CA1106120A - Process for producing expanded article of thermoplastic resin - Google Patents
Process for producing expanded article of thermoplastic resinInfo
- Publication number
- CA1106120A CA1106120A CA294,070A CA294070A CA1106120A CA 1106120 A CA1106120 A CA 1106120A CA 294070 A CA294070 A CA 294070A CA 1106120 A CA1106120 A CA 1106120A
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- Prior art keywords
- resin
- expanded
- mass
- nozzle
- zone
- Prior art date
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Abstract
ABSTRACT OF THE DISCLOSURE
A process for producing an expanded article of a thermoplastic resin by extruding and expanding a foamable resin using an extruder equipped, on a resin channel in a die, with a nozzle having a number of apertures, which comprises flowing a resin mixture stream through an expansion zone while maintaining the resin mixture at a temperature above the melting point thereof, dividing the resin mixture stream into a plurality of separate streams, exiting these streams from the extursion zone directly into a confined zone, thereby forming a plurality of soft expanded resin strands corresponding in number to the number of strands, bringing the strands into surface contact with each other to fuse and bond them together to form a bonded expanded resin mass while simultaneously removing gases generated in the course of extrusion and expansion, passing the bonded mass into an unconfined zone to permit the mass to further expand while still in a softened condition, passing the further expanded mass into a confined receiving zone of a smaller cross-sectional -area than the further expanded mass, and cooling the mass to form an expanded article.
A process for producing an expanded article of a thermoplastic resin by extruding and expanding a foamable resin using an extruder equipped, on a resin channel in a die, with a nozzle having a number of apertures, which comprises flowing a resin mixture stream through an expansion zone while maintaining the resin mixture at a temperature above the melting point thereof, dividing the resin mixture stream into a plurality of separate streams, exiting these streams from the extursion zone directly into a confined zone, thereby forming a plurality of soft expanded resin strands corresponding in number to the number of strands, bringing the strands into surface contact with each other to fuse and bond them together to form a bonded expanded resin mass while simultaneously removing gases generated in the course of extrusion and expansion, passing the bonded mass into an unconfined zone to permit the mass to further expand while still in a softened condition, passing the further expanded mass into a confined receiving zone of a smaller cross-sectional -area than the further expanded mass, and cooling the mass to form an expanded article.
Description
BACKGROUND OF THE INVENT ION
~ . ._ . _._ . _ . . . _ 1. Field of_the Invention This invention relates to a process for producing an expanded article of a thermoplastic resin. More Particularly~
this invention relates to a process for producing an expanded article of (1) a polypropylene resin, a polypropylene copolymer resin or a mixture of a polypropylene resin and less than about 50% by weight of a thermoplastic resin, or (2) a polyamide resin, which has excellent chemical and heat resistance and toughness.
~ . ._ . _._ . _ . . . _ 1. Field of_the Invention This invention relates to a process for producing an expanded article of a thermoplastic resin. More Particularly~
this invention relates to a process for producing an expanded article of (1) a polypropylene resin, a polypropylene copolymer resin or a mixture of a polypropylene resin and less than about 50% by weight of a thermoplastic resin, or (2) a polyamide resin, which has excellent chemical and heat resistance and toughness.
2. Description of_the Prior Art Processes for producing a thermoplastic resin foamed article for use as a synthetic wood with woodgrain pattern by extruding a molten foamable thermoplastic resin through a nozzle having a number of apertures to expand the resin have already been known as described in, for example, U.S. Patents
3,720,572 and 3,993,721 and Japanese Patent Application ~OPI~
No. 59,969/76.
These processes for producing a thermoplastic resin foamed article are directed to the production of a foamed resin primarily comprising a polystyrene resin. Since a polystyrene resin has a good foamability, desired resin foamed articles can be produced continuously over a long period of time according to the above-described processes.
However, in applying the above conventional processes to crystalline thermoplastic resins other than polystyrene, e.g., polypropylene, a resin containing polypropylene as a major component or a polyamide, it is very difficult to con~
tinuously produce resin foamed articles having good quality.
i~'6~2V
1 No process suitable for foaming such crystalline thermoplastic resins has so far been practically used. That is, since poly-propylene and polyamide resins are crystalline thermoplastic resins, their melt viscosity is sensitively temperature-dependent, and a viscosity suitable for their expansion is in a narrow temperature range close to a temperature at which the resins crystallize. Generally, it is extremely difficult to conduct extrusion and expansion while controlling the nozzle temperature in such a narrow temperature range. In extruding such resins 10 using a nozzle having a number of apertures, the resin streams flow in some portions with difficulty and partially crystallize and solidify to prevent expansion. In addition, such adverse affects on uniform, stable extrusion in respective apertures make it difficult to produce a resin foamed article having high quality of crystalline thermoplastlc resin.
It has been considered that such problems could be solved by controlling a temperature of the nozzle with high accuracy in order to avoid crystallization and solidification of the resin. In fact, however, it is technically difficult to control the nozzle temperature within a critical narrow ran~e suitable for expansion in order to avoid crystallization, since extrusion molding involves many factors which may vary widely.
For example, to equip a nozzle with a temperature-controlling mechanism as disclosed in Japanese Patent Application tOPI) No. 59,969/76 is not satisfactory for a polypropylene resin or a polyamide resin; the resin crystallizes in part of a number of apertures, which prevents stable extrusion of resin streams. -In addition, when the resin is cooled through a frame adjacent to a nozzle having a projection in its center as described in U.S.
Patent 3,993,721, it is difficult to extrude polyrpopylene resin ll~e~ilZO
1 quantitatively in respective apertures of the nozzle because plugging partly occurs. Thus, stable production of a thermo-plastic resin foamed article, such as a polypropylene resin foamed article or a mixture thereof, or a polyamide resin foamed article, having good quality over a long time a~ foun~
to be very difficult.
SUMMARY OF THE INVENTION
.
As a result of extensive investigations to solve the above-described technical problems associated with the conventional processes in the continuous production ~f a crystalline thermoplastic resin foamed article used, for example, as a synthetic wood with woodgrain pattern, it was found that desired resin foamed articles with woodgrain pattern can be stably and continuously produced by elevating the temperature of a nozzle having a number of apertures to a level higher than the melting point of the resin mixture used, reducing the temperature of a frame directly connected to the nozzle, simultaneously restricting the cross-sectional area at the exit of extrusion zone to a given size to thereby control expansion after extrusion through respective apertures of the nozzle, thereby forming a plurality of soft expanded resin strands corresponding in number to the number of strands, bringing the strands into surface contact with each other to fuse and bond them together to form a bonded expanded resin mass while simultaneously removing gases generated in the course of extrusion and expansion, passing the bonded mass into an unconfined zone to permit the mass to further expand while still in a softened condition, passing the further expanded mass into a confined receiving zone of a smaller cross-sectional area than the further expanded mass, and cooling the mass to form an expanded article.
BF<I~:F DESCRIPTION OF THE DRAWINGS
. . _ . .
Figure 1 is a part of sectional view showing an embodiment of the process of the present invention.
Figures 2 and 3 show an example of a nozzle which can be used in the extruder used in the present invention. Figure 2 is a vertical side sectional view of the nozzle and Figure 3 is a part of hack view of the nozzle.
Figures 4 and 5 similarly show another example of a nozzle. Figure 4 is a vertical side sectional view of the nozzle and Figure 5 is a part of front view of the nozzle.
Figures 6 and 7 are vertical side sectional views showing other examples of frames used in the present invention.
Figures 8 and 9 similarly show a further example of a nozzle in which Figure 8 is a vertical side sectiona~ view of the nozzle and Figure 9 is a part of front view of the nozzle.
Figures 10 and 11 similarly show a still further example of a nozzle in ~hich Figure 10 is a vertical side sectional view of the nozzle and Figure 11 is a part of front view of the nozzle.
