JPH0277436A - Polyolefin based resin foamed particle having gas adsorbing ability, molded article and production of above-mentioned foamed particle - Google Patents

Abstract

PURPOSE:To obtain the title obtained by blending zeolite and capable of using as various kind of gas adsorbing agents and providing a buffer packaging material having excellent deodorizing properties and freshness retaining properties. CONSTITUTION:A polyolefin based resin formed particle having a gas adsorbing ability and containing 5-50wt.% zeolite. The aimed particle is produced by dispersing a polyolefin based resin particle containing 5-50wt.% zeolite and volatile foaming agent into water in a pressure resistant vessel in the presence of a dispersing agent, heating the dispersion to give state of high temperature and pressure and releasing the dispersion from a releasing port provided in the lower part of pressure resistant vessel to low pressure area to foam the particle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to expanded polyolefin resin particles having gas adsorption ability that can be used as various gas adsorbents, molded articles thereof, and a method for producing the expanded particles.

[Prior Art/Problems to be Solved by the Invention] Zeolites are widely used as adsorbents, separation agents, ion exchange agents, catalysts, etc. due to their unique crystal structure and ionic properties. In particular, by taking advantage of its adsorption ability, it is suitably used for purposes such as drying, purification, and recovery.

In the packaging field, zeolite-added film packaging materials are used to maintain freshness and deodorize perishable foods.

However, the film packaging material does not have sufficient deodorizing properties.
Depending on the form of the packaged item, there are problems such as it is not possible to deodorize efficiently, and it cannot be expected to be effective as a cushioning packaging material.

[Means for Solving the Problems] As a result of intensive research in order to improve the above-mentioned problems, the present inventors foamed specific resin particles containing zeolite, and created a molded article from the obtained expanded particles. The inventors have discovered that when produced and used in packaging containers, it exhibits excellent effects on freshness retention and deodorization of perishable foods while having buffering properties. In addition, it is difficult to achieve a high expansion ratio with certain resin particles to which zeolite has been added by impregnating the resin particles with a volatile blowing agent and heating and foaming them with a heating medium such as water vapor, but in the presence of a dispersant. In addition, foamed particles of zeolite-containing polyolefin resin with a high expansion ratio can be obtained by dispersing them in water together with a volatile foaming agent in a pressure-resistant container, bringing them to a high temperature and high pressure state, and then releasing them into a low pressure region to foam them. This discovery led to the completion of the present invention.

The present invention contains 5 to 50% (weight%, the same applies hereinafter) of zeolite,
Expanded polyolefin resin particles having gas adsorption ability, a molded article formed from the expanded polyolefin resin particles, polyolefin resin particles containing 5 to 50% of zeolite, and a volatile blowing agent are placed in a pressure-resistant container, and a dispersant is added to the foamed particles. Dispersed in water in the presence of a substance, heated and raised to a high temperature and high pressure state,
The present invention relates to a method for producing foamed polyolefin resin particles having gas adsorption ability, which is characterized by foaming by discharging into a low pressure region from a discharge port provided at the bottom of a pressure-resistant container.

[Example] The foamed particles of the present invention are foamed particles made of a polyolefin resin containing zeolite.

Although there are no particular limitations on the size, expansion ratio, density, etc. of the foamed particles, those having a diameter of about 1 to 20+em and an expansion ratio of about 5 to 100 times are usually used.

The zeolite includes natural zeolite and synthetic zeolite, and the main components are 5I02, /V2O3, CaO,
Na2O, K2O, 820. Natural zeolite is a mineral collectively known as zeolite, and is a crystalline hydrated aluminosilicate mineral that vitrifies by heating at a relatively low temperature and becomes foamed by releasing a large amount of water during this process, and has a three-dimensional network structure. . It mainly occurs as clinoptilolite and mordenite. Synthetic zeolites are known as molecular sieves and are similar in structure to natural zeolites.

All zeolites have molecular-level pores (2 to 15 pores) based on their unique crystal structure. The characteristics of zeolite as an adsorbent are (1) the ability to adsorb and separate molecules according to their shape and size due to the molecular sieving action of zeolite crystals;
The reason is that it can selectively and strongly adsorb highly polar molecules.

Zeolite can be in the form of powder or granules, and the grain size varies from 1μ to about 1CI11.

Examples of the polyolefin resin used in the present invention include ethylene resins such as high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-methyl methacrylate copolymer, polypropylene, Examples include, but are not limited to, propylene resins such as ethylene-propylene copolymer, ethylene-propylene-butene terpolymer, butene-propylene copolymer, polybutene-11 polypentene, and the like. Blends with other resins containing 50% or more of polyolefin resin may also be used.

Polyolefin resins have low gas barrier properties compared to other resins, and this is considered a drawback when used in membranes, but for purposes of gas adsorption materials such as the present invention, gas permeability is low compared to polyolefin resins. It is preferable that the zeolite has high properties, and since such a resin is used, gas molecules easily diffuse through the resin, reach the zeolite, and are adsorbed, resulting in high adsorption performance. Therefore, it is essential to use a polyolefin resin as the base resin of the expanded particles.

The content of zeolite in the expanded particles of the present invention is 5 to 50%
, preferably 10 to 50%. If the content is less than 5%, the effect as a gas adsorbent is insufficient, and if it exceeds 50%, it becomes difficult to foam.

The polyolefin resin foamed particles of the present invention as described above may be used as is for purposes such as cushioning materials, but they can also be made into molded articles in the same manner as in the molding of ordinary pre-expanded particles.

The molded product obtained in this way has physical properties such as mechanical strength similar to molded products made from normal pre-expanded particles, and also has excellent adsorption ability, so it is better than molded products made from normal pre-expanded particles. Can be used for similar purposes. In particular, when used in applications such as fresh foods that require gas adsorption properties such as deodorizing properties, molded products with excellent deodorizing properties and freshness retention properties can be used.

Next, the method for producing expanded particles of the present invention will be explained.

The foamed particles of the present invention are produced by dispersing polyolefin resin particles containing 5 to 50% zeolite and a volatile blowing agent in water in the presence of a dispersant in a pressure-resistant container, and then heating and raising the temperature to achieve high temperature and high pressure. After the pressure is brought to this state, it is released into a low-pressure area from an outlet provided at the bottom of the pressure-resistant container. Atmospheric pressure is usually used as the low pressure region.

Examples of the volatile blowing agent include hydrocarbons such as propane, butane, pentane, and hexane, trichloromonofluoromethane, dichlorodifluoromethane, monochlorotrifluoromethane, monochlorodifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane, and monochloromethane. Examples include, but are not limited to, halogenated hydrocarbons such as lomethane, dichloromethane, and monochloroethane. These volatile foaming agents may be used alone or in combination of two or more.

Examples of the dispersant include poorly water-soluble inorganic powders such as basic tricalcium phosphate, basic magnesium carbonate, basic zinc carbonate, calcium carbonate, and magnesium birophosphate, and the amount used is usually, for example, 100 parts of water. (parts by weight, the same applies hereinafter) is used in an amount of about 0.1 to 5 parts.

In addition to the dispersant, a small amount of a surfactant such as sodium dodecylbenzenesulfonate, sodium n-paraffin sulfonate, sodium α-olefin sulfonate, etc. may be added to improve dispersibility.

The above-mentioned high temperature and high pressure state varies depending on the type of polyolefin resin used, the type and amount of volatile blowing agent, etc., but is usually in the range of 90 to 180°C and 5 to 50 kg4 (gauge pressure).

Next, the present invention will be explained based on examples.

Example 1 Linear low-density polyethylene containing 30% of naturally produced zeolite (manufactured by Nitto Funka Kogyo ■, activated zeolite 5PII2300) with an average particle size of 5 μm was placed in a pressure-resistant container with an internal volume of 4 g and equipped with a stirrer. (hereinafter referred to as LLDPE) pellets (melt flow index (old) 0.8g710
minute, density 1.10g/cj, pellet particle size approximately 3mm
) was dispersed in 300 parts of water using 1.2 parts of basic tertiary calcium phosphate and o, oe parts of sodium n-paraffin sulfonate as dispersants. While stirring, add 40 parts of dichlorodifluoromethane as a blowing agent, and do not raise the temperature. The internal temperature ILB of the pressure vessel is 5℃, the internal pressure is 27.5, and η(
A ball valve provided at the bottom of the container was opened under pressure (gauge pressure), and the contents were discharged to atmospheric pressure through a discharge port with a diameter of 151 Ilol to cause foaming. The obtained expanded particles have an expansion ratio of 40 times (
(high magnification) and the bubble diameter was 50 to ioo Jl.

