JPH03139547A - Soft fluororesin composition - Google Patents

Abstract

PURPOSE:To prepare a soft fluororesin compsn. used in extrusion molding and improved in the breaking elongation during melt molding and surface flatness of the molded article by compounding a soft fluororesin with a specific powdered filler and a fibrous polytetrafluoroethylene. CONSTITUTION:A soft fluororesin compsn. used in extrusion molding is prepd. by compound: 100 pts.wt. soft fluororesin; 0.1-80 pts.wt., pref. 0.1-60 pts.wt., powdered filler having an m.p. of 130 deg.C or higher (e.g. an inorg. metal carbonate or oxide, or a thermoset or thermoplastic resin powder); and 0.05-10 pts.wt. fibrous polytetrafluoroethylene. The soft fluororesin is prepd. by copolymerizing a monomer component contg. a fluoromonomer with a monomer having a double bond and a peroxy bond in the molecule to give a fluorocopolymer having peroxy groups in the molecule and a glass transition point lower than room temp. and then grafting a fluoromonomer onto the resulting fluorocopolymer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a filler-containing soft fluororesin composition that improves the elongation characteristics of a molten resin during extrusion molding and the surface properties of molded articles. Fluororesins are used in a wide range of fields due to their excellent properties (heat resistance, oil and fat resistance, chemical resistance, weather resistance, etc.) derived from the C-F bonds they contain. Soft fluororesin, which has both moldability and moldability, is used in a wide range of applications in the form of tubes, sealants, films, etc.

(Prior Art) The present inventors have disclosed a soft fluororesin having both flexibility and melt moldability in Japanese Patent Publication No. 6234324. Attempts have also been made to improve the properties of soft fluororesins by blending various fillers with them.

For example, a method of improving conductivity by mixing carbon black with a soft fluororesin (Japanese Unexamined Patent Publication No. 61-11845). Furthermore, it is also known to blend polytetrafluoroethylene powder as a method of improving sliding properties (Japanese Patent Application Laid-Open No. 1983-1999).
195035).

On the other hand, polytetrafluoroethylene (PTFE) powder forms fine fibers (fibrils) when subjected to compression and shear force.
There is a tendency to become PTFE is (Ch
It is a completely symmetrical linear polymer having a structure of CFz)fl, and is known to have extremely small intermolecular cohesive force. For this reason, it is generally said that PTFE particles peel off from the interface between molecules and form fibrils.

As a method of incorporating such PTFE fibrils into a resin to improve various properties of the resin, for example, when mixing a plurality of mutually immiscible polymers, PTFE fibrils can be incorporated into the resin.
Method of forming a network of fibrils in a mixture to prevent separation of immiscible polymers
260).

Adding PTFE to flame-retardant polycarbonate, PT
A method of forming a network of FE fibrils in a molded article to prevent ignition caused by melting and dripping of high-temperature polycarbonate (Japanese Patent Laid-Open No. 6023442). and a method of increasing the mechanical strength of a membrane by mixing an ion exchange resin and PTFE to fibrillate the PTFE and forming a membrane (Japanese Patent Laid-Open No. 53
149881) are known.

(Problems to be Solved by the Invention) The soft fluororesin disclosed in Japanese Patent Publication No. 62-34324 is widely used in the form of extrusion molded products such as tubes, sheets, films, rondo, and Y4 type products. , various fillers may be mixed to improve its properties.

For example, to improve sliding properties, PTFE powder, graphite, spherical phenol resin, etc. are filled, and to improve conductivity, carbon blanks, metal powder, etc. are filled. Furthermore, antimony oxide to reduce smoke generation, titanium oxide, calcium carbonate, etc. to reduce the light transmittance of the film are used. It has been pointed out that a common problem when mixing these fillers with soft fluororesin is that the molten resin loses its elongation during extrusion molding, and the surface smoothness of the molded product deteriorates. This tendency becomes particularly noticeable when the amount of filler is increased, resulting in problems such as the inability to reduce the thickness of the film or the inability to obtain an extrusion molded product of a desired shape, such as inability to obtain a tube with a small diameter. Moreover, the surface roughness of the molded product increases, which poses a practical problem.

Such a phenomenon is also observed in the case of general thermoplastic resins, but the soft fluororesin is made by graft-polymerizing a crystalline fluororesin to a fluororubber segment, which has substantially poor melt moldability, to impart melt moldability. However, it is said that the extrudability deteriorates particularly when fillers are mixed.

