Acrylic resin composition for sensor cover

Abstract

An acrylic resin composition for a sensor cover, comprising: an acrylic resin (A); and a light absorber (B). The acrylic resin composition has a deflection temperature under load of 110 DEG C or more. A molded body of the acrylic resin composition having a thickness of 1 mm has optical properties satisfying all requirements (i) to (v). (i) The maximum transmittance is 10% or less when light having a wavelength of 380-700 nm is caused to enter the molded body at an angle of incidence of 0 DEG. (ii) the minimum transmittance is 85% or more when light having a wavelength of 850-950 nm is caused to enter the molded body at an angle of incidence of 0 DEG; (iii) the average transmittance is 85% or more when light having a wavelength of 1,500-1,600 nm is caused to enter the molded body at an angle of incidence of 0 DEG; (iv) 0.9 < = (transmittance of light when light having a wavelength of 900 nm enters the molded body at an angle of incidence of 60 DEG) / (transmittance of light when light having a wavelength of 900 nm enters the molded body at an angle of incidence of 0 DEG) < = 1.1; and (v) 0.9 < = (transmittance of light when light having a wavelength of 1,550 nm enters the molded body at an incidence angle of 60 DEG) / (transmittance of light when light having a wavelength of 1,550 nm enters the molded body at an incidence angle of 0 DEG) < = 1.1.

Description

Technical Field

[0001] The present invention relates to an acrylic resin composition for a sensor protective cover. Background Art

[0002] In recent years, optical sensors have been developed for various uses. In particular, optical sensors using infrared rays have been considered. Since infrared rays have a longer wavelength than visible light, they have the advantage of being less likely to scatter and are used for distance measurement, three-dimensional measurement, face recognition, etc. In optical sensors using near-infrared rays, an infrared transmission filter that blocks visible light and transmits infrared rays is applied to further improve near-infrared sensitivity. In automotive applications, such optical sensors are used in driver monitoring systems that identify the driver's condition and alert the driver, and in LiDAR (light detection and ranging) for achieving autonomous driving.

[0003] LiDAR for autonomous vehicles uses near-infrared lasers with wavelengths of 905 nm and 1550 nm, which are less likely to scatter in the atmosphere and can easily propagate over long distances. In addition, the use of infrared lasers with wavelengths of 1064 nm and 1310 nm, which are used in existing measurements, has been considered in LiDAR.

[0004] As a means of blocking visible light and transmitting near-infrared rays of a specific wavelength, a band-pass filter in which a high refractive index material and a low refractive index material are alternately laminated on a glass substrate has been disclosed (Patent Document 1). However, the optical characteristics of such an optical filter in which multiple thin films are formed vary greatly depending on the incident angle of the incident light.

[0005] Devices are becoming smaller and thinner in size, so the distance from the light incident window to the optical sensor has become shorter than before, and as a result, the proportion of light incident from an oblique direction tends to increase compared to the past. To improve sensor accuracy, it is required that the transmission amount reaching the entrance sensor remains constant even for light incident from an oblique direction.

[0006] As an optical filter that can block visible light regardless of the incident angle, a filter containing a coloring pigment is known (Patent Document 2). However, in the case of a polycarbonate resin, the surface hardness is insufficient and the scratch resistance is insufficient. In the case of an acrylic resin, the heat resistance is usually insufficient and the dimensional stability at high temperatures (such as inside an automobile) is insufficient.

[0007] Citation List

[0008] Patent Document

[0009] Patent Document 1: JP2015-184627A

[0010] Patent Document 2: JPS60-139757A Summary of the Invention

[0011] Technical Problem

[0012] An object of the present invention is to provide an acrylic resin composition for a sensor protective cover, which has high scratch resistance and high dimensional stability, and can achieve excellent visible light blocking performance and excellent near-infrared transmission performance at a specific wavelength even when the incident angle increases due to the miniaturization of the device in which an optical sensor device is provided.

[0013] Technical Solution

[0014] The inventors of the present invention have conducted in-depth research to achieve the above object, and have found that the object of the present invention can be achieved by an acrylic resin composition containing an acrylic resin and a light absorber, having a heat deflection temperature of 110° C. or higher, and the optical properties of the molded body of the acrylic resin composition satisfying specific conditions. Thus, the present invention has been completed.

[0015] Specifically, the present invention provides the following items [1] to [8].

[0016] [1]. An acrylic resin composition for a sensor protective cover, comprising:

[0017] an acrylic resin (A); and

[0018] a light absorber (B),

[0019] wherein

[0020] the acrylic resin composition has a heat deflection temperature of 110° C. or higher, and

[0021] the 1-mm-thick molded body containing the acrylic resin composition has optical properties satisfying all of the following conditions (i) to (v):

[0022] (i) When light with a wavelength of 380 nm to 700 nm is incident on the molded body at an incident angle of 0°, the maximum transmittance is 10% or less;

[0023] (ii) When light with a wavelength of 850 nm to 950 nm is incident on the molded body at an incident angle of 0°, the minimum transmittance is 85% or more;

[0024] (iii) When light with a wavelength of 1500 nm to 1600 nm is incident on the molded body at an incident angle of 0°, the average transmittance is 85% or more;

[0025] (iv) 0.9 ≤ (Transmittance when light with a wavelength of 900 nm is incident on the molded body at an incident angle of 60°) / (Transmittance when light with a wavelength of 900 nm is incident on the molded body at an incident angle of 0°) ≤ 1.1; and

[0026] (v) 0.9 ≤ (Transmittance when light with a wavelength of 1550 nm is incident on the molded body at an incident angle of 60°) / (Transmittance when light with a wavelength of 1550 nm is incident on the molded body at an incident angle of 0°) ≤ 1.1.

[0027] [2]. The acrylic resin composition according to [1], wherein when the acrylic resin composition is formed into a molded body with a thickness of 3 mm, the surface hardness of the molded body is 70 or more on a Rockwell hardness tester.

[0028] [3]. The acrylic resin composition according to [1] or [2], wherein based on the entire resin composition, the amount of the light absorber (B) is 0.01% by mass or more and 5% by mass or less.

[0029] [4]. The resin composition according to any one of [1] to [3], wherein the light absorber (B) is an anthraquinone dye.

[0030] [5]. The acrylic resin composition according to any one of [1] to [4], wherein the acrylic resin (A) comprises an acrylic resin having a triad syndiotacticity (rr) of 70% or more.

[0031] [6]. The acrylic resin composition according to any one of [1] to [5], wherein the acrylic resin (A) comprises a structural unit (R), and the structural unit (R) has at least one cyclic structure selected from the group consisting of N-substituted or unsubstituted glutarimide units, glutaric anhydride units, maleimide units, and lactone units in the main chain.

[0032] [7]. A molded body comprising the acrylic resin composition according to any one of [1] to [6].

[0033] [8]. The molded body according to [7], wherein the molded body is a sensor protection cover.

[0034] Advantageous Effects

[0035] The present invention provides an acrylic resin composition for a sensor protection cover, which has excellent visible light blocking performance and excellent near-infrared transmission performance at a specific wavelength, has a small incident angle dependence of transmittance, and has high scratch resistance and high dimensional stability. Detailed Embodiments

[0036] Acrylic resin composition

[0037] The acrylic resin composition of the present invention comprises an acrylic resin (A) and a light absorber (B).

[0038] Acrylic resin (A)

[0039] The acrylic resin (A) preferably contains 25% by mass or more, more preferably 65% by mass or more, even more preferably 90% by mass or more, particularly preferably 99% by mass or more, and most preferably 100% of structural units derived from methyl methacrylate based on the total monomer units. When the acrylic resin (A) contains 25% by mass or more of structural units derived from methyl methacrylate, the surface hardness of a molded article containing the acrylic resin composition of the present invention can be improved. The content of the structural units derived from methyl methacrylate in the acrylic resin (A) can be determined by subjecting the acrylic resin (A) purified by reprecipitation in methanol to pyrolysis gas chromatography for pyrolysis and separation of volatile components, and calculating the content from the ratio of the peak area of methyl methacrylate obtained to the peak area of the copolymer components.

