WO2009087102A2

WO2009087102A2 - Abatement apparatus and processing method

Info

Publication number: WO2009087102A2
Application number: PCT/EP2009/000075
Authority: WO
Inventors: Stephen Richard Coulson
Original assignee: P2I Limited
Priority date: 2008-01-09
Filing date: 2009-01-09
Publication date: 2009-07-16
Also published as: GB201009351D0; WO2009087102A3; TW200942316A; GB2467276B; GB0800305D0; GB2467276A

Abstract

The present invention relates to a method of processing an article (16) to remove outgassing substances. The method comprises: placing an article in a closed processing region (12); reducing a pressure in the processing region so that the article (16) is exposed to a pressure to control a rate of outgassing from the article; and disposing outgases (15) released from the article. The present invention also relates to abatement apparatus (10) for processing an article (16) to remove outgassing substances. The apparatus comprises: a processing region (12); vacuum pumping means (20) for reducing a pressure in the processing region (12); control means (28) for controlling a rate of outgassing from the article (16); and disposal means (22) for disposing of outgases (15) released from the article.

Description

ABATEMENT APPARATUS AND PROCESSING METHOD

Field of the Invention

This invention relates to an abatement apparatus for processing an article to remove outgassing substances and to a processing method for removing outgassing substances from an article.

Background of the Invention

Outgassing is the slow release of a gas or vapour from a material by evaporation, sublimation or other phase transition, or by desorption, seepage, or by chemical reaction. An outgassing substance may be contained or trapped in material for example by absorption or adsorption, or may constitute the material itself.

Outgassing in a closed environment can be significant, since outgases can accumulate in greater density. Even substances which are not generally prone to outgassing, such as wood or metal, may release significant outgases if stored in a closed environment for some time.

There is concern that some outgassing substances such as solvents or other chemical additives, whilst not deleterious to health or the environment in a solid or liquid state, may nevertheless produce hazardous outgases particularly if allowed to accumulate in a closed environment.

Solvents and other chemical constituents are often used in manufacture of articles, such as clothing or footwear. Such articles are generally stored in a closed environment for extended periods prior to purchase. It is desirable to reduce outgassing of outgassing substances contained in articles by processing the articles. Prior Art

US Patent US 5 789 024 (Levy) disclose a low pressure chemical vapour deposition (LPCVD) reactor and illustrates this in Figure 1. US 5 789 024 describes a reaction chamber which is typically used in the fabrication of semiconductor wafers. The chamber in Figure 1 includes a composite high permeability filter.

Although the variable flow chamber is ideally suited for wafer fabrication purposes, it is completely impractical to propose the use of the variable flow chamber for depositing surface coatings on larger items such as household articles, items of clothing, footwear or other consumer goods.

US Patent US 5 664 997 (Hess) describes a locker for extracting toxic materials which may saturate or stick to clothing, in particular fire fighters composite membrane which could present a safety problem, for example if the material contacting and sticking to the fire-fighters clothing is flammable. The locker is adapted to extract at relatively low vapour pressures all such hazardous materials, effectively by way of forced outgassing.

Another degassing system is described in US Patent US 4 781 358 (Langan) in which measurement and regulation of degassing is determined in a continuous reactor, by way of a mass spectrometer which is configured to obtain a sample of the gas species present in the chemical vapour, so that quantitative measurements of residual chemicals can be determined.

The furnace and apparatus is ideally suited to measuring the amount of degassing that occurs, for example, in sintering and similar systems.

Summary of the Invention

According to first aspect of the present invention there is provided a method of processing an article to remove outgassing substances, the method comprising: placing an article in a closed processing region; reducing the pressure in said processing region so that said article is exposed to a pressure to control a rate of outgassing from said article; and disposing outgases released from said article, characterised in that a reduction in outgassing substances in said article is measured by weighing said article prior to and after exposure to said pressure.

Ideally the pressure in the closed processing region is reduced to less than substantially 10 x 10^'10 Torr.

Preferably the pressure within the closed processing region or vacuum chamber is less than around 1 Torr and 50 x 10^"10 Torr and ideally the pressure is les than around 1 x 10¹⁰ Torr.

