JP7557155B2 - Manufacturing method of molded product and molded product - Google Patents

Description

This disclosure relates to a method for producing a molded article and the molded article.

Patent Document 1 describes a method for producing a stabilized fluoropolymer, which is characterized in that, prior to stabilization of the fluoropolymer by melt-kneading in a kneader including a stabilization treatment zone in which a melt-processable fluoropolymer having unstable groups is stabilized in the presence of water and oxygen, a melting zone in which the fluoropolymer is melt-kneaded at a temperature and for a time sufficient to decompose or volatilize low molecular weight substances in the fluoropolymer is disposed as a zone preceding the stabilization treatment zone, and the low molecular weight substances are decomposed and/or volatilized in the melting zone and released outside the kneader prior to the stabilization treatment zone.

International Publication No. 2002/050135

An object of the present disclosure is to provide a method for producing a molded article that can produce a molded article with a reduced amount of particle generation.
Another object of the present disclosure is to provide a molded product with reduced particle generation.

According to the present disclosure, there is provided a method for producing a molded product, which includes a preparation step of preparing a molding material by molding a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer at a temperature T1 (°C), and a molding step of extruding the molding material at a temperature T2 (°C) to obtain a molded product, in which the temperature T1 and the temperature T2 satisfy the relationship 20≦T1-T2≦80.

The temperature T1 (° C.) in the preparation step is preferably 390° C. or higher.
The melting point of the tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer used in the preparation step is preferably 295° C. or higher.
The tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer used in the preparation step preferably has a perfluoro(alkyl vinyl ether) unit content of 3.5 to 7.0 mass %.
In the preparation step, the molding material is preferably prepared by extrusion molding.
The molding material obtained in the preparation step is preferably in the form of pellets.
The molded product obtained in the molding step is preferably a tube.

The present disclosure also provides a molded article that contains a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer with a melting point of 295°C or higher, and that, when in contact with isopropyl alcohol, disperses in isopropyl alcohol at a count of 700 particles/ml or less that are 30 nmφ or larger in size.

The molded article of the present disclosure is preferably a tube.

According to the present disclosure, it is possible to provide a method for manufacturing a molded article that can produce a molded article with a reduced amount of particle generation.
Furthermore, according to the present disclosure, it is possible to provide a molded product with reduced particle generation.

FIG. 1 is a diagram for explaining the mechanism by which particles adhere to a tube in a conventional tube molding process. FIG. 2 is a diagram for explaining an example of the preparation process. FIG. 3 is a diagram for explaining a method for measuring the number of particles.

Specific embodiments of the present disclosure are described in detail below, but the present disclosure is not limited to the following embodiments.

As semiconductor miniaturization processes progress, it is becoming increasingly important to reduce contaminants from molded products used in semiconductor devices and chemical supply equipment. For example, JP 2014-222756 A points out the problem of particles being generated from piping for supplying chemicals and getting into the chemicals.

Molded articles containing a copolymer containing tetrafluoroethylene units (TFE units) and perfluoro(alkyl vinyl ether) units (PAVE units) (hereinafter referred to as TFE/PAVE copolymer (or PFA)) are used in large numbers in semiconductor devices and chemical supply equipment due to their excellent resistance to chemicals, and the area in contact with high-purity chemicals is also large. However, in the prior art including Patent Document 1, no method has been considered for suppressing particle generation from molded articles containing TFE/PAVE copolymer, which can exhibit a very high melting point depending on the composition, etc.

Therefore, the inventors of the present invention conducted extensive research into particle reduction technology and discovered that by strictly controlling the temperature at which the TFE/PAVE copolymer is heated in the series of steps used to manufacture molded products from raw materials, it is possible to suppress particle generation from the final molded product to an unprecedented level.

Furthermore, according to the findings of the present inventors, even if a molded product is washed with ultrapure water until particles are no longer detectable, if the washed molded product is then brought into contact with isopropyl alcohol, particles will be detected in the isopropyl alcohol. In other words, the conventional evaluation method of washing a molded product with ultrapure water, recovering the ultrapure water (washing water), and measuring the particles dispersed in the ultrapure water does not allow for an accurate evaluation of the particle count, and it has also been discovered that the new evaluation method using isopropyl alcohol makes it possible, for the first time, to accurately evaluate the particle count.

The manufacturing method disclosed herein has been completed based on these findings, and is characterized in that in the manufacturing method including a preparation step in which a TFE/PAVE copolymer is molded at a temperature T1 (°C) to prepare a molding material, and a molding step in which the molding material is extruded at a temperature T2 (°C) to obtain a molded product, the temperature T1 and the temperature T2 satisfy the relationship 20≦T1-T2≦80.

The temperature T1 (°C) in the preparation process is the molding temperature when the TFE/PAVE copolymer is molded to prepare the molding material. In the preparation process, the molding temperature may be set to be constant within a range that does not interfere with molding, or the molding temperature may be changed. When changing the molding temperature, the molding temperature can be changed so that the temperature T1 and the temperature T2 satisfy the relationship 20≦T1-T2≦80, with the temperature at any point in the preparation process being T1. In other words, the temperature T1 in the preparation process may be the temperature at any point in the preparation process, or may be the maximum temperature in the preparation process. The temperature T1 is not the copolymer temperature, but the set temperature of the molding machine used for molding.

