Directional structure board
(Oriented Strand Board OSB), comprises sandwich layer and two surface layers, and wherein surface layer comprises adhesive compound at least to the present invention relates to a kind of directional structure board.
The directional structure board of present commercial preparation comprises the sandwich layer of batten and adhesive compound be combined into, and this sandwich layer is covered by two surface layers of batten and another kind of tackiness agent be combined into.Batten among the OSB has following size usually: length is between 5mm and 150mm, and width is between 1mm and 50mm, and thickness is between 0.1mm and 2mm.Sandwich layer can constitute the 10wt% of OSB to 90wt%, and the 40wt% of preferred OSB is to 70wt%.Adhesive compound in the sandwich layer of known OSB comprises polymerization diphenylmethane diisocyanate (pMDI) resin or phenolic aldehyde (PF) resin of 2-8wt% (dried resin/dried timber).Adhesive compound in the surface layer comprises melamine urea aldehyde (MUF) resin, can also comprise a spot of phenol or resol or the pMDI resin that wherein add releasing agent.The resin content of surface layer is generally 9-12wt% dried resin/dried timber for MUF, is generally 2-6wt% dried resin/dried timber for PF.By convention, the tackiness agent among the OSB for preparing is partly solidified at least, preferred all curing.These known OSB can meet OSB/3 or the OSB/4 standard in EN 300 standards.
The shortcoming of known OSB is, in order to ensure meeting OSB/3 or OSB/4 standard, among the OSB particularly in the surface layer amount of required resin higher.
The objective of the invention is to overcome said shortcoming.
Said purpose reaches in the following manner: the adhesive compound at least one surface layer comprises the resin that contains melamine, formaldehyde, optional urea and optional aromatic hydroxy compound; Wherein the mol ratio of melamine and formaldehyde is 1: 0.8-1: 4.0; The mol ratio of melamine and urea is 1: 0-1: 2.0, and the mol ratio of melamine and aromatic hydroxy compound is 1: 0-1: 2.0.Preferably, the adhesive compound in two surface layers all comprises according to resin of the present invention.
Advantage according to OSB of the present invention is, during the resin of the type known in using the application, can make the OSB that meets OSB/3 or OSB/4 standard of the resin that has low amount in the surface layer.Through the resin that as above limited being used to prepare at least one surface layer of OSB, the amount of the resin that in surface layer, must use can be reduced to 2.5-8wt% dried resin/dried timber in order to make the OSB that meets OSB/3 or OSB/4 standard.Therefore make the cost value of OSB be lower than the cost value of above-mentioned known OSB.In addition, if OSB according to the present invention comprises the resin of said same amount at least one surface layer, then this OSB compares with known OSB and can demonstrate superior character, particularly with boiling water contact after the internal bond strength and the relevant character that expands.
OSB according to the present invention is meant the OSB for preparing; As known, this means that all resins and/or adhesive compound all are cured at least in part.Preferably, they are all by completely solidified.
Resin combination according to the present invention comprises melamine and formaldehyde.Melamine in the resin combination and formaldehyde are with mol ratio 1: 0.8-1: 4.0 exist; Preferably, said melamine: formaldehyde mole ratio is between 1: 0.85 and 1: 3.5; More preferably, said ratio is between 1: 0.9 and 1: 3.25; Even more preferably, said ratio is between 1: 1.0 and 1: 3.0; Especially, said ratio is between 1: 1.05 and 1: 2.8; Most preferably, said ratio is between 1: 1.1 and 1: 2.6.Know that as common cured resin is in order to reach its final performance.In the present invention, term " resin " relate to exist with its uncured state and when its resin that in the finished product, exists during as the OSB for preparing a part of with part or all of solid state.
Resin normally prepares through dry melamine powder mixed with formalin.The concentration of formaldehyde of this solution for example is the formaldehyde that contains 30-55wt%.
Resin combination can also contain urea and/or aromatic hydroxy compound.
