JP2010195039A - Method for producing multilayer molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for making the mechanical/physical properties and surface appearance of a molding made of a thermoplastic resin material sufficiently excellent and for efficiently producing the molding. <P>SOLUTION: The method for producing the multilayer molding 10 includes a process for arranging a base material layer 1 in the cavity V of a mold 100 and a process in which a second molten thermoplastic resin material is supplied at an injection speed of 500 mm/s or above into a clearance C formed between the base material layer 1 and a cavity surface 21a facing the base material layer 1 to form a coating layer 2 on the surface of the base material layer 1. The second thermoplastic resin material contains a polyolefin resin having a melt flow rate of 5-400 g/10 min and an inorganic filler, and the thickness of the coating layer 2 is 0.5 mm or below. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a multilayer molded article having a base material layer made of a first thermoplastic resin composition material and a coating layer made of a second thermoplastic resin material provided on the base material layer. .

  Thermoplastic resin molded articles produced by injection molding or compression molding are used in various fields because they are economical, lightweight, and formable. This thermoplastic resin molded body is also used as a member of an expensive industrial product, and higher quality is required for such applications. For example, a thermoplastic resin molded body used for automobile exterior parts and the like is required to have high appearance quality such as no appearance defects such as weld lines on the surface in addition to quality related to mechanical properties such as impact resistance and rigidity. .

  The mechanical properties and appearance quality of thermoplastic resin moldings are often in a trade-off relationship, and a technique for improving both in good balance is desired. The following Patent Documents 1 to 3 relate to a multilayer molded body having a base material layer and a coating layer provided on the base material layer. These documents describe a technique of using different resin materials for the base material layer and the coating layer.

Japanese Patent No. 3347892 JP 2001-225348 A JP-A-2005-132016

  However, in recent years, higher appearance quality has been demanded while maintaining excellent mechanical properties, and it has been difficult to sufficiently cope with conventional techniques. For this reason, development of the technique which manufactures the above high quality thermoplastic resin moldings efficiently at low cost is desired.

  The present invention has been made in view of the above circumstances, and it is possible to sufficiently improve both the mechanical properties and the surface appearance of a molded article made of a thermoplastic resin composition. It aims at providing the method of manufacturing efficiently.

  The present invention is a method for producing a multilayer molded article having a base material layer made of a first thermoplastic resin material and a coating layer made of a second thermoplastic resin material provided on the base material layer. , A step of disposing a base material layer in a cavity formed between a pair of molds, and a second molten state in a space formed between the base material layer and a cavity surface of a mold facing the base material layer A step of supplying a thermoplastic resin material at an injection speed of 500 mm / second or more, wherein the second thermoplastic resin material contains a polyolefin-based resin having a melt flow rate of 5 to 400 g / 10 minutes, and an inorganic filler, The thickness of the coating layer is 0.5 mm or less. The injection speed here means the moving speed of the screw (screw injection speed) when the molten resin is filled in the mold.

  According to the present invention, it is possible to improve both the mechanical properties and surface appearance of a molded article made of a thermoplastic resin composition, and it is possible to efficiently produce such a molded article.

It is a schematic cross section which shows an example of the multilayer molded object manufactured by the method of this invention. It is a schematic cross section which shows an example of the shaping | molding die used for the method of this invention. It is a schematic cross section which shows the state which the metal mold | die of the shaping | molding die closed. It is a schematic cross section which shows the state which has arrange | positioned the base material layer in the cavity of a shaping | molding die. It is a schematic cross section which shows the shaping | molding die in the state where the metal mold | die opened, and the multilayer molded object taken out from the said type | mold. It is a schematic cross section which shows the other example of the shaping | molding die used for the method of this invention. (A)-(c) is a schematic cross section which shows the weld part of a multilayer molded object or a base material layer.

<Multilayer molded product>
A multilayer molded body 10 shown in FIG. 1 includes a layer (base material layer) of a base material 1 formed in a flat plate shape and a coating layer 2 provided so as to cover one surface of the base material 1. Both the base material 1 and the coating layer 2 are made of a thermoplastic resin material.

