JP5558738B2 - Method for producing molded body and method for suppressing blister generation - Google Patents

Description

  The present invention relates to a method for producing a molded article obtained by injection molding a liquid crystalline resin composition, and a method for suppressing the generation of blisters during injection molding of a liquid crystalline resin composition.

  A group of plastics called engineering plastics has high strength and is being replaced by metal parts. Among them, a group of plastics called liquid crystalline resins melts while maintaining the crystal structure, so the volume changes between melting and solidification due to the high strength based on the crystal structure and the fact that the crystal structure does not change significantly during solidification. Is small and molding shrinkage is small.

  The liquid crystalline resin as described above is excellent in moldability and heat resistance, and is preferably used as a constituent material for small electronic components. Among them, it is known that a liquid crystalline resin composition with improved heat resistance and the like can be obtained by appropriately melting and kneading the liquid crystalline resin and the inorganic filler. For example, a liquid crystalline resin composition in which a liquid crystalline resin is filled with a fibrous reinforcing material typified by glass fiber or carbon fiber, or an inorganic powder such as silica, mica, clay, glass beads, etc. Since the balance with the mechanical strength is good, it is a material suitable for an electric / electronic component having a thin portion or a complicated shape. The liquid crystalline resin composition as described above is used for sealing parts such as relay parts, coil bobbins, connectors, volume parts, motor parts such as commutators and separators, or elements such as coils, crystal resonators and IC chips. ing.

  As described above, the liquid crystalline resin composition is a very excellent material and can be used for various applications. However, the liquid crystalline resin composition has a problem to be improved upon molding. The problem in molding this liquid crystalline resin composition is that the liquid crystalline resin composition that is in a molten state at the time of molding entrains gas generated from air or material, so that bubbles are contained inside the molded product. is there. When bubbles are contained inside the molded product, the molded product is exposed to a high temperature by heat treatment or the like, whereby air or gas in the bubbles expands and the surface of the molded product expands. This swelling of the surface of the molded product is called a blister.

  Measures for suppressing the occurrence of blisters as described above include sufficiently degassing from the vent hole during melt extrusion of the resin composition, and not allowing the resin composition to stay in the molding machine for a long time during molding. . However, the occurrence of blisters cannot be sufficiently suppressed only by changing the conditions during molding.

  Therefore, in order to suppress the generation of the blisters, improvement of the liquid crystalline resin composition, improvement of the liquid crystalline resin composition and improvement of molding conditions have been performed. For example, Patent Document 1 discloses a specific liquid crystalline resin composition containing a specific amount of an inorganic filler in a kneading machine having an open port for removing volatile components from a material to be kneaded and a pair of two screws. In a method for producing a liquid crystal polyester composition having a deflection temperature under load of 230 ° C. or higher obtained by melting and kneading the above, a method for producing a liquid crystalline resin composition is disclosed in which the screw engagement rate of the kneader is adjusted to 1.60 or more. Yes. According to the technique described in Patent Document 1, it is said that a liquid crystalline resin composition having excellent blister resistance can be provided while maintaining basic heat resistance such as melting point and deflection temperature under load of the liquid crystalline resin composition. .

JP 2003-211143 A

  As described above, studies for suppressing the generation of blisters are being actively conducted. In the method for improving the above liquid crystalline resin composition, it is necessary to examine whether or not the physical properties are suitable for the application. That is, when the blister generation of a liquid crystal resin composition preferable for a specific application is suppressed, the liquid crystal resin composition is changed in the conventional method of improving the material. It is necessary to reexamine whether or not has the desired physical properties. Therefore, a technique for suppressing the generation of blisters is required regardless of the type of liquid crystalline resin composition to be used so that it is not necessary to examine the above physical properties.

  Further, when the liquid crystalline resin composition is injection-molded, the generation of blisters can be suppressed by reducing the injection speed. However, from the viewpoint of improving the productivity of molded products, it is strongly demanded to increase the injection speed.

  The present invention has been made in order to solve the above-mentioned problems, and the object thereof is to suppress the generation of blisters and to improve the productivity of the molded product regardless of the type of liquid crystalline resin composition to be used. It is providing the manufacturing method of the molded object which can be raised to the limit, and the method of suppressing generation | occurrence | production of a blister.

