CA2362750A1 - Processes for preparing molded composite material and wax-based release agents - Google Patents

Abstract

The invention provides methods of preparing molded composite materials such as oriented strand board, waferboard or plywood in a press plate-containing apparatus using waxes and emulsions containing the same wax having specifically defined ranges of physical characteristics. The methods include a) treating the press plate surfaces of a molding apparatus which contact a composite mixture with an effective amount of an oxidized wax having a Brookfield viscosity which is less than about 80 mPas at 149 ~C, a droppoint of from about 80 to about 120~C and a hardness of less than about 18 decimillimeters (dmm) at 25~C, prior to the composite material contacting the press plate surfaces, and thereafter b) applying the wax-treated press plate surfaces to the composite mixture under conditions sufficient to mold the composite.

Description

PROCESSES FOR PREPARING MOLDED COMPOSITE MATERIAL
AND WAX-BASED RELEASE AGENTS
BACKGROUND OF THE INVENTION
The present invention relates to improvements in processes for preparing molded articles such as oriented strand board, waferboard or plywood. In particular, the invention relates to 1 o processes which include select wax-based release agents which demonstrate enhanced utility in continuous molding processes for preparing molded articles.
It is known in the art that molded lignocellulosic or wood-based products can be prepared using standard batch procedures or, more recently, using continuous techniques. The i s preparation of wood composites typically includes introducing an aqueous composite mixture of wood chips or the like between two heated metal plates which press and shape the composite mixture under pressure. Furthermore, the use of wax release agents in processes for the binding of lignocellulosic materials with polyisocyanates has also been previously described.
See, for example, WO 98/00464, the contents of which are incorporated herein by reference.

2 o WO 98/00464, however, discloses a broad range of waxes which are allegedly useful in emulsions as either internal or external release agents. No apparent distinction is made between the physical characteristics of waxes used in external ap,~lication versus those used in internal applications. For example, the document discloses that release agent emulsions can contain a wide spectrum of oxidized polyethylene waxes having a melting temperature of from 2 s 80 to 120°C, a viscosity of from 25 to 200 cps at l 49°C , a hardness of from 0.5 to 98 dmm.
A wide range of polypropylene waxes are also disclosed as being useful.

