WO1999038670A1

WO1999038670A1 - Thermoplastic resin molded product and manufacturing and using methods thereof

Info

Publication number: WO1999038670A1
Application number: PCT/JP1999/000371
Authority: WO
Inventors: Sadaatsu Yamaguchi
Original assignee: Daikin Industries, Ltd.
Priority date: 1998-01-29
Filing date: 1999-01-29
Publication date: 1999-08-05

Abstract

A thermoplastic resin molded product improved in tensile strength and surface smoothness over another product using the same molding material and manufacturing and using methods thereof. The thermoplastic resin molded product which is obtained by forming a molding material containing thermoplastic resin under a highly reduced pressure and has at least 5 % larger tensile strength than another molded product formed of the same molding material containing thermoplastic resin and under the identical conditions except that the latter is not formed under a reduced pressure.

Description

Specification

TECHNICAL FIELD

The present invention relates to a thermoplastic resin molded article having excellent mechanical strength, particularly excellent tensile strength and surface smoothness, and a method for producing and using the same. Background art

Molded articles made of thermoplastic resins such as polyethylene and polypropylene are widely used in extremely diverse fields due to their ease of molding. Molded articles made of fluororesin have excellent properties such as heat resistance, chemical resistance, and friction resistance, and are widely used in the daily necessities field, office automation equipment fields, and high-tech fields such as space. In recent years, such molded products, especially those made of polyethylene and fluororesin, have been developed with the advancement of semiconductor manufacturing technology, making use of these excellent chemical resistances to make high-purity chemical containers for semiconductor manufacturing, piping for transferring ultrapure water, etc. It is used for

Generally, it is desired that these molded products have high mechanical properties, for example, high tensile strength.

In addition, in semiconductor-related applications, there has been a demand to extremely dislike the entry and retention of impurities in order to store and transport extremely high-purity chemicals. Since the surface is not so smooth, contaminants adhere to the surface and become chewy, and there is a problem that the contaminants are difficult to be removed even by washing. Therefore, supply of a molded product having a high surface smoothness has been desired.

By the way, molding under reduced pressure has been conventionally performed in the molding industry, but it is for removing moisture, residual monomers, bubbles, etc., which are absorbed by the molding material. there were. They have been applied to resins that may contain moisture, residual monomers, etc., for example, polystyrene, polyacrylates, polyamides, polyethylene terephthalate, polyimides, polyarylates, and the like.

Japanese Unexamined Patent Publication No. 60-171110 discloses tetrafluoroethylene / hexaflu Disclosed in the extrusion finishing method of a polypropylene copolymer molding material is a technique for removing the source of volatile substances that cause bubbles and voids in the copolymer by limiting the temperature and the shear rate under reduced pressure. Have been. However, this technology is not concerned with the conditions under which the final part is formed.

Japanese Patent Application Laid-Open No. 7-73097 discloses that in order to smooth the surface of a melt-molded product of tetrafluoroethylene nofluoroalkoxy trifluoroethylene copolymer (PFA), There is disclosed a technique in which a small amount of specific polytetrafluoroethylene (PTFE) is added and contained to refine the spherulites of PFA to obtain the surface smoothness of a molded product. However, this technique has been far from satisfactory in terms of the surface smoothness of the resulting molded article. Summary of the Invention

In view of the above situation, an object of the present invention is to provide a molded article having improved tensile strength compared to the case of the same molding material and exhibiting superior surface smoothness, and a method for producing and using the same. It is.

The present invention relates to a thermoplastic resin molded product obtained by subjecting a molding material containing a thermoplastic resin to molding under high pressure, wherein the molding material is the same as the molding material containing the thermoplastic resin. This is a thermoplastic resin molded product characterized in that its tensile strength is increased by at least 5% with respect to other molded products obtained by molding under the same conditions except that it is not performed under reduced pressure.

Further, the present invention provides the method for producing a thermoplastic resin molded article, wherein the molded article obtained by molding a molding material containing the thermoplastic resin is processed under a high vacuum. This is a method for producing a thermoplastic resin molded product.

Further, the present invention is a method of using the thermoplastic resin molded product described above as a high-purity chemical container, an insulator, and an inflation film. BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows the crystal of polyvinylidene fluoride (PVdF) obtained in Example 1. It is an electron micrograph (400000 magnification) which shows a structure.