The present inventors paid attention to the point that the liquid crystalline resin composition in the molten state at the time of molding embraced air, and conducted intensive studies to solve the above problems. As a result, it has been found that the main air entrainment that causes blistering occurs at the sprue, and further, the maximum injection capacity (Vc _max ) without blistering, the sprue outlet diameter and the nozzle outlet diameter The ratio (φs / φn) of the liquid crystal resin composition is derived under a condition satisfying Vc _max <f (φs / φn) by deriving the relationship between the ratio (φs / φn) and a function of a predetermined form (Vc _max = f (φs / φn)) It has been found that the above-mentioned problems can be solved by injection molding, and the present invention has been completed. More specifically, the present invention provides the following.

(1) a step of measuring a maximum injection capacity (Vc _max ) _{1 at} which no blister occurs on the surface of the molded article when the liquid crystalline resin composition is injection-molded under predetermined molding conditions, and among the predetermined molding conditions When the ratio (φs / φn) of the outlet diameter (φs) of the sprue and the outlet diameter (φn) of the nozzle is changed and the liquid crystalline resin composition is injection molded, the blister is not generated on the surface of the molded body. The injection capacity (Vc _max ) ₂ of the above, the relationship between the step of measuring the maximum injection capacity (Vc _max ) where no blister occurs and the ratio (φs / φn) of the sprue outlet diameter to the nozzle outlet diameter And a step of deriving with a function of a predetermined form (Vc _max = f (φs / φn)), and a liquid crystalline resin composition under a condition satisfying Vc _max (cm ³ / sec) <f (φs / φn) Characterized by injection molding Process for producing a molded article to be.

(2) The function of the predetermined format is represented by the following formula (I), and the liquid crystalline resin composition is injection molded under molding conditions satisfying the following formula (II): The manufacturing method of the molded object of description.
Vc _max (cm ³ / sec) <− 45 (φs / φn) +240 (I)
φn <3mm (II)

  (3) The method for producing a molded article according to (1) or (2), wherein an outlet diameter (φn) of the nozzle is 2 mm or less.

  (4) The method for producing a molded article according to any one of (1) to (3), wherein the liquid crystalline resin composition contains glass fibers.

  (5) The method for producing a molded body according to any one of (1) to (4), wherein a ratio (φs / φn) between an outlet diameter of the sprue and an outlet diameter of the nozzle is 4.5 or less.

  (6) By setting the ratio (φs / φn) of the outlet diameter (mm) of the sprue and the outlet diameter (mm) of the nozzle to a predetermined value or less, the generation of blisters when the liquid crystalline resin composition is injection molded. How to suppress.

  (7) The method for suppressing blister generation according to (6), wherein the predetermined value is 4.5 or less, and an outlet diameter (φn) of the nozzle is 3 mm or less.

  According to the present invention, it is possible to easily derive a condition with as much injection capacity as possible. As the injection capacity increases, the productivity of the resulting molded product increases. For this reason, when shape | molding a liquid crystalline resin composition, productivity of a molded article can be raised to a limit. Moreover, this invention does not have a restriction | limiting in the liquid crystalline resin composition to be used. Therefore, it is not necessary to reexamine the physical properties by changing the material, and the productivity of a molded product obtained by easily molding the liquid crystalline resin composition can be improved.

It is a figure which shows the state to which the runner, the sprue, and the nozzle were connected. It is a graph showing the relationship between the ratio (φs / φn) and the injection volume _{(Vc max).} Is a graph showing the relationship between the ratio of Example (φs / φn) and the injection volume _{(Vc max).}

  Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiment, and may be implemented with appropriate modifications within the scope of the object of the present invention. it can.

The method for producing a molded article of the present invention comprises a step of measuring the maximum injection capacity (Vc _max ) _{1 at} which no blister is generated on the molded article surface when the liquid crystalline resin composition is injection molded under predetermined molding conditions (hereinafter referred to as the following). And the ratio (φs / φn) between the sprue outlet diameter (φs) and the nozzle outlet diameter (φn) among the predetermined molding conditions described above. When the liquid crystalline resin composition is injection-molded, a step of measuring the maximum injection capacity (Vc _max ) _{2 at} which no blister is generated on the surface of the molded body (hereinafter, referred to as “second injection capacity measuring step”). ) And the maximum injection capacity (Vc _max ) at which no blister is generated and the ratio (φs / φn) between the sprue outlet diameter and the nozzle outlet diameter (Vc _max = f (φs / φn)) Degree (hereinafter referred to as "relationship deriving step") and a step of injection molding the liquid-crystalline resin composition under the conditions satisfying _{Vc max <f (φs / φn} ) ( hereinafter, referred to as "injection molding step" And the like.

