CN103214871B - Preparation method for completely biodegradable environment-friendly composite material - Google Patents

Abstract

The invention relates to an environmentally friendly composite material with complete degradability and a preparation method. This environmentally friendly composite material is made of straw, seed shells, stems, leaves of plants such as crops and grasses, environmental adhesives, and mixed media as raw materials through hot pressing. Straw, seed shells, stems and leaves are the main components of the composite material, with a mass percentage of 50% to 90%. When preparing environmentally friendly composite materials, the plant raw materials are first dried so that the water content in the raw materials is below 5%, and then chopped, agitated shearing, mixed with a mixing medium, mixed with an adhesive, hot-pressed, Post-processing and other steps are realized, the production process is simple, no pollutant discharge, closed system operation, no dust pollution, and each step has high production efficiency. The prepared environmentally friendly composite material can be used to manufacture toys, furniture, containers, inner packaging boxes, support parts of composite food packaging boxes, interior decoration and decoration materials, advertising materials in buildings, and the like.

Description

A preparation method of an environmentally friendly composite material with complete degradability

technical field

The invention relates to a preparation method of an environment-friendly composite material, in particular to a preparation method of a completely degradable environment-friendly composite material.

Background technique

Resource shortage and environmental pollution are by-products of economic and social development. As the pace of economic development continues to accelerate, resource shortages and environmental pollution are also intensifying, which have become stumbling blocks to economic and social development. Resource shortages increase the cost of development; environmental pollution damages air resources, water resources, and soil resources, which in turn damages human health and normal social life. Resource shortage and environmental pollution have become severe problems faced by countries all over the world, especially developing countries. Under such circumstances, making full use of renewable resources and developing environmentally friendly and resource-saving processes and products has become a research hotspot in the field of science and engineering technology.

Plant resources are an important renewable resource. The poem "Wild fires are endless, spring breeze blows and regenerates" is a vivid portrayal of the renewable nature of plant resources. The stalk of the plant supports the growth of the plant, the leaves of the plant stretch in the air for photosynthesis, and the seed shell of the plant wraps and protects the seeds of the plant. These parts of the plant show good mechanical properties during the growth process, thus playing a role of support and protection, and it also indicates that the plant straw, stem leaves, and seed shells have important application prospects in material manufacturing. Although there are various types and huge quantities of plant resources, the current utilization rate of these plant resources is not high. A considerable part of straw, weeds, and artificial vegetation clippings are burned in the field, which not only pollutes the air, but also wastes resources. If these plant resources are effectively used, it will alleviate the shortage of energy and resources, reduce pollution, reduce greenhouse gas emissions, improve the biological safety and environmental safety of products, and protect human health.

There have been some reports on the preparation of composite materials from plant stalks, stems and leaves, and seed husks, but there are some problems that the types of plant resources are not widely used, only part of the organs of plants are used, the processing requirements of raw materials are high, the preparation process is cumbersome, the ingredients are complex, and plants Raw materials are often used as fillers, the proportion of plant raw materials in composite materials is low, and the combination with non-degradable polymer materials makes the degradability insufficient. Aiming at the above problems, the present invention has explored a new type of environmentally friendly composite material with complete degradability and a simple, efficient and pollution-free preparation method on the basis of systematic research.

Contents of the invention

The purpose of the present invention is to provide a method for preparing an environmentally friendly composite material with complete degradability. The fully degradable environmentally friendly composite material has the following characteristics: it is mainly composed of plant raw materials, which improves the utilization rate of plant raw materials on the one hand, and on the other hand endows the prepared composite material with higher biological safety, and The cost of materials is reduced; plant stalks, stems and leaves, seed shells and even roots can be used as raw materials for the environmentally friendly composite material of the present invention, and the overall utilization rate of plants is greatly improved; the types of plants include not only crops, but also field weeds , weeds, aquatic weeds, artificially cultivated vegetation and other types, the utilization rate of plant species is more comprehensive; the adhesive used in the preparation of composite materials is biopolymer or derivative biopolymer, which has plant homology and can Degradability: The plant material and the adhesive are mixed through an environmentally friendly medium, and at the same time, the spreading, wetting and bonding of the adhesive on the surface of the plant material are realized under the action of the medium and heat and pressure.