In these Figures, E designates an extruder, 1 designates a temperature controller, 2 a die, 3 a nozzle, 31 a projection, 32 apertures, 33 a gas-releasing groove, 4 and 4' frames, 41 and 41' channels for a cooling medium, 5 a receiving frame, 6 a plate, 7 a water bath, 71 rolls, 8 a surface-processing apparatus, 9 take-up rolls, and 100 a foamed article.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for producing a foam of a thermoplastic resin, such as (1) a polypropylene resin, a polypropylene copolymer resin or a mixture of a 11~61ZO
1 polypropylene resin and less than about 50%, preferably 1 to 30~, by weight of a thermoplastic resin, or (2) a polyamide resin, by extruding and expanding the resin using an extruder equipped, on a resin channel in a die, with a nozzle having a number of apertures, which comprises flowing a resin mixture stream through an expansion zone while maintaining the resin . mixture at a temperature above the melting point thereof, for - example, up to about 20C, preferably up to 10C, above the melting point, dividing the resin mixture stream into a plurality of separate streams, the cross-sectional area occupied by these streams being from about 5 to about 30%, preferably 5 to 15~, of the cross-sectional area at the exit of the extrusion zone, exiting these streams from the extrusion zone directly into a confined zone maintained at a temperature at least about 30C, preferably at a temperature in the range of 50C to 100C, lower than the temperature of the resin streams prior to the exiting, thereby forming a plurality of soft expanded resin strands corresponding in number to the number of strands, bringing the strands into surface contact with each other to fuse and bond them together to form a bonded expanded resin mass while simultaneously removing gases generated in the course of extrusion and expansion, passing the bonded mass into an unconfined zone to permit the mass to further expand while still in a softened condition, passing the further expanded mass into a confined receiving zone of a smaller cross-sectional area than the further expanded mass, and cooling the mass to form an expanded article.
. The process of the present invention will now be illustrated in greater detail by reference to the attached drawings.
.-- 5 --O
1 Figure 1 shows an embodiment of the present invention, wherein temperature controller 1 is provided at the forward end of extruder E. Temperature controller 1 includes torpedo 12 in outer cylinder 11, and the space between them forms resin channel 13. A cavity is formed inside torpedo 12, and a heating or cooling medium is circulated in the cavity through pipe 14 to thereby heat or cool torpedo 12. Outer cylinder 11 has spiral channel 15 piercing therethrough, through which spiral channel a heating or cooling medium is circulated via pipes 16 tO to thereby heat or cool outer cylinder 11. Thus, a molten resin mixture flowing through channel 13 is controlled to a temperature within an extremely narrow range suitable for subsequent expansion.
Band heaters 17 can be provided around outer cylinder 11.
Die 2 isprovided subsequent to temperature controller 1. Band heater 21 is provided around this die 2, and resin channel 22 of die 2 is provlded with resin stream-adjusting plate 23 having a number of openings and nozzle 3. Since the resin stream in resin chanel 22 flows faster at the central portion than that of peripheral portion, diameters of the openings of resin stream-adjusting plate 23 are properly adjusted so that the resin stream becomes uniform. Resin channel 22 is provided with narrow neck 24 between resin stream-adjusting plate 23 and nozzle 3, which functions to avoid premature expansion and maintain expanding pressure.
Nozzle 3 having a number of apertures 32, 32, ...
arranged in two rows has continuous projection 31 on a resin-entering side between these two rows, and has gas-releasing groove 33 which is provided inward between the two rows of apertures 32, 32,... on a resin-leaving side. Further, square frame 4 having a plurality of channels 41 for controlling tem-perature is connected to the forward end of this nozzle 3 1~61~0 1 subsequent to die 2. The frame 4 is connected via space 42 having a heat-insulating effect in order to avoid direct transmission of heat from die 2. Still further, similar other A~ frame 4' having an-o~cnir~-~ slightly enlarged sectional area and having a plurality of similar channels 41' and similar space 42' is provided at the forward end of frame 4. Both ends of the above-described gas-releasing groove 33 are opened to atmosphere and gases genera~ed after extrusion through respective apertures 32 r 32,... are directly released into atmosphere.
Numeral 5 designates a tapered receiving frame functioning to compress an expanded mass for reducing the sectional area with a given compression ratio. Numeral 6 designates a plate controlling the appearance and the dimension of the expanded mass, numeral 7 designates a water bath for cooling and solidifying the expanded mass, and numeral 71 designates rolls provided in the water bath 7, which cools the mass while controlling its dimension. Surface-processing apparatus 8 is provided subsequent to water bath 7. This surface-processing apparatus 8 is constituted by heating and tapered compressing 20 member 81 and subsequent cooling member 82, whereby the surface of resin foamed article is re-heated and compressed to such a degree that the sectional area of the foam is reduced by about 3% to about 20% as compared with the sectional area prior to the pre-heating and the compression to provide a hard surface layer and a high dimensional accuracy of the resulting shaped expanded -~
article. Numeral 9 designates take-up rolls.
In the above-described production apparatus, the resin kneaded with, for example, nucleating agents, blowing agents and pigments, etc. and melted by means of heated extruder 30 E is controlled, by temperature controller 1, to a temperature i120 1 slightly higher than the temperature suitable for expansion and also above the crystallization temperature of the resin mixture, and the resin stream is made uniform upon passing through resin stream-adjusting plate 23, then reaching nozzle 3. Subsequently, the resin stream is divided into a plurality of separate streams (two streams in Figure 1) by projection 31 without causing dwelling of the resin mixture, and further separated through respective apertures 32, 32... and finally extruded into frame 4 thereby forming a plurality of soft expanded resin strands corresponding in number to the number of strands.
Gases generated at the exit of the nozzle 3 in the course of extrusion and eY.pansion is directly removed by releasing into atmosphere through gas-releasing groove 33 and never enter into the expanded mass. A plurality of soft expanded resin strands which have been extruded and expanded after being extruded through apertures 32, 32... are cooled from the surface thereof by frame .4 adjusted to a suitable temperature for expansion which is lower than the temperature of nozzle 3, thus being successively expanded and fusion bonded together in frame 4 to form a 20 bonded expanded resin mass.
Then, the resulting bonded mass passed through frame
No. 59,969/76.
These processes for producing a thermoplastic resin foamed article are directed to the production of a foamed resin primarily comprising a polystyrene resin. Since a polystyrene resin has a good foamability, desired resin foamed articles can be produced continuously over a long period of time according to the above-described processes.
However, in applying the above conventional processes to crystalline thermoplastic resins other than polystyrene, e.g., polypropylene, a resin containing polypropylene as a major component or a polyamide, it is very difficult to con~
tinuously produce resin foamed articles having good quality.
i~'6~2V
1 No process suitable for foaming such crystalline thermoplastic resins has so far been practically used. That is, since poly-propylene and polyamide resins are crystalline thermoplastic resins, their melt viscosity is sensitively temperature-dependent, and a viscosity suitable for their expansion is in a narrow temperature range close to a temperature at which the resins crystallize. Generally, it is extremely difficult to conduct extrusion and expansion while controlling the nozzle temperature in such a narrow temperature range. In extruding such resins 10 using a nozzle having a number of apertures, the resin streams flow in some portions with difficulty and partially crystallize and solidify to prevent expansion. In addition, such adverse affects on uniform, stable extrusion in respective apertures make it difficult to produce a resin foamed article having high quality of crystalline thermoplastlc resin.
It has been considered that such problems could be solved by controlling a temperature of the nozzle with high accuracy in order to avoid crystallization and solidification of the resin. In fact, however, it is technically difficult to control the nozzle temperature within a critical narrow ran~e suitable for expansion in order to avoid crystallization, since extrusion molding involves many factors which may vary widely.
For example, to equip a nozzle with a temperature-controlling mechanism as disclosed in Japanese Patent Application tOPI) No. 59,969/76 is not satisfactory for a polypropylene resin or a polyamide resin; the resin crystallizes in part of a number of apertures, which prevents stable extrusion of resin streams. -In addition, when the resin is cooled through a frame adjacent to a nozzle having a projection in its center as described in U.S.
Patent 3,993,721, it is difficult to extrude polyrpopylene resin ll~e~ilZO
1 quantitatively in respective apertures of the nozzle because plugging partly occurs. Thus, stable production of a thermo-plastic resin foamed article, such as a polypropylene resin foamed article or a mixture thereof, or a polyamide resin foamed article, having good quality over a long time a~ foun~
to be very difficult.
SUMMARY OF THE INVENTION
.
As a result of extensive investigations to solve the above-described technical problems associated with the conventional processes in the continuous production ~f a crystalline thermoplastic resin foamed article used, for example, as a synthetic wood with woodgrain pattern, it was found that desired resin foamed articles with woodgrain pattern can be stably and continuously produced by elevating the temperature of a nozzle having a number of apertures to a level higher than the melting point of the resin mixture used, reducing the temperature of a frame directly connected to the nozzle, simultaneously restricting the cross-sectional area at the exit of extrusion zone to a given size to thereby control expansion after extrusion through respective apertures of the nozzle, thereby forming a plurality of soft expanded resin strands corresponding in number to the number of strands, bringing the strands into surface contact with each other to fuse and bond them together to form a bonded expanded resin mass while simultaneously removing gases generated in the course of extrusion and expansion, passing the bonded mass into an unconfined zone to permit the mass to further expand while still in a softened condition, passing the further expanded mass into a confined receiving zone of a smaller cross-sectional area than the further expanded mass, and cooling the mass to form an expanded article.
