JP2006306030A - Molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding which is lightweight and has excellent flexural rigidity and compressive strength. <P>SOLUTION: The molding is formed by integrally molding a rib and a base. The rib and the base are composed of a thermoplastic resin foam. Bubbles in the center of a cross section of the rib satisfies formula (1): Xh>Xt (where Xh is a diameter of the bubble in a height direction of the rib and Xt is a diameter of the bubble in a thickness direction of the rib). Formula (2): Xb<Xa is also satisfied (where Xa is an expansion ratio of the center of the rib and Xb is an expansion ratio of the base). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a molded body.

  Thermoplastic resin foam molded articles are excellent in light weight, recyclability, heat insulation, and the like, and are therefore used in various applications such as automotive parts materials, building materials, and packaging materials. The thermoplastic resin foam molded article used in these applications is also required to have bending rigidity corresponding to the application. As a thermoplastic resin foam molded article excellent in the balance of light weight, heat insulation and bending rigidity, it consists of a general part and a thick part having different thicknesses, and the average foaming ratio of the thick part is 1. There is known a thermoplastic resin foam molded article having a thickness of 2 times or more and a maximum thickness of the thick part being 1.5 times or more of the thickness of the general part (see Patent Document 1).

JP 2001-310380 A

  However, even in the thermoplastic resin foam molded body as described above, the bending rigidity and the compressive strength of the thick part were not satisfactory. The present invention provides a molded article having a rib and a substrate excellent in lightness, bending rigidity and compressive strength.

That is, the present invention is a molded body in which a rib and a substrate are integrally molded, and the rib and the substrate are made of a thermoplastic resin foam, and a bubble located at the center of the rib cross section is expressed by the following formula (1). ).
Xh> Xt Formula (1)
(Where Xh is the bubble diameter in the height direction of the rib and Xt is the bubble diameter in the thickness direction of the rib)

The molded article of the present invention is a molded article excellent in lightness, bending rigidity and compressive strength.

The molded body of the present invention is a molded body in which a rib and a substrate are integrally molded. The rib is used to reinforce the base body and improve the bending rigidity of the molded body, and is a plate-like thing that is provided on the counter-design surface of the molded body so as to protrude from the base body. Usually, the length of the rib is about 10 to 100 times the thickness or height.
In the molded body of the present invention, the bubbles located at the center of the rib satisfy the following formula (1). However, in Formula (1), Xh is a bubble diameter in the height direction of the rib, and Xt is a bubble diameter in the thickness direction of the rib.
Xh> Xt Formula (1)
The molded product of the present invention that satisfies the formula (1) is excellent in light weight and bending rigidity, and also excellent in compressive strength. The bubble diameter of the bubble located at the center of the rib cross section is a value determined by the following method.

  FIG. 6 shows a schematic diagram of how to obtain the bubble diameter located at the center of the rib cross section in the present invention. First, the rib portion of the molded body is cut in a direction perpendicular to the length direction of the base body and the rib to expose the cross section. A cross-sectional photograph is taken so that the entire rib cross section can be confirmed, and a center line in the height direction and a center line in the thickness direction of the rib are drawn. A rectangle with a side in the rib height direction of 30% of the rib height and a side in the rib thickness direction of 30% of the rib maximum thickness is drawn on the photograph with the intersection of both center lines as the center. The bubble included in the rectangle is defined as a bubble located at the center of the rib cross section. Expand the cross-sectional photograph to a size where the bubble structure of the cross-section can be confirmed, measure the bubble diameter in the rib height direction and thickness direction for each bubble that includes the entire outer periphery in the rectangle, and bubble in the rib height direction. The average value of the diameter is Xh, and the average value of the bubble diameter in the rib thickness direction is Xt.

In the molded article of the present invention, it is preferable that the expansion ratio Xa of the rib center portion and the expansion ratio Xb of the substrate satisfy the following formula (2). A molded body satisfying the formula (2) is more excellent in bending rigidity. Xb <Xa Formula (2)
The expansion ratio of the rib center portion and the substrate is obtained by the following method.

