Patent Description:
In recent years, various types of fiber-reinforced resin materials in which a resin is reinforced with reinforcing fibers such as carbon fibers and glass fibers have attracted attention.

For example, Patent Document <NUM> discloses a method for producing a fiber-reinforced thermoplastic resin molded article made from a thermoplastic resin composition containing from <NUM> to <NUM> mass% of (A) an amorphous thermoplastic resin and from <NUM> to <NUM> mass% of (B) reinforcing fibers having a cross section that is a flat shape with a flatness of <NUM> or more, a mass-average fiber length of the reinforcing fibers in the molded article being <NUM> or longer, and the method including performing injection-molding of pellets prepared by coating the roving-type reinforcing fiber with the thermoplastic resin followed by cutting into pellets having a length of <NUM> or longer, using a slow compression type screw.

Patent Document <NUM>: <CIT>
<CIT> discloses a molded product having a thickness gradient. <CIT> describes a method for producing a decorative molded article. <CIT>deals with the production of a V-belt. <CIT>describes a production method for a fiber-reinforced component. <CIT> discloses a method for producing a bumper beam. <CIT> deals with the production of a fiber-reinforced thermoplastic resin random sheet.

However, the present inventors conducted research, and discovered that when a material containing a thermoplastic resin and reinforcing fibers with a length of less than <NUM> is molded, even when molded with a closed mold, bending of the reinforcing fibers occurs and the surface appearance is degraded.

Therefore, an object of the present invention is to solve such problems and provide a production method, with which a molded article excelling in surface appearance can be provided.

The present inventors conducted diligent research to address the problems above, and as a result, discovered that the problems can be resolved by molding with a closed mold, and then once again molding with a closed mold. Specifically, the above problems can be solved by the method as defined in the appended claims.

According to the present invention, a production method with which a molded article excelling in surface appearance can be produced is provided.

Contents of the present invention will be described in detail below. In the present specification, "from. " is used to mean that the numerical values described before and after "to" are included as the lower limit and the upper limit, respectively.

The present invention provides a method for producing a molded article, the molded article containing a thermoplastic resin and reinforcing fibers having a number-average fiber length of <NUM> or longer, and the production method is characterized by including molding a material containing the thermoplastic resin and reinforcing fibers having a number-average fiber length of less than <NUM> using a first closed mold, and then molding only the molded material once again using a second closed mold. under the conditions defined in claim <NUM>. Through such a configuration, a molded article excelling in surface appearance can be obtained.

While merely an assumption, the mechanism is assumed to be as follows. That is, it was found that when a material containing a thermoplastic resin and reinforcing fibers with a length of less than <NUM> is molded, bending of the reinforcing fibers occurs, and the surface appearance is degraded. Furthermore, as a result of examinations performed by the present inventors, the present inventors discovered that, by molding a single material twice in a closed mold, the resin flow occurs in a vicinity of a surface layer of the molded article in the second molding, increasing dispersion of the reinforcing fibers, and alleviating bending of the reinforcing fibers. It is speculated that this leads to the solution of the problem described above.

Furthermore, as a result of the increased dispersion of the reinforcing fibers, the isotropic strength can also be increased.

The present invention will be described in detail below with reference to <FIG>. Of course, the production method of the present invention is not limited to the embodiment of <FIG>.

The present invention includes molding a material containing a thermoplastic resin and reinforcing fibers having a number-average fiber length of less than <NUM>, using a first closed mold. For example, as illustrated in <FIG>, a material <NUM> containing a thermoplastic resin and reinforcing fibers having a number-average fiber length of less than <NUM> is applied to a first closed mold <NUM> and molded.

When the reinforcing fibers having a number-average fiber length of less than <NUM> are blended and kneaded in a thermoplastic resin and then molded, the reinforcing fibers tend to aggregate or bend in the obtained molded article, resulting in a degradation of appearance in the molded article. As a method to solve this problem, it is also conceivable to use reinforcing fibers with a shorter number average fiber length in the molded article, but this may result in a problem of inferior mechanical strength. In an embodiment of the present invention, while using a material containing a thermoplastic resin and reinforcing fibers having a number-average fiber length of less than <NUM>, molding is performed twice. Through this method, appearance is successfully improved while the number average fiber length is maintained as long as <NUM> or longer in the obtained molded article.

In an embodiment of the present invention, the shape of the molded article is substantially formed by molding in the first closed mold. The term 'closed mold' means a mold that is tightly sealed in all directions to the extent that the molten resin does not flow out of the mold during molding. The closed mold is preferably a mold having recesses and protrusions.

In the method of applying the material into the first closed mold, it is preferable that a fiber-reinforced resin material containing a thermoplastic resin, reinforcing fibers, and other components that are blended as necessary is heated, and then applied to the first closed mold. Furthermore, the material is preferably applied to the first closed mold in a molten state. Such a configuration of the method can improve molding cycle compared to a case of heating the material in the mold. Also, the material can be more uniformly heated compared to a case in which the material is placed in the mold and then heated.

An example includes, as illustrated in <FIG>, a method of applying the material into the first closed mold by injection molding. In <FIG>, reference numeral <NUM> indicates an injection molding machine. Injection molding may be performed by melting pellets prepared using the thermoplastic resin and reinforcing fibers serving as raw materials and other components that are blended as necessary and performing injection molding using the melt pellets, or it may be performed by directly melt-kneading the thermoplastic resin and reinforcing fibers serving as raw materials of the material, and other components that are blended as necessary and then performing injection molding.

