GB2226565A - The preparation of temperature activated catalysts - Google Patents

Abstract

A polymeric catalyst or accelerator, capable of enhancing reaction rate in the case of liquid polymer cures, is made from a precursor polymer or copolymer with a suitable coreagent and is obtained directly by the reaction of the precursor polymer or copolymer and the said coreagent in conventional polymer processing equipment, the precursor polymer or copolymer providing the principal medium for reaction. In the examples, various polymers functionalised with carboxylic acid or hydroxyl groups are reacted with cobalt acetate, N; N-dimethylaniline or bis(tributyltin)oxide in roll mills, cavity transfer mixers or extruders.

Description

IMPROVEMENT IN OR RELATING TO THE PREPARATION OF TEMPERATURE ACTIVATED CATALYSTS In United Kingdom Patent Application No. 8729069 filed 12th December, 1987, there is disclosed an invention relating to the preparation and use of temperature activated catalysts.

The said invention relates to catalysts which control the dependence of reaction rate on temperature in the case of liquid polymer cures and provide the means of doing so over a pre-determined temperature range.

The preparation of the catalysts referred to in the said patent a pplication is characterised in that the catalyst for the cure is mounted on a polymer which is phase separated from the reacting polymer phase. Binding the catalyst into a glassy polymer phase provides catalysis with marked temperature-dependent characteristics. It has also been found that with a phase-separated catalyst, high activity is obtained if the catalyst-supporting polymer is mobile or rubbery.

The process of mounting the catalyst on to the polymer is conventionally carried out by dissolving the polymer in a suitable solvent system and then adding the co-reagent as in the said U.K. Patent Application No. 8729069 . The solvent is then removed in order to obtain the reaction product in solid form. To accomplish this synthesis,the solvent is normally present in substantial amounts to ensure a low viscosity reaction medium amenable to being handled in conventional reactors. Other approaches to the synthesis of linear polymeric catalysts have attempted to dispense with such solvents by functionalising only polymers of lower molecular weight which are themselves free-flowing liquids, as in United Kingdom Patent Application No.8320904 filed 3rd August 1983.

We have now found that useful polymer catalysts having similar properties to the catalysts described in the said United Kingdom Patent Application may be prepared by direct reaction using conventional polymer processing equipment, the precursor polymer providing the principal medium for reaction. This enables catalyst preparation to be effected by processes which are essentially solvent-free and which require no subsequent separation steps.

According to the present invention, there is provided a process for the preparation of a polymeric catalyst or accelerator being capable of enhancing reaction rate in the case of liquid polymer cures. In this process the catalyst or accelerator is made from a precursor polymer or copolymer of two or more monomers with a suitable coreagent, the catalyst or accelerator being obtained directly from the polymer or copolymer and the said coreagent in conventional polymer processing equipment, the precursor polymer or copolymer providing the principal medium for reaction.

Examples 1 and 2 show how this may be accomplished, the precursor polymer being an ethylene acrylic copolymer bearing a proportion of acidic groupings, and the co-reagent being an appropriate metal compound. In Example 1 the co-reagent in cobalt acetate and the execution of reaction on a heated two-roll mill allows for a rapid reaction with release of volatile byproducts (acetic acid) as the reaction proceeds. The speed of reaction is illustrated with reference to the observation that a strong odour of acetic acid is confined to only the period of incorporation of cobalt acetate and the first half-minute thereafter. The product obtained is a bluish-purple rubber.

Example 2 covers a reaction of the same polymer type used in Example 1 but with an organometallic coreagent, bis(tributyltin oxide). This reaction is also accomplished on a heated two-roll mill with concurrent volatilisation of by-products (water vapour) as the only separation process.

In this case the product is a colourless translucent rubber which shows an absorption in the infra red characteristic of metal carboxylate groups.

It may be seen from these, that with an appropriate combination of polymer and co-reagent catalytic polymers may be conveniently and rapidly obtained in melt phase reactions which can be accomplished in conventional polymer processing equipment.

