Patent Application
20080026154
The present invention relates to urethane-group containing diol or polyol polymer products as well as a process for their production. The polymer products can be used in cross-linking reactions to produce coatings containing carbamate groups, for example polyurethane coatings.
Polyester based polyurethanes are well known and used widely for many applications, including surface coatings. These materials are manufactured from polyester resins, typically produced by reacting difunctional alcohols and difunctional acids to produce hydroxyl functional polyesters, which are then cross-linked with di- or tri-functional isocyanates in order to produce polyurethanes. However, isocyanates are highly dangerous and there is increasing pressure to minimise the use of these materials for environmental, and health and safety reasons.
Various alternatives to isocyanate chemistry are already available but they do not offer the same benefits as the use of isocyanates. For example, melamine-based resins (and similar products such as ureas, benzoguanamine or glycoluril resins) are widely used to cross-link hydroxyl functional polyesters but this often leads to coatings which are too hard, brittle and/or inflexible, particularly when high hydroxyl containing acrylic resins are used.
When the use of free isocyanate is undesirable on health and safety grounds or for technical reasons, it is widely practised to incorporate isocyanate prepolymer or polyisocyanate, either containing free isocyanate functionality or having chemically protected isocyanate (“blocked isocyanate”). However, whilst providing polyurethanes which are flexible and highly chemically resistant, blocked isocyanates are expensive materials and their use is therefore not always cost-effective. Further, even blocked isocyanates are becoming unfavoured from a safety point of view. Alternative routes to polyurethanes are therefore desired which are not detrimental to the properties of the final polyurethane product, but avoid the safety issues connected with isocyanates and blocked isocyanates.
A further problem associated with known isocyanate technology is the restriction in the range of polyurethane materials which can be produced due to the limited number of commercially available starting materials. Many diols and diacids are currently available. For example, diethylene glycol, ethylene glycol, 1,4-butanediol, 1,6-hexanediol and neopentylglycol are typically used along with adipic acid, succinic acid, terephthalic acid and many other diacids. However, commercially available isocyanates are more limited. A new process is therefore desired which enables a broader range of polyurethanes to be produced from commercially available starting materials.
The present inventors have developed a new technology which allows polyester based polyurethanes to be manufactured without involving isocyanate reagents. A urethane diol or polyol is used to initiate polymerisation of a lactone or lactam, leading to a novel polyester diol or polyol product containing a urethane linkage. The resulting diol or polyol can then be cross-linked, for example with non-isocyanate cross-linking agents such as melamine, to produce a polyurethane coating.
The technology allows the introduction of urethane groups or carbamate groups into the coating compositions. This means that the beneficial physical properties of coatings produced using isocyanate technology, including flexibility and chemical resistance, are retained but in the complete absence of isocyanate reagents, offering health and safety and environmental benefits and making the process a viable alternative to the use of free or blocked isocyanates. The process is also significantly more cost effective than the use of blocked isocyanates in the production of one-component coating formulations.
The use of the process of the present invention also enables a broader range of polymers to be manufactured than is possible using the isocyanate route since certain diisocyanates, such as ethylene diisocyanate, are not commercially available or easily synthesised, whereas the corresponding urethane diol or polyol precursors can be obtained economically.
The provision of a broader range of polyurethanes will, in turn, provide the skilled person in the art with access to polymers with new and different combinations of properties. This may lead to improvements in the currently known applications such as coatings and adhesives and may further lead to new applications for polyurethanes.
Thus, the present invention provides a polymeric product of the structure (I)
wherein:
The present invention also provides a process for producing the polymeric products of the invention, as depicted below. The process involves initiating the polymerisation of a lactone or lactam with a urethane diol or polyol.
The polymeric products of the invention are useful in the production of polyurethanes. The present invention therefore also provides a process for preparing a polyurethane comprising curing a polymeric product of the invention in the presence of a cross-linking agent, as well as a polyurethane obtained or obtainable thereby.
The polymeric products of the invention are envisaged to be particularly useful in the production of coatings. The invention therefore also provides a coating composition comprising
The coating composition of the invention can be used to form a coated article by
The present invention therefore also provides a process for coating an article as set out above as well as a coated article obtained or obtainable thereby.
