JPH07113028A - Ionomer composition and production thereof - Google Patents

Abstract

PURPOSE:To obtain the composition excellent in optical properties, mechanical strength and biodegradability and useful for a molded article, e.g. film by compounding an ionomer of a specific ethylene-unsaturated carboxylic acid copolymer with starch or its derivative at a specific ratio. CONSTITUTION:The composition is composed of (A) 50-97wt.% of an ionomer of ethylene-unsaturated carboxylic acid copolymer (preferably, the copolymer ionomer consisting of 75-90wt.% of ethylene, 10-25wt.% of an unsaturated carboxylic acid and 0-20wt.% of another monomer) containing a 1-3 valent metal (alkali metal, e.g. Na or K is preferable from a transparency point of view) as an ion source, (B) 3-50wt.% of starch or its derivative and preferably further (C) a compatibilizing agent (e.g. polyalkylene polyol). The above mentioned composition is obtained, e.g. by kneading a molten ionomer with a past-state starch or its derivative.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a homogeneous composition comprising an ionomer and starch (starch) or a starch derivative, and a method for producing the same. More specifically, it relates to an ionomer composition having excellent optical properties, mechanical strength, biodegradability and the like, which is useful for the production of films and other molded articles, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, reducing the amount of resin waste has become a major issue from the viewpoint of global environmental protection. In order to solve this problem, interest in biodegradable resins is increasing along with resin recycling and use regulations, and development is being promoted. Known techniques for imparting biodegradability to resins include microbial utilization, natural product utilization, and synthetic polymer utilization. Among natural resin, starch is economical, widely available and rapidly biodegraded, so research is progressing. Starch consists of amylose, which is a long-chain molecule with a molecular weight of tens of thousands, and amylopectin, which has a large number of branches and a molecular weight of hundreds of thousands, and is difficult to crystallize and does not exhibit thermoplasticity, so it is impossible to make plastics from starch alone. is there.

When starch is blended with polyethylene, the higher the starch content, the faster the decomposition rate, but the mechanical strength is greatly reduced and the optical properties are poor. This is because the starch particles are not completely compatible with the resin as a homogeneous phase, so that the renewal force at the interface between the starch particles and the resin is not sufficient and the strength decreases.

[0004] A method has been proposed in which starch particles are treated with silicone to make them hydrophobic so as to improve compatibility with a resin, but the resulting composition has insufficient physical properties. As a method of mixing starch and a resin with good compatibility, a system composed of ethylene / acrylic acid copolymer (EAA) and starch has been proposed. This system is suitable for film molding but not for injection molding.

As a further quality improvement measure, EA is added with a sufficient amount of ammonia, amine, etc. to neutralize the acid groups of EAA.
In addition to the A-starch system, it has been proposed to improve moldability. Also, an improved method has been proposed in which the presence of urea destroys the crystal structure of starch with a small amount of water, thereby eliminating the need to use large amounts of water in mixing with EAA. However, although the production conditions are improved by these methods, the mechanical strength of the obtained composition is not sufficiently satisfactory. Further, in a system in which ammonia, amine or the like is added, there is a drawback that workability is deteriorated due to an amine odor.

[0006]

Therefore, in the present invention, investigations were made to improve the above-mentioned physical properties and processing defects and difficulties. As a result, it has been found that a desired improvement can be achieved in an addition system of an ionomer of an ethylene / unsaturated carboxylic acid copolymer using a metal as an ion source and starch or its derivative. Therefore, an object of the present invention is to provide a starch-added resin having excellent uniformity, transparency and mechanical properties.

[0007]

DISCLOSURE OF THE INVENTION The present invention comprises 50 to 97% by weight of an ionomer of an ethylene-unsaturated carboxylic acid copolymer using a monovalent metal as an ion source and 3 to 50% by weight of starch or its derivative. And an ionomer composition comprising The above composition is produced by kneading a melt of an ionomer and a pasty starch or starch derivative, and a compatibilizer can be added during the production.

[0008]

In the present invention, an ethylene-unsaturated carboxylic acid copolymer ionomer having a monovalent metal to an ion source as an ion source is selected and blended with starch or a derivative thereof to uniformly knead both. It becomes possible and the moldability thereof can be improved, and it is possible to provide a composition which is excellent in optical properties, mechanical strength, biodegradability and the like and which is useful for the production of films and other molded articles.