BF<I~:F DESCRIPTION OF THE DRAWINGS
. . _ . .
Figure 1 is a part of sectional view showing an embodiment of the process of the present invention.
Figures 2 and 3 show an example of a nozzle which can be used in the extruder used in the present invention. Figure 2 is a vertical side sectional view of the nozzle and Figure 3 is a part of hack view of the nozzle.
Figures 4 and 5 similarly show another example of a nozzle. Figure 4 is a vertical side sectional view of the nozzle and Figure 5 is a part of front view of the nozzle.
Figures 6 and 7 are vertical side sectional views showing other examples of frames used in the present invention.
Figures 8 and 9 similarly show a further example of a nozzle in which Figure 8 is a vertical side sectiona~ view of the nozzle and Figure 9 is a part of front view of the nozzle.
Figures 10 and 11 similarly show a still further example of a nozzle in ~hich Figure 10 is a vertical side sectional view of the nozzle and Figure 11 is a part of front view of the nozzle.
In these Figures, E designates an extruder, 1 designates a temperature controller, 2 a die, 3 a nozzle, 31 a projection, 32 apertures, 33 a gas-releasing groove, 4 and 4' frames, 41 and 41' channels for a cooling medium, 5 a receiving frame, 6 a plate, 7 a water bath, 71 rolls, 8 a surface-processing apparatus, 9 take-up rolls, and 100 a foamed article.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for producing a foam of a thermoplastic resin, such as (1) a polypropylene resin, a polypropylene copolymer resin or a mixture of a 11~61ZO
1 polypropylene resin and less than about 50%, preferably 1 to 30~, by weight of a thermoplastic resin, or (2) a polyamide resin, by extruding and expanding the resin using an extruder equipped, on a resin channel in a die, with a nozzle having a number of apertures, which comprises flowing a resin mixture stream through an expansion zone while maintaining the resin . mixture at a temperature above the melting point thereof, for - example, up to about 20C, preferably up to 10C, above the melting point, dividing the resin mixture stream into a plurality of separate streams, the cross-sectional area occupied by these streams being from about 5 to about 30%, preferably 5 to 15~, of the cross-sectional area at the exit of the extrusion zone, exiting these streams from the extrusion zone directly into a confined zone maintained at a temperature at least about 30C, preferably at a temperature in the range of 50C to 100C, lower than the temperature of the resin streams prior to the exiting, thereby forming a plurality of soft expanded resin strands corresponding in number to the number of strands, bringing the strands into surface contact with each other to fuse and bond them together to form a bonded expanded resin mass while simultaneously removing gases generated in the course of extrusion and expansion, passing the bonded mass into an unconfined zone to permit the mass to further expand while still in a softened condition, passing the further expanded mass into a confined receiving zone of a smaller cross-sectional area than the further expanded mass, and cooling the mass to form an expanded article.
. The process of the present invention will now be illustrated in greater detail by reference to the attached drawings.
.-- 5 --O
1 Figure 1 shows an embodiment of the present invention, wherein temperature controller 1 is provided at the forward end of extruder E. Temperature controller 1 includes torpedo 12 in outer cylinder 11, and the space between them forms resin channel 13. A cavity is formed inside torpedo 12, and a heating or cooling medium is circulated in the cavity through pipe 14 to thereby heat or cool torpedo 12. Outer cylinder 11 has spiral channel 15 piercing therethrough, through which spiral channel a heating or cooling medium is circulated via pipes 16 tO to thereby heat or cool outer cylinder 11. Thus, a molten resin mixture flowing through channel 13 is controlled to a temperature within an extremely narrow range suitable for subsequent expansion.
Band heaters 17 can be provided around outer cylinder 11.
Die 2 isprovided subsequent to temperature controller 1. Band heater 21 is provided around this die 2, and resin channel 22 of die 2 is provlded with resin stream-adjusting plate 23 having a number of openings and nozzle 3. Since the resin stream in resin chanel 22 flows faster at the central portion than that of peripheral portion, diameters of the openings of resin stream-adjusting plate 23 are properly adjusted so that the resin stream becomes uniform. Resin channel 22 is provided with narrow neck 24 between resin stream-adjusting plate 23 and nozzle 3, which functions to avoid premature expansion and maintain expanding pressure.
Nozzle 3 having a number of apertures 32, 32, ...
arranged in two rows has continuous projection 31 on a resin-entering side between these two rows, and has gas-releasing groove 33 which is provided inward between the two rows of apertures 32, 32,... on a resin-leaving side. Further, square frame 4 having a plurality of channels 41 for controlling tem-perature is connected to the forward end of this nozzle 3 1~61~0 1 subsequent to die 2. The frame 4 is connected via space 42 having a heat-insulating effect in order to avoid direct transmission of heat from die 2. Still further, similar other A~ frame 4' having an-o~cnir~-~ slightly enlarged sectional area and having a plurality of similar channels 41' and similar space 42' is provided at the forward end of frame 4. Both ends of the above-described gas-releasing groove 33 are opened to atmosphere and gases genera~ed after extrusion through respective apertures 32 r 32,... are directly released into atmosphere.
Numeral 5 designates a tapered receiving frame functioning to compress an expanded mass for reducing the sectional area with a given compression ratio. Numeral 6 designates a plate controlling the appearance and the dimension of the expanded mass, numeral 7 designates a water bath for cooling and solidifying the expanded mass, and numeral 71 designates rolls provided in the water bath 7, which cools the mass while controlling its dimension. Surface-processing apparatus 8 is provided subsequent to water bath 7. This surface-processing apparatus 8 is constituted by heating and tapered compressing 20 member 81 and subsequent cooling member 82, whereby the surface of resin foamed article is re-heated and compressed to such a degree that the sectional area of the foam is reduced by about 3% to about 20% as compared with the sectional area prior to the pre-heating and the compression to provide a hard surface layer and a high dimensional accuracy of the resulting shaped expanded -~
article. Numeral 9 designates take-up rolls.
In the above-described production apparatus, the resin kneaded with, for example, nucleating agents, blowing agents and pigments, etc. and melted by means of heated extruder 30 E is controlled, by temperature controller 1, to a temperature i120 1 slightly higher than the temperature suitable for expansion and also above the crystallization temperature of the resin mixture, and the resin stream is made uniform upon passing through resin stream-adjusting plate 23, then reaching nozzle 3. Subsequently, the resin stream is divided into a plurality of separate streams (two streams in Figure 1) by projection 31 without causing dwelling of the resin mixture, and further separated through respective apertures 32, 32... and finally extruded into frame 4 thereby forming a plurality of soft expanded resin strands corresponding in number to the number of strands.
Gases generated at the exit of the nozzle 3 in the course of extrusion and eY.pansion is directly removed by releasing into atmosphere through gas-releasing groove 33 and never enter into the expanded mass. A plurality of soft expanded resin strands which have been extruded and expanded after being extruded through apertures 32, 32... are cooled from the surface thereof by frame .4 adjusted to a suitable temperature for expansion which is lower than the temperature of nozzle 3, thus being successively expanded and fusion bonded together in frame 4 to form a 20 bonded expanded resin mass.
Then, the resulting bonded mass passed through frame
4 is further successively expanded and allowed to pass through receiving frame 5 reducing the sectional area of the resin mass and through plate 6, whereby apparent dimension is con-trolled and the bonded mass is more strongly fusion-bonded by compression, then directly cooled with water in water bath 7 while supporting the form by rolls 71. The thus obtained cooled expanded resin mass is, under heating, compressed by 3 to 20~
and cooled by means of heated compressing member 81 and cooling 30 member 82 to convert the surface to a hard surface layer with Z~
1 luster. T~us, there is obtained a shaped expanded article 1~0 with good dimensional accuracy by means of take-up rolls 9.
As the other example of nozzle 3 structure which can be used in the process of the present invention, Figures 2 and 3 show nozzle 3 which has horizontally continuing projection 311 between two rows of a number of apertures 32, 32... spaced at an equal distance, and which has projections 312, 312 in contact with the upper or lower side of resin channel 22 and reaching the upper or lower row of apertures 32, 32... . Nozzle 3 is also provided with gas releasing groove 33 in the same manner as nozzle 3 shown in Figure 1. Figures 4 and 5 show another type of nozzle 3 which has two rows of horizontally continuing projections 31 on the resin-entering side, each of which projections 31 has on both sides thereof a number of apertur~s 32, 32... spaced at an equal distance from each other (therefoxe 3 rows in all).
