WO2023146815A1 - Polytetrafluoroethylene granulated powder and method for producing the same - Google Patents

Polytetrafluoroethylene granulated powder and method for producing the same Download PDF

Info

Publication number
WO2023146815A1
WO2023146815A1 PCT/US2023/011323 US2023011323W WO2023146815A1 WO 2023146815 A1 WO2023146815 A1 WO 2023146815A1 US 2023011323 W US2023011323 W US 2023011323W WO 2023146815 A1 WO2023146815 A1 WO 2023146815A1
Authority
WO
WIPO (PCT)
Prior art keywords
coupling agent
silane coupling
filler
granulated powder
group
Prior art date
Application number
PCT/US2023/011323
Other languages
French (fr)
Inventor
Tsuneo ECHIZEN
Original Assignee
Chemours-Mitsui Fluoroproducts Co., Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Chemours-Mitsui Fluoroproducts Co., Ltd filed Critical Chemours-Mitsui Fluoroproducts Co., Ltd
Publication of WO2023146815A1 publication Critical patent/WO2023146815A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/12—Powdering or granulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B7/00—Mixing; Kneading
    • B29B7/002—Methods
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B7/00—Mixing; Kneading
    • B29B7/80—Component parts, details or accessories; Auxiliary operations
    • B29B7/88—Adding charges, i.e. additives
    • B29B7/90—Fillers or reinforcements, e.g. fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B9/00—Making granules
    • B29B9/12—Making granules characterised by structure or composition
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B9/00—Making granules
    • B29B9/16—Auxiliary treatment of granules
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/20—Compounding polymers with additives, e.g. colouring
    • C08J3/205—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase
    • C08J3/21—Compounding polymers with additives, e.g. colouring in the presence of a continuous liquid phase the polymer being premixed with a liquid phase
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B9/00—Making granules
    • B29B9/12—Making granules characterised by structure or composition
    • B29B2009/125—Micropellets, microgranules, microparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B9/00—Making granules
    • B29B9/02—Making granules by dividing preformed material
    • B29B9/06—Making granules by dividing preformed material in the form of filamentary material, e.g. combined with extrusion
    • B29B9/065—Making granules by dividing preformed material in the form of filamentary material, e.g. combined with extrusion under-water, e.g. underwater pelletizers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F114/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
    • C08F114/18—Monomers containing fluorine
    • C08F114/26—Tetrafluoroethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
    • C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
    • C08J2327/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
    • C08J2327/18—Homopolymers or copolymers of tetrafluoroethylene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/08—Metals
    • C08K2003/085—Copper
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/24—Acids; Salts thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/04—Ingredients treated with organic substances
    • C08K9/06—Ingredients treated with organic substances with silicon-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/08—Ingredients agglomerated by treatment with a binding agent

Definitions

  • Polytetrafluoroethylene has a low coefficient of friction and is very excellent in heat resistance and chemical resistance but is characterized by being susceptible to wear and deformation. Therefore, in order to improve wear resistance and creep resistance, compositions containing various fillers are often used as sliding members and seal members.
  • a PTFE composition is obtained by mixing a PTFE powder with a filler, and a granulated powder having a high apparent density is produced in order to improve the handleability and fluidity of the powder. In addition, granulation is also performed for the PTFE powder alone for improving the handleability.
  • the multi-hydrolyzable group-type silane coupling agent is preferably a bissilane coupling agent represented by Formula (1 ) below or a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2) below.
  • the multi-hydrolyzable group-type silane coupling agent is a bissilane coupling agent represented by Formula (1)
  • R1 does not contain a substituent or contains an imino group (-NH-) as a substituent.
  • the multi-hydrolyzable group-type silane coupling agent is a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2)
  • R a and Rb do not contain a substituent or contain an imino group (-NH-) as a substituent.
  • R1 is a linear or branched hydrocarbon having 2 to 12 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen.
  • A is -CH- or N
  • HFP hexafluoropropylene
  • PMVE perfluoro(methyl vinyl ether)
  • PEVE perfluoro (ethyl vinyl ether)
  • PPVE perfluoro(propyl vinyl ether)
  • PBVE perfluoro(butyl vinyl ether)
  • the molecular chains are less likely to slip due to presence of the comonomer, so the strength or elastic modulus of the resin increases, and the creep resistance is also enhanced.
  • the amount of the comonomer exceeds 1 wt%, then the slidability of the PTFE will decrease, and the composition will exhibit fluidity at a temperature greater than or equal to the melting point, so the composition will not be suitable for use at high temperatures.
  • the comonomer content is preferably in the range from 0.001 to 1 wt% in terms of comonomer units.
  • a known polymerization method such as suspension polymerization or emulsion polymerization may be used as the polymerization method for the polytetrafluoroethylene.
  • a powdered PTFE (molding powder) obtained by suspension polymerization is preferably used in the resin composition of the present invention due to the reasons described below.
  • a polytetrafluoroethylene obtained by emulsion polymerization is unlikely to cause fibrillization due to shearing stress, so it can be dry-mixed at room temperature.
  • suspension polymerization is excellent in handleability because powder does not solidify even in a charging operation at the time of molding and is also excellent in terms of low cost.
  • this polytetrafluoroethylene is ordinarily used to mold various products in a powdered state.
  • the average particle size is not greater than 100 pm, preferably in the range from 5 to 100 pm, and more preferably in the range from 10 to 50 pm.
  • a polytetrafluoroethylene having an average particle size within this range has excellent uniform mixing properties with various fillers.
  • Such polytetrafluoroethylene can be directly produced in powder form by a suspension polymerization method.
  • a commercially available molding powder may also be used as long as it has such an average particle size.
  • R1 is a linear or branched hydrocarbon having 2 to 12 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen.
  • the number of carbon atoms of the hydrocarbon is preferably 5 to 10, and the hydrocarbon is preferably linear. It is preferable that the number of carbon atoms of the hydrocarbon is large because the hydrophobicity is increased and the affinity with PTFE is improved.
  • Ri does not have a substituent, it is considered that the affinity with PTFE is improved by increasing the hydrophobicity, and the effect of suppressing the desorption of the filler into the aqueous phase is also increased, which is preferable.
  • R a and Rb are each independently a hydrocarbon having 1 to 10 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen, preferably having 2 to 8 carbon atoms, and more preferably having 2 to 6 carbon atoms.
  • the number of carbon atoms of the hydrocarbon is two or more, it is considered that hydrophobicity is enhanced and affinity with PTFE is improved, which is preferable.
  • R a and Rb do not have a substituent because it is considered that the hydrophobicity is enhanced and the affinity with PTFE is improved, and it is also preferable that the effect of suppressing the desorption of the filler into the aqueous phase is enhanced.
  • the silane coupling agent used in the present invention is preferably used as a solution dissolved in a solvent from the viewpoint of uniformly dispersing the silane coupling agent in the mixing step.
  • the solvent is not particularly limited, and examples thereof include various organic solvents such as toluene, isopropyl alcohol, 1 ,3-dichloro-1 , 1 ,2,2,3- pentafluoropropane, and 1-chloro-2,3,3-trifluoropropene.
  • 1- chloro-2,3,3-trifluoropropene can be used.
  • the water-insoluble organic liquid and the above mixture may be mixed to obtain a slurry, and the slurry may be granulated by stirring the slurry at high speed with a large amount of water. Thereafter, the granulated powder is taken out from the water and dried to obtain a granulated powder. During high-speed stirring in water, a surfactant may be added to water to produce a granulated powder.
  • PTFE raw material powder Teflon (registered trademark) PTFE 7-J (homo-PTFE, average particle size: 50 pm) available from Chemours-Mitsui Fluoroproducts Co., Ltd.
  • Turbidity The granulated wastewater was diluted 10 times, and the turbidity was measured with a portable turbidity meter 21 OOP type available from HACH.
  • OOP portable turbidity meter 21 OOP type available from HACH.
  • the filler or the like separated without bonding to the resin migrates from the water-insoluble organic liquid to the aqueous phase. Therefore, by measuring the turbidity of the granulated wastewater, the degree of desorption due to the migration of the filler to the aqueous phase can be indirectly evaluated.
  • Example 7 and Comparative Example 8 when the bronze powder was used as a filler, the specific gravity of the bronze was large, and the bronze settled immediately, and thus it was not possible to measure the turbidity. For this reason, the granulated wastewater was visually evaluated (refer to FIGS. 1 and 2).
  • Comparative Example 8 in which the silane F was used, the bronze powder was settled on the entire bottom surface of a container (white plastic bucket) containing granulated wastewater (FIG. 2).
  • FIG. 1 the bottom surface of the container (white plastic bucket) containing granulated wastewater was visible (FIG. 1) (the bronze powder desorbed and settled at the center of the bottom surface was collected). From the comparison between Example 7 and Comparative Example 8, it was found that the use of the bissilane A instead of the silane F reduced the desorption of the bronze powder to the aqueous phase.

