JP781H - Polytetrafluoroethylene fine powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a novel polytetrafluoroethylene huaine.
Powder (hereinafter abbreviated as "PTFE fine powder")
It ) Concerning. Conventionally, PTFE fine powder has been used for electric wire coating and fine diameter chow.
Used as a cable, large-diameter tube, seal tape, etc.
In relation to raw material PTFE fine powder and its processability
Even then, much research has already been done. For example,
PTFE fine pow suitable for wire coating or small diameter tube
Higher drawing ratio (extruder cylinder cross section and nozzle
It is possible to extrude according to the ratio of the cross-sectional area).
7-4643, JP-A-51-36291
A PTFE fiber that is almost suitable for the purpose due to the written technology such as writing
Powder is obtained. Aperture ratio for large diameter tubes
The raw material that can be extruded at low temperature is good, and the sealing tape (not
High-speed calendering process for sintered tape)
The tape may break or wavy due to the shearing force
As for the stone, PTFE fine powder which is hard to cause devitrification is used.
Be done. For this purpose, PT that can be extruded with the high drawing ratio
FE Huain powder is not suitable. Thus, the application and
A PTFE foil with properties suitable for the purpose depending on the construction conditions
Ein powder has been developed and used effectively. Recently, as a special application field of PTFE,
And some of its manufacturing methods have already been published.
However, for example, as described in Japanese Patent Publication No. 51-18991.
The invention described is a typical example, and this is PTFE.
Fine paste paste extrudate 10
Matrix drawing by stretching at a high stretching speed of at least% / sec.
Tensile strength 514kg / cm ² The method for producing the above porous body
Unsintered paste extrudate is stretched at high temperature
Highly stretched without cutting at extremely high speeds
Is based on the discovery of the extremely unique property that
It The PTFE molded product thus stretched is
It is a porous material with high strength and low apparent density.
After firing, it is used as a useful porous material. The object of the present invention is to provide a new PTFE fine impeller having excellent stretchability.
To provide wood. Also, for another purpose,
Introducing a new PTFE fine powder with high crystallinity and high molecular weight
To serve. As disclosed in Japanese Patent Publication No. 51-18991.
When stretching the unsintered PTFE paste extrudate,
It is difficult to cut, and the higher the drawing speed, the higher the
It can be stretched. Therefore, the stretching speed is
Depending on the situation, 5000% / sec to 40,000% / sec
Which high speed applies. Stretchability (stretching without cutting
The properties that can be achieved depend on the raw material PTFE fine powder.
For example, it is disclosed in Japanese Patent Publication No. 37-4643.
The modified PTFE huain powder obtained by the method
Stretchability is poor and faster stretching due to obtaining porous material
It requires a stretching step at speed and higher temperature. Note that
Generally, the raw material PTFE fine powder has high crystallinity.
The better the stretchability, the better the raw material PTFE fiber.
At a temperature above 200 ° C and below the melting point
When heat treatment is applied, the stretchability tends to improve.
It is also known to show. The PTFE huain powder according to the present invention has an average molecular weight of
5 million or more, more preferably 5.5 million or more, non-
Crystal coefficient (abbreviated as "AI" below)
Is 0.1 or less, more preferably 0.09 or less, the number average
Primary particle size of 0.10 micron to 0.40 micron, more
Preferably 0.15 to 0.38 microns, or
Differential Scanning Calorimete
r Hereinafter abbreviated as "DSC". ) To measure the melting point
Sharp endothermic peak in the range of 347 ℃ ± 2 ℃ on the crystal melting diagram
Between 330 ° C and the temperature of the endothermic peak
Does not show a clear peak or shoulder, or
Even if it is shown, the result is only a slight scale.
It is characterized by showing a crystal melting diagram. The sharpness of this peak
The presence or absence of other peaks or shoulders is determined by the endotherm described below.
It is quantitatively expressed by the ratio and the half width of the endothermic peak,
The endothermic ratio is 0.3 or less, preferably 0.27 or less.
If the half width of the peak is less than 6deg., Preferably less than 5.5deg.
is there. In the present invention, the average molecular weight depends on the specific gravity (SG) of the polymer.
