CN100532453C - A polylactic acid foam plastic sheet for plastic absorption and its preparation method - Google Patents

Abstract

This invention relates to a method for preparing polylactic acid foamed plastic, especially polylactic acid foamed plastic sheet material for sucking-plasticization. The raw materials for the sheet material are: polylactic acid resin 100 parts, chain extender 0.2-2 parts, nucleating agent 0.1-5 parts, foamer 0.3-2.5 parts, toughener 0.5-15 parts, reinforcer 0.5-5 parts, and antioxidant 0.1-1 part. The method comprises: extruding the raw materials without the foamer to obtain master batch, adding the foamer, extruding, stretching unidirectionally, and shaping, cutting, spreading, coiling and packaging. The foamed plastic sheet material has good mechanical properties and obstructive ability, and is biodegradable, thus the cost performance is high. The sucking-plasticized products can be used to manufacture bottles for cosmetics, pesticides and drinks, food packaging containers, dishwares, trays and vacuum-shaped products.

Description

A polylactic acid foam plastic sheet for plastic absorption and its preparation method

technical field

The invention belongs to the technical field of engineering plastics, and in particular relates to a polylactic acid foamed plastic, in particular to a polylactic acid foamed plastic sheet for plastic absorption and a preparation method thereof.

Background technique

Since the beginning of the 21st century, protecting the earth's environment, building a resource-recycling society, and taking the road of sustainable development have become the focus and urgent task of the world. Biodegradable plastics have been confirmed as low-environmental load materials through product life cycle analysis. In addition, a considerable part of the main raw materials of biodegradable plastics come from renewable agricultural resources. As a supplementary replacement for limited, dwindling, and depleting non-renewable petroleum resources, it has also become a global development trend. Therefore, biodegradable plastics have become a global research and development hotspot.

Polylactic acid (PLA), also known as polylactide, belongs to the family of polyesters. As a new type of fully degradable plastic, it has attracted the attention of more and more countries and enterprises. Polylactic acid is a polymer obtained by polymerizing lactic acid as the main raw material. The raw material source is sufficient and can be regenerated. Polylactic acid can be completely decomposed into carbon dioxide and water through hydrolysis reaction and microbial decomposition, and the decomposition time required in the atmosphere, in soil or water containing microorganisms, in landfills and in compost is 3- 5 years, 2-3 years, 2-4 months and 1-4 weeks. The production process of polylactic acid is non-polluting, and the product can be biodegraded to realize the cycle in nature, so it is an ideal green polymer material.

However, due to the limitation of high production cost of polylactic acid, its use as a degradable plastic started late. In recent years, due to environmental protection requirements and the shortage of petroleum resources, people have paid more attention to polylactic acid, and began to explore and develop polylactic acid products. At present, there are many foamed plastic blister products made of polyethylene, polystyrene, and mostly polyurethane on the market. They have light weight, material saving, low thermal conductivity, good heat insulation performance, and shock load absorption. And other properties, play a huge role in the packaging industry. However, after these foamed plastics are used, it is difficult to recycle and recycle them, and they are discarded into the environment, which cannot be assimilated with the environment and cause great harm to the environment. The development of polylactic acid foam can not only effectively solve the above problems, but also reduce the cost of polylactic acid products.

Due to the excellent extensibility of PLA, but high brittleness, some original polylactic acid foaming processes have some shortcomings. People such as Sterzel adopt the method for mixing physical foaming agent in polylactic acid to prepare polylactic acid structural foam (US Patent No. 5,348,983,1994), but polylactic acid must be made into particles with a smaller particle size before foaming. People such as Kameoka adopt the method for directly extruding by mixing chemical blowing agent and physical blowing agent to prepare polylactic acid foam (US Patent 5763098,1998), but property is brittle, and impact resistance is not good.

Contents of the invention

The purpose of the present invention is to provide a degradable polylactic acid foam sheet for plastic absorption with low process requirements and good impact resistance and a preparation method thereof.

A polylactic acid foam sheet for plastic absorption proposed by the present invention is directly extruded by an extruder and prepared by foaming and shaping, and its raw material components are proportioned as follows by weight:

Polylactic acid resin 100,

Chain extender 0.2-2,

Nucleating agent 0.1-5,

Foaming agent 0.3-2.5,

Toughener 0.5-15,

Antioxidant 0.1-1,

Enhancer 0.5-5.

In the present invention, the apparent density of the foam plastic sheet is between 0.40 g/cm ³ and 1.0 g/cm ³ .

In the present invention, the resin is levorotatory or de-optical polylactic acid resin, the number average molecular weight is between 30,000 and 150,000, the molecular weight distribution is 1-2, and the crystallinity is 20-60%.