[0040] The acrylic resin (A) may be composed of an acrylic resin having a triad syndiotacticity (rr) of 70% or more or an acrylic resin containing a structural unit derived from methyl methacrylate and a structural unit (R).

[0041] In the first embodiment, the triad syndiotacticity (rr) of the acrylic resin (A) is preferably 70% or more, more preferably 70% to 90%, and even more preferably 70% to 80%. Such a syndiotacticity of 70% or more can increase the glass transition temperature of the resin composition of the present invention. Further, when the syndiotacticity is 70% or more, a molded article having a high surface hardness can be obtained.

[0042] As used herein, the triad syndiotacticity (rr) (hereinafter sometimes simply referred to as "syndiotacticity (rr)") is the percentage in which two pairs of adjacent structural units (diads) in three consecutive structural units (triads) are both racemic diads (denoted as "rr"). When two adjacent structural units (diads) in a polymer molecule have the same configuration, the diad is called "meso". When they have opposite configurations, the diad is called "racemic". Meso and racemic are denoted as "m" and "r", respectively.

[0043] The triad isotacticity (rr) (%) can be calculated as follows: measured in deuterated chloroform at 30 °C 1 1H-NMR spectrum; from this spectrum, measure the area (X) of the region from 0.6 to 0.95 ppm and the area (Y) of the region from 0.6 to 1.35 ppm with the peak of TMS set to 0 ppm; and calculate using the formula (X / Y)×100. When two or more acrylic resins (A) with different rr are used in combination, rr can be determined based on the mass ratio according to the additive rule.

[0044] In the second embodiment, the acrylic resin (A) contains a structural unit derived from methyl methacrylate and a structural unit (R).

[0045] The structural unit (R) is a structural unit having at least one cyclic structure selected from the group consisting of N-substituted or unsubstituted glutarimide units, glutaric anhydride units, maleimide units, and lactone units in its main chain. The structural unit (R) can be used alone or in combination of two or more.

[0046] The N-substituted or unsubstituted glutarimide unit is a unit having an N-substituted or unsubstituted 2,6-dioxopiperidine diyl structure.

[0047] Examples of the unit having an N-substituted or unsubstituted 2,6-dioxopiperidine diyl structure include the structural unit represented by formula (I):

[0048]

[0049] where R 1 is a hydrogen atom, C1-C 18 alkyl, C3-C 12 cycloalkyl, or a C6-C 15 organic group containing an aromatic ring, preferably a hydrogen atom, methyl, n-butyl, cyclohexyl, phenyl, or benzyl, and more preferably methyl, n-butyl, or cyclohexyl.

[0050] The unit having an N-substituted or unsubstituted 2,6-dioxopiperidine diyl structure is preferably the structural unit represented by formula (Ia).

[0051]

[0052] The N-substituted or unsubstituted glutarimide unit can be obtained by the methods described in WO2005 / 10838A1, JP2010-254742A, JP2008-273140A, JP2008-274187A, etc. Specifically, for example, by including reacting two adjacent structural units derived from methyl methacrylate with amines containing an aliphatic hydrocarbon group (such as ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine or n-hexylamine); amines containing an aromatic hydrocarbon group (such as aniline, toluidine or trichloroaniline); amines containing an alicyclic hydrocarbon group (such as cyclohexylamine); urea, 1,3-dimethylurea, 1,3-diethylurea or 1,3-dipropylurea. Among them, methylamine is preferred.

[0053] The glutaric anhydride unit is a unit having a 2,6-dioxodihydropyran-2-yl structure. The unit having a 2,6-dioxodihydropyran-2-yl structure is preferably a structural unit represented by formula (II).

[0054]

[0055] The unit having a 2,6-dioxodihydropyran-2-yl structure can be introduced into the acrylic resin (A) by the methods described in JP2007-197703A, JP2010-96919A, etc., for example, by intramolecular cyclization of two adjacent structural units derived from methacrylic acid or intramolecular cyclization of a structural unit derived from methacrylic acid and a structural unit derived from methyl methacrylate.

[0056] The maleimide unit is a unit having an N-substituted or unsubstituted 2,5-pyrrolidinedione structure.

[0057] Examples of the unit having an N-substituted or unsubstituted 2,5-pyrrolidinedione structure include the structural unit represented by formula (III):

[0058]

[0059] wherein R 2 is a hydrogen atom, C1-C 18 alkyl, C3-C 12 cycloalkyl or a C6-C 15 organic group containing an aromatic ring, preferably a hydrogen atom, methyl, n-butyl, cyclohexyl, phenyl or benzyl, more preferably methyl, n-butyl or cyclohexyl.

[0060] The structural unit represented by (III) is prepared by the reaction of maleic anhydride (m) with an imidizing agent represented by R 2 NH2.

[0061] The N-substituted or unsubstituted maleimide unit can be obtained by the methods described in JPS61-026924B, JPH7-042332B, JPH9-100322A, JP2001-329021A, etc. Specifically, it is obtained by reacting a maleic anhydride unit with an imidizing agent. Examples of the imidizing agent include amines containing an aliphatic hydrocarbon group, such as ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, tert-butylamine, or n-hexylamine; amines containing an aromatic hydrocarbon group, such as aniline, toluidine, or trichloroaniline; amines containing an alicyclic hydrocarbon group, such as cyclohexylamine; urea, 1,3-dimethylurea, 1,3-diethylurea, or 1,3-dipropylurea. Among them, methylamine is preferred.

[0062] The lactone unit is a structural unit containing a >CH-O-C(=O)- group in a cyclic structure. In the structural unit containing a >CH-O-C(=O)- group in the cyclic structure, the number of ring-constituting elements is preferably 4 to 8, more preferably 5 to 6, and most preferably 6. Examples of the structural unit containing a >CH-O-C(=O)- group in the cyclic structure include lactone diyl structural units, such as β-propiolactone diyl structural unit, γ-butyrolactone diyl structural unit, and δ-valerolactone diyl structural unit. The structural unit containing a >CH-O-C(=O)- group in the cyclic structure can be obtained, for example, by intramolecular cyclization of a polymer having a hydroxyl group and an ester group using the hydroxyl group and the ester group. The “>C” in the formula means that the carbon atom C has two bonding hands.

[0063] Examples of the δ-valerolactone diyl structural unit include the structural unit represented by formula (IV):

[0064]

[0065] wherein R 3 、R 4 and R 5 are each independently a hydrogen atom or a C1-C 20 organic group, preferably a hydrogen atom or a C1-C 10 organic group, and more preferably a hydrogen atom or a C1-C5 organic group. The organic group is not particularly limited as long as the organic group contains 1 to 20 carbon atoms. Examples include linear or branched alkyl groups, linear or branched aryl groups, -OCOCH3, -CN, etc. The organic group may contain heteroatoms, such as an oxygen atom. R 3 and R 4 are preferably methyl groups, and R 5 is preferably a hydrogen atom.

[0066] The lactone unit can be introduced into the methacrylic copolymer by the methods described in JP2000-230016A, JP2001-151814A, JP2002-120326A, JP2002-254544A, JP2005-146084A, etc., for example, by intramolecular cyclization of a structural unit derived from 2-(hydroxyalkyl) acrylate and a structural unit derived from methyl (meth)acrylate.

[0067] Based on the total structural units, the acrylic resin (A) preferably contains 1 to 60% by mass, more preferably 2 to 55% by mass, and even more preferably 3 to 50% by mass of the structural unit (R). By changing the proportion of the structural unit (R), the heat resistance and rigidity of the acrylic resin (A) can be changed. A content of the structural unit (R) of 1% by mass or more is preferred because it improves the heat resistance and rigidity of the acrylic resin (A). From the perspective of improving flexibility to enhance formability and having no excessive absorption component in the near-infrared region to achieve good transmittance, a content of the structural unit (R) of 60% by mass or less is preferred.

