JP2003236908A - Ptfe sheetlike molded object and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel melt molding method capable of continuously performing a process from supply of a raw material to molding and inexpensively manufacturing a PTFE sheetlike molded object having a groove shape of screw of an extruder and not present heretofore as a PTFE molding processing method. <P>SOLUTION: The PTFE sheetlike molded object is manufactured by softening or melting unmodified polytetrafluoroethylene and/or modified polyterafluoroethylene using a cylinder having a screw. In this manufacturing method, unmodified polytetrafluoroethylene and/or modified polytetrafluoroethylene is a granulated non-gelled article, a non-granulated gelled ground article and/or a non-granulated non-gelled article, and the PTFE sheetlike molded object has the groove shape of the screw. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a PTFE sheet-shaped molded product, and more particularly to a method for manufacturing a PTFE sheet-shaped molded product having a screw groove shape using a screw extruder, and the above-mentioned method. The present invention relates to a PTFE sheet-shaped molded product manufactured by a manufacturing method.

[0002]

2. Description of the Related Art Polytetrafluoroethylene [PTF
E] has a highly symmetrical molecular structure, and therefore has excellent properties such as heat resistance, chemical resistance, weather resistance, electrical insulation, and non-adhesiveness among the fluororesins, and thus has a wide range of applications. is there.

PTFE is a thermoplastic resin, but since it has a very high molecular weight and a long main chain, it has a very high melt viscosity due to strong entanglement of the molecular chains and the like, so that it generally has a lower melt viscosity. It has been said that it is not possible to apply the usual plastic molding processing methods used for the thermoplastic resin of (1), such as general extrusion molding and injection molding.

Therefore, as the molding method of PTFE, in addition to compression molding, extrusion molding by a ram extrusion molding method or a paste extrusion molding method is applied instead of the usual plastic molding processing method, and skiving is performed on the molded body. The method of performing the secondary processing as described above is used.

In the ram extrusion molding method, a resin powder intermittently supplied (charged) from one end is press-fitted using a piston (ram) for each charge in the cylinder, and the individual press-fitted bodies are lowered to the front. The molded body is continuously extruded from the other end of the cylinder after being joined to the press-fitted body for the charge and fused by firing to form a continuous body.

However, the ram extrusion molding method is an application of batch molding, and continuous molding in which the raw materials are continuously supplied to the molding without performing batch processing is impossible due to the process method.

[0007] In the ram extrusion molding method, the physical properties are likely to become discontinuous at the interface where the press-fitting bodies of the respective charges are joined. This discontinuity causes a bridge caused by fusion of the resin powder at the high temperature charging port. It is exacerbated by the gelling agents normally used to prevent it. The discontinuity of physical properties causes problems such as reduction in mechanical strength of the obtained molded product and difficulty in performance control.

In the ram extrusion molding method, the heating means is further limited to the heat conduction from the outer wall of the cylinder, and it takes a lot of time to completely burn the thicker material to the center. There is a problem that it is difficult to improve the sex.

In order to shorten the firing time in the ram extrusion molding method, it is conceivable to lengthen the heating portion of the cylinder, but the frictional force between the material and the inner wall surface of the cylinder depends on the length of the cylinder tube wall and the set temperature. Since this frictional force affects the reaction force (back pressure) when the piston is press-fitted, the length of the cylinder is limited, and it is still difficult to improve productivity in the ram extrusion molding method.

In the paste extrusion molding method, in order to impart fluidity, an extrusion aid such as an organic solvent is added to PTFE fine powder to preform the paste mixture into a cylindrical shape, and the resulting billet is extruded. In a cylinder, and is extruded from a die while pressurizing with a ram to cause plastic deformation of particles, and a preform having a predetermined shape is heated or extracted to remove the extrusion aid, and then sintered.

However, according to the paste extrusion molding method, continuous molding from the process method to the raw material supply to the molding is impossible. In the paste extrusion molding method, the fine powder to be used is obtained by emulsion polymerization, and the price is higher than that of the molding powder obtained by suspension polymerization used in the ram extrusion molding method, and the physical properties are low. is there.

[0012] In the paste extrusion molding method, PTFE is further used.
Since a large amount of an extrusion aid of about 20% by weight is added, the obtained molded product is liable to cause problems such as contamination and internal defects, and even though it is completely removed in the subsequent step, There is also a problem that it is uneconomical in that a large amount of extrusion aid is added.

In the paste extrusion molding method, it is necessary to leave the mixture of the extrusion aid and the fine powder for about 1 day to adjust the mixture to each other, and it is necessary to leave it for the purpose of increasing only one batch. Since the preformed body is produced in a shape that does not necessarily match the conventional molded body, there is a problem that production efficiency is poor.

The skiving process is usually carried out by attaching a molded body prepared in advance by a usual method such as compression molding into a shape such as a thick pipe and then firing it, while rotating the molded body in the manner of stripping the radish wig. The thin film is cut from the side surface to obtain a sheet or film.

However, in skiving, since both the forming process and the cutting process of the molded body are batch type, PT
It is theoretically impossible to continuously perform from the raw material such as the powder of FE until the sheet or film is obtained. In the skiving, the sheet length and the film length are limited by the size of the molded body, and these lengths cannot be made arbitrary.

In the skiving process, the production of the compact and the cutting must be performed as separate steps, and in some cases, additional steps such as annealing of the compact and preliminary cutting are required.
Poor industrial productivity, because multiple steps are required and the lowering of the molded body due to its own weight may cause deformation of the lower part of the molded body due to the decrease in viscosity when firing the molded body, resulting in changes in waste and physical properties during cutting. There is a problem.

In the skiving process, when the molded body is heated and cooled, the crystallinity and the shrinkage amount are varied due to the difference in heat conduction in the molded body which is usually a thick product. As a result, the obtained sheet or film is wavy. In addition, since the molded body has a large residual strain because it has not undergone a process of completely heat-melting and uniformly mixing, the sheet or film obtained by cutting may be gradually deformed and the dimensions may change.
There is a problem of poor shape stability.