  The base material 1 forms the main body of the multilayer molded body 10 and has high impact resistance and rigidity in order to ensure excellent mechanical properties. What is necessary is just to select suitably the thermoplastic resin which makes the main component of the thermoplastic resin material (1st thermoplastic resin material) which comprises the base material 1 according to the mechanical physical property calculated | required by the multilayer molded object 10, The kind is It is not particularly limited. Specific examples of the thermoplastic resin include olefin resins, styrene resins, acrylic resins, amide resins, thermoplastic ester resins, polycarbonates, and thermoplastic elastomers. These resins may be used alone or in combination of two or more. Among these thermoplastic resins, an olefin resin or a mixture of an olefin resin and a thermoplastic elastomer is preferably used.

  The olefin resin is a resin containing 50% by mass or more of olefin-derived repeating units. For example, ethylene, propylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene- A homopolymer of an α-olefin having 20 or less carbon atoms such as 1; a copolymer obtained by copolymerizing at least two monomers selected from these α-olefins; and a copolymer with the α-olefin. Examples thereof include a copolymer of another possible unsaturated monomer and the α-olefin.

  Examples of the unsaturated monomer include unsaturated carboxylic acids such as acrylic acid and methacrylic acid; unsaturated carboxylic acids such as methyl (meth) acrylate, 2-ethylhexyl acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate. Alkyl ester derivatives of acids; unsaturated dicarboxylic acids or anhydrides such as fumaric acid, maleic acid, maleic anhydride, itaconic acid; acrylamide, N- (hydroxymethyl) acrylamide, glycidyl (meth) acrylate, acrylonitrile, methacrylonitrile, Mention may be made of unsaturated carboxylic acids or unsaturated dicarboxylic acid derivatives such as mono- or diethyl ester of maleic acid, N-phenylmaleimide, N, N′-metaphenylenebismaleimide.

  It is preferable to use a propylene resin as the olefin resin. Examples of the propylene-based resin include a propylene homopolymer, and a copolymer of propylene and at least one selected from the group consisting of ethylene and an α-olefin having 4 to 12 carbon atoms. These homopolymers or copolymers may be used alone or in combination of two or more. Here, examples of the α-olefin having 4 to 12 carbon atoms include 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene.

  When a copolymer of propylene and at least one selected from the group consisting of ethylene and an α-olefin having 4 to 12 carbon atoms is used, the propylene-derived repeating unit is used with respect to 100 parts by mass of the copolymer. It is preferable to use a copolymer containing at least 50 parts by mass. Further, when the copolymer has a repeating unit derived from two or more kinds of monomers in addition to the propylene unit, the total amount of the repeating units derived from the monomer of the propylene unit is 35 parts by mass or less. Is preferred. The flexibility and impact resistance of the copolymer can be controlled by adjusting the amount of the repeating unit derived from ethylene or the α-olefin having 4 to 12 carbon atoms in the copolymer. When the propylene-based resin is a copolymer, the copolymer may be a random copolymer or a block copolymer.

  As the olefin resin, it is also preferable to use, for example, a mixture of the propylene resin and a copolymer of ethylene / α-olefin copolymer. The ethylene / α-olefin copolymer is a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms, and examples thereof include ethylene and butene-1, hexene-1, octene-1, and decene-1. And the like. Preferred ethylene / α-olefin copolymers include, for example, ethylene / butene-1 copolymer rubber (EBR), ethylene / hexene copolymer rubber (EHR), and ethylene / octene copolymer rubber (EOR). It is done.

The content of the ethylene-derived repeating unit in the ethylene / α-olefin copolymer is 50 to 90% by mass, and preferably 60 to 90% by mass. The content of ethylene-derived repeating units in the ethylene / α-olefin copolymer can be measured by a 13 C-NMR method. The density of the copolymer of ethylene and α-olefin is usually 0.85 to 0.89 g / cm ³ , and preferably 0.86 to 0.88 g / cm ³ . The density is a value measured according to JIS K7112.

  Further, a thermoplastic resin obtained by adding a vinyl aromatic compound-containing elastomer to the olefin resin may be used. Examples of the vinyl aromatic compound-containing elastomer include styrene-ethylene-butene-styrene rubber (SEBS), styrene-ethylene-propylene-styrene rubber (SEPS), styrene-butadiene rubber (SBR), and styrene-butadiene-. Examples thereof include block copolymers such as styrene rubber (SBS) and styrene-isoprene-styrene rubber (SIS), or block copolymers obtained by hydrogenating these rubber components.