  Based on the rib cross section when measuring the bubble diameter of the bubble located at the center of the rib described above, a test of 10 mm square is included so as to include the intersection of the center line in the height direction of the rib and the center line in the thickness direction. Make a piece. The specific gravity of the test piece is measured, and the value calculated using the density of the material constituting the rib is the expansion ratio Xa of the rib center. The expansion ratio Xb of the substrate is calculated by using a density of the material constituting the substrate by preparing a 10 mm square test piece from the substrate so as to include a portion in contact with the rib and measuring the specific gravity of the test piece. Value. However, when a 10 mm square test piece cannot be produced due to the structure of the molded body, the measurement may be performed using a test piece having a shape as close to 10 mm square as possible.

In the molded article of the present invention, it is preferable that the maximum rib thickness L and the rib height H satisfy the following formula (3). A molded body in which H and L satisfy the relationship of formula (3) is superior in bending rigidity and compressive strength.
0.5L ≦ H ≦ 2.5L Formula (3)
The maximum rib thickness L and the rib height H are determined by the following method.

  In the rib cross section when the bubble diameter of the bubble located at the center of the rib cross section is measured, the thickest portion is defined as the maximum thickness L. In the same cross section, two contact points of the rib and the base are connected by a straight line so as to cross the rib. The distance between the straight line and the apex of the rib is defined as the height H of the rib. Usually, L is the length of a straight line connecting the two contact points of the rib and the base so as to cross the rib.

  In the molded body of the present invention, the rib and the base are integrally formed, and the rib and the base are made of a thermoplastic resin foam. The molded body of the present invention can be obtained by molding a thermoplastic resin foam sheet by a method such as vacuum molding or double-sided vacuum molding. The thermoplastic resin constituting the thermoplastic resin foam sheet is selected from olefin homopolymers having 2 to 6 carbon atoms such as ethylene, propylene, butene, pentene, hexene, and olefins having 2 to 10 carbon atoms. Olefin resins such as olefin copolymers obtained by copolymerizing two or more types of monomers, ethylene-vinyl ester copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid Examples include ester copolymers, ester resins, amide resins, styrene resins, acrylic resins, acrylonitrile resins, and ionomer resins. These resins may be used alone or in combination with a plurality of resins. Olefin resins are preferably used from the viewpoints of moldability, oil resistance, cost, and the like, and propylene resins are particularly preferably used from the viewpoint of bending rigidity, heat resistance, and the like of the obtained molded body.

  Examples of the propylene resin include propylene homopolymers and propylene copolymers containing 50 mol% or more of monomer units derived from propylene. The copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer. As an example of the propylene copolymer preferably used, a copolymer of ethylene or an α-olefin having 4 to 10 carbon atoms and propylene can be given. Examples of the α-olefin having 4 to 10 carbon atoms include 1-butene, 4-methylpentene-1, 1-hexene and 1-octene. The content of monomer units other than propylene in the propylene-based copolymer is preferably 15 mol% or less for ethylene and 30 mol% or less for α-olefins having 4 to 10 carbon atoms. One type of propylene resin may be used, or two or more types may be mixed and used.

By using 50% by weight or more of the thermoplastic resin constituting the foam layer of a long-chain branched propylene resin or a high molecular weight propylene resin having a weight average molecular weight of 1 × 10 ⁵ or more, a propylene resin foam having fine bubbles is used. A molded body can be obtained. Furthermore, among such propylene resins, non-crosslinked propylene resins are preferably used because they are unlikely to form gels during recycling.

Here, the long-chain branched propylene-based resin refers to a propylene-based resin having a degree of branching index [A] satisfying 0.20 ≦ [A] ≦ 0.98.
An example of a long-chain branched propylene-based resin satisfying the branching index [A] of 0.20 ≦ [A] ≦ 0.98 is propylene PF-814 manufactured by Basel.

