JP2012092325A - Glass fiber-reinforced polyamide resin molded product and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass fiber-reinforced polyamide resin molded product having excellent mechanical strength and a method of manufacturing the same.SOLUTION: The glass fiber-reinforced polyamide resin molded product includes a glass fiber fabric whose surface is treated with an amino group-containing silane coupling agent and an isocyanate compound, and has a bending strength of ≥100 MPa at 150°C.

Description

  The present invention relates to a glass fiber reinforced polyamide resin molded body and a method for producing the same, and more particularly to a glass fiber reinforced polyamide resin molded body having excellent mechanical strength and a method for producing the same.

Polyamide, particularly monomer cast nylon, is self-lubricating and withstands wear, and is used as a material for bearings and various sliding members used without lubrication.
As a means for improving the mechanical strength of polyamide resin, it is known to disperse an inorganic filler such as glass fiber in the resin (see, for example, Patent Document 1), but a resin having higher mechanical strength. Is required.

JP 2007-224118 A

  An object of this invention is to provide the glass fiber reinforced polyamide resin molding which has the outstanding mechanical strength, and its manufacturing method.

The present invention provides the following glass fiber reinforced polyamide resin molded article and method for producing the same.
[1] A glass fiber reinforced polyamide resin molded article containing a glass fiber cloth surface-treated with an amino group-containing silane coupling agent and an isocyanate compound, and having a bending strength at 150 ° C. of 100 MPa or more.
[2] The glass fiber reinforced polyamide resin molded article according to [1], wherein a bending strength at 110 ° C. is 100 MPa or more.
[3] The bending strength at 150 ° C. is 2.5 times or more of the bending strength at 150 ° C. of a polyamide resin molded body not containing a glass fiber cloth surface-treated with an amino group-containing silane coupling agent and an isocyanate compound. The glass fiber reinforced polyamide resin molded product according to [1] or [2].
[4] The glass fiber-reinforced polyamide resin molded article according to any one of [1] to [3], wherein the polyamide resin is monomer cast nylon obtained by polymerizing a cyclic amide.
[5] The glass fiber-reinforced polyamide resin molded article according to any one of [1] to [4], wherein the polyamide resin is monomer cast nylon obtained by polymerizing ε-caprolactam.
[6] The glass fiber reinforced polyamide resin molded body according to any one of [1] to [5], wherein the content of the glass fiber cloth is 25 to 60% by volume.
[7] A method for producing a glass fiber reinforced polyamide resin molded article according to any one of [1] to [6],
(A) after heat-treating the glass fiber cloth, surface-treating with an amino group-containing silane coupling agent and an isocyanate compound, and (b) the glass fiber cloth surface-treated in the step (a) in the mold A method for producing a glass fiber reinforced polyamide resin molded article, comprising a step of casting and polymerizing a composition for polymerization containing a cyclic amide, a polymerization catalyst and a polymerization promoter in the mold after placing.
[8] The glass fiber reinforced polyamide according to [7], wherein in the step (a), the glass fiber cloth is surface-treated with an amino group-containing silane coupling agent and then surface-treated with an isocyanate compound. Manufacturing method of resin molding.

  The glass fiber reinforced polyamide resin molded article of the present invention has excellent mechanical strength not only at a low temperature but also at a high temperature. In particular, strength reduction at high temperatures can be suppressed, and mechanical strength at high temperatures can be dramatically improved as compared to polyamide resin molded articles not using glass fiber cloth. As a result, the practical usable temperature of the polyamide resin molded body can be raised to a higher temperature side.

Hereinafter, the present invention will be described in detail.
The glass fiber reinforced polyamide resin molded article of the present invention comprises a fiber reinforced resin containing a glass fiber cloth surface-treated with an amino group-containing silane coupling agent and an isocyanate compound.

  The polyamide resin is preferably monomer cast nylon from the viewpoint of mechanical strength and efficient production, and is preferably monomer cast nylon obtained by polymerizing ε-caprolactam. Monomer cast nylon can be produced by polymerizing a cyclic amide by a monomer cast method as described later. Examples of the cyclic amide include C 4-12 ω-lactam, γ-butyrolactam, ε-caprolactam, ω-enantolactam, ω-caprolactam, ω-laurolactam, or a mixture of two or more thereof. Of these, ε-caprolactam is preferred.