  A rubber obtained by reacting an olefin copolymer rubber such as ethylene-propylene-nonconjugated diene rubber (EPDM) with a vinyl aromatic compound such as styrene can also be suitably used. Two or more kinds of vinyl aromatic compound-containing elastomers may be used in combination. The vinyl aromatic compound-containing elastomer is an elastomer obtained by polymerization using a vinyl aromatic compound as a kind of monomer, for example, a block comprising a vinyl aromatic compound polymer block and a conjugated diene polymer block. Copolymer, a block polymer in which the double bond of the conjugated diene portion of the block copolymer is hydrogenated, and the like. The double bond of the conjugated diene portion of the block copolymer is hydrogenated by 80% or more. It is preferable. Moreover, when it is set as 100 mass% of vinyl aromatic compound containing elastomers, it is preferable that content of the repeating unit derived from a vinyl aromatic compound monomer is 10-20 mass%.

  The covering layer 2 is provided so as to cover the surface of the base material 1 in order to achieve mainly the excellent appearance quality of the multilayer molded body 10. The thickness of the coating layer 2 is 0.5 mm or less, preferably 0.4 mm or less, and more preferably 0.3 mm or less. The thickness of the coating layer 2 is preferably 0.01 mm or more, and more preferably 0.05 mm or more. When the thickness of the coating layer 2 exceeds 0.5 mm, the amount of the resin material required for forming the coating layer 2 increases. On the other hand, when the thickness of the coating layer 2 is less than 0.01 mm, the appearance quality of the multilayer molded body 10 tends to be insufficient.

  As the thermoplastic resin constituting the main component of the thermoplastic resin material (second thermoplastic resin material) constituting the coating layer 2, the same thermoplastic resin as that used for the substrate 1 can be used. It is preferable to use a crystalline polyolefin resin. Crystalline polyolefin-based resins are characterized by excellent mechanical properties and easy formation of a thin coating layer compared to amorphous ones. Therefore, even if the thickness of the coating layer 2 is reduced to 0.5 mm or less, high mechanical properties of the coating layer 2 itself can be achieved. Further, by reducing the thickness of the coating layer 2, the amount of the second thermoplastic resin composition used can be reduced, and the manufacturing cost can be kept low.

  The crystalline polyolefin resin here refers to the heat quantity of crystals observed in the range of −100 ° C. to 300 ° C. in the differential scanning calorimetry performed based on JIS K7122 among the above-mentioned polyolefin resins. It means a polyolefin-based resin having a larger crystal melting peak or a crystallization peak having a crystallization heat amount of more than 1 J / g. The crystalline polyolefin resin is particularly preferably a crystalline polypropylene resin from the viewpoint of the rigidity and impact resistance of the molded product.

  The crystalline polyolefin resin contained in the coating layer 2 has a melt flow rate (MFR) of 5 to 400 g / 10 minutes, preferably 10 to 200 g / 10 minutes. If the MFR is less than 5 g / 10 min, the pressure required for filling the resin may be extremely high. On the other hand, if the MFR exceeds 400 g / 10 min, the impact strength of the coating layer 2 tends to decrease, and the impact strength of the resulting multilayer molded product tends to decrease. The melt flow rate (MFR) here means a value measured at a temperature condition of 230 ° C. based on JIS K6758.

As the crystalline polyolefin resin contained in the coating layer 2, a modified polyolefin resin (A) modified with an unsaturated carboxylic acid and / or an unsaturated carboxylic acid derivative may be used. These modified polyolefin resins may be used alone or in combination of two or more.
Modified polyolefin resin (A): A simple compound based on a vinyl compound (X) (general formula CH2 = CH-R, R represents an alicyclic hydrocarbon group having 3 to 10 carbon atoms). A monomer unit based on a vinyl compound (X) having a monomer unit, a monomer unit based on an α-olefin having 2 to 20 carbon atoms, and a monomer unit based on an unsaturated carboxylic acid And the monomer unit based on the vinyl compound (X) is 3 to 50 mol%, with the total amount of the monomer unit based on the α-olefin having 2 to 20 carbon atoms being 100 mol%, α -Content of the monomer unit based on an olefin is 97-50 mol%.

