BE606833A - - Google Patents

Description

       

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  Thermoplastic films and method and apparatus for producing them.
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  The present invention relates to a pr'Jcéi 'ft a device 1'}: the eye for 1? production of Mutièrc film sheets ther- "l01"} lQsti., "uc. more particularly, it relates to a method and apparatus for the appearance of rolls of film.



  Specifically, the invention relates to a pncr'd and r¯ n4reil capable of causing a variation in distributed thickness in a sheet of sti3re therraoplf stiou extruded from fH; on 3. -1 s, with the effects of variation. '-' produced rpctilines rar ner-- small defects and?; ¯rr ^ 1 ^ ri: s of an extrusion die.
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  The invention relates to thin films of polymers
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 nor. ^. 1 eent solids of substances. non-¯ + w + i ^.: L: .iwa tolE P'lC the polymers therJiloplé "3ti,; ue:.; ¯; r¯.ß .-"; r¯ .. li-

 <Desc / Clms Page number 2>

 
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 monoolfinic compounds with low molecular weight ': l - :;'. <,! J.0Ü; FIF-nt l ': tzrlene, propylene, butene-1 Pt their copolymers as well as peppers and copolymers of vinyl compounds such as styrene, polyamides such as nylon, acrylic polymers and cellulosic polymers.



   Small defects in the lips of the extrusion dies and small variations in the gap of the lips can cause certain difficulties in the manufacture of planar extruded sheets of thermoplastic material. The foregoing defects and / or variations tend to cause straight line thickness variations in the extruded sheet. If these rectilinear variations are in fact a reduction in thickness, the roll obtained by winding the sheet has a depression extending in the peripheral direction. If the variation is an increase in thickness, the roll obtained has a ridge at its periphery.

   In either case, the effect of variations in thickness in the completed roll is cumulative and gives it an undesirable appearance.



   An object of the present invention is to avoid the cumulative effects of a variation in rectilinear thickness on the appearance of the rolls of sheets of extruded thermoplastic material. Another object of the invention is to provide a method and an apparatus.
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 cause a variation in thickness This ended in a sheet j- pe1 'icple of these materials, iIJ1.Jl1éditE': 'slow after the release of 3? film extruded from the lips of the filibi-el cotte variation being distributed over the surfaces of the film so as to avoid <:: plifi- c2tion ie the variation of - '' rectili.¯ne a < --ns ua ro: l - .. ae-ille ae film.

   Another object of the invention is that to provide ..: .. "1 process and an apparatus for extruding: films of thermal material; 1cplé-ti: lc in which regions ;; dteI ... l1! 1 : es ue 1; C1.1'īii- cmt 'Jr'lseUé'1ent cooled t "v'.4CltE': e: lt" vent que 1; sheet ""! 11 ", re d-ns a end of coolant for stacil. ' ': er - F: "1

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 ICx "t.r1;, /. O; :: eu on 1 l; -91e tj''f1lersi0n (<: \ s ('" b-in.



  The invention follows, in a ¯rac, 0 'ne Jroucti2P' -'r 4 ',, iilles of film of material ther'11opl'.sti'; 'lC, one extrune 1: natural under pressure, and to hot to form a sheet of skin.
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 cule; we pass the film under tension and "bare a. = r'Lôsio: 1. yr rt ic: slle in a cooling zone comprising a p li bath which fie cooling have a srf2ce st] p: rurs; on -iri - ga stream of coolant against a surf: - this exposed sheet of film substantially level with the upper surface of the bath so that it strikes the exposed surface of the film sheet; and this current is moved back and forth transversely to the path followed by the film.

   The invention is also extended. apparatus for carrying out the process and the films thus obtained.



   The invention and its objects will become more apparent from the description given below with reference to the accompanying drawings, in the following;
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 Fig. 1 is a perspective view ;; ecppri-iclr tlcraents. the apparatus comprising by way of illustration an extrusion head
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 and the arrangement of cocauun die lips to this kind of rI1; Fi °. 2. -Is a plan view of an alternative means of acplEcer the reciprocating block of FIG. 1; and,
Fig. 3 is a similar view of a third day system
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 "'Place the wire binding block. 1.



   In Fig. 1, the number 1 designates a brooding extruder head to be connected in 2 to the outlet of an extrusion tube (not
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 represents) - In the drawing, lp l; '' '11th axis of the excrusion tube and the direction of passage of the material forr-uc t. extrude by 3 - têt - are indicated by a dotted line and an arrow. The numbers 3 and, indicate the? die lips that have a shape and
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 well-known layout. The film of,.!: = - tiè1'P '-. = .. t: r¯;' - '<::' ¯ "., L .: ..nt

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 between the lips of the die is designated by the number 5.



