WO2007122412A1

WO2007122412A1 - Process for the manufacture of a polymer composition

Info

Publication number: WO2007122412A1
Application number: PCT/GB2007/001508
Authority: WO
Inventors: Pierre-Rachel Tchale Deugoue; Martin Keith Partridge; Geoffrey Robert Mitchell; Wayne Cord Hayes; Howard Matthew Colquhoun
Original assignee: The University Of Reading
Priority date: 2006-04-25
Filing date: 2007-04-25
Publication date: 2007-11-01
Also published as: GB0708014D0; GB2437644B; GB2437644A; GB0608161D0

Abstract

The present invention relates to a process for manufacturing a polymer composition comprising an adsorbent solid entrained within a polymer matrix, the process comprising polymerising a molten monomer composition containing the adsorbent solid. The adsorbent solid may be a desiccant or an odour control solid. The polymer matrix is preferably nylon-6.

Description

Process for the Manufacture of a Polymer Composition

This invention relates to a process for the manufacture of a polymer composition. In particular, this invention relates to a process for the manufacture of a polymer composition comprising an adsorbent solid entrained in a polymer matrix.

Adsorbent solids such as desiccants or odour- controlling materials are widely used in numerous applications.

Desiccants are used to control moisture in various environments so as to avoid damage to moisture-sensitive products such as scientific/electronic » instruments, speciality chemicals or pharmaceuticals and leather goods. Desiccants are typically contained in discrete moisture-permeable packages and these packages are included within the packaging for the moisture-sensitive product e.g. in a jar of tablets, or in a shoe box, or within the housing of a scientific/electronic instrument. There are several problems with the use of these desiccant packages. Firstly, there have been instances where the packages have been consumed, for example, by children. Secondly, as the packages are unfixed, they may cause damage by their movement during transit of the product. This is of particular concern when the desiccant package is provided to control moisture in the housing of a scientific/electronic instrument.

Odour-controlling materials are known and are used to control unpleasant or toxic odours caused by volatile organic chemicals. For example, products formed of plastics material may emit unpleasant or toxic odours as a result of unpolymerised volatile monomer remaining within the plastic material. Similarly, volatile solvents may remain in chemical products and these solvents often smell unpleasant and/or are injurious to health.

It is known to provide a polymer composition comprising a solid desiccant such as a synthetic zeolite (type 4A) or silica gel (a hygroscopic material) . The polymer matrix in which the desiccant is dispersed may be a moisture-transmissive polymer or it may include a proportion of a moisture-transmissive channelling agent which forms channels within the polymer matrix through which moisture is communicable to the desiccant. An advantage of these polymer/desiccant compositions is that they can be formed into a desired shape and fixed in their location of use.

These polymer compositions are obtained by blending the desiccant/hygroscopic solid with the molten polymer (and optionally the molten channelling agent) .

One problem with the method used to obtain these known polymer compositions is that that the high viscosity of the molten polymer impedes homogenous distribution of the desiccant. The high viscosity also imposes a practical upper limit of desiccant/hygroscopic solid loading because at high loadings the inability to obtain sufficient mixing of the solid and molten polymer

(as a result of the high viscosity) leads to aggregation of the solid.

Furthermore, these methods require considerable energy expenditure in order to melt the polymer.

It is a preferred aim of the present invention to provide a process for producing a polymer composition comprising an adsorbent solid which allows facile homogenous distribution of the adsorbent solid, reduces aggregation of the adsorbent solid and reduces energy expenditure in forming/shaping the composite material. In a first aspect, the present invention provides a process for manufacturing a polymer composition comprising an adsorbent solid entrained within a polymer matrix, the process comprising polymerising a molten monomer composition containing the adsorbent solid.

