CN1074433C - Polyester type starch plastic - Google Patents

Abstract

The invention is a polyester starch plastic, which is characterized in that the composition includes starch, glycerol, 1,2-propanediol, fatty acid, sorbitol, alkaline substances, gelatin water, and white carbon black, and is extruded by a twin-screw Extrusion machine can get the desired plastic. Plastic products are degradable and non-toxic. Wastes can be directly used as animal feed or mixed with other feeds after recycling and crushing. They can also be mixed with polyethylene, polypropylene, polystyrene plastics, and natural rubber, butadiene rubber, nitrile rubber, Blended with styrene rubber to make degradable films, sheets, and foamed products.

Description

Polyester starch plastic and its preparation method and application

The invention relates to a biodegradable starch-based plastic composition and a preparation method thereof.

As we all know, since the advent of plastic, it has been widely used because of its light weight, beautiful and practical products. But the ensuing sharp increase in plastic waste has seriously polluted the environment. In order to solve this problem, people study various treatment methods, the important method of which is to research and develop materials that have little burden on the environment and are easy to dispose of after use, such as the development and application of various biodegradable plastics. For example, the patent applications whose publication numbers are CN1050390A, CN1049854A and CN1112143A all propose to prepare biodegradable plastics by blending starch and polymers, but this type of degradable plastics also has complex processes, poor compatibility, poor dispersibility, and high cost. Higher problems, and the polymer left after the starch component is decomposed is difficult to continue to degrade.

The purpose of the present invention is to overcome the shortcomings of the prior art, and propose a degradable starch-based plastic composition with simple process, uniform dispersion and no polymer, and a preparation method thereof.

The object of the present invention is to be realized by the following scheme: starch, plasticizer, superfine white carbon black, high-carbon fatty acid, auxiliary agent, gelatin water composition are mixed in a certain proportion, extruded by twin-screw extruder into required plastic.

The plastic composition of the present invention includes starch, glycerol, 1,2-propanediol, fatty acid, sorbitol, alkaline substance, gelatin water and white carbon black. Composition content:

Starch accounts for 60-80% of the weight of the composition, and other components are based on the weight of starch, and the specific content is: glycerol 15-30%, 1,2-propanediol 8-15%, fatty acid 0.5-3.5%, sorbitol 0.5-10%, alkaline substance 5-25%, gelatin water 10-50%, white carbon black 1-20%.

Vegetable oil can also be added to the above composition, and its amount is 5-30% of the total amount of starch.

The preparation process of the plastic of the present invention comprises:

(1) Soak gelatin in water at 30-50°C for 0.5-2h to obtain gelatin water, then add alkaline substances, heat to dissolve completely, then add glycerin, 1,2-propanediol or/and vegetable oil to obtain mixture A , the weight ratio of gelatin to water is 1:10-30;

(2) Add starch, sorbitol, white carbon black, and fatty acid into a container with a stirrer in proportion, and stir at a high speed at 70°C for 5-10 minutes to obtain a mixture B;

(3) Mixture A is fed into the screw extruder at a flow rate of 140-400 g/min, and mixture B is added to the extruder hopper at a speed of 800-1800 g/min, and the two mixtures are completed in the extruder Vibration, stirring, shearing, and reaction process to achieve gel polymerization, the screw speed of the main machine is 80-180r/min, the temperature is 60-150°C, and the head pressure is 2-8Mpa.

Above-mentioned step (1) glycerol or/and vegetable oil can also be added in step (2). The starch includes corn, potato, rice, cassava, beans, starch or starch, preferably selected from medical starch, mung bean starch or starch.

The white carbon black of the present invention is a reinforcing agent for plastics, which has an important influence on the strength, transparency, tear resistance, hardness and other properties of plastics. The white carbon black used in the present invention is an ultra- Fine white carbon black, its product code is TS-3.

The fatty acid described in the invention is a lubricant for plastics, which can make the surface of the plastics smooth and increase the light transmission. The fatty acids described in the present invention include C ₁₀ -C ₂₀ fatty acids or salts thereof.

Glycerol, 1,2-propanediol, and sorbitol described in the present invention are all commercially available products, and they play a plasticizing effect on plastics, and they can maintain sufficient strength.

Vegetable oil of the present invention includes soybean oil, peanut oil, salad oil, corn oil. In the manufacture of waterproof products, vegetable oil needs to be added to the plastic composition.

The alkaline substances described in the present invention include ammonium bicarbonate, urea, potassium aluminum sulfate.

The physical properties of the plastic of the present invention include tensile strength of 0.78-20Mpa, elongation at break of 125-150%, low-temperature embrittlement temperature of -12-35°C, oxygen index of 25-35, and hardness of 50-85.

The extruded material-plastic of the present invention can be produced by a common calendering method and can be used for various products in the fields of food, medicine, chemical industry and packaging, as well as disposable tableware and medical outer packaging. Ordinary injection methods can also be used to directly produce non-polluting toys and other products.