It is determined by the following formula from the value of SG. 1og _Ten Mn = 28.524-9.967 × (SG) According to this formula, for example, the average molecular weight of 5,000,000 is SG2.19.
Equivalent to. In other words, in the present invention, the average molecular weight is 50
Saying that it is more than 0,000 is synonymous with being SG 2.19 or less.
Is. Similarly, having an average molecular weight of 5.5 million or more is S.
It is synonymous with G.2.185 or less. The SG of a polymer is determined by the following method. That is,
Cross-section 5g of sample powder in an atmosphere adjusted to 23-25 ° C.
Is 200 kg / cm in a mold with a diameter of 32 mm ² Pressure
Compressed by force, take it out of the mold and air at 380 ° C
Put in a furnace and bake for 30 minutes, then cool down at 70 ℃ / hr
Cooling to 300 ° C, removing from the furnace and releasing at room temperature.
Cool. SG is the same volume as the weight of this sample in air
The ratio of 23 ° C water and weight is calculated, and this value is multiplied by 0.9822,
It is a value obtained by adding 0.04864. In the present invention, the AI value is the infrared absorption spectrum of the polymer.
Wavelength 778 cm at tor ^-1 Absorbance at wavelength 236
7 cm ^-1 It is the value divided by the absorbance at. In the present invention, the melting test by DSC is performed by the following method.
Be seen. That is, 10 mg of unsintered PTFE fine powder
Precisely weighed, stored in a dedicated aluminum pan, and highly sensitive D
Using the Perkin Elmer DSC II type SC
The melting of the crystals at the melting point is measured. At this time, at the melting point
Of heat on the recording paper in proportion to the amount of heat of fusion
Is recorded. The peak of the endothermic peak due to melting appears
The temperature rise rate is 20 at least 80 ° C lower than the temperature.
Must be adjusted exactly to ° C / min. Because good
As is well known, the temperature dependence of the melting peak of PTFE crystals
The shape of the peaks and peaks are affected by the heating rate during the thermal measurement.
Because it will be echoed (If it is cold Appl.Polymer Symposia.N
o.2, pp. 101-109 (1966)). Thus measured
Of the unsintered PTFE fine powder
Read the temperature of the heat peak, and at the same time
Between other peaks and / or
Existence is measured. If two or more peaks appear
In the case of (for example, see FIG. 5), the highest peak is the endothermic peak.
It For example, FIG. 1 shows a PTFE foil obtained according to Example 2.
It shows the endothermic pattern of in powder by DSC.
This powder has a sharp endotherm at about 346 ° C (619 ° K).
It can be seen that it has a peak. Where the endothermic peak
Sharpness and presence / absence of scaler are half of endothermic ratio and endothermic peak.
It can be shown by the price range. How to obtain it is shown in Fig. 1.
Explain in, the vertical line from the peak (A),
The intersection with the line (L) is (B), and this peak
At a temperature 10 ° C lower than the temperature of 346 ° C parallel to the perpendicular line
Draw a line, the intersection with the endothermic curve (C), the baseline
When the intersection with (L) is (D), ▲ ▼ / ▲
▼ is defined as “endothermic ratio”. Also, the middle point of ▲ ▼
When drawing a parallel line with the horizontal axis in (F), the intersection with the endothermic peak
Distance of point ▲ ▼, that is, baseline of endothermic peak
The width of the peak at half the height from the
It has a unit of deg. Each of the above properties that define the PTFE fine powder of the present invention
The significance of the will be described below. The PTFE fine powder of the present invention has an average molecular weight of 50.
It is at least 0,000, and more preferably at least 5.5 million. Molecular weight
If the value of is 5 million or more, PTFE that satisfies other requirements
Fine powder gives unfavorable stretchability
It Also, AI value is 0.1 or less, more preferably 0.09 or less
Should be. Higher AI value means more imperfect PTFE crystals
, Which means that there is an AI value higher than 0.1
Indicates less stretchability. Number average less than 0.1 micron
Fine powder with a primary particle size of
Unsuitable for processing process to increase extrusion pressure during operation
And has a mean primary particle size of 0.4 microns or more.
In-powder is preferable because it lowers the extrusion pressure.
No The PTFE fine powder of the present invention is measured by DSC.