Abstract

An object of the present invention is to provide a granulated powder having good handleability and causing little desorption of a filler during production (granulation) or use. The present invention is a method for producing a polytetrafluoroethylene granulated powder, including stirring a mixture containing a filler, a polytetrafluoroethylene powder, and multi-hydrolyzable group-type silane coupling agent is in a mixed liquid of water and a water-insoluble organic liquid to perform mixed granulation.

Description

POLYTETRAFLUOROETHYLENE GRANULATED POWDER AND METHOD FOR PRODUCING THE SAME TECHNICAL FIELD
[0001] The present invention relates to a polytetrafluoroethylene granulated powder in which desorption of a filler is reduced during production and use, and a method for producing the same.
CONVENTIONAL TECHNOLOGY
[0002] Polytetrafluoroethylene (PTFE) has a low coefficient of friction and is very excellent in heat resistance and chemical resistance but is characterized by being susceptible to wear and deformation. Therefore, in order to improve wear resistance and creep resistance, compositions containing various fillers are often used as sliding members and seal members. A PTFE composition is obtained by mixing a PTFE powder with a filler, and a granulated powder having a high apparent density is produced in order to improve the handleability and fluidity of the powder. In addition, granulation is also performed for the PTFE powder alone for improving the handleability.
[0003] As a method for producing a granulated powder, a method in which a powder is wetted with an organic solvent, slurried, and rolled to granulate the powder (Patent Document 1) is known, but since it is difficult to completely discharge the powder for each batch, it is not preferable in terms of quality when the powder is continuously produced. In addition, a method for stirring a mixture of a powder and a water-insoluble organic solvent in water (Patent Document 2) is also used because of high productivity thereof. Such a method is called underwater granulation. However, this method has a problem that when a filler having a hydrophilic surface is used, the filler is desorbed into water. As a result, the desorbed filler agglomerates during the process, and is mixed into a product, thereby generating a defective product, and a content ratio is lowered from a target value due to loss of the filler.
[0004] Therefore, there have been proposed a method for treating a hydrophilic filler with an amino group-containing silane (aminosilane) or a silicone resin (Patent Document 3), a method for treating a hydrophilic filler with an amino group-containing silicone resin (Patent Document 4), a method for using a specific fluorine-containing solvent as a solvent (Patent Document 5), and the like. However, when a metal powder or a metal compound (a metal salt, a metal oxide, or the like) having a high surface hydrophilicity and a high specific gravity is used as a filler, particularly when a filler having a small particle size is used, even if the above-described method is used, desorption occurs. A filler having a small particle size can obtain an effect of the filler even in a small amount and is preferably used in this respect, but there is a problem in that the filler is easily desorbed.
[0005] In addition, PTFE is excellent in non-adhesiveness of the surface, but there is also a problem that desorption of the filler from the obtained granulated powder is likely to occur. This problem occurs not only when a filler having a hydrophilic surface is used but also when a filler having a hydrophobic surface is used, and the filler having a hydrophobic surface is also required to have improved adhesion to PTFE. In addition, when a filler having a large particle size is used, there is also a problem that the filler is relatively easily desorbed from the obtained granulated powder, although the filler is hardly desorbed during granulation.
PRIOR ART DOCUMENTS
Patent Documents
[0006] Patent Document 1 : Japanese Examined Patent Application, Publication No. S44-22620
[0007] Patent Document 2: Japanese Examined Patent Application, Publication No. S60-21694
[0008] Patent Document 3: Japanese Unexamined Patent Application, Publication No. S51-549
[0009] Patent Document 4: Japanese Unexamined Patent Application,
Publication No. 2001-220482 [0010] Patent Document 5: Japanese Unexamined Patent Application,
Publication No. 2002-201287
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0011] An object of the present invention is to provide a granulated powder having good handleability and causing little desorption of a filler during production (granulation) or use.
MEANS FOR SOLVING THE PROBLEM
[0012] The present inventors have found that when a PTFE powder is mixed with a filler in particular, a filler having a hydrophilic particle surface, the use of a specific silane coupling agent reduces the desorption of the filler, and further suppresses the desorption of the filler from the obtained granulated powder, thereby completing the present invention.
[0013] That is, one embodiment of the present invention is a method for producing a polytetrafluoroethylene granulated powder, including stirring a mixture containing a filler, a polytetrafluoroethylene powder, and multi- hydrolyzable group-type silane coupling agent in a mixed liquid of water and a water-insoluble organic liquid to perform mixed granulation.
[0014] The order of mixing the filler, the polytetrafluoroethylene powder, and the multi-hydrolyzable group-type coupling agent is not particularly limited, and the multi-hydrolyzable group-type coupling agent may be added to the filler, and then the polytetrafluoroethylene powder may be added, or the filler, the polytetrafluoroethylene powder, and the multi-hydrolyzable group-type coupling agent may be simultaneously mixed.
[0015] The multi-hydrolyzable group-type silane coupling agent is preferably a bissilane coupling agent represented by Formula (1 ) below or a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2) below.
X - Ri - X (1) wherein X is a hydrolyzable silyl group (-Si-(OR2)n(R3)3-n) (n = 1 to 3), R2 and R3 are each -CH3 or -C2H5, and
R1 is a linear or branched hydrocarbon having 2 to 12 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen.
Figure imgf000005_0001
wherein X is a hydrolyzable silyl group (-Si-(OR2)n(R3)3-n) (n = 1 to 3), R2 and R3 are each -CH3 or -C2H5, and
A is -CH- or N,
Ra and Rb are each independently a hydrocarbon having 1 to 10 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen,
Rc is a hydrocarbon having 1 to 5 carbon atoms in which hydrogen may be substituted with halogen, and
P = 3 to 30.
[0016] When the multi-hydrolyzable group-type silane coupling agent is a bissilane coupling agent represented by Formula (1), it is preferable that R1 does not contain a substituent or contains an imino group (-NH-) as a substituent. When the multi-hydrolyzable group-type silane coupling agent is a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2), it is preferable that Ra and Rb do not contain a substituent or contain an imino group (-NH-) as a substituent. [0017] Another embodiment of the present invention is a granulated powder containing from 3 to 40 vol% of a filler and from 60 to 97 vol% polytetrafluoroethylene powder, and the polytetrafluoroethylene granulated powder contains 1 wt.% or less of a multi-hydrolyzable group-type silane coupling agent with respect to the total amount of the granulated powder.
[0018] The multi-hydrolyzable group-type silane coupling agent is preferably a bissilane coupling agent represented by Formula (1 ) below or a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2) below.
X - Ri - X (1) wherein X is a hydrolyzable silyl group (-Si-(OR2)n(R3)3-n) (n = 1 to 3), R2 and R3 are each -CH3 or -C2H5, and
R1 is a linear or branched hydrocarbon having 2 to 12 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen.
Figure imgf000006_0001
wherein X is a hydrolyzable silyl group (-Si-(OR2)n(R3)3-n) (n = 1 to 3), R2 and R3 are each -CH3 or -C2H5, and
A is -CH- or N,
Ra and Rb are each independently a hydrocarbon having 1 to 10 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen, Rc is a hydrocarbon having 1 to 5 carbon atoms in which hydrogen may be substituted with halogen, and
P = 3 to 30.
[0019] The multi-hydrolyzable group-type silane coupling agent is preferably a bissilane coupling agent represented by Formula (1 ) below. The multi-hydrolyzable group-type silane coupling agent is preferably a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2) below.
[0020] The granulated powder preferably has an average particle size from 200 to 800 pm.
EFFECT OF THE INVENTION
[0021] The PTFE granulated powder of the present invention can be produced by an underwater granulation method with high productivity. In addition, in the method for producing the PTFE granulated powder of the present invention, even when a hydrophilic filler having a small particle size is used, granulation in which the filler is uniformly dispersed can be performed without desorption of the filler into the aqueous phase. Since the obtained granulated powder hardly causes desorption of the filler and is excellent in handleability, a molded product can be easily produced by compression molding and can be used for various applications such as a sliding member and a sealing material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a photograph of wastewater of Example 7 shown in Table 5.