<First injection volume measurement process>
The first injection volume measuring step is a step of measuring the maximum injection volume (Vc _max ) _{1 at} which no blister is generated on the surface of the molded body when the liquid crystalline resin composition is injection molded under predetermined molding conditions. The method for measuring the maximum injection capacity at which no blister is generated is not particularly limited. For example, until the ratio (φs / φn) between the sprue outlet diameter and the nozzle outlet diameter is fixed to a predetermined value, the blister is generated. By gradually increasing the injection capacity condition, the injection capacity condition that is one step lower than the injection capacity condition in which the blister is generated can be determined as the “maximum injection capacity (Vc _max ) at which no blister is generated”. When increasing the injection capacity condition step by step, the interval at which the injection capacity is increased to measure the maximum injection capacity is appropriately changed depending on the liquid crystalline resin composition used. As described later, the present invention is characterized in that the relationship between the maximum injection capacity (Vc _max ) at which no blister is generated and the ratio (φs / φn) between the outlet diameter of the sprue and the outlet diameter of the nozzle is obtained. In this step, the maximum injection capacity (Vc _max ) at a predetermined ratio (φs / φn) necessary for obtaining the above relationship is obtained. The above ratio and injection capacity obtained in this step are (φs / φn) ₁ and (Vc _max ) ₁ .

  FIG. 1 shows a state in which a runner, a sprue and a nozzle are connected. As shown in FIG. 1, the sprue outlet diameter is the sprue diameter of the connection portion between the sprue and the runner. Further, as shown in FIG. 1, the nozzle outlet diameter is the nozzle inner diameter of the nozzle tip outlet.

With respect to “the blister occurs on the surface of the molded body”, how to determine whether or not the blister occurs is not particularly limited. In the present invention, five or more molded bodies are molded by injection molding under predetermined molding conditions, and a reflow process with a peak temperature of 280 ° C. is performed on all molded bodies (for example, a reflow process performed under the conditions described in the examples). For example, if even one blister is generated by visual observation, a determination method of evaluating that “a blister occurs” is preferable. By performing blister evaluation of five or more molded bodies by injection molding under the same predetermined molding conditions, the ratio between the maximum injection capacity (Vc _max ) at which no blisters are generated and the outlet diameter of the sprue and the outlet diameter of the nozzle ( (φs / φn) can be expressed by a more accurate relational expression.

[Predetermined molding conditions]
The predetermined molding conditions are conditions at the time of injection molding such as the type of molding machine, mold temperature, injection speed, screw rotation speed, and the like. These conditions are appropriately changed to preferable conditions according to the type of the liquid crystalline resin composition to be used. In this step, only the injection capacity condition is changed and injection molding is repeated to measure the maximum injection capacity at which blisters are not generated on the surface of the molded body.

As described above, in the present invention, the relationship between the maximum injection capacity (Vc _max ) at which no blister is generated and the ratio (φs / φn) between the outlet diameter of the sprue and the outlet diameter of the nozzle is obtained. Therefore, in the present invention, the maximum injection capacity at which blisters are not generated on the surface of the molded body is measured. Any method that obtains the above relationship by measuring the injection capacity rather than the injection speed or the like has the advantage of being applicable to molding machines having various screw diameters.

  The ratio of the sprue outlet diameter to the nozzle outlet diameter (φs / φn) is preferably 4.5 or less, as will be described later.

  The present invention can derive conditions under which blisters are not generated on the surface of a molded product when injection molding a liquid crystalline resin composition. The blisters on the surface of the molded body tend to be generated when the nozzle outlet diameter is less than 3 mm. Therefore, it is useful to use the method for producing a molded body of the present invention in the case of predetermined molding conditions in which the nozzle outlet diameter is less than 3 mm. If the nozzle outlet diameter is 3 mm or more, problems such as “nose dripping” occur. As a result, in many liquid crystalline resin compositions, it is necessary to set the nozzle diameter to less than 3 mm. Therefore, the present invention is useful for a large number of liquid crystal resin compositions. Here, “nose sag” is a phenomenon in which the molten resin flows out from the nozzle. In particular, according to the method for producing a molded article of the present invention, even when the nozzle outlet diameter is 2 mm or less, other problems such as blistering and nasal discharge do not occur, and the liquid crystalline resin composition has high productivity. A molded body formed by molding can be obtained. Moreover, it is preferable that the exit diameter of a nozzle is 1 mm or more from a viewpoint of ensuring fluidity | liquidity (filling resin in a metal mold cavity completely).

