JPH0425439A - Thermoplastic-resin foam molding - Google Patents

Abstract

PURPOSE:To prevent the formation of the mark, etc., of a steam hole, and to obviate the possibility of the formation of unnecessary irregularities in a casting product when the title foam molded form is used as a section for manufacturing a casting by specifying the surface roughness of the foam molded form in the foam molded form, in which the inside of a mold is filled with thermoplastic resin foamed particles and the particles are fused mutually and molded according to a mold. CONSTITUTION:A large number of fine irregularities are formed to the surface of a molded form, but the surface roughness of the surface is limited to 700mum or less in ten-point mean roughness R2 stipulated in JISB0601. In a molding equipment used for manufacturing the molded form, a large number of through-holes 16 are shaped to molds 11, 12, and core vents 17 are inserted into each through-hole 16. A plurality of steam holes 18 are shaped to the core vents 17, and foamed particles filled into a mold cavity 19 are heated by a heating medium such as steam fed from the steam holes 18. When the molded form is manufactured, the surfaces on the mold cavity side of the molds 11, 12 are coated with air-permeable porous sheets 26. It is favorable that a mean hole diameter is 10Angstrom -100mum, particularly 100Angstrom -10mum in order to prevent the permeation of the resin melted by the heating medium in the porous sheet 26 and excellently permeate steam and air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a thermoplastic resin foam molded product, and more particularly to a foam molded product with an excellent surface condition.

[Conventional technology]

Conventionally, foam particles are molded into an arbitrary shape to form a mold cavity formed by a pair of so-called molds that can be closed but cannot be sealed, and have many steam holes through which steam can pass through. Thermoplastic resin foam molded products are widely known, which are filled with foamed thermoplastic resin particles, and then heated with a heat medium such as steam to fuse the particles together and molded into a shape.

These thermoplastic resin foam moldings are used as packaging materials, cushioning materials,
Widely used for casting mold models, etc.

On the other hand, the molds used to manufacture conventional thermoplastic resin foam moldings have many through holes formed on their surfaces, and these through holes have holes called corehents that can be removed from the mold and used for heating. A member having a steam hole for introducing steam is attached to serve as a steam hole.

When molding is performed with such a mold, the temperature near the steam holes becomes particularly high, so the foamed particles near the steam holes may be partially melted, and the molten resin gradually flows into the steam holes. There is a risk that the steam may adhere to or enter the mold, clogging the steam holes, and prevent the steam from reaching the inside of the mold, making it impossible to heat the mold. In other words, when removing these blockages from molds with core vents attached, only the core vents are removed without removing the entire mold, and the part where the resin is clogged is held at 200 to 300 degrees.
The resin can be heated to C to melt and remove the resin easily, and resin molding can be performed efficiently with good workability.

[Problem I that the invention attempts to solve]

However, in molded bodies manufactured using conventional molds with core vents, traces of steam holes caused by the core vents may remain as unevenness on the surface of the molded body, and voids may remain between the foam particles of the molded body. There were many. In general, the foamed particles near the core vent are more heated than the foamed particles in the area without the core vent, so secondary foaming can be performed better.
The resin constituting the foamed particles enters the gap between the core vents, which causes unevenness on the surface of the molded product.

Furthermore, foamed particles located in areas without core vents may not be completely heated, and secondary foaming may not occur properly, resulting in voids being formed on the surface of the molded product.

If the heating temperature is lowered to prevent overheating of the foamed particles near the core vent, the amount of voids will increase.On the other hand, if the heating temperature of the foamed particles is increased to suppress the amount of voids generated, the molded product will The marks of the holes mentioned above will remain large and conspicuous. As described above, conventional foam molded products lack surface smoothness, resulting in decreased commercial value and the following quality defects.

Quality problems with foams include, for example, when these foams are used as mold materials for castings and are used to manufacture castings using the full mold method, if there are traces of steam holes on the surface of the foam, manufacturing Unnecessary irregularities are also imparted to the cast products as objects, so extra processes such as mechanically grinding the surface of these cast products are required after casting, which causes problems such as reduced workability. there were.

The present invention has been made in view of the above points, and an object of the present invention is to provide a thermoplastic resin foam molding that solves the conventional drawbacks.