  Further, the polyamide resin used in the present invention preferably has a melt flow rate (MFR) value at a temperature of 300 ° C. and a load of 21.2 N (2.16 kgf) in accordance with JIS K7210 B method, preferably 5 g / 10 min or more. Yes, more preferably 7.5 g / 10 min or more, still more preferably 10 g / 10 min or more. The MFR is preferably 18 g / 10 min or less. Since the polyamide resin used in the present invention is preferably obtained by the monomer casting method, it has a property of high degree of polymerization of the polymer and a relatively high molecular weight as compared with the polyamide resin molded by other production methods. Therefore, mechanical strength is easy to improve. From this, it is preferable that the polyamide molded body obtained by the monomer cast method belongs to the range of the MFR value.

The glass fiber fabric used in the present invention may be a woven fabric (woven fabric) or a nonwoven fabric, but is preferably a woven fabric. The glass fiber reinforced polyamide resin molded article of the present invention can be improved in mechanical strength by being produced by a monomer casting method after surface treatment of a glass fiber cloth as will be described later. A glass cloth can be suitably used as the glass fiber cloth. Glass cloth is made by weaving glass fibers vertically and horizontally into a cloth such as plain weave.
In the present invention, the “surface treatment” refers to a surface treatment in which a glass fiber cloth is treated in combination using an amino group-containing silane coupling agent and an isocyanate compound. The surface treatment using an amino group-containing silane coupling agent and the surface treatment using an isocyanate compound may be performed at the same time, but after the surface treatment using an amino group-containing silane coupling agent, the surface treatment is performed using an isocyanate compound. It is preferable to do.

  In the present invention, the content of the glass fiber cloth is preferably 25% by volume or more, more preferably 30% by volume or more with respect to the glass fiber reinforced polyamide resin molded body from the viewpoint of mechanical strength, and preferably It is 60 volume% or less, More preferably, it is 50 volume% or less. When the content of the glass fiber cloth is 25% by volume or more, a bending strength of 100 MPa or more at 150 ° C. can be expressed. Moreover, if the content rate of a glass fiber cloth is 60 volume% or less, there will be no low polymerization of monomer cast nylon and the favorable molded object which does not have an unimpregnated part can be obtained.

The glass fiber reinforced polyamide resin molded body of the present invention can be produced by a method having the following steps (a) and (b).
Step (a): A step of subjecting the glass fiber cloth to a surface treatment using an amino group-containing silane coupling agent and an isocyanate compound after heat treatment.
Step (b): After placing the glass fiber cloth surface-treated in the step (a) in a mold, a polymerization composition containing a cyclic amide, a polymerization catalyst and a polymerization promoter is cast into the mold. And polymerizing.
The above method is a method using a monomer cast method, and can be polymerized and molded simultaneously with the impregnation of a polyamide resin into a fiber cloth by using a liquid cyclic amide. This is preferable because the polyamide resin can be impregnated in detail.

(Process (a))
First, the glass fiber cloth is heat-treated. Since the sizing agent applied to the glass fiber cloth causes low polymerization during the polymerization reaction of the polyamide resin, it is removed by heat treatment. The treatment conditions are not particularly limited, and the reaction temperature is usually 300 to 350 ° C., and the reaction time is usually 20 to 24 hours.

  Next, the glass fiber cloth after the heat treatment is surface-treated using an amino group-containing silane coupling agent and an isocyanate compound. By combining the amino group-containing silane coupling agent and the isocyanate compound on the glass fiber cloth, the isocyanate group of the isocyanate compound chemically bonded to the glass surface via the silane coupling agent improves the adhesion between the glass and the resin. The mechanical strength of the molded body can be improved. The surface treatment using an amino group-containing silane coupling agent and the surface treatment using an isocyanate compound may be performed at the same time, but after the surface treatment using an amino group-containing silane coupling agent, the surface treatment is performed using an isocyanate compound. It is preferable to do.

  Specific examples of the amino group-containing silane coupling agent include 3-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-phenyl-γ-. A simple substance such as aminopropyltrimethoxysilane or a mixture thereof may be used.