By mixing the adsorbent solid with a molten monomer composition prior to polymerisation, it is possible to obtain a homogenous distribution and reduced aggregation of the adsorbent, solid within the molten monomer composition, even at high levels of solid adsorbent, and consequently within the resulting polymer matrix as a result of the lower viscosity of the molten monomer compared to the viscosity of the corresponding molten polymer. Furthermore, considerably less energy is required to shape or otherwise process the monomer composition than for the corresponding polymer composition as a result of its lower viscosity. Moreover, very much lower temperatures are required for the present process so that, for example, simultaneous moulding and polymerisation of ε-caprolactam-based compositions can be achieved at around 110-150⁰C, whereas compositions based on nylon-β (the corresponding polymer from this monomer) melt between 215-23O⁰C and can be processed only above around 25O⁰C. Preferably, the method involves heating the monomer composition to form the molten monomer composition and then adding the adsorbent solid to the molten monomer composition prior to polymerisation.

By adding the adsorbent solid to the molten monomer composition, it is possible (for example, by stirring, co-extrusion or some other form of mechanical blending) to thoroughly mix the adsorbent solid and molten monomer such that the distribution of the adsorbent solid in the resulting polymer matrix is essentially homogenous. Preferably, the process comprises polymerising the molten monomer composition containing the adsorbent solid by reaction moulding, for example by resin-transfer moulding, by vacuum casting and most preferably by reaction injection moulding (RIM) . This allows the process to yield the polymer composition in a desired, moulded/extruded shape suitable, for example, for attachment into the body of a scientific/electronic instrument or, for example, for lining a bottle or jar used to contain a pharmaceutical product.

Alternatively (or additionally) , the process may include machining the polymer composition to obtain an article of the desired shape.

Preferably the polymerisation of the molten monomer composition yields a water transmissive polymer matrix such as a polyamide (e.g. nylon-β) , a polyurethane, an epoxy resin, a phenolic resin or a vinylic polymer such as a polyacrylate or polymethacrylate copolymer. The water transmissive nature of the polymer matrix allows moisture vapour to penetrate the polymer matrix so as to be communicable with the adsorbent solid.

The monomer composition may comprise diisocyanate and polyol so that the resulting polymer matrix is a polyurethane. The monomer composition may comprise a phenol-formaldehyde condensate such as a resole so that the resulting polymer matrix is a phenolic resin. The monomer composition may comprise bis-epoxide and polyamine so that the resulting polymer matrix is an epoxy resin. The monomer composition may comprise a mixture of alkylmethacrylates such as methylmethacrylate and hydroxyethylmethacrylate so that the resulting polymer matrix is a polymethacrylate copolymer. The monomer composition may comprise 2-pyrollidone so that the resulting polymer matrix is nylon-4. The monomer composition may comprise δ-valerolactam so that the resulting polymer matrix is nylon-5. The monomer composition may comprise l-aza-2-cyclooctanone so that the resulting polymer matrix is nylon-7. Most preferably, the monomer composition comprises ε- caprolactam and the resulting polymer matrix is nylon-β. The monomer composition may contain two or more co- monomers selected from those listed above.

The polymerisation of the molten monomer composition may yield a porous polymer matrix (which may or may not be water transmissive) . This porosity assists penetration of the polymer matrix by the moisture/organic vapour thus increasing uptake of the moisture/organic vapour by the adsorbent solid. Most preferably, the polymerisation of the molten monomer composition yields a porous, water-transmissive polymer matrix such as porous nylon-6.

The porosity of the polymer matrix may be increased by adding a gas-generating compound/foaming agent to the molten monomer composition prior to polymerisation. The gas-generating compound may generate hydrogen (e.g. NaH which generates hydrogen by reaction with ε-caprolactam) , nitrogen, carbon dioxide, or a hydrocarbon gas (e.g. a low molecular weight (volatile) hydrocarbon such as pentane) . The gas generating compound/foaming agent may be added directly to the molten monomer composition e.g. NaH may be added to ε-caprolactam to generate the sodium salt and hydrogen prior to polymerisation. Alternatively or additionally, the gas-generating compound/foaming agent may be pre-adsorbed onto the adsorbing solid prior to addition of this solid to the monomer composition e.g. a volatile hydrocarbon such as pentane may be adsorbed onto the adsorbent solid. The dwell time, i.e. the amount of time after the addition of the gas-generating compound/foaming agent to the molten monomer composition and before polymerisation, should be minimised (e.g. between 2-5 minutes) to achieve maximum porosity in the resulting polymer matrix.