(Means for Solving the Problems) The present invention has been made in order to improve the extrusion moldability when fillers are mixed with these soft resins. This is to improve these problems.

The material to be filled must have properties that can exhibit a reinforcing effect at high temperatures without impairing the characteristics of soft fluororesin, such as acid resistance, alkali resistance, oil resistance, and K4 weatherability. The present inventors studied various fibrous fillers including glass fibers, carbon fibers, and aramid fibers from this point of view, and found that fine fibers (fibrils) obtained by applying shearing force to PTFE powder were The present invention was achieved by discovering that the above conditions match the above.

The target soft fluororesin was developed by the inventors in the
-34324, one or more types of monomers containing at least one type of fluorine-containing monomer are copolymerized with a #l-mer having both a double bond and a peroxy bond in the molecule. The first step is to produce a fluorine-containing elastic copolymer that contains peroxy groups in its molecules and whose glass transition temperature is below room temperature, and the second step
step, at least one type of fluorine-containing II which gives a crystalline polymer whose melting point is 130° C. or higher in an aqueous emulsion or dispersion solvent of the copolymer obtained in the first step.
It is a soft fluororesin produced by graft copolymerization of one or more types of IP-i forms including an i-mer.

Various unsaturated peroxides, peroxycarbonates, and the like are known as unsaturated peroxides used here, but the type must be selected depending on the co+n combination system.

Specific examples of unsaturated peroxyesters include t-butylperoxy methacrylate, di(t-butylperoxy) fumarate, and (-butylperoxycrotonate). Examples of unsaturated peroxycarbonates include t-butylperoxy Allyl carbonate, L-hexylberroquine allyl carboy, -1.,!, 1.3.
3. -tetramethylbutylperoxyallyl carbonate, E-phthylberoxymethallyl carbonate, 1.
Examples include 1.3°3,-tetramethylbutylperoxymethallyl carbonate, P-methantaperoxyallyl carbonate, and P-menthane peroxymethallyl carbonate.

Here, the elastic polymer having the composition of fluororubber refers to a polymer whose Tg is below room temperature and has high quality. ) and hexafluoropropene (hereinafter referred to as RFP), a terpolymer of VDF, RFP, and tetrafluoroethylene (hereinafter referred to as TFE), a terpolymer of VDF and chlorotrifluoroethylene (hereinafter referred to as C
There are copolymers of TFE and propylene (abbreviated as TFE), copolymers of TFE and fluorine-containing vinyl ether, copolymers of hydrocarbon diene compounds and fluorine-containing intermediates, etc. The composition is not particularly limited.

On the other hand, examples of fluorine-containing crystalline polymers having a melting point of 130°C or higher include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, copolymers of TFE and ethylene, and CTFE.
Copolymers of TFE and ethylene and copolymers of TFE and fluorine-containing vinyl ether are widely known, but their compositions are not particularly limited.

Here, as the filler to be mixed with the soft fluororesin,
It means something that does not melt at the molding temperature of soft fluororesin.
Specifically, it refers to a substance that does not melt at temperatures below 130°C.

There are many examples of such fillers, both inorganic and organic. For example, inorganic systems include calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, zinc oxide, magnesium oxide, carbon black, graphite, aluminum silicate, magnesium silicate, calcium silicate, mica, asbestos, potassium titanate, Examples include antimony oxide, barium sulfate, bismuth oxide, and glass balloons. Among organic types, thermosetting resin powders such as phenol resin and melamine resin, P
Thermoplastic resin powders with high melting points such as TFE resin and PPS resin are exemplified, but the type thereof is not particularly limited as long as it is selected depending on the intended use of the functionality of the various fillers.

The amount of filler mixed into the soft fluororesin varies greatly depending on the type of filler and the purpose of mixing it, but it is preferably in the range of 0.1 to 80 parts by weight, preferably 0.1 to 80 parts by weight, based on 100 parts by weight of the soft fluororesin. ~60 parts by weight. If the amount is less than this range, it will not be effective as a filler, and if it is mixed beyond this range, the viscosity of the mixture will increase and the load on the extruder during extrusion molding will become excessive, making molding difficult. Become.

Further, when a relatively large amount of filler is mixed, a resin compatible with the crystalline resin contained in the soft fluororesin may be further mixed in order to reduce the melt viscosity during molding. In this case, the rigidity of the mixed resin increases as the melt viscosity decreases, but the present invention does not deny them.