Alternatively, a fiber-reinforced resin material in a shape such as a flat plate shape, a tape shape, or the like may be heated using an infrared heater or the like, and then applied to the first closed mold. Examples of fiber-reinforced resin materials such as flat plate-shaped and tape-shaped fiber-reinforced resin materials include UD tapes as well as random chopped sheets, mixed fiber nonwoven fabrics, and prepregs. Furthermore, they may also be fibrous, such as a mixed fiber yarn.

One embodiment of the material of the present invention includes a UD tape that is cut to a length of less than <NUM> and then used in a method including applying the cut UD tape to the first closed mold.

Details of the thermoplastic resin, details of the reinforcing fibers, and details of the other components used in the material will be described later.

When the first closed mold and the second closed mold are different molds, a temperature of the material when the material is applied to the first closed mold is preferably <NUM> or higher, more preferably <NUM> or higher, and even more preferably <NUM> or higher, and may be <NUM> or higher. When expressed as a relationship with the melting point (Tm), the temperature thereof is preferably equal to or higher than Tm - <NUM>. When the temperature of the material when applied to the first closed mold is set to the lower limit described above or higher, the material tends to fill the entire mold more favorably. The temperature of the material when applied to the second closed mold is preferably <NUM> or lower, more preferably <NUM> or lower, and even more preferably <NUM> or lower, and may be <NUM> or lower. When expressed as a relationship with the melting point (Tm), the temperature thereof is preferably equal to or lower than Tm + <NUM>. When the temperature of the material when applied to the second closure-type mold is set to the upper limit described above or lower, the reinforcing fibers in the material tend to be dispersed more favorably.

When the first closed mold and the second closed mold are the same mold, the temperature of the material when applied to the first closed mold is preferably <NUM> or higher, and more preferably <NUM> or higher. When expressed as a relationship with the glass transition temperature (Tg), the temperature of the material when applied to the first closure-type mold is preferably Tg °C or higher, and is more preferably Tg + <NUM> or higher. When the temperature of the material when applied to the first closed mold is set to the lower limit described above or higher, the material tends to fill the entire mold more favorably. The temperature of the material when applied to the second closed mold is preferably <NUM> or lower and more preferably <NUM> or lower. When expressed as a relationship with the melting point (Tm), the temperature thereof is preferably equal to or lower than Tm + <NUM>, and more preferably equal to or lower than Tm. When the temperature of the material when applied to the second closure-type mold is set to the upper limit described above or lower, dispersibility of the reinforcing fibers in the material tends to improve further.

'The temperature of the material when applied to the first closed mold' refers to the temperature of the material just prior to application to the first closed mold, meaning the temperature of the molten resin. For example, in the case of injection molding, the temperature of the material is the maximum temperature of the cylinder.

When two or more types of thermoplastic resins are included, the temperature is determined in term of the mixture. The same applies to the other temperatures.

The first closed mold is preferably a press mold, and a mold that is adaptable to a high speed, temperature-adjustable electromagnetic induction heating system, or a Thermo Assisted Molding system is preferable. Furthermore, molds such as single-shot molds, transfer molds, and forward feeding molds that are suited for mass production are preferable. Other examples include molds that are divided into three, four, or more sections to enable molding of complex shapes. Furthermore, a mold for a hybrid molding machine in which an injection molding machine and a press molding machine are integrated is preferable. In addition, a high-speed temperature-adjustable system is preferably introduced into a hybrid molding machine.

The temperature of the first closed mold is preferably <NUM> or higher, more preferably <NUM> or higher, and even more preferably <NUM>, and may be <NUM> or higher. When the temperature of the first closed mold is set to the lower limit temperature described above or higher, molding can be implemented at a higher cycle. Furthermore, the temperature of the first closed mold is preferably <NUM> or lower, more preferably <NUM> or lower, and even more preferably <NUM> or lower, and may be <NUM> or lower, <NUM> or lower, <NUM> or lower, <NUM> or lower, or <NUM> or lower. When the temperature of the first closed mold is set to the upper limit described above or lower, the dimensions of the molded article tend to be more stabilized.

The production method according to an embodiment of the present invention includes molding only the molded material, which has been molded using the first closed mold, once again using the second closed mold. For example, as illustrated in <FIG>, a molded article <NUM> molded in the first closed mold <NUM> is removed from the first closed mold <NUM> (<FIG>), applied to a second closed mold <NUM> (<FIG>, and molded using the second closed mold (<FIG>). In this manner, when the molded article molded using the first closed mold is molded once again using the second closed mold, the fluidity of the thermoplastic resin near the surface layer of the molded article is improved, the reinforcing fibers are more effectively dispersed, and a molded article having more excellent surface appearance can be obtained. Note that "only the material" herein may be referred to the material from which a portion thereof has been removed. For example, when the material is molded in injection molding, the material may undergo a process involving removal of burrs from the molded article. The material is typically a material molded using the first closed mold, and only <NUM> mass% or more (preferably <NUM> mass% or more, and more preferably <NUM> mass% or more) of the material molded using the first closed mold is again molded using the second closed mold.

