JPH03224727A - Polyolefin resin foam molded body and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a polyolefin resin foam molded product having water permeability and excellent compressive strength and which can be used mainly as a base material for drainage, etc., and a method for producing the same.

[Conventional technology and Problems that the invention seeks to solve]

Roads, golf courses, etc. have structures where pebbles are placed in the lower layers to improve drainage, but if clogging occurs and drainage is reduced, construction work must be carried out to improve drainage. was an extremely difficult task.

For this reason, geotextiles, which are water-permeable materials composed of fibers in the form of knitted, woven, or non-woven fabrics, are widely used in the civil engineering and architectural fields. The drawback was that it required skill. In addition, Styrofoam, which is normally used as an ultra-light embankment material for road foundations, is impervious to water, so it is extremely useful as a civil engineering structure because it is directly exposed to buoyancy by water that circulates below the Styrofoam after rainfall or depending on the location where it is used. There were serious shortcomings. In addition, water-permeable block molded products made of synthetic resin have recently begun to be proposed; for example, molded products with a structure in which spherical polystyrene foam particles are hardened with an adhesive to provide continuous voids are known. However, this water-permeable block is weak in terms of strength (for example, the adhesion between foamed particles may peel off), and it is manufactured using a special adhesive to fix the foamed particles. Since it requires a secondary processing process, there were difficulties in terms of cost and productivity. Moreover, polystyrene resin is oil resistant,
Since the heat resistance is poor, when a molded product made of the above-mentioned expanded polystyrene particles is used as a road base material, it is difficult to finish the surface of the molded product with asphalt or the like.

Furthermore, foamed polyolefin particles made by blending an inorganic filler with a base resin are foam-molded in a mold, and the porosity between the particles is 5.
A foam molded body used as a wall material is known which has a large number of voids of up to 40% (Japanese Utility Model Publication No. 63-760
7), this foamed molded product is composed of spherical foamed particles as shown in the figure, and the voids are formed by insufficient fusion between the particles. In the end, the voids were not necessarily interconnected, and although they had sound absorption and heat insulation properties, it was difficult to say that they had water permeability or good water permeability. In addition, this molded product has increased compressive strength by incorporating an inorganic filler into the base resin, but it is brittle due to poor fusion between the foamed particles to form voids, making it difficult to use for road use. It was unsuitable for uses such as base materials.

The present invention has been made to solve the problems of the prior art described above, and is a polyolefin resin foam molded product that is easy to manufacture and inexpensive, and has excellent water permeability and compressive strength, which are mainly required as a base material for drainage, etc. The purpose is to provide a method for producing the same.

[Means to solve the problem]

That is, the present invention has the following features: (]) Columnar polyolefin resin foam particles having L/D (1,: length of longest part, D: cross-sectional length of maximum body part) of 2 to 10 are oriented in irregular directions. A molded body that is fused to each other, has communicating voids between the expanded particles with a porosity of 5 to 30%, and has a compressive strength of 1.1 kg at 5% compression.
/cd or more.

(2) DSC curve obtained by differential scanning calorimetry (
However, 1 to 3 cm of foamed particles were measured by differential scanning calorimeter.
It has a crystal structure in which two exothermic peaks appear in the DSC curve obtained when the temperature is raised to 220 °C at a temperature increase rate of C/min, and the energy of the endothermic peak on the high temperature side is 10 to 30 J/g. and L/D (L: length of the longest part, D=
Columnar foamed polyolefin resin particles having a maximum body length of 2 to 10 are placed in a mold that can be closed but cannot be sealed so that the filling rate is 40 to 55% and the particles are arranged in irregular directions. 1. A method for producing a polyolefin resin foam molded article, which comprises filling the particles so as to face each other, and then heating the particles with steam at a temperature ranging from the Vicat softening point of -20° C. to the melting point of the base resin to fuse the particles together.

The main points are as follows.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

The polyolefin resin foam molded article 1 of the present invention has a plurality of columnar polyolefin resin foam particles 2 as shown in FIG.
It is a molded body having a structure in which the foamed particles 2 are oriented in irregular directions and fused together. The present invention is characterized by the use of columnar expanded particles rather than spherical ones, and the columnar shape is defined by the length of the longest part of the expanded particle 2: L and the length of the maximum body, as shown in Fig. 2. Between D and L/D-2
~10. In the case of foamed particles with L/D<2, when filled into a mold, the filling rate becomes high and a molded product having the desired porosity for obtaining water permeability cannot be obtained, and conversely, when L/D>l When O foam particles are filled into a mold, they tend to clog at the filling port, causing filling defects. Considering such porosity and filling workability,
Expanded particles having an L/D of 5 to 8 are particularly preferred.

The molded product 1 of the present invention is formed by randomly orienting and fusing foamed particles 2 as described above, and also has voids 3 communicating between the foamed particles (the blacked out areas in the figure and the spaced apart particles 2). It has a structure in which the porosity (
The proportion of voids in the total volume of the molded body is 5 to 30%. Water permeability is obtained through this continuous void portion 3, but if the porosity is less than 5%, good water permeability cannot be ensured, and on the other hand, if it exceeds 30%, the porosity at 5% compression is 1.1 kg/r.
It is less than rr (G) and cannot be used as a road base material in terms of strength. The porosity (C%) is calculated using the following formula.