WO 00/53381 PCT/US00/06099 ~ _ In a typical process, an organic isocyanate binder such as a polyisocyanate, which is usually in the form of a solution or an aqueous emulsion, is applied to a lignocellulosic material which is then subjected to heat and pressure. The quality of the resulting articles, e.g. sheets or molded bodies such as chipboard or plywood, is largely due the adhesive s properties of the organic polyisocyanates. Unfortunately, these adhesive polyisocyanates are the cause of significant problems during the molding process. For example, isocyanates often cause severe sticking of the lignocellulosic material to the hot metal press plate surfaces it is in contact with during the hot-pressing operation.
Consequently, the molded product is often harmed as a result of trying to remove it from the press plates.
1o Another problem associated with polyisocyanates is that the time required for cleaning the contaminated hot metal surfaces can be substantial. Thus, in spite of the usefulness of polyisocyanates as adhesive binders, they are associated with drawbacks which can be costly.
is Alternative adhesive or binder products such as urea formaldehydes, phenol formaldehydes and phenolic impregnated papers have been used as replacements for polyisocyanates. Such alternative binders, however, have not met with success for various reasons. For example, the moisture resistance associated with the formaldehydes is less than that which is desirable. Furthermore, these products are associated with certain 2 o health risks. Interest has therefore been focused on developing "release agents", that is, additives specifically intended to favor the release of the manufactured articles from the metal plates of the press and overcome other processing difficulties associated with polyisocyanates.
Often release agents are combined with the polyisocyanates as part of the binding emulsion.
2s Such agents are typically referred to as internal release agents.
Alternatively, external release agents which are usually applied to the press surfaces which come into contact with the lignocellulosic composite mixture have been suggested. For example, conventional release agents such as oils, wax polishes, metallic soaps, silicones and polytetrafluoroethylene have been applied externally on the metal surfaces but have proved unsatisfactory.
The shortcomings associated with currently available release agents which can be used s with isocyanates are particularly evident in the context of commercial scale, continuous or semi-continuous molding operations. The press equipment is used repeatedly in short cycle times. If one wishes to rapidly produce articles having uniform quality, the problems associated with adhesion to the press parts must be essentially eliminated.
Furthermore, the time required for cleaning the press parts surfaces to remove resinuous material to formed on the hot surfaces of the press parts due to thermal decomposition must be reduced to a minimum.
It has thus been determined that there is a continued need for improvements in release agents. Specifically, there is a need to provide release agents which have a desirable z5 combination of several physical attributes, such as viscosity and hardness, to overcome the shortcomings associated with isocyanate-based binding systems. For example, some external release agents such as emulsions containing A-C~ 6702 wax, a product of AlliedSignal, Morristown, NJ having a viscosity of about 35 mPas, a droppoint of about 86.5°C and a hardness of about 83 dmm at 25°C, have good release properties and do not 2o cause a build up on the forming belts. These emulsions, however, are sometimes associated with overspray problems, that is, they may leave a sticky residue on many of the surfaces surrounding the spinning disk equipment which applies the emulsion to the platen and cause clogging. Emulsions of A-C~ 659 wax, another AlliedSignal product having a viscosity of about 180 mPas 140°C, a droppoint of from about 90 to about 97°C
25 and a hardness of from about 20 dmm at 25°C, on the other hand do not leave a residue near the spinning disk equipment. The dried emulsion is deposited as small, white particles that are easily removed with compressed air. Continuous use of these release agent emulsions, however, leads to a considerable build up of wax and rosin on the forming PCT/(JS00/06099 -belts, a problem often referred to as a plate-out. In sum, currently available release agents have some desirable properties and some undesirable properties. Some have sufficient hardness to form depositions around the spinning disk equipment which are easily removable, but the viscosity of these agents is too high to be absorbed by the wood.
Conversely, if the release agent has a viscosity which is low enough to be absorbed by the wood, and thereby solve the problem of plating-out, it is so soft that it leaves sticky deposits in the areas surrounding the spinning disks.
It has now been found that processes for preparing molded articles in press-plate-containing 1 o apparatus can be done substantially without the problems associated with many of the prior art waxes and emulsions containing the same. In particular, the process includes using a wax or wax-like release agent, preferably in emulsion form, having physical characteristics which fall within carefully defined specific ranges within those broad ranges described in the aforementioned '464 PCT publication. The selected waxes unexpectedly provide release agent 15 emulsions which solve not only the overspray problems associated some release agent systems but also the plating out associated with other release agent systems. The wax-based release agents of the present invention are thus especially well-suited for use in continuous molding processes.
2 o DESCRIPTION OF THE INVENTION
The invention provides methods of preparing molded composite materials in a press plate-containing molding apparatus. The methods include a) treating the surfaces of the press plates which contact a composite mixture with an effective amount of an oxidized wax which has a 2s Brookfield viscosity which is less than about 80 mPas at 149 °C, a droppoint offrom about 80 to about 120°C and a hardness of less than about I 8 decimillimeters (dmm) at 25 °C, prior to the composite mixture contacting the press plate surface, and b) applying the wax treated press plate surfaces to the composite mixture under conditions sufficient to mold the composite.

In some preferred embodiments, the waxes used in the process of the present invention have a Brookfield viscosity which is in the range of from about 5 mPas to about 50 mPas at 149°C
and, in more preferred embodiments, the wax has a Brooldeld viscosity which is in the range of from about 20mPas to about 40mPas at 149°C. The droppoint of the wax is preferably from about 104 to about 115°C and more preferably is from about 110 to about 113°C.
In accordance with one aspect of the invention, the inventive process uses oxidized wax-based release agents having specific and controlled viscosity, hardness, crystallinity and o melting point ranges as well as easy emulsifiability. The combination of these properties substantially reduce and/or overcome the problems associated with prior art single wax-release agents used in combination with polyisocyanate binders, especially in continuous and semi-continuous molding processes.
In alternative embodiments, the inventive emulsions can include one or more additional waxes in order to obtain additional release properties. The supplemental waxes) can be included in amounts which do not substantially detract from the advantageous release properties described herein. Depending upon the ingredient selected, the amount can range from less than 1% to up to about 50% or more by weight, if desired.
The waxes used in the inventive process preferably have a hardness of from about 0.1 to about 18 dmm. at 25°C. In alternative embodiments, the wax hardness ranges from about Z to about 8 and preferably from about 4 to about 8 dmm at 25°C.
The oxidized waxes of the invention may have acid numbers of from about 14 to about 45 mg KOH/g. The preferred range is from about 16 to about 25. In general, although lower acid number products may be used, e.g. less than about 5, they often require higher amounts of surfactant for satisfactory emulsifiability.

