JPS60110431A - Polypropylene resin-foamed molding - Google Patents

Abstract

PURPOSE:To make flexibility and shock resistance favorable, by making a crystalline propylene resin random copolymer having crystallizing quantity of heat falling within a specific range into basic resin. CONSTITUTION:A crystalline propylene resin random copolymer whose crystallizing quantity of heat through differential scanning measurement is 5-16cal/g is used as basic resin. A polypropylene resin random copolymer particulate and a foaming agent are made to disperse into water by a dispersant within a closed container, to begin with, and the foaming agent is made to impregnated within the particulate by heating the same at a temperature of more than softening one of the particulate. Then one end of the container is released and a prefoaming particulate is obtained by releasing the particulate and water at the same time. After the prefoaming particulate obtained in this manner has been treated by pressure with inorganic gas such as air and nitrogen, molded article is obtained by filling the prefoaming particulate into a molding die, making the same heat, foam and expand and fusing the particulates each other.

Description

[Detailed description of the invention] The present invention relates to a polypropylene resin foam molded article.

It is obtained by filling pre-expanded particles into a mold and heating and foaming them. The so-called bead foam molded body (in-mold molded body) has cushioning properties,
Excellent insulation properties, cushioning material, packaging material.

It is widely used in insulation materials, construction materials, etc., and the demand for it has increased tremendously in recent years.

Conventionally, polystyrene resin foam moldings have been known as this type of in-mold molding, but they have the fatal drawback of being brittle and have poor chemical resistance. It was wanted.

A crosslinked polyethylene resin foam product has been proposed as a solution to these drawbacks. However, in the case of cross-linked polyethylene resin foam particles, it is difficult to obtain a low-density (highly foamed) molded product by indoor molding. However, as a result, only molded bodies with poor physical properties such as significant shrinkage, low impact resilience and high water absorption were obtained, and it was impossible to obtain molded bodies that could be put to practical use.

ttIn order to obtain a product with a high closed cell ratio, it was inevitable to obtain a product with a high density (low foaming). Therefore, the present inventors focused on the excellent physical properties of polypropylene resin, We have been conducting research on polypropylene resin foam moldings in order to solve the drawbacks of conventional indoor moldings. However, while polystyrene resin foam moldings have excellent physical properties such as excellent cushioning properties, high impact resilience, light weight, high mechanical strength, and small thermal changes,
More flexible than cross-linked polyethylene resin foam moldings.

It had the problem of being somewhat inferior in impact resistance, and there was still room for improvement.

In view of these points, the present inventors conducted further intensive research and found that crystallization +f&! has a specific range of heat of crystallization. The present inventors have discovered that the above-mentioned problems can be solved by a polypropylene resin foam molded product using a propylene resin random copolymer as a base resin, and have completed the present invention.

That is, the present invention provides a polypropylene resin foam molded product obtained by heating and forming pre-expanded polypropylene resin particles indoors, in which the base resin of the foamed material is crystallized by differential scanning calorimetry. Calorific value is 5-16 cal/
The gist of the present invention is a polypropylene resin foam molded product characterized by being made of a crystalline propylene resin random copolymer of No. 11.

Polypropylene resin foam molded body of the present invention.

Pre-expanded polypropylene resin particles in a mold/'
It is a molded body made by filling the molded body into a molded body and heating it to fuse the two particles together and molding it into a predetermined shape.
cal/I-La-Kanubi, 7-based resin, and 72-mu copolymer are used. The above crystallization heat amount is approximately 6 to 8 ml of base resin.
10℃ from room temperature to 220℃ using a differential scanning calorimeter.
The temperature is raised at a heating rate of /min.

When the temperature is then lowered to approximately 50°C at a cooling rate of 10°C/min, the exothermic energy required for crystallization of the molten random copolymer is υ, and the crystallization heat amount is as shown in Figure 1.
It can be determined from the area of the part surrounded by the straight line 1 connecting points a and b of the curve and the peak 2 (the shaded part in FIG. 1). If the heat of crystallization of the base resin exceeds 16 cal/& t-, the molded product will have poor flexibility and impact resistance, and if it is less than 5 cal/9, the dimensional change of the molded product will be large. Undesirable.

Examples of the nζ cocopylene resin random copolymer used as the base resin in the present invention include a random copolymer of propylene and ethylene, a random copolymer of propylene 3' and 1-butene, etc. In particular, a random copolymer of propylene and 1-butene is preferred. These random co-I polymers include those obtained by polymerizing propylene monomer and ethylene monomer or 1-butene monomer using a titanium-based polymerization catalyst, a vanadium-based polymerization catalyst, etc. In particular, a vanadium-based polymerization catalyst is used. It is preferable to use polymerized polymers. Also.

In the case of a random copolymer using a propylene component in a propylene-based resin random copolymer and a component-based polymerization catalyst such as ethylene or 1-butene.

The heat of crystallization of the commercially available random copolymer is 5 to 16 cal/J.
For example, in a random copolymer of propylene and 1-butene, the 1-butene component must be within the range of 15
It is preferable that it is 40 mol.

The propylene resin foam molded article of the present invention can be developed, for example, as follows.