Figure 6 shows still another type of nozzle.3 wherein screen 43 containing channel 41 is additionally provided in frame 4. Figure 7 shows the structure wherein another square frame 4' having channel 41' is s].ightly narrowed along the way of extrusion and is provided at the forward end o square frame 4 via space 42'.
Figures 8 and 9 show the structure wherein gas-releasing groove 33 with both ends opening to atmosphere is provided inside of nozzle 3, and gas-releasing holes 331 are provided at an equal distance from each other on the resin-leaving side between two rows of apertures 32, 32... .
As a further example, Figures 10 and 11 show nozzle 3 wherein arc projections 31 are provided on the resin-entering 30 side and a number of gas-releasing grooves 33, 33... having both .
_ g _ llÇ~lZO
1 ends opening to atmosphere are provided crossing at right angles to each other, and to the forward end of which is connected square frame 4 which is narrowed along the way of extrusion.
Apertures 32 in nozzle 3 are 1 mm to 4 mm in diameter (with respect to round apertures) and of 10 mm to 30 mm in land length, which are spaced at a center distance of 2 mm to 20 mm from each other. They allow to pass the foamable resin mixture while setting the temperature of nozzle 3 to a temperature higher than the melting point of the resin mixture used.
10 Projection 31 for preventing dwelling of a molten resin mixture on the resin-entering side can more effectively prevent dwelling of the resin mixture when its surface is subjected to a smoothing finish or to chromium plating or Teflon* coating. It is necessary to provide a gas-releasing means on the outlet side of apertures in the nozzle in order not-to contaminate resin streams with gases generated upon extrusion and expansion through respective apertures 32. For this purpose, there is provided a gas-releasing groove having communicated to atmo-sphere on the outlet side of the nozzle.
Where wide or large moldings are formed, it is preferable to connect a suction pump to this gas-releasing groove for sucking generated gases.
The frame is provided for fusion bonding a plurality of soft expanded resin strands which has been extruded through the nozzle and slightly expanded, and for cooling to a tem-perature suitable for expansion while restricting free expansion.
Total cross-sectional area of resin channels of respective apertures must be set to about 5% to about 30%, preferably 5 to 15%, of the sectional area of resin channel in the frame.
30 That is, if the sectional area of resin channel in the apertures * Trade Mark - 10 -1 is less than about 5~, contact of the strands with the inside surface of the frame would be so weak that the strands are difficultly cooled and became poor in foamability, whereas if the sectional area of the apertures is more than about 30~, gases xeleased from the strands extruded at a higher temperature than the temperature suitable for expansion would not be completely removed through the gas-releasing groove and would remain between respective strands to form voids or gaps in the resulting art-icle or, since respective strands cannot be fully expanded within the frame, cells would rather be extended in an extrusion di-rection than in a vertical direction to provide a foamed article having weak compression strength.
In addition, the section of the resin channel in the frame may ~e enlarged or constricted in the direction of extrus-ion. That is, the cross-sectional area of the outlet of the frame may be enlarged or c~nstricted by about 10% aæ compared with that of the inlet of the frame, and the length of the frame is preferably 30 mm to lQa mm. Where expansion force is weak, this length is preferably prolonged. Also, the temperature of this frame must be adjusted to a lower temperature than that of the nozzle. It is particularly preferable to adjust the temper-ature of the frame lower than the melting point of the resin mixture by at least about 3QC, preferably by from 50C to 100C.
For this purpose, it is desirable to provide a plurality of channels in the frame and to circulate a cooling medium which has been adjusted to a desired temperature through the channels.
For example, when using a polypropylene resin or a polypropylene resin having 1 to 30% by weight of other thermo~
plastic resin mixed, the melting point of theresin mixture is about l50 to a~out 170C the temperature of the frame is about ;lZO
1 150 to about 120C, preferably 70 to 100C. If the temperature of the frame is higher than about 120C, resin strands are not ~ully expanded, or the resin adheres to an inner wall of the frame, or the cells rupture break. On the other hand, when the temperature of the ~rameis less than about 50C, a hard skin is formed on the surface of the resin strands in the frame and thus, the resin stran~s are not fully expanded, and sometimes, the resin solidifies in the nozzle due to cooling of the frame.
Cross-sectional shape of the resin channel of receiving frame S is almost analogous to that of the resin channel in frame 4, and it is preferable to reduce, by a~out 5% to about 5~%, the section of the expanded mass having heen expanded with an expansion ratio of about 1.2 to about 2.5 upon extrusion through the frame into an unconfined zone Receiving frame 5 can also be constituted by arranging rolls in parallel crosses~ That is, the surface of the expanded mass extruded through frame 4 into an unconfined zone is uneven, and reduction by less than about
and cooled by means of heated compressing member 81 and cooling 30 member 82 to convert the surface to a hard surface layer with Z~
1 luster. T~us, there is obtained a shaped expanded article 1~0 with good dimensional accuracy by means of take-up rolls 9.
As the other example of nozzle 3 structure which can be used in the process of the present invention, Figures 2 and 3 show nozzle 3 which has horizontally continuing projection 311 between two rows of a number of apertures 32, 32... spaced at an equal distance, and which has projections 312, 312 in contact with the upper or lower side of resin channel 22 and reaching the upper or lower row of apertures 32, 32... . Nozzle 3 is also provided with gas releasing groove 33 in the same manner as nozzle 3 shown in Figure 1. Figures 4 and 5 show another type of nozzle 3 which has two rows of horizontally continuing projections 31 on the resin-entering side, each of which projections 31 has on both sides thereof a number of apertur~s 32, 32... spaced at an equal distance from each other (therefoxe 3 rows in all).
Figure 6 shows still another type of nozzle.3 wherein screen 43 containing channel 41 is additionally provided in frame 4. Figure 7 shows the structure wherein another square frame 4' having channel 41' is s].ightly narrowed along the way of extrusion and is provided at the forward end o square frame 4 via space 42'.
Figures 8 and 9 show the structure wherein gas-releasing groove 33 with both ends opening to atmosphere is provided inside of nozzle 3, and gas-releasing holes 331 are provided at an equal distance from each other on the resin-leaving side between two rows of apertures 32, 32... .
As a further example, Figures 10 and 11 show nozzle 3 wherein arc projections 31 are provided on the resin-entering 30 side and a number of gas-releasing grooves 33, 33... having both .
_ g _ llÇ~lZO
1 ends opening to atmosphere are provided crossing at right angles to each other, and to the forward end of which is connected square frame 4 which is narrowed along the way of extrusion.
Apertures 32 in nozzle 3 are 1 mm to 4 mm in diameter (with respect to round apertures) and of 10 mm to 30 mm in land length, which are spaced at a center distance of 2 mm to 20 mm from each other. They allow to pass the foamable resin mixture while setting the temperature of nozzle 3 to a temperature higher than the melting point of the resin mixture used.
10 Projection 31 for preventing dwelling of a molten resin mixture on the resin-entering side can more effectively prevent dwelling of the resin mixture when its surface is subjected to a smoothing finish or to chromium plating or Teflon* coating. It is necessary to provide a gas-releasing means on the outlet side of apertures in the nozzle in order not-to contaminate resin streams with gases generated upon extrusion and expansion through respective apertures 32. For this purpose, there is provided a gas-releasing groove having communicated to atmo-sphere on the outlet side of the nozzle.
Where wide or large moldings are formed, it is preferable to connect a suction pump to this gas-releasing groove for sucking generated gases.
The frame is provided for fusion bonding a plurality of soft expanded resin strands which has been extruded through the nozzle and slightly expanded, and for cooling to a tem-perature suitable for expansion while restricting free expansion.
Total cross-sectional area of resin channels of respective apertures must be set to about 5% to about 30%, preferably 5 to 15%, of the sectional area of resin channel in the frame.
30 That is, if the sectional area of resin channel in the apertures * Trade Mark - 10 -1 is less than about 5~, contact of the strands with the inside surface of the frame would be so weak that the strands are difficultly cooled and became poor in foamability, whereas if the sectional area of the apertures is more than about 30~, gases xeleased from the strands extruded at a higher temperature than the temperature suitable for expansion would not be completely removed through the gas-releasing groove and would remain between respective strands to form voids or gaps in the resulting art-icle or, since respective strands cannot be fully expanded within the frame, cells would rather be extended in an extrusion di-rection than in a vertical direction to provide a foamed article having weak compression strength.
In addition, the section of the resin channel in the frame may ~e enlarged or constricted in the direction of extrus-ion. That is, the cross-sectional area of the outlet of the frame may be enlarged or c~nstricted by about 10% aæ compared with that of the inlet of the frame, and the length of the frame is preferably 30 mm to lQa mm. Where expansion force is weak, this length is preferably prolonged. Also, the temperature of this frame must be adjusted to a lower temperature than that of the nozzle. It is particularly preferable to adjust the temper-ature of the frame lower than the melting point of the resin mixture by at least about 3QC, preferably by from 50C to 100C.