Whilst such equipment might be expected to include: two-roll mills, internal mixers, calenders, etc., we have also discovered that continuous processing equipment may also be applied to catalyst manufacture. Such equipment includes: single and twin-screw extruders and the Cavity Transfer Mixer (CTM). Indeed we have found the CTM to be an especially effective melt reactor. Example 3 shows how a linear polystyrene copolymer can be converted to an organotin derivative by continuous reaction within a CTM. At least 70% conversion, as determined by infra-red spectral analysis, is achieved in the reactions of this example at a throughput of around 1 kg per hour. Figure 1 shows a CTM in which the total volume of the cavities when assembled has been measured at 53.2 cm3.On this basis it will be seen that the conversion of greater than 70% has been achieved with a mean residence time within the CTM of around 3 minutes (the density of the polystyreneallyl alcohol is reported to be 1.055 g cm3 at ambient temperature; a value which might be expected to fall by about 3% over the temperature range up to 140"C if the behaviour mirrors that of polystyrene homopolymer).

Whilst this illustrates the effectiveness of a CTM for catalyst manufacture, the process of this invention is not limited to this particular CTM or to CTM's of this configuration or size.

The products C-E of this reaction are milky-white glasses when cooled: these can be powdered to provide useful catalysis of a polyurethane cure (Example 4). In this case the powdered catalytic polymer is simply dispersed in the polyurethane-forming mix, in the conventional manner for incorporating other solid additives.

A similar configuration of equipment can be used to prepare an organotin carboxylate of an elastomer, in Example 5 the starting polymer is carboxylated nitrile rubber. Such a product is also a catalyst for a polyurethane cure as illustrated in Example 6 where the polyurethane is cured in contact with a continuous layer of the organotin rubber.

Catalysis from a surface in this manner offers scope for the exploitation in a diverse range of processes from surface coating (e.g. with a catalytic primer coat) to adhesion, laminating, co-extrusion or blending.

A somewhat different procedure has been adapted for the manufacture of a glassy cobalt catalyst. In this case both the polymer and reagent are introduced at the extruder hopper. Example 7 describes the production of cobalt carboxylate functional polymers at two different cobalt loadings (Catalysts K and L). That these cobalt salt polymers are catalysts is demonstrated for the unsaturated polyester cures in Example 8. In this example the catalysts are introduced as powders although they may also be introduced as a coating following the approach described for the polyurethane catalysis in Example 6. It will be seen from this there is the opportunity to catalyse the resin cure from coating on an appropriate reinforcing matrix if required: the catalysis of such cure from coated glass fibres was described in UK Application No.8320904.

The mode of action of such catalysts is not specified: they may participate advantageously in any stage of the cure.

Catalysts such as the cobalt salt described above will be recognised as catalysts for initiation of cure (hydroperoxide decomposition). Any redox catalyst such as selected ions of metals in the first transition series may be used in such a role, and their polymeric salts will be amenable to preparation by the process of this invention.

Polymeric metal salts can also enhance the rates of other curing reactions such as polyurethane or epoxy cures and these also will be amenable to preparation by the process of this invention. Catalytic polymers containing a diverse range of metal types were described in UK Application No.

8320904.

That same patent application described the use of catalytic polymers which are soluble in the curing formulation. The approach described in this current application may also be employed for these. Thus Example 9 describes the preparation of a catalytic or accelerating polymer which can be dissolved in an unsaturated polyester resin mix (Example 10). Whilst this polymer was produced in a CTM in a manner similar to other preparations of this invention, this example differed from previous materials described in that it was not a metal compound. The product of Example 9 is an amino derivative of a polymer illustrating that this invention is applicable to a wide range of polymer types which may be usefully exploited to catalyse or accelerate polymer cures.

Thus it will be seen that the processes of this invention can produce polymers which are rubbery or glassy and which may exploit for activity: metal salt, organometallic or organonitrogen groupings.

The various examples indicate the processes of this invention are generally applicable, operating on suitably functionalised polymers or copolymers of two or more monomers. Amongst the examples listed are copolymers derived from various combinations of monomers selected from ethylene, acrylic, styrene,allylic and diene types, but this range in no way limits the scope of the invention. Any polymer amenable to processing in the equipment described can be regarded as amenable to treatment by the process of this invention. Even polymers not hitherto functional can be included if they are amenable to functionalisation as a first stage operation.

The processes of this invention have been shown to produce catalysts of similar character to those described in two earlier patent applications (UK Appl. Nos. 8320904 and 8729069) and those familiar with these applications and skilled in the art of curing technologies will recognise the range of systems to which they can be usefully applied.