In the formula, the true volume refers to the increased volume when the foamed molded product is submerged in alcohol.

Furthermore, the molded product 1 of the present invention has a compressive strength of 1, 1 when compressed by 5%.
kg/c- or more, and if this compressive strength is less than 1.1 kg/c+i, it is insufficient in strength for applications where loads are applied, such as road base materials. becomes.

The olefin resin that is the base material resin of the foam particles 2 constituting the foam molded product 1 of the present invention includes high-density polyethylene,
Polyethylene such as medium density polyethylene, low density polyethylene, linear low density polyethylene, linear very low density polyethylene, polypropylene, polybutene, ethylene-propylene block copolymer, ethylene-propylene random copolymer, ethylene-butene random Examples include copolymers, ethylene-butene-propylene random copolymers, and the like. Among these, non-crosslinked linear low density polyethylene, ethylene-propylene random copolymer,
Ethylene-butene random copolymers and ethylene-butene-propylene random copolymers are preferred.

The foam molded article 1 of the present invention has a bulk density of 0.03 to 0.18 g.
/ cd is preferable because of compressive strength and manufacturing cost reduction. The bulk density is the weight of the foam divided by the bulk volume of the foam.

Next, the manufacturing method of the present invention will be explained.

As described above, the production method of the present invention uses columnar polyolefin resin foam particles having a D/L of 2 to 1O and follows the conventional in-mold molding method to obtain the foam molded article of the present invention having the above-mentioned structure. It can be done in such a way that In the method of the present invention, columnar foamed particles are filled into a mold at a filling rate of 40 to 55% in order to form continuous voids having the specific porosity in the molded product obtained. It is important to avoid secondary foaming as much as possible by simply fusing them by steam heating, and even if secondary foaming occurs, it is necessary to suppress the secondary foaming ratio to within about 1.7 times.

Therefore, in the method of the present invention, first, the columnar polyolefin resin foam particles are DS obtained by differential scanning calorimetry.
Two endothermic peaks appear on the C curve (the DSC curve obtained when expanded particles 1 to 3 cm are heated to 220°C at a heating rate of 10°C/min using a differential scanning calorimeter), and two endothermic peaks appear on the high temperature side. It is necessary to have a crystal structure with an endothermic peak energy of 10 to 30 J/g. In particular, the higher the energy of the endothermic peak on the high temperature side, the lower the secondary foamability, which is preferable. The method for obtaining the expanded particles used in the present invention includes, for example, adding base resin particles to which inorganic substances such as talc, calcium carbonate, borax, and aluminum hydroxide are added together with a volatile blowing agent and water in a closed container. The resin particles and foaming agent are dispersed in water in the container, heated to a temperature higher than the softening temperature of the resin particles, and the foaming agent is impregnated into the particles. A method can be used to obtain foamed particles by holding the container at a pressure higher than the above pressure, opening one end below the water surface in the container, and simultaneously releasing the resin particles and water into an atmosphere at a lower pressure than in the container. . In order to obtain expanded particles with a large endothermic peak energy on the high temperature side, for example, it is sufficient to heat and pressurize the resin particles in a closed container for a longer period of time near the melting point or within +20"C of the melting point. 15 to 3 in consideration of productivity etc.
It will wear off in about 0 minutes. In addition, considering the compressive strength after molding, it is preferable that the foamed particles have an internal pressure of 0 to 0.5 kg/cd (G) and a true density of 0 to 0.11 g/c, especially 0. .02 to 0.11 g/cd is preferred.

Next, in the method of the present invention, columnar expanded particles are filled into a mold at a filling rate of 40 to 55% with the particles facing each other in irregular directions, and then the softening point of the base resin is adjusted to -
It is necessary to heat the particles with steam at a temperature ranging from 20° C. to the melting point to fuse the particles together.

The filling rate (%) in the present invention is expressed as a percentage by dividing the volume (cd) occupied by the foamed particles when the foamed particles are filled into the mold by the volume (c4) of the cavity inside the mold. It is a value. The filling ratio of the foamed particles can be adjusted by appropriately adjusting the filling air pressure according to the true density and L/D value of the foamed particles.
This can be done by adjusting the opening (cranking) of the mold when filling the mold with foamed particles. Moreover, the Vicat softening point mentioned above is measured by the test method of JIS K7206. Also, the melting point of the base resin is 5~
This is the peak temperature of the endothermic peak that appears in the DSC curve obtained when the temperature of the sample 10<1> is raised at a heating rate of 10° C./min using a differential scanning calorimeter. By heating at the above-mentioned specific temperature, there is less risk of secondary foaming of the foamed particles, and the particles are sufficiently fused together. This heating temperature is the softening point -20
If the temperature is below .degree. C., the fusion between the expanded particles will be insufficient, and if the temperature exceeds the melting point, a molded product with sufficient fusion may be obtained, but shrinkage may occur after molding. In addition, in the method of the present invention, the heating steam pressure is 0.2 to 4.0 kg in order to prevent secondary foaming of the expanded particles.
/c (G), preferably 0.2-3.5 kg/cd
(G), and as mentioned above, it is desirable to use expanded particles whose endothermic peak energy on the high temperature side is 10 to 30 J/g, preferably 15 to 30 J/g.