   As the film 5 exits between the lips of the die of the extrusion head, it descends between a hollow cooling roll 11 and a water roll 12. The cooling roll is mounted on hollow journals! and 11b yes respectively allow the introduction and the discharge of a refrigerated heat exchange liquid passing through the cooling roll as indicated by arrows in the drawing.



  A suitable liquid is ice water.



   The water roller 12 is mounted on the shaft 13 in tangent parallel contact with the cooling roller 11. Conventional devices, not shown, are provided to support the trunnions of the rollers and to adjust the spacing as required. and / or the contact pressure between the rollers. These devices can be, for example, of the type described in US Patent Application No. 814,479 of May 20, 1959. Also as described in this patent application the apparatus according to the present invention comprises a water bowl 21 which partially surrounds the roller. water 12.

   In the construction described, this bowl is provided at one end with a weir 22 making it possible to maintain a level of water in the bowl where the roller 12 is partially immersed. Near the weir 22, the basin 21 comprises an overflow basin 23 provided with an evacuation orifice 24. The opposite end of the basin and the weir 22 are provided with means which make it possible to produce an at least partially sealed seal in - be the cup and the corresponding surface of the rollers 11 and 12.



   The water is brought into the bowl 21 by a rigid but deformable liquid supply pipe 31. As shown, the pipe 31 is fixed to a clamp 32 at the upper surface of a block 33 and is provided with a nozzle 34 which directs a stream of water downward against the extruded sheet 5, substantially at ground level

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 of water held between the sheet and the surface of the water roller 12 by the weir 22 or a little above or below this level.



   The water is brought to the pipe 31 by a flexible pipe 31a connected to a supply pipe 35 by a valve 36.



   Block 33 is mounted on a pair of guide rails
37 and 38 crossing the block in the longitudinal direction. Of the two rails
37 and 38, the last is a threaded cylindrical shaft and constitutes a not thwarted screw 38a. The shaft 38 is mounted so as to be able to be driven in rotation by a motor 39 whose shaft is connected to the shaft 38 by a coupling 39a. The hole in block 33 through which pin 38 passes is provided with a tooth or other similar means for engaging screw 38a in known manner.



   In the reciprocating mounting of block 33 shown alternatively in FIG. 2, the rails 47 and 48 are smooth. At one end of the rails, a reversing motor 49 drives a noulie 49a which can receive a flexible cable or belt 50. The ends of the cable are attached to opposite ends of block 33, as shown, and the cable passes over a pulley 51 arranged at the other end of the rails and opposite to 1 & pulley 49a. Reversing contacts 52 and 53 also arranged at both ends of rails 47 and 48 are interposed in the circuit of motor 49, for example by connections 52a and 53a.

   On the path of the block 33, the contacts 52 and 53 operate when the block comes into contact with them at their opposite ends of its stroke periodically and in turn to reverse the direction of rotation of the motor. Preferably, the contacts are mounted so that their position can be adjusted in the longitudinal direction of the rails, which allows variable adjustment of the stroke of the block according to the width of the extruded film.



   Another way of moving the block 33 back and forth on the rails 47 and 48 is illustrated in FIG. 3. In the assembly shown in this figure, a cylinder 59 is disposed at one end.

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 mite of the ^: they and mounted so as to be centered on a line crus the axis of the rails. The cylinder 59 is provided with a piston rod 60 with a piston head 60a, shown in broken lines, housed inside the cylinder. The head 60a and the rod 60 can be reciprocated in the axial direction of the cylinder under the action of fluid pressure applied alternately to the opposite faces of the piston.

   Pipes 61 and 62 communicate with the opposing extracts in the cylinder provide a means of supplying pressurized fluid to the cylinder from part. on the other side of the piston 60a. Each of these pipes is in turn connected to a four-way motorized valve 63 which is also connected by pipe 64 to a source of fluid below. ion, and through line 65 to a reservoir for the fluid from the cylinder. Neither the source of pressurized fluid nor the reservoir are shown in the drawing.

   When compressed air is the pressurized fluid used, line 65 can be opened to the atmosphere.
In operation of the apparatus shown, and in practical application to the process, the dark film descends between the die lips 3 and 4, and between the cooling roller 11 and the water roller 12 to be drawn into it through. the direction indicated by the arrow.

