GB2099439A - Method for making rim elastomers using a catalyst system containing a polymeric component - Google Patents

Abstract

Polymers containing tertiary amine groups, and substantially free from active hydrogen atoms, are useful catalysts for the production of reaction injection moulded (RIM) polyurethanes. These catalysts do not interfere with the curing of paints on a moulded article or interfere in the urethane network. They are advantageously employed as a solution or dispersion in one of the polyurethane- forming components. Advantageous catalysts are polymers made from monomers of the formula <IMAGE> wherein Y = -O- or -NH-, R1= H or CH3, R2-R7 independently = H, CH3, or alkyl, m = 0-1, n = 0-6, and R8 and R9 independently = CH3, or alkyl, or together with the nitrogen atom to which they are attached form a N-containing heterocyclic group. The catalyst composition may additionally comprise a fast gelation organotin catalyst, e.g. dibutyltin dilaurate, and a delayed action organotin catalyst, e.g. an alkyltin mercaptide. The catalyst composition may be prepared by polymerizing the tertiary amine-containing monomer in a liquid which is a polyurethane forming component, e.g. the polyol, chain-extender or crosslinker.

Description

SPECIFICATION Method for making rim elastomers using a catalyst system containing a polymeric component The invention concerns the production of reaction injection moulded polyurethanes, and a catalyst composition for use in the production of such polyurethanes.

Reaction Injection Moulding (RIM) is a technique for the rapid mixing and moulding of large, fast curing urethane parts. RIM polyurethane parts are used in a variety of exterior body applications on automobiles where their light weight contributes to energy conservation. RIM parts are generally made by rapidly mixing active hydrogen-containing materials with polyisocyanate and placing the mixture in a mould where reaction proceeds. These active hydrogencontaining materials comprise a high molecular weight polyhydric polyether and a low molecular weight active hydrogen-containing compound. After reaction and demoulding, the parts may be subjected to an additional curing step which comprises placing the parts in an ambient temperature of at least 1 20 C.

Our published British Patent Application No. 2073220A discloses a catalyst system for RIM polyurethane elastomers which comprises dimorpholinodiethylether, dibutyltin dilaurate and an alkyl tin mercaptide. This catalyst combination imparts superior processing characteristics to RIM polyurethane elastomer systems, but, we have since discovered that the use of dimorpholinodiethylether, while advantageous in many RIM systems, interferes in the cure of certain important paint systems known as high solids enamel paints. We have discovered that by use of a reactive amine catalyst, which is tied up in the polymer network by reactions, the processing benefits already described in the above mentioned patent application are retained, and the RIM part can be painted using the high solids enamel paint systems.

We have now discovered that the use of polymeric amines as urethane catalysts has the advantage over reactive amines of not interfering in the urethane network. Also, they are not significantly incorporated into the polymer network since they are substantially free of active hydrogens. Thus these catalysts do not substantially interfere with the properties of the urethane polymer and do not migrate from the finished urethane product because of their high molecular weight, as is the case for low molecular weight unreactive amine catalysts.

A general discussion of catalysis by soluble polymers is set out in The British Polymer Journal, 12, 70 (1980) by D. C. Sherrington.

This invention provides a catalyst composition for polyurethane formation which comprises a tertiary amine-containing polymer substantially without active hydrogen atoms dissolved or suspended in a liquid which is a reactive component for polyurethane formation.

This invention also provides a method for making reaction injection moulded polyurethane of improved processing characteristics and properties by injecting an aromatic polyisocyanate, a polyol having an equivalent weight of above 500, a chain extending agent comprising a low molecular weight active hydrogen-containing compound having a functionality and a catalyst system via a RIM machine into a mould cavity of the desired configuration, wherein the catalyst system comprises a tertiary amine-containing polymer substantially without active hydrogen atoms dissolved or suspended in a liquid which is a reactive component for polyurethane formation. The invention also provides the resulting RIM polyurethane composition.

In making RIM polyurethane elastomers, two streams are generally employed. One stream (the A-component) consists primarily of the polyisocyanate and the other stream (the Bcomponent) comprises the polyol, chain extenders, catalysts and other ingredients used to form the RIM elastomer. Although variations from this generalized procedure are acceptable in the preparation of the RIM polyurethane products, this description is given for information only to define which ingredients are being discussed below and how they relate to the A- and Bcomponents.

