Methacrylic resin molding materials, resin molded articles, vehicle components, housing equipment components, optical components, medical components, containers, and methods for manufacturing resin molded articles.

Abstract

To provide a methacrylic resin molding material that has excellent release properties from high-temperature molds, is less prone to surface defects, and can produce resin molded articles with excellent color tone, as well as resin molded articles, vehicle components, optical components, containers, and medical components made by molding the methacrylic resin molding material, and a method for manufacturing resin molded articles. [Solution] A methacrylic resin molding material comprising methacrylic resin pellets with an added fatty acid, wherein the amount of added fatty acid is 0.002 parts by mass or more per 100 parts by mass of methacrylic resin pellets.

Description

[Technical Field]

[0001] The present invention relates to a methacrylic resin molding material, a resin molded article obtained by molding this methacrylic resin pellet, a vehicle component, an optical component, a container, and a medical component, as well as a method for manufacturing the resin molded article. This application claims priority based on Japanese Patent Application No. 2021-199415, filed in Japan on December 8, 2021, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] Methacrylic resins are widely used as vehicle components such as interior and exterior materials for taillights, headlights, instrument panels, pillar garnishes, front grilles, and emblems; building materials; residential equipment components such as washbasins, bathtubs, and toilets; optical components such as lenses and light guides; and pellets for cosmetic containers and medical components such as cuvettes.

[0003] When applied to these uses, methacrylic resins are molded by methods such as press molding, injection molding, gas-assisted injection molding, welding, extrusion, blow molding, film molding, hollow molding, multilayer molding, and melt spinning. For example, in injection molding, methacrylic resin pellets are transported into a high-temperature cylinder of an injection molding machine. Subsequently, the molten resin is injected into molds processed into various shapes. Then, the resulting molded body is cooled, released from the mold, and removed as a product. Furthermore, in press molding, the resin is set between upper and lower press molds and the product is molded by pressing.

[0004] Patent Document 1 describes a method for manufacturing a thick-walled molded product, which involves applying a lubricant to the surface of a granular thermoplastic resin and injection molding it by adjusting the cylinder temperature of an injection molding machine to a temperature range higher than the glass transition temperature of the thermoplastic resin. Patent Document 2 describes a manufacturing method for producing thick-walled molded articles by injection molding using particles based on an acrylic polymer and a monovalent salt of a saturated or unsaturated fatty acid as an external lubricant. Patent Document 3 describes a method for preventing blocking of (meth)acrylic block copolymer pellets, which involves applying a lubricant to pellets of (meth)acrylic block copolymer containing polymer blocks mainly composed of acrylate monomers and polymer blocks mainly composed of methacrylate monomers. Patent Document 4 describes a manufacturing method for obtaining thermoplastic resin pellets containing additives by using an apparatus equipped with a device for spraying additives onto the surface of thermoplastic resin pellets, which includes a stirrer equipped with a screw that rotates and revolves along the inner wall surface of a conical casing. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2009-137068 [Patent Document 2] Japanese Patent No. 3615618 [Patent Document 3] Japanese Patent No. 4734313 [Patent Document 4] Japanese Patent Application Publication No. 2004-168056 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In Patent Documents 1, 3, and 4, it was noted that in injection molding of acrylic resin, when molding is performed under harsh molding conditions such as high screw rotation speed or long cycles, surface defects (mainly silver) tend to occur, leading to a decrease in yield. In Patent Documents 1 to 4, when lubricants other than fatty acids were used, there was a problem in that the release properties were insufficient when the molten resin flowed into a high-temperature mold and was removed from the mold after solidification.

[0007] The present invention has been made in view of the above circumstances, and aims to provide a methacrylic resin molding material that has excellent release properties from high-temperature molds, is less prone to appearance defects, and can produce resin molded articles with excellent color tone, as well as resin molded articles made by molding the methacrylic resin molding material, vehicle components, optical components, containers and medical components, and a method for manufacturing resin molded articles. [Means for solving the problem]

[0008] The present invention has the following configuration. [1] A methacrylic resin molding material comprising methacrylic resin pellets with an added fatty acid, wherein the amount of added fatty acid is 0.002 parts by mass or more per 100 parts by mass of methacrylic resin pellets. [2] The methacrylic resin molding material according to [1], wherein the amount of the fatty acid added is 0.005 parts by mass to 1 part by mass per 100 parts by mass of the methacrylic resin pellet. [3] The methacrylic resin molding material according to [1] or [2], wherein the fatty acid is a linear hydrocarbon compound. [4] The methacrylic resin molding material according to any one of [1] to [3], wherein the melting point of the fatty acid is 50°C or higher. [5] The methacrylic resin molding material according to any one of [1] to [4], wherein the fatty acid is a fatty acid having 8 to 22 carbon atoms. [6] The methacrylic resin molding material according to any one of [1] to [5], wherein the fatty acid is palmitic acid, stearic acid, myristic acid, lauric acid, or montanic acid. [7] The methacrylic resin molding material according to any one of [1] to [6], wherein the methacrylic resin pellet contains a methacrylic polymer, and the content of repeating units derived from methyl methacrylate in the methacrylic polymer is 70% by mass or more. [8] The methacrylic resin molding material according to any one of [1] to [7], wherein the methacrylic resin pellet contains a methacrylic polymer, and the content of repeating units derived from methyl methacrylate in the methacrylic polymer is 80% by mass or more. [9] The methacrylic resin molding material according to any one of [1] to [8], wherein the methacrylic resin pellet contains a methacrylic polymer, and the content of repeating units derived from methyl methacrylate in the methacrylic polymer is 90% by mass or more.

[10] A methacrylic resin molding material for press molding, extrusion molding, injection molding or film molding, as described in any one of items [1] to [9].

[11] A methacrylic resin molding material for injection molding, as described in any one of items [1] to [9].

