阅读说明：本技术 含六硼化镧的复合粒子的制造方法和成形品的制造方法 (Method for producing lanthanum hexaboride-containing composite particle and method for producing molded article ) 是由 片山肇 有贺广志 于 2018-04-23 设计创作，主要内容包括：本发明提供通过简易的操作,即使不进行高温下的烧成也能够制造可充分地提高成形品的透明性、且耐候性优良的含六硼化镧的复合粒子的制造方法、以及使用该制造方法的成形品的制造方法。含六硼化镧的复合粒子的制造方法的特征是,在六硼化镧粒子、沸点在200℃以下的碱、水和有机溶剂的存在下,使选自四烷氧基硅烷、其水解物和其缩合物的至少一种二氧化硅前体反应,得到第一反应混合物,接着,使上述第一反应混合物与选自氨基改性硅氧烷、烷基硅烷和氨基硅烷的至少一种硅化合物、或上述硅化合物和追加的上述二氧化硅前体反应,得到包含含六硼化镧的复合粒子的第二反应混合物。(The invention provides a method for producing lanthanum hexaboride-containing composite particles, which can sufficiently improve the transparency of a molded article without firing at high temperature by a simple operation and has excellent weather resistance, and a method for producing a molded article using the same. A method for producing lanthanum hexaboride-containing composite particles, characterized by reacting at least one silica precursor selected from tetraalkoxysilanes, hydrolysates thereof, and condensates thereof in the presence of lanthanum hexaboride particles, a base having a boiling point of 200 ℃ or lower, water, and an organic solvent to obtain a first reaction mixture, and subsequently reacting the first reaction mixture with at least one silicon compound selected from amino-modified siloxanes, alkylsilanes, and aminosilanes, or the silicon compound and an additional silica precursor to obtain a second reaction mixture containing lanthanum hexaboride-containing composite particles.)

1. A method for producing a composite particle containing lanthanum hexaboride,

Reacting at least one silica precursor selected from tetraalkoxysilanes, hydrolysates thereof, and condensates thereof in the presence of lanthanum hexaboride particles, a base having a boiling point of 200 ℃ or lower, water, and an organic solvent to obtain a first reaction mixture,

Next, the first reaction mixture is reacted with at least one silicon compound selected from the group consisting of amino-modified siloxanes, alkylsilanes, and aminosilanes, or the silicon compound and the silica precursor, to obtain a second reaction mixture containing composite particles containing lanthanum hexaboride.

2. The production method according to claim 1, wherein after the second reaction mixture is obtained, the second reaction mixture is dried and the lanthanum hexaboride-containing composite particles are recovered.

3. The production method according to claim 2, wherein the second reaction mixture is a dispersion liquid in which the lanthanum hexaboride-containing composite particles are dispersed in an organic solvent, the second reaction mixture is subjected to a centrifugal separation treatment to remove an upper phase and recover a precipitated phase, and then the precipitated phase is dried.

4. The method of any one of claims 1 to 3, wherein the first reaction mixture comprises unreacted silica precursor.

5. The production method according to any one of claims 1 to 4, wherein the reaction of the silica precursor in obtaining the first reaction mixture is carried out in the presence of zirconia particles.

6. The production method according to any one of claims 1 to 5, wherein the tetraalkoxysilane is an alkoxysilane having an alkoxy group with 1 to 4 carbon atoms.

7. The method according to any one of claims 1 to 5, wherein the tetraalkoxysilane is tetraethoxysilane.

8. The production method according to any one of claims 1 to 7, wherein the silicon compound is an amino-modified siloxane.

9. The method according to claim 8, wherein the amino-modified silicone is a side chain type amino-modified silicone, a both terminal type amino-modified silicone, a single terminal type amino-modified silicone, or a side chain both terminal type amino-modified silicone.

10. The method according to claim 8, wherein the amino-modified silicone is a side-chain type amino-modified silicone in which an amino-containing organic group is introduced into a part of a side chain of dimethylpolysiloxane.

11. The production method according to any one of claims 1 to 10, wherein the base having a boiling point of 200 ℃ or lower is ammonia, an alkyl primary amine, or an alkyl tertiary amine.

12. The production method according to any one of claims 1 to 11, wherein the base having a boiling point of 200 ℃ or lower is present in an amount such that the pH at the time of the reaction to obtain the first reaction mixture is 8.0 to 12.0.

13. The production method according to any one of claims 1 to 12, wherein the average primary particle diameter of the lanthanum hexaboride-containing composite particles is 10 to 1000 nm.

14. a method for producing a molded article, characterized in that the lanthanum hexaboride-containing composite particles are produced according to the production method of any one of claims 1 to 13, the lanthanum hexaboride-containing composite particles and a thermoplastic resin are mixed to obtain a thermoplastic resin composition, and the thermoplastic resin composition is molded to obtain a molded article.

15. The production method according to claim 14, wherein the content of the lanthanum hexaboride-containing composite particle is 0.01 to 1 part by mass with respect to 100 parts by mass of the thermoplastic resin.

16. The production method according to claim 14 or 15, wherein the thermoplastic resin is a fluororesin.

Technical Field

The present invention relates to a method for producing lanthanum hexaboride-containing composite particles and a method for producing molded articles, which can sufficiently improve the transparency of molded articles and have excellent weather resistance.

Background

Conventionally, particles of an infrared-blocking substance are dispersed in a molded product of a film. As an infrared-blocking substance, lanthanum hexaboride (LaB6), for example, is known. However, lanthanum hexaboride particles and a molded article in which lanthanum hexaboride particles are dispersed have a problem that infrared ray blocking properties are deteriorated (water resistance is low) when exposed to water vapor or water.

Patent document 1 discloses a method in which tetraalkylsilicate, hydrochloric acid or ammonia is added to a dispersion of lanthanum hexaboride particles, water is further added to hydrolyze the tetraalkylsilicate, the resulting amorphous silica is fixed to the lanthanum hexaboride particles, and the resulting slurry is washed with water, filtered, dried at 120 ℃, calcined at 500 ℃, and pulverized to obtain composite particles.

Patent document 2 describes composite particles obtained by surface-treating lanthanum hexaboride particles with a siloxane-based water repellent treatment agent containing a cohydrolytic condensation product obtained by cohydrolytic condensation of a specific amino-containing alkoxysilane or a partial hydrolysate thereof and a specific bis (alkoxysilane) group-containing compound or a partial hydrolysate thereof in the presence of an organic acid or an inorganic acid.

Disclosure of Invention

Technical problem to be solved by the invention

The present inventors have confirmed, by the method described in patent document 1, that in order to make a coating film made of adhered amorphous silica into a dense structure into which only water vapor and water cannot penetrate, that is, in order to impart sufficient water resistance to composite particles, it is necessary to perform firing at a high temperature of 500 ℃. Further, it was found that the particle diameter of the obtained composite particles was several μm, and the film containing the composite particles had high haze and low transparency. Further, it is also known that the particles after the surface treatment are cleaned by filtration are particles having a size enough to allow a filtration operation. If the particles are pulverized to be small, the specific surface area of the particles increases, or the lanthanum hexaboride particles are exposed, there is a possibility that the water resistance of the composite particles decreases, and the infrared ray blocking performance of the film decreases with time.

The method described in patent document 2 is very complicated in the management of the production process. Further, depending on the state of mixing of the lanthanum hexaboride particles and the silicone water repellent agent, the coating may be uniformly affected, and composite particles having excellent water resistance may not be obtained.

The purpose of the present invention is to provide a method for producing lanthanum hexaboride-containing composite particles, which is easy to handle, can produce lanthanum hexaboride-containing composite particles that have sufficiently improved transparency of molded articles without firing at high temperatures, and has excellent weather resistance, and a method for producing molded articles using the method.

Technical scheme for solving technical problem

The present invention has the following technical contents.

[1] A method for producing lanthanum hexaboride-containing composite particles, characterized by reacting at least one silica precursor selected from tetraalkoxysilanes, hydrolysates thereof, and condensates thereof in the presence of lanthanum hexaboride particles, a base having a boiling point of 200 ℃ or lower, water, and an organic solvent to obtain a first reaction mixture, and subsequently reacting the first reaction mixture with at least one silicon compound selected from amino-modified siloxanes, alkylsilanes, and aminosilanes, or the silicon compound and an additional silica precursor to obtain a second reaction mixture containing lanthanum hexaboride-containing composite particles.

[2] The production method according to [1], wherein the second reaction mixture is obtained, and then the composite particles containing lanthanum hexaboride are dried and recovered.

[3] The production method according to [2], wherein the second reaction mixture is a dispersion liquid in which the lanthanum hexaboride-containing composite particles are dispersed in an organic solvent, the second reaction mixture is subjected to a centrifugal separation treatment to remove an upper phase and recover a precipitated phase, and then the precipitated phase is dried.

[4] The production method according to any one of [1] to [3], wherein the first reaction mixture contains unreacted silica precursor.

[5] The production method according to any one of [1] to [4], wherein the reaction of the silica precursor in obtaining the first reaction mixture is performed in the presence of zirconia particles.

[6] The production process according to any one of [1] to [5], wherein the tetraalkoxysilane is an alkoxysilane having an alkoxy group with 1 to 4 carbon atoms.

[7] The production process according to any one of [1] to [5], wherein the tetraalkoxysilane is tetraethoxysilane.

[8] The production method according to any one of [1] to [7], wherein the silicon compound is an amino-modified siloxane.

[9] The production method according to [8], wherein the amino-modified siloxane is a side chain type amino-modified siloxane, both terminal type amino-modified siloxane, one terminal type amino-modified siloxane, or both terminal type amino-modified siloxane.

[10] The production method according to [8], wherein the amino-modified siloxane is a side-chain type amino-modified siloxane in which an amino-containing organic group is introduced into a part of a side chain of dimethylpolysiloxane.

[11] The production process according to any one of [1] to [10], wherein the base having a boiling point of 200 ℃ or lower is ammonia, an alkyl primary amine or an alkyl tertiary amine.

[12] The production method according to any one of [1] to [11], wherein the base having a boiling point of 200 ℃ or lower is present in an amount such that the pH at the time of the reaction to obtain the first reaction mixture is 8.0 to 12.0.

[13] The production method according to any one of [1] to [12], wherein the average primary particle diameter of the lanthanum hexaboride-containing composite particles is 10 to 1000 nm.

[14] A process for producing a molded article, characterized by producing lanthanum hexaboride-containing composite particles according to any one of the production processes of [1] to [13], mixing the lanthanum hexaboride-containing composite particles with a thermoplastic resin to obtain a thermoplastic resin composition, and molding the thermoplastic resin composition to obtain a molded article.

[15] The production method according to [14], wherein the content of the lanthanum hexaboride-containing composite particle is 0.01 to 1 part by mass with respect to 100 parts by mass of the thermoplastic resin.

[16] The production method according to [14] or [15], wherein the thermoplastic resin is a fluororesin.

Effects of the invention

According to the present invention, by a simple operation, lanthanum hexaboride-containing composite particles which can sufficiently improve the transparency of a molded article without firing at high temperature and have excellent weather resistance can be produced.

According to the present invention, since the composite particles are produced by the method for producing composite particles of the present invention, a molded article having excellent transparency and weather resistance and suppressed deterioration of infrared-blocking properties with time can be produced by a simple operation.

Drawings

Fig. 1 is a transmission electron microscope image of LaB6 particles contained in the liquid (1) dispersion in example 1.

Fig. 2 is a graph showing the Zr distribution obtained by analyzing the element distribution of LaB6 particles contained in the dispersion in example 1.

Fig. 3 is a graph showing the distribution of La obtained by analyzing the element distribution of LaB6 particles contained in the dispersion in example 1.

Fig. 4 is a transmission electron microscope image of the composite particles obtained in example 1.

Fig. 5 is a graph showing the distribution of Si obtained by analyzing the element distribution of the composite particles obtained in example 1.

Fig. 6 is a graph showing the distribution of Zr obtained by analyzing the element distribution of the composite particles obtained in example 1.

Fig. 7 is a graph showing the distribution of La obtained by analyzing the element distribution of the composite particles obtained in example 1.

Detailed Description

The meanings and descriptions of the following terms in the present specification are as follows.

The compound represented by the formula (1) is referred to as "compound (1)". The same applies to compounds represented by other formulae.

The "infrared-blocking property" refers to a property of transmitting visible light rays having a wavelength of 400 to 700nm and blocking near infrared rays having a wavelength of 700 to 1800 nm.