The preparation method of the environmentally friendly composite material with complete degradability of the present invention has the following characteristics: the process is simple, easy to operate on a large scale, and the production efficiency is high; raw material processing and mixing are carried out in a closed system to prevent dust pollution; the production temperature is relatively low. Low, reduce the damage of plant raw materials under the action of heat, prevent the degradation of material performance, prevent the generation of pyrolysis products and air pollution in the production environment; the demoulding method is reliable and effective, not only protecting the material from mechanical damage, but also becoming a part of the material. Enhance the performance of composite materials.

The present invention is achieved through the following technical solutions: a fully degradable environmentally friendly composite material, characterized in that it is composed of any one or more than two of plant straw, seed shells, stems, and leaves, as well as adhesives and mixing media. The composite material is made of raw materials, wherein any one or a mixture of two or more of plant straw, seed husk, stem and leaf is the main component of the composite material, and the weight percentage is 50%-90%.

The types of plants mentioned therein are very extensive, including rice, wheat, corn, cotton, soybean, sesame, sugar beet and other crops and various aquatic and terrestrial, wild and planted grasses;

The main component of the adhesive is starch or starch acetate;

The adhesive can be based on starch, with any one or a mixture of cellulose and carboxymethyl cellulose; or with acetate starch as the main, with cellulose, carboxymethyl cellulose Any one or a mixture of two of methyl cellulose; when starch or acetate starch is used in conjunction with cellulose, carboxymethyl cellulose or a mixture of two of them as a binder, starch Or starch acetate is the main body, the weight percentage of starch or starch acetate in the adhesive is 50%-100%, and cellulose and its modified products are auxiliary components.

The mixing medium used is water or an aqueous solution of starch or an aqueous solution of carboxymethyl cellulose;

The present invention also provides a method for preparing the above-mentioned environmentally friendly composite material with complete degradability, comprising the following steps:

S1, drying the plant raw material so that the water content in the raw material is below 5%, and then chopping;

S2, performing agitation shearing on the chopped plant material;

S3, uniformly mixing the sheared raw material with the mixing medium;

S4, uniformly mixing the product of S3 with the adhesive;

S5. Hot pressing the product of S4 to obtain a fully degradable environmentally friendly composite material.

In step S1, the plant raw material is chopped into short cuts of 1 mm to 15 cm; in step S2, the cutting time is

1min～1h.

In step S3, the sheared raw materials refer to all the materials after shearing, and can also be sieved powder or the remaining materials after sieving the powder to be used separately; the amount of the mixed medium is 10ml per 100 grams of plant raw materials - 50ml vehicle.

In step S5, the hot pressing time is 7 minutes to 2 hours, the hot pressing temperature is 110° C. to 200° C., and the hot pressing pressure is 6 MPa to 100 MPa. The release agent used for demoulding is paper and vegetable oil.

The adhesive used in the present invention has three characteristics. The first characteristic is that the adhesive material belongs to a polymer substance, and the process of chain growth has been completed before the preparation of the composite material, not during the preparation of the composite material like using liquid resin. In this way, the composite material has a higher dimensionality, prevents the thermal influence of the curing process on the material, and improves the production efficiency of the material; no need to use organic solvents, reducing pollution in the production process, and It is beneficial to protect the health of on-site operators; the degradation form of the prepared composite material is mainly hydrolysis, and there is basically no degradation in the absence of water, which solves the contradiction between the application and degradation of the product; no organic solvent is used, no residue and release of harmful and easy Volatile pollutants improve the safety of the product and help protect the health of users. The second feature is that the adhesive has structural similarity and chemical compatibility with the plant material, and no external coupling agent is needed, which simplifies the formulation of the composite material and improves the safety of the composite material; the third feature is that the bonding material And it is a natural polymer material or a modified natural polymer material, which is also a renewable resource, with convenient sources and low prices. On the one hand, it ensures the degradability and biological safety of the entire composite material, and on the other hand, it also reduces the degradation of the composite material. manufacturing cost.