[0068] In addition to the structural unit (R), the acrylic resin (A) may also contain a structural unit (O). Based on the total structural units, the proportion of the structural unit (O) in the acrylic resin (A) is preferably 30% by mass or less, more preferably 25% by mass or less. The proportions of the structural unit (R) and the structural unit (O) can be measured by 1 1H-NMR, etc.

[0069] Examples of the structural unit (O) include structural units derived from the following: alkyl methacrylates other than methyl methacrylate, such as ethyl methacrylate and butyl methacrylate; aryl methacrylates, such as phenyl methacrylate; cycloalkyl methacrylates, such as cyclohexyl methacrylate and norbornene methacrylate; alkyl acrylates, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; aryl acrylates, such as phenyl acrylate; cycloalkyl acrylates, such as cyclohexyl acrylate and norbornene acrylate; aromatic vinyl compounds, such as styrene and α-methylstyrene; acrylic acid; methacrylic acid; acrylamide; methacrylamide; acrylonitrile; methacrylonitrile; etc., vinyl monomers having only one polymerizable carbon-carbon double bond in one molecule. These can be used alone or in combination of two or more.

[0070] The weight-average molecular weight (Mw) of the acrylic resin (A) is preferably from 30,000 to 150,000, more preferably from 40,000 to 120,000, and even more preferably from 50,000 to 100,000. When the Mw is equal to or greater than the lower limit, the impact resistance and toughness of the molded article obtained from the resin composition tend to be improved. When the Mw is equal to or less than the upper limit, the fluidity of the resin composition tends to be improved, and thus, the moldability tends to be improved.

[0071] In the acrylic resin (A), the lower limit of the ratio of Mw to the number-average molecular weight (the number-average molecular weight is hereinafter referred to as "Mn") (Mw / Mn: this value is hereinafter referred to as "molecular weight distribution") is preferably 1.01, more preferably 1.02, and even more preferably 1.03. The upper limit of the ratio is preferably 2.5, more preferably 2.4, and even more preferably 2.3. When Mw / Mn is within this range, the acrylic resin (A) has excellent mechanical strength. Mw and Mn can be controlled by adjusting the type, amount, and addition time of the polymerization initiator, chain transfer agent, etc. used in the production. The number-average molecular weight Mn and the weight-average molecular weight Mw are values calculated by converting the chromatogram measured by gel permeation chromatography into the corresponding molecular weights of standard polymethyl methacrylate.

[0072] In the molecular weight distribution measured by gel permeation chromatography, the proportion of the acrylic resin (A) having a molecular weight of less than 15,000 is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less. The smaller the proportion of the acrylic resin (A) having a molecular weight of less than 15,000, the higher the mechanical strength tends to be.

[0073] The glass transition temperature of the acrylic resin (A) is 120 °C or higher, preferably 125 °C or higher, and more preferably 128 °C or higher. The upper limit of the glass transition temperature of the acrylic resin (A) is preferably 160 °C. The glass transition temperature can be controlled by adjusting the molecular weight, syndiotacticity (rr), introduction of a cyclic structure, etc. As the glass transition temperature of the acrylic resin (A) increases, the heat deflection temperature of the resulting resin composition increases, and the molded article of the resin composition is less likely to deform, such as thermal shrinkage. All glass transition temperatures mentioned in the present invention are the glass transition temperatures at the midpoint measured by the method described in the examples.

[0074] The amount of the acrylic resin (A) contained in the resin composition of the present invention is preferably 50 to 99.9% by mass, more preferably 60 to 99.8% by mass, and even more preferably 70 to 99.7% by mass. The amount of the acrylic resin (A) is preferably 50% by mass or more because the heat resistance is improved.

[0075] One type of acrylic resin (A) may be incorporated into the resin composition, or two or more types of acrylic resins (A) may be incorporated into the resin composition in combination.

[0076] Method for preparing acrylic resin (A)

[0077] The polymerization method of the acrylic resin (A) is not particularly limited. The acrylic resin (A) can be obtained by polymerizing methyl methacrylate alone, or by polymerizing methyl methacrylate, a copolymerizable monomer for forming the structural unit (O), etc., and further performing a cyclic structure forming reaction as needed.

[0078] In the first embodiment, from the viewpoints of high productivity, high thermal decomposition resistance, fewer foreign matters, fewer dimers and trimers of methyl methacrylate, and excellent appearance of the molded body, it is preferable to prepare the acrylic resin (A) by adjusting the polymerization temperature, polymerization time, type and amount of the chain transfer agent, type and amount of the polymerization initiator, etc. in the anionic polymerization method.

[0079] Examples of the anionic polymerization method include: a method of performing anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an inorganic acid salt (such as an alkali metal or alkaline earth metal salt) (see JPH7-25859B), a method of performing anionic polymerization using an organic alkali metal compound as a polymerization initiator in the presence of an organoaluminum compound (see JPH11-335432A), a method of performing anionic polymerization using an organic rare earth metal complex as a polymerization initiator (see JPH6-93060A), etc.

[0080] In the anionic polymerization method for preparing the acrylic resin (A), preferably, an alkyllithium such as n-butyllithium, sec-butyllithium, isobutyllithium, or tert-butyllithium is used as the polymerization initiator. From the viewpoint of productivity, it is preferable to perform the anionic polymerization method in the presence of an organoaluminum compound.

[0081] Examples of the organoaluminum compound include a compound represented by AlR1R2R3, where R1, R2, and R3 are each independently an optionally substituted alkyl group, an optionally substituted cycloalkyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, an optionally substituted alkoxy group, an optionally substituted aryloxy group, or an N,N-disubstituted amino group; in addition, R 2and R 3 may be combined with each other to form an optionally substituted arylenedioxy group.

[0082] Specific examples of the organoaluminum compound include isobutylbis(2,6-di-tert-butyl-4-methylphenoxy)aluminum, isobutylbis(2,2-di-tert-butylphenoxy)aluminum, isobutyl[2,2'-methylenebis(4-methyl-6-tert-butylphenoxy)]aluminum, and the like.

[0083] In the anionic polymerization method, an ether, a nitrogen-containing compound, etc. may be present to control the polymerization reaction.

[0084] In the second embodiment, the acrylic resin (A) includes a structural unit (R) having at least one cyclic structure selected from the group consisting of an N-substituted or unsubstituted succinimide unit, a glutaric anhydride unit, a maleimide unit, and a lactone unit in its main chain. For example, the acrylic resin (A) can be obtained by a method including a cyclic structure-forming reaction.

[0085] Specifically, the method for preparing the acrylic resin (A) includes the following steps: continuously supplying reactants to a tank reactor, the reactants including a monomer mixture, a radical polymerization initiator, and optionally a chain transfer agent, etc., the monomer mixture including, for example, 70 to 100% by mass of methyl methacrylate and 0 to 30% by mass of a copolymerizable monomer for forming a structural unit (O); subjecting the monomer mixture to bulk polymerization in the tank reactor until a polymerization conversion rate of 30 to 60% by mass is achieved to obtain a reaction product; removing the monomer mixture from the reaction product to obtain a precursor polymer; and subjecting the obtained precursor polymer to a cyclic structure-forming reaction. Each step can be implemented by known techniques.

[0086] The cyclic structure-forming reaction can be carried out, for example, using an extruder. Examples of the extruder include a single-screw extruder, a twin-screw extruder, and a multi-screw extruder, etc. From the perspective of mixing performance, a twin-screw extruder is preferred. Examples of the twin-screw extruder include a non-intermeshing co-rotating extruder, an intermeshing co-rotating extruder, a non-intermeshing counter-rotating extruder, and an intermeshing counter-rotating extruder. The intermeshing co-rotating extruder is preferred because high-speed rotation is possible and mixing can be carried out efficiently. These extruders can be used alone or in series.