After drying the obtained expanded particles at 60°C for 24 hours, 1 kg4 (
The material was heated with steam at a pressure of 1.25 mm (gauge pressure) and fusion-molded. After cooling, it was taken out from the mold, immediately dried at 75°C for 18 hours, and then taken out to room temperature.

The outside dimensions of the mold are width 150cm and length 300mm.
1 height 150cm, inner dimensions width 100cm, length 2
It was box-shaped, measuring 50cm and 25IllII in height.

The obtained molded product had good internal fusion properties and surface properties, had a slightly eyelid color, and had an expansion ratio of 30 times.

Comparative Example 1 Using the same 4II pressure container as in Example 1, the DSC method containing 0.01 part of talc as the base resin had a melting point of 117°C.
Foaming was carried out under the same conditions as in Example 1, except that an LLDPE pellet with a density of 0.920 g/cj, a former weight of 0.8 g, 710 minutes, and a sphere equivalent diameter of 2 cm was used, and the foaming was carried out at a foaming ratio of 40 times (high magnification). Expanded particles with a diameter of 210 to 250 jJn were obtained.

The obtained expanded particles were molded and dried in the same manner as in Example 1 to obtain a molded product with an expansion ratio of 30 times and good internal fusion properties and surface properties.

Examples 2 to 4 and Comparative Examples 2 to 4 Using the expanded particles obtained in Example 1 and Comparative Example 1, ammonia gas (Example 2 and Comparative Example 2) and ethylene gas (Example 3) were prepared by the following method. and Comparative Example 3), and the gas adsorption properties for trimethylamine gas (Example 4 and Comparative Example 4) were evaluated. The results are shown in Figure 1.

(Gas adsorption evaluation method) A 1000 cc wide mouth bottle with an inner stopper is prepared at a temperature of 25° C. and a humidity of 50%, and the inside of the bottle is kept saturated with a predetermined gas.

To check the saturation state, inject a small amount of the specified gas into a wide mouth bottle,
Approximately 3 cc of the gas in the wide-mouthed bottle is removed and the gas concentration is measured by gas chromatography. When there is no change in gas concentration, it is considered to be saturated. Next, open the inner stopper, quickly add 10 g of foam particles, close the lid, draw out about 3 cc of gas from the needle of the syringe inserted into the inner stopper, and measure the concentration using gas chromatography.

Assuming that the concentration in the saturated state is 100, how the concentration changes over time is determined.

The elapsed time of 0 minutes is when the foamed particles are placed in a wide mouth bottle and the lid is placed on the bottle.

From FIG. 1, it can be seen that the foamed particles of Example 1 have better adsorption and deodorization properties than the foamed particles of Comparative Example 1.

Furthermore, when the cushioning properties were evaluated using the in-mold foam molded products obtained in Example 1 and Comparative Example 1, there was no difference.

[Effects of the invention] The foamed particles of the present invention can be used as a cushioning material with excellent deodorizing properties and freshness retention properties, and the in-mold foam molded product of the present invention can be used as a cushioning packaging material with excellent deodorization properties and freshness retention properties. It can be used as such.

The expanded particles of the present invention can also be produced by the method of the present invention.

[Brief explanation of the drawing]

Figure 1 shows the results of Examples 2 to 4 and Comparative Examples 2 to 4, in which the gas adsorption performance of the expanded particles obtained in Example 1 and Comparative Example 1 to ammonia gas, ethylene gas, and trimethylamine gas was evaluated. It is a graph. Figure 1 Elapsed time (minutes)

Claims (1)

[Scope of Claims] 1. Polyolefin resin foam particles containing 5 to 50% by weight of zeolite and having gas adsorption ability. 2. A molded article formed from the expanded particles according to claim 1. 3 Polyolefin resin particles containing 5 to 50% by weight of zeolite and a volatile blowing agent are dispersed in water in the presence of a dispersant in a pressure-resistant container, heated and heated to a high temperature and high pressure state, and then A method for producing foamed polyolefin resin particles having gas adsorption ability, which comprises blowing the particles into a low pressure region through a discharge port provided at the bottom of a container.