Molded body and method for manufacturing the same

Abstract

A molded body according to the present invention is a surface-modified molded body containing a fluorine-based resin, a bonding strength is 10 MPa or higher when the atomic ratio (N / F) of nitrogen atoms to fluorine atoms determined by XPS of the molded body is 0.04 or less, the atomic ratio (Si / F) of silicon atoms to fluorine atoms is 0.10 or less, and the molded body and an aluminum plate are bonded to each other through pressure bonding at 5°C above the melting point of the fluorinated resin for 5 minutes at a pressure of 3 MPa.

Description

[Technical Field]

[0001] The present invention relates to a molded body and a method for manufacturing the molded body. [Background technology]

[0002] Fluorine-based resins are used in many fields due to their excellent heat resistance and chemical resistance. In particular, vinylidene fluoride resins have a wide range of applications due to their excellent water vapor barrier properties, gas barrier properties, and electrical resistance in addition to the above properties.

[0003] For example, films containing vinylidene fluoride resin are sometimes used by bonding them to objects to be bonded, such as resin sheets and metal plates. However, fluororesins such as vinylidene fluoride resin have low surface tension (surface free energy), have the property of repelling many substances, and have a stable structure due to the large bond energy between carbon atoms and fluorine atoms, making them difficult to bond to objects to be bonded. Therefore, studies have been conducted to improve the adhesive strength between molded articles containing fluororesins and objects to be bonded.

[0004] For example, Patent Documents 1 and 2 disclose a bonded body in which a molded body made of vinylidene fluoride polymer and a bonded body such as an Al plate are bonded via a silane coupling agent (molecular bonding agent) having an amino group. It is disclosed that this bonded body can be obtained by, for example, applying an aqueous solution of a silane coupling agent having an amino group at a concentration of 1.0 mass % to a molded body made of vinylidene fluoride polymer to modify the surface, and then placing the bonded body on top of the molded body and hot pressing it.

[0005] Patent Document 3 discloses an antenna substrate in which a dielectric layer mainly composed of a fluorine-based resin and an antenna element layer are bonded via a silane coupling agent having a reactive functional group. It is disclosed that this antenna substrate is obtained by immersing the antenna element layer in an aqueous solution of a silane coupling agent having a reactive functional group, and then overlaying the dielectric layer and heat pressing. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2020 / 026575 [Patent Document 2] International Publication No. 2020 / 003873 [Patent Document 3] Patent Publication No. 2015-53564 Summary of the Invention [Problem to be solved by the invention]

[0007] Patent Documents 1 to 3 disclose a method for manufacturing a bonded body in which a molded body containing a fluororesin and a bonded body are bonded together by applying an aqueous solution of a silane coupling agent to the molded body containing a fluororesin or the bonded body to modify the surface, and then overlapping and heat-pressing the molded body and the bonded body. Because the production of the molded body containing a fluororesin and the bonded body are not necessarily performed simultaneously, efficient mass production of a bonded body of the molded body and the bonded body is desirable. However, when the molded body containing the surface-modified fluororesin is left at high temperature for a long period of time and then heat-pressed to form a bonded body, there is a problem in that the adhesive strength of the bonded body decreases. As an alternative to long-term storage of the molded body containing the surface-modified fluororesin, an accelerated test by high-temperature storage is possible. From this perspective, a surface-modified molded body containing a fluororesin that can maintain high adhesive strength with the bonded body even when held at high temperature and a method for manufacturing the same are desired.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a molded article containing a fluororesin that has been surface-modified so as to exhibit high adhesive strength even when bonded to a substrate after being held at a high temperature, and a method for manufacturing the molded article. [Means for solving the problem]

[0009] The above problem can be solved by the following configuration.

[0010] The molded article of the present invention is a surface-modified molded article containing a fluororesin, and when the atomic ratio of nitrogen atoms to fluorine atoms (N / F) of the molded article, as determined by X-ray photoelectron spectroscopy (XPS), is 0.04 or less and the atomic ratio of silicon atoms to fluorine atoms (Si / F) is 0.10 or less, the adhesive strength of the bonded article when the molded article and an aluminum plate are pressure-bonded together at a temperature of the melting point of the fluororesin + 5°C for 5 minutes under a pressure of 3 MPa is 10 MPa or more.

[0011] The method for producing a molded article of the present invention is a method for producing a surface-modified molded article, and includes a step of immersing a molded article containing a fluorine-based resin in a solution containing a silane coupling agent having an amino group at a concentration of 0.5 mass% or less at a minimum immersion temperature T (°C) or higher, The minimum immersion temperature T is When the solvent of the solution is an organic solvent, the temperature is calculated from the following formula (a): Equation (a): T (°C) = SP × 16-140 (SP is the Hildebrand solubility parameter of the organic solvent). 100°C when the solvent is water; When the solvent is a mixed solvent, the minimum immersion temperature is the weighted average of the minimum immersion temperatures of the individual solvents constituting the mixed solvent. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a molded article containing a fluororesin that has been surface-modified so as to exhibit high adhesive strength even when bonded to a substrate after being held at a high temperature, and a method for producing the molded article. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1A is a schematic plan view showing a bonded body used in measuring adhesive strength, and FIG. 1B is a schematic cross-sectional view of FIG. 1A. DETAILED DESCRIPTION OF THE INVENTION

[0014] As described above, functional groups containing nitrogen and silicon atoms (hereinafter also referred to as "nitrogen functional groups" and "silicon functional groups") can be introduced into a molded article containing a fluororesin by treating it with a solution containing a compound such as a silane coupling agent having an amino group (hereinafter also referred to as "aminosilane coupling agent"). The mechanism by which the nitrogen functional groups are introduced is thought to be that the amino group acts on the carbon atom to which the fluorine atom of the fluororesin is bonded, and the introduction of the nitrogen functional groups proceeds while defluorination occurs. The reaction of the nitrogen atoms with the fluororesin simultaneously introduces silicon functional groups into the fluororesin. Hydrolysis of the silicon functional groups generates silanol groups, and the hydroxyl groups of the silanol groups undergo a condensation reaction with surface functional groups of the bonded object (e.g., hydroxyl groups of the oxide film on the surface of a metal material), resulting in adhesion between the molded article and the bonded object. It is believed that advancing this reaction can increase adhesive strength.