WO 00/53381 PCT/US00/06099~ -Oxidation of waxes is known in the art as a suitable way to render waxes dispersible in an aqueous medium to form an aqueous emulsion. In a typical process, the wax is placed in a suitable reactor vessel such as a pressure autoclave and subjected to sufficient heat and s pressure while being sparged with air or oxygen. In the case of the release agents of the present invention, the oxidizing is carried out under relatively mild temperatures of from about 120 to about 160° C.
It is preferred to combine raw material feedstocks that exhibit the following combination ~o properties:
1. Heat stability in air-up to 200°C.
2. Good metal release properties - non-sticking , non-fouling characteristics.
3. Non-crystallizing with formation of powdery surfaces.

4. Good interface lubricity.

5. Non-reactive with the substrates, i.e. wood and isocyanate binder:
A skilled artisan will appreciate that there are many waxes which meet the viscosity and droppoint limitations of Applicants' invention. A representative, non-limiting list of preferred waxes which are suitable for use herein is provided below.

PCT/US00/06099 w APPROX. DROPPOINT HARDNESS ACm #

BROOKFIELD C (dmm) mg KOH/g VISCOSITY

OXmIZED 29 80 18 35-45 OXmIZED 13 90 4-8 25-30 low viscosity by 20-40 112 4-5 16-24 -product waxes prepared by the production of high densi of eth lenes Preferred waxes include low viscosity, by-product waxes produced by the production of s high density polyethylenes. Such waxes have a Brookfield viscosity of from about 20 to about 40 mPas at 149°C, a droppoint of from about I 10 to about 114°C, and preferably about 110°C, and a hardness of from about 3 to about 6 dmm at 25°C, and preferably from about 4 to about 5 dmm. Furthermore, the preferred waxes have an acid number which is preferably from about I 6 to about 24 mg KOH/g . For purposes of the present to invention, "low viscosity" shall be understood to mean oxidized waxes having a viscosity lower than about 80 mPas at 149°C and "high density" shall be understood to mean polyethylene waxes having a density ranging from about 0.96 to about 1Ø
In addition to the above-mentioned waxes, the artisan may select waxes from among other 15 known waxes, provided the above mentioned viscosity limitations are met.
Other suitable waxes include polyolefin-based waxes, low density and high density polyethylene waxes, preferably of low viscosity, polypropylene-based waxes both mildly oxidized and grafted PCT/US00%06099 -.
with unsaturated acids as well as their metal base derivatives, Fischer-Troph waxes such as Sasol waxes. Hydrocarbon waxes such as paraffins and microcrystalline waxes, fatty acid derivatives of waxy consistency such as free long chain fatty acids, metallic soaps, amides and esters falling with the viscosity, droppoint and hardness ranges described herein are s also useful.
The release agent may also include other ingredients, including for example, natural waxes such as fatty acid derivatives of waxy consistency such as free long chain fatty acids, metallic soaps, amides and esters. Such products can be combined by emulsification or by to high shear dispersion to form suitable agents for the processing of wood fiber chipboard.
Additional dispersing agents or surfactants may be used to optimize the emulsification or dispersion processes as well as enhance processability.
In another embodiment, process includes using an aqueous emulsion of the specific wax 15 release agent. Suitable aqueous emulsions according to the present invention can be made by any method known to those skilled in the art, such as by high shear mixing.
Preferably, the emulsion is made using a direct pressure method which can include the steps of charging all ingredients into a stirred pressure vessel; closing the vessel, agitating and heating the ingredients to about 120-125 °C; maintaining the temperature for a time 2o suflycient to allow an emulsion to form, e.g. about 15 minutes for usual-sized batches; and cooling the batch as quickly as possible to about room temperature (25-30°C) which will result in a clear emulsion forming.
The emulsions can be diluted with distilled or demineralized water from about 40% solids 25 down to about I% solids, if desired.
In many aspects of the invention, the emulsion will preferably further comprise an emulsifier or surfactant. Suitable emulsifiers used can either be anionic, non-ionic or a cationic. See, for example, the emulsifiers found in the aforementioned WO