For this purpose, it is desirable to provide a plurality of channels in the frame and to circulate a cooling medium which has been adjusted to a desired temperature through the channels.
For example, when using a polypropylene resin or a polypropylene resin having 1 to 30% by weight of other thermo~
plastic resin mixed, the melting point of theresin mixture is about l50 to a~out 170C the temperature of the frame is about ;lZO
1 150 to about 120C, preferably 70 to 100C. If the temperature of the frame is higher than about 120C, resin strands are not ~ully expanded, or the resin adheres to an inner wall of the frame, or the cells rupture break. On the other hand, when the temperature of the ~rameis less than about 50C, a hard skin is formed on the surface of the resin strands in the frame and thus, the resin stran~s are not fully expanded, and sometimes, the resin solidifies in the nozzle due to cooling of the frame.
Cross-sectional shape of the resin channel of receiving frame S is almost analogous to that of the resin channel in frame 4, and it is preferable to reduce, by a~out 5% to about 5~%, the section of the expanded mass having heen expanded with an expansion ratio of about 1.2 to about 2.5 upon extrusion through the frame into an unconfined zone Receiving frame 5 can also be constituted by arranging rolls in parallel crosses~ That is, the surface of the expanded mass extruded through frame 4 into an unconfined zone is uneven, and reduction by less than about
5~ is not enough to smooth the surface, whereas reduction by about more than 50~ causes too much resistance.
Thus, expanded resin strands are ~trongly fusion bonded through constriction pressure in this occasion to provide a bonded mass having good dimensional accuracy, which can be used, for example~ as a smooth surface synthetic wood with distinct woodgrain pattern.
Thus~ by appropriately settling the shape of the channels for the resin, such as a nozzle, frame, receiving frame, etc,, an expanded resin long article having a cross-section of, for example, plate type, s~uare type, round type and complicated type such as threshold or doorsill can be obtained. Further, an expanded resin article having a high compression strength is ~r 11~61ZO
1 obtained in which each strand constituting the expanded resin article has, in cross-sectional-wise, a long rectangle or approximate triangle in the thickness direction.
Examples of resins which can be used in the process of the present invention are (1) a polypropylene resin, a poly-; propylene copolymer resin, a mixture of polypropylene and less than about 50~ by weight of a thermoplastic resin, or (2) a polyamide resin.
Polypropylene resins which can be used are preferably one having a melt index of less than about 5 ~measured accordingto ASTMD-1238, hereinafter the same)~
Examples of polypropylene copolymer resins which can by used include an ethylene-propylene copolymer resin.
Examples of the thermoplastic resins which can be blended with a polyproylene resin are a polystyrene resin, pre-ferably one having a melt index of less than a~out 15; a poly-methyl methacrylate resin, preferably one having a melt index of less than about 5; a high density polyethylene resin, preferably one having a melt index of less thanabout 3; a polycarbonate resin; an acrylonitrile-styrene copolymer resinr preferably one having a melt index of less than about 7; a polyamide resin; and the like. These resins are blended usually in a proportion of 1% by weight to 30% by weight, preferably 2% by weight to 25% by weight r based on the total resin components. Blending poly-propylene with these resins serves to improve foamability of the polypropylene resin and to provide a stable molding property r thus good resin foams being continuously produced, Of the above-descri~ed resins to be blended, a polystyrene resin, a polymethyl methacrylate resin and a high density polyethylene resin are particularly preferable.
.
y~
, .. ..
11~6120 1 Examples of polyamide resins which can be used alone are nylon 6, nylon 66, nylon 12 and the like. A particularly preferred example of polyamide resins is nylon 12.
In the present invention, various foaming agents can be used. Examples of foaming agents are easily volatile liquids of aliphatic hydrocarbons such as pentane, butane, propane, petroleum ether, etc., or halogenated hydrocarbons such as monochloro-methane,trichlorofluoromethane, dichlorotetrafluoroethane,etc.,and ~ .z~d /~ r b onq m ide thermally decomposable foaming agents such as ~--~U~r~ rLDe~
acid am~e~, dinitrosopentamethylenetetramine, etc. These foaming agents can be previously mixed with the resin to be fed to an extruder, or can be poured into the extruder to mix upon extrusion. The amount of the foaming agent can vary widely depending upon the desired expansion ratio, but is usually about 1 to about 15% by weight based on the total amount of the resin composition.
In order to uniformly form fine cells in the resin, addition of a foaming aid or a nucleating agent in addition to the above-described foaming agent is desirable. Examples of such additives are fine powdery talc, silica powder,a mixture of sodium dicarbonate and citric acid, and the like, which are well known in the art.
The process of the present invention is constituted as described above and, since the expanded resin strands which have been extruded through apertures in the nozzle and once expanded are adjusted to a suitable temperature for expansion by means of the frame, it enables to continuously produce further expanded mass with good quality. On the other hand, the tem-perature of the nozzle itself can be maintained at a comparatively hlgh level, and hence neither crystallization nor solidification 1~61~0 1 occurs in the apertures o~ the nozzle, thus not causing change in extrusion and expansion. This point also ensures stable extrusion production of a foamed article with good quality.
In addition, the present invention enables to directly release into atmosphere gases generated in the course of extrusion and expansion, and enables to produce a wide or large foamed article having no voids or gaps between a plurality of expanded resin strands due to the generated gases.
The thus obtained shaped expanded article is superior to polystyrene foams in heat resistance, chemical resistance and toughness without producing black smoke upon combustion, and hence it can be suitably used as materials for a heating apparatus or a hot water-feeding equipment or as structural materials for apparatus for producing industrial chemicals, packaging materials, feeding materials, press molding materials, etc.
The present invention will now be illustrated in greater detail by referring to the embodiment using the molding apparatus shown in Figure l. Unless otherwise indicated, all parts, percents, ratios and the like are by weight.
A mixture prepared by uniformly mixing 2 parts of fine powdery talc (as a nucleating agent) and 0.2 part of a brown pigment with l00 parts of polypropylene resin (NOBLEN MH-8, made by Mitsubishi Petrochemical Co., Ltd.) was charged into a hopper of extruder E, which was set to 200 to 250C in the feed portion and lS0 to 170C in the forward end. The mixture and a foaming agent of butane added into the extruder on the way were uniformly kneaded in the extruder and transferred to the resin temperature controller. The mixture was transferred to nozzle 3 maintained * Trade Mark - l5 -llC6120 1 at a temperature o~ 170C to 180C through resin stream adjusting plate 23 in die 2 and extruded into frame ~ and expanded on the .
outlet side of a number of apertures in nozzle 3. Then, a plurality of soft expanded resin strands extruded through res-pective apertures were fusion bonded together in the above-described frame 4 controlled by circulating an oil of 85 to go&
and also circulating water of room temperature into frame 4' with the apparent shape maintained, and, subsequently, the bonded expanded resin mass was once released into atmosphere to further permit expansion to such degr.ee that cross sectional area thereof became 1.2 to 2.5 times that of the opening of mold 4, then constricted by 5 to 50% in sectional area based on the secc;n ola.~v ~ sectional area of the-~rrhrr/expanded resin mass by means of receiving frame 5. The thus constricted resin mass was cooled by passing through water bath 7, and surface-processed by surface processing apparatus 8, followed by continuously drawing by take-up rolls 9. Thus, there was obtained foamed article 100 having luster, hard surface and woodgrain pattern wherein lines of juncture formed in a longitudinal direction between respective resin streams appeared as brown lines, thus providing synthetic wood-like appearance.
In this example, a nozzle of the structure shown in Figures 2 and 3 was used as nozzle 3. That is, at the forward end of die 2 was provided nozzle 3 having a rectangular cross section of 22 mm in height and 152 mm in width and having 96 apertures of 1.6 mm in diameter in the center thereof aligned in parallel two rows with a vertical distance of 10 ~m, with respective apertures in each row being spaced from each other at a horizontally equal distance of 3 mm. Outlet side of nozzle 3 was in a vertical form, and gas-releasing groove 33 of 6 mm in width and 5 mm in depth communicated to atmosphere was provided
Thus, expanded resin strands are ~trongly fusion bonded through constriction pressure in this occasion to provide a bonded mass having good dimensional accuracy, which can be used, for example~ as a smooth surface synthetic wood with distinct woodgrain pattern.
