JP2008184493A - Resin composite material, its manufacturing method, and resin composite material molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composite material thermally recyclable and exhibiting excellent mechanical strength. <P>SOLUTION: The resin composite material comprises a resin material and, incorporated as a reinforcing material therein, a surface-treated microfibrilized cellulose (MFC), where the surface-treated MFC has the surface thereof coated with an emulsion of the matrix resin of the resin composite material. The manufacturing method of the resin composite material comprises mixing the MFC with the emulsion of the matrix resin and subsequently adding the matrix resin followed by kneading. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a resin composite material, a method for producing the same, and a resin composite material molded article.

  Conventionally, glass fibers having excellent strength have been used as reinforcing materials contained in fiber-reinforced plastics. However, when performing thermal recycling to recover thermal energy by burning fiber reinforced plastic using this glass fiber, the glass fiber is incombustible, so the combustion furnace is damaged or the combustion efficiency is lowered. There was a problem such as. There is also a problem that the residue after incineration increases. For this reason, in practice, fiber-reinforced plastics are hardly thermally recycled and are mainly disposed of in landfills.

  In order to cope with such a problem, a composite material using plant fibers as a reinforcing material has been proposed (for example, see Patent Documents 1 and 2).

  However, even if the above plant fiber is used as the reinforcing fiber, a sufficient reinforcing effect is not exhibited. Several factors can be considered on this point.

  For example, first, the plant fiber itself does not necessarily have a structure suitable as a reinforcing material. When the tensile performance is compared, the tensile strength and tensile modulus of general plant fibers are much smaller than those of high-strength and high-modulus fibers such as glass fibers. This is because there are many structural defects in the plant fiber. For example, there are voids called wall holes on the fiber wall. This void is responsible for the horizontal movement of moisture during the process of plant growth. Moreover, the plant fiber has a straw-like structure, and there are large voids in the fiber along the fiber direction. This gap is for transporting moisture in the vertical direction as the plant grows.

  Second, the following formula, which is an element that forms the skeleton structure of plant fibers

The arrangement direction of cellulose microfibrils (hereinafter referred to as microfibrils) represented by A microfibril is an element of a crystal structure in which cellulose, which is a linear polymer, is oriented in one direction, and the strength of a single microfibril exhibits performance comparable to that of existing high-strength and high-modulus fibers. If all the microfibrils are arranged along the fiber direction, the tensile performance of the plant fiber is maximized, but actually about 20% of the microfibrils are arranged in a direction perpendicular to the fiber direction.

  Therefore, in order to solve the above-mentioned problems caused by the structural defects of plant fibers, a composite material (for example, patents) that separates and recovers plant fiber skeleton parts and microfibrils themselves and uses them as resin reinforcements. Document 3) has been proposed.

  The separated and recovered microfibrils are called microfibrillated cellulose (MFC). In general, after removing components other than cellulose (especially lignin) in plant fibers with chemicals, a shearing force is applied between the fibrils in the plant fibers in the presence of moisture by mechanical treatment to extract MFC. is there. MFC is produced in a state where it coexists with moisture.

MFC has an aspect ratio that is about two orders of magnitude greater than the plant fiber that is the raw material. In general, the strength performance of a composite material is improved when a fiber having a large aspect ratio is used as a reinforcing material. From the viewpoint of aspect ratio, MFC is expected to exhibit a reinforcing effect superior to that of ordinary plant fibers.
JP-A-5-92527 JP 2002-69208 A JP 2003-201695 A

  MFC has a high potential as a reinforcing material for composite materials, but its use is not straightforward. This is because it is difficult to combine MFC and resin in a state where MFC is uniformly dispersed in the resin.

  This is because MFC is composed of a polysaccharide called cellulose. Cellulose has a number of hydroxyl groups. The hydroxyl group is a highly polar functional group, and MFC composed of cellulose having a large number of these functional groups is a very polar and hydrophilic component.

  MFC is produced in the form of coexistence with a large amount of moisture in the manufacturing process. When moisture that coexists with MFC is removed, MFCs aggregate and form a strong hydrogen bond with each other. It is extremely difficult to separate the MFC agglomerates once linked by hydrogen bonding into individual fibers again.

  When the MFC is combined with the resin, it is necessary to remove moisture coexisting with the MFC during the composite process. If MFC and moisture coexist, moisture penetrates into the amorphous region of MFC, and the binding force of cellulose molecular chains constituting the amorphous region is relaxed, so the strength of MFC itself is reduced and the reinforcing effect on the resin is weakened. It will be. In addition, if moisture in the composite material is removed during the use of the composite material, problems such as shrinkage of the composite material or generation of internal stress due to drying occur.

  Therefore, when MFC is combined with a resin, it is important to combine both while maintaining a state in which the MFC is not aggregated and dispersed in the resