JP2002012626A - Fluorine-containing copolymer and molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluorine-containing copolymer having a high melt tension and excellent blow moldability. SOLUTION: This fluorine-containing copolymer has the molar ratio of a polymerization unit of tetrafluoroethylene, a polymerization unit of a fluorine- containing monomer containing one double bond and a polymerization unit of a monomer containing two or more double bonds of 50-99/0.99-49.99/0.01-1 and 1×102-5×104 Pa.s melt viscosity at 380 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorine-containing copolymer, and more particularly to a fluorine-containing copolymer excellent in blow moldability.

[0002]

2. Description of the Related Art A tetrafluoroethylene / perfluoro (propyl vinyl ether) copolymer (hereinafter, referred to as PFA) and a tetrafluoroethylene / hexafluoropropylene copolymer (hereinafter, referred to as FEP) are melt-moldable. It is a fluororesin, and is widely used as a molded product such as tubes, pipes, joints, and containers, and as a material for wire coating, coating, and lining. PFA
FEP and FEP can be formed by methods such as extrusion molding, injection molding, transfer molding, and blow molding, which are the usual methods for molding a melt-moldable resin. In particular, containers in the form of bottles, tanks, drums and the like used for storing and transporting organic liquids and corrosive liquids are manufactured by blow molding PFA or FEP.

However, due to the large specific gravity of PFA and FEP, a cylindrical resin (hereinafter, referred to as a parison) which is in a softened state in a mating mold during blow molding is easily pulled downward by its own weight. . As a result, there is a problem that the parison on the upper portion is elongated, the thickness of the portion is reduced, and the thickness of the molded body becomes uneven. In particular, when blow molding a large molded body, the thickness of the upper part of the parison is significantly reduced.

In order to prevent the upper part of the parison from being thinned, it is sufficient to suppress the elongation of the parison by its own weight. However, the present inventor has found that it is effective to increase the melt tension of PFA or FEP. Was found. As a method to increase the melt tension, we investigated the use of a high molecular weight fluoropolymer to be used.However, the melt viscosity of the fluoropolymer during molding increased, resulting in a decrease in the moldability of the fluorocarbon resin when extruding a parison. However, there is a problem that productivity is reduced.

On the other hand, a method of molding while maintaining a high melt tension has been studied. However, it is necessary to extrude the parison at a low temperature, and as a result, the parison is easily solidified in a mating die, and blow molding is difficult. There was a problem. Also,
When a parison is extruded at a low temperature, there is a problem that the melt viscosity of the fluorine-containing resin increases and the productivity decreases as described above.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and provides a fluorine-containing copolymer which can suppress the thinning of the upper part of the parison in blow molding without lowering the productivity. The purpose is to provide.

[0007]

The present invention relates to (a) a polymerized unit based on tetrafluoroethylene (hereinafter referred to as TFE), and (b) a fluorine-containing monomer having one double bond (excluding TFE). ) And (c) a fluorinated copolymer essentially comprising a polymerized unit based on a monomer having two or more double bonds, wherein (a) / (b) in the fluorinated copolymer / (C) is 50 to 99 / 0.99 to 49.99 / 0.01 to 1 in molar ratio, and the melt viscosity at 380 ° C. is 1 × 10 ^{2 to} 5 × 10 ⁴ Pa.
-Provide a fluorine-containing copolymer characterized by being s.

In the present invention, (a) is a polymerized unit based on TFE. (B) is preferably a polymerized unit based on the monomers described below. Examples of the monomer (b) include fluoroethylenes such as chlorotrifluoroethylene, vinylidene fluoride and trifluoroethylene, and hexafluoropropylene (hereinafter HF), excluding TFE.
It is called P. ), Fluoropropylenes such as pentafluoropropylene, perfluoroalkyl groups such as CF ₃ CF ₂ CF ₂ CF ₂ CH = CH ₂ and CF ₃ CF ₂ CF ₂ CF ₂ CF = CH ₂ having 4 to 12 carbon atoms. (Perfluoroalkyl) ethylenes, perfluoro (alkyl vinyl ether) and the like. The monomer (b) may be used alone or in combination of two or more.

