JPH03224438A - Resin molded product for retaining freshness - Google Patents

Abstract

PURPOSE:To provide the subject molded product having a good molded shape, excellent safety, and ethylene-treating functions (absorption and decomposition) by employing a thermoplastic resin containing a palladium compound carried on carbon black. CONSTITUTION:The objective molded product comprises a thermoplastic resin (preferably low density PE) containing a palladium compound (preferably palladium chloride) carried on carbon black (preferably having a specific surface area of 150-400m<2>/g measured by BET method).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin molded article useful for preserving the freshness of fruits, vegetables, and flower petals. More specifically, the present invention relates to a resin molded article for preserving the freshness of fruits and vegetables, which has a function of treating (absorbing, decomposing, etc.) ethylene, which is a cause of deterioration in the freshness of fruits and vegetables, in order to maintain the freshness of fruits and vegetables.

[Prior Art] When fruits and vegetables respire, they generate ethylene, which is a plant ripening and aging hormone, and this promotes the ripening of fruits and vegetables. In particular, in sealed packaging, the ethylene concentration inside the package increases and significantly accelerates the ripening of fruits and vegetables, causing them to age, discolor, or soften at an early stage.
There is a problem that the product value decreases. Currently, in order to prevent such problems caused by ethylene, various ethylene absorbents that process (absorb, decompose, etc.) ethylene have been developed and used.
No. 750), potassium permanganate (JP-A-55-15)
4901, 56-18901, 56-68346), bromine-impregnated carbon (Japanese Patent Publication No. 57-39149), palladium chloride-supported activated carbon (Japanese Patent Publication No. 61-25340), and the like. However, activated carbon and zeolite have strong water adsorption properties, so when preserving fruits and vegetables that coexist with water, their ethylene adsorption ability decreases significantly due to water adsorption.
In addition, due to the low ethylene adsorption capacity at low ethylene concentrations,
It has poor ethylene processing ability and is insufficiently effective as a freshness-preserving agent. Since potassium permanganate contains heavy metals, it is extremely dangerous to use in food due to its toxicity and explosive properties. Bromine-impregnated carbon is not suitable for food use because bromine and ethylene react to produce ethylene tribromide, which is carcinogenic. In the case of palladium chloride-supported activated carbon, although there is no problem with toxicity, the ethylene processing rate is slow and the activated carbon carrier has a strong water adsorption ability, so in actual use, the ethylene processing capacity is significantly reduced and the effectiveness is lost. That's enough. As described above, current ethylene absorbents have problems in terms of performance and safety. On the other hand, when using freshness-preserving agents, there is the problem of having to insert them into containers containing fruits and vegetables, which is a time-consuming problem, so there is a desire for the development of freshness-preserving materials such as containers and films that can process ethylene. There is. For example, a synthetic resin film containing crystalline zeolite with a particle size of 20 μm or less (Japanese Unexamined Patent Publication No. 6
3-309137), a freshness-preserving film containing Oya stone with ethylene absorption capacity (Japanese Patent Application Laid-Open No. 62-18403)
No. 5), a freshness-keeping film for fruits and vegetables in which activated carbon (brominated activated carbon) capable of decomposing and adsorbing ethylene is dispersed and contained in a thermoplastic synthetic resin (Japanese Patent Application Laid-Open No. 110186/1986) has been reported. However, there are problems with the performance and toxicity of the ethylene absorbent itself, and the particles of the absorbent are coated with resin, which significantly reduces the ethylene processing ability.
Since the particles are large), problems arise in moldability, and it is difficult to obtain containers etc. that have a sufficient freshness-keeping effect.

[Problem to be Solved by the Invention 1] As a result of intensive study by the present inventors on a new freshness-preserving material that overcomes all the problems of conventional freshness-preserving materials, such as toxicity, ethylene processing ability, and moldability, The inventors have discovered that a freshness-preserving resin molded article free from the above-mentioned problems can be obtained by incorporating carbon black carrying a palladium compound as an ethylene absorbent into a thermoplastic resin, and have arrived at the present invention.

[Means for Solving the Problems] That is, the gist of the present invention resides in a freshness-preserving resin molded article characterized by being made of a thermoplastic resin containing carbon black supporting a palladium compound.

The present invention will be explained in more detail below.

Examples of the palladium compound in the present invention include palladium chloride, palladium bromide, palladium nitrate, palladium sulfate, and palladium acetate, with palladium chloride being particularly preferred. Carbon black, which supports palladium compounds, is a particle obtained by thermally decomposing gaseous or liquid hydrocarbons or heavy oil, and is usually composed of several layers of aromatic planar molecules gathered together to form a turbostratic structure. A complex collection of crystals forms a type of amorphous carbon primary particle, and these primary particles are connected in a chain to form a structure called a strafe.