  Specific examples of the isocyanate compound include tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, hexamethylene diisocyanate, metaxylylene diisocyanate and the like. The NCO groups of these isocyanate compounds may be stabilized with a blocking agent so that they can be used dispersed in water.

Surface treatment of glass fiber cloth with an amino group-containing silane coupling agent and an isocyanate compound is carried out by using a solution of an organic solvent such as alcohols, ethers or dimethylformamide, or a mixed solution of water and these organic solvents (hereinafter these are treated). It can be performed by immersing the glass fiber cloth in the liquid) and then drying it. The immersion treatment of the glass fiber cloth in the treatment liquid can be performed at room temperature and normal pressure.
The concentration of the treatment liquid of the amino group-containing silane coupling agent is preferably 0.01 to 2% by mass, more preferably 0.1 to 1% by mass. Moreover, the density | concentration of the processing liquid of an isocyanate compound becomes like this. Preferably it is 0.01-5 mass%, More preferably, it is 0.1-3.5 mass%.
As a method of attaching these treatment liquids to the glass fiber cloth, any method such as a dipping method, a spraying method, a gasification method, etc. can be used, but a dipping method is preferred.

It does not specifically limit as a method to dry, It can dry by arbitrary means, such as a hot air and electromagnetic waves.
The drying temperature when the treatment liquid of the amino group-containing silane coupling agent is attached to the glass fiber cloth is preferably 100 to 200 ° C. The drying temperature when the isocyanate compound treatment liquid is adhered to the glass fiber cloth is preferably set so that the solvent used does not remain (considering the boiling point of the solvent), and is usually 90 to 170 ° C., more preferably 100 to 100 ° C. 160 ° C.

(Process (b))
The surface-treated glass fiber cloth is placed in a mold. The amount of the fiber cloth used is appropriately determined according to the thickness and usage of the obtained glass fiber reinforced polyamide resin molded body.
After placing the surface-treated glass fiber cloth in the mold, a polymerization composition containing a cyclic amide, a polymerization catalyst and a polymerization promoter is poured into the mold and polymerized. As a casting method, it is possible to inject in the atmosphere, or to make a negative pressure in the mold and inject using the differential pressure. Moreover, you may inject | pour the said mixing | blending raw material into a type | mold with a nitrogen pressure. Any polymerization catalyst and polymerization promoter can be used.

Examples of the polymerization catalyst include alkali metals, alkaline earth metals, hydrides of these metals, oxides, hydroxides, carbonates, alkylates, alkoxides and Grignard compounds, and reaction products of these with ω-lactams. Is mentioned. For example, lithium, sodium, potassium, magnesium, calcium, lithium hydride, sodium hydride, potassium hydride, sodium oxide, potassium oxide, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, methyl sodium, ethyl sodium, Examples include methyl potassium, ethyl potassium, sodium methylate, sodium ethylate, potassium methylate, potassium ethylate, methyl magnesium bromide, ethyl magnesium bromide and the like. These polymerization catalysts can be used alone or in combination of two or more.
The content of the polymerization catalyst in the polymerization composition is preferably 0.1 to 15 mol%, more preferably 3 to 10 mol%, based on the total number of moles of the cyclic amide.

Examples of the polymerization cocatalyst include isocyanates, acyllactams, carbamide lactams, acid halides, urea derivatives and the like, and monofunctional and bifunctional ones can be exemplified. For example, examples of the monofunctional polymerization cocatalyst include n-butyl isocyanate, phenyl isocyanate, octyl isocyanate, N-acetyl-ε-caprolactam, 1,6-hexamethylenebiscarbamide caprolactam, 1,3-diphenylurea, and the like. It is done. Examples of the bifunctional polymerization cocatalyst include tolylene diisocyanate, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, m-xylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and the like. These polymerization promoters can be used alone or in combination of two or more.
The content of the polymerization promoter in the polymerization composition is preferably 0.02 to 1 mol%, more preferably 0.1 to 0.5 mol%, based on the total number of moles of the cyclic amide. .