Fibrillar polytetrafluoroethylene is
Obtained by applying shear force to a highly crystalline tetrafluoroethylene polymer, these fibrils form a dendritic or web-like three-dimensional network structure of fibers between the soft fluororesin and the filler. This improves the elongation properties of the mixed resin when it is melted, and prevents the filler particles from floating loosely on the surface of the molded product, thereby improving the surface properties of the extrusion molded product.

As the tetrafluoroethylene polymer that causes such fibrillation, so-called fine powder obtained by emulsion polymerization of tetrafluoroethylene monomer is preferable, and so-called molding powder obtained by suspension polymerization has a small degree of fibrillation and is similar to soft fluororesin. It does not provide a sufficient moldability improvement effect in a filler mixture system.

The addition ratio of fibrous PTFH varies depending on the type of filler and the amount mixed, but is suitably 0.05 to 10 parts by weight. Below this range, sufficient moldability improvement cannot be obtained;
If it is added in excess of this range, the three-dimensional network structure described above will increase, and the melt viscosity of the mixed resin will increase, making extrusion molding difficult.

Soft plastic resin, filler and fibrous PTF I?
For mixing, methods such as kneading between two rolls used in ordinary resin molding, kneading in a Banbury mixer, kneading in a -screw or twin-screw extruder, etc. can be adopted, but PTF
In order to promote the fibrillation of E, a powdered soft fluororesin or powdered filler and PTFE powder obtained by emulsion polymerization are mixed in advance with a mixer capable of applying high shearing force, such as a Henschel mixer. It is preferable to use the above-mentioned kneading machine.

The mixture of the soft fluororesin, filler, and fibrous PTFE obtained in this way has improved elongation characteristics of the molten resin during extrusion molding, compared to a mixed resin that does not contain fibrous PTFE, resulting in a drop rate. The molding properties are improved, the degree of freedom in extrusion molding is increased, and a molded product with a superior surface can be obtained.

Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 (A) Production of soft fluororesin (1) 50% pure water was placed in a stainless steel autoclave with a capacity of 100N.
．． 0 kg, 100 g of potassium persulfate, 150 g of ammonium perfluorooctanoate, and 100 g of t-butyl peroxyallyl carbonate were added, and after evacuation, 12.5 kg of vinylidene fluoride monomer and 7.55 kg of chlorotrifluoroethylene monomer were charged, and the temperature was heated to 50°C while stirring. The reaction was carried out for 20 hours at a temperature of . The product was obtained in the form of a white latex, which was salted out to obtain rubbery particles. After washing with water and vacuum drying, washing with n-hexane to remove unreacted t-butyl peroxyallyl carbonate and vacuum drying again produced a white powder copolymer 16.
Obtained 0 kg. The DSC curve of this copolymer had an exothermic peak at 160 to 180°C due to decomposition of peroxy groups, and the amount of active oxygen in the copolymer was determined to be 0.042% by iodometric titration.

In the next step, 12.0 kg of the white powder copolymer and 0 kg of Freon R-11375.
In addition to a stainless steel autoclave with a capacity of 0.01, after evacuation, 6.0 kg of vinylidene fluoride monomer was charged.
Polymerization was carried out at ℃ for 24 hours.

The produced polymer was separated from the solvent and dried to obtain 16.6 kg of white powder. The melting point of this polymer was determined to be 155-160°C by DSC measurement.

(B) Mixed soft fluororesin (1) In order to reduce the coefficient of friction to 100 parts by weight, low molecular weight PTFE powder (Central Glass nW1 trade name Cefral Lube 1 molecular weight 8,5
00, particle size 5 to 10 μm, melting point 315°C), and PTFE powder produced by emulsion polymerization (Teflon @ 10J, MP, 327°C manufactured by Mitsui DuPont Fluoro).
A total of 3 kg at the ratio shown in the table was charged into a 20ff capacity Hexiel mixer and mixed for 5 minutes at 1500 revolutions/rotation speed. As the mixing time elapsed, the mixed powder became less dusty, confirming the effect of fibrillation of PTFE.

(C) Pellet production The mixed resin obtained in (B) was processed using a 30 mm single-screw extruder (
Extrusion molding (L/D: 22) into a 3n diameter rod (
(temperature of 180 to 210° C.) and cut into 2 to 4 lengths to produce pellets.

