JP2787224B2 - Olefin-based resin foam molded article and method for producing the same - Google Patents

Description

The present invention relates to an olein-based resin foam molded article that can be used as a drainage material, a horticultural material, and the like, and a method for producing the same.

[Problems to be solved by conventional technology and invention]

Conventionally, the lower part of the ground where grass was planted was laid with stones for the purpose of improving drainage at golf courses, etc.However, if clogging occurs and drainage is reduced, drainage is improved. It was a very difficult task to carry out the construction work. For this reason, in recent years, a water-permeable block made of a synthetic resin has been used as a drainage material, but such a water-permeable block is not only used as a drainage material for golf courses and the like, but also for hydroponics. It is also used as materials and building materials. As this type of water-permeable block, a structure having a structure in which continuous pores are provided by solidifying polystyrene foam particles with an adhesive is known, and this water-permeable block is particularly preferable as a building material because of its excellent heat insulating properties. Although they are brittle, they are brittle and have a problem in chemical resistance (for example, the adhesion between the foamed particles is peeled off), and the use of a special adhesive as an adhesive for fixing the foamed particles increases the cost. There was a disadvantage that it becomes. Further, in such a structure, the porosity is limited to about 30% by volume, and if an attempt is made to obtain a porosity of more than 30% by volume, the adhesion between the foamed particles is reduced and the particles are liable to fall off. In addition, there is a disadvantage that water permeability is poor for the porosity.

On the other hand, in a molded product obtained by foaming and molding polyolefin foamed particles in a mold, by setting the internal pressure of the particles immediately before filling the mold to 0 to 3 kg / cm ² (G), 30 volume% is obtained.
It is also known that even when the porosity is as described above, the foamed particles are fused to each other, so that a foamed molded body without falling off of the foamed particles can be obtained (Japanese Utility Model Publication No. 63-7607). However, the porosity is limited to about 40% by volume, and the voids of this foamed molded article are not always connected, and it is difficult to say that the water-absorbing property and the heat insulating property are good but the drainage property is good. .

[Means for solving the problem]

The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, filled a mold with foamed olefin-based resin particles having a closed cell structure, and heated with steam having a melting point of −5 ° C. to a melting point + 5 ° C. of the foamed particles. By heating and molding, a foamed molded article having a network structure having interconnected voids with a porosity of 40 to 80% by volume is obtained. Since the foamed molded articles are fused to each other, the foamed molded article is expanded. There is no danger of particles falling off, and it has excellent drainage properties.In addition, the foam inside the foamed particles has a partially open cell structure, so it has excellent water retention, and it has unprecedented performance as a horticultural material. Thus, the present invention has been completed.

That is, the present invention provides: (1) a foamed molded product obtained by heating and foaming non-crosslinked olefin resin foamed particles in a mold and fusing the particles together, and having a porosity of 40 to 80% by volume between the particles. Characterized by having a network-like structure in which foamed particles are fused so as to form voids communicating with each other.

(2) The olefin resin foam molded article according to claim 1, wherein the foam molded article has a bulk density of 0.2 to 0.018 g / cm ³ .

(3) A non-crosslinked olefin resin foamed particle having a closed cell structure having a cell membrane thickness of 0.1 to 5 μm is filled in a mold that can be closed but not sealed, and then the melting point of the resin constituting the foamed particle The method is characterized in that the foamed particles are heated and foamed by heating with steam at a temperature of -5 ° C to a melting point + 5 ° C to cause secondary foaming of the foamed particles and fusion of the particles to each other, and thereafter, the foamed particles are contracted. A method for producing an olefin resin foam molded article according to claim 1.

It is the gist.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the foam molded article 1 of the present invention has a network structure in which a porosity 3 communicating with a plurality of foam particles 2 is formed and the foam particles 2 are fused. The gap 3 is 40 to
80% by volume. The porosity is calculated by the following equation.

However, the weight of the foam when dried is W ₁ and the bulk volume of the foam is
V ₁ , the increased volume when the foam is put in the water in the measuring cylinder is V ₂ , and the weight of the water-absorbing foam when the foam is put in the water in the measuring cylinder is W ₂ .

Examples of the olefin resin which is the base resin of the expanded particles 2 constituting the expanded molded article 1 of the present invention include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, and linear ultra-low-density polyethylene. Polyethylene, polypropylene, polybutene, ethylene-propylene block copolymer, ethylene-propylene random copolymer, ethylene-butene-propylene random copolymer, and the like. Among these, non-crosslinked linear low-density polyethylene, ethylene-propylene random copolymer, and ethylene-butene-propylene random copolymer are particularly preferable.

In the foamed molded article 1 of the present invention, since the cells in the expanded particles 2 have a partially open cell structure, water is absorbed in the cells, and therefore, it has excellent drainage and water retention.
When used as a horticultural material, it is possible to provide a suitable amount of water for plant growth without causing excessive or insufficient water. The foam molded article 1 of the present invention has a bulk density of 0.2 to
Those having 0.018 g / cm ³ are preferable because of their excellent heat insulating properties and sound absorbing properties. The bulk density is a value obtained by dividing the weight of the foam by the bulk volume of the foam.