The temperature T1 is preferably equal to or higher than the melting point or softening point of the TFE/PAVE copolymer, more preferably equal to or higher than the melting point of the TFE/PAVE copolymer, even more preferably equal to or higher than 350°C, even more preferably equal to or higher than 370°C, particularly preferably equal to or higher than 390°C, and most preferably equal to or higher than 400°C, because it is possible to obtain a molded product with a further reduced amount of particle generation without damaging the TFE/PAVE copolymer, and it is also possible to obtain a molded product with a further reduced amount of particle generation ...

The temperature T2 (°C) in the molding process is the molding temperature when molding the molding material. In the molding process, the molding temperature may be set to be constant within a range that does not interfere with molding, or the molding temperature may be changed. When changing the molding temperature, the molding temperature can be changed so that the temperature T1 and the temperature T2 satisfy the relationship 20≦T1-T2≦80, with the temperature at any point in the molding process being T2. In other words, the temperature T2 in the molding process may be the temperature at any point in the molding process, or may be the maximum temperature in the molding process. The temperature T2 is not the copolymer temperature, but the set temperature of the molding machine used for molding.

Temperature T2 is set to a temperature lower than temperature T1 so as to satisfy the inequality: 20≦T1-T2≦80. That is, in the manufacturing method disclosed herein, by controlling the temperature difference between temperature T1 and temperature T2 to a range of 20 to 80°C, the generation of particles from the finally obtained molded product can be suppressed to an unprecedented level. On the other hand, when molding into the above molded product, if a conventional method is adopted in which the molding temperature is set as high as possible in order to increase the extrusion speed with an emphasis on productivity, the amount of particle generation cannot be sufficiently suppressed. Temperatures T1 and T2 preferably satisfy the inequality: 30≦T1-T2, more preferably satisfy the inequality: 40≦T1-T2, and more preferably satisfy the inequality: T1-T2≦70, since a molded product with a further reduced amount of particle generation can be obtained. Also, the larger the molded product to be manufactured, the greater the temperature difference between T1 and T2 is preferably.

The reason why a molded product with reduced particle generation can be manufactured by strictly controlling the temperatures T1 and T2 is not clear, but is presumed to be as follows. Figure 1 is a diagram for explaining the mechanism by which particles adhere to a tube in a conventional tube molding process. As shown in Figure 1, the TFE/PAVE copolymer 101 molten in the cylinder 111 passes through the adapter 112 and is extruded from the die 113 to form a cone 102 of the molten TFE/PAVE copolymer that extends to the sizing die 114, and then passes through the sizing die 114 to form the tube 103. The outer shape of the tube 103 is determined by the sizing die 114, and the wall thickness of the tube 103 is determined by the extrusion amount controlled by the rotation speed of the screw 115. Outside air 121 is sent into the inside of the cone 102 and the tube 103 from holes 116 provided in the die 113, and the molten TFE/PAVE copolymer is cooled and solidified. The outside air 121 is usually filtered to remove environmentally derived contaminant particles. When the TFE/PAVE copolymer 101 heated to the die temperature is extruded from the die 113, low molecular weight substances 131 volatilize from the surface of the molten TFE/PAVE copolymer, and as the TFE/PAVE copolymer cools, they adhere to the inner surface of the cone 102 and the tube 103. This phenomenon occurs in the conventional tube molding process, and it is presumed that the adhered low molecular weight substances are dissolved into the chemical solution as particles. The low molecular weight substances have a chemical structure similar to that of the TFE/PAVE copolymer, and adhere to the inner surface of the tube due to strong hydrophobic interactions in water or in the chemical solution, making it extremely difficult to wash them off with water.

On the other hand, in the manufacturing method disclosed herein, by strictly controlling temperatures T1 and T2, it is presumed that even if the TFE/PAVE copolymer is melted in the molding process, low molecular weight substances are unlikely to be generated, and a molded product with reduced particle generation can be produced.

In the above preparation step, the molding method for preparing the molding material is not particularly limited, but a method that can mold the material into a shape suitable for extrusion molding in the above molding step is preferable, and an extrusion molding method is more preferable. By preparing the molding material by extrusion molding in the above preparation step, the molding material can be prepared with high productivity, and a molded product with even lower particle generation can be obtained.

The shape of the TFE/PAVE copolymer used in the above preparation process is not particularly limited, but it is preferably in the form of particles or powder, as this is easy to manufacture.

The shape of the molding material is not particularly limited, but a shape suitable for extrusion molding in the molding process is preferable. The molding material may be in the form of powder, pellets, crumbs, etc., but extrusion molding can be used as a molding method for preparing the molding material. It is preferable that the molding material is in the form of pellets, since this shape is suitable for extrusion molding in the molding process, has excellent productivity, and allows the production of molded products with even reduced particle generation.

The pellets are preferably roughly cylindrical with a length of 1 to 3 mm and a diameter of 0.5 to 3 mm, as these are easy to produce and handle. A pellet diameter of 1 to 2 mm is more preferable.

In the above preparation process, it is particularly preferable to prepare pellets as the molding material by extrusion molding, since this allows the molding material to be prepared with high productivity and produces a molded product with even lower particle generation.

In the preparation step, when the molding material is prepared by extrusion molding, an extruder can be used. The extruder may be a single screw extruder or a twin screw extruder.