The polyols useful in the RIM elastomers of this invention include polyether polyols, polyester diols, triols or tetrols, having an equivalent weight of at least 500, and preferably at least 1 000, more preferably at least 3000. Those polyether polyols based on trihydric initiators having a molecular weight of at least 4000 are especially preferred. The polyethers may be prepared from alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide or mixtures of propylene oxide, butylene oxide and/or ethylene oxide. In order to achieve the rapid reaction rates which are normally required for moulding RIM polyurethane elastomers, it is preferable that the polyol be capped with enough ethylene oxide to increase the reaction rate of the polyurethane mixture.Normally at least 50% primary hydroxyl is preferred, although amounts of primary hydroxyl less than this are acceptable if the reaction rate is rapid enough to be useful in industrial application. Other high molecular weight polyols which may be useful in this invention are polyesters or hydroxyl-terminated rubbers (such as hydroxyl-terminated polybutadiene).

Hydroxyl-terminated quasi-prepolymers of polyols and isocyanates are also useful in this invention.

The chain-extenders useful in this invention are preferably difunctional. Mixtures of difunctional and trifunctional chain-extenders are also useful. Suitable chain-extenders include diols, amino alcohols, diamines or mixtures thereof. Low molecular weight linear diols such as 1,4butanediol and ethylene glycol have been found very suitable for use in this invention. Ethylene glycol is especially preferred. Other chain-extenders, including cyclic diols such as 1,4cyclohexane diol and ring containing diols such as bishydroxyethylhydroquinone, amide or ester containing diols or amino alcohols, aromatic diamines and aliphatic amines would also be suitable as chain-extenders in the practice of this invention.

The crosslinkers useful in this invention are those known in the art and have a functionality of 3 or greater. These compounds include glycerine, trimethylolpropane, and 1,2,6-hexane triol.

One skilled in the art will readily see other crosslinkers which would have value as needed.

A wide variety of aromatic polyisocyanates may be used according to this invention. Typical aromatic poiyisocyanates include p-phenylene diisocyanate, polymethylene polyphenylisocyanates, 2,6-toluene diisocyanate, dianisidine diisocyanate, bitolylene diisocyanate, naphthalene 1 , 4-diisocyanate, bis(4-isocyanatophenyl) methane, bis(3-methyl-3-isocyanatophenyl)methane, bis(3-methyl-4-isocyanatophenyl)methane, and 4,4'-diphenylpropane diisocyanate.

Other aromatic polyisocyanates used in the practice of the invention are methylene-bridged polyphenyl polyisocyanate mixtures which have a functionality of from 2 to 4. These latter isocyanate compounds are generally produced by the phosgenation of corresponding methylenebridged polyphenyl polyamines, which are conventionally produced by the reaction of formaldehyde and primary aromatic amines, such as aniline, in the presence of hydrochloric acid and/or other acidic catalysts. Known processes for preparing polyamines and corresponding methylene-bridged polyphenyl polyisocyanates therefrom are described in the literature and in many patents, for example, U.S. Patents No. 2,683,730; 2,950,263; 3,012,008; 3.344,162 and 3,362,979.

Usually methylene-bridged polyphenyl polyisocyanate mixtures contain 20 to 100 weight % of methylene diphenyldiisocyanate isomers, with any remainder being polymethylene polyphenyl diisocyanates having higher functionalities and higher molecular weights. Typical of these are polyphenyl polyisocyanate mixtures containing 20 to 100 weight % of methylene diphenyldiisocyanate isomers, of which 20 to 95 weight % thereof is the 4,4'-isomer, with the remainder being polymethylene polyphenyl polyisocyanates cyanates of higher molecular weight and functionality that have an average functionality of from 2.1 to 3.5. These isocyanate mixtures are known, commercially-available materials and can be prepared by the process described in U.S. Patent No. 3,362,979.

