KR100641272B1 - A degradable plastic composition - Google Patents

Abstract

Provided are a degradable plastic composition which is degraded by microorganism and light simultaneously, is improved in degradation and has a degradation period capable of being controlled, and its preparation method. The degradable plastic composition comprises 15-60 wt% of a synthetic resin selected from the group consisting of a polyolefin-based polymer, a polyester-based polymer, a polyamide-based polymer and a polyacrylate-based polymer; 15-70 wt% of at least one inorganic filler selected from the group consisting of silica, talc, mica, kaolin and titanium dioxide; 5-30 wt% of starch; 5-5,000 ppm of at least one photolysis activator selected from the group consisting of Fe, Zn, Mn and Ti; 5-5,000 ppm of at least one UV stabilizer selected from the group consisting of Ni, CO, Cu, Ca and Cd; and 0.1-5 wt% of a lubricant, wherein the synthetic resin has a unit represented by the formula in the polymer chain; and X is O or S.

Description

Degradable Plastic Composition {A DEGRADABLE PLASTIC COMPOSITION}

The present invention relates to a degradable plastic composition, and more particularly, to a plastic composition decomposable in any environment by photolysis and biodegradation at the same time.

In the late 20th century, due to the rapid development of human civilization, the industrial structure was mass-produced and mass-consumed.In particular, synthetic plastics are widely used as packaging materials that are indispensable for life due to their excellent properties and cheap and light properties. The interest in the disposal of such waste is increasing because the conventional plastic products used are not decomposed naturally within a reasonable period of time.

Conventionally, methods for treating plastic waste have been landfilled, incinerated, recycled, etc. However, in the case of landfilling, since ordinary plastics are not decomposed by microorganisms, they are the main culprit of soil pollution and have a limited amount of landfill space. Incineration involves secondary pollution from combustion residues and toxic gases. Meanwhile, in the case of recycling, there is a difficulty in classifying and classifying according to the type of material, and there is a problem in that economic losses due to collection, transportation, and reprocessing are large.

Biodegradable plastics are largely biodegradable and photodegradable. Biodegradation is the decomposition of plastics by microorganisms, and photolysis refers to the degradation of molecular weight caused by sunlight.

The first biodegradable plastics were mixtures of partially biodegradable starch and non-biodegradable polyolefins. These plastics cannot be used in waste treatment facilities such as composting processes and are generally disposed of in sanitary landfills.

U.S. Patent No. 4,873,270 to Aime et al. Describes a mixture of carbohydrates and polyurethanes, such as poly (vinyl chloride) and potato flour, and U.S. Pat.Nos. 3,850,862 and No. 3 of Clendining et al. 3,850,863 discloses mixtures of dialkanoyl polymers such as poly (alkyrene adipate) or oxyalkanoyl polymers such as poly (caprolactone) and natural biodegradable products such as bark, protein, starch, peat, sawdust and the like. have. Improved biodegradable plastic compositions are described in US Pat. No. 5,314,754 and German patent application 44404840.

In addition, U.S. Patent No. 5,384,183, filed by Novacor Chemicals, and U.S. Patent No. 5,096,941, filed by Dow Chem., Etc., are formed by mixing a photodegradable additive with a general purpose plastic such as polyethylene to cause photolysis by sunlight in an atmospheric environment. One photodegradable film is disclosed.

However, the conventional photodegradable polymer material has a problem in that the part covered in the soil is not decomposed, and the biodegradable polymer material manufactured using the conventional starch, etc., although the price is cheap, it is practical in terms of physical properties due to its low strength and impact resistance. The recent bio / photodegradable plastics, which fall short of the standard and were developed to solve these problems, are also very limited in application because they are five times more expensive than general-purpose plastics.

The present invention has been made in order to solve the above problems, biodegradation and photolysis occurs at the same time can be decomposed in any environment, to minimize the toxic gas emissions during incineration, inexpensive to provide a degradable plastic composition with practicality. Has its purpose. That is, it is an object of the present invention to provide a decomposable plastic composition configured to be photodegraded by ultraviolet light when buried, and the part covered by soil is accelerated by heat generated while biodegradation occurs.