The degree of branching index indicates the degree of long chain branching in a polymer, and is a numerical value defined in the following formula.
Branch index [A] = [η] _Br / [η] _Lin
Here, [η] _Br is the intrinsic viscosity of the propylene resin having a long chain branch, and [η] _Lin is a straight chain having the same monomer unit and the same weight average molecular weight as the propylene resin having the long chain branch. It is an intrinsic viscosity of a chain propylene resin.
Intrinsic viscosity, also called intrinsic viscosity, is a measure of the ability of a polymer to enhance solution viscosity. Intrinsic viscosity depends in particular on the molecular weight of the polymer molecules and the degree of branching. Therefore, by comparing the intrinsic viscosity of a polymer having long chain branches with the intrinsic viscosity of a linear polymer having the same weight average molecular weight as that of the polymer having long chain branches, the degree of branching of the polymer having long chain branches can be determined. It can be a scale. The method for measuring the intrinsic viscosity of a propylene resin is described by Elliott et al. Appl. Polym. Sci. , 14, 2947-2963 (1970)], for example, a propylene resin is dissolved in tetralin or orthodichlorobenzene, and the intrinsic viscosity at 135 ° C. Can be measured.
The weight average molecular weight (Mw) of the propylene-based resin can be measured by various commonly used methods. L. The method disclosed by McConnel in American Laboratory, May, 63-75 (1978), that is, a low-angle laser light scattering intensity measurement method is particularly preferably used.
As an example of a method for polymerizing a high molecular weight propylene resin having a weight average molecular weight of 1 × 10 ⁵ or more, as described in JP-A No. 11-228629, a high molecular weight component is first polymerized and subsequently a low molecular weight polymer is used. Examples thereof include a method of polymerizing components.

Among long-chain branched propylene resins or high molecular weight propylene resins, propylene resins having a uniaxial melt-extension viscosity ratio η ₅ / η _0.1 of 5 or more measured under the following conditions around (melting point + 30) ° C. of the resin are: The resin is preferably 10 or more. The uniaxial melt extensional viscosity ratio is a value measured using an apparatus such as a uniaxial extensional viscosity measurement apparatus (for example, a uniaxial extensional viscosity measurement apparatus manufactured by Rheometrics, Inc.) at an elongation strain rate of 1 sec ⁻¹ . the uniaxial melt elongation viscosity after 0.1 seconds from the strain initiation and eta _0.1, the uniaxial melt elongation viscosity after 5 seconds and eta _5. By using a propylene-based resin having such uniaxial extensional viscosity characteristics, a foam sheet having finer bubbles can be produced.

  A method for producing a thermoplastic resin foam sheet suitable for molding the molded article of the present invention will be described below. Examples of the method for producing a thermoplastic resin foam sheet suitably used for producing the molded article of the present invention include a method of extrusion molding using a flat die (T die) or a circular die. A method of extruding a molten resin from a circular die while foaming, stretching and cooling along a mandrel or the like is particularly preferable. When the foamed sheet is produced by extrusion molding, the molten resin can be extruded from a die and solidified by cooling and then stretched. The foamed sheet may be a single layer or a multilayer, but from the viewpoint of preventing foam breakage during sheet production, a multilayered foam sheet having non-foamed layers in both outer layers is preferred. As the resin constituting the non-foamed layer, those described above as examples of the resin constituting the foamed layer can be used, but the same type of resin as that constituting the foamed layer is preferable. In the case of a propylene-based resin, the non-foamed layer is also preferably composed of a propylene-based resin. The foaming ratio and thickness of the thermoplastic resin foam sheet to be used are not particularly limited, and a foam sheet having a foaming ratio of 2 to 10 times and a thickness of about 1 to 10 mm is usually used.