[Liquid Crystalline Resin Composition]
The liquid crystalline resin used in the present invention refers to a melt processable polymer having a property capable of forming an optically anisotropic molten phase. The property of the anisotropic molten phase can be confirmed by a conventional polarization inspection method using an orthogonal polarizer. More specifically, the anisotropic molten phase can be confirmed by using a Leitz polarizing microscope and observing a molten sample placed on a Leitz hot stage under a nitrogen atmosphere at a magnification of 40 times. When the liquid crystalline resin applicable to the present invention is inspected between crossed polarizers, the polarized light is normally transmitted even in a molten stationary state, and optically anisotropic.

  The liquid crystalline resin as described above is not particularly limited, but is preferably an aromatic polyester or an aromatic polyester amide, and a polyester partially including an aromatic polyester or an aromatic polyester amide in the same molecular chain is also within the range. It is in. They preferably have a logarithmic viscosity (IV) of at least about 2.0 dl / g, more preferably 2.0-10.0 dl / g when dissolved in pentafluorophenol at 60 ° C. at a concentration of 0.1% by weight. .) Are used.

  The aromatic polyester or aromatic polyester amide as the liquid crystalline resin applicable to the present invention is particularly preferably at least one compound selected from the group of aromatic hydroxycarboxylic acids, aromatic hydroxyamines, and aromatic diamines. Aromatic polyesters and aromatic polyester amides as constituent components.

More specifically,
(1) A polyester mainly composed of one or more aromatic hydroxycarboxylic acids and derivatives thereof;
(2) mainly (a) one or more of aromatic hydroxycarboxylic acids and derivatives thereof; and (b) one or more of aromatic dicarboxylic acids, alicyclic dicarboxylic acids and derivatives thereof; c) Polyester comprising at least one or more of aromatic diol, alicyclic diol, aliphatic diol and derivatives thereof;
(3) mainly (a) one or more of aromatic hydroxycarboxylic acids and derivatives thereof; (b) one or more of aromatic hydroxyamines, aromatic diamines and derivatives thereof; and (c). A polyester amide comprising one or more of aromatic dicarboxylic acid, alicyclic dicarboxylic acid and derivatives thereof;
(4) mainly (a) one or more of aromatic hydroxycarboxylic acids and derivatives thereof; (b) one or more of aromatic hydroxyamines, aromatic diamines and derivatives thereof; and (c). One or more of aromatic dicarboxylic acid, alicyclic dicarboxylic acid and derivatives thereof, and (d) at least one or more of aromatic diol, alicyclic diol, aliphatic diol and derivatives thereof, and And polyester amides composed of Furthermore, you may use a molecular weight modifier together with said structural component as needed.

（Ｘ：アルキレン（Ｃ１〜Ｃ４）、アルキリデン、−Ｏ−、−ＳＯ−、−ＳＯ_２−、−Ｓ−、−ＣＯ−より選ばれる基である）

（Ｙ：−（ＣＨ_２）_ｎ−（ｎ＝１〜４）、−Ｏ（ＣＨ_２）_ｎＯ−（ｎ＝１〜４）より選ばれる基である。） Preferable examples of specific compounds constituting the liquid crystalline resin applicable to the present invention include p-hydroxybenzoic acid, aromatic hydroxycarboxylic acids such as 6-hydroxy-2-naphthoic acid, 2,6-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 4,4′-dihydroxybiphenyl, hydroquinone, resorcin, aromatic diols such as compounds represented by the following general formula (I) and the following general formula (II); terephthalic acid, isophthalic acid, 4 , 4′-diphenyldicarboxylic acid, 2,6-naphthalenedicarboxylic acid and aromatic dicarboxylic acids such as compounds represented by the following general formula (III); aromatic amines such as p-aminophenol and p-phenylenediamine Can be mentioned.

(X: alkylene (C1 -C4), _{alkylidene, -O -, - SO -,} - SO 2 -, - S -, - is a group selected from CO-)

(Y is a group selected from — (CH ₂ ) _n — (n = 1 to 4) and —O (CH ₂ ) _n O— (n = 1 to 4).

  The liquid crystalline resin composition used in the present invention may contain two or more kinds of liquid crystalline resins or may contain a resin other than the liquid crystalline resin. In addition, a composition imparted with desired characteristics by adding additives such as a nucleating agent, carbon black, a pigment such as an inorganic fired pigment, an antioxidant, a stabilizer, a plasticizer, a lubricant, a release agent, and a flame retardant Is also included.