Another object of the present invention is to arbitrarily control the dispensing so that the decomposition occurs in accordance with the product life, so that the decomposition hardly occurs until the product life, so that the decomposition occurs rapidly at the end of the product life to prevent environmental pollution It is.

The present invention is 15 to 60 wt% of synthetic resin, 15 to 70wt% of inorganic filler, 5 to 30 wt% of starch, additive (photodegradable activator + UV stabilizer: 10 to 10000 ppm) and 0.1 to 5 wt% of lubricant. It is about.

Examples of the synthetic resin that can be used in the present invention include polyolefins such as LDPE, HDPE, MDPE, LLDPE, VLDPE, PP, PVC, EVA, vinyl acetate and copolymers thereof, polyesters such as PET and PBT, Polyamides such as NYLON-6, NYLON-66 and NYLON-11, and polyacrylates such as PMMA and acrylic copolymers, and are preferably used in an amount of 15 to 60 wt% in the degradable plastic composition. .

If the amount of the resin is less than 15 wt%, the strength drops sharply, making it difficult to use the product. If the amount is more than 60 wt%, the amount of harmful gas generated during combustion becomes excessive. Since it is difficult to achieve the object of the present invention to reduce the amount, it is limited to the range of 15 to 60 wt%. In particular, in order to maintain sufficient strength in the state of the product, it is more preferable that the amount of the resin contained in the composition is 30 to 50 wt%.

In addition, examples of the inorganic filler that can be used in the present invention include silica (SiO ₂ ), talc (Talc), mica (Mica), kaolin (a kind of clay: Kaolin) and titanium dioxide (TiO ₂ ), and the like. It is preferably used in an amount of 15 to 70 wt% in the degradable plastic composition. The reason for this is that if the amount of the inorganic filler is 15 wt% or less, the amount of harmful gas is increased during incineration, and if the amount of the inorganic filler is 35 wt% or more, the durability of the product is inferior. However, in order to improve the durability and economical efficiency of the product, it is more preferable to set it as 25 to 35 wt%.

The starch content is preferably in the range of 5 to 30 wt%. This is because, if the content of starch is 5 wt% or less, the biodegradability of the composite decomposition ability is inferior, and if it is 30 wt% or more, the strength of the product decreases and durability is low.

The additive used in the present invention is composed of a photolytic activator (M ₁ ) and an ultraviolet stabilizer (M ₂ ). Examples of the photolytic activator (M ₁ ) include iron (Fe), zinc (Zn), and manganese, which promote oxidation of a polymer. Metal components such as (Mn) and titanium (Ti), and examples of ultraviolet light stabilizers (M ₂ ) include nickel (Ni), cobalt (Co), copper (Cu), and calcium (Ca) that prevent oxidation of polymers. ) And metal components such as cadmium (Cd). In the present invention, the additive may be added to the composition as a metal itself, but alkyl dithiophosphate, alkyl dithiocarbamates, ketones, thioketones, xanthates and phosphorus compounds (e.g., Phophoric, Phosphorus ester, Phosphorus amide) and the like may be added in the form of an organic complex combined with an organic compound, an example of such an organic compound can be represented by the following general formula.

In the above formula, R _i (i = 1-n) is an alkyl, aralkyl or aryl, aromatic group substituted with hydrogen, an alkyl group, an aralkyl group, an aryl group, nitrogen, sulfur, phosphorus or a heterocyclic ring, respectively. , A substituent selected from the group consisting of an alkylene group, a heterocyclic cyclic compound substituted with nitrogen, sulfur or phosphorus.

Preferably, the additive is added in an amount of M ₁ and M _{2 in an amount} of 5 to 5000 ppm each (when added to an organic complex with an organic compound, the addition amount is based only on the amount of the metal component). In particular, since the physical property retention period of the plastic can be adjusted differently according to the combination ratio of the oxidation promoter and the antioxidant, when it is added to the plastic at a predetermined ratio, the decomposition and decomposition induction time of the polymer can be controlled to determine the lifetime of the plastic arbitrarily. . Considering the service life of the plastic product to be about 10 years, it is preferable to adjust the content ratio of the photodegradation activator (M1) and the UV stabilizer (M2) as additives within the range of 7/3 to 6/4. . Since M ₁ and M ₂ play a role of a catalyst, they may not play a role when added at 5 ppm or less, but the effect may not be greatly improved even when added at 5000 ppm or more.

A more preferable range is 300 ppm to 1500 ppm, which is a sufficiently stable range, in which quality can be stabilized in mass production.

Explaining the role of the additive, if the expected period of the plastic product is short, by increasing the addition ratio of the photocatalytic activator (M1), an oxidation promoter, so that photolysis starts at a fast time, on the contrary, if the expected period of the plastic product is long, oxidation By increasing the addition ratio of the ultraviolet light stabilizer (M2) as an inhibitor is to start a late period of photolysis.

The lubricants usable in the present invention include waxes, and are preferably used in an amount of 0.1 to 5 wt%. If it is 0.1 wt% or less, the effect of sufficient wax cannot be obtained at the time of product molding, and if it is 5 wt% or more, defects or economic effects cannot be obtained inside the product.

In the present invention, the decomposable plastic composition comprises a first step of mixing the inorganic filler and the additives first to form a uniform blend, a second step of adding a synthetic resin and starch to the blend and performing a second blend, and And a third step of reacting and extruding the resulting mixture with a single screw or twin screw extruder, and a fourth step of cooling the extrudate to dry pellets.

First, the photodegradation mechanism of plastic is described as follows.

The polymer chain is composed of carbon-carbon and carbon-hydrogen bonds and its binding energy is about 82 ~ 84 ㎉. Therefore, when the same amount or more of energy (including heat, light and mechanical energy) is applied to the polymer, the polymer undergoes Norrish I reaction, in which the chain is broken and becomes radical, or Norrish, monomerized. Ⅱ reaction.

Light can be converted into energy quantified by the following equation, and the shorter the wavelength, the larger the energy value.

E = hυ = h (c / λ)

              E = energy

              h = Planck's constant

              c = speed of light

              λ = wavelength

              υ = frequency

It can be seen from the above equation that the wavelength of light for breaking the polymer chain is 290-320 nm ultraviolet rays, and the sunlight reaching the earth's surface contains ultraviolet rays in this range. When the polymer is destroyed by ultraviolet light, the catalyst is bound to oxygen and rapidly decomposed by free radical reaction.

The free radical oxidation is as follows.

As described above, the synthetic resin is decomposed into carboxylic acid by an oxidation reaction by ultraviolet rays, and such low molecular weight carboxylic acid compound is decomposed by microorganisms and returned to nature.

However, as described above, when the synthetic resin is buried and decomposed, the buried site cannot be exposed to ultraviolet rays, so that initial decomposition is difficult, and thus, such low-molecular-weight carboxylic acid compounds cannot be produced. It has a disadvantage. Therefore, the present invention is to produce a degradable plastic composition by the above-described method in order to improve the resolution of the buried site difficult to photolysis.

The synthetic resin of the degradable plastic composition produced by the above manufacturing process is characterized by having the following units in the polymer chain, which unit is mixed with the photolytic activator and the synthetic resin in the composition and subjected to high temperature extrusion through high temperature extrusion. It can be said to be the result of a pre-oxidation reaction.

The triangular ring in the polymer chain as described above has a very high energy due to the ring strain, and has a property of being easily decomposed. Therefore, not only the UV-reaching area but also the landfill area where the UV-rays do not reach may be easily decomposed due to moisture and latent heat of the soil. In this case, starch also acts to accelerate the decomposition of the resin in the soil. The content of starch contained in the composition according to the present invention is preferably in the range of 5 to 30 wt%. This is because, if the content of starch is 5 wt% or less, the biodegradability of the composite decomposition ability is inferior, and if it is 30 wt% or more, the strength of the product decreases and durability is low. In particular, starch is first decomposed by microorganisms when the polymer product is buried in the ground to create a plurality of pores to increase the surface area of the product to increase the area in contact with light or water. In addition, the heat generated when the starch is decomposed may serve to promote additional decomposition of the triangular ring portion in the polymer chain structure as described above.

In addition, it is possible to control the addition ratio of the above-mentioned additives, that is, the photolytic activator and the UV stabilizer, and the decomposition rate is increased when the photolytic activator is added relatively more than the UV stabilizer, and the decomposition rate is increased when the photolytic activator is added relatively less than the UV stabilizer. Since it becomes slow, the addition rate can be adjusted and the decomposition rate of resin can be adjusted.

In addition, since the decomposable plastics according to the present invention contain about 15 to 35 wt% of inorganic fillers, which are non-combustible materials, the amount of harmful gases generated during incineration is greatly reduced, and combustion residues are very stable because of the same components as soil. In addition, since the landfill contains a large amount of inorganic fillers, there is less possibility of ground breakdown often caused by gasification reaction by decomposition. In the above, when the amount of the inorganic filler is 15 wt% or less, the amount of harmful gas when incinerated becomes excessive, and when the amount of the inorganic filler is 35 wt% or more, there is a problem that the durability of the product is inferior. However, in order to improve the durability and economical efficiency of the product, it is more preferable to set it as 25 to 35 wt%.

Hereinafter, the present invention will be described in more detail with reference to Examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

<Example>

After preparing a degradable resin composition composed of the components shown in Table 1 below, the physical performance and the decomposition performance of each composition were evaluated, and the results are shown in Tables 2 and 3, respectively. When evaluating the performance of the degradable resin according to the present invention, the tensile elongation test is ASTM D882-83, the outdoor light resistance test is ASTM D4363-84, the outdoor weather resistance test is ASTM D1435-85, the accelerated light resistance test is ASTM D54329-84, The weather resistance test was conducted by ASTM D2565-89. Specific decomposition performance test methods are as follows.

 (a) outdoor degradability test

Ⓐ Film is prepared from the degradable composition and adhered to a fixed plate and exposed to sunlight.

Ⓑ Tensile specimens are made of unexposed film to measure tensile strength and elongation, and analyzed by infrared spectroscopy (IR).

Ⓒ After 10 days of exposure to sunlight, the film is taken at regular time intervals to prepare a tensile specimen, and the tensile force and elongation are measured, and the change of carbonyl group content in the film is measured by IR.

Ⓓ The induction cycle is defined as the end of the period when the tensile property is lowered below 30% or the carbonyl group (C = O) content is increased to 15% or more.

Ⓔ Every 24 hours after the induction cycle, the changes and disappearance of the appearance of the film are observed and recorded, and the time required to completely disappear is recorded.

Ⓕ Determine whether the test result matches the scheduled decomposition time and measure the error.

(b) accelerated weathering tests (including accelerated light resistance tests);

Ⓐ Aging the film under UV radiation in a weather tester capable of UV 290 ~ 320 nm.

Ⓑ Take the film at regular time intervals from the beginning of Aging to 0, 24, 48, 72, 96, 120, 150, 200, 300 hours or more, measure tensile properties, and perform IR analysis.

Ⓒ Find the time when the tensile property is 30% or less of the initial value or the time when the carbonyl group content is 15% or more, and define it as an induction cycle.

Ⓓ In the weathering tester, observe and record the appearance change, decomposition process and complete decomposition time of the film, and convert it to external time.

Ⓔ Compare the results of the accelerated test and the outdoor test, and check the difference. If there is a difference, calculate the degree of error.

Ⓕ Investigate whether the test results correspond to the scheduled decomposition time and investigate the error.

(c) If the error is calculated and the difference from the scheduled decomposition time is large (± 15 days of expected decomposition time), investigate the cause, eliminate the cause, and retest. Prepare and test a new sample.

     sample Synthetic Resin (content w%) Mineral filler (% content) Starch, wt% M1 / M2 (ppm / ppm) Lubricant (content wt%) Example 1 LLDPE (54.4) CaCO3 (35.0) 10.0 500/220 0.5 Example 2 LLDPE (54.4) CaCO3 (35.0) 10.0 486/251 0.5 Example 3 LLDPE (54.4) CaCO3 (35.0) 10.0 480/304 0.5 Example 4 PET (52.3) CaCO3 (36.0) 11.0 510/225 0.6 Example 5 PET (52.3) CaCO3 (36.0) 11.0 480/250 0.6 Example 6 PET (52.3) CaCO3 (36.0) 11.0 485/312 0.6 Example 7 NYLON-66 (51.5) Talc (38.0) 10.0 510/224 0.4 Example 8 NYLON-66 (51.5) Talc (38.0) 10.0 480/250 0.4 Example 9 NYLON-66 (51.5) Talc (38.0) 10.0 479/320 0.4

Degradability evaluation experiments were carried out for the composition as shown in Table 1 above.

Degradability test was carried out at UVB 313 Lamp, 5000 hours exposure, 50 ± 5 ℃, film thickness 30 ㎛, the results are as follows. sample Percent conversion elongation (%) according to UV irradiation time 0 hours 24 hours 48 hours 72 hours 96 hours 120 hours 150 hours 200 hours 300 hours Example 1 100 100 95 70 59 35 20 - - Example 2 100 100 100 85 63 42 28 - - Example 3 100 100 100 98 85 65 41 24 - Example 4 100 100 96 72 58 28 15 - - Example 5 100 100 100 84 61 40 25 - - Example 6 100 100 100 100 86 62 40 21 - Example 7 100 100 94 73 60 32 18 - - Example 8 100 100 100 82 69 46 30 15 - Example 9 100 100 100 99 80 67 43 22 -

Looking at the experimental results, in Example 1, decomposition starts after 24 hours, Example 2 starts decomposition after 48 hours, and in Example 3, decomposition starts from around 72 hours. . These results show that the starting point of decomposition can be adjusted by adjusting the content ratio of the photolytic activator (M1) and the UV stabilizer (M2) as additives.

In other words, if the ratio of the photocatalytic activator (M1), which is an oxidation promoter, is increased, complex decomposition starts at a fast time, whereas if the ratio of the ultraviolet stabilizer (M2), which is an antioxidant is increased, a late stage of complex decomposition begins.

These results have similar results in other resin compositions, which are shown in Examples 4-9.

As described above, according to the present invention, not only can biodegradation and photolysis occur at the same time, thereby providing a plastic composition having an excellent resolution when buried and a method of manufacturing the same, but also the control of dispensing can occur so that the decomposition occurs according to the life of the product. It is possible.

In particular, the present invention absorbs energy by a triangular ring in the polymer chain, there is an advantage that the decomposition by moisture or heat in the soil is possible even when buried in the soil of the depth that will not reach.

Although the invention has been described with reference to the preferred embodiments mentioned above, many other possible modifications and variations can be made without departing from the spirit and scope of the invention. Accordingly, the appended claims are intended to cover such modifications and variations as fall within the true scope of the invention.

Claims (3)

15 to 60 wt% of a synthetic resin selected from the group consisting of polyolefin polymers, polyester polymers, polyamide polymers and polyacrylate polymers, 15 to 70 wt% of at least one inorganic filler selected from the group consisting of silica, talc, mica, kaolin and titanium dioxide, Starch 5-30 wt%, 5 to 5000 ppm of at least one photolytic activator (M ₁ ) selected from the group consisting of iron (Fe), zinc (Zn), manganese (Mn) and titanium (Ti), 5 to 5000 ppm of at least one UV stabilizer (M ₂ ) selected from the group consisting of nickel (Ni), cobalt (Co), copper (Cu), calcium (Ca) and cadmium (Cd); Consisting of 0.1 to 5 wt% of lubricant, A degradable plastic composition, characterized in that the following units are included in the polymer chain of the synthetic resin,

A first step of firstly mixing the inorganic filler and the additive (M ₁ + M ₂ ) to form a uniform blend, A second step of adding a synthetic resin and starch to the blend of the first step and performing secondary mixing; A third step of reacting and extruding the mixture produced in the second step by a single screw or twin screw extruder; Decomposable plastic composition, characterized in that it is produced by a method consisting of a fourth step of cooling the extrudate of the third step to dry pellets. The method of claim 1, wherein the additive compounds M ₁ and M ₂ are alkyl dithiophosphate (Akyl Dithiophosphate), alkyl dithiocarbamates (ke), thioketone, xanthate or phosphorus compounds (Phophoric, Phosphorus ester, Phosphorus amide) is added in the form of an organic complex. In this case, however, the addition amount is based on the amount of the metal component in the organic complex. According to claim 1 or 2, wherein M ₁ and degradable plastic compositions, characterized in that defined within the scope of the paste to 6/4 in weight ratio is of 7/3 M ₁ / M ₂ of M _2.