  The foaming agent used to form the foamed sheet may be either a so-called chemical foaming agent or a physical foaming agent, or may be used in combination. Examples of the chemical foaming agent include a thermal decomposition type foaming agent that decomposes to generate nitrogen gas (azodicarbonamide, azobisisobutyronitrile, dinitrosopentamethylenetetramine, p-toluenesulfonylhydrazide, p, p'- Oxy-bis (benzenesulfonyl hydrazide) and the like, and pyrolytic inorganic foaming agents that decompose to generate carbon dioxide (sodium hydrogen carbonate, ammonium carbonate, ammonium bicarbonate, etc.) . Specific examples of the physical foaming agent include propane, butane, water, carbon dioxide gas, and the like. Of the above exemplified foaming agents, water, carbon dioxide, and the like are suitably used because they are less likely to be deformed by secondary foaming during heating, are high temperature conditions, and are inert to fire. The amount of the foaming agent used is appropriately selected according to the type of foaming agent and resin used so that a desired foaming ratio can be obtained. Usually, the foaming agent is used in an amount of 0.5 to 20 with respect to 100 weight of the thermoplastic resin. Parts by weight.

The thermoplastic resin foam sheet used when molding the molded article of the present invention may be a composite sheet obtained by bonding a single-layer or multilayer foam sheet and other materials. Such a composite sheet is obtained by laminating a foam sheet and another material by dry lamination, sand lamination, hot roll bonding, hot air bonding, or the like.
Examples of other materials to be laminated with the foamed sheet include materials that act as decoration, reinforcement, protection, and the like, and examples thereof include woven fabrics, nonwoven fabrics, sheets, films, foams, and nets. These materials include thermoplastic resins such as olefin resins, vinyl chloride resins, and styrene resins, rubbers such as polybutadiene and ethylene-propylene copolymers, thermoplastic elastomers, and cellulose fibers such as cotton, hemp, and bamboo. Can be mentioned. These materials may be provided with a concavo-convex pattern such as a texture, printed or dyed, and may have a single layer structure or a multilayer structure.

  The thermoplastic resin foam sheet used when molding the molded article of the present invention may contain an additive. Examples of the additive include a filler (filler), an antioxidant, a light stabilizer, an ultraviolet absorber, a plasticizer, an antistatic agent, a colorant, a release agent, a fluidity-imparting agent, and a lubricant. Specific examples of the filler include inorganic fibers such as glass fibers and carbon fibers, inorganic particles such as talc, clay, silica, titanium oxide, calcium carbonate, and magnesium sulfate.

The method for producing the molded article of the present invention is not particularly limited, but a method of vacuum forming a thermoplastic resin foam sheet is preferable, and a method of double-sided vacuum forming is particularly preferable among vacuum forming.
When the thermoplastic resin foam sheet is vacuum-formed to produce the molded article of the present invention, a pair of molds in which concave portions for shaping a rib shape are formed in at least one mold is used. As the pair of molds, a mold corresponding to a target molded product such as one male and the other female, both female and both plate-shaped molds may be used.
Examples of the mold used for vacuum forming include a mold in which at least a part of the molding surface of the mold is made of a sintered alloy, and a mold in which holes are provided in at least a part of the molding surface. The number and position of holes provided in the mold and the hole diameter are not particularly limited. However, when vacuum suction is performed from the mold, the mold and the foamed sheet are in close contact with each other, and the ribs are formed by the thermoplastic resin foam sheet. It is necessary that a hole is provided so that the concave portion for shaping is filled. The material of the mold is not particularly limited, but is usually made of metal from the viewpoint of dimensional stability and durability, and is preferably made of aluminum or stainless steel from the viewpoint of cost and light weight. Moreover, it is preferable that a shaping | molding die is a structure which can adjust temperature with a heater, a heat medium, etc. The molding die preferably has a molding surface of 30 to 80 ° C., more preferably 50 to 60 ° C. during the production of the molded body.

  In order to maintain the confidentiality at the time of molding, it is desirable that the mold used for vacuum forming has a buffer material at the outer edge of the molding surface of at least one of the molds. Usually, the foam sheet has minute irregularities on the surface. In the case of a mold having a cushioning material, the cushioning material comes into close contact with the surface of the foamed sheet having minute irregularities when the mold is closed, so that it is easy to maintain the degree of vacuum in the cavity when vacuum suction is performed. Examples of the buffer material include rubber and foam. In addition, a pair of molds having a configuration in which the other mold is covered by the airtight holding portion provided on the outer periphery of the one mold when the mold is closed can be used.

