JP3045534B2 - Biodegradable resin composition and product thereof - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a biodegradable and photo-degradable resin composition, and more specifically to an antioxidant which depends on commonly used starch and nature. (Hereinafter also referred to as an antioxidant) to provide a composition whose biodegradability has been accelerated by several steps and a product comprising the composition.

(Prior art)

In recent years, as the amount of plastic used has increased, the environmental pollution problem caused by plastic waste has rapidly increased, and its disposal method has become a problem.

The processing of these plastic wastes, which came conventional incineration primarily with such premature failure of the incinerator is a problem with respect to deterioration of environmental pollution due to the release gas such as carbon dioxide, NO _x, regulation both at home and abroad Is getting tougher.

On the other hand, biodegradable resins that are degraded by living organisms, photodegradable resins that are degraded by light, and resin compositions thereof have been proposed when the plastic waste is buried or dumped in soil.

For example, a resin composition containing starch has been put to practical use so as to exhibit biodegradability when actually buried or dumped in soil (JP-B-52-42187, JP-B-60-4).
No. 1089, Japanese Patent Publication No. 52-21530). However, simply blending the starch into the resin significantly reduces the inherent properties of the resin and makes it unpractical,
The problem that only starch is decomposed by living organisms, and the resin portion remains without being decomposed, has not been solved.

In addition, in order to prevent deterioration during molding and prolong the service life of the thermoplastic resin, various antioxidants are blended, or to improve slipperiness, or in the case of polyolefin. Various additives are blended, for example, metal soap or the like is added to inactivate the remaining catalyst. In addition, phenolic and thioether-based antioxidants usually used in thermoplastic resins have the drawback of significantly delaying biodegradation, and metal soaps also slow biodegradation.

On the other hand, a photo-degradable resin or a photo-degradable resin composition which is decomposed by light when discarded is a transition metal which introduces a C ＝ O group having photosensitizing properties into a molecule or promotes photodegradation. It is manufactured by a method of blending.
However, recent reports have shown that if the molecular weight of the resin is not reduced to about several hundreds by collapse, it will not be degraded by natural organisms and will not completely disappear, thus causing secondary pollution. Have been.

Further, conventionally, alkylphenol compounds are generally used as stabilizers for polyolefin resins, and among them,
2,6-Di-t-butyl-p-cresol (BHT) is widely used, but recently, the safety of these phenolic compounds on human bodies has been regarded as a serious problem, and particularly, food packaging, toys, and medical devices. Stabilizers for polyolefin resin products used in such applications are becoming a major social problem.

[Problems to be solved by the invention]

The present invention solves the above-mentioned problems, and promotes the degradability of a conventional biodegradable composition, and improves the stability during molding (reduction in physical properties due to oxidative deterioration during resin processing). Prevention) can be improved.

Another object is to reduce secondary pollution by blending a specific additive into the photo-degradable resin or the photo-degradable resin composition to further decompose the photo-degraded resin by living organisms in the natural world and completely eliminate it. It is to provide a biodegradable composition that can be prevented.

Another object of the present invention is to provide a biodegradable resin composition capable of preventing foaming of a molded article or the like which is considered to be caused by blending of a hygroscopic starch or a modified product thereof.

Further, the present invention provides a product such as a film using the above composition, which is suitable for food packaging and the like, and has biodegradability and photodisintegrability.

[Means for solving the problem]

A feature of the present invention is a biodegradable thermoplastic resin composition obtained by blending (a) starch or a modified product thereof and (b) a natural antioxidant or a synthetic product corresponding thereto with a thermoplastic resin. is there.

Another feature of the present invention is that the thermoplastic resin comprises (a) starch or a modified product thereof, (b) a natural pore antioxidant or a synthetic compound corresponding thereto, and (c) a fatty acid ester.
A biodegradable thermoplastic resin composition comprising at least one compound selected from (d) an organic carboxylic acid and (e) a moisture absorbent.

Still another feature of the present invention is that the photodegradable resin or the photodegradable resin composition comprises (a) starch or a modified product thereof,
(B) natural antioxidants or synthetic equivalents thereof,
And a biodegradable resin composition comprising, if desired, at least one compound selected from (c) a fatty acid ester, (d) an organic carboxylic acid, and (e) a moisture absorbent.

Still another feature of the present invention is a biodegradable thermoplastic resin composition obtained by blending (a) starch or a modified product thereof with (b) a natural antioxidant or a synthetic product corresponding thereto, to a thermoplastic resin. It is a product molded from a product.