The shape of the second closed mold may be identical to that of the first closed mold, but is preferably different. By the use of a mold with a different shape, the thermoplastic resin may undergo softening, the reinforcing fibers are further dispersed, and the appearance is further improved. Note that, in the case of injection molding or the like, a flow channel (meaning a portion that does not remain in the final molded article, also called a sprue or runner) may be provided for injection of resin into a mold. In such a case, molds that differ only by the presence or lack of such a flow channel is considered to be of an identical type. That is, when a mold that lacks only the flow channel of the first closed mold is used as the second closed mold, these molds are considered to be identical. The final molded article here means a finished product, not a component. For example, even in a case in which a plurality of components are formed using one mold, a flow channel may be provided in the mold. However, such a flow channel is not included in the finished product obtained by assembling the components, and therefore is not a final molded article.

The molded article molded in the first closed mold is preferably heated before being applied to the second closed mold.

'The temperature of the material when applied to the second closed mold' refers to a temperature just prior to application of the material to the second closed mold, and it refers to a surface temperature of the material. The surface temperature of the material can be measured with a non-contact thermometer (e.g., an infrared radiometer).

When the first closed mold and the second closed mold are different molds, the temperature of the material when applied to the second closed mold is preferably <NUM> or higher, and more preferably <NUM> or higher. When the temperature of the material is set to the lower limit described above or higher, the resin undergoes melting, and the reinforcing fibers can be more effectively dispersed such that the resin can suitably follow variation in the shape. In addition, the temperature of the material when applied to the second closed mold is preferably <NUM> or lower, and more preferably <NUM> or lower, and may be <NUM> or lower or <NUM> or lower. When the temperature of the material is set to the upper limit described above or lower, a deterioration in dispersibility of the reinforcing fibers due to excessive flow of the resin can be more effectively suppressed.

When the first closed mold and the second closed mold are the same mold, the temperature of the material when applied to the second closed mold is preferably <NUM> or higher, and more preferably <NUM> or higher. When the temperature of the material is set to the lower limit described above or higher, the resin undergoes softening, and the reinforcing fibers can be dispersed with a higher degree of dispersion. In addition, the temperature of the material when applied to the second closed mold is preferably <NUM> or lower and more preferably <NUM> or lower. When the temperature of the material is set to the upper limit described above or lower, a deterioration in dispersibility of the reinforcing fibers due to excessive flow of the resin can be more effectively suppressed.

Moreover, in a case where the first and second closed molds are different molds, the difference between the mold temperature when the material is molded using the first closed mold and the material temperature when the material is applied to the second closed mold is preferably <NUM> or higher, and more preferably <NUM> or higher, and may be <NUM> or higher or <NUM> or higher. In addition, the temperature difference is preferably <NUM> or lower, and more preferably <NUM> or lower, and may be <NUM> or lower or <NUM> or lower. When the temperature difference is set to the range described above, exposure of the reinforcing fibers on the surface during shaping can be more effectively suppressed.

Moreover, in a case where the first and second closed molds are the same molds, the difference between the mold temperature when the material is molded using the first closed mold and the material temperature when the material is applied to the second closed mold is preferably <NUM> or higher, more preferably <NUM> or higher, and even more preferably <NUM> or higher, and may be <NUM> or higher or <NUM> or higher. In addition, the temperature difference is preferably <NUM> or lower, and more preferably <NUM> or lower, and may be <NUM> or lower or <NUM> or lower. When the temperature difference is set to the range described above, continuous moldability tends to be better.

Furthermore, in the present invention, in a case where the first closed mold and the second closed mold are different in shape, the material temperature when the material is applied to the second closed mold is at least <NUM> lower, preferably at least <NUM> lower, and more preferably at least <NUM> lower, than the material temperature when the material is applied to the first mold. The difference in material temperatures is <NUM> or lower, preferably <NUM> or lower, more preferably <NUM> or lower, yet even more preferably <NUM> or lower, still even more preferably <NUM> or lower, and further preferably <NUM> or lower. With such a configuration, oxidation degradation of the resin can be more effectively reduced. The material temperature refers to the temperature of the resin contained in the material.

Furthermore, in the present invention, in a case where the first closed mold and the second closed mold have the same shape, the material temperature when the material is applied to the second closed mold is at least <NUM> lower, preferably at least <NUM> lower, and more preferably at least <NUM> lower, than the material temperature when the material is applied to the first mold. The difference in material temperatures is
<NUM> or lower, preferably <NUM> or lower, more preferably <NUM> or lower, yet even more preferably <NUM> or lower, still even more preferably <NUM> or lower, and further preferably <NUM> or lower. With such a configuration, oxidation degradation of the resin can be more effectively reduced. The material temperature refers to the temperature of the resin contained in the material.

The second closed mold is preferably a press mold, and a mold that is adaptable to a high speed, temperature-adjustable electromagnetic induction heating system, or a Thermo Assisted Molding system is preferable. Furthermore, molds such as single-shot molds, transfer molds, and forward feeding molds that are suited for mass production are preferable. Other examples include molds that are divided into three, four, or more sections to enable molding of complex shapes. Furthermore, a mold for a hybrid molding machine in which an injection molding machine and a press molding machine are integrated is preferable.

