JP5132890B2 - Liquid crystalline resin molded product and method for producing the same - Google Patents

Description

  The present invention relates to a liquid crystalline resin molded article having excellent surface impact strength useful as an electric / electronic device part, a mobile phone casing, an automobile outer plate, and the like, and a method for producing the same.

  Liquid crystalline resins typified by liquid crystalline polyester resins are widely used as highly functional engineering plastics because they have excellent mechanical strength, heat resistance, chemical resistance, electrical properties and the like in a well-balanced manner. However, liquid crystalline resins are known to exhibit high impact strength in the Charpy test due to molecular orientation during molding, but low surface impact strength such as falling weight impact.

  So far, various techniques for blending an olefin copolymer have been proposed in order to improve the surface impact strength of a liquid crystalline resin.

  For example, in Patent Document 1, in order to improve the surface impact strength of a liquid crystalline polyester resin, 0.01 to 10% by weight of an unsaturated carboxylic acid based on an olefin copolymer composed of ethylene and an α-olefin having 3 or more carbon atoms. Alternatively, a modified ethylene copolymer obtained by grafting a derivative thereof, or 0.01 to 10% by weight of an unsaturated carboxylic acid or a copolymer thereof composed of ethylene, an α-olefin having 3 or more carbon atoms and a non-conjugated diene A liquid crystalline polyester resin composition containing a modified ethylene copolymer obtained by grafting a derivative is disclosed.

  Similarly, Patent Document 2 discloses a liquid crystalline polyester resin composition in which an olefin copolymer composed of an α-olefin and a glycidyl ester of an α, β-unsaturated acid is blended.

However, none of the compositions sufficiently improves the surface impact strength of the liquid crystalline polyester resin, and the liquidity polyester resin inherently has fluidity and elastic modulus due to excessive addition of the reactive olefin copolymer. It is damaged and difficult to use for thin-walled injection molded products.
JP-A-8-12862 JP 7-316402 A

  The present invention solves the above-mentioned problems of the prior art, and provides a liquid crystalline resin molded article having improved surface impact strength while maintaining the mechanical properties, particularly fluidity and elastic modulus, of the liquid crystalline resin. Objective.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors injection molded a resin composition containing (B) a specific compound in an appropriate amount to (A) liquid crystalline resin, and formed a core layer of the molded product. The inventors found that a liquid crystalline resin molded article having improved surface impact strength can be obtained by reducing the thickness, and the present invention has been completed.

  That is, the present invention has a weight average molecular weight of 12000 or more or a melt flow rate measured according to JIS K7210 of 10 g / 10 min or less with respect to (A) liquid crystal resin and (B) a functional group having reactivity with liquid crystal resin. This is a liquid crystalline resin molded product obtained by injection molding a resin composition containing 2 to 15% by weight of the above polymer compound, wherein the core layer thickness of the molded product with respect to the total thickness of the molded product is 28% or less.

  The liquid crystalline resin molded product of the present invention has significantly improved surface impact strength compared to conventional liquid crystalline resin molded products, and is excellent in rigidity and fluidity. It can be used in various fields.

  Hereinafter, the components of the composition of the present invention will be described in detail. The liquid crystalline resin (A) used in the present invention is a nematic liquid crystalline resin that exhibits optical anisotropy when melted, and is an indispensable element in the present invention for having both heat resistance and easy processability. The property of melt anisotropy can be confirmed by a conventional polarization inspection method using an orthogonal polarizer. Specifically, it can be confirmed by melting a sample placed on a Leitz hot stage using a Leitz polarizing microscope and observing it at a magnification of about 40 times in a nitrogen atmosphere. When the optically anisotropic polymer is inserted between crossed polarizers, polarized light is transmitted even in a molten stationary liquid state.

  The liquid crystalline resin (A) used in the present invention is preferably an aromatic polyester containing at least 30 mol% or more of an aromatic hydroxycarboxylic acid group having the following general formula (1), and other general formula (2) Also included are aromatic polyethers containing 35 mol% or less of repeating units each consisting of a dicarboxylic acid group represented by formula (3) and a diol represented by formula (3).

