CA1122045A - Apparatus and process for preparing hard or medium density board - Google Patents
Apparatus and process for preparing hard or medium density boardInfo
- Publication number
- CA1122045A CA1122045A CA000213257A CA213257A CA1122045A CA 1122045 A CA1122045 A CA 1122045A CA 000213257 A CA000213257 A CA 000213257A CA 213257 A CA213257 A CA 213257A CA 1122045 A CA1122045 A CA 1122045A
- Authority
- CA
- Canada
- Prior art keywords
- board
- resin
- central layer
- suspension
- slurry
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
- B27N1/00—Pretreatment of moulding material
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
- D21J1/00—Fibreboard
- D21J1/16—Special fibreboard
- D21J1/18—Hardboard
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Wood Science & Technology (AREA)
- Forests & Forestry (AREA)
- Dry Formation Of Fiberboard And The Like (AREA)
- Laminated Bodies (AREA)
- Paper (AREA)
- Reinforced Plastic Materials (AREA)
Abstract
Abstract Hard and medium density board are described having a central layer with substantially higher concentration of set resin than both the outer lay-ers of said board. Also a process for the preparation of said board is des-cribed, whereby a thermosetting resin solution or a high resin content pulp is introduced in the central layer of the pulp or the wet slab to be proces-sed to said board; furthermore, an apparatus for said introduction is described.
Description
1~2~0~5 This pxo oess relates to a hard or pxeferably a medil~m density board a process for the production of this fiberboard and a means for practicizing the process.
It is kno~l from the Swedish Patent No. 318,466 that addition of a thermosetting resin and a thermoplastic resin ~h the production of a fiber-board improv~s the mechanical properties of the board, above all its internal bonding strength and its dimensional stability, and that addition of laxge am~unts of resin will make it possible to remove the slab (boaxd or wet lap) from the hot pxess at a moisture content of 10 - 25%, which will shorten the pxess cycle and consequently increase the capacity.
We have now found that impxovem,ents of the strength properties of f~Derboards axe obtained in a walLboaxd being a hard board having a density of 800 - llOOkg/m3 or a medium density board having a density of 400 - 800 - kg/m3 both made from lignocellulosic fibers, the thickness of the board being
It is kno~l from the Swedish Patent No. 318,466 that addition of a thermosetting resin and a thermoplastic resin ~h the production of a fiber-board improv~s the mechanical properties of the board, above all its internal bonding strength and its dimensional stability, and that addition of laxge am~unts of resin will make it possible to remove the slab (boaxd or wet lap) from the hot pxess at a moisture content of 10 - 25%, which will shorten the pxess cycle and consequently increase the capacity.
We have now found that impxovem,ents of the strength properties of f~Derboards axe obtained in a walLboaxd being a hard board having a density of 800 - llOOkg/m3 or a medium density board having a density of 400 - 800 - kg/m3 both made from lignocellulosic fibers, the thickness of the board being
2 - 25 m~ and the board having two surface layers each oomprising at least 10% of the boaxd thickness and therebetween a central layer comprising 10-70% of the board thickness and the board keing pxepared according to the wet ~ process. The improvements of the strength properties are obtained with a less ; total amount of xesin than that of the above-mentioned Swedish Patent in ~ 20 a board of which the central layer has a mean content of 1 - 15% by weight of a set resin and the surfaoe layers having a mean oontent of said resin of less than 1% by weight, the ratio of the mean resin content of said central layer and that of each of said surface layers being at least 4:1 and there being continuous changes of the resin content from the central layer to the surfaoe layers.
e oe ntral layer is preferably between 20 and 50% of the board `~ thickness and the set resin is preferably a phenolformfldehyde resin. A
preferred resin content of said central layer is between 2 and 6%.
With "continuous changes of the resin oontent" is meant that the resin content of the central layer is steadily decreasing to that of the sur-face layers and there being no zone of the board having higher resin content than the central layer. Thus, between the central layer and the surface l~er - ~ :
. .
i~2ZV~15 th~re is no sn~ll or narrow zone, which has a very hiyh resin content, up to approxin~tely 100~. In other words, no abrupt changes of the resin content are found between the central layer and the surface layers.
In one asp~ct of the present inventlon there is provided an improv~nent in a process for the preparation of building board selected from the group consisting of hard and medi~n density board made from ligno- -cellulosic fibers, wherein an aqueous suspension of said lignocellulosic fibers having a consistency in the range of 1.0 - 4.0~ is fed onto a moving wire screen of Fourdrinier type in a board machine for dewatering, whereafter the wet lap dewatered on said moving wire screen is subjected to the normal steps of pressing and baking, which improvenlent comprises introducing evenly across the width of the suspension an aqueous solutionofa thermosetting resin into a central layer of said lignocellulosic fiber suspension having a consistency in said range near the headbox of said board machine such that the resin content of the central layer steadily dec~eases to that of the sur-faoe layers and such that there is no zone of the board having higher resin content than the central layer.
In another aspect of the present invention there is provided an imprcvement in a process for the preparation of building board selected from the group consisting of hard and medium density board made from ligno-cellulosic fibers, wherein an aqueous suspension of said lignocellulosic fibers having a consistency in -the range of 1~0 - 4.0% is fed onto a moving wire screen of Fourdrinier type in a board machine for dewatering, where-after the wet lap dewatered on said moving wire screen is subjected to the normal steps of pressing and heat treatment, which improve~ent comprises introducing evenly across the width of the suspension a slurry of lignocell-ulosic fibers having a content of 1 - 15~ by weight of a thermosetting resin into a central layer of said lignocellulosic fiber suspension having a consistency in said range ne æ the headbox of said board n~chine such that the resin content oE the central layer s-teadily decreases to that of the surface layers and such that there is no zone of the board having higher resin content than the central layer.
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In a further aspect, the present invention provides an improved board making machine wherein a pulp slurry flow of a consistency of less than 4~ is fed on to a moving wire screen, the improvemen-t comprising a device for introducing a thermosetting resin solu-tion into the pulp slurry flow in tne direction of the slurry flcw, said device comprising a straight pipe having ends closed the pipe being disposed in the slurry and transverse-ly to the direction of the slurry flcw and being provided wi-th an mternal partition plate provided with holes for distributing solution admitted to the pipe uniformly along the pipe, nozzles connected to the pipe and direct-ed in the pulp flow direction, inlet means for feeding solution to the portion of the pipe other than that connected to the nozzles and means for holding the device in position in the pulp flow.