[12] The surface area of ​​the methacrylic resin pellet is 10 mm 2 ~450mm 2 The methacrylic resin molding material described in any one of items [1] to

[11] . Use of methacrylic resin molding materials described in any one of items

[13] [1] to [9] for press molding, extrusion molding, injection molding, or film molding. Use of methacrylic resin molding materials described in any one of items

[14] [1] to [9] for injection molding. A resin molded article obtained by molding a methacrylic resin molding material described in any one of items

[15] [1] to [9]. A vehicle component, housing equipment component, optical component, medical component, or container, which is made by molding a methacrylic resin molding material described in any one of items

[16] [1] to [9].

[17] A method for producing a resin molded article comprising a methacrylic resin molding material having fatty acids attached to or coated onto methacrylic resin pellets, wherein the amount of added fatty acids is 0.002 parts by mass or more per 100 parts by mass of methacrylic resin pellets, and the method comprises molding the methacrylic resin molding material to obtain a resin molded article.

[18] The manufacturing method according to

[17] , comprising injection molding the methacrylic resin molding material to obtain a resin molded article.

[19] The manufacturing method according to

[17] or

[18] , comprising injection molding the methacrylic resin molding material at a mold temperature of 70 degrees or higher to obtain a resin molded article. [Effects of the Invention]

[0009] According to the present invention, there are provided a methacrylic resin molding material capable of obtaining a resin molded body having excellent mold release properties from a high-temperature mold, hardly causing appearance defects, and having an excellent color tone, a resin molded body formed by molding the methacrylic resin molding material, a vehicle member, an optical member, a container, and a medical member, and a method for manufacturing a resin molded body.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail. "~" indicating a numerical range means including the numerical values described before and after it as a lower limit value and an upper limit value. Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and various modifications can be made and implemented within the scope of the gist.

[0011] [Methacrylic Resin Molding Material] The methacrylic resin molding material of the present invention is a methacrylic resin molding material obtained by externally adding a fatty acid to methacrylic resin pellets, and the amount of the externally added fatty acid is 0.002 parts by mass or more with respect to 100 parts by mass of the methacrylic resin pellets. Hereinafter, attaching or applying a fatty acid to methacrylic resin pellets is referred to as "external addition". On the other hand, containing a fatty acid in methacrylic resin pellets is referred to as "internal addition". The methacrylic resin molding material of the present invention is obtained by externally adding a fatty acid to methacrylic resin pellets. According to the methacrylic resin molding material of the present invention, a resin molded body having excellent mold release properties from a high-temperature mold, appearance, and color tone can be obtained.

[0012] [Mechanism] According to the present invention, the mechanism by which a resin molded body having excellent mold release properties from a high-temperature mold, appearance, and color tone can be obtained by externally adding a fatty acid to methacrylic resin pellets is considered as follows.

[0013] Fatty acids are chain-like hydrocarbon compounds having at least one carboxyl group in their molecule. Fatty acids consist of a chain-like hydrocarbon portion and a carboxyl group at one end. Among chain-like hydrocarbons, linear hydrocarbons are particularly preferred. The hydrocarbon portion is hydrophobic, and the terminal carboxyl group is hydrophilic. Therefore, when fatty acids are added internally to methacrylic resin pellets and the methacrylic resin and fatty acids are molten, the chain-like hydrocarbon portion of the fatty acid has good affinity for the hydrophobic methacrylic resin, and it is thought that the fatty acid forms aggregates with the carboxyl group portion aggregated toward the center. As a result, the amount of fatty acid present on the surface of the methacrylic resin pellets is reduced. Therefore, in the present invention, it is thought that by externally adding fatty acids to methacrylic resin pellets within a predetermined range, it is possible to achieve both the suppression of appearance defects and the effect of excellent color tone.

[0014] Since fatty acids have carboxyl groups, after injection molding of methacrylic resin pellets to which fatty acids have been added externally, the carboxyl groups of the fatty acids are adsorbed onto the mold surface. This forms a film layer made of fatty acids between the methacrylic resin and the mold. However, the adsorption force described above tends to weaken as the mold temperature increases when functional groups other than carboxyl groups, such as hydroxyl groups and amide groups. Therefore, in the present invention, by externally adding fatty acids to methacrylic resin pellets, a resin molded article can be obtained that quickly forms a film layer during injection molding and has excellent mold release properties even at high mold temperatures.

[0015] <Methacrylic resin pellets> The methacrylic resin pellets contained in the methacrylic resin molding material of the present invention contain a methacrylic resin composition. The methacrylic resin composition in the present invention contains at least a methacrylic polymer (synonymous with methacrylic resin).

[0016] <Methacrylic polymer> The methacrylic polymer is a polymer containing repeating units derived from methyl methacrylate (hereinafter also referred to as "methyl methacrylate units"). In the present invention, the methacrylic resin composition, by containing a methacrylic polymer, improves the color tone of the resulting resin molded article, suppresses thermal decomposition of the resin molded article, and improves color tone and moldability. Furthermore, it is preferable that the methacrylic polymer is a polymer mainly composed of methyl methacrylate units. In one embodiment, "mainly composed of methyl methacrylate units" means, in one embodiment, that the content ratio of methyl methacrylate units in the methacrylic polymer (100% by mass) is 70% by mass or more. The content ratio of methyl methacrylate units in the methacrylic polymer (100% by mass) is more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0017] For the reasons stated above, it is preferable that the content of methyl methacrylate units in the methacrylic polymer (100% by mass) be 70% by mass or more. Examples of such methacrylic polymers include a homopolymer of methyl methacrylate, and a copolymer containing 70% by mass or more and less than 100% by mass of methyl methacrylate units and more than 0% by mass and 30% by mass or less of repeating units derived from monomers other than methyl methacrylate (hereinafter also referred to as "other monomer units").

[0018] Other monomers that form other monomer units are not particularly limited as long as they are copolymerizable with methyl methacrylate. Monomers other than methyl methacrylate may be monofunctional monomers having one radically polymerizable double bond in one molecule, or polyfunctional monomers having two or more radically polymerizable double bonds in one molecule. From the viewpoint of having an excellent balance of fluidity, moldability, and thermal decomposition properties of the methacrylic polymer, acrylic acid esters are preferred as monomers other than methyl methacrylate.