  Next, a method for producing the molded article of the present invention by double-sided vacuum forming will be described in detail. Double-sided vacuum molding is a method in which a thermoplastic resin foam sheet is disposed between a pair of molds, and the foamed sheet is molded into a desired shape by vacuum suction from both molds. It is a method including steps (1) to (4).

In the step (1), a heat-softened thermoplastic resin foam is formed between a vacuum-suckable mold A in which a recess for shaping a rib is formed and a mold B that forms a pair with the mold A. This is a step of supplying a sheet. The method for heating the thermoplastic resin foam sheet is not particularly limited, and it can be usually heated with a heater or hot air.
Step (2) is a step of closing the mold A and the mold B. The closing timing of the mold may be either one of the molds A and B preceding or simultaneously, but when either one is preceded, after moving one mold to the final stop position, the other mold It is preferable that the time until moving to the final stop position is within 5 seconds. If it is longer than 5 seconds, the sheet may be cooled and molding may be difficult. The clearance between the molds A and B when the molds are closed is preferably about the same as the sheet thickness before molding in the base portion. When the clearance is remarkably larger than the sheet thickness before forming, the thickness and magnification of the sheet are increased by vacuum suction, and the compressive strength of the base portion may be decreased.

In the step (3), vacuum suction is started from both the mold A and the mold B when the mold is closed in the step (2) or after the mold is closed, and the recess for shaping the rib is formed of a thermoplastic resin foam. This is a step of bringing the thermoplastic resin foam sheet into close contact with the mold so as to be filled with the sheet. The degree of vacuum suction is not particularly limited, but it is preferable to perform vacuum suction so that the degree of vacuum between the mold and the foamed sheet is −0.05 to −0.1 MPa. The degree of vacuum is the pressure between the mold and the foam sheet with respect to atmospheric pressure. That is, “the degree of vacuum is −0.05 MPa” indicates that the pressure between the mold and the foamed sheet with respect to atmospheric pressure is 0.95 MPa. The degree of vacuum of the pressure between the mold and the foamed sheet with respect to atmospheric pressure is measured in a vacuum suction passage in the mold.

The timing for starting vacuum suction from the molding dies A and B may be preceded by either one or at the same time. However, when either one is preceded, after the vacuum suction is started from one mold, the other mold is started. It is preferable that the time from the start to the vacuum suction is within 5 seconds. If it is longer than 5 seconds, the sheet may be cooled and molding may be difficult. The vacuum suction from both molds A and B is preferably performed by vacuum suction from both molds for at least 1 second after both molds are closed.

The time for vacuum suction from the molds A and B is preferably about 5 to 60 seconds from the viewpoint of moldability and productivity. Alternatively, vacuum suction may be performed from both molds A and B, and the molds may be opened while maintaining the state where each mold and the thermoplastic resin foam sheet are in close contact. By this method, a molded body having a high expansion ratio can be obtained.
Step (4) is a step of stopping vacuum suction from the molds A and B, opening the mold, and taking out the molded body. The vacuum suction from the molds A and B may be stopped at the same time, or after one vacuum suction is stopped first, the other may be stopped.

  In order to obtain the molded article of the present invention, it is important to control the bubble diameter and rib shape of the thermoplastic resin foam sheet to be used. Specifically, the average cell diameter is 0.5 ≦ Rh / Rm and 0.5 ≦ Rh / Rt (Rh: average cell diameter in the foam sheet thickness direction, Rm: average cell diameter in the foam sheet MD direction, Rt: When a thermoplastic resin foam sheet having an average cell diameter in the foam sheet TD direction is used, the rib shape is 0.1 L ≦ H (L: maximum rib thickness, H: rib height). Generally, when the bubbles of the foamed sheet to be used are long in the MD direction and TD direction of the sheet, the molded body of the present invention can be obtained by forming a rib shape having a high height.

Since the molded article of the present invention is excellent in light weight and bending rigidity and excellent in compressive strength, it can be used for automobile part materials, building materials, packaging materials, home appliances, and the like. Specifically, there are door trims and trim materials that form the trunk side for automobile parts materials, mat materials such as floor mats and trunk mats, molded ceiling materials, and wall materials, ceiling materials, and packaging for building materials. Examples of materials include food containers such as donbri, cups and trays, and home appliances.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to an Example at all.