[0087] When the structural unit (R) is an N-substituted or unsubstituted glutarimide unit, in the cyclic structure formation reaction using an extruder, for example, a precursor polymer as a starting material is fed from the starting material feeding section of the extruder, the precursor polymer is melted to fill the inside of the barrel, and an imidizing agent or the like is injected into the extruder using an addition pump, whereby the cyclic structure formation reaction can be carried out in the extruder.

[0088] The resin temperature in the reaction zone in the extruder is preferably set in the range of 180 to 300 °C, more preferably in the range of 200 to 290 °C. When the resin temperature in the reaction zone is lower than 180 °C, the reaction efficiency of the cyclic structure formation reaction is low, and the heat resistance of the acrylic resin (A) tends to decrease. When the resin temperature in the reaction zone exceeds 300 °C, resin decomposition becomes apparent. The "reaction zone" in the extruder refers to the region in the barrel of the extruder from the injection position for injecting an imidizing agent or the like to the resin discharge port (die head).

[0089] By increasing the reaction time in the reaction zone of the extruder, the cyclic structure formation reaction can be further carried out. The reaction time in the reaction zone of the extruder is preferably 10 seconds or more, more preferably 30 seconds or more. A reaction time of 10 seconds or more is preferred because the cyclic structure formation reaction will proceed well.

[0090] The resin pressure in the extruder is preferably in the range of atmospheric pressure to 50 MPa, more preferably in the range of 1 to 30 MPa. A pressure of 50 MPa or less falls within the mechanical pressure resistance range of an ordinary extruder and does not require a special device, which is cost-effective.

[0091] For the cyclic structure formation reaction, an extruder having a vent hole capable of reducing the pressure below atmospheric pressure is preferably used. By using an extruder having a vent, unreacted materials, by-products (such as methanol) or monomers can be easily removed, and the breaking strength of the molded body containing the acrylic resin (A) tends to be improved.

[0092] For the cyclic structure formation reaction, a reactor for high viscosity, such as a horizontal twin-screw reaction device (such as Vyborac manufactured by Sumitomo Heavy Industries, Ltd.) or a vertical twin-screw stirring tank (such as Super Blend), can also be appropriately used instead of the extruder.

[0093] During the cyclic structure forming reaction, carboxyl groups may be produced as by-products in the acrylic resin (A). The carboxyl groups can be converted into ester groups as needed, for example, by an esterifying agent or a catalyst. This can reduce the foaming of the resin during melt molding. The ester group may vary depending on the esterifying agent or catalyst used, but from the perspectives of reducing the melt viscosity of the resin during melt molding, esterification reactivity, and heat resistance of the resin after esterification, it preferably contains methyl methacrylate units, and more preferably contains both methyl methacrylate units and ethyl methacrylate units.

[0094] Examples of the esterifying agent include dimethyl carbonate, diethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluenesulfonate, methyl trifluoromethanesulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethylcarbodiimide, dimethyl tert-butylsilyl chloride, isopropenyl acetate, dimethylurea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-n-butoxysilane, dimethyl(trimethylsilyl)phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether, etc. These can be used alone or in combination of two or more. Among these esterifying agents, dimethyl carbonate is preferred from the perspectives of cost, reactivity, etc.

[0095] For example, the amount of the esterifying agent can be set such that the acrylic resin (A) has a desired acid value.

[0096] Based on the esterifying agent, a catalyst can be used together. The type of the catalyst is not particularly limited, and examples include amine compounds such as trimethylamine, triethylamine, monomethyldiethylamine, and dimethylmonoethylamine. Among them, triethylamine is preferred from the perspectives of cost, reactivity, etc.

[0097] Light absorber (B)

[0098] Examples of the light absorber (B) used together with the acrylic resin (A) include dyes (organic and inorganic), pigments (organic and inorganic), etc. Among them, from the perspective of reducing the incident angle dependence of the transmittance, dyes with less diffused reflected light are generally preferably used instead of pigments that diffusely reflect light on the particle surface. These light absorbers can be used alone or in combination of two or more.

[0099] Examples of the dyes include azo dyes, anthraquinone dyes, indigo dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methylene dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, naphthalimide dyes, perinone dyes, and the like. Among them, oil-soluble dyes are preferred because they can be easily and uniformly dispersed in the resin composition. Anthraquinone dyes, azoanthraquinone dyes, and diazo dyes are more preferred, and anthraquinone dyes are particularly preferred. The anthraquinone dyes preferably include at least one selected from the group consisting of Solvent Yellow 163, Disperse Violet 28, Solvent Violet 36, Solvent Blue 97, Solvent Green 28, Solvent Green 3, and Disperse Blue 60.

[0100] Examples of the pigments include organic pigments such as azo pigments (oil-soluble azo pigments and insoluble azo pigments), polycyclic pigments, polycyclic pigments (phthalocyanine pigments), threne pigments, quinacridone pigments, di azine pigments, and isoindoline pigments; inorganic pigments such as titanium oxide, iron oxide, chromium oxide, carbon black, ultramarine, barium sulfate, calcium carbonate, zinc oxide, lead sulfate, titanium black, and synthetic iron black; and the like.

[0101] In one embodiment, in addition to anthraquinone dyes, the acrylic resin composition of the present invention may further contain a variety of other colorants as the light absorber (B) in combination. For example, a combination of anthraquinone dyes, pigments, and pigments; a combination of anthraquinone, pigments, and dyes; or a combination of anthraquinone dyes, dyes, and dyes can be used, and a combination of anthraquinone dyes, dyes, and dyes is preferably used. Combining multiple dyes is preferred because it can inhibit or block light of a desired wavelength and provide good light transmittance in the desired wavelength region.

[0102] The amount of the light absorber (B) contained in the resin composition of the present invention is preferably 0.1 to 5% by mass, more preferably 0.2 to 4% by mass, and even more preferably 0.3 to 3% by mass. An amount of 0.1% by mass or more is preferred because stable light-blocking performance is achieved, and from the perspective of reducing manufacturing costs, an amount of 5% by mass or less is preferred.

[0103] Other additives, etc.

[0104] The acrylic resin composition of the present invention may contain additives such as antioxidants, thermal degradation inhibitors, UV absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, impact modifiers, light diffusers, matting agents, and fluorescent agents, as long as the effects of the present invention are not impaired.

[0105] Antioxidants alone have the effect of preventing the oxidative degradation of the resin in the presence of oxygen. Examples include phosphorus antioxidants, hindered phenol antioxidants, thioether antioxidants, etc. These antioxidants can be used alone or in combinations of two or more. Among them, from the perspective of the effect of preventing the deterioration of optical properties due to coloring, phosphorus antioxidants and hindered phenol antioxidants are preferred, and a combination of phosphorus antioxidants and hindered phenol antioxidants is more preferred.

[0106] When a phosphorus antioxidant and a hindered phenol antioxidant are used in combination, the mass ratio of the amount of the phosphorus antioxidant to the amount of the hindered phenol antioxidant is preferably in the range of 1:5 to 2:1, more preferably in the range of 1:2 to 1:1.

[0107] Preferred examples of the phosphorus antioxidant include 2,2-methylenebis(4,6-di-tert-butylphenyl) octyl phosphite (trade name: ADK STAB HP-10, manufactured by Adeka Corporation), tris(2,4-di-tert-butylphenyl) phosphite (trade name: Irgafos 168, manufactured by BASF), 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane (trade name: ADK STAB PEP-36, manufactured by Adeka Corporation), etc.

[0108] Preferred examples of the hindered phenol antioxidant include pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (trade name: Irganox 1010, manufactured by BASF), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (trade name: Irganox 1076, manufactured by BASF), etc.