Thus~ by appropriately settling the shape of the channels for the resin, such as a nozzle, frame, receiving frame, etc,, an expanded resin long article having a cross-section of, for example, plate type, s~uare type, round type and complicated type such as threshold or doorsill can be obtained. Further, an expanded resin article having a high compression strength is ~r 11~61ZO
1 obtained in which each strand constituting the expanded resin article has, in cross-sectional-wise, a long rectangle or approximate triangle in the thickness direction.
Examples of resins which can be used in the process of the present invention are (1) a polypropylene resin, a poly-; propylene copolymer resin, a mixture of polypropylene and less than about 50~ by weight of a thermoplastic resin, or (2) a polyamide resin.
Polypropylene resins which can be used are preferably one having a melt index of less than about 5 ~measured accordingto ASTMD-1238, hereinafter the same)~
Examples of polypropylene copolymer resins which can by used include an ethylene-propylene copolymer resin.
Examples of the thermoplastic resins which can be blended with a polyproylene resin are a polystyrene resin, pre-ferably one having a melt index of less than a~out 15; a poly-methyl methacrylate resin, preferably one having a melt index of less than about 5; a high density polyethylene resin, preferably one having a melt index of less thanabout 3; a polycarbonate resin; an acrylonitrile-styrene copolymer resinr preferably one having a melt index of less than about 7; a polyamide resin; and the like. These resins are blended usually in a proportion of 1% by weight to 30% by weight, preferably 2% by weight to 25% by weight r based on the total resin components. Blending poly-propylene with these resins serves to improve foamability of the polypropylene resin and to provide a stable molding property r thus good resin foams being continuously produced, Of the above-descri~ed resins to be blended, a polystyrene resin, a polymethyl methacrylate resin and a high density polyethylene resin are particularly preferable.
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11~6120 1 Examples of polyamide resins which can be used alone are nylon 6, nylon 66, nylon 12 and the like. A particularly preferred example of polyamide resins is nylon 12.
In the present invention, various foaming agents can be used. Examples of foaming agents are easily volatile liquids of aliphatic hydrocarbons such as pentane, butane, propane, petroleum ether, etc., or halogenated hydrocarbons such as monochloro-methane,trichlorofluoromethane, dichlorotetrafluoroethane,etc.,and ~ .z~d /~ r b onq m ide thermally decomposable foaming agents such as ~--~U~r~ rLDe~
acid am~e~, dinitrosopentamethylenetetramine, etc. These foaming agents can be previously mixed with the resin to be fed to an extruder, or can be poured into the extruder to mix upon extrusion. The amount of the foaming agent can vary widely depending upon the desired expansion ratio, but is usually about 1 to about 15% by weight based on the total amount of the resin composition.
In order to uniformly form fine cells in the resin, addition of a foaming aid or a nucleating agent in addition to the above-described foaming agent is desirable. Examples of such additives are fine powdery talc, silica powder,a mixture of sodium dicarbonate and citric acid, and the like, which are well known in the art.
The process of the present invention is constituted as described above and, since the expanded resin strands which have been extruded through apertures in the nozzle and once expanded are adjusted to a suitable temperature for expansion by means of the frame, it enables to continuously produce further expanded mass with good quality. On the other hand, the tem-perature of the nozzle itself can be maintained at a comparatively hlgh level, and hence neither crystallization nor solidification 1~61~0 1 occurs in the apertures o~ the nozzle, thus not causing change in extrusion and expansion. This point also ensures stable extrusion production of a foamed article with good quality.
In addition, the present invention enables to directly release into atmosphere gases generated in the course of extrusion and expansion, and enables to produce a wide or large foamed article having no voids or gaps between a plurality of expanded resin strands due to the generated gases.
The thus obtained shaped expanded article is superior to polystyrene foams in heat resistance, chemical resistance and toughness without producing black smoke upon combustion, and hence it can be suitably used as materials for a heating apparatus or a hot water-feeding equipment or as structural materials for apparatus for producing industrial chemicals, packaging materials, feeding materials, press molding materials, etc.
The present invention will now be illustrated in greater detail by referring to the embodiment using the molding apparatus shown in Figure l. Unless otherwise indicated, all parts, percents, ratios and the like are by weight.
A mixture prepared by uniformly mixing 2 parts of fine powdery talc (as a nucleating agent) and 0.2 part of a brown pigment with l00 parts of polypropylene resin (NOBLEN MH-8, made by Mitsubishi Petrochemical Co., Ltd.) was charged into a hopper of extruder E, which was set to 200 to 250C in the feed portion and lS0 to 170C in the forward end. The mixture and a foaming agent of butane added into the extruder on the way were uniformly kneaded in the extruder and transferred to the resin temperature controller. The mixture was transferred to nozzle 3 maintained * Trade Mark - l5 -llC6120 1 at a temperature o~ 170C to 180C through resin stream adjusting plate 23 in die 2 and extruded into frame ~ and expanded on the .
outlet side of a number of apertures in nozzle 3. Then, a plurality of soft expanded resin strands extruded through res-pective apertures were fusion bonded together in the above-described frame 4 controlled by circulating an oil of 85 to go&
and also circulating water of room temperature into frame 4' with the apparent shape maintained, and, subsequently, the bonded expanded resin mass was once released into atmosphere to further permit expansion to such degr.ee that cross sectional area thereof became 1.2 to 2.5 times that of the opening of mold 4, then constricted by 5 to 50% in sectional area based on the secc;n ola.~v ~ sectional area of the-~rrhrr/expanded resin mass by means of receiving frame 5. The thus constricted resin mass was cooled by passing through water bath 7, and surface-processed by surface processing apparatus 8, followed by continuously drawing by take-up rolls 9. Thus, there was obtained foamed article 100 having luster, hard surface and woodgrain pattern wherein lines of juncture formed in a longitudinal direction between respective resin streams appeared as brown lines, thus providing synthetic wood-like appearance.
In this example, a nozzle of the structure shown in Figures 2 and 3 was used as nozzle 3. That is, at the forward end of die 2 was provided nozzle 3 having a rectangular cross section of 22 mm in height and 152 mm in width and having 96 apertures of 1.6 mm in diameter in the center thereof aligned in parallel two rows with a vertical distance of 10 ~m, with respective apertures in each row being spaced from each other at a horizontally equal distance of 3 mm. Outlet side of nozzle 3 was in a vertical form, and gas-releasing groove 33 of 6 mm in width and 5 mm in depth communicated to atmosphere was provided
6~2o 1 between the upper and lower rows of apertures 32, 32,... . In addition, frames 4 and 4' which were connected to each other had a section, in longitudinal direction, of 13 mm in height and 150 mm in width, had a length of 35 mm in parallel to the extrusion direction, and supplementally had an opening of 14 x 152 mm in cross sectional and 35 mm in length, inner surface of which was uniformly coated with a Teflon. In addition, the frame contained channels 41 for circulating a temperature-controlling oil and channels 41' for circulating cooling water provided in upper and lower parts of the mold. In the further stage, receiving frame 5 with a cross section of 13 x 150 mm, plate 6, and rolls 71 having an opening of rectangular cross section in a longitudinal direction for controlling apparent dimension were provided, followed by a water bath for cooling the foamed resin mass with water, wherein the foamed resin mass was cooled while being supported and constricted by rolls 71. Then, :
the once cooled resin foam was guided to surface-processing apparatus 8 comprising heating and compressing plates 81 and cooling plates 82 to reduce the sectional area of the resulting article by 3 to 20% to obtain smooth surface expanded article 100 having good surface luster, surface hardness and compression strength.
The expanded artic~e 100 thus prepared was a plane plate of 12 mm in thickness and 150 mm in width having been expanded
the once cooled resin foam was guided to surface-processing apparatus 8 comprising heating and compressing plates 81 and cooling plates 82 to reduce the sectional area of the resulting article by 3 to 20% to obtain smooth surface expanded article 100 having good surface luster, surface hardness and compression strength.
The expanded artic~e 100 thus prepared was a plane plate of 12 mm in thickness and 150 mm in width having been expanded
7.3 times. The resulting plate had a cross~sectional structure comprising two parallel rows of fusion-bonded strands, each strand having a height of 6 mm and a width of 3 mm. They did not contain voids at the interface between fusion-bonded resin foam streams, and the surface thereof had straight lines of juncture between resin foam ~ streams, which provided the appearance ~ 17 ~
ll"~ilZO
1 analogous to grains of natural wood. Thus, they appeared like natural wood having the light-weight appearance thereof.