More preferable examples of the monomer (b) include HFP and / or perfluoro (alkyl vinyl ether). Preferred examples of the perfluoro (alkyl vinyl ether) of (b) include a compound represented by the formula R ^f3 (O
CFXCF ₂ ) _m OCF ＝ CF ₂ (where R ^f3 is a perfluoroalkyl group having 1 to 8 carbon atoms, X is a fluorine atom or a trifluoromethyl group, and m is an integer of 0 to 5). Monomers. More preferred examples are
In the above formula, R ^f3 is a perfluoroalkyl group having 1 to 8 carbon atoms and m is 0. In particular, perfluoro (propyl vinyl ether) (hereinafter referred to as PPVE) is used.
It is most preferable in terms of availability of raw materials.

In the present invention, (c) is a polymerized unit based on a monomer having usually two or three double bonds. (C) may or may not contain a fluorine atom, but more preferably contains a fluorine atom.

The monomer having two double bonds includes:
CF_Two= CFO-R^f4-OCF = CF_Two(Where R^f4Is
A fluoroalkylene group having 1 to 8 carbon atoms (however,
Even if the alkylene group contains an etheric oxygen atom
Good. ). ), CF _Two= CFO-R^f5-CF = C
F_Two, CF_Two= CFO-R^f5-CH = CH_Two, CF_Two= CF
-R^f5-CF = CF_Two, CF_Two= CF-R^f5-CH = CH
_Two, CH_Two= CH-R ^f5-CH = CH_Two(Where R^f5Is
A single bond or a fluoroalkylene group having 1 to 8 carbon atoms (only
Containing an etheric oxygen atom in the fluoroalkylene group.
You may go out. ). ).

The monomer having three double bonds includes:
C2-C8 fluoroalkane tri-substituted by three trifluorovinyloxy groups or three trifluorovinyl groups (however, the fluoroalkane skeleton may contain an etheric oxygen atom) or trisubstitution. Aromatic compounds and the like.

In particular, as the monomer (c), CF ₂
^{= CFO-R f1 -OCF = CF} 2 and / or CF ₂ = CF
_{^{O-R f2 -CF = CF 2}} ( wherein, R ^f1 is 1 to 8 carbon atoms
Wherein R ^f2 is a single bond or a perfluoroalkylene group having 1 to 8 carbon atoms (provided that the perfluoroalkylene group may contain an etheric oxygen atom in the perfluoroalkylene group). An alkylene group may contain an etheric oxygen atom). ) Are preferred from the viewpoint of easy availability of raw materials.

Preferred specific examples of the monomer (c) include CF ₂ ＣＦCFOCF ＝ CF ₂ and CF ₂ ＣＦCFOCF ₂ O
CF = CF ₂ , CF ₂ = CFO (CF ₂ ) ₂ OCF = C
F ₂ , CF ₂ = CFO (CF ₂ ) ₃ OCF = CF ₂ , CF ₂ =
_{CFO (CF 2) 4 OCF =} CF 2, CF 2 = CFO (CF
₂ ) ₅ OCF = CF ₂ , CF ₂ ＯCFO (CF ₂ ) ₆ OCF =
CF ₂ , CF ₂ = CFOCF ₂ OCF (CF ₃ ) CF ₂ OC
F = CF ₂ , CF ₂ = CFO (CF ₂ ) ₂ OCF (CF ₃ )
_{CF 2 OCF = CF 2, CF} 2 = CFOCF 2 CF = C
_{F 2, CF 2 = CFO (} CF 2) 2 CF = CF 2, CF 2 = C
FO (CF ₂ ) ₃ CF = CF _{2 and the} like.