Since the composite material of the present invention is basically composed of plant raw materials and bonding materials derived from plants, it is non-toxic and harmless during use, has certain durability under suitable use conditions, and is discarded in the environment after use. Medium is easy to degrade and has complete degradability. The degradation products can re-participate in the natural cycle without causing pollution and metabolic burden to the environment. Pollution, burning increases the content of greenhouse gases and harmful gases in the air.

In order to achieve good mixing of the adhesive and the plant material, the present invention uses water, an aqueous solution of biopolymers, and an aqueous solution of biopolymer derivatives as a mixing medium. First, the liquid mixed medium is mixed with the plant material to realize the distribution of the mixed medium on the surface of the plant material, so that it has the ability to adsorb the adhesive material, and then the plant material with the mixed medium distributed on the surface is mixed with the adhesive. The use of a liquid mixing medium can make the plant material and the adhesive mix evenly and prevent stratification during the mixing process; it can reduce the fluidity of the plant material, increase the plasticity and shape retention of the plant material, and make the molding process easy; If a solution is used as the mixing vehicle, the solute components in the solution also have an effect on composite modification and surface coating.

The preparation method of the fully degradable environment-friendly composite material of the present invention adopts the hot pressing method, and compared with the extrusion method, the production efficiency is higher and the operation is simpler. At the same time, due to the use of liquid mixed media, the hot pressing process has the characteristics of hydrothermal processing. In the hydrothermal state, the adhesive is easier to plasticize, and realizes the bonding between the plant raw materials, eliminates the influence of the wax on the surface of the plant raw materials on the performance of the composite material, eliminates the dewaxing step, and simplifies the production process. The water in the mixed medium can be released in gaseous form when the mold is opened, leaving uniform pores inside the material, which improves the thermal insulation and shock absorption of the material. The production site is odorless and pollution-free, on the contrary there is a pleasant smell of cooked corn.

The preparation method of the fully degradable environment-friendly composite material of the present invention innovatively adopts the paper and vegetable oil demoulding method, and the method is simple, effective and low in cost. If it is not used to make food containers, there are all kinds of recycled waste paper that can be used. Put the paper around the composite material, and then brush a little vegetable oil on the mold. After hot pressing, the sample can be easily taken out, which is much more efficient than using vegetable oil alone, and the release paper is tightly combined with the composite material without removal, which improves the The strength of the composite material improves the surface smoothness of the composite material and realizes the transformation of waste paper into treasure.

The fully degradable environmentally friendly composite material of the present invention can be used instead of some plastics to reduce white pollution and the consumption of petroleum resources; it can be used instead of part of wood to reduce soil erosion caused by deforestation. The prepared composite material can be used to manufacture toys, furniture, containers, inner packing boxes, supporting parts of composite food packaging boxes, interior decoration and decoration materials, advertising materials in buildings, etc. after surface coating, and has a wide range of uses. Its use is beneficial to reduce environmental pollution, protect people's health and improve people's environmental awareness. Since the types of plant resources used are not limited to crops, they can also be field weeds, weeds, aquatic weeds, artificially cultivated vegetation, etc., which is conducive to solving the problem of insufficient resources caused by seasonal harvesting of crop resources.

Description of drawings

Fig. 1 shows the variation law of the tensile strength of a series of environmentally friendly composite materials prepared by changing the amount of adhesive in the present invention according to Embodiment 1.

Fig. 2 shows the change rule of Shore hardness of a series of environment-friendly composite materials prepared by changing the amount of adhesive according to Embodiment 1 of the present invention.

Fig. 3 shows the variation law of tensile strength of a series of environment-friendly composite materials prepared by changing the amount of mixed media in Embodiment 1 of the present invention.

Fig. 4 shows the change law of Shore hardness of a series of environment-friendly composite materials prepared by changing the amount of mixed media according to Embodiment 1 of the present invention.

Fig. 5 shows the variation law of tensile strength of a series of environment-friendly composite materials prepared by changing the hot-pressing temperature according to Embodiment 1 of the present invention.