Example 1 A two roll mill was preheated to 1500C. An ethylene acrylic copolymer bearing a proportion of carboxylic acid groupings, (Vamac G, Du Pont; 300 g) was banded onto this mill and then cobalt(II) acetate, tetrahydrate (6.0 g) was added over a period of 2 minutes. The cobalt(II) compound was easily dispersed and dissolved into the rubber, on the 2 roll mill. A strong smell of acetic acid was noticed as the cobalt(II) acetate was being mixed into the rubber.

The smell diminished about 30 seconds after the cobalt(II) acetate had been added. The reaction mixture was worked on the mill for 20 minutes. The product (Catalyst A) was a bluish-purple rubber which was soluble in toluene.

Example 2 An ethylene-acrylic copolymer, bearing a proportion of carboxylic acid groupings (Vamac G, 300 g), was banded onto a two roll mill which had been preheated to 1500C.

Bis(tributyltin)oxide (15.0 g) was added to the copolymer in aliquots of approximately 1 ml in volume. Each aliquot required about 10 seconds to become mixed into the copolymer. All the bis(tributyltin)oxide was added and mixed into the copolymer over a period of 5 minutes. The reaction mixture was worked on the mill for 20 minutes.

The product was a colourless, translucent rubber. Infrared analysis of this product (Catalyst B) indicates the presence of carboxylate groups, such groupings are not present in the starting materials.

Example 3 The assembly used is that of a CTM attached onto an extruder. The polymer poly(styrene-allyl alcohol)(RJ100, Monsanto), is metered into the extruder using a vibrating tray feeder. The vibrating tray feeder can be replaced by an extruder or any other metering device. The liquid reactant (bis(tributyltin)oxide) is introduced upstream of the CTM using a plunger pump.

Since the poly(styrene-allyl alcohol) was available in irregularly sized granules, it was ground into a fine powder using a granulator (Christy Norris granulator). This was then fed into an extruder (1 inch) using a vibrating tray feeder.

Although the CTM used has 55 Cavities (Figure 1), other CTMs could also be as effective when used as reactors.

Table 1 describes the feed rates of the starting materials poly(styrene-allyl alcohol) and bis(tributyltin)oxide and the process settings used in the preparation of catalysts C-E. The properties of the products, which were all milky white glassy solids, are also described.

Table 1: Preparation of Catalysts C-E Catalyst C D E Poly(styrene-allyl alcohol) 900 910 Feed rates (g/hr) Bis(tributyltin)oxide 110 90 120 Catalyst C - - 1300 CTh rotational speed (rpm} 90 90 90 Extruder Temperature (OC) 120 120 120 Process settings CTM Temperature (OC) 120 150 120 Process pressure at injection port (psi) 32 32 29 Injection pressure (psi) 150 150 150 Extrudate Temperature (OC) 110-115 138 116 Expected Sn content 0.038 0.030 0.056 Product properties (mol Sn/100 g) Amount of Sn reacted with poly 0.029 0.022 0.048 (styrene-allyl)alcohol2 (mol Sn/100 g) Extent of reaction 76% 73% 87% Notes to Table 1 1.Catalyst E was prepared by reacting Catalyst C with bis(tributyltin)oxide, in order to obtain a catalyst with a higher Sn content.

2. The extent of reaction was assessed by measuring the reduction in the absorption in the infra-red caused by the hydroxyl groups of the poly(styrene-allyl alcohol).

This was done using a Nicolet 5DX Fourier Transform Infra-Red Spectrophotometer.

Example 4 Portions of Catalysts C-E were ground to fine powders in a pestle and mortar. These powders were then incorporated into the polyurethane formulations described in Table 2.

The cure of these formulations, at ambient and elevated temperatures, were monitored using the Vibrating Needle Curemeter (VNC), (European Adhesives and Sealants, September 1987, p.28). The traces obtained, shown in Figures 2-4, clearly indicate the catalytic activity of Catalyst C - E in this type of formulation.