FIG. 2 is an electron micrograph (× 3000) showing the crystal structure of PV dF obtained in Comparative Example 2.

FIG. 3 is a scanning electron micrograph (× 30) showing the crystal structure of PVd F obtained in Comparative Example 1.

FIG. 4 is a schematic perspective view showing a method for creating a closed molding space in a compression molding machine. FIG. 5 is a schematic sectional view showing a method for creating a closed molding space in a compression molding machine.

FIG. 6 is a schematic cross-sectional view showing a method for creating a closed molding space in a melt extrusion molding machine. Detailed Disclosure of the Invention

In the thermoplastic resin molded article of the present invention, the tensile strength is increased by at least 5%. In the present specification, “tensile strength” is defined as follows according to the method described in ASTM D 638-94b and ASTM D 882-91 in accordance with the thickness of the sample. A sample punched out with a dumbbell was measured at a speed of 500 mm / min.

(1) If the sample thickness exceeds 1 mm, ASTM D 638—94b: No. 3 dumbbell

(2) When the sample thickness is 1 mm or less, ASTM D 8 8 2 9 1: Micro dumbbell

The above-mentioned increase in tensile strength of at least 5% means that a molded material containing the same thermoplastic resin is used as a raw material and is not subjected to reduced pressure, and other molded products are molded under the same conditions. 5% or more, and the tensile strength at break also increased by 5% or more.

In the present invention, the cause of the increase in the tensile strength is not necessarily clear, but for example, a molding method close to vacuum can be used. In the present invention, the increase in the tensile strength is 5% or more, and more preferably 10% or more. In the present specification, “thermoplastic resin” means polyethylene, ultra-high molecular weight polyethylene, polypropylene, and fluororesin. The thermoplastic resin in the present specification has not been molded under reduced pressure to obtain a final molded product.

Examples of the fluororesin include those that cannot be melt-processed include polytetrafluoroethylene and modified polytetrafluoroethylene, and those that can be melt-processed include tetrafluoroethylene. Polyethylene Z hexafluoropropylene copolymer, Tetrafluoroethylenenoperfluoro (alkyl vinyl ether) copolymer, Ethylene Z tetrafluoroethylene copolymer, Ethylene / Chloro trifluoro Tylene copolymer, polychloro trifluoroethylene, polyvinylidenefluoride, vinylidenefluoride / tetrafluoroethylene copolymer, vinylidenefluoride / tetrafluoroethylene / chlorotrifluoroethylene copolymer, vinylidenefluoride Raid Z Trifluorene Mention may be made of the body or the like.

Among the above thermoplastic resins, general-purpose resins are preferably polyethylene, ultra-high molecular weight polyethylene and polypropylene, and fluorine resins are preferably polytetrafluoroethylene, modified polytetrafluoroethylene, and tetrafluoroethylene hexafluoro. Preferred are a polypropylene copolymer, a vinylidene fluoride z-tetrafluoroethylene copolymer, and a vinylidene fluoride trifluoroethylene copolymer.

The molding material containing a thermoplastic resin used in the present invention may have a filler added thereto. The above-mentioned filler is not particularly restricted but includes, for example, rubbers such as titanium oxide, zircon, fibrous glass short fibers, asbestos, flaky graphite, mica, talc: ethylene-propylene rubber, fluorine rubber and the like. it can. These can be used alone or in combination of two or more. In addition, the size of the filler and the amount of the filler are not particularly limited, and a commonly used size and the amount of the filler can be applied.

The shape of the molding material containing a thermoplastic resin used in the present invention is not particularly limited. For example, any shape can be used as a usual molding material such as a powder or a pellet. Good. Further, the shape may be a block shape, a plate shape, a sheet shape, a film shape, a hollow shape, or another shape.

The method for molding the molding material containing the thermoplastic resin of the present invention is not particularly limited, but it is important that this is performed at least at the time of heating and melting or firing the thermoplastic resin under a specific high vacuum.