[0023] FIG. 2 is a photograph of wastewater of Comparative Example 8 shown in Table 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The PTFE granulated powder of the present invention is produced from a filler, a polytetrafluoroethylene powder, and a specific silane coupling agent. First, each component will be described below. (1) Polytetrafluoroethylene (PTFE)
[0025] As the PTFE powder used in the present invention, a homopolymer (homo-PTFE) of tetrafluoroethylene (TFE), a TFE copolymer (modified PTFE) containing a monomer copolymerizable with TFE within a range of not greater than 1 wt.%, or a mixture thereof may be used.
[0026] As a monomer (comonomer) that is copolymerizable with TFE contained in a modified PTFE, a monomer which contains an unsaturated bond and can be subjected to radical polymerization can be used. In order to maintain the excellent performance of the PTFE, such as heat resistance and chemical resistance, it is preferable to use a fluorine-containing monomer as a comonomer. Specific examples of comonomers include perfluoroalkenes having 3 or more carbons - preferably from 3 to 6 carbons - perfluoro(alkyl vinyl ethers) having from 1 to 6 carbons, and chlorotrifluoroethylene. Of these, it is preferable to use hexafluoropropylene (HFP), perfluoro(methyl vinyl ether) (PMVE), perfluoro (ethyl vinyl ether) (PEVE), perfluoro(propyl vinyl ether) (PPVE), perfluoro(butyl vinyl ether) (PBVE), and chlorotrifluoroethylene.
[0027] When a modified PTFE is used, the molecular chains are less likely to slip due to presence of the comonomer, so the strength or elastic modulus of the resin increases, and the creep resistance is also enhanced. However, if the amount of the comonomer exceeds 1 wt%, then the slidability of the PTFE will decrease, and the composition will exhibit fluidity at a temperature greater than or equal to the melting point, so the composition will not be suitable for use at high temperatures. In addition, it will be difficult to produce a molded product by a free-baking method, wherein a compression-molded composition is heat-fired at or above the melting point thereof. Therefore, the comonomer content is preferably in the range from 0.001 to 1 wt% in terms of comonomer units.
[0028] A known polymerization method such as suspension polymerization or emulsion polymerization may be used as the polymerization method for the polytetrafluoroethylene. A powdered PTFE (molding powder) obtained by suspension polymerization is preferably used in the resin composition of the present invention due to the reasons described below. In comparison to a polytetrafluoroethylene obtained by emulsion polymerization, a polytetrafluoroethylene obtained by suspension polymerization is unlikely to cause fibrillization due to shearing stress, so it can be dry-mixed at room temperature. In addition, suspension polymerization is excellent in handleability because powder does not solidify even in a charging operation at the time of molding and is also excellent in terms of low cost.
[0029] Polytetrafluoroethylene can be used as a molding material as long as it has a molecular weight allowing it to be molded by a means such as compression molding. The melting point of PTFE is known to be correlated with the molecular weight thereof, and a polymer having a melting point of approximately 327°C can be suitably used as a molding resin for a sliding component with good mechanical strength and heat resistance.
[0030] In addition, this polytetrafluoroethylene is ordinarily used to mold various products in a powdered state. The average particle size is not greater than 100 pm, preferably in the range from 5 to 100 pm, and more preferably in the range from 10 to 50 pm. A polytetrafluoroethylene having an average particle size within this range has excellent uniform mixing properties with various fillers. Such polytetrafluoroethylene can be directly produced in powder form by a suspension polymerization method. In addition, a commercially available molding powder may also be used as long as it has such an average particle size.
[0031] Examples of such a PTFE molding powder include Teflon (registered trademark) PTFE 7-J (homo-PTFE, average particle size: 50 pm) available from Chemours-Mitsui Fluoroproducts Co., Ltd., Teflon (registered trademark) PTFE 7A-J (homo-PTFE, average particle size: 30 pm) available from Chemours-Mitsui Fluoroproducts Co., Ltd., and Teflon (registered trademark) PTFE 70-J (modified PTFE, average particle size: 35 pm) available from Chemours-Mitsui Fluoroproducts Co., Ltd. (2) Filler
[0032] In the present invention, the “filler” is a powdery substance used for improving various physical properties of a molded product, and examples of the filler used in the present invention include various organic substances and inorganic substances mixed with the PTFE powder for molding. Examples of organic substances include engineering plastics such as polyphenylene sulfides, polyether sulfones, polyphenyl sulfones, polyamides, polyimides, phenolic resins, urea resins, epoxy resins, urethane resins, melamine resins, polyester resins, polyether resins, acrylic resins, acrylic silicone resins, silicone resins, and silicone polyester resins. Examples of inorganic substances include metal powders, metal oxides (aluminum oxide, zinc oxide, tin oxide, titanium oxide (titanate), and the like), glass, ceramics, silicon carbides, silicon oxides, calcium fluorides, carbon black, carbon fillers, graphites, cokes, micas, talc, barium sulfates, molybdenum disulfide, and the like. Combinations of these can be used as necessary.
[0033] In the present invention, a filler having a hydrophilic particle surface, which has been difficult to handle in the known underwater granulation method, can also be used. Specific examples of the filler having a hydrophilic particle surface include metals (bronze, aluminum, and the like), metal compounds (metal oxides, metal salts, and metal halides), inorganic salts (silicon carbide, silicon oxide, boron nitride, calcium fluoride, and the like), glass, silica, and the like. In the present invention, by using a specific silane coupling agent, even the filler having a hydrophilic particle surface can be prevented from being desorbed due to migration of the filler to an aqueous phase in the underwater granulation, and even a filler having a large specific gravity such as a metal or a metal compound which is particularly likely to migrate to an aqueous phase in the underwater granulation can be prevented from being desorbed.
[0034] In addition, particles of engineering plastic having a hydrophobic surface such as wholly aromatic polyester resin, or a carbon-based filler having a graphene structure having a hydrophobic particle surface such as carbon black, carbon fiber, graphite, or coke may be used. By using a specific silane coupling agent, the filler can be attached to the granulated powder with sufficient strength, and desorption of the filler due to vibration or the like can be suppressed in a step after granulation or in use of the granulated powder. Further, when the imino group remains, an effect of preventing static electrification of the granulated powder is also obtained.
[0035] As the particle shape of the filler, there are various shapes such as a particle shape, a fiber shape, and a flake shape, and any shape can be used. When the particle size is small, the effect of improving the physical properties by the filler can be obtained even in a small amount, but there is a problem that the filler easily migrates into water during the underwater granulation. In the present invention, by using a specific silane coupling agent, it is possible to suppress the desorption of the filler having a small particle size and a hydrophilic surface, and thus it is also possible to use a filler having a small particle size of 0.1 pm to 100 pm.
[0036] However, from the viewpoint of efficiently producing granulated particles having good quality, the average particle size of the filler is preferably 1 pm to 500 pm, and more preferably 3 pm to 300 pm. The average particle size of the filler refers to the particle size at an integrated value of 50% (volume basis) in the particle size distribution obtained by laser diffraction and scattering.
(3) Silane coupling agent (multi-hydrolyzable group-type silane coupling agent)
[0037] In general, a silane coupling agent is a compound having a hydrolyzable silyl group as shown below, which reacts with an inorganic material to form a covalent bond.
R-Si-(OR2)n(R3) 3-n(n = 1 to 3) (3)
R2 and R3 are each independently a methyl group or an ethyl group, and R is called an organic substituent and is a saturated or unsaturated alkyl group containing one or a plurality of reactive groups such as a vinyl group, an epoxy group (alicyclic epoxy group, glycidyl group), a methacryl group, an acryl group, a styryl group, an amino group, an imino group, a sulfide group, a disulfide group, an aryl group, a diamino group, a mercapto group, a ureido group, and an isocyanate group depending on desired characteristics.
