JPH0132055B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in compression stretch molding or extrusion stretch molding of thermoplastic resins. The objects of the present invention are to improve the moldability of resins such as ultra-high molecular weight resins that are difficult to extrude and stretch mold due to their high viscosity, and to improve the extrusion and stretch molding of easily heat decomposable resins such as polyvinylidene chloride. Improvements in the method of forming biaxially oriented sheets or pipes by biaxially stretching in an extrusion die in a high viscosity state, improvements in the method of forming biaxially oriented sheets by compressing thermoplastic resin in a compression mold, etc. The object of the present invention is to provide a stretch forming method that achieves the following. In order to improve resin flow within the die during extrusion stretch molding or compression stretch molding of thermoplastic resins,
It is known to coat the inner surface of the die with a lubricant (e.g. USP2597553, USP2688153,
USP3504075). Coating the inner surface of the die with a lubricant significantly improves the flow of the thermoplastic resin within the die, allowing molding to be performed at low pressure. However, there are various problems with lubricant coating on the inner surface of the die. The biggest problem is that it is difficult for the lubricant to uniformly wet the inner surface of the die above a certain level, and the resin flows faster in areas covered with more lubricant than in other areas. This makes it difficult to achieve uniform molding. Roughening the inner surface of the die makes it easier to coat the lubricant uniformly on the inner surface of the die.
Although it is described in USP4087222, this is insufficient. Furthermore, it is necessary to clean the lubricant adhering to the molded product, and there are problems such as there being no easy cleaning method. A patent application has already been filed in Japanese Patent Application No. 57-234239 (Japanese Unexamined Patent Publication No. 59-124814) for a molding method that improves these problems. This Japanese Patent Application No. 57-234239 discloses that in compression stretch molding or extrusion stretch molding in which a heated thermoplastic resin is stretched by compression or extrusion in a die, the inner surface of the die is coated with a lubricant. The thermoplastic resin has at least three layers, the surface layer resin has a lower viscosity than the inner core resin during molding, the surface layer resin and the inner core resin have non-adhesive properties that can be easily peeled off after molding, and the thickness of the surface layer A stretch molding method is shown in which the thickness is less than 1/10 of the thickness of the inner core layer. In other words, a thin layer with good fluidity is provided on the surface layer of the thermoplastic resin, and the surface layer with good fluidity compensates for poor flow due to unevenness or thinness of the lubricant on the inner surface of the die, and improves the inner core layer of the resin. It is made to flow. Although this molding method has significantly improved stretch formability, since this molding method uses a low-viscosity resin as the surface layer resin, the surface of the inner core resin layer after molding is difficult to form a highly smooth surface. Therefore, depending on the application, there is a problem that surface treatment of the molded product is required after molding. The present invention further improves this problem and improves both the moldability and the surface condition of the molded product. That is, the present invention relates to compression stretch molding or extrusion stretch molding in which a heated thermoplastic resin is stretched by compression or extrusion within a die.