In yet a further aspect, the present invention provides an improved board making machine wherein a pulp slurry flow of a consistency of less than 4~ is fed on to a moving wire screen, the improvement comprising a device for introducing a thermosetting resin solution into the pulp slurry in the direction of the slurry flow, said device comprising hollcw~ elongated means having circular cross section said elongated means being disposed in the slurry flow and transversely to the direction of slurry flcw and being provided with a partition wall which divides the hollow means into two chambers and which is provided with holes to uniformly distribute solution flowing fron one chamber to the other, this latter chamber being provided with at least one slot in alignment along the elongated means to admit solution into a central layer of said pulp slurry flow in the same direction as this flow, the elongated means being surrounded by a ma-tching turnable envelope having at least one slot matching said at least one slot in the elongated hollow means so that the flcw through both said at least one slot can be controlled and means for feeding said elongated hollow n~eans with solution and means for fastening the device in position in the pulp slurry on the board nEking n~achine.
me fiberboard according to the invention can be prepæ ed accord-ing to a process comprising intmducing a solution (including emulsion, dis-- lb -- . ~ - . ' : , . ' -- , - , .:
~220~15 persion and the like) of a thermose-tting resin or a fiber slurry having a high content of thermosetting resin into the pulp slurry just before or after the outflcw of the pulp slurry from the head box onto -the wire of a board machine. The slab obtai~ed is then processed in a conventional way, as e.g. heat treated, conditioned, etc. By the process according to the invention it is achieved that the period of hot pressing is shortened, normally 10 to 40% when preparing fiberboards in the wet way, so that the slabs (boards or wet lap) can be withdra~ from the press at an average moisture content of 10 - 25% throughout the cross section of the board wqthout any delaminiating tendency of the bcard when the press is opened and the board withdrawn. The final drying of the board takes place in the following heat treatment.
Accordingly, the reinforcing resin acoording to the invention is -- lc --. ,j.;, ,~
.
'. . `'.
~22(~
concentrated to the central layer (middle), where it has proved to have its maximum importance and to be as advantageous as possible. It has been folmd, that delamination usually occurs in the central layer of the board, where the moisture content is highest. The internaL bonding strength and the screw hold of the board at edge is moreover substantially dependent on the strength of the central layer. By the present invention there is obtained an overall rein-forcement of fiberboards having substantially less amounts of resin than used in prior processes, in which a resin has been added to the whole stock and therefore has been more or less uniformly distributed throughout the cross section of the board.
me term "central layer" is meant to be the layer which can be as much as 70% of the thickness of the board and in which the~mathematical cen-- tre plane of the board is situated. The central layer can be displaced to one of the surfaces (main surfaces of the board) and, thus, must not be sym-metric in relation to the mathematical centre plane. The surface layer being at least 10% of the thickness of the board, must nevertheless always be sit-uated on both sides of the central layer. me thickness of the central layer can vary, as e.g. depending on the thickness of the board, the qualities of the stock and the type of board (hard or medium density). For medium density boards having a density of 500 - 800 kg/m and a thickness of 9 - 19 mm the thickness of the central layer is between 10 and 70% of the thickness of the board, preferably between 10 and 50%~ e.g. between 20 and 35%. When 70% of the thickness of the board is central layer, i.e. having a higher content of cured resin, the central layer is about 50% of the fibers of the board.
The resin content of the central layer can also vary between 1 and 15%, as stated, and is preferably between 2 and 6%. The resin content of the cen-tral layer is advantageously at least ten times more than the resin content of the surface layer. The resin content is in this case analyzed in the cen-trum plane of the central layer and at the surface of the board. When an . ~ ~ . .
aqueous solution (including dispersion or emMlsion) of the thermc-setting resin is used as addi-tive when producing the koard, the resin content of this solution is 20 - 50% by weight, for instance.
The resin content of a pulp slurry, to be used to add resin to the central layer is normally also -the satne as mentioned ~or the aqueous solution.
As thermosetting resin preferably phenol-formaldehyde resin is used, but a plurality of other thermosetting resins are useful, eg. melamine resins, acrylic plastics, resorcinol resins, urea-formaldehyde resins and proteins, such as blood album m.
Preferably in the above device the transverse distribution means comprises a separate head box for the stock of the central layer which is imnersed in the noEmal stock -flow conven~ionally formed at the wet end of a board machine of Fourdrinier type, so that said stock flow encloses the stock flcw coming from the separate head box and comprising a slurry of lignocellulosic fibers havin~ thermosetting resin precipitated thereon.
The accompanying drawings illustrate preferred embodi~ents of the invention. In the drawings:
Figure 1 shows an apparatus, which is suitable to dispose above the wire section at such a height that in operation the distribution takes place in a central layer of the pulp Rlurry on the wire.
. ~ :
: ' . .. .. : .
~Z~f~5 Figure ~ is a vertical cross section along the line II-II of Figure 1.
Figure 3 is a cross section along the line III-III of Figure 2 and shows a detail of the apparatus illustrated in Figure I and Figure 2.
Figure 4 is another embodiment of an apparatus to be used similar to the apparatus of Figure 1 - 3.
The embodiments of the Figures 1 - 4 are preferably used when supply-ing a solution of a thermosetting resin to the fiber slurry or wet slab.
Figure 5 and Figure 7 are other embodiments of the apparatus accord-ing to ~he invention, which are especially suitable for supply of a pulp slur-ry with a high concentration of a thermosetting resin to the fiber slurry or preferably the wet slab.
Figure 6 and Figure 8 are cross sections along the line VI-VI of Figure S and VIII-VIII of Figure 7, respectively.
In Figure 1 a device comprising a horizontal pipe I is shown, which is adapted to be immersed in the pulp slurry on the wire. The device can also be immersed in the pulp slurry in a head box. A solution of a thermoset-ting resin is supplied to the pipe 1 through pipes 2, the number of which depends on the length of the pipe 1. In Figure 2 the pipes 1 and 2 are shown in cross section. The pipe 1 is provided with a plate 3 arranged transversely to the flow direction of the resin solution, long sides ~edges) of the plate
e oe ntral layer is preferably between 20 and 50% of the board `~ thickness and the set resin is preferably a phenolformfldehyde resin. A
preferred resin content of said central layer is between 2 and 6%.
With "continuous changes of the resin oontent" is meant that the resin content of the central layer is steadily decreasing to that of the sur-face layers and there being no zone of the board having higher resin content than the central layer. Thus, between the central layer and the surface l~er - ~ :
. .
i~2ZV~15 th~re is no sn~ll or narrow zone, which has a very hiyh resin content, up to approxin~tely 100~. In other words, no abrupt changes of the resin content are found between the central layer and the surface layers.
In one asp~ct of the present inventlon there is provided an improv~nent in a process for the preparation of building board selected from the group consisting of hard and medi~n density board made from ligno- -cellulosic fibers, wherein an aqueous suspension of said lignocellulosic fibers having a consistency in the range of 1.0 - 4.0~ is fed onto a moving wire screen of Fourdrinier type in a board machine for dewatering, whereafter the wet lap dewatered on said moving wire screen is subjected to the normal steps of pressing and baking, which improvenlent comprises introducing evenly across the width of the suspension an aqueous solutionofa thermosetting resin into a central layer of said lignocellulosic fiber suspension having a consistency in said range near the headbox of said board machine such that the resin content of the central layer steadily dec~eases to that of the sur-faoe layers and such that there is no zone of the board having higher resin content than the central layer.