[0019] When a methacrylic polymer contains repeating units derived from acrylic acid esters (hereinafter also referred to as "acrylic acid ester units") as other monomer units, it is preferable that the methacrylic polymer (100% by mass) contains 70% or more by mass of methyl methacrylate units and less than 100% by mass of acrylic acid ester units, more preferably 80% or more by mass of methyl methacrylate units and 0.1% or more by mass of acrylic acid ester units and 20% by mass of acrylic acid ester units, and even more preferably 90% or more by mass of methyl methacrylate units and 0.5% or more by mass of acrylic acid ester units and 10% by mass of acrylic acid ester units.

[0020] Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, isobornyl acrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate, norbornyl acrylate, adamantyl acrylate, dicyclopentenyl acrylate, dicyclopentanyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate. Preferably, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate are used, with methyl acrylate and ethyl acrylate being more preferred. One type of acrylic acid ester may be used alone, or two or more types may be used in combination.

[0021] Another embodiment of the methacrylic polymer is polymer (A), which has a main chain containing repeating units derived from (meth)acrylic acid ester monomers (hereinafter also referred to as "(meth)acrylic acid ester units," where "(meth)acrylic acid ester" means "acrylic acid ester," "methacrylic acid ester," or "methacrylic acid ester and acrylic acid ester") and structural units derived from ring structures (hereinafter abbreviated as "ring structural units"). Examples of ring structural units include glutaric acid anhydride structural units, maleic acid anhydride structural units, glutarimide structural units, lactone ring structural units, and N-substituted maleimide structural units. One type of ring structural unit may be used alone, or two or more types may be used in combination.

[0022] The lower limit of the content of (meth)acrylic acid ester units in polymer (A) is not particularly limited. From the viewpoint of not impairing the inherent performance of methacrylic resins, such as excellent color tone, processability, and mechanical properties of the resulting resin molded article, the content of (meth)acrylic acid ester units is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 94 mol% or more, relative to the total number of moles (100 mol%) of repeating units (including structural units; the same applies hereinafter) contained in polymer (A). The upper limit of the content of (meth)acrylic acid ester units in polymer (A) is not particularly limited. From the viewpoint of excellent heat resistance of the resulting resin molded article, the content of (meth)acrylic acid ester units is preferably 99.999 mol% or less, more preferably 99.9 mol% or less, and even more preferably 99.5 mol% or less, relative to the total number of moles (100 mol%) of repeating units contained in polymer (A). The above upper and lower limits can be arbitrarily combined. For example, 80 to 99.999 mol% is preferred, 90 to 99.9 mol% is more preferred, and 94 to 99.5 mol% is even more preferred.

[0023] The lower limit of the content of ring structural units in polymer (A) is not particularly limited. From the viewpoint of excellent heat resistance of the resulting resin molded article, it is preferable that the content be 0.001 mol% or more, more preferably 0.1 mol% or more, and even more preferably 0.5 mol% or more, relative to the total number of moles (100 mol%) of repeating units contained in polymer (A). The upper limit of the content of ring structural units in polymer (A) is not particularly limited. From the viewpoint of excellent heat resistance, suppression of molded coloring, molded appearance, and weather resistance of the resulting resin molded article, it is preferable that the content be 10 mol% or less, more preferably 3 mol% or less, and even more preferably 0.3 mol% or less, relative to the total number of moles (100 mol%) of repeating units contained in polymer (A). The above upper and lower limits can be arbitrarily combined. For example, 0.001 to 10 mol% is preferred, 0.01 to 3 mol% is more preferred, and 0.05 to 0.3 mol% is even more preferred.

[0024] Among the (meth)acrylic acid esters other than methyl methacrylate that form (meth)acrylic acid ester units, examples of acrylic acid esters include those exemplified in the description of methacrylic polymers above. Examples of methacrylic acid esters other than methyl methacrylate include ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, norbornyl methacrylate, adamantyl methacrylate, dicyclopentenyl methacrylate, dicyclopentanyl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. These (meth)acrylic acid esters may be used individually or in combination of two or more.

[0025] Polymer (A) may contain constituent units derived from monomers having carboxyl groups (hereinafter also referred to as "carboxyl group monomer units"). Some carboxyl group monomer units can form ring structural units through cyclization reactions with ester groups, for example, and introduce ring structural units into the main chain of the methacrylic polymer. Therefore, methacrylic polymers may contain carboxyl group monomer units. Examples of carboxyl group monomers include acrylic acid, methacrylic acid (hereinafter, one or both of acrylic acid and methacrylic acid will be referred to as "(meth)acrylic acid"), 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, and crotonic acid. Methacrylic acid is preferred because the resulting resin molded article has excellent heat resistance. One type of carboxyl group monomer may be used alone, or two or more types may be used in combination.

[0026] One embodiment of polymer (A) is a polymer that includes, as (meth)acrylic acid ester units, repeating units (A1) derived from methyl methacrylate (hereinafter also referred to as "unit (A1)"), repeating units (A2) derived from (meth)acrylic acid (hereinafter also referred to as "unit (A2)"), and as ring structural units, glutaric acid anhydride structural units (A3) (hereinafter also referred to as "unit (A3)").

[0027] The inclusion of unit (A3) in polymer (A) makes it easier to improve the heat resistance of the resulting resin molded article. Unit (A3) is represented by the following chemical structural formula (1).

[0028] [ka]

[0029] (In the formula, R A and R B Each of these independently represents either a hydrogen atom or a methyl group.