In the present invention, the chain extender is one or a mixture of butanediol, toluene diisocyanate (TDI), xylylene diisocyanate (XDI), and diphenylmethane diisocyanate (MDI).

In the present invention, the nucleating agent is composed of one or more mixtures of montmorillonite, talc, calcium carbonate, magnesium carbonate, titanium dioxide, pottery clay and mica. The montmorillonite is made of smectite clay (including calcium-based, sodium-based, sodium-calcium-based, magnesium-based montmorillonite clay) after peeling and dispersing, purification and modification, ultra-fine classification, and organic compounding, with an average wafer thickness of less than 25nm , The montmorillonite content is greater than 95%.

In the present invention, the foaming agent is an AC foaming agent, and its decomposition temperature is between 140°C and 190°C.

In the present invention, the toughening agent is polyethylene glycol (PEG) with a number average molecular weight of 1000-20000, and one or two mixtures of PEG4000 and PEG6000 can be selected.

In the present invention, the antioxidant is one or a mixture of catechol and hydroquinone.

In the present invention, the reinforcing agent is one or a mixture of methyl cellulose or ethyl cellulose.

The preparation method of the plastic-absorbing polylactic acid foam sheet that the present invention proposes, concrete steps are as follows:

(1) Mix polylactic acid, nucleating agent, chain extender and antioxidant uniformly by metering, extrude with an extruder to make a masterbatch, cool and cut into pellets;

(2) Evenly mix the masterbatch and foaming agent according to the measurement, extrude foaming with an extruder, inject toughening agent and reinforcing agent into the extruder during extrusion, and control the temperature of the extruder at 160- Between 220°C, extrude foam and cool;

(3) Unidirectional stretching, shaping, cutting, flattening, coiling and packaging.

The polylactic acid foamed plastic sheet for plastic absorption prepared by the invention has a closed-cell foam structure, and is obtained after unidirectional stretching and setting after a direct extrusion process. Products prepared by blistering of such sheets can be automatically degraded after use and discarded, and the degradation products are environmentally friendly. The invention has advanced production technology, good product performance, wide source of raw materials and high cost performance. Blistered products can be used to make cosmetic bottles, pesticide bottles, beverage bottles, food packaging containers, tableware, trays, vacuum formed products, etc., and are widely used. Wide range of sources of raw materials, high cost performance, the products after blister can be used to make cosmetic bottles, pesticide bottles, beverage bottles, food packaging containers, tableware, trays, vacuum forming products, etc., which are widely used.

The following will illustrate the present invention in further detail through the examples of the present invention. In the examples, parts and percentages are by weight unless otherwise indicated. But the invention is not limited to these examples.

Detailed ways

It is necessary to point out that the following examples are only used to further illustrate the present invention, and should not be interpreted as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention according to the foregoing.

Example 1

There will be 100 parts by weight of polylactic acid resin (Shanghai Tongjieliang Biomaterials Co., Ltd., number average molecular weight 3-150,000), 0.5 parts by weight of chain extender toluene diisocyanate, and 2 parts by weight of nucleating agent montmorillonite (sodium base) , Antioxidant hydroquinone 0.5 parts by weight of raw materials are mixed evenly, added to the extruder and extruded, the temperature of the extruder is 160-200 ℃, the speed of the host is 850rpm, and the speed of the screw is 30rpm. The masterbatch is cooled and diced. Evenly mix the masterbatch and 0.3 parts by weight of the foaming agent and add them to the extruder for extrusion and foaming. The extrusion temperature, the speed of the main engine, and the speed of the screw are the same as above, and the toughening agent polyethylene glycol is added through a metering pump during the extrusion process. (PEG4000) 2 parts by weight, 0.5 parts by weight of methylcellulose. Extruded foam, cooling, unidirectional stretching, shaping, cutting, flattening, traction and coiling. The stretch ratio is 5%, the pulling speed is 28rpm, and the specifications of the obtained product are: thickness 3mm, width 800mm. The sheet is made into a standard sample (140mm×10mm×4mm), under constant temperature and humidity conditions, the tensile speed is 5.0/(mm/min), the measured tensile strength is 30Mpa, and the elongation at break 5%. The apparent density of the sheet was 0.75 g/cm ³ . Biodegradation test confirmed that it can be completely degraded.