(D) Measurement of melt elongation of mixed resin (evaluation of drawdown property) °ζ was carried out using a cavilograph manufactured by Toyo Seiki ■. The method is to fill a 1 ctA cylinder heated to a temperature of 200° (:) with 25 g of the pellet obtained in (C), and after preheating for 5 minutes, press the pellet from the top with a cylinder at a constant speed of 10 mm/min. The resin was allowed to flow out from a 1 am diameter and 10 mm diameter orifice.

The flowing resin in the form of a thin string was taken up by two variable speed rubber rolls via a pulley below the orifice. The speed of this take-up roll was continuously increased from 10111 minutes, and the melt elongation was evaluated based on the speed at which the thin string was cut. Since the diameter of the extrudate becomes smaller as the speed of the take-off roll increases, evaluation of the draw-off property during actual extrusion molding can be obtained by this method.

On the other hand, the extrusion pressure at this time was measured, and the extrusion torque during actual extrusion molding was evaluated. The results are shown in Table 1.

(E) The beret obtained by tube forming (C) was uniaxially extruded with a diameter of 30 mm.
Outer diameter using (L/D: 22)? , 4 ss inner diameter 5
It was extruded from a nozzle of nφ and drawn down by adjusting the speed of the take-off machine to produce a tube with an outer diameter of 6B and an inner diameter of 4φ.

(F) Measurement of surface roughness The surface roughness of the outer surface of the tube obtained in (E) was thinly shaved using a Taylor Hobson II surface roughness needle Talystep. Measurements were performed at three locations with a length of 2 mm, and the average difference between the highest and lowest values of the obtained waveforms was taken as a measure of surface roughness. The results are shown in Table 1.

(G) Measurement of friction coefficient The pellet obtained in (C) was compression molded at a temperature of 200°C,
Thickness 2■l×40mm1! A disc was manufactured.

The coefficient of friction between this disc and iron (545C) was measured using the Orientic friction tester EFM-II [-EN].
Measurements were made at a pressure of f/cIIt and a speed of 0.2 m/sec.

The friction coefficient was measured t&1 hours after the start of the measurement, and the results are shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 (B) was carried out except that Teflon@K-10J was not added. The results are shown in Table 1.

Comparative Example 2 In (B) of Example 1, 90 parts by weight of Cephural Lube 1 was added, and the same procedure as in Example was carried out except that Teflon@K-10J was added and not added. The results are shown in Table 1.

As can be seen from Table 1, even when PTFE powder is mixed as a filler to improve sliding properties, the elongation rupture rate of the molten resin is 3 to 5 times higher than that of the comparative example, which means that the production per unit time is This means that the amount is large enough to correspond to its magnification. In addition, the tube surface layer of the extrusion molded product maintains extremely uniform smoothness, but in the comparative example, the extrusion pressure was high < 300
If the pressure exceeds kgf/cj, the load on the molding machine will be large and cause damage.

Example 2 100 parts by weight of soft fluororesin (1) was added with carbon black (Kao Soap F
10 J was mixed with Ketchen Black (specific surface area: 950 rrr/g) and Teflon Φ in the proportions shown in Table 2. The mixing method was carried out according to (B) of Example 1, and then the operations (C) to (F) were carried out in the same manner as in Example 1.

In addition, the pellet of the mixture was compression molded and
A sheet of 60 n×160 μl was manufactured, and the volume resistivity was measured using this sheet by the method specified in JIS K6911. The results are shown in Table 2.

Comparative Example 3 The same procedure as in Example 2 was carried out except that 110 J of Teflon Φ was removed from the mixture of Example 2. The results are shown in Table 2.

Comparative Example 4 The same procedure as in Example 2 was carried out except that 12.0 parts by weight of -10J was added to the Teflon Φ in Example 2. The results are shown in Table 2.

(Hereinafter referred to as f white) L---, -: , -J As can be seen from Table 2, even if a carbon blank for imparting conductivity was mixed, the elongation rupture rate of the molten resin was 3 to 7 of the comparative example. It is found that the tube surface of the molded product has extremely good smoothness.

Example 3 (A) Production of soft fluororesin (II) In a 21'aH stainless steel autoclave that can withstand 100 atmospheres, 1000 g of pure water, 3 g of potassium persulfate, 1 g of ammonium perfluorooctanoate, and Freon R-113 as an unsaturated peroxide were placed. t diluted to 5% at
-butyl peroxyallyl carbonate) was added, and after repeating evacuation and nitrogen substitution, 169 g of vinylidene fluoride monomer and 13 g of chlorotrifluoroethylene monomer were added.
3 g was charged, and the polymerization reaction was carried out at a temperature of 50° C. for 20 hours with stirring to obtain a product in the form of a white latex.