[ method for producing composite particles containing lanthanum hexaboride ]

In the method for producing lanthanum hexaboride-containing composite particles (hereinafter, also simply referred to as composite particles) of the present invention, first, a silica precursor of at least one selected from tetraalkoxysilanes, hydrolysates thereof, and condensates thereof is reacted in the presence of lanthanum hexaboride particles (hereinafter, also referred to as LaB6 particles), a base having a boiling point of 200 ℃ or lower (hereinafter, also referred to as a volatile base), water, and an organic solvent to obtain a first reaction mixture (hereinafter, also referred to as a primary step).

Next, the first reaction mixture is reacted with at least one silicon compound selected from the group consisting of amino-modified siloxane, alkylsilane, and aminosilane, or the silicon compound and the additional silica precursor to obtain a second reaction mixture containing composite particles (hereinafter, also referred to as a secondary step).

After the secondary step, the second reaction mixture is dried as necessary to obtain composite particles (hereinafter also referred to as a drying step).

The composite particles obtained as described above have LaB6 particles and a silica coating formed on the surface thereof. The silica coating film contains an amino group or an alkyl group derived from the silicon compound.

(Primary Process)

The primary step is performed by, for example, mixing LaB6 particles, a volatile base, water, an organic solvent, a silica precursor, and other components added as needed, and reacting them. The order of mixing is not particularly limited, but it is preferable to add the volatile base and the silica precursor to a dispersion containing the organic solvent, water, and LaB6 particles. When the LaB6 particles are pulverized, it is preferable to pulverize a liquid containing an organic solvent and LaB6 particles by a known method such as bead milling, add water thereto, and if necessary, an additional organic solvent to prepare a dispersion, and then add a volatile base and a silica precursor.

In the case of using zirconia particles at the same time, it is preferable to add the zirconia particles to the dispersion of LaB6 particles in advance before adding the silica precursor.

The silica precursor is diluted with an organic solvent and added. Examples of the organic solvent include alcohols (e.g., methanol and ethanol) and ketones (e.g., acetone).

The silica precursor may be added in a total amount used in one step, may be added continuously by dropping or the like, or may be added in a plurality of times.

The temperature at which the silica precursor is reacted is preferably 10 to 50 ℃, and particularly preferably 20 to 40 ℃. If the temperature is not lower than the lower limit of the above range, the reaction rate is not too slow, and the precipitation of silica does not take too much time. If the temperature is not higher than the upper limit of the above range, the particles in the dispersion are less likely to agglomerate.

The reaction time in the primary step is preferably 20 minutes to 6 hours, particularly preferably 40 minutes to 2 hours, in view of the water resistance of the LaB6 particles.

When the unreacted silica precursor is contained in the first reaction mixture, an amino group or an alkyl group derived from the silicon compound can be easily introduced into the silica coating film in the second step. However, the present invention is not limited thereto. The first reaction mixture, which is free of unreacted silica precursor, may also be reacted with a silicon compound. The first reaction mixture, the silicon compound, and the additional silica precursor may also be reacted.

The method for obtaining the first reaction mixture containing the unreacted silica precursor may, for example, be a method in which the reaction time in the first step is set to a time in which the first reaction mixture is a mixture containing the unreacted silica precursor. The silica precursor may be added to the first reaction mixture in the second step.

The time during which the first reaction mixture becomes a reaction mixture containing unreacted silica precursor means a time during which a part of the silica precursor used in the primary step is reacted (not the entire amount is reacted).

The reaction time for a part of the silica precursor to react can be estimated from the change in pH of the reaction solution. The tetraalkoxysilane is first hydrolyzed in the liquid to form silanol groups. Since the silanol group exhibits acidic characteristics, the pH of the reaction solution tends to decrease while the alkoxy group of the tetraalkoxysilane remains and the hydrolysis reaction proceeds.

The first reaction mixture obtained in the primary step typically contains a substance produced by the reaction (hydrolysis, polycondensation) of the silica precursor, LaB6 particles, a volatile base, water, an organic solvent, and the like. In addition, unreacted silica precursor may also be included. In case other ingredients are used, the other ingredients are also comprised in the first reaction mixture. The material produced by the reaction of the silica precursor is typically silica.

The average primary particle diameter of LaB6 particles is preferably 5 to 1000nm, more preferably 10 to 400nm, and particularly preferably 20 to 200 nm. When the average primary particle diameter is not less than the lower limit of the above range, the composite particles are more excellent in weather resistance. When the primary step is performed by dispersing the LaB6 particles in a dispersion medium such as water or alcohol, the LaB6 particles have excellent dispersion stability, and are not easily coagulated and precipitated without using a dispersant, and can be maintained in a stable dispersion state. By not using a dispersant, it is possible to suppress the inclusion of an organic substance (dispersant) that causes coloration during molding of a molded article including composite particles, in the composite particles. When the average primary particle diameter is not more than the upper limit of the above range, a molded article comprising the composite particles is more excellent in transparency and infrared ray-blocking property.

The average primary particle diameter is a value obtained by measuring the maximum diameter of primary particles of 10 LaB6 particles by a transmission electron microscope and averaging the measured values.

The volatile base is a catalyst for allowing a reaction of a silica precursor (hydrolysis of tetraalkoxysilane or partial hydrolysate, condensation between hydrolysates, further condensation between condensates, and the like) to proceed to generate silica. Although the acid also functions as a catalyst, when the catalyst is an alkali, a silica coating having a higher density can be formed as compared with the case where the catalyst is an acid. In addition, the volatile base is volatilized at the time of drying, and does not easily remain in the composite particles. If the catalyst remains, the composite particles are bonded to each other and precipitated as large particles in which a plurality of LaB6 particles are captured, and there is a possibility that transparency of the molded product is lowered or the molded product is thermally decomposed during melt kneading with a resin to cause coloring.

As the volatile base, a base having a boiling point of 200 ℃ or less, more preferably 150 ℃ or less is preferable. Among them, preferred are alkyl primary to tertiary amines having 1 to 3 carbon atoms such as ammonia, methylamine and dimethylamine, and cyclic amines such as pyridine. From the viewpoint of easy availability and easy handling, ammonia is preferred.