-Ar _{1-in the} formula (1) constituting the main repeating unit of the liquid crystalline polyester preferably used in the present invention comprises a phenylene group and / or a naphthalene group, and these aromatic hydroxycarboxylic acids or ester-forming compounds thereof Obtained by polycondensation of Examples of such aromatic hydroxycarboxylic acid compounds include fragrances such as 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 7-hydroxy-2-naphthoic acid, and 4- (4-hydroxyphenyl) benzoic acid. Group hydroxycarboxylic acid or its ester-forming compound may be mentioned, and one or a mixture of two or more thereof may be used. In particular, as the structural unit of formula (1), those having mainly a 4-hydroxybenzoic acid group and partially containing a hydroxynaphthoic acid group are preferable. In particular, when the constituent unit of the polyester to be used is absent or extremely small, the constituent unit (1) is preferably composed of the above two types in view of moldability.

Next, -Ar _{2-in the} formula (2) constituting the polyester (A) preferably used in the present invention is a phenylene group, a naphthalene group, or a diphenylene group, and is an aliphatic group as long as it retains liquid crystallinity. May be. In the formula (3), -R- is a phenylene group, a naphthalene group, a biphenylene group or the like, and may be an aliphatic group having 2 to 8 carbon atoms. (2) Formula and (3) The structural unit is formed from a dicarboxylic acid (HOOC-Ar ₂ -COOH) or an ester-forming compound thereof and a diol (HO-R-OH) as raw materials. Is introduced by a polycondensation reaction with the aromatic hydroxycarboxylic acid or its ester-forming compound. (2) Dicarboxylic acid components for constituting the formula unit include known fragrances such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, 2,7-naphthalenedicarboxylic acid, 4,4′-diphenylcarboxylic acid, etc. Group dicarboxylic acid or an ester-forming compound thereof. The diol for constituting the formula unit (3) is a known aromatic diol such as hydroquinone, nucleus-substituted hydroquinone, 4,4′-biphenol, 2,6-dihydroxynaphthalene, bisphenol A, or aliphatic diol. For example, one or more of ethylene glycol and cyclohexanedimethanol can be used.

  In the liquid crystalline polyester (A) preferably used in the present invention, the structural unit (1) is at least 30 mol% or more, and the units (2) and (3) are each 35 mol% or less, preferably (1 ) Formula 40% or more, formula (2) and formula (3) are each 30% or less, more preferably formula (1) formula 50% or more, formula (2) and formula (3) are each 25% or less . The liquid crystalline resin (A) used in the present invention is a comonomer having an ether bond or an amide bond within the range showing liquid crystallinity when melted in addition to the above formulas (1) and (2) and (3). Ingredients may be introduced, and polyfunctional ester forming monomers such as pentaerythritol, trimellitic acid, trimesic acid, 4-hydroxyisophthalic acid, sodium sulfoisophthalate, An ester-forming monomer having an ionic group such as sodium parahydroxyethyl phenylsulfonate may be introduced. Particularly preferable liquid crystalline polyester resin (A) includes 4-hydroxybenzoic acid, a copolymerized aromatic polyester composed of 6-hydroxy-2-naphthoic acid, and an acid component composed of terephthalic acid and isophthalic acid in addition to these, An aromatic copolyester obtained by copolymerizing a combination monomer with a diol component comprising hydroquinone, 4,4′-biphenol, and ethylene glycol.

The liquid crystalline thermoplastic resin (A) used in the present invention can be prepared by a known method using a direct polymerization method or a transesterification method from the above-mentioned monomer compound. Legal etc. are used. The above compounds having ester-forming ability may be used for polymerization as they are, or may be modified from a precursor to a derivative having ester-forming ability in the previous stage of polymerization. In the polymerization, various catalysts can be used, and typical ones are dialkyl tin oxide, diaryl tin oxide, titanium dioxide, alkoxy titanium silicates, titanium alcoholates, alkalis and alkalis of carboxylic acids. Examples include earth metal salts and Lewis acid salts such as BF ₃ . The amount of catalyst used is generally about 0.001 to 1% by weight, particularly about 0.01 to 0.2% by weight, based on the total weight of the monomers. If the polymer produced by these polymerization methods is further necessary, the molecular weight can be increased by solid-phase polymerization by heating in a reduced pressure or an inert gas. The melt viscosity of the liquid crystalline resin (A) used in the present invention is not particularly limited and may be any as long as it can be injection molded. In general, those having a melt viscosity at a molding temperature of 10 Pa · s to 600 Pa · s at a shear rate of 1000 sec ⁻¹ can be used. However, those having a very high viscosity are not preferable because the fluidity is extremely deteriorated. The liquid crystalline resin (A) may be a mixture of two or more liquid crystalline resins.