There are no particular restrictions on the method for producing carbon blanks, but examples include furnace black, lamp black, thermal blank, acetylene black, roller blank, disk blank, heavy oil decomposition byproduct carbon black, and the like. As for the quality of the carbon black used in the present invention, it is preferable that it has a certain specific surface area, and in particular, BE
The specific surface area measured by the T method is 1000 m2/g or less, preferably 100 to 800 m2/g, more preferably 150 to 500 m2/g, particularly preferably 150 to 500 m2/g.
400 m2/g. Furthermore, the oil absorption amount of dibutyl phthalate (DBP), which indicates the physical properties of carbon blank, is 50.
~400 ml/100g, preferably 100-3
00 ml/100g, more preferably 150-2
A range of 50 ml/100 g is preferably used. Further, the secondary particle size is about 10 to 300 mμ, preferably 15 to 80 mμ, more preferably 20 to 80 mμ.
A material with a diameter of 40 mμ is used.

In the present invention, carbon black carrying a palladium compound is used as an ethylene absorbent.

The loading method is to use a palladium compound containing a concentration of 0.
A carbon blank is poured into an aqueous solution of 1 to 5 N mineral acid, such as hydrochloric acid, nitric acid, sulfuric acid, etc., stirred to adsorb the palladium compound, filtered, and heated to 110 to 300°C.
A palladium compound-supported carbon blank is obtained by drying the carbon blank. The amount of palladium compound supported is 0.05 to 10% by weight, preferably 0.1% by weight in the ethene absorbent consisting of carbon black and palladium compound.
~5% by weight. If the supported amount is too small, a sufficient ethylene removal effect cannot be obtained, and if it is too large, the effect will not increase in proportion to the increased supported amount, resulting in a decrease in usage efficiency.

In the present invention, the above-mentioned ethylene absorbent is contained in a thermoplastic resin to form a resin molded article.

Examples of the thermoplastic resin include, but are not particularly limited to, polyolefin resins such as polyethylene, polypropylene, and poly4-methylpentene-1, polystyrene, and AB8.
Polystyrene resins such as polyvinyl chloride, polyvinyl acetate, polymethyl methacrylate, etc.
Typical examples include polyamide resins such as nylon 6 and nylon 12, and polyester resins such as polyethylene terephthalate and polybutylene terephthalate. Alternatively, these may be used as a blend. In view of the ethylene processing ability of a resin molded article containing an ethylene absorbent, polyolefin resins are preferred, and low-density polyethylene is particularly preferred. The content of the ethylene absorbent is usually 0.1 to 30% by weight, preferably 1 to 20% by weight based on the thermoplastic resin. If it is less than 0.1% by weight, there is no sufficient ethylene processing capacity, and if it is more than 30% by weight, molding becomes difficult.

Examples of molded objects include films, sheets, trays, bags, boxes, containers, and the like. The composition of the present invention can be molded by mixing an ethylene absorbent into the resin and using a known resin molding method. For example, when molding into a film or sheet, Banbury type mixer - shaft or multi-shaft kneading. The ethylene absorbent can be uniformly kneaded with a resin using a machine or the like, and then processed into a film or sheet by a conventional molding method such as an inflation method, a T-die method, or a calendar method. At this time, multilayering may be performed by coextrusion or lamination with other films or sheets in order to provide strength or other functions.

In addition, in order to increase the ethylene processing ability of the molded product, it tends to be preferable to have a low cross-wire shear rate when kneading the ethylene absorbent and resin, so the kneading speed should be selected appropriately depending on the cross-mixing machine used. Bye.

Alternatively, a mixture of an ethylene absorbent and a resin may be foamed to form a molded product. Conventional foaming methods can be used; for example, chemical foaming agents that decompose to generate nitrogen gas, or physical foaming that uses easily volatile liquids such as butane, pentane, xane, and halogenated carbon, can be used. Examples include a method of extrusion molding the agent together with an ethylene absorbent-containing resin.

Note that plasticizers, heat stabilizers, antioxidants, fillers, lubricants, anti-blocking agents, ultraviolet absorbers, colorants, modifiers, etc. that are usually added to resins can be used as necessary. Further, antifogging agents, antibacterial agents, etc. used in food packaging materials may also be used at the same time.

The resin molded product thus formed usually contains particles with a particle size of 0.1 to
There are fine particles of 10 μm consisting of an ethylene absorbent and a resin, but in order to increase the ethylene processing ability, it is preferable to expose these fine particles as much as possible on the surface of the molded product. For example, when molded into a film, it is preferable to It is preferable to stretch the film.