According to second aspect of the present invention there is provided an abatement apparatus for processing an article to remove outgassing substances, the apparatus comprising: a processing region; vacuum pumping means for reducing a pressure in said processing region; control means for controlling a rate of outgassing from said article; and disposal means for disposing of outgases released from said article characterised in that a means is provided for weighing said article prior to and after exposure to said pressure.

Advantageously the means for weighing said article is provided within the chamber.

Other preferred and/or optional features of the invention are defined in the accompanying claims.

The invention will now be described, by way of example only, with reference to the accompanying drawing, in which:-

Brief Description of the Drawings

Figure 1 shows an abatement apparatus for processing an article to remove outgassing substances. Detailed Description of the illustrated embodiments

Referring to Figure 1 , abatement apparatus 10 comprises a processing chamber 12 having a platform 14 for supporting an article 16 to be processed. The article may alternatively be positioned on the floor of the chamber. Chamber 12 has a sealable closure 18 to allow articles to be placed into and removed from the chamber. Closure 18 is shown in an open condition in broken lines.

A vacuum pump 20 is connectable to evacuate gas or vapour from the chamber. Pump 20 is connected at its outlet to a disposal unit 22 for disposing of outgases 15, for instance by absorption into a charcoal bed or if the outgases are non-hazardous or environmentally friendly, they may simply be released to atmosphere.

Disposal unit 22 may comprise means for measuring a flow rate of outgases from the processing chamber 12. Alternatively, means for measuring a flow rate of outgases from the processing chamber 12 may be provided elsewhere in the apparatus downstream of the processing chamber. Another means which may be used to measure the removal of outgassing substances from an article is by weighing an article prior to and after or during exposure to a reduced pressure. In this regard, the platform 14 may be provided with means for weighing an article.

The vacuum pump 20, disposal unit 22, vacuum gauge 24 and the heat source 26 (and weighing means) are connected to a control unit 28 so that outgassing from the article 16 can be controlled. The control unit 28 may be connected to a human user interface 30 by which a user can interface with the control unit. A vacuum gauge 24 may be positioned to measure a vacuum in the processing chamber. A cold cathode vacuum gauge is suitable for pressure measurement. A heat source 26 may be provided for increasing the temperature of the processing chamber. The heat source may be placed inside the chamber or the heat source may be operable to heat the chamber itself, particularly where the chamber is made from a thermally conductive material, such as steel. The purpose of the heat source is to raise the temperature of the outgassing substances in the article in order to promote controlled outgassing. The control 28 is configured to control the vacuum 20 to achieve a selected reduction in outgassing substances in the article. In this regard, the control unit is configured to determine a rate at which an article produces outgases when the article is exposed to a pressure so that a selected reduction of outgassing substances in said article can be achieved or to trigger a specific action at a predefined pressure or outgassing rate. Such a specific action includes for example initiation of a plasma processing step in the processing chamber or introduction of a selected species to the processing chamber for processing. Such a determination permits outgassing substances to be reduced in an article by any chosen percentage. For instance it may be a requirement to reduce outgassing substances by a percentage such as 90%. As the control unit 28 is configured to determine a rate of outgassing such a percentage reduction can be readily achieved.

As described above the apparatus may comprise means for measuring a reduction in outgassing substances in an article when the article is exposed to a pressure over time (rate of reduction over the time during which an article is exposed to a varying pressure in the processing region) and the control unit is configured to receive a measurement from the measurement means in order to achieve a selected reduction in outgassing substances in the article. Such measuring means may comprise the previously mentioned weighing means.

Many articles comprise outgassing substances which have a tendency to produce outgases when the article is exposed to ambient conditions normally encountered when the article is for instance in storage, in packaging or in use. Outgassing substances may take the form of solvents, sealants, adhesives, colourants, additives or may additionally take the form of the material constituents of the articles themselves, for example wool, cotton, polyester (or other fabric), wood, metal, leather, rubbers or plastics.

Articles comprising such outgassing substances include without limitation, clothes, shoes, home or office furnishings, building materials, filtration products, bio- consumables, electronic devices, performance textile product or any other article of convenience or utility. For example, a sports or utility shoe may comprise colourants, sealants or polish for a synthetic or natural material of the shoe, and adhesive for securing a shoe lower to a shoe upper. Many or all of such substances produce outgases, which are particularly apparent when a shoe is stored in a closed environment such as a shoe box and the box is opened.