The obtained crystal melting endothermic peak is in the temperature range of 347 ± 2 ° C.
Surrounded by Conversely, if the endothermic peak does not fall within this range,
It is not the PTFE fine powder of the present invention. This endothermic pee
Generally, the higher the temperature of the polymer, the higher the temperature of the polymer.
Considering the points, the PTFE huain powder of the present invention
Belongs to the highest molecular weight class among conventional ones
Can be called a thing. In addition to the above, the PTFE film of the present invention
The endothermic peak measured by DSC of Ein powder is not
It is characterized by the fact that it is always sharp, and this sharpness makes this powder endothermic.
Ratio of 0.3 or less and half width of endothermic peak is 6deg. Or less
Will be displayed. Those without such sharpness,
Even in the range where other properties are required, good
It shows no stretchability. Such a D found in the present invention
The relationship between the SC pattern and the extrudability of the paste extrudate is very
I'm interested. FIGS. 1 to 5 show an example of a DSC measurement diagram with an example and a ratio.
The PTFE huain powder obtained in the comparative example is also shown.
Of. Endothermic peak around 340 to 450 ° C
It shows only the front and back of the, and the horizontal axis shows the temperature (° K),
The vertical axis represents the amount of heat absorbed per unit time, and the unit amount is shown in the drawing.
(Mcal / sec) is entered and the endothermic peak and
A vertical dashed line is added to the temperature 10 ° C. lower than that.
Among these, FIGS. 1 and 2 satisfy the conditions of the present invention.
It is a DSC measurement diagram regarding the powder, and the endothermic peak is one
Very sharp to look at. 3 to 5 are comparative examples 1 to 3, respectively.
3 is a DSC measurement chart of the powder of No. 3, which shows endothermic peaks.
No sharpness or below endothermic peak
Has other peaks or shoulders in the range. The PTFE fine impeller of the present invention having the above properties of the present invention
In addition to the above-mentioned stretchability, Uder is a commercially available fiber.
Extruded products such as tubes, tapes, etc.
It has excellent mechanical properties, especially when repeatedly bent.
It has a characteristic of showing high resistance to. The PTFE huain powder according to the present invention is used in an aqueous medium.
Of anionic surfactants, dispersion stabilizers and polymerization initiators
When polymerizing tetrafluoroethylene in the presence of
At least 10% by weight of the final polymer production after the start of the combination,
Preferably 25% by weight, more preferably 30% by weight
After combining, 95% by weight, preferably 80% by weight
(A) Add an alkali to the polymerization system before
Adjust the pH of the combined system to 8-10 or (b) add water to the polymerization system.
The radical scavenger is used in an amount of 2 to 5 based on the weight of the polymerization initiator used.
Add in double amount, or (c) the temperature of the polymerization system is 5 to 30 ° C.
Change the polymerization conditions by either of the following methods.
It can be manufactured by the following methods. As anionic surfactants, water-soluble fluorine-based surfactants
A sexing agent, such as the general formula X (CF ₂ ) _n COOH [where X is H or Cl
Or F, n is an integer of 6 to 12], the general formula Cl (CF ₂ CFCl) _n CF
₂ COOH [where n is an integer of 2 to 6], general formula F (CF ₂ ) _m O [CF
(X) CF ₂ O] _n CF (X) COOH [where X is F or lower perfume
Oroalkyl group, m is an integer of 1 to 5, n is an integer of 0 to 10
Number] etc. and their salts are used
The amount used is about 0.05-0.5% by weight based on the aqueous medium.
The degree is appropriate. The polymerization initiator is usually a water-soluble persulfate (for example, a persulfate).
Ammonium sulfate, potassium persulfate), water-soluble aliphatic dibasic
Carboxylic acid peroxides (eg disuccinic acid cidopa)
-Oxide, diglutaric acid peroxide)
Alternatively, a mixture of these is used. The polymerization initiator is relatively
A lower concentration has a better effect on the extrudability of the extrudate.
give. For example, in the case of ammonium persulfate, the polymerization temperature is 7
The concentration at 0 ° C is 0.002% by weight or less, more preferably
It is 0.001% by weight or less. In addition,
-In the case of oxide, under the same conditions, 0.02% by weight or less, especially
It is preferably 0.01% by weight or less. Specific examples of the dispersion stabilizer include polymerized products having 12 or more carbon atoms.