[0030] The lower limit of the content of unit (A1) in polymer (A) is not particularly limited. From the viewpoint of not impairing the inherent properties of methacrylic resins, such as excellent color tone, processability, and mechanical properties, the content of unit (A1) is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 94 mol% or more, relative to the total number of moles (100 mol%) of repeating units contained in polymer (A). The upper limit of the content of unit (A1) in polymer (A) is not particularly limited. From the viewpoint of excellent heat resistance of the resulting resin molded article, the content of unit (A1) is preferably 99.4 mol% or less, more preferably 99 mol% or less, and even more preferably 98 mol% or less, relative to the total number of moles (100 mol%) of repeating units contained in polymer (A). The above upper and lower limits can be arbitrarily combined. For example, the content of unit (A1) in polymer (A) is preferably 80 to 99.4 mol%, more preferably 90 to 99 mol%, and even more preferably 94 to 98 mol%.

[0031] As for the unit (A2), methacrylic acid is preferred because the resulting resin molded article has excellent heat resistance.

[0032] The lower limit of the content of unit (A2) in polymer (A) is not particularly limited. From the viewpoint of excellent heat resistance and mechanical properties of the resulting resin molded article, it is preferable that the content be 0.5 mol% or more, more preferably 1 mol% or more, and even more preferably 2 mol% or more, relative to the total number of moles (100 mol%) of repeating units contained in polymer (A). The upper limit of the content of unit (A2) in polymer (A) is not particularly limited. From the viewpoint of not impairing the inherent properties of acrylic resin, such as excellent molded appearance, low water absorption, and moldability of the resulting resin molded article, it is preferable that the content be 20 mol% or less, more preferably 7 mol% or less, and even more preferably 3.5 mol% or less, relative to the total number of moles (100 mol%) of repeating units contained in polymer (A). The above upper and lower limits can be arbitrarily combined. The content of unit (A2) in polymer (A) is, for example, preferably 0.5 to 20 mol%, more preferably 1 to 7 mol%, and even more preferably 2 to 3.5 mol%.

[0033] The lower limit of the content of unit (A3) in polymer (A) is not particularly limited. From the viewpoint of excellent heat resistance of the resulting resin molded article, it is preferably 0.001 mol% or more, more preferably 0.01 mol% or more, and even more preferably 0.05 mol% or more, relative to the total number of moles (100 mol%) of repeating units contained in polymer (A). The upper limit of the content of unit (A3) in polymer (A) is not particularly limited. From the viewpoint of excellent suppression of molded coloring, molded appearance, and weather resistance of the resulting resin molded article, it is preferably 10 mol% or less, more preferably 3 mol% or less, and even more preferably 0.3 mol% or less. The above upper and lower limits can be arbitrarily combined. The content of unit (A3) in polymer (A) is, for example, preferably 0.001 to 10 mol%, more preferably 0.01 to 3 mol%, and even more preferably 0.05 to 0.3 mol%.

[0034] Unit (A3) may be a unit constructed in a copolymer of methyl methacrylate and (meth)acrylic acid by a cyclization reaction between a methoxycarbonyl group derived from unit (A1) and a carboxyl group derived from the adjacent unit (A2).

[0035] In the present invention, the content of each unit in a methacrylic resin such as polymer (A) is 1 The values ​​shall be those calculated from 1H-NMR measurements. Specifically, the content of each unit in a methacrylic resin such as polymer (A) can be calculated using the method disclosed in International Publication No. 2019 / 013186.

[0036] The method for producing methacrylic polymers is not particularly limited. Examples of such methods include bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. From the viewpoint of superior productivity, bulk polymerization and suspension polymerization are preferred.

[0037] The method for producing polymer (A), which contains units (A1), (A2), and (A3) among methacrylic polymers, is not particularly limited. For example, the production methods disclosed in International Publication No. 2017 / 022393 and International Publication No. 2019 / 013186 can be used.

[0038] <Other additives> In the methacrylic resin pellets of the present invention, one or more of various additives usually incorporated in the methacrylic resin pellets may be included within a range that does not impair the effects of the present invention. Examples of the additive include ultraviolet absorbers, light diffusing agents, antioxidants, colorants, pigments, dyes, heat stabilizers, reinforcing agents, fillers, flame retardants, foaming agents, lubricants, plasticizers, antistatic agents, light stabilizers, impact resistance improvers, fluidity improvers, mold release agents, and processing elasticity imparting agents.

[0039] <Shape, size, surface area> The methacrylic resin pellets in the present invention are, for example, those supplied to a molding machine such as an injection molding machine. The shape of the methacrylic resin pellets is not particularly limited, and for example, a columnar shape, a spherical shape, a dice shape, etc. are preferable, a columnar shape and a spherical shape are more preferable, and a columnar shape is even more preferable. There is also no particular limitation on the size of the methacrylic resin pellets. For example, in the case of a columnar shape, the length of the axis (axial length) of the column is preferably 1.5 to 6 mm, and the length of the major diameter of the surface perpendicular to the axial direction is preferably about 1.5 to 5 mm, and the length of the minor diameter of the surface perpendicular to the axial direction is preferably about 1.5 to 4.5 mm. In the case of other shapes, it is preferably a size such that the volume is equivalent to that of the columnar pellets having the above-described dimensions.

[0040] There is also no particular limitation on the surface area of the methacrylic resin pellets. For example, in the case of a columnar shape, it is preferably 10 mm 2 ~450 mm 2 and more preferably 30 mm 2 ~300 mm 2 and even more preferably 40 mm 2 ~200 mm 2This is particularly preferable. In the case of other shapes, it is preferable that the surface area be equivalent to that of cylindrical pellets of the above dimensions. If the surface area of ​​the methacrylic resin pellet is within the above range, it becomes possible to add fatty acids within a predetermined range, making it possible to provide a resin molded article with excellent appearance and release properties from high-temperature molds.

[0041] <Fatty acid> Fatty acids are linear hydrocarbon compounds having at least one carboxyl group in their molecule. A linear hydrocarbon compound having at least one carboxyl group in its molecule means a compound in which the carbon atom to which the carboxyl group is bonded is a constituent atom of the carbon chain. The carbon chain in a linear hydrocarbon compound having at least one carboxyl group in its molecule may be saturated or unsaturated, and may be linear or branched. Among the fatty acids, linear hydrocarbon compounds are preferred.