In another aspect of the present invention there is provided an imprcvement in a process for the preparation of building board selected from the group consisting of hard and medium density board made from ligno-cellulosic fibers, wherein an aqueous suspension of said lignocellulosic fibers having a consistency in -the range of 1~0 - 4.0% is fed onto a moving wire screen of Fourdrinier type in a board machine for dewatering, where-after the wet lap dewatered on said moving wire screen is subjected to the normal steps of pressing and heat treatment, which improve~ent comprises introducing evenly across the width of the suspension a slurry of lignocell-ulosic fibers having a content of 1 - 15~ by weight of a thermosetting resin into a central layer of said lignocellulosic fiber suspension having a consistency in said range ne æ the headbox of said board n~chine such that the resin content oE the central layer s-teadily decreases to that of the surface layers and such that there is no zone of the board having higher resin content than the central layer.
- la -~ ~., ' ' , .
~ .. .
~L220~S
In a further aspect, the present invention provides an improved board making machine wherein a pulp slurry flow of a consistency of less than 4~ is fed on to a moving wire screen, the improvemen-t comprising a device for introducing a thermosetting resin solu-tion into the pulp slurry flow in tne direction of the slurry flcw, said device comprising a straight pipe having ends closed the pipe being disposed in the slurry and transverse-ly to the direction of the slurry flcw and being provided wi-th an mternal partition plate provided with holes for distributing solution admitted to the pipe uniformly along the pipe, nozzles connected to the pipe and direct-ed in the pulp flow direction, inlet means for feeding solution to the portion of the pipe other than that connected to the nozzles and means for holding the device in position in the pulp flow.
In yet a further aspect, the present invention provides an improved board making machine wherein a pulp slurry flow of a consistency of less than 4~ is fed on to a moving wire screen, the improvement comprising a device for introducing a thermosetting resin solution into the pulp slurry in the direction of the slurry flow, said device comprising hollcw~ elongated means having circular cross section said elongated means being disposed in the slurry flow and transversely to the direction of slurry flcw and being provided with a partition wall which divides the hollow means into two chambers and which is provided with holes to uniformly distribute solution flowing fron one chamber to the other, this latter chamber being provided with at least one slot in alignment along the elongated means to admit solution into a central layer of said pulp slurry flow in the same direction as this flow, the elongated means being surrounded by a ma-tching turnable envelope having at least one slot matching said at least one slot in the elongated hollow means so that the flcw through both said at least one slot can be controlled and means for feeding said elongated hollow n~eans with solution and means for fastening the device in position in the pulp slurry on the board nEking n~achine.
me fiberboard according to the invention can be prepæ ed accord-ing to a process comprising intmducing a solution (including emulsion, dis-- lb -- . ~ - . ' : , . ' -- , - , .:
~220~15 persion and the like) of a thermose-tting resin or a fiber slurry having a high content of thermosetting resin into the pulp slurry just before or after the outflcw of the pulp slurry from the head box onto -the wire of a board machine. The slab obtai~ed is then processed in a conventional way, as e.g. heat treated, conditioned, etc. By the process according to the invention it is achieved that the period of hot pressing is shortened, normally 10 to 40% when preparing fiberboards in the wet way, so that the slabs (boards or wet lap) can be withdra~ from the press at an average moisture content of 10 - 25% throughout the cross section of the board wqthout any delaminiating tendency of the bcard when the press is opened and the board withdrawn. The final drying of the board takes place in the following heat treatment.
Accordingly, the reinforcing resin acoording to the invention is -- lc --. ,j.;, ,~
.
'. . `'.
~22(~
concentrated to the central layer (middle), where it has proved to have its maximum importance and to be as advantageous as possible. It has been folmd, that delamination usually occurs in the central layer of the board, where the moisture content is highest. The internaL bonding strength and the screw hold of the board at edge is moreover substantially dependent on the strength of the central layer. By the present invention there is obtained an overall rein-forcement of fiberboards having substantially less amounts of resin than used in prior processes, in which a resin has been added to the whole stock and therefore has been more or less uniformly distributed throughout the cross section of the board.
me term "central layer" is meant to be the layer which can be as much as 70% of the thickness of the board and in which the~mathematical cen-- tre plane of the board is situated. The central layer can be displaced to one of the surfaces (main surfaces of the board) and, thus, must not be sym-metric in relation to the mathematical centre plane. The surface layer being at least 10% of the thickness of the board, must nevertheless always be sit-uated on both sides of the central layer. me thickness of the central layer can vary, as e.g. depending on the thickness of the board, the qualities of the stock and the type of board (hard or medium density). For medium density boards having a density of 500 - 800 kg/m and a thickness of 9 - 19 mm the thickness of the central layer is between 10 and 70% of the thickness of the board, preferably between 10 and 50%~ e.g. between 20 and 35%. When 70% of the thickness of the board is central layer, i.e. having a higher content of cured resin, the central layer is about 50% of the fibers of the board.
The resin content of the central layer can also vary between 1 and 15%, as stated, and is preferably between 2 and 6%. The resin content of the cen-tral layer is advantageously at least ten times more than the resin content of the surface layer. The resin content is in this case analyzed in the cen-trum plane of the central layer and at the surface of the board. When an . ~ ~ . .
aqueous solution (including dispersion or emMlsion) of the thermc-setting resin is used as addi-tive when producing the koard, the resin content of this solution is 20 - 50% by weight, for instance.
The resin content of a pulp slurry, to be used to add resin to the central layer is normally also -the satne as mentioned ~or the aqueous solution.
As thermosetting resin preferably phenol-formaldehyde resin is used, but a plurality of other thermosetting resins are useful, eg. melamine resins, acrylic plastics, resorcinol resins, urea-formaldehyde resins and proteins, such as blood album m.
Preferably in the above device the transverse distribution means comprises a separate head box for the stock of the central layer which is imnersed in the noEmal stock -flow conven~ionally formed at the wet end of a board machine of Fourdrinier type, so that said stock flow encloses the stock flcw coming from the separate head box and comprising a slurry of lignocellulosic fibers havin~ thermosetting resin precipitated thereon.
The accompanying drawings illustrate preferred embodi~ents of the invention. In the drawings:
Figure 1 shows an apparatus, which is suitable to dispose above the wire section at such a height that in operation the distribution takes place in a central layer of the pulp Rlurry on the wire.
. ~ :
: ' . .. .. : .
~Z~f~5 Figure ~ is a vertical cross section along the line II-II of Figure 1.
Figure 3 is a cross section along the line III-III of Figure 2 and shows a detail of the apparatus illustrated in Figure I and Figure 2.
Figure 4 is another embodiment of an apparatus to be used similar to the apparatus of Figure 1 - 3.
The embodiments of the Figures 1 - 4 are preferably used when supply-ing a solution of a thermosetting resin to the fiber slurry or wet slab.