  In particular, the method for producing a molded article of the present invention is suitable when a liquid crystalline resin composition containing an inorganic filler is used. The inorganic filler which can be used is not specifically limited, A conventionally well-known thing can be used. Examples of conventionally known inorganic fillers include, as fibrous fillers, asbestos fibers, silica fibers, silica / alumina fibers, alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, potassium titanate fibers, Furthermore, inorganic fibrous materials, such as metal fibrous materials, such as stainless steel, aluminum, titanium, copper, and brass, are mentioned. The granular fillers include carbon black, graphite, silica, quartz powder, glass beads, milled glass fiber, glass balloon, glass powder, calcium silicate, aluminum silicate, kaolin, talc, clay, diatomaceous earth, wollastonite, etc. Salts, iron oxide, titanium oxide, zinc oxide, antimony trioxide, oxides of metals such as alumina, carbonates of metals such as calcium carbonate and magnesium carbonate, sulfates of metals such as calcium sulfate and barium sulfate, other ferrites, Examples thereof include silicon carbide, silicon nitride, boron nitride, and various metal powders. Those containing a plurality of these inorganic fillers are also included in the liquid crystalline resin composition usable in the present invention. Examples of the plate-like filler include mica, glass flakes, various metal foils and the like. Among these inorganic fillers, glass fiber and talc are preferably used as described later.

<Second injection volume measurement process>
The second injection volume measuring step is to change the ratio (φs / φn) between the sprue outlet diameter (φs) and the nozzle outlet diameter (φn) among the predetermined molding conditions in the first injection volume measuring step. This is a step of measuring the maximum injection capacity (Vc _max ) at which blisters are not generated on the surface of the molded product when the liquid crystalline resin composition is injection molded. The ratio (φs / φn) set in this step and the injection capacity (Vc _max ) obtained in this step are (φs / φn) ₂ and (Vc _max ) ₂ , respectively. As will be described later, the present invention obtains the relationship between the maximum injection capacity (Vc _max ) at which no blister is generated and the ratio (φs / φn) between the sprue outlet diameter and the nozzle outlet diameter. In addition to (φs / φn) ₁ and (Vc _max ) ₁ obtained in the first injection volume measuring step, (φs / φn) ₂ and (Vc _max ) ₂ obtained in this step are obtained, The relationship between (φs / φn) and the injection capacity (Vc _max ) can be obtained. The method for measuring the maximum injection volume at which no blister is generated is not particularly limited as in the case of the first injection volume measurement step.

The injection capacity (Vc _max ) is preferably 30 (cm ³ / s) or more. When the injection capacity is lower than 30 (cm ³ / s), it is a region that is not usually molded when handling a liquid crystalline resin from the viewpoint of productivity.

After the second injection volume measuring step, the ratio (φs / φn) is further changed to perform the third injection volume measuring step, and the maximum injection volume (Vc _max ) _{3 at} which no blister is generated on the surface of the molded body is measured. Is preferred. This is because the relationship between the ratio (φs / φn) and the injection capacity (Vc _max ) can be obtained more accurately by using a lot of data. Moreover, the injection volume _{(Vc max)} in measurement performed after said second injection volume measurement step is preferably 30 ^(cm 3 / s) or more. This is because the relational expression described later can be obtained more accurately.

<Relationship derivation process>
In the relational expression derivation step, the relationship between the maximum injection capacity (Vc _max ) at which no blister is generated and the ratio (φs / φn) between the outlet diameter of the sprue and the outlet diameter of the nozzle (φc / φn) _This is a step of deriving with _max = f (φs / φn)). One of the features of the present invention is that there is a correlation between the ratio (φs / φn) and the maximum injection capacity (Vc _max ) at which no blisters are generated. The present invention has found that an adhesive resin composition can be applied.

A specific relational derivation method is (φs / φn) ₁ , (Vc _max ) ₁ obtained in the first injection volume measurement step, and (φs / φn) ₂ obtained in the second injection volume measurement step. , (Vc _max ) ₂ , an approximate function (Vc _max = f (φs / φn)) is obtained as shown in FIG. The form of the approximation function is not particularly limited, and examples include power approximation, logarithmic approximation, linear approximation, polynomial approximation, and exponential approximation. The approximate function can be obtained by a conventionally known method. For example, it can be obtained by a method using Microsoft Excel spreadsheet software.