The coatings produced in accordance with the present invention have the advantages of flexibility and chemical resistance that are usually associated with coatings produced using isocyanates. In addition, the polyurethanes and coatings of the invention have enhanced phase separation within the polyurethane structure. Previously known polyurethanes have a random separation of urethane groups through the backbone of the polymer, leading to the disruption of phase separation. This effect is described further in “Polyurethane” 2nd edition (Gunter Oertel, published Carl Hanser Verlag, 1994) pages 37 to 46. In contrast, the polyurethanes of the present invention have single urethane groups which are uniformly separated by polyester phases. The polyurethanes thus display good phase separation of hard and soft segments, which in turn may lead to improvements in the elastomeric properties of the polyurethane.
As used herein and unless otherwise defined, a C1-C12 alkyl or C2-C12 alkylene group is typically a C1-C8 alkyl or C2-C8 alkylene group which is either straight or branched, and is preferably straight. Examples of C1-C8 alkyl and C2-C8 alkylene groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, ethylene, n-propylene, n-butylene, n-pentylene and n-hexylene. A C1-C12 alkoxy or alkylthio group is typically a C1-C12 alkyl group as defined above attached to an oxygen or sulfur atom respectively.
As used herein and unless otherwise defined, a C2-C12 alkenyl or C2-C12 alkenylene group is a C2-C12 hydrocarbon group or moiety containing one or more double bonds. A C2-C12 alkenyl or C2-C12 alkenylene group is typically a C2-C8 alkenyl or C2-C8 alkenylene group which is either straight or branched, and is preferably straight. Examples of C2-C8 alkenyl and alkenylene groups include ethyenyl, n-propenyl, ethenylene, n-propenylene, n-butenylene, n-pentenylene and n-hexenylene.
As used herein and unless otherwise defined, a C2-C12 alkynyl or C2-C12 alkynylene group is a C2-C12 hydrocarbon group or moiety containing one or more triple bonds. A C2-C12 alkynyl or C2-C12 alkynylene group is typically a C2-C8 alkynyl or C2-C8 alkynylene group which is either straight or branched, and is preferably straight. Examples of C2-C8 alkynyl and alkynylene groups include ethynyl, n-propynyl, ethynylene, n-propynylene, n-butynylene, n-pentynylene and n-hexynylene.
As used herein, a halogen atom is a fluorine, chlorine or bromine atom.
As used herein, an alkyl group or alkylene moiety wherein one or more non-adjacent, saturated carbon atoms of said alkyl group is replaced with a nitrogen, oxygen or sulfur atom, is typically a group of formula —(C1-C4 alkylene)-Y—(C1-C4 alkyl(ene)) wherein Y is N, O or S. Examples include —(CH2)n—O—(C1-C2 alkyl(ene)), —(CH2)n—NH—(C1-C2 alkyl(ene)) and —(CH2)n—S—(C1-C2 alkyl(ene)), wherein each n is the same or different and is 1 or 2.
The group R1 of the compounds of formula (I) is typically derived from an aliphatic or aromatic polyamine compound having m amine groups, wherein m is as defined above, in which the amine groups are replaced with the substituents —N(R2)C(O)—X1—R3—Yn—R4 as depicted in formula (I). Thus, a wide variety of different aliphatic and aromatic groups can be used as the group R1.
Examples of suitable R1 groups include C1-C12 alkyl, C2-C12 alkenyl and C2-C12 alkynyl groups, one or more non-adjacent, saturated carbon atoms of said alkyl, alkenyl or alkynyl groups optionally being replaced with a nitrogen, oxygen or sulfur atom. Further possible R1 groups include groups of formula R6, (C1-C4 alkyl)-R6, R6—(C1-C4 alkyl), (C1-C4 alkyl)-R6—(C1-C4 alkyl) or R6—(C1-C2 alkylene)-R6, wherein R6 is a C6-C10 aryl or C3-C10 carbocyclyl group, or a 5- to 7-membered heteroaryl or heterocyclyl group containing one, two or three atoms selected from nitrogen, oxygen and sulfur.
When R6 is a C6-C10 aryl group it is typically phenyl or naphthyl. When R6 is a C3-C10 carbocyclyl group, it is typically a C3-C8 single ring cycloalkyl compound, for example cyclopentyl or cyclohexyl, or a C8-C10 fused ring system, for example decalinyl. When R6 is a 5- to 7-membered heteroaryl group it is typically pyridyl, thienyl, furyl or pyrrolyl. When R6 is a 5- to 7-membered heterocyclyl group it is typically tetrahydrofuranyl, piperidinyl or pyrrolidinyl. Preferably R6 is a C6-C10 aryl or C3-C10 carbocyclyl group. Most preferably, R6 is phenyl, naphthyl, cyclopentyl, cyclohexyl or decalinyl.