Figure 5 and Figure 7 are other embodiments of the apparatus accord-ing to ~he invention, which are especially suitable for supply of a pulp slur-ry with a high concentration of a thermosetting resin to the fiber slurry or preferably the wet slab.
Figure 6 and Figure 8 are cross sections along the line VI-VI of Figure S and VIII-VIII of Figure 7, respectively.
In Figure 1 a device comprising a horizontal pipe I is shown, which is adapted to be immersed in the pulp slurry on the wire. The device can also be immersed in the pulp slurry in a head box. A solution of a thermoset-ting resin is supplied to the pipe 1 through pipes 2, the number of which depends on the length of the pipe 1. In Figure 2 the pipes 1 and 2 are shown in cross section. The pipe 1 is provided with a plate 3 arranged transversely to the flow direction of the resin solution, long sides ~edges) of the plate
3 are provided with holes, preferably shaped as a semi-circle. The plate 3 distributes the resin solution uniformly over the whole length of the pipe 1. me resin solution flows through a slot 4 in the pipe 1 to one or more nozzles 5. There may be only one nozzle extending like a slot along the whole length of the pipe 1 or be divided into several small slots or circular noz-zles, which distribute the resin solution evenly along the length of the pipe 1 in the pulp slurry on the wire. The flow direction of the resin solution in the nozzle 5 is substantially the same as that of the pulp slurry on the 1~2Z~5 wire.
The embodiment of a device according to the invention shown in Figure
The embodiment of a device according to the invention shown in Figure
4 comprises a pipe 1, one, two or more supply pipes 2 and a plate 3, which three parts are arranged analogously with the corresponding parts according to Figures 1 and 2. Furthermore~ in the pipe 1 a slot 4 is arranged, from which the solution of thermosetting resin flows substantially in the same direction as the pulp slurry, which flows across the pipe 1. The pipe 1 is further surrounded by a pipe 6 with a slot 7. By turning the pipe 6 the slots 4 and 7 can be adjusted so that a suitable width is obtained for the outlet slot for controlling the amount of thermosetting resin solution.
It is also possible to use an arrangement consisting of a series of noz21es mounted on a pipe.
s~bs~an~;al/y 2~ ~ree In these three embodiments described the solution of~thermosetting resin is preferably fed to the pipe by means of a highlift pump from a high pressure tank. These arrangements can in a simple way be mounted in existing board machines without it` being necessary to alter the machine in other res-pects. It is also possible to use these arrangements for supply ofother chemi-càls, e.g. fire retardant chemicals, at a desired level in the stock flow.
If the higher content of resin in the central layer of the board is to be obtained by supplying a slurry of pulp fiber (lignocellulosic fibers) having an increased content of resin as central layer, the thermosetting re-sin already being precipitated on the fibers, the supply, however, preferably takes place through a separate head box, which is immersed in the normal stock flow on the wet end of the board machine. In Figures ~ and 6 an embodiment of such a separate box is shown, which is preferably immersed in the stock flow in the normal head box. The pulp slurry, the stock, is supplied to this head box through a transverse distributing device 10, This device may be dis-posed directly in cormection with the additional head box, so that said box as well as said distributing device are immersed in the stock flow. At 2~45 the head box l1 sho~m in Figures 5 and 6 the transverse distributing device 10 is outside the normal head box and the stoek is fed through a pipe 12 from the distributing device to the additional head box. In this ease the rear portion 13 of the head box 11 has a triangular form so ~hat the stock flow in the normal head box is not substantially disturbed. This additional head box 11 is also provided with baffles 1~ to render the stock flow in this box uniform.
The embodiment of the present device shown in Figures 7 and 8 com-prises a head box 11 containing a transverse distributing device. The head box is also provided with baffles 14. mis head box can be placed in the stoek flow on the wire, the stock being supplied to the transverse distribut-ing device 10 through pipes 15, whieh are lead through the deckle boards of - the board machine. This box 11 has also a triangular rear portion 13. It is also possiblè to plaee this box in a normal head box of a board maehine.
e additional head boxes according to Figures 5 - 8 can in a simple way be used with usual board machines of Fourdrinier type with very small~
ehanges of the maehine construction~
The present process can also be carried out in sueh a way that a stock ;
for the eentral layer with an inereased concentration of thermosetting resin is supplied centrally in a head box with several vertically separated dis-eharge gates. me stoek eonsisteney (fiber eoneentration) is usually between :
1 and 5% and the machine speed between 5 and 50 meters per minute.
me invention is illustrated more closely in the following examples.
:~` ` EXA~LE l.
A slurry in water was prepared at a temperature of 50C from a plant stoek without any acLditions, which stock was intended for the preparation of medium density boarcLs. 0.5% al~um (aluminum sulphate) caleulated on the weight of dry fibers and sulphuric aeid were added to the slurry in sueh an amount that the pH of the slurry was brought to 4Ø me pulp suspension was moulded - 6 - ;
1~.2Z~
on a board machine to a slab with a basis weight of about 7.5 kg/m . The wet slab formed was dewatered partially through suction boxes and wet pressed to a dry content of about 40%. ~len the wet slab was sawed to a format of 60 ~ 60 and pressed in a hot press provided with distance rims to a thickness C of 10 mm with a closing pressure of 0.59 MPa~ The press temperature was 230C
and the wet slab was pressed until the temperature in the central layer of the slab reached 200C. The required press time was 23 minutes. This corresponds to a normally used press cycle of such a board. Immediately after the pres-sing the bending strength and the modulus of elasticity on bending were mea-sured on a part of the hot board sawed in advance. The rest of the board was then heat-treated for 2 hours at 160C. After conditioning the board obtained the following properties~
density 750 kg/m internal bonding strength0.22 MPa bending strength 26 MPa modulus of elasticity on bending 3300 MPa bending strength directly after hot pressing and before heat-treatment 13 MPa 2% by weight of phenol-formaldehyde resin based on the weight of dry fiber were added before pH-adjustment to the same fiber slurry as in the pre-vious test~ after which the pH of the slurry was reduced to 4.0 with 0.5% of alum and sulphuric acid. Also this suspension was moulded to wet slabs, which were cold pressed and hot pressed in a way as described; some slabs were pres-sed with a press t:ime of 23 minutes and some with a press time of 11 minutes.
These latter slabs reached after hot pressing a dry content of 80%. After heat-treatment for 2 hours at 160 C and conditioning the board showed the following properties.
~1 ~IPQ _ tO ~//~
, ~z~ a5 Press time 1L m~n. Press _ime 23 min.
thickness l0.6 mm 10 mm density 710 kg/m 750 kg/m internal bonding strength 0.33 MPa 0.60 MPa bending strength 23 MPa 27 MPa modulus of elasticity on bending 2600 MPa 3300 MPa bending strength directly after hot pressing and before heat-treatment 5.6 MPa 13 MPa It is apparent from the table that the boards pressed for 11 minutes had a much lower bending strength directly after pressing, which shows that they are more easily damaged during the following treatments. Moreover it is apparent from the tablethat these boards have a lower density with the same basis weight, which indicates that the board had expanded back after hot pres-sing.