  The present invention aims to improve the surface impact strength, which is a drawback of the liquid crystalline resin as described above. The action mechanism for improving the surface impact strength of the liquid crystalline resin in the present invention will be described below.

  Generally, deformation patterns when a polymer material is subjected to a surface impact force can be roughly classified into two types: craze deformation (brittle type) and shear yield deformation (ductility type). Which deformation occurs is almost determined by the basic structure of the polymer material. Craze deformation is roughly classified by molecular entanglement density and shear yield deformation by looking at the flexibility of molecular chains. In order to increase the toughness of the polymer material, an elastomer is usually added, but the role of this elastomer varies depending on each deformation pattern. In the craze deformation type, the elastomer provides a place for stress concentration, Therefore, optimization of the elastomer particle size is an important point, and the optimum particle size is said to vary depending on the entanglement density of the polymer material. On the other hand, in the shear yield deformation type, the impact force is considered to be mitigated by voids due to internal fracture of the elastomer particles or interfacial delamination between the elastomer and the polymer material, so optimization of the distance between the walls of the elastomer particles is important. It is supposed to be.

  However, there is no correlation between the surface impact strength, the elastomer particle diameter, and the distance between the walls of the elastomer particles in increasing the toughness of the liquid crystalline resin, and the toughening mechanism of the liquid crystalline resin is a general polymer. This is different from the toughening theory.

  The inside of the liquid crystalline resin injection-molded product is a surface skin layer, a central core layer, and an intermediate layer between the skin layer and the core layer, as shown in a polarizing micrograph of FIG. 1 (Comparative Example 1 described later). It is known that it has a three-kind five-layer structure. In a general liquid crystal resin injection-molded product, the skin layer and the intermediate layer have a high degree of molecular orientation and a large optical anisotropy as shown in the polarizing micrograph of FIG. It can be seen that the discoloration is relatively weak and has a low degree of molecular orientation. Due to the difference in the degree of molecular orientation between the layers, it is considered that when the liquid crystalline resin receives an impact force, stress is concentrated between the layers and brittle fracture occurs.

  FIG. 2 is a polarizing microscope photograph of a liquid crystalline resin injection molded product (Example 3 described later) containing 5% by weight of an ethylene-glycidyl methacrylate copolymer. As can be seen from FIG. 2, when the ethylene-glycidyl methacrylate copolymer is added, the thickness of the intermediate layer and the core layer changes. As a result of the experiment, it was found that when the thickness of the intermediate layer exceeds 72%, that is, when the thickness of the core layer becomes 28% or less, the impact strength is rapidly improved. It is thought that the intermediate layer having a low degree of molecular orientation relaxes the impact force. That is, the thickness of the core layer of a general liquid crystalline resin molded product is 30% or more, but by increasing the thickness of the intermediate layer, the core layer thickness is 28% or less, preferably 23% or less. The resin-molded product has high toughness.