Of the ordinary plastic molding methods used for general thermoplastic resins, general extrusion molding often uses a screw extruder. In this case,
Usually, a raw material such as resin pellets supplied from a hopper is heated and melted in a cylinder containing a screw, and is extruded by a die at the tip of the cylinder so as to have a desired shape such as a tube and molded.

In general extrusion molding, the screw has a groove such as a spiral on the surface, and by rotating this, the resin is kneaded and fed to the tip of the cylinder. It is carried out by a die, shaping or processing in a subsequent step.

[0020]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to enable continuous feeding from raw material to molding and to provide a screw having a groove shape of an extruder extruder.
It is an object of the present invention to provide a novel method for melt-molding a TFE sheet-like molded article at a low cost, which has never existed as a PTFE molding method in the past.

[0021]

According to the present invention, a cylinder having a screw is used to soften or melt unmodified polytetrafluoroethylene [unmodified PTFE] and / or modified polytetrafluoroethylene [modified PTFE].
A method for producing a PTFE sheet-shaped molded product for producing a TFE sheet-shaped molded product, comprising:
Alternatively, the modified PTFE is a granulated non-gelled product, a non-granulated gelled pulverized product and / or a non-granulated non-gelled product.
The FE sheet-shaped molded product is a method for manufacturing a PTFE sheet-shaped molded product, which has the shape of the groove of the screw.

The above-mentioned PTFE sheet-shaped molded product is preferably obtained by open extrusion. The screw is preferably a full flight screw.

The non-modified PTFE and / or the modified P
TFE preferably has an apparent density of 0.2 to 1 g / cm ³ . The non-modified PTFE and / or the modified PTFE has an apparent density of 0.3 to 1 g / cm ³ and a heat of fusion of 20 to 40 J / g, and an apparent density of 0.3 to 1 g / cm. ³ and one having a melting peak at 320 to 330 ° C., or an apparent density of 0.3 to 1 g / cm ³ and a heat of fusion of 30 to 60 J / g, and Melting peak is 320 ~
Two at 350 ° C. are preferred. Non-modified PTF
E and / or the modified PTFE may contain a colorant, an additive and / or a filler.

The above unmodified PTFE and / or the above modified P
TFE has an apparent density of 0.2 to 1 g / cm ³ ,
And a heat of fusion of 50 to 70 J / g, or
Those having an apparent density of 0.2 to 1 g / cm ³ and one melting peak at 340 to 350 ° C. are preferable.
The present invention will be described in detail below.

The method for producing a PTFE sheet-shaped molded product according to the present invention is for producing a PTFE sheet-shaped molded product by using a cylinder having a screw.
The FE sheet-shaped molded product is characterized by having the shape of the groove of the screw.

In the present specification, the "PTFE sheet-shaped molded product" means polytetrafluoroethylene [PTF
It means a product obtained by softening or melting E] and molding it into a sheet. In the present specification, the "sheet-like" is not particularly limited as long as it is derived from the shape of the groove of the screw as described later, and not only the shape generally used as a sheet, but also ribbon-like or strip-like. It includes various flat or thin shapes such as shape, film, T-shape, C-shape, E-shape, etc., and other shapes such as flat shape or spiral shape, winding, etc. It is a concept that includes those held by, and that has been subjected to shaping, size regulation, stretching, etc. by a roll, a sizing die, etc. after coming out of the cylinder.

In the present specification, "softening" means PTF.
It means a state of exhibiting softness below the so-called melting point of E. In the present specification, "melting" is a state of PTFE at a temperature equal to or higher than the so-called melting point of PTFE and lower than the decomposition temperature of PTFE. In the present specification, the melting point refers to a value measured by a differential scanning calorimeter (DSC-50, manufactured by Shimadzu Corporation). Melting can also be said to be in a molten state.

In general, a screw has a convex portion 2 called a flight as shown in FIG.
It is formed by spirally winding the surface of.
The concave portion 3 between the convex portion 2a and the convex portion 2b becomes a spiral groove and exists on the screw surface. In the present specification, the “groove of the screw” means a groove which is a recess between such flights.

The screw is, as described later, the PT
The point that the FE sheet-shaped molded body has the groove shape of the screw, and the PTFE sheet-shaped molded body having the groove shape of the screw is transferred to the cylinder tip portion along the flight. From the point of view, it is particularly preferable to use a full flight screw which does not have a complicated uneven shape such as a mixing mechanism on the surface particularly at the screw tip.

As shown in FIG. 1, the cylinder is a cylinder-shaped part that includes the screw 1 at a position closest to the screw 1 and has at least one end opened, and is a part 4 of the molding machine. Although the cylinder is not particularly limited, there is a cylinder having irregularities such as a helical groove on the inner wall, but in the present invention, a PTFE sheet-shaped molded product having a groove shape of the above-mentioned screw which has surface smoothness. From the viewpoint of obtaining the above, it is particularly preferable that the tip of the cylinder has an inner wall having a smooth curved surface without undercut such as a special uneven shape.

In the present specification, the "shape of the groove of the screw" means the shape of the space formed by the bottom of the groove of the screw, the flights at both ends of the groove of the screw and the inner wall of the cylinder. Means
The shape of the groove of such a screw is, for example, as shown in a schematic sectional view in FIG. 2, a bottom portion 24 of the groove of the screw 21, a flight 22 at one end of the groove of the screw, and a flight 23 at the other end. , And the shape of the space 27 formed by being surrounded by the inner wall 26 of the cylinder 25.

The shape of the groove of the screw is not limited to the one in which the cross section parallel to the axial direction of the screw is a rectangle such as the space 27 in FIG. 2, but is semicircular, trapezoidal, inverted triangular, T-shaped, The shape does not matter, such as the downward E-shape.
These various shapes preferably depend on the bottom of the groove of the screw rather than the inner wall of the cylinder.

In the present specification, "having the shape of the groove of the screw" means that PTFE enters the space forming the shape of the groove of the screw and the shape is formed depending on this space. Means that.

In this case, the shape of the groove of the screw may be the shape of the space itself, or the shape of the space having a corner. The corner of the shape of the space is not particularly limited, and examples thereof include a corner formed by the flight and the bottom of the groove of the screw, and a corner formed by the flight and the inner wall of the cylinder. Such a corner-like shape is caused by the fact that the softened or melted PTFE does not enter all the corners, or contracts during cooling.