By far the most preferred aromatic polyisocyanate is methylene bis(4-phenylisocyanate) or MDI. This can be employed in the form of pure MDI, quasi-prepolymers of MDI or modified pure MDI. Materials of this type may be used to prepare suitable RIM elastomers. Since pure MDI is a solid and, thus, often inconvenient to use, liquid products based on MDI are often used and are included in the scope of the terms MDI or methylene bis(4-phenylisocyanate) used herein. U.S. Patent No. 3,394,164 discloses an example of a liquid MDI product. More generally uretonimine-modified pure MDI is included also. This product is made by heating pure distilled MDI in the presence of a catalyst.The liquid product is a mixture of pure MDI and modified MDI:

2COCN OOCH2 -NCOJ 1 Catiilyst OCN\CH2ON=C=N C\ CH2O-NCO CH2&commat;N=C-N eQ CH2O-NCO + Co2 Carbodiimide OCNOOCH2 N-C=N Go CH2QONCO 1I O=C-N Go CH2GONCO Urebonimine Examples of commercial materials of this type are Upjohn's ISONATE 1 25M (pure MDI) and ISONATE 1 43L ("liquid" MDI). Preferably the amount of isocyanate used is the stoichiometric amount, based on all the ingredients in the formulation, or greater than the stoichiometric amount.

It has been found that an improvement in the processing characteristics of reaction injection moulded (RIM) polyurethanes using a combination of ingredients chosen from those enumerated above may be had by employment of the particular catalysts according to the present invention.

Our catalysts are polymers containing tertiary amine moieties. In one general embodiment, the following monomers can be polymerized to make the catalysts of our invention.

R, CH2 = CCOYRao wherein R1 is H or CH3, R10 is any tertiary amino containing group with a pKa in water of at least 7.5, and Y is -O- or -NH-. One group of such compounds has the formula: (R1) CH2 = CC0YC(R2R3)rn(CR4R5)nCR6R7NR8R9 wherein Y = -O- or -NH-, R, = h or CH3, R2-R7 independently = H, CH3, or alkyl, m =0-1, n = 0-6, and R8 and R9 independently = CH3, or alkyl; or together with the nitrogen atom to which they are attached, form a N-containing heterocyclic group.

In a particularly preferred embodiment the monomer is N-(3-Dimethylaminopropyl)methacrylamide.

In another embodiment of our invention, polyvinyl pyridines, e.g. polymers of 2-vinylpyridine or 4-vinyl-pyridine may also be used as urethane catalysts. Substituted vinyl pyridines may also be used as monomers.

Co-polymers of the above mentioned amine-containing monomers (acrylates, acrylamides and vinyl pyridines) with non-tertiary amine containing monomers are also useful as urethane catalysts. Comonomers such as styrene, alkyl(meth)acrylates, acrylamide, alkyl(meth)acrylamides, olefins, diolefins such as butadiene, vinyl acetate, acrylonitrile, and substantially any other chemically unreactive vinyl monomers are suitable to form polymers which are urethane catalysts. The amounts of comonomer may be from 1 to 90% by weight in the copolymer. The amounts are governed by the desired polymer properties and by the monomer reactivity ratios.

The polymers may be preformed, then dissolved or suspended in one of the pre-urethane components (isocyanate, or polyol or chain extender), or the polymers may be formed in one of the two general components, preferably the B-component.

The tertiary amine-containing monomers can also be polymerized in many other solvents such as water, alcohols, ketones, ethers or hydrocarbons. To use the resulting polymers as catalysts for the formation of polyurethanes, the polymers must be then dissolved in one of the polyurethane-precursor components, usually the B-component as mentioned above. Many solvents will interfere with the formation of polyurethanes, so solvent removal from the aminecontaining polymer would be necessary before its use as a urethane catalyst.

To avoid the use of undesired solvents, urethane precursors or precursor components are preferably used as solvents for the preparation of the polymeric tertiary amine containing urethane catalyst described herein. Preferably, the polyol, crosslinker or chain extender to be used in the desired urethane formulation is selected for the polymerization solvent, thus avoiding the need to eliminate the solvent, before use of the catalyst.

The tertiary amine-containing polymers used according to our invention are substantially free of active hydrogen atoms, but may have a small amount of grafted active hydrogen atoms if formed in a liquid containing active hydrogen atoms such as a polyol, crosslinker or chain extender. Thus, they are referred to as being substantially without active hydrogens.