In particular, the relationship between the ratio (φs / φn) and the injection capacity (Vc _max ) is as shown in FIG. 2B, at what ratio (φs / φn) when the injection capacity becomes lower than a certain value. Even if it exists, it will be in the state which does not generate a blister. Usually, the “certain constant value” is 30 (cm ³ / s). For this reason, a part important for examination of molding conditions is a part of 30 (cm ³ / s) or more. This is because the invention is intended to increase the productivity of the molded body by producing the molded body under conditions where the injection capacity is as large as possible, and there is a risk of blisters occurring under conditions of a high injection capacity of 30 (cm ³ / s) or more. Because there is. Therefore, the above relational expression is preferably obtained from data of an injection capacity (usually 30 (cm ³ / s)) or more at which no blister is generated at any ratio (φs / φn). In particular, as shown in FIG. 2 (b), the ratio (φs / φn) and the injection capacity (by the linear approximation only from the data (data less than the predetermined ratio) before the injection capacity (Vc _max ) becomes constant. By deriving the relationship with Vc _max ), an accurate relational expression can be easily obtained (a and b in FIG. 2B are constants).

The liquid crystalline resin composition can contain an inorganic filler as described above. Glass fiber is often blended to improve physical properties, but the present invention can be preferably applied to a liquid crystalline resin composition containing glass fiber. In the case of a liquid crystalline resin composition containing glass fibers, the relationship between the ratio (φs / φn) and the injection capacity (Vc _max ) is Vc _max (cm ³ / sec) = − 45 (φs / φn) +240 Tend to be. In particular, this relational expression can be applied to many liquid crystalline resin compositions containing glass fibers.

As described above, when obtaining an approximate function, a more accurate relational expression can be obtained by obtaining an approximate function from more data of the ratio (φs / φn) and the injection capacity (Vc _max ). In particular, the relational expression can be obtained more accurately by using data of three or more points. The data of the ratio (φs / φn) and the injection capacity (Vc _max ) is equal to or greater than the injection capacity (usually 30 (cm ³ / s)) where no blister is generated at any ratio (φs / φn). It is preferable that the data is.

  As for the lower limit of the ratio (φs / φn) between the sprue diameter and the nozzle diameter, it is preferable that the ratio (φs / φn) is 1.2 or more from the viewpoint of maintaining fluidity.

<Injection molding process>
The injection molding step is a step of injection molding the liquid crystalline resin composition under conditions that satisfy Vc _max (cm ³ / sec) <f (φs / φn). In addition to the desired molding conditions, a step of producing a molded body by adjusting the sprue outlet diameter, nozzle outlet diameter, and injection volume so as to satisfy Vc _max (cm ³ / sec) <f (φs / φn) It is. That is, the conditions of the outlet diameter of the sprue, the outlet diameter of the nozzle, and the injection capacity are set from the shaded area in FIGS. 2 (a) and 2 (b). The desired molding conditions are the mold temperature, screw rotation speed, etc. as described in the above “predetermined molding conditions”, and the desired molding conditions are usually set in the first injection volume measuring step. The predetermined molding conditions are determined from the liquid crystalline resin composition to be used.

  As described above, the sprue outlet diameter, nozzle outlet diameter, and injection volume conditions are set from the shaded area in FIGS. 2 (a) and 2 (b). The above-mentioned conditions are set within a range in which an excellent molded product can be obtained without causing a problem.

  In particular, when the ratio (φs / φn) between the sprue outlet diameter and the nozzle outlet diameter is 4.5 or less, blisters tend not to occur even at a high injection capacity. Therefore, it is preferable to perform injection molding under the condition that the ratio (φs / φn) is 4.5 or less. Thus, by setting the ratio (φs / φn) between the outlet diameter (mm) of the sprue and the outlet diameter (mm) of the nozzle to a predetermined value or less, the liquid crystalline resin composition can be obtained under the conditions of the highest injection capacity. The generation of blisters when an object is injection-molded can be suppressed. Blisters tend to occur when the nozzle outlet diameter is less than 3 mm. Therefore, the method for suppressing the generation of blisters of the present invention is particularly useful when the nozzle outlet diameter is less than 3 mm. In addition, it is preferable to perform molding in the range where the ratio (φs / φn) is 1.2 or more for the reason of fluidity retention.