PTF having the above-mentioned screw groove shape
E, when present on the surface of the screw, may have softness due to heat, but retains the shape of the groove of the screw to the extent that there is almost no fluidity, and Depending on the width, it is usually a spiral ribbon-like shape. Such PTFE is transferred to the cylinder tip portion along the flight by the rotation of the screw while maintaining the shape of the groove of the screw, and is extruded from the cylinder tip portion. In the present specification, the “cylinder tip portion” means the end of the cylinder on the side of the metering portion of the screw that is far from the feed portion of the raw material PTFE.

PTF having the above-mentioned screw groove shape
After being extruded from the tip portion of the cylinder E, the shape of the groove of the screw, such as a spiral ribbon-like shape, may be maintained, or the spiral may be untwisted to be flat. Alternatively, it may be shaped, dimensionally regulated, or stretched as described below.

As is apparent from the above-mentioned characteristics of the PTFE sheet-shaped molded product, as long as necessary conditions such as continuous supply of raw material and continuous operation of the molding machine are satisfied, the raw material is supplied. It is theoretically possible to carry out the molding continuously.

Therefore, the above PTFE sheet-shaped molded product is
It can be obtained as having no discontinuity in physical properties. In the present specification, "there is no discontinuity in physical properties" means that the physical properties do not suddenly differ between adjacent parts in any part of the PTFE sheet-shaped molded product. Therefore, the above-mentioned PTFE sheet-shaped molded product has the same physical properties or continuously changes in any part.

The method for producing a PTFE sheet shaped article of the present invention is for producing a PTFE sheet shaped article by softening or melting PTFE. In this specification,
"PTFE" means non-modified PTFE and / or modified PT
It means FE.

The above-mentioned PTFE sheet-shaped molded product may be one in which only non-modified PTFE is used as a raw material, or one in which only modified PTFE is used,
A non-modified PTFE and a modified PTFE may be used, or in addition to these, a mixture containing another thermoplastic resin, an additive and the like may be used as described later.

In the present specification, the above-mentioned "modified PTFE"
Means tetrafluoroethylene [TF
E] and a small amount of other comonomer, and means a copolymer obtained by copolymerization. In the present specification, the “non-modified PTFE” means a homopolymer of TFE obtained by polymerizing without containing the other comonomer as a monomer component.

The above-mentioned other comonomer is not particularly limited as long as it can be copolymerized with TFE.
Perfluoroolefins such as hexafluoropropene [HFP]; chlorotrifluoroethylene [CTFE];
Trifluoroethylene; perfluorovinyl ether and the like can be mentioned.

The above-mentioned perfluorovinyl ether is not particularly limited and is represented by, for example, the following general formula (I) CF ₂ ═CF—ORf (I) (wherein Rf represents a perfluoroaliphatic hydrocarbon group). The perfluoro unsaturated compound etc. which are mentioned are mentioned. In the present specification, the “perfluoroaliphatic hydrocarbon group” means an aliphatic hydrocarbon group in which all hydrogen atoms bonded to carbon atoms are replaced with fluorine atoms. The perfluoroaliphatic hydrocarbon group may have ether oxygen.

The perfluorovinyl ether is, for example, a perfluoro (alkyl vinyl ether) in which Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms in the general formula (I). PFVE].

Examples of the perfluoroalkyl group in the above PFVE include a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group and a perfluorohexyl group. Perfluoropropyl groups are preferred.

Examples of the perfluorovinyl ether include perfluoro (alkoxyalkyl vinyl ether) in which Rf in the general formula (I) is a perfluoro (alkoxyalkyl) group. In this case, the perfluoroalkoxyl group in Rf is
The carbon chain may be a linear or branched chain carbon chain, or may have a cyclic ether structure having 1 to 3 oxygen atoms. Such Rf
Is not particularly limited, and includes, for example, a perfluoro (alkoxyalkyl) group having 4 to 9 carbon atoms and the following general formula:

[0047]

[Chemical 1]

(In the formula, m represents 0 or an integer of 1 to 4) or an organic group represented by the following general formula:

[0049]

[Chemical 2]

(In the formula, n represents an integer of 1 to 4) and the like.

The ratio (% by weight) of the above-mentioned other comonomer to the entire monomer components depends on the kind, but is preferably 2% by weight or less, more preferably 0.01 to 1% by weight.

The above-mentioned non-modified PTFE and the above-mentioned modified PTFE
It is preferable that the number average molecular weight is 2,000,000 to 20,000,000. When the number average molecular weight is within the above range,
According to the method for producing a PTFE sheet-shaped molded product of the present invention, PTF
The E sheet-shaped molded product can be molded, and the obtained PTFE sheet-shaped molded product has good physical properties such as mechanical strength. Preferably, it is 4 to 10 million.

As the above-mentioned modified PTFE, for example, one kind or two or more kinds having different average molecular weights, copolymer compositions and the like may be used, and as the non-modified PTFE, for example, one kind or two kinds having different average molecular weights are used. The above may be used.

The above unmodified PTFE and the above modified PTFE
The production method of is not particularly limited, and conventionally known polymerization methods such as suspension polymerization, emulsion polymerization, and bulk polymerization can be used. However, from the viewpoint of being industrially widely used, suspension polymerization or emulsion polymerization Is preferably used. The conditions of the above various polymerization methods are not particularly limited.

The as-polymerized PTFE virgin polymer obtained by the above-mentioned various polymerization methods is, for example, powdered. In the present specification, a PTFE virgin polymer in a powder form, which has not been subjected to granulation or gelation described later, is referred to as "PTFE powder".

The above PTFE powder is generally obtained by subjecting the raw powder just after polymerization to general pulverization in order to make the particle diameters uniform. If necessary, the PTFE powder may be one that has been classified after the above general pulverization, or one that has been subjected to coarse pulverization, washing, drying, etc. of the virgin polymer taken out from the polymerization tank. .