It is preferable to use a hydrocarbon that is liquid under the conditions. All of the above compounds are conventional tetrafluoroethylene.
It is used for the polymerization of benzene and is easily available. The polymerization of the present invention is carried out at a relatively high temperature, for example, about 55 to 85 ° C,
More preferably, it is performed within a temperature range of about 60 to 80 ° C.
And are appropriate. If the polymerization temperature is too high,
The decomposition rate of the initiator is too high, and the amount of the solvent is small.
Not suitable for the method. Also, if the polymerization temperature is too low, reverse
In addition, the decomposition rate of the polymerization initiator was too low and a sufficient polymerization rate was not obtained.
I can't. The polymerization pressure is 5 to 20 kg / cm ² Lines in the range
It is possible, but preferably 5-10kg / cm ² Carried out in
To do. The change of the polymerization conditions after the start of the polymerization can be done in any of the above three cases.
It is done by some method. Either of these methods
Therefore, if the polymerization conditions are not changed, the obtained PTFE
The molecular weight is too low, or the absorption of crystal melting in DSC analysis.
The tape that is the object of the present invention has a heat peak that is too broad.
No PTFE fine powder with excellent stretchability can be obtained.
These three methods will be further described below. The first method of changing the polymerization conditions is the addition of alkali.
It The types of alkali added are ammonium hydroxide and caustic.
Suitable is soda, caustic potash, etc.
It is convenient to use it as an aqueous solution. How much alkali is added
The amount necessary to keep the polymerization system after addition on the alkaline side,
Especially the amount necessary to keep the pH of the system within the range of 8-10
To use. Therefore, the actual addition amount depends on the pH of the system at the time of addition and
Type and amount of polymerization initiator used, presence / absence of buffering agent, etc.
Should be determined by
The amount of addition can be easily determined by preliminary experiments.
It For example, as a polymerization initiator, ammonium persulfate or persulfate is used.
When using persulfate such as potassium sulfate, the pH of the polymerization system is
Before the start of polymerization, those that have a range of about 6 to 7 are after the start of polymerization.
Although it rapidly decreases to about 3 to 4, the method of the present invention
Addition of alkali changes this pH value to 8-10
It The addition of alkali is generally higher than when it is not added.
Decrease the polymerization rate.
Polymerization speed due to decrease in the middle of polymerization and addition of radical scavenger
It is slow compared to the decrease in degree. That is, after adding alkali
The pH in the polymerization tank rises sharply to reach 8-10.
However, the polymerization rate gradually decreases. The second method of changing the polymerization conditions is to add a radical scavenger in water.
Is. The compounds used as radical scavengers in water are
Ammon thiocyanate (NH _Four SCN), potassium thiocyanate (KSC
N), sodium thiocyanate (NaSCN), cupric chloride (CuCl ₂ )etc
Is. If the amount added is excessive, the stability of the dispersion system will be reduced.
The PTFE fine powder which is the object of the present invention is damaged.
In order to obtain
Five times the amount is suitable. The timing of changing the polymerization conditions by the above two methods depends on the final weight.
At least 10% by weight of coalescence, more preferably 3
90% by weight after 0% by weight of polymer is formed
%, More preferably 80% by weight of polymer before formation
Should be. Emulsion polymerization of TFE is mainly the first to form particle nuclei.
Two stages, a second stage where particle growth occurs
It is known that polymerization proceeds in stages. Obey
Polymerization at the beginning of the polymerization period, which is the nucleation stage
Changing the conditions is not preferable because it increases the instability of the system.
Also, if the polymerization conditions are changed after 90% by weight, the purpose is
No physical properties of PTFE fine powder can be obtained. Another method of changing the polymerization conditions is to lower the temperature of the polymerization system.
Method and the temperature to be lowered is 5 ° C or higher, preferably
Is required to be lowered by 10 ° C. or less. Actually temperature
Automatic to control the temperature of the whole tank to reduce
What to do by changing the set temperature of the temperature controller
Can be done. At this time, even if the temperature of the controller is changed,
After that, the temperature is not changed in the tank and there is a time delay.