In addition, the content of the monomer unit based on the unsaturated carboxylic acid is such that the content of the monomer unit based on the unsaturated carboxylic acid is 0.01 to 5% by mass with the modified polyolefin resin (A) being 100% by mass. It is.
By using such a resin as the crystalline polyolefin resin contained in the coating layer 2, it is possible to obtain a molded article having an excellent surface appearance free from weld line defects on the surface and excellent coating performance.

  Examples of the substituent R of the vinyl compound (X) used in the modified polyolefin resin (A) include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group.

  Examples of the α-olefin having 2 to 20 carbon atoms used in the modified polyolefin resin (A) include ethylene, propylene, butene-1, pentene-1, hexene-1, 3-methylbutene-1, 4-methylpentene- 1 etc. are mentioned.

  Examples of the unsaturated carboxylic acids used in the modified polyolefin resin (A) include acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid, methyl nadic acid, Unsaturated carboxylic acids such as hymic acid, angelic acid, tetrahydrophthalic acid, sorbic acid, and mesaconic acid; Carboxylic anhydride: methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, acrylic acid-n-propyl, methacrylic acid-n-propyl, acrylic acid-i-propyl, methacrylic acid-i-propyl, acrylic Acid-n-butyl, methacrylic acid-n Butyl, i-butyl acrylate, i-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, hydroxymethyl acrylate, tert-butyl methacrylate, tert-butyl methacrylate , Hydroxymethyl acrylate, hydroxymethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, glycidyl acrylate, glycidyl methacrylate, acrylonitrile Acrylamide, methacrylamide, maleic acid monoethyl ester, maleic acid diethyl ester, fumaric acid monomethyl ester, fumaric acid dimethyl ester, itaconic acid monomethyl Unsaturated carboxylic acid esters such as stealth and itaconic acid dimethyl ester; acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, maleic acid-N-monoethylamide, maleic acid-N, N-diethylamide, maleic acid-N- Monobutylamide, maleic acid-N, N-dibutylamide, fumaric acid monoamide, fumaric acid diamide, fumaric acid-N-monoethylamide, fumaric acid-N, N-diethylamide, fumaric acid-N-monobutylamide, fumaric acid Unsaturated carboxylic acid amides such as acid-N, N-dibutylamide; unsaturated carboxylic acid imides such as maleimide, N-butylmaleimide and N-phenylmaleimide; unsaturated carboxylic acid halides such as maleoyl chloride; sodium acrylate, methacrylic acid Sodium acid, acrylic Examples thereof include unsaturated carboxylic acid metal salts such as potassium acid and potassium methacrylate. Moreover, you may use combining said unsaturated carboxylic acid.

  Unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, hydroxymethyl acrylate, hydroxymethyl methacrylate, hydroxyethyl acrylate , Hydroxyethyl methacrylate, glycidyl acrylate, and glycidyl methacrylate are preferred, and maleic anhydride and hydroxyethyl methacrylate are particularly preferred.

  In the modified polyolefin resin (A) used in the present invention, the content of the monomer derived from the vinyl compound (X) is preferably 6 to 30 mol%, more preferably from the viewpoint of enhancing the coating performance. Is 7 to 20 mol%. However, the total monomer unit in the modified polyolefin resin (A) is 100 mol%.

  In the modified polyolefin resin (A) used in the present invention, the content of unsaturated carboxylic acids is preferably 0.01 to 30% by mass, more preferably 0.05 to 20% by mass, from the viewpoint of enhancing the coating performance. %, And more preferably 0.1 to 15% by mass. However, the total monomer unit in the modified polyolefin resin (A) is 100% by mass.

  Content of the said vinyl compound and unsaturated carboxylic acid can be calculated | required using a 1H-NMR spectrum or a 13C-NMR spectrum.

  A known method is used as a method for producing the modified polyolefin resin (A). For example, in the presence of a catalyst obtained by contacting isopropylidenebis (indenyl) zirconium dichloride and methylalumoxane, the vinyl compound (X) and carbon Examples thereof include a method of copolymerizing a monomer based on an α-olefin having 2 to 20 atoms and an unsaturated carboxylic acid. Specifically, the method described in European Patent Application No. 1219648 is used. be able to.