[0038] The silane coupling agent used in the present invention contains a hydrolyzable silyl group: -Si-(OR2)n(R3)3-n) (n = 1 to 3) is a multi- hydrolyzable group-type silane coupling agent. Specific examples of the multi-hydrolyzable group-type silane coupling agent include a bissilane coupling agent (A) having a structure having hydrolyzable silyl groups at both terminals of an organic substituent, and a polymeric silane coupling agent (B) having a structure having a repeating structure of an organic substituent and having a hydrolyzable silyl group at a side chain thereof, and these are preferably used.
(A) Bissilane coupling agent
[0039] The bissilane coupling agent (A) used in the present invention is a bissilane having two hydrolyzable silyl groups in the molecule and represented by Formula (1 ) below.
X-Ri-X (1 )
X is a hydrolyzable silyl group [-Si-(OR 2]n(R3)3-n] (n = 1 to 3), and preferably a trialkoxysilyl group: -Si-(OR2)s or a dialkoxysilyl group: -Si-Rs (OR2)2. R2 and R3 each represent an alkyl group, and preferably -CH3 or -C2H5. X is more preferably a trimethoxysilyl group.
[0040] R1 is a linear or branched hydrocarbon having 2 to 12 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen. The number of carbon atoms of the hydrocarbon is preferably 5 to 10, and the hydrocarbon is preferably linear. It is preferable that the number of carbon atoms of the hydrocarbon is large because the hydrophobicity is increased and the affinity with PTFE is improved. When Ri does not have a substituent, it is considered that the affinity with PTFE is improved by increasing the hydrophobicity, and the effect of suppressing the desorption of the filler into the aqueous phase is also increased, which is preferable. When a substituent is present, the substituent may be present between carbon atoms of the hydrocarbon, for example, as -NH-, -S-, -S- S-, -C6H4- or the like, and preferably includes -NH- (imino group). The number of imino groups in R1 is preferably one. When an imino group is present in the molecule, it can contribute to the prevention of static charge, and as a result, the water solubility of the molecule is improved, and the effect can be obtained in a small amount for many fillers, so that the mixing at the time of granulation is improved. Hydrogen of the hydrocarbon may be substituted with halogen, and may be substituted with chlorine or the like.
[0041] Specific examples of the bissilane coupling agent include, but are not limited to, 1 ,2-bis(triethoxysilyl) ethane, 1 ,2-bis(triethoxysilyl) ethylene, 1 ,6-bis(trimethoxysilyl) hexane, 1 ,8-bis(trimethoxysilyl) octane, 1 ,8-bis(triethoxysilyl) octane, bis[3-tri(methoxysilyl) propyl] amine, bis[3- tri(ethoxysilyl) propyl] amine, N,N’-bis[3-tri(methoxysilyl) propyl] ethylenediamine, 1 ,4-bis(trimethoxysilylethyl) benzene, 1 ,3- bis(trimethoxysilylpropyl) benzene, 1 ,6-bis(trimethoxysilyl)-2,5- dimethylhexane, bis(triethoxysilylpropyl) disulfide, and a mixture of two or more kinds selected from these. Among these, 1 ,6-bis(tri methoxysilyl) hexane, 1 ,8-bis(trimethoxysilyl) octane, or bis[3-tri(methoxysilyl) propyl] amine is preferable, and 1 ,8-bis(trimethoxysilyl) octane is more preferable. Since the bissilane coupling agent used in the present invention has two or more hydrolyzable silyl groups, it is considered that the bissilane coupling agent is bonded to the filler to be mixed and acts to suppress the separation thereof.
[0042] Such a bissilane coupling agent can be produced by the methods disclosed in Japanese Unexamined Patent Application, Publication No. 5- 194551 , Published Japanese Translation No. 2005-509683 of the PCT International Publication for Patent Applications, and US Patent No. 6242627, or commercially available SIB1824. 0 and SIB1832. 7 available from Gelest, Inc., Dynasilane 1124 available from Evonik, and KBM-3086 available from Shin-Etsu Chemical Co., Ltd. can be used.
(B) Polymeric silane coupling agent
[0043] The polymeric silane coupling agent is a silane coupling agent containing a repeating monomer unit represented by Formula (2) below.
Figure imgf000014_0001
[0044] X is a hydrolyzable silyl group (-Si-(OR 2]n(R3)s-n) (n = 1 to 3), and preferably a trialkoxysilyl group: -Si-(OR2)s or a dialkoxysilyl group: -Si-Rs (OR2)2. R2 and R3 each represent an alkyl group, and preferably -CH3 or - C2H5. X is more preferably a trimethoxysilyl group. A is -CH- or N.
[0045] Ra and Rb are each independently a hydrocarbon having 1 to 10 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen, preferably having 2 to 8 carbon atoms, and more preferably having 2 to 6 carbon atoms. When the number of carbon atoms of the hydrocarbon is two or more, it is considered that hydrophobicity is enhanced and affinity with PTFE is improved, which is preferable. It is preferable that Ra and Rb do not have a substituent because it is considered that the hydrophobicity is enhanced and the affinity with PTFE is improved, and it is also preferable that the effect of suppressing the desorption of the filler into the aqueous phase is enhanced. Ra and Rb may be present, for example, as -NH-, -S-, -S-S-, -C6H4- or the like, and those containing -NH- (imino group) are preferable. When an imino group is contained in Ra or Rb, a repeating structure having two or more carbon atoms in the main chain per imino group is preferable. When an imino group is present in the molecule, it can contribute to the prevention of static charge, and as a result, the water solubility of the molecule is improved, and the effect can be obtained in a small amount for many fillers, so that the mixing at the time of granulation is improved. Rc is a hydrocarbon having 1 to 5 carbon atoms in which hydrogen may be substituted with halogen and is preferably a linear hydrocarbon.
[0046] The molecular weight of the polymeric silane coupling agent depends on the molecular structure of the basic skeleton, and is, for example, from 500 to 5000, preferably from 900 to 3000, and more preferably from 1200 to 2000. A degree of polymerization p of the polymeric silane coupling agent depends on the molecular structure of the basic unit, and p = 3 to 30, preferably 3 to 20, and more preferably 3 to 10.
[0047] In the polymeric silane coupling agent (B) used in the present invention, A is preferably N, that is, a hetero-bonded nitrogen atom, for example, a polyethyleneimine structure.
[0048] Specific examples thereof include trimethoxysilylpropyl-modified polyethyleneimine as a polymeric silane coupling agent, and it is preferable to use a modified polyethyleneimine polymer having a basic unit of Formula (4) below.
Figure imgf000015_0001
[0049] An amine structure portion in the polymer unit becomes an ammonium ion and may form a salt with any anion (for example, Cl’).
P = 3 to 30.
[0050] Examples of a such polymeric silane coupling agent having a hydrolyzable silyl group side chain include X-12-1048 and X-12-972F available from Shin-Etsu Chemical Co., Ltd., and SSP 060, SSP 065, SSP 050 available from Gelest, Inc. and the like can be used.
[0051] Since the polymeric silane coupling agent used in the present invention contains a plurality of hydrolyzable silyl groups, the polymeric silane coupling agent acts to be bonded to the filler and/or PTFE to be mixed and suppress separation thereof, and since the polymeric silane coupling agent has a hydrophobic polymer main chain, it is considered that desorption due to migration of the filler into the aqueous phase is suppressed in the granulation step.
[0052] It is considered that the silane coupling agent used in the present invention, particularly one having an imino group, not only strengthens the adhesion between PTFE and the filler but also imparts an antistatic effect to the particles after granulation. As a result, the granulated particles are believed to be less likely to clog the sieve.
[0053] The silane coupling agent used in the present invention is preferably used as a solution dissolved in a solvent from the viewpoint of uniformly dispersing the silane coupling agent in the mixing step. The solvent is not particularly limited, and examples thereof include various organic solvents such as toluene, isopropyl alcohol, 1 ,3-dichloro-1 , 1 ,2,2,3- pentafluoropropane, and 1-chloro-2,3,3-trifluoropropene. For example, 1- chloro-2,3,3-trifluoropropene can be used.
(4) Granulated powder of the present invention and method for producing the same
[0054] The granulated powder of the present invention is created from a mixture containing a filler, a polytetrafluoroethylene (PTFE) powder, and a multi-hydrolyzable group-type silane coupling agent. PTFE: The composition ratio of the filler is 99 to 20 vol%: 1 to 80 vol%, preferably 97 to 60 vol%: 3 to 40 vol%, more preferably 94 to 75 vol%: 6 to 25 vol%. When the content of the filler in the mixture is small, it is difficult to obtain the effect of improving the physical properties by the filler; whereas when the content of the filler is too large, the physical properties such as elongation of a molded product produced from the granulated powder to be obtained are deteriorated.