   The bowl 21 is filled with liquor from this cooling which overflows at the tank 22 and a refrigerated liquid, such as ice water, by entering the hollow cooling roll by the journals 11a and 11b.



   At the same time, a stream of liquid is directed against the outer surface of the sheet of melted material to strike it substantially flush with the weir 22. Preferably, the coolant exits at a pressure of about 1/2 to 10 pounds / square inch (35-700 g / cm2) and at a temperature c at least 3 C higher or lower than that of the coolant in the bowl 21.

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     When the object is to provide a change in thickness of the film sheet greater than its average thickness, a stream of liquid cooled to about 3 ° C below the temperature of the liquid in the bowl 21 is directed against the surface. outside of the sheet at weir 22 or one cuprt of an inch (6 mins) above.

   When the object is to create in the film sheet a variation in thickness less than its average thickness, the flow of liquid directed against the sheet is at a temperature of about 3 C above that of the coolant. and at the level of the weir 22 or about a quarter of an inch (6 min) below this level.



   When a cooled liquid is thus projected against the surface of the film, it causes an abrupt cooling of the film at the point of impact of the liquid stream. This action tends to set the semi-soft film together and prevent it from being stretched or compressed to a lower thickness as it passes between the cooled roll and the water roll. Thus, by moving the current side to side over the sheet surface at a determined steady rate as the sheet passes through the bath, a line of induced thickness variation is produced. By flight from the linear movement of the film sheet, this line has substantially the shape of a sinusoidal curve, a median of which is in the longitudinal axis of the sheet.

   A similar result is obtained by using a hotter current but on the thickness variation file, the thickness is then less than that of the neighboring surface. The adjustment of the point of impact of the liquid stream, the temperature difference above or below the temperature of the bath, and the pressure at the outlet of the liquid are adjusted so as to obtain a variation in thickness which does not exceed Substantially 0.5 thousandth of an inch (0.013 mm) more or less than the desired thickness for the finished sheet.



   In the apparatus shown in the drawings, the current of

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 liquid projected by the nozzle 34 moves from side to side transversely to the plane of the sheet of film passing between the rollers 11 and 12 and is directed so as to strike the sheet substantially at the level of the weir 22. is obtained in this apparatus by fixing the nozzle and the pipe 31 on the block 33 which, as shown in FIG. 1, is mounted to move back and forth on the rails 37 and 38, for example by constituting the rotary rail 38 by a screw with opposed pitch engaged with a tooth provided in the hole of the block 33.



   In the other form of the apparatus shown in FIG. 2 and 3, the reciprocating motion of the block 33 is produced on rails with a smooth surface 47 and 48, either by a reversible motor and a cable 49 and 50 or by a piston 60 mounted in a cylinder 59 and controlled by a fluid pressure applied alternately to opposite faces of piston 60a.



   Of course, the method according to the present invention is not limited to any of the apparatus? described but only to an operation in which a flow of the aid strikes an exposed surface of a sheet of film immediately before or after the sheet is introduced into a cooling bath, and to the movement of this flow back and forth transversely to the sheet and 3 its direction of movement.



   R E V F M D I C A T ION S.

** ATTENTION ** end of DESC field can contain start of CLMS **.


    

Claims (1)

