KR100836496B1 - A biodegradable rigid foam - Google Patents

Abstract

A biodegradable rigid foam is provided to contain polylactic acid resin and an inorganic chemical blowing agent, and to show excellent tensile strength and impact strength. An injection foaming type biodegradable rigid foam includes: a biodegradable resin comprising polylactic acid resin, or polylactic acid resin and poly(butylene succinate); an inorganic chemical blowing agent; and natural fiber. The foam further contains a nucleator and an antioxidant. The inorganic chemical blowing agent is at least one selected from the group comprising sodium bicarbonate, citric acid, ammonium carbonate, and mixtures thereof. The inorganic chemical blowing agent is contained in an amount of 0.5-3.0 parts by weight, based on 100 parts by weight of the biodegradable resin.

Description

Biodegradable rigid foam

The present invention relates to a biodegradable rigid foam, more specifically, a polylactic acid (PLA) resin and an inorganic chemical foaming agent, characterized in that the expansion ratio is 1.2 to 2 times, injection-foaming type biodegradation It relates to a rigid rigid foam.

In general, plastic injection molding technology mostly melts pellets made of synthetic resin such as polypropylene, polyethylene, ethylene vinyl acetate copolymer, etc., using electric heat and mechanical friction, and then applies a force to a mold made into a desired shape. As the manufacture of various plastic products with a certain shape by extrusion, the material occupies a very high proportion of the manufacturing cost of the product, the foaming technology was developed by efforts to reduce the material cost and further reduce the weight of the plastic product. It is improving. Foaming technology is a technology that creates a large number of bubbles having a fine size in a plastic product, the chemical or physical blowing agent is mixed well with the pellets and then heated outside to allow the foaming material to vaporize to form bubbles inside the product. When bubbles are formed, a large portion of the product is occupied by bubbles, so that the material cost can be greatly reduced, the weight of the product can be reduced, and the thermal insulation performance due to bubbles can be obtained. In the case of the product of such an injection-foaming method, bubbles are uniformly distributed throughout the plastic molded article, and have a high density foam property, and thus can be easily applied to a field requiring mechanical strength.

Plastic foams made of general petrochemicals, for example, foams made of plastic resins such as polystyrene, polyvinylchloride, polyethylene or polyurethane, can be mass-produced at low cost and with excellent properties such as buffering, thermal insulation and chemical resistance. Because of its advantages, it is usefully used throughout the industry. However, such plastic foams are mostly incinerated after use due to their low recyclability, and in this case, harmful substances such as dioxins are generated and environmental hormones are discharged. In addition, since it is almost impossible to disintegrate by microorganisms in the soil, it will remain in the ground semi-permanently when landfilled.

Due to the environmental pollution caused by plastics as described above, biodegradable polymers and molded products thereof that decompose in the natural environment are required, and research on biodegradable resins such as aliphatic polyesters is being actively conducted.

In particular, polylactic acid (PLA) resin is a biodegradable resin based on starch, which has low calories generated by combustion, is easily hydrolyzed in soil or water, and completely dissolved in water and carbon dioxide by soil microorganisms. Since it is decomposed, it does not have to go through a separate disposal process such as incineration or recycling, and is an environmentally friendly resin. It also has a melting point of 140 to 180 ° C., which is sufficiently high, and exhibits excellent high rigidity and transparency. Therefore, it is used in various industrial fields, especially molded articles requiring production and transparency of disposable cups, containers, packaging materials, cushioning materials, automotive interior materials, and the like. have.

However, until now, research and development on biodegradable foams have almost never been made except for packaging buffers using starch. However, as a foam manufacturing technique using polylactic acid resin, European Patent No. 0510999 B1, European Patent No. 0507554 B1 and Japanese Patent Laid-Open No. 2000-7816 and the like are known. However, they only mention only sheet-like continuous foams and articles using extruders. It is difficult to obtain a high-density rigid foam by the extrusion foaming technique, and at present there is no satisfactory technology for the production of the injection foam and the product.