The amount of the volatile base used in the primary step is preferably an amount such that the pH during the reaction is 8.0 to 12.0, and particularly preferably an amount such that the pH during the reaction is 8.5 to 10.5. If the pH is not less than the lower limit of the above range, the reaction rate does not become too slow. When the pH is not more than the upper limit of the above range, generation of silica particles which are not coated with the lanthanum boride particles can be suppressed, and the water resistance and transparency of the molded article are excellent.

In the reaction of the first step, it is preferable to add a volatile base so that the pH is always in the above-mentioned range. The pH here is the value at the reaction temperature.

Water is used to hydrolyze the silica precursor. The amount of water used in the primary step is preferably an amount such that the proportion of water is 200 mol% or more, particularly preferably 500 mol% or more, based on the total amount of the silica precursor used in the primary step in terms of tetraalkoxysilane. That is, the amount of water used is preferably 2 moles or more, and particularly preferably 5 moles or more, based on 1 mole of alkoxy groups in the alkoxysilane. The upper limit of the amount of water is not particularly limited.

The organic solvent is used to form the dispersion in a single process. Further, by using an organic solvent, the silane precursor is well dissolved, and a uniform silica coating can be formed.

The organic solvent may, for example, be an alcohol such as ethanol, 2-propanol or tert-butanol, or an organic solvent having a boiling point of preferably 20 to 150 ℃ such as a ketone such as acetone. The amount of the organic solvent used in the primary step is preferably 40 to 95% by mass, and more preferably 50 to 90% by mass, based on the total amount of water and the organic solvent.

The concentration of the LaB6 particles in the primary step is preferably 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, and particularly preferably 1 to 5% by mass, in the reaction solution (the total amount of LaB6 particles, water, organic solvent, volatile base, and silica precursor). If the concentration is 0.1 mass% or more, a sufficiently high productivity can be obtained. Further, if the concentration is 10% by mass or less, the obtained particles are less likely to aggregate, and handling becomes easy.

The silica precursor is at least one selected from the group consisting of tetraalkoxysilanes, hydrolysates thereof, and condensates thereof.

The number of carbon atoms of the alkoxy group of the tetraalkoxysilane is typically 1 to 4, preferably 2 to 4 in view of not excessively high reaction rate, and particularly preferably 2 in view of appropriate reaction rate. The larger the number of carbons of the alkoxy group, the slower the reaction rate (hydrolysis rate) tends to be. The water resistance (uniformity of the silica coating) is improved by not excessively increasing the reaction rate of the tetraalkoxysilane, and the productivity of the composite particle is improved by not excessively decreasing the reaction rate.

The 4 alkoxy groups of the tetraalkoxysilane may be the same or different. Examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, and tetra-n-butoxysilane. Among them, any one of them may be used alone, or 2 or more kinds thereof may be used in combination. Among them, tetraethoxysilane is particularly preferable from the viewpoint of an appropriate reaction rate.

When the tetraalkoxysilane is hydrolyzed, at least a part of alkoxy groups of the tetraalkoxysilane is changed to OH groups, and a hydrolysate having silanol groups (-Si-OH) is produced. The silanol groups react with each other (condense) to form a condensate having a siloxane bond.

The hydrolysate of tetraalkoxysilane may be a partial hydrolysate in which a part of alkoxy groups is changed to OH groups, or silicic acid in which all alkoxy groups are changed to OH groups.

Hydrolysis and condensation of tetraalkoxysilanes can be carried out by a known method. For example, a method of mixing tetraalkoxysilane, water and a catalyst such as a volatile base and maintaining the mixture at a temperature of about 10 to 70 ℃.

The amount of the silica precursor used in the primary step (in terms of SiO 2) is preferably 30 to 300 parts by mass, more preferably 70 to 250 parts by mass, and particularly preferably 100 to 200 parts by mass, based on 100 parts by mass of the LaB6 particles. When the amount of the silica precursor is not less than the lower limit of the above range, the composite particles are more excellent in weather resistance. If the amount of the silica precursor is not more than the upper limit of the above range, the transparency of the molded article is further improved.

the silica precursor may be the total amount of the silica precursor used for producing the composite particle, or may be a part of the silica precursor used for producing the composite particle. When a part of the silica precursor is used in the primary process, the remaining part is used in the secondary process.

The amount of the silica precursor used in the primary step (in terms of SiO 2) is preferably 5 mass% or more, and particularly preferably 10 mass% or more, of the total amount of silica precursors used for producing the composite particles (in terms of SiO 2). When the amount of the silica precursor is not less than the lower limit, the composite particles have more excellent water resistance.

When the silicon compound used in the secondary step is an amino-modified siloxane, the upper limit of the amount of the silica precursor used in the primary step (in terms of SiO 2) to the total amount of the silica precursors used in the production of the composite particles (in terms of SiO 2) is not particularly limited, and may be 100% by mass.

When the silicon compound used in the secondary step is an alkylsilane or aminosilane, the amount of the silica precursor used in the primary step (in terms of SiO 2) is preferably 50 mass% or less with respect to the total amount of the silica precursors used for producing the composite particles (in terms of SiO 2) from the viewpoint of transparency and water resistance of the molded article.

The total amount of the silica precursor (in terms of SiO 2) used for producing the composite particles is preferably 30 to 350 parts by mass, more preferably 70 to 300 parts by mass, and particularly preferably 100 to 250 parts by mass, based on 100 parts by mass of the LaB6 particles. When the total amount is not less than the lower limit of the above range, the composite particles are more excellent in weather resistance. If the total amount of the silica precursors is equal to or less than the upper limit of the above range, the ratio of LaB6 particles in the composite particles is sufficiently high, and it is not necessary to excessively increase the amount of the composite particles blended in the molded article in order to obtain sufficient infrared blocking property.

In the first step, when the silica precursor is reacted, other components than LaB6 particles, a volatile base, water, and an organic solvent may be present. As the other component, for example, zirconia particles and the like are preferable.

The reaction of the silica precursor in the primary step is preferably carried out in the absence of the silicon compound. At this time, if the silicon compound is present, the weather resistance of the composite particles may become insufficient.

In the reaction of the silica precursor in the primary step, the zirconia particles are present, whereby the composite particles are more excellent in water resistance. The reason for this is considered that the zirconia particles aggregate around the LaB6 particles to form a shell, and the zirconia has a high affinity for silica, so that the zirconia particles enter the silica film when the silica film is formed, and a silica film having a higher density and high water resistance is formed.