When having urea in the resin combination, the mol ratio of melamine and urea is 1: 0-2.0; Preferably, said melamine: urea mol ratio is between 1: 0.05 and 1: 1.8, more preferably between 1: 0.1 and 1: 1.6, particularly between 1: 0.15 and 1: 1.4 or between 1: 0.25 and 1: 1.2.Have surprisingly been found that the final character according to OSB of the present invention to be had favorable influence, it has been generally acknowledged that urea itself has caused performance degradation yet compare with melamine according to the existence of some urea in the resin combination of the present invention.Therefore in a preferred implementation, the melamine in the resin: urea mol ratio is between 1: 0.25 and 1: 0.9.When having aromatic hydroxy compound in the resin combination, the mol ratio of melamine and aromatic hydroxy compound is 1: 0-2.0, preferred 1: 0.05-1.0.
The example of aromatic hydroxy compound is Resorcinol, Resorcinol or dihydroxyphenyl propane.Yet preferably use phenol as aromatic hydroxy compound.
Can be through adding solid urea or through adding aqueous solution of urea and it being mixed with melamine and formaldehyde solution and urea is introduced in the resin compound.Also can use the aqueous solution of formaldehyde and urea and the combination of melamine powder.
When the preparation resin combination, phenol can perhaps be added with the form of formaldehyde/phenol precondensate with regard to itself.
In a preferred implementation according to OSB of the present invention, at least one surface layer does not comprise polymerization diphenylmethane diisocyanate (pMDI) resin; More preferably, two surface layers all do not comprise the pMDI resin.In according to another preferred embodiment of the present invention, sandwich layer does not comprise the pMDI resin.Also more preferably, OSB does not comprise the pMDI resin on the whole.This advantage that has is, OSB can be by preparation quickly, and reason is and compares the adhesive compound that contains aminoplastics based on the adhesive compound of pMDI and have higher curing speed usually.
A nonrestrictive indication to the used resin of preparation OSB according to the present invention is following: the component of under 20 ℃ to 40 ℃ temperature, adding and mixing the formation resin combination mutually.Then temperature is risen between 70 ℃ and 100 ℃.The pH value of mixture is preferably between 7.0 and 10.0.Mixture reacts with this understanding, promptly carries out condensation, up to the viscosity of resin combination between 10mPas and 1000mPas, preferably between 200mPas and 900mPas.Then resin combination is cooled to 20-75 ℃, preferably to room temperature.The pH of chilled resin combination is usually between 7 and 10.
Is the method that comprises substep metered charge component to preparation as another the nonrestrictive indication according to the resin combination of the part of OSB of the present invention.For example, urea can be added when condensation or after the condensation.
In order to regulate the pH of resin combination; Can use the common additives that produces alkaline condition, like the tertiary amine of the basic metal of preferred aqueous solutions form or alkaline earth metal hydroxides, for example Tributylamine or triethylamine, or the alkanol tertiary amine of trolamine and methyldiethanolamine for example.
The viscosity of aqueous resin composition under 20 ℃ is generally 10-900mPas, and its solids content is between 50% and 80%.
Usually, product can be preserved several weeks down at 20 ℃.As known, also can add a spot of other additive in the resin.
When the resin in the surface layer that is used as directional structure board (OSB), resin combination according to the present invention has surprising advantageous property.Its method is described below.
In order in surface layer, to use, form adhesive compound thereby usually resin is mixed with catalyzer or stiffening agent.Usually use that for example ammonium sulfate is as stiffening agent, its amount is no more than the dried stiffening agent/dried resin of 5wt%.But also can use other stiffening agent; For example ammonium chloride or an ammonium nitrate.Can randomly comprise one or more other resins according to adhesive compound of the present invention.When the preparation adhesive compound, also can use paraffin; Do so normally in order to strengthen the wet fastness of OSB.In a preferred implementation according to OSB of the present invention, above given about in the adhesive compound resinous three mol ratios (mol ratio of the mol ratio of the mol ratio of melamine and formaldehyde, melamine and urea and melamine and aromatic hydroxy compound) also be applicable to adhesive compound as a whole.Preferably, adhesive compound does not comprise any other resin except that above-mentioned resin combination.
After adding catalyzer, use adhesive compound in several hours in OSB makes usually; Adhesive compound is sprayed on the batten, to apply batten with it.The length of batten is usually between 5mm and 200mm, preferably between 20mm and 150mm, more preferably between 40mm and 140mm, particularly between 60mm and 130mm, most preferably between 80mm and 120mm.The width of batten is usually between 1mm and 60mm, preferably between 5mm and 50mm, more preferably between 10mm and 40mm, particularly between 14mm and 30mm, most preferably between 18mm and 25mm.The thickness of batten is usually between 0.1mm and 2mm, preferably between 0.2mm and 1.5mm, more preferably between 0.3mm and 1.2mm, particularly between 0.4mm and 1mm, most preferably between 0.5mm and 0.8mm.Be cured/harden once the heating adhesive compound, thereby batten is adhered to each other.Heating and curings/sclerosis occur in when suppressing final OSB material.