The tertiary amine-containing polymers are prepared by polymerization, preferably radical polymerization.

In a preferred embodiment of our invention, the tertiary amine polymer catalyst is used in a combination with other catalysts.

This combination comprises generally the polymer containing-tertiary amine groups, a fast gelation organo tin catalyst and a delayed action gelation organo tin catalyst. A delayed action catalyst begins catalytic activity after a period of time has passed after mixing with the reactants.

This particular combination of catalyst types results in valuable processing improvements including excellent flow properties in the mould, a minimum of surface defects due to shrinkage, and excellent green strength. This has been difficult to achieve by prior art catalyst systems especially in the high flex modulus elastomers (5600 Kg/cm2 and above). Although several amine and tin catalysts may be used in combination to perform the particular function sought here, it is particularly preferred that the polymer containing tertiary amine groups be combined with dibutyltin dilaurate as the fast gelation tin catalyst, and an alkyltin mercaptide as the delayed action gelation tin catalyst. This alkyltin mercaptide may preferably be the commercial product known as FOMREZ UL-29.

The RIM formulation includes a great number of other recognized ingredients, such as additional cross-linkers, catalysts, extenders, and blowing agents. Blowing agents may include halogenated low-boiling hydrocarbons, such as trichloromonofluoromethane and methylene chloride, carbon dioxide and nitrogen.

Other conventional formulation ingredients may also be employed, for example, foam stabilizers, also known as silicone oils or emulsifiers. The foam stabilizer may be an organic silane or siloxane, for example, compounds having the formula: RSi[O-(r2SiO)n-(oxyalkylene)mR]3 wherein R is an alkyl group containing from 1 to 4 carbon atoms; n is from 4 to 8; m is from 20 to 40; and the oxyalkylene groups are derived from propylene oxide and ethylene oxide, see, for example, U.S. Patent No.3,194,773.

Although not essential for the practice of this invention, commonly known additives which enhance the colour or properties of the polyurethane elastomer may be used as desired. For example, chopped or milled glass fibers, chopped or milled carbon fibers and/or other mineral fibers are useful.

In a preferred embodiment of this invention, a high molecular weight polyether polyurethane polyol having a molecular weight of at least 5000 is combined with 4,4'-diphenylmethane diisocyanate (MDI) and allowed to react in the presence of a catalyst combination of a tertiary amine-containing polymer dissolved in ethylene glycol, dibutyltin dilaurate and an alkyltin mercaptide in a standard RIM machine using known processing techniques. In an especially preferred embodiment of this invention the moulded RIM part from just above is post-cured at a temperature of at least 120"C, preferably 1 60 to 165"C for one half of an hour. The invention may be exemplified by the following examples which are not intended to limit the scope of the invention.

GLOSSARY OF TERMS AND MATERIALS RIM-Reaction Injection Moulding.

PolyoI-A high molecular weight compound having at least two OH groups composed of ether groups, such as ethylene, propylene or butylene.

MDI-4,4' diphenylmethane diisocyanate.

ISONATE 1 43L-Pure MDI isocyanate modified so that it is a liquid at temperatures where MDI crystallizes-(product of the Upjohn Co.) THANOL SF-S 505-A 5500 molecular weight polyether triol containing approximately 80% primary hydroxyl groups.

THANOL C-64-A blend of ethylene glycol and PLURONIC F-98.

THANCAT DMDEE-Dimorpholinodiethylether.

FOMREZ UL-29-A stannic diester of a thiol acid (an alkyltin mercaptide). The exact composition is unknown. (Product of Witco Chemical Co.) THANATE L55-0-A prepolymer of THANOL SF-5505 and ISONATE 143L.

DMAPMA-N-(3-Dimethylaminopropyl)methacrylamide.

VAZO 52-2,2'-azobis(2,4-dimethylvaleronitrile EXAMPLE 1 A polymerization kettle was charged with 1009 of N-(3-Dimethylaminopropyl)methacrylamide (DMAPMA) monomer and 0.5g of VAZO 52 (initiator). This was stirred magnetically until solution was achieved. Then 400 9 of ethylene glycol was added. Nitrogen was bubbled through the solution for one hour while stirring, then a heating bath was raised to immerse the reactor. The solution was heated at 55"C for 4.2 hours, and during this time a mild exotherm to 58"C was observed.