The zirconia particles preferably have an average primary particle diameter of 5 to 500nm, more preferably 10 to 400nm, and particularly preferably 20 to 200 nm. When the average primary particle diameter is not less than the lower limit of the above range, the composite particles are more excellent in weather resistance. When the average primary particle diameter is not more than the upper limit of the above range, the transparency of a molded article comprising the composite particles is further excellent. The average primary particle size was measured in the same manner as for the LaB6 particles.

The amount of the zirconia particles used in the primary step is preferably 10 to 200 parts by mass, and particularly preferably 20 to 100 parts by mass, based on 100 parts by mass of the LaB6 particles. If the amount is not less than the lower limit of the above range, the water resistance of the composite particles is further improved. When the amount of the zirconia particles is not more than the upper limit of the above range, the transparency of a molded article comprising the composite particles is more excellent.

(Secondary Process)

In the secondary step, the first reaction mixture is reacted with a silicon compound, or the first reaction mixture, the silicon compound, and an additional silica precursor are reacted to obtain a second reaction mixture containing composite particles.

The second step can be performed, for example, by mixing the first reaction mixture with a silicon compound or a silicon compound and an additional silica precursor and holding the mixture for an arbitrary period of time.

The silicon compound and the additional silica precursor may be mixed with the first reaction mixture as they are, or may be diluted with an organic solvent and mixed into the first reaction mixture. Examples of the organic solvent include alcohols (e.g., methanol and ethanol) and ketones (e.g., acetone).

The silicon compound is at least one selected from the group consisting of amino-modified siloxanes, alkylsilanes and aminosilanes. Since an amino group or an alkyl group derived from a silicon compound is introduced into the silica coating, water vapor or water is less likely to penetrate into the silica coating, and the weather resistance, particularly the water resistance, of the composite particle is improved.

The amino-modified silicone is a silicone having an amino-containing organic group.

Examples of the organic group having an amino group include monoamine-type organic groups such as-R1 NH2 (herein, R1 is an alkylene group) and diamine-type organic groups such as-R2 NHR3NH2 (herein, R2 and R3 are each independently an alkylene group). The number of carbon atoms of the alkylene group in R1 to R3 is preferably 1 to 3.

Examples of the amino-modified silicone include side chain type amino-modified silicones having an amino group-containing organic group in a part of the side chain, both terminal type amino-modified silicones having amino group-containing organic groups at both terminals of the main chain, one terminal type amino-modified silicones having an amino group-containing organic group at a single terminal of the main chain, both terminal type amino-modified silicones having an amino group-containing organic group at a part of the side chain and both terminals of the main chain. The main chain in the amino-modified siloxane represents a polymer chain formed by linking 2 or more [ -Si-O- ] units, and the side chain represents a group bonded to a silicon atom of the [ -Si-O- ] unit.

Examples of the side chain-type amino-modified siloxane include amino-modified siloxanes obtained by introducing an amino group-containing organic group into a part of the side chain of dimethylpolysiloxane. Typically, there are [ -Si (CH3)2-O- ] units and [ -Si (CH3) (RN) -O- ] units (where RN is an amino-containing organic group).

Examples of the both-terminal type amino-modified silicone include amino-modified silicones obtained by introducing amino-containing organic groups to both terminals of the main chain of dimethylpolysiloxane.

Examples of the one-terminal type amino-modified silicone include amino-modified silicones obtained by introducing an amino group-containing organic group to a single terminal of the main chain of dimethylpolysiloxane.

Examples of the side chain both-end type amino-modified siloxane include amino-modified siloxanes obtained by introducing amino group-containing organic groups into a part of the side chain and both ends of the main chain of dimethylsiloxane.

These amino-modified silicones may also have other organic groups than methyl and amino-containing organic groups. In the case of having another organic group, the side chain of the amino-modified siloxane may be a part of the other organic group, or the end of the main chain may be present.

Examples of the other organic group which may be present in a part of the side chain include a polyether group and a phenyl group. Examples of the other organic group which may be present at the end of the main chain include alkoxy groups such as methoxy group.

The alkylsilane is a silane compound having an alkyl group and a hydrolyzable group directly bonded to a silicon atom. The hydrolyzable group is preferably an alkoxy group having 1 to 4 carbon atoms from the viewpoint of excellent reactivity.

The alkylsilane is preferably the following compound (1).

R-Si(OR)…(1)

Wherein R4 is an alkyl group having 1 to 8 carbon atoms, R5 is a methyl group, and m is an integer of 1 to 3.

By having R4, the molded article including the composite particles is more excellent in transparency and water resistance than the case without R4 (for example, the case where R4 is OR 5). When the carbon number of R4 is not more than the upper limit of the above range, the transparency of a molded article comprising the composite particles is further improved. When R5 is a methyl group, the reactivity with a silanol group is more excellent than that when R5 is an alkyl group having 2 or more carbon atoms.

The alkyl group in R4 may be linear or branched, and is preferably an alkyl group having 1 to 4 carbon atoms. When m is 1 or 2, (4-m) R4 may be the same or different. m is preferably 3.

Examples of the compound (1) include methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, dimethyldimethoxysilane, diisobutyldimethoxysilane, trimethylmethoxysilane, propyldimethylmethoxysilane and octyldimethylmethoxysilane. Among them, methyltrimethoxysilane is preferable.

The aminosilane is a silane having an amino group and a hydrolyzable group directly bonded to a silicon atom. The hydrolyzable group is preferably an alkoxy group having 1 to 4 carbon atoms from the viewpoint of excellent reactivity.

The aminosilane is preferably the following compound (2).

R-Si(OR)(R)…(2)

Wherein R6 is-R1 NH2 or-R2 NHR3NH2, R7 is methyl, R8 is C1-8 alkyl, p is an integer of 1-3, q is an integer of 0-2, and p + q is an integer of 1-3. R1 to R3 are the same as described above.

Examples of the compound (2) include 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane and N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane.

These silicon compounds can be used alone in 1, also can be more than 2 combination.

As the silicon compound, amino-modified siloxane is particularly preferable. When the silicon compound is an amino-modified siloxane, the transparency of the molded article is further improved. In addition, when a dispersion liquid in which composite particles are dispersed in water is obtained as the second reaction mixture and this dispersion liquid is subjected to centrifugal separation in the drying step, the composite particles are likely to settle, and the efficiency of recovering the composite particles from the dispersion liquid is excellent.