The method of making OSB is normally known, and is for example describing to some extent in the following document: " Holzwekstoffe und Leime, M.Dunky and P.Niemz; p 133-135, Springer-Verlag, 2002 " and " Taschenbuch der Spanplatten Technik; Deppe & Ernst; p258-266,1991, DRW Verlag ".
Manufacturing comprises according to the method for directional structure board of the present invention adhesive compound according to the present invention is sprayed on the batten of preferred two surface layers of at least one surface layer of OSB.In order to reach the quality according to OSB/3 or OSB/4 standard, the amount of the resin in a said surface layer or two surface layers can be 2.5 to 8wt% dried resins/dried timber.Preferably, the amount of the resin in a surface layer or two surface layers is at least 2.75%, more preferably at least 3.0%; This advantage that has is that along with the amount increase of resin, the performance of OSB also improves; Especially, the amount of the resin in a surface layer or two surface layers is at least 3.25%, more preferably 3.5wt% dried resin/dried timber at least.In order to guarantee to keep competitive according to the cost of OSB of the present invention, the amount of the resin in a surface layer or two surface layers preferably at the most 7.5%, more preferably at the most 7.0%, particularly at the most 6.5%, 6wt% dried resin/dried timber at the most most preferably.
Core material prepares through applying batten.Usually, the batten in the sandwich layer is less than the batten in the surface layer.In known OSB, the coating of batten (also claim handle) normally uses the adhesive compound be made up of polymerization diphenylmethane diisocyanate (pMDI) or phenolic aldehyde (PF) resin basically to carry out.In OSB according to the present invention, also can carry out this processing.Yet in preferred implementation according to OSB of the present invention; The batten of sandwich layer comprises the adhesive compound that contains resin combination, and wherein said resin combination mainly comprises or even basically is made up of melamine, formaldehyde, optional urea and optional aromatic hydroxy compound.Resin in the sandwich layer in the adhesive compound preferably has 1: 0.8-1: 9 melamine and formaldehyde mole ratio, 1: 0-1: 6 melamine and urea mol ratio, 1: 0-1: 2 melamine and aromatic hydroxy compound mol ratio.More preferably, the resin in the sandwich layer in the adhesive compound has 1: 0.8-1: 4 melamine and formaldehyde mole ratio, 1: 0.1-1: 1.5 melamine and urea mol ratio.This advantage that has is; As the situation in the surface layer; Compare with known adhesive compound based on pMDI or pure PF resin; In sandwich layer, can use more a spot of adhesive compound, simultaneously still reach the final performance of ideal of the performance that requires in OSB/3 for example or the OSB/4 standard.In this embodiment, preferably do not comprise any pMDI (uncured, partly solidified or whole solidified) according to OSB of the present invention.Preferably, above-mentioned given mol ratio also is applicable to adhesive compound as a whole, thereby adhesive compound does not preferably comprise any other resin.
Used resin combination has certain solids content in adhesive compound according to the present invention.Like what the technician knew, the solids content of resin is to measure in 2 hours through the baking oven of low amounts of resin (for example 1 or 2 gram) being put into 120 ℃.Solids content is defined as the relative weight of surplus materials, representes with the weight percent of the resin of putting into baking oven.In a preferred implementation according to the method for the invention, the solids content of the resin combination that the batten of processing sandwich layer is used is at least 60% or 62%.More preferably, solids content is at least 64% or 66%.Rise with solids content, the water yield of introducing in the sandwich layer reduces.Anhydrate owing in follow-up pressing step, should remove, it is favourable therefore introducing few water of trying one's best.Thereby especially, the solids content of resin is at least 68%.Most preferably, solids content is at least 70%.The viscosity of resin also increases along with the rising of solids content.Practice shows, if the solids content of resin keeps below 80%, more preferably less than 78%, particularly be lower than 76% and most preferably be lower than 75%, then helps reaching the uniform distribution of adhesive compound on batten.Preferably, the viscosity of adhesive compound is between 700mPas and 900mPas; Shown in preceding, the influence of the condensation level that the viscosity of adhesive compound is also taken place.