The temperature of the second closed mold is preferably <NUM> or higher, and more preferably <NUM> or higher. When the temperature of the second closed mold is set to the lower limit described above or higher, the dispersibility of the fibers tends to further improve. In addition, the temperature of the material when the material is applied to the second closed mold is preferably <NUM> or lower and more preferably <NUM> or lower. By setting the temperature thereof to the upper limit described above or lower, the dimensions of the molded article tend to be more stabilized.

The material temperature refers to the temperature of the resin contained in the material.

Furthermore, in an embodiment of the present invention, the mold temperature during molding using the second closed mold is preferably at least <NUM> lower than the mold temperature during molding using the first closed mold, is more preferably at least <NUM> lower therefrom, and is more preferably at least <NUM> lower therefrom. The difference in mold temperatures is preferably <NUM> or lower, more preferably <NUM> or lower, even more preferably <NUM> or lower, yet even more preferably <NUM> or lower, still even more preferably <NUM> or lower, and further preferably <NUM> or lower. With such a configuration, the appearance of the molded article tends to improve.

After molding with the second closed mold (<FIG>), a molded article <NUM> is removed from the second closed mold <NUM> (<FIG>). Subsequently, the molded article <NUM> may be further molded using a third closed mold. In such a case, the molding material may be only the molded article obtained from the second closed mold, or the molded article obtained from the second closed mold may be combined with another material and molded.

Furthermore, a molded article having a more complex shape can be obtained using an open mold or using a combination with another molding method.

The shape of the molded article (in particular, a molded article that is molded after molded using the second closed mold) molded by the production method according to an embodiment of the present invention is not particularly limited, and can be selected, as appropriate, according to the application and purpose of the molded article. Examples of the shape include a board shape, a plate shape, a rod shape, a sheet shape, a film shape, cylindrical, annular, circular, elliptical, a gear shape, polygonal, a heteromorphic article, a hollow-shaped article, a frame shape, a box shape, and a panel shape.

The fields of application of the molded articles described above are not particularly limited, and the molded articles can be widely used in applications such as components for automobiles and other such transportation devices, general mechanical components, precision mechanical components, electronic and electrical device components, OA device components, building materials and building-related components, medical devices, leisure sporting goods, gaming devices, medical products, household goods such as food packaging films, and defense and aerospace products.

Next, the thermoplastic resin fibers used in the present invention are described. The thermoplastic resin used in the molded article is not particularly limited as long as it is a thermoplastic resin, but is preferably selected from a polyamide resin, a polycarbonate resin, a polyester resin, a polyolefin resin, a styrene-based resin, a polyethylene resin, an acrylic resin, and a thermoplastic polyimide resin. Among these, the thermoplastic resin is more preferably at least one selected from the group consisting of polyamide resins and polyolefin resins, and is more preferably a polyamide resin.

In the present invention, the thermoplastic resin preferably includes a polyamide resin, and <NUM> mass% or more of the thermoplastic resin may be a polyamide resin.

The polyamide resin is a polymer including, as at least one constituent unit, an acid amide obtained by ring-opening polymerization of a lactam, polycondensation of an aminocarboxylic acid, or polycondensation of a diamine and a dicarboxylic acid, and examples specifically include polyamide <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, 6I, <NUM>/<NUM>, 6T/6I, <NUM>/6T, <NUM>/6T, <NUM>/6T/6I, and 9T, polyamide XD6, polyamide XD10, polyamide XD12, poly(trimethylhexamethylene terephthalamide), poly bis(<NUM>-aminocyclohexyl)methane dodecamide, poly bis(<NUM>-methyl-<NUM>-aminocyclohexyl)methane dodecamide, and poly(undecamethylene hexahydroterephthalamide). "I" described above denotes an isophthalic acid component, "T" denotes a terephthalic acid component, and "XD" denotes a xylylenediamine component. In addition, for the polyamide resin, reference can be made to the disclosures in paragraphs [<NUM>] to [<NUM>] of <CIT>, the contents of which are incorporated herein by reference.

The polyamide resin used in an embodiment of the present invention is constituted of a diamine-derived constituent unit and a dicarboxylic acid-derived constituent unit, and is preferably a xylylenediamine-based polyamide resin in which <NUM> mol% or more of the diamine-derived constituent units are derived from xylylenediamine and <NUM> mol% or more of the dicarboxylic acid-derived constituent units are derived from an α,ω-linear aliphatic dicarboxylic acid having from <NUM> to <NUM> carbons.

Of the diamine-derived constituent units of the xylylenediamine-based polyamide resin, more preferably <NUM> mol% or more, even more preferably <NUM> mol% or more, still more preferably <NUM> mol% or more, and still even more preferably <NUM> mol% or more are derived from at least one of m-xylylenediamine or p-xylylenediamine.

Of the dicarboxylic acid-derived constituent units of the xylylenediamine-based polyamide resin, preferably <NUM> mol% or more, more preferably <NUM> mol% or more, even more preferably <NUM> mol% or more, and still more preferably <NUM> mol% or more are derived from an α,ω-linear aliphatic dicarboxylic acid having from <NUM> to <NUM> carbons. For the α,ω-linear aliphatic dicarboxylic acid having from <NUM> to <NUM> carbons, adipic acid, sebacic acid, suberic acid, dodecanedioic acid, eicodione acid, or the like can be suitably used, and adipic acid and sebacic acid are more preferred.