Among the amino-modified siloxanes, side chain type amino-modified siloxanes having-R1 NH2 in a part of the side chain are particularly preferable.

The amount of the silicon compound used in the secondary step (in terms of solid content) is preferably 0.01 to 100 parts by mass, more preferably 0.02 to 80 parts by mass, and particularly preferably 0.03 to 50 parts by mass, based on 100 parts by mass of the total amount of the silica precursors used for producing the composite particles (in terms of SiO 2). When the amount of the silicon compound is not less than the lower limit of the above range, the composite particles are more excellent in weather resistance. When the amount of the silicon compound is not more than the upper limit of the above range, the infrared shielding property per unit mass of the composite particle is more excellent.

The preferable ranges of pH and temperature in the reaction in the secondary step are the same as those in the primary step. In the reaction in the second step, it is preferable to appropriately add a volatile base so that the pH is always within the above range. The reaction in the second step is preferably carried out under conditions such that the change in pH per 1 hour becomes 0.02 or less.

The second reaction mixture obtained in the secondary step contains composite particles. In addition, volatile bases, water, organic solvents are typically included. Further, unreacted silica precursor or silicon compound, a substance resulting from a reaction thereof, that is, a substance not incorporated into the composite particles, or the like may be contained. Where other ingredients are used, the other ingredients are also included in the second reaction mixture.

The second reaction mixture can be used as it is for the production of a molded article, etc., but it is preferable to recover the composite particles after drying.

(drying Process)

Examples of the method in the drying step include a method of drying the whole amount of the second reaction mixture as it is, a method of concentrating a solid content from the second reaction mixture to obtain a concentrate, and then drying the concentrate.

The drying temperature is preferably 60 to 200 ℃, particularly preferably 60 to 150 ℃. If the drying temperature is not lower than the lower limit of the above range, the deterioration of the operability due to insufficient drying can be suppressed. Further, since the amount of the residue is reduced, coloring and foaming of the molded article due to thermal decomposition of the residue are suppressed. When the drying temperature is not higher than the upper limit of the above range, the amino group or the alkyl group derived from the silicon compound does not easily disappear. In addition, bonding between silanol groups remaining in the composite particles is suppressed.

As a method of concentrating the solid content from the second reaction mixture and then drying the concentrate, a method of removing the non-precipitated content from the second reaction mixture, recovering the precipitated content, and drying the precipitated content is preferable. The sedimented component is a component that can be sedimented when the second reaction mixture is subjected to a treatment such as standing or centrifugal separation. The non-sedimenting component is a component other than the sedimenting component.

In the second reaction mixture, as a non-precipitating component, a hydrolysis and condensation product of tetraalkoxysilane (silica sol) or a silicon compound not incorporated into the silica coating film may remain. If the second reaction mixture containing these components is dried as it is or a solid component is concentrated and the concentrate is dried, these components adhere to the composite particles at the time of drying, and function as a binder for binding the composite particles to each other, forming aggregated composite particles. The aggregated composite particles are a cause of generation of particles (lumps) having a size that can be visually confirmed in the molded article. Therefore, it is preferable to remove the non-sedimenting components in advance.

The method of removing the non-sedimented component from the second reaction mixture and recovering the sedimented component may, for example, be centrifugal separation or decantation, and centrifugal separation is preferred in view of reducing the drying energy required for recovering the sedimented component at a high concentration.

The conditions for the centrifugal separation treatment are not particularly limited, and may be, for example, 10 to 40 ℃ for 2 to 5 minutes at 2000 to 4000G.

The powder obtained by drying is usually an aggregate in which a plurality of composite particles are aggregated. After drying, the resulting powder may be disintegrated.

The method of pulverization is not particularly limited, and the pulverization can be carried out using a known apparatus used for pulverization or pulverization of a general powder. A blender with blades, a rock mixer in which only a vessel without blades rotates by itself, a jet mill, or the like can be used. The powder may be packed in a plastic bag and then the powder may be crushed into several mm aggregates with fingers.

The disintegrating conditions may be appropriately set depending on the apparatus used, and examples thereof include a treatment for 10 seconds with a Waring blender.

The powder obtained by drying may be subjected to surface treatment with a hydrophobizing agent as needed. The surface of the composite particles becomes more hydrophobic, and when the composite particles and the thermoplastic resin are mixed to prepare a thermoplastic resin composition or when the thermoplastic resin composition is molded to obtain a molded article, the composite particles are less likely to aggregate with each other, and the molded article has higher transparency. Further, when the thermoplastic resin is molded by an extruder, the thermoplastic resin is less likely to stay in the extruder, and foreign matter in the molded product can be reduced.

In addition, although alkylsilanes belong to the hydrophobizing agents in the silicon compounds used in the secondary step, the following differences exist between the secondary step and the surface treatment of the powder obtained by drying: the former is a treatment in the presence of water, an organic solvent, or the like, and the latter is a treatment of particles in a dry state.

Examples of the hydrophobizing agent include a silane coupling agent having a hydrophobic organic group, an organic silicon compound having a hydrophobic organic group (e.g., silicon oil), and the like. The hydrophobizing agent preferably does not have a reactive functional group such as an epoxy group or an amino group, or a hydrophilic group.

Examples of the hydrophobic organic group include an alkyl group, an alkenyl group, an aryl group, an aralkyl group, a fluoroalkyl group, and a fluoroaryl group. Among them, preferred are an alkyl group having 1 to 20 carbon atoms, a fluoroalkyl group having 1 to 20 carbon atoms and a phenyl group which may be substituted with an alkyl group or a fluoroalkyl group.

Examples of the silane coupling agent include methyltrimethoxysilane, ethyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, (3,3, 3-trifluoropropyl) trimethoxysilane, and ethyltriethoxysilane.

Examples of the silicone oil include dimethyl silicone oil, methylhydrogen silicone oil, phenylmethyl silicone oil, and the like.

The hydrophobizing agent is preferably at least one member selected from the group consisting of isobutyltrimethoxysilane, hexyltrimethoxysilane, ethyltriethoxysilane, dimethylsilicone oil and phenylmethylsiloxane. They have high reactivity with silica coatings and can hydrophobize the surface of silica coatings in small amounts.