The foamed molded article 1 of the present invention can be obtained by a molding method similar to a conventional in-mold molding method in which olefin-based resin foamed particles 2 are filled in a mold and heated and foamed by steam. However, in order to obtain the foamed molded article 1 of the present invention,
As the olefin-based resin foamed particles 2, the thickness of the cell membrane is 0.
It is necessary to use foamed particles having a closed cell structure of 1 to 5 μm. When a cell membrane having a thickness of more than 5 μm is used, a network-like structure is not obtained, and a normal foam molded article is obtained. When the cell membrane is further heated, the whole foam becomes a contracted foam. When the thickness of the cell membrane is less than 0.1 μm or when foamed particles having an open cell structure are used, secondary foaming does not occur or shrinkage becomes significant, and the foamed structure cannot be maintained. Further, in order to obtain the foamed molded article 1 of the present invention, the expanded particles 2 as described above are mixed with the resin having a melting point of −5 ° C. to + 5 ° C., particularly preferably −3 ° C. to + 4 ° C. of the base resin of the expanded particles 2. It needs to be heated with a range of steam. If the temperature of the heating steam is lower than the melting point of the base resin of the expanded particles 2 −5 ° C., the network structure is not obtained, and if the temperature of the heating steam exceeds the melting point + 5 ° C., the expanded particles 2 are melted and the molded body is formed. No longer available.

The thickness of the cell membrane of the expanded particles is obtained by measuring the cell diameter with a microscope and calculating the thickness from the value according to the following equation.

However, d is an average cell diameter, t is the bubble thickness, V _S is the solid phase volume fraction, the [rho _f density of the expanded particles, [rho _s is the density of the solid phase, [rho
_g is the density of the gas in the bubble, and in the case of air, ρ _g = 0.0012 _g / cm
^{It was set to 3} .

The expanded particles 2 used for producing the expanded molded article 1 of the present invention preferably have a bulk density of 0.2 to 0.018 g / cm ³ .

Next, the present invention will be described in more detail with reference to specific examples.

Examples 1 to 5, Comparative Examples 1 to 3 Expanded particles shown in Table 1 were 300 mm long, 300 mm wide, and 60 mm thick.
(Inner dimensions) were filled into a mold and heated with steam at the temperature shown in the table to foam. Table 1 shows the properties of the obtained molded foam.

* 1 Permeability when water was dropped at a speed of 25 cc / sec from a tube with a diameter of 5 mm from a height of 50 mm at the center of a circle of a cylindrical foam having a thickness of 100 mm and a thickness of 25 mm was determined according to the following criteria. .

 …: Water permeates down to the lower surface of the foam.

×: Water spills from the upper surface without permeating the foam.

* 2 The following formula is defined as the amount of water absorption when a 100 mm x 100 mm x 40 mm test piece is immersed in water for 30 minutes. However A: water absorption (volume%), W _1: weight of foam on drying (g), W _2: weight of foam during water absorption, d: density of water (g / c
c), V: Calculated by the bulk volume (cc) of the foam, and ○: water absorption rate of 2% or more ×: water absorption rate of less than 2%

* 3 A test piece of 150mm x 50mm x 10mm is measured by Tensilon for 500
Observation of the fracture surface at the time of pulling at a speed of mm / min.

 ×: Breakage has occurred between foamed particles.

Was determined.

〔The invention's effect〕

As described above, the foamed molded article of the present invention has a network-like structure in which foamed particles are fused so as to form a communicating void having a porosity of 40 to 80% by volume between the foamed particles, and Since some of the internal bubbles have an open-cell structure, they have excellent drainage properties and excellent water retention, and are suitable as drainage materials for golf courses, gardening materials such as beds for hydroponics, and the like. Also, since the foam molded article of the present invention is made of a foam,
In particular, those having a bulk density of 0.2 to 0.018 g / cm ³ also have good heat insulating properties and sound absorbing properties (however, in this case, those having a relatively small porosity depending on the thickness are preferable), building materials and the like. Also available as Further, since the foamed molded article of the present invention has the foamed particles adhered to each other by fusion, there is no danger that the foamed particles will fall off even if the porosity is increased. Thus, more excellent drainage performance can be obtained.

Further, in the method of the present invention, foamed olefin-based resin particles having a cell membrane thickness of 0.1 to 5 μm are filled in a mold, and heated with steam having a melting point of the base resin of the foamed particles of −5 ° C. to + 5 ° C. By adopting the method of foam molding, it is possible to obtain a foam molded article having a network structure in which the expanded particles do not fall off even if the porosity is increased, and it is possible to easily obtain a foam molded article having a high porosity. it can. In addition, since it is not necessary to use a special adhesive for fixing the particles to each other, there is an effect that an excellent foam molded article can be provided at low cost.

[Brief description of the drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional view of the foam molded article of the present invention. 1 foam molded article 2 foam particles 3 voids

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 67/20 B29C 44/00-44/60 C08J 9/00-9/42

Claims (3)

(57) [Claims] 1. A foamed molded article obtained by heat-foaming non-crosslinked foamed olefin resin particles in a mold and fusing the particles to each other, wherein the particles have a porosity of 40 to 80% by volume. An olefin-based resin foam molded article having a network structure in which foamed particles are fused so as to form voids. 2. The olefin resin foam molded article according to claim 1, wherein the foam molded article has a bulk density of 0.2 to 0.018 g / cm ³ . 3. A non-crosslinked olefin resin foamed particle having a closed cell structure having a cell membrane thickness of 0.1 to 5 .mu.m is filled in a mold that can be closed but not sealed, and then the resin constituting the foamed particle is filled. Is heated with steam having a melting point of −5 ° C. to + 5 ° C. to cause the foamed particles to be heated and foamed to cause secondary foaming of the foamed particles and fusion of the particles to each other, followed by contraction of the foamed particles. The method for producing an olefin resin foam molded article according to claim 1.