[0055] In addition, the content of the silane coupling agent used in the present invention is 0.001 to 1 .0 wt%, preferably 0.01 to 0.3 wt%, and more preferably 0.01 to 0.15 wt.% in the mixture (total amount of granulated powder). By using the silane coupling agent in an amount in this range, the desorption of the filler can be suppressed. Other additives can be added to the mixture as optional components. As an additive, for example, one or two or more of solid lubricants, oxidation stabilizers, heat stabilizers, wearresistant materials, weather stabilizers, flame retardants, pigments, and the like can be mentioned, and the physical properties of the granulated particles are not affected (for example, 5 wt.% or less).
[0056] As a method for mixing the filler, the polytetrafluoroethylene (PTFE) powder, and the multi-hydrolyzable group-type silane coupling agent, it can be produced by mixing the PTFE powder and the filler to form a mixed powder and treating the mixed powder with a silane coupling agentcontaining solution. Alternatively, it may be produced by surface treating the filler by mixing with a solution containing a silane coupling agent and then mixing with PTFE powder. Alternatively, it may be produced by simultaneously mixing the PTFE powder, the filler, and the solution of the silane coupling agent.
[0057] The granulated powder of the present invention is produced from the mixture described above by various known granulation methods, and is preferably produced by an underwater granulation method. As a specific underwater granulation method, a mixture containing a filler, a polytetrafluoroethylene powder, and a multi-hydrolyzable group-type silane coupling agent is added to a mixed liquid of a water-insoluble organic liquid and water, and the mixture is stirred.
[0058] In addition, the water-insoluble organic liquid and the above mixture may be mixed to obtain a slurry, and the slurry may be granulated by stirring the slurry at high speed with a large amount of water. Thereafter, the granulated powder is taken out from the water and dried to obtain a granulated powder. During high-speed stirring in water, a surfactant may be added to water to produce a granulated powder.
[0059] As the water-insoluble organic liquid used in the present invention, various organic solvents having small surface energy and being incompatible with water can be used, and examples thereof include hydrocarbons such as hexane, kerosene, cyclohexane, benzene, toluene, and xylene; ethers such as diethyl ether and dipropyl ether; halogenated hydrocarbons such as methylene chloride, dichloroethylene, trichloroethylene, tetrachloroethylene, chlorobenzene, dichlorobenzene, fluorotrichloromethane, fluorodichloroethane, dichlorotrifluoroethane, trichlorotrifluoroethane, difluorotetrachloroethane, dichloropentafluoropropane, and decafluoropentane; and fluoroethers such as perfluoropropyl methyl ether, perfluorobutyl methyl ether, perfluoro butyl ethyl ether, perfluoropentyl methyl ether, and perfluoropentyl ethyl ether. Two or more kinds thereof may be mixed and used.
[0060] The granulated powder of the present invention preferably has an average particle size of 200 to 800 pm. If the size is too large, voids remain when compression molding is performed, and tensile and compression characteristics are deteriorated. If the particle size is too small, the filler deviated from the granulated powder particles is agglomerated, and defects are likely to occur.
EXAMPLES
[0061] The present invention is described more specifically below through examples. The raw materials used in Examples and Comparative Examples and the obtained PTFE molding powders were evaluated by the following methods.
1 . Raw materials
(a) PTFE raw material powder: Teflon (registered trademark) PTFE 7-J (homo-PTFE, average particle size: 50 pm) available from Chemours-Mitsui Fluoroproducts Co., Ltd.
(b) Filler: 8 potassium titanate particle powder: TERRACESS (registered trademark) JP (available from Otsuka Chemical Co., Ltd.) (average particle size: 4 to 12 pm)
Coke powder (trade name At-No. 5C available from Oriental Industry Co.
LTD) (average particle size 50 pm)
Bronze powder (average particle size 15 pm)
Solvent for mixing silane coupling agent: 1-chloro-2,3,3-trifluoropropene (AMOLEA (registered trademark) AS-300 available from AGC Inc.)
(c) Silane coupling agent:
Table 1
Figure imgf000020_0001
(d)Water-insoluble organic liquid: tetrachloroethylene
2. Physical property evaluation method
(a) Permeability measurement
Turbidity: The granulated wastewater was diluted 10 times, and the turbidity was measured with a portable turbidity meter 21 OOP type available from HACH. When the resin and the filler are mixed and granulated by underwater granulation method, the filler or the like separated without bonding to the resin migrates from the water-insoluble organic liquid to the aqueous phase. Therefore, by measuring the turbidity of the granulated wastewater, the degree of desorption due to the migration of the filler to the aqueous phase can be indirectly evaluated. (b) Average particle size: measured by RPS-02 type available from Seishin Enterprise Co., Ltd.
[0062] Standard sieves of 14, 16, 20, 28, 35, 48, 70, and 100 meshes were stacked in 8 stages in order from the top, and the weight of the powder remaining on each sieve was determined. Based on each weight, the particle sizes of 16 wt.%, 50 wt.%, and 84 wt.% on logarithmic probability paper were determined and used as a criterion for determining whether the particle size distribution was wide or narrow.
Example 1
[0063] 3.5 kg of a composition containing 85 wt.% (89.9 vol%) of PTFE molding powder (Teflon (registered trademark) 7-J, melting point: 327°C) and 15 wt.% (10.1 vol%) of 8 potassium titanate (Telacess (registered trademark) JP , available from Otsuka Chemical Co., Ltd.) was added to a Henschel mixer and mixed for 5 minutes. Subsequently, a solution prepared by dissolving 3.5 g of bis[3-(trimethoxysilyl) propyl] amine (bissilane compound A) as a silane coupling agent in 20 g of 1-chloro-2,3,3- trifluoropropene (AMOLEA (registered trademark) AS-300 available from AGC Inc.) was added thereto, the mixture was stirred for 15 minutes, then 20 g of pure water was added the mixture, and the mixture was stirred for 40 minutes to obtain a uniform mixture.
[0064] 20 L of water was added to a sealed vessel with a stirrer having an internal volume of 50 L, and maintained at 70°C, the mixture obtained above was added thereto, 50 wt.% of tetrachloroethylene was added to 100 wt.% of the mixture, then the mixture was stirred at a rotation speed of 630 rpm for 10 minutes, then the rotation speed was reduced to 236 rpm, and the mixture was further stirred for 40 minutes to be sized. This was separated from water with a 150 mesh sieve and dried at 170°C for 5 hours to obtain a granulated powder. Example 2
[0065] A granulated powder was obtained in the same manner as in Example 1 except that 1 ,8-bis(trimethoxysilyl) octane (bissilane compound B) was used as the silane coupling agent instead of bis[3-(trimethoxysilyl) propyl] amine (bissilane compound A).
Example 3
[0066] A granulated powder was obtained in the same manner as in Example 1 except that trimethoxysilylpropyl-modified polyethyleneimine (polymeric silane compound C) was used as the silane coupling agent instead of bissilane A.
Comparative Example 1
[0067] A granulated powder was obtained in the same manner as in Example 1 except that 3-glycidoxypropyltrimethoxysilane (silane compound D) was used as the silane coupling agent instead of bissilane A.
Comparative Example 2
[0068] A granulated powder was obtained in the same manner as in Example 1 except that 3-methacryloxypropyltrimethoxysilane (silane compound E) was used as the silane coupling agent instead of bissilane A.
Comparative Example 3
[0069] A granulated powder was obtained in the same manner as in Example 1 except that 3-acryloxypropyltrimethoxysilane (silane compound F) was used as the silane coupling agent instead of bissilane A.
[0070] The compositions and results of Examples 1 to 3 and Comparative Examples 1 to 3 are summarized in Table 2 below. In Comparative Examples 1 to 3 using the silane compounds D, E, and F, the average turbidity of the granulated wastewater was 150 or greater. On the other hand, it was reduced to 110.3 in Example 1 using bissilane A, 62.7 in Example 2 using bissilane B, and 15.9 in Example 3 using polymeric silane C. From these results, it was confirmed that desorption of the filler into the aqueous phase was suppressed by using the bissilane coupling agent and the polymeric silane coupling agent.
Table 2
Figure imgf000023_0001
Example 4
[0071] 3.5 kg of a composition containing 90 wt.% (93.4 vol%) of PTFE molding powder (Teflon (registered trademark) 7 -J, melting point: 327°C) and 10 wt.% (6.6 vol%) of 8 potassium titanate (Telacess (registered trademark) JP , available from Otsuka Chemical Co., Ltd.) was added to a Henschel mixer and mixed for 5 minutes. Subsequently, 20 g of pure water was added and stirred for 15 minutes, a solution prepared by dissolving 3.5 g of trimethoxysilylpropyl modified polyethyleneimine (polymeric silane compound C) as a silane coupling agent in 20 g of 1-chloro-2,3,3- trifluoropropene (AMOLEA (registered trademark) AS-300 available from AGC Inc.) was added thereto, and the mixture was stirred for 40 minutes to obtain a uniform mixture.