The amount of the hydrophobizing agent to be used may be appropriately selected depending on the specific surface area of the powder, the reactivity of the powder with the hydrophobizing agent, and the like. The amount of the hydrophobizing agent to be used is preferably 1 to 50 parts by mass, more preferably 3 to 20 parts by mass, and particularly preferably 5 to 10 parts by mass, based on 100 parts by mass of the powder. When the amount of the hydrophobizing agent used is within the above range, the composite particles are less likely to aggregate with each other, and the appearance of the molded article is less likely to be deteriorated.

The method of treating the powder with the hydrophobizing agent is not particularly limited, and a method of dispersing the powder in a solution of water, alcohol, acetone, n-hexane, toluene or the like in which the hydrophobizing agent is dissolved, and then drying the dispersion is preferable.

After the drying, the obtained powder may be fired. The firing temperature is preferably 230 to 300 ℃. The firing time is preferably 1 to 24 hours, and particularly preferably 1 to 10 hours. The firing atmosphere may be in air or in a reducing atmosphere such as nitrogen.

The thickness of the silica coating in the composite particles is preferably 2 to 50nm, particularly preferably 5 to 30 nm. When the thickness is not less than the lower limit of the above range, the composite particles are more excellent in weather resistance (water resistance, etc.). If the thickness is not more than the upper limit of the above range, the ratio of the silica coating to the LaB6 particles is not excessively high, and therefore, it is not necessary to excessively increase the amount of the composite particles blended in the molded article in order to obtain sufficient infrared ray blocking property. If the amount of the composite particles is suppressed, the moldability and transparency of the molded article are improved. The thickness of the silica coating can be measured by a transmission electron microscope.

The mass ratio of the LaB6 particles to the silica coating in terms of SiO2 in the composite particles is preferably 10:2 to 10:50, and particularly preferably 10:5 to 10: 20. The more the ratio is within the above range, the more excellent the weather resistance tends to be. When the ratio is smaller in the above range, the composite particles per unit mass are more excellent in infrared ray blocking performance and transparency.

The mass ratio can be calculated from the amounts of LaB6 particles and the silica precursor used in the primary step and the amounts of the silicon compound and the optional silica precursor used in the secondary step.

The average primary particle diameter of the composite particles is preferably 10 to 1000nm, more preferably 20 to 500nm, and particularly preferably 20 to 200 nm. When the average primary particle diameter is not more than the upper limit of the above range, the transparency of the molded article is further excellent.

The average of the maximum particle diameters of 10 particles covered with the silica film was defined as the average primary particle diameter of the composite particles by observation using a transmission electron microscope.

The composite particles preferably have a pore distribution curve having a peak at 5 to 10nm as measured by a nitrogen adsorption method. Such a silica coating film having a peak is a film composed of a plurality of silica fine particles arranged on the surface of LaB6 particles, and fine pores are formed between the plurality of silica fine particles.

The BET specific surface area of the composite particles is preferably 10 to 50m2/g, and particularly preferably 10 to 30m 2/g. When the BET specific surface area is not less than the lower limit of the above range, the water resistance is excellent. When the BET specific surface area is not more than the upper limit of the above range, the infrared ray blocking performance is excellent.

The BET specific surface area can be measured by a nitrogen adsorption method using a BET specific surface area apparatus.

The pore volume of the composite particles is preferably 0.01 to 0.15mL/g, particularly preferably 0.01 to 0.10 mL/g. When the pore volume is not less than the lower limit of the above range, the dispersion in the film is good and the transparency is excellent. If the pore volume is not more than the upper limit of the above range, the water resistance is excellent.

The pore volume can be measured by a nitrogen adsorption method.

In the method for producing composite particles of the present invention, the composite particles can be obtained by performing the above-described primary step and secondary step, and optionally performing post-treatments such as drying, disintegration, surface treatment with a hydrophobic treatment agent, and firing. In the present invention, the composite particles are considered to be formed as follows.

In the primary step, hydrolysis and condensation reactions of the silica precursor are carried out with a volatile base and water to produce silica, silica is precipitated in the dispersion to form silica fine particles, and the silica fine particles are attached to the surface of LaB6 particles or zirconia particles attached to the surface of LaB6 particles to form a silica coating. By performing the primary step before the secondary step, the adhesion between the surface of LaB6 particles and the silica coating can be improved, and the silica coating can be prevented from falling off by physical force.

In the case where the silicon compound is an amino-modified siloxane in the secondary step, the silica fine particles contained in the first reaction mixture entrain the silicon compound and adhere to the surfaces of the LaB6 particles on which the silica coating film was formed in the primary step, thereby forming a silica coating film containing an amino group derived from the silicon compound. When the silicon compound is an alkylsilane or aminosilane, the silicon compound is also hydrolyzed and reacts with the fine silica particles contained in the first reaction mixture to introduce an alkyl group or an amino group derived from the silicon compound into the fine silica particles, and the fine silica particles adhere to the surfaces of the LaB6 particles on which the silica coating was formed in the primary step to form a silica coating containing an alkyl group or an amino group.

In particular, when the first reaction mixture contains a silica precursor, or when the silica precursor is added in the second step, the silica precursor is reacted with a volatile base and water (which may be added as needed) already present in the first reaction mixture. In the case where the silicon compound is an amino-modified siloxane, the silicon compound is entrained with the fine silica particles produced in the secondary step and adheres to the surfaces of the LaB6 particles, and the silicon compound forms a silica coating together with the fine silica particles so as to fill the gaps between the fine silica particles.

The most preferable embodiment of the secondary step of the present invention is a case where the first reaction mixture contains a silica precursor, or a case where a silica precursor is added in the secondary step, that is, a case where the silicon compound is an amino-modified siloxane.

Further, the alkyl silane or amino silane has low reactivity with silanol groups of the silica coating film covering the surface of LaB6 particles due to steric hindrance caused by the alkyl group or amino group, and does not cause strong bonding between particles.

The LaB6 particles tend to have poor weather resistance due to the influence of moisture or the like because the surface area increases as the particle diameter decreases, but the composite particles obtained according to the present invention have excellent weather resistance even in the state of fine particles (for example, particle diameter of 100nm or less) that can sufficiently maintain the transparency of the molded article.

The reason why the above-described effects are exhibited is considered as follows.