[0042] The lower limit of the melting point of the fatty acid is preferably 50°C or higher, from the viewpoint of improving mold release from the mold during injection molding and further improving the appearance of the resulting resin molded article. The reason for this is not entirely clear, but it is presumed to be as follows: If the melting point of the fatty acid is 50°C or higher, the decrease in viscosity of the methacrylic resin composition can be suppressed when releasing it from a high-temperature mold, so that the fatty acid contained in the methacrylic resin composition can easily diffuse in the molten resin when the resin is filled into the mold during injection molding. As a result, the fatty acid that adheres to the mold surface and liquefies or condenses diffuses and migrates to the methacrylic resin composition injected into the mold later, so that the surface and vicinity of the final resin molded article have a high content of fatty acids. As a result, the above-mentioned effects and benefits are more easily obtained. The melting point of the fatty acid is more preferably 55°C or higher, and even more preferably 60°C or higher.

[0043] On the other hand, the upper limit of the melting point of the fatty acid is preferably 100°C or lower, from the viewpoint of obtaining better mold release properties for the resulting resin molded article. The reason for this is not entirely clear, but it is presumed to be as follows: If the melting point of the fatty acid is 100°C or lower, the fatty acid that volatilizes in the high-temperature mold will liquefy or condense on the mold surface, making it easier to form a film layer made of the fatty acid on the mold surface. As a result, the effects and benefits described above are more easily obtained. The melting point of the fatty acid is more preferably 90°C or lower, and even more preferably 80°C or lower. The preferred upper and lower limits for the melting point of the fatty acid described above can be combined in any way. For example, the melting point of the fatty acid is preferably 50°C to 100°C, more preferably 55°C to 90°C, and even more preferably 60°C to 80°C.

[0044] The fatty acids are preferably one or both of saturated fatty acids having 8 to 22 carbon atoms and unsaturated fatty acids having 8 to 22 carbon atoms, more preferably one or both of saturated fatty acids having 10 to 20 carbon atoms and unsaturated fatty acids having 10 to 20 carbon atoms, even more preferably one or both of saturated fatty acids having 12 to 18 carbon atoms and unsaturated fatty acids having 12 to 18 carbon atoms, and particularly preferably one or both of saturated fatty acids having 16 carbon atoms and unsaturated fatty acids having 16 carbon atoms. Examples of saturated fatty acids with 8 to 22 carbon atoms include caprylic acid (8 carbon atoms), pelargonic acid (9 carbon atoms), capric acid (10 carbon atoms), lauric acid (12 carbon atoms), myristic acid (14 carbon atoms), pentadecyl acid (15 carbon atoms), palmitic acid (16 carbon atoms), margaric acid (17 carbon atoms), stearic acid (18 carbon atoms), arachidic acid (20 carbon atoms), henicosyl acid (21 carbon atoms), and behenic acid (22 carbon atoms).

[0045] Examples of unsaturated fatty acids with 8 to 22 carbon atoms include myristoleic acid (14 carbon atoms), palmitoleic acid (16 carbon atoms), sapienic acid (16 carbon atoms), oleic acid (18 carbon atoms), elaidic acid (18 carbon atoms), vaccenic acid (18 carbon atoms), gadoleic acid (20 carbon atoms), eicosenoic acid (20 carbon atoms), erucic acid (22 carbon atoms), linoleic acid (18 carbon atoms), eicosadienoic acid (20 carbon atoms), docosadienoic acid (22 carbon atoms), α-linolenic acid (18 carbon atoms), γ-linolenic acid (18 carbon atoms), and pinolenic acid (1 carbon atom). 8) Examples include α-eleostearic acid (18 carbon atoms), β-eleostearic acid (18 carbon atoms), meadic acid (20 carbon atoms), dihomo-γ-linolenic acid (20 carbon atoms), eicosatrienoic acid (20 carbon atoms), stearidonic acid (18 carbon atoms), arachidonic acid (20 carbon atoms), eicosatetraenoic acid (20 carbon atoms), adrenaline (22 carbon atoms), boseopentaenoic acid (18 carbon atoms), eicosapentaenoic acid (20 carbon atoms), osbondic acid (22 carbon atoms), sardine acid (22 carbon atoms), and docosahexaenoic acid (22 carbon atoms).

[0046] These fatty acids may be used individually or in combination of two or more.

[0047] Among the above fatty acids, saturated fatty acids with 8 to 22 carbon atoms are preferred because they offer excellent release properties from high-temperature molds for the resin molded product and are less prone to surface defects in the resin molded product. From the viewpoint of preventing mold contamination during molding, palmitic acid, stearic acid, myristic acid, lauric acid, or montanic acid are preferred, with palmitic acid, stearic acid, and myristic acid being particularly preferred, and palmitic acid being the most preferred.

[0048] The amount of fatty acid added is 0.002 parts by mass or more per 100 parts by mass of methacrylic resin pellets. From the viewpoint of the resulting resin molded article having excellent appearance and release properties from high-temperature molds, 0.005 parts by mass or more is preferred, 0.01 parts by mass or more is more preferred, and 0.1 parts by mass or more is particularly preferred, per 100 parts by mass of methacrylic resin pellets. The upper limit of the amount of fatty acid added is not particularly limited, but from the viewpoint of clouding and color tone of the resulting resin molded article, 1 part by mass or less is preferred, 0.7 parts by mass or less is more preferred, 0.5 parts by mass or less is even more preferred, and 0.3 parts by mass or less is particularly preferred. The above upper and lower limits can be arbitrarily combined. For example, the amount of fatty acid added is preferably 0.002 to 1 part by mass, more preferably 0.005 to 0.7 parts by mass, even more preferably 0.01 to 0.5 parts by mass%, and particularly preferred 0.1 to 0.3 parts by mass.

[0049] The methacrylic resin molding material of the present invention may contain a lubricant, to the extent that it does not impair the effects of the present invention. Examples of lubricants include fatty acid soaps, metal soaps, paraffin waxes, hydrocarbon oils, aliphatic alcohols, fatty acid esters, low molecular weight polyethylene, synthetic waxes, and silicones. The lubricant used should not impair the properties of the methacrylic resin, such as color tone, weather resistance, and scratch resistance.

