JPS6042433A - Expanded synthetic resin in-mold molding and its production - Google Patents

Abstract

PURPOSE:To produce the titled molding in which expanded particles constituting the surface layer have a specified flattened shape, by filling surface layer portions with pre- expanded particles having a heat expansion force smaller than that of the pre-expanded particles in the inner layer portion and heat-molding the whole. CONSTITUTION:A molding die 7 is protioned into three compartments by diaphragms 6, 6, and molding chambers 9, 9 are filled with pre-expanded particles 13, 13 having a heat expansion force Ps (kg/cm<2>.abs) satisfying the relationship: Pi/Ps>1.5 (wherein Pi (kg/cm<2>.abs) is the heat expansion force of the pre-expanded particles with which molding chamber 10 is filled). After removing the diaphragms 6, 6, the whole system is heated. By the expansion of the pre-expanded particles of the pre-expanded particles 12 in the inner portion, the pre-expanded particles 13, 13 having a smaller heat expansion force in the surface layre portion are pressed and expand flatly to form a molding in which the ratio, Lf/Ld, is larger than 3.5, wherein Lf(mm.) is the average diameter along the face and Ld(mm.) is the average diameter along the thickness. This molding has a smooth surface, so that when used as a core material, it shows excellent adhesion to a covering material and forms a product of good appearance particularly in the case of a thin covering material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an indoor molded article of foamed synthetic resin particles obtained by filling a mold with pre-expanded synthetic resin particles and heating and molding the same, and a method for producing the same.

The present invention relates to an indoor molded product of synthetic resin foam particles in which the foamed particles constituting the surface layer of the molded product have a specific flat shape, and a method for producing the same.

In recent years, it has been used as core material for furniture such as tables and kotatsu boards.

Synthetic resin foams are widely used as construction materials such as core materials for tatami mats, insulation materials for bathtubs, slatted boards, interior materials for scar removal, and automobile parts, and there are no preliminary methods for manufacturing these foams. The expanded particles are filled into a mold and heated and molded. A so-called bead molding method is known. However, in the foamed molded product obtained by the conventional bead molding method, the foamed particles constituting the molded product are all approximately spherical, including the foamed particles located in the surface layer of the molded product and the foamed particles located in the inner layer. Since they have the same shape, although the molded body as a whole has shock absorbing properties, the surface layer has a disadvantage of poor rigidity. Moreover, since the foamed particles in the surface layer of the molded product have a nearly spherical shape, the surface of the molded product has poor smoothness, and when the molded product is used as a core material, the bondability with the nucleating material decreases, especially for wallpaper. When a thin nucleating material such as nucleating material is provided on the surface of a molded product, there are drawbacks such as noticeable irregularities on the surface of the molded product, resulting in a significant deterioration in appearance.

As a result of intensive research by the present inventors to eliminate the above drawbacks,
It was discovered that a molded product in which the foamed particles constituting the surface of the molded product were flattened at a specific ratio had overall shock absorbing properties and excellent surface rigidity and surface smoothness. They also discovered a method for producing the same and completed the present invention. I ended up doing it.

That is, the gist of the present invention is to provide a synthetic resin foam particle in-mold molded product obtained by foam-molding 9 synthetic resin pre-expanded particles in a mold, in which the foam constituting the surface layer of the molded product is The ratio of the average diameter Lf (mQ) of the particles in the plane direction and the average diameter Ld (*) in the thickness direction is Lf /Ld>
There is an indoor molded article of foamed synthetic resin particles characterized in that the particle size is 3.5.

Another aspect of the present invention is that the heating expansion force Ps (kg/lri・
(absolute pressure) is Pi / Ps > 1. The average diameter Lf in the planar direction of the foamed particles that are filled with pre-expanded particles having a relationship of /Ld > 3
．． 5. A method for producing an in-mold molded article of foamed synthetic resin particles is provided.

The in-mold molded synthetic resin foam particles of the present invention are obtained by a bead molding method in which pre-expanded beads are heated and molded in a mold. The base resin of the pre-expanded particles includes polyethylene, polypropylene, ethylene-propylene copolymer,
Examples include ethylene-butene copolymer, ethylene-vinyl acetate copolymer, polystyrene, polyester elastomer, polyamide elastomer, polyurethane elastomer, etc., and these may be either crosslinked or non-crosslinked.