Alternatively, a thermally-activated foaming agent such as an azodicarbonamide (which decomposes only above ca. 15O⁰C generating nitrogen gas) may be included so that porosity is only generated (for example in the mould) once the molten monomer composition is raised to a polymerisation temperature which is above the decomposition temperature of the foaming agent.

Even when no gas-generating compound/foaming agent is added, a significant level of porosity can be achieved by minimising the dwell time between the addition of the adsorbent solid to the monomer composition and polymerisation. It is believed that such porosity arises from the expansion of air trapped in the adsorbent solid on contact with the molten monomer composition, resulting in foaming/porosity in the polymer matrix (provided that the trapped air is not allowed to disperse before polymerisation.)

The polymerisation of the molten monomer composition may yield a polymer matrix (which may or may not be water transmissive) containing interconnecting channels through which the vapour, e.g. moisture or volatile organic, is communicable with the adsorbent solid. The channels may be obtained by adding a polymeric channelling agent to the molten monomer composition prior to its polymerisation. A suitable channelling agent is one which is more hydrophilic than the monomer (s) in the monomer composition and has a melting point lower than the temperature of polymerisation of the monomer (s) in the monomer composition. The channelling agent is immiscible with the polymer matrix but not necessarily with the monomer composition. Examples include poly (ethylene-co-vinyl alcohol) (EVOH), polyvinyl alcohol

(PVA) , polyvinylpyrrolidone, polyethers such as polyethylene oxide or polypropylene oxide, and polyols such as polyethylene glycol (PEG) . Preferably, the channelling agent is added to the monomer composition so as to be present in the polymer composition in an amount of l-20wt%. The amount of channelling agent can be used to control the rate at which the polymer composition can take-up moisture; the higher the percentage of channelling agent, the greater the rate of moisture take- up. This channelling agent forms, after polymerisation, a separate phase in the polymer matrix. The two phases of the polymer matrix (i.e. the channelling agent phase and the polymer phase) preferably form a co-continuous interconnecting channel morphology.

Preferably the polymerisation of the molten monomer composition yields a thermoplastic polymer matrix such as nylon-6 which has a good toughness, impact-resistance and machinability. Alternatively, the polymerisation of the molten monomer composition may yield a thermoset polymer matrix which has good temperature resistance.

The process preferably comprises polymerising the molten monomer composition containing a desiccant and/or an odour-control material.

Any known desiccant can be used. However, preferred desiccants include: molecular sieves such as synthetic or natural aluminosilicates known as zeolites (including types 3A, 4A, 5A and 13X) , silica gels and clays; or mixtures thereof. Especially preferred are the zeolite- based molecular sieves 4A and 13X. The desiccant may be an indicating desiccant i.e. one which indicates the uptake of water by a change of colour. A suitable indicating desiccant is silica gel containing cobalt chloride (which changes from blue to pink upon uptake of water) .

Any known odour-control material (i.e. material which can adsorb vapours) may be used. However, preferred odour-control materials are activated carbon and molecular sieves such as natural or synthetic aluminosilicates known as zeolites (especially type 13X) .

The preferred particle size of the adsorbent solid is in the range 0.01 to 100 microns, more preferably 0.1 to 10 microns.

The adsorbent solid is preferably one which does not generate dust when the polymer composition is machined.