Is maintained at the second temperature before 90% of final polymer production.
It can be adjusted so that it sags, but temperature adjustment is difficult.
This is not a proper operation. If the polymerization temperature is changed within 5 ° C,
We cannot obtain PTFE huain powder with the desired physical properties.
Yes. Also, changing the temperature above 30 ° C will make the system unstable and
It is not preferable because the powder may coagulate. Polymerization in emulsion polymerization of tetrafluoroethylene in general
The rate is such that the half-life of the polymerization initiator is relatively long.
At a constant temperature and with a relatively low concentration of initiator.
When polymerizing under constant monomer pressure,
Increase. This is a radical generated by decomposition of the initiator
Polymer formed by the reaction of ethylene with tetrafluoroethylene
-Radical deactivation is the entire polymerization period during which particles are formed
Is relatively hard to occur through the
Radicals and tetrafluoro generated in water by decomposition of
Absorbs polymer radicals generated by reaction with ethylene
Therefore, the number of radicals in the entire system
It is thought that this is due to the result of increasing to. On the other hand, the decomposition rate of the initiator reveals the effects of system pH and temperature.
As the pH of the system is lower and the temperature is higher, the decomposition rate is higher.
It becomes big. Emulsion polymerization of tetrafluoroethylene
Using the above-mentioned polymerization initiator at a constant temperature and a constant monomer pressure.
If the polymerization proceeds under force, do not add any pH regulator.
The pH of the system will gradually decrease and the decomposition rate of the initiator will increase.
Shows the tendency to As a result, tetrafluoroethylene
Make the overall polymerization rate even more accelerated. Addition of alkali and / or polymerization temperature during polymerization
Decrease reduces the decomposition rate of undecomposed initiator remaining in the system.
Lower the number of polymer radicals that are generated sequentially.
Control effect and, as a result, the polymerization rate depends on these polymerization conditions.
Will be smaller than if no changes were made. Thiocyanic acid
Ammon, potassium thiocyanate, sodium thiocyanate, salt
Cupric chloride acts as an aqueous phase radical scavenger,
Radicals generated after that are trapped by the addition of
As a result of deactivation, the polymerization rate decreases. Such a boom
The scavenger also results in the sequential generation of polymer radicals.
It can be said that it has a suppressing effect. The PTFE fine powder of the present invention thus obtained has a high
It has a high molecular weight and high crystallinity, and it is
Since new radicals generated are suppressed, the
It seems that PTFE with a narrow cloth can be obtained. For DSC measurement
Crystalline fusion of the PTFE fine powder of the present invention thus obtained
The solution implies a narrow molecular weight distribution. The PTFE huain powder of the present invention is a seed after being manufactured by the pider.
Post-treatment, eg heat treatment at 300 ° C or below,
Kneading as disclosed in JP-A-46-4657, or
Can be pickled. According to such processing,
The crystal melting diagram hardly changes, but the stretchability is generally improved.
To be done. The PTFE fine powder of the present invention is a short glass fiber, a car
Including bon powder, graphite powder, inorganic pigment powder, etc.
be able to. PTFE fine powder with such filler
Is the coagulation process of the dispersion sponge obtained by polymerization.
It is desirable to mix them in a certain amount. The powder thus obtained
The powder also shows good stretchability. Next, the present invention will be described with reference to examples. Concentration in the examples
"%" In the case of expressing the polymerization ratio is the weight unless otherwise specified.
%. The extrusion test and the stretching test were conducted as follows. Extrusion test: -Extrusion aid (trademark) on 100 parts by weight of PTFE fine powder
"Isopar E") 20 parts by weight at room temperature according to a conventional method.
And store in a closed container for 12 to 24 hours.
Cylinder with inner diameter 25.4mm, die angle 30 degrees, nozzle diameter
Chamber using an extrusion mold with 2.54 mm and nozzle length 7 mm
Extrude string at a ram speed of 20 mm / min at high temperature
You Record the equilibrium extrusion pressure in this extrusion test.
It The string is then dried. Stretching test: -Stretching test is from the extruded string obtained in the extrusion test.
Check the cut sample at a temperature of 310 ° C.