The term "under reduced pressure" used in the present specification for a molding process refers to a thermoplastic resin molding machine having a closed molding space connected to at least one operating vacuum line and having a vacuum gauge disposed on the vacuum line. Alternatively, in the molding apparatus, the degree of pressure reduction in one of the vacuum lines in the closed molding space where the thermoplastic resin to be molded is present in a molten state, and the portion closest to the obtained molded product is obtained by reading the above vacuum gauge. 1 OT orr, preferably less than 5 Torr.

The degree of decompression of the part closest to the obtained molded product means the reduced pressure state of the vacuum line when there are only one vacuum line, and the obtained molded product when there are two or more vacuum lines. Is the decompression state of the vacuum line that is closest to the space that is connected in a sealed state, and the interval between them is not specified.

For the latter, for example, in FIG. 6, the degree of pressure reduction in the vacuum line on the right side of the two vacuum lines is the degree of pressure reduction in the portion closest to the molded product that can be obtained.

In the present invention, such a reduced pressure condition is necessary when molding a thermoplastic resin molded product, but it is more preferable to employ it also in the steps of pelletization and transfer thereof.

The molded article referred to in the present invention means only a molded article giving a final shape, and does not include a pellet used as a raw material of a molded article giving a final shape, and a molded article for producing the pellet.

The closed molding space can be formed, for example, as follows in a typical molding method.

(1) For thermoplastic resin that cannot be melt-processed

(1-1) Compression molding: The same compression molding is the same as powder metallurgy pre-molding, in which a molding material is poured into a mold of a desired shape or a similar shape, and is pressed at room temperature and pressed from a certain direction. The molding material inside the machine is compressed to obtain a preform. In this case, for example, as shown in FIG. 4 and FIG. 5, the above-mentioned closed molding space is obtained by mounting a 0 ring in a mold, drawing a vacuum, and placing these compression molding machine molding spaces under high pressure reduction. Can be made.

(1-2) Firing and cooling of the preform: The firing means that the raw material is present inside a furnace having a heating device for raising the temperature to a constant temperature of, for example, about 360 to 380 ° C. The heating is continued for a certain time and then cooled. It is not always necessary to reduce the pressure during cooling.

In this case, the sealed molding space can be created by placing a sealed container in a furnace for performing the above-described firing, placing the preformed product therein, and evacuating the container.

(1-3) Ram extrusion: The extrusion is the simultaneous compression molding and baking. In ram extrusion, a type of extrusion molding, a ram extruder consisting of a feeding section, a baking section, and a cooling section is used, and the molding powder is intermittently injected with a ram from the top of a single cylinder and heated in the baking section. Then, after cooling in the lower cooling section, molding era is obtained.

In this case, first, in order to keep the inside of the extruder hermetically sealed, the entire cylinder and ram should be sealed by installing a 0 ring at the connection part, sealing with a copper seal or other methods as necessary, and further molding powder. At the hopper part to be supplied, a nozzle is provided by sealing the upper part of the hopper without opening, and the nozzle is opened to supply molding powder, and the nozzle is closed to shut off the outside. The evacuation can be performed in the nozzle portion above the hopper or in the closed portion of the cylinder.

(2) For thermoplastic resin that can be melt processed

(2-1) Melt extrusion molding: Examples of the molding include extrusion molding and injection molding. Extrusion molding is performed using an ordinary molding machine composed of a barrel, a screw, a die and the like. Injection molding is performed using an ordinary molding machine composed of a cylinder, a screw, a plunger, a nozzle and the like.

In this case, a closed molding space can be created in the same manner as in (1-3) above. Figure 6 shows a typical device. In Figure 6, where no pressure is applied Vacuum with. In an extruder, since a vent hole exists in the molding machine itself, it is desirable to evacuate the vent hole.

(2-2) In extrusion molding, high pressure is applied from the hopper to the die to eliminate voids in the resin and extrude into the atmosphere.Therefore, there is almost no voids in the molded product. Meet the requirements of the invention.

Therefore, it is preferable to apply a vacuum to the outside of the die, but it is not necessary to put it under high vacuum.

(2-3) In the case of injection molding, by keeping the pressure from the hopper to the die under high vacuum, when the molten resin enters the mold, the air in the mold is discharged to the outside. There is no need to draw a vacuum.