[0015] Here, the present inventors have found that a surface-modified molded article containing a fluororesin that has high adhesive strength with a substrate, even after removing functional groups having nitrogen atoms and silicon atoms present on the surface of the surface-modified molded article, can obtain high adhesive strength even when the molded article is held at high temperature and then bonded to a substrate.

[0016] Specifically, the molded body and the object to be bonded are bonded by applying pressure at a temperature close to the melting point of the molded body. Since the bonding is performed at a temperature close to the melting point, it is thought that not only the functional groups on the outermost surface layer but also the functional groups on the inner surface layer contribute to the bonding. The functional groups formed on the outermost surface layer may lose their adhesive ability to the object to be joined in a short period of time due to the influence of various molecules such as moisture in the atmosphere and reactions between the functional groups. On the other hand, the functional groups on the inner surface layer are less affected by the atmosphere, and it is presumed that the rate at which their adhesive ability to the object to be joined deteriorates due to reactions between the functional groups is slow. Therefore, in order to achieve high adhesive strength when joining the object to be joined even after the molded body has been kept at high temperatures (accelerated long-term storage test), it is important to form functional groups on the inner surface layer that are less susceptible to the influence of foreign molecules such as moisture in the atmosphere.

[0017] The adhesive strength of a surface-modified molded body is developed by a reaction between the functional groups of the molded body and the object to be joined. It is presumed that the functional groups exist in both the outermost layer of the molded body and the inner surface layer. The surface depth of atoms detected by X-ray photoelectron spectroscopy (XPS) is considered to be 10 nm or less. The ratio of nitrogen atoms to fluorine atoms (N / F) and the ratio of silicon atoms to fluorine atoms (Si / F) determined by XPS indicate the amount of functional groups present in the outermost layer of the molded body. For example, by cleaning the molded body until the atomic ratio is equal to or less than a predetermined value and then measuring the adhesive strength with the object to be joined, the functional groups in the outermost layer can be eliminated, and the presence of functional groups in the inner surface layer, which has excellent storage properties and is stable, can be quantitatively determined. This idea led to the present invention.

[0018] Here, the present inventors have discovered that the above-mentioned molded body can be obtained by surface modification with an aminosilane coupling agent solution. A surface-modified molded body containing a fluororesin can be produced by the following method. Specifically, as in the past, when a high-concentration aminosilane coupling agent solution is applied to a molded body as a raw material, many functional groups are introduced by reaction with the fluororesin. However, there is a risk that sufficient adhesive strength is difficult to obtain due to embrittlement of the molded body surface caused by alteration of the fluororesin due to excessive reaction, and a decrease in reaction sites with the bonded body due to reaction between the functional groups. On the other hand, when a low-concentration aminosilane coupling agent solution is applied, the amount of functional groups introduced into the fluororesin is small, making it difficult to obtain sufficient adhesive strength. In contrast, the inventors have discovered that by immersing a molded body containing a fluororesin as a raw material in a low-concentration aminosilane coupling agent solution at a predetermined temperature or higher, heat-stable functional groups can be generated in the fluororesin while suppressing embrittlement of the fluororesin, thereby obtaining sufficient adhesive strength with the bonded body. That is, it was found that high adhesive strength can be achieved even after being maintained at high temperatures by 1) immersing in an aminosilane coupling agent solution (hereinafter also referred to as "immersion solution"), 2) lowering the concentration of the aminosilane coupling agent in the immersion solution, and 3) setting the immersion temperature to a predetermined temperature or higher.

[0019] That is, the present invention can exhibit high adhesive strength even after removing, for example, by washing, functional groups containing nitrogen atoms or silicon atoms present in the outermost surface layer treated by such treatment methods and conditions. Furthermore, such a molded article exhibits significant adhesive strength to the object to be joined even after being held at high temperatures. The molded article of the present invention and its manufacturing method are described in detail below.

[0020] 1. Molded body As described above, the molded article of the present invention is a surface-modified molded article containing a fluororesin.

[0021] The type of fluorine-based resin is not particularly limited, and examples thereof include polytetrafluoroethylene (PTFE), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene / ethylene copolymer (ECTFE), and polyvinyl fluoride and vinylidene fluoride resin (PVDF). Among these, fluorine-based resins that react with the amino group of the aminosilane coupling agent, specifically fluorine-based resins having a -CF2-CH2- or -CF=CH- structure, are preferred. Among these, ETFE and PVDF are preferred.

[0022] The vinylidene fluoride resin may be a homopolymer consisting only of structural units derived from vinylidene fluoride, or may be a copolymer containing structural units derived from vinylidene fluoride and structural units derived from a monomer other than vinylidene fluoride. When the vinylidene fluoride resin is a copolymer, it may be a random copolymer or a block copolymer.

[0023] The content of the structural units derived from vinylidene fluoride is not particularly limited, but is preferably 50% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, and particularly preferably 80% by mass or more and 100% by mass or less, based on the total structural units of the vinylidene fluoride resin.