The above-mentioned improvement will be apparent from the description of the examples described later, and in the case of an ethylene-unsaturated carboxylic acid copolymer containing no metal ion, when blended with starch, the mechanical strength is low and the haze is large. On the other hand, when an ethylene-unsaturated carboxylic acid copolymer ionomer having a metal as an ion source is blended, the mechanical strength is remarkably improved and Haze is suppressed to a small value.

The reason for this is presumed that the hydroxyl group of starch or its derivative and the metal ion or carboxyl group of the ionomer are chemically bonded to each other to improve the compatibility between the ionomer and the starch. This also allows
It is considered that the obtained resin composition has improved mechanical properties and optical properties.

The mixing ratio of the ionomer and starch or starch derivative is 50 to 97% by weight of the former, preferably 60 to 95% by weight, and 50 to 3% by weight of the latter, preferably 40 to 5%.
It is preferable to set it in the range of wt%. If the amount of starch or starch derivative is less than the above range, it does not have sufficient biodegradability, and conversely, if the amount is too large, transparency and mechanical strength are impaired, which is not preferable.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The ethylene-unsaturated carboxylic acid copolymer ionomer used in the present invention has a structure in which a carboxylic acid is partially or completely neutralized with a metal ion, and optionally vinyl acetate or acrylic acid. It may be a copolymer of other monomers such as methyl, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, methyl methacrylate, methacrylic acid and isobutyl.

The ionomer preferably has a carboxylic acid moiety content of 5 to 90 mol%, particularly preferably 2 mol%.
What is neutralized from 0 to 85 mol% is used. Here, considering the compatibility with starch, the metal ion is Li, N
Metals having a valence of 1 to 3, such as a, K, Mg, Ca, and Zn, particularly alkali metals such as Na and K are preferable in terms of transparency. Of course,
Other metals may also be used when transparency is not required.

Examples of the unsaturated carboxylic acid component in the ionomer include acrylic acid, methacrylic acid, monomethyl maleate, maleic anhydride and the like, but acrylic acid or methacrylic acid is particularly preferable. The ionomer may be one kind, or two or more kinds having different compositions, melt flow rates and the like may be used.

The ethylene / unsaturated carboxylic acid copolymer has a composition of 60 to 97% by weight of ethylene, preferably 75 to 90% by weight, and 3 to 30% by weight of unsaturated carboxylic acid, preferably 10 to 25% by weight. %, Other monomers are 0
Preference is given to using copolymeric ionomers having a weight unit of -30% by weight, preferably 0-20% by weight. When two or more ionomers are used, one or more ionomers different from the above composition may be used as long as the average polymerization composition falls within the above range.

When the unsaturated carboxylic acid content in the ethylene / unsaturated carboxylic acid copolymer is less than 3% by weight,
It is difficult to mix uniformly with starch or starch derivative, and it is difficult to obtain a composition having excellent transparency. Further, when the ionomer having a very small degree of neutralization is used, it is difficult to obtain a composition having a good transparency in the same manner.
The ionomer has a melt flow rate of 0.1 to 100 g / 10 min, especially 0.2 at 190 ° C. and a load of 2160 g, though it varies depending on the purpose of use of the composition.
It is preferable to use the one of about 20 g / 10 min.

The starch used in the present invention generally includes natural products, mainly starches composed of amylose and amylopectin derived from plants such as corn, potato, wheat and rice. The water content of starch is about 15 wt% for natural products, but it is not necessary to use dry products. Silicone treatment as starch,
Various modified starch derivatives such as cross-linking and water-solubilization can also be used. An example is carboxymethylated starch.

A compatibilizing agent may be added to the ionomer composition of the present invention for the purpose of, for example, improving the compatibility of starch with the ionomer and improving the chemical bonding, although it is not essential. As the compatibilizer, a polyalkylene polyol rich in polar groups,
Examples thereof include urea as a starch modifier, ammonia and water for the purpose of neutralizing an unsaturated carboxylic acid that has not been neutralized to metal ions.

The method for producing the resin composition of the present invention is not particularly limited, and the resin composition is manufactured by melt-kneading a mixture of an ionomer and starch with a Banbury mixer, an extruder or the like. In this production, in order to uniformly mix the starch or starch derivative and the ionomer, it is desirable that the starch is partly or wholly pasted with water in advance or during the kneading of the ionomer. For example, 60 ℃
The starch can be gelatinized by heating and stirring the starch in the presence of hot water.