Liquid chromatography by the reverse phase ion-pair method showed that 96.5% of the monomer was converted into polymer. The viscosity of a 0.5% active solution of the polymer in water was 1.5 cp as measured by a vibrating sphere viscometer (Nameter Mod. 7.006PB viscometer).

EXAMPLE 2 DMAPMA (15009) and VAZO 52 (7.59) were combined and stirred until solution was achieved.

Then 50009 of ethylene glycol was added and the solution was purged with nitrogen for 1.5 hours. The sealed kettle was then heated as follows: 50'C-1 hour 60'C-1.5 hour 55'C-1.5 hour 65"C-0.5 hour The conversion was determined as above as 92%. A 3% active solution of polymer in ethylene glycol had a viscosity of 102 cp at 25"C as measured by a vibrating viscometer.

EXAMPLE 3 A preparation similar to Example 2 was made with the following ingredients: 11 25g DMAPMA 7.5g VAZO 52 3500g Ethylene glycol 1.0g Ethylenediamine tetraacetic acid, disodium salt, dihydrate Heating was conducted according to the following schedule: 50'C-3 hours 60'C-2 hours 55'C-2 hours 80'C-1 hour Conversion was 96.7%.

The viscosity at 38"C was 82,600 cs as measured by the capillary viscometer.

EXAMPLE 4 THANOL SF-5505 (16 pbw), THANOL C-64 (5.83 pbw), dibutyltin dilaurate (0.015 pbw), FOMREZ UL-29 (0.025 pbw) and polymeric amine/ethylene glycol master batch (1.00 pbw) were premixed and charged into the B-component working tank of an Accuratio VR-100 reaction injection moulding machine. The material designated polymeric amine/ethylene glycol is a 20% by weight master batch of a high molecular weight polymer in ethylene glycol prepared as in Example 2. Thus, 0.2 pbw of the polymeric amine catalyst and 0.8 pbw of ethylene glycol compose the 1.00 pbw of the master batch. ISONATE 1 43L (29.83 pbw) and THANATE L55-0 quasi prepolymer (5.78 pbw) were premixed and charged in the A-component working tank.

The A-component temperature was adjusted to 27"C and the B-component temperature was adjusted to 43"C. The machine was then calibrated to deliver the exact weight ratio described above which represents an isocyanate to hydroxyl equivalent ratio of 1.02. The ingredients were impingement mixed at 1 55 to 1 50 Kg/cm2 impingement pressure on each stream and injected into a steel mould at 77"C. The mould is made to deliver plaques which are 45.7 X 45.7 X 0.32 cm. A three second shot gave parts which have an overall density of about 1025 Kg/m3. Plaques of this material were postcured at 163"C for 30 minutes and submitted for paintability studies. The materials were painted with high solids enamel paint systems as described below.The paint tests were favourable. When a similar system, differing only in that the 0.2 pbw of polymeric amine catalyst is replaced by 0.25 pbw THANCAT DMDEE, another amine catalyst, the resulting materials fail when tested for paintability by high solids enamel paint systems.

Paint Testing for RIM Polyurethane Elastomers A 10.2 X 30.5 x 0.32 cm. sample of RIM polyurethane is first washed thoroughly to eliminate all the mould release agent on the surface. Even small amounts of mould release agent will interfere with the adhesion of the paint film to the substrate. After washing and drying, the samples are then painted. The paint systems most important in reinforced RIM are presently the so-called "high solids" enamel paints. When RIM elastomers containing THANCAT DMDEE, an unreactive tertiary amine catalyst, are painted with PPG 430 high solids enamel paint system, interference with paint cure and adhesion failure are observed. When polymeric DMAPMA as described herein is used, the above mentioned problems do not occur.

Claims (24)

1. A catalyst composition for polyurethane formation which comprises a tertiary aminecontaining polymer substantially without active hydrogen atoms dissolved or suspended in a liquid which is a reactive component for polyurethane formation.

