CN1644595A - Production of pte polymer - Google Patents

Abstract

An object of the present invention is to provide an industrially advantageous method for producing high molecular weight PTFE. The present invention relates to the production method of tetrafluoroethylene polymer, it is to produce tetrafluoroethylene polymer by monomer polymerization in the presence of terpene, it is characterized in that, the standard specific gravity ratio of described tetrafluoroethylene polymer is in the absence of terpene The standard specific gravity of the tetrafluoroethylene polymer (A) produced by polymerization under certain conditions is small, and the tetrafluoroethylene polymer and the tetrafluoroethylene polymer (A) are tetrafluoroethylene homopolymer or modified poly Tetrafluoroethylene.

Description

Method for producing tetrafluoroethylene polymer

technical field

The present invention relates to a method for the manufacture of tetrafluoroethylene polymers.

Background technique

As a method for producing high-molecular-weight polytetrafluoroethylene (PTFE), a method of adding hydroquinone during polymerization is disclosed (see, for example, JP-A-58-39443). However, since hydroquinone is water-soluble, it exists in the same phase as the polymer when it is polymerized in an aqueous medium, so there is a problem that hydroquinone is mixed into the obtained polymer. In addition, hydroquinone must be added during the polymerization process, but cannot be added at the initial stage of polymerization, and there is a problem that it is difficult to control the polymerization reaction.

Conventionally, terpene as a polymerization inhibitor was added in advance, and the terpene was removed before monomers such as tetrafluoroethylene (TFE) were charged into the polymerization tank.

It has been described that PTFE is produced in the presence of terpenes without removing them during polymerization. However, among them, if terpene is present in TFE polymerization, a low molecular weight polymer is obtained (see, for example, JP-A-2000-143707 [0060]).

In addition, a method of producing a fluorine-containing polymer having a small molecular weight distribution by adding a terpene compound at the initial stage of polymerization is also disclosed (see, for example, JP-A-2002-3514). However, this method is a method for producing a TFE/perfluoro(alkyl vinyl ether) copolymer.

Contents of the invention

In view of the above circumstances, an object of the present invention is to provide an industrially advantageous method for producing high molecular weight PTFE.

The present invention relates to a method for producing tetrafluoroethylene polymers, which produce tetrafluoroethylene polymers by polymerization of monomers in the presence of terpenes, characterized in that the standard specific gravity ratio of said tetrafluoroethylene polymers is higher than that in the absence of terpenes. The standard specific gravity of the tetrafluoroethylene polymer (A) produced by polymerization under the conditions is small, and the tetrafluoroethylene polymer and the tetrafluoroethylene polymer (A) are tetrafluoroethylene homopolymer or modified polytetrafluoroethylene Vinyl fluoride.

The present invention will be described in detail below.

The method for producing a tetrafluoroethylene polymer of the present invention is a method for producing a tetrafluoroethylene polymer by monomer polymerization in the presence of terpene. As described later, the monomers are tetrafluoroethylene (TFE) and other comonomers used on an as-needed basis.

The tetrafluoroethylene polymer and the tetrafluoroethylene polymer (A) described later are tetrafluoroethylene homopolymer (TFE homopolymer) or modified polytetrafluoroethylene (modified PTFE).

The TFE homopolymer is a homopolymer of TFE.

The modified PTFE is a copolymer of TFE and small amounts of other comonomers.

The modified PTFE differs from TFE homopolymer in that TFE homopolymer is obtained by polymerization of TFE only, without other comonomers.

For other comonomers of the modified PTFE, there are no particular restrictions as long as they can be copolymerized with TFE, for example, perfluoroolefins such as hexafluoropropylene (HFP), fluorochlorines such as chlorotrifluoroethylene, etc. Hydrogenated olefins, trifluoroethylene and other hydrofluoroolefins, fluorovinyl ethers, etc.

The fluorovinyl ether is not particularly limited, and examples thereof include fluorine-containing unsaturated compounds represented by the following general formula (I). In this specification, the "fluorine-containing organic group" refers to an organic group in which some or all of the hydrogen atoms bonded to carbon atoms are replaced by fluorine. The fluorine-containing organic group may also have ether oxygen.