which was previous incorporated herein by reference. The emulsifiers are generally used in an amount of about I to about 10 and preferably about 4 to about 7 wt % of the total emulsion. One preferred emulsifier is Marlipal 013.90, an ethoxylated fatty alcohol with s 9 moles of ethoxylation.
Examples of suitable anionic emulsifiers or surfactants include carboxylates, sulphates, sulphonates and phosphates, such as alkylbenzene derivatives; alkyl ether carboxylic acids and salts, e.g., sodium alkyl ether carboxylates; alkyl sulphosuccinates, e.g., all-sodium to monoalkylsulphosuccinate, sodium di-alkyl sulphosuccinates and disodium monoalkyl ethoxy sulphosuccinates; alpha olefin sulphonates; aromatic hydrocarbon sulphonic acids, e.g., benzene sulphonic acid blends, cumene sulphonic acid, phenol sulphonic acid, toluene sulphonic acid and xylene sulphonic acid; aromatic hydrocarbon sulfonate salts, e.g., ammonium xylene sulfonate, dihydroxyl diphenyl sulphones, naphthalene sulphonates and is sodium toluene sulphonates; fatty alcohol ethoxy sulfates, e.g., ammonium lauryl ethoxy sulfates and triethanolamine lauryl ethoxy sulfate; fatty alcohol sulfates, e.g., ammonium lauryl sulfates, monoethanolamine lauryl sulfate and sodium alkyl sulfates;
and phosphate esters, e.g., alkyl phenol ethoxy phosphate ester and fatty alcohol phosphate eater.
2o The aqueous emulsion of the polyolefin wax useful in the present process should contain a sufficient amount of the wax release agent to provide a coverage of about 0.1 to about 0.9 and preferably about 0.2 to about 0.5 milligrams of the oxidized wax release agent per square cm of the lignocellulosic material. When taking the emulsifiers into account, the aqueous emulsions used in the present invention will contain about 1 to about 40%, and 2s preferably about 1 to about 25% by weight of total solids.
In general, it has been found that emulsions containing the wax-based release agents of the present invention can be applied to the lignocellulosic material and/or press plate surfaces as a spray or liquid coating in an amount of from about 2 to about 35 and preferably about 8 to about 16 and most preferably about 10 milligram/square cm. However, it is understood that the amount of application can be varied as needed for a particular purpose.
The aqueous emulsions of the present invention may also contain other additives known to those of ordinary skill, such as anti-foam agents such as Leasol 472 in amounts ranging from about 0.2 to about 1 % by weight of the total emulsion, biocides such as Mergal K14, ranging from about 0.2 to about 0.4% by weight of the total emulsion, flame retardants, to lignocellulosic preserving agents, fungicides, waxes, sizing agents, fillers, surfactant, other binders and catalysts in amounts which are standard in the industry when so included.
Using a wax based release agent emulsion as described above in a process for binding lignocellulosic material with polyisocyanates provides improved release and shortened downtime for cleaning when compared to the conventional processes. Board properties are not detrimentally influenced. These wax-based release agents in emulsions are effective over a wide temperature range. Thus, higher press temperatures can be used (up to 235°C) which speed up the cure process.
2 o In another aspect of the invention, there is provided a method of preparing molded articles such as oriented strand boards, fiber boards, wafer boards and the like.
Suitable lignocellulosic-containing raw materials which may be used in the processes of the present invention include all types known in the industry, such as wood strands, wood chips, wood fibers, shavings, veneers, wood wool, cork, tree bark, sawdust and similar waste products of the woodworking industry as well as other materials having a lignocellulosic basis such as paper, bagasse, straw, flax, sisal fibers and coconut fibers, hemp, rushes, reeds, rice hulls, husks, grass, nutshells, bamboo, alfalfa grass and the like. Moreover, the to WO 00/53381 PCT/US00/06.099 lignocellulosic material may be mixed with other particulate or fibrous materials such as mineral fillers, glass fiber, mica, rubber, textile waste such as plastic fibers and fabrics.
These raw materials may be in the form of granules, chips, fibers or powders and may have a water content of from 0 to 35 wt. % (preferably from 5 to 25 wt. %).
The s composite mixture will also contain a binder such as a polyisocyanate, described in more detail below, and molded generally with the application of heat and pressure to form boards or shaped products. Molded products may, of course, also be produced in accordance with the present invention from other organic (e.g. plastic waste of all kinds) and/or inorganic raw materials (e.g. expanded mica or silicate pellets).
The organic polyisocyanates which are useful as lignocellulosic binders in the present ';'~
invention include any organic polyisocyanate compound or mixture of organic polyisocyanate compounds which are known to those of ordinary skill. A non-limiting representative list of polyisocyanates includes diisocyanates, particularly aromatic diisocyanates, and isocyanates of higher functionality; aliphatic isocyanates such as hexamethylene diisocyanate; aromatic isocyanates, such as m and p-phenylene diisocyanate, tolylene-2,4- and -2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate, chlorophenylene-2,4-diisocyanate, naphthylene-1,5-diisocyanateldiphenylene 4,4'-diisocyanate, 4,4'-diisocyanate-3,3'-dimethyldiphenyl, 3-methyldiphenylmethane-4,4'-2o diisocyanate and Biphenyl ether diisocyanate; and cycloaliphatic diisocyanates such as cyclohexane-2,4- and -2,3-diisocyanate, 1-methylcyclohexyl-2,4- and -2,6-diisocyanate and mixtures thereof and bis(isocyanatocyclohexyl)methane and triisocyanates such as 2,4,6-triisocyanato toluene and 2,4,4-triisocyanatodiphenylether.