In the adhesive compound of the sandwich layer of OSB, using the resin combination that comprises melamine, formaldehyde, optional urea and optional aromatic hydroxy compound, except relating to the consideration of surface layer, is favourable to itself.Therefore; The invention still further relates to the OSB that comprises sandwich layer and two surface layers; Wherein sandwich layer comprises adhesive compound at least, and the adhesive compound in its center core layer comprises the resin combination that contains melamine, formaldehyde, optional urea and optional aromatic hydroxy compound, and wherein the mol ratio of melamine and formaldehyde is 1: 0.8-1: 9; The mol ratio of melamine and urea is 1: 0-1: 6, and the mol ratio of melamine and aromatic hydroxy compound is 1: 0-1: 2.Preferably, the melamine of the resin in the adhesive compound of sandwich layer and the mol ratio of formaldehyde are 1: 0.8-1: 4, and the mol ratio of melamine and urea is 1: 0.1-1: 2.The amount of resin is of the present invention given in the above in this respect in the sandwich layer.Therefore, the amount of urea is preferably the 0-0.025kg/kg sandwich layer in the sandwich layer, more preferably 0.005-0.015kg urea/kg sandwich layer.The solids content of the used resin of sandwich layer is preferably in the above-mentioned scope that provides.
Surface layer according to this OSB of the present invention can comprise known adhesive compound, promptly comprises based on pMDI resin or PF resin.Yet preferably, preferred two surface layers of at least one surface layer comprise adhesive compound, wherein resin comprise or even basically by according to the present invention aforesaid compound form.Preferably, in two surface layers and sandwich layer, use identical adhesive compound.This advantage that has is in the preparation of OSB, only to need to handle one type resin and adhesive compound.
Usually prepare OSB through following method: at first disperseing (realizing directed simultaneously usually) surface material, is that core material is another surface material layer then afterwards, then its hot pressing is formed OSB.When hot pressing, solidify.Compacting can be the perhaps intermittent mode of continuous mode.In sandwich layer and surface layer, can use different size and directed batten.Compare with the batten in the surface layer, the batten in the sandwich layer has littler size and lower degree of orientation usually.
So the place is stated, and OSB has three layers, a sandwich layer and two surface layers.Can prepare have 4 or more multiwalled OSB also be known, for example through between sandwich layer and at least one surface layer, introducing at least one layer.In context of the present invention, preferably will all not that the layer of surface layer is regarded sandwich layer as and according to the present invention it handled.
Known typical pressing conditions is 1-7MPa, 150-270 ℃, and the press time is 3-12sec/mm, preferred 5-10sec/mm.Known like those skilled in the art, the press time be with second every mm OBS thickness provide.
Say that briefly preparation preferably includes following steps according to the method for directional structure board of the present invention (OSB):
A) preparation comprises the adhesive compound of the resin combination that contains melamine, formaldehyde, optional urea and aromatic hydroxy compound; Wherein the mol ratio of melamine and formaldehyde is 1: 0.8-4.0; The mol ratio of melamine and urea is 1: 0-2.0, and the mol ratio of melamine and aromatic hydroxy compound is 1: 0-2.0;
B) stick with glue agent compositions-treated batten;
C) with the sandwich layer on formation surface layer, this surface layer and another surface layer on this sandwich layer, wherein the batten of at least one surface layer is that the adhesive compound of preparation is handled in using a) through the batten of adhesive treated in dispersion;
D) the compacting batten is to form OSB, and wherein adhesive compound solidifies at least in part.
Preferably, the batten of two surface layers all uses the adhesive compound for preparing in the step a) to handle.Preferably, the solids content of the resin in the adhesive compound for preparing in the step a) is between 67% and 77%, more preferably between 70% and 75%.Preferably, sandwich layer is also handled with the adhesive compound for preparing in the step a).
Can at least one surface layer, comprise certain amount of urea according to OSB of the present invention, major part is the form with bonding usually.This amount can be expressed as the kilogram number of the contained urea of every kg surface layer.Preferably, the amount of the urea that comprises according at least one surface layer of finished product OSB of the present invention is the 0.001-0.025kg/kg surface layer, more preferably the 0.005-0.015kg/kg surface layer.The amount of the urea in the surface layer can adopt currently known methods, and for example Raman spectrum or solid state NMR are measured.Urea in the OSB surface layer that in context of the present invention, relates to is meant urea itself and with the bonding scheme in the resin.Preferably, the urea content of sandwich layer is also within the above-mentioned scope that provides.