1. A process for the production of film sheets of thermoplastic material, characterized in that the material is extruded under pressure and hot to form a film sheet; the film is passed under tension and under surface pressure along a path passing through a cooling zone and comprising a cooling liquid bath having a higher level; directing a stream of liquid against an exposed surface of the film sheet with substance at the surface <Desc / Clms Page number 9> upper part of the bath so as to strike the exposed surface of the film sheet, and the liquid stream is reciprocated in a path extending transversely to the path of the film. 2. Method according to claim 1, characterized in that the liquid stream is directed against an exposed surface of the. film sheet under an imposed pressure in the range of 1/2 to 10 pounds per square inch (35-700 g / cm2). 3. A method according to claim 1 or 2, characterized in that the liquid stream is directed over an exposed surface of the film sheet at a temperature which is not more than about 3 ° C lower than that of the bath. of liquid and at a level between that of the bath and no more than about one quarter of an inch (6 mm) above the level of the bath. 4. A method according to claim 1 or 2, characterized in that the liquid stream is directed against an exposed surface of the film sheet at a temperature which is not more than about 3 ° C higher than that. liquid in the bath and at a level between that of the bath and a maximum of one quarter of an inch (6 mm) below the level of the bath. 5. Method according to one or the other of claims 1 to 4, characterized in that one obtains a variation of thickness determined in the extruded sheet of thermoplastic material by suddenly cooling a limited region of the sheet which comes from be extruded while passing the sheet through the bath of a cooling liquid, and it is extended. region of sudden cooling limited in a continuous line so as to form a sinusoidal curve having a modular dimension substantially equal to the lateral dimension of the sheet and extending in the longitudinal direction of the sheet. 6. As a new industrial product, an ex- EMI9.1 trudee de.: 1 '- tièrt, themopisstique of which a part linCs.iJ7? ± one <Desc / Clms Page number 10> EMI10.1 thickness between 0.5 thousandths of an inch (0.013 mm) more or less than the average thickness of the film sheet, and the shape of a sine curve with a median common to the axis EMI10.2 '<r: - 410; (..; ": - #'; /" # <- #; longitudinal of, the. sheet of, film. 0+, - ".J; 't .., Jy ,, . i .. :: f. r; (, ..... t. 7 '- ":'" -. '': '\ .- 7.- Agparei, i, rgôur.firlqiér' dës feuilles- of: films ex- "';" l}' ...; .., .. 1 :: "". '. ij 2;. # Y;.! J "K1. Pr '... ^ s. ^ ,, a.w:. :: i.r; i. zij .. trud6es in thermoplastic material; characterized: when it includes ": .. i:" "J - ;;;" p,; ² ;! ; ::; t):.:; .t. ;; ::::. ,, "! ..; ::: - a die-cast extrusion die; aroitê; Sun ', roller cools- *' '" 40 ::. "' ',.;. ^': ;: '? ""' \ * '\.' ment and a roll 'to .; eaû; / t'eéé \ Tant.¯lL; pellicu1e', extr'ddée between them. - # '. :: -. , {= 1 "fw .: i: -: ::. ::: f: 04: 'i'. (/ And a device. To maintain 'uÍl; bath: de., L1quide' cooling-., ' , ..... P 1I:, '' t.; ->. "., -. '' '\': <- ', -'. '., .. ,: '4 f' "'T" If}: ""' ''. '' T -, "\.: - 1 !:, .." "". '' F "'S', t .. ., ........; ..; ..-, '1 "' J '..., ... between -the' rc6; uleja; -ux -, - veal, 'de; -It void determined in advance ...,: '..; ii, \;.,;' I''t-If.? Jt $ J:; t! I '! {T:' l: "/ "":""'" in the bath. tm \ avail3tiormeimeparie ou'amin- '\' "- l: ttf! ...: .1", '\ "I;, JD; Jt it7'4l: .t1'-' '" "vxw: t.' ; '-.i,' .'... '$ s..rr "^' '' '' -, nh'Yi." ..; a, "'a <J -...", ix " ', cie having the IC' pe'1,1, ïcule; e 'g f; , -, '' 3. i. a y:, .. j I have there. c'r: "',.' ¯s. "'' .Rc." F '.y' z; , .. - a median of this; couxtè | scdrrespohdfesëiislplementA axis -Ion-, p -: 3., S.rd '-; .. 5' ': t ?. x. "x '^?'" 'v: 1.'Y ". =" i.wV: ^ lf.> ,,: i. '.' -, r. gitudinal of 3a.feûille, deë.iicu7.efôre and "âoren.antun, dispo- tudinal" '' x :: $ - r-y ''. St.:i '; -, 1;. ,, r, 4s ; "1%, '2f,' y ^ ':' '. Fy, - ,, ..- s.,.;", A', '-. # .. - - positive for à; rgex, iuuç (, oun., de, i'cüite cooled3sémén, t. against .. '..y' <., ^, Y 7: .. E, & r ,, f!> A .'qia ..: ... 5, e..i ..... u: lez. f ^: K> "<riwfik. ' t17 * r - 2. EMI10.3 a surface* EMI10.4 :, i # w .. # 4 ': ^ a, -' y. ' y'k-t. . "t.4i 'f'.t' 'R -: .- s''r" w. rv 'b! , - ',;:. {::; 9':: ". 'RJ.". 'ment with the level of * liquidated in the., bath. cé8ipôsitif'coinprèant a conduct of liqü1de:, e1; únè ': output' túylne 'for the coolant stream .. and sub-device: to move the EMI10.5 pipe and the nozzle reciprocating in a path substantially perpendicular to the longitudinal axis of the formed film sheet. 8. A process for the production of thermoplastic film sheets, substantially as described. 9. A new industrial product consisting of a sheet of extruded film of thermoplastic material, substantially as described. described. 10. Apparatus for producing extruded sheets of thermoplastic material, substantially as described.