[0109] The thermal degradation inhibitor can prevent the thermal degradation of the resin by capturing polymer free radicals generated when exposed to high heat in a substantially oxygen-free state.

[0110] Preferred examples of the thermal degradation inhibitor include 2-tert-butyl-6-(3'-tert-butyl-5'-methyl-hydroxybenzyl)-4-methylphenyl acrylate (trade name: Sumilizer GM, manufactured by Sumitomo Chemical Company), 2,4-di-tert-amyl-6-(3',5'-di-tert-amyl-2'-hydroxy-α-methylbenzyl)phenyl acrylate (trade name: Sumilizer GS, manufactured by Sumitomo Chemical Company), etc.

[0111] A UV absorber is a compound having the ability to absorb ultraviolet rays. A UV absorber is a compound that is considered to have the function of mainly converting light energy into heat energy.

[0112] Examples of UV absorbers include benzophenone, benzotriazole, triazine, benzoate, salicylate, cyanoacrylate, oxanilide, malonate, formamidine, etc. These can be used alone or in combination of two or more. Among them, benzotriazole, triazine or the maximum value ε of the molar extinction coefficient at a wavelength of 380 to 450 nm max is 1200 dm 3 mol -1 cm -1 or less of the UV absorber is preferred.

[0113] A light stabilizer is a compound that is considered to have the function of mainly capturing free radicals formed due to photooxidation. Preferred examples include hindered amines, such as compounds having a 2,2,6,6-tetraalkylpiperidine skeleton.

[0114] Examples of lubricants include stearic acid, behenic acid, stearamide, methylene bisstearamide, triglycerol monostearate, paraffin wax, ketone wax, octanol, and hydrogenated oil.

[0115] Examples of mold release agents include higher alcohols such as cetyl alcohol and stearyl alcohol; glycerol higher fatty acid esters such as glycerol monostearate and glycerol distearate; etc. In the present invention, it is preferable to use a higher alcohol and glycerol fatty acid monoesters in combination as a mold release agent. When a higher alcohol and glycerol fatty acid monoesters are used in combination, the ratio is not particularly limited, and the mass ratio of the amount of the higher alcohol to the amount of the glycerol fatty acid monoesters is preferably in the range of 2.5:1 to 3.5:1, more preferably in the range of 2.8:1 to 3.2:1.

[0116] The polymer processing aid is polymer particles with a particle size of 0.05 to 0.5 μm, which can generally be manufactured by emulsion polymerization. The polymer particles can be single-layer particles containing a polymer with a single composition ratio and a single intrinsic viscosity, or can be multi-layer particles containing two or more polymers different in composition ratio or intrinsic viscosity. Among them, preferred examples include particles with a two-layer structure, which includes a polymer layer with a low intrinsic viscosity as the inner layer and a polymer layer with a high intrinsic viscosity of 5 dl / g or more as the outer layer. The polymer processing aid preferably has an intrinsic viscosity of 3 to 6 dl / g. When the intrinsic viscosity is too small, the effect of improving formability tends to be low. When the intrinsic viscosity is too large, the formability of the resin composition tends to decrease. Specific examples include the Metablen P series manufactured by Mitsubishi Rayon Co., Ltd. and the Paraloid series manufactured by Rohm and Haas Company, Dow Chemical Company, and Kureha Chemical Industry Co., Ltd. Based on the acrylic resin, the amount of the polymer processing aid incorporated into the film or sheet is preferably 0.1 part by mass or more and 5 parts by mass or less. When the amount of the polymer processing aid is less than 0.1 part by mass, excellent processing characteristics cannot be obtained. When the amount of the polymer processing aid exceeds 5 parts by mass, problems such as deterioration of surface properties will occur.

[0117] Examples of the impact modifier include core-shell modifiers containing acrylic rubber or diene rubber as the core layer component, modifiers containing multiple rubber particles, etc.

[0118] Examples of the light diffusing agent and the matting agent include fine glass particles, cross-linked fine silicone particles, cross-linked polymer fine particles, talc, calcium carbonate, barium sulfate, etc.

[0119] Examples of the phosphor include fluorescent pigments, fluorescent dyes, fluorescent brightening dyes, fluorescent brighteners, fluorescent bleaching agents, etc.

[0120] The total amount of the antioxidant, heat deterioration inhibitor, UV absorber, infrared absorber, light stabilizer, lubricant, mold release agent, polymer processing aid, impact modifier, light diffusing agent, matting agent, and phosphor that can be contained in the resin composition of the present invention is preferably 7% by mass or less, more preferably 5% by mass or less.

[0121] The acrylic resin composition of the present invention may contain other polymers as long as the effects of the present invention are not impaired. Examples of other polymers include polyolefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene; ethylene ionomers; styrene resins such as polystyrene, styrene-maleic anhydride copolymer, high impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin, and MBS resin; methyl methacrylate polymers and methyl methacrylate-styrene copolymers other than the acrylic copolymer (A); polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyamides such as nylon 6, nylon 66, and polyamide elastomers; polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacetal, polyvinylidene fluoride, polyurethane, phenoxy resin, modified polyphenylene ether, polyphenylene sulfide, silicone-modified resin; silicone rubber; styrene thermoplastic elastomers such as SEPS, SEBS, and SIS; olefin rubbers such as IR, EPR, and EPDM; etc. The amount of such other polymers that can be contained in the acrylic resin composition of the present invention is preferably 10% by mass or less, more preferably 5% by mass or less, and most preferably 0% by mass.

[0122] Method for preparing an acrylic resin composition

[0123] The method for preparing the acrylic resin composition of the present invention is not particularly limited. For example, a method of melt-kneading the acrylic resin (A) and the light absorber (B) can be used. During the melt-kneading, other polymers, additives, etc. can be mixed as needed. The acrylic resin (A) can be first mixed with other polymers and additives and then with the light absorber (B); the light absorber (B) can be first mixed with other polymers and additives and then with the acrylic resin (A); or other methods can be used. Kneading can be carried out using known mixing equipment or kneading equipment such as a kneader-ruder, an extruder, a mixing roll, or a Banbury mixer. Among them, a twin-screw extruder is preferred.

[0124] In order to increase convenience during storage, transportation, or shaping, the acrylic resin composition of the present invention can be prepared in the form of granules or the like.

[0125] Physical properties

[0126] The heat deflection temperature under load can be used as a criterion for the dimensional stability of the acrylic resin composition of the present invention. As measured according to JIS K 7191, the heat deflection temperature under a load of 1.8 MPa of the acrylic resin composition of the present invention is 110 °C or higher, preferably 115 °C or higher. Since the acrylic resin composition of the present invention has a heat deflection temperature under load of 110 °C or higher, the heat resistance of a molded article containing the acrylic resin composition of the present invention can be improved; for example, even when a molded article containing the acrylic resin composition of the present invention is used in automotive sensor applications expected to be in a high-temperature environment, the dimensional stability is good, which is preferable. In this specification, the heat deflection temperature under load is a value measured based on the method described in the following examples.

[0127] The Rockwell hardness can be used as a criterion for the scratch resistance of the acrylic resin composition of the present invention. When the acrylic resin composition of the present invention is formed into a molded article with a thickness of 3 mm, in terms of the Rockwell hardness measured according to JIS K 7202, the surface hardness of the molded article is preferably 70 or higher, more preferably 80 or higher, and particularly preferably 90 or higher. A Rockwell hardness of 70 or higher is preferable because the molded article containing the acrylic resin composition of the present invention is not easily deformed and not easily scratched. In this specification, the Rockwell hardness is a value measured based on the method described in the following examples. In the present invention, an acrylic resin composition in which the surface hardness of the molded article is 70 or higher on a Rockwell hardness tester when the acrylic resin composition is formed into a molded article with a thickness of 3 mm means an acrylic resin composition that satisfies the above Rockwell hardness when formed into a molded article with a thickness of 3 mm, and is not limited to an acrylic resin composition actually formed into a 3 mm molded article.