[0024] Examples of monomers other than vinylidene fluoride include fluorine-containing alkyl vinyl compounds, unsaturated dibasic acids, unsaturated dibasic acid monoesters, and compounds containing a vinyl group and a polar group.

[0025] The content of structural units derived from fluororesin in the surface-modified molded body is preferably 40% by mass or more and 100% by mass or less, more preferably 60% by mass or more and 100% by mass or less, even more preferably 80% by mass or more and 100% by mass or less, and particularly preferably 90% by mass or more and 100% by mass or less.

[0026] The surface-modified molded article may further contain other components besides the fluororesin, as needed. Examples of other components include resins other than the fluororesin, elastomers for imparting impact resistance, lubricants, antioxidants, slip agents, flame retardants, antiblocking agents, light stabilizers, dehydrating agents, tackifiers, and crystal nucleating agents. However, from the viewpoint of fully utilizing the properties of the fluororesin, the total content of these components is preferably 30% by mass or less, and more preferably 5% by mass or less.

[0027] As described above, the surface-modified molded body is characterized in that, when the atomic ratio of nitrogen atoms to fluorine atoms (N / F) measured by XPS is 0.04 or less and the atomic ratio of silicon atoms to fluorine atoms (Si / F) is 0.10 or less, the adhesive strength of the bonded body when the molded body and an aluminum plate are pressure-bonded together at a temperature of the melting point of the fluororesin +5°C for 5 minutes at a pressure of 3 MPa is 10 MPa or more.

[0028] (Atomic ratio measurement of molded body by XPS) The surface-modified molded article is preferably one that has been washed until the content of nitrogen atoms and silicon atoms derived from the aminosilane coupling agent remaining in the outermost surface layer of the molded article is reduced. Specifically, the atomic ratio of nitrogen atoms to fluorine atoms (N / F) measured by XPS of the molded article, which provides a bond strength of 10 MPa or more, is preferably 0.04 or less, more preferably 0.03 or less, and even more preferably 0.02 or less. The atomic ratio of silicon atoms to fluorine atoms (Si / F) is preferably 0.10 or less, more preferably 0.05 or less, even more preferably 0.03 or less, and particularly preferably 0.02 or less. The lower limits of N / F and Si / F are not particularly limited, but are, for example, 0.001, preferably 0.005.

[0029] The N / F and Si / F of the molded body can be adjusted by the treatment conditions with the aminosilane coupling agent solution in the manufacturing method of the molded body, the subsequent washing conditions, and the washing conditions immediately before measurement. For example, if the concentration of the aminosilane coupling agent solution is reduced, the N / F and Si / F of the obtained molded body tend to be low. Furthermore, if the washing time is extended, the N / F and Si / F of the obtained molded body tend to be low.

[0030] The cleaning method is not particularly limited, as long as the immersion-treated molded body is washed with denatured ethanol at 25°C, but the immersion-treated molded body can be cleaned, for example, by the following method: 0.3 g of the immersion-treated molded body is placed in a 400 ml container containing 200 ml of denatured ethanol (Dorazol NM, ethyl alcohol: 86.9%, 2-propanol: 4.9%, 1-propanol: 8.2%, manufactured by Kanto Chemical Co., Inc.), and the mixture is stirred for 10 minutes, after which the denatured ethanol is dried and removed.

[0031] XPS measurement can be performed according to the following procedure. The elemental composition ratio of fluorine, the elemental composition ratio of nitrogen, and the elemental composition of silicon in the surface-modified region of the surface-modified molded body are measured using an X-ray photoelectron spectrometer (e.g., JPS 9010MC, JEOL Ltd.) to measure the spectra corresponding to each element. Without removing the measurement sample from the measurement device and without changing the measurement environment, the binding energy ranges of the nitrogen atom 1s (N1s) spectrum (409 eV-389 eV), the fluorine atom 1s (F1s) spectrum (696 eV-676 eV), and the silicon atom 2P spectrum (109 eV to 89 eV) are measured under the following conditions. The measurement conditions are as follows: AlKα radiation is used as the X-ray source without being made monochromatic, acceleration voltage is 12 kV, analysis diameter is 3 mmΦ, photoelectron take-off angle is 90°, pass energy is 10 eV, energy step is 0.1 eV, and to prevent charging, a neutralization gun is used to irradiate at 2 mA and 2 V. The background is subtracted from the spectrum obtained by accumulating eight or more times using the Shirley method, the peak area is determined, and the abundance (atom%) of each atom is calculated using the following formula. Atom abundance = peak area / correlation sensitivity coefficient

[0032] Here, the correlation sensitivity coefficient of nitrogen is 7.5129, the correlation sensitivity coefficient of fluorine is 17.3911, and the correlation sensitivity coefficient of silicon atoms is 3.5266. The abundances of nitrogen, fluorine, and silicon are calculated from the above formula, and the abundances of nitrogen atoms and silicon atoms are respectively divided by the abundance of fluorine atoms to obtain N / F and Si / F.

[0033] (Adhesive strength) The surface-modified molded article can exhibit high adhesive strength when bonded to a bonded object. That is, when the molded article and an aluminum plate are bonded together by pressure bonding at a pressure of 3 MPa for 5 minutes at the melting point (Tm) of the fluororesin + 5°C, the adhesive strength is preferably 10 MPa or more, more preferably 14 MPa or more, even more preferably 17 MPa or more, and particularly preferably 20 MPa or more. The upper limit of the adhesive strength is not particularly limited, but is, for example, 40 MPa.

