JPH04136047A - Easily degradable resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition improved in thermoplasticity, ease of degradation by microbes in soil and physical strengths by mixing a composition comprising starch and an ethylene/vinyl alcohol copolymer with a specified filler. CONSTITUTION:10-90wt.% starch is mixed with 90-10wt.% ethylene/vinyl alcohol copolymer of an ethylene content of 20-65mol% to obtain a composition. 100 pts.wt. this composition is mixed with 5-100 pts.wt. filler comprising an inorganic filler selected from among talc, clay and mica and/or a fibrous filler selected between cellulosic and PVA fibers and optionally a plasticizer, a heat stabilizer, an ultraviolet absorber, an antioxidant, a food oil a colorant, etc., to obtain the title composition.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an easily disintegrating resin composition with excellent physical strength.

B2 Prior Art In general, synthetic polymers have advanced material properties, are easy to process, and are inexpensive, so they are widely used in all fields. However, these molded products are bulky and durable, so they do not disintegrate naturally even if they are dumped or buried in a landfill, and they have a high calorific value when incinerated, which can damage incineration equipment. This has become a problem. Therefore, research has been conducted to reduce the bulk of plastic waste by partially decomposing it using light or microorganisms, and to effectively utilize waste processing facilities or landfills.

In particular, research has been actively conducted on thermoplastic resin compositions that are biodegradable by blending thermoplastic resin with starch, which is a natural product that is completely biodegradable. In this case, as the thermoplastic resin to be blended with the starch, it is necessary to select a thermoplastic resin that is compatible with the starch and has a high thermoplasticizing effect on the entire composition. However, ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH)
It is known that because EVOH has excellent compatibility with starch, a composition consisting of starch and EVOH can exhibit good thermoplasticity and easy disintegration with a small amount of addition, and can also provide a composition with good transparency. be.

However, the mosquito composition has the disadvantage that it cannot obtain physical properties, particularly high strength and high elastic modulus, due to its low physical properties derived from starch.

In order to compensate for these drawbacks, thermoplastic reinforced plastics with improved tensile strength and/or elastic modulus of molded products can be obtained by blending fillers as reinforcing materials or synthetic resins with physical strength into thermoplastic resins. is publicly known.

However, when various reinforcing agents are blended into a resin composition consisting of starch and EVOH for the purpose of improving physical strength, some reinforcing agents may inhibit the biodegradability derived from starch.
Resin compositions that have physical strength but have low or no disintegrability by microorganisms have often been obtained.

The purpose of the invention is to provide a resin composition having good thermoplasticity, easy disintegration by microorganisms in soil, and physical strength.

In order for the overall composition to have physical strength, it is important that the interface between the starch/EVOH composition and the reinforcing material adheres strongly. At the same time, it is important that by blending a reinforcing material into the biodegradable tanu, it does not have an effect that inhibits biological attack on the phase consisting of the starch and EVOH composition.

This effect is, for example, when one component contained in the reinforcing material is transferred to a phase consisting of a composition of starch and EVOH through blending,
The effect of inhibiting biodegradability, or reinforcing materials, starch and E
Molecular entanglement occurs at the phase interface with the phase consisting of the VOH composition, which has the effect of physically inhibiting biodegradability.

As a result of intensive studies by the present inventors, it was surprisingly found that starch and E.
VOH1 If necessary, by adding at least one filler selected from the following (a) to (b) to the composition blended with a plasticizer, it has thermoplasticity and is excellent when used as a molded product. It has two properties: physical strength and easy disintegration, which means that it has physical strength and then, after being dumped as waste or buried in a landfill, it is destroyed by microorganisms in the soil and quickly loses its physical strength. We have now discovered a resin composition that has the following.

(a) At least one inorganic filler selected from talc, clay and mica; Cb'') Cellulose fiber, polyvinyl alcohol (P
At least one type of fibrous filler selected from VA) type fibers In the present invention, the inorganic filler (a) includes talc,
Clay and mica are used. Among inorganic fillers, glass peas, wollastonite, etc. do not improve physical strength even when blended, and calcium carbonate, barium sulfate, etc. do not improve physical strength or are biodegradable. descend.

Furthermore, in the present invention, PV is used as the fibrous filler (b).
A-based fibers and cellulose fibers are used.

Among the fibrous fillers, polyester fibers, glass fibers, and polyolefin fibers do not show an effect of improving physical strength, and polyamide fibers show an effect of improving physical strength, but their biodegradability decreases. In addition, the fibrous filler may be used in the form of short fibers or chopped strands, and depending on the application, roving or chopped strands may be used.
It may be used in the form of woven or non-woven fabrics. Here, the PVA fiber has a degree of polymerization of 1500 or more, preferably 2000 or more, more preferably 3000 or more, and a saponification degree of 90 mol% or more, preferably 96 mol% or more, and more preferably 9
Examples include fibers obtained from vinyl alcohol polymers or copolymers containing 9 mol% or more, or fibers obtained by acetalization (formalization, butyralization, etc.) thereof.

Examples of cellulose fibers include bistoothrayon, cupro, and cellulose acetate fibers.

These inorganic fillers (a) and fibrous fillers (b)
) may be used alone or in combination of two or more. Among these fillers, talc, mica, and PVA fibrous fillers are preferred.

A resin composition composed of starch, EVOH, and an extender is described in JP-A-2-14228, but this publication does not mention the use of fillers, especially inorganic fillers or fibrous fillers, and specific examples include organic natural products. Alternatively, synthetic polymers are cited and these are simply used as fillers.

On the other hand, since the purpose of the present invention is to use a filler as a reinforcing material, the technical idea is different from the resin composition of the present invention.

In the present invention, starch refers to raw starches such as corn starch and potato starch, and modified starches that have undergone physical or chemical treatment (dextrin, oxidized starch, etc.).
etherified starch, cationized starch, etc.).

The EVOH used in the present invention is typically a saponified ethylene-vinyl acetate copolymer, the ethylene content of which is 20 to 65 mol%, preferably 25 to 60 mol%.
The saponification degree of the vinyl acetate component is 90% or more, preferably 96% or more. When the ethylene content is less than 20 mol %, the molding temperature becomes close to the decomposition temperature, making molding difficult. On the other hand, when the ethylene content is 65 mol% or more, the compatibility with starch decreases and the physical strength of the composition decreases.

Further, the EVOH may be freely modified by addition or copolymerization with propylene, butylene, vinylpyrrolidone, vinylane-based compounds, unsaturated carboxylic acid anhydrides, etc., as long as the effects of the present invention are not impaired.

The blending ratio of each component to obtain the resin composition of the present invention is 5 to 1 part by weight of the filler per 100 parts by weight of the composition consisting of 10 to 90% by weight of starch and 90 to 10% by weight of EVOH.
00 parts by weight.

Less than 10% starch or 90% EVOH by weight
If the amount exceeds that amount, sufficient disintegration by microorganisms will not be achieved after disposal as waste. On the other hand, if the starch content exceeds 90% by weight or the EVOH content exceeds 10% by weight, thermoplasticity is lost and thermoforming becomes impossible.

If the amount of filler is less than 5 parts by weight, physical strength cannot be obtained, while if it exceeds 100 parts by weight, the thermoformability or biodegradability of the composition will be poor.

down. A suitable blending ratio is 30 to 90% starch by weight.
, EV OH7!1 (20 to 50 parts by weight of the filler per 100 parts by weight of the composition consisting of 10 to 70% by weight).

In the present invention, a plasticizer may be freely added to increase the moldability and flexibility of the resin composition.

Examples of plasticizers include polyethylene glycol, ethylene glycol, diglycerin, glycerin, 1,3- and 1,4-butanediol, 12-propylene glycol, sorbitol, ε-caprolactam, urea, toluenesulfonamide, lauramide, acetamide. , formamide, dimethyl sulfoquine, dioctyl phthalate, butyl phthalate, water, etc., or a mixture of two of them is used. Glycerin, water, urea, etc. are preferably used.

Furthermore, the resin composition of the present invention may contain heat stabilizers, ultraviolet absorbers, antioxidants, dietary oils,
You are also free to blend colorants etc.

As a means of blending each component to obtain the resin composition,
Ribo blender High-speed mixer co-kneader Mixing rolls, extruders, inten knob mixers, etc. are used.

The resin composition of the present invention can be obtained into any molded product (eg, film, sheet, various containers, various injection molded products) using a well-known extruder, injection molding machine, press molding machine, or the like.

Examples of molded products include, but are not limited to, molded products that are discarded after being used for a certain period of time, such as cups, bottles, and trays used as food containers, sheets used as agricultural materials, stakes, mulch, planters, and pesticides.・Container or carrier material for fertilizers, soil conditioners, etc., binding string for daily necessities, etc.
Examples include children's toys, trash cans, and industrial items such as cushion materials, packing materials, and various containers.

In addition, when disposing of the molded product after use, it begins to disintegrate immediately after being dumped in the same garbage collection area as general garbage, but in order to enhance the effect of disintegration by microorganisms in the soil, it is recommended to fill it in the soil. A processing method according to the above is preferred.

The present invention will be explained in more detail in Examples below, but the present invention is not limited thereto.

LjJL Random Example 1 100 parts by weight of a composition obtained by tri-blending 75% by weight of corn starch (corn starch manufactured by Nkinoma Starch) as starch and 25% by weight of ethylene content of 44 mol% and saponification degree of 99% as EVOH , 20 parts by weight of talc (PKP-80 manufactured by FujiTalc) as a filler, 20.10 parts by weight each of glycerin and water as plasticizers were blended in advance using a Henlen mixer, and a screw diameter of 40+% m1L/D = 26 full was prepared. Melt and knead using a single screw extruder with a flight type screw, extrude from a pellet die attached to the tip of the extruder at a temperature of 130°C to form strands, and then use a pelletizer to form pellets.

The i-bullet was molded using a screw injection molding machine with a screw diameter of 40ffiffi, at an injection temperature of 140°C and an injection pressure of 4.
A dumbbell-shaped injection molded product was obtained at 0 kg/c+n' and a mold temperature of 70°C. The dumbbell tested 51ff on a tensile tester.
It was pulled at a speed of III/win, and the tensile strength at break was measured. Furthermore, using the same measuring machine, the span length was 96.
A bending test was conducted at a compression rate of 3 mm/win, and the bending elastic modulus was measured. The results are shown in Table-1.

On the other hand, the pellets were prepared using a hot press at a temperature of 130°C.
A uniform notebook with a thickness of about 100 μm was molded at a press pressure of 100 kg/c+a′ and stored at 35° C. for 6 months in standard activated sludge. The condition of the notebook after 6 months was evaluated on the following four levels, and the results are shown in Table IJ.

A...Severely damaged B...Significantly damaged C...Slightly damaged D...Unchanged Examples 2 to 3 Evaluation was carried out under the same conditions as in Example 1 except for the conditions shown in Table-1. The results are shown in Table-1.

Example 4 As a filler, an aqueous solution containing 9% by weight of fully saponified polyvinyl alcohol (PVA) with a degree of polymerization of 3500 and 35% by weight of boric acid was heated to 105°C, and 15g of sodium hydroxide was added.
/ρ, and sodium sulfate 350g/6 containing 12
Spun in a coagulation bath consisting of an aqueous solution at 0°C through a nozzle with a circular nozzle of a 1000-hole mold, followed by washing with water, stretching, drying, and cutting in the usual manner, resulting in a total stretching ratio of 25 times and a fineness of 2.5 drs cut. Using short PVA fibers with a length of 3 cm, evaluation was carried out under the same conditions as in Example 1 except for the conditions shown in Table 1. The results are shown in Table-1.

Example 5 and Comparative Examples 1 to 4 Evaluation was carried out under the same conditions as in Example 1 except for the conditions shown in Table-1. The results are shown in Table-1.

F Effects of the Invention The resin composition of the present invention is a thermoplastic resin composition exhibiting excellent physical strength and biodegradability.

Patent applicant RiRashi Co., Ltd. representative person

Claims (1)

[Claims] (1) Starch 10-90% by weight and ethylene content 20%
~65 mol% ethylene-vinyl alcohol copolymer 9
The following (
At least one filler 5 selected from a) to (b)
-100 parts by weight of an easily disintegrating resin composition. (a) At least one inorganic filler selected from talc, clay, and mica (b) At least one fibrous filler selected from cellulose fibers and polyvinyl alcohol fibers