WO2004052602A2

WO2004052602A2 - Hydrophobing process and apparatus

Info

Publication number: WO2004052602A2
Application number: PCT/GB2003/005202
Authority: WO
Inventors: Michael Bruce Danvers; Harold Adrianus Daniel Cornelis Van Oevelen
Original assignee: Bp Global Special Products Limited
Priority date: 2002-12-11
Filing date: 2003-12-03
Publication date: 2004-06-24
Also published as: AU2003285560A1; WO2004052602A3; EP1572426A2; GB0228912D0

Abstract

A process for manufacturing reconstituted wood products comprising (A) producing a hydrophobing emulsion in a homogeniser in a mother plant and also in one or more mini plant homogenisers remote from the mother plant, the miniplant homogenisers being operably connected, optionally with intermediate storage, for supplying hydrophobing emulsion to one or more impregnators and (B) impregnating fibrous and/or particulate material with hydrophobing emulsion from the mother plant and from the one or more miniplant homogenisers. The invention also relates to an apparatus for performing the process. The impregnators are thus provided with alternative sources of emulsion.

Description

HYDROPHOBING PROCESS AND APPARATUS

The present invention relates in general to hydrophobing and in particular to a process for hydrophobing fibrous and particulate material in the manufacture of reconstituted wood products (RWP).

It is known to hydrophobe fibrous and/or particulate material using water-based, wax emulsions in the manufacture of reconstituted wood products (RWP). The fibrous and/or particulate wood matter (called furnish) are impregnated with emulsions and resin glue. The emulsions may be used pre-blended with the glue, or the two components may be used separately. Heat and pressure are used to cure the resin glue and drive off water to form the RWP. The RWP may be in the form of boards which can be used as construction material.

Generally, such water based emulsions have hitherto been generated at a location remote from the impregnator. Thus it has been necessary to transport the water-based wax emulsion from the point of manufacture to their point of use. In order to reduce the amount of water which is transported, attempts have been made to generate increasingly more concentrated emulsions. This has presented technical difficulties as the emulsifier system (surfactant composition) becomes progressively more complex in order to achieve the higher concentration. More complex and high level of emulsifier systems have more chance of reacting with the components of the reconstituted wood blend with the possible result of reducing the hydrophobing benefit of the wax emulsion. Alternatively, if the water based emulsions are manufactured solely at their point of use, difficulties may arise in providing continuity of supply for example any problems either mechanical or logistical will result in an interruption of the customer's production process.

There is thus a need for an improved hydrophobing process which overcomes or at least mitigates these difficulties. Thus according to the present invention there is provided a process for the manufacture of reconstituted wood products which process comprises the steps :

(i) providing a mother plant comprising a first homogeniser for producing a hydrophobing emulsion from water, surfactant composition and wax; (ii) introducing water, surfactant composition and wax into the mother plant homogeniser to produce a hydrophobing emulsion;

(iii) providing one or more miniplants at one or more locations remote from said mother plant, each miniplant comprising an homogeniser for producing a hydrophobing emulsion from water, surfactant composition and said wax and being operably connected, optionally with intermediate storage, for supplying hydrophobing emulsion to one or more impregnators for impregnating fibrous and/or particulate material with hydrophobing emulsion in the manufacture of reconstituted wood products' (iv) introducing water, surfactant composition and said wax to each miniplant homogeniser to produce a hydrophobing emulsion; (v) supplying hydrophobing emulsion to said impregnators from said mother plant and from said one or more miniplant homogenisers; and (vi) impregnating fibrous and/or particulate material with hydrophobing emulsion in each impregnator to produce reconstituted wood products.

Also, according to the present invention there is provided apparatus for hydrophobing fibrous and/or particulate material in the manufacture of reconstituted wood products which comprises :

(a) a mother plant comprising a first homogeniser for generating a hydrophobing emulsion from wax, surfactant composition and water; and (b) one or more miniplants at one or more locations remote from said mother plant, each miniplant comprising an homogeniser for generating a hydrophobing emulsion from water, surfactant composition and said wax and being connected, optionally with intermediate storage, to one or more impregnators for impregnating fibrous and/or particulate material with hydrophobing emulsion in the manufacture of reconstituted wood products. The present invention solves the technical problem identified above by providing each impregnator with alternative sources of supply of hydrophobing emulsion. Thus, one source of supply of hydrophobing emulsion is the mother plant homogeniser and another source of supply is the one or more miniplant homogenisers.

A further advantage of the present invention is that at least part of the services required for the miniplant homogeniser may be integrated with those associated with the impregnator. This could result in cost savings and the like. Such integrated services may comprise water, steam, storage tanks, electricity, water softening and sites buildings. For example, existing storage facilities at the customer site, which were previously used to store the high stock levels of emulsion needed when supplied from a remote manufacturing facility, could be utilised for the raw material and finished product storage from the one or more mini plants. Also, sites which have resin- manufacturing facilities, will have excess steam and softened water as part of said resin manufacture. These materials can be utilised advantageously as services for the one or more miniplants. Preferably, each miniplant has a production capacity which is less than that of the mother plant homogeniser. The impregnators may be supplied simultaneously with emulsion from the mother plant and from one or more miniplants. The impregnators may be supplied with emulsion alternatively from the mother plant and the one or more miniplants. Preferably, the majority (>50%) and more preferably between 90 % and 95 % of the emulsion supplied to the one or more impregnators is supplied from the one or more miniplants.