  Moreover, as a manufacturing method of modified polyolefin resin (A), you may use a multistage polymerization method, for example, after copolymerizing vinyl compound (X) and ethylene and / or alpha-olefin, by this copolymerization Graft polymerization of the obtained polymer and unsaturated carboxylic acid; after copolymerizing unsaturated carboxylic acid and ethylene and / or α-olefin, the polymer obtained by the copolymerization and vinyl compound ( Examples thereof include a method of graft polymerization of I) and / or vinyl compound (II).

  As the graft polymerization method, for example, after the precursor is melted, a monomer (vinyl compound (X), α-olefin monomer, unsaturated carboxylic acid, etc.) is added and graft polymerization is performed; For example, a method may be used in which a monomer is dissolved in a solvent such as toluene or xylene, and then a monomer (vinyl compound (X), α-olefin monomer, unsaturated carboxylic acid, etc.) is added and graft polymerization is performed. The temperature of graft polymerization is usually about 40 to 350 ° C. In the graft polymerization, a radical initiator is usually used, and the amount of the radical initiator used is usually 0.001 to 0.5 mol, preferably 0.005 to 0, per 1 kg of the precursor. .1 mole.

  In the present invention, the content of the modified polyolefin resin (A) in the coating layer 2 is 50 to 100% by mass, and preferably 60 to 100% by mass, more preferably from the viewpoint of adhesiveness with the first resin composition. Is 80-99 mass%.

  The coating layer 2 may further contain a filler. Fillers include talc, mica, clay, calcium carbonate, aluminum hydroxide, magnesium hydroxide, wollastonite, barium sulfate, glass fiber, carbon fiber, silica, calcium silicate, potassium titanate, metal fiber, and metal. The organic fiber etc. which were coat | covered are mentioned. These fillers may be used individually by 1 type, and may use 2 or more types together. The content of the filler is preferably 5 to 50 parts by mass and more preferably 10 to 40 parts by mass with respect to 100 parts by mass of the second thermoplastic resin material. By setting the content of the filler to 5 parts by mass or more, the mechanical properties and appearance quality of the coating layer 2 can be improved. On the other hand, when the content of the filler is 50 parts by mass or less, problems such as peeling of the coating layer 2 and generation of welds on the surface of the multilayer molded body 10 can be sufficiently suppressed.

  In addition, the thermoplastic resin material which forms the base material 1 may also contain the above inorganic fillers. In addition, the thermoplastic resin composition for forming the substrate 1 and the coating layer 2, respectively, is an antioxidant, heat stabilizer, ultraviolet absorber, antistatic agent, dispersant, chlorine scavenger, lubricant, decomposition agent, metal You may further contain an activator, a flame retardant, an organic pigment, an inorganic pigment, an organic filler, an inorganic antibacterial agent, an organic antibacterial agent, a crystal nucleating agent, etc.

<Molding mold>
An example of a mold used for manufacturing a multilayer molded body will be described with reference to FIGS. The mold 100 is for producing the multilayer molded body 10 by providing the coating layer 2 on the surface of the substrate 1 shown in FIG. The mold 100 includes an upper mounting plate 20 and a lower mounting plate 30 that are arranged to face each other. The upper mounting plate 20 is fixed to the side of an injection device that injects a molten resin material. The lower mounting plate 30 reciprocates in the X-axis direction shown in FIGS. 2 and 3 by a mold opening / closing mechanism (not shown).

  A cavity fixing plate 21 and a core fixing plate 31 are arranged between the upper mounting plate 20 and the lower mounting plate 30 so as to face each other. The cavity fixing plate 21 is configured to be movable in the X-axis direction and is guided by four guide pins 22 protruding from the inner surface of the upper mounting plate 20. The core fixing plate 31 is fixed to the lower mounting plate 30 via the spacer block 32 and the receiving plate 33, and reciprocates in the X-axis direction as the lower mounting plate 30 moves.