Dust pollutes the work place and its inhalation may be injurious to health. Furthermore, the polymer compositions may be used in a dust sensitive environment

(such as inside a scientific/electronic instrument) . The zeolite adsorbent solids preferably used in the invention have been found not to generate dust upon machining. The process may comprise blending both a desiccant and an odour-control material in the monomer composition.

Preferably, a single adsorbent solid is used which has both desiccant and odour-control properties. A suitable adsorbent solid having both properties is zeolite type 13X having a pore diameter around 10 Angstroms.

Preferably, the adsorbent solid is blended with the monomer composition so as to be present in the polymer composition in an amount of l-90wt%, more preferably in an amount of 20-90wt% or 30-80wt%, even more preferably in an amount of 40-70wt% and most preferably in an amount around 50wt%. The low viscosity of the molten monomer composition allows high loading values of the adsorbent solid. At higher loadings, e.g. above 60%, care must be taken to ensure that adequate mixing of the molten monomer composition and the adsorbent solid occurs.

The process may further comprise adding an indicating agent to the molten monomer composition. The indicating agent is intended to indicate . the uptake up moisture in the resulting polymer matrix. A suitable indicating agent is cobalt chloride which turns from blue to pink (via purple) upon uptake of water. The indicating agent is preferably added so as to be present in the polymer composition in an amount of 0.1-5wt%.

The process may further comprise adding any desirable additives such as initiators, activators, light stabilisers, heat stabilisers, plasticisers, curing agents, accelerators, antioxidants and processing aids. The following examples are given to illustrate the present invention but should not be construed as limiting the invention in any way. Various modification and variations will be readily apparent to the person skilled in the art. Chemicals

Monomer - ε-caprolactam - ACROS Organics (Fisher Scientific) and sodium hydride, 60% dispersed in oil - ACROS Organics (Fisher Scientific) - for examples 1-12 and 18-19. Monomer - ε-caprolactam and Bruggolen ClO (sodium caprolactam, 17-19% in ε-caprolactam) - Bruggemann Chemical - for examples 13-16.

Initiator/activator - N-acetylcaprolactam 99% Aldrich - for examples 1-12 and 18-19. Initiator/activator - Bruggolen C20P (blocked diisocyanate, ca. 17% in ε-caprolactam) - Bruggemann Chemical - for examples 13-16. Desiccant and odour-control material - zeolite 13X (UOP) - pre-dried in a vacuum oven at 25O⁰C for about 12 hours .

Desiccant - zeolite 4A (UOP) - pre-dried in a vacuum oven at 250⁰C for about 12 hours.

Odour control material - activated carbon powder - Nigxia Huahui Activated Carbon Co. Ltd.

Indicating agent - cobalt chloride (II) (Fisher Scientific) - pre-dried in a vacuum oven at 250⁰C for about 12 hours until blue in colour.

Indicating agent - indicating silica gel (Fisher Scientific) - pre-dried in a vacuum oven at about 120oC for 12 hours and subsequently ground.

Channelling agent - Polyethylene oxide average m.w. 6000 (ACROS Organics (Fisher Scientific)). Example 1 - polymer composition 1

2Og of ε-caprolactam and 0.1414g of sodium hydride were heated in a 5OmL round bottom flask equipped with a magnetic stirrer using an oil bath at around 9O⁰C to yield the sodium salt of ε-caprolactam (and hydrogen) . Dry nitrogen was bubbled through the molten monomer composition to remove residual moisture. 2Og (50wt%) of zeolite 13X was added and blended with the molten monomer by stirring. 0.5ml of N-acetylcaprolactam 99% was added to the blend with stirring and then the blend was transferred to a glass tube which was subsequently sealed and heated for about 4 minutes in an oil bath at around 18O⁰C. The blend was then allowed to cool and the glass tube was broken to yield the resulting polymer composition. Example 2 - polymer composition 2