[0128] When the molded article is a molded article with a thickness of 1 mm, or when converted to a thickness of 1 mm, the optical properties of the molded article containing the acrylic resin composition of the present invention satisfy all of the following conditions (i) to (v):

[0129] (i) When light with a wavelength of 380 nm to 700 nm is incident on the molded article at an incident angle of 0°, the maximum transmittance is 10% or less;

[0130] (ii) When light with a wavelength of 850 nm to 950 nm is incident on the molded article at an incident angle of 0°, the minimum transmittance is 85% or more;

[0131] (iii) When light with a wavelength of 1500 nm to 1600 nm is incident on the molded article at an incident angle of 0°, the average transmittance is 85% or more;

[0132] (iv) 0.9 ≤ (Transmittance when light with a wavelength of 900 nm is incident on the shaped body at an incident angle of 60°) / (Transmittance when light with a wavelength of 900 nm is incident on the shaped body at an incident angle of 0°) ≤ 1.1; and

[0133] (v) 0.9 ≤ (Transmittance when light with a wavelength of 1550 nm is incident on the shaped body at an incident angle of 60°) / (Transmittance when light with a wavelength of 1550 nm is incident on the shaped body at an incident angle of 0°) ≤ 1.1.

[0134] The acrylic resin composition of the present invention is not limited to the acrylic resin composition actually formed into a shaped body, and may be an acrylic resin composition that satisfies all conditions (i) to (v) when formed into a shaped body.

[0135] In this specification, "maximum transmittance" means the maximum value when the transmittance is measured in the wavelength range at 1 nm increments. In this specification, "minimum transmittance" means the minimum value when the transmittance is measured in the wavelength range at 1 nm increments. In this specification, "average transmittance" means the arithmetic mean of the transmittances measured in the wavelength range at 1 nm increments. In this specification, the transmittance is a value measured based on the method described in the following examples.

[0136] Regarding the above (i), in a 1 mm thick shaped body or when the shaped body is converted to 1 mm thick, at an incident angle of 0°, the maximum transmittance at wavelengths from 380 nm to 700 nm is 10% or less, preferably 5% or less. In an optical sensor device using near-infrared light, it is important to block light of unwanted wavelengths, especially visible light, so that the sensing function works accurately. Meeting condition (i) can reduce noise during use and improve the characteristics of the optical sensor device.

[0137] Regarding the above (ii), since the near-infrared sensor emits and receives near-infrared light, in a 1 mm thick shaped body or when the shaped body is converted to 1 mm thick, at an incident angle of 0°, the minimum transmittance at wavelengths from 850 nm to 950 nm is 85% or more, preferably 87% or more, more preferably 90% or more.

[0138] Regarding the above (iii), since the near-infrared sensor emits and receives near-infrared light, in a 1 mm thick shaped body or when the shaped body is converted to 1 mm thick, at an incident angle of 0°, the average transmittance at wavelengths from 1500 nm to 1600 nm is 85% or more, preferably 87% or more, more preferably 90% or more.

[0139] Regarding the above (iv), the miniaturization of the sensor tends to shorten the distance between the cover material and the near-infrared light emission and reception. Therefore, the incident angle during near-infrared light emission and reception increases, and a low dependence on the incident angle is required to improve the accuracy of the sensor. Therefore, in a 1-mm thick molded body or when the molded body is converted to a 1-mm thickness, the transmittance at a wavelength of 900 nm has an angular dependence within the following range:

[0140] 0.9 ≤ (transmittance when light with a wavelength of 900 nm is incident on the molded body at an incident angle of 60°) / (transmittance when light with a wavelength of 900 nm is incident on the molded body at an incident angle of 0°) ≤ 1.1.

[0141] Similarly, regarding the above (v), in a 1-mm thick molded body or when the molded body is converted to a 1-mm thickness, the transmittance at a wavelength of 1550 nm has an angular dependence within the following range:

[0142] 0.9 ≤ (transmittance when light with a wavelength of 1550 nm is incident on the molded body at an incident angle of 60°) / (transmittance when light with a wavelength of 1550 nm is incident on the molded body at an incident angle of 0°) ≤ 1.1.

[0143] Since the molded body containing the acrylic resin composition of the present invention satisfies the above conditions (i) to (v) regarding visible light blocking performance and near-infrared light transmission, it is possible to sufficiently reduce visible light noise and sufficiently transmit near-infrared light. In addition, due to the low dependence on the incident angle, the acrylic resin composition of the present invention can be suitably used for a sensor cover.

[0144] In addition, since infrared lasers with wavelengths of 1064 nm and 1310 nm used for existing measurements are being considered for use in LiDAR, in a 1-mm thick molded body or when the molded body is converted to a 1-mm thickness, the average transmittance at wavelengths from 1014 nm to 1114 nm at an incident angle of 0° is preferably 85% or more, and the average transmittance at wavelengths from 1260 nm to 1360 nm at an incident angle of 0° is preferably 85% or more.

[0145] Molded body

[0146] The shaped article of the present invention contains the acrylic resin composition of the present invention. The method for manufacturing the shaped article of the present invention is not particularly limited. Examples include melt forming methods such as the T-die method (lamination method, co-extrusion method, etc.), blow-up method (co-extrusion method), compression molding method, blow molding method, calendering method, vacuum forming method, injection molding method (insertion method, two-color method, pressing method, core-back method, sandwich method, etc.), and solution casting method. The temperature of the resin composition to be melt formed is preferably set to 180 to 280 °C, more preferably 200 to 250 °C.

[0147] Since the shaped article containing the acrylic resin composition of the present invention can sufficiently reduce visible light noise, can sufficiently transmit near-infrared light, has low dependence on the incident angle, and has high dimensional stability and high scratch resistance, the shaped article can be suitably used as a sensor protective cover. For example, the optical component can be particularly suitable for use as a protective cover for 3D sensors and distance measurement sensors for measuring the shape and distance of an object.

[0148] Examples

[0149] The present invention will be described in more detail below with reference to Examples and Comparative Examples; however, the present invention is not limited to the Examples. The values of physical properties, etc. were measured by the following methods.

[0150] Tacticity (rr) between triads

[0151] For the acrylic resin (A) obtained in each Example and Comparative Example, 1 1H-NMR measurement was performed. The area (X) of the region from 0.6 to 0.95 ppm and the area (Y) of the region from 0.6 to 1.35 ppm were measured with the peak of TMS set to 0 ppm, and the value obtained by calculation using the formula (X / Y) × 100 was defined as the tacticity (rr) (%) between triads.

[0152] Equipment: Nuclear magnetic resonance equipment (Ultrashield 400 Plus manufactured by Bruker Corporation)

[0153] Solvent: Deuterated chloroform

[0154] Measured nuclide: 1 1H

[0155] Measurement temperature: Room temperature

[0156] Number of accumulations: 64 times

[0157] Glass transition temperature

[0158] According to JIS K 7121, the resin compositions obtained in the respective examples were heated to 230 °C using a differential scanning calorimeter (model DSC-50, manufactured by Shimadzu Corporation), cooled to room temperature, and then heated from room temperature to 230 °C at a rate of 10 °C / min. Under these conditions, the DSC curve was measured. The glass transition temperature at the midpoint determined from the DSC curve measured during the second heating was defined as the glass transition temperature (Tg) in the present invention.

[0159] Weight average molecular weight and molecular weight distribution

[0160] Mw and the molecular weight distribution were calculated by measuring the chromatogram by gel permeation chromatography (GPC) under the following conditions.