The inner surface of the die is molded while being coated with a lubricant, and there are at least three layers of thermoplastic resin, and at least one layer of the surface resin in contact with the inner core resin layer has a higher viscosity during molding than the inner core resin, and the surface resin This is a thermoplastic resin stretch molding method characterized in that the inner core resin is non-adhesive and can be easily peeled off after molding, and the thickness of the surface layer is 1/10 or less of the thickness of the inner core resin layer. In particular, the present invention is a molding method suitable for stretch molding, in which the inner surface of the die is molded while being coated with a lubricant, and a plug flow is caused to flow into the inner core resin layer. The surface resin described in the present invention is a layer that is peeled off and removed from the inner core resin after molding, and the surface resin layer is on the front and back of the inner core resin, and each surface resin layer may be one layer or a multilayer of two or more layers. good. When the surface resin layer is multilayered, it is necessary that the viscosity of the surface resin layer in contact with the inner core resin layer when molded is greater than the viscosity of the inner core resin when molded. Although the inner core resin layer described in the present invention may be one layer,
A multilayer body having two or more layers may also be used. In this case, each layer of the inner core resin must be in close contact with each other, and the viscosity of the inner core resin layer during molding described in the present invention is the viscosity of the inner core layer in contact with the surface layer. As the thermoplastic resin mentioned in the present invention, all thermoplastic resins that are generally used in extrusion stretch molding or compression stretch molding can be used, and furthermore, thermoplastic resins that can be thermoplasticized in an extrusion molding machine can be used. Examples include polystyrene, styrene-acrylonitrile copolymer, ABS resin, polyvinyl chloride, polymethyl methacrylate, polycarbonate, polyester, nylon, polyphenylene ether, or blends and copolymers of these resins. As the surface resin described in the present invention, polyolefins and nylon resins having a low glass transition temperature, such as polyethylene, polypropylene, nylon 12, nylon 6, and various modified polypropylenes, are particularly preferable, but resins having a viscosity within the range described in the present invention can be widely used. . As the surface resin having a higher viscosity during molding than the core resin, a crystalline resin having a melting point slightly higher than the molding temperature of the present invention can be favorably used. That is, the crystals cause uniform deformation during molding and maintain a uniform surface condition. Next, the method of the present invention in which the inner surface of the die is coated with a lubricant and causes plug flow will be explained with reference to the drawings. The present invention will be explained with reference to the drawings. FIG. 1 is an explanatory diagram showing the flow state of resin and polymer in the die. FIGS. 2 and 6 are graphs showing the relationship between temperature and viscosity of various thermoplastic resins or polymers. FIG. 3 is an explanatory view showing the process of forming a biaxially oriented sheet by a compression stretch forming method. FIG. 4 is a cross-sectional view showing an apparatus for forming a biaxially oriented sheet by an extrusion stretch molding method. FIG. 5 is an explanatory diagram showing an enlarged stretching portion for forming a biaxially oriented sheet using the apparatus shown in FIG. 4. FIG. 1 shows the velocity at each position when the thermoplastic resin or thermoplastic resin and polymer flows through the die. When the thermoplastic resin is flowed through the die at a low speed, a speed 1 and a speed curve 2 shown in 1-1 are shown. When flowing at high speed, a velocity curve 3 shown in 1-2 is shown. In 1-1 and 1-2, shearing force acts in the resin, and as a result, flow resistance becomes significantly large when high-viscosity resin flows in the die. Also, 1-1 and 1-2
The in-die flow of the resin shown in is not suitable for biaxial stretching in the die. When the inner surface of the die is uniformly and sufficiently coated with lubricant, the resin slides on the die surface, resulting in a so-called plug flow state 1-3. However, it is difficult to uniformly coat the inner surface of the die with the lubricant, and if the lubricant becomes non-uniform, the flow becomes a mixed flow of 1-1 or 1-2 and 1-3, resulting in large turbulence. That is, depending on the position as shown in 1-4,
The velocity distribution becomes as shown in 4, 5, and 6, and the resin flow becomes turbulent. If a thin layer 8 with good fluidity is provided on the surface layer of the resin layer as in the patent application No. 1982-234239 that we have already filed, the inner core layer 7 will exhibit a flow close to a stable plug flow, with a preferable velocity distribution. 1-5 to become 9. However, when molding is performed with a thin, well-flowing layer 8 provided on the surface layer of the resin layer, if the inner core layer 7 and surface layer 8 are peeled off after molding to create a molded product with only the inner core layer, the surface of the molded product will not be good. Therefore, a smooth surface cannot be obtained. In the present invention, the covering surface resin has a higher viscosity during molding than the inner core resin layer, and the surface resin and inner core resin have non-adhesive properties that allow them to be easily peeled off after molding.As a result, the inner core layer and surface layer can be peeled off after molding. If the molded product is made of only the inner core layer, the surface of the molded product will be good and a smooth surface will be obtained. In this case, if the coefficient of friction between the surface resin layer 11 and the inner surface of the die during molding is smaller than that of the inner core resin layer 10, the surface resin will become slippery, and as a result, the inner core layer 10 will have a stable plug flow. 1-6, which shows a similar flow and results in a favorable velocity distribution of 12. Further, in a preferred embodiment of the present invention, the first layer, the second layer
1-7, which is a five-layer body consisting of the surface layer resin of the fourth layer and the fifth layer, and the inner core resin of the third layer.In 1-7, the outermost layer resin 13 of the first layer and the fifth layer has a lower viscosity during molding than the inner core resin 10 of the third layer;
layer, the surface layer resin 11 of the fourth layer is the inner core resin 1 of the third layer.