A wet slab was moulded by the additional head box described in Figure 3 and with the transverse distributing device 10 arranged behind the ordinary head box on a board machine of Fourdrinier type, 2/3 of the stock being sup-plied through the ordinary head box and 1/3 of it through the additional head box. This was so immersed in the flow of the main stock that the fiber slurry from it formed a central layer in the finished board. The fiber slurry, which was supplied through this additional head box was provided with 6~o of phenol-formaldehyde resin and its pH had been adjusted to 4.0 with 0.5% of alum and sulphuric acid. Also the flow of the main stock, which was free of resin, was adjusted to a pH of 4Ø The wet slabs obtained from this production thus contained 2% of resin based on the dry content of the whole slab like the slabs prepared in the previous test. However, in this case the resin was concentrated to the central one third of the slab. The wet slab was cold pressed and hot pressed in a way as described above with a hot press time of 11 minutes. After the same heat-treatment and conditioning as at the previous :
~Z2~45 tests the boards obtained had the following properties:
thickness 10 mm density 750 kg/m internal bonding strength 0.62 MPa bending strength 26 MPa modulus of elasticity on bending3300 MPa bending strength directly after hot pressing and before heat-treatment 13 MPa dry content after hot pressing 81 %
In spite of the short press time this board showed the same strength after hot pressing as the boards obtained in the first two tests with 0 and 2% concentration of phenol resin~ the resin however being distributed in the whole board in this board with 2% of phenol resin. The boards with the resin concentrated to the central layer showed as good handling ability after hot pressing as a conventionally pressed board. The internal bonding strength of the board after heat treatment and conditioning thereof are also very good.
EXAMPLE 2.
~ et slabs were manufactured in a way as described with a separate ~ ;
stock of central layer, to which 15% of phenol resin, i.e. 5% of resin based on the whole board had been added. After hot pressing forllminutes, heat-treatment and conditioning this board had the same properties as that with 6% of resin in the central layer. Thus an increase from 6% to 15% of resin does not influence the board properties with the phenol resin here used.
~ et slabs were prepared from the same fiber slurry on a laboratory sheet form, 6% of phenol resin being added to the central layer of the board.
This time the thickness of the central layer was 1/4 of the total board thick- -ness. The slabs were cold pressed to a dry content of about 40% and then hot pressed for 11 minutes at 230 C as described. These boards showed the same high bending strength directly after hot pressing and did not show any :~22~5 expansion effect after pressing. After heat treatment and conditioning the board showed the following properties:
thickness 10 mm density 750 kg/m internal bonding strength 0.45 MPa bending strength 26 MPa modulus of elasticity on bending 3300 MPa bending strength after hot pressing and before heat-treatment12 MPa Boards were manufactured in indicated manner, the content of phenol resin in the central layer however being 4% and the thickness of the central layer being 1/3 of the total board thickness. The boards were hot pressed at 230C for 16 minutes, which provided a dry content after pressing of 90%.
The boards obtained showed the following properties:
~: :
thickness 10 mm density 750~kg/m internal bonding strength 0.43 MPa bending strength 25 MPa modulus of elaat1city on bending 3200 MPa bending strength after hot pressing ~ ~ and before heat-treatment 11 MPa.
; ~ EXAMPLE 3.
~` Wet slabs were prepared in a way as described above in the form of laboratory sheets. The thiclmess of the central layer was one third of that of the wet slab and contained 3% of phenol resin, i.e. the total resin con-tent of the board was about 1%. The board had a density of 700 kg/m .
In the following table the properties of a board prepared with 1%~
of phenol resin uniformly distr1buted in the whole board and those of the ;
board prepared according to the present examples and the present invention , ~
~1%2~
with 3% of phenol resin in a central layer were compared. In both cases a full pressing time was used.
1% of phenol resin 3% of phenol resin uniformly distributed in a central lay-in the whole boarder of 1/3 internal bonding strength ~a 0.38 0.53 specific screw hold in edge kN/m 26 42 in flat side kN/m 47 61 splitting tendency 0.35 0.20 l~ater absorption % 13.5 13.8 10 thickness swelling % 7.5 7.6 The splitting tendency in a sawed section is defined as z ~~zs ~ , zwherein ~ means the internal bonding strength with a wood screw screwed into the edge and ~ means the internal bonding strength without screw. The screw, uhich is a wood screw of 22 mm x 6 mm, is screwed 15 mm into the edge in a hole bored in advance to 10 mm and ~th the diameter 2 mm. Normally the sensitivity to cracks is reported within 0.05.
The specific screw hold has been indicated in kN/m of screwing length.
At the test the same bore diameter, bore depth and screwing depth were used at screwing in edge as for measuring splitting tendency. At screwing in a flat side the bore depth was 2/3 of the thickness of the board and the screw was screwed through ~the whole board, however, not so far that it stuck out on the underside. The extraction rate was 1 mm/min.
EXAMPLE 4.
At another test a board with a density of ?00 kg/m and a total resin content of 2% was pr~pared as mentioned above. When the resin content was uni-formly distributed the internal bonding strength was 0.42 MPa. When all the resin was applied in a central layer, which was 1/3 of the thickness of the wet slab and thus contained 6% of resin, the internal bonding strength _ 11 --~Z;~5 increascd to 0.52.~1Pa in spitc of the fact that tl~e ~o~rd was taken from the hot press at a dry content of about 85~ in con~parison with 100% of dry content at tlle board with ~uliformly distributcd resin.
Internal bonding strcngth, screw hold and splitting tendcncy are of very great importance for the assembly possibilities of boards, as they in-clude different types of joining strength and joining possibility. Boards can be joined and mounted in several different malmers. It may be simple nailing through tllc ~hole board or in a :lap joint of type groo~re and tenom or with a rabbet. ~lese board edges and joints can be easlly damaged in ass-embly. Therefore a good joining strength is essential for an easy and rapidassembly work. In the last decade the demands on Internal bonding strength of particle boards and medium density fiberboards ha~e increased. A conse-- quence thereof has been that the density of marketed boards has been increased.
The result of the invention is thus that a sufficiently high interllal bonding strength can be obtained at a lower density.
A later invention frcm the same group in Sweden, described in Canadian Patent 1,023,179 by E. Back, can be combined with the present invention. This later invention describes a process of`optimizing the bend-ing stiffness of board by stripwise addition of fibre stock for strips of increased density in the machine and cross machine direction. This~
adaitional stock can be applied first and the additional resin in the mid-layer thereafter on the forn~ng machine, using the ap~aratus de-cribed herein.
.
.. , - .
:: -
It is also possible to use an arrangement consisting of a series of noz21es mounted on a pipe.
s~bs~an~;al/y 2~ ~ree In these three embodiments described the solution of~thermosetting resin is preferably fed to the pipe by means of a highlift pump from a high pressure tank. These arrangements can in a simple way be mounted in existing board machines without it` being necessary to alter the machine in other res-pects. It is also possible to use these arrangements for supply ofother chemi-càls, e.g. fire retardant chemicals, at a desired level in the stock flow.