2s Modified polyisocyanates containing isocyanurate, carbodiimide or uretonimine groups may also be used according to the present invention. Furthermore, blocked polyisocyanates, such as the reaction product of a phenol or an oxide and a polyisocyanate, having a deblocking temperature below the temperature applied when PCT/US00/06099 -.
using the polyisocyanate composition may be utilized as the organic polyisocyanate binder.
Mixtures of the foregoing are also contemplated.
The organic polyisocyanate binder is generally applied to the lignocellulosic material in an amount of about 0.1 to about 25% weight, preferably about 1 to about 10 and most preferably about 2 to about 6 % by weight based upon the dry weight of the lignocellulosic material.
The boards or molded articles based on lignocellulose-containing other organic and/or to inorganic raw materials produced in accordance with the present invention are particularly suitable for use in the building industry because of their excellent mechanical properties. In order to impart to these boards or molded articles the necessary resistance to mold, insects, or fire, the usual commercial additives (such as organic or inorganic protective agents) may be added to the binders or raw materials, either neat or as solutions. These z5 additives are generally used in a quantity of about 0.05 to 30 wt. %, preferably 0.5 to 20 wt. %, based on the entire quantity of composite. Solvents which may be used in the present invention include water and organic solvents such as residual oils from the petroleum industry, chlorinated hydrocarbons, etc. These solvents generally do not impair adhesive quality. In contrast to boards glued with phenol/formaldehyde resin, the materials 2o produced in accordance with the present invention have the advantage that neither efflorescence of salt nor "bleeding" occurs.
According to the process of the present invention, the lignocellulosic material is brought into contact with the organic polyisocyanate binder material by means of mixing, blending, 25 spraying and/or spreading the polyisocyanate composition with or onto the lignocellulosic material. Such application may generally take place in a conventional blender.
Thereafter, the treated lignocellulosic material is formed into a mat, preferably upon a screen. The treated lignocellulosic material is then conveyed to a press where pressure is applied thereto at elevated temperatures. The pressing operation generally consists of pressing at 120°C to 260°C at pressures of about 2 to 6 MPa. Such binding processes are commonly known in the art. However, it will be recognized by those in the art that the pressing operation may be modified as needed for a particular operation. One particularly preferred continuous press is available from Siempelkamp under the tradename "Conti-roll" system and is used in continuous oriented strand board (OSB) processes.
According to one preferred embodiment, the emulsion containing the selected wax is used as an external release agent. The emulsion is then preferably applied to the surface of the to mat of polyisocyanate treated lignocellulosic material. It will be understood by those of ordinary skill that it may be helpful, but not essential, to condition or "prime" the caul plates of the pressing equipment at the start of a manufacturing run by spraying their surfaces with the emulsion of the present invention or any other conventional external release agent. A preconditioned press may then be used many times without further z5 treatment. Alternatively, boards can be pressed continuously between endless steel belts which are coated with the inventive emulsion prior to starting and periodically as needed in presses having the temperature and pressure requirements discussed above.
In yet a further embodiment of the invention, the selected waxes of the present invention 2 o can also be used in processes for molding articles as internal release agents, if desired without undue experimentation using standard techniques. In such situations, the polyolefin wax emulsion can be pre-mixed with a suitable polyisocyanate binder and applied to a lignocellulosic material as one stream. This route is advisable when the polyisocyanate is used as an aqueous emulsion or suspension. Alternatively, the oxidized 2s wax emulsion and the polyisocyanate binder are applied, preferably simultaneously, to the lignocellulosic material as two separate streams. When used as internal release agent, the weight ratio of the oxidized wax emulsion/polyisocyanate composition is in the range of WO 00/53381 PCT/IJS00/06099 ~ -from about 1:10 to about 3:1 and preferably about 1:1. See also, for example, the aforementioned WO 98/00464.
While the processes of the present invention and waxes included therewith are particularly s suitable for the manufacture of oriented strand board (OSB), they are not limited in this regard. The processes can also be used in the manufacture of various types of composite structures, such as medium density fiberboard, particle board (also known as chipboard) and plywood.
1 o EXAMPLES
The following non-limiting examples serve to illustrate the invention. It will be appreciated that variations in proportions and alternatives will be apparent to those skilled in the art and are within the scope of the present invention.