The propensity of an article to produce outgases is dependent on a number of different factors, for instance, the potential for a substance to evaporate in ambient conditions of heat and pressure. The propensity also relates to the proximity of the substance to a free surface of the article. In this regard, an outgassing substance proximate or on a surface of an article may more readily outgas than the same substance if it is more deeply within the article.

Other relevant factors are the porosity and surface area of the material substrate of the article. It is common that outgassing substances in an article produce outgases at a rate which decreases over time as the substances become depleted or the substances proximate a surface of the article reduce.

The production of outgases over time may generally decrease exponentially depending upon the particular article, the substances present and ambient conditions. In particular, outgassing is dependent on pressure in the region surrounding an article. If pressure is reduced the rate of outgassing is increased. Increased temperature additionally increases the rate of outgassing.

The abatement apparatus 10 enables an article to be exposed to conditions which increase a rate of outgassing from the article. It can be determined by experimentation or calculation the rate at which outgases are produced and a graph produced plotting outgassing against time. As it is often not practical to completely deplete outgassing substances from an article, such a prior determination allows efficient processing to achieve a required reduction of outgassing substances from the article. For instance, it may be required to reduce outgassing substances to 10% of outgassing substances present in an unprocessed article.

Accordingly, abatement apparatus 10 can be controlled to expose an article to a required pressure for a required duration to achieve a selected percentage reduction in outgassing substances. It may also be desirable to increase ambient temperature to increase a rate of outgassing. Each type or make of article may require prior determination of the characteristic rate of outgassing in order to correctly expose articles of that type or make to required conditions for a required duration.

It will be appreciated that the invention may be used in conjunction with a range of different activated species in dependence upon the desired characteristics and properties of the item to be coated, and in order to achieve a desired technical effect.

For example, an antiseptic species may be introduced in order to provide an antiseptic coating, in or on medical and dental equipment, appliances and devices.

Alternatively, other chemicals may be introduced in order to provide such properties as fire resistance to clothing, leather, fabric materials and covers, paper goods, electrical goods, personal electronic devices such as BLUETOOTH (Trade Mark) devices mobile telephones, pagers, personal digital assistant (PDA), MP3 devices, electronic cables, compact discs (CDs), banknotes and credit cards.

In a yet further embodiment, the species to be introduced is a protein binder which is adapted to be introduced into bone and dental implants.

In a further embodiment, the species to be introduced may be an electrically conductive material which is adapted to be introduced into specific areas/regions of the item to be coated.

Apparatus 10 may be controlled manually by an operator by selection of duration, pressure and temperature according to a previously determined graph or look up table. Alternatively, control means 28 is configured to determine a rate of outgassing of a sample article and then to apply a required exposure to subsequent articles in order to achieve a selected percentage depletion of outgassing substances. In this regard, the control means may comprise timing means for timing duration of exposure, a storage means for storing a prior determination of a rate of outgassing and processing means for operating the vacuum pump to achieve a required pressure for a required duration. The processing means may be configured, as shown in Figure 1, for receiving a pressure signal from pressure gauge 24 to allow accurate control of pressure in the processing chamber 12. The processing means may additionally be capable of controlling heat delivered by heat source 26 and a rate of disposal required by disposal unit 22.

The apparatus described above may optionally have further functionality, for instance, the processing chamber 12 may form part of a plasma processing apparatus in which a surface of the articles may be plasma processed. Controlled reduction in outgassing substances from articles may take place prior to or during plasma processing so that articles have reduced propensity to outgas and also have enhanced properties due to plasma processing.

Operation of one example of an abatement apparatus 10 will now be described.

Operation may include a first step for determining a rate of outgassing from a sample article and a second plurality of steps for reducing outgassing substances from subsequent articles. The first step may be omitted if a rate of outgassing from an article can be calculated or approximated within acceptable tolerances.