2 is a diagram for explaining an example of the preparation process. In the preparation process shown in FIG. 2, an extruder 210 includes a cylinder 211, a screw 212 housed in the cylinder 211, a die 213 attached to the tip of the cylinder 211, a hopper 214 for supplying raw materials to the cylinder 211, and a drive unit 215 for rotating the cylinder 211. In this embodiment, first, a powder of TFE/PAVE copolymer (not shown) as a raw material is supplied from the hopper 214 to the cylinder 211, and the TFE/PAVE copolymer is melted in the cylinder 211. Next, the melted TFE/PAVE copolymer 201 is extruded from the die 213 to form a strand 202. The strand 202 extruded from the die 213 is fed into a water tank 221 and cooled after traveling a certain distance. Finally, the cooled strand 202 is fed into a pelletizer 222, cut by a cutter (not shown) provided in the pelletizer 222, and discharged as pellets 231. At this time, it is presumed that low molecular weight substances volatilize from the high-temperature strand 202 extruded from the die 213.

A vent hole (not shown) may be provided in the cylinder 211 of the extruder 210, and a vacuum pump (not shown) may be connected to the vent hole. By providing a vent hole, low molecular weight substances volatilized from the molten TFE/PAVE copolymer 201 can be discharged outside the cylinder 211.

For example, when pellets are prepared by a hot-cut method in which a strand immediately after being extruded from a die is cut before being cooled, or an underwater-cut method in which a strand immediately after being extruded from a die is put into water and cut underwater, rather than a method in which a cooled strand is cut to prepare pellets as in the preparation process shown in Figure 2, it is preferable to provide a vent hole in the cylinder, since there is a possibility that low molecular weight substances may not be sufficiently volatilized from the TFE/PAVE copolymer.

Since the low molecular weight substances can be sufficiently volatilized to obtain a molded product with further reduced particle generation, when the cylinder of the extruder does not have a vent hole, it is usually easiest for the low molecular weight substances to volatilize from the strand extruded from the die, so it is convenient to set the die temperature as temperature T1 so as to satisfy the relationship between temperatures T1 and T2 described above. Also, when the cylinder of the extruder has a vent hole, it is preferable to set the temperature of the cylinder where the vent hole is located as temperature T1, since it is easiest for the low molecular weight substances to volatilize from the vent hole. Also, when a vacuum pump is connected to the vent hole, it is expected that the volatilization of the low molecular weight substances will proceed smoothly, so temperature T1 may be lowered than when the vacuum pump is not connected. From the above, in the above preparation process, it is preferable to provide a low molecular weight substance volatilization region (a region where low molecular weight substances are easily volatilized) and control the temperature of the TFE/PAVE copolymer in the low molecular weight substance volatilization region as temperature T1. In addition, in the above preparation process, it is more preferable to use an extruder equipped with a die set to a temperature T1, or an extruder equipped with a cylinder set to a temperature T1 and a vent hole provided in the cylinder.

The extruder may be equipped with a breaker plate to stabilize the extrusion of the strands. The number of strands extruded from the die is not particularly limited, but may be 5 to 350. The rotation speed of the screw of the extruder is not particularly limited, and is set in consideration of the extrusion amount and extrusion stability, and is, for example, in the range of 5 to 40 rpm.

From the viewpoint of producing a molded product with even lower particle generation, it is preferable that the diameter of the strand extruded from the die is small, but if the strand is too thin, problems such as the strand breaking during the preparation process may occur. Therefore, the diameter of the strand is preferably 0.5 to 3 mm, and more preferably 1 to 2 mm.

The molding material obtained in the above preparation process may be molded again at a temperature T1 (°C) to prepare a molding material. By repeating the above preparation process, a molded product with even lower particle generation can be manufactured.

In the molding step, the molding material obtained in the preparation step is extruded at a temperature T2 (°C) to obtain a molded product. The shape of the molded product is not particularly limited as long as it can be molded by extrusion molding, and examples of the molded product include pellets, films, sheets, plates, rods, blocks, cylinders, containers, electric wires, tubes, bottles, and the like. The molded product is preferably a tube, film, or bottle, and more preferably a tube. As described above, with conventional molding methods, low molecular weight substances tend to adhere to the inner surface of the tube, which is presumed to be a source of particle generation. However, with the manufacturing method of the present disclosure, even when a tube is manufactured, a tube with reduced particle generation can be obtained.

An extruder can be used for the extrusion molding in the molding step. The extruder may be a single-screw extruder or a twin-screw extruder. The extruder usually includes a cylinder, a screw housed in the cylinder, a die attached to the tip of the cylinder, an adapter for connecting the die to the cylinder, a hopper for supplying raw materials to the cylinder, and a drive device for rotating the cylinder. As described above, pellets are preferable as the molding material prepared in the preparation step because they can be easily charged from the hopper. The molding material charged into the cylinder is melted in the cylinder and extruded from the die to be molded into a tube. The temperatures of the cylinder, adapter, die, etc. can be set according to the size and shape of the molded product, and are preferably set so that the die temperature is the highest. As described above, in the tube molding step, it is presumed that low molecular weight substances volatilize from the molten TFE/PAVE copolymer extruded from the die and tend to adhere to the inner surface of the tube, so it is preferable to control the die temperature to temperature T2.

A particularly preferred embodiment of the manufacturing method of the present disclosure includes a preparation step of extruding the TFE/PAVE copolymer to prepare pellets using an extruder equipped with a die set to temperature T1, or an extruder equipped with a cylinder set to temperature T1 and a vent hole provided in the cylinder, and a molding step of extruding the pellets to obtain a tube using an extruder equipped with a die set to temperature T2 (°C), in which the temperatures T1 and T2 satisfy the above-mentioned relationship.

Next, we will explain the tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer used in the above preparation process.