  In other words, the toughening of liquid crystalline resins does not necessarily require an elastomer component (rubber component), unlike functional polymers with high toughness, and functional groups that are reactive with the terminal groups of liquid crystalline resins. The molecular orientation of the liquid crystalline resin is obtained by blending a polymer compound having a long molecular chain with a weight average molecular weight of 12000 or more or a melt flow rate measured in accordance with JIS K7210 of about 10 g / 10 min or less and introducing cross-linked molecules. Is achieved by increasing the entanglement density of the liquid crystalline resin and increasing the entanglement density of the liquid crystalline resin, and the liquid crystalline resin matrix itself is changed from a craze deformation type (brittle type) to a shear yield deformation type (ductile type). ). The thickness of the intermediate layer and the core layer of the liquid crystalline resin molded product changes in the molded product changed to the shear yield deformation type (the thickness of the intermediate layer increases, and the core layer thickness is 28% or less of the total thickness of the molded product) It is shown in the form of

  Next, (B) a polymer compound having a weight average molecular weight of 12000 or more or a melt flow rate measured according to JIS K7210 of 10 g / 10 min or less for setting the core layer thickness of the liquid crystalline resin molded product to 28% or less, It has a functional group having reactivity with a liquid crystalline resin such as an epoxy group, an oxazolyl group, an imide group, an amino group, and an acid anhydride group.

  These functional groups may be present as a part of other functional groups. For example, a glycidyl group is preferably exemplified as the functional group having an epoxy group. As the monomer having a glycidyl group, unsaturated carboxylic acid glycidyl ester, unsaturated carboxylic acid glycidyl ether and the like are preferably used.

Further, considering the effect of decreasing the degree of molecular orientation of the liquid crystalline resin and the effect of increasing the entanglement density of the liquid crystalline resin, the weight average molecular weight of the polymer serving as the base of the polymer compound (B) was 12000 or more, or measured according to JIS K7210 The melt flow rate is preferably 10 g / 10 min or less. When the molecular weight is smaller than 12000 or the melt flow rate measured according to JIS K7210 is larger than 10 g / 10 min, the effect of decreasing the degree of molecular orientation of the liquid crystalline resin and the effect of increasing the entanglement density of the liquid crystalline resin are small. Therefore, the increase in melt viscosity is small, the core layer thickness of the injection-molded molded product is not 28% or less, and a sufficient surface impact strength cannot be obtained, which is not preferable. However, if the melt viscosity of the liquid crystalline resin composition is excessively increased, the core layer thickness is more than 28%, which is not preferable. Accordingly, the ratio ( η ₂ / η ₁ ) between the melt viscosity (η1) of the liquid crystal resin and the melt viscosity (η2) of the liquid crystal resin composition is preferably 2.0 to 5.0, particularly preferably 2.0 to 4.0. The melt viscosity was measured in accordance with ISO 11443 under the condition of a shear rate of 1000 sec-1 using an orifice having an inner diameter of 1 mm and a length of 20 mm at a melting point of the liquid crystalline resin + 20 ° C.

  The amount of the polymer compound having a functional group reactive with the liquid crystalline resin is preferably 2 to 15% by weight, particularly preferably 2 to 9% by weight, based on the liquid crystalline resin. If the amount is less than 2% by weight, the liquid crystalline resin and the polymer compound do not sufficiently react to obtain sufficient surface impact strength. If the amount is more than 15% by weight, the core layer thickness becomes more than 28%. It is not preferable because good molded products such as poor fluidity and gelation cannot be obtained. However, (B) the amount of the polymer compound added is an important factor for improving the surface impact strength, but not only that, but depending on the type of polymer compound, the surface impact strength can be improved even within the above range. However, in order to obtain sufficient surface impact strength, it is necessary to satisfy the requirements of both (B) the amount of the polymer compound added and the core layer thickness.

  (B) Although the polymer used as the base of the polymer compound is not particularly limited, an olefin resin or a styrene resin is preferable, and an α-olefin combined with a glycidyl group, which is a preferable functional group described above, Those composed of glycidyl ester of α, β-unsaturated acid and those composed of styrenes and glycidyl ester of α, β-unsaturated acid are preferred.

  Specific examples of the α-olefin include ethylene, propylene, and butene. Among them, ethylene is preferably used. Examples of styrenes include styrene, α-methylstyrene, divinylbenzene and the like, and styrene is preferable.

  The glycidyl ester of α, β-unsaturated acid is represented by the following general formula (4).

(In the formula, R ′ is hydrogen or a lower alkyl group having 1 to 5 carbon atoms.)
Examples of the glycidyl ester unit of α, β-unsaturated acid include glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, glycidyl itaconate and the like, and glycidyl methacrylate is particularly preferable.