In one embodiment of the present invention, the hydrophobing emulsion is predominantly (> 50%) supplied to the one or more impregnators from the one or more miniplant homogenisers. Hydrophobing emulsion is then supplied from the mother plant intermittently, when the miniplant homogeniser(s) is/are not available, for example because of maintenance or other shutdown reasons. This has an advantage that the transportation cost of the emulsion can be reduced because the emulsion need not be predominantly transported from the mother plant. However, continuity of supply is assured by the presence of the mother plant. Whilst the same wax is used in the emulsions produced by the mother plant homogeniser as is used in the miniplant homogenisers, the surfactant composition used to produce the emulsions in the mother plant homogeniser may be different to the surfactant composition used to produce the emulsions in the one or more miniplant homogenisers. The concentration of surfactant composition in the emulsions produced by each of the one or more miniplants homogenisers may be different to the concentration of surfactant composition in the emulsion produced by the mother plant homogeniser.

Preferably, the emulsions produced by the one or more miniplant homogenisers have a lower concentration of surfactant composition than in the emulsion produced by the mother plant homogeniser.

The concentration of water in the emulsions produced by each of the one or more miniplant homogenisers may be different to the concentration of water in the emulsion produced by the mother plant homogeniser. Preferably, the emulsions produced by the one or more miniplant homogenisers have a larger concentration of water than in the emulsion produced by the mother plant homogeniser.

In a particularly preferred embodiment, the hydrophobing emulsion produced by each of the one or more miniplant homogenisers is more dilute than the hydrophobing emulsion produced by the mother plant. If a high shear type homogeniser is used there is a further advantage that the emulsion particle sizes and more dilute emulsion means that a lower concentration of surfactant composition can be used with the miniplant homogeniser emulsions, with associated lower cost.

Thus a hydrophobing emulsion produced by the one or more miniplants may comprise a wax in a concentration in the range 30 to 70 % by weight and a surfactant composition in a concentration of less than 5 % by weight, preferably less than 3 % by weight, the balance consisting essentially of water. Suitable waxes are Slackwax. The surfactant compositions used in the present invention may be selected from the group consisting of non-ionic surfactant compositions, anionic surfactant compositions, cationic surfactant compositions and mixtures thereof. Anionic and nonionic surfactant compositions may comprise one or more fatty acids and/or esters thereof, or one or more ammonium compounds. Suitable fatty acids include C14 and C16 fatty acids, oleic acid, stearic acid and tallows. Suitable ammonium compounds include ammonia, monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), morpholine and dimethyl aminό ethanol (DMAE). Additionally or alternatively, the surfactant compositions may comprise compounds other than stearic acid which have stearyl functional groups such as glycerol monostearate (GMS) and stearyl alcohols, for example, acetostearyl alcohol. The surfactant compositions used in the present invention may comprise one or more additives selected from the group consisting of stabilisers, neutralisers and biocides.

The hydrophobing emulsions used in the present invention may comprise one or more additives selected from the group consisting of stabilisers, neutralisers and biocides.

The low surfactant emulsions of the present invention are not normally producible using conventional homogenisation technology. Advantages of using an emulsion with a lower concentration of surfactant composition include reduced cost and an improved hydrophobing capability.

Preferably, the miniplant homogenisers are of the high sheer mixer type such as a Supraton^® manufactured by BWS, rather than the high pressure type. Most preferably, the homogeniser is skid-mounted so that it may be moved and located at impregnation plants wherever required. Particularly preferred emulsion compositions by weight are :

The invention will now be described by reference to the examples and drawings in which Figure 1 illustrates in schematic form a mother plant according to the present invention. Figure 2 represents in schematic form a miniplant according to the present invention. Figure 1 illustrates in schematic form a mother plant according to the present invention. The mother plant comprises a storage tank (1) for wax phase and a storage tank (2) for a water phase including surfactant composition. The tanks (1) (2) are operably connected to a blend tank or metered blend pump (3) and thence to a homogeniser (4). In use water phase (including surfactant composition) and wax phase from the storage tanks (1) (2) are passed through the blend tank or metered blend pump (3) and introduced into the homogeniser (4) which produces a mother plant emulsion. The mother plant emulsion is stored in tank (5) and may be dispatched through loading facility (6). Figure 2 represents in schematic form a miniplant according to the present invention. The miniplant is located remotely from a mother plant such as shown in Figure 1. The miniplant comprises a storage tank for wax (21) and a storage¹ tank (22) for water phase including surfactant composition. The tanks (21)(22) are operably connected to a blend tank or metered blend pump (23) and thence to a homogeniser (24) such as a high sheer mixer type homogeniser e.g. a Supraton^® manufactured by BWS The homogeniser (24) is operably connected to an intermediate storage tank (25). The intermediate storage tank (25) and the homogeniser (24) are operably connected to an impregnator (30).