[0050] [Methacrylic resin molding material manufacturing method] There are no particular limitations on the method for producing the methacrylic resin molding material of the present invention by externally adding fatty acids to the methacrylic resin pellets of the present invention. Examples of such production methods include a dry blending method, a method of spraying or adding fatty acids in powder form to the methacrylic resin pellets of the present invention using a stirring device and stirring, and a method of dispersing methacrylic resin pellets in a liquid containing fatty acids and then removing the solvent from the surface of the methacrylic resin pellets.

[0051] One method of dry blending is to mix methacrylic resin pellets and fatty acid metal salts using a general-purpose blender such as a ribbon blender, tumbler, Nauter mixer, or Henschel mixer.

[0052] An example of a stirring device used when spraying fatty acids onto the methacrylic resin pellets mentioned above is one that comprises a bottomed cylindrical container, a screw that rotates and revolves along the inner wall of the container, and a spraying means for spraying fatty acids onto the methacrylic resin pellets placed inside the container. Examples of spraying means include spray nozzles for spraying fatty acids. The spraying means may also include heating means such as heaters for heating the fatty acids.

[0053] The methacrylic resin pellets of the present invention are placed into the container of such a stirring device, and the fatty acid is sprayed onto the methacrylic resin pellets of the present invention in the container under stirring conditions using a spraying means in powder, liquid, or molten state. Next, the methacrylic resin pellets, to which the fatty acids have been sprayed and impregnated, are further uniformly agitated by a screw that rotates and revolves along the inner wall of the container. This allows the fatty acids to be uniformly externally added to the methacrylic resin pellets.

[0054] To more uniformly add fatty acids to methacrylic resin pellets, it is preferable to vary the temperature inside the container depending on the type of fatty acid. For example, raising the temperature inside the container to around 60-80°C allows for more uniform addition of fatty acids to the methacrylic resin pellets. Methods for changing the temperature inside a container include, for example, circulating heated inert gas through the container, heating the inside of the container with a heater, and controlling the temperature by circulating a heat transfer medium through the container's jacket.

[0055] A method for dispersing methacrylic resin pellets according to the present invention in a liquid containing fatty acids, and then removing the solvent from the surface of the methacrylic resin pellets, includes, for example, preparing a solution or dispersion in which the total amount of fatty acids added to the solvent is 0.05% to 1% by mass, spraying this onto the methacrylic resin pellets, or immersing the methacrylic resin pellets according to the present invention into the liquid for treatment.

[0056] One method for applying fatty acids to methacrylic resin pellets in the present invention by spraying a fatty acid-containing liquid is to arrange methacrylic resin pellets on a transfer device such as a conveyor and continuously spray the fatty acid-containing liquid as the pellets pass through a sprayer.

[0057] The method of adding methacrylic resin pellets to a fatty acid-containing liquid and attaching the fatty acids to the methacrylic resin pellets in the present invention can be carried out by commonly known methods. For example, one method of attaching the fatty acids to the methacrylic resin pellets is to add the fatty acid-containing liquid and the methacrylic resin pellets to a mixing tank equipped with a stirrer, mix them for a predetermined time at a temperature of 0°C to below the boiling point of the solvent, and then separate the methacrylic resin pellets and the liquid by methods such as filtration.

[0058] Next, the solvent is dried by blowing air or, if necessary, by applying hot air. During this process, the fatty acids do not volatilize and remain on the surface of the methacrylic resin pellets. Therefore, after drying, it becomes possible to add fatty acids to the methacrylic resin pellets externally.

[0059] As a solvent, it is possible to use a commonly used solvent. Preferably, as a solvent, one is used in which the methacrylic resin in the methacrylic resin pellets of the present invention does not dissolve or hardly dissolves at all in the solvent. For example, water can be used as such a solvent. As for preferred solvents, a solvent with a boiling point of 30°C to 150°C at atmospheric pressure is preferred in terms of the efficiency of the drying process and ease of workability, and water is particularly preferred in terms of cost and safety.

[0060] [Resin molded product] The resin molded article of the present invention is obtained by molding the methacrylic resin molding material of the present invention. The resin molded articles of the present invention are not particularly limited as long as they are formed by known molding methods, such as press molding, injection molding, gas-assisted injection molding, welding molding, extrusion molding, blow molding, film molding, hollow molding, multilayer molding, and melt spinning. From the viewpoint of obtaining excellent plasticity properties, the methacrylic resin molding material of the present invention is preferably a methacrylic resin molding material for press molding, extrusion molding, injection molding, or film molding, more preferably a methacrylic resin molding material for press molding, extrusion molding, or injection molding, even more preferably a methacrylic resin molding material for extrusion molding or injection molding, and most preferably a methacrylic resin molding material for injection molding.

[0061] While there is no particular lower limit to the temperature of the mold used in the molding process, from the viewpoint of excellent release properties of the resulting resin molded article and further improvement of production efficiency, a temperature of 40°C or higher is preferred, more preferably 50°C or higher, even more preferably 60°C or higher, and most preferably 70°C or higher. While there is no particular upper limit to the temperature of the mold used in the molding process, from the viewpoint of excellent mechanical strength of the resulting resin molded article, a temperature of 200°C or lower is preferred, more preferably 150°C or lower, even more preferably 100°C or higher, and most preferably 90°C or lower.