  In addition to the above two components, one or two olefinic unsaturated esters such as acrylonitrile, acrylic acid ester, methacrylic acid ester, α-methylstyrene, maleic anhydride or the like as the third component in the range not impairing the object of the present invention. You may contain seed | species or more 0-48 weight part with respect to 100 weight part of said 2 components.

The liquid crystalline resin of the present invention includes various fillers such as silica and talc (excluding glass fibers) , and known substances generally added to synthetic resins, that is, stabilizers such as antioxidants and ultraviolet absorbers. Antistatic agents, flame retardants, colorants such as dyes and pigments, lubricants, mold release agents, crystallization accelerators, crystal nucleating agents, and the like can be appropriately added according to the required performance.

  The composition of the present invention is prepared by adding and blending the above components (A) and (B), melt-kneading treatment, and optionally blending other desired components and melt-kneading, and then subjected to injection molding. The In general, the melt kneading of each component is once pelletized using a single-screw or twin-screw extruder and then subjected to injection molding.

  The liquid crystalline resin molded product of the present invention is suitably used for injection molded products such as electrical / electronic device parts, mobile phone casings, and automobile outer panels. In particular, since it is excellent in thin-wall formability, it is effective for injection molded products having a wall thickness of 2 mm or less such as a casing.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Each component used is as follows.
Production Example 1 (Synthesis of wholly aromatic polyester liquid crystal resin (component (A)))
p-Hydroxybenzoic acid 345 parts by weight (73 mol%), 6-hydroxy-2-naphthoic acid 175 parts by weight (27 mol%), potassium acetate 0.02 parts by weight, acetic anhydride 350 parts by weight, stirrer and distillation tube After the reactor was charged and sufficiently purged with nitrogen, the temperature was raised to 150 ° C. under normal pressure, and stirring was started. The mixture was stirred at 150 ° C. for 30 minutes, and the temperature was gradually raised, and acetic acid by-produced was distilled off. When the temperature reached 300 ° C., the reactor was gradually depressurized, and stirring was continued for 1 hour at a pressure of 5 Torr (ie, 665 Pa). When the target stirring torque was reached, a discharge hole at the bottom of the reactor was opened, The resin was taken out into strands using nitrogen pressure. The discharged strand was made into particles by a pelletizer. The wholly aromatic polyester liquid crystal resin had a melting point of 280 ° C. and a melt viscosity at 300 ° C. of 50.1 Pa · s.

The following compounds were used as the polymer compound (B).
-(B-1) Nippon Oil & Fats Co., Ltd., Marproof G1005S [styrene-glycidyl methacrylate copolymer (containing 4.3% by weight of glycidyl methacrylate), weight average molecular weight 98000]
-(B-2) Nippon Oil & Fats Co., Ltd., Marproof G1010S [styrene-glycidyl methacrylate copolymer (containing 8.4% by weight of glycidyl methacrylate), weight average molecular weight 92000]
-(B-3) manufactured by Sumitomo Chemical Co., Ltd., Bondfast 2C [ethylene-glycidyl methacrylate copolymer (containing 6% by weight of glycidyl methacrylate), melt flow rate = 3 g / 10 min]
-(B-4) manufactured by Sumitomo Chemical Co., Ltd., Bondfast E [ethylene-glycidyl methacrylate copolymer (containing 12% by weight of glycidyl methacrylate), melt flow rate = 3 g / 10 min]
(B-5) LOTADAR AX8900 [ethylene-maleic acid-modified glycidyl methacrylate copolymer (containing 8% by weight of glycidyl methacrylate and 25% by weight of maleic acid)], melt flow rate = 6 g / 10 minutes]
・ (B'-1) (Comparative product) manufactured by NOF Corporation, Marproof G0130S [styrene-glycidyl methacrylate copolymer (containing 26.8% by weight of glycidyl methacrylate), weight average molecular weight 10900]
Examples 1-2, Reference Examples 1-3 , Comparative Examples 1-3
The above components (A) and (B) were melt kneaded at a cylinder temperature of 300 ° C. using a twin screw extruder (TEX30α type, manufactured by Nippon Steel Co., Ltd.) in the proportions shown in Table 1, and pellets of the resin composition were obtained. Obtained, subjected to injection molding and evaluated. As a test piece, a 0.7 mm thick flat plate was molded under the conditions of a cylinder temperature of 300 ° C. and a mold temperature of 80 ° C. using a FANUC Roboshot α-100iA molding machine.