CY ¹ ₂ =CY ² -ORf (I)

In the formula, ^Y1 and ^Y2 are the same or different, and represent a hydrogen atom or a fluorine atom. Rf represents a fluorine-containing organic group.

The fluorovinyl ethers include, for example, perfluoro(alkyl vinyl ethers) (PAVE), that is, ^Y1 and ^Y2 in the above formula (I) are both fluorine atoms, and Rf represents that the number of carbon atoms is from 1 to 10 perfluoroalkyl. The perfluoroalkyl group preferably has 1-6 carbon atoms.

Examples of the perfluoroalkyl group in the PAVE include perfluoromethyl, perfluoroethyl, perfluoropropyl, perfluorobutyl, perfluoropentyl, perfluorohexyl and the like, preferably perfluoropropyl.

In the molecular structure of the modified PTFE, the proportion (mass %) of the other comonomers is related to the type of the other comonomers, but it is preferred that the proportion is small. The degree of fluidity of PTFE melt. For example, when the other comonomer is the fluorovinyl ether, as described above, its proportion is usually preferably 1% by mass or less, more preferably 0.001% by mass to 1% by mass.

In the method for producing a tetrafluoroethylene polymer of the present invention, the above-mentioned monomers are polymerized in the presence of terpenes.

As the polymerization method, conventionally known polymerization methods such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization and the like can be used. Among them, the emulsion polymerization method is preferably used. There are no particular limitations on the terpene used, but when polymerization is performed using an aqueous medium such as emulsion polymerization or suspension polymerization, terpenes with low water solubility are preferred.

The terpene is preferably a cyclic terpene, more preferably a monocyclic terpene.

The monocyclic terpene is not particularly limited, and examples thereof include terpinolene, D-limonene, and α-terpinene, among which menthane-type or monocyclic terpenes having two double bonds are preferred. .

From the viewpoint of reducing the molecular weight distribution, a bicyclic terpene may be used as the cyclic terpene. Examples of the bicyclic terpene include β-pinene and the like. The terpene is preferably terpineolene and/or β-pinene, more preferably terpineolene.

Preferably, terpene accounts for 1 ppm to 100 ppm of the total mass of monomers. When the terpene content is less than 1 ppm, it is difficult to obtain a high molecular weight polymer. When the terpene content exceeds 100 ppm, the polymerization reaction may stop. A more preferable upper limit is 80 ppm, a more preferable upper limit is 50 ppm, a more preferable lower limit is 15 ppm, and a more preferable lower limit is 25 ppm.

The terpene may be added several times or continuously, and may be added during the polymerization, but it is preferable that the terpene is present when the polymerization is initiated. The presence of a terpene when the polymerization is initiated allows easy control of the polymerization conditions. Preferably, the polymerization is carried out under the condition that the polymerization pressure is 0.5 MPa to 4 MPa. A more preferable lower limit of the polymerization pressure is 2 MPa, and a more preferable upper limit is 3 MPa.

During polymerization, the preferable polymerization temperature is 20°C to 100°C. A more preferable lower limit of the polymerization temperature is 50°C, and a more preferable upper limit is 90°C.

In the present invention, it is preferable to carry out the polymerization in the presence of paraffin.

In the past, hydroquinone, which has been used in the polymerization of tetrafluoroethylene polymers, is water-soluble, whereas terpenes are oil-soluble. Therefore, terpenes are transferred to the paraffin phase usually present in the polymerization reaction medium, and the polymerization After removing the paraffin phase, terpenes are also discharged out of the system along with the removal of the paraffin phase. Therefore, basically no terpene is mixed into the obtained tetrafluoroethylene of the present invention.

When performing polymerization using an aqueous medium, such as emulsion polymerization and suspension polymerization, the paraffin is preferably used in an amount of 1% by mass to 10% by mass of the aqueous medium. The preferable lower limit of the usage-amount of the said paraffin is 3 mass %, and a preferable upper limit is 5 mass %.