Drying in the process of obtaining the above-mentioned PTFE powder is usually carried out by a method such as heating, if necessary, in order to remove washing water, water derived from a medium for carrying out the polymerization, a liquid consisting of an organic solvent and the like. It is something to do. The heating for drying is performed at a temperature lower than the melting point of PTFE.

The average particle size of the PTFE powder is not particularly limited, and is, for example, less than 100 μm, preferably
It may be 20 to 50 μm. In the present specification, the average particle diameter of the PTFE powder is a value obtained according to the wet sheave method described in WO99 / 06475.

The above-mentioned unmodified PTFE and / or modified PTF
As E, an ungranulated gelled pulverized product, a granulated ungelled product and / or an ungranulated ungelled product is used. In this specification,
The "ungranulated gelled pulverized product" means a product obtained by gelling the PTFE powder and then pulverizing it, which has not been granulated. In the present specification, the above-mentioned “granulated ungelled product” means a product obtained by granulating the PTFE powder, which has not been subjected to gelation and subsequent pulverization. In the present specification, the “non-granulated and non-gelled product” means one in which the PTFE powder is neither granulated, gelled nor pulverized thereafter.

In the present specification, the "granulation" means a treatment for making individual particles of the PTFE powder into a spherical shape or an approximate shape of a spherical shape. The granulation may be similar to what is commonly referred to as granulation or granulation. The method of granulation is not particularly limited, for example,
A conventionally known method such as an underwater granulation method can be used.

The individual particles of the PTFE powder before the granulation usually have a molecular chain terminal projecting from the surface in many cases, and there is no tightening as exemplified by the relatively large surface area. It is usually amorphous. Such individual particles have a spherical shape or a shape close to a spherical shape to reduce the surface area by performing the above-mentioned granulation, and the protruding molecular chain ends are contained in this particle shape and are in a tight state. Become.

The change caused in the PTFE powder due to the granulation is also caused mainly by the fact that the individual particles of the PTFE powder are in a tight state as described above, and the apparent density of the PTFE powder is, for example, It can be also represented by the fact that it was about 0.1 to 0.6 g / cm ³ before the above granulation, but increased to about 0.6 to 1 g / cm ³ after the above granulation. This change in apparent density can change depending on the shape and average particle size of individual particles before the above granulation, the above granulation conditions, and the like. In this specification, the apparent density is JIS K
It is a value obtained by measuring according to 6891-5.3.

Due to the above-mentioned granulation, the average particle diameter of the above-mentioned PTFE powder usually tends to increase. For example, the particle size of about 20 to 40 μm before the granulation increases to about 200 to 700 μm after the granulation.
However, since the average particle diameter can be widely controlled if desired, the above granulation does not always increase the average particle diameter. In the present specification, the average particle size after granulation and the average particle size after pulverization after gelling described below are obtained according to the method for measuring the average particle size of granular powder described in WO99 / 06475. It is a value.

In the present specification, among the above-mentioned PTFE powder and those obtained by subjecting the above-mentioned PTFE powder to the above-mentioned granulation, those obtained by suspension polymerization may be collectively referred to as “molding powder”, and obtained by emulsion polymerization. Some things are collectively called "fine powder".

In the present specification, the above "gelling" means
A heat treatment is applied to the PTFE powder, and the heat treatment here does not include the above-mentioned heating for drying in the process of obtaining the PTFE powder.

The heat treatment in the gelation is carried out by the above PTF.
It is preferable that the individual particles of the E powder are fused and fused as a whole so that they are integrally bonded with a weak bonding force. When such gelling is carried out, it can be suitably used in the method for producing a PTFE sheet-shaped molded product of the present invention, as will be described later, through subsequent pulverization. The fusion of the particles of the PTFE powder with each other does not necessarily have to be completely performed on all the particles, and may be in a semi-gelled state, so to speak.

In the present specification, the above "gelling" means "complete gelling" in which the heat treatment of each particle of the PTFE powder is completely performed for all particles, and some particles or It is a concept that includes both "semi-gelling", which is a state performed on a part of particles. That is, in the present specification, the term “complete gelation” or “semi-gelation” is not particularly limited, and simply “gelation” may include both “complete gelation” and “semi-gelation”. Because
When the term is used by limiting to "complete gelation", it means "complete gelling", not by "semi-gelling", but when using the term by limiting to "semi-gelling" Is
It refers to "semi-gelling" and not "complete gelling". Therefore, the above non-granulated gelled pulverized product,
The gelation may include both a completely gelled one and a half gelled one.

The one which has undergone the complete gelation has a heat of fusion of 20 to 40 J / g and / or one melting point peak at 320 to 330 ° C. as described later. The above semi-gelled product has two melting peaks at 320 to 350 ° C. as described later, and
It has a heat of fusion of 30 to 60 J / g and two melting peaks at 320 to 350 ° C. In the present specification, the above-mentioned “one having a melting point peak at 320 to 330 ° C.” means the above “melting point peak at 320 to 350 ° C. 2”.
"Things that exist" are not included. The heat of fusion and the melting peak are measured by the measuring method described below.

The heat treatment in the gelation is, for example, 100 ° C. or higher, and the PTF is
It is preferable to heat at a temperature equal to or lower than the decomposition start temperature of E for 1 minute to 5 hours. More preferably, 300-
It is 10 minutes to 3 hours at 390 ° C, and more preferably 1 to 2 hours at 350 to 380 ° C.

The heat treatment is preferably performed in an inert atmosphere or air. The gelation may include a step of cooling to a temperature equal to or lower than the melting temperature of PTFE after the heat treatment, and in this case, slow cooling is preferable.

Since the ungranulated product is not gelled as described above, it may be heated for drying in the process of obtaining the PTFE powder. It has not been subjected to heating (heat history) other than such heating for drying. Therefore, the granulated non-gelled product is not subjected to any heat history at a temperature exceeding the melting point of PTFE.

It is considered that the PTFE powder has a certain degree of crystallinity at least in part before the gelation. Such individual particles of the PTFE powder are heated by the heat treatment, the polymer chains in the particles increase in momentum and are entangled with each other, and the content of the crystalline portion in the particle decreases and the content of the amorphous portion decreases. It is expected to increase. As a result, the PTFE powder was
It is considered that the energy required for melting or softening is lower after the gelation than before.