[0072] 20 L of water was added to a sealed vessel with a stirrer having an internal volume of 50 L, and maintained at 70°C, the mixture obtained above was added thereto, 50 wt.% of tetrachloroethylene was added to 100 wt.% of the mixture, then the mixture was stirred at a rotation speed of 630 rpm for 10 minutes, then the rotation speed was reduced to 236 rpm, and the mixture was further stirred for 40 minutes to be sized. This was separated from water with a 150 mesh sieve and dried at 170°C for 5 hours to obtain a granulated powder.
Example 5
[0073] A granulated powder was obtained in the same manner as in Example 4 except that 1 ,8-bis(trimethoxysilyl) octane (bissilane compound B) was used as the silane coupling agent instead of trimethoxysilylpropyl modified polyethyleneimine (polymeric silane compound C).
Comparative Example 4
[0074] A granulated powder was obtained in the same manner as in Example 4 except that N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (silane compound G) was used as the silane coupling agent instead of the polymeric silane compound C.
Comparative Example 5
[0075] A granulated powder was obtained in the same manner as in Example 4 except that 3-glycidoxypropyltrimethoxysilane (silane compound D) was used as the silane coupling agent instead of polymeric silane compound C.
Comparative Example 6
[0076] A granulated powder was obtained in the same manner as in Example 4 except that 3-acryloxypropyltrimethoxysilane (silane compound F) was used as the silane coupling agent instead of polymeric silane compound C.
[0077] The compositions and results of Examples 4 and 5 and Comparative Examples 4 to 6 are summarized in Table 3 below. First, when the particle size distribution (d16, d50, and d84) of the granulated powder was observed, a powder having a particle size within a predetermined distribution range was able to be granulated in each of Examples 4 and 5 and Comparative Examples 4 to 6. On the other hand, when the average turbidity of the granulated wastewater was compared, in Comparative Examples 4 to 6 using the silane compounds G, D, and F, the average turbidity was 100 or greater in each case. On the other hand, in Example 4 using the polymeric silane compound C, it was 9.6, and in Example 5 using bissilane B, it was 16.1 , and it was confirmed that desorption of the filler into the aqueous phase was remarkably suppressed.
Table 3
Figure imgf000025_0001
Example 6
[0078] 4.0 kg of a composition containing 75 wt.% (75.3 vol%) of PTFE molding powder (Teflon (registered trademark) 7-J, melting point: 327°C) and 25 wt.% (24.7 vol%) of Coke powder (At-No. 5C, a product available from Oriental Industry Co. LTD.) was added to a Henschel mixer and mixed for 5 minutes. Subsequently, 20 g of pure water was added and stirred for 15 minutes, silane coupling agent solution, prepared by dissolving 4.0 g of trimethoxysilylpropyl modified polyethyleneimine (polymeric silane compound) as a silane coupling agent in 20 g of 1-chloro-2,3,3- trifluoropropene (AMOLEA (registered trademark) AS-300 available from AGC Inc.) was added thereto, and the mixture was stirred for 40 minutes to obtain a uniform mixture.
[0079] 20 L of water was added to a sealed vessel with a stirrer having an internal volume of 50 L, and maintained at 70°C, the mixture obtained above was added thereto, 50 wt.% of tetrachloroethylene was added to 100 wt.% of the mixture, then the mixture was stirred at a rotation speed of 630 rpm for 10 minutes, then the rotation speed was reduced to 236 rpm, and the mixture was further stirred for 40 minutes to be sized. This was separated from water with a 150 mesh sieve and dried at 170°C for 5 hours to obtain a granulated powder.
Comparative Example 7
[0080] A granulated powder was obtained in the same manner as in Example 6 except that N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (silane compound G) was used as the silane coupling agent instead of trimethoxysilylpropyl modified polyethyleneimine (polymeric silane compound C).
[0081] The compositions and results of Example 6 and Comparative Example 7 are shown in Table 4 below. When the average turbidity of the granulated wastewater was compared, in a case where coke having a hydrophobic surface was used as a filler, the turbidity of the granulated wastewater of Example 6 and Comparative Example 7 showed low values of 2.6 and 4.0, respectively. However, in Example 6 in which the polymeric silane C was used, the desorption of the filler to the aqueous phase was able to be slightly improved as compared with Comparative Example 7 in which the silane G was used. In addition to the measurement of the turbidity of the granulated wastewater, the ratio of the fine granulated powder passing through the 70 mesh and the desorbed filler (coke) was simply measured for the produced granulated particles, and it was 39.2% in Example 6 using the polymeric silane compound C. On the other hand, in Comparative Example 7 using silane G, the ratio was 50.3% Table 4
Figure imgf000027_0001
Example 7
[0082] 4.0 kg of a composition containing 60 wt.% (85.7 vol%) of PTFE molding powder (Teflon (registered trademark) 7 -J, melting point: 327°C) and 40 wt.% (14.3 vol%) of bronze powder was added to a Henschel mixer and mixed for 5 minutes. Subsequently, a silane coupling agent solution prepared by dissolving 4.0 g of bis[3-(trimethoxysilyl)propyl]amine (bissilane compound A), as a silane coupling agent in 20 g of 1 ,3-dichloro-1 , 1 ,2,2,3- pentafluoropropane (HCFC-225cb) was added thereto, the mixture was stirred for 15 minutes, then 20 g of pure water was added the mixture, and the mixture was stirred for 40 minutes to obtain a uniform mixture.
[0083] 15 L of water was added to a sealed vessel with a stirrer having an internal volume of 50 L, and maintained at 70°C, the mixture obtained above was added thereto, 50 wt.% of tetrachloroethylene was added to 100 wt.% of the mixture, then the mixture was stirred at a rotation speed of 565 rpm for 10 minutes, then the rotation speed was reduced to 236 rpm, and the mixture was further stirred for 40 minutes to be sized. This was separated from water with a 150 mesh sieve and dried at 170°C for 5 hours to obtain a granulated powder.
Comparative Example 8
[0084] A granulated powder was obtained in the same manner as in Example 7 except that 3-acryloxypropyltrimethoxysilane (silane compound F) was used as the silane coupling agent instead of bis[3-(tri methoxysilyl) propyl] amine (bissilane compound A).
[0085] In Example 7 and Comparative Example 8, when the bronze powder was used as a filler, the specific gravity of the bronze was large, and the bronze settled immediately, and thus it was not possible to measure the turbidity. For this reason, the granulated wastewater was visually evaluated (refer to FIGS. 1 and 2). In Comparative Example 8 in which the silane F was used, the bronze powder was settled on the entire bottom surface of a container (white plastic bucket) containing granulated wastewater (FIG. 2). On the other hand, in Example 7 in which bissilane A was used, the bottom surface of the container (white plastic bucket) containing granulated wastewater was visible (FIG. 1) (the bronze powder desorbed and settled at the center of the bottom surface was collected). From the comparison between Example 7 and Comparative Example 8, it was found that the use of the bissilane A instead of the silane F reduced the desorption of the bronze powder to the aqueous phase.
Example 8
[0086] A granulated powder was obtained in the same manner as in Example 7 except that 0.03 wt% of polymeric silane C was used as the silane coupling agent instead of 0.1 wt.% of bissilane A. In the same manner as in Example 7 and Comparative Example 8, the granulated wastewater of Example 8 was visually evaluated, and as a result, it was confirmed that the settled bronze powder was reduced as compared with Example 7, and the desorption due to the migration of the bronze powder to the aqueous phase was reduced as compared with not only Comparative Example 8 but also Example 7. From this result, it was confirmed that the polymeric silane C has a high effect of suppressing the desorption of the filler due to the transition to the aqueous phase even at a low concentration as compared with the bissilane. Example 9
[0087] A granulated powder was obtained in the same manner as in Example 8 except that the amount of the silane coupling agent (polymeric silane C) was changed to 0.02 wt.%. The granulated wastewater in Example 9 was in the same manner as in Example 8, and it was confirmed that desorption due to the migration of the bronze powder to the aqueous phase was reduced. From the results of Examples 8 and 9, it was confirmed that even when the content of the silane coupling agent was reduced, the effect of suppressing the desorption of the filler due to the migration to the aqueous phase was obtained.
Industrial Applicability
[0088] In the method for producing the granulated powderof the present invention, it is possible to reduce the desorption of the filler from the granulated powder. Since the method for producing the granulated powder of the present invention is an underwater granulation method, the granulated powder can be produced efficiently with high productivity. The PTFE granulated powder of the present invention can be easily produced into molded products by compression molding and can be used for various applications such as sliding members and sealing materials.