The standard specific gravity of the tetrafluoroethylene polymer obtained under the above conditions in the presence of terpene is smaller than that of the tetrafluoroethylene polymer (A) obtained by polymerization in the absence of terpene.

The standard specific gravity (SSG) of the tetrafluoroethylene polymer is preferably 2.163-2.173. Since the SSG of the tetrafluoroethylene polymer obtained by the method for producing a tetrafluoroethylene polymer of the present invention is within the above range, it can be said to be a high molecular weight polymer.

In this specification, the SSG is based on the value measured by ASTM D 4895.

In the manufacturing method of the tetrafluoroethylene polymer of the present invention, the amount of the tetrafluoroethylene polymer attached on the polymerization device after polymerization can be controlled at 2% of the total mass of monomers added for the manufacture of the tetrafluoroethylene polymer % or 2% by mass or less. A more preferable upper limit is 1% by mass, and an even more preferable upper limit is 0% by mass. The amount of adhesion on the polymerization device is the amount attached to the place in the polymerization device that is in contact with the polymerization reaction field, for example, the total amount attached to the inner wall of the polymerization tank, the surface of the stirring paddle, etc. After the polymerization reaction is completed, the polymer is removed from the polymerization tank reaction medium, and then actually measure the amount of adhesion remaining in the polymerization tank, thereby obtaining the amount of adhesion.

As described above, since the amount of tetrafluoroethylene polymer adhered to the polymerization apparatus is small, the method for producing a tetrafluoroethylene polymer of the present invention can reduce the burden of cleaning, which can be said to be industrially advantageous.

The tetrafluoroethylene polymer in the present invention can achieve a specific melt viscosity of, for example, greater than or equal to 0.67 Pa·s, preferably greater than or equal to 2.0 Pa·s.

The tetrafluoroethylene polymer in the present invention can further achieve a specific melt viscosity greater than or equal to 2.3 Pa·s. It can be said that the greater the specific melt viscosity, the greater the molecular weight. Industrially, the upper limit of the specific melt viscosity can be set to 2.4 Pa·s.

The calculation method of the specific melt viscosity η is as follows. The flakes (round shape, thickness 1 centimeter) that will be made for the measurement of SSG are cut and processed to obtain strips with a thickness of 0.5 millimeters. For a small piece of L _T (cm), accurately measure the width and thickness, and calculate the cross-sectional area A _T ( ^cm2 ), and then install the metal device for installing the sample on both ends of the small piece, with an installation interval of 1 mm, using thermomechanical Analytical apparatus (TMA), at 380 ° C to the small piece of load W (grams), according to the ratio of elongation to time (dL _T /dT) (cm / sec) during the period of 60 minutes to 120 minutes of load application, based on the following Calculate by formula, obtain described specific melt viscosity η.

η=(W× _LT ×g)/[3×( _dLT /dT)× _AT ]

where g is the gravitational constant (cm/s ² ).

Compared with the tetrafluoroethylene polymer obtained by polymerization in the absence of terpene, the tetrafluoroethylene polymer in the present invention can reduce the endothermic ratio, for example, it can be less than or equal to 0.7. By setting the reaction time and the amount of terpene added to appropriate values, the endothermic ratio of the tetrafluoroethylene polymer can be further reduced, for example, less than or equal to 0.6. A more preferable upper limit is 0.3, a more preferable upper limit is 0.29, and a particularly preferable upper limit is 0.28. When the endothermic ratio is within the above range, the molecular weight distribution (MWD) is small.

The endothermic ratio is the ratio of the peak at x°C to the peak at (x-10)°C when measured with a differential scanning calorimeter (DSC) at a heating rate of 10°C/min.