[0034] The adhesive strength can be measured by the following procedure. 1) An Al plate (A5052P, manufactured by Test Piece Co., Ltd.) measuring 25 mm in width, 100 mm in length, and 1.6 mm in thickness is immersed in a 5% by mass aqueous solution of alkaline immersion degreasing agent (SK-144, manufactured by JCU Corporation) at 70°C for 1 minute, and then ultrasonically cleaned in ion-exchanged water for 3 minutes to obtain a bonded body. Two bonded bodies are prepared. Then, as shown in FIGS. 1A and 1B, one molded body 12 is sandwiched between two bonded bodies 11A and 11B so that the overlap length is 12.5 mm. These are then pressure-bonded at a pressure of 3 MPa for 5 minutes at a temperature of the melting point Tm of the fluororesin + 5°C to obtain a bonded body 10. 2) The tensile strength of the resulting bonded body 10 is measured. The tensile strength is measured using a tensile tester at a pulling rate of 10 mm / min.

[0035] The melting point (Tm) of the fluororesin is a value measured by calorimetry using a differential scanning calorimeter (DSC). Specifically, 10 mg of the fluororesin is weighed into an aluminum pan, which is placed in the DSC. After the DSC is purged with pure nitrogen gas, pure nitrogen gas is passed through at a flow rate of 100 ml / min. The temperature is raised from room temperature at 10°C / min (first temperature rise), and the melting peak is identified by DSC. The maximum melting peak temperature observed during the temperature rise is taken as the melting point of the fluororesin.

[0036] The adhesive strength between the surface-modified molded body and the object to be bonded can be controlled by the treatment conditions with the aminosilane coupling agent solution. For example, by immersing the molded body as a raw material in a low-concentration aminosilane coupling agent solution at a temperature higher than a predetermined temperature, the adhesive strength between the molded body and the object to be bonded tends to be high. A molded body having such high adhesive strength and a low number of nitrogen atoms and silicon atoms near the surface exhibits high adhesive strength when bonded to the object to be bonded, even when exposed to a high-temperature environment.

[0037] The form of the surface-modified molded article is not particularly limited.

[0038] 2. Manufacturing method of molded body As described above, the molded article of the present invention can be obtained by immersing a molded article containing a fluorine-based resin in a solution of an aminosilane coupling agent.

[0039] The molded article containing the fluororesin can be produced by any method, such as injection molding, press molding, calendar molding, extrusion molding, melt spinning, etc. Powder obtained by polymerization can also be used.

[0040] The aminosilane coupling agent contained in the immersion solution has an amino group (-NX 1 X 2 ) and an alkoxysilyl group or a silanol group. 1 X 2 X in 1 and X 2 are each a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.1 is preferably a hydrogen atom. The number of carbon atoms in the alkoxy moiety of the alkoxysilyl group is not particularly limited, but is preferably 1 to 5, for example.

[0041] That is, the aminosilane coupling agent is preferably a compound represented by formula (1). [ka]

[0042] In formula (1), R 1 is hydrogen, an alkyl group having 1 to 5 carbon atoms, or an aminoalkyl group having 1 to 5 carbon atoms. Of these, hydrogen or an aminoalkyl group having 1 to 3 carbon atoms is preferred.

[0043] In formula (1), R 2 is an alkylene group having 1 to 10 carbon atoms. Among these, an alkylene group having 1 to 5 carbon atoms is preferred, and an alkylene group having 2 to 5 carbon atoms is more preferred.

[0044] R 3 ~R 5 are each independently a hydroxy group, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms, and R 3 ~R 5 At least one of R is a hydroxy group or an alkoxy group having 1 to 5 carbon atoms. 3 ~R 5 is more preferably an alkoxy group having 1 to 3 carbon atoms.

[0045] Among them, R in Eq. (1) 1 is a hydrogen atom or an aminoalkyl group having 1 to 5 carbon atoms, and R 2 is an alkylene group having 1 to 10 carbon atoms, and R 3 ~R 5 However, compounds in which the alkoxy group has 1 to 5 carbon atoms are preferred; 3-aminopropyltriethoxysilane (APS) and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPS) are more preferred.

[0046] The solvent contained in the immersion solution is not particularly limited. It may be water, an organic solvent, or a mixture thereof. Examples of the organic solvent include alcohol-based solvents such as ethyl alcohol, glycol-based solvents such as ethylene glycol, ether-based solvents such as ethylene glycol monomethyl ether, ester-based solvents such as ethyl acetate, ketone-based solvents such as acetone, and mixtures thereof.

[0047] As described above, from the viewpoint of achieving high adhesive strength when bonded to a bonded object, it is preferable to perform the treatment with the aminosilane coupling agent solution under conditions that allow the aminosilane coupling agent to penetrate into the fluororesin without embrittling the surface of the molded article made of the fluororesin. Specifically, it is preferable to 1) perform an immersion treatment in the aminosilane coupling agent solution, 2) reduce the concentration of the aminosilane coupling agent in the immersion solution, and 3) maintain the immersion temperature at a predetermined level or higher.

[0048] The concentration of the aminosilane coupling agent in the immersion solution is preferably 0.50% by mass or less, more preferably less than 0.25% by mass, even more preferably 0.20% by mass or less, particularly preferably 0.15% by mass or less, and most preferably 0.10% by mass or less. If this concentration is low, fewer nitrogen atoms and fewer Si atoms remain on the surface of the resulting molded article, which tends to result in smaller atomic ratios N / F and Si / F. Furthermore, the fluororesin contained in the molded article is less likely to become embrittled, making it easier to achieve high adhesive strength. Furthermore, the concentration of the aminosilane coupling agent in the immersion solution is preferably greater than 0.00% by mass, more preferably 0.01% by mass or more, and even more preferably 0.05% by mass or more. If the concentration of the aminosilane coupling agent is too low, the amount of aminosilane coupling agent contributing to adhesion is small, which tends to reduce adhesive strength.