(1) Foaming ratio measurement Using a submersible density meter (automatic hydrometer model D-H100 manufactured by Toyo Seiki Seisakusho Co., Ltd.), the specific gravity of the product sampled to 20 mm x 20 mm is measured, and each material constituting the product The foaming ratio was calculated using the density of.

(2) Bubble diameter of the bubble located at the center of the rib cross section The rib portion of the molded body was cut in a direction perpendicular to the length direction of the base body and the rib to expose the cross section. A cross-sectional photograph was taken so that the entire rib cross section could be confirmed, and a center line in the height direction and a center line in the thickness direction of the rib were drawn. A rectangle with a side length in the rib height direction of 30% of the rib height and a side length in the rib thickness direction of 30% of the maximum rib thickness is drawn on the photograph centering on the intersection of both center lines. Expand the cross-sectional photograph to a size where the bubble structure of the cross-section can be confirmed, measure the bubble diameter in the rib height direction and thickness direction for each bubble that includes the entire outer periphery in the rectangle, and bubble in the rib height direction. The average value of the diameter was Xh, and the average value of the bubble diameter in the rib thickness direction was Xt.

(3) Foaming ratio of rib center portion and substrate The center line in the height direction of the rib and the center in the thickness direction based on the rib cross section when measuring the bubble diameter of the bubble located at the center portion of the rib cross section. A 10 mm square test piece was prepared so as to include the intersection with the line. The specific gravity of the test piece was measured, and the expansion ratio Xa at the center of the rib was calculated using the density of the material constituting the rib. Further, the expansion ratio Xb of the substrate was calculated using a 10 mm square test piece so as to include a portion in contact with the rib, measuring the specific gravity of the test piece, and using the density of the material constituting the substrate.

(4) Maximum rib thickness L and rib height H
In the rib cross section at the time of measuring the bubble diameter of the bubbles located at the center of the rib, the thickest portion is defined as the maximum thickness L. In the same cross section, the two contact points of the rib and the base were connected by a straight line so as to cross the rib, and the distance between the straight line and the apex of the rib was defined as the height H of the rib.

(5) A test piece having a width of 50 mm (TD direction) and a length of 150 mm (MD direction) was obtained from the bending-rigid molded body so that one rib was at the center of the test piece. The sample was set on the support base for bending measurement of an autograph (model AGS-500D manufactured by Shimadzu Corporation) adjusted to a span of 100 mm by aligning the center of the sample and the support base. Applying a bar-shaped pressing jig with a tip with a radius of curvature of 5 to the center of the sample, bending the sample at 10 mm / min, creating a correlation curve of displacement (cm) and load (N), and the slope of the gradient that appears first (N / cm) was evaluated as bending rigidity.

(6) The compression strength molded body was sampled to a 50 mm square and set on a flat stage of an autograph (model AGS-500D manufactured by Shimadzu Corporation). The rib was positioned at the center of the compression jig (30 mmφ), compressed from the rib side to 20% of the rib height at 0 mm / min, and the maximum load was measured.