[0161] GPC equipment: HLC-8320, manufactured by Tosoh Corporation

[0162] Detector: Differential refractive index detector

[0163] Columns: Two TSKgel SuperMultipore HZM-M columns and SuperHZ4000 columns manufactured by Tosoh Corporation connected in series

[0164] Eluent: Tetrahydrofuran

[0165] Eluent flow rate: 0.35 ml / min

[0166] Column temperature: 40 °C

[0167] Calibration curve: Prepared using data of ten standard polymethyl methacrylates

[0168] Imidization rate

[0169] Using 1 1H-NMR (trade name: Ultrashield 400 Plus, manufactured by Bruker Corporation) was used to perform 1 1H-NMR measurement on the resin, and the value determined according to the following formula using the area A of the peak derived from the O-CH3 group in the methyl methacrylate unit around 3.5 to 3.8 ppm and the area B of the peak derived from the N-CH3 group in the N-methylglutarimide unit around 3.0 to 3.3 ppm was defined as the imidization rate (mol%).

[0170] Imidization rate (mol%) = [B / (A + B)] × 100

[0171] The mass% of the imide unit was calculated from the imidization rate (mol%).

[0172] Rockwell hardness

[0173] The resin composition obtained in the examples was injection-molded at 230 °C to obtain specimens with dimensions of 50 mm × 50 mm × 3.0 mm (thickness). The hardness of each specimen was measured according to JIS K 7202 (M scale).

[0174] Heat deflection temperature

[0175] The resin composition obtained in the examples was injection-molded at 230 °C to obtain specimens with dimensions of 80 mm × 10 mm × 4.0 mm (thickness). The heat deflection temperature of each specimen was measured according to JIS K 7191 (1.8 MPa).

[0176] Transmittance

[0177] The resin composition obtained in the examples was injection-molded at 230 °C to obtain specimens with dimensions of 100 mm × 100 mm × 1.0 mm (thickness). The spectral transmittance was measured using a spectrophotometer (U4100, manufactured by Hitachi High-Tech Science Corporation).

[0178] Preparation Example 1: Preparation of acrylic resin (A-1)

[0179] The inside of an autoclave equipped with a stirrer and a collection tube was purged with nitrogen. 100 parts by mass of purified methyl methacrylate, 0.0052 parts by mass of 2,2'-azobis(2-methylpropionitrile) (hydrogen abstraction ability: 1%, 1-hour half-life temperature: 83 °C), and 0.26 parts by mass of n-octyl mercaptan were added to the autoclave and stirred to obtain a raw material liquid. Nitrogen was introduced into the raw material liquid to remove the oxygen dissolved in the raw material liquid.

[0180] The raw material liquid was poured into a tank reactor connected to the autoclave through a pipe until 2 / 3 of the reactor volume. The raw material liquid inlet of the tank reactor and the reaction liquid discharge port of the tank reactor were closed, and the temperature was maintained at 140 °C to initiate the polymerization reaction in a batch manner. When the polymerization conversion reached 55% by mass, the raw material liquid inlet of the tank reactor and the reaction liquid discharge port of the tank reactor were opened, and the raw material liquid was supplied from the autoclave to the tank reactor at a flow rate corresponding to an average residence time of 150 minutes, the reaction liquid was taken out from the tank reactor at a flow rate corresponding to the flow rate of the fed raw material liquid, the temperature of the reaction liquid in the reactor was maintained at 140 °C, and the polymerization reaction was switched to a continuous flow mode. After the switch, the polymerization conversion at steady state was 55% by mass.

[0181] The reaction solution taken out from the tank reactor under steady state is supplied to a multitubular heat exchanger with an internal temperature of 230 °C at a flow rate with an average residence time of 2 minutes and heated. Then, the heated reaction solution is introduced into a flash evaporator, and volatile substances containing unreacted monomers as the main component are removed to obtain a molten resin. The molten resin from which the volatile substances have been removed is fed into a twin-screw extruder with an internal temperature of 260 °C and extruded into the form of a wire, and the wire is cut with a granulator to obtain an acrylic resin (A-1) having a weight-average molecular weight Mw of 82,000, a ratio of weight-average molecular weight to number-average molecular weight (i.e., Mw / Mn ratio) of 1.9, a triad syndiotacticity (rr) of 51%, and a glass transition temperature of 118 °C (Table 1).

[0182] Preparation Example 2: Preparation of acrylic resin (A-2)

[0183] The inside of a 5 L glass reaction vessel equipped with stirring blades and a three-way stopcock is purged with nitrogen. At 23 °C, 1600 g of toluene, 2.49 g (10.8 mmol) of 1,1,4,7,10,10-hexamethyltriethylenetetramine, 53.5 g (30.9 mmol) of a 0.45 M solution of isobutylbis(2,6-di-tert-butyl-4-methylphenoxy)aluminum in toluene, and 7.07 g (11.8 mmol) of a 1.3 M solution of sec-butyllithium (solvent: cyclohexane (95%), n-hexane (5%)) are placed in the reaction vessel. While stirring, at 15 °C, 550 g of purified methyl methacrylate is added dropwise to the reaction vessel over 30 minutes. After the dropwise addition is completed, the mixture is stirred at 25 °C for 90 minutes. At this time, the polymerization conversion rate of methyl methacrylate is 100%. 1500 g of toluene is added to dilute the resulting solution. Subsequently, the diluted solution is poured into 100 kg of methanol to obtain a precipitate. The precipitate is dried at 80 °C and 140 Pa for 24 hours to obtain an acrylic resin (A-2) having a weight-average molecular weight Mw of 70,000, a ratio of weight-average molecular weight to number-average molecular weight (i.e., Mw / Mn ratio) of 1.1, a triad syndiotacticity (rr) of 74%, and a glass transition temperature of 131 °C (Table 1).

[0184] Preparation Example 3: Preparation of imidized acrylic resin (A-3)

[0185] Precursor polymer

[0186] 68.0 parts by mass of purified methyl methacrylate (MMA), 28.0 parts by mass of α-methylstyrene (αMSt), 7.0 parts by mass of styrene (St), 0.05 parts by mass of 2,2'-azobis(2-methylpropionitrile) (AIBN), and 0.01 parts by mass of n-octyl mercaptan (n-OM) were placed in an autoclave equipped with a stirrer and uniformly dissolved to obtain a polymerization raw material. Nitrogen was blown into the reactants to remove dissolved oxygen to 3 ppm. Subsequently, the interior of a continuous flow tank reactor equipped with a brine-cooled condenser was purged with nitrogen. The polymerization raw material was continuously supplied to the tank reactor at a constant flow rate such that the average residence time was 3.0 hours to carry out bulk polymerization at a polymerization temperature of 140°C, and the liquid containing the precursor polymer was continuously discharged from the tank reactor. The pressure in the tank reactor was controlled by a pressure regulating valve connected to the brine-cooled condenser. The resulting polymerization conversion rate is shown in Table 1. Subsequently, the liquid discharged from the reactor was heated to 210°C and supplied to a twin-screw extruder controlled at 230°C. In the twin-screw extruder, volatile substances containing unreacted monomers as the main component were separated and removed, and the precursor polymer was extruded into a strand form. The strand was cut with a granulator to obtain a precursor polymer.

[0187] Imidization

[0188] The precursor polymer was charged into the conveying unit of a twin-screw extruder (trade name: TEX30α-77AW-3V, manufactured by Japan Steel Works, Ltd.) at a rate of 15 kg / h. The twin-screw extruder was equipped with the conveying unit, a melting and kneading unit, a volatilization unit, and a discharging unit and was set at a screw rotation speed of 150 rpm and a temperature of 210 to 270°C. In the melting and kneading unit equipped with kneading blocks, the amount of monomethylamine was adjusted such that the content of the structural unit derived from glutarimide was 61% by weight (48 mol%), and monomethylamine was injected from the additive feed port of the twin-screw extruder, thereby allowing the reaction between the precursor polymer and monomethylamine to proceed. The melting and kneading unit was mainly composed of kneading disks and was attached with sealing elements at both ends. In the volatilization unit, by-products and excess monomethylamine were volatilized from the molten resin passing through the melting and kneading unit and discharged through a plurality of vents.