In addition, the molding apparatus of the present invention is appropriately employed in a molding apparatus such as a T-die method or an inflation method for forming a film, and a blow molding method for forming a hollow product in the same manner as in (2-1). There are various types of articles, including pipes, tubes, films, irregularly shaped articles, hollow molded articles, monofilaments, wire coatings, laminate molded articles, etc.The molded article of the present invention Eliminates ultra-fine voids that have not been known to improve mechanical strength and smoothness, and greatly improves stress crack resistance. When a molded product is used as a chemical container, etc., or when a temperature from room temperature to about 200 ° C is used under a cycle, voids (micropores formed by air) exist in the molded product. Then, the chemical penetrates into it, and then expands and contracts repeatedly, causing distortion and cracks. Since the molded article of the present invention has almost no voids, there is no concern about occurrence of such distortion and cracks.

In addition, when used in semiconductor-related containers that dislike dust especially among chemical containers, if the surface is low in smoothness, it becomes a pool of contaminants and reduces container performance. The product has no or very few spherulites, as will be described in detail later in the examples, so the surface is extremely smooth and free of voids, so there is no place for contaminants to accumulate and the condition is extremely good Can be kept. Thermoplastic resin molded articles suitable for these uses include those made of polyethylene, ultra-high molecular weight polyethylene, fluororesin, and the like.

The thermoplastic resin molded article of the present invention has a very low dielectric breakdown voltage due to a small amount of voids in the molded article, and is suitable for application to products requiring this. Examples of such a product include an insulator, and specific examples include an insulating film and an insulating sheet. As the thermoplastic resin molded article of the present invention suitable for these uses, a molded article made of polyethylene, ultrahigh molecular weight polyethylene, PTFE, or the like is preferable.

Since the molded article of the present invention has an improved tensile strength of 5% or more, it can be made thinner and requires less molding material. Therefore, it is also suitable as an inflation film. Polyethylene, melt-processable fluororesin, etc. are suitable for this application. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention. However, the present invention is not limited to these Examples. Comparative Example 1

The PvdF film was injection molded at a temperature of 230 ° C and atmospheric pressure to create a sheet with a thickness of 2 mm. The surface was observed with a scanning electron microscope (30 ×). Figure 3 shows the results. It was found that there were irregularities on the surface that seemed to indicate that bubbles had escaped.

In addition, a portion where no bubble was present was partially selected, and further observed with an electron microscope (40000 magnification). Clear spherulites were formed, indicating no surface smoothness. Example 1

The sheet obtained in Comparative Example 1 was placed in a sealed glass container, and the whole container was immersed in a thermostat kept at 230 ° C. for 10 minutes while drawing a vacuum of 2 Torr from one location. Then, after air-cooling at room temperature under the same reduced pressure, it is taken out of the container and the surface is Observation was performed with a microscope (400,000 times). The results are shown in FIG. No spherulites could be observed, indicating that the surface smoothness was clear. Comparative Example 2

The sheet obtained in Comparative Example 1 was melted in the air, and cooled in the air at room temperature. . The results are shown in FIG. Plane smoothness is not sufficient. Example 2

The PVdF powder was put into a mold and kept at a temperature of 237 ° C. for 30 minutes. At least the last 10 minutes of the 30 minutes was kept at a reduced pressure of 2 T 0 rr. After applying a pressure of 30 kg / cm ² for 90 seconds with a compression press, the mold was cooled with circulating cooling water to produce a compression molded sheet. The resulting create five specimens from the sheet, by Shimadzu Sakushosha made Otogurafu DC S 5 0 0, was measured each tensile strength, an average 6 3 0 kgf / cm ^2. Comparative Example 3

A PV dF sheet was prepared in the same manner as in Example 2 except that the operation was performed under the atmospheric pressure, and five test pieces were prepared from the obtained sheets, and the tensile strength at break was measured. As a result, the average was 570 kgf / cm ² .