[0049] The immersion temperature is set to a minimum immersion temperature T (°C) or higher, which is determined depending on the type of solvent. The minimum immersion temperature T (°C) is determined as follows:

[0050] Specifically, when the solvent of the immersion solution is an organic solvent, the minimum immersion temperature T can be calculated from the following formula (a). Formula (a): T(℃)=SP×16-140 (T: immersion temperature (°C), SP: Hildebrand solubility parameter of the organic solvent (cal / cm 3 ) 0.5 ) When the solvent is water, the minimum immersion temperature T is 100°C. Furthermore, when the solvent is a mixed solvent, the minimum immersion temperature T is the weighted average of the minimum immersion temperatures of the individual solvents constituting the mixed solvent, as determined above. The upper limit of the immersion temperature varies depending on the solvent, but is not particularly limited as long as it is equal to or lower than the temperature at which the resin constituting the molded body does not dissolve in the solvent.

[0051] For example, when the solvent is ethyl alcohol, the SP value is 12.7, so the minimum immersion temperature T is 69°C. When the solvent is a mixed solvent of two or more types, the solubility parameter SP of each solvent can be determined as described above, and then the minimum immersion temperature T can be determined by a weighted average. The upper limit of the immersion temperature is not particularly limited, but can be, for example, a temperature 10°C lower than the dissolution temperature of the molded article. The Hildebrand solubility parameter of organic solvents can be cited, for example, from J. Brandrup and Ehimergut, "Polymer Handbook," INTERSCIENCE PUBLISHERS, IV341-IV368, John Wily & Sons (1966). If the solubility parameter of the solvent is not described in the literature, the solubility parameter SP can be determined using the following method.

number

[0052] On the other hand, when the solvent of the immersion solution is water, the immersion temperature is preferably 100° C. or higher, and more preferably 120° C. or higher. The upper limit when the solvent is water varies depending on the melting point of the fluororesin that constitutes the molded article. For example, when the fluororesin is a PVDF homopolymer, if the melting point is 170° C., the upper limit immersion temperature is 160° C. When immersion is performed at these temperatures, liquid water is used in a pressure-resistant container.

[0053] By setting the immersion temperature at a predetermined temperature or higher, the solution can easily penetrate into the surface and inner layer of the molded article, and therefore, even if the concentration of the aminosilane coupling agent in the immersion solution is low, the aminosilane coupling agent that contributes to the introduction of functional groups into the fluororesin can be maintained, thereby achieving high adhesive strength and preventing a decrease in high adhesiveness even after being kept at a high temperature.

[0054] The immersion method is not particularly limited as long as the joining portion of the molded article containing a fluororesin with the object to be joined is immersed in the immersion solution. The immersion container and the immersion solution can be appropriately selected so that the joining portion of the molded article is immersed in the immersion solution. If the immersion temperature becomes too high, there is a risk that the immersion solvent will volatilize, so the immersion can be performed in an immersion container that is sealed. The immersion container is preferably heat-resistant and pressure-resistant and can be sealed. The material of the container is not particularly limited as long as it is heat-resistant and pressure-resistant, and can be selected from, for example, metal, resin, and glass.

[0055] The immersion time is the retention time at the immersion temperature during the immersion. The retention time may be a continuous time or an accumulated time when the immersion is performed intermittently. The immersion time is not particularly limited as long as it is within the conditions for the aminosilane coupling agent to penetrate into the molded product. The immersion time varies depending on the immersion temperature and the type of solvent, but is preferably, for example, from 1 minute to 300 minutes, more preferably from 10 minutes to 180 minutes, even more preferably from 20 minutes to 180 minutes, and particularly preferably from 30 minutes to 120 minutes. When immersing at high temperatures, an immersion time of 1 minute or more ensures sufficient penetration of the aminosilane coupling agent into the fluororesin in any solvent, while an immersion time of more than 300 minutes may result in excessive reaction between the aminosilane coupling agent and the fluororesin, resulting in embrittlement of the fluororesin.

[0056] The molded body immersed in the immersion solution may be cooled to room temperature as needed, then removed from the immersion container, and excess aminosilane coupling agent adhering to the surface of the molded body may be removed to reduce the amount of aminosilane coupling agent on the surface. That is, after the immersion step, a cleaning step may be further performed to clean the molded body until the atomic ratio of nitrogen atoms to fluorine atoms (N / F) measured by X-ray photoelectron spectroscopy (XPS) reaches 0.04 or less and the atomic ratio of silicon atoms to fluorine atoms (Si / F) reaches 0.10 or less. The cleaning method may involve immersing the molded body in a cleaning solution, or by rinsing the surface of the molded body after the immersion step with a cleaning solvent. The cleaning solvent is not particularly limited as long as it dissolves the aminosilane coupling agent, but may be, for example, an alcohol-based solvent, a ketone-based solvent, or an ester-based solvent. It is preferable to use the same solvent as used in the immersion solution as the cleaning solvent.

[0057] The molded article treated with the aminosilane coupling agent solution can be dried to obtain a surface-modified molded article.

[0058] 3. Joint and manufacturing method thereof (zygote) The molded article of the present invention is bonded to various objects to be bonded to form a bonded article. That is, the bonded article has the molded article of the present invention and objects to be bonded, and they are bonded together via the aminosilane coupling agent bonded to the molded article.

[0059] The material of the objects to be joined is not particularly limited, and may be any of a metal material, a resin material, a ceramic material, and a composite material thereof.

[0060] The metallic material may be any of various metals or alloys thereof, examples of which include Be, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg, Al, Ge, Sn, Pb, Sb, Bi, and Nd.