15 Preparation of Wax Emulsions In this example, two difi'erent types of emulsions were prepared using the waxes and the formulations provided below. Both of the emulsion formulations are suitable for external application to the metal plates of a oriented strand board molding press.
Several dii~erent emulsions were prepared, each with a different wax but otherwise according to the 2o formulations set forth below. The waxes used in the emulsions were either low viscosity, by-product waxes prepared by the production of high density polyethylenes having a Brookfield viscosity of from about 20 to about 40 mPas at 149°C, a droppoint of from about 110 to about 114°C and a hardness of from about 3 to about 6 dmm at 25°C or other waxes meeting the physical characteristics for hardness, viscosity and droppoint set 25 forth above.

Emulsion formulation 1 l0 Ingredient Parts by Wt.

Wax 40.0 Surfactant (Marlipa1013.90) 10.0 KOH(85%) 0.6 NazSZ05 0.4 Water 120.0 Total: 171.0 Emulsion formulation 2 Ingredient Parts by Wt.

Wax 40. 0 Surfactant (Marlipal 013.90)10.0 KOH(85%) 0.4 NazS205 0.4 Water 120.0 Total: 170.8 2 o In each case, the emulsions were prepared as follows:
The wax was charged into a pressure vessel eduipped with an agitator along with the surfactant, potassium hydroxide, sodium meta-bisulfate and water. The pressure vessel was sealed and then heated to an internal temperature of 125°C at which point the mixture was rapidly agitated for I S minutes while the temperature was maintained at 125°C. The pressure vessel was then rapidly cooled to room temperature to form the emulsion.

In this example, the emulsions made in Example 1 are compared against each other and a reference standard to observe the differences in the various physical characteristics and 3o differences in release performance.
In order to determine the release properties of the various emulsions, woodchips S mesh (available from Wood Treatment Ltd) are sprayed with a 50/50 emulsion of a polyisocyanate composition (SUPRASEC 1042, available from Imperial Chemical Industries) and one of the release wax emulsions of Example 1 at 6% loading based on dry wood. Wood moisture content before blending was estimated to be about 2% ;
Press platen temperature: 195°C; Press factor: 15 sec/mm; Board size: 200 mm x 400 MM X 4 mm; caul plates: sandblasted mild steel; density: 650 kg/m3.The release performance was s assessed using the release test procedure described below.
Release test procedure The test included the following steps:
l0 1) Remove all dirt and impurities from the caul plates (S00 x 500 mm) by sandblasting.
2) Remove remaining dust and degrease the caul plates with acetone.
3) Divide the caul plates in two halves. Coat one half with 12 g/m2 of the reference wax, and coat the other half with 12 g/m2 of a test wax before the 15 first press load).
4) Separately, prepare two wax- emulsions; one containing the reference wax, the other containing a test wax.
5) Make two separate mats with the split matformer on the caul plates. The mat with the reference wax goes on the reference side of the caul plate, the other 2o mat on the other side.
6) Move the Gaul plates into the press and start the press cycle Both boards will be pressed at the same time.
7) After the press cycle is finished, remove the caul plates from the press and separate the plates releasing the boards. At this stage carefully observe the 2s release process of both boards. Compare the force to release the suspect board and the resulting wood failure to the reference.
8) Give a mark to the reference and the suspect board according to the following scale:

The board is free from the caul plates. Perfect release. 0% wood failure.
4 The board is attached to the caul. plate but only needs a little, force to release 5 it- 0-10% wood failure.
3 The board is firmly attached to the caul plate and needs a lot more force to be released. 10-50% wood failure.
2 The board is stuck to the caul plate but still-can be removed from it in to one piece.
50% wood failure.
1 The board is stuck to the caul plates and cannot be removed from it in one piece.