Finished product OSB according to the present invention can satisfy EN 300 require in to the requirement of OSB/3 or OSB/4 material.It is to the internal bond strength after the boiling and the requirement of thickness swelling that the typical case here requires.
Measure thickness swelling according to EN 317, and for the OSB that meets OSB/3 or OSB/4 standard, thickness swelling must be lower than 15% or 12% respectively.Measure the internal bond strength after seething with excitement according to EN 321 and EN319.Internal bond strength minimum value under the different OSB thickness is:
Further describe the present invention through following examples.
Example I
Resins
The formalin of 50wt% is mixed with the solution of phenolic aldehyde precondensate, and stir.With NaOH the pH of mixture is transferred to 9.At room temperature add melamine.
Then temperature is risen to 90 ℃.Dissolving melamine and condensation takes place is 1.5-2 until fastness to water.Measure fastness to water down at 20 ℃.
Then mixture is cooled off.Add urea down at 60 ℃, when stirring, mixture further is cooled to room temperature afterwards.
In the resin combination relatively every mole of melamine comprise: 2.2mol formaldehyde; 0.26mol urea and 0.16mol phenol.
The character of resin is:
Viscosity=300mPas (under 20 ℃),
pH=10,
Solids content=62.5%,
Gelation time=50 second,
Fastness to water=1.5
The OSB preparation
Through in resin, adding as the ammonium sulfate of stiffening agent and 1wt% (based on " wet " resin) thus paraffin wax emulsions prepare the adhesive compound of two surface layers that are used for OSB.Then adhesive compound is sprayed on the batten.
The surface layer of OSB comprises dried resin/dried timber of 5.8% and dried stiffening agent/dried resin of 1%.
The adhesive compound that will be used for sandwich layer also is sprayed on batten.The sandwich layer of OSB comprises 3.0% the dried timber of dried pMDI/.Then through disperse one deck batten as surface layer, redispersion one deck batten as redispersion one deck batten after the sandwich layer as second surface layer, thereby preparation OSB.
The weight ratio of sandwich layer and surface layer is 50/50.With the press factors of 9.4sec/mm, 235 ℃ medial temperature and the pressure of 5MPa OSB is suppressed.
Having made thickness is the OSB of 22mm, and its thickness swelling is 8.9%, and the internal bond strength value after the boiling is 0.155N/mm
2
Example II
Use as for example preparing the OSB of thickness as 18mm in the identical method described in the example I.For this OSB, surface layer comprises dried resin/dried timber of 6.0% and dried stiffening agent/dried resin of 1.5%.
With the press factors of 9.2sec/mm, 235 ℃ medial temperature and the pressure of 5MPa OSB is suppressed.
Made OSB, its thickness swelling is 11.0%, and the internal bond strength after the boiling is 0.15N/mm
2
The contrast experiment
Resins
The formalin of 50wt% is mixed with the solution of phenolic aldehyde precondensate, and stir.With NaOH the pH of mixture is transferred to 9.At room temperature add melamine.
Then temperature is risen to 90 ℃.During this period,, temperature adds urea when reaching 82 ℃.Dissolving melamine (and urea), it is 3 until fastness to water that condensation takes place.Measure fastness to water down at 20 ℃.When condensation, pH is remained on 9 through adding NaOH; When water tolerance reaches 3, pH is risen to 10.Then mixture is cooled to room temperature.
In the resin combination relatively every mole of melamine comprise: 4.17mol formaldehyde; 2.27mol urea and 0.2mol phenol.
The character of resin is:
Viscosity=300mPas (under 20 ℃),
pH=10,
Solids content=62.5%,
Gelation time=50 second,
Fastness to water=3
The OSB preparation
Through in resin, adding as the ammonium sulfate of stiffening agent and 1wt% (based on " wet " resin) thus paraffin wax emulsions prepare the adhesive compound of two surface layers that are used for OSB.Then adhesive compound is sprayed on the batten.
The surface layer of OSB comprises dried resin/dried timber of 11wt% and dried stiffening agent/dried resin of 1%.