[Example 1]
Using a polypropylene foam sheet (1) having a foaming ratio of 3 times and a thickness of 2 mm (trade name Sumiceller foam PP sheet manufactured by Sumika Plustech), a molding surface with vacuum suction holes, and a height of 5 mm in the molding surface, A molding die A (3) having a rib shaping recess (4) having a thickness of 5 mm and a length of 285 mm, and a molding die B (5) having a molding surface having a vacuum suction hole paired with the molding die A The foam sheet was shaped into a molded body composed of ribs and a flat substrate by the method shown in FIG. The clearance between the mold A (3) and the mold B (5) was 3 mm. Mold A (3) and Mold B (5) were used at a temperature adjusted to 60 ° C.
In a state where the polypropylene foam sheet (1) is fixed with a clamp frame (2) of a vacuum forming machine (VAIM0301 manufactured by Sato Tekko Co., Ltd.) equipped with an extruder, it is heated and softened by an infrared heater so that the sheet surface becomes 160 ° C. After that, it was supplied between the mold A (3) and the mold B (5). The mold A (3) and the mold B (5) are closed at the same time when they reach the final position, and at the same time they reach the final position, vacuum suction is performed from the mold A (3) and the mold B (5). The foamed sheet (1) was shaped so that the foamed sheet (1) was brought into close contact with the molding surface of each mold and the recess (4) was filled with the foamed sheet. The degree of vacuum between the mold A (3) and the foam sheet (1) and between the mold B (5) and the foam sheet (1) was -0.09 MPa.
After 10 seconds from the start of vacuum suction, the vacuum suction was stopped, air was blown from a cooling fan to cool the molded body, the mold was opened, and the molded body was taken out. Unnecessary end portions were cut to obtain a plate-like molded body (7) having ribs (6) as shown in FIG. Table 1 shows the physical properties of the obtained molded body.

[Example 2]
Using the same foamed sheet as in Example 1, a flat molded body having ribs was produced. The outline is shown in FIG.
Mold C with polypropylene foam sheet (1) having a molding surface with vacuum suction holes and a rib shaping recess (8) having a height of 5 mm, a thickness of 15 mm and a length of 285 mm in the molding surface (9) and the molding die B (5) having a molding surface provided with a vacuum suction hole paired with the molding die C, the foamed sheet is shaped into a flat plate-like compact having ribs by the method shown in FIG. did. The clearance between the molding surfaces of the mold C (9) and the mold B (5) was 3 mm. Mold C (9) and Mold B (5) were used with the temperature adjusted to 60 ° C.
In a state where the polypropylene foam sheet (1) is fixed with a clamp frame (2) of a vacuum forming machine (VAIM0301 manufactured by Sato Tekko Co., Ltd.) equipped with an extruder, it is heated and softened by an infrared heater so that the sheet surface becomes 160 ° C. After that, it was supplied between the mold C (9) and the mold B (5). The molds C (9) and B (5) are closed at the same time when they reach the final arrival position, and at the same time they reach the final arrival position, vacuum suction is performed from the molds C (9) and B (5). The foamed sheet (1) was shaped so that the foamed sheet (1) was brought into close contact with the molding surface of each mold and the recess (4) was filled with the foamed sheet. The degree of vacuum between the mold C (9) and the foamed sheet (1) and between the mold B (5) and the foamed sheet (1) was -0.09 MPa.
After 10 seconds from the start of vacuum suction, the vacuum suction was stopped, air was blown from a cooling fan to cool the molded body, the mold was opened, and the molded body was taken out. Unnecessary end portions were cut to obtain a plate-like molded body (11) having a rib (10). Table 1 shows the physical properties of the obtained molded body.

[Comparative Example 1]
The same foamed sheet as in Example 1 was used to produce a flat molded body without ribs. The outline is shown in FIG.
Using the polypropylene foam sheet (1), a molding die D (12) having a flat molding surface with vacuum suction holes and a flat molding surface with vacuum suction holes paired with the molding die D are used. The foam sheet was shaped into a flat plate by the method shown in FIG. The clearance between the molding surfaces of the mold D (12) and the mold (B) was 3 mm. Mold D (12) and Mold B (5) were used after adjusting the temperature to 60 ° C.
In a state where the polypropylene foam sheet (1) is fixed with a clamp frame (2) of a vacuum forming machine (VAIM0301 manufactured by Sato Tekko Co., Ltd.) equipped with an extruder, it is heated and softened by an infrared heater so that the sheet surface becomes 160 ° C. After that, it was supplied between the mold D (12) and the mold B (5). The mold D (12) and the mold B (5) are closed at the same time when they reach the final position, and at the same time they reach the final position, vacuum suction is performed from the mold D (12) and the mold B (5). The foam sheet (1) is adhered to the molding surface of each mold. The degree of vacuum between the mold D (12) and the foamed sheet (1) and between the mold B (5) and the foamed sheet (1) was -0.09 MPa.
After 10 seconds from the start of vacuum suction, the vacuum suction was stopped, air was blown from a cooling fan to cool the molded body, the mold was opened, and the molded body was taken out. Unnecessary end portions were cut to obtain a plate-like molded body (13). Table 1 shows the physical properties of the obtained molded body.