[0061] Examples of the resin material include thermoplastic resins, thermosetting resins, fiber-reinforced plastics, photocurable resins, vulcanized rubber, and uncrosslinked rubber. Examples of these include rubbery polymers such as olefin polymers, acrylic polymers, styrene polymers, polyesters, polyamides, polyglycolic acid, polyacetals, polycarbonates, polyphenylene oxides, polyphenylene sulfides, polyether ether ketones, polysulfones, polyether sulfones, polyoxybenzenes, polyimides, polyamide-imides, polybutadiene rubbers, and acrylic rubbers.

[0062] Among resin materials, resins having a C=O group in their structure are preferred. When the resin structure does not contain a C=O group but does contain a CH group, it is preferable to perform a pretreatment to bond an aminosilane coupling agent to the resin material. Examples of pretreatment methods include a method of bonding a silane coupling agent to the surface of a resin material. More specifically, it is preferable to bond a silane coupling agent having an azide group. There are no particular limitations on the method of bonding such a silane coupling agent to the surface of a resin material, but examples include a method of applying a silane coupling agent to the surface of a resin material and then irradiating it with ultraviolet light to cause a radical-generating reaction. Furthermore, at this time, the bonded objects may be subjected to a corona treatment or the like in advance to enhance the wettability of the bonded objects.

[0063] The shape of the bonded body is not particularly limited, but it is preferably a shape that allows the adhesive interface to be sufficiently heated when bonding with the molded body of the present invention containing a fluororesin. In addition, from the viewpoint of adhesion with the molded body, it is particularly preferable that the surface of the bonded part of the bonded body is smooth.

[0064] (Method of manufacturing a bonded body) The bonded body can be obtained by bonding a bonded body and the molded body of the present invention. The bonding method is not particularly limited, and examples thereof include pressing, powder coating, and pressure molding.

[0065] When the melting point of the fluororesin is Tm (°C), the bonding temperature is preferably, for example, from ((Tm)-50)°C to (Tm+50)°C, more preferably from ((Tm)-20)°C to (Tm+30)°C, even more preferably from ((Tm)-10)°C to (Tm+30)°C, and particularly preferably from (Tm)°C to (Tm+30)°C. [Example]

[0066] Hereinafter, the embodiments of the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to these.

[0067] 1. Preparation of the compact [Example 1] A 15 mm wide, 100 mm long, 100 μm thick polyvinylidene fluoride (PVDF) film (Kureha Corporation, #1000, homopolymer) was ultrasonically cleaned in denatured ethanol (Kanto Chemical Co., Ltd., Drysol NM) for 10 minutes and then dried. The PVDF film was placed in a high-pressure tube (ACE GLASS Corporation). A 0.1% by weight aqueous solution of 3-aminopropyltriethoxysilane (Tokyo Chemical Industry Co., Ltd., hereafter sometimes referred to as "APS") was then added so that the entire film was immersed. The high-pressure tube was sealed, and the liquid temperature was raised to 140°C, maintained for 15 minutes, and then allowed to cool. It was confirmed that the entire PVDF film remained immersed in the immersion solution even after the temperature reached 140°C. After the heat treatment, the PVDF film was removed from the high-pressure tube and placed in a 400 ml container containing 200 ml of denatured ethanol (Dorazol NM, ethyl alcohol: 86.9%, 2-propanol: 4.9%, 1-propanol: 8.2%, Kanto Chemical) at room temperature (25°C). After stirring and washing for 10 minutes, the film was dried to produce a surface-modified PVDF film. This surface-modified PVDF film was cut into two pieces of 30 mm length, one of which was used as the surface-modified PVDF film before heat treatment (surface-modified molded body). The remaining piece was placed in a constant temperature blower dryer (EYELA WHO-400) and left to stand at an ambient temperature of 100°C for 2 hours to be used as the surface-modified PVDF film after heat treatment (surface-modified molded body).

[0068] [Example 2] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the immersion conditions were changed to 120°C for 30 minutes.

[0069] [Example 3] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the immersion conditions were changed to 100°C for 180 minutes.

[0070] [Example 4] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the immersion solution was changed to a 0.1% by mass APS ethyl alcohol solution and the immersion conditions were changed to 100°C for 15 minutes.

[0071] [Example 5] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the immersion solution was changed to a 0.1% by mass APS acetone solution and the immersion conditions were changed to 20°C for 60 minutes.

[0072] [Example 6] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the immersion solution was changed to a 0.1% by mass APS ethylene glycol solution and the immersion conditions were changed to 120°C for 15 minutes.

[0073] [Example 7] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the immersion solution was changed to a 0.1% by mass APS ethyl acetate solution and the immersion conditions were changed to 23°C for 15 minutes.

[0074] [Example 8] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the PVDF film (manufactured by Kureha Corporation, #1000, homopolymer) was changed to a PVDF film (manufactured by Kureha Corporation, #2300, copolymer).

[0075] [Example 9] A surface-modified PVDF film before and after heat treatment was obtained in the same manner as in Example 1, except that the immersion solution was changed to a 0.1% by mass ethyl alcohol solution of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter sometimes referred to as "AEAPS") and the immersion conditions were changed to 100°C for 15 minutes.

[0076] [Example 10] A surface-modified ETFE film was obtained in the same manner as in Example 1, except that the PVDF film (manufactured by Kureha Corporation, #1000, homopolymer) was replaced with an ethylene tetrafluoroethylene copolymer (ETFE) film (manufactured by Toray Advanced Film Co., Ltd.) with a width of 15 mm, a length of 100 mm, and a thickness of 50 μm, and the immersion conditions were changed to immersion in a 0.1 mass % APS acetone solution at 80°C for 15 minutes.