Therefore, due to the gelation, the PTFE
The heat of fusion of the powder is, for example, 5 before the gelation.
What was about 0 to 70 J / g, for example, about 60 J / g, is reduced to 20 to 40 J / g, for example, about 30 J / g after the complete gelation. When the gelling is performed in a semi-gelled state, the heat of fusion after the semi-gelling is 20
The value is more than J / g and less than 70 J / g, preferably 30 to 60 J / g. In the present specification, the heat of fusion is a value obtained by using a differential scanning calorimeter (DSC-50, manufactured by Shimadzu Corporation).

By the gelation, for example, the PT
The melting point peak of the FE powder is, for example, about 340 to 350 ° C. before the gelation, but is lowered to about 320 to 330 ° C. after the complete gelation. When the gelling is performed in a semi-gelled state, the melting point peak after the semi-gelling usually has two peaks in the range of 320 to 350 ° C.

As a result of the gelation, as described above, the PT
As a result of increasing the momentum of the polymer chains in the individual particles of the FE powder and intertwining with each other, the individual particles tend to shrink with a small size and a dense structure, which increases the apparent density of the PTFE powder. it is conceivable that.

In the present specification, the "pulverization" after the gelation means that the gelled PTFE powder is fused and integrated into individual particles to form a lump.
This means crushing this agglomerate to a desired size.
By pulverizing in this way, the gelled PT
Since the FE powder can have a small average particle size and a small particle size distribution, it is difficult to cause bridges in the hopper when it is supplied to the molding machine, and stable supply is possible.

The pulverizing method is not particularly limited,
For example, a crusher used for general crushing can be used, and examples thereof include a rotary blade crusher commonly used for crushing general molten resin products and the like.

The average particle size of the PTFE powder after the gelation and crushing is appropriately determined according to the molded product, the conditions of the molding machine and the like, and usually depends on the hole diameter of the screen of the crusher, but is usually 500.
~ 1000 μm, 10 μm to 5 mm depending on the purpose
It is also possible to

The non-granulated gelled and pulverized product is the PT of the present invention.
It can be used in a method for producing an FE sheet-shaped molded product. As described above, the ungranulated gelled and pulverized product is
The above granulation is not performed on the powder, but the gelation and the subsequent pulverization are performed, which is considered as follows.

That is, the ungranulated gelled and pulverized product is considered to have a high apparent density mainly due to the gelation as described above. Generally, when the apparent density is high, the powder fluidity is good, so that When feeding to the hopper, it is difficult to cause a bridge. The ungranulated gelled pulverized product is also
As described above, it is considered that the energy required for melting or softening mainly decreases due to the gelation as described above, and it is easy to soften or melt by heating in the molding machine.
It can be easily formed into the shape of a TFE sheet-shaped molded body.

The ungranulated gelled and pulverized product further has an appropriate viscosity when heated in a molding machine, and therefore can move on the screw groove while maintaining the shape of the screw groove. it is conceivable that. Therefore, there is no problem that the viscosity is too high to make it difficult to move in the cylinder of the molding machine, or the viscosity is too low to maintain the groove shape of the screw.

The reason why the above-mentioned ungranulated gelled and pulverized product has such an appropriate viscosity is that since it is made of PTFE, the melt viscosity is originally considered to be extremely high.
It is considered that the energy required for melting or softening is relatively low as described above, and it tends to be easily melted or softened by heating, and it is considered that the increase in viscosity is suppressed.

As described above, as the non-modified PTFE and / or modified PTFE, the ungranulated gelled and ground product and / or the granulated ungelled product can be preferably used.
In the case of supplying to the hopper of the molding machine, bridges can be reduced or prevented, and it is possible to form the above PTFE sheet-shaped molded body by softening or melting by heating in the molding machine, and in the cylinder. In the above, since it is possible to move the PTFE sheet-shaped molded body while maintaining its shape and extrude it from the cylinder with this shape as described later, the PTF of the present invention
It is necessary in the method for producing the E-sheet shaped body.

The above-mentioned unmodified PTFE and / or modified PTF
Since E can be suitably used in the method for producing a PTFE sheet-shaped molded product of the present invention, the apparent density is preferably 0.2 to 1 g / cm ³ . Within the above range, bridging is less likely to occur when supplying to the hopper of the molding machine.

The above-mentioned unmodified PTFE and / or modified PTFE
More preferably, E has an apparent density of 0.3 to 1
g / cm ³ and a heat of fusion of 20 to 40 J / g
Not more, an apparent density of 0.3 to 1 g / cm ^3, and those melting peak there is one in three hundred and twenty to three hundred thirty ° C., or an apparent density of 0.3 to 1 g / cm ^3,
In addition, the heat of fusion is 30 to 60 J / g, and there are usually two melting peaks at 320 to 350 ° C.
Within the above range, PTFE is usually the above ungranulated gelled pulverized product, which is less likely to cause bridge in the hopper,
It is easy to soften or melt the FE, and then to form and move the PTFE sheet-shaped molded body.

The above-mentioned non-modified PTFE and / or modified PTF
More preferably, E has an apparent density of 0.
2-1 g / cm ³ , and the heat of fusion is 50-70.
J / g or apparent density of 0.2 to 1 g /
cm ³ , and there is one melting peak at 340 to 350 ° C. Within the above range, PTFE is usually the above-mentioned non-gelled product which does not easily cause a bridge in the hopper, softens or melts the PTFE, and then the above-mentioned PT.
It is easy to form and move the FE sheet-shaped molded body.

The above-mentioned non-modified PTFE and / or modified PTF
As E, in addition to the ungranulated gelled and crushed product and / or the ungranulated ungelled product, the ungranulated ungelled product can be used.

The above-mentioned non-modified PTFE and / or modified PTF
E is, if necessary, other components such as other thermoplastic resins and colorants within a range in which the above-mentioned PTFE sheet-shaped molded product can be molded by the method for producing a PTFE sheet-shaped molded product of the present invention. , Additives, fillers and the like may be used together in appropriate amounts. In this case, the colorants, additives, fillers, etc. are usually mixed in the step of granulating or gelling the PTFE powder from the viewpoint of uniformly dispersing it in the obtained PTFE sheet-shaped molded product. Preferably.