Detailed ways

Example 1

Dry the waste grass obtained from the lawn pruning, cut it into short pieces with a length of about 4.0 cm, and cut it in a four-bladed turbo mechanical mixer for 5 minutes in a closed manner. Weigh 1000 grams of sheared material, put it in a mixing tank, add 400 mL of tap water, and stir for 5 minutes to make the surface of the grass evenly wet, then weigh 200 grams of cornstarch, add it to the raw material tank, and stir for 5 minutes to make the grass and the bonding The agent is evenly mixed. Brush a thin layer of rapeseed oil on the surface of the mold, place release paper in the lower mold, then put the mixed material into the mold, cover the material with a layer of release paper, and cover the upper mold. Place the mold filled with the material between the platens at a temperature of 135°C, pressurize to 12MPa, heat press for 10 minutes, remove the mold, cool to 30°C and open the mold to obtain a completely degradable environmentally friendly composite material, composite material The tensile strength reaches 4.5MPa.

Fig. 1 shows the variation law of the tensile strength of a series of environmentally friendly composite materials prepared by changing the amount of adhesive in the present invention according to Embodiment 1. It can be seen from the figure that with the increase of the amount of adhesive, the tensile strength of the composite material presents a trend of first increasing and then decreasing. As the amount of adhesive increases, the bonding points between the sheared plant materials increase, the stronger the bonding, and the tensile strength gradually increases. But when the amount of bonding is too much, the adhesive will be unevenly distributed in the composite material, forming an aggregation area of the adhesive, forming a new structural defect in the material, and the tensile strength of the composite material will decrease instead.

Fig. 2 shows the change rule of Shore hardness of a series of environment-friendly composite materials prepared by changing the amount of adhesive according to Embodiment 1 of the present invention. When measuring, take a square with a side length of 4cm in the center of the plate-shaped sample, and measure the hardness of the four vertices of the square. The four vertices are respectively expressed as 1, 2, 3, and 4. It can be seen from the figure that the fluctuation range of the surface hardness of each sample is small, and it is less affected by the amount of adhesive.

Fig. 3 shows the variation law of tensile strength of a series of environment-friendly composite materials prepared by changing the amount of mixed media in Embodiment 1 of the present invention. It can be seen from the figure that with the increase of the amount of medium, the tensile strength of the composite material shows a trend of first increasing and then decreasing. As the amount of the agent increases, the dispersion ability of the adhesive in the material increases, and the tensile strength of the material increases gradually; if the amount of the agent is too large, it will partially remain in the composite material, playing a plasticizing role, so that The strength of the composite material is reduced.

Fig. 4 shows the change law of Shore hardness of a series of environment-friendly composite materials prepared by changing the amount of mixed media according to Embodiment 1 of the present invention. It can be seen from the figure that, just like the samples prepared by changing the amount of adhesive, the hardness of the composite material is relatively uniform under the condition of different amount of medium. When the amount of medium is too much or too little, the hardness is relatively low. When the amount of the medium is too much, the residual medium acts as a plasticizer and the material is softer; when the amount of the medium is too small, the degree of plasticization of the adhesive is low, and the strength of the material is low, so the hardness is also small.

Fig. 5 shows the variation law of tensile strength of a series of environment-friendly composite materials prepared by changing the hot-pressing temperature according to Embodiment 1 of the present invention. It can be seen from the figure that with the increase of hot pressing temperature, the tensile strength of the composite material first increases and then decreases. As the hot-pressing temperature increases, the degree of plasticization of the adhesive increases, the distribution uniformity in the plant material increases, the bonding performance increases, and the tensile strength of the composite material increases; Under the action of the formation of internal structural defects or denaturation, which in turn reduces the tensile strength of the composite material.