In the fluorine-containing copolymer of the present invention, (a) /
The ratio of (b) / (c) is 50 to 99 / 0.9 in molar ratio.
9-49.99 / 0.01-1. If the ratio of (a) is less than 50, the resulting molded article will have reduced mechanical strength, heat resistance, chemical resistance and the like. On the other hand, if it exceeds 99, blow moldability becomes poor. If the ratio of (b) is less than 0.99, the blow moldability becomes poor, and if it exceeds 49.99, the mechanical strength, heat resistance, chemical resistance, etc. of the obtained molded body are reduced. If the ratio of (c) is less than 0.01, there is almost no effect of improving the melt tension, and if it exceeds 1, the melt viscosity increases and molding becomes difficult. (A) / (b) /
The ratio of (c) is 60-99 / 0.99-3 in molar ratio.
9.99 / 0.01-1 is more preferable, and 70-99 /
0.97 to 29.97 / 0.03 to 0.7 is more preferable.

The fluorine-containing copolymer of the present invention comprises (a)
In addition to (b) and (c), a polymer unit containing 10 mol% or less of a polymer unit based on another vinyl monomer may be used. Examples of other vinyl monomers include ethylene, propylene, olefins such as butene, vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butenyl vinyl ether, chloroethyl vinyl ether, hydroxybutyl vinyl ether, cyclohexyl vinyl ether, and glycidyl vinyl ether. Compounds, allyl compounds such as allyl alcohol and allyl glycidyl ether, vinyl esters such as vinyl acetate, vinyl pivalate, vinyl butyrate and vinyl chloroacetate, and acrylic acid derivatives such as acrylic acid, methacrylic acid, methyl acrylate and methyl methacrylate Or a methacrylic acid derivative is mentioned.

The process for producing the fluorine-containing copolymer of the present invention comprises:
There is no particular limitation, and conventionally known methods such as bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization are employed. In the case of solution polymerization, hydrofluorocarbon as a polymerization medium,
Chlorofluorocarbon, hydrochlorofluorocarbon, alcohol, hydrocarbon and the like are used. In the case of suspension polymerization, hydrofluorocarbon,
A medium obtained by adding water to a medium such as chlorofluorocarbon, hydrochlorofluorocarbon or hydrocarbon is used as a polymerization medium. In the case of emulsion polymerization, water is used as a polymerization medium, but a similar polymerization medium used in solution polymerization may be used in combination.

As the polymerization initiation source, a radical initiator, a redox catalyst initiator, light, heat, ionizing radiation and the like are employed. Specific examples of preferred radical initiators include azo initiators such as azobisisobutyronitrile, diacyl peroxides such as isobutyryl peroxide, octanoyl peroxide, benzoyl peroxide and lauroyl peroxide, and diisopropyl peroxide. Peroxydicarbonates such as peroxydicarbonate,
Peroxyesters such as tert-butylperoxypivalate, tert-butylperoxyisobutyrate, tert-butylperoxyacetate, (X
(CF ₂ ) _n COO) ₂ (where X is a hydrogen atom, a fluorine atom or a chlorine atom, and n is an integer of 1 to 10), such as an organic peroxide such as a fluorinated diacyl peroxide. And inorganic peroxide initiators such as potassium persulfate, sodium persulfate and ammonium persulfate.

[0019] The polymerization temperature is preferably in the range of 0 ° C to 200 ° C, particularly preferably in the range of 10 ° C to 100 ° C. The polymerization pressure is preferably in the range of 0.01 to 10 MPa, and 0.5 to 10 MPa.
A range of 3 MPa is particularly preferred.

The melt viscosity at 380 ° C. of the fluorinated copolymer of the present invention is from 1 × 10 ^{2 to} 5 × 10 ⁴ Pa · s. 1x
If it is smaller than 10 ² Pa · s, it is disadvantageous in terms of mechanical strength of the obtained molded body, and if it is larger than 5 × 10 ⁴ Pa · s, it is disadvantageous in terms of melt moldability. Preferably 5
X 10 ^{2 to} 2 x 10 ⁴ Pa · s, most preferably 1
× 10 ³ to 1 × 10 ⁴ Pa · s.

In the present invention, by using a specific amount of (c), it is possible to increase the melt tension while suppressing the increase in melt viscosity, and obtain a fluorine-containing copolymer excellent in blow moldability. Can be On the other hand, if the molecular weight is increased to increase the melt tension of the fluorinated copolymer, the melt viscosity increases and the extrusion moldability decreases.