Accordingly, the present inventors have made diligent efforts to solve the above problems, and when foaming a composition containing a polylactic acid resin, which is a biodegradable resin, and an inorganic chemical foaming agent in a mold, it is possible to produce a foam exhibiting excellent tensile strength and impact strength. With this in mind, the present invention has been completed.

Accordingly, it is an object of the present invention to provide a biodegradable rigid foam containing a polylactic acid resin and an inorganic chemical foaming agent and exhibiting excellent tensile strength and impact strength.

In order to achieve the above object, the present invention provides an injection-foaming biodegradable foam containing a biodegradable resin and an inorganic chemical foaming agent, and manufactured using an injection apparatus.

The biodegradable resin of the present invention described above is composed of a polylactic acid resin or a polybutylene succinate resin for masterbatches of a polylactic acid resin and an inorganic chemical foaming agent.

The foam of the present invention as described above may have a composition further containing natural fibers.

In addition, the foam of the present invention can be made by further containing additives such as nucleating agent, antioxidant.

Hereinafter, the present invention will be described in detail.

Each component of the foam of the present invention will be described in more detail as follows.

In the foam of the present invention, polylactic acid resin is one of a variety of biodegradable resins, and due to the nature-friendly nature of disintegrating into water and carbon dioxide almost completely molecularly upon disposal, it is considered that it will be able to replace the current general purpose resin in many parts in the future. have. The polylactic acid resin in the present invention can be purchased and used, it is preferable to use the pelletized.

Specific examples of the polylactic acid resin include PLA of Cargill-Dow, USA, and LACEA of Mitsui Chemicals.

In the case of injection foaming, a chemical blowing agent is mixed with a resin and supplied to an injection molding machine, and decomposed by electric heat and a shear force by a screw in a cylinder to generate gas such as carbon dioxide or carbon dioxide to enable foaming of the resin. . In the present invention, it is preferable to use, as the chemical blowing agent, an inorganic chemical blowing agent which is low in decomposition residue, harmless to the human body, and which is easy to refine the bubbles. Specific examples are selected from the group consisting of sodium bicarbonate, citric acid, ammonium carbonate, sodium bicarbonate and mixtures thereof.

The inorganic chemical foaming agent is preferably added in the form of a master batch (M / B). However, when the polylactic acid resin is used in the foaming agent master batch, since its melting point is around 170 ° C., there is a disadvantage in that the inorganic foaming agent is decomposed in advance in the process of melting it, and thus the biodegradable resin having a melting point around 90 to 120 ° C., eg For example, it is preferable to use polybutylene succinate (PBS) resin.

The amount of the inorganic chemical foaming agent added varies depending on the type and the concentration of the masterbatch, but is 0.5 to 3.0 parts by weight, more preferably 1.0 to 2.5 parts by weight based on 100 parts by weight of the biodegradable resin (in terms of solid content) of the present invention. Used as a negative range. If the inorganic chemical foaming agent is used in less than 0.5 parts by weight, it is not possible to obtain the foaming ratio as desired, and when used in excess of 3.0 parts by weight, the effect is less than the amount of use and causes a cost increase.

The master batch of the inorganic chemical foaming agent of the present invention is 5 to 30 parts by weight of sodium hydrogen carbonate, 5 to 30 parts by weight of citric acid, and 10 to paraffin oil, based on 100 parts by weight of polybutylene succinate resin (in terms of solid content). It is preferably prepared to contain 70 parts by weight.

When the biodegradable resin is composed of polylactic acid resin and polybutylene succinate resin, it is preferable that the biodegradable resin is composed of a ratio of 7: 3 to 9.7: 0.3.

In addition, the foam of the present invention may further contain natural fibers as an additive for improving impact resistance. Examples of the natural fiber may include jute, flax, yam, hemp, kenaf, banana fiber, and the like, and these may be used alone or in combination of two or more, and are not limited to the natural fibers listed above.

The foam of the present invention contains 1 to 5 parts by weight of the natural fiber with respect to 100 parts by weight of the biodegradable resin (in terms of solid content) of the present invention. If the amount of the natural fiber is less than 1 part by weight, the required impact strength can not be obtained, if the amount exceeds 5 parts by weight, the foam of the foam becomes non-uniform and foaming is not easy due to the viscoelastic degradation of the polylactic acid resin This can happen.