Table 2: Polyurethane formulations containing Catalysts C-E Diorez 520 Hyperlast 000 Catalyst Sn content Figure (MDI) 100 parts 15.4 parts None - 2-4 100 parts 15.4 parts C 0.36% 2 10 parts 100 parts 15.4 parts D 0.15% 3 5 parts 100 parts 15.4 parts E 0.28% 4 5 parts Thus it will be seen that the present invention provides a method for the preparation of temperature activated catalysts which control the dependence of reaction rate on temperature in the case of liquid polymer cures.

Example 5 The assembly used is that of Example 3, except that the polymer is metered into the extruder using a Colormax hopper. The liquid reagent (bis(tributyltin)oxide) is introduced upstream of the CTM using a plunger pump.

The polymer used was carboxylated nitrile rubber (Krynac 221, Polysar) which had been chilled and then granulated using a Burtonwood Cumberland plastics granulating machine.

Table 3 describes the feed rates of the raw materials and the process settings used in the preparation of catalysts F-H.

Table 3: Preparation of Catalysts F-H Catalyst F G H Feed rates (g/hr) Carboxylated nitrile rubber 1255 1045 940 bis (tributyltin) oxide 50 270 122 CTN rotational speed (rpm) 87 87 87 Extruder temperature (OC) 90 90 90 Cm temperature (OC) 120 120 120 Injection pressure (psi) 500 500 500 Temperature upstream of Cm (OC) 97 97 97 Extrudate temperature ( C) 121 121 121 Expected tin content (mol Sn/100 g) 0.0128 0.0688 0.0386 Amount of Sn reacted with poly (styrene allyl) alcohol (Mol Sn/100 g) 0.0115 0.0598 0.0387 Extent of reaction 90% 87% 100% Example 6 A portion of Catalyst H was cast as a film from a solution in dichloromethane onto a metal plate.

A polyurethane formulation was prepared by dissolving 5.46 g of polycaprolactone diol (MW 2000) and 0.84 g of Hyperlast Isocyanate 2875/000 (a polymeric MDI of equivalent weight 140), in dichloromethane. A film of this PU formulation was cast onto the previous film of Catalyst H and the solvent allowed to evaporate off. A similar PU film was cast onto a metal plate. The two films were put in an oven at 600C and their gel times observed. The PU film cast on Catalyst H gelled after 27 minutes, and that cast on the metal plate only gelled after 60 minutes.

Example 7 In the first stage of this process, poly(styrene allyl alcohol) and succinic anhydride were reacted together. The poly(styrene allyl alcohol) (RJ100) was granulated in a Burtonwood Cumberland plastics granulating machine; succinic anhydride was granulated in a Glen Creston granulator.

The mixture of the composition mentioned in Table 4, is introduced into the CTM extruder assembly as described in Example 5. The product from this experimental run was coded I and was seen from its infra-red spectrum to contain residual anhydride. A portion of this product I was put back into the assembly. The second product obtained was coded J and its infra-red spectrum shows that the reaction between succinic anhydride and poly(styrene allyl alcohol) was substantially complete.

The process conditions used to make products I and J are described in Table 4.

Table 4: Manufacture of the intermediate products I and J Product Code I J The mixture introduced poly(styrene allyl alcohol) 100 succinic anhydride 31.7 Extruder set temperature 1100C 1100C CTM set temperature 1100C 1300C Temperature upstream of CTM 1000C 1060C Extruder speed of rotation 60 rpm 60 rpm CTM speed of rotation 60 rpm 60 rpm In the second stage of this process the products I and J are derivatised with cobalt acetate. The equipment layout was as used for the first stage.

Table 5 describes the ratios of the reactants used for the reaction and the process settings used in the preparation of catalyst K.

Table 5: The manufacture of the Catalyst K Catalyst K Product I 100 parts Cobalt acetate tetrahydrate 63 parts Extruder speed 61 rpm CTM speed of rotation 61 rpm CTM set temperature 1100C Extruder set temperature 1300C Temperature upstream of CTM 1060C Table 6 describes the ratios of the reactants used for the reaction and the process settings used in the preparation of catalyst L.

Table 6: The manufacture of the Catalyst L Catalyst L Product J 100 parts Cobalt acetate tetrahydrate 63 parts Extruder speed 61 rpm CTM speed of rotation 61 rpm CTM set temperature 1100C Extruder set temperature 1300C Temperature upstream of CTM 1060C Example 8 Catalysts K and L were powdered and incorporated into the following unsaturated polyester resin (Crystic D293, Scott Bader) formulation containing styrene and cumene hydroperoxide.