  Further, as described above, when the liquid crystalline resin composition is injection-molded, the nozzle outlet diameter is preferably 1.0 mm or more and less than 3 mm. A more preferable range of the nozzle diameter is 1.2 mm to 1.5 mm. Further, as described above, the ratio (φs / φn) between the outlet diameter of the sprue and the outlet diameter of the nozzle is preferably 1.2 to 4.5. Here, when the outlet diameter of the nozzle is 1.2 mm, the outlet diameter of the sprue is preferably 1.44 mm to 5.4 mm. When the nozzle outlet diameter is 1.5 mm, the sprue outlet diameter is preferably 1.8 mm to 6.75 mm. As a result, the sprue outlet diameter is preferably 1.44 mm to 6.75 mm. Usually, the outlet diameter of the sprue used when molding the liquid crystalline resin composition is about 7.0 mm. The liquid crystalline resin composition in a molten state has high fluidity. For this reason, it is possible to set the outlet diameter of the sprue small. However, if the outlet diameter of the sprue is set too small, the molten resin will not flow easily, and the productivity of the molded product will decrease even if it is a liquid crystalline resin with high fluidity in the molten state. For this reason, conventionally, the sprue outlet diameter has been set with a sufficient margin so as not to hinder the flow of the molten resin. In the present invention, molding can be performed under conditions where the injection capacity is as high as possible without impairing the flow of the molten resin and without causing problems such as blistering. As a result, a high-quality molded product can be obtained with high productivity. Further, the liquid crystalline resin composition remaining in the sprue portion after molding and solidified in this portion is reused. With the method for producing a molded body of the present invention, the sprue outlet diameter can be made smaller than the conventional one, so the volume of the resin remaining in the sprue portion is also reduced, and the amount of the liquid crystalline resin composition that must be reused Can be suppressed. As a result, the labor of reuse is reduced, and the productivity of high-quality molded products is increased.

  Such an effect can be obtained by adjusting the ratio (φs / φn) of the sprue outlet diameter to the nozzle outlet diameter so that the molten resin discharged from the nozzle is applied to the inner wall surface of the sprue near the sprue inlet. It is considered that sticking and the molten resin proceeds to the sprue outlet along the inner wall surface, so that it is difficult to entrap air in the sprue and prevent bubbles from being mixed into the molded product.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Material>
Liquid crystalline resin composition 1: Liquid crystalline resin (manufactured by Polyplastics, “Vectra E950i”), melting point 336 ° C., melt viscosity 30 Pa · s (measured at 350 ° C., shear rate 1000 / s) and glass fiber 30% by mass Liquid crystalline resin composition in which liquid crystal resin composition 2: Liquid crystalline resin (manufactured by Polyplastics, “Vectra E950i”), melting point 336 ° C., melt viscosity 30 Pa · s (350 ° C., shear rate 1000 / s) Liquid crystalline resin composition containing 20% by mass of glass fiber and 15% by mass of talc

<Example 1>
[First injection volume measurement process]
Using the liquid crystalline resin compositions 1 and 2, the nozzle outlet diameter was fixed to 1.5 mm, the ratio (φs / φn) ₁ was 2, and the other molding conditions were as shown below. (“Α-50-C” manufactured by FANUC) was used for injection molding. Also, the injection ^{volume, 26.5 (cm 3 /sec),39.8(cm 3 /sec),53.1(cm} 3 /sec),66.3(cm 3 / sec) 79.6 ( ^{cm 3 /sec),92.9(cm 3 /sec),106.1(cm 3 /sec),119.4(cm 3} /sec),132.7(cm 3 /sec)145.9(cm ³ / sec), 159.2 (cm ³ / sec), and after molding five shots for each injection capacity in order from the lowest, reflow treatment at a peak temperature of 280 ° C. (detailed conditions will be described later) If no blisters can be confirmed by visual observation among 5 molded products, 5 shots are molded under a higher injection capacity, and the same reflow treatment is performed. Eyes until it happens Evaluation was made visually, and the maximum injection volume (Vc _max ) at which no blister was generated (not observed at all) was determined. The results of the first injection volume measurement process are shown in Table 1.