If the higher content of resin in the central layer of the board is to be obtained by supplying a slurry of pulp fiber (lignocellulosic fibers) having an increased content of resin as central layer, the thermosetting re-sin already being precipitated on the fibers, the supply, however, preferably takes place through a separate head box, which is immersed in the normal stock flow on the wet end of the board machine. In Figures ~ and 6 an embodiment of such a separate box is shown, which is preferably immersed in the stock flow in the normal head box. The pulp slurry, the stock, is supplied to this head box through a transverse distributing device 10, This device may be dis-posed directly in cormection with the additional head box, so that said box as well as said distributing device are immersed in the stock flow. At 2~45 the head box l1 sho~m in Figures 5 and 6 the transverse distributing device 10 is outside the normal head box and the stoek is fed through a pipe 12 from the distributing device to the additional head box. In this ease the rear portion 13 of the head box 11 has a triangular form so ~hat the stock flow in the normal head box is not substantially disturbed. This additional head box 11 is also provided with baffles 1~ to render the stock flow in this box uniform.
The embodiment of the present device shown in Figures 7 and 8 com-prises a head box 11 containing a transverse distributing device. The head box is also provided with baffles 14. mis head box can be placed in the stoek flow on the wire, the stock being supplied to the transverse distribut-ing device 10 through pipes 15, whieh are lead through the deckle boards of - the board machine. This box 11 has also a triangular rear portion 13. It is also possiblè to plaee this box in a normal head box of a board maehine.
e additional head boxes according to Figures 5 - 8 can in a simple way be used with usual board machines of Fourdrinier type with very small~
ehanges of the maehine construction~
The present process can also be carried out in sueh a way that a stock ;
for the eentral layer with an inereased concentration of thermosetting resin is supplied centrally in a head box with several vertically separated dis-eharge gates. me stoek eonsisteney (fiber eoneentration) is usually between :
1 and 5% and the machine speed between 5 and 50 meters per minute.
me invention is illustrated more closely in the following examples.
:~` ` EXA~LE l.
A slurry in water was prepared at a temperature of 50C from a plant stoek without any acLditions, which stock was intended for the preparation of medium density boarcLs. 0.5% al~um (aluminum sulphate) caleulated on the weight of dry fibers and sulphuric aeid were added to the slurry in sueh an amount that the pH of the slurry was brought to 4Ø me pulp suspension was moulded - 6 - ;
1~.2Z~
on a board machine to a slab with a basis weight of about 7.5 kg/m . The wet slab formed was dewatered partially through suction boxes and wet pressed to a dry content of about 40%. ~len the wet slab was sawed to a format of 60 ~ 60 and pressed in a hot press provided with distance rims to a thickness C of 10 mm with a closing pressure of 0.59 MPa~ The press temperature was 230C
and the wet slab was pressed until the temperature in the central layer of the slab reached 200C. The required press time was 23 minutes. This corresponds to a normally used press cycle of such a board. Immediately after the pres-sing the bending strength and the modulus of elasticity on bending were mea-sured on a part of the hot board sawed in advance. The rest of the board was then heat-treated for 2 hours at 160C. After conditioning the board obtained the following properties~
density 750 kg/m internal bonding strength0.22 MPa bending strength 26 MPa modulus of elasticity on bending 3300 MPa bending strength directly after hot pressing and before heat-treatment 13 MPa 2% by weight of phenol-formaldehyde resin based on the weight of dry fiber were added before pH-adjustment to the same fiber slurry as in the pre-vious test~ after which the pH of the slurry was reduced to 4.0 with 0.5% of alum and sulphuric acid. Also this suspension was moulded to wet slabs, which were cold pressed and hot pressed in a way as described; some slabs were pres-sed with a press t:ime of 23 minutes and some with a press time of 11 minutes.
These latter slabs reached after hot pressing a dry content of 80%. After heat-treatment for 2 hours at 160 C and conditioning the board showed the following properties.
~1 ~IPQ _ tO ~//~
, ~z~ a5 Press time 1L m~n. Press _ime 23 min.
thickness l0.6 mm 10 mm density 710 kg/m 750 kg/m internal bonding strength 0.33 MPa 0.60 MPa bending strength 23 MPa 27 MPa modulus of elasticity on bending 2600 MPa 3300 MPa bending strength directly after hot pressing and before heat-treatment 5.6 MPa 13 MPa It is apparent from the table that the boards pressed for 11 minutes had a much lower bending strength directly after pressing, which shows that they are more easily damaged during the following treatments. Moreover it is apparent from the tablethat these boards have a lower density with the same basis weight, which indicates that the board had expanded back after hot pres-sing.
A wet slab was moulded by the additional head box described in Figure 3 and with the transverse distributing device 10 arranged behind the ordinary head box on a board machine of Fourdrinier type, 2/3 of the stock being sup-plied through the ordinary head box and 1/3 of it through the additional head box. This was so immersed in the flow of the main stock that the fiber slurry from it formed a central layer in the finished board. The fiber slurry, which was supplied through this additional head box was provided with 6~o of phenol-formaldehyde resin and its pH had been adjusted to 4.0 with 0.5% of alum and sulphuric acid. Also the flow of the main stock, which was free of resin, was adjusted to a pH of 4Ø The wet slabs obtained from this production thus contained 2% of resin based on the dry content of the whole slab like the slabs prepared in the previous test. However, in this case the resin was concentrated to the central one third of the slab. The wet slab was cold pressed and hot pressed in a way as described above with a hot press time of 11 minutes. After the same heat-treatment and conditioning as at the previous :
~Z2~45 tests the boards obtained had the following properties:
thickness 10 mm density 750 kg/m internal bonding strength 0.62 MPa bending strength 26 MPa modulus of elasticity on bending3300 MPa bending strength directly after hot pressing and before heat-treatment 13 MPa dry content after hot pressing 81 %
In spite of the short press time this board showed the same strength after hot pressing as the boards obtained in the first two tests with 0 and 2% concentration of phenol resin~ the resin however being distributed in the whole board in this board with 2% of phenol resin. The boards with the resin concentrated to the central layer showed as good handling ability after hot pressing as a conventionally pressed board. The internal bonding strength of the board after heat treatment and conditioning thereof are also very good.
EXAMPLE 2.
~ et slabs were manufactured in a way as described with a separate ~ ;
stock of central layer, to which 15% of phenol resin, i.e. 5% of resin based on the whole board had been added. After hot pressing forllminutes, heat-treatment and conditioning this board had the same properties as that with 6% of resin in the central layer. Thus an increase from 6% to 15% of resin does not influence the board properties with the phenol resin here used.
~ et slabs were prepared from the same fiber slurry on a laboratory sheet form, 6% of phenol resin being added to the central layer of the board.