The TFE/PAVE copolymer is preferably a melt-processable fluororesin. In this disclosure, melt-processable means that the polymer can be melted and processed using conventional processing equipment such as an extruder and an injection molding machine. Therefore, melt-processable fluororesins typically have a melt flow rate of 0.01 to 500 g/10 min, as measured by the measurement method described below.

The content of the monomer units based on PAVE in the TFE/PAVE copolymer is preferably 1.0 to 10% by mass, more preferably 2.0% by mass or more, even more preferably 3.5% by mass or more, particularly preferably 4.0% by mass or more, most preferably 5.0% by mass or more, more preferably 8.0% by mass or less, even more preferably 7.0% by mass or less, particularly preferably 6.5% by mass or less, and most preferably 6.0% by mass or less, based on the total monomer units. The amount of the monomer units based on PAVE is measured by ¹⁹ F-NMR.

The PAVE constituting the PAVE unit is represented by the general formula (1):
CF ₂ =CFO(CF ₂ CFY ¹ O) _p - (CF ₂ CF ₂ CF ₂ O) _q - R ^f (1)
(wherein ^Y1 represents F or _CF3 , ^Rf represents a perfluoroalkyl group having 1 to 5 carbon atoms, p represents an integer of 0 to 5, and q represents an integer of 0 to 5), and a monomer represented by general formula (2):
CFX=CXOCF ₂ OR ¹ (2)
(wherein X may be the same or different and represents H, F or _CF3 ; ^R1 represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms which may contain 1 to 2 atoms of at least one type selected from the group consisting of H, Cl, Br and I, or a cyclic fluoroalkyl group having 5 or 6 carbon atoms which may contain 1 to 2 atoms of at least one type selected from the group consisting of H, Cl, Br and I).

Among them, the above-mentioned PAVE is preferably a monomer represented by the general formula (1), more preferably at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether) (PPVE), and even more preferably PPVE.

The TFE/PAVE copolymer is not particularly limited, but is preferably a copolymer in which the molar ratio of TFE units to PAVE units (TFE units/PAVE units) is 70/30 or more and less than 99/1. A more preferred molar ratio is 70/30 or more and 98.9/1.1 or less, and an even more preferred molar ratio is 80/20 or more and 98.9/1.1 or less. If the TFE units are too few, the mechanical properties tend to decrease, and if the TFE units are too many, the melting point tends to become too high and moldability tends to decrease.

It is also preferred that the TFE/PAVE copolymer is a copolymer in which the monomer units derived from monomers copolymerizable with TFE and PAVE are 0.1 to 10 mol %, and the total of TFE units and PAVE units is 90 to 99.9 mol %.

Examples of monomers copolymerizable with TFE and PAVE include HFP, vinyl monomers represented by CZ ³ Z ⁴ ═CZ ⁵ (CF ₂ ) _n Z ⁶ (wherein Z ³ , Z ⁴ and Z ⁵ are the same or different and represent H or F, Z ⁶ represents H, F or Cl, and n represents an integer of 2 to 10), and alkyl perfluorovinyl ether derivatives represented by CF ₂ ═CF-OCH ₂ -Rf ⁷ (wherein Rf ⁷ represents a perfluoroalkyl group having 1 to 5 carbon atoms). Among these, HFP is preferred.

As the TFE/PAVE copolymer, at least one selected from the group consisting of copolymers consisting only of TFE units and PAVE units, and the TFE/HFP/PAVE copolymers is preferred, and copolymers consisting only of TFE units and PAVE units are more preferred.

The melting point of the TFE/PAVE copolymer is preferably 280 to 322°C, more preferably 290°C or higher, even more preferably 295°C or higher, particularly preferably 300°C or higher, and more preferably 315°C or lower. In order to mold a copolymer with a high melting point, it is necessary to heat the copolymer to a high temperature for molding, which makes it easy for low molecular weight substances to adhere to the surface of the molded product and generate particles. This is thought to be because the higher the molding temperature, the easier it is for low molecular weight substances to volatilize from the copolymer during molding. According to the manufacturing method disclosed herein, even when a TFE/PAVE copolymer with a high melting point is used, a molded product with reduced particle generation can be manufactured. The melting point can be measured using a differential scanning calorimeter [DSC].

The glass transition temperature (Tg) of the TFE/PAVE copolymer is preferably 70 to 110°C, more preferably 80°C or higher, and more preferably 100°C or lower. The glass transition temperature can be measured by dynamic viscoelasticity measurement.

The melt flow rate (MFR) of the TFE/PAVE copolymer at 372°C is preferably 0.1 to 100 g/10 min, more preferably 0.5 g/10 min or more, even more preferably 1 g/10 min or more, more preferably 80 g/10 min or less, even more preferably 40 g/10 min or less, and particularly preferably 30 g/10 min or less. The MFR is a value obtained according to ASTM D1238 as the mass (g/10 min) of polymer flowing out of a nozzle with an inner diameter of 2 mm and a length of 8 mm under a load of 5 kg at 372°C and using a melt indexer (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) per 10 minutes.

As the TFE/PAVE copolymer, a copolymer having a small number of functional groups is preferred because it allows the production of molded articles with even lower particle generation, and it preferably has a total of 0 to 50 functional groups per ^{106 carbon atoms. The number of functional groups per 106 carbon} atoms is more preferably 0 to 30, and even more preferably 0 to 15.

The functional group is a functional group present at the main chain end or side chain end of the TFE/PAVE copolymer, or a functional group present in the main chain or side chain. The functional group is preferably at least one selected from the group consisting of -CF= _CF2 , _-CF2H , -COF, -COOH, _-COOCH3 , _{-CONH2 and -CH2OH .}

Infrared spectroscopy can be used to identify the types of functional groups and measure the number of functional groups.