When the silica coating is formed by bonding a plurality of primary particles of lanthanum hexaboride, the particle diameter of the composite particle increases, for example, to 1000nm or more. When the composite particles having such a particle diameter are directly blended into a molded article, the transparency of the molded article is impaired. In addition, uniform dispersibility in the film is poor, and the infrared blocking performance is lowered. When the composite particles are pulverized in order to reduce the particle size, the silica film is broken or chipped, or a part of the LaB6 particles is exposed, so that the LaB6 particles are easily affected by moisture or a component derived from a thermoplastic resin (for example, hydrofluoric acid derived from a fluororesin), and the weather resistance is insufficient.

In the present invention, a silica coating is formed on the surface of each of the primary particles of LaB6 particles, and composite particles having a structure in which a silica coating is formed around 1 LaB6 particle are easily formed. In the composite particles thus formed, the silica coating contains an amino group or an alkyl group derived from a silicon compound, and therefore sintering between particles is not easily caused during drying, so that the cohesive force between particles is small, and the particles can be easily disintegrated even when aggregated, and thus cracking or chipping of the silica coating is not easily caused. Therefore, the protective effect of the silica coating film can be sufficiently exhibited, and excellent weather resistance can be obtained. Further, since the composite particles obtained by the present invention have a small cohesive force between the particles and excellent dispersibility, aggregates of the composite particles are less likely to be generated during kneading and molding with a thermoplastic resin, and a decrease in transparency (an increase in haze) due to the aggregates is less likely to occur.

The above-mentioned effects are particularly excellent in the case where the silicon compound is an amino-modified siloxane. This is considered to be because: when the amino-modified siloxane is introduced into the silica coating film in the secondary step, the amino group side of the amino-modified siloxane is oriented toward the silica coating film formed in the primary step, whereby the hydrophobic groups such as methyl groups of the amino-modified siloxane are oriented toward the outside of the composite particles, the hydrophobicity of the surface is improved, and the dispersibility is further improved.

In addition, when the silicon compound is an amino-modified siloxane, there is an advantage that the composite particles are easily sedimented when the dispersion of the composite particles is centrifuged, and the efficiency of recovering the composite particles from the dispersion is excellent.

When the reaction of the silica precursor in obtaining the first reaction mixture is carried out in the presence of zirconia particles, the zirconia particles are aggregated at the periphery of LaB6 particles, and the periphery is covered with silica particles, whereby a silica coating film having more excellent water resistance can be formed.

[ method for producing molded article ]

In the method for producing a molded article of the present invention, composite particles are produced according to the method for producing composite particles described above, and the obtained composite particles and a thermoplastic resin are mixed to obtain a thermoplastic resin composition, which is molded to obtain a molded article comprising the composite particles and the thermoplastic resin.

Examples of the thermoplastic resin include fluororesins, polyethylene, polypropylene, polyesters, polyvinyl chloride, polyamides, and polycarbonates. The fluororesin is preferable from the viewpoint of excellent weather resistance, chemical resistance and the like of the molded article.

Examples of the fluororesin include an ethylene-tetrafluoroethylene copolymer (ETFE), a hexafluoropropylene-tetrafluoroethylene copolymer (FEP), a tetrafluoroethylene-propylene copolymer, a tetrafluoroethylene-hexafluoropropylene-propylene copolymer, a perfluoro (alkyl vinyl ether) -tetrafluoroethylene copolymer (PFA), a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV), polyvinylidene fluoride (PVDF), a vinylidene fluoride-hexafluoropropylene copolymer, polyvinyl fluoride, a chlorotrifluoroethylene polymer, an ethylene-chlorotrifluoroethylene copolymer (ECTFE), and polytetrafluoroethylene. These fluororesins may be used alone or in combination of two or more.

The fluororesin is preferably at least 1 selected from ETFE, FEP, PFA, PVDF, ECTFE, and THV, and ETFE is particularly preferable from the viewpoint of excellent transparency, processability, and weather resistance.

The content of the composite particles may be appropriately set in accordance with the infrared ray-blocking property required for the molded article, the thickness of the molded article, and the like. Among these, the amount is preferably 0.01 to 1 part by mass, and particularly preferably 0.05 to 0.5 part by mass, based on 100 parts by mass of the thermoplastic resin. When the content is not less than the lower limit of the above range, the molded article has more excellent infrared ray blocking properties. If the content is less than the upper limit of the above range, the visible light transmittance is more excellent.

The thermoplastic resin composition may contain known additives. Examples of the additives include inorganic pigments and dyes for adjusting color, talc for improving abrasion resistance, ultraviolet absorbers, light stabilizers, antioxidants, and flame retardants.

When the additive is contained, the content thereof is preferably 0.1 to 40 parts by mass, and particularly preferably 0.1 to 20 parts by mass, based on 100 parts by mass of the thermoplastic resin.

The method of mixing the composite particles and the thermoplastic resin is not particularly limited, and known methods such as kneading and dry blending between powders may be mentioned.

When the thermoplastic resin can be melt-molded, it is preferably melt-kneaded. Being melt-formable means exhibiting melt fluidity. The melt kneading may be carried out using a known extruder such as a single-screw extruder or a twin-screw extruder. The kneaded product (thermoplastic resin composition) obtained by melt kneading may be directly molded or may be molded after being pelletized.

As a method for molding the thermoplastic resin composition, a known molding method such as injection molding, extrusion molding, coextrusion molding, blow molding, compression molding, blow molding, transfer molding, calender molding, or the like can be used depending on the molded article to be produced.

The shape of the molded article is not particularly limited, and the molded article may be formed into a film, a sheet, a tube, or other various shapes according to the application.

After molding, the molded article obtained may be subjected to surface treatment such as corona discharge treatment, application of dripping agent, printing for imparting design, or the like.

The average primary particle diameter of the composite particles contained in the molded article obtained by the present invention is preferably 10 to 1000nm, and particularly preferably 20 to 200 nm. When the average primary particle diameter is not less than the lower limit of the above range, the weather resistance is more excellent and the infrared-blocking property is less likely to be deteriorated. When the average primary particle diameter is not more than the upper limit of the above range, the molded article is more excellent in transparency and infrared ray-blocking property.

When the molded article is a film or a sheet, the thickness of the molded article is typically in the range of 100 to 3000 μm. In the present specification, a molded article having a thickness of 1000 μm or less is referred to as a film, and a molded article having a thickness of more than 1000 μm is referred to as a sheet. Films and sheets are also collectively referred to as "films and the like".