JP2001150435A - Method of manufacturing fluorine-containing polymer molding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a fluorine-containing polymer molding material reduced in the elution amount of a metal of a molding member. SOLUTION: Pellets comprising a fluorine-containing polymer molding material are fluorinated to stabilize the molecular terminal of the molding material and the fluorinated pellets are washed to reduce the elution amount of a metal from the pellets by 20% or more as compared with that before washing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention provides a molded article of a fluorinated copolymer having a reduced metal elution amount.
The present invention relates to a method for producing a molding material.

[0002]

2. Description of the Related Art Tetrafluoroethylene (hereinafter, referred to as TFE) is used as a chemical storage tank member and a transport piping member of a semiconductor manufacturing apparatus.
That. ) / Perfluoro (alkyl vinyl ether)
Copolymers (hereinafter, referred to as PFA), TFE / hexafluoropropylene (hereinafter, referred to as HFP), copolymers (hereinafter, referred to as FEP), polytetrafluoroethylene (hereinafter, referred to as PTFE), and the like. Its heat resistance,
It is used as a molding material due to its good chemical resistance.
The molding materials of PFA and FEP can be melt-molded, and can be molded by various molding methods such as injection molding, extrusion molding, and rotational molding. In recent years, high integration and miniaturization of semiconductor devices have been progressing further, and it has become necessary to suppress metal impurities mixed in a semiconductor manufacturing process in order to realize finer devices and improve yield. I have. Therefore, it is required to reduce the amount of metal elution from the chemical storage tank member and the transport piping member of the semiconductor manufacturing apparatus.

On the other hand, there has been a demand for reducing the elution of fluoride ions, and PFA having stabilized molecular terminals has been used as a member for semiconductor manufacturing equipment.
The chemical solution storage tank member and the transport piping member of A are also required to reduce the amount of metal elution. Most of the PFA and FEP chemical storage tank members and the transport piping members are obtained by injection molding or extrusion molding of PFA and FEP pellet-like molding materials. Molding materials manufactured by reducing the metal content of the raw materials used and by keeping the raw materials and copolymers from contacting the metal surface of the equipment as much as possible could significantly reduce the amount of metal elution. , Further reduction is required.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a molding material of a fluorine-containing copolymer in which the amount of metal elution from a molding member is reduced.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, in the present invention, after fluorinating pellets of a fluorinated copolymer molding material to stabilize the molecular terminals of the fluorinated copolymer, the pellets are washed to reduce the amount of metal eluted from the pellets by 2% before washing. It is intended to provide a method for producing a fluorine-containing copolymer molding material, characterized in that it is reduced by more than a percentage. Further, the present invention provides the method for producing a fluorine-containing copolymer molding material, wherein the fluorine-containing copolymer is a tetrafluoroethylene / perfluoro (alkyl vinyl ether) -based copolymer or a tetrafluoroethylene / hexafluoropropylene-based copolymer. Provided is a method for producing a fluorinated copolymer molding material which is a united product. Further, the present invention provides the method for producing a fluorine-containing copolymer molding material according to the method for producing a fluorine-containing copolymer molding material, wherein the washing is water washing.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The raw material used in the present invention is a fluorine-containing copolymer. As the fluorinated copolymer, a copolymer of fluorinated monomers, particularly a copolymer of perfluoromonomer is preferable. The preferred copolymer is a tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer, and the alkyl group of the perfluoro (alkyl vinyl ether) has a linear or branched structure having 1 to 8 carbon atoms. And an alkyl group having the same. Further, oxygen of an ether bond may be present in the alkyl group. Further, one or more kinds of perfluoro (alkyl vinyl ether) may be used. Further, a perfluoromonomer such as hexafluoropropylene may be copolymerized as the third component. In particular,
A tetrafluoroethylene / perfluoro (propyl vinyl ether) copolymer is preferred. Another preferred copolymer is a tetrafluoroethylene / hexafluoropropylene-based copolymer, and a perfluoromonomer such as perfluoro (alkyl vinyl ether) may be copolymerized as the third component.