Claims

Claims
1 . A method for producing a polytetrafluoroethylene granulated powder, comprising: stirring a mixture containing a filler, a polytetrafluoroethylene powder, and multi-hydrolyzable group-type silane coupling agent is in a mixed liquid of water and a water-insoluble organic liquid to perform mixed granulation.
2. The method for producing a granulated powder according to claim 1 , wherein the multi-hydrolyzable group-type silane coupling agent is a bissilane coupling agent represented by Formula (1 ) or a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2),
X-Ri-X (1 ) wherein X is a hydrolyzable silyl group (-Si-(OR2)n(R3)3-n) (n = 1 to 3), R2 and R3 are each -CH3 or -C2H5, and
R1 is a linear or branched hydrocarbon having 2 to 12 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen,
Figure imgf000030_0001
wherein X is a hydrolyzable silyl group (-Si-(OR2)n(R3)3-n) (n = 1 to 3),
R2 and R3 are each -CH3 or -C2H5,
A is -CH- or N, Ra and Rb are each independently a hydrocarbon having 1 to 10 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen,
Rc is a hydrocarbon having 1 to 5 carbon atoms in which hydrogen may be substituted with halogen, and
P = 3 to 30.
3. The method for producing a granulated powder according to claim 2, wherein the multi-hydrolyzable group-type silane coupling agent is preferably a bissilane coupling agent represented by Formula (1).
4. The method according to claim 3, wherein Ri contains no substituent or contains an imino group (-NH-) as a substituent.
5. The method for producing a granulated powder according to claim 2, wherein the multi-hydrolyzable group-type silane coupling agent is a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2).
6. The method according to claim 5, wherein Ra and Rb contain no substituent or contain an imino group (-NH-) as a substituent.
7. A polytetrafluoroethylene granulated powder comprising: from 3 to 40 vol% of a filler; and from 60 to 97 vol% of polytetrafluoroethylene powder, wherein 1 wt.% or less of a multi-hydrolyzable group-type silane coupling agent is contained based on a total amount of the granulated powder.
8. The polytetrafluoroethylene granulated powder according to claim 7, wherein the multi-hydrolyzable group-type silane coupling agent is a bissilane coupling agent represented by Formula (1) or a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2), X-R1-X (1 ) wherein X is a hydrolyzable silyl group (-Si-(OR2)n(R3)3-n) (n = 1 to 3), R2 and R3 are each -CH3 or -C2H5, and
R1 is a linear or branched hydrocarbon having 2 to 12 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen,
Figure imgf000032_0001
wherein X is a hydrolyzable silyl group (-Si-(OR2)n(R3)3-n) (n = 1 to 3), R2 and R3 are each -CH3 or -C2H5,
A is -CH- or N,
Ra and Rb are each independently a hydrocarbon having 1 to 10 carbon atoms which may contain a substituent and in which hydrogen may be substituted with halogen,
Rc is a hydrocarbon having 1 to 5 carbon atoms in which hydrogen may be substituted with halogen, and
P = 3 to 30.
9. The polytetrafluoroethylene granulated powder according to claim 8, wherein the multi-hydrolyzable group-type silane coupling agent is preferably a bissilane coupling agent represented by Formula (1 ).
10. The polytetrafluoroethylene granulated powder according to claim 8, wherein the multi-hydrolyzable group-type silane coupling agent is a polymeric silane coupling agent containing a repeating monomer unit represented by Formula (2).
11. The granulated powder according to any one of claims 7 to 10, wherein an average particle size is from 200 to 800 pm.
PCT/US2023/011323 2022-01-25 2023-01-23 Polytetrafluoroethylene granulated powder and method for producing the same WO2023146815A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2022-009384 2022-01-25
JP2022009384A JP2023108326A (en) 2022-01-25 2022-01-25 Polytetrafluoroethylene granulated powder and method for producing the same