Examples of the diamine that can be used as a raw material diamine component of the xylylenediamine-based polyamide resin, other than m-xylylenediamine and p-xylylenediamine, include aliphatic diamines, such as tetramethylenediamine, pentamethylenediamine, <NUM>-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, <NUM>,<NUM>,<NUM>-trimethylhexamethylenediamine, and <NUM>,<NUM>,<NUM>-trimethylhexamethylenediamine; alicyclic diamines, such as <NUM>,<NUM>-bis(aminomethyl)cyclohexane, <NUM>,<NUM>-bis(aminomethyl)cyclohexane, <NUM>,<NUM>-diaminocyclohexane, <NUM>,<NUM>-diaminocyclohexane, bis(<NUM>-aminocyclohexyl)methane, <NUM>,<NUM>-bis(<NUM>-aminocyclohexyl)propane, bis(aminomethyl)decalin, and bis(aminomethyl)tricyclodecane; and diamines having an aromatic ring, such as bis(<NUM>-aminophenyl)ether, p-phenylenediamine, and bis(aminomethyl)naphthalene. One of these can be used alone, or two or more can be mixed and used.

Examples of the dicarboxylic acid component other than the α,ω-linear aliphatic dicarboxylic acid having from <NUM> to <NUM> carbon atoms include phthalic acid compounds, such as isophthalic acid, terephthalic acid, and orthophthalic acid; naphthalenedicarboxylic acid isomers, such as <NUM>,<NUM>-naphthalenedicarboxylic acid, <NUM>,<NUM>-naphthalenedicarboxylic acid, <NUM>,<NUM>-naphthalenedicarboxylic acid, <NUM>,<NUM>-naphthalenedicarboxylic acid, <NUM>,<NUM>-naphthalenedicarboxylic acid, <NUM>,<NUM>-naphthalenedicarboxylic acid, <NUM>,<NUM>-naphthalenedicarboxylic acid, <NUM>,<NUM>-naphthalenedicarboxylic acid, <NUM>,<NUM>-naphthalenedicarboxylic acid, and <NUM>,<NUM>-naphthalenedicarboxylic acid. One of these can be used alone, or two or more types can be mixed and used.

The polyamide resin used in an embodiment of the present invention is constituted by, as main components, a constituent unit derived from a diamine and a constituent unit derived from a dicarboxylic acid, but constituent units other than these are not entirely excluded, and of course, the polyamide resin may contain a constituent unit derived from a lactam such as ε-caprolactam or laurolactam, or from an aliphatic aminocarboxylic acid such as aminocaproic acid and aminoundecanoic acid. Here, the term "main component" indicates that, of the constituent units constituting the polyamide resin, the total number of the constituent units derived from a diamine and the constituent units derived from a dicarboxylic acid is the largest among all the constituent units. In the present invention, the total of the constituent units derived from a diamine and the constituent units derived from a dicarboxylic acid in the polyamide resin preferably accounts for <NUM> mass% or more and more preferably <NUM> mass% or more of all the constituent units.

In an embodiment of the present invention, the melting point of the polyamide resin is preferably from <NUM> to <NUM>, and more preferably from <NUM> to <NUM>.

Furthermore, the lower limit of the glass transition temperature of the polyamide resin is preferably <NUM> or higher, more preferably <NUM> or higher, even more preferably <NUM> or higher, and particularly preferably <NUM> or higher. When the glass transition temperature is in this range, thermal resistance tends to be favorable. An upper limit of the glass transition temperature of the polyamide resin is preferably <NUM> or lower, more preferably <NUM> or lower, and even more preferably <NUM> or lower. When the glass transition temperature is in this range, thermal resistance tends to be favorable.

Note that the "melting point" refers to a temperature at which an endothermic peak reaches its maximum during a temperature increase when observed by a differential scanning calorimetry (DSC) method. Moreover, the "glass transition temperature" is determined by a measurement in which, after a sample has been heated and melted once so that thermal history effects on crystallinity has been eliminated, the sample was heated again. For the measurement, a DSC apparatus may be used to determine the melting point from the temperature at which the endothermic peak reaches its maximum. The endothermic peak is observed when approximately <NUM> of a sample is melted by heating from room temperature (<NUM>) to a temperature that is equal to or higher than an expected melting point at a temperature increase rate of <NUM>/min while nitrogen is streamed at <NUM>/min as the atmosphere gas. Next, the melted polyamide resin is rapidly cooled using dry ice, and then the temperature is increased again to a temperature equal to or higher than the melting point at the rate of <NUM>/min, and the glass transition temperature can be determined.

As the DSC apparatus, for example, the "DSC-<NUM>" available from Shimadzu Corporation can be used.

In an embodiment of the present invention, the thermoplastic resin preferably includes a polyolefin resin, and <NUM> mass% or more of the thermoplastic resin may be a polyolefin resin.

The polyolefin resin is not particularly defined, and a known polyolefin resin can be used. Specific examples of the polyolefin resin include the polyolefin resins described in paragraphs [<NUM>] to [<NUM>] of <CIT>, the contents of which are incorporated herein.