The above-mentioned other thermoplastic resin is not particularly limited, and for example, when the obtained PTFE sheet-shaped molded product is used at high temperature, a heat resistant resin is preferable. The heat-resistant thermoplastic resin is not particularly limited, and examples thereof include polyester resin, polyamide resin, acrylic resin, acetal resin, polysulfone resin, polyimide resin, polyphenylene oxide resin, and the like.

Examples of the additives include catalysts and supporting materials. Examples of the filler include glass fibers, graphite, molybdenum disulfide, carbon fibers, reinforcing materials such as bronze, and conductive substances.

The method for producing a PTFE sheet shaped article of the present invention is for producing a PTFE sheet shaped article by using a cylinder having a screw to soften or melt PTFE. The cylinder having the screw is not particularly limited, and a molding machine having such a cylinder can be usually used. A general extrusion molding machine may be used as such a molding machine.

The method for producing the PTFE sheet-shaped molded product of the present invention will be described with reference to the schematic sectional view of FIG.
In the molding machine, the ungranulated gelled and pulverized product, the granulated ungelled product and / or the ungranulated ungelled product [hereinafter sometimes simply referred to as "PTFE" as PTFE. ] Is supplied from a hopper 5, and this PTFE is softened or melted in a cylinder 4 having a screw type material supply method, and the screw 1
It is carried out by taking out the above-mentioned PTFE sheet-shaped molded product formed while rotating the above from the cylinder tip portion 6.

The hopper is not particularly limited, but the temperature of the material supply port of the hopper is such that the raw material to be charged so as to prevent bridging does not agglomerate, and the softening or melting of PTFE in the subsequent step is performed. It is preferable that the temperature has a certain height so that it can be performed quickly. As such a temperature, for example, 10 to 30 ° C. is suitable. In the present invention, since the ungranulated gelled pulverized product and / or the ungranulated ungelled product is used as described above, bridging is unlikely to occur, but in order to sufficiently prevent the occurrence of bridging, the hopper has a temperature control function. Alternatively, it may have a cooling device.

The method of softening or melting the PTFE is not particularly limited, and for example, a melting method generally used in extrusion molding can be applied. Examples of such a general melting method include a method of transferring heat generated by a temperature control function of a cylinder and / or a screw to a resin, and a shearing when PTFE is kneaded between the screw and the cylinder. Examples include a method of utilizing heat generated by energy.

When the temperature control function of the cylinder and / or screw is used, the set temperature is not particularly limited, but the cylinder temperature near the hopper is
PTFE so that it can be quickly softened or melted
While a temperature as close as possible to the melting point of is suitable, the temperature under the hopper needs to be too high due to heat conduction to cause a bridge in the hopper, so that it is preferably set to, for example, 10 to 200 ° C.

The set temperature of the cylinder and / or screw depends on the screw shape, the number of revolutions and the discharge amount, but is preferably 20 to 420 ° C. depending on the screw portion. As shown in FIG. 1, the set temperature is preferably 100 ° C. or less, more preferably 5 to 5 ° C. in the cylinder rear part 11.
30 ° C., more preferably 10 to 20 ° C., in the rear part 12 in the cylinder, preferably 20 to 250 ° C., more preferably 50 to 150 ° C.
3, preferably 150 to 390 ° C., more preferably 300 to 360 ° C., in the cylinder front part 14, preferably 200 to 390 ° C., more preferably 300 to 360 ° C., in the cylinder front part 15, Preferably 300-420 ° C, more preferably 30
It is 0-380 degreeC.

When the screw rotation speed is increased, for example, the set temperature is preferably set lower because the shear rate increases, internal heat generation increases, and the temperature of PTFE increases, while the screw rotation speed increases. As a result, the supply amount increases and a large amount of heat is required, so it is desirable to set a high value. Thus, the set temperature is
Adjustment is made within the above range so as to be appropriate according to various molding conditions.

The size of the cylinder is not particularly limited. For example, the inner diameter is preferably 30 to 90 mmφ, and L / D, which is the ratio of the length to the inner diameter of the cylinder, is preferably 20 to 30. The L / D is preferably large from the viewpoint of moldability, but is preferably small from the viewpoint of miniaturization, so it is selected according to needs.

As the shape of the screw, the full flight type is preferable as described above, and as schematically shown in FIG. 3, the groove depth h _f under the hopper is preferably as deep as the screw strength allows. The axial length ratio [FCM ratio] of the section F, the compression section C, and the metering section M is F: C:
It is preferable that M is 2 to 19:19 to 2: 3 to 8, and the compression portion C may be either slow compression or rapid compression.
Rapid compression of 2-4 pitches is preferred. Here, one pitch is the length in the axial direction of the screw, as represented by P in FIG. 3, and is the length between adjacent flights. L / D, which is the ratio of the length to the outer diameter of the screw
Is preferably 20 to 30.

The compression ratio (volume) of the screw is the molding temperature.
However, 1.5 to 10 is sufficient, and 2 to 6 is preferable.
Yes. Within the above range, PTFE is softened or melted.
And fusing particles together to form a sheet.
It is suitable. More preferably, it is 2-4. Where pressure
The reduction ratio (volume) is the body per pitch under the hopper.
Product (V_f) And per pitch in the metering section M
Volume of (V_m) And (V _f/ V_m). Screw
The rotation speed of the rotor is preferably 5 to 120 rpm, and 10 to 6 rpm.
0 rpm is more preferred.

The PTFE sheet-shaped molded product is preferably taken out by open extrusion. In the present specification, the term "open extrusion" means that a molded product is directly taken out from the cylinder tip without installing parts such as a die and a screen to be installed in general extrusion molding at the cylinder tip. Means that.