In the present invention, in order to achieve the above effects, melt tension (unit: mN) / melt viscosity (unit: Pa)
It is desirable to control the ratio of (s) in the range of 0.07 to 0.5. If it is smaller than 0.07, it becomes disadvantageous in terms of stretching due to the weight of the parison in blow molding, and it is not preferable to use a parison.
If it exceeds 5, blow molding becomes difficult. 0.07
The range of -0.15 is more preferable.

In the present invention, the reason why the above effect is achieved is not necessarily clear, but it is considered to be based on the following action mechanism by using a specific amount of (c). In the synthesis reaction of the fluorine-containing copolymer of the present invention,
First, one double bond in the monomer of (c) is represented by (a)
Is copolymerized with the monomer (b) and the monomer (b) to form a fluorine-containing copolymer having the remaining double bond in the side chain in the monomer (c). In addition to this double bond in the side chain, (a)
And the monomer of (b) are copolymerized to form a long side chain. It is considered that the structure of the long side chain increases the melt tension by some effect while suppressing the increase in the melt viscosity.

In the present invention, the fluorinated copolymer produced by polymerization may be fluorinated in order to stabilize unstable sites in the fluorinated copolymer which cause foaming or coloring during molding. It is preferably adopted. Fluorination (b)
Is particularly preferably employed in the case of a polymerization unit based on perfluoro (alkyl vinyl ether) or hexafluoropropylene. For the fluorination, it is preferable in terms of handling to use a mixed gas of fluorine gas / nitrogen gas.

The fluorination temperature is preferably from 200 to 280 ° C. If the temperature is lower than 200 ° C., it takes a long time for fluorination,
If it exceeds 280 ° C., the copolymer may melt and handling may be difficult. More preferably, 220-2
A range of 50 ° C is employed. The fluorination time depends on the fluorination temperature, but usually 1 to 24 hours is preferably employed. Fluorination is completed in a short time at a high temperature and for a long time at a low temperature.

By the fluorination, a small amount of double bonds, --COF, --CF ₂ CH ₂ OH,
Results such as unstable end groups, such as -COOH is converted into stable end groups, such as a -CF ₃ group, and improved thermal stability of the fluorinated copolymer is a fluorinated copolymer is foamed and colored during molding It is thought to be gone. The fluorinated copolymer of the present invention is preferably used as a raw material for blow molding.

[0027]

EXAMPLES Examples of the present invention and comparative examples will be described below, but the present invention is not limited thereto. The evaluation of the melt viscosity, melt tension, composition and blow molding of the fluorinated copolymer was measured according to the following methods. Melt viscosity of fluorocopolymer (unit: Pa · s): Diameter 2.1 using Koka type flow tester (manufactured by Shimadzu Corporation).
This is the value of the apparent melt viscosity when extruded at 380 ° C. with a die having a length of 8 mm and a length of 8 mm. Melt tension (unit: mN): Using a Capillograph (manufactured by Toyo Seiki Seisakusho), a die having a diameter of 3 mm and a length of 10 mm,
Extruded at a speed of 5 mm / min at 380 ° C. and a speed of 10 m / min.
It is the value of the withdrawal strength when it is withdrawn in min. Composition of fluorinated copolymer: determined by ¹⁹ F-melt NMR method.

Evaluation of blow molding: The following simulation test was performed. In the extruded fluorine-containing copolymer strand at the time of measuring the melt viscosity, the strand diameter when the strand was extruded by 1 cm and the strand diameter when extruded by 10 cm were measured, and the strand diameter at 10 cm / 1 cm
Is determined (hereinafter referred to as DC ratio). Those having a large DC ratio have a small degree of elongation by their own weight during melting and are suitable for blow molding.