The weight of the obtained latex was 1262 g, the concentration of the sampled latex was 21.1%, and the rubber latex had a polymer weight of 270 g.

The DSC curve of this copolymer had an exothermic peak at 160 to 180°C due to decomposition of peroxy groups, and the amount of active oxygen in the copolymer was determined to be 0.04% by iodometric titration. Furthermore, the Tg of the copolymer was determined to be 15° C. by DSC measurement at low temperature. Furthermore, when the composition of the backbone polymer was investigated by elemental analysis, the molar composition ratio of VDF and CTFE was 30.8/69.2.

The latex made of the rubber-like copolymer having peroxy groups as a constituent element obtained in this way has a solid content of 100%.
g (474 g of latex H) was weighed and placed in an 11 autoclave equipped with an electromagnetic stirring device capable of withstanding 100 atm, and after adding pure water to adjust the volume to 500 ml, evacuation and nitrogen substitution were repeated three times. After charging 79.1 g of chlorotrifluoroethylene monomer and 19.8 g of ethylene, 0.9 g of NaH3O:+ as a reducing agent was added as an aqueous solution, and polymerization was carried out at 30° C. for 8 hours.

After purging the remaining tops, open the autoclave and
The produced polymer was taken out.

Thereafter, water was separated and washed, followed by drying in a vacuum dryer to obtain 164.8 g of white powder.

The melting point of this polymer by DSC was 217°C.

(B) Antimony oxide powder (Poen 5KN54 manufactured by Kikuchi Shiki All Co., Ltd. with a particle size of 1.5
A powder prepared by mixing 10 J of Teflon (μm) and Teflon (III) in the ratio shown in Table ff13 was mixed in the same manner as in Example 1 (B).

(C) Pellet production The mixed resin obtained in (B) was heated to a temperature of 220 to 250°C using a 30 mm uniaxial extruder (L/D 22) in the same manner as in Example 1 (C). Pellets were produced.

(I) Measurement of melt elongation of mixed resin Measurement was carried out in the same manner as in Example 1, except that the temperature of the heating cylinder was 250°C.

(E) Pellets obtained in film forming (C) are processed using a 30ml extruder (L/D・22
) is extruded through a slit with a tip thickness of 0.5 mm, and then pulled with a take-up roll to a thickness of approximately 0.21-
A film was produced.

(F) Compression molding of the pellets obtained in (C) smoke generation measurement (230°C)
to produce a prismatic test piece of 25 x 25 x 6 am,
Using this test piece, Arapaphoe Smoke Ch
Combustion tests were conducted using amber, and the oxygen index and smoke amount (%) were measured. The results are shown in Table 3.

Comparative Example 5 In Example 3, extrusion molding was carried out without mixing 10J with Teflon [phase], but it was not possible to draw down during extrusion molding of (E), and only a 0.4 l thick film was obtained. .

(11F!6') From Table 3, it can be seen that even with the addition of antimony oxide as a smoke preventive agent, the elongation rupture rate is 4 to 7 times higher and the film surface smoothness is also good.Also, the amount of smoke generated in the combustion test , a significant improvement in the elongation rupture rate was observed without any change in the oxygen content.

(Effects of the Invention) The soft fluororesin composition containing the powdered filler and fibrillated PTFE of the present invention improves the draw-down property (elongation at break) during melt molding of the soft fluororesin, and provides a smooth surface of the molded product. improvement in sexual performance is achieved.

Claims (1)

[Scope of Claims] 1) 0.1 to 80 parts by weight of a powdery filler that does not melt at a temperature of 130°C or less and 0.05 to 80 parts by weight of fibrous polytetrafluoroethylene based on 100 parts by weight of a soft fluororesin. 1
0 parts by weight of a soft fluororesin composition for extrusion molding. 2) The soft fluororesin is copolymerized with at least one kind of monomer containing at least one kind of fluorine-containing monomer, and a double bond and a peroxy bond in the molecule to contain a peroxy group in the molecule, The first step is to produce a fluorine-containing elastic copolymer (stem polymer) whose glass transition temperature is below room temperature, and the second step is to produce a fluorine-containing elastic copolymer (stem polymer) whose glass transition temperature is below room temperature. 2. The soft resin according to claim 1, which is a resin obtained by graft polymerizing one or more monomers containing at least one fluorine-containing monomer to give a crystalline polymer having a temperature of 130° C. or higher. Fluororesin composition.