When molding is performed with a viscosity greater than 0, the flow in the second to fourth layers becomes a stable plug flow due to the good fluidity of the surface resin layer 13, resulting in a preferable velocity distribution 14. Even if the frictional resistance between the die inner surface and the resin layer is uneven due to uneven lubricant coating, the inner core resin layer maintains a velocity distribution 14 close to plug flow due to the presence of the low-viscosity resin layer on the surface. show. Furthermore, the inner core resin 10 of the third layer is a second layer having a higher viscosity.
Since the fourth layer is molded while being in contact with the surface resin 11 of the fourth layer, the surface condition of the surface resin 11 is transferred to the surface of the inner core resin layer, resulting in a good surface of the inner core resin layer. When a mirror-like sheet with a smooth surface is used as the surface resin 11 of the second and fourth layers, the surface is transferred to the inner core resin layer and becomes an inner core resin layer with a smooth surface. The viscosity-temperature curve of a thermoplastic resin that can be favorably used in the present invention is shown in FIG. Each resin is PMMA (MW, 4.4 million): polymethyl methacrylate (hereinafter abbreviated as PMMA), with a weight average molecular weight of 4.4 million MMA (MW, 150,000): methyl methacrylate (hereinafter abbreviated as MMA); It is a copolymer with a weight average molecular weight of 95:5 and has a weight average molecular weight of 150,000 PP (MI.8): a homopolymer of polypropylene (hereinafter abbreviated as PP) and MI.8 PE (MI.0.06): high density polyethylene (hereinafter referred to as PE). (abbreviation) and MI.0.06. The viscosity was measured using a DYNAMIC spectrometer manufactured by RHEOMETRICS.Inc.
SPECTROMETER) RDS-7700, shear rate (SHEAR RATE) 1 RAD./
Measured with SEC. and 10RAD./SEC., Figure 2 2-1
and shown in 2-2. Since PP and PE are crystalline resins, the viscosity differs when measured while increasing the temperature and when measuring while decreasing the temperature, which is shown in the figure as the temperature increases and decreases. The temperature was raised and lowered by 10°C, and the viscosity was measured after being left for 15 minutes after reaching the measurement temperature. When PMMA is used as the inner core resin, it is preferable to use PP as the surface resin, and perform molding at a temperature of 130 to 160°C by controlling the temperature by raising the temperature. It is preferable that the surface resin has a small coefficient of friction with the inner surface of the die. When the thermoplastic resin slides on the inner surface of the die, the frictional force that acts on the resin and the die surface is equal to the product of the pressure applied to the resin and the coefficient of dynamic friction. Therefore,
The smaller the coefficient of dynamic friction and the lower the resin pressure, the smaller the frictional force, which makes it easier for the resin to slide inside the die and cause plug flow. In general, the coefficient of dynamic friction between the steel (S45C) that makes up the die and various resins is the following value. (lubrication, 11 , 12
(1966) 485) Polymethyl methacrylate 0.568 Polystyrene 0.368 ABS resin 0.366 Polyvinyl chloride 0.219 Polypropylene 0.300 High-density polyethylene 0.139 Resins with a small coefficient of dynamic friction, such as PP and PE, easily slide inside the die and are suitable as surface resins. be. In particular, PP or
When PE is used as the surface layer, the effect is noticeable. Next, a case will be described in which biaxially oriented molding of a thermoplastic resin is performed using the present invention. FIG. 3 shows the process of forming a biaxially oriented sheet by compression stretch forming. A thick-walled base material 16 heated to a temperature above the glass transition temperature and below the melting point of the thermoplastic resin is placed in the excessively heated compression molding die 15 3-1. Compression molding die 1
The inner surface of 5 is coated with a lubricant. The thick-walled base material 16 consists of an inner core 17 and a surface layer 18 of thermoplastic resin, the viscosity of the surface resin at the molding temperature is greater than the viscosity of the inner core resin, and the coefficient of friction between the surface resin and the inner surface of the die during molding is It is smaller than that of the inner core resin, and the thickness of the surface layer is 1/1 of the thickness of the inner core layer.