(Molding condition)
Screw diameter: φ26mm
Screw rotation speed: 100rpm
Back pressure: 3MPa
Holding pressure: 50 MPa
Holding time: 1 second Cooling time: 5 seconds Suckback: 3 mm
Cycle time: 15 seconds Cylinder temperature: 340 ° C-340 ° C-330 ° C-320 ° C
Mold temperature: 80 ℃

(Reflow conditions)
Equipment: Infrared reflow furnace ("RE-300", manufactured by Nippon Pulse Technology Laboratories)
Preheat zone temperature setting: 150 ° C. × 3 minutes Heat zone temperature setting: 218 ° C. × 2 minutes Heating furnace passage time: 5 minutes Molded product surface peak temperature: 280 ° C.
(The peak temperature of the molded product is the highest temperature measured by attaching a thermocouple to the molded product surface under reflow heating conditions.)

<Second injection volume measurement process>
Except that the ratio (φs / φn) was changed from 2 to 3.3, the maximum injection volume at which no blisters were generated was determined in the same manner as in the first injection volume measurement step. The results of the second injection volume measurement step are shown in Table 1.

  Further, the maximum injection capacity at which blisters are not generated at the ratio (φs / φn) as shown below was obtained. The ratio (φs / φn) was changed to 4.7, and the maximum injection volume at which no blisters were generated was determined in the same manner as in the first injection volume measurement step. The ratio (φs / φn) was changed to 6, and the maximum injection volume at which no blisters were generated was determined in the same manner as in the first injection volume measurement step. By changing the ratio (φs / φn) to 7.3, the maximum injection volume at which no blisters were generated was determined in the same manner as in the first injection volume measurement step. These results are also shown in Table 1. Further, a graph of the results of Table 1 is shown in FIG.

<Relationship derivation process>
The relationship between the ratio (φs / φn) and the injection capacity (Vc _max ) of the liquid crystalline resin compositions 1 and 2 showed the same behavior. Therefore, the relationship between the ratio (φs / φn) and the injection capacity (Vc _max ) is obtained using the data of the liquid crystalline resin compositions 1 and 2 having a ratio (φs / φn) of 2, 3.3, and 4.7. An approximate expression representing the value was obtained as a linear function by a method using Microsoft Excel spreadsheet software. The obtained linear function was Vc _max = −45 (φs / φn) +240 (broken line in FIG. 3).

  As described above, the injection capacity condition can be increased as much as possible by using the manufacturing method of the present invention. Moreover, the manufacturing method of this invention is applicable regardless of the kind of liquid crystalline resin composition to be used. As a result, it is possible to suppress the generation of blisters without improving the material change or the like, and it is possible to easily increase the productivity of the molded body to the limit.

Claims (7)

A step of measuring a maximum injection capacity (Vc _max ) _{1 at} which no blister occurs on the surface of the molded article when the liquid crystalline resin composition is injection-molded under predetermined molding conditions;
When the ratio (φs / φn) of the sprue outlet diameter (φs) to the nozzle outlet diameter (φn) is changed and the liquid crystalline resin composition is injection-molded in the predetermined molding conditions, Measuring the maximum injection volume (Vc _max ) _{2 at} which no blisters are generated on the surface;
A relationship between the maximum injection capacity (Vc _max ) at which no blister is generated and the ratio (φs / φn) between the sprue outlet diameter and the nozzle outlet diameter (Vc _max = f (φs / φn) ))
A liquid crystalline resin composition was injection molded under the conditions satisfying Vc _max (cm ³ / sec) <f (φs / φn) ;
A method for producing a molded body, wherein an outlet diameter (φn) of the nozzle is less than 3 mm . The function of the predetermined format is represented by the following formula (I):
Furthermore, the liquid crystalline resin composition is injection-molded under molding conditions satisfying the following formula (II).
Vc _max (cm ³ / sec) <− 45 (φs / φn) +240 (I)
φn <3mm (II)   The method for producing a molded body according to claim 1 or 2, wherein an outlet diameter (φn) of the nozzle is 2 mm or less.   The said liquid crystalline resin composition contains glass fiber, The manufacturing method of the molded object in any one of Claim 1 to 3 characterized by the above-mentioned.   5. The method for producing a molded body according to claim 1, wherein a ratio (φs / φn) between an outlet diameter of the sprue and an outlet diameter of the nozzle is 4.5 or less. The ratio (φs / φn) of the sprue outlet diameter (mm) to the nozzle outlet diameter (mm) should be 4.5 or less , and the sprue outlet diameter (φs) should be 1.44 mm to 6.75 mm. The method of suppressing blister generation | occurrence | production at the time of injection-molding a liquid crystalline resin composition. Before Symbol method of suppressing the blistering of claim 6, wherein outlet diameter of the nozzle (.phi.n) is less than 3mm.

Images