The melt-kneading of the ionomer and the starch or starch derivative can be carried out at a temperature of about 100 to 180 ° C., for example. It is assumed that this step causes a chemical bond between the hydroxyl group of starch and the metal ion or carboxyl group of the ionomer to improve the compatibility of the ionomer and starch. As a result, the optical characteristics of the obtained resin composition are excellent.

The proportion of the ionomer and the starch or starch derivative is 50 to 97% by weight, preferably 60 to 95% by weight, and 50 to 3% by weight, preferably 40 to 5%, for the latter.
It is in the range of% by weight. If the amount of starch or starch derivative is less than the above range, it does not have sufficient biodegradability, and conversely, if the amount is too large, transparency and mechanical strength are impaired, which is not preferable.

The resin composition of the present invention can be mixed with other thermoplastic resins such as polyethylene and polypropylene to improve the performance as long as the object of the present invention is not impaired. In addition, antioxidants, pigments, weathering stabilizers, ultraviolet absorbers, slip agents, antiblocking agents, inorganic fillers,
Various commonly used additives such as flame retardants can be added.

[0023]

【Example】

Examples 1 to 6 and Comparative Examples 1 to 3 Powdered corn starch (manufactured by Kanto Chemical Co., Inc.) was added with the same amount or more of hot water (80 to 90 ° C.) and stirred for 2 to 3 minutes,
Gelatinized. Toyo Seiki Co., Ltd. Labo Plastomill (100
(ml volume), pasty starch, raw material resin [and compatibilizer (polyethylene glycol # 600, manufactured by Kanto Kagaku Co., Ltd.)] were added at the ratio shown in Table 1, and 140 ° C. and 60 rpm for 15 minutes. Kneaded It was stable after the torque was increased due to the evaporation of water and the chemical bond between the starch and the ionomer (each example). Remove the mixture from the Labo Plastomill and press 160
0.5mm by hot press molding at ℃, 50kg / cm ²
A thick sheet was obtained. The results of physical property measurements are also shown in Table 1.

The following materials were used as raw material resins. (1) Ionomer: Metal Partially Neutralized Ionomer of Ethylene-Methacrylic Acid Copolymer Methacrylic Acid Content Ion Species Neutralization Degree MFR (wt%) (%) (g / 10 min) Ionomer 1 15 Zn 60 0.7 Ionomer 2 15 Na 60 0.9 Ionomer 3 15 Na 30 2.8 Ionomer 4 12.5 K 82 0.4

(2) Thermoplastic resin other than ionomer Low density polyethylene: M16 MFR 3.7 g / 10 min Mitsui Petrochemical Co., Ltd. ethylene-methacrylic acid copolymer: Methacrylic acid content MFR (wt%) (g / 10 minutes) Copolymer 1 10 35 Copolymer 2 15 60 Copolymer 3 20 60

The physical properties were measured by the following methods. (1) MFR JIS K6760 (2) Optical characteristics JIS K7105 (3) Breaking point strength JIS K6760 The results are shown below.

[0027]

[Table 1]

[0028]

According to the present invention, a uniform mixture of an ionomer and starch or starch derivative can be provided. In particular, when an alkali metal ionomer is used as the ionomer, a composition having excellent transparency and mechanical strength can be provided. Further, when the polyvalent metal ionomer is used, the optical properties are inferior to those using the alkali metal ionomer, but the breaking strength is the same.

The degree of biodegradability of such a composition can be adjusted according to the content of starch or starch derivative.
By making use of such features, it is possible to mold various molded products. For example, it can be formed into a film, a sheet, a tube, a tube, a filament, various other extrusion molded products, injection molded products, hollow molded products, press molded products, vacuum molded products and the like. In these molded articles, it can be used as one or more layers having a multilayer structure. The film can be used for applications such as agricultural films and various packaging films.

Claims (3)

[Claims] 1. An ethylene / unsaturated carboxylic acid copolymer ionomer having an ion source of a monovalent to trivalent metal, 50 to 97.
An ionomer composition comprising 3% by weight and 3 to 50% by weight of starch or starch derivative. 2. The ionomer composition according to claim 1, which further comprises a compatibilizer. 3. The method for producing an ionomer composition according to claim 1, wherein a melt of the ionomer and a pasty starch or starch derivative are kneaded.