Preferred R1 groups include C2-C4 alkyl and groups of formula R6, (C1-C2 alkyl)-R6, R6—(C1-C2 alkyl), (C1-C2 alkyl)-R6—(C1-C2 alkyl) or R6—(C1-C2 alkylene)-R6, wherein R6 is phenyl, naphthyl, cyclopentyl, cyclohexyl, or decalinyl. More preferred groups R1 include ethylene, n-propylene, n-butylene, phenyl, naphthyl, methylbenzyl, decalin, cyclohexyl-(CH2)-cyclohexyl and phenyl-(CH2)-phenyl.
The group R1 is substituted with 2, 3 or 4 groups of formula —N(R2)C(O)—X1—R3—Yn—R4 as depicted in formula (I), thus m is 2, 3 or 4. These substituents may be located at any position on the group R1 including, where relevant, on either the cyclic or the linear part of the group. R1 is optionally further substituted with one or more, such as 1, 2 or 3 further substituents. These further substituents are typically selected from halogen atoms and C1-C4 alkoxy, C1-C4 alkylthio and C1-C4 alkyl groups.
Each R2, which may be the same or different, is typically a methyl or ethyl group or a hydrogen atom. R2 is preferably a hydrogen atom.
Each R3 is typically a straight or branched C2-C12 alkylene group, preferably a C2-C8, more preferably a C2-C6 or a C2-C3 alkylene group. Typically, R3 is a straight-chain alkylene group. R3 is typically unsubstituted or substituted with 1, 2 or 3 substituents selected from halogen atoms and C1-C4 alkoxy and C1-C4 alkylthio groups. Preferably R3 is unsubstituted. Examples of typically R3 groups include ethylene and n-propylene, in particular ethylene (—CH2—CH2—).
Each R4 is typically OH.
Each X1 and each X2 is typically O.
Each n may be the same or different and typically has a value from 1 to 25, for example from 2 to 10, such as from 2 to 5. Preferably the average values of n are the same and are about 3.
Each R5, which may be the same or different, is typically a straight or branched C2-C12 alkylene group, preferably a C2-C8, more preferably a C3-C6, for instance a C5 alkylene group. Typically, R5 is a straight-chain alkylene group. R5 is typically unsubstituted or substituted with 1, 2 or 3 substituents selected from halogen atoms and C1-C4 alkoxy and C1-C4 alkylthio groups. Preferably R5 is unsubstituted. Examples of typical R5 groups include —(CH2)p— wherein p is 3, 4, 5 or 6, in particular 5.
Typically m is 2 or 3, preferably 2.
Preferred polymeric products of the invention have the structure (IV)
wherein
Particularly preferably, in formula (IV), R3 is —CH2—CH2— and R5 is —(CH2)5—.
The polymeric products of the present invention are typically produced by a polymerisation reaction of a lactone or lactam with a urethane diol or polyol. The products therefore contain a number of individual compounds each of formula (I) or (IV). Typically, the polymeric product comprises a number of different compounds of formula (I) or (IV), each of which can be prepared by polymerisation of the same starting materials. Thus, a polymeric product may, for example, contain a number of compounds which differ only in terms of their values of m and n in formula (I) or (IV).
The polymeric products of the invention typically have weight average molecular weights (Mw) in the region of 500 to 3000 and number average molecular weights (Mn) in the region of 500 to 2500 when measured by GPC with reference to a polystyrene standard.
The polymeric products of the invention can be prepared by polymerising a lactone or lactam (VI) in the presence of a urethane dial or polyol compound (V), in accordance with Scheme I.
In the above Scheme I, R1, R2, R3, R4, R5, X1, X2, n and m have the meanings set out above. The reaction is typically carried out in the presence of a Lewis acid catalyst or at a pH of less than 7 and at a temperature of approximately 50-150° C. In the polymerisation process of the present invention, the polymerisation can be promoted by any type of catalyst known in the art. Particularly attractive are metal oxides, halides or carboxylates, the metals of which contain free p, d or f orbitals of a favourable energy, e.g. Mg, Ti, Zr, Zn, Sn, Al, Y, La, Hf and rare earth atoms such as Sm, in the presence of protic species such as alcohols, amines, thiols and water.