The plastic of the present invention can also be mixed with polymers including polyethylene, polypropylene, and polystyrene in a certain proportion, and made into degradable films by methods such as extrusion, injection, blow molding, molding, and calendaring. For sheets and foamed products, when preparing films, plastic: polymer = 15-40: 60-85; when preparing sheets, plastic: polymer 15-50: 50-85; when preparing foamed products, plastic: polymer 30- 80: 20-70. The plastic of the present invention can also be added to rubber materials including natural rubber and styrene-butadiene rubber to replace fillers to produce different products, and the addition amount is plastic: rubber material = 50-80: 20-50.

Main advantage of the present invention:

The plastic preparation method of the present invention is simple, and the required product can be obtained by extruding the composition through a general-purpose twin-screw extruder, and the strength, hardness, and elongation at break of the product can be adjusted in a wide range according to the application; The starch content of the plastic reaches 60-80%, and its cost is significantly lower than the current degradable plastic products containing high polymers; the plastic product of the present invention is not only degradable, but also non-toxic, and is a disposable short-term product made by common calendering and other methods. After the used products are discarded, they can be directly used as animal feed or mixed with other feeds after recycling and crushing, so that environmental pollution can be reduced or eliminated; the plastics of the present invention can also be blended with polyethylene, polypropylene, polystyrene, rubber, etc. It can be made into various degradable films, sheets, and foamed products, and the film made by blending with polyethylene is superior to the current domestic filled starch plastics, and has good light transmission.

Further illustrate characteristics of the present invention with example below.

Example 1

This example is a plastic containing 70.4% starch.

Soak gelatin and water at a weight ratio of 1:15 at 40° C. for 1 hour to obtain gelatin water. Take out 2.8kg of gelatin water and put it in another container, then add 3.5kg of urea, heat to make it melt, then add 5.6kg of glycerol, 10.6kg of 1,2-propylene glycol, and 3.5kg of salad oil, and mix thoroughly to obtain mixture A; Add 70.4kg of starch, 0.7kg of sorbitol, 2.1kg of white carbon black, and 0.1kg of stearic acid into a container with a stirrer, and stir at 70°C for 8 minutes to obtain mixture B; then mix A and B respectively at a flow rate of 300 G/min and 1500 g/min are added to the screw extruder, and the desired product can be obtained through extrusion blending. The longitudinal tensile strength of the product is 14.7Mpa, the longitudinal elongation at break is 434%, the transverse tensile strength is 13.8Mpa, the transverse elongation at break is 480%, the low temperature brittleness is -20°C, and the hardness is 60.

Example 2-4

Examples 2-4 are plastics containing 80%, 60.2%, and 74% starch respectively. Preparation process is with example 1. See Table 1 for component contents.

Example 5

In this example, polyethylene is mixed with the product of Example 4 in a weight ratio of 75:25 and a film is prepared in the usual way. Physical properties of the film: longitudinal tear strength 66.4N/mm, longitudinal elongation at break 573%, transverse tensile strength 8.9Mpa, longitudinal tensile strength 10.7Mpa transverse elongation at break 587%, transverse tear strength 77.7N/mm mm.

Example 6

This example is the film toxicity test that invention example 4 plastics and example 5 make.

Test equipment: FTIR-Compute, Ms-Dp-Computer.

Testing environment conditions: 25°C, 70% relative humidity.

After Fourier transform infrared spectroscopy and organic mass spectrometry and computer spectrogram mixing and decomposition processing including difference spectrum technology, spectral analysis and comparative analysis, combined with compound chemical properties and synthesis mechanism analysis. Detection conclusion: the plastics of the present invention and the products after compounding of plastics and polyethylene, except producing a very small amount (less than 1%) carbamate (non-toxic), do not find formaldehyde, nitroso, polycyanic acid ( Esters) and other harmful substances.

Example 7

This example is the biodegradation test of the product film of Example 5.

1. Buried soil test

1. Bury 8 pieces of 20×10cm and weighed test film in the 10cm of the farmland plow layer, take out 2 pieces after 26 days, wash off the soil and dry it before weighing. After that, take two pieces every 1-2 weeks and weigh them to detect the degradation rate of the membrane in the soil.

2. In the same way as above, bury 18 test membranes of 5×8cm and weighed in pots with fertile topsoil, place them in an incubator at 30°C and a relative humidity of 75%, and take out 2 pieces at regular intervals Wash, dry and weigh.

The test results are shown in Table 2.

2. High temperature composting test

Mix orchard soil and horse manure at a ratio of 2:1, add NPK fertilizer and bacterial fertilizer, add water and stir well, put it into 9 large flower pots (upper mouth diameter 30cm, height 15cm) for stack retting, and bury a piece in each pot and weigh it in advance. The 20×10cm test film, six of which are unirradiated test films, and the other two were continuously irradiated by 20W ultraviolet lamp for 72 hours. Place the flower pots in a greenhouse where the room temperature is >25°C at night and >35°C during the day. The test results are shown in Table 3.

