specimens (produced by equimolar crosslinking of the above-mentioned polyols with polymer MDI, 31% NCO and addition of 5% by weight of molecular sieve paste to bind the residual water in the polyols) in% by weight after storage in deionized water at 80 ° C . Table 1

z = destroyed

Comparison of glass transition temperatures (DIN 53445):

Glass transition temperatures of polyurethane test specimens (produced by equimolar crosslinking of the above-mentioned polyols with polymer MDI, 31% NCO and addition of 5% molecular sieve paste to bind the residual water in the polyols):

Appearance after curing:

Appearance of polyurethane test specimens (see above) when 10 g reaction mass (0 80 mm) has hardened at 30 ° C and 80% relative humidity:

According to the invention:

Polyol El: foam-free casting compound, 2 mm layer thickness

Comparative examples:

Polyol VI foam, 3 - 9 mm layer thickness Polyol V2 foam, 3 - 9 mm layer thickness Polyol V3 foam-free casting compound, 2 mm layer thickness Polyol V4 foam-free casting compound, 2 mm layer thickness

The examples show that, by using the ring opening products according to the invention with alcohols as the polyol component, it is possible, for example, to produce PUR casting resins which, in contrast to polyurethanes based on ethylene or propylene oxide derivatives, cure bubble-free in moist air.

While this requirement is also met by comparable polyurethanes based on monounsaturated fatty acids (polyols V3 and V4), the analysis of the hydrolysis resistance clearly shows the superiority of the casting resins according to the invention.

Claims

claims

1. Use of ring opening products of epoxidized fatty acid esters, obtainable from fatty acids and / or fatty acid mixtures with 16 to 20 C atoms and monofunctional alcohols with 1 to 8 C atoms, the proportion of two or more unsaturated fatty acids totaling at least about 40% by weight and the proportion of monounsaturated fatty acids is on average less than 35% by weight, based in each case on the total content of fatty acids, with at least trifunctional alcohols, for the production of polyurethanes.

2. Use according to claim 1, characterized in that for the production of the fatty acid ester fatty acid mixtures, the proportion of two or more unsaturated fatty acids in total 40 to 85, in particular 50 to 76 wt .-%, are used.

3. Use according to one of claims 1 or 2, characterized in that mixtures of ring opening products of epoxidized fatty acid esters, such as those obtained by transesterification of natural triglycerides such as soybean oil, linseed oil, cottonseed oil and sunflower oil with monofunctional alcohols having 1 to 8 carbon atoms and subsequent ring opening are used.

4. Use according to one of claims 1 to 3, characterized in that polyols having a functionality of 3 to 8, in particular 3 to 6, are used for ring opening.

5. Use according to one of claims 1 to 4, characterized in that trimethylolpropane, glycerol, trimethylolethane, pentaerythritol and / or sorbitol are used for ring opening.

6. Use according to one of claims 1 to 5, characterized in that the isocyanate component is aromatic diisocyanates, preferably diphenylmethane diisocyanate and in particular technical diphenylmethane diisocyanate having a functionality greater than 2 or tolylene diisocyanate.

7. Use according to one of claims 1 to 6, characterized in that the isocyanate component is isophorone diisocyanate, tris (6-isocyanatohexyl) isocyanurate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate (HDI), HDI biuret and / or HDI- Trimer acts.

8. Use according to one of claims 1 to 7, characterized in that the isocyanate component is polyurethane prepolymers with an average of 2 or more isocyanate groups per molecule, e.g. an isocyanurate, in particular adducts of aliphatic or aromatic diisocyanates with diols and / or triols.

9. Use according to one of claims 1 to 8, characterized in that the casting resin or the coating composition contains at least one of the components: accelerators, stabilizers, solvents and / or retarders which are not reactive toward isocyanate groups.

10. Use according to one of claims 1 to 9, characterized in that the casting resin or the coating composition contains conventional fillers such as chalk, gypsum, gelled silicas, organic or inorganic fibers or zeolite.

1 1. Use of the polyurethane compositions according to one of claims 1 to 10 in composite materials or blends.