In the case of using a general extruder, it is natural to install parts such as a die at the tip portion of the cylinder and pass the melt-kneaded resin in the cylinder through the die to create a shape. It is supposed to be.
However, in the method for producing a PTFE sheet-shaped molded product of the present invention, such common sense is overridden, and a shape depending on the shape of the groove of the screw is given to the softened or melted PTFE inside the cylinder, and the shape is maintained. It is totally different from the conventional extrusion molding in that it is pushed along the flight along the screw groove toward the cylinder tip, and is directly extruded from the cylinder tip without passing through a die or the like in its shape. .

A guide part (guide) for guiding the sheet pushed out from the cylinder tip may be provided in front of the cylinder tip. The guide part may have a temperature control function. After being extruded from the cylinder, the PTFE sheet-shaped molded product can be transferred to a shaping device, a take-up device or the like described later by the guide portion.

A shaping device for shaping a sheet extruded from the cylinder tip may be provided in front of or on the side of the cylinder tip or the guide. The shaping device is not particularly limited, and examples thereof include a heat roll and a sizing die. The above shaping device,
It may have a temperature control function. Above PTF
The E-sheet shaped product can be obtained by the shaping apparatus, for example, as a product in which the size and shape are adjusted and the size is regulated, a flat sheet-shaped product, a stretched product and the like.

The above PTFE sheet-shaped molded product may be subjected to a surface treatment such as cutting for surface smoothing or the like, if necessary, such as when a highly smooth surface is required. A treatment for imparting adhesiveness such as corona treatment may be performed. It is effective to carry out such a surface treatment in a soft state or in a relatively high temperature state.

A cooling device may be provided in front of the tip portion of the cylinder, the guide portion or the shaping device. The cooling device is not particularly limited, for example, a cooling water tank,
Examples thereof include an air shower layer and a cooling die. When performing sizing using a sizing plate or the like as the shaping device, the cooling device may perform shaping and cooling at the same time. The above PTFE sheet-shaped molded product is
It can be obtained by being cooled under various conditions by the above cooling device. For example, slow cooling can increase the crystallinity to give an opaque white color, and rapid cooling can decrease the crystallinity. It can be translucent white.

The PTFE sheet-shaped molded product is a take-up device having a take-up speed control function and / or a take-up force control function after passing through the cylinder tip end portion, the guide portion, the shaping device or the cooling device. It may be one collected by. The installation location of the take-up device is not particularly limited, and may be, for example, the front end portion of the cylinder, the guide portion, the shaping device, or the cooling device. The take-up speed control function and the take-up force control function are not particularly limited, and may be, for example, those provided in a general apparatus for taking a molded product.

As described above, the method for producing a PTFE sheet-shaped molded product of the present invention uses the above-mentioned ungranulated gelled product, the above ungranulated gelled and crushed product and / or the ungranulated ungelled product and a screw. Since it uses a cylinder having, it theoretically enables a continuous operation from the supply of raw materials to the molding, which was impossible in the past in the molding of PTFE. It is possible to obtain a continuous molded body directly from a softened or melted raw material without performing a secondary operation, and it is possible to remarkably improve the productivity.

In the method for producing a PTFE sheet-shaped molded product of the present invention, since it is not necessary to add an extrusion aid or the like,
It is possible to obtain a PTFE sheet-shaped molded product of excellent quality, which is free from contamination due to residual extrusion aid and the like and internal defects.

In the method for producing a PTFE sheet-shaped molded product of the present invention, it is not necessary to use an additive such as an extrusion aid which is removed in a subsequent step, and a relatively inexpensive molding powder can be used. In addition, a PTFE sheet-shaped molded product can be obtained from at least one step from the above-mentioned ungranulated gelled and ground product and / or the above-mentioned granulated ungelled product which is a raw material, which is economical.

In the method for producing a PTFE sheet-shaped molded product of the present invention, a molding machine which has been conventionally used can be used without requiring a special machine, and moreover, the most used and inexpensive full flight screw can be used. Since it is possible to preferably use an extrusion molding machine having, it is possible to easily apply without requiring expensive equipment investment.

Therefore, according to the method for producing a PTFE sheet-shaped molded product of the present invention, the above-mentioned PTFE sheet-shaped molded product can be produced, for example, as a single sheet, film, ribbon, strip or the like by continuous molding with high productivity and economical efficiency. It can be preferably used for forming.

[0113] A PTFE sheet-shaped molded product characterized by being manufactured by the above-mentioned method for manufacturing a PTFE sheet-shaped molded product is also one aspect of the present invention.

The PTFE sheet-shaped molded product of the present invention can be theoretically obtained as a continuous product by continuously supplying the raw materials and operating the molding machine as described above, and the physical properties do not become discontinuous. You can

The method for processing the PTFE sheet-shaped molded product of the present invention is not particularly limited, and, for example, bulk compression molding for compression-molding a sheet-shaped molded product piece obtained by cutting the PTFE sheet-shaped molded product extruded by a certain amount. Sheet blow molding continuously performed by using two PTFE sheet-shaped molded products extruded from two extruders, multilayer extrusion by laminating a plurality of PTFE sheet-shaped molded products extruded by a certain amount and rolling and adhering them. The formation of objects is included. It is also possible to continuously laminate a plurality of extrudates.

As the above-described processing method, an electric wire is formed by forming a middle boring portion on two extruded PTFE sheet-shaped molded bodies having a semicircular cross section, and inserting an electric wire into the middle boring portion and bonding and fixing the electric wire. Examples include coatings. In the method for producing a PTFE sheet-shaped molded product of the present invention, since the molding temperature can be set to the melting point of PTFE or less in some cases as described above, it is considered that the crystalline portion of the PTFE polymer can be left. Since the crystal part has orientation and the obtained PTFE sheet-shaped molded article has a low dielectric constant, it is suitable as a covering material for electric wires.

Therefore, the PTFE sheet-shaped molded product of the present invention is obtained by heat-resistant, weather-resistant, non-adhesive, water- and oil-repellent, antifouling, chemical liquid permeation, chemical resistance, electrical insulation, and resistance of PTFE. Taking advantage of characteristics such as abrasion resistance, for example, coating materials such as wire coatings; sealing materials such as seam seals for piping materials, seal auxiliary materials such as packings; release films, insulating films, corrosion resistant films, surface protection films, etc. Can be used for various purposes such as various functional sheet linings, functional films, and masking materials.