Compared with the tetrafluoroethylene polymer obtained by polymerization in the absence of terpene, the tetrafluoroethylene polymer in the present invention can reduce the half width of the DSC peak, for example, 15.5°C or less. By setting the reaction time and the amount of terpene added to appropriate values, the half-width of the DSC peak of the tetrafluoroethylene polymer can be further reduced, for example, less than or equal to 6°C. A more preferable upper limit of the half width is 4.5°C, and a more preferable upper limit is 4°C. When the half width is within the above range, the molecular weight distribution (MWD) is small. If the half width is within the above range, the lower limit thereof may be, for example, 2°C.

In the DSC measurement, the temperature at which the endothermic curve reaches the maximum value (P _MAX ) is set as T _MAX , and the temperature at which both sides of T _MAX represent (1/2) P _MAX heat absorption (release) is set as T _A and T _B (where T _A >T _B ), the half-peak width refers to the value of (T _A -T _B ).

The method for producing a tetrafluoroethylene polymer of the present invention has the above configuration, so high molecular weight PTFE can be obtained.

Detailed ways

Experimental examples are given below to describe the present invention in detail, but the present invention is not limited by these experimental examples.

Experimental example 1

In a stainless steel horizontal autoclave with a volume of 3 liters and stirring, 1.77 liters of deionized water, 2.7 grams of ammonium perfluorooctanoate (10.4 mass % aqueous solution), 63 grams of paraffin (56° C. of melting point), and 0.0018 grams of isocyanate were added. Terpinene (trade name: タピノノーレン, purity greater than or equal to 90%, produced by Nippon Oil & Fat Co., Ltd.), stirring in the polymerization tank, and simultaneously exchanging with nitrogen, raising the temperature to 60 ° C, after further exhausting, using TFE gas Make an exchange. Increase the stirring rotation speed, then heat the temperature in the polymerization tank to 85°C, increase the pressure to 2.65MPa with TFE after stabilization, and put in 0.0054 g of ammonium persulfate (APS) to initiate polymerization. TFE gas was continuously supplied to keep the pressure inside the polymerization tank constant. After the start of the polymerization, the end of the reaction was reached after 100 minutes, the stirring was stopped, and the inside of the polymerization tank was cleaned. After coagulation and precipitation, a polymer solid was obtained from an aqueous dispersion with a solid content of 30.7% by mass, and the obtained polymer solid was dried at 145° C. for 18 hours to obtain a tetrafluoroethylene polymer a. The obtained tetrafluoroethylene polymer a had a standard specific gravity (SSG) of 2.171 based on ASTM D 4895, and an endothermic ratio of 0.656 measured at 10°C/min by a differential scanning calorimeter (DSC), half peak The width was 14.7° C., and the specific melt viscosity measured using a thermomechanical analyzer (TMA) was 0.99 Pa·s.

Experimental example 2

Polymerization was carried out under the same conditions as in Experimental Example 1 except that 0.0038 g of terpinolene was added to obtain a tetrafluoroethylene polymer b. Table 1 shows the evaluation results of physical properties of the obtained tetrafluoroethylene polymer b.

Experimental example 3

Polymerization was carried out under the same conditions as in Experimental Example 1 except that 0.0068 g of terpinolene was added to obtain a tetrafluoroethylene polymer c. Table 1 shows the evaluation results of physical properties of the obtained tetrafluoroethylene polymer c.

Experimental example 4

Polymerization was carried out under the same conditions as in Experimental Example 1 except that 0.0068 g of D-limonene (trade name: D-limonene, manufactured by NOF Corporation) was added instead of terpinolene. When 100 minutes had elapsed after the start of the reaction, the polymer in the dispersion was coagulated, so the polymerization was stopped. Table 1 shows the evaluation results of physical properties of the obtained tetrafluoroethylene polymer d.

Experimental example 5

Polymerization was carried out under the same conditions as in Experimental Example 1 except that 0.0068 g of α-terpinene (trade name: α-terpinene, manufactured by NOF Corporation) was added instead of terpinolene. The tetrafluoroethylene polymer e was obtained. Table 1 shows the evaluation results of the physical properties of the obtained tetrafluoroethylene polymer e.