A mixture prepared by uniformly mixing 1 part of fine powdery talc and 2 parts of azodicarbonamide with 100 parts of polyamide resin (A~ILAN X-5021, made by Toray Industries Inc.) was fed into extruder E, which was set to 180 to 260 C. The mixture was extruded and expanded by nozzle 3 set to 160 to 170C. The temperature of frame 4 was controlled at 100 to 110C by air passing through channels 41. The thus extruded foamable polyamide resin streams were expanded in frame 4 and passed successively through receiving frame 5, plate 6 and rolls 71 shown in Figure 1 to thereby be fusion-bonded. Subsequently, the bonded expanded resin mass was water-cooled with water bath 7 and solidified to obtain desired article 100 comprising an expanded article of the polyamide resin.
The expanded article 100 thus prepared was a continuous plane plate of 18 mm in thickness and 30 mm in width and the density thereof was 0.4 to 0.5 g/cm .
In this example, a nozzle of the structure shown in Figures 10 and 11 was used as nozzle 3. That is, at the forward end of die 2 was provided nozzle 3 having a rectangular cross section of 24 mm x 29 mm and having 39 apertures of 1.6 mm in diameter and of 10 mm in depth, with respective apertures in each row being spaced from each other at a horizontally equal distance of 5 mm, as shown in Figure 11. At the outlet side of nozzle 3 was provided gas-releasing grooves 33 of 1 mm in width and 3 mm in depth crossly. In addition, a frame of the structure shown in Figure 7 was used as frame 4. That is, frame 4 had an orifice opening of 24 mm x 29 mm at inlet and * Trade Mark - 18 -~612(~
1 18 mm x 29 mm at outlet and of 20 mm in length, the inner surface of which frame being plated with chromium.
Comparative Exa~
When the temperature of nozzle 3 in the foregoing Example 1 was set to 160C, there was observed slight breakage in the streams of foamable resin in apertures 32, whereas when the temperature of nozzle 3 was set to 150C, there was observed complete breakage due to crystallization of resin, resulting in unstable extrusion and preventing subsequent expansion. Thus, there was not obtained a uniformly expanded article with high expansion ratio.
In addition, when frame 4 was cooled with the temperature- :
controlling oil raised to 120C, expansion of the foamable . extruded resin streams did not start unless the temperature of nozzle 3 was lowered to less than 160C. However, polypropylene c ~ys~ z ~
. ~, resin used is liable to fv~m-er~t~linc at this temperature r~l f~U rel of nozzle 3, and eracked or broken inner portions are formed in the resulting article. Thus, there cannot be obtained satisfactory plane plates comprising polypropylene foam.
Next, the kind of resin and the amount of butane to be used were changed and the resin temperature at the forward end of extruder E, the resin temperature at the inlet of nozzle 3 and the temperature of frame 4 were controlled as shown in the following table using the molding apparatus used in Example 1 to obtain similarly a good resin foamed article with good quality.
ll~'t;120 Polypropylene Parts by Resin Weiqht *1 *2 *3 *4 *5 *6 *7 Poly- *8 propylene100 11.0 173165 13xlS0 35 80 12x150 7.3 14x152 35 -Talc 2 9.8 177167 13x150 35 80 12x150 4.5 Pigment 90.2 14x152 35 Poly- *8 propylene100 5.5 176 166 13x150 30 100 14x160 8.4 . Polystyrene 10 20 Talc 2 6.5 189 178 13x150 30 100 14x160 7.0 propylene100 Polystyrene 10 5 9.0 180 166 13x150 50 90 13x150 10.0 - Talc 2 - -propylene100 *1 Polymethyl methacrylate 20 8.3 189 178 " 90 " 8.0 Talc 2 Poly- *8 . pr~pylene 100 20 High density 12 polyethylene 20 8.3 174 169 " 85 " 8.2 Talc 2 Poly- *8 100 Polycarbonate 13 20 7.6 191 174 " 90 " 11.8 Talc 2 Ethylene-*14 propylene 100 Acrylonitrile-15 Styrene 20 8.3 187 169 " 85 " 6.5 Talc 2 lla~l~o 1 Polypropylene Parts by ResinWeight *1 *2 *3 *4 *5 *6 *7 __ .
Polypro*-8 pylene 100 Polyamide 16 20 7.4 188 176 13x150 50 85 13x150 8-5 Talc 2 Ethylene- *14 propylene 100 Talc 2 10.0 172 164 13x150 35 78 12x150 5.0 *g Pigment0.2 *l Amount of butane added, ~ by weight.
*2 Temperature of resin at the forward end of the Extruder, C.
*3 Temperature of resin at the inlet of nozzle, C.
*4 Structure of frame mold; cross section, length(mm).
*5 Temperature of oil circulated in the frame mold.
*6 Cross sectional area of molding frame in mm.
*7 Expansion ratio.
**
*8 NOBLEN MH-8, made by Mitsubishi Petrochemical Co., Ltd., was used as polypropylene resin, which has a melt index of 0.3 (ASTM D-1238), a heat-distortion temperature of 120 to 130C (ASTM D-648), and a Vicat softening point of 145 to 150C (ASTM D-1525).
*9 PPMSSC 46315(C), made by Dainichiseika Colour & Chemicals MFG., Co., Ltd., was used as a rouge type pigment.
**
*10 STYRON 666, made by Asahi Dow Co., Ltd., was used as a polystyrene resin, which has a melt index of 7.5 (ASTM
D-1238), a heat-distortion temperature of 94C (JIS K-6871), and a Vicat softening point of 97C (ASTM D-1525).
*11 DELPET 70H, made by Asahi Kasei Kogyo K.K., was used as a polymethyl methacrylate resin, which has a melt index of 0.5 (ASTM D-1238), a heat-distortion temperature of 92 C
(ASTM D-648), and a Vicat softening point of 120C (ASTM D-152~.
** Trade Mark - 21 -~ ',,~,' .
t;12() 1 *12 Hi-ZEX 7000F, made by Mitsui Petrochemical Ind., Co., Ltd., was used as a high density polyethylene resin, which has a melt index of 0.04 (ASTM D-1238), and a Vicat softening point of 124 C t~STM D-1525).
*13 IUPILON S2000, made by Mitsubishi Edogawa Chemical Co., Ltd., was used as a polycarbonate resin, which has a heat-distortion temperature of 134 to 140 C (ASTM D-648).
*14 NOBLEN EC-9, made by Mitsubishi Petrochemical Co., Ltd., - was used as an ethylene/propylene copolymer resin, which has an ethylene content of 10~ by weight and has a melt index of 0.4 (ASTM D-1238).
*15 TYRIL 783, made by Asahi Dow Co ., Ltd., was used as an acrylonitrile/styrene copolymer resin, which has a melt index of 3.5 (ASTM D-1238), a heat-distortion temperature of 94 C (JIS K-6871), and a Vicat softening point of 112 C
(ASTM D - 1525) .
*16 AMILAN X-5021, made by Toray Industries Inc., was used as a polyamide resin, which has a heat-distortion temperature of 52 C (ASTM D-648) .
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
** Trade Mark - 22 -
ll"~ilZO
1 analogous to grains of natural wood. Thus, they appeared like natural wood having the light-weight appearance thereof.
A mixture prepared by uniformly mixing 1 part of fine powdery talc and 2 parts of azodicarbonamide with 100 parts of polyamide resin (A~ILAN X-5021, made by Toray Industries Inc.) was fed into extruder E, which was set to 180 to 260 C. The mixture was extruded and expanded by nozzle 3 set to 160 to 170C. The temperature of frame 4 was controlled at 100 to 110C by air passing through channels 41. The thus extruded foamable polyamide resin streams were expanded in frame 4 and passed successively through receiving frame 5, plate 6 and rolls 71 shown in Figure 1 to thereby be fusion-bonded. Subsequently, the bonded expanded resin mass was water-cooled with water bath 7 and solidified to obtain desired article 100 comprising an expanded article of the polyamide resin.
The expanded article 100 thus prepared was a continuous plane plate of 18 mm in thickness and 30 mm in width and the density thereof was 0.4 to 0.5 g/cm .
In this example, a nozzle of the structure shown in Figures 10 and 11 was used as nozzle 3. That is, at the forward end of die 2 was provided nozzle 3 having a rectangular cross section of 24 mm x 29 mm and having 39 apertures of 1.6 mm in diameter and of 10 mm in depth, with respective apertures in each row being spaced from each other at a horizontally equal distance of 5 mm, as shown in Figure 11. At the outlet side of nozzle 3 was provided gas-releasing grooves 33 of 1 mm in width and 3 mm in depth crossly. In addition, a frame of the structure shown in Figure 7 was used as frame 4. That is, frame 4 had an orifice opening of 24 mm x 29 mm at inlet and * Trade Mark - 18 -~612(~
1 18 mm x 29 mm at outlet and of 20 mm in length, the inner surface of which frame being plated with chromium.