In the use of the inorganic chemical foaming agent, it is preferable to add a nucleating agent such as, for example, inorganic fine particles such as barium sulfate, talc, lithium carbonate, in order to stably and uniformly make bubbles of the foam stable. Although the kind in particular is not specifically limited as said nucleating agent in this invention, It is preferable that talc is contained. It is preferable that the average particle diameter of the said talc is 10-13 micrometers.

The foam of the present invention contains 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight of the nucleating agent with respect to 100 parts by weight of the biodegradable resin (in terms of solid content) of the present invention. When the quantity of the said nucleating agent is less than 0.5 weight part, the effect of addition is not acquired very much, and when it exceeds 10 weight part, the viscoelasticity of polylactic acid falls rapidly and a uniform bubble cannot be obtained.

The foam of the present invention is an antioxidant as tetrakis [methylene-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane (IRGANOX®1010, Ciba) and It is preferable to contain at least one antioxidant selected from tris (2 ', 4'-di-t-butylphenyl) phosphite. In the case where both of the antioxidants are used, it is preferable to use the mixture in a ratio of 1: 1.

The foam of the present invention contains 0.1 to 0.4 parts by weight, preferably 0.15 to 0.3 parts by weight of the antioxidant, based on 100 parts by weight of the biodegradable resin (in terms of solid content) of the present invention.

In addition, the foam of the present invention, if necessary, conventionally known plasticizers, heat stabilizers, light stabilizers, ultraviolet absorbers, pigments, colorants, various fillers, antistatic agents, mold release agents, fragrances, lubricants, flame retardants, foaming agents, fillers, antibacterial antifungal agents You may mix | blend various additives, such as another nucleating agent.

In the injection foaming method according to the present invention, for example, a pellet containing polylactic acid resin and other additives, an inorganic chemical foaming agent masterbatch pellets are introduced into a cylinder in the injection machine, and the shearing force and electric heat are applied to the foaming agent. Is decomposed to contain small bubbles in the polylactic acid product, and the molten polylactic acid is pushed into the mold to cause a pressure difference so that the gas is foamed by the pressure difference. In addition, by adding a small amount of natural fibers to the injection foaming has the advantage of high dimensional stability and impact properties. The foam thus obtained has a foaming density of 0.83 to 0.5 g / cm 3 and a foaming ratio of 1.2 to 2 times.

Biodegradable injection-foaming products manufactured according to the present invention will be easily applied at a lower cost in a wide range of fields, such as disposable containers and household goods due to the feature of being hardened, lightweight compared to conventional polylactic acid (PLA) resin.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the present embodiment is only illustrative for the purpose of understanding and is not intended to limit the present invention.

Foam  Produce

Example  One

As shown in Table 1, with respect to 100 parts by weight of the total biodegradable resin (in terms of solids), polylactic acid resin PLA (Cargill-Dausa, USA) (in terms of solids) 90 parts by weight, average particle size 10 Dry mixing of 1.5 parts by weight of talcum talc (multielement chemical) and 0.2 parts by weight of Iganox® 1010 (Ciba) was carried out by melt mixing for 10 minutes with a 200 ° C biaxial kneading extruder (die diameter 3.5 mm), Extruded and pelletized.

As the foaming agent masterbatch, 10 parts by weight of polybutylene succinate resin (from Chemistry, Korea) (in terms of solids), based on 100 parts by weight of total biodegradable resins (in terms of solids), sodium bicarbonate and citric acid 1.0 parts by weight of this mixed blowing agent hydrocerol (Clariant) and 5.0 parts by weight of paraffin oil were mixed for 5 minutes in a dry mixer (Hensel mixer), and then 50 to 200 rpm using a twin screw extruder (die diameter 3.0 mm) at 130 ° C. Melt mixed for 10 minutes, extruded into a strand shape, cooled in a cooling bath at room temperature and then cut to prepare an inorganic foam master batch.