[Means to solve the problem]

The present invention provides a foam molded article in which a mold is filled with foamed thermoplastic resin particles, the particles are fused together, and molded according to the mold, and the surface of the foam molded article has fine irregularities. Surface roughness is JISBO60I (definition and display of surface roughness)
700 in the ten-point average roughness (R2) specified by
This is a thermoplastic resin foam molded product characterized by having a diameter of μm or less.

Figure 1 shows a roughness curve showing the results of measuring the surface of the thermoplastic resin foam molded product of the present invention using a surface roughness meter (■ Koita Research Institute: Model 5E30D), and Figure 2 shows the results of measuring the surface of the thermoplastic resin foam molded product of the present invention. It is a roughness curve showing the results of measuring the surface of a molded body under similar conditions. Note that 1 is the direction of vertical magnification, and 2 is the recording direction.

Although the molded product of the present invention has many fine irregularities formed on its surface compared to conventional molded products, the roughness of this surface is JIS
The ten-point average roughness (R2) specified in B0601 (Definition and Display of Surface Roughness) is 7QO6m or less. In contrast, the conventional molded body has a ten-point average roughness (R2)
is 800 to 1000 μm.

The ten-point average roughness (R2) is determined as follows. The ten-point average roughness (R2) is a straight line or a curved line that has the geometrical shape of the surface to be measured in the sampled portions at arbitrary points A and B of the roughness curve 3 as shown in Fig. 3. - Find a line (hereinafter referred to as the average line) set so that the sum of squares of deviations from that line to the roughness curve is minimum, and from a straight line that is parallel to this average line C and does not cross the roughness curve. The average value of the elevations of the highest to fifth mountain peaks (R+, Rs, Rs, Rv, R,,) measured in the direction of vertical magnification and the elevations of the fifth to deepest valley bottoms (RZ R4, R
6, R8, R1°) expressed in micrometers (μm). Ten point average roughness (R2
) can be found by the following 2.

R2= ((R1+R3+Rs +Rt +R?)-
(R2+R4+R, 10Rf+R,.) 15 It is important that the foam molded product of the present invention has a ten-point average roughness (R2) of 700 μm or less, and if this value is within the above range, the core vent Protrusions that differ from the original design, such as marks, are not perceived by the naked eye and result in a good surface shape.

The numerical range of surface roughness is 600 for ten point average roughness (R2).
A thickness of μm or less is preferable because it provides a smoother surface shape.

The reference length (L) varies depending on the shape of the molded product, but can be determined as appropriate depending on the case, and the reference length is usually 3.6 times the distance between the centers of the steam holes. For example, if the steam holes are provided at 25-mm intervals, 90 cm can be set as the reference length (L).

The surface roughness may be measured on a line connecting the centers of adjacent steam holes at a length 3.6 times the distance between the steam holes, and in cases where no steam holes are confirmed, such as in the molded product of the present invention. In this step, the measurement location is determined based on the part of the mold that corresponds to the position of the steam hole.

Various methods can be used to measure the surface roughness of a foam molded product. Specifically, for example, optical reflectance measurement methods such as a stylus measuring device, a gloss meter, and a light dispersion spectrometer, optical cutting, and It can be measured using an optical microscope such as a beam interferometer, a multiplex interferometer, a differential contrast microscope, a transmission type or scanning type electron microscope, and the like.

The foamed thermoplastic resin particles used in the production of the molded product of the present invention may be based on any resin as long as the foamed particles are made of a thermoplastic resin, such as polystyrene, polyp-methylstyrene, styrene-acrylonitrile. Copolymers, styrene resins such as styrene-acrylic acid copolymers, styrene-maleic anhydride copolymers, polyethylene of various densities (high-density polyethylene, low-density polyethylene, linear low-density polyethylene), polypropylene,
Consists of olefin resins such as ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, propylene-ethylene-butene three-dimensional copolymer, vinyl chloride, vinylidene chloride, various nylons, various polyesters, etc. can be used.

Next, a method for manufacturing the thermoplastic resin foam molded article of the present invention will be explained.