In addition, when applying to a sliding member use, you may contain waxes. As waxes, those usually used for polyamide resins can be used, for example, polyethylene wax, microcrystalline wax, petrolactam wax, hydrogenated poly-α-olefin wax, paraffin wax, isoparaffin wax, Fischer-Tropsch wax and the like. These may be used alone or in combination of two or more.
Waxes can be dispersed in the polyamide resin by polymerizing them by containing them in a polymerization composition containing a cyclic amide. The content of the waxes in the polymerization composition varies depending on the type of wax used and the required slidability, but preferably 3 to 40 parts by weight, more preferably 100 parts by weight of the cyclic amide. Is 5-30 parts by mass.

The polymerization / molding is preferably performed under heating. Moreover, you may pressurize to the surface direction of a plate-shaped object when making it superpose | polymerize and shape | mold. When polymerization is carried out under pressure, it is preferable to use a molding machine comprising an outer mold and an inner mold fitted to the outer mold. Specifically, after placing the fiber cloth in the outer mold, a polymerization composition containing a cyclic amide, a polymerization catalyst and a polymerization promoter is poured into the outer mold so that the fiber cloth is completely immersed. It is preferable that the inner mold is fitted into the outer mold, and then the polymerization composition is polymerized and molded under heating and pressure.
The reaction conditions are appropriately determined according to the types of the monomer and the polymerization catalyst and the size and shape of the obtained glass fiber reinforced polyamide resin molding. The reaction temperature is usually 130 to 180 ° C. The pressure is preferably about 0.1 to 0.5 MPa. The reaction time is preferably about 10 minutes to 1 hour.

  The bending strength of the glass fiber reinforced polyamide resin molded article of the present invention is 100 MPa or more, preferably 150 MPa or more, more preferably 170 MPa or more at 150 ° C. Since the bending strength at 150 ° C. of a conventional polyamide resin molded body is about 30 MPa, there is a problem that the bending strength at high temperature is insufficient and cannot be used continuously at high temperature. In contrast, the glass fiber reinforced polyamide resin molded article of the present invention has a bending strength of at least 100 MPa at 150 ° C., so that it can maintain practical strength as a polyamide resin and can be used continuously at 150 ° C. The effect is obtained.

  Similarly, the bending strength of the glass fiber reinforced polyamide resin molded article of the present invention is preferably 100 MPa or more, more preferably 150 MPa or more, and further preferably 170 MPa or more at 110 ° C. Similarly to 150 ° C., the bending strength at 110 ° C. can maintain a practical strength as a polyamide resin, and can be used continuously at 110 ° C.

Further, the glass fiber reinforced polyamide resin molded article of the present invention has a bending strength at 150 ° C. of 150 ° C. of a polyamide resin molded article not containing a glass fiber cloth surface-treated with an amino group-containing silane coupling agent and an isocyanate compound. The bending strength is preferably 2.5 times or more, more preferably 3.0 times or more, and further preferably 3.5 times or more. If the bending strength at 150 ° C. is 2.5 times or more compared to the polyamide resin molded body not containing the surface-treated glass fiber cloth, a polyamide molded body not containing the glass fiber cloth even at a high temperature condition of 150 ° C. There is an advantage that the same bending strength can be expressed.
The measurement of the bending strength in the present invention is as described in Examples described later.

  Further, the bending elastic modulus of the glass fiber reinforced polyamide resin molded article of the present invention is preferably 12 GPa or more at 23 ° C., more preferably 14 GPa or more, and still more preferably 20 GPa or more. Also. The same flexural modulus at 150 ° C. is preferably 10 GPa or more, and more preferably 15 GPa or more. The measurement of the flexural modulus in the present invention is as described in the examples described later.

  The shape of the glass fiber reinforced polyamide resin molded body of the present invention is preferably a flat plate shape, but may be an irregular shape such as a round bar, a pipe shape or a corrugated plate shape.