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

Examples 1 to 6, Comparative Examples 1 to 7 The expanded particles shown in the table below were filled into a mold with a length of 300 m, a width of 300 m, and a thickness of 60 nm (inner dimensions), and heated with steam at the temperature shown in the table. Foamed. The properties of the obtained foam molded product are shown in the same table.

*l...Porosity is 50II! l×5011IL1×5
The apparent volume of the test piece of 011II11 is ■. (C-), and the volume increased when the test piece was submerged in alcohol was determined by the following formula, V+ (c+J).

■. -■1 Porosity-×100 ■.

*2...Fusionability was determined based on the following criteria by observing the cutting conditions when cutting the foamed molded body with a cutting blade.

○: Possible to cut without breaking between foam particles.

Partial destruction of ΔD is observed.

×: Many broken parts occurred.

*3...Secondary foamability was determined based on the following criteria by visually observing the condition of the foam surface and cut surface using a cutting machine.

O: There are irregular gaps between expanded particles.

Δ: There are slight gaps between particles.

×: There is almost no gap.

Next 4...Water permeability is 11 permeable to water on the surface of the molded body! ,/l11
At n, the water was dropped using a funnel and the movement of the water was observed, and the judgment was made as follows.

◎: Drainage water passes through the inside of the foam and is drained from the bottom surface without pooling (stagnation) on the surface of the molded product.

O: After pooling on the surface of the molded product, it passes through the inside of the foam and is drained from the bottom surface.

Δ: After pooling on the surface of the molded body, water is drained little by little from the bottom surface.

×: Spills out from the front without penetrating into the molded body.

[Effects of the Invention] As explained above, the foam molded product of the present invention has a structure in which columnar foam particles are fused to each other in irregular directions, and the porosity between the foam particles is 5 to 5. It has 30% open voids and the compressive strength at 5% compression is 1.1kg/
Since it exhibits a value of c- or higher, it has excellent water permeability and extremely high compressive strength, and can be used as a drainage base material and embankment material for roads, soft ground, golf courses, etc. that have drainage functions,
It is most suitable as agricultural material such as seedbeds. In addition, the foam has heat insulating properties and the open voids provide breathability, so it can also be used as a construction material.

In addition, columnar foamed particles are used, and because they are irregularly oriented and fused, the number of foamed particles is deliberately reduced in order to increase the porosity, as in the case of spherical foamed particles. In addition to being easy to secure without causing problems such as cracking or poor adhesion, it also has a strong structure, and at the same time, it is easy to prevent clogging of voids due to earth and sand when used as a base material, and it maintains good water permeability over a long period of time. can.

In addition, the method of the present invention employs a method in which columnar foamed particles with specific properties are randomly filled into a mold at a specific filling ratio, and foam molding is performed by heating with steam having a Vicat softening point of the base resin of -20°C to melting point. By doing so, it is possible to achieve good fusion between particles with no secondary foaming, and to obtain a high-strength foam molded product in which continuous voids with high porosity are accurately formed. Furthermore, since there is no need to use a special adhesive to bond the particles to each other, there are also effects such as the ability to provide an excellent foam molded product at a low cost.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing one embodiment of the foam molded article of the present invention;
FIG. 2 is an explanatory diagram for defining the columnar shape of expanded particles. 1...Polyolefin resin foam molded product 2...Columnar polyolefin resin foam particles 3...Void portion Lμ=

Claims (2)

[Claims] (1) Columnar polyolefin resin foam particles with L/D (L: length of longest part, D: cross-sectional length of maximum body part) of 2 to 10 are fused to each other in irregular directions. A molded product, which has continuous voids with a porosity of 5 to 30% between expanded particles, and has a compressive strength of 1.1 kg/cm when compressed by 5%.
A polyolefin resin foam molded product characterized by having a polyolefin resin foam of ^2 or more. (2) DSC curve obtained by differential scanning calorimetry (
However, 1 to 3 mg of expanded particles were measured using a differential scanning calorimeter.
It has a crystal structure in which two endothermic peaks appear in the DSC curve obtained when the temperature is raised to 220 °C at a heating rate of 0 °C/min, and the energy of the endothermic peak on the high temperature side is 10 to 30 J/g. , and filled with columnar polyolefin resin foam particles having a L/D (L: length of the longest part, D: length of the maximum body part) of 2 to 10 in a mold that can be closed but cannot be sealed. After filling the particles so that the ratio is 40 to 55% and the particles are oriented in irregular directions, the particles are fused together by heating with steam at a temperature between -20°C and the melting point of the Vicat softening point of the base resin. 1. A method for producing a polyolefin resin foam molded article.