FIG. 4 shows a molding apparatus used for manufacturing a molded body according to the present invention. In the figure, reference numeral 11.12 denotes a mold, and the molds 11.12 are each fixed to a frame 13.14. Frame 13
is slidably connected to a piston shaft 15 of a cylinder or the like, and is configured to open and close the mold by sliding the frame 13. Each mold 11, 12 is provided with a large number of through holes 16, and a core vent 17 is fitted into each through hole 16. The core vent 17 is provided with a plurality of steam holes 18, as shown in FIG. Heated by a heating medium such as steam. In addition, in the figure,
22.23 is the inlet of heating medium such as steam and cooling water, 24
．． 25 is an outlet for steam and cooling water.

In order to produce the molded product of the present invention, the surface of the cavity side of the molds 11 and 12 is covered with an air-permeable porous sort 26. Any material may be used as long as it has sufficient air permeability to allow water to pass through and is not easily attacked by the heat of the heating medium. However, in order to prevent the resin melted by the heating medium from penetrating, and to allow steam and air to pass through, the porous sheet has an average pore diameter of 10 to 100 μm.
m, particularly preferably 100 to 10 μm. Heat-resistant base materials used for the porous sheet 26 include polytetrafluoroethylene, polyamide, polyarylate, polysulfone, polyethersulfone, polyetherimide, polyamideimide, polyphenylene sulfide, polyetheretherketone, polyoxyhenzoate, etc. These can be used alone or in a mixture of two or more. Among these, polytetrafluoroethylene is particularly preferred since it has excellent mold releasability from molded products. The porous sheet 26 used for producing the molded product of the present invention can be prepared by, for example, the method described in JP-A-1-176549, or by adding 35% by weight or more, particularly 35 to 70% by weight, of an inorganic filler to the above-mentioned resin. Obtained by stretching a sheet.

When forming a porous sheet by stretching a sheet containing an inorganic filler, the resin containing the inorganic filler may be formed into a sheet shape and then stretched by a conventional uniaxial or two-wheel stretching method. This stretching is not particularly limited, but
Generally, the area stretching ratio is 1.5 times or more at a temperature below the softening point,
Preferably, a method of increasing the amount by 2 to 6 times is adopted. When a sheet containing 35% by weight or more of an inorganic filler is stretched, gaps are created between the resin portion of the sheet and the inorganic filler, and these gaps become minute pores, resulting in a porous sheet. The above-mentioned inorganic filler generally has an average particle size of 0.
Examples include metal oxides, hydroxides, salts, etc. having a diameter of 1 to 100 μm, particularly preferably about 0.5 to 20 μm. More specifically, metal oxides include calcium oxide, alumina, silica, etc., hydroxides include aluminum hydroxide, calcium hydroxide, etc., and salts include calcium carbonate, mag2sium chloride, and basic mag2 carbonate. Examples include sium, calcium sulfate, magnesium sulfate, aluminum sulfate, and the like. Furthermore, other than these, clays such as silicic acids, cements, zeolites, and talc can also be used. A porous sheet using polytetrafluoroethylene as a base resin is sold by Nitto Electric Industry Co., Ltd. under the trade name Microtex NET-5200. The thickness of the porous sheet 26 is 5 to 100μ
m is preferred.

As shown in FIG. 5(a), the porous sheet 26 covers the entire surface of the cavity side of the mold (however, only the portion where the foamed particle supply port 21 is provided has holes or is attached separately).
It may be provided to cover only the surface portion of the core vent 170 and the surrounding mold portion as shown in FIG. 5). Furthermore, although not specifically shown,
The entire inner surface of the mold cavity 19 may be covered with the porous sheet 26 (of course, even in this case, the expanded particle supply port 21
Parts may be left uncovered or mounted separately.

). Since the porous sheet 26 is thin,
Even if only a part of the inner surface of the mold is covered with the porous sheet 26 as shown in FIG. figure(
As shown in C), when the core vent 17 is fitted so as to be retracted by the thickness of the porous sheet 26 and the surface of the core vent is covered with the porous sheet 26, marks due to the thickness of the porous sheet 26 will be left on the molded product. It is preferable that almost no residue remains.