In use, wax phase from tank (21) and water phase (including surfactant composition) from tank (22) are passed through blend tank or metered blend pump (24) and introduced into the homogeniser (24) which produces a hydrophobing emulsion. The emulsion is supplied directly to the impregnator (30). The emulsion maybe supplied indirectly to the impregnator through storage tank (25).

In the impregnator fibrous and/or particulate material is hydrophobed with the emulsion to produce reconstituted wood products. The emulsion supplied to the impregnator may be predominantly supplied by the miniplant homogeniser. However, when emulsion from the miniplant is not available then emulsion may be provided from the remote mother plant such as shown in Figure 1 by road tanker or other transport means through dispatch loading facility (6).

This has an advantage that the miniplant may be integrated with services such as electricity,, softened water etc at the impregnator site.

This has the further advantage that the emulsion used for hydrophobing which is supplied by the miniplants may have a lower surfactant composition concentration than the emulsion produced by the mother plant, which reduces costs for example. Experiment illustrating the invention Using apparatus such as illustrated in Figures 1 and 2 (although the miniplant was not operably connected to the impregnator, but rather emulsion was transported promptly by road tanker) a 20 tonne batch of emulsion was produced by a high sheer mixer type Supraton" homogeniser manufactured by BWS. The emulsion was successfully used to hydrophobe fibrous and/or particulate material over a three day period. Thereafter emulsion was supplied from a motherplant.

No problems were encountered during the trial and the particleboard produced was of equivalent quality to the standard produced material.

The compositions of the mother plant and miniplant emulsions are shown in the Table. The wax used was a hydrocarbon wax and the surfactant composition was an anionic surfactant composition comprising stearic compounds and monoethanolamine.

This experiment illustrates that the impregnator can be supplied with emulsion from both a mother plant and a miniplant.

Claims

1. A process for the manufacture of reconstituted wood products which process comprises the steps :

(i) providing a mother plant comprising a first homogeniser for producing a hydrophobing emulsion from water, surfactant composition and wax; (ii) introducing water, surfactant composition and wax into the mother plant homogeniser to produce a hydrophobing emulsion; (iii) providing one or more miniplants at one or more locations remote from said mother plant, each miniplant comprising an homogeniser for producing a hydrophobing emulsion from, water, surfactant composition and said wax and being operably connected, optionally with intermediate storage, for supplying hydrophobing emulsion to one or more impregnators for impregnating fibrous and/or particulate material with hydrophobing emulsion in the manufacture of reconstituted wood products; (iv) introducing water, surfactant composition and said wax to each miniplant homogeniser to produce a hydrophobing emulsion;

(v) supplying hydrophobing emulsion to said impregnators from said mother plant and from said one or more miniplant homogenisers; and (vi) impregnating fibrous and/or particulate material with hydrophobing emulsion in each impregnator to produce reconstituted wood products.

2. A process as claimed in claim 1 in which the hydrophobing emulsion is predominantly supplied to the impregnators from the miniplant homogenisers.

3. A process as claimed in any preceding claim in which the surfactant composition used to produce the emulsions in the mother plant homogeniser is different to the surfactant composition used to produce the emulsions in the one or more miniplant homogenisers.

4. A process as claimed in any preceding claim in which the concentration of surfactant composition in the emulsions produced by each of the one or more miniplants homogenisers is different to the concentration of surfactant composition in the emulsion produced by the mother plant homogeniser.

5. A process as claimed in claim 4 in which the emulsions produced by the one or more miniplant homogenisers have a lower concentration of surfactant composition than in the emulsion produced by the mother plant homogeniser.

6. A process as claimed in any one of the preceding claims in which the concentration of water in the emulsions produced by each of the one or more miniplant homogenisers is different to the concentration of water in the emulsion produced by the mother plant homogeniser.

7. A process as claimed in claim 6 in which the emulsions produced by the one or more miniplant homogenisers have a larger concentration of water than in the emulsion produced by the mother plant homogeniser.

8. A process as claimed in any one of the preceding claims in which in the emulsion produced by the mother plant homogeniser, the wax concentration is in the range 40 to 70 % w/w, the water concentration is in the range 30 to 60 % w/w and the surfactant concentration is in the range 1.5 to 5 % w/w.

9. A process as claimed in any one of the preceding claims in which in the emulsions produced by the one or more miniplant homogenisers, the wax concentration is in the range 30 to 60 % w/w, the water concentration is in the range 40 to 70 % w/w and the surfactant concentration is in the range 0.5 to 1.5 % w/w.

10. Apparatus for hydrophobing fibrous and/or particulate material in the manufacture of reconstituted wood products which comprises : (a) a mother plant comprising a first homogeniser for generating a hydrophobing emulsion from wax, surfactant composition and water; and

(b) one or more miniplants at one or more locations remote from said mother plant, each miniplant comprising an homogeniser for generating a hydrophobing emulsion from water, surfactant composition and said wax and being connected, optionally with intermediate storage, to one or more impregnators for impregnating fibrous and/or particulate material with hydrophobing emulsion in the manufacture of reconstituted wood products.