It can be seen from Table 3 that the degradation rate of the non-irradiated biodegradable film after high-temperature stacking and retting for nearly a month is almost the same as the degradation rate of the general soil test in the field or in the incubator, at 44-45%. Even if the stacking retting time is only half of the former, the degradation rate reaches 47%, and there are many light red or dark green microbial corrosion spots on the film. At the same time, there is almost no change in the irradiated ordinary polyethylene film. Table 1 instance component Example 1 Example 2 Example 3 Example 4 Starch ^* , kg 70.4 80 60.2 74 Glycerol, kg 5.6 6.4 6 7.4 1.2-Propanediol, kg 10.6 4 6 7.4 Gelatin water, kg 2.8 9 3 Sorbitol, kg 0.7 0.8 1.8 0.7 Salad oil, kg 3.5 Ammonium bicarbonate, kg 2.4 1.5 Urea, kg 3.5 10.2 3.7 Potassium aluminum sulfate, kg 2.4 White carbon black, kg 2.1 2.4 6 1.9 Stearic acid, kg 0.7 1.6 0.6 0.4

^* Example 1-Example 3 is mung bean powder, and Example 4 is medical starch.

Table 2 project Embedded film in soil box of incubator Embed film at 10cm of corn field for 26 days 21 days buried Buried for 35 days Original weight, g 0.2489 0.2575 0.2568 0.2551 0.2913 0.2968 1.6300 1.6207 current weight, g 0.1386 0.1423 0.1434 0.1404 0.1612 0.1648 0.9569 0.9247 weightless, g 0.1103 0.1152 0.1134 0.1147 0.1301 0.1320 0.6731 0.6260 Degradation rate,% 44.3 44.7 44.2 45.0 44.7 44.5 41.3 38.6 Average degradation rate, % 44.4 44.7 40.0

table 3 project Unirradiated test film stack retting for 29 days Continuously irradiated by 20W ultraviolet light for 72 hours, and stacked for 17 days test film polyethylene film Original weight, g 1.9609 1.8672 0.2155 current weight, g 1.0813 0.9816 0.2138 weightless, g 0.8796 0.8856 0.0017 Degradation rate,% 44.8 47.4 0.8

Claims (10)

1. a kind of polyester starch plastic, it is characterized in that composition composition comprises starch, glycerol, 1,2-propanediol, fatty acid, sorbitol, gelatin water, white carbon black and be selected from urea, bicarbonate amine, Any one or two mixtures of aluminum potassium sulfate, their content: starch accounts for 60%-80% of the weight of the composition, and other components are based on the weight of starch, and the content is respectively: 15-30%, 8-15% %, 0.5-3.5%, 0.5-10%, 10-50%, 1-20%, 5-25%. 2. according to the described polyester starch plastic of claim 1, it is characterized in that adding the vegetable oil that comprises soybean oil, corn oil, peanut oil, salad oil in the composition, and its amount is 5-30% of starch weight. 3. according to the described polyester starch plastic of claim 1, it is characterized in that described starch comprises corn, potato, rice, cassava, bean starch or lotus root starch. 4. according to the described polyester starch plastic of claim 1, it is characterized in that described starch is medical starch, mung bean powder or lotus root starch. 5. according to the described polyester starch plastic of claim 1, it is characterized in that described white carbon black is the superfine white carbon black of particle diameter＜20 nanometers, and described fatty acid comprises C ₁₀ -C ₂₀ fatty acid or its salt kind. 6. the preparation method of the described polyester starch plastic of claim 1 is characterized in that preparation process comprises: (1) Soak gelatin in water at 30-50°C for 0.5-2 hours to obtain gelatin water, then add one or two mixtures of urea, ammonium bicarbonate, and potassium aluminum sulfate, heat to dissolve, and then add glycerin , 1,2-propanediol or/and vegetable oil to obtain mixture A, the weight ratio of the gelatin to water is 1: 10-30; (2) Add starch, sorbitol, white carbon black, and fatty acid into the container in proportion, and stir at 70°C for 5-10 minutes to obtain mixture B; (3) Mixture A is fed into the screw extruder at a flow rate of 140-400 g/min, and mixture B is added to the extruder hopper at a speed of 800-1800 g/min, and the two mixtures are extruded and blended To obtain the required plastic, the screw speed of the screw extruder is 80-180 rpm, the temperature is 60-150° C., and the head pressure is 2-8 MPa. 7. according to the described method of claim 6, it is characterized in that step (1) glycerol, 1,2 propanediol or/and vegetable oil are added in step (2). 8. The application of the polyester starch plastic as claimed in claim 1, characterized in that the calendering method is used to produce disposable tableware and medical packaging, or the injection method is used to produce non-polluting toys. 9. the application of the described polyester starch plastic of claim 1 is characterized in that being mixed with the polymer comprising polyethylene, polypropylene, polystyrene, styrene-diene-styrene triblock copolymer After mixing, degradable films, sheets and foamed products are made. When preparing films, the plastic: polymer weight ratio is 15-40: 60-85, and the plastic: polymer weight ratio for preparing sheets is 15-50: 50-85, and the plastic: polymer weight ratio is 30-80: 20-70 when preparing foamed products. 10. the application of the described polyester starch plastics of claim 1 is characterized in that plastics substitute filler is added in the sizing material that comprises natural rubber, styrene-butadiene rubber, to make different products, addition is plastics: sizing material The weight ratio is 50-80:20-50.