PFA has a copolymer molar ratio of TFE / perfluoro (alkyl vinyl ether) of 99.5 / 0.5 to
97/3, wherein FEP is TFE / HF
It is a copolymer having a copolymerization molar ratio of P of 95/5 to 85/15. The raw material molding material is in the form of pellets, and can be obtained by injection molding, extrusion molding, or other molding methods. This molding method includes a step of melting a molding material at least in part. The shape of the pellet is not particularly limited, and has, for example, a cylindrical column, an elliptic column, a spherical column, a polygonal column having a polygonal cross-sectional shape such as a triangle, a square, a pentagon, a hexagon, and an octagon, and a modified cross-sectional shape such as a star. Columns and the like are mentioned, and the average length may be usually 1 to 10 mm.

As the raw material of the present invention, a fluorine-containing copolymer molding material produced by various methods can be used, but a fluorine-containing copolymer molding material having a small amount of metal elution is preferable. The fluorinated copolymer molding material with low metal elution amount is
In the polymer production process such as polymerization process, granulation process, drying process, pelletizing process, etc., and in the process of processing into a molding material, molding such that the fluorocopolymer and molding material do not contact the metal part surface of equipment as much as possible. It can be produced by producing a material and, in addition, making the raw material of the fluorine-containing copolymer as little as possible in contact with the surface of the metal part of equipment such as a storage tank and a pipe for transfer. Further, the fluorinated copolymer molding material having a small amount of metal elution is a raw material such as a fluorinated monomer, a comonomer, a polymerization medium, a chain transfer agent, and a medium used for fluorinated copolymer granulation having a small content of a metal component. It is preferable to manufacture by using.

In the pelletizing step, it is preferable to use a corrosion-resistant metal material such as Hastelloy as a material of at least a portion in contact with the molten fluorine-containing copolymer. The metal elution amount of the raw material fluorine-containing copolymer molding material of the present invention is N
The total of a, Mg, Cu, Cr, Ni, K, Ca and Fe is preferably 20 ppb or less, particularly preferably 10 ppb or less. The fluorination in the present invention is performed for fluorinating the unstable terminal group of the fluorine-containing copolymer molecule to stabilize the molecular terminal. Unstable terminal groups include carbon-carbon unsaturated double bonds, carbonyl fluoride groups, carbinol groups, carboxylic acid groups, amide groups, and the like.

The fluorination can be carried out by reacting pellets of the fluorinated copolymer molding material with a fluorinating agent. As the fluorinating agent, fluorine gas is preferable. The fluorine gas is preferably used in a mixture with an inert gas. Examples of the inert gas include a nitrogen gas, a helium gas, a neon gas, and a krypton gas, and a nitrogen gas is preferable. The mixing ratio of the inert gas and the fluorine gas is preferably in the range of 1/1 to 10/1 by volume, and particularly preferably in the range of 2/1 to 6/1. The ratio of the fluorinating agent to be used is usually 0.1 to 10 parts by mass, preferably 0.2 to 1 part by mass, per 100 parts by mass of the fluorinated copolymer. The reaction temperature of the fluorination is not particularly limited, but is preferably from 150 to 300 ° C, particularly preferably from 180 to 250 ° C. The reaction time of the fluorination may be appropriately selected, and is usually from 1 to 30 hours. In the fluorination, it is preferable that the fluorinated copolymer molding material does not contact the metal surface of the equipment as much as possible. Therefore, it is preferable that the surface of the metal part of the equipment is covered with a fluororesin or the like.

In the present invention, the washing is performed to bring the pellets of the fluorocopolymer molding material into contact with the solvent to remove the metal adhering to the surface of the pellets. The solvent is preferably water, and most preferably ultrapure water, but a solvent having a low metal content, for example, an acidic aqueous solution containing chlorine or fluorine,
An alkaline aqueous solution containing ammonia or the like, an aqueous solution containing a water-soluble organic compound such as methanol or ethanol, or an organic solvent such as alcohol, hydrocarbon, hydrofluorocarbon, hydrochlorocarbon, fluorochlorocarbon, or hydrofluorochlorocarbon may be used. The metal content of the solvent is Na, Mg, C
u, Cr, Ni, K, Ca and Fe total 10 pp
b or less, more preferably 5 ppb or less, and 2p
Particularly preferred is pb or less.