Example 2

There will be 100 parts by weight of polylactic acid resin (Shanghai Tongjieliang Biomaterials Co., Ltd., number average molecular weight 3-150,000), 0.5 parts by weight of chain extender toluene diisocyanate, 4 parts by weight of nucleating agent montmorillonite (sodium base) , the raw materials composed of 0.5 parts by weight of antioxidant catechol are mixed evenly, and then added to the extruder for extrusion. Masterbatch, cooled and diced. Mix the masterbatch and 0.5 parts by weight of foaming agent evenly and add them to the extruder for extrusion and foaming. The extrusion temperature, the speed of the host machine and the speed of the screw are the same as above, and polyethylene glycol (PEG4000) is added through a metering pump during the extrusion process. 2.5 parts by weight, 2.5 parts by weight of polyethylene glycol (PEG6000), and 1 part by weight of methylcellulose. The extruded foam is coiled after cooling, unidirectional stretching, shaping, cutting, flattening and traction. The stretch ratio is 5%, the pulling speed is 30rpm, and the specifications of the obtained product are: thickness 2.8mm, width 800mm. The sheet is made into a standard sample (140mm×10mm×4mm), under constant temperature and humidity conditions, the tensile speed is 5.0/(mm/min), the measured tensile strength is 28Mpa, and the elongation at break was 5.6%. The apparent density of the sheet was 0.71 g/cm ³ . Biodegradation test confirmed that it can be completely degraded.

Example 3

There will be 100 parts by weight of polylactic acid resin (Shanghai Tongjieliang Biomaterials Co., Ltd., number average molecular weight 3-150,000), 0.5 parts by weight of chain extender toluene diisocyanate, 0.5 parts by weight of xylylene diisocyanate, nucleating agent 5 parts by weight of montmorillonite (sodium base), 0.5 parts by weight of antioxidant catechol and 0.5 parts by weight of hydroquinone are mixed evenly, and are added into an extruder to extrude, and the extruder temperature is 170—210°C, the speed of the main machine is 850rpm, the speed of the screw is 30rpm, the masterbatch is prepared, cooled and diced. Evenly mix the masterbatch and 0.7 parts by weight of the foaming agent and add them to the extruder for extrusion foaming. The extrusion temperature, the speed of the main engine, and the speed of the screw are the same as above. During the extrusion process, the toughening agent polyethylene glycol is added through a metering pump. (PEG4000) 5 parts by weight, polyethylene glycol (PEG6000) 5 parts by weight, reinforcing agent methylcellulose 1.5 parts by weight. Extruded foam, cooling, unidirectional stretching, shaping, cutting, flattening, traction and coiling. The stretching ratio is 5%, the pulling speed is 35 rpm, and the specifications of the obtained product are: thickness 2.5 mm, width 800 mm. The sheet is made into a standard sample (140mm×10mm×4mm), under constant temperature and humidity conditions, the tensile speed is 5.0/(mm/min), the measured tensile strength is 25Mpa, and the elongation at break was 6.2%. The apparent density of the sheet was 0.67 g/cm ³ . Biodegradation test confirmed that it can be completely degraded.

Example 4

There will be 100 parts by weight of polylactic acid resin (Shanghai Tongjieliang Biomaterials Co., Ltd., number average molecular weight 3-150,000) and 0.5 parts by weight of chain extender xylylene diisocyanate and 0.5 parts by weight of diphenylmethane diisocyanate, The raw materials consisting of 5 parts by weight of nucleating agent talcum powder and 1 part by weight of antioxidant hydroquinone are mixed evenly, and then added to the extruder for extrusion. The rotation speed of the screw is 40rpm, and the masterbatch is prepared, cooled and diced. Evenly mix the masterbatch and 1.0 parts by weight of the foaming agent and add them to the extruder for extrusion and foaming. The extrusion temperature, the speed of the main engine, and the speed of the screw are the same as above. During the extrusion process, the toughening agent polyethylene glycol is added through a metering pump. (PEG4000) 7.5 parts by weight, polyethylene glycol (PEG6000) 2.5 parts by weight, reinforcing agent methylcellulose 1.5 parts by weight. Extruded foam, cooling, unidirectional stretching, shaping, cutting, flattening, traction and coiling. The stretching ratio is 5%, the pulling speed is 35 rpm, and the specifications of the obtained product are: thickness 2.7 mm, width 800 mm. The sheet is made into a standard sample (140mm×10mm×4mm), under constant temperature and humidity conditions, the tensile speed is 5.0/(mm/min), the measured tensile strength is 22Mpa, and the elongation at break was 6.7%. The apparent density of the sheet was 0.61 g/cm ³ . Biodegradation test confirmed that it can be completely degraded.