Experimental example 6

Polymerization was carried out under the same conditions as in Experimental Example 1 except that 0.0078 g of β-pinene (trade name: β-pinene, manufactured by NOF Corporation) was added instead of terpinolene. The tetrafluoroethylene polymer f was obtained. Table 1 shows the evaluation results of the physical properties of the obtained tetrafluoroethylene polymer f.

Experimental example 7

Polymerization was carried out under the same conditions as in Experimental Example 1, except that terpinolene was not added, to obtain a tetrafluoroethylene polymer (A). Table 1 shows the evaluation results of the physical properties of the tetrafluoroethylene polymer (A).

Table 1 Terpenes Response time (minutes) Solids (mass%) SSG Heat absorption ratio Width at half peak (°C) Specific melt viscosity (Pa·s) type Relative monomer addition amount (ppm) Experimental example 1 Terpinolene 13 100 30.7 2.171 0.656 14.7 0.99 Experimental example 2 Terpinolene 27 128 30.5 2.166 0.467 5.4 0.83 Experimental example 3 Terpinolene 48 165 29.8 2.164 0.272 3.7 2.35 Experimental example 4 D-limonene 48 94 twenty four 2.172 0.98 15.8 0.67 Experimental example 5 alpha-terpinene 48 120 28 2.172 0.554 5.0 1.75 Experimental example 6 β-pinene 56 102 29.7 2.168 0.665 11.3 2.25 Experimental example 7 - - 105 31.5 2.174 0.898 16.0 0.63

As can be seen from Table 1, experimental example 1, experimental example 2 and experimental example 3 using terpineolene increase with the addition of terpineolene, endothermic ratio, half-peak width become smaller, in addition, standard specific gravity also get smaller.

Industrial availability

The production method of the tetrafluoroethylene polymer of the present invention is suitable as an industrial synthesis method of high molecular weight PTFE.

Claims (12)

1. A method for producing a tetrafluoroethylene polymer, which produces a tetrafluoroethylene polymer by monomer polymerization in the presence of a terpene, wherein the standard specific gravity ratio of the tetrafluoroethylene polymer is in the absence of a terpene The standard specific gravity of the tetrafluoroethylene polymer (A) produced by polymerization is small, and the tetrafluoroethylene polymer and the tetrafluoroethylene polymer (A) are tetrafluoroethylene homopolymer or modified polytetrafluoroethylene vinyl. 2. The method for producing a tetrafluoroethylene polymer according to claim 1, wherein the terpene is terpinene and/or β-pinene. 3. The method for producing tetrafluoroethylene polymer according to claim 1 or 2, characterized in that the terpene accounts for 1 ppm to 100 ppm of the total mass of monomers. 4. The method for producing tetrafluoroethylene polymer according to claim 1 or 2, characterized in that the polymerization is carried out at a polymerization pressure of 0.5 MPa-4 MPa. 5. The method for producing tetrafluoroethylene polymer according to claim 3, characterized in that the polymerization is carried out under the condition of polymerization pressure of 0.5MPa-4MPa. 6. The method for producing a tetrafluoroethylene polymer according to claim 1 or 2, wherein the terpene is present when the polymerization is initiated. 7. The method for producing a tetrafluoroethylene polymer according to claim 3, wherein the terpene is present when the polymerization is initiated. 8. The method for producing a tetrafluoroethylene polymer according to claim 4, wherein the terpene is present when the polymerization is initiated. 9. The method for producing tetrafluoroethylene polymer according to claim 1 or 2, characterized in that the standard specific gravity of the tetrafluoroethylene polymer is 2.163-2.173. 10. The method for producing tetrafluoroethylene polymer according to claim 3, characterized in that the standard specific gravity of the tetrafluoroethylene polymer is 2.163-2.173. 11. The method for producing tetrafluoroethylene polymer according to claim 4, characterized in that the standard specific gravity of the tetrafluoroethylene polymer is 2.163-2.173. 12. The method for producing tetrafluoroethylene polymer according to claim 6, characterized in that the standard specific gravity of the tetrafluoroethylene polymer is 2.163-2.173.