The washing temperature and washing time can be arbitrarily selected, but the washing must be carried out so that the metal elution amount shown below is at least 20% less after washing than before washing. If the decrease is less than 20%, no decrease in the amount of eluted metal in a molded article molded using the molding material is observed. Various methods can be applied to the method of contacting the pellets of the fluorinated copolymer molding material with the solvent, for example, a method of immersing the pellets in a solvent, a method of passing the solvent through a packed layer of the pellets, and the like. . In the case of the former contact method, stirring is preferred. In the latter contact method, the solvent may be used by circulating the solvent once passed through the packed bed of pellets.

The washing solvent is preferably used in an amount of 100 to 10000 parts by mass per 100 parts by mass of the pellets. Using the molding material obtained according to the present invention, the molded article of the fluorocopolymer obtained by injection molding, extrusion molding, etc., has a higher metal elution in the molded article than the molded article molded using the molding material without a washing step. The amount is small. The molding material obtained by the present invention can be used for molding alone or by adding various compounding materials. It is also possible to add the molding material obtained according to the present invention, various compounding materials and polymers, and pelletize again to obtain a molding material.

[0014]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The melt index (hereinafter referred to as MI), which is an index of the molecular weight of the fluorinated copolymer, is at a temperature of 372 ° C.
Using a die having a diameter of 2.1 mm and a length of 8 mm, the flow rate of the fluorocopolymer when extruded under a load of 5 kg (g / g)
10 minutes). The polymer composition is 34 for PFA
A film having a thickness of 30 μm was prepared by press molding at 0 ° C., and the infrared spectrum of the film was measured. In the case of PFA, the content (% by mass) of polymerized units based on perfluoro (propyl vinyl ether) (hereinafter referred to as PPVE) in PFA is 993.
The absorbance at cm ^-1, divided by the absorbance at 2350 cm ^-1, was determined as a value obtained by multiplying 0.95. FE
For P, the content of polymerized units based on hexafluoropropylene in FEP (wt%) is the absorbance at 980 cm ^-1, divided by the absorbance at 2350 cm ^-1, it was determined as a value obtained by multiplying 3.2.

The metal contents of the polymerization solvent, the granulating solvent, the washing solvent water and the chain transfer agent methanol used in the examples and comparative examples are shown below. The metal content of ultrapure water is
The total of Na, Mg, Cu, Cr, Ni, K, Ca and Fe was 1.0 ppb. The metal content of high-purity methanol was 1.5 ppb in total of Na, Mg, Cu, Cr, Ni, K, Ca and Fe. As the high-purity methanol, an EL grade manufactured by Kanto Chemical was used. The amount of metal elution was determined by heating a container with a lid made of PFA in ultrapure nitric acid and ultrapure water at 80 ° C. for 1 week, and then dispensing 5 g of the molding material into the treated container. Add 3 ml of 0.8% ultra-high purity nitric acid, cover and heat on a hot plate at 80 ° C for 2 hours, and then extract ultra-high-purity nitric acid containing the eluted metal element by inductively coupled plasma mass spectrometry (ICP-MS)
It was measured by the method of quantitative analysis.

Example 1 (Comparative Example) Each of the equipment for the polymerization step, the granulation step, the washing step, and the drying step where the raw material and the fluorine-containing copolymer come into contact, and the piping were lined and covered with PFA. 188 L of ultrapure water, 78 L of perfluorohexane as a polymerization solvent, 9.5 L of high-purity methanol, and 14.0 kg of PPVE were charged into a 400 L polymerization tank, TFE was charged after the temperature in the tank was raised to 50 ° C., and TFE was charged in the polymerization tank. The pressure was set to 1.3 MPa. The metal component content of TFE is N
The total of a, Mg, Cu, Cr, Ni, K, Ca and Fe was 1.0 ppb. The metal component content of perfluorohexane is Na, Mg, Cu, Cr, Ni, K,
The total of Ca and Fe was 5.0 ppb. PPV
The metal component content of E is Na, Mg, Cu, Cr, N
The total of i, K, Ca and Fe was 4.0 ppb.