The number of functional groups is specifically measured by the following method. First, the TFE/PAVE copolymer is melted at 330 to 340° C. for 30 minutes and compression molded to prepare a film having a thickness of 0.25 to 0.3 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain an infrared absorption spectrum of the TFE/PAVE copolymer, and a difference spectrum is obtained from a base spectrum that is completely fluorinated and has no functional groups. From the absorption peak of a specific functional group that appears in this difference spectrum, the number of functional groups N per 1×10 ⁶ carbon atoms in the TFE/PAVE copolymer is calculated according to the following formula (A).
N=I×K/t (A)
I: absorbance K: correction coefficient t: film thickness (mm)

For reference, the absorption frequencies, molar absorption coefficients, and correction coefficients for the functional groups in this disclosure are shown in Table 1. The molar absorption coefficients were determined from FT-IR measurement data of low molecular weight model compounds.

The absorption frequencies of -CH ₂ CF ₂ H, -CH ₂ COF, -CH ₂ COOH, -CH ₂ COOCH ₃ and -CH ₂ CONH ₂ are several tens of Kaiser (cm ^-1 ) lower than the absorption frequencies of -CF ₂ H, -COF, -COOH free, -COOH bonded, -COOCH ₃ and -CONH ₂ shown in the table, respectively.
Therefore, for example, the number of functional groups of --COF is the sum of the number of functional groups determined from the absorption peak at 1883 _cm.sup. ^-1 due to _--CF.sub.2 COF and the number of functional groups determined from the absorption peak at 1840 cm.sup. ^-1 due to --CH.sub.2 COF.

The number of functional groups may be the total number of -CF=CF ₂ , -CF ₂ H, -COF, -COOH, -COOCH ₃ , -CONH ₂ and -CH ₂ OH.

The functional group is introduced into the TFE/PAVE copolymer by, for example, a chain transfer agent or a polymerization initiator used in producing the TFE/PAVE copolymer. For example, when an alcohol is used as a chain transfer agent or a peroxide having a -CH ₂ OH structure is used as a polymerization initiator, -CH ₂ OH is introduced into the main chain end of the TFE/PAVE copolymer. In addition, the functional group is introduced into the side chain end of the TFE/PAVE copolymer by polymerizing a monomer having a functional group.

The TFE/PAVE copolymer having such a functional group can be fluorinated to obtain the TFE/PAVE copolymer having the number of functional groups within the above range. That is, the TFE/PAVE copolymer used in the production method of the present disclosure is preferably a fluorinated copolymer. In addition, the TFE/PAVE copolymer used in the production method of the present disclosure also preferably has a _-CF3 end group.

The above fluorination treatment can be carried out by contacting a non-fluorinated TFE/PAVE copolymer with a fluorine-containing compound.

The fluorine-containing compound is not particularly limited, but may be a fluorine radical source that generates fluorine radicals under fluorination treatment conditions _{, such as F2 gas, CoF3, AgF2, UF6, OF2, N2F2, CF3OF , or halogen fluorides ( e.g. , IF5} , _ClF3 ).

The fluorine radical source such as _F2 gas may be of 100% concentration, but from the viewpoint of safety, it is preferable to mix it with an inert gas and dilute it to 5 to 50% by mass, and more preferably to dilute it to 15 to 30% by mass. Examples of the inert gas include nitrogen gas, helium gas, argon gas, etc., and nitrogen gas is preferable from the viewpoint of economy.

The conditions of the fluorination treatment are not particularly limited, and the molten TFE/PAVE copolymer may be contacted with a fluorine-containing compound, but the fluorination treatment is usually carried out at a temperature below the melting point of the TFE/PAVE copolymer, preferably 20 to 220°C, more preferably 100 to 200°C. The fluorination treatment is generally carried out for 1 to 30 hours, preferably 5 to 25 hours. The fluorination treatment is preferably carried out by contacting a non-fluorinated TFE/PAVE copolymer with fluorine gas ( _F2 gas).

The TFE/PAVE copolymer can be produced by a conventional method such as emulsion polymerization or suspension polymerization by appropriately mixing the monomers that form its constituent units and additives such as a polymerization initiator.

Next, the molded article of the present disclosure will be described. The molded article of the present disclosure contains a TFE/PAVE copolymer having a melting point of 295°C or higher, and when it comes into contact with isopropyl alcohol, the number of particles having a size of 30 nm or more dispersed in isopropyl alcohol is 700 particles/ml or less.

The TFE/PAVE copolymer contained in the molded article of the present disclosure may be the same as the TFE/PAVE copolymer used in the manufacturing method of the present disclosure, and is preferably the same as the TFE/PAVE copolymer used in the manufacturing method of the present disclosure.

The melting point of the TFE/PAVE copolymer contained in the molded article of the present disclosure is 295°C or higher. In order to mold a copolymer with a high melting point, it is necessary to heat the copolymer to a high temperature and mold it, so that low molecular weight molecules in particular tend to adhere to the surface of the molded article, easily generating particles. Although the molded article of the present disclosure contains a TFE/PAVE copolymer with a melting point of 295°C or higher, it generates a small amount of particles. The melting point of the TFE/PAVE copolymer is more preferably 300°C or higher, preferably 322°C or lower, and more preferably 315°C or lower.