Example 1 A 1 L autoclave equipped with a stirrer was evacuated to a vacuum, and 1,3-dichloro-1,1,2,2
2,3-pentafluoropropane (hereinafter referred to as AK225c
It is called b. 1000 g of Asahi Glass Co., Ltd., 2.5 g of methanol, 120 g of PPVE, CF ₂ = CFOCF ₂ C
F ₂ CF ₂ CF ₂ OCF = CF ₂ (hereinafter referred to as DVB)
Was charged. The internal temperature of the autoclave was set to 50 ° C., and TFE was charged to 0.7 MPa. A 1% solution of bis (perfluorobutyryl) peroxide (solvent: AK225cb) was charged as an initiator to initiate polymerization.

Since the pressure was lowered as the polymerization proceeded, TFE was charged and the pressure was maintained at 0.7 MPa. Since the polymerization did not progress with the passage of time, the polymerization was advanced by sequentially charging the initiator solution in 1 mL portions. When the amount of TFE charged later reaches 100 g, the internal temperature of the autoclave is cooled to 10 ° C.
E was purged. The obtained slurry suspension was filtered and dried to obtain 105 g of a white fluorinated copolymer.

The composition of the fluorine-containing copolymer is TF in molar ratio.
E / PPVE / DVB = 98.4 / 1.5 / 0.1. The melt viscosity was 2100 Pa · s, and the melt tension was 158 mN. The melt tension / melt viscosity ratio is 0.0
75 and the DC ratio was 0.9.

Example 2 Polymerization was carried out in the same manner as in Example 1 except that the amount of DVB was changed to 30 g to obtain 110 g of a white fluorinated copolymer. The composition of the fluorinated copolymer is TFE / PPVE / DVB = 98.0 / 1.5 / 0.
It was 5. The melt viscosity was 4100 Pa · s, and the melt tension was 316 mN. The ratio of melt tension / melt viscosity was 0.077 and the DC ratio was 0.98.

Example 3 Instead of 5 g of DVB, CF ₂ =
Polymerization was carried out in the same manner as in Example 1 except that 5 g of CFOCF ₂ CF ₂ CF ₂ CF ₂ CF ₂ OCF = CF ₂ (hereinafter, referred to as DVP) was used to obtain 105 g of a white fluorinated copolymer. The composition of the fluorinated copolymer is TFE / PP in molar ratio.
VE / VDP = 98.4 / 1.5 / 0.1. The melt viscosity is 1900 Pa · s and the melt tension is 153 m
N. The melt tension / melt viscosity ratio was 0.081 and the DC ratio was 0.90.

Example 4 Instead of 5 g of DVB, CF ₂ =
CFOCF ₂ CF ₂ CF ₂ CF ₂ CF = CF ₂ (hereinafter, DV
Except using 5g of that B ₂₎ is polymerized in the same manner as Example 1 to obtain 105g of white fluorine-containing copolymer. The composition of the fluorinated copolymer is TFE / PPVE / DV in molar ratio.
B ₂ = 98.4 / 1.5 / 0.1. The melt viscosity was 1600 Pa · s, and the melt tension was 112 mN. The melt tension / melt viscosity ratio was 0.07 and the DC ratio was 0.85.

Example 5 500 g of AK225cb instead of 1000 g and 0.1 g of methanol instead of 2.5 g
Polymerization was carried out in the same manner as in Example 1 except that 2 g and 600 g of HFP were used instead of PPVE to obtain 130 g of a white fluorinated copolymer. The composition of the fluorinated copolymer was TFE / HFP / DVB = 93.4 / 6.5 / 0.1 in a molar ratio. The melt viscosity was 2500 Pa · s, and the melt tension was 189 mN. The ratio of melt tension / melt viscosity is 0.
076 and the DC ratio was 0.95.

Example 6 The fluorinated copolymer obtained in Example 1 was
Fluorination was carried out at 240 ° C. for 6 hours in a fluorine gas atmosphere of fluorine gas / nitrogen gas = 20/80 in volume ratio.
As a result of measuring an infrared absorption spectrum of the obtained fluorinated fluorinated copolymer, it was found that -C detected before fluorination.
No absorption derived from F = CF ₂ was detected. The melt viscosity was 2100 Pa · s, the melt tension was 158 mN, the same value as before fluorination. The DC ratio was 0.90.