[0189] The molten resin extruded into a strand form from the die provided at the end of the discharging unit of the twin-screw extruder was cooled in a water bath and then cut with a granulator to obtain pelletized imidized acrylic resin (A-3) (Table 1).

[0190]

[0191] Preparation Example 4

[0192] 65 parts by mass of purified methyl methacrylate (MMA), 28 parts by mass of α-methylstyrene (αMSt), 7 parts by mass of styrene (St), 100 ppm of n-octyl mercaptan (n-OM) as a chain transfer agent, and 1000 ppm of ditertiary dodecyl disulfide (DDS) were placed in an autoclave equipped with a stirrer and a collection tube and uniformly mixed. 500 ppm of 2,2'-azobis(2-methylpropionitrile) (AIBN) was added thereto as a polymerization initiator, and the mixture was uniformly mixed to obtain a polymerization raw material. Nitrogen was blown into the polymerization raw material so that the dissolved oxygen concentration was 3 ppm. The composition of the polymerization raw material is also referred to as the "feed composition".

[0193] Subsequently, a continuous flow tank reactor equipped with a brine-cooled condenser was prepared, and the inside of the reactor was purged with nitrogen. The polymerization raw material was continuously supplied to the reactor at a constant flow rate so that the average residence time was 3.0 hours to carry out bulk polymerization at a polymerization temperature of 140°C, and a resin solution containing a methacrylic resin as a reaction product was continuously discharged from the reactor. The pressure in the reactor was controlled by a pressure regulating valve connected to the brine-cooled condenser. The polymerization conversion was 37%.

[0194] A twin-screw extruder was prepared, which had a resin inlet for introducing the resin solution discharged from the reactor and a die including a resin outlet for discharging the prepared resin, and also had a first vent (also referred to as the "rear vent") relatively close to the resin inlet, a second vent (also referred to as the "front vent") relatively close to the resin outlet, and an additive inlet located between the second vent (front vent) and the resin outlet.

[0195] The resin solution discharged from the reactor is heated using a heat exchanger and supplied to an extruder through the resin feed port. The set temperature of the heat exchanger is 200 °C, and the set temperature of the barrel of the extruder is 245 °C. Volatile substances mainly composed of unreacted monomers are flash-evaporated from the resin solution supplied to the barrel of the extruder and discharged from the first vent (rear vent). In addition, the resin is conveyed in the axial direction of the barrel by a screw, and the volatile substances evaporated during this period are discharged from the second vent (front vent). The screw rotation speed is 164 rpm. The resin is extruded in the form of a strand from the resin discharge port of the extruder. The temperature of the molten resin in the die (also referred to as "die resin temperature") is 244 °C. The obtained strand is cut using a pelletizer to obtain pellets of a methacrylic resin containing a methacrylic copolymer (A-6) which contains methyl methacrylate (MMA) units and α-methylstyrene (αMSt) units.

[0196] The light absorbent (B) used in the examples

[0197] Macrolex (registered trademark) Green G: Anthraquinone dye (manufactured by Lanxess Corporation)

[0198] Macrolex (registered trademark) Green 5B: Anthraquinone dye (manufactured by Lanxess Corporation)

[0199] Macrolex (registered trademark) Violet 3R: Anthraquinone dye (manufactured by Lanxess Corporation)

[0200] Macrolex (registered trademark) Yellow 3G: Pyrazolone dye (manufactured by Lanxess Corporation)

[0201] Example 1

[0202] 1000 g of an acrylic resin (A-1) was mixed with 5 g of Macrolex Green G as a dye and 1 g of Macrolex Violet 3R, and the mixture was melt-kneaded using a twin-screw extruder (trade name: KZW20TW-45MG-NH-600, manufactured by Technovel Corporation) at a barrel heating temperature of 270 °C to obtain a resin composition (C-1) in the form of pellets.

[0203] Subsequently, 1006 g of the resin composition (C-1) in the form of pellets was mixed with 4000 g of an acrylic resin (A-2) in the form of pellets, and the mixture was melt-kneaded using a twin-screw extruder (trade name: KZW20TW-45MG-NH-600, manufactured by Technovel Corporation) at a barrel heating temperature of 270 °C to obtain a resin composition in the form of pellets.

[0204] Thereafter, the resin composition was injection-molded using an injection molding machine (M-100C, manufactured by Meiki Co., Ltd.) under the molding conditions of a barrel temperature of 230°C and a mold temperature of 50°C to obtain a molded article. Table 2 shows the evaluation results.

[0205] Examples 2 to 5 and Comparative Examples 1 to 2

[0206] The same procedure as in Example 1 was carried out, except that the resins and light absorbent (B) used were as shown in Table 2. Tables 2 and 3 show the evaluation results.

[0207] Comparative Example 3

[0208] The same procedure as in Example 1 was carried out, except that polycarbonate manufactured by Covestro was used instead of the acrylic resin (A). Table 3 shows the evaluation results.

[0209] Comparative Example 4

[0210] The same procedure as in Example 1 was carried out, except that the precursor polymer in Preparation Example 3 was replaced with an acrylic resin (A-1), imidization was carried out, and an imidized acrylic resin (A-4) containing 30% by mass of MMA units and 70% by mass of glutarimide units was used. Table 3 shows the evaluation results.

[0211] Comparative Example 5

[0212] The same procedure as in Example 1 was carried out, except that the imidized acrylic resin (A-5) containing 15% by mass of MMA units and 85% by mass of glutarimide units was used instead of the imidized acrylic resin (A-4) used in Comparative Example 4. Table 3 shows the evaluation results.

[0213]

[0214]

Claims

1. An acrylic resin composition for a sensor protective cover, comprising: Acrylic resin (A); and Light absorber (B), wherein, The acrylic resin composition has a heat deflection temperature of 110 °C or higher, and a 1-mm thick molded article containing the acrylic resin composition has optical properties satisfying all of the following conditions (i) to (v): (i) When light with a wavelength of 380 nm to 700 nm is incident on the molded article at an incident angle of 0°, the maximum transmittance is 10% or less; (ii) When light with a wavelength of 850 nm to 950 nm is incident on the molded article at an incident angle of 0°, the minimum transmittance is 85% or more; (iii) When light with a wavelength of 1500 nm to 1600 nm is incident on the molded article at an incident angle of 0°, the average transmittance is 85% or more; (iv) 0.9 ≤ (transmittance when light with a wavelength of 900 nm is incident on the molded article at an incident angle of 60°) / (transmittance when light with a wavelength of 900 nm is incident on the molded article at an incident angle of 0°) ≤ 1.1; and (v) 0.9 ≤ (transmittance when light with a wavelength of 1550 nm is incident on the molded article at an incident angle of 60°) / (transmittance when light with a wavelength of 1550 nm is incident on the molded article at an incident angle of 0°) ≤ 1.

1.

2. The acrylic resin composition according to claim 1, wherein, When the acrylic resin composition is formed into a 3-mm thick molded article, the surface hardness of the molded article is 70 or higher on a Rockwell hardness scale.

3. The acrylic resin composition according to claim 1, wherein, Based on the entire resin composition, the amount of the light absorber (B) is 0.01% by mass or more and 5% by mass or less.

4. The resin composition according to claim 1, wherein, The light absorber (B) is an anthraquinone dye.

5. The acrylic resin composition according to claim 1, wherein, The acrylic resin (A) contains an acrylic resin having a triad syndiotacticity (rr) of 70% or higher.

6. The acrylic resin composition according to claim 1, wherein, The acrylic resin (A) contains a structural unit (R) having at least one cyclic structure selected from the group consisting of N-substituted or unsubstituted glutarimide units, glutaric anhydride units, maleimide units, and lactone units in the main chain.

7. A molded article comprising the acrylic resin composition according to claim 1.

8. The molded article according to claim 7, wherein the molded article is a sensor protective cover.

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