[0077] [Example 11] After the immersion treatment was carried out in the same manner as in Example 4, surface-modified PVDF films before and after the heat treatment were obtained in the same manner as in Example 4, except that the washing treatment with denatured ethanol was not carried out.

[0078] [Comparative Example 1] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the immersion conditions were changed to 80°C for 180 minutes.

[0079] Comparative Example 2 Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the immersion was carried out at 25°C for 10 minutes.

[0080] Comparative Example 3 A surface-modified PVDF film before and after heat treatment was obtained in the same manner as in Example 1, except that the immersion solution was changed to a 1.0 mass % APS aqueous solution.

[0081] Comparative Example 4 Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 1, except that the immersion solution was changed to a 10% by mass APS aqueous solution.

[0082] Comparative Example 5 After washing with the denatured ethyl alcohol described in Example 1, a 0.1% by mass APS ethyl alcohol solution was applied to the dried PVDF film at room temperature using a wire bar with a wet thickness of 12 μm, and then air-dried within a few seconds to produce a surface-modified PVDF film. Two pieces of the surface-modified PVDF film were cut into 30 mm lengths, one of which was used as a molded body before heat treatment. The remaining piece was placed in a constant-temperature blower dryer (EYELA WHO-400) and left to stand at an ambient temperature of 100°C for 2 hours to produce a molded body after heat treatment.

[0083] Comparative Example 6 Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Comparative Example 5, except that the coating solution was changed to a 1.0 mass % APS ethyl alcohol solution.

[0084] Comparative Example 7 Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Comparative Example 5, except that the coating solution was changed to a 10.0 mass % APS ethyl alcohol solution.

[0085] [Comparative Example 8] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 4, except that the immersion conditions were changed to 25°C for 15 minutes.

[0086] Comparative Example 9 Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Comparative Example 5, except that the coating solution was changed to a 1.0 mass % APS aqueous solution.

[0087] [Comparative Example 10] After applying the APS solution, the film was placed in a 400 ml container containing 200 ml of denatured ethanol (Dorazol NM, ethyl alcohol: 86.9%, 2-propanol: 4.9%, 1-propanol: 8.2%, Kanto Chemical), and the container was placed in an ASU CLEANER (ASU-10M, manufactured by ASONE) filled with water and subjected to ultrasonic cleaning for 10 minutes. After that, the denatured ethanol was dried and removed. In the same manner as in Comparative Example 6, a surface-modified PVDF film was obtained.

[0088] [Comparative Example 11] Surface-modified PVDF films before and after heat treatment were obtained in the same manner as in Example 4, except that the aminosilane concentration in the immersion solution was 0.0 mass % and washing treatment was not performed.

[0089] 2. Evaluation (Measurement of atomic ratios (N / F) and (Si / F) by XPS) The elemental composition ratios of fluorine, nitrogen, and silicon on the surfaces of the compacts obtained in Examples 1 to 11 and Comparative Examples 1 to 11 were measured. Each elemental composition ratio was measured using an X-ray photoelectron spectrometer (JPS 9010MC, manufactured by JEOL Ltd.). The relative values ​​of the elemental composition ratios of nitrogen (N / F) and silicon (Si / F), where the elemental composition ratio of fluorine is taken as 1, are shown in Table 1.

[0090] (Measurement of adhesive strength) An aluminum plate (Test Piece Corporation, Model A5052P) measuring 25 mm in width, 100 mm in length, and 1.6 mm in thickness was immersed in a 5% by mass aqueous solution of degreasing agent SK-144 (JCU Corporation) at 70°C for 1 minute, followed by ultrasonic cleaning with ion-exchanged water for 3 minutes to obtain a bonded body. Two bonded bodies were prepared. Next, as shown in FIGS. 1A and 1B, one molded body 12 was sandwiched between two bonded bodies 11A and 11B so that the overlap length was 12.5 mm. This was then pressure-bonded using a heater plate molding machine (NPA Systems Corporation, Model P4054-00) at a temperature above the melting point of the fluororesin + 5°C for 5 minutes at a pressure of 3 MPa to obtain a bonded body. In Examples 1 to 9, the melting point of PVDF grade #1000 was 172°C and the pressure bonding temperature was 177°C; in Example 8, the melting point of PVDF grade #2300 was 152°C and the pressure bonding temperature was 157°C; and in Example 10, the melting point of ETFE was 256°C and the pressure bonding temperature was 261°C.

[0091] The melting point (Tm) of the fluororesin was determined by calorimetry using a differential scanning calorimeter (DSC). Specifically, 10 mg of the fluororesin was weighed into an aluminum pan, which was then placed in the DSC. After the DSC interior was purged with pure nitrogen gas, pure nitrogen gas was introduced at a flow rate of 100 ml / min, and the sample was heated from room temperature at a rate of 10 °C / min (first heating). The melting peak was identified by DSC. The maximum melting peak temperature observed during the heating process was determined as the melting point of the fluororesin.

[0092] The tensile strength of the resulting bonded body was measured to evaluate the adhesive strength. The tensile strength was measured using a tensile tester (AG-2000E, manufactured by Shimadzu Corporation) at a pulling rate of 10 mm / min. The adhesive strength was evaluated for both the molded body before and after heat treatment. The results are shown in Table 1.

[0093] [Table 1]

[0094] (Minimum immersion temperature) When the solvent for the aminosilane coupling agent solution was an organic solvent, the minimum immersion temperature (°C) was calculated based on the above formula (a). The Hildebrand solubility parameter (SP value) of the organic solvent was cited from the Polymer Handbook. When the solvent for the aminosilane coupling agent solution was water, the minimum immersion temperature was set to 100°C. The results are shown in Table 2.