The polyolefin resin is preferably one or more types selected from the group consisting of cycloolefin-based polymers and polypropylene-based polymers (PP), and is more preferably a polypropylene-based polymer.

The cycloolefin-based polymer may be a cycloolefin polymer (COP) or a cycloolefin copolymer (COC).

The COP is, for example, a polymer in which norbornene is subjected to ring-opening polymerization and hydrogenation. COP is described, for example, in <CIT>, and is commercially available as ZEONEX (trade name) or ZEONOR (trade name) available from Zeon Corporation, or as Daikyo Resin CZ (trade name) available from Daikyo Seiko, LTD.

Examples of the COC include copolymers made from olefins such as norbornene and ethylene as raw materials, and copolymers made from olefins such as tetracyclododecene and ethylene as raw materials. COC is commercially available as, for example, Apel (trade name), available from Mitsui Chemicals, Inc.

Known polymers such as propylene homopolymers, propylene-ethylene block copolymers, and propylene-ethylene random copolymers can be used as the PP. Commercially available products include Bormed RB845MO available from Borealis AG.

The material and molded article of an embodiment of the present invention contain the thermoplastic resin at a total of preferably <NUM> mass% or higher, more preferably <NUM> mass% or higher, and even more preferably <NUM> mass% or higher. In addition, the material and molded article of an embodiment of the present invention contain the thermoplastic resin at a total of preferably <NUM> mass% or less, more preferably <NUM> mass% or less, even more preferably <NUM> mass% or less, and still more preferably <NUM> mass% or less.

One type of thermoplastic resin may be used alone, or two or more types of thermoplastic resins may be used. When two or more types are used, the total content is in the above range.

The material and molded article of the present invention contain reinforcing fibers. In an embodiment of the present invention, the reinforcing fibers included in the material and the molded article are the same, but due to breakage of the reinforcing fibers during molding, the fiber length of the reinforcing fibers is typically shortened. On the other hand, the fiber diameter of the reinforcing fibers is relatively resistant to change even when molded.

The reinforcing fibers used in an embodiment of the present invention may be organic reinforcing fibers or inorganic reinforcing fibers, and inorganic reinforcing fibers are preferable. Examples of the reinforcing fibers include plant fibers, carbon fibers, glass fibers, alumina fibers, boron fibers, ceramic fibers, and aramid fibers, and the reinforcing fibers preferably include at least one type of the group consisting of glass fibers and carbon fibers, and more preferably include glass fibers.

As the glass fibers, fibers obtained by melt spinning glass such as E glass, C glass, A glass, S glass, and alkali-resistant glass, which are available generally, are used, but as long as the fibers can be formed into glass fibers, such glass fibers can be used, and the type of glass fibers is not particularly limited. In an embodiment of the present invention, the glass fibers preferably include E glass.

The glass fibers are preferably surface-treated with a surface treatment agent, such as a silane coupling agent, such as γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-aminopropyltriethoxysilane. The deposition amount of the surface treatment agent is preferably from <NUM> to <NUM> mass% of the glass fibers. Furthermore, optionally, glass fibers surface-treated with a lubricant, such as a fatty acid amide compound and a silicone oil; an antistatic agent, such as a quaternary ammonium salt; a resin having film-forming ability, such as an epoxy resin and a urethane resin; or a mixture containing components, such as a resin having film-forming ability, a thermal stabilizer, and a flame retardant; can be used.

The glass fibers used in the present invention can be obtained as commercially available products. Commercially available products include, for example, T257H, T286H, T756H, T289, T289DE, T289H, and T296GH available from Nippon Electric Glass Co. ; DEFT2A available from Owens Corning; HP3540 available from PPG Industries, Inc. ; CSG3PA-<NUM> and CSG3PA-<NUM> available from Nitto Boseki Co. ; and EFH50-<NUM> available from Central Glass Co. (all product names are trade names).

The carbon fibers are preferably a polyacrylonitrile-based carbon fiber or a pitch-based carbon fiber. Additionally, carbon fibers of plant-derived raw materials, such as lignin and cellulose, can also be used.

The cross section of the reinforcing fibers used in an embodiment of the present invention may be circular or non-circular.

The reinforcing fibers used in the present invention have a number-average fiber length of less than <NUM> in the material. A lower limit of the number-average fiber length of the reinforcing fibers in the material is preferably not less than <NUM> and more preferably not less than <NUM>. An upper limit of the number-average fiber length of the reinforcing fibers in the material is preferably not greater than <NUM>, and may be not greater than <NUM> or not greater than <NUM>. When the molded article is molded using short fibers or long fibers, a deterioration in appearance caused by the reinforcing fibers in the molded article has been a frequent problem, but through the present invention, this problem can be effectively avoided.

Furthermore, the reinforcing fibers in the material preferably have a number-average fiber diameter of <NUM> or more, more preferably <NUM> or more, and even more preferably <NUM> or more. An upper limit of the number-average fiber diameter is preferably <NUM> or less, more preferably <NUM> or less, and even more preferably <NUM> or less.