Example 2

The soybean stalks were dried in the sun, chopped into 2.0cm short pieces, and cut in a four-bladed turbo mechanical mixer for 20 minutes. Weigh 1000 grams of sheared material, place it in a stirring tank, add 200 mL of starch solution with a mass content of 2%, stir for 5 minutes, so that the surface of the planted soybean stalk sheared material is evenly wetted, then weigh 300 grams of cornstarch, add Put it into the raw material tank and stir for 10 minutes to make the plant raw material and adhesive evenly mixed. Brush a thin layer of rapeseed oil on the surface of the mold, place release paper in the lower mold, then put the mixed material into the mold, cover the material with a layer of release paper, and cover the upper mold. Place the mold filled with the material between the pressing plates at a temperature of 140°C, pressurize to 20MPa, heat press for 15 minutes, remove the mold, cool to 30°C and open the mold to obtain a completely degradable environmentally friendly composite material, composite material The tensile strength reaches 6.3MPa.

Example 3

The cotton stalks were dried in the sun, chopped into 2.0cm short pieces, and cut in a four-bladed turbo mechanical mixer for 20 minutes. Weigh 1000 grams of sheared material, place it in a stirring tank, add 200 mL of starch solution with a mass content of 2%, and stir for 5 minutes to make the surface of the cotton stalk sheared material evenly wetted, then weigh 300 grams of cornstarch, add Put it into the raw material tank and stir for 10 minutes to make the plant raw material and adhesive evenly mixed. Brush a thin layer of rapeseed oil on the surface of the mold, place release paper in the lower mold, then put the mixed material into the mold, cover the material with a layer of release paper, and cover the upper mold. Place the mold filled with the material between the pressing plates at a temperature of 140°C, pressurize to 20MPa, heat press for 15 minutes, remove the mold, cool to 30°C and open the mold to obtain a completely degradable environmentally friendly composite material, composite material The tensile strength reaches 8.1MPa.

Example 4

Cotton stalks and lawn pruned grasses were dried in the sun, chopped into 3.0 cm short pieces, and cut in a four-bladed turbo mechanical mixer for 15 minutes in a closed manner. Weigh 1000 grams of sheared material, put it in a stirring tank, add 200 mL of starch solution with a mass content of 1%, stir for 5 minutes, so that the surface of the plant raw material is evenly wetted, then weigh 400 grams of corn starch, and add it to the raw material tank , stirring for 8 minutes to mix the plant material and the adhesive evenly. Brush a thin layer of rapeseed oil on the surface of the mold, place release paper in the lower mold, then put the mixed material into the mold, cover the material with a layer of release paper, and cover the upper mold. Place the mold filled with the material between the pressing plates at a temperature of 140°C, pressurize to 20MPa, heat press for 15 minutes, remove the mold, cool to 30°C and open the mold to obtain a completely degradable environmentally friendly composite material, composite material The tensile strength reaches 9.6MPa.

Claims (2)

1. A method for preparing an environmentally friendly composite material with complete degradability. The composite material is made of any one or two or more mixtures of plant straw, seed shells, stems, and leaves, as well as adhesives and mixing media. Made, wherein, any one or mixture of two or more of plant straw, seed husk, stem, and leaf is the main component of the composite material, and the weight percentage is 50%-90%, and the adhesive is starch or Acetate starch is mainly used together with any one or a mixture of cellulose and carboxymethyl cellulose, wherein the weight percentage of starch or acetate starch in the adhesive is 50%-100%, Used mixing medium is the aqueous solution of water or starch or the aqueous solution of carboxymethyl cellulose, it is characterized in that, comprises the following steps: S1. Drying the plant material so that the water content in the material is below 5%, and then chopping the plant material into chopped pieces of 1 mm to 15 cm; S2. Perform stirring shearing on the chopped plant material, and the shearing time is 1 minute to 1 hour; S3, uniformly mixing the sheared raw material with the mixing medium; S4, uniformly mixing the product of S3 with the adhesive; S5, hot pressing the product of S4 to obtain a completely degradable environmentally friendly composite material; In step S3, the amount of the mixed medium is 10ml-50ml of medium per 100g of plant material. 2. The preparation method according to claim 1, characterized in that, in step S5, the hot-pressing time is 7min-2h, the hot-pressing temperature is 110°C-200°C, and the hot-pressing pressure is 6MPa-100MPa.