Example 1 was repeated except 13.33g (40wt%) of zeolite 4A was used in place of the zeolite 13X. Example 3 - polymer composition 3 Example 2 was repeated except O.llg (0.3wt%) of cobalt chloride II was added to the monomer composition prior to the blending with the zeolite 4A. Example 4 - polymer composition 4 Example 2 was repeated except 13.33g (40wt%) of indicating silica gel was used in place of the zeolite 4A. Example 5 - polymer composition 5

Example 2 was repeated except that 1.75g (5wt%) of polyethylene glycol was added to the monomer composition prior to the blending with the zeolite 4A. Example 6, - polymer composition 6

Example 5 was repeated except 3.7Og (10wt%) of polyethylene glycol was added. Example 7 - polymer composition 7

Example 6 was repeated except l.Oβg (3wt%) polyethylene glycol was added. Furthermore, O.llg (0.3wt%) cobalt chloride II was added prior to the addition of the zeolite 4A. Example 8 - polymer composition 8

Example 2 was repeated except the blend of molten monomer composition, zeolite 4A and N-acetylcaprolactam was stirred and heated (using the oil bath at around 90⁰C) for a dwell time of 2 minutes prior to polymerisation i.e. prior to the raising of the temperature to 18O⁰C. Example 9 - polymer composition 9

Example 8 was repeated except a dwell time of 3 minutes was used.

Example 10 - polymer composition 10 Example 8 was repeated except a dwell time of 5 minutes was used. Example 11 - polymer composition 11

Example 8 was repeated except a dwell time of 10 minutes was used. Example 12 - polymer composition 12

Example 8 was repeated except a dwell time of 30 minutes was used.

Example 13 - polymer composition 13 27.5Og of ε-caprolactam and 1.25g of Bruggolen ClO were heated in a 50ml round bottom flask equipped with a magnetic stirrer using an oil bath at around 9O⁰C to form a melt.

13.75g of ε-caprolactam and 1.25g of Bruggolen C20P were heated in a second 50ml round bottom flask equipped with a magnetic stirrer using an oil bath at around 9O⁰C to form a melt.

After 10 minutes of stirring the melts, 15g of zeolite 4A was added to each flask (total 3Og) and each melt was stirred for a dwell time of 2 minutes.

After the dwell time stirring, the contents of the first flask were transferred to the second flask with stirring and after complete mixing (ca. 30 seconds), the blend was transferred to a glass tube which was subsequently sealed and heated at 180⁰C for 4 minutes in an oil bath at around 18O⁰C. The blend was then allowed to cool and the glass tube was broken to yield the resulting polymer composition. Example 14 - polymer composition 14 Example 13 was repeated except a dwell time of 3 minutes was used. Example 15 - polymer composition 15

Example 13 was repeated except a dwell time of 5 minutes was used. Example 16 - polymer composition 16

Example 13 was repeated except a dwell time of 10 minutes was used. Example 17 - polymer composition 17 Example 13 was repeated except a dwell time of 30 minutes was used. Example 18 - polymer composition 18

2Og of ε~^"caprolactam and 0.1414g of sodium hydride were heated in a 5OmL round bottom flask equipped with a magnetic stirrer using an oil bath at around 90⁰C to yield the sodium salt of ε-caprolactam (and hydrogen) . Ten minutes after melting, 6.7g (24.4wt%) of activated carbon powder was added and blended with the molten monomer by stirring for a further 3 minutes.

O.5ml of N-acetylcaprolactam 99% was added to the blend with stirring and then the blend was transferred to a glass tube which was subsequently sealed and heated for about 4 minutes in an oil bath at around 18O⁰C. The blend was then allowed to cool and the glass tube was broken to yield the resulting polymer composition. Example 19 - polymer composition 19

Example 18 was repeated except lO.ββg (34wt%) of activated carbon was added. Figures

Figure 1 shows the uptake of moisture by polymer composition 1 standing in ambient conditions; Figure 2 shows the uptake of moisture by polymer composition 1 standing in humid conditions; Figure 3 shows the uptake of moisture by polymer composition 2 standing in ambient conditions; Figure 4 shows the uptake of moisture by polymer composition 2 standing in humid conditions; Figure 5 shows the uptake of moisture by polymer compositions 8-11 standing in ambient conditions;

Figure 6 shows the uptake of moisture by polymer compositions 13-17 standing in ambient conditions; Figure 7 shows an electron micrograph of polymer composition 8; and Figure 8 shows an electron micrograph of polymer composition 12.

