Degradable plastic and its processing use process

Abstract

This invention discloses a biodegradable plastic containing a layered structure I with a stabilizer and a layered structure II that disrupts the stabilizer. The raw materials for this biodegradable plastic are not limited and can be traditional polyethylene, polypropylene, PLA, PBAT, etc. Its biodegradability is improved by changing its processing formulation and technology.

Description

Technical Field

[0001] This invention belongs to the field of plastic processing technology, and specifically relates to a biodegradable plastic and its processing technology. Background Technology

[0002] Currently, biodegradable plastics can be categorized by mechanism into photodegradation, biodegradation, and hybridization. Based on the resin raw materials used in their production, they can be classified into bio-based PLA (polylactic acid), or non-bio-based but biodegradable PBAT (butylene adipate and butylene terephthalate copolymer), as well as blends with other materials such as starch and calcium carbonate, either chain-extended or modified. However, these raw materials are relatively expensive and degrade slowly, especially in the field of agricultural films, making widespread application difficult. Summary of the Invention

[0003] This invention relates to a biodegradable plastic and its processing technology. The raw materials for this biodegradable plastic are not limited and can be traditional polyethylene, polypropylene, PLA, PBAT, etc. Its biodegradability is improved by changing its processing formula and process.

[0004] The present invention adopts the following technical solution:

[0005] A biodegradable plastic comprising a layered structure one containing a stabilizer and a layered structure two containing a stabilizer destructor.

[0006] Preferably, the stabilizer layer comprises 0.1-2% hindered amine light stabilizer, 0.01-0.05% catalyst, and 95-99% resin.

[0007] Preferably, the catalyst is a complex of iron or other metals.

[0008] Preferably, the catalyst is a chlorophyll derivative or a phthalocyanine complex.

[0009] Preferably, the resin is linear low-density polyethylene or metallocene polyethylene.

[0010] Preferably, the component of the destructive stabilizer layer is 0.2-2% ester, and the catalyst promotes the decomposition of the ester into acid and alcohol under certain temperature and light conditions. The ester or the acid decomposed into it can be released into the stabilizer layer with the help of alcohol and ester. The hindered amine stabilizer becomes ineffective after encountering acid.

[0011] Preferably, the layered structure is as follows: when there are two layers, the stabilizer layer is usually located on the side exposed to light, and the other layer is located on the side exposed to water, which facilitates the stabilization of the upper layer and the hydrolysis of the lower ester; when there are three or more layers, an isolation layer is set between the two layers, which is a high-barrier material of ethylene-vinyl alcohol copolymer or a nylon layer; when there are four or more layers, the number of stabilizer layers is greater than the number of destructive stabilizer layers.

[0012] The beneficial effects of this invention are:

[0013] The raw materials for this biodegradable plastic are not limited and can include traditional polyethylene, polypropylene, PLA, PBAT, etc. Its biodegradability can be improved by changing its processing formula and technology. The plastic is less prone to degradation in winter when there is insufficient sunlight and low temperatures, but degrades more quickly in summer when there is ample sunlight and high temperatures. Detailed Implementation

[0014] Example

[0015] A biodegradable plastic comprising a layered structure one containing a stabilizer and a layered structure two containing a stabilizer destructor.

[0016] The stabilizer layer comprises 1% (by mass, the same below) hindered amine light stabilizer, such as Tiangang® HS-625 light stabilizer 625, 950 / 944 from Beijing Tiangang Additives Co., Ltd.; 0.03% catalyst, preferably an iron or other metal complex, such as a chlorophyll derivative or phthalocyanine complex, preferably oil-soluble sodium copper chlorophyll (CAS No.: 11006-34-1); and 98.97% resin, such as linear low-density polyethylene (LLDPE) and metallocene polyethylene, wherein the LLDPE is selected from PetroChina Puyang Co., Ltd.'s 7050, and the metallocene polyethylene is selected from MVLDPE metallocene Singapore Exxon 3518CB.

[0017] The stabilizer layer is composed of 1% ester, specifically isobutyl trimethylglutarate produced by Puyang Shengkai Environmental New Materials Co., Ltd. The catalyst promotes the decomposition of the ester into acid and alcohol under certain temperature and light conditions. The ester or its decomposed acid can be released into the stabilizer layer with the help of alcohol and ester. Hindered amine stabilizers become ineffective upon encountering acid, thus accelerating the degradation rate of plastics without stabilizers.

[0018] The layered structure is as follows: When there are two layers, the stabilizer layer is typically located on the side exposed to light (upwards), and the other layer is located on the side exposed to water (downwards), facilitating the stabilization of the upper layer and the hydrolysis of the lower ester. When there are three or more layers, a barrier layer is placed between the two layers, using a high-barrier material such as ethylene-vinyl alcohol copolymer or a nylon layer, to prevent excessively high processing temperatures from causing migration and rapid degradation. When there are four or more layers, the number of stabilizer layers is greater than the number of destabilizing stabilizer layers, but the above principles are still met.

[0019] The ester, calcium carbonate, starch, etc. are mixed to form masterbatch granules, which are then added to the main ingredient.

[0020] The processing technology is a conventional process, but the processing temperature for destroying the stabilizer layer is 10°C lower to prevent the ester from decomposing due to heat.

[0021] Two control groups (1 and 2) and a blank group were set up, with the addition of catalyst in the stabilizing layer and ester in the disrupting layer being varied, respectively. The film was blow-molded to a thickness of 0.012 mm and a width of 2 meters using the same three-layer co-extrusion unit, and a field experiment was conducted in the experimental field of the Sijiqing planting base in Wangzhu Town, Hualong District, Puyang City, Henan Province. Laying began on November 1st of the previous year.

[0022]

[0023] As can be seen from the above, only the simultaneous addition of the catalyst in the stabilizing layer and the ester in the degrading layer can accelerate the degradation of plastics. In the actual example, under the influence of light and temperature in the second summer, the ester in the degrading layer decomposes to produce acid that decomposes the anti-aging agent in the stabilizing layer, causing the mulch film to pulverize. Other examples only pulverize after the third year.

Claims

1. A biodegradable plastic, characterized in that: It has a layered structure containing a stabilizer and a layered structure that destroys the stabilizer; The components of the layered structure containing stabilizer include 0.1-2% by mass of hindered amine light stabilizer, 0.01-0.05% by mass of catalyst, and 95-99% by mass of resin. The catalyst is sodium copper chlorophyllin, and its CAS number is 11006-34-1. The resin is linear low-density polyethylene or metallocene polyethylene; The second layer structure of the destructive stabilizer is composed of 0.2-2% by mass of ester. The catalyst promotes the decomposition of the ester into acid and alcohol under certain temperature and light conditions. The acid decomposed from the ester is released into the first layer structure containing the stabilizer with the help of alcohol and ester. The hindered amine light stabilizer becomes ineffective after encountering acid. The ester is trimethylglutarate isobutyl alcohol ester; The layered structure of the biodegradable plastic is as follows: when there are two layers, the first layer containing the stabilizer is located on the side exposed to light, and the other layer is located on the side exposed to water, which facilitates the stabilization of the upper layer and the hydrolysis of the lower ester; when there are three or more layers, a barrier layer is set between the two layers, and the barrier layer is made of ethylene-vinyl alcohol copolymer high barrier material or nylon layer; when there are four or more layers, the number of the first layer containing the stabilizer is greater than the number of the second layer that destroys the stabilizer.

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