An adhesive is used to attach the porous sheet 26 to the cavity side surface of the mold 11.12, but it is preferable to use an adhesive with excellent heat resistance. For example, phenolic/vinyl type, phenolic/nitrile type, phenolic/neoprene type, epoxy/phenolic type, epoxy/
Mixed adhesives such as polyamide, epoxy/polysulfide, epoxy/silicone, nitrile rubber/Evoquin, etc., epoxy resin adhesive, phenoxo resin adhesive, polysulfone resin adhesive, polyallylsulfone resin adhesive, silicone resin adhesive Examples include adhesives, polyamide-imide adhesives, polyimide adhesives, and the like.

Steam is normally used as a heating medium for heating the foamed thermoplastic resin particles filled in the mold cavity 19. The pressure of the steam used for heating varies depending on the type of base resin of the foamed particles, the vapor permeability of the porous sheet 26, etc., but if the porous sheet 26 has a thickness of 5 to 100 μm as described above,
When using particles with a pore diameter of about 10 to 100 μm, foam particles based on styrene resin generally weigh 0 to 2 kg.
/Cl1l (G), in the case of foamed particles whose base resin is an olefin resin, is about 0.5 to 5 kg/c-j (G).

In the above example, a case was shown in which a core vent was fitted into a through hole provided in a mold to form a steam hole, but in the method of the present invention, at least the surface of the steam hole is covered with an air permeable porous sheet. Since the steam holes are not clogged with molten resin, it is possible to use a mold with steam holes directly formed on the mold surface.Also, when releasing the molded product from the mold, it is necessary to use an eject pin. (In this case, only the porous sheet is not attached to the eject pin part, or it is attached separately.) However, if the eject pin is not used, 3 to 15 kg from the foam particle supply port can be used.
It is also possible to install a device that can supply compressed air of /d(G) and use a method of blowing the compressed air onto the molded product to release it from the mold.In this case, the resulting molded product has even higher product value. Become something.

[Example]

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples.

Examples 1 to 4 In an autoclave with a volume of 4001, water 2201 and a first
100 kg of the resin particles shown in the table (about 7 g per particle for Examples 1 and 2, about 1.8 g per particle for Examples 3 and 4)
g, foaming side of the type and amount shown in Table 1, and 50 g of aluminum oxide were mixed, and then the autoclave was kept at the foaming temperature shown in Table 1 for 20 minutes, and then the valve located at the bottom of the autoclave was opened. The contents of the autoclave were then discharged to atmospheric pressure to obtain pre-expanded particles having the expansion ratio shown in Table 1.

These particles were placed inside the mold of the manufacturing equipment shown in Figure 4 (on the surface with the steam holes, Nitto Denko's product name ``Microtex NFT-5200J'' was pasted with a silicone adhesive. A part of the feeder and other parts are separated from each other. The expansion ratio, ten-point average roughness (R2), presence or absence of steam hole marks, and appearance are also shown in Table 1.

Comparative Examples 1 and 2 Molded bodies were obtained according to Examples 1 and 3, except that the steam "Microtyphoid NFT-5200" was not attached to the inner surface of the mold. The ten-point average roughness (R2
), the presence or absence of steam vent marks and the appearance are also shown in Table 1.

For reference, charts of the molded bodies obtained in Example I and Comparative Example 1 measured with a surface roughness measuring device (Surf Kneader 3E30D: ■ manufactured by Kosaka Institute) are shown in Figures 1 and 2, respectively.
Shown in the figure.

The conditions for measuring the surface roughness are as follows.

Standard length The line connecting the steam vents and spanning the steam vents is an arbitrary 90m, the cutoff value is 0.8, and the radius of the stylus tip is 2μ.
It was m.

〔Effect of the invention〕

As explained above, the thermoplastic resin foam molded article of the present invention has a surface roughness in which the ten-point average roughness (R2) specified by JISB0601 (definition and display of surface roughness) is 700 μm or less. As a result, the commercial value of the molded product may be lowered due to the surface roughness, where the conventional ten-point average roughness (R2) exceeds 800 μm, such as the presence of traces of brown pores and a molded product lacking surface smoothness. There's nothing to do.

Furthermore, when the molded product of the present invention is used as a mold material for manufacturing castings, since the surface smoothness is better than that of conventional molded products, there is no need to spread the molded product with unnecessary unevenness. These molded products have excellent surface properties, such as eliminating the need for extra steps such as mechanically grinding the surface of these cast products after casting, and contributing to improved casting workability.