Particularly preferred is a non-crosslinked ethylene-propylene random copolymer.

The above-mentioned pre-expanded particles can be prepared by dispersing the resin particles in a dispersion medium together with a blowing agent in a closed container, for example, and heating it to a predetermined temperature, then opening one end of the container, and dispersing the resin particles and dispersion medium inside the container. The resin particles can be obtained by a method such as foaming the resin particles by discharging the resin particles into an atmosphere (usually an atmospheric pressure atmosphere). Examples of the blowing agent include inorganic blowing agents such as carbon dioxide, propane, butane, pentane, hexane, heptane, etc., and chlorofluoromethane and cyclodifluoromethane.

Dichlorotetrafluoroethane, methylchloride.

Volatile blowing agents such as halogenated hydrocarbons such as ethyl chloride and methylene chloride are used. These blowing agents are usually used in an amount of 5 to 40 parts by weight per 100 parts by weight of the resin particles. The dispersion medium may be any solvent that does not dissolve the resin particles, such as water or ethylene glycol.

1f1 of glycerin, methanol, ethanol, etc.
Or a mixture of two or more thereof is exemplified, but water is usually preferred.

In the present invention, the heating expansion force of the pre-expanded particles is defined as @300I+l! x Length 300mm x Thickness 3
This is the maximum surface pressure that acts on the mold surface due to the expansion of the pre-expanded particles when they are filled into a mold with zero pressure and heated, and the heating expansion force depends on the type of base resin at the time of producing the pre-expanded particles. Selection 9 Foaming agent addition amount 1 Foaming temperature.

Pressure during foaming 9Curing conditions for pre-expanded particles after foaming.

It can be set to a predetermined value by adjusting the conditions for pressurizing the pre-expanded particles.

Next, one embodiment of the present invention will be described based on the drawings.

As shown in FIG. 1, the synthetic resin foam particle in-mold molded body 1 of the present invention has foamed particles 3 constituting the surface Wi2 of the molded body 1.
However, it has a flattened disk shape, and the foamed particles 5 forming the inner surface M4'li have a shape close to a spherical shape. The foamed particles 3 of the surface layer 2 have a relationship between the average diameter Lf in the planar direction and the average diameter Ld in the thickness direction (1111) such that Lf/Ld>3.5, preferably Lf/Ld>5. .

When Lf/Ld is 3.5 or less, surface smoothness 1 surface rigidity decreases. As shown in the figure, Lf is the average value of the particle diameter f in the planar direction of the expanded particles 3, and Ld is the average value of the particle diameter d in the thickness direction. Ld is usually 0.0
It is preferable that the length is 1 to 2 mm, and Lf is 1 to 10 mm.

In addition, the thickness d of the surface layer 2 is normally set to 15 in order to maintain the impact absorption properties of the molded body 1 and to improve the surface rigidity.
It is preferable that it is 2% to 10% of the thickness D of . The surface layer 2 containing the above structure is not limited to the case where it is provided on both the front and back surfaces of the molded body 1, but may be provided only on one side.

The molded article 1 of the present invention described above can be manufactured as follows. That is, for example, a forming chamber 7 is divided into three parts by a partition plate 6.6 as shown in FIG. In this case, a supply port 11 is provided in the finishing chamber 10 located inside the finishing chambers 9, 9.
Pi/Ps>1 with respect to the heating expansion force Pi (kg/d・absolute pressure) of the pre-expanded particles 12 supplied and filled.
．． 5, preferably Pi/Ps)2 heating expansion force P
Pre-expanded particles 13 having a pressure of s (kl/crl/absolute pressure) are supplied through the supply port 14 and filled. The rear partition plate 6゜6'? : Removed, 1.0kl? /
cJ(G) ~5. Heating with water vapor, etc. of Okg/cJ (G). When heated, both the surface pre-foamed particles 13 filled in the molding chamber 9°9 and the inner layer pre-foamed particles 12 filled in the molding chamber 10 expand; Since the heating expansion force is smaller than that of the pre-expanded particles 12 in the in-house layer section, the expansion of the pre-expanded particles 12 in the inner layer section causes the pre-expanded particles 12 to be pressed between the pre-expanded particles 12 and the wall surface 8 of the mold 7, resulting in flattening. The molded body 1 having the structure shown in FIG. 1 is obtained.