It is 10 or less. In this state, when a compression force is applied to the compression molding die 15 to compress the thick-walled base material 16, the thick-walled base material 16 is biaxially oriented 3-2. After the compression molding die 15 is cooled and the molded article 19 is cooled and solidified, it is taken out from the die and the surface resin is peeled off from the molded article to obtain a biaxially oriented molded article with a good thermoplastic resin inner core layer. By this compression stretch molding method, a biaxially oriented sheet having a thickness of 1 to 10 mm and a stretching ratio of 1.5 to 7 times in terms of area ratio can be favorably molded. This compression stretch molding method is particularly
This is a molding method suitable for molding biaxially oriented sheets with a thickness of mm or more. When a mirror-like sheet with a smooth surface is used as the surface resin, the mirror surface is transferred to the inner core resin due to the high viscosity of the surface resin, and when the surface resin is peeled off after molding, a biaxially oriented sheet of the inner core resin with a smooth surface and a mirror-like surface is created. can get. In FIG. 3 3-3, the thick-walled base material 20 has five layers,
The outermost resin 21 of the first and fifth layers has a lower viscosity during molding than the inner core resin 17 of the third layer, and the surface resin 18 of the second and fourth layers has a lower viscosity during molding than the inner core resin 17 of the third layer. has a large viscosity. The five-layer thick-walled base material 20 is compressed and stretched in the same manner as described in 3-1 and 3-2 to obtain a biaxially oriented sheet 22. If you use mirror-like sheets with smooth surfaces for the second and fourth layers and peel off the surface resin of the first, second, fourth, and fifth layers after molding, you will see a mirror-like sheet with a smooth surface. A biaxially oriented sheet of core resin is obtained. PE sheets are used for the first and fifth layers, and the second layer,
A mirror-like PP sheet is used for the fourth layer, and a mirror-like PP sheet is used for the third layer.
Using PMMA, 130 ~
A PMMA biaxially oriented sheet with a good surface can be obtained by performing compression molding with heating in the range of 160°C. It is preferable that no air remains between the layers of the three-layer and five-layer thick-walled substrates formed by compression and stretch molding shown in FIG. 3, and for this reason, it is preferable to vacuum pack the inner core resin with the surface resin sheet. FIG. 4 shows an apparatus for forming biaxially oriented sheets by extrusion stretch molding according to the present invention. In FIG. 4, the thermoplastic resin for the inner core layer that has been heat-plasticized by the first extruder 23 is press-fitted into a die 24 in the form of a sheet. The thermoplastic resin for the surface layer heat-plasticized by the second extruder 25 is press-fitted into the die 24 to become the surface layer of the thermoplastic resin, and is formed into a three-layer sheet-like thick-walled molded product at the A portion of the die 24. Part A of the die 24 is cooled, and here 3
The layered sheet-like thick-walled molded body is cooled to a temperature above the glass transition temperature and below the melting point of the thermoplastic resin.