Results

1) Polymer composition melting point Polymer compositions 1 to 9 each exhibited a melting point between 215 and 220°C as detected by differential scanning calorimetry (DSC) . The melting point for commercial (pure) nylon-6 is 215-23O⁰C.

2) Moisture capture properties Polymer composition 1

Polymer composition 1 (obtained in Example 1) was weighed and allowed to stand in the laboratory ambient atmosphere (average temperature 20.6⁰C and average dew point of 5.6°C). The sample was re-weighed at regular intervals using a Sartorius balance model MasterPro LA620S-OCE, connected to a computer to enable continuous monitoring of the weight increase resulting from moisture uptake. Figure 1 shows a graph of weight against time for polymer composition 1. After 11 days (285 hours) 13.425g of polymer composition 1 had adsorbed 1.1532g of water vapour i.e. polymer composition 1 had adsorbed 17.2% of the zeolite's weight in water. Saturation of the desiccant was not achieved after this time. The experiment was repeated with polymer composition 1 standing in a high humidity chamber (average air temperature 30.4⁰C, average water temperature 33.2⁰C and average dew point 30.3⁰C). The results are shown in Figure 2. After 10 days, polymer composition 1 had adsorbed 39.5% of the zeolite's weight in water. Saturation was not achieved after this time. No swelling of polymer composition 1 was observed. Polymer composition^

Polymer composition 2 (obtained in Example 2) was weighed and allowed to stand in the laboratory ambient atmosphere (average temperature 23⁰C and average dew point of 11.5°C). The sample was re-weighed at regular intervals as described for polymer composition 1.

Figure 3 shows a graph of weight against time for polymer composition 2.

After 20 days, 12.436g of polymer composition 2 had adsorbed 1.243g of water vapour i.e. polymer composition

2 had adsorbed 20% of the zeolite's weight in water.

Saturation of the desiccant was not achieved after this time.

The experiment was repeated with polymer composition 2 standing in a high humidity chamber (average air temperature 29.6⁰C, average water temperature 33.1⁰C and average dew point 29.5°C). The results are shown in

Figure 4.

After 13 days, polymer composition 2 had adsorbed 43.3% of the zeolite's weight in water. Saturation was not achieved after this time. No swelling of polymer composition 2 was observed.

3) Indicating function

Polymer composition 3 Polymer composition 3 was allowed to equilibrate under ambient laboratory conditions and a colour change from blue-green to yellow-green was observed. Thus cobalt chloride can be used as an indicator that the polymer composition is adsorbing moisture. Polymer composition 4

Polymer composition 4 was allowed to equilibrate under ambient laboratory conditions and a colour change from blue to pink was observed. Thus the indicating silica gel can be used as an indicator that the polymer composition is adsorbing moisture. Polymer composition 7

Polymer composition 7 was allowed to equilibrate under ambient laboratory conditions and a colour change from blue-green to yellow-green was observed. Thus the cobalt chloride can be used as an indicator that the polymer composition is adsorbing moisture.

4) Moisture take-up rate control Polymer composition 5

Polymer composition 5 (containing 5% PEG) was allowed to equilibrate under ambient laboratory conditions (average temperature 22.5°C and average dew point 4°C) . After 21 days, polymer composition 5 had adsorbed 10% of the zeolite's weight in water. Polymer composition 6

Polymer composition 6 (containing 10% PEG) was allowed to equilibrate under ambient laboratory conditions (average temperature 22.5°C and average dew point 4°C) . After only 14 days, polymer composition 6 had adsorbed 10.2% of the zeolite's weight in water.