The pre-expanded particles used in the above method have an expansion ratio of 10 to
Pre-expanded particles 13 in the surface layer have a thermal expansion force P8 of less than 2 kg/cyd (absolute pressure), and the pre-expanded particles 12 in the inner layer have a thermal expansion force of less than 2 kg/cyd (absolute pressure). Force pt is 2 kg/tri
(absolute pressure) or more and as mentioned above (Pi /Ps
>1.5, preferably Pi/Ps>2.

In addition, it is not limited to the case where a mold having a partition plate as described above is used, but after filling a mold configured to expand the internal volume of the molding chamber with pre-expanded particles having a thermal expansion force Pi, Alternatively, while enlarging the mold, the surface layer side may be filled with pre-expanded particles having a thermal expansion force Pt+ such that Pl/ps>t,s with respect to the thermal expansion force Pi, and then heated.

As explained above, in the molded article of the present invention, the foamed particles constituting one surface layer have an average diameter Lf in the plane direction and an average diameter Ld in the thickness direction Lf/Ld compared to the foamed particles constituting the inner surface layer.
> 3.5, the surface of the molded body is extremely smooth compared to conventional molded bodies, and the rigidity of the surface layer can be improved while maintaining the impact absorption properties of the molded body as a whole. It has the effect that can be achieved.

Further, according to the method of the present invention, the above-mentioned molded body can be manufactured reliably and easily by a simple operation of filling pre-expanded particles having different heating expansion powers in layers and heating and foaming them.

Hereinafter, the present invention will be explained in more detail by giving specific examples.

Examples 1-3. Comparative Examples 1 to 4 Pre-expanded particles 1 to 5 used in Examples and Comparative Examples were manufactured as follows.

Pre-expanded particles 1> 100 parts by weight of resin particles with an average particle size of 1.5 mm made of ethylene-propylene random copolymer with an ethylene content of 3.0 weight and a melt index of 7.8 J9/10, dichlorosif 18 parts by weight of methane, 0.5 parts by weight of finely divided aluminum oxide, and 250 parts by weight of water were placed in an autoclave, and the autoclave was heated to 143°C\J. The internal pressure of the autoclave at this time was 24 k.
g/d(G). Next, one end of the autoclave was opened while maintaining the internal pressure of the autoclave at -30 kg/6A (G) using nitrogen gas, and the resin particles and water were discharged to atmospheric pressure to foam the resin particles.

These pre-expanded particles were allowed to stand at room temperature and under normal pressure for 48 hours, and the dichlorodifluoromethane in each particle was replaced with air, thus forming pre-expanded particles 1.

Pre-expanded particles 2〉 Put the above-mentioned pre-expanded particles 1 into a pressurized tank and blow air into it.
2 at a boost rate of 0.05 kl/cd/hr
．． The pressure is increased to 6 kg #J (G) and the internal pressure of the particles is 3. s kg/tri (absolute pressure) 1i- was applied to obtain pre-expanded particles 2.

<Pre-expanded particles 3> The same raw materials as those for pre-expanded particles 1 were charged into an autoclave with the same composition, and the temperature was once raised to 155°C, then 140°C.
At that temperature, the autoclave internal pressure was increased to 5ok.
1? /cr/1 (G), the resin particles and water were released under atmospheric pressure to cause the resin particles to foam. The pre-expanded particles were left at room temperature and under normal pressure for 48 hours to obtain pre-expanded particles 3.

1111 Expanded particles 4> Pre-expanded particles 1'Ii - Same method as pre-expanded particles 2! The pressure was increased to +0.7 kg/d (G) and the pressure was applied.

Pre-expanded particles 4 were obtained by applying a particle internal pressure of 1.5 kl/crli (absolute pressure).