It is however preferred that the polymerisation process employs
(herein referred to as stannous octoate) as a catalyst.
As will be readily understood (and is capable of being determined) by one skilled in the art, the precise concentration of the catalyst to be employed in the process of the present invention may be varied as needed to obtain the polymer which is desired to be obtained thereby.
If desired, two or more different compounds of formula (V) and/or two or more different compounds of formula (VI) may be used as starting materials. Typically, however, a single compound (V) and a single compound (VI) are used.
The lactone or lactam (VI) should be present in sufficient quantities to provide the desired values of n in the product (I). For example, when m=2 and each n=about 3, six equivalents of lactone or lactam (VI) are required for each equivalent of compound (V). At least two equivalents of lactone or lactam (VI) must be used in any case.
It is noted that the reaction is carried out at relatively low temperatures, in particular when compared with typical temperatures for carrying out a conventional polyesterification, i.e. up to 240° C., typically from 220 to 240° C. The use of low temperatures enables urethane diols or polyols to be used without discolouration of the final polymer. It is thought that urethane diols or polyols degrade when subjected to higher temperatures and therefore cannot be conveniently used in conventional polyesterifications.
The above reaction can, if desired, be carried out using an enzymatic polymerisation process such as that described in GB-B-2 272 904 and EP-B-0 670 906.
The lactams and lactones (VI) are typically available commercially. For example, a preferred compound of formula (VI) is caprolactone which is widely available. The urethane diols or polyols of formula (V) can be produced from the corresponding di- or poly-amines of formula (VII) by reaction with a cyclic carbonate or oxazolone of formula (VIII), as is depicted in Scheme II.
In the above Scheme II, R1, R2, R3, X1 and m have the meanings set out above. This reaction can be carried out in an inert organic solvent such as toluene and at a temperature of approximately 50° C., or in accordance with any techniques known in the art. The di- or polyamines of formula (VII) and the carbonates or oxazolones of formula (VIII) are commercially available or can be produced by techniques well known to the skilled chemist. An example of a commercially available diamine of formula (VII) is Lonzacure DETDA 80 from Lonza Ltd, Switzerland. This product is a mixture of about 80% 3,5-diethyltoluene-2,4-diamine and about 20% 3,5-diethyltoluene-2,6-diamine. The use of this starting material therefore leads to a mixture of polymeric products of the formula
wherein the R1 group is derived from the 2,4- and the 2,6-isomers.
The polymeric products of the invention can be further reacted using known techniques to produce cured polyurethanes. The process comprises curing a polymeric product of the invention in the presence of a cross-linking agent. Typically, the polymer products are combined with a cross-linking agent and one or more solvents, optionally together with one or more chain extenders, such as polyols or polyamines, and a catalyst system. Further polymer(s) reactive with the cross-linking agent(s) may also be added. The composition thus produced is subsequently cured to produce a final polyurethane product.
Suitable cross-linking agents are known in the art. Preferred cross-linking agents are non-isocyanate containing components such as aminotriazine compounds, in particular melamine, ureas, benzoguanamine or glycoluril; the resins can be alkylated or partially alkylated. Such resins and their chemistry are described in “Organic Coatings Science and Technology” 2nd Edition (edited by Wicks, Jones and Papas), Pub. Wiley Interscience, 1999. Chapter 9 p 162-179 is devoted entirely to these resins. Melamine type cross-linkers are, for instance, manufactured by Cytec (www.cytec.com). However, isocyanate and blocked isocyanate cross-linking agents can be employed if desired. Suitable catalyst systems, solvents and chain extenders will also be well known to the skilled person in the art.
The polymer products of the invention are particularly useful in the production of polyurethane coatings, for example clear coatings for the automobile industry and coil coatings. An article is coated by (i) applying a coating composition containing the polymer products of the invention to the article to be coated, and (ii) curing the applied coating. The application and curing steps can be carried out by techniques generally known in the art. For example, the curing step is typically carried out by heating to approximately 150° C.