The adhesive compound that will be used for sandwich layer also is sprayed on batten.The sandwich layer of OSB comprises 3.0% the dried timber of dried pMDI/.Then through disperse one deck batten as surface layer, redispersion one deck batten as redispersion one deck batten after the sandwich layer as second surface layer, thereby preparation OSB.
The weight ratio of sandwich layer and surface layer is 50/50.With the press factors of 9.4sec/mm, 235 ℃ medial temperature and the pressure of 5MPa OSB is suppressed.
Having made thickness is the OSB of 22mm, and its thickness swelling is 10%, and the internal bond strength value after the boiling is 0.14N/mm
2
EXAMPLE III
Be used for the preparation of the resin-Resin A of surface layer
Use identical resin as preparing in the example I.
Be used for the preparation of the resin-resin B of sandwich layer
The formalin of 50wt% is mixed with the solution of phenolic aldehyde precondensate, and stir.With NaOH the pH of mixture is transferred to 9.At room temperature add melamine.
Then temperature is risen to 90 ℃.During this period,, temperature adds urea when reaching 82 ℃.Dissolving melamine (and urea), it is 3 until fastness to water that condensation takes place.Measure fastness to water down at 20 ℃.When condensation, pH is remained on 9 through adding NaOH; When water tolerance reached 3, pH rose to 10.Then mixture is cooled to room temperature.
In the resin combination relatively every mole of melamine comprise: 2.6mol formaldehyde; 0.9mol urea and 0.16mol phenol.
The character of resin is:
Viscosity=300mPas (under 20 ℃),
pH=9.6,
Solids content=62%,
Gelation time=55 second,
Fastness to water=1
The OSB preparation
Through in Resin A, adding as the ammonium sulfate of stiffening agent and 1wt% (based on " wet " resin) thus paraffin wax emulsions prepare the adhesive compound of two surface layers that are used for OSB.Then adhesive compound is sprayed on the batten.
The surface layer of OSB comprises dried resin/dried timber of 5.8wt% and dried stiffening agent/dried resin of 1%.
Through in resin B, adding as an ammonium nitrate of stiffening agent and 1wt% (based on " wet " resin) thus paraffin wax emulsions prepare the adhesive compound of the sandwich layer that is used for OSB.Then adhesive compound is sprayed on the batten.
The sandwich layer of OSB comprises dried resin/dried timber of 4wt% and dried stiffening agent/dried resin of 2%.
Then through disperse one deck batten as surface layer, redispersion one deck batten as redispersion one deck batten after the sandwich layer as second surface layer, thereby preparation OSB.
The weight ratio of sandwich layer and surface layer is 50/50.With the press factors of 8sec/mm, 200 ℃ medial temperature and the pressure of 5MPa OSB is suppressed.
Having made thickness is the OSB of 16mm, and the internal bond strength value after its boiling is 0.13N/mm
2
EXAMPLE IV
Be used for the preparation of the resin-Resin A of surface layer
Use identical Resin A as preparing in the EXAMPLE III.
Be used for the preparation of the resin-resin B of sandwich layer
Use identical resin B as preparing in the EXAMPLE III.
The OSB preparation
Prepare the OSB of adhesive compound and 16mm with the mode identical with EXAMPLE III, difference is that sandwich layer comprises dried resin/dried timber of 5%.Internal bond strength value after the boiling of OSB is 0.25N/mm
2
Additional data
To peel off fully like the surface layer of the OSB of example II and EXAMPLE IV preparation.Subsequently, the internal bond strength value after the boiling of such sandwich layer is measured.Two sandwich layer income values are 0.25N/mm
2
Can find out from example I and contrast experiment; Compare with OSB by the aminoplast(ic) resin preparation that becomes known for this purpose; The amount of OSB according to the present invention contained aminoplast(ic) resin in surface layer is wanted much less, and the performance with known OSB is good equally at least according to the performance of OSB of the present invention.Example II, III and IV explanation when two surface layers and sandwich layer all comprise according to the tackiness agent by the aminoplast(ic) resin preparation of the present invention, can also prepare the OSB that approaches according to the present invention, also demonstrate satisfactory performance.In addition, additional data shows, the adhesive compound in two surface layers and sandwich layer comprises or basically by when being made up of aminoplast(ic) resin, being favourable according to of the present invention, reason is that this causes OSB to have higher internal bond strength value.