When the molded article of the present disclosure comes into contact with isopropyl alcohol (the number of particles of 30 nmφ size or more is 30 particles/ml or less), the number of particles dispersed in the isopropyl alcohol is 700 particles/ml or less, preferably 600 particles/ml or less, and more preferably 500 particles/ml or less, and although there is no particular lower limit, it is preferably 50 particles/ml or more. The method for measuring the number of particles dispersed in isopropyl alcohol will be described later.

The shape of the molded product of the present disclosure is not particularly limited, and examples include pellets, films, sheets, plates, rods, blocks, cylinders, containers, electric wires, tubes, bottles, and the like. The molded product of the present disclosure is preferably a tube, film, or bottle, and more preferably a tube. As described above, with conventional molding methods, low molecular weight substances tend to adhere to the inner surface of the tube, which is presumed to be a source of particle generation, but the molded product of the present disclosure generates a small amount of particles, even when it is a tube.

The above tube is filled with an amount of isopropyl alcohol (number of particles of 30 nmφ or more per ml) equivalent to the content of the tube, left at room temperature for one day, and then the isopropyl alcohol is recovered. The number of particles of 30 nmφ or more dispersed in the recovered isopropyl alcohol is preferably 700 particles/ml or less, more preferably 600 particles/ml or less, and even more preferably 500 particles/ml or less, and although there is no particular lower limit, is preferably 50 particles/ml or more. The method for measuring the number of particles dispersed in isopropyl alcohol will be described later.

The outer diameter of the tube is not particularly limited, but may be 2 to 100 mm, or 5 to 50 mm. The thickness of the tube may be 0.1 to 10 mm, or 0.3 to 5 mm. According to the manufacturing method disclosed herein, even if a relatively large tube is manufactured, particularly one with an outer diameter of 20 mm or more and a thickness of 1 mm or more, the number of particles dispersed in isopropyl alcohol can be kept within the above range. Therefore, the tube disclosed herein may be a tube with an outer diameter of 20 mm or more and a thickness of 1 mm or more.

The molded article of the present disclosure and the molded article obtained by the manufacturing method of the present disclosure can be used for, but is not limited to, the following applications:
Diaphragm parts of diaphragm pumps, bellows molded products, wire coating products, semiconductor parts, packing seals, thin-walled tubes for copy rolls, monofilaments, belts, gaskets, optical lens parts, tubes for oil drilling, tubes for geothermal power generation, electric wires for oil drilling, electric wires for satellites, electric wires for nuclear power generation, electric wires for aircraft, solar panel films, gaskets for secondary batteries and electric double-layer capacitors, office automation rolls, etc.

The above molded products can also be suitably used as tubes for circulating gases or liquid medicines, bottles for storing medicines, gas bags, liquid medicine bags, liquid medicine containers, bags for freezing and storing medicines, etc.

The above molded products can also be used favorably for the bodies and parts of on-off valves, sleeves used to connect fittings and tubes, screw caps for chemical bottles and containers, gears, screws, frying pans, pots, rice cookers, products with a fluororesin coating on a metal base, and release films.

Particularly suitable applications for the above molded products are perfluoro-based fluororesin components such as piping for chemical supply equipment in semiconductor manufacturing, tubes for semiconductor manufacturing equipment, joints, valves, tanks, containers, chemical bags, and wafer carriers.

One preferred embodiment is that the molded article of the present disclosure and the molded article obtained by the manufacturing method of the present disclosure are tubes.

In semiconductor factories, tubes are often used to distribute ultrapure water and high-purity chemicals used in semiconductor manufacturing. Fine particles generated from molded products containing TFE/PAVE copolymers are hydrophobic. Therefore, particularly when aqueous chemicals are distributed inside the tubes, the fine particles tend to adhere to the inner surface of the tube due to the interaction between the fine particles and the tube, and the adhered fine particles are difficult to remove with cleaning water such as pure water. Therefore, when new tubes are used in semiconductor factories, problems arise such as the need for large amounts of ultrapure water or chemicals to flush the inside of the tube, and the need for long cleaning times.

Since the tube has the above-mentioned configuration, almost no particles adhere to the inner surface, and particles are unlikely to be generated. Since the tube has such an effect, it is preferable that the tube is a tube for piping a chemical liquid for circulating the chemical liquid. Examples of the chemical liquid include chemical liquids used in semiconductor manufacturing, such as ammonia water, ozone water, hydrogen peroxide water, hydrochloric acid, sulfuric acid, resist liquid, thinner liquid, and developer liquid.

Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims.

Next, we will explain the embodiments of the present disclosure by giving examples, but the present disclosure is not limited to these examples.

The values in the examples were measured using the following methods.

(Melting Point)
It was determined as the temperature corresponding to the maximum value on the heat of fusion curve when the temperature was raised at a rate of 10° C./min using a differential scanning calorimeter (DSC).

(MFR)
For the powders and pellets of the copolymers used in the examples and comparative examples, the mass of polymer flowing out per 10 minutes (g/10 minutes) from a nozzle having an inner diameter of 2 mm and a length of 8 mm under a load of 5 kg at 372° C. was determined using a melt indexer (manufactured by Yasuda Seiki Seisakusho) in accordance with ASTM D1238.

(Monomer unit content)
The content of each monomer unit was measured by ¹⁹ F-NMR.

(Number of functional groups)
The sample is melted at 330-340°C for 30 minutes and compression molded to prepare a film with a thickness of 0.25-0.3 mm. This film is scanned and analyzed 40 times using a Fourier transform infrared spectrometer [FT-IR (product name: Model 1760X, manufactured by PerkinElmer) to obtain an infrared absorption spectrum, and a difference spectrum is obtained from a base spectrum in which the sample is completely fluorinated and no functional groups are present. From the absorption peak of a specific functional group that appears in this difference spectrum, the number of functional groups N per 1 x ¹⁰⁶ carbon atoms in the sample is calculated according to the following formula (A).