[0095] [Table 2]

[0096] As shown in Table 1, the molded articles of Examples 1 to 9, obtained by immersing a PVDF film in a 0.5% by mass or less APS or AEAPS solution at a temperature above the minimum immersion temperature, had an N / F ratio of 0.04 or less and an Si / F ratio of 0.10 or less, and also exhibited high adhesive strength before and after heat treatment. In other words, immersion treatment at a temperature above the minimum immersion temperature demonstrated high adhesive strength even after removing the nitrogen and silicon functional groups from the film's outermost surface by washing. This is presumably due to the introduction of sufficient amounts of nitrogen and silicon functional groups into the inner surface layer of the PVDF film. Furthermore, the surface-modified ETFE films of Examples 10 and 11 also exhibited high adhesive strength, with an N / F ratio of 0.04 or less and an Si / F ratio of 0.10 or less.

[0097] In contrast, the molded articles of Comparative Examples 1 and 2, in which the PVDF film was immersed in the APS aqueous solution at a temperature below 100°C (below the minimum immersion temperature), and the molded article of Comparative Example 8, in which the PVDF film was immersed in the APS ethanol solution at a temperature below 69°C (below the minimum immersion temperature), had low N / F values ​​of 0.04 or less and Si / F values ​​of 0.10 or less, but still had low adhesive strength. This is presumably because immersion below the minimum immersion temperature makes it difficult for the aminosilane coupling agent to penetrate into the surface inner layer of the molded article, preventing the formation of nitrogen and silicon functional groups in the surface inner layer. Furthermore, the molded article of Comparative Example 5, which was coated with the APS solution, had low N / F values ​​of 0.04 or less and Si / F values ​​of 0.10 or less, and despite not being subsequently washed, still had low adhesive strength. Thus, it can be seen that coating treatment at a temperature below the minimum immersion temperature resulted in low adhesive strength, even though nitrogen and silicon functional groups remained in the outermost surface layer of the film. This is presumably because fewer nitrogen and silicon functional groups are introduced into the inner surface layer of the PVDF film.

[0098] Furthermore, the molded body of Comparative Example 6 exhibits high adhesive strength before heat treatment when the N / F is 0.04 or higher, but the adhesive strength after heat treatment is low. On the other hand, the molded body of Comparative Example 10, which was obtained by cleaning the molded body of Comparative Example 6 to an N / F of 0.04 or lower and an Si / F of 0.10 or lower, exhibits low adhesive strength before and after heat treatment. These results suggest that the high adhesive strength of the molded body of Comparative Example 6 before heat treatment is due to functional groups in the extreme surface layer, and that the functional groups of Comparative Example 6 are formed in the extreme surface layer and do not exhibit high strength after heat treatment, suggesting that these functional groups do not contribute to long-term stable improvement of adhesive strength.

[0099] Furthermore, the molded articles of Comparative Examples 3 and 4, in which the concentration of the APS aqueous solution was 1% by mass or 10% by mass, had a high N / F ratio exceeding 0.04 and low adhesive strength. The molded articles of Comparative Examples 6 to 7 and 9, in which an APS solution with a concentration of 1% by mass or more was applied, had a high N / F ratio exceeding 0.04 and low adhesive strength. On the other hand, the molded article of Comparative Example 11, in which the concentration of the APS aqueous solution was 0% by mass, was not surface-modified and had low adhesive strength.

[0100] This application claims priority from Japanese Patent Application No. 2022-47154, filed March 23, 2022. The entire contents of the specification and drawings of that application are incorporated herein by reference. [Industrial Applicability]

[0101] According to the present invention, it is possible to provide a molded article containing a fluororesin, which can provide a bonded body that can maintain high adhesive strength even when treated at high temperatures, and a method for producing the molded article. [Explanation of symbols]

[0102] 10 zygote 11A, 11B object to be joined

Claims

1. A surface-modified molded article containing a fluorine-based resin, the atomic ratio of nitrogen atoms to fluorine atoms (N / F) in the surface-modified region of the molded body, as determined by X-ray photoelectron spectroscopy (XPS), is 0.001 or more and 0.04 or less, and the atomic ratio of silicon atoms to fluorine atoms (Si / F) is 0.001 or more and 0.10 or less; the adhesive strength when the molded body and an aluminum plate are bonded together by pressure bonding at a temperature of the melting point of the fluororesin + 5°C for 5 minutes at a pressure of 3 MPa is 10 MPa or more; Molded body.

2. The fluorine-based resin is vinylidene fluoride resin. The molded article according to claim 1.

3. A method for producing a surface-modified molded body according to claim 1 or 2, comprising: The method includes a dipping step of dipping a molded body containing a fluorine-based resin in a solution containing a silane coupling agent having an amino group at a concentration of more than 0.00 mass % and not more than 0.5 mass % at a minimum dipping temperature T (°C) or higher, The minimum immersion temperature T is When the solvent of the solution is an organic solvent, the temperature is calculated from the following formula (a): Formula (a): T (°C) = SP x 16-140 (SP is the Brunt solubility parameter of the organic solvent) When the solvent is water, the temperature is 100°C. When the solvent is a mixed solvent, the minimum immersion temperature is a weighted average of the minimum immersion temperatures of the solvents constituting the mixed solvent. A method for manufacturing a molded body.

4. After the immersion step, the method further includes a cleaning step of cleaning the molded body until the atomic ratio of nitrogen atoms to fluorine atoms (N / F) in the region surface-modified by the immersion step, as determined by X-ray photoelectron spectroscopy (XPS), is 0.04 or less and the atomic ratio of silicon atoms to fluorine atoms (Si / F) is 0.10 or less. A method for producing the molded article according to claim 3.

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