In the field of printed wiring boards, it is known that the glass cloth is surface-treated with a silane coupling agent and an isocyanate compound in order to improve the adhesion of the glass cloth to the matrix resin (epoxy resin) ( For example, see Japanese Patent No. 4,030,167).
On the other hand, in the glass fiber reinforced polyamide resin molded article of the present invention, an isocyanate compound is used as a polymerization co-catalyst for the polyamide resin (particularly monomer cast nylon). Therefore, in the present invention, glass fiber cloth surface-treated with an amino group-containing silane coupling agent and an isocyanate compound is impregnated with a polyamide resin at the same time as polymerization and molding, so that in addition to the isocyanate compound as a polymerization promoter, glass It is thought that the isocyanate group bonded to the fiber cloth is also the starting point of the reaction. As a result, the glass fiber cloth and the polyamide resin (especially monomer cast nylon) are compared with those obtained by simply adding the glass fiber cloth to the epoxy resin. It is considered that can be firmly bonded to each other and mechanical strength can be improved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited by these Examples.

The performance evaluation methods performed in the following examples and comparative examples will be described.
[Performance evaluation method]
About the obtained glass fiber reinforced polyamide resin molding, bending strength and a bending elastic modulus were measured as follows. A three-point bending test was performed in accordance with ISO 178. A universal testing machine (trade name: Model 2500, manufactured by INTESCO) is used, the crosshead speed is 2.0 mm / min, the shape of the test piece is 10 mm wide × 80 mm long × 4 mm thick, and the distance between the columns is It was 64 mm. The test piece was put in a thermostat controlled at a predetermined measurement temperature (23 ° C., 110 ° C., or 150 ° C.) provided in the universal testing machine, and after sufficient time was taken, measurement was performed. The measurement was performed 5 times, and the average value was obtained.

Example 1
(Surface treatment of glass cloth)
A glass fiber plain woven cloth (manufactured by Nittobo Co., Ltd., trade name: roving cloth) was used as the glass fiber substrate. Since the sizing agent applied to the glass fiber causes low polymerization during the polymerization reaction in the impregnation step, the glass fiber substrate was previously heat treated at 350 ° C. for 24 hours. The glass cloth was immersed in a 1% by mass 3-aminopropyltriethoxysilane methanol solution for 7 hours and then dried in a hot air oven at 110 ° C. for 5 hours to remove the solvent. Thereafter, the glass cloth was immersed in a hexane solution of 3% by mass tolylene diisocyanate (TDI) for 7 hours, and then dried in a hot air oven at 110 ° C. for 5 hours to remove the solvent.

(Manufacture of glass fiber reinforced polyamide resin moldings)
50 parts by mass of anhydrous ε-caprolactam was taken in a stainless steel beaker and adjusted to 140 ° C. To this was added 0.5 part by mass of tolylene diisocyanate as a polymerization promoter.
In another stainless steel beaker, 50 parts by mass of anhydrous ε-caprolactam was taken, to which 3 parts by mass of sodium lactamate (concentration 20%) as a polymerization catalyst was added, and the temperature was adjusted to 140 ° C. to homogenize the system.
Next, the glass cloth subjected to the above treatment was placed in a 4 mm thickness inside the concave mold heated and held at 165 ° C. (male and female mold clearance t = 5.0 mm), the mold was clamped, and the composition obtained above The composition was poured into the mold. The infusion was completed in 1 minute. A surface pressure of 0.5 MPa was applied, and the mold temperature was maintained at 165 ° C. and held for 30 minutes. Thereafter, the mold was removed to obtain a glass fiber reinforced polyamide resin molded product (monomer cast nylon molded product). The fiber content (Vf) in the obtained glass fiber reinforced polyamide resin molded product was 30% by volume. The fiber volume was measured by specific gravity measurement.

Example 2
Glass fiber reinforced in the same manner as in Example 1 except that the amount of the glass cloth placed inside the concave mold was changed so that the fiber content in the glass fiber reinforced polyamide resin molded body was 50% by volume. A polyamide resin molded body was obtained.

Example 3
Glass fiber reinforced in the same manner as in Example 1, except that the amount of glass cloth placed inside the concave mold was changed so that the fiber content in the glass fiber reinforced polyamide resin molded body was 25% by volume. A polyamide resin molded body was obtained.

Example 4
A glass fiber reinforced polyamide resin molded article was obtained in the same manner as in Example 1 except that in the surface treatment of the glass cloth, the isocyanate compound was changed to hexamethylene diisocyanate (HMDI).

Example 5
In the surface treatment of glass cloth, a glass fiber reinforced polyamide resin molded article was obtained in the same manner as in Example 1 except that the amino group-containing silane coupling agent was changed to γ- (2-aminoethyl) aminopropyltrimethoxysilane. Obtained.