The measurement methods used for evaluating the characteristic values are as follows.
[Melt viscosity]
The apparent melt viscosity under conditions of a temperature T1 (melting point of the resin + 20 ° C.) and a shear rate of 1000 sec ⁻¹ was measured according to ISO 11443 using a capillary rheometer (Capillograph 1B manufactured by Toyo Seiki: piston diameter 10 mm). For the measurement, an orifice having an inner diameter of 1 mm and a length of 20 mm was used.
[Core layer thickness]
For a 0.7 mm thick flat plate, the ratio (%) of the core layer thickness to the total thickness of the molded product was evaluated by observation with a polarizing microscope photograph.
[Punching test]
A punch test was conducted using a 0.7 mm-thick flat plate test piece with an Orientec Tensilon UTA-50kN testing machine. The test was conducted at a test speed of 100 mm / min using a hemispherical punching jig having a tip diameter of 16 mm.
[Falling weight test]
A jig with a hemispherical tip (sphere diameter: 9 mm) as shown in FIG. 3 is placed on the center of the fixed flat plate test piece, and a weight of any weight is dropped from this height on this jig. It was confirmed whether the test piece was broken.

  Based on the following calculation formula, 50% fracture energy was calculated.

  The height at which the weight was dropped was changed at 1 cm intervals, and the height at which 50% of the test pieces were broken (50% breaking height) was determined. The 50% fracture energy was calculated from the calculated 50% fracture height using the following formula.

50% fracture energy (E / (J)) = (mass of weight (kg)) x (gravity acceleration (9.80665m / s ² )) x (50% fracture height (m))
The results are shown in Table 1.

2 is a polarizing micrograph of a liquid crystalline resin injection molded product of Comparative Example 1. 2 is a polarizing micrograph of a liquid crystalline resin injection-molded product of Reference Example 1 . It is a figure which shows the hemispherical jig | tool used for the falling weight test.

Claims (4)

(A) To a liquid crystalline resin (B) A polymer compound having a functional group having reactivity with the liquid crystalline resin and having a weight average molecular weight of 12000 or more or a melt flow rate measured in accordance with JIS K7210 of 10 g / 10 min or less 2 to 15% by weight, a liquid crystalline resin molded product obtained by injection molding a resin composition not containing glass fiber, wherein the core layer thickness of the molded product with respect to the total thickness of the molded product is 28% or less,
The polymer compound is a copolymer of styrene and a glycidyl ester of α, β-unsaturated acid, and has an epoxy group as the functional group,
(A) Melt viscosity (η ₁ ) measured by the following method of the liquid crystalline resin, and melt viscosity (η ₂ ) measured by the following method of the resin composition comprising the (A) component and the (B) component. The liquid crystalline resin molded product having a ratio (η ₂ / η ₁ ) of 2.0 to 4.0.
(Measuring method of melt viscosity)
Measurement was performed in accordance with ISO 11443 under the condition of a shear rate of 1000 sec ⁻¹ using an orifice having an inner diameter of 1 mm and a length of 20 mm at a melting point of the liquid crystalline resin + 20 ° C.   The liquid crystalline resin molded article according to claim 1, wherein the thickness of the core layer of the molded article is 23% or less with respect to the total thickness of the molded article.   The liquid crystalline resin molded article according to claim 1 or 2, wherein the glycidyl ester of α, β-unsaturated acid is glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, or glycidyl itaconate. A method for producing a liquid crystalline resin molded product according to any one of claims 1 to 3,
A method for producing a liquid crystalline resin molded article with improved surface impact strength, wherein the resin composition is injection molded, and the core layer thickness of the molded article is 28% or less with respect to the total thickness of the molded article.