Example 7 (Comparative Example) Polymerization was carried out in the same manner as in Example 1 except that no DVB was charged, to obtain 97 g of a white fluorinated copolymer. Results of infrared absorption spectrum of the obtained fluorine-containing copolymer was measured, absorption derived from -CF = CF ₂ was detected. Melt viscosity is 1800Pa · s
The melt tension was 97 mN, which was lower than that of the fluorinated copolymer of Example 1. The melt tension / melt viscosity ratio was 0.054 and the DC ratio was 0.7.

Example 8 (Comparative Example) Polymerization was carried out in the same manner as in Example 5 except that DVB was not charged, to obtain 120 g of a white fluorinated copolymer. Results of infrared absorption spectrum of the obtained fluorine-containing copolymer was measured, absorption derived from -CF = CF ₂ was detected. Melt viscosity is 1900Pa · s
The melt tension was 71 mN, which was lower than that of the fluorine-containing copolymer of Example 5. The melt tension / melt viscosity ratio was 0.038 and the DC ratio was 0.7.

Example 9 (Comparative Example) Polymerization was carried out in the same manner as in Example 1 except that 100 g of DVB was used instead of 5 g to obtain 105 g of a white fluorinated copolymer. The composition of the fluorinated copolymer was TFE / PPVE / DVB = 98.
4 / 1.5 / 1.2. The melt viscosity was too large to be measured.

[0040]

The fluorinated copolymer of the present invention has a high melt tension and is excellent in blow moldability. Further, by fluorinating this fluorinated copolymer, the thermal stability of the fluorinated copolymer is improved, and an effect of completely eliminating foaming and coloring of the fluorinated copolymer during molding is exhibited.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C08F 216: 14 C08F 216: 14 214: 28 214: 28 216: 12) 216: 12) B29K 27:12 B29K 27:12 C08L 27:18 C08L 27:18 F term (reference) 4F071 AA27 AA27X AA30X AA76 BB01 BC04 4F208 AA16E AG07 AR17 LB01 LG01 4J100 AC22Q AC24Q AC25Q AC26P AC27Q AC31Q AE09Q CA05 FA19

Claims (6)

[Claims] 1. A polymerization unit based on (a) a tetrafluoroethylene-based polymerization unit, (b) a polymerization unit based on a fluorine-containing monomer having one double bond (excluding tetrafluoroethylene), and (c) a double bond. Is a fluorinated copolymer essentially comprising a polymerized unit based on a monomer having two or more monomers, and the molar ratio of (a) / (b) / (c) in the fluorinated copolymer is 50 to 99. /0.99-49.99/0.
01 to 1 and a melt viscosity at 380 ° C. of 1 × 10 ² to
A fluorine-containing copolymer having a pressure of 5 × 10 ⁴ Pa · s. 2. The fluorine-containing copolymer according to claim 1, wherein the polymerized unit (b) is a polymerized unit based on perfluoro (alkyl vinyl ether) and / or hexafluoropropylene. 3. The polymerized unit of (c) is CF ₂ ＣＦCFO-R.
^f1 -OCF = CF ₂ and / or CF ₂ = CFO-R ^f2 -C
F = CF ₂ (where R ^f1 represents a fluoroalkylene group having 1 to 8 carbon atoms (however, the fluoroalkylene group may contain an etheric oxygen atom), and R ^f2 represents a single bond or carbon atom 3. A polymerized unit based on a monomer represented by the following formula (1): a fluoroalkylene group of 1 to 8 (however, the fluoroalkylene group may contain an etheric oxygen atom). Fluorine copolymer. 4. The fluorine-containing copolymer according to claim 1, wherein the ratio of melt tension (unit: mN) / melt viscosity (unit: Pa · s) is 0.07 to 0.5. 5. A stabilized fluorinated copolymer obtained by fluorinating the fluorinated copolymer according to claim 1, 2, 3 or 4. 6. A molded article obtained by blow molding the fluorinated copolymer according to claim 1, 2, 3, 4, or 5.