As a polymerization initiator, a 0.05% perfluorohexane solution of di (perfluorobutyryl) peroxide was added to initiate polymerization. TFE was charged so that the pressure was constant. The polymerization initiator solution was continuously charged so that the polymerization rate was substantially constant during the polymerization, and the total was 5.1.
L was charged. The metal component content of a 0.05% perfluorohexane solution of bis (perfluorobutyryl) peroxide is Na, Mg, Cu, Cr, Ni, K, C
The sum of a and Fe was 5.0 ppb. Eight hours after the start of the polymerization, the total amount of the TFE charged later was 40
After reaching kg, the polymerization tank was cooled to room temperature, and the unreacted gas was purged to obtain a slurry containing the produced polymer. This slurry was transferred from the bottom of the polymerization tank through a pipe to the granulation tank by pressurizing the polymerization tank with nitrogen. The contents of a 1000 L granulation tank previously charged with 500 L of ultrapure water were heated to 90 ° C. while stirring to evaporate perfluorohexane.
The polymer was granulated while distilling off. The obtained granules were transferred to a dryer through a pipe and dried at 150 ° C. for 8 hours.
The metal component elution amount of the dried granulated product is Na: 1.0 pp
b, Mg: 0 ppb, Cu: 0 ppb, Cr: 0 pp
b, Ni: 0.1 ppb, K: 1.0 ppb, Ca:
2.0 ppb and Fe: 0.1 ppb.

Further, the terminal group of the obtained fluorocopolymer was analyzed by an infrared spectrum, and as a result, a carbinol group and a carbonyl fluoride group were present. The dried granules were transferred to an extruder in a clean room via a pipe and pelletized. The extruder has a diameter of 65 mm, L / D = 25,
The screw material is Hastelloy, a corrosion-resistant material. Extrusion conditions were as follows: C1 = 340 ° C., C2 = 360 ° C., C3 = 380
° C, C4 = 380 ° C, C5 = 380 ° C, die temperature 380
° C and the screw rotation speed is 40 rpm. The obtained pellets were cylindrical and had a diameter of about 1.5 mm and a length of about 2 mm. The pelletized polymer had an MI of 12.1, and the content of polymerized units based on perfluoro (propyl vinyl ether) in the polymer was 3.6% by mass.

Example 2 (Example) The pelletized polymer obtained in Example 1 was lined with PFA to a pressure resistance of 30%.
L, the inside of the container is degassed, a mixed gas of nitrogen / fluorine (nitrogen / fluorine = 4/1 vol ratio) is charged to atmospheric pressure, the temperature in the container is raised to 220 ° C., and the temperature is raised for 6 hours. Held. Thereafter, the temperature was lowered to room temperature, and after completely replacing the fluorine in the container with nitrogen, the pellet was taken out. The metal component elution amount of the obtained pellet was Na: 2.5 ppb, M
g: 0.1 ppb, Cu: 0.1 ppb, Cr: 0.5
ppb, Ni: 0.1 ppb, K: 1.0 ppb, C
a: 3.5 ppb, Fe: 2.5 ppb, and the total metal elution amount was 10.3 ppb. Also, as a result of infrared spectrum measurement, the fluorinated pellet did not have a carbinol group or a carbonyl fluoride group, and it is considered that the molecular terminal was fluorinated and became a stable terminal. 30 kg of the resulting pelletized polymer was transferred to a 400 L washing tank whose inner surface was coated with PFA, and 300 kg of ultrapure water was transferred.
It stirred and stirred at room temperature for 1 hour. Thereafter, the pellet was transferred to a dryer and dried at 150 ° C. for 8 hours. The metal component elution amount of the obtained pellets was Na: 1.0 ppb, Mg: 0 p
pb, Cu: 0 ppb, Cr: 0 ppb, Ni: 0 pp
b, K: 1.0 ppb, Ca: 1.0 ppb, Fe:
It was 0.2 ppb, and the total amount of metal elution was 3.2 ppb.