The thus obtained freshness-preserving molded product is molded into a film, sheet, bag-like object, container, etc., and can easily preserve the freshness of fruits and vegetables. [Example] Examples are given below. The present invention will be explained in more detail below, but the present invention is not limited to these Examples.

Example 1 Carbon black #3250 (manufactured by Mitsubishi Kasei Corporation,
Particle size 28mH1 Specific surface area 240BET -m2/g
, DBP oil absorption 180ml/100g) 66.6g
1 N aqueous hydrochloric acid solution containing 666 mg of palladium chloride 6
00ml and stirred for 1 hour to adsorb the palladium compound onto the carbon blank. After that, the carbon black was separated into a furnace at 200°C under a nitrogen stream (330mlN2/m
m) for 1 hour to obtain carbon black carrying about 1% by weight of palladium. This was used as an ethylene absorbent (hereinafter abbreviated as EA). This EA and low density polyethylene (
F131) manufactured by Mitsubishi Kasei Corporation is a pulverized product with an EA content of 20.
% by weight, and a twin-screw kneading extruder (TEM).
-35B) at a resin temperature of 250°C to obtain a masterbanochiperent. At this time, the extruder screw outer speed was 46 cm/sec and the extruder was a high shear mixed tile (hereinafter referred to as H
Two types of masterbatches were obtained: one with low shear kneading of 9.2 cm/see (abbreviated as below) and one with low shear kneading of 9.2 cm/see. Each masterbatch was mixed with low-density polyethylene pellets (Mitsubishi Kasei)
Co., Ltd. F131), EA content 5% by weight, 10
% by weight and 20% by weight using the inflation method to produce 6 types of freshness-preserving films with a thickness of 301.1 m (
Examples 1-a to 1-f) were obtained. All of the films had good molding stability and were of good quality with little thickness unevenness.

Comparative Example 1 Low-density polyethylene (Mitsubishi Kasei Corporation F131) pellets were molded using the same inflation method as in Example 1,
A film with a thickness of 30 μm was obtained.

Comparative Example 2 10% by weight of the pulverized Oya stone product (passed through 250 mesh) was processed into low density polyethylene (Mitsubishi Kasei Corp. F1) in the same manner as in Example 1 using an extruder screw peripheral speed of 46 cm/sec.
31) was mixed in an amount of 5% by weight, and a film with a thickness of 30 μm was obtained by an inflation method.

Experiment-1 Ethylene processing ability test> Example 1. -6 types of films from -a to 1-f and Comparative Example 1
The ethylene processing capacity of the films No. 2 to 2 was measured by the following method.

Examples 1-a to 1 were added to glass flasks with an internal volume of 2e.
- Put each film in an amount with a palladium content of 100 mg, or the films of Comparative Examples 1 and 2 of the same mass as these, put in a 30 ml glass container containing distilled water, seal it, and leave it at 23°C for 24 hours. did. After 2 ml of ethylene gas was introduced into the tank to bring the internal ethylene concentration to 11,000 pp, the internal gas was sampled at regular intervals, and the ethylene concentration was determined by gas chromatography to examine its change over time. The ethylene treatment M (cumulative value) of each freshness-preserving material was determined from the change in ethylene concentration, and the results are shown in FIG.

Experiment-2 Tomato Freshness Retention Test> Two tomatoes (400 g) were placed in a rectangular box made of wire measuring 20 cm x 11 cm x 21 cm, and each of Examples 1-a to 1-f and Comparative Examples 1 to 2 was placed on top. Wrapped in film and sealed with heat seal (film area 1720cm)
m. After storing this in an environment of 23°C for 9 days, the quality of the tomatoes was inspected. The ripeness was examined and the results are shown in Table 1.

Experiment-3 Broccoli freshness retention test Pro saw in the same way as Experiment-2. Example of No 300g 1-a to 1-f and Sealed with each film of Comparative Examples 1 and 2 After storage at 5°C for 10 days, quality evaluation was performed.

result are shown in Table 2.

Table 2 *1: Visual judgment 1 - Dark green 2 - Green 3 - Pronoco 4 - Pronoco 5 - Yellow 30% of the surface of No is yellow J - 60% of the surface is yellow [Effect of the invention 1 Freshness preservation of the present invention The resin molded product contains carbon black supporting a palladium compound as a freshness-preserving agent, so it has good moldability, safety, and ethylene treatment performance that is significantly superior to conventional products and maintains sufficient freshness. It is extremely useful because of its effectiveness.

[Brief explanation of drawings]

FIG. 1 shows the processing ability of each freshness-preserving material used in the examples. The vertical axis represents the amount of ethylene processed (cumulative value) [m months], and the horizontal axis represents the number of days that have passed.

Claims (1)

[Claims] A freshness-preserving resin molded article made of a thermoplastic resin containing carbon black supporting a palladium compound.