In a determination step, closure 18 is opened and a sample article is placed in processing chamber 12. Closure 18 is sealed to provide a closed environment in the processing chamber. Vacuum pump 20 is operated to decrease pressure in the processing chamber 12 to a selected pressure which is ideally less than 10 x 10^"10 Torr and ideally between 1 Torr and 1x10 ¹⁰ Torr. In one arrangement as shown in Figure 1 , the disposal unit 22 measures a flow of outgases from processing chamber and accordingly a rate of outgassing can be determined by processing unit 28. Alternatively or additionally, a weight of a sample article can be measured prior to and after processing by weighing means and a signal according to a reduction in weight is transmitted to the control unit. The heat source may supply a fixed amount of heat during processing of an article. Alternatively, the heat source 26 may be controlled during processing to increase (or decrease) a rate of outgassing as required. When a rate of reduction in outgassing substances has been determined, processing of articles can be controlled to achieve a selected rate or amount of outgassing.

When a rate of outgassing under selected conditions has been determined for an article, it can be further determined the correct duration and conditions required in a processing step in order to achieve a selected reduction in outgassing substances from subsequent articles.

In the processing step, one or more subsequent articles are placed in processing chamber 12. Vacuum pump 20 is operated to achieve a required pressure in the chamber and over a required duration so that a selected reduction in outgassing substances can be obtained. Additionally, heat source 26 may be operated to increase a rate of outgassing. The disposal unit 22 may optionally measure a flow of outgases from chamber 12 and disposes of the outgases in an appropriate manner. Processed articles are finally removed from processing chamber 12.

Alternatively or additionally, the previously described weighing means may be operable to weigh an article during processing and communicate with the control unit which is operable to terminate processing of an article when a selected reduction in outgassing substances has been achieved.

Thus, for example, an antiseptic species may be introduced in order to provide an antiseptic coating, in or on such items as: bandages, dressings, and emergency medical equipment; specialised items of furniture, bathroom furniture, first aid kits, items of clothing; and medical, surgical and dental devices.

Alternatively a fire retardant species can be introduced in order to provide fire resistant properties to such items as: items of clothing, leather, fabric materials and covers, paper goods, electrical goods, personal electronic devices such as BLUETOOTH (Trade Mark) devices mobile telephones, pagers, personal digital assistant (PDA), MP3 devices, electronic cables, compact discs (CDs), banknotes and credit cards.

In a yet further embodiment, the species to be introduced is a protein binder which is adapted to be introduced into bone and dental implants in order to promote bone growth and binding of a bone material, thereby enhancing re-growth/repair of broken bones or teeth.

In a still further embodiment, the species to be introduced may be an electrically conductive material which is adapted to be introduced into specific areas/regions of the item to be coated.

Claims

1. A method of processing an article to remove outgassing substances, the method comprising: placing an article in a closed processing region; reducing the pressure in said processing region so that said article is exposed to a pressure to control a rate of outgassing from said article; and disposing outgases released from said article, characterised in that a reduction in outgassing substances in said article is measured by weighing said article prior to and after exposure to said reduced pressure.

2. A method as claimed in claim 1, wherein said article is exposed to a pressure to achieve a selected reduction of outgassing substances in said article.

3. A method as claimed in claim 1 or 2, wherein a rate at which an article produces outgases is determined when said article is exposed to a pressure to achieve a selected reduction of outgassing substances in said article.

4. A method as claimed in claim 3, wherein a rate at which an article produces outgases is determined by exposing said article to a pressure over time and measuring a reduction in outgassing substances in said article.

5. Abatement apparatus for processing an article to remove outgassing substances, the apparatus comprising: a processing region; vacuum pumping means for reducing a pressure in said processing region; a control means for controlling a rate of outgassing from said article; a disposal means for disposing of outgases released from said article; and a means for weighing an article.

6. Apparatus according to claim 5 wherein the means for weighing the article is provided in said processing region.

7. Apparatus as claimed in claim 6, wherein said control means is configured to control said vacuum pumping means to achieve a selected reduction in outgassing substances in said article.

8. Apparatus as claimed in claim 7, wherein said control means is configured to determine a rate at which an article produces outgases when said article is exposed to a pressure so that a selected reduction of outgassing substances in said article can be achieved.

9. Apparatus as claimed in any of claims 5 to 7, comprising means for measuring a reduction in outgassing substances in said article when said article is exposed to a pressure over time and said control means is configured to receive a measurement from said measurement means in order to achieve a selected reduction in outgassing substances in said article.