Example 3 (Application Example) A tube having an inner diameter of 8 mm and an outer diameter of 10 mm was formed using the pellet of Example 1 and the pellet washed with water in Example 2. The molding conditions were as follows: the extruder had a caliber of 30 mm, L / D = 25, and the screw material was Hastelloy, a corrosion-resistant material. Extrusion conditions are C1 = 320
° C, C2 = 320 ° C, C3 = 340 ° C, C4 = 340
° C, C5 = 340 ° C, die temperature 340 ° C, screw rotation speed 10 rpm. Each of the obtained tubes was cut by 1 m, 80% of 6.8% ultra-high purity nitric acid was charged therein, and both ends were covered with a PTFE stopper washed with ultra-purified nitric acid and ultra-pure water, and heated at 80 ° C. for 2 hours. Ultra-pure nitric acid containing the eluted metal element was quantified by ICP-MS. Table 1 shows the amounts of the eluted metal elements.

[0021]

[Table 1]

Example 4 (Comparative Example) Each of the equipment for the polymerization step, the granulation step, the washing step, and the drying step, in which the raw material and the fluorine-containing copolymer come into contact, and the piping were lined with PFA and covered. 160L of polymerization solvent perfluorohexane, 0.5L of high purity methanol, HFP in a 400L polymerization tank
After charging 170 kg and setting the temperature in the tank to 50 ° C., T
FE was charged and the pressure in the polymerization tank was adjusted to 1.3 MPa.
The metal component content of TFE is Na, Mg, Cu, Cr,
The total of Ni, K, Ca and Fe was 1.0 ppb. The metal component content of perfluorohexane is Na,
The total of Mg, Cu, Cr, Ni, K, Ca and Fe was 5.0 ppb. The metal component content of HFP is N
The total of a, Mg, Cu, Cr, Ni, K, Ca and Fe was 2.0 ppb. A 0.5% perfluorohexane solution of di (perfluorobutyryl) peroxide was added as a polymerization initiator to initiate polymerization. TFE was charged so that the pressure was constant. The polymerization initiator solution is
The polymerization rate was continuously charged so that the polymerization rate was substantially constant during the polymerization, and a total of 3.6 L was charged. The metal component content of a 0.5% perfluorohexane solution of bis (perfluorobutyryl) peroxide was Na, Mg, Cu, Cr,
The total of Ni, K, Ca and Fe was 5.0 ppb.

Eight hours after the start of the polymerization, after the total amount of the TFE charged afterwards reached 36 kg, the polymerization tank was cooled to room temperature, and the unreacted gas was purged to obtain a slurry containing the produced polymer. This slurry was transferred from the bottom of the polymerization tank through a pipe to the granulation tank by pressurizing the polymerization tank with nitrogen. The contents were heated to 90 ° C. while stirring the contents in a 1000 L granulation tank previously charged with 500 L of ultrapure water, and the polymer was granulated while evaporating and distilling off HFP and perfluorohexane. Transfer the obtained granules to the dryer by piping,
Dry at 150 ° C. for 8 hours. The amount of the metal component eluted from the dried granulated product is Na: 1.5 ppb, Mg: 0 ppb, C
u: 0 ppb, Cr: 0.1 ppb, Ni: 0 ppb,
K: 1.0 ppb, Ca: 1.0 ppb, Fe: 0.2
ppb. In addition, as a result of analysis by an infrared spectrum, a terminal group of the obtained fluorinated copolymer had a carbinol group and a carbonyl fluoride group. The dried granules were transferred to an extruder in a clean room via a pipe and pelletized. Extruder diameter 65mm, L / D = 25
The material of the screw is Hastelloy, a corrosion-resistant material. Extrusion conditions were as follows: C1 = 340 ° C., C2 = 360 ° C., C3 = 3
80 ° C, C4 = 380 ° C, C5 = 380 ° C, Die temperature 3
80 ° C., screw rotation speed 40 rpm. The obtained pellets are cylindrical, about 1.5 mm in diameter and about 2 m in length.
m. The pelletized polymer had an MI of 7.5.
And the content of the polymerized units based on HFP in the polymer was 12.8% by mass.