5) Foaming Effect Polymer compositions 8-12

Polymer compositions 8-11 (obtained in Examples 8- 11) were weighed and allowed to stand in the laboratory ambient atmosphere (average temperature 23°C and 36% relative humidity) . The samples was re-weighed at regular intervals using a Sartorius balance model MasterPro LA620S-0CE, . connected to a computer to enable continuous monitoring of the weight increase resulting from moisture uptake. Figure 5 shows a graph of % adsorption (relative to the weight of zeolite present in the sample) against time for polymer compositions 8-11.

After 19 days (456 hours), polymer composition 8 (prepared using a 2 minute dwell time) had adsorbed around 9% of the zeolite's weight of water whilst polymer composition 11 (prepared using a 10 minute dwell time) had adsorbed only around 2.3% of the zeolite's weight in water.

Figures 7 and 8 show electron micrographs for polymer compositions 8 (2 minute dwell time) and 12 (30 minute dwell time) . It can be clearly seen that polymer composition 8 is highly porous whilst polymer composition 12 has very few pores. Polymer compositions 13-17

Polymer compositions 13-17 (obtained in Examples 13-17) were weighed and allowed to stand in the laboratory ambient atmosphere (average temperature 23⁰C and 36% relative humidity) . The samples was re-weighed at regular intervals using a Sartorius balance model MasterPro LA620S-0CE, connected to a computer to enable continuous monitoring of the weight increase resulting from moisture uptake. Figure 6 shows a graph of % adsorption (relative to the weight of zeolite present in the sample) against time for polymer compositions 12-17.

After 12 days (286 hours) , polymer compositions 13 and 14 (prepared using a 2 or 3 minute dwell time) had adsorbed over 5% of the zeolite's weight in water whilst polymer compositions 15-17 (prepared using a 5, 10 or 30 minute dwell time) had adsorbed less than 2% of the zeolite's weight in water. 6) Vapour/odour capture properties Polymer composition 19

Three samples of polymer composition 19 (obtained in Example 19) were weighed and exposed to trichloroethane, methanol and propan-2-ol respectively. The samples were re-weighed after 240 hours using a Sartorius balance model MasterPro LA620S-0CE to monitor the weight increase resulting from vapour uptake. Relative to the weight of activated carbon present, 25.1% of trichloroethene was adsorbed, 3.0% of methanol was adsorbed and 0.8% of propan-2-ol was adsorbed. 7 ) Dust control

Machining (on a lathe) of the polymer compositions containing zeolite 13X and 4A yielded essentially no dust . Discussion

The experimental data shows that the polymer composition can adsorb moisture from the air to an extent at least as great as that achievable by the entrained adsorbent alone and that it is possible to include a desiccant with an indicating function (polymer composition 4) or that an indicating agent can be included in addition to a desiccant (polymer composition 3) . These polymer compositions provide an indication of moisture uptake. The experimental data also shows that the adsorption rate can be controlled a) by controlling the amount of channelling agent added to the molten monomer (polymer compositions 5 and 6) and b) by controlling the porosity of the polymer composition by including a gas-generating compound (NaH) and/or by minimising the dwell time before polymerisation (polymer compositions 8-12 and 13-17) .

The experimental data also shows that the polymer composition can adsorb organic vapours/odours such as trichloroethene, methanol and propan-2-ol (polymer composition 19) .

Finally, the experimental data shows that the polymer composition is resistant to damage and fragmentation, in that there is essentially no dust production upon machining. This suggests' that the polymer compositions can be used in dust sensitive environments such as scientific/electronic instruments.

Claims

1. A process for manufacturing a polymer composition comprising an adsorbent solid entrained within a polymer matrix, the process comprising polymerising a molten monomer composition containing the adsorbent solid.