100% / sec. And 1000% / sec. At a distance of 50 mm
20 times the original length at a pulling speed of 10,000% / sec.
Stretch. What can be drawn 20 times at 100% / sec.
Can be cut in the middle of stretching under the other two conditions
Therefore, it is determined that the film has the highest stretchability.
Also, in the stretching test of 10,000% / sec.
In the sample to be cut, the cutting will occur even under the other two stretching conditions.
Therefore, the stretchability is judged to be the lowest. Example 1 Auto with a stirrer and glass lining with a volume of 3 liters
Deionized deoxygenated water (1.5 liters) and paraffin resin in a clave
Tux (mp 56 ° C) 60g, perfluorooctanoic acid
Charge 2g of ammonium and keep at 70 ℃
After replacement with nitrogen gas several times, tetrafluoroethylene
(Hereinafter abbreviated as "TFE") internal pressure 8.0kg / cm ² G and
I pressed it in until. Then ammonium persulfate (hereinafter
Abbreviated as "APS". ) Add 5 mg to start the polymerization
It When the polymerization starts, the pressure in the system begins to decrease and the pressure
7.0 kg / cm ² When the pressure decreases to G, the TFE pressure in the system
8.0 kg / cm ² Pressurize and pressurize until it reaches G, and then proceed with polymerization.
Repeat pressure drop-re-pressurization in the same way for 5 hours 1
The polymerization is stopped after 0 minutes. In the middle of this polymerization, start the polymerization
Ammonia water (concentration 28
%) 0.8 ml was added to the system, before adding ammonia
The apparent polymerization rate, which had been increasing, was slightly decreased.
A tendency to decrease was recognized. In addition, this ammonia water addition
For the pH in the system at that time, 4.1
After the addition of ammonia water, the pH became 10, and the polymerization was terminated.
It kept at about 10 with almost no decrease until the end. Also this
Polymer production by adding ammonia water by sampling
It was confirmed that the amount of product was 51% of the final amount of product.
In this way, the polymerization was stopped after 5 hours and 10 minutes. Full weight
The average polymerization rate throughout the mixing period was 47 g / l.hr.
The PTFE dispersion thus obtained had a concentration of 20.9% and an average particle size.
It had 0.29 micron. Coagulate and wash this dispersion
Perform, dry at 120 ° C for 16 hours, and use PTFE fine powder
Got a dah. The SG of this powder is 2.177 and the molecular weight is 674.
The AI value obtained from the infrared absorption spectrum is
It was 0.089. Also, in the DSC analysis of this powder
A melting diagram near the melting point is shown in FIG. This figure shows 347 ℃
It has a sharp peak and a slight scaler is recognized at 337 ° C.
The endothermic ratio is 0.21, half-value of the endothermic peak
The width is 4.3 deg. 50 g of this powder was added with 10 g of extrusion aid (Isopar E).
Mix well and store in a closed container for 15 hours, then ram inner diameter 2
5.4 mm, die angle 30 degrees, inner diameter 2.54 mm, length 7 mm run
Push at a ram speed of 20 mm / min using a mold
I went out. Extrusion pressure at equilibrium is 182 kg / cm ² And
Ivy. After the extruded string was dried, it was stretched at 310 ° C.
When a test is conducted, it is 20 times at a pulling speed of 100% / sec.
The appearance of the drawn product is uniform.
It was Examples 2-4 Using the same equipment as used in Example 1, the polymerization temperature was 7
65 ° C instead of 0 ° C and addition of ammonia water
Example 1 was repeated except that the time was as shown in Table 1.
Polymerization was carried out according to the procedure. The obtained PTFE aqueous dispersion and
The properties of the powder and powder are shown in Table 2. In addition, the powder of Example 2
The crystal melting pattern by DSC is shown in FIG. Example 3
About 4 and 4, it was almost the same as that of FIG. Example 5 In Example 1, persulfuric acid was used instead of APS as the polymerization initiator.
Same procedure as in Example 1 except that 6 mg of potassium was used.
Emulsion polymerization of TFE was carried out. Weight of the obtained PTFE dispersion
The coalescence concentration was 20.3%. Obtained PTFE Huain Pau
The properties of the dough are shown in Table 2. Comparative Example 1 Polymerization was started by using the same apparatus as in Example 1 and the same operation.