Portion A requires a length to cool the resin almost uniformly, and after cooling, it may be heated slightly to make the temperature uniform, if necessary. Further, in the middle of part A, there is a series of devices for oozing lubricant in order to apply lubricant to the interface between the surface of the thick-walled molded body and the die surface. The high-pressure lubricant is guided from the lubricant introduction path 26 to a plurality of seepage ports 27, seeps out onto the surface of the resin molded article, and is applied to the interface between the molded article surface and the die surface. The lubricant seepage port 27 is made of a substance having a small slit shape or a fine communicating hole such as sintered metal, and the lubricant seeps out from the fine hole. A resin molded body that is cooled to a temperature above the glass transition temperature and below the melting point temperature and whose surface is uniformly coated with a lubricant has a so-called plug flow in which the core resin flows at approximately the same speed within the die. Next, in part B of the die, the plug flow molded body is rolled and biaxially oriented. Portion B of the die has a structure in which the thickness of the resin is reduced. Figure 5 shows the change in flow of the molded product in part B. The molded body is simultaneously rolled biaxially in the flow direction and in a direction perpendicular to the flow direction while maintaining the plug flow, and is biaxially oriented. The force for rolling the molded body is the force for extruding it from an extrusion molding machine. The biaxially oriented molded body is further cooled in the C portion of the die, preferably to a temperature below the glass transition temperature of the resin, and exits the die 24. If necessary, it is further cooled with cold water 28 or the like, passes through a rubber roll 29, and becomes a biaxially oriented sheet. In order to uniformize the sheet coming out of the die 24, it is also effective to provide resistance to the rotation of the rubber roll 29 to prevent the sheet coming out. When the surface layer of the sheet that has come out of the rubber roll is peeled off, a biaxially oriented sheet of thermoplastic core resin is obtained. This extrusion stretch forming method is particularly effective for forming thick biaxially oriented sheets with a thickness of 1 mm or more at a stretching ratio of 1.5 to 7 times in terms of area ratio.
Suitable for axially oriented sheets. If desired, the formed biaxially oriented sheet can be subsequently further formed into a corrugated sheet. Such corrugated sheets are also included in the sheet of the present invention. In the compression molding shown in FIG. 3 and the extrusion stretch molding shown in FIGS. 4 and 5, the resin is biaxially oriented by plug flow. The shear rate applied to the resin when it is biaxially oriented by plug flow is small, and ω= under the resin viscosity measurement conditions shown in Figures 2 and 6.
This corresponds to a shear rate of about 1 rad./sec. or less. The surface layer thickness of the surface layer resin of the present invention is 1/10 or less of the inner core layer thickness of the inner core resin, and the thickness is 0.01 mm.
The thickness is approximately 2 mm, preferably 0.05 mm to 1 mm.
If it becomes too thin, the effect of improving resin flow is lost, and if it is too thick, it is not economical to peel off the surface layer resin after molding and use only the core resin. It is preferable that the surface layer be thin as long as the flow improvement effect is sufficiently recognized. The thickness at which the flow improvement effect is observed varies depending on the viscosity of the surface layer resin, and is appropriately determined depending on the purpose of use. By peeling the surface resin layer from the molded body after molding, the lubricant adhering to the molded body can also be removed at the same time. Of course, it is possible to use the method of the present invention only for removing lubricant adhering to a molded article, but in this case, it is economically preferable that the surface layer be thinner. The lubricants mentioned in the present invention include liquid paraffin,
Various silicone oils such as polydimethylsiloxane,
In addition to stearic acid, various fatty acids and their metal salts such as stearic acid metal salts, various surfactants, and mixtures of these fluids, commonly used lubricants can be used. The viscosity during molding described in the present invention is the viscosity when biaxially oriented in biaxially oriented molding, for example,