9) Make a series of S consecutive boards using the same set of Gaul plates.
Make sure the caul plates do not cool down too far between two pressings.

10) After completion of a series, compare the release properties of the test sample to the reference.
The results show that the wax emulsions of the invention compare favorably to the 2 o reference standard.

In this example, several of the emulsions made in Example 1 are tested as external release 2s agents on a Conti-roll OSB apparatus. For comparison purposes, the emulsions are tested against A-C 6702 and A-C 659.

WO 00/53381 PCT/US00/06099~ -The results unexpectedly show that the emulsions made with waxes having a Brookfield viscosity of less than about 80 mPas at 149°C, a droppoint of between 80-120 °C and a hardness of less than about 18 dmm at 25 °C have superior release performance in comparison to the reference standard. Moreover, unlike the reference standard, the s molding processes carried out with the emulsions containing the waxes having the inventive viscosity, droppoint and hardness do not demonstrate the overspray problems or plating out problems associated with emulsions using waxes having physical characteristics outside the ranges described herein.

Claims (18)

What is claimed is:

1. A method of preparing molded composite materials in a press plate-containing apparatus, comprising: a) treating the press plate surfaces of a molding apparatus which contact a composite mixture with an effective amount of an oxidized wax having a Brookfield viscosity which is less than about 80 mPas at 149 °C, a droppoint of from about 80 to about 120°C and a hardness of less than about 18 decimillimeters (dmm) at 25 °C, prior to said composite material contacting said press plate surfaces, and b) applying the wax-treated press plate surfaces to said composite mixture under conditions suffcient to mold the composite.

2. The method of claim 1, wherein said oxidized wax has a Brookfield viscosity of from about 5 to about 50 mPas at 149 °C.

3. The method of claim 1, wherein said oxidized wax has a Brookfield viscosity which is from about 20 mPas to 40 mPas at 149°C.

4. The method of claim 1, wherein said oxidized wax has a droppoint of from about 104 to about 115°C.

5. The method of claim 4, wherein said oxidized wax has a droppoint of from about 110 to about 113°C.

6. The method of claim 1, wherein said oxidized wax has a hardness of from about 0.1 to about 10 decimillimeters (dmm) at 25 °C.

7. The method of claim 6, wherein said oxidized wax has a hardness of from about 2 to about 8 decimillimeters (dmm) at 25 °C.

8. The method of claim 7, wherein said oxidized wax has a hardness of from about 4 to about 8 decimillimeters (dmm) at 25 °C.

9. The method of claim 1, wherein said oxidized wax has an acid number of from about 14 to about 45.

10. The method of claim 9, wherein said oxidized wax has an acid number of from about 16 to about 25.

11. The method of claim 1, wherein said oxidized wax has a viscosity of from about 20 to about-40 mPas at 149À C, a droppoint of about 112ÀC and a hardness of from about 4 to about 5 dmm at 25ÀC.

12. The method of claim 11, wherein said oxidized wax has an acid number of from about 16 to about 24 mg KOH/g.

13. The method of claim 1, wherein said oxidized wax is selected from the group consisting of Polywaxes, Sasol waxes, Fischer Tropsch waxes, and low viscosity by-product waxes generated during the production of high density polyethylene resins.

14. The method of claim 1, wherein said oxidized wax is applied as an emulsion.

15. The method of claim 14, wherein said emulsion comprises from about 1 to about 40% by weight total solids.

16. The method of claim 15, wherein said emulsion comprises from about 1 to about 25% by weight total solids.

17. The method of claim 16, wherein said emulsion comprises a surfactant in an amount of from about 1 to about 10% by weight.

18. The method of claim 14, wherein said emulsion comprises a member of the group consisting of anti-foam agents, biocides, flame retardants, lignocellulosic preservatives, fungicides and mixtures thereof.