[Brief explanation of the drawing]

The drawings show one example of the present invention, the first one shows the surface roughness curve of the thermoplastic resin foam molded product of the invention (Example 1), the second one shows the surface roughness curve of the thermoplastic resin foam molded product of the present invention (Example 1),
The figure shows the surface roughness curve of the molded product of Comparative Example (Comparative Example 1),
The figure is an explanatory diagram of ten-point average roughness (R2), FIG.
FIGS. 5(a) to 5(C) are longitudinal cross-sectional views showing different installation states of the porous sort. Patent applicant: Ike Ltd. 1) Processing Figure 1 Figure 3 Procedure amendment (voluntary) July 27, 1990 1. Indication of the case 1990 Patent Application No. 130633 2. Invention Name: Thermoplastic resin foam molding 3, relationship with the amended case Patent applicant address: 5 Satsuki-cho, Kanuma City, Tochigi Prefecture Name: Ike Ltd. 1) Processing representative: Koji Ikeda Address: Within Chiyoda-ku, Tokyo Sachi 2-1-1 Name J-NIS P Co., Ltd. Representative Masayo Uchiyama 4, Agent 101 Address 2-10-2 Iwamoto-cho, Chiyoda-ku, Tokyo Address Same
The amendments will be made as per the voluntary amendment 6 on the date of the amendment order, column 7 for the detailed description of the invention in the specification to be amended, and the contents of the amendment attached. Contents of amendment (1) "loooλ~10/l/m" on page 10, line 9 of the specification
Correct J to "1 to 100 μm". (2) "As a heat-resistant base material" on page 10, lines 10 to 11 is corrected to "as a heat-resistant polymer." (3) Insert "polyethylene terephthalate, polybutylene terephthalate" after "polytetrafluoroethylene," in line 11 of the original text in line 10 of the same. (4) "Polytetrafluoroethylene is preferred" on page 10, lines 18-19 of the same page is corrected to "J, preferably polytetrafluoroethylene, polyethylene terephthalate, and polybutylene terephthalate." Correct "resin" to "polymer". (6) "Correct resin J with 'polymer'" on page 111, line 6. (Correct the "resin part" in page 11, line 12 of the same document to "polymer part." As the perforated sheet used for body manufacturing, it is also suitable to process the above-mentioned heat-resistant polymer into threads with a thickness of 1 to 70 μm, and form a woven fabric having the above-mentioned holes between the threads from these threads. used.”
Insert. (9) On page 12, line 5, "J as base resin is corrected to "in addition, as the above polymer." Mr. Satoshi Uematsu, Commissioner of the Patent Office, 1. Display of the case 1990 Patent Application No. 130633 2 Name of the invention Thermoplastic resin foam molded product 3 Person making the amendment Relationship to the case Patent applicant address 5 Satsuki-cho, Kanuma City, Tochigi Name Company Limited Ike 1) Processing representative: Ike 1) Koji (1 other person) 4. Agent Address: 2-10-25 Iwamoto-cho, Chiyoda-ku, Tokyo 101 Address: Date correction of amendment order Page 16, 6-8 Correct the line "Made by Nitto Denko ■...pasted" as follows. Product name: Microtex NFT-52 manufactured by Nitto Denko
00J was cut into 900m x 1200m and pasted with silicone adhesive. The silicone-based adhesive is applied five times around the surface of the mold to which the porous sheet is to be attached. In addition, there are 2 parts in the center of the mold.
From the dots of adhesive applied to the center, apply it to dots of 20 kakus on all sides so that the distance between the centers is 30 kakus, and then from each of these dots to the center. By sequentially applying dots of 20 dia in all directions so that the distance between the centers is 30 m, the dots of adhesive with 2 dia are 30 m apart.
It was made to be spread out in all directions in 0 cabinets. ”

Claims (1)

[Claims] In a foam molded product that is formed according to the mold by filling a mold with foamed thermoplastic resin particles and fusing the particles to each other, the foam molding has fine irregularities on the surface, and the surface roughness A thermoplastic resin foam molded article, characterized in that the ten-point average roughness (R_2) specified by JISB0601 (definition and display of surface roughness) is 700 μm or less.