The present invention particularly provides a biodegradable resin composition obtained by adding the components (a) and (b) to a photo-degradable resin or a photo-degradable resin composition, and a resin molded using the biodegradable resin composition. It is about products.

 Hereinafter, the present invention will be described more specifically.

The thermoplastic resin used in the present invention corresponds to a general thermoplastic resin and is not particularly limited. That is, ethylene, propylene, 1-butene, 4
-Polyolefin resin composed of a homopolymer or mutual copolymer of α-olefins such as methylpentene-1 or a copolymer of these α-olefins and other comonomers; polystyrene resin; ABS resin; polyvinyl chloride Polyvinylidene chloride-vinyl copolymer resin; Polycarbonate resin; Polyester resin; Polyamide resin; Polyphenylene oxide resin; Polyvinyl alcohol resin (saponified ethylene-vinyl acetate copolymer); Polyurethane resin; Polyether resins; rubbers such as natural rubber, isoprene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, and mixtures thereof; Among these, high-medium density polyethylene, linear low-density polyethylene by high-medium-low pressure method, ultra-low density polyethylene,
Polyethylene resins such as low-density polyethylene by high-pressure radical polymerization, ethylene-vinyl ester copolymers such as ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid copolymer, and ethylene- (meth) acrylate Ethylene and unsaturated carboxylic acids represented by ethylene- (meth) acrylate copolymers such as copolymers, ethylene-ethyl (meth) acrylate copolymer, ethylene-propyl (meth) acrylate copolymer Or an ethylene-based polymer such as a copolymer with a derivative thereof; polypropylene, a propylene-based polymer such as a copolymer of propylene and ethylene, and polystyrene.

The photodisintegrable resin referred to in the present invention is a resin in which a carbonyl group or the like is introduced as a photosensitizing group into a main chain during polymer polymerization, and specifically, an ethylene-containing resin comprising ethylene and a small amount of carbon monoxide. Examples include a carbon monoxide copolymer (ECO copolymer), an ethylene-vinyl ketone copolymer, and a styrene-methyl vinyl ketone copolymer.

Examples of the photo-degradable resin composition include a resin composition containing the photo-degradable resin or an additive having a photosensitizing effect. As an additive having a photosensitizing effect,
In addition to the photosensitizer, a transition metal salt, an oxidation promoter and the like can be mentioned. For example, compounds containing transition metal salts such as iron, nickel, cobalt and cerium, and UV such as cerium stearate
A sensitizer or the like is preferably used.

The starch (a) or a modified product thereof used in the present invention is starch obtained from rice, corn, potato, sweet potato, wheat, or the like, or a product obtained by grafting a polymerizable monomer such as styrene to the starch, or coating silicon. And at least one of those modified with an organic substance such as lactose, glucose or the like, a sugar as a main component, molasses, casein or the like which the organism prefers to take.

(A) The amount of starch or a modified product thereof (hereinafter, simply referred to as starch) is 2 to 60% by weight, preferably 3 to 50% by weight, more preferably 3% by weight, based on the photo-degradable resin or the photo-degradable resin composition. Ranges from 5 to 40% by weight. If the amount of starch is 2% by weight or more, the biodegradability gradually increases as the amount increases. However, if it exceeds 60% by weight, the physical properties of the resin are greatly reduced, and practically effective physical properties cannot be exhibited. For example, depending on the thickness of the molded product, 5 to 20% by weight, preferably 6% by weight in the case of a film.
Satisfactory results are obtained with a loading of ~ 15% by weight.

The (b) natural antioxidant or a synthetic product corresponding thereto used in the present invention is a product originally extracted from a compound existing in a natural product, or a product including a synthetic product corresponding to these natural products. And, for example, α-, β-, γ-,
Tocophenols (vitamin Es) such as δ-tocopherol and dimers thereof; vitamin B groups such as B ₁ , B ₂ and B ₆ and derivatives thereof; vitamin K groups such as K _{1 to} K ₇ And derivatives thereof.

Among them, vitamins such as vitamins E and K are particularly preferred in terms of suppressing oxidative deterioration of the photo-degradable resin or the photo-degradable resin composition and having high thermal stability.

The inventors added tetrakis- [methylene-3- (3,5-di-t-butyl-4'-hydroxyphenyl) propionate] methane, a phenolic antioxidant usually added to polyolefin resins. Resin composition, and dilauryl thiodipropionate (DL) which is a typical thioether-based antioxidant for the resin composition.
A test was conducted by adding starch to the resin to which TDP was added and burying it in the soil, but the disintegration rate was very slow, and the effect of adding starch was not observed. The above thioether-based antioxidant is a peroxide decomposer, and the addition thereof suppresses the rate of autoxidation occurring in a living body system, so that the biodegradation is considered to be slow. On the other hand, in the composition to which a natural antioxidant such as the above vitamins was added, progress of biodegradation was recognized, and the present invention was achieved based on this.

The compounding amount of the component (b) of the present invention is added in the range of 0.03 to 3% by weight. If the amount is less than 0.03% by weight, the antioxidant effect is insufficient, and if it exceeds 10% by weight, the antioxidant effect does not change. In particular, since the antioxidant of the present invention is a natural product or a synthetic product corresponding thereto, it is most suitable for food packaging and medical use without toxicity. Therefore, in some cases, the surface of a product such as a film can be coated (including application / lamination) to prevent oxidative decay of food.

The resin acid ester (c) used in the present invention may be a natural fat or oil itself (triglyceride), or may be a fat or oil modified by epoxidation or the like to enhance compatibility with the resin. Further, diglycerides and monoglycerides obtained by partially hydrolyzing fats and oils may be used.

In the present invention, the purpose of blending the component (c) is to increase the compatibility between starch and the resin to prevent a decrease in the physical properties of the composition, and to further increase the biodegradability. First,
By adding the component (c) to the starch, the lipophilicity of the starch can be increased, and the performance inherent in the resin in the composition can be maintained. Next, when starch, a thermoplastic resin composition containing vitamins and fatty acid esters is buried in the soil, at the interface between the composition and the soil, by the promoting action of transition metals such as iron present in the soil, The autoxidation of the fatty acid ester occurs, and the resulting hydroperoxide causes the decomposition of the resin component. In addition, fatty acid esters are easily taken into living bodies in soil and are decomposed by microorganisms and enzymes, thereby promoting biodegradation.

In the present invention, it is desirable that the component (c) is preliminarily mixed with the starch. This results in a surface treatment of the starch, which increases the lipophilicity of the starch, thereby increasing the affinity between the starch and the resin and preventing the physical properties from being reduced by the addition of the starch.

The compounding amount of the component (c) is in the range of 0.05 to 10% by weight. If the blending amount is less than 0.05% by weight, the blending effect is not exhibited. If the amount is large, the biodegradability is enhanced, but if added in excess of 10% by weight, the frictional resistance with the extruder during molding of the composition becomes very small, and the resin becomes slippery, and the solid in the extruder becomes solid. Since transport becomes impossible, there is a possibility that molding cannot be performed.

(D) The organic carboxylic acid used in the present invention is formic acid,
Acetic acid, propionic acid, butyric acid, caproic acid, enanthic acid,
Examples include organic acids or saturated fatty acids such as caprylic acid, malic acid, citric acid, tartaric acid, gluconic acid, and lactic acid, and unsaturated resin acids such as oleic acid and fumaric acid, with aliphatic carboxylic acids being particularly preferred.

Usually, when a film is formed by extrusion using a photo-degradable resin or a photo-degradable resin composition to which starch has been added, eye-like shapes accumulate on the die surface, making continuous operation difficult. Conventionally, in such a case, a method of adding a metal salt of a resin to the resin to eliminate friction between the resin and the metal in the die has been used. Become. However, among the (d) organic carboxylic acids used in the present invention, higher saturated fatty acids and higher unsaturated fatty acids have an effect of reducing the coefficient of friction between the resin and the metal, as in the case of the above-mentioned fatty acid metal salt. Prevents eye spots. In addition, it is easily taken up into living organisms, and mold is generated in the photo-degradable resin or the photo-degradable resin composition in a mold generation test, which is expected to contribute to biodegradability. In addition, it is considered that the peroxide itself is autoxidized in the soil to generate a peroxide, and this peroxide has an effect of promoting the decomposition of the thermoplastic resin.

In order to facilitate the above-mentioned autoxidation,
Among organic carboxylic acids, at least one 2
It is desirable to use unsaturated fatty acids having a heavy bond.

The amount of the component (d) is in the range of 0.05 to 10% by weight. If the amount is less than 0.05% by weight, the effect of preventing eye shine is insufficient. Regarding biodegradability, the higher the blending amount, the faster it is degraded, but in the case of higher fatty acids,
If it is added in excess of 10% by weight, the resin becomes slippery as in the case of blending the component (c), and there is a fear that molding processing becomes impossible.

Examples of the (e) hygroscopic agent used in the present invention include calcium oxide, anhydrous calcium chloride, anhydrous calcium sulfate, activated alumina, anhydrous zinc chloride, anhydrous zinc bromide, silica gel, and the like. Calcium oxide is the most effective. is there.

A photo-degradable resin or a photo-degradable resin composition containing starch in a single operation adsorbs moisture in the air with the passage of time, which causes foaming during molding. To prevent this, it is necessary to devise measures such as heating and drying the composition for several hours before molding, or special packaging and shipping in a metal bag, for example, a packaging bag with aluminum foil laminated. It causes up. Therefore, the incorporation of a moisture absorbent such as the component (e) is effective for performing smooth molding.

The particle size of the above-mentioned desiccant is preferably from 0.05 to 10 μm, more preferably from 1 to 8 μm. With a particle size smaller than 0.05 μm, dispersion with the resin becomes very difficult,
If it exceeds m, continuous forming becomes difficult due to film breakage in film forming and stretching forming.

The amount of the moisture absorbent is preferably 0.05 to 10% by weight. 0.05
If the amount is less than 10% by weight, the effect as a hygroscopic agent is insufficient.
If the content is more than 10% by weight, molding becomes difficult.

As the kneading apparatus for obtaining the composition of the present invention, conventionally known apparatuses such as an open-type mixing roll, a non-open-type Banbury mixer, a kneader, a single-screw extruder, and a twin-screw extruder can be used.

The product comprising the composition of the present invention is not particularly limited, and includes all products molded by master batch, extrusion molding, injection molding, blow molding, rotational molding, and the like.

For example, films, sheets, tapes, yarns, strings,
Packaging materials such as nets, industrial materials such as civil engineering and marine products, shopping bags, garbage bags, light weight packaging bags, diaper films, multi-films for agriculture, carriers for soft drinks, sandbags, curing sheets, vegetation nets It is suitably used for food containers, tableware, containers such as buckets, toys, medical equipment and the like.

In the present invention, rubbers, plasticizers, lubricants, ultraviolet absorbers, other antioxidants, foaming agents, crosslinking agents, antistatic agents, antifogging agents, flame retardants, within a range not departing from the gist of the present invention, Additives such as colorants and fillers can be blended.

〔The invention's effect〕

The composition of the present invention remarkably promotes the biodegradability of conventional biodegradable resin compositions and photodegradable resin compositions, and provides stability during molding (prevention of deterioration in physical properties due to oxidative deterioration during resin processing). Improve).

Further, as another effect, it is possible to prevent foaming of a molded article or the like which is considered to be caused by blending of a hygroscopic starch or a modified product thereof, and to provide a good product.

Furthermore, since it uses a natural antioxidant, it is suitable for food packaging materials, medical equipment, toys, etc., especially when used in the food industry, prevents oxidative decay of food for a long time It also has the attendant effect.

〔Example〕

Examples are shown below, but the present invention is not limited by these.

[Materials] (a) Ingredient: Corn starch (water content about 1)
%) (B) component: dl-α-tocopherol (c) component: soybean oil (d) component: oleic acid (e) component: calcium oxide [Evaluation of biodegradability] For mountain soil, compost, and annelids, etc. The molded article is buried in two types of soil containing habitats to a depth of about 20 to 30 cm, watered, excavated after half a year, excavated, visually inspected, tensile tested, microscope FT-IR ( The measurement of the C ＝ O group by a Fourier transform infrared spectrophotometer), the observation with an electron microscope, and the measurement of the melting point by DSC were performed.

(1) Visual test The surface state and collapse state of the molded article were visually observed.

(2) Residual tensile elongation and residual maximum load A JIS No. 3 dumbbell was punched from the molded product, and a tensile test was performed using a universal tensile tester at a tensile speed of 300 mm / min., A gripping distance of 60 mm, and a gauge line distance of 20 mm. The residual ratio (%) was determined by setting the measured value of the sample before embedding in the soil to 100.

(3) Measurement of C = O group by FT-IR The C = O group before and after the test of the molded article was measured by a microscope FT-IR manufactured by Nihon Bio-Rad Co., Ltd., and the absorbance before embedding in soil was measured.
The rate of increase with respect to this was shown as (%) as 100.

(4) Observation by scanning electron microscope After gold-sputtering the sample, an accelerating voltage of 1 was applied with a scanning electron microscope JSM-T130 manufactured by JEOL Ltd.
The surface was observed at 0 KV.

Examples 1-4 and Comparative Examples 1-2 High-density polyethylene (43% by weight of starch pre-adjusted to a water content of 0.5% by weight as a component (a) in a non-added powder of Nisseki Staphrene E707, natural anti-oxidant as a component (b) 0.3% by weight of an oxidizing agent, tocopherol, 6% by weight of soybean oil as a component (c), 1.25% by weight of oleic acid as a component (d), and 8% by weight of calcium oxide as a component (e) The mixture was mixed by tri-blend using a mixer, and the mixture was melt-mixed with an extruder to obtain a high-concentration masterbatch pellet.

The masterbatch pellets were blended with 20% by weight of non-added high-density polyethylene (trade name: Nisseki Staphrene E707, manufactured by Nippon Petrochemical Co., Ltd.) and dry-mixed. Then, an extruder having a screw diameter of 40 mmφ was used. Then, a 50 μm film was produced by an inflation molding method.

The film was formed into a stretched tape (stretching ratio = 6 times, thickness: 20 μm) by a hot plate stretching method, and this was used as a sample to evaluate the biodegradability by the method described above.

As a comparative sample, phenolic antioxidant tetrakis- [methylene-3- (3,5-di-t-butyl-
4'-hydroxyphenyl) propionate] methane
An example of high-density polyethylene containing 0.1% by weight is shown in Comparative Example 1,
Comparative Example 2 shows an example in which only 8.6%, 1.2% and 1.6% by weight of components (a), (c) and (e) were added to this sample. The results are shown in Table 1.

The stretched tapes shown in Examples (1) to (4) showed that the tensile elongation was lowered by burying in the soil for half a year, the C ＝ O group was increased, and the resin part was also deteriorated. Large pores were also observed.

In particular, it indicates that the deterioration is accelerated compared to the inhabitants such as annelid animals.

Examples 5-8 and Comparative Examples 3-6 Vitamin K0.0 was added to the additive-free powder of each resin shown in Table 2.
After mixing 5 wt% by dry blending, the mixture was melt-kneaded by an extruder. Next, 20% by weight of a photodisintegrable masterbatch (trade name: Ecostar Plus, manufactured by St. Lawrence Co.) was blended with the above resin composition, and a 50 μm film was produced by inflation molding.

The above film contains 8.6% by weight of starch (component a), 0.04% by weight of vitamin K (component b), 1.2% by weight of soybean oil (component c), stearic acid (component d) and calcium oxide (component e). Contains 1.6% by weight.

For comparison, phenolic antioxidant 2,6-di-
0.05% by weight of t-butyl-p-gresol (BHT), 0.1% by weight of dilaurylthiodipropionate (DLTDP) and 0.25% by weight of calcium stearate were added to each of the above resins, and an inflation film was prepared in the same manner as in each Example. It was molded and used as a comparative example.

Each of the above films was buried in soil in the same manner as in Example 1 to evaluate biodegradability, and the same sample was left outdoors to measure the residual tensile elongation (%) of the film and determine the photodegradability. evaluated. Table 2 shows the results.

As is clear from the table, it can be seen that the composition of the present invention has both biodegradable and photodegradable properties.

────────────────────────────────────────────────── (5) References JP-A-4-131171 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 1/00-101/16 C08K 3 / 00-13/08

Claims (3)

(57) [Claims] 1. A photo-degradable resin or a photo-degradable resin composition comprising: (a) 2 to 60% by weight of starch or a modified product thereof; and (b) α-, β-, γ-, δ-tocopherol and the like. And at least one natural antioxidant selected from the group consisting of vitamin B group and derivatives thereof; and vitamin K group and derivatives thereof; A biodegradable resin composition added. 2. The biodegradable resin composition according to claim 1, further comprising: (c) 0.05 to 10% by weight of a fatty acid ester; (d) 0.05 to 10% by weight of an organic carboxylic acid; A biodegradable resin composition comprising at least one additive selected from the group consisting of 0.05 to 10% by weight. 3. A biodegradable resin product molded from the biodegradable resin composition according to claim 1.