N=I×K/t (A)
I: absorbance K: correction coefficient t: film thickness (mm)

For reference, the absorption frequencies, molar absorption coefficients, and correction coefficients for the functional groups in this disclosure are shown in Table 2. The molar absorption coefficients were determined from the FT-IR measurement data of low molecular weight model compounds.

(Number of particles)
(1) Preparation of isopropyl alcohol Commercially available high purity isopropyl alcohol (IPA) was filtered using a 5 nmφ filter. The filtered IPA was left for one day, and it was confirmed that the number of particles with a size of 30 nmφ or more was 30 pieces/ml or less. The filtered IPA was used for washing the tube and measuring the number of particles.

(2) Preparation of sample tubes In a clean bench in a clean room, the tubes prepared in the examples and comparative examples were cut to a length of 3 m. The inner surface of the obtained sample tube was washed with ultrapure water in an amount five times the content volume of the sample tube to remove environmentally derived contaminant particles. Next, filtered IPA was supplied into the sample tube, and the same amount of high-purity IPA as the content volume of the tube was sealed, and then the liquid was immediately drained and the ultrapure water was replaced with IPA.

(3) Measurement of particle count The sample tube obtained in (2) above was filled with high-purity IPA in an amount equivalent to the content of the tube, and left at room temperature for one day. In the case of a sample tube with an outer diameter of 10 mm, an inner diameter of 8 mm, and a length of 3 m, 150 mL of IPA was sealed. In addition, in the case of a sample with an outer diameter of 25.4 mm, an inner diameter of 22.2 mm, and a length of 3 m, 1160 mL of IPA was sealed. Furthermore, in the case of a sample with an outer diameter of 6.0 mm, an inner diameter of 4.0 mm, and a length of 3 m, 37 mL of IPA was sealed.

Next, the IPA sealed in the sample tube was introduced into a particle counter (KS-19F light scattering liquid particle detector, manufactured by Rion Co., Ltd.) using a syringe pump to measure the number of particles.

The maximum particle count was measured immediately after introducing IPA into the particle counter, and the number of particles measured thereafter showed a gradual decrease. The maximum total number of particles 30 nmφ or larger after the start of measurement was compared as the number of particles eluted from the sample tube.

Figure 3 is a diagram to explain the method for measuring the number of particles.

First, nitrogen gas 331 is supplied into the first chemical liquid container 321 to pressurize the isopropyl alcohol (IPA) 311 stored in the chemical liquid container 321. The pressurized IPA 311 passes through a filter 322 and is stored in the second chemical liquid container 323. The IPA 312 in the second chemical liquid container 323 is left for one day and then used for measurement.

A valve 324 is connected to the bottom of the second chemical container 323, and the sample tube 301 is connected to the second chemical container 323 via the valve 324. The other end of the sample tube 301 is connected to the particle counter 341 via a valve 326. Furthermore, a syringe pump 342 is provided downstream of the particle counter 341 so that the IPA in the sample tube 301 can be introduced into the particle counter 341.

In addition, a separate line is provided to supply ultrapure water 332 to the sample tube 301, and the sample tube 301 is also connected to this line via a filter 328 and a valve 325.

In order to prevent particles from being mixed into the IPA 312 and ultrapure water 332 by opening and closing the valves 324 to 326 connected to the sample tube 301, it is necessary to use diaphragm valves as the valves 324 to 326.

Once the system for measuring the particle count has been configured in this manner, ultrapure water 332 that has passed through filter 328 is supplied to sample tube 301 to clean the inside of sample tube 301 and discharged as waste liquid 333. Next, IPA 312 is supplied from second chemical container 323 to sample tube 301 to replace the ultrapure water with IPA, and then a predetermined amount of IPA is sealed in sample tube 301.

After the IPA is sealed in and a predetermined time has elapsed, the syringe pump 342 is operated to introduce the IPA in the sample tube 301 into the particle counter 341. In this disclosure, the number of particles is measured in this manner.

In the above measurement method, the IPA sealed in the sample tube was introduced directly into the particle counter using a syringe pump, but it is also possible to collect the IPA sealed in the sample tube in a container that has been thoroughly washed with IPA, and then introduce the collected IPA into the particle counter.

The above-mentioned measurement method is a method for measuring the number of particles generated from the inner surface of a tube, but the number of particles generated from the surface of a molded product other than a tube can also be measured by the same method. That is, after thoroughly washing the surface of the molded product with ultrapure water, the ultrapure water adhering to the surface is replaced with IPA. The obtained molded product is placed in high-purity IPA and left at room temperature for one day. The IPA after the molded product is immersed is introduced into a particle counter and the number of particles is measured. If the molded product is too large to be immersed in IPA, a measurement sample prepared by cutting it to an appropriate size may be used, but in order to accurately measure the number of particles generated from the molded product surface, it is preferable that the cut surface is as small as possible.