On the other hand, with the reinforcing fibers used in the present invention, a number-average fiber length of the reinforcing fibers in the molded article is <NUM> or longer, and preferably <NUM> or longer, and may be <NUM> or longer depending on the application. An upper limit of the number-average fiber length is less than <NUM>, and depending on the application, may be <NUM> or less, <NUM> or less, or <NUM> or less. When the number-average fiber length of the reinforcing fibers in the molded article is set to <NUM> or longer, the strength of the obtained molded article can be increased. Furthermore, when the number-average fiber length of the reinforcing fibers in the molded article is set to less than <NUM>, the appearance of the obtained molded article can be further improved.

For example, when the material is a pellet, the number-average fiber length of the reinforcing fibers in the molded article is preferably not smaller than <NUM> and less than <NUM>, more preferably from <NUM> to <NUM>, even more preferably from <NUM> to <NUM>, yet even more preferably from <NUM> to <NUM>, and still even more preferably from <NUM> to <NUM>.

In addition, when the material is formed by cutting a UD tape, the number-average fiber length of the reinforcing fibers in the molded article is preferably not smaller than <NUM> to less than <NUM>, and more preferably from <NUM> to <NUM>.

In the material and molded article of an embodiment of the present invention, a proportion of reinforcing fibers is preferably from <NUM> to <NUM> vol. %, more preferably from <NUM> to <NUM> vol. %, and even more preferably from <NUM> to <NUM> vol.

In addition, a total content of reinforcing fibers in the material and molded article of the present invention is preferably <NUM> mass% or more, more preferably <NUM> mass% or more, even more preferably <NUM> mass% or more, and yet even more preferably <NUM> mass% or more. Furthermore, the total content of reinforcing fibers in the material and molded article of the present invention is preferably <NUM> mass% or less, more preferably <NUM> mass% or less, and even more preferably <NUM> mass% or less.

One type of reinforcing fibers may be used, or two or more types of reinforcing fibers may be used. When two or more types of reinforcing fibers are used, the total content is in the above range.

The material used in the present invention may contain other components besides the thermoplastic resin reinforcing fibers.

Examples of other components include additives such as nucleating agents, mold release agents, flame retardants, flame retardant aids, thermal stabilizers, photostabilizers, fluorescent brighteners, anti-dripping agents, antistatic agents, anti-fogging agents, anti-blocking agents, fluidity modifiers, plasticizers, dispersants, antibacterial agents, and coloring agents. For details on these other components, refer to the description in paragraphs [<NUM>] to [<NUM>] of <CIT>, the contents of which are incorporated in the present specification.

A total of the other components in the material is preferably from <NUM> to <NUM> mass%. A single type of these other components may be used alone, or two or more types may be used in combination. When two or more types are used, the total amount thereof is preferably within the above range.

The present invention will be described more specifically with reference to examples below. Materials, amounts used, ratios, processing details, processing procedures, and the like described in the following examples can be changed as appropriate as long as they are within the appended claims. Thus, the scope of the present invention is not limited to the specific examples described below but is only limited by the appended claims.

A reaction vessel equipped with a stirrer, a partial condenser, a total condenser, a thermometer, a dropping funnel, a nitrogen introduction tube, and a strand die was charged with <NUM> (<NUM> mol) of sebacic acid (TA grade, available from Itoh Oil Chemicals Co. ) and <NUM> of sodium acetate/sodium hypophosphite monohydrate (molar ratio = <NUM>/<NUM>), and after sufficient nitrogen purging, the mixture was heated to <NUM> and melted while the system was stirred under a small nitrogen stream.

Under stirring, <NUM> of a mixed xylylenediamine (<NUM> mol of m-xylylenediamine, <NUM> mol of p-xylylenediamine) in which the molar ratio of m-xylylenediamine (available from Mitsubishi Gas Chemical Company, Inc. ) and p-xylylenediamine (available from Mitsubishi Gas Chemical Company, Inc. ) was <NUM>/<NUM> was added dropwise to the molten sebacic acid, and the internal temperature was continuously increased to <NUM> over a period of <NUM> hours while condensation water that was generated was discharged outside of the system.

After dropwise addition was completed, the internal temperature was increased, and when the temperature reached <NUM>, the pressure inside the reaction vessel was reduced. The internal temperature was then further increased, and a melt polycondensation reaction was continued for <NUM> minutes at <NUM>. Next, the inside of the system was pressurized with nitrogen, and the obtained polymer was removed from the strand die and pelletized to obtain a polyamide resin (MP10). The melting point of the obtained MP10 was <NUM>, and the glass transition temperature was <NUM>.

Glass fibers (continuous fibers): ECDE150 <NUM>/<NUM><NUM>. 0Z, available from Nitto Boseki Co.

Carbon fibers: TR50S-<NUM>, available from Mitsubishi Chemical Corporation, number-average fiber diameter: <NUM>.

Continuous glass fiber bundles (rovings) were passed through an impregnating die while being opened and drawn, and were impregnated with a molten thermoplastic resin supplied to the impregnating die, after which long glass fiber-reinforced thermoplastic resin pellets having a reinforcing fiber content of <NUM> mass% and a length of <NUM> were produced according to a pultrusion molding method of shaping, cooling, and cutting. The number-average fiber length of the reinforcing fibers obtained by this method was equal to the number-average length of the pellets.