Example 5 (Example) The pelletized polymer obtained in Example 4 was lined with PFA to a pressure resistance of 30%.
L, the inside of the container is degassed, a mixed gas of nitrogen / fluorine (nitrogen / fluorine = 4/1 vol ratio) is charged to atmospheric pressure, the temperature in the container is raised to 220 ° C., and the temperature is raised for 6 hours. Held. Thereafter, the temperature was lowered to room temperature, and after completely replacing the fluorine in the container with nitrogen, the pellet was taken out. The metal component elution amount of the obtained pellet was Na: 2.8 ppb, M
g: 0.1 ppb, Cu: 0.3 ppb, Cr: 0.4
ppb, Ni: 0.4 ppb, K: 1.0 ppb, C
a: 1.5 ppb, Fe: 4.5 ppb, and the total metal elution amount was 11.0 ppb. Also, as a result of infrared spectrum measurement, the fluorinated pellet did not have a carbinol group or a carbonyl fluoride group, and it is considered that the molecular terminal was fluorinated and became a stable terminal. 30 kg of the resulting pelletized polymer was transferred to a 400 L washing tank whose inner surface was coated with PFA, and 300 kg of ultrapure water was transferred.
It stirred and stirred at room temperature for 1 hour. Thereafter, the pellet was transferred to a dryer and dried at 150 ° C. for 8 hours. The metal component elution amount of the obtained pellets was Na: 1.2 ppb, Mg: 0 p
pb, Cu: 0.1 ppb, Cr: 0.1 ppb, N
i: 0 ppb, K: 1.0 ppb, Ca: 0.5 pp
b, Fe: 0.2 ppb;
It was 1 ppb.

Example 6 (Application) Using the pellets of Example 4 and the pellets washed with water in Example 5, the inner diameter was 8 m.
m, a tube having an outer diameter of 10 mm was formed. The molding conditions are
The extruder has a diameter of 30 mm, L / D = 25, and the screw material is Hastelloy, a corrosion-resistant material. Extrusion conditions are C1 =
320 ° C, C2 = 320 ° C, C3 = 340 ° C, C4 = 3
40 ° C., C5 = 340 ° C., die temperature 340 ° C., screw rotation speed 10 rpm. Each of the tubes obtained was 1
m, and 6.8% ultra-high purity nitric acid is charged 80%,
Both ends were covered with a stopper of PTFE washed with ultrapure nitric acid and ultrapure water, heated at 80 ° C. for 2 hours, and ultrapure nitric acid containing the eluted metal element was quantified by ICP-MS. Table 2 shows the amounts of the eluted metal elements.

[0026]

[Table 2]

[0027]

According to the present invention, a molded member molded from the fluoropolymer molding material obtained by the production method of the present invention has a reduced metal elution amount.

Claims (3)

[Claims] After fluorinating pellets of a fluorine-containing copolymer molding material to stabilize the molecular terminals of the fluorine-containing copolymer, the pellets are washed to reduce the amount of metal eluted from the pellets by 20% before washing. A method for producing a fluorine-containing copolymer molding material, characterized in that the above-mentioned reduction is achieved. 2. The fluorine-containing copolymer according to claim 1, wherein the fluorine-containing copolymer is a tetrafluoroethylene / perfluoro (alkyl vinyl ether) -based copolymer or a tetrafluoroethylene / hexafluoropropylene-based copolymer. Manufacturing method of molding material. 3. The method for producing a fluorine-containing copolymer molding material according to claim 1, wherein the washing is water washing.