[0062] Specific examples of the resin molded articles of the present invention include vehicle components such as taillight covers, headlight covers, meter panels, pillar garnishes, front grilles, and emblems; building components; residential equipment components such as washbasins, bathtubs, and toilets; optical components such as lenses and light guides; containers for cosmetics, etc.; and medical components such as cuvettes. Of these, the resin molded articles of the present invention are particularly suitable for use in vehicle components, residential equipment components, optical components, containers, and medical components due to their excellent appearance, weather resistance, color tone, and chemical resistance. [Examples]

[0063] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0064] [Raw materials used] The raw materials used in the following examples and comparative examples are as follows:

[0065] PMMA: Methacrylic resin "ACRYPET(registered trademark) VH" manufactured by Mitsubishi Chemical Corporation, shape: cylindrical, surface area: 95 mm² 2 Size: Long diameter 3.2mm, short diameter 2.2mm, height 3.0mm Fatty acids: palmitic acid, stearic acid Fatty acid compounds: Stearyl alcohol Fatty acid compound: Stearyl stearate Fatty acid compounds: Stearic acid amide

[0066] [Example 1] A Henschel mixer (model name: FM10C / I, manufactured by Nippon Coke Industries Co., Ltd.) was used as the stirring device, which consisted of a cylindrical container and a screw that rotated and revolved along the inner wall of the container. Cooling water was circulated through the jacket of the above container to maintain the jacket temperature at 75°C. Palmitic acid (melting point approximately 60°C) was used as the fatty acid. Methacrylic resin pellets (product name: VH, manufactured by Mitsubishi Chemical Corporation) were placed in the container of the stirring device, the container was sealed, and the methacrylic resin pellets were stirred while powdered fatty acids were added to obtain the methacrylic resin molding material of Example 1. At this time, the temperature of the methacrylic resin molding material was approximately 75°C. The amount of palmitic acid added was set to 0.25 parts by mass relative to the total mass (100 parts by mass) of methacrylic resin pellets. The obtained methacrylic resin molding materials were evaluated as follows. The results are shown in Table 1.

[0067] [Examples 2-4] Except for the amount of palmitic acid added as an external additive relative to the total mass (100 parts by mass) of methacrylic resin pellets, as shown in Table 1, a methacrylic resin molding material was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0068] [Example 5] Except for using stearic acid (melting point approximately 69°C) as the fatty acid and the amount of fatty acid added relative to the total mass (100 parts by mass) of methacrylic resin pellets as shown in Table 1, a methacrylic resin molding material was manufactured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0069] [Comparative Example 1] A twin-screw extruder (model name: TEM35, manufactured by Shibaura Machine Co., Ltd.) was used as the mixing device. Methacrylic resin pellets (product name: VH, manufactured by Mitsubishi Chemical Corporation) and palmitic acid were supplied to a twin-screw extruder, and the methacrylic resin pellets and palmitic acid were melt-kneaded at a cylinder temperature of 250°C to obtain the methacrylic resin molding material of Comparative Example 1. The amount of palmitic acid added was 0.05 parts by mass relative to the total mass (100 parts by mass) of the methacrylic resin pellets. The obtained methacrylic resin molding materials were evaluated as follows. The results are shown in Table 1.

[0070] [Comparative Example 2] A methacrylic resin molding material was manufactured in the same manner as in Comparative Example 1, without kneading fatty acids into methacrylic resin pellets, and evaluated in the same manner. The results are shown in Table 1.

[0071] [Comparative Example 3] A methacrylic resin molding material was prepared in the same manner as in Comparative Example 1, except that stearyl alcohol was added to the methacrylic resin pellets instead of fatty acids, and the amount of stearyl alcohol added was 0.05 parts by mass relative to the total mass (100 parts by mass) of the methacrylic resin pellets. The material was then evaluated in the same manner. The results are shown in Table 1.

[0072] [Comparative Example 4] A methacrylic resin molding material was manufactured in the same manner as in Comparative Example 1, except that stearyl stearate was added to the methacrylic resin pellets instead of fatty acids, and the amount of stearyl stearate added was 0.05 parts by mass relative to the total mass (100 parts by mass) of the methacrylic resin pellets. The material was then evaluated in the same manner. The results are shown in Table 1.

[0073] [Comparative Example 5] A methacrylic resin molding material was prepared in the same manner as in Comparative Example 1, except that stearic acid amide was added to the methacrylic resin pellets instead of fatty acids, and the amount of stearic acid amide added was 0.05 parts by mass relative to the total mass (100 parts by mass) of the methacrylic resin pellets. The material was then evaluated in the same manner. The results are shown in Table 1.

[0074] [Evaluation of the frequency of silver defects] The pelletized methacrylic resin compositions obtained in the examples and comparative examples were hot-air dried at 80°C for approximately 16 hours, and then injection molded under the following conditions. The presence or absence of silver defects on the molded articles was visually determined, and the frequency of occurrence was measured. The results are shown in Table 1. • Injection molding machine: Model name: EC75-SXII, manufactured by Shibaura Machinery Co., Ltd. • Mold: 120mm x 140mm x 4mm plate molded body Cylinder temperature: 230℃ • Hopper bottom temperature: 50℃ • Mold temperature: 60℃

[0075] (1) Evaluation of the dependence on screw rotation speed Cycle: 60 seconds • Screw rotation speed: 50 rpm, 90 rpm, 120 rpm • Number of sampling shots: 10 shots per screw rotation.

[0076] [Evaluation of mold release properties from high-temperature molds during injection molding] (1) Release properties during injection molding As an indicator of mold release properties during injection molding, the ejector pin pressure was measured using the following method. The pelletized methacrylic resin compositions obtained in the examples and comparative examples were hot-air dried at 80°C for approximately 16 hours, and then supplied to an injection molding machine (model name: EC5-SXII, manufactured by Shibaura Machinery Co., Ltd.) set to a cylinder temperature of 260°C. Continuous molding was performed using a mold equipped with a gas vent (capable of molding a disc-shaped molded body with a vertical diameter of 75 mm and a thickness of 3 mm. This disc-shaped mold has a gate at its center. One ejector pin for releasing the molded product is located in the center of the disc-shaped mold, and four are arranged at equal intervals around the periphery of the mold.) under conditions of mold temperature 90°C and injection pressure 80 MPa. The ejector pin pressure (unit: MPa) when releasing the molded body from the mold was measured using a pressure sensor installed on the back of the central ejector pin. A lower ejector pin pressure value indicates better mold release properties. The results are shown in Table 1.