Example 5

There will be 100 parts by weight of polylactic acid resin (Shanghai Tongjieliang Biomaterials Co., Ltd., number average molecular weight 3-150,000), 1 part by weight of chain extender toluene diisocyanate, 1 part by weight of diphenylmethane diisocyanate, nucleating agent The raw materials consisting of 7.5 parts by weight of montmorillonite (sodium base) and 1 part by weight of antioxidant hydroquinone are mixed evenly, and then added to the extruder for extrusion. 1000rpm, the rotation speed of the screw is 40rpm, the masterbatch is prepared, cooled and diced. Evenly mix the masterbatch and 1.5 parts by weight of the foaming agent and add them to the extruder for extrusion and foaming. The extrusion temperature, the speed of the main engine, and the speed of the screw are the same as above. During the extrusion process, the toughening agent polyethylene glycol is added through a metering pump. (PEG4000) 10 parts by weight, polyethylene glycol (PEG6000) 5 parts by weight, methylcellulose 3 parts by weight. Extruded foam, cooling, unidirectional stretching, shaping, cutting, flattening, traction and coiling. The stretch ratio is 5%, the pulling speed is 40rpm, and the specifications of the obtained product are: thickness 2.3mm, width 800mm. The sheet is made into a standard sample (140mm×10mm×4mm), under constant temperature and humidity conditions, the tensile speed is 5.0/(mm/min), the measured tensile strength is 23Mpa, and the elongation at break was 5.9%. The apparent density of the sheet was 0.55 g/cm ³ . Biodegradation test confirmed that it can be completely degraded.

Example 6

There will be 100 parts by weight of polylactic acid resin (Shanghai Tongjieliang Biological Materials Co., Ltd., number average molecular weight 3-150,000) and 1 part by weight of chain extender diphenylmethane diisocyanate, nucleating agent montmorillonite (sodium base) The raw materials consisting of 5 parts by weight and 1 part by weight of antioxidant hydroquinone are mixed evenly, and then added to the extruder for extrusion. , to prepare the masterbatch, cooling and dicing. Evenly mix the masterbatch and 0.5 parts by weight of the foaming agent and add them to the extruder for extrusion and foaming. The extrusion temperature, the speed of the main engine, and the speed of the screw are the same as above. During the extrusion process, the toughening agent polyethylene glycol is added through a metering pump. (PEG4000) 15 parts by weight, reinforcing agent ethyl cellulose 5 parts by weight. Extruded foam, cooling, unidirectional stretching, shaping, cutting, flattening, traction and coiling. The stretch ratio is 5%, the pulling speed is 28rpm, and the specifications of the obtained product are: thickness 2.8mm, width 800mm. The sheet is made into a standard sample (140mm×10mm×4mm), under constant temperature and humidity conditions, the tensile speed is 5.0/(mm/min), the measured tensile strength is 17Mpa, and the elongation at break 7.5%. The apparent density of the sheet was 0.66 g/cm ³ . Biodegradation test confirmed that it can be completely degraded.

Claims (3)

1. A polylactic acid foamed plastic sheet for plastic absorption is characterized in that it is directly extruded by an extruder, and is prepared by foaming and shaping, and its raw material components are as follows by weight: Polylactic acid resin 100, Chain extender 0.2-2, Nucleating agent 0.1-5, Foaming agent 0.3-2.5, Toughener 0.5-15, Enhancer 0.5-5, Antioxidant 0.1-1; The apparent density of the foam plastic sheet is between 0.40g/cm ³ and 1.0g/cm ³ ; The resin is levorotatory or de-optical polylactic acid resin, with a number average molecular weight of 30,000-150,000, a molecular weight distribution of 1-2, and a crystallinity of 20-60%; The chain extender is a mixture of one or more of butylene glycol, toluene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate; The nucleating agent is: montmorillonite, talcum powder, calcium carbonate, magnesium carbonate, titanium dioxide, pottery clay, mica one or more of the mixture; The foaming agent is an AC foaming agent, and its decomposition temperature is between 140°C and 190°C; The toughening agent is polyethylene glycol, and the number average molecular weight is between 1000-20000; The antioxidant is a mixture of one or two of catechol and hydroquinone; The reinforcing agent is a mixture of one or two of methylcellulose or ethylcellulose. 2. the polylactic acid foam plastic sheet for plastic absorption according to claim 1, is characterized in that described montmorillonite is that montmorillonite clay forms through stripping and dispersing, purifying and remodeling, superfine classification, and organic compounding, The average wafer thickness is less than 25nm, and the montmorillonite content is greater than 95%. 3. a preparation method of plastic-absorbing polylactic acid foam sheet as claimed in claim 1, is characterized in that concrete steps are as follows: (1) Mix polylactic acid, nucleating agent, chain extender and antioxidant uniformly by metering, extrude with an extruder to make a masterbatch, cool and cut into pellets; (2) Evenly mix the masterbatch and foaming agent according to the measurement, extrude foaming with an extruder, inject toughening agent and reinforcing agent into the extruder during extrusion, and control the temperature of the extruder at 160- Between 220°C, extrude foam and cool; (3) Unidirectional stretching, shaping, cutting, flattening, coiling and packaging.