2. A process according to claim 1 comprising heating a monomer composition to form the molten monomer composition and then adding the adsorbent solid to the molten monomer composition prior to polymerisation.

3. A process according to claim 1 or claim 2 comprising polymerising the molten monomer composition containing the adsorbent solid by reaction moulding.

4. A process according to claim 3, comprising polymerising the molten monomer composition containing the adsorbent solid by reaction injection moulding (RIM) .

5. A process according to any one of the preceding claims, the process further comprising machining the polymer composition to obtain a shaped article.

6. A process according to any one of the preceding claims comprising polymerising the molten monomer composition containing the adsorbent solid to form a water transmissive polymer matrix.

7. A process according to claim 6 comprising polymerising the molten monomer composition containing the adsorbent solid to form a polymer matrix selected from the group consisting of polyamide, polyurethane, an epoxy resin, a phenolic resin and a vinylic polymer.

8. A process according to claim 7 comprising polymerising the molten monomer composition containing the adsorbent solid to form a polymer matrix selected from the group consisting of nylon-4, nylon-5, nylon-6 and nylon-7.

9. A process according to any one of the preceding claims comprising polymerising the molten monomer composition containing the adsorbent solid, the molten monomer composition comprising ε-caprolactam.

10. A process according to any one of the preceding claims comprising polymerising the molten monomer composition containing the adsorbent solid to form a porous polymer matrix.

11. A process according to claim 10 comprising polymerising the molten monomer composition containing the adsorbent solid, the monomer composition containing a gas-generating compound.

12. A process according to claim 11 comprising polymerising the molten monomer composition containing the adsorbent solid, the gas-generating compound being pre-adsorbed onto the adsorbent solid.

13. A process according to any one of the preceding claims comprising polymerising the molten monomer composition containing the adsorbent solid to form a polymer matrix containing interconnecting channels through which a vapour is communicable with the adsorbent solid.

14. A process according to claim 13 comprising polymerising the molten monomer composition containing the adsorbent solid, the molten monomer composition comprising a channelling agent.

15. A process according to claim 14 comprising polymerising the molten monomer composition containing the adsorbent solid, the molten monomer composition comprising l-20wt% of the channelling agent.

16. A process according to claim 14 or 15 comprising polymerising the molten monomer composition containing the adsorbent solid, the molten monomer composition comprising poly (ethylene-co-vinyl alcohol) (EVOH), polyvinyl alcohol (PVA) , polyvinylpyrrolidone, polyether or polyol as the channelling agent.

17. A process according to any one of the preceding claims comprising polymerising the molten monomer composition containing the adsorbent solid, the adsorbent solid being a desiccant and/or an odour-control material.

18. A process according to claim 17 comprising polymerising the molten monomer composition containing the adsorbent solid, the adsorbent soli^'d being a synthetic or natural aluminosilicate .

19. A process according to claim 18 comprising polymerising the molten monomer composition containing the adsorbent solid, the adsorbent solid being a zeolite type 4A or 13X.

20. A process according to any one of the claims 1 to 17 comprising polymerising the molten monomer composition containing the adsorbent solid, the adsorbent solid being an indicating desiccant.

21. A process according to any one of claims 1 to 17 comprising polymerising the molten monomer composition containing the adsorbent solid, the adsorbent solid being activated carbon.

22. A process according to any one of the preceding claims comprising polymerising the molten monomer composition containing the adsorbent solid, the adsorbent solid being present in an amount of l-90wt%.

23. A process according to claim 22 comprising polymerising the molten monomer composition containing the adsorbent solid, the adsorbent solid being present in an amount of around 50%.

24. A process any one of the preceding claims comprising polymerising the molten monomer composition containing the adsorbent solid, the molten monomer composition comprising an indicating agent.

25. A process substantially as any one embodiment herein described with reference to the Examples.