[0077] (2) Molded appearance after injection molding As an indicator of the molded appearance after injection molding, the presence or absence of delamination defects was observed using the following method. A disc-shaped molded body was continuously molded for 40 shots using the same method as for evaluating mold release properties during injection molding. The surface of the obtained molded body was visually inspected, and if surface roughness due to delamination defects from the mold was observed on the surface of the molded body even in one shot, it was determined to be a delamination defect. The results are shown in Table 1.

[0078] (3) Color tone For resin molded test pieces, the yellow index (YI) value was measured using a Hitachi High-Technologies Corporation U-4100 spectrophotometer in accordance with JIS K7105, using the C light source transmission method with a path length of 140 mm. Measurements were performed on three test pieces, and the average value was calculated and evaluated according to the following criteria. The results are shown in Table 1. A: YI value is less than 10.0 B: YI value is 10.0 or higher

[0079] [Table 1]

[0080] The results shown in Table 1 indicate that the methacrylic resin molding materials of Examples 1-5, due to the external addition of fatty acids to the surface of the methacrylic resin pellets, are less prone to appearance defects and possess excellent color tone.

[0081] Although the methacrylic resin molding material of Comparative Example 1 exhibited excellent release properties from high-temperature molds, it was found that the frequency of silver defects increased as the screw rotation speed increased or the cycle time lengthened, making it more prone to appearance defects compared to Examples 1-5. This difference is thought to be due to the fatty acids being internalized rather than on the surface of the methacrylic resin pellets.

[0082] In Comparative Example 2, the methacrylic resin molding material had an ejection pin pressure of 50 MPa, which was higher than in Examples 1-5, and peeling defects were also observed. Furthermore, it was found that the frequency of silver defects increased with higher screw rotation speeds or longer cycle times, making it more prone to appearance defects compared to Examples 1-5. This difference is thought to be due to the absence of fatty acids in the methacrylic resin pellets.

[0083] The methacrylic resin molding material in Comparative Example 3 had an ejection pin pressure of 48 MPa, which was higher than that of Examples 1-5, and peeling defects were also observed. This difference is thought to be due to the use of stearyl alcohol instead of fatty acids.

[0084] The methacrylic resin molding material in Comparative Example 4 had an ejection pin pressure of 48 MPa, which was higher than that of Examples 1-5, and peeling defects were also observed. This difference is thought to be due to the use of stearyl stearate instead of fatty acids.

[0085] The methacrylic resin molding material in Comparative Example 5 had an ejection pin pressure of 47 MPa, which was higher than that of Examples 1-5, and peeling defects were also observed. This difference is thought to be due to the use of stearyl stearate instead of fatty acid.

Claims

1. A methacrylic resin molding material in which fatty acids are attached to or coated onto methacrylic resin pellets, A methacrylic resin molding material in which the amount of fatty acid added externally is 0.002 parts by mass or more and 0.1 parts by mass or less per 100 parts by mass of methacrylic resin pellets.

2. The methacrylic resin molding material according to claim 1, wherein the amount of the fatty acid added externally is 0.005 parts by mass or more and 0.1 parts by mass or less per 100 parts by mass of the methacrylic resin pellet.

3. The methacrylic resin molding material according to claim 1, wherein the fatty acid is a linear hydrocarbon compound.

4. The methacrylic resin molding material according to claim 1, wherein the melting point of the fatty acid is 50°C or higher.

5. The methacrylic resin molding material according to claim 1, wherein the fatty acid is a fatty acid having 8 to 22 carbon atoms.

6. The methacrylic resin molding material according to claim 1, wherein the fatty acid is palmitic acid, stearic acid, myristic acid, lauric acid, or montanic acid.

7. The methacrylic resin molding material according to claim 1, wherein the methacrylic resin pellet contains a methacrylic polymer, and the content of repeating units derived from methyl methacrylate in the methacrylic polymer is 70% by mass or more.

8. The methacrylic resin molding material according to claim 1, wherein the methacrylic resin pellets contain a methacrylic polymer, and the content of repeating units derived from methyl methacrylate in the methacrylic polymer is 80% by mass or more.

9. The methacrylic resin molding material according to claim 1, wherein the methacrylic resin pellet contains a methacrylic polymer, and the content of repeating units derived from methyl methacrylate in the methacrylic polymer is 90% by mass or more.

10. The methacrylic resin molding material according to claim 1, which is a methacrylic resin molding material for press molding, extrusion molding, injection molding, or film molding.

11. The methacrylic resin molding material according to claim 10, which is a methacrylic resin molding material for injection molding.

12. The surface area of ​​the methacrylic resin pellet is 10 mm² ２ ~450mm ２ The methacrylic resin molding material according to claim 1.

13. Use of the methacrylic resin molding material according to any one of claims 1 to 9 for press molding, extrusion molding, injection molding, or film molding.

14. Use of the methacrylic resin molding material according to any one of claims 1 to 9 for injection molding.

15. A resin molded article obtained by molding a methacrylic resin molding material according to any one of claims 1 to 9.

16. A vehicle component, a housing equipment component, an optical component, a medical component, or a container, which is made by molding a methacrylic resin molding material according to any one of claims 1 to 9.

17. A method for producing a resin molded article comprising a methacrylic resin molding material obtained by attaching or coating fatty acids to methacrylic resin pellets, A manufacturing method comprising molding a methacrylic resin molding material in which the amount of fatty acid added externally is 0.002 parts by mass or more and 0.1 parts by mass or less per 100 parts by mass of methacrylic resin pellets, thereby obtaining a resin molded article.

18. The manufacturing method according to claim 17, comprising raising the temperature inside the container to 60 to 80°C when attaching or coating methacrylic acid to methacrylic resin pellets.

19. The manufacturing method according to claim 17, comprising injection molding the methacrylic resin molding material to obtain a resin molded article.

20. The manufacturing method according to claim 17, comprising injection molding the methacrylic resin molding material at a mold temperature of 70 degrees Celsius or higher to obtain a resin molded product.

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