Rolls of continuous glass fiber bundles (rovings) <NUM> were evenly spaced apart and aligned, and then passed through a spreader and spread to a width of <NUM>. When the spread glass fibers were inserted between two upper and lower impregnating rolls, a thermoplastic resin melted by a twin screw extruder (TEM26SX, available from Toshiba Machine Co. ) was supplied, and the glass fibers were impregnated with the thermoplastic resin in the impregnating rolls. The orientation direction of the glass fibers was adjusted by adjusting the number of spreaders and the tension at which the glass fibers were drawn. Subsequently, while being cooled by a cooling roller, the glass fibers were continuously drawn for a length of <NUM> and wound onto a cylindrical core material, and a UD tape was obtained. The temperature of the extruder was set to <NUM>. The obtained UD tape was <NUM> wide with an average thickness of <NUM> and a length of <NUM>.

As the molding machine, the VPM1013H available from Sato Iron Works Co. As the first closed mold, a mold configured to mold a flat plate and having a depth of <NUM>, a length of <NUM>, and a width of <NUM> was used. As the second closed mold, a mold configured to mold a flat plate and having a depth of <NUM>, a length of <NUM>, and a width of <NUM> was used. However, in Example <NUM>, the same type of mold as that of the first closed mold was used as the second closed mold.

The long fiber pellets obtained above were dried for <NUM> hours at <NUM>, and then injection molded into the first closed mold in the molding machine (VPM1013H) at the material temperature (maximum temperature of the cylinder) shown in the tables below. At this time, the first closed mold temperature was the temperature shown in the tables below.

After the molded article was removed from the first closed mold, the molded article obtained using the first closed mold was heated with an infrared heater. After the material temperature of the molded article reached the value shown in the tables below, the molded article was placed in the second closed mold and molded at the second closed mold temperature shown in the tables.

The number-average fiber length of the reinforcing fibers in the molded article, the surface appearance, and the isotropic strength were evaluated for the obtained molded article.

The number-average fiber length of the reinforcing fibers in the material was determined by incinerating <NUM> of the material for <NUM> minutes at <NUM>, observing the remaining reinforcing fibers using an optical microscope, and then calculating the average value.

The number-average fiber length of the reinforcing fibers in the obtained molded article was determined by cutting out a <NUM> x <NUM> area from the molded article, incinerating for <NUM> minutes at <NUM>, observing the remaining reinforcing fibers using an optical microscope, and then calculating the average value.

An X-ray image of the surface of the molded article was measured using a CT scanner (TDM <NUM>-II available from Yamato Scientific Co. The images were analyzed using the image analysis software Azo-Kun (available from Asahi Kasei Engineering Corporation).

<NUM> x <NUM> strip pieces were cut from a planar portion of the molded article in directions of <NUM> degrees, <NUM> degrees, <NUM> degrees, and <NUM> degrees with respect to the long side. Using a strograph available from Toyo Seiki Kogyo Co. , the flexural strength was measured at a measurement temperature of <NUM>, a measurement humidity of <NUM>% RH (relative humidity), a distance between chucks of <NUM>, and a speed of <NUM>/min. The relationship between the cut-out direction and the mechanical properties was evaluated.

Molding was performed in the same manner as in Example <NUM> with the exception that molding was not performed using the second closed mold. That is, the number-average fiber length of the reinforcing fibers in the molded article, the surface appearance, and the isotropic strength of the molded article were evaluated for the molded article removed from the first closed mold.

The same molding machine, first closed mold, and second closed mold as those in Example <NUM> were used.

The UD tape obtained above was cut to a length of <NUM> and heated with an infrared heater, and after the material temperature reached the temperature shown in the following table, the UD tape was randomly placed in the first closed mold, and was molded at the first closed mold temperature shown in the table. The molded article obtained using the first closed mold was removed from the first closed mold, and burrs were removed, after which the molded article was heated with an infrared heater. After the material temperature of the molded article reached the temperature shown in the table below, the molded article was placed in the second closed mold and molded at the second closed mold temperature shown in the table below.

Molding was implemented in the same manner as in Example <NUM> with the exception that molding was not performed using the second closed mold. That is, the number-average fiber length of the reinforcing fibers in the molded article, the surface appearance, and the isotropic strength of the molded article were evaluated for the molded article removed from the first closed mold.

As is clear from the above results, the molded articles obtained by the production method of the present invention had excellent surface appearance. The isotropic strength was also high.

Claim 1:
A method for producing a molded article (<NUM>), the molded article comprising a thermoplastic resin and reinforcing fibers having a number-average fiber length of <NUM> or longer, the method comprising:
molding a material (<NUM>) containing the thermoplastic resin and reinforcing fibers having a number-average fiber length of less than <NUM>, using a first closed mold (<NUM>); and then
molding only the molded material (<NUM>) once again using a second closed mold (<NUM>);
wherein
either the shape of the second closed mold (<NUM>) differs from the shape of the first closed mold (<NUM>) and the material temperature when the material is applied to the second closed mold (<NUM>) is from <NUM> to <NUM> lower than a material temperature when the material is applied to the first closed mold (<NUM>),
or the shape of the second closed mold (<NUM>) is identical to the shape of the first closed mold (<NUM>) and the material temperature when the material is applied to the second closed mold (<NUM>) is from <NUM> to <NUM> lower than a material temperature when the material is applied to the first closed mold (<NUM>).