In biaxial orientation by extrusion molding, the viscosity is in the B part in FIG. 4, which is the viscosity at the most important part during molding. By the extrusion stretch molding of the present invention, uniaxially oriented molding can also be performed in the same manner. Uniaxially oriented round bars and the like can be formed well. A strong linear body can be obtained by forming a uniaxially oriented round bar of polyoxymethylene, nylon, polyethylene terephthalate, etc. by the method of the present invention, and then superstretching the round bar by a tensile method. In the present invention, the inner core resin layer may be one layer or two or more layers, and a three-layer structure can also be used satisfactorily. For example, the inner core resin layer is PMMA/polycarbonate/
There are three layers of PMMA, and the surface can be well molded while being coated with the surface layer resin of the present invention. Although the present invention has been explained using biaxially oriented molding, it can also be used to improve the stretch formability of resins that are difficult to extrude and stretch mold due to their high viscosity, such as ultra-high molecular weight resins, and to improve the stretch moldability of polyvinylidene chloride. It can also be used to improve extrusion and stretch molding of easily thermally decomposable resins. Example 1 Biaxially oriented molding was performed using the following resins using the compression stretch molding method and apparatus shown in FIG. PMMA: 20mm thick sheet of PMMA (MW4.4 million) PP: 0.2mm thick sheet of MI8 PP homopolymer, with a smooth mirror surface on both front and back surfaces. PE: 0.2mm thick sheet of high-density PE with MI0.06, with a smooth mirror surface on both the front and back sides. Molding was carried out using a multilayered three types of resin base made by laminating a PMMA base and the three types of resins mentioned above. (A): PMMA (B): 3 layers of PE/PMMA/PE (C): 3 layers of PE/PMMA/PP (D): 5 layers of PE/PP/PMMA/PP/PE Inner surface of compression die was coated with a lubricant, polydimethylsiloxane, and the die was heated to 150°C. (A)〜
The resin base of (D) was heated between iron plates heated to 150°C for 10 minutes to raise the temperature. The surface temperature of the substrate is
It was 145℃. The base material was placed in a die and compressed to a thickness of 4 mm, cooled as it was, and stretched to 5 times the thickness to form a biaxially oriented sheet. The resin temperature during compression molding was 140 to 150°C. After molding, the surface layer was peeled off and the surface condition of the PMMA sheet was observed.
The following table shows the minimum required compressive force per 1 cm ² of biaxially oriented sheet and the surface condition of the sheet.

【table】

[Table] (A) required high compression force and required cleaning to remove the lubricant on the sheet surface. (B) has small undulations on the entire surface. The sheet surfaces in (C) and (D) were smooth mirror surfaces onto which the PP sheet surface was transferred.
The minimum required compressive force is smaller in (B), (C), and (D), indicating that the fluidity within the die of the multilayer substrate is improved. (C) and (D) are the molding methods of the present invention, and both moldability and sheet surface are good. Example 2 Biaxial orientation molding was performed in the same manner as in Example 1 using the following resins. MMA-MAAmid: 20 mm thick sheet of MMA (92 wt%) and methacrylamide (8 wt%) copolymer MMA-St-MAH: MMA (70 wt%), styrene (20 wt%), maleic anhydride (10 wt%) weight%)
20mm sheet of copolymer consisting of Nylon12: A sheet of 0.1mm thick smooth surface made of nylon 12 (mp178℃) (Daicel Chemical Industries, Ltd.)
Nylon6: 0.1mm thick smooth surface sheet of nylon 6 (MP225℃) (Toray Synthetic Film Co., Ltd.)
PE: Sheet with a 0.2 mm thick smooth surface made of high-density PE with an MI of 0.06. The viscosity-temperature curves of each resin are shown in Figure 6. Molding was carried out using a multilayer resin base made of the above-mentioned resins stacked on top of each other. (E): MMA−MAAmid (F): PE/MMA−MAAmid/PE (G): PE/Nylon12/MMA−MAAmid/
Nylon12/PE (H): PE/Nylon6/MMA-MAAmid/
Nylon6/PE (I): MMA-St-MAH (J): PE/MMA-St-MAH/PE (K): PE/Nylon12/MMA-St-MAH/
Nylon12/PE (L): PE/Nylon6/MMA-St-MAH/
The inner surface of the Nylon6/PE compression die was coated with a lubricant, polydimethylsiloxane, and the die was heated to 170°C. (E)〜
The resin base (L) was placed between iron plates heated to 170°C for 10 minutes and heated. The surface temperature of the substrate is
It was 165℃. The base material was placed in a die and compressed to a thickness of 4 mm, cooled as it was, and stretched to 5 times the thickness to form a biaxially oriented sheet. The resin temperature during compression molding was 160 to 170°C. After molding, peel off the surface layer to form MMA-MAAmid and MMA-St-
The surface condition of the MAH sheet was observed. The following table shows the minimum required compressive force per 1 cm ² of biaxially oriented sheet and the surface condition of the sheet.