2. A catalyst composition as claimed in Claim 1 wherein the polymer is made from a monomer having the formula

wherein R1 is H or CH3, R10 is any tertiary amino containing group with a pKa in water of at least 7.5, and Y is -O- or -NH-.

3. A catalyst composition as claimed in Claim 1 wherein the polymer is made from a monomer having the formula

wherein Y = -O- or -NH-, R, = H or CH3, R2-R7 independently = H, CH3, or alkyl, m = 0-1, n = 0-6, and R8 and R9 independently = CH3, or alkyl, or together with the nitrogen atom to which they are attached form a N-containing heterocyclic group.

4. A catalyst composition as claimed in Claim 1 wherein the polymer is made from N-(3 Dimethylaminopropyl) methacrylamide.

5. A catalyst composition as claimed in any preceding Claim which additionally comprises a fast gelation organo tin catalyst and a delayed action organo tin catalyst.

6. A catalyst composition as claimed in Claim 5 wherein the fast gelation organo tin catalyst is dibutyl tin dilaurate.

7. A catalyst composition as claimed in Claim 5 or 6 wherein the delayed action organo tin catalyst is an alkyl tin mercaptide.

8. A method for making a polyurethane-formation catalyst composition according to any of the preceding Claims which method comprises polymerizing a tertiary amine-containing monomer substantailly without active hydrogen atoms in the liquid which is a component of the polyurethane reaction.

9. A method as claimed in Claim 8 wherein the liquid is the polyol, the chain extender, or the cross-linker.

1 0. A method for making a polyurethane elastomer by injecting an aromatic polyisocyanate, a polyol having an equivalent weight of about 500, a chain extending agent comprising a low molecular weight active hydrogen-containing compound having a functionality of at least 2, and a catalyst system via a RIM machine into a mould cavity of the desired configuration, wherein the catalyst system comprises a tertiary amine-containing polymer substantially without active hydrogen.

11. A method as claimed in Claim 10, wherein the polyol comprises a polyether having a molecular weight of about 5000 based on a trihydric initiator.

1 2. A method as claimed in Claim 10 or 11 wherein the polyisocyanate comprises 4,4'diphenylmethane diisocyanate.

1 3. A method as claimed in any of Claims 10 to 1 2 wherein the elastomer is post-cured at a temperature of at least 1 20"C.

1 4. A method as claimed in any of Claims 10 to 13, wherein the polymer is dissolved or suspended in a liquid which is a reactive component for polyurethane formations.

1 5. A method as claimed in any of Claims 10 to 14, wherein the polymer is made from a monomer having the formula

wherein R, is H or CH3 , R10 is any tertiary amino containing group with a pKa in water of at least 7.5, and Y is -O- or -NH-.

1 6. A method as claimed in any of Claims 10 to 1 4 wherein the polymer is made from a monomer having the formula

wherein Y = -O- or -NH-, R, = H or CH3, R2-R7 independently = H, CH, or alkyl, m=0-1, n = 0-6, and R8 and R9 independently = CH3, or alkyl, or together with the nitrogen atom to which they are attached form a N-containing heterocyclic group.

1 7. A method as claimed in any of Claims 10 to 14, wherein the polymer is made from N (3-Dimethyl-aminopropyl) methacrylamide.

1 8. A method as claimed in any of Claims 10 to 1 7 wherein the catalyst composition additionally comprises a fast gelation organo tin catalyst and a delayed action organo tin catalyst.

1 9. A method as claimed in Claim 1 8 wherein the fast gelation organo tin catalyst is dibutyl tin dilaurate.

20. A method as claimed in Claim 1 8 or 1 9 wherein the delayed action organo tin catalyst is an alkyl tin mercaptide.

21. A polyurethane elastomer when made by a method according to any of Claims 10 to 20.

22. A catalyst composition as claimed in Claim 1 and substantially as hereinbefore described with reference to any of Examples 1 to 3.

23. A method as claimed in Claim 8 and substantially as hereinbefore described with reference to any of Examples 1 to 3.

24. A method as claimed in Claim 10 and substantially as hereinbefore described with reference to Example 4.