First, the aforementioned polypropylene-based random copolymer particles and a foaming agent are dispersed in water in the presence of a dispersant in a closed container, and the foaming agent is incorporated into the particles by heating to a temperature higher than the temperature at which the particles soften. After that, one end of the container is opened, and while the pressure inside the container is maintained at a predetermined pressure, the particles and water are simultaneously released inside the container into a low-pressure atmosphere (usually under atmospheric pressure).

The particles are expanded to obtain pre-expanded particles. Foaming agents used in this process include propane, butane, dichlorosif
Examples include volatile blowing agents such as lomethane and trichloro-70 lomethane, and inorganic blowing agents such as carbon dioxide, and these are usually used in an amount of 10 to 40 parts by weight per ioo parts by weight of the copolymer particles. Examples of the dispersant include finely divided aluminum oxide, titanium oxide, etc., and these are usually used in an amount of 0.04 to 2.0 parts by weight per 100 parts by weight of the copolymer particles.

Further, the foaming temperature is defined as T-T-
Temperatures in the range of 5"C are preferred.

The pre-expanded particles obtained as described above are heated with air, an inorganic gas such as nitrogen, or a mixed gas of an inorganic gas and the above-mentioned volatile blowing agent, usually at a rate of 2 to 5'Kg/d (G).

After pressure treatment for 20 to 100 hours, the pre-expanded particles are filled into a mold and heated with pressurized steam of 2 to 51 V/c, t(G) to expand and fuse the particles together. As a result, a molded article of the present invention which is molded in a transparent manner is obtained.

The molded product of the present invention can be used as a cushioning material, a packaging material, a heat insulating material, a dew-proofing material, a building material, an automobile part, a miscellaneous goods, and other uses such as floor desks.

As explained above, by using the polypropylene dumb copolymer of the present invention as a base resin, the present invention has excellent cushioning properties, 1 impact resilience, and lightweight mechanical strength that conventional polypropylene resin foams have. It has excellent physical properties such as a large dimensional change and a small dimensional change upon heating, which was a drawback of conventional polypropylene resin foam molded products.

Flexibility.

Improved impact resistance. It has the effect of providing a foam molded product with excellent physical properties, and its application range is extremely wide9. For example, when the foam molded product of the present invention is used as a cushioning material,
It is not too hard, not too soft, and is also strong, making it ideal for use as a cushioning material, making it extremely useful.

The present invention will be explained in more detail below by giving Examples and Comparative Examples.

Examples 1-4. Comparative examples 1-2 The base resin particles io shown in Table 1 were placed in a pressure-resistant container.

Parts by weight, 300 parts by weight of water 9 0.3 parts by weight of finely divided aluminum oxide as a dispersant and dichlorodifluoromethane in the amount shown in Table 1 as a blowing agent were mixed and heated to 145°C with stirring. It was warm. Next, one end of the container was opened at the same temperature, and the internal pressure of the container was increased to a5kCg/m (G
) while releasing the resin particles and water under atmospheric pressure,
Pre-expanded particles were obtained by foaming the resin particles. Each of the obtained pre-expanded particles was pressurized with air at 3 Yu/I:tl (G) to give an internal pressure of 1.5 kg/nJ (G), and was A, 2 kg/cd (G) (7
) to obtain a foamed molded product. After drying the obtained foamed molded product in an open air at 60° C. for 24 hours, various physical properties of the cough foamed molded product were measured.

The results are also shown in Table 1. Further, as a reference example, various physical properties of a cross-linked low-density polyethylene pre-foamed product are shown in Table 1.

() (Draw a 1100m x 100+i square and a cross line that intersects at the center of the square in the center of the foam molded sample cut into 10*1150mm squares.

After carefully measuring the length of each line segment from the center of the square to the point where the square and crosshair intersect.

The sample was placed in a constant temperature bath adjusted to 90 ± 1°C for 22 hours, left to cool at 25°C for 1 hour, and the length of each line segment was precisely measured to determine the rate of change from the original length. It was determined that the average value was less than 4% (no problem in practical use) - 4% or more (unsuitable for use) - x.

*2 Thickness 20nm + length 300wm x width 4Qmi +
When you bend a sample cut into a rectangular parallelepiped in the direction of 300 stories so that both sides are facing each other, it will not break when it is completely folded in half. It won't break...
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Qin 3 A disk weighing 5 kg and having a diameter of 155 fins was dropped horizontally from a height of 1 m onto a sample measuring 300 mm x 300 mm with a thickness of 50 fins, and the degree of damage to the sample was observed.

Damage is less than 10 cm (115 of the disk circumference)------
−−−−0 damage is 25a++ or more −−−−−−−−−
−−−−−−−−−−−−−−−−−x.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a method of calculating the heat of crystallization of the p base resin from the DSC curve of the base resin.

Claims (1)

[Scope of Claims] In a polypropylene resin foam molded product obtained by heating and forming polypropylene resin pre-expanded particles in a mold, the base resin of the cross-shaped foam molding is: Crystallization heat amount by differential scanning calorimetry is 5 to 16 cal/
11. A polypropylene resin foam molded product characterized by being made of a propylene resin random copolymer.