Comparative Example 1
A glass fiber reinforced polyamide resin molded body was obtained in the same manner as in Example 1 except that the surface treatment of the glass cloth was not performed.

Comparative Example 2
Glass fiber reinforced in the same manner as in Example 1 except that the amount of glass cloth placed inside the concave mold was changed so that the fiber content in the glass fiber reinforced polyamide resin molded product was 65% by volume. A polyamide resin molded body was obtained.

Comparative Example 3
As in Example 1, except that the amount of glass cloth placed inside the concave mold was changed so that the fiber content was 30% by volume as a reinforcing fiber with an average fiber diameter of 10 μm. Thus, a glass fiber reinforced polyamide resin molded product was obtained.

Comparative Example 4
Glass fiber reinforcement in the same manner as in Example 1 except that the amino group-containing silane coupling agent was changed to epoxy group-containing silane coupling (3-glycidoxypropylmethyldiethoxysilane) in the surface treatment of the glass cloth. A polyamide resin molded body was obtained.

Comparative Example 5
A polyamide resin molded body was obtained under the same conditions as in Example 1 except that no glass cloth was used.

  The glass fiber reinforced polyamide resin molded bodies obtained in Examples 1 to 5 and Comparative Examples 1 to 5 were measured for bending strength and bending elastic modulus. The results are shown in Table 1.

  From Table 1, it can be seen that in Examples 1 to 5, the bending strength was improved compared to Comparative Example 1 in which the glass fiber cloth was not surface-treated using the amino group-containing silane coupling agent and the isocyanate compound. In particular, it can be seen that in Examples 1 and 2, the flexural modulus was improved in addition to the flexural strength. In Comparative Example 2, when the fiber content exceeded 65% by volume, unreacted polymerization or non-impregnation into the polyamide resin occurred, and a good molded product could not be obtained. Further, in Comparative Example 3, discontinuous long fibers that are not woven fabrics were filled, but sufficient strength could not be expressed with respect to Example 1 using the same amount of woven fabric. Further, in Comparative Example 4, a coupling treatment other than containing an amino group was used, but it acted on the inhibition of the polymerization reaction of the monomer cast nylon, and the reaction did not proceed so that a molded product could not be obtained.

Claims (8)

  A glass fiber reinforced polyamide resin molded article containing a glass fiber cloth surface-treated with an amino group-containing silane coupling agent and an isocyanate compound, and having a bending strength at 150 ° C. of 100 MPa or more.   The glass fiber reinforced polyamide resin molded article according to claim 1, wherein the bending strength at 110 ° C is 100 MPa or more.   The bending strength at 150 ° C is at least 2.5 times the bending strength at 150 ° C of a polyamide resin molded body not containing a glass fiber cloth surface-treated with an amino group-containing silane coupling agent and an isocyanate compound. The glass fiber reinforced polyamide resin molded article according to 1 or 2.   The glass fiber-reinforced polyamide resin molded article according to any one of claims 1 to 3, wherein the polyamide resin is monomer cast nylon obtained by polymerizing a cyclic amide.   The glass fiber reinforced polyamide resin molded product according to any one of claims 1 to 4, wherein the polyamide resin is monomer cast nylon obtained by polymerizing ε-caprolactam.   The glass fiber reinforced polyamide resin molded body according to any one of claims 1 to 5, wherein a content of the glass fiber cloth is 25 to 60% by volume. A method for producing a glass fiber reinforced polyamide resin molded body according to any one of claims 1 to 6,
(A) after heat-treating the glass fiber cloth, surface-treating with an amino group-containing silane coupling agent and an isocyanate compound, and (b) the glass fiber cloth surface-treated in the step (a) in the mold A method for producing a glass fiber reinforced polyamide resin molded article, comprising a step of casting and polymerizing a composition for polymerization containing a cyclic amide, a polymerization catalyst and a polymerization promoter in the mold after placing.   The glass fiber reinforced polyamide resin molded article according to claim 7, wherein in the step (a), the glass fiber cloth is surface-treated with an isocyanate compound after the surface treatment with an amino group-containing silane coupling agent. Production method.