[Comparative Example 2]
Using the same foamed sheet as in Example 1, a flat molded body having ribs was produced. The outline is shown in FIG.
A molding die E having a molding surface having a vacuum suction hole using a polypropylene foam sheet (1), and a concave portion (14) for rib shaping having a height of 15 mm, a thickness of 5 mm and a length of 285 mm in the molding surface. (15) and the molding die B (5) having a molding surface provided with a vacuum suction hole paired with the molding die E, the foamed sheet is shaped into a plate-like molding having ribs by the method shown in FIG. did. The clearance between the molding surfaces of the molding die E (15) and the molding die B (5) was 3 mm. Mold E (15) and Mold B (5) were used at a temperature adjusted to 60 ° C.
In a state where the polypropylene foam sheet (1) is fixed with a clamp frame (2) of a vacuum forming machine (VAIM0301 manufactured by Sato Tekko Co., Ltd.) equipped with an extruder, it is heated and softened by an infrared heater so that the sheet surface becomes 160 ° C. After that, it was supplied between the mold E (15) and the mold B (5). The mold E (15) and the mold B (5) are closed at the same time when they reach the final position, and at the same time they reach the final position, vacuum suction is performed from the mold E (15) and the mold B (5). The foamed sheet (1) was shaped so that the foamed sheet (1) was brought into close contact with the molding surface of each mold and the recess (4) was filled with the foamed sheet. The degree of vacuum between the mold E (15) and the foam sheet (1) and between the mold B (5) and the foam sheet (1) was -0.09 MPa.
After 10 seconds from the start of vacuum suction, the vacuum suction was stopped, air was blown from a cooling fan to cool the molded body, the mold was opened, and the molded body was taken out. Unnecessary ends were cut to obtain a plate-like molded body (17) having ribs (16). The rib (16) of the flat molded body (17) could not be shaped into the shape of the recess (14), and the foam was crushed. Table 1 shows the physical properties of the obtained molded body.

Schematic of one embodiment of a method for producing a molded article of the present invention Schematic of the other aspect of the manufacturing method of the molded object of this invention Schematic of the manufacturing method of the molded object described in Comparative Example 1 Schematic of the manufacturing method of the molded object described in Comparative Example 2 Perspective view of a flat molded body having ribs Schematic showing the method of measuring the bubble diameter of bubbles located in the center of the rib

Explanation of symbols

1 Thermoplastic resin foam sheet 2 Clamp frame 3 Mold A
4 Concavity 5 Mold B
6 Ribs 7 Plate-shaped molded body having ribs 8 Recesses 9 Mold C
DESCRIPTION OF SYMBOLS 10 Rib 11 Flat plate-shaped molded object 12 which has rib Mold D
13 Flat shaped body 14 Recess 15 Mold D
16 Rib 17 Flat plate shaped body 18 having rib 18 Rib 19 Base 20 Contact point between rib and base

Claims (4)

A molded body in which a rib and a base are integrally molded, wherein the rib and the base are made of a thermoplastic resin foam, and a cell located at the center of the rib cross section satisfies the following formula (1) .
Xh> Xt Formula (1)
(Where Xh is the bubble diameter in the height direction of the rib and Xt is the bubble diameter in the thickness direction of the rib) The molded product according to claim 1, wherein the expansion ratio Xa of the rib center portion and the expansion ratio Xb of the substrate satisfy the following formula (2).
Xb <Xa Formula (2) The molded body according to claim 1 or 2, wherein the maximum rib thickness L and the rib height H satisfy the following formula (3).
0.5L ≦ H ≦ 2.5L Formula (3) The molded object according to any one of claims 1 to 3, obtained by double-sided vacuum molding of a thermoplastic resin foam sheet.

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