  The cavity fixing plate 21 and the core fixing plate 31 are in an open state (see FIG. 2) in which the cavity fixing plate 21 and the core fixing plate 31 are separated from each other as the lower mounting plate 30 reciprocates. And a closed state in which the core fixing plate 31 is in contact (see FIG. 3). In the closed state, the cavity fixing plate 21 and the core fixing plate 31 form a rectangular plate-like cavity V therein. A cavity surface is formed by the surface 21 a of the cavity fixing plate 21 and the surface 31 a of the core fixing plate 31. As will be described later, in this embodiment, the base material 1 is disposed so as to contact the surface 31 a of the core fixing plate 31, and a clearance C is formed between the base material 1 and the surface 21 a of the cavity fixing plate 21. The

  In the center of the upper mounting plate 20, a substantially funnel-shaped sprue bush 25 into which a nozzle tip of an injection device (not shown) enters is provided. Further, a runner stopper plate 23 penetrating the guide pin 22 is disposed between the upper mounting plate 20 and the cavity fixing plate 21. The runner stopper plate 23 and the cavity fixing plate 21 are in a molten resin. A runner molding portion 26 constituting the material flow path is formed (see FIG. 3). The runner molding portion 26 is connected to the outlet side of the sprue bushing 25 and extends in the Y-axis direction with the connection portion with the sprue bushing 25 as the center.

  In the cavity fixing plate 21, a sprue molding portion 27 that penetrates the cavity fixing plate 21 in the X-axis direction is formed. The sprue forming part 27 is formed near the tip of the runner forming part 26 in the Y-axis direction. A gate portion 28 that forms the entrance of the cavity V is formed between the cavity fixing plate 21 and the core fixing plate 31. The gate portion 28 and the runner molding portion 26 communicate with each other via a sprue molding portion 27.

  A receiving plate 33 is fixed to the surface of the core fixing plate 31 opposite to the cavity V. An ejector plate 36 that holds four ejector pins 35 for removing the multilayer molded body 10 formed in the cavity V from the mold is provided between the receiving plate 33 and the lower mounting plate 30. . Spacer blocks 32 are disposed between the receiving plate 33 and the lower mounting plate 30 on both sides of the ejector plate 36 that moves in the X-axis direction.

  In the present embodiment, for example, an injection device equipped with an inline screw can be used. The injection device includes a barrel, a screw that can rotate in the barrel and that can advance and retreat in the axial direction, a hopper that supplies a resin material into the barrel, and a motor that controls forward, backward, and rotation of the screw. .

<Method for producing multilayer molded article>
In order to manufacture the multilayer molded body 10, first, the base material 1 processed into a predetermined shape is prepared. The molding method of the substrate 1 is not particularly limited, and the substrate 1 may be produced by injection molding or compression molding.
As shown in FIG. 4, the base material 1 is disposed in the cavity V so that the surface 31a of the core fixing plate 31 and one surface of the base material 1 are in contact with each other (first step). As a result, a clearance C is formed between the other surface of the substrate 1 and the surface 21a of the cavity fixing plate 21 facing the other surface. The coating layer 2 is formed by filling the clearance C with a thermoplastic resin material. In order to make the thickness of the covering layer 2 0.5 mm or less, the width of the clearance C may be set to 0.5 mm or less. By setting the clearance C in this way, the thickness of the coating layer 2 can be prevented from becoming thicker than desired, and the resin material for forming the coating layer 2 can be made to flow smoothly. Occurrence of appearance defects such as glossiness can be suppressed. In the present embodiment, the case where the entire surface of the substrate 1 is covered with the coating layer 2 is exemplified. May be provided.

  In order to dispose the base material 1 in the cavity V in the first step, a pre-made base material may be inserted between the pair of molds and used to manufacture a multilayer molded body. It may be produced in the pair of molds using a known method such as a core back method, a core rotation method, a stripper plate rotation method, a core slide method, or a cavity slide method.

  The molten thermoplastic resin material supplied from the injection device is injected from the gate 28a of the gate portion 28 and filled in the clearance C. The injection speed of the thermoplastic resin material is 500 mm / second or more, preferably 600 mm / second, and more preferably 700 mm / second. By setting the injection speed to 500 mm / second or more, the viscosity of the resin material can be sufficiently reduced, and the molten resin material can be sufficiently distributed to the clearance C. Thereby, it is easy to form the coating layer 2 having an excellent appearance. In general, if the thermoplastic resin material to be injected contains a filler, a weld line is likely to occur on the surface of the molded body. However, by increasing the injection speed and reducing the thickness of the coating layer 2 as described above. , Generation of weld lines can be sufficiently suppressed. The injection speed is preferably 3000 mm / second or less, and more preferably 2000 mm / second or less. By setting the injection speed to 3000 mm / second or less, a significant increase in the injection pressure can be prevented.