The polylactic acid resin pellet and the inorganic foaming agent masterbatch were introduced into a cylinder through a hopper of an injection molding machine, melt-blended and injected into a mold to obtain a foam having a thickness of 3.0 mm. The density of the obtained foam was in the range of 0.83 to 0.5 g / cm 3, and the foaming ratio was 1.2 to 2 times. Using the foam specimens, specific gravity, tensile strength, elongation, and impact strength were measured based on the following criteria.

[Property test criteria]

* Specific gravity: measured by ASTM D297 method.

* Tensile strength: measured by ASTM D412 method.

Elongation: measured by ASTM D751 method.

* Izod Impact: Measured by ASTM D256 method.

Example  2 ~ 3

A foam was prepared in the same manner as in Example 1, except that the composition ratio was changed to a composition as shown in Table 1 below. Specifically, in Example 2, 1.5 parts by weight of the chemical foaming agent component was added based on 100 parts by weight of the total biodegradable resin (in terms of solid content), and in the case of Example 3, the natural fiber component was used. 3.0 parts by weight based on 100 parts by weight of a solid) was added.

As described above, the foam containing the biodegradable polylactic acid resin and the inorganic foaming agent according to the present invention shows excellent tensile strength and impact strength, and more excellent impact in the case of the foam in which the natural fiber is added to the above composition. Because of their strength, the foams can be used to produce foam moldings with high dimensional stability and improved impact properties.

Claims (17)

Biodegradable resins composed of polylactic acid resins or polylactic acid resins and polybutylenesuccinate resins; Inorganic chemical foaming agents; And Injection foamed biodegradable rigid foam containing natural fibers. delete delete The injection foam biodegradable rigid foam according to claim 1, wherein the foam further contains a nucleating agent and an antioxidant. The injection foam biodegradable rigid foam according to claim 1, wherein the inorganic chemical foaming agent is at least one selected from the group consisting of sodium bicarbonate, citric acid, ammonium carbonate, sodium bicarbonate and mixtures thereof. The injection-foaming biodegradable rigid foam according to claim 1, wherein the inorganic chemical foaming agent is contained in an amount of 0.5 to 3.0 parts by weight based on 100 parts by weight of the biodegradable resin (converted in solid content). The injection foam biodegradable rigid foam according to claim 1, wherein the inorganic chemical foaming agent is added in a masterbatch form. The method according to claim 7, wherein when the inorganic chemical foaming agent is added in the form of a masterbatch, 5 to 15 parts by weight of sodium hydrogen carbonate, based on 100 parts by weight of polybutylene succinate resin (in terms of solid content), Injection foamed biodegradable rigid foam comprising 5 to 15 parts by weight of citric acid and 10 to 70 parts by weight of paraffin oil. The injection foam biodegradable rigid foam according to claim 1, wherein the biodegradable resin is a polylactic acid resin and a polybutylene succinate resin composed of 7: 3 to 9.7: 0.3. The injection foam biodegradable rigid foam according to claim 1, wherein the natural fiber is at least one selected from the group consisting of jute, flax, germ, kenaf, hemp, and banana fiber. The injection-expandable biodegradable rigid foam according to claim 1, wherein the natural fiber is contained in an amount of 1 to 5 parts by weight based on 100 parts by weight of the biodegradable resin (converted in solid content). The injection foam biodegradable rigid foam according to claim 4, wherein the nucleating agent is talc, and its average particle diameter is 10 to 13 µm. The injection foam biodegradable rigid foam according to claim 4, wherein the nucleating agent is contained in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the biodegradable resin (in terms of solid content). The injection foam biodegradable rigid foam according to claim 4, wherein the antioxidant is contained in an amount of 0.1 to 0.4 parts by weight based on 100 parts by weight of the biodegradable resin (in terms of solid content). The method of claim 4, wherein the antioxidant is tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane and tris (2 ′, 4′- Injection foamed biodegradable foam, characterized in that at least one selected from the group consisting of di-t- butylphenyl) phosphite. The injection foam biodegradable foam according to claim 15, wherein when the antioxidant is used in two kinds of mixtures, the antioxidant is mixed in a ratio of 1: 1. The injection foam biodegradable foam according to claim 1, wherein the foam density is 0.83 to 0.5 g / cm 3 and the foaming ratio is 1.2 to 2 times.