The contact area between the surface of the molded article and IPA measured in this way is different from the contact area between the inner surface of the tube and IPA measured in the above-mentioned tube measurement method. However, the measured particle count value measured above can be converted into the particle count measured with the same contact area as the above-mentioned tube (outer diameter 25.4 mm × inner diameter 22.2 mm × length 3 m) measurement method (referred to as the "converted value of the particle count of the molded article" in the following formula).
Conversion value of number of particles in molded product (pieces/ml) = C x A/B x 0.56
A: Surface area of the molded product immersed in IPA (cm ² )
B: Amount of IPA in which the molded product was immersed (ml)
C: Measured particle count (particles/ml)

In this disclosure, such measurement and conversion methods are used to determine the number of particles that disperse in isopropyl alcohol when a molded product other than a tube comes into contact with isopropyl alcohol.

Comparative Example 1
(1) Preparation process Powder of TFE/PPVE copolymer 1 (composition ratio (mass%) of TFE and PPVE: TFE/PPVE=94.5/5.5, melting point: 304°C, MFR: 2.1g/10min, number of functional groups: ^6/6 C10) was charged into a screw-type extruder (shaft diameter 32mm, L/D=52.5), melted in the cylinder, and then extruded from the die. At this time, the cylinder temperature of the screw-type extruder was set to 320-350°C, the adapter temperature to 340-350°C, and the die temperature to 350°C. In addition, the cylinder of the screw-type extruder did not have a vent hole. Therefore, in the preparation process of Comparative Example 1, it was assumed that low molecular weight substances would volatilize most easily from the strand extruded from the die, so the die temperature was controlled to temperature T1. In fact, it was possible to visually observe the state in which volatile matter (polymer fumes) volatilized from the strand extruded from the die.
The strand extruded from the die was then cooled in a water tank placed at a certain distance from the die, and then fed to a pelletizer and cut into pellets with a cutter. The pellets obtained were cylindrical with a length of 3.0 mm and a diameter of 2.0 mm, and had an MFR of 2.0 g/10 mm.

(2) Molding process The pellets obtained above were extruded using a tube extruder (cylinder shaft diameter 50 mm, L/D = 22) at a take-up speed of 85 cm/min to obtain a tube with an outer diameter of 10.0 mm and an inner diameter of 8.0 mm. At this time, the cylinder temperature of the tube extruder was set to 330 to 360 ° C, the adapter temperature was set to 370 ° C, and the die temperature was set to 370 ° C. In the molding process of Comparative Example 1, it is considered that low molecular weight substances volatilized from the copolymer 1 in a molten state extruded from the die tend to adhere to the inner surface of the obtained tube, and 370 ° C is the maximum temperature, so the die temperature was controlled at temperature T2.
The obtained tube had an outer diameter of 10.0 mm and an inner diameter of 8.0 mm. The number of particles generated from the obtained tube was determined by the above-mentioned method. The results are shown in Table 3.

Examples 1 to 3
Pellets were prepared in the same manner as in Comparative Example 1, except that the temperature T1 was changed to the temperatures shown in Table 3 by changing the cylinder temperature, adapter temperature, and die temperature.
Using each of the obtained pellets, tubes were obtained in the same manner as in Comparative Example 1, except that the cylinder temperature, adapter temperature, and die temperature were changed to change the temperature T2 to the temperature shown in Table 3, and the tube size was changed to the size shown in Table 3.
The results are shown in Table 3.

Comparative Examples 2 to 3, Examples 4 to 5
Pellets were prepared in the same manner as in Comparative Example 1, except that TFE/PPVE copolymer 2 (composition ratio (mass%) of TFE and PPVE: TFE/PPVE=94.3/5.7, melting point: 303° C., MFR: 14.0 g/10 min, number of functional groups: 4/C10: ⁶ ) was used, and the cylinder temperature, adapter temperature, and die temperature were changed to change the temperature T1 to the temperatures shown in Table 3.
Using each of the obtained pellets, tubes were obtained in the same manner as in Comparative Example 1, except that the cylinder temperature, adapter temperature, and die temperature were changed to change the temperature T2 to the temperature shown in Table 3, and the tube size was changed to the size shown in Table 3.
The results are shown in Table 3.

Comparative Example 4, Example 6
Pellets were prepared in the same manner as in Comparative Example 1, except that TFE/PPVE copolymer 3 (composition ratio (mass%) of TFE and PPVE: TFE/PPVE=96.7/3.3, melting point: 307° C., MFR: 10.4 g/10 min, number of functional groups: 10/ ^C106 ) was used, and the cylinder temperature, adapter temperature, and die temperature were changed to change the temperature T1 to the temperatures shown in Table 3.
Using each of the obtained pellets, tubes were obtained in the same manner as in Comparative Example 1, except that the cylinder temperature, adapter temperature, and die temperature were changed to change the temperature T2 to the temperature shown in Table 3, and the tube size was changed to the size shown in Table 3.
The results are shown in Table 3.

101, 201 TFE/PAVE copolymer 102 Cone 103 Tube 111, 211 Cylinder 112 Adapter 113, 213 Die 114 Sizing die 115, 212 Screw 116 Hole 121 Outside air 131 Low molecular weight material 202 Strand 210 Extruder 214 Hopper 215 Drive unit 221 Water tank 222 Pelletizer 231 Pellet 301 Sample tube 311, 312 Isopropyl alcohol (IPA)
313, 333 Drainage 321, 323 Chemical container 322, 328 Filter 324, 325, 326, 327 Valve 331 Nitrogen gas 332 Ultrapure water 341 Particle counter 342 Syringe pump

Claims (1)

A tube containing a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer having a melting point of 295°C or higher, wherein when the tube is filled with an amount of isopropyl alcohol equivalent to the tube's content and left at room temperature for one day , the number of particles having a diameter of 30 nm or more dispersed in the isopropyl alcohol is 700 particles/ml or less.

Images