Publications (1)

Publication Number Publication Date
WO2023146815A1 true WO2023146815A1 (en) 2023-08-03

Family

ID=85328623

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2023/011323 WO2023146815A1 (en) 2022-01-25 2023-01-23 Polytetrafluoroethylene granulated powder and method for producing the same

Country Status (2)

Country Link
JP (1) JP2023108326A (en)
WO (1) WO2023146815A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117343455A (en) * 2023-12-06 2024-01-05 广州市晶邦密封技术有限公司 High-rebound-resilience polytetrafluoroethylene composite material and preparation method thereof

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS51549A (en) 1974-05-24 1976-01-06 Du Pont
JPS6021694B2 (en) 1980-07-08 1985-05-29 ダイキン工業株式会社 Method for manufacturing filler-containing polytetrafluoroethylene molding powder
JPH05194551A (en) 1991-09-09 1993-08-03 Dow Corning Corp Process for producing silylorganoamine
US6242627B1 (en) 2000-12-05 2001-06-05 Crompton Company Process for preparing primary aminoorganosilanes
JP2001220482A (en) 2000-02-09 2001-08-14 Du Pont Mitsui Fluorochem Co Ltd Polytetrafluoroethylene granulate powder and method for producing the same
JP2002201287A (en) 2000-12-27 2002-07-19 Du Pont Mitsui Fluorochem Co Ltd Process for preparing filler-containing polytetrafluoroethylene powder for molding
JP2005509683A (en) 2001-11-15 2005-04-14 ゼネラル・エレクトリック・カンパニイ Method for producing bis (silylorgano) amine
US20190264005A1 (en) * 2018-02-23 2019-08-29 Rogers Corporation Polytetrafluoroethylene hexaferrite composites

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS51549A (en) 1974-05-24 1976-01-06 Du Pont
JPS6021694B2 (en) 1980-07-08 1985-05-29 ダイキン工業株式会社 Method for manufacturing filler-containing polytetrafluoroethylene molding powder
JPH05194551A (en) 1991-09-09 1993-08-03 Dow Corning Corp Process for producing silylorganoamine
JP2001220482A (en) 2000-02-09 2001-08-14 Du Pont Mitsui Fluorochem Co Ltd Polytetrafluoroethylene granulate powder and method for producing the same
US6242627B1 (en) 2000-12-05 2001-06-05 Crompton Company Process for preparing primary aminoorganosilanes
JP2002201287A (en) 2000-12-27 2002-07-19 Du Pont Mitsui Fluorochem Co Ltd Process for preparing filler-containing polytetrafluoroethylene powder for molding
JP2005509683A (en) 2001-11-15 2005-04-14 ゼネラル・エレクトリック・カンパニイ Method for producing bis (silylorgano) amine
US20190264005A1 (en) * 2018-02-23 2019-08-29 Rogers Corporation Polytetrafluoroethylene hexaferrite composites

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
ANONYMOUS: "Understanding Particle Size Distribution Calculations - HORIBA", 26 September 2019 (2019-09-26), XP055626647, Retrieved from the Internet <URL:http://www.horiba.com/scientific/products/particle-characterization/education/general-information/data-interpretation/understanding-particle-size-distribution-calculations/> [retrieved on 20190926] *
BARRY ARKLES ET AL: "Enhanced Hydrolytic Stability of Siliceous Surfaces Modified with Pendant Dipodal Silanes", CHEMISTRY - A EUROPEAN JOURNAL, JOHN WILEY & SONS, INC, DE, vol. 20, no. 30, 14 July 2014 (2014-07-14), pages 9442 - 9450, XP071839837, ISSN: 0947-6539, DOI: 10.1002/CHEM.201402757 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117343455A (en) * 2023-12-06 2024-01-05 广州市晶邦密封技术有限公司 High-rebound-resilience polytetrafluoroethylene composite material and preparation method thereof
CN117343455B (en) * 2023-12-06 2024-04-26 广州市晶邦密封技术有限公司 High-rebound-resilience polytetrafluoroethylene composite material and preparation method thereof

Also Published As

Publication number Publication date
JP2023108326A (en) 2023-08-04

Similar Documents

Publication Publication Date Title
CN1106414C (en) Preparation of a modified polytetrafluoroethylene and use thereof
WO2023146815A1 (en) Polytetrafluoroethylene granulated powder and method for producing the same
US11041061B2 (en) Polytetrafluoroethylene composition
US8648149B2 (en) Radically coupled PTFE polymer compounds and method for the production thereof
US20060293432A1 (en) Fluorine-containing elastomer composition and molded article comprising the same
WO2001085848A1 (en) Polymer composition containing clean filler incorporated therein
EP1857492B1 (en) Process for producing filler-containing polytetrafluoroethylene granule
EP0148512B1 (en) Improved elastomeric compositions
EP3807353A1 (en) Fluoropolymer nanoparticle coating composition
JP2010535922A (en) Polyphenylene sulfide (per) fluoropolymer materials and methods for their production and use
WO2013165846A1 (en) Compositions with a sulfur-containing polymer and graphenic carbon particles
EP1605011B1 (en) Granulated powder of low-molecular polytetrafluoro- ethylene and powder of low-molecular polytetrafluoro- ethylene and processes for producing both
CA1127789A (en) Stabilized copolymers based on ethylene and tetrafluoroethylene, and processes for their preparation
US20110195879A1 (en) Inert wear resistant fluoropolymer-based solid lubricants, methods of making and methods of use
WO2012067937A2 (en) Method of coagulating an amorphous fluoropolymer using modified inorganic nanoparticles
JP5034150B2 (en) Polytetrafluoroethylene granulated product and molded product thereof
Dierkes et al. Overcoming incompatibility problems in elastomer blends by tailored surface properties of rubber additives
CA3183558A1 (en) Functionalized graphene, method for producing a functionalized graphene, and its use
EP0411550B1 (en) Process for mixing polytetrafluoroethylene molding powder and organic filler
JP3036065B2 (en) Process for producing filled polytetrafluoroethylene granulated powder
JP4424696B2 (en) Polytetrafluoroethylene composition containing surface coating filler
CN104428329B (en) Fluoroelastomer and vulcanizable compositions thereof
EP4006100A1 (en) Resin composition, molded article, and automatic transmission
Iacono et al. Fluorinated polyhedral oligosilsesquioxane surfaces and superhydrophobicity
CN1878833A (en) Melt processible copolymer composition

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 23706894

Country of ref document: EP

Kind code of ref document: A1