From the results of Example 2 and Comparative Example 3, it was found that the operation under a high vacuum reduced the tensile strength at break by about 10%. Example 3, Comparative Example 4

And Takashi塡powder PTF E in the mold under atmospheric pressure, and the pre-molding pressure to ² 0 0 kgf Zc m 2, created a 7 0 0 mm0 x 1 0 0 mm0 preformed blocks. After firing in an electric furnace set at 380 ° C. under atmospheric pressure for 8 hours, the sintering block was obtained by cooling at 40 ° C.Z time. A tape having a thickness of 0.5 mm was skived from this block to obtain a test tape. After re-baking this tape in air at 380 ° C for 40 minutes After cooling at room temperature, a test piece A (comparative example) was obtained, and calcined at 38 ° C. for 40 minutes under reduced pressure, and then cooled in air to obtain a test piece B (example). After calcining at 0 ° C for 40 minutes under reduced pressure, it was air-cooled under the reduced pressure to obtain a test piece C (Example). The decompression conditions were maintained at 2 Torr for at least the last 10 minutes of the 40-minute aging process.

In order to examine the tensile strength at break, five test pieces were prepared, and the tensile strength at break was measured. The average value of the tensile strengths was as follows.

A ^ OS kgf / cm ²

B: 4600 kgf / cm ²

C: 4 4 7 kgf / cm ²

From these results, it was found that the tensile strength of the test piece prepared under high vacuum was more than 10% higher than that of the test piece prepared in air.上の Business availability

Since the molded article of the present invention increases mechanical strength and achieves excellent surface smoothness, it can be favorably applied to, for example, applications requiring extremely high purity containers such as semiconductor-related applications. it can.

Claims

The scope of the claims

1. A thermoplastic resin molded product obtained by molding and molding a molding material containing a thermoplastic resin under reduced pressure of 10 Torr or less, the same as the molding material containing the thermoplastic resin. A thermoplastic resin molded article characterized in that its tensile strength is increased by at least 5% with respect to other molded articles obtained by molding under the same conditions except that the molding material is not subjected to reduced pressure. .

2. The thermoplastic resin molded article according to claim 1, wherein the reduced pressure is 5 T or less.

3. A filler is added to a molding material containing a thermoplastic resin.

Thermoplastic resin molding according to 1 or 2,

Chloro o

4. The thermoplastic resin molding according to claim 1, 2 or 3, wherein the molding material containing the thermoplastic resin is in the form of powder, pellet, block, plate, sheet, film or hollow. Goods.

5. The method for producing a thermoplastic resin molded product according to claim 1, 2, 3, or 4, wherein the molding of the molding material containing a thermoplastic resin is performed under a reduced pressure of 1 OT orr or less. A method for producing a thermoplastic resin molded product, characterized in that:

6. The method for producing a thermoplastic resin molded product according to claim 5, wherein the reduced pressure is 5 T or less.

7. The method for producing a thermoplastic resin molded product according to claim 5, wherein the thermoplastic resin is polytetrafluoroethylene or ultra-high molecular weight polyethylene that cannot be melt-processed.

8. The thermoplastic resin molded article according to claim 7, wherein the molding process performed under reduced pressure includes at least one of a step of preforming and a step of firing a molding material containing polytetrafluoroethylene. Manufacturing method.

9. The method for producing a thermoplastic resin molded article according to claim 7, wherein the thermoplastic resin can be melt-processed.

10. The method for producing a thermoplastic resin molded article according to claim 9, wherein the molding performed under reduced pressure includes at least a step of ripening and melting a molding material containing a thermoplastic resin.

11. The method for producing a thermoplastic resin molded product according to claim 5, 6, 9, or 10, wherein the thermoplastic resin is a melt-processable fluororesin.

12. A method of using the thermoplastic resin molded product according to claim 1 or 2 as a high-purity chemical container for semiconductor production.

13. The method according to claim 12, wherein the thermoplastic resin molded article is obtained by molding and processing polyethylene, ultra-high molecular weight polyethylene, or fluororesin.

14. A method using the thermoplastic resin molded product according to claim 1 or 2 as an insulator.

15. The method according to claim 14, wherein the thermoplastic resin molded product is obtained by molding and processing polyethylene, ultrahigh molecular weight polyethylene, or fluororesin.

16. A method of using the thermoplastic resin molded product according to claim 1 or 2 as an inflation film.

17. The method according to claim 16, wherein the thermoplastic resin is obtained by molding and processing polyethylene or a melt-processable fluororesin.