(Pre-expanded particles 5) Pre-expanded particles 3t - Pressurized by increasing the pressure to 1.2 ky/ca (G) in the same manner as for pre-expanded particles 2.

A particle internal pressure of 2.0 kg/ca (absolute pressure) was applied to obtain pre-expanded particles 5.

After filling a mold with a thickness of 50cm x 300m x length of 300cm (inner dimensions) and removing the partition plate.

The pre-expanded particles were heated with steam of 3.4 ky/c+J (G) to form foamed PI# to obtain a molded article. Table 2 shows the results of the t-measurement of the physical properties of each of the obtained grown bodies.

Further, Table 2 shows the results of measuring the average diameter Lf in the plane direction and the average diameter Ld in the thickness direction of the foamed particles constituting the surface layer t at 2IIIt from the bottom of the molded body.

Table 2 also shows the types of pre-expanded particles that were filled in the surface layer portions of the molds that were in contact with the opposing wall surfaces, and the inner layer portions between the surface layer portions and the inner layer portions.

*Lf and Ld are the average values of the values measured using a microscope (Digital Microscope MS-224 manufactured by Fu-Co., Ltd.) selected from 50 foamed particles within 3 degrees of the top surface of the vertical section of the molded product. be.

*2 Molding properties of the molded object.

A molded body of type iJ1 can be obtained with a shrinkage rate of the molded body in the direction of the mold surface of less than 2%.
−−−1−−・−・−=0 If the shrinkage rate is less than 2 to 3%, a round-shaped molded product can be obtained, but it takes a long time to cool down.−−−−−−−− -----------------------------------------------------------------------------------------------------------------------------------------

*3 The bending strength is 1J25, and the deflection that occurs when a 300n long test piece is fixed on a test stand with a length of 150 nm protruding from the test stand and a 500g load is placed on the tip of the protruding test piece. 1 (jIII).

*41rlj Shock absorption was measured by dropping a 2kll weight with a circular base of 65 mm in diameter naturally onto the surface of the molded product in a horizontal state from a height of 1 m (at this time).

(Drop the weight with its circular bottom horizontally).

Judgment was made based on the surface condition of the molded product after it was dropped.

The surface is not torn and there is almost no deformation.
・-----Deformation remains on the surface-----------
〜−−−−・−−１−−−−・Δ Tears occur on the surface−・−−−−−−−−・−−１−−−−・−−−−x※
5 The surface condition is smooth with very small irregularities and wrinkles ---------0 Surface irregularities and wrinkles are somewhat large ---------
---6 Poor surface smoothness, large unevenness, and wrinkles -------x

[Brief explanation of the drawing]

The drawings are enlarged to show one embodiment of the present invention. Fig. 1 is a longitudinal cross-sectional view of a main part of a molded body of the present invention, and Fig. 2 is an example of a mold used in the method for manufacturing a target body of the present invention. FIG. 1-11 Synthetic resin foamed particle in-mold molded body 8 --- Foamed particles in the surface layer 8 --- One wall surface 1.2 --- Pre-expanded particles in the inner layer + 8 --- - Figure 1 of pre-expanded particles in one surface layer

Claims (2)

[Claims] (1) In an indoor molded synthetic resin foamed particle obtained by foam-molding synthetic resin pre-expanded particles indoors for molding, the average diameter Lf in the planar direction of the foamed particles constituting the surface layer of the molded object. An in-mold molded article of foamed synthetic resin particles, characterized in that the ratio of Lf/Ld to the average diameter Ld in the thickness direction is Lf/Ld>3.5. (2) The heating expansion force Ps (kg/cd・absolute pressure) is applied to the surface layer in contact with the wall surface of the mold, and the heating expansion force Pi (
kf/d・absolute pressure) vs. Pi/Ps>
Average diameter L in the planar direction of foamed particles that are filled with pre-expanded particles having a relationship of 1.5 and then heat-molded to form a surface layer.
The ratio of f (m) to the average diameter Ld (mm) in the thickness direction is L
A method for producing an in-mold molded article of foamed synthetic resin particles, characterized by obtaining a molded article in which f /Ld > 3.5.