This time the thickness of the central layer was 1/4 of the total board thick- -ness. The slabs were cold pressed to a dry content of about 40% and then hot pressed for 11 minutes at 230 C as described. These boards showed the same high bending strength directly after hot pressing and did not show any :~22~5 expansion effect after pressing. After heat treatment and conditioning the board showed the following properties:
thickness 10 mm density 750 kg/m internal bonding strength 0.45 MPa bending strength 26 MPa modulus of elasticity on bending 3300 MPa bending strength after hot pressing and before heat-treatment12 MPa Boards were manufactured in indicated manner, the content of phenol resin in the central layer however being 4% and the thickness of the central layer being 1/3 of the total board thickness. The boards were hot pressed at 230C for 16 minutes, which provided a dry content after pressing of 90%.
The boards obtained showed the following properties:
~: :
thickness 10 mm density 750~kg/m internal bonding strength 0.43 MPa bending strength 25 MPa modulus of elaat1city on bending 3200 MPa bending strength after hot pressing ~ ~ and before heat-treatment 11 MPa.
; ~ EXAMPLE 3.
~` Wet slabs were prepared in a way as described above in the form of laboratory sheets. The thiclmess of the central layer was one third of that of the wet slab and contained 3% of phenol resin, i.e. the total resin con-tent of the board was about 1%. The board had a density of 700 kg/m .
In the following table the properties of a board prepared with 1%~
of phenol resin uniformly distr1buted in the whole board and those of the ;
board prepared according to the present examples and the present invention , ~
~1%2~
with 3% of phenol resin in a central layer were compared. In both cases a full pressing time was used.
1% of phenol resin 3% of phenol resin uniformly distributed in a central lay-in the whole boarder of 1/3 internal bonding strength ~a 0.38 0.53 specific screw hold in edge kN/m 26 42 in flat side kN/m 47 61 splitting tendency 0.35 0.20 l~ater absorption % 13.5 13.8 10 thickness swelling % 7.5 7.6 The splitting tendency in a sawed section is defined as z ~~zs ~ , zwherein ~ means the internal bonding strength with a wood screw screwed into the edge and ~ means the internal bonding strength without screw. The screw, uhich is a wood screw of 22 mm x 6 mm, is screwed 15 mm into the edge in a hole bored in advance to 10 mm and ~th the diameter 2 mm. Normally the sensitivity to cracks is reported within 0.05.
The specific screw hold has been indicated in kN/m of screwing length.
At the test the same bore diameter, bore depth and screwing depth were used at screwing in edge as for measuring splitting tendency. At screwing in a flat side the bore depth was 2/3 of the thickness of the board and the screw was screwed through ~the whole board, however, not so far that it stuck out on the underside. The extraction rate was 1 mm/min.
EXAMPLE 4.
At another test a board with a density of ?00 kg/m and a total resin content of 2% was pr~pared as mentioned above. When the resin content was uni-formly distributed the internal bonding strength was 0.42 MPa. When all the resin was applied in a central layer, which was 1/3 of the thickness of the wet slab and thus contained 6% of resin, the internal bonding strength _ 11 --~Z;~5 increascd to 0.52.~1Pa in spitc of the fact that tl~e ~o~rd was taken from the hot press at a dry content of about 85~ in con~parison with 100% of dry content at tlle board with ~uliformly distributcd resin.
Internal bonding strcngth, screw hold and splitting tendcncy are of very great importance for the assembly possibilities of boards, as they in-clude different types of joining strength and joining possibility. Boards can be joined and mounted in several different malmers. It may be simple nailing through tllc ~hole board or in a :lap joint of type groo~re and tenom or with a rabbet. ~lese board edges and joints can be easlly damaged in ass-embly. Therefore a good joining strength is essential for an easy and rapidassembly work. In the last decade the demands on Internal bonding strength of particle boards and medium density fiberboards ha~e increased. A conse-- quence thereof has been that the density of marketed boards has been increased.
The result of the invention is thus that a sufficiently high interllal bonding strength can be obtained at a lower density.
A later invention frcm the same group in Sweden, described in Canadian Patent 1,023,179 by E. Back, can be combined with the present invention. This later invention describes a process of`optimizing the bend-ing stiffness of board by stripwise addition of fibre stock for strips of increased density in the machine and cross machine direction. This~
adaitional stock can be applied first and the additional resin in the mid-layer thereafter on the forn~ng machine, using the ap~aratus de-cribed herein.
.
.. , - .
:: -
Claims (16)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a process for the preparation of building board selected from the group consisting of hard and medium density board made from ligno-cellulosic fibers, wherein an aqueous suspension of said lignocellulosic fibers having a consistency in the range of 1.0 - 4.0% is fed onto a moving wire screen of Fourdrinier type in a board machine for dewatering, whereafter the wet lap dewatered on said moving wire screen is subjected to the normal steps of pressing and baking, the improvement comprising introducing evenly across the width of the suspension an aqueous solution of a thermosetting resin into a central layer of said lignocellulosic fiber suspension having a consistency in said range near the headbox of said board machine such that the resin content of the central layer steadily decreases to that of the sur-face layers and such that there is no zone of the board having higher resin content than the central layer.
2. A process as in claim 1 wherein the aqueous solution of a thermo-setting resin is introduced into the suspension where there is a water level on the top of the suspension.
3. The process of claim 1, wherein said resin solution is introduced into the aqueous suspension of said lignocellulosic fibers within the head box of the board machine.
4. The process of claim 1, wherein said resin solution is introduced into said aqueous suspension of said lignocellulosic fibers on the wire.
5. The process of claim 1, wherein the thermosetting resin content of said solution is 20 - 50%.
6. In a process for the preparation of building board selected from the group consisting of hard and medium density board made from lignocellulosic fibers, wherein an aqueous suspension of said lignocellulosic fibers having a consistency in the range of 1.0 - 4.0% is fed onto a moving wire screen of Fourdrinier type in a board machine for dewatering, whereafter the wet lap dewatered on said moving wire screen is subjected to the normal steps of pressing and heat treatment, the improvement comprising introducing even-ly across the width of the suspension a slurry of lignocellulosic fibers having a content of 1 - 15% by weight of a thermosetting resin into a central layer of said lignocellulosic fiber suspension having a consistency in said range near the headbox of said board machine such that the resin content of the central layer steadily decreases to that of the surface layers and such that there is no zone of the board having higher resin content than the central layer.
7. The process of claim 6, wherein said lignocellulosic fiber slurry is introduced into the aqueous suspension of said lignocellulosic fibers within the headbox of the board machine.
8. The process of claim 6, wherein the lignocellulosic fiber slurry is introduced into said aqueous suspension of said lignocellulosic fibers on the wire, said suspension having said consistency range of 1.0 - 4.0%.
9. A process as in claim 6 wherein the slurry of fibers containing the resin is introduced into the suspension where there is a water level on top of the suspension.