Crystic D293 50 parts Styrene 50 parts Cumene hydroperoxide 5 parts Catalyst K or Catalyst L 5 parts The formulations were cured at 600C and the following gel times were observed: Catalyst K 13 minutes Catalyst L 15 minutes No catalyst 1385 minutes This cure data clearly demonstrates that both these catalysts show high catalytic activity in this type of formulation.

Example 9 The assembly used is that of a CTM attached onto an extruder. The modified polymer K (Example 7) is metered into the extruder using a Colourmax hopper. This hopper can be replaced by an extruder or any other metering device.

The liquid reagent (NN-dimethylaniline) is introduced upstream of the CTM using a plunger pump. Since in this case, liquid injection was possible at such low injection pressures (due to the low viscosity of the reaction mixture), other metering pumps could be used in place of the plunger pump. The product obtained was coded M.

In this experiment, the 55L CTM was used; however, other CTMs could also be used.

Table 7 shows the process conditions used to manufacture the accelerator coded M.

Table 7: Preparation of Accelerator M Accelerator M Feed rates Product K 605 g/hr NN-dimethylaniline 119 g/hr Process conditions Extruder speed of rotation 80 rpm CTM speed of rotation 80 rpm The extruder set temperature 1100C The CTM set temperature 1000C The temperature upstream of CTM 1000C The injection pressure 100 psi Product properties The extrudate temperature 800C Example 10 Catalyst M was incorporated into the following unsaturated polyester resin (Crystic D293, Scott Bader) formulation containing styrene and dibenzoyl peroxide: Crystic D293 50 parts Styrene 50 parts Dibenzoyl peroxide 3 parts Catalyst N 5 parts The formulation was cured at room temperature and requires only 10 minutes to gel. A similar formulation free of catalyst required 320 minutes to gel at 600C, remaining uncured for 3 days at room temperature. This cure data clearly demonstrates that both these catalysts show high catalytic activity in this type of formulation.

Claims (13)

1. A process for the preparation of a polymeric catalyst or accelerator, said catalyst or accelerator being capable of enhancing reaction rate in the case of liquid polymer cures, said catalyst or accelerator being made from a precursor polymer or copolymer of two or more monomers with a suitable coreagent, in which the catalyst or accelerator is obtained directly from the precursor polymer or copolymer and the said coreagent in conventional polymer processing equipment, the precursor polymer or copolymer providing the principal medium for reaction.

2. A process as claimed in claim 1, in which the polymer processing equipment is selected from two-roll mills, internal mixers, calenders or continuous processing equipment.

3. A process as claimed in claim 2, in which the continuous processing equipment includes one or more extruders and a cavity transfer mixer.

4. A process as claimed in any preceding claim, in which the catalyst or accelerator is a metal salt or a compound having organo-metallic or organo nitrogen groupings.

5. A process as in claim 4 in which the catalyst is a redox catalyst prepared from a coreagent which is compound of a first transition series metal in a higher oxidation state.

6. A process as in claim 4 in which the catalyst is a polyurethane or silicone curing catalyst based on a compound of tin.

7. A process as in claim 4 in which the catalyst or accelerator is a salt, associated complex, or derivative of an amine.

8. A process as claimed in claim 4, in which the catalyst or accelerator is made from cobalt acetate, a cobalt carboxylate, bis(tributyltin) oxide or an amino compound.

9. A process as claimed in any preceding claims, in which the precursor copolymer is selected from copolymers of two or more monomers selected from ethylene, acrylic, styrene allylic and diene types.

10. A process as claimed in claims 1 - 8, in which the precursor polymer is selected from carboxylated nitrile rubber or carboxylated ethylene acrylic rubber.

11. A process as claimed in claims 1 - 8 in which the precursor polymer is polybtyrene-allvl alcohol) or functional derivative thereof.

12. A process as claimed in claims 1 - 8 in which the precursor polymer is a glass functionalised by carboxylic acid or hydroxyl groups.

13. A process for the preparation of a temperature activated polymeric catalyst as claimed in any preceding claim, substantially as hereinbefore described and exemplified.