  In the present embodiment, the distance from the gate 28a to the flow end portion (point P1 shown in FIG. 4) supplied through the gate 28a is preferably 100 mm or more, more preferably 200 mm or more, and 300 mm or more. More preferably. By setting this distance to 100 mm or more, the number of gates provided in the mold can be relatively reduced even when a large multilayer molded body is manufactured, and appearance defects such as welds on the surface of the multilayer molded body are further reduced. It becomes possible to do. Moreover, it becomes easy to manufacture a large sized multilayer molded object efficiently by making this distance 200 mm or more.

  The temperature of the cavity surface is appropriately determined depending on the thermoplastic resin used, but is about 10 to 150 ° C, preferably about 20 to 140 ° C. The cooling time is about 1 to 60 seconds. After cooling, the lower mounting plate 30 is moved, the cavity fixing plate 21 and the core fixing plate 31 are opened, and the multilayer molded body 10 is removed from the core fixing plate 31 using the ejector pins 35 (see FIG. 5). Then, the process which removes the unnecessary parts 10a and 10b etc. is given, and the multilayer molded object 10 as a product is completed.

The multilayer molded body 10 obtained by the method according to this embodiment is sufficiently excellent in both mechanical properties and surface appearance, and is widely used as an automobile interior part or exterior part, a motorcycle part, a part of furniture or an electrical product, a building material, etc. In particular, it is useful as an automobile exterior part.
Moreover, according to the method which concerns on this embodiment, such a molded object can be manufactured efficiently.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment. For example, in the above embodiment, the case where the multilayer molded body 10 having the shape as shown in FIG. 1 is manufactured is illustrated, but the shape of the multilayer molded body is not limited to this.

  Moreover, in the said embodiment, although the case where the resin material was inject | emitted in the cavity V from one gate 28a using the apparatus which has one sprue molding part 27 and one gate part 28 was illustrated, several You may inject from the gate. In this case, the distance from each gate to the flow end of the resin material supplied through the gate is calculated based on the amount of resin injected from each gate per unit time, the sectional area of the clearance, and the like.

  The molding die 200 shown in FIG. 6 has two sprue molding parts 27 and two gate parts 28, and is configured so that a resin material can be injected into the cavity V simultaneously from the two gates 28a. The two gate portions 28 are formed so as to sandwich the cavity V in the Y-axis direction. The gate portion 28 and the runner forming portion 26 communicate with each other via the corresponding sprue forming portions 27. When two gates 28a are respectively provided at both ends of the cavity V, and the same amount of resin material is injected from these gates 28a per unit time, the flow end portion is positioned at the center of the cavity V in the Y-axis direction (see FIG. 6). It becomes point P2) shown.

Example 1
As a thermoplastic resin material for forming the coating layer, a mixture of crystalline polypropylene, talc and rubber was used. Table 1 shows the blending ratio. The melt flow rate of the mixture was 40.5 g / 10 min. A configuration similar to that shown in FIG. 6 was used, that is, a device having two gates on the cavity surface. The thermoplastic resin material is supplied into the cavity from the two gates, and a coating layer is formed so as to cover the entire surface of the base material (width: 200 mm, length: 40 mm, thickness: 2.7 mm) made of the thermoplastic resin material. And the multilayer molded object was produced. The coating layer was formed under the conditions shown in the column of Example 1 in Table 2.

(Comparative Examples 1-3)
A multilayer molded body was produced in the same manner as in Example 1 except that the coating layers were formed under the conditions shown in the columns of Comparative Examples 1 to 3 in Table 2, respectively.

(Evaluation test)
About the multilayer molded object of Example 1 produced as mentioned above and Comparative Examples 1-3, the following item was evaluated. Table 2 shows the results.
(1) Raised Height of Weld Portion Using a surface roughness measuring device (trade name: Surfcom manufactured by Mitutoyo Corporation), the raised height of the welded portion of the multilayer molded body was measured. In Table 2, "raised height H _C" means the height H _C of the weld portion 2a of the coating layer 2 shown in Figure 7 (a).