[0118]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Production Example 1 Production of ungranulated gelled and ground product of molding powder Unmodified PTFE molding powder ungranulated product (average particle diameter 25 μm, apparent density 0.29 g / cm ³ , trade name: Polyflon PTFE M
-12, manufactured by Daikin Industries, Ltd.) was spread on a stainless steel vat with a thickness of 5 cm, placed in an oven and heated in the air. The heating was performed by raising the oven temperature from room temperature to 370 ° C. over 3 hours and holding the temperature for 2 hours, and then cooling to room temperature over 3 hours. The obtained block was crushed by a rotary blade crusher to obtain a granular ungranulated gelled crushed product having an average particle size of about 1 mm. The average particle size of this ungranulated gelled pulverized product is 1000 μm.
m, the apparent density was 0.5 g / cm ³ .

Example 1 Granulated ungelled product of modified PTFE molding powder (average particle diameter 400 μm, apparent density 0.9 g / cm 3
³ , product name: New Polyflon PTFE M-139,
Daikin Industries, Ltd.) was supplied to the hopper of a 40φ extruder (manufactured by Tanabe Plastic Co., Ltd.) while the cylinder temperature near the hopper was set to 100 ° C. and the temperature of the hopper was kept at 20 ° C. Cylinder with inner diameter 40mmφ, L / D25, compression ratio 4, FCM ratio F: C: M = 1
9: 2: 4, groove depth under hopper 6.5 mm, compression part 2
Using a full-pitch type screw with rapid pitch compression, the cylinder temperature was set to 320 to 360 ° C., the screw speed was set to 10 rpm, and a ribbon-shaped sheet having the shape of the groove of the screw was obtained from the opened cylinder tip. It was

Example 2 Molding powder Granulated modified PTFE fine powder (average particle size 500 μm,
Apparent density 0.45 g / cm ³ , product name: Polyflon P
A ribbon-shaped sheet having the shape of the groove of the screw was obtained in the same manner as in Example 1 except that TFE F-104 manufactured by Daikin Industries, Ltd.) was used.

Example 3 The same procedure as in Example 1 was carried out except that the unpelled gelled pulverized product of the molding powder obtained in Production Example 1 was used in place of the unpellified pelletized molding powder. A ribbon-like sheet having a shape was obtained.

From the examples, the ungranulated gelled pulverized product, the ungranulated ungelled product, and / or the ungranulated ungelled product of PTFE were heated by using a general extrusion molding machine and subjected to open extrusion. By performing the above, the PTFE having the shape of the groove of the screw is obtained.
It was found that a sheet-shaped compact was obtained.

[0124]

EFFECTS OF THE INVENTION Since the method for producing a PTFE sheet-shaped molded product of the present invention has the above-mentioned constitution, it is possible to use a relatively inexpensive molding powder without using an extrusion aid or the like and to carry out the raw material without performing the batch treatment. To theoretically enable continuous operation from the feeding to the molding, and to economically obtain a PTFE sheet-shaped molded product having no physical property discontinuity directly from a softened or melted raw material without secondary processing. You can

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an extruder.

FIG. 2 is a schematic partial cross-sectional view of a screw and a cylinder containing the screw.

FIG. 3 is a schematic diagram of a screw.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Koji Fukuyama             Daiichi Nishiichitsuya 1-1, Settsu City, Osaka Prefecture             Yodogawa Manufacturing Co., Ltd. F-term (reference) 4F207 AA17 AG01 KA01 KA17 KK12

Claims (9)

[Claims] 1. A cylinder having a screw is used.
A PTFE sheet-shaped molded article manufacturing method for manufacturing a PTFE sheet-shaped molded article by softening or melting unmodified polytetrafluoroethylene and / or modified polytetrafluoroethylene, comprising the unmodified polytetrafluoroethylene and / or Alternatively, the modified polytetrafluoroethylene is a granulated ungelled product, an ungranulated gelled pulverized product and / or an ungranulated ungelled product, and the PTFE sheet-shaped molded product has a groove shape of the screw. A method for producing a PTFE sheet-like molded article, comprising: 2. The method for producing a PTFE sheet-shaped molded product according to claim 1, wherein the PTFE sheet-shaped molded product is obtained by open extrusion. 3. The method for producing a PTFE sheet-shaped molded product according to claim 1, wherein the screw is a full flight screw. 4. The unmodified polytetrafluoroethylene and / or modified polytetrafluoroethylene has an apparent density of 0.2 to 1 g / cm ^3.
Alternatively, the method for producing a PTFE sheet-shaped molded article according to item 3. 5. The unmodified polytetrafluoroethylene and / or modified polytetrafluoroethylene has an apparent density of 0.3 to 1 g / cm ³ and a heat of fusion of 20.
-40 J / g, apparent density 0.3-1 g /
cm ³ and one melting peak at 320 to 330 ° C., or apparent density of 0.3 to 1 g / cm
³ and the heat of fusion is 30 to 60 J / g,
The method for producing a PTFE sheet-shaped molded product according to claim 1, 2 or 3, which has two melting peaks at 320 to 350 ° C. 6. The unmodified polytetrafluoroethylene and / or modified polytetrafluoroethylene has an apparent density of 0.2 to 1 g / cm ³ and a heat of fusion of 50.
~ 70 J / g or an apparent density of 0.2 ~
1 g / cm ³ and a melting peak of 340 to 35
The P according to claim 1, 2 or 3, which is one at 0 ° C.
A method for producing a TFE sheet-shaped molded body. 7. The non-modified polytetrafluoroethylene and / or the modified polytetrafluoroethylene contains a colorant, an additive and / or a filler, as claimed in claim 1, 2. 2. A method for producing a PTFE sheet-shaped molded body according to the above. 8. A PTFE sheet-shaped molded product, which is manufactured by using the method for manufacturing a PTFE sheet-shaped molded product according to claim 1, 2, 3, 4, 5, 6 or 7. 9. The PTFE sheet-shaped molded product according to claim 8, which has no discontinuity in physical properties.