Comparative Exa~
When the temperature of nozzle 3 in the foregoing Example 1 was set to 160C, there was observed slight breakage in the streams of foamable resin in apertures 32, whereas when the temperature of nozzle 3 was set to 150C, there was observed complete breakage due to crystallization of resin, resulting in unstable extrusion and preventing subsequent expansion. Thus, there was not obtained a uniformly expanded article with high expansion ratio.
In addition, when frame 4 was cooled with the temperature- :
controlling oil raised to 120C, expansion of the foamable . extruded resin streams did not start unless the temperature of nozzle 3 was lowered to less than 160C. However, polypropylene c ~ys~ z ~
. ~, resin used is liable to fv~m-er~t~linc at this temperature r~l f~U rel of nozzle 3, and eracked or broken inner portions are formed in the resulting article. Thus, there cannot be obtained satisfactory plane plates comprising polypropylene foam.
Next, the kind of resin and the amount of butane to be used were changed and the resin temperature at the forward end of extruder E, the resin temperature at the inlet of nozzle 3 and the temperature of frame 4 were controlled as shown in the following table using the molding apparatus used in Example 1 to obtain similarly a good resin foamed article with good quality.
ll~'t;120 Polypropylene Parts by Resin Weiqht *1 *2 *3 *4 *5 *6 *7 Poly- *8 propylene100 11.0 173165 13xlS0 35 80 12x150 7.3 14x152 35 -Talc 2 9.8 177167 13x150 35 80 12x150 4.5 Pigment 90.2 14x152 35 Poly- *8 propylene100 5.5 176 166 13x150 30 100 14x160 8.4 . Polystyrene 10 20 Talc 2 6.5 189 178 13x150 30 100 14x160 7.0 propylene100 Polystyrene 10 5 9.0 180 166 13x150 50 90 13x150 10.0 - Talc 2 - -propylene100 *1 Polymethyl methacrylate 20 8.3 189 178 " 90 " 8.0 Talc 2 Poly- *8 . pr~pylene 100 20 High density 12 polyethylene 20 8.3 174 169 " 85 " 8.2 Talc 2 Poly- *8 100 Polycarbonate 13 20 7.6 191 174 " 90 " 11.8 Talc 2 Ethylene-*14 propylene 100 Acrylonitrile-15 Styrene 20 8.3 187 169 " 85 " 6.5 Talc 2 lla~l~o 1 Polypropylene Parts by ResinWeight *1 *2 *3 *4 *5 *6 *7 __ .
Polypro*-8 pylene 100 Polyamide 16 20 7.4 188 176 13x150 50 85 13x150 8-5 Talc 2 Ethylene- *14 propylene 100 Talc 2 10.0 172 164 13x150 35 78 12x150 5.0 *g Pigment0.2 *l Amount of butane added, ~ by weight.
*2 Temperature of resin at the forward end of the Extruder, C.
*3 Temperature of resin at the inlet of nozzle, C.
*4 Structure of frame mold; cross section, length(mm).
*5 Temperature of oil circulated in the frame mold.
*6 Cross sectional area of molding frame in mm.
*7 Expansion ratio.
**
*8 NOBLEN MH-8, made by Mitsubishi Petrochemical Co., Ltd., was used as polypropylene resin, which has a melt index of 0.3 (ASTM D-1238), a heat-distortion temperature of 120 to 130C (ASTM D-648), and a Vicat softening point of 145 to 150C (ASTM D-1525).
*9 PPMSSC 46315(C), made by Dainichiseika Colour & Chemicals MFG., Co., Ltd., was used as a rouge type pigment.
**
*10 STYRON 666, made by Asahi Dow Co., Ltd., was used as a polystyrene resin, which has a melt index of 7.5 (ASTM
D-1238), a heat-distortion temperature of 94C (JIS K-6871), and a Vicat softening point of 97C (ASTM D-1525).
*11 DELPET 70H, made by Asahi Kasei Kogyo K.K., was used as a polymethyl methacrylate resin, which has a melt index of 0.5 (ASTM D-1238), a heat-distortion temperature of 92 C
(ASTM D-648), and a Vicat softening point of 120C (ASTM D-152~.
** Trade Mark - 21 -~ ',,~,' .
t;12() 1 *12 Hi-ZEX 7000F, made by Mitsui Petrochemical Ind., Co., Ltd., was used as a high density polyethylene resin, which has a melt index of 0.04 (ASTM D-1238), and a Vicat softening point of 124 C t~STM D-1525).
*13 IUPILON S2000, made by Mitsubishi Edogawa Chemical Co., Ltd., was used as a polycarbonate resin, which has a heat-distortion temperature of 134 to 140 C (ASTM D-648).
*14 NOBLEN EC-9, made by Mitsubishi Petrochemical Co., Ltd., - was used as an ethylene/propylene copolymer resin, which has an ethylene content of 10~ by weight and has a melt index of 0.4 (ASTM D-1238).
*15 TYRIL 783, made by Asahi Dow Co ., Ltd., was used as an acrylonitrile/styrene copolymer resin, which has a melt index of 3.5 (ASTM D-1238), a heat-distortion temperature of 94 C (JIS K-6871), and a Vicat softening point of 112 C
(ASTM D - 1525) .
*16 AMILAN X-5021, made by Toray Industries Inc., was used as a polyamide resin, which has a heat-distortion temperature of 52 C (ASTM D-648) .
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
** Trade Mark - 22 -
Claims (8)
- Claim 1 continued .....
receiving zone defined by a tapered receiving frame and of a smaller cross-sectional area than the further expanded mass, and cooling the mass to form an expanded article. - 2. The process as claimed in claim 1, wherein said resin is (1) a polypropylene resin, a polypropylene copolymer resin, or a mixture of a polypropylene resin and less than about 50% by weight of a thermoplastic resin, or (2) a polyamide resin,
- 3. The process as claimed in claim 2, wherein said poly-propylene copolymer resin is a copolymer of propylene and ethylene.
- 4. The process as claimed in claim 2, wherein said mixture contains 1% to 30% by weight of said thermoplastic resin.
- 5. The process as claimed in claim 2, wherein said mixture contains 2% to 25% by weight of said thermoplastic resin.
- 6. The process as claimed in claim 2, wherein said thermo-plastic resin is a polystyrene resin, a polymethyl methacrylate resin, a polyamide resin, a polycarbonate resin, an acrylonitrile-styrene copolymer resin or a high density polyethylene resin.
- 7. The process. as claimed in claim 1, wherein said confined receiving zone of a smaller cross-sectional area has a sectional area smaller than that of the further expanded mass by about 5% to about 50%.
- 8. The process as claimed in claim 1, wherein said expanded article is further passed through a heated compressing zone thereby reducing the thickness of said expanded article by 3 to 20% and subsequently through a cooling zone to convert the sur-face to a hard surface layer with luster.
1. A process for producing an expanded article of a crystalline thermoplastic resin having a sensitively temperature-dependent melt viscosity by extruding and expanding a foamable resin mixture using an extruder equipped, on the forward end thereof with a die having a resin channel therein a nozzle having a plurality of apertures therein and a frame for expansion, which comprises conveying said foamable resin mixture stream through said resin channel while maintaining the resin mixture at a temperature above the melting point thereof, dividing the resin mixture stream into a plurality of substantially parallel sepa-rate streams in said nozzle, the cross-sectional area occupied by the streams at the entrance of the extrusion area being reduced to the extent that the cross-sectional area occupied by said streams is about 5 to about 30% of the total cross-sectional area at the exit of the extrusion area, exiting said streams from said extrusion zone in a common plane perpendicular to the axes of the streams directly into a confined zone defined by said frame and maintained at a temperature at least about 30°C lower than the temperature of the resin streams prior to the exiting, thereby forming a plurality of soft expanded resin strands corresponding in number to the number of strands, bringing the strands into surface contact with each other to fuse and bond them together to form a bonded expanded resin mass while simul-taneously removing gases generated in the course of extrusion and expansion, passing the bonded mass into an unconfined zone to permit the mass to further expand while still in a softened condition, passing the further expanded mass into a confined
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA294,070A CA1106120A (en) | 1977-12-29 | 1977-12-29 | Process for producing expanded article of thermoplastic resin |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA294,070A CA1106120A (en) | 1977-12-29 | 1977-12-29 | Process for producing expanded article of thermoplastic resin |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1106120A true CA1106120A (en) | 1981-08-04 |
Family
ID=4110408
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA294,070A Expired CA1106120A (en) | 1977-12-29 | 1977-12-29 | Process for producing expanded article of thermoplastic resin |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1106120A (en) |
-
1977
- 1977-12-29 CA CA294,070A patent/CA1106120A/en not_active Expired
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