[Table] (E) and (I) required high compression force and required cleaning to remove the lubricant on the sheet surface. (F) and
(J) had small undulations on the entire surface. (G), (H),
The sheet surfaces of (K) and (L) were smooth surfaces onto which the top sheet surface was transferred. The minimum required compression force is (F), (G),
(H), (J), (K), and (L) are smaller, indicating that the in-die fluidity of the multilayer substrate is improved. (G),
(H), (K), and (L) are the molding methods of the present invention, and both moldability and sheet surface are good.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the flow state of resin and polymer in the die. FIGS. 2 and 6 are graphs showing the relationship between temperature and viscosity of various thermoplastic resins or polymers. Figure 3 shows 2
FIG. 3 is an explanatory diagram showing the process of forming an axially oriented sheet. FIG. 4 is a cross-sectional view showing an apparatus for forming a biaxially oriented sheet by an extrusion stretch molding method. FIG. 5 is an explanatory diagram showing an enlarged stretching portion for forming a biaxially oriented sheet using the apparatus shown in FIG. 4. 1...Speed, 2, 3, 4, 5, 6, 9, 12,
14... Speed curve or speed distribution, 7, 10, 1
7... Inner core layer, 8, 18... Surface layer, 11... Surface layer resin, 13, 21... Outermost layer resin, 15... Compression molding die, 16, 20... Thick wall base material, 22... 2
Axial orientation sheet, 23...first extruder, 24...
Die, 25... Second extruder, 26... Lubricant introduction path, 27... Seepage port, 28... Cold water, 29
...Rubber roll.

Claims (1)

[Scope of Claims] 1. In compression stretch molding or extrusion stretch molding in which a heated thermoplastic resin is stretched by compression or extrusion in a die, the inner surface of the die is coated with a lubricant, and The thermoplastic resin has at least three layers, and at least one layer of the surface resin in contact with the inner core resin layer has a higher viscosity during molding than the inner core resin, and the surface resin and the inner core resin are non-adhesive and can be easily separated after molding. A method for stretch-molding a thermoplastic resin, wherein the thickness of the surface layer is 1/10 or less of the thickness of the inner core layer. 2 The thermoplastic resin has three layers, both surface layer resins have a higher viscosity during molding than the inner core resin, and the coefficient of dynamic friction between the surface layer resin and the inner surface of the die during molding is smaller than that of the inner core resin. Range 1
Molding method described in section. 3 The thermoplastic resin consists of surface layer resins of the first layer, second layer, fourth layer, and fifth layer, and an inner core resin of the third layer.
It is a layered body, and the outermost resin of the first layer and the fifth layer is the third layer.
The viscosity during molding is lower than that of the inner core resin of the layer, and the second
The molding method according to claim 1 or 2, wherein the surface layer resin of the fourth layer has a higher viscosity during molding than the inner core resin of the third layer. 4 Compression stretch molding involves heating a preformed thermoplastic resin to a temperature above the glass transition temperature and below the melting point of the core resin, and then compressing it in a die heated to approximately the same temperature to achieve biaxial orientation. , cooled to a thickness of 1~
The molding method according to any one of claims 1 to 3, which is carried out by taking out a 10 mm biaxially oriented sheet. 5 In extrusion stretch molding, the temperature of the extruded thermoplastic resin is controlled to be above the glass transition temperature and below the melting point temperature of the core resin, and then it is biaxially oriented in a die by extrusion pressure to form a resin with a thickness of 1 to 10 mm. The molding method according to any one of claims 1 to 4, which is carried out by taking out a biaxially oriented sheet.