(2) Degree of conspicuous weld part The surface of the multilayer molded body was visually observed and the degree of conspicuous weld part was evaluated based on the following criteria.
A: A weld line is hardly confirmed.
B: A slight weld line can be confirmed.
C: A weld line can be clearly confirmed.

(3) Warpage amount of multilayer molded body The multilayer molded body was placed on a horizontal base, and the distance between the lower surface of the both ends of the molded body and the base surface was measured. The average value of the measured values was taken as the amount of warpage of the multilayer molded body.

(Example 2)
Example 1 except that only one of the two gates on the cavity surface was used and a coating layer was formed so as to cover the entire surface of the substrate on which the weld portion was already present. A multilayer molded body was produced.

(Comparative Example 4)
A multilayer molded body was produced in the same manner as in Example 2 except that the coating layer was formed under the conditions shown in the column of Comparative Example 4 in Table 3.
(Evaluation test)
The following evaluation was performed about the weld part of the multilayer molded object of Example 2 and the comparative example 4 which were produced as mentioned above. Using a surface roughness measuring instrument (trade name: Surfcom, manufactured by Mitutoyo Corporation), the unevenness of the weld part before and after forming the coating layer was measured. In Table 3, “swelling height H _R1 ” before forming the coating layer means the height H _R1 of the weld portion 1a of the substrate 1 shown in FIG. 7B, and “depth” after forming the coating layer. “H _R2 ” means the depth H _R2 of the weld 2b of the coating layer 2 shown in FIG. The “conspicuous degree” of the weld portion was evaluated based on the same criteria as in Example 1 by visually observing the surface of the base material layer or the multilayer molded body. Table 3 shows the results.

Example 4
A base material and a coating layer were formed using one gate on the cavity surface to produce a multilayer molded body. A mixture having the composition shown in Table 1 was used for forming the coating layer. The clearance width was adjusted so that the thickness of the coating layer was 0.3 mm, and the injection speed was set to 800 mm / second. The mechanical properties of the obtained multilayer molded body were evaluated. Table 4 shows the results. The Izod impact value was measured by the Izod impact test method defined in ASTM D256. The flexural modulus was measured by a bending test method specified in ASTM D790. The tensile elongation was measured by a tensile property test method defined in JIS K7127.

(Comparative Example 5)
As the thermoplastic resin material for forming the coating layer, instead of using the mixture having the composition shown in Table 1, crystalline polypropylene was used in the same manner as in Example 3 except that crystalline polypropylene was used alone. The evaluation was performed. Table 4 shows the results.

  DESCRIPTION OF SYMBOLS 1 ... Base material (base material layer), 2 ... Covering layer, 10 ... Multilayer molded object, 20 ... Upper mounting plate, 21 ... Cavity fixing plate (mold), 21a ... Surface of cavity fixing plate (cavity surface), 28 ... Gate part, 28a ... Gate, 30 ... Lower mounting plate, 31 ... Core fixing plate (mold), 31a ... Surface of movable side mold (cavity surface), 100, 200 ... Mold, C ... Clearance, P1, P2 ... flow end, V ... cavity.

Claims (4)

A method for producing a multilayer molded body having a base material layer made of a first thermoplastic resin material and a coating layer made of a second thermoplastic resin material provided on the base material layer,
Placing the substrate layer in a cavity formed between a pair of molds;
Supplying the molten second thermoplastic resin material at an injection speed of 500 mm / second or more into a space formed between the base material layer and the cavity surface of the mold facing the base layer. ,
A multilayer molded article, wherein the second thermoplastic resin material contains a polyolefin resin having a melt flow rate of 5 to 400 g / 10 min and an inorganic filler, and the thickness of the coating layer is 0.5 mm or less. Production method.   The method for producing a multilayer molded body according to claim 1, wherein the polyolefin resin is a crystalline polyolefin resin.   The multilayer according to claim 1 or 2, wherein the amount of the inorganic filler contained in the second thermoplastic resin material is 5 to 50 parts by mass with respect to 100 parts by mass of the second thermoplastic resin material. Manufacturing method of a molded object.   The distance from the gate which supplies the said 2nd thermoplastic resin material of a molten state in the said cavity to the flow end part of the said 2nd thermoplastic resin material supplied through the said gate is 100 mm or more. The manufacturing method of the multilayer molded object as described in any one of -3.

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