10. In a board making machine wherein a pulp slurry flow of a con-sistency of less than 4% is fed on to a moving wire screen, the improvement comprising a device for introducing a thermosetting resin solution into the pulp slurry flow in the direction of the slurry flow, said device comprising a straight pipe having the ends closed, the pipe being disposed in the slurry and transversely to the direction of the slurry flow and being provided with an internal partition plate provided with holes for distributing solu-tion admitted to the pipe uniformly along the pipe, nozzles connected to the pipe and directed in the pulp flow direction, inlet means for feeding solution to the portion of the pipe other than that connected to the nozzles and means for holding the device in position in the pulp flow.
11. The device of claim 10, wherein the inlet means comprises at least one pipe connected to the upper part of the horizontal pipe.
12. The device of claim 10, wherein tile nozzles are combined to form at least one slot.
13. In a board making machine wherein a pulp slurry flow of a consistency of less than 4% is fed on to a moving wire screen, the improve-ment comprising a device for introducing a thermosetting resin solution in-to the pulp slurry in the direction of the slurry flow, said device compris-ing hollow, elongated, means having circular cross section said elongated means being disposed in the slurry flow and transversely to the direction of slurry flow and being provided with a partition wall which divides the hollow means into two chambers and which is provided with holes to uniformly distribute solution flowing from one chamber to the other, this latter chamber being provided with at least one slot in alignment along the elongated means to admit solution into a central layer of said pulp slurry flow in the same direction as this flow, the elongated means being surrounded by a matching turnable envelope having at least one slot matching said at least one slot in the elgonated hollow means so that the flow through both said at least one slot can be controlled and means for feeding said elongated hollow means with solution and means for fastening the device in position in the pulp slurry on the board making machine.
14. The device of claim 13, wherein the device is positioned with said at least one slot in a central layer of the pulp flow on the board making machine.
15. The device of claim 14, wherein the device is positioned in the headbox of the board making machine.
16. The device of claim 14, wherein the device is positioned in the pulp slurry flow on a moving wire screen of the board making machine.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7315156-5 | 1973-11-08 | ||
| SE7315156A SE391759B (en) | 1973-11-08 | 1973-11-08 | METHOD AND DEVICE FOR MANUFACTURE OF A HARD OR SEMI-HARD FIBER SHEET |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1122045A true CA1122045A (en) | 1982-04-20 |
Family
ID=20319053
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000213257A Expired CA1122045A (en) | 1973-11-08 | 1974-11-07 | Apparatus and process for preparing hard or medium density board |
Country Status (16)
| Country | Link |
|---|---|
| JP (1) | JPS5812150B2 (en) |
| AT (1) | AT351742B (en) |
| BR (1) | BR7409379A (en) |
| CA (1) | CA1122045A (en) |
| CH (1) | CH586601A5 (en) |
| DE (1) | DE2452170C2 (en) |
| DK (1) | DK578074A (en) |
| ES (1) | ES431732A1 (en) |
| FI (1) | FI321974A (en) |
| FR (1) | FR2250856B1 (en) |
| GB (1) | GB1489407A (en) |
| IT (1) | IT1025472B (en) |
| NL (1) | NL7414523A (en) |
| NO (1) | NO744019L (en) |
| SE (1) | SE391759B (en) |
| ZA (1) | ZA747154B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4168200A (en) * | 1975-03-17 | 1979-09-18 | Abitibi Paper Company Ltd. | Method for controlling caliper and edge and corner delamination of hardboard |
| JPS602633U (en) * | 1983-06-21 | 1985-01-10 | 東洋製罐株式会社 | Container support handle |
| JPH0562437U (en) * | 1992-02-04 | 1993-08-20 | 株式会社吉野工業所 | Synthetic resin container with handle |
| JP2010121058A (en) * | 2008-11-20 | 2010-06-03 | Nichiha Corp | Environmentally-friendly wet process type hard fiberboard |
| CN111648157A (en) * | 2020-05-25 | 2020-09-11 | 潍坊汇胜绝缘技术有限公司 | Production process of medium-density insulating paperboard |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2970644A (en) * | 1958-06-02 | 1961-02-07 | Webster David Richan | Liquid dispersion conduit |
| US3386879A (en) * | 1965-03-09 | 1968-06-04 | Abitibi Power & Paper Co | Process for forming board containing cellulosic fibers, thermosetting binder and pinewood resin |
| CH516992A (en) * | 1969-11-24 | 1971-12-31 | Fahrni Peter | Process for the production of single- or multilayer boards by pressing particles mixed with binder |
-
1973
- 1973-11-08 SE SE7315156A patent/SE391759B/en unknown
-
1974
- 1974-10-31 CH CH1458374A patent/CH586601A5/xx not_active IP Right Cessation
- 1974-11-02 DE DE2452170A patent/DE2452170C2/en not_active Expired
- 1974-11-04 FR FR7436596A patent/FR2250856B1/fr not_active Expired
- 1974-11-04 FI FI3219/74A patent/FI321974A/fi unknown
- 1974-11-05 AT AT885174A patent/AT351742B/en not_active IP Right Cessation
- 1974-11-06 IT IT29165/74A patent/IT1025472B/en active
- 1974-11-06 DK DK578074A patent/DK578074A/da unknown
- 1974-11-07 CA CA000213257A patent/CA1122045A/en not_active Expired
- 1974-11-07 ZA ZA00747154A patent/ZA747154B/en unknown
- 1974-11-07 NL NL7414523A patent/NL7414523A/en not_active Application Discontinuation
- 1974-11-07 BR BR9379/74A patent/BR7409379A/en unknown
- 1974-11-07 ES ES431732A patent/ES431732A1/en not_active Expired
- 1974-11-07 NO NO744019A patent/NO744019L/no unknown
- 1974-11-08 GB GB48424/74A patent/GB1489407A/en not_active Expired
- 1974-11-08 JP JP49128822A patent/JPS5812150B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DK578074A (en) | 1975-06-30 |
| SE391759B (en) | 1977-02-28 |
| SE7315156L (en) | 1975-05-09 |
| ZA747154B (en) | 1975-11-26 |
| ES431732A1 (en) | 1977-05-16 |
| NO744019L (en) | 1975-06-02 |
| DE2452170C2 (en) | 1986-11-13 |
| GB1489407A (en) | 1977-10-19 |
| AT351742B (en) | 1979-08-10 |
| BR7409379A (en) | 1976-05-18 |
| CH586601A5 (en) | 1977-04-15 |
| JPS5089486A (en) | 1975-07-17 |
| FR2250856A1 (en) | 1975-06-06 |
| DE2452170A1 (en) | 1975-05-15 |
| NL7414523A (en) | 1975-05-12 |
| FR2250856B1 (en) | 1978-06-09 |
| JPS5812150B2 (en) | 1983-03-07 |
| ATA885174A (en) | 1979-01-15 |
| FI321974A (en) | 1975-05-09 |
| IT1025472B (en) | 1978-08-10 |
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