At 6 o'clock without adding ammonia water on the way
Polymerization was carried out. Polymerization rate gradually increases throughout the period
However, the average polymerization rate was 4
It was 3 g / l · hr. Also, the pH of the system is set at the end of the polymerization.
It was 3.2. The obtained PTFE aqueous dispersion had an average particle size of 0.274 microns.
And the concentration was 18.7%. Coagulate, wash and dry
The properties of the soup powder are shown in Table 2. This powder DSC
Figure 3 shows the melting endotherm obtained by the method shown in Fig. 3.
And has a clear shoulder at 337 ° C.
It The paste extrusion pressure of the powder obtained here is 181 kg.
/cm ² For stretching test of extruded string at 310 ℃
At 100% / sec. And 1000% / sec.
At a stretch of 20 times, cut halfway and cut off at 10,000% / sec.
20 times stretching at a speed causes numerous uneven cracks on the outer surface
There has occurred. Comparative Example 2 Using the same polymerization apparatus as in Example 1, ammonia was added during the polymerization.
Instead of adding
Natsuta. In other words, 77% of the total TFE is
The pressure of TFE is 8kg / cm during the matching period. ² G to 7 kg /
cm ² Polymerization is carried out by keeping at G, then 4 kg / cm ² G to 3
kg / cm ² The polymerization was continued under the pressure of G until the polymerization was completed. Other
The conditions are the same as in Example 1. The total polymerization time was 5 hours and 18 minutes,
After squeezing, the polymerization rate decreased, but the average polymerization rate
Was 52 g / l · hr. The concentration of the obtained PTFE aqueous dispersion was 21.2%.
The properties of the powder obtained by coagulation, washing and drying are shown in Table 2.
Exactly. Also, the melting diagram of this powder by DSC
The shape is as shown in Fig. 4, which has a peak at 346 ° C, and
A clear broad shoulder was observed near 338 ° C.
The extrusion pressure for paste extrusion of this powder is 181 kg / cm.
² In the stretching test of the extruded string, 1000
20% stretched at 0% / sec., Ununiform appearance, unsatisfactory
It was a porous body. Comparative Example 3 Using the same polymerization apparatus as in Example 1, polymerization was carried out at 90 ° C.
It was Deionized water, paraffin wax, and
-Ammonium chlorooctanoate and polymerization initiator dicohaku
100 mg of acid peroxide (hereinafter abbreviated as “DSP”)
After charging and replacing with nitrogen gas, TFE internal pressure is 8kg / cm ² G and
Press it in until it stirs and stir it. 1 hour after adding DSP
Afterwards 10 mg of APS are added. Actual when APS is added
Polymerization starts qualitatively and a pressure drop is observed. Internal pressure is 7
kg / cm ² When it reaches G, TFE is 8 kg / cm ² Pressure until G
After that, repeat the operation of pressure drop-repressurization to repeat the polymerization.
Proceed. The concentration of the PTFE dispersion after the polymerization was 25%,
The properties of the powder obtained by coagulating, washing and drying are the second
As shown in the table. Crystal melting of this powder by DSC
The solution pattern is as shown in Fig. 5, with a peak at 342 ° C.
Further, it has another peak near 332 ° C. pace
Extrusion pressure during extrusion is 143 kg / cm ² And is extruded
The string is cut off at a stretch rate of 20 times at 10,000% / sec.
I refused. Example 6 A pressure-resistant glass polymerization tank of 1.5 liters was used, and the polymerization temperature was 70 ° C.
TFE emulsion polymerization was carried out. Deionized water, paraffin
Nwax and ammonia perfluorooctanoate
Used half the amount of Example 1, but used 5 mg of APS
It was The pressure of TFE is 8 kg / cm as in the first embodiment. ² G
~ 7kg / cm ² Maintained at G. When 54% of total yield polymerized
Ammonium thiocyanate (NH _Four SCN) 20mg added
It was After the addition, the polymerization rate tended to decrease. At full polymerization
5 hours 17 minutes, the average polymerization rate is 48 g / l · hr.