The coating compositions of the invention comprise (a) the polymer product of the invention, (b) one or more cross-linking agents, optionally (c) a catalyst, optionally (d) one or more solvents, optionally (e) another polymer or polymers reactive with the cross-linker (e.g. a hydroxy-functional acrylic polymer) and optionally (f) one or more chain extenders (for instance amino-functional chain extenders such as diethyl toluene diamine and hydroxy-functional chain extenders such as butane diol). Preferred coating compositions comprise (a) the polymer product of the invention, (b) one or more cross-linking agents and (d) one or more solvents. Further preferred coating compositions comprise (c) a catalyst in addition to components (a), (b) and (d). Suitable coating composition formulations are known in the art and are described, for example, in “Organic Coatings Science and Technology” 2nd Edition (edited by Wicks, Jones and Papas), Pub. Wiley Interscience, 1999, see in particular page 4.
Whilst the polymer products of the invention are particularly useful in the production of coatings, other uses can also be envisaged. For example, the polymer products can be employed as adhesives, foams and moldings.
Ethylene carbonate (160 g-1.82 moles) and toluene (200 g) were stirred together and heated to 50° C., creating a homogeneous mixture. Ethylene diamine (54.6 g to 0.91 moles) was added dropwise, maintaining the temperature below 60° C. The reaction mixture was separated into two phases and a white solid separated from the reaction mixture. Toluene was removed by evaporation yielding 208 g of a white powder, mp 92-93° C.
The white powder (70 g) was charged to a reactor, followed by caprolactone (202.9 g) and heated, with stirring, to 110° C. 0.1 g of stannous octoate was added and the consumption of caprolactone monitored by thin layer chromatography. Reaction temperature was maintained at 110-120° C., with subsequent additions of stannous octoate as required to maintain progress of reaction. When all caprolactone was consumed, the reaction was cooled and the contents discharged. On cooling the material became a waxy solid with the following characteristics:
Free caprolactone—1.8%
Mp 1505
Mw 1572
Mn 1315
OHv 134.2 mg KOH/g
1,6-Hexanediamine (91.8 g-0.79 moles) and toluene (200 g) were stirred together and heated to 50° C., creating a homogeneous mixture. Ethylene carbonate (140 g-1.59 moles) was added dropwise, maintaining the temperature below 60° C. The reaction mixture was separated into two phases and a white solid seperated from the reaction mixture. Toluene was removed by evaporation yielding 228.1 g of a white powder mp 92° C.
The white powder (40 g) was charged to a reactor, followed by caprolactone (94.3 g) and heated, with stirring, to 120° C. 0.1 g of stannous octoate was added and the consumption of caprolactone monitored by thin layer chromatography. Reaction temperature was maintained at 110-120° C., with subsequent additions of stannous octoate as required to maintain progress of reaction. When all caprolactone was consumed, the reaction was cooled and the contents discharged. On cooling the material became a waxy solid with the following characteristics:
Mp 1933
Mw 2042
Mn 1431
OHv 107.8 mg KOH/g
A coating formulation was prepared by mixing together the following components:
A coating formulation was prepared by mixing together the following components:
The formulations of Examples 3 and 4 were coated onto panels as follows:
The coatings were then cured at 140° C. for 30 mins, giving a tack free continuous film.
The cured coatings showed the following characteristics (test methods described below):
The coatings showed a combination of good flexibility, solvent resistance, adhesion and hardness and demonstrates that the urethane containing diol of the invention is suitable for the application.
As comparative examples the following formulations were prepared:
(note 1)
Trixene BI7982 is a 70% solids 3,5-dimethylpyrazole blocked HDI trimer in methoxypropanol
The formulations were coated onto panels in the same manner as described for Examples 3 and 4 and cured at 140° C. for 30 mins.
The cured coatings showed the following characteristics (test methods are described below):
Comparative Example 5A is an example of an acrylic based coating cured with both melamine and blocked isocyanate, representative of the current art for preparation of 1-pack heat curable coating.
Comparative Example 5B shows the effect of not including an isocyanate/urethane component in the formulation.
Comparative Example 5C shows the effect of incorporating polymerised caprolactone without additional urethane groups. These coatings provide flexibility, but at the expense of MEK resistance.
Polymer products were prepared using substantially the same process as is set out in Example 1, except that the nature of the amines used, and the amounts of ethylene carbonate and caprolactone used, were as set out in the table below. Melting point and molecular weight measurements were taken for each polymer product (test methods are described below).
Test Methods
| Number | Date | Country | Kind |
|---|---|---|---|
| 0413707.1 | Jun 2004 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB05/02357 | 6/16/2005 | WO | 2/1/2007 |