It was The concentration of PTFE dispersion is 20%, powder obtained from this
Has an average particle size of 0.236 microns, SG of 2.186, and molecular weight of
It was 5.37 million and the AI was 0.073. Heat of fusion by DSC
The shape is almost the same as in Fig. 2 and has a sharp peak at 347 ° C.
However, it does not have a shoulder at low temperature,
The full width at half maximum was 4.2 deg. And the endothermic ratio was 0.2. This powder
Paste extrusion pressure is 145kg / cm ² And is extruded
The string can be stretched 20 times at 100% / sec.
The drawn product has a uniform appearance and is a satisfactory porous material.
It was Example 7 Instead of ammonium thiocyanate in Example 6, thiocyanate was used.
Using 20 mg of potassium cyanate, the polymerization of Example 6 was carried out.
Repeated. As a result, the concentration of the final polymer dispersion was 19.6.
%, The average particle size of the powder obtained from this is 0.250 Miku
Ron, SG is 2.185, molecular weight is 5.6 × 10 ⁶ , AI value is 0.075
The melting point by DSC is 347 ° C, the endothermic ratio is 0.19,
The full width at half maximum of the thermal peak was 4.2 deg. This powder page
Extrusion pressure in strike extrusion test is 142kg / cm ² Then press
The drawn string is stretched at 20% at 100% / sec.
It was able to be stretched twice and a satisfactory porous body was obtained. Comparative Example 4 In Example 6, the amount of APS used as the polymerization initiator was changed to 2
The procedure of Example 6 was repeated except that the amount was 5 mg (0.0033%).
Repeated. As a result, the final polymer dispersion had a concentration of 24.5.
%, The average particle size of the powder obtained from this is 0.21 micro
, SG is 2.200, molecular weight is 3.90 × 10 ⁶ , AI value is 0.101
And the melting point by DSC was 347 ° C.
The ratio was 0.4, and the half width of the endothermic peak was 5 deg. This
The extrusion pressure of the paste extrusion test of the powder is 150kg
/cm ² The extruded string is 100% / se in the stretching test.
When stretched in c., it was cut in the middle. Example 8 In the operation of Comparative Example 1, the system temperature was set to 70 ° C.
It started to work. The amount of polymer produced is 60 to 6 of the final amount produced.
When the temperature reaches 5%, the system temperature is lowered from 70 ℃ to 60 ℃.
The subsequent polymerization was continued at 60 ° C. until the end. Polymer
The polymerization rate when the production of 70% reached 70%
At the same amount produced when polymerization is continued while maintaining
It was confirmed to be about 15% lower than the polymerization rate. Got
The PTFE dispersion has a concentration of 18.5% and the average of the powder obtained from this.
Particle size is 0.29 micron, SG is 2.175, molecular weight is 7.00 x 1
0 ⁶ , AI value was 0.086. Melting endotherm by DSC
Has a peak at 347 ° C and the endothermic ratio is 0.17,
The full width at half maximum of the heat peak was 4 deg. The pace of this powder
Extrusion pressure is 190kg / cm ² And the extruded string is 10
It could be stretched at 0% / sec.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, FIG. 2, FIG. 3, FIG. 4 and FIG. 5 are obtained in Example 2, Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3, respectively. Fig. 3 shows a melting measurement diagram of the PTFE fine powder obtained by differential scanning calorimetry.

Claims (1)

[Correction specification] [Claims] [Claim 1] An average molecular weight of 5,000,000 or more and an amorphous coefficient of 0.
1 or less, the number average primary particle size is 0.1 to 0.4 micron, has a sharp endothermic peak in the range of 347 ± 2 ° C on the crystal melting diagram by a differential scanning calorimeter, and is between 330 ° C and the temperature of the endothermic peak. Is a polytetrafluoroethylene fine powder, which does not show a clear peak or scaler, has an endothermic ratio of 0.3 or less based on the crystal melting diagram, and has a half-value width of the endothermic peak of 6 deg. Or less. 2. The polytetrafluoroethylene fine powder according to claim 1, which has an average molecular weight of 5.5 million or more. 3. A polytetrafluoroethylene fine powder according to claim 1, which has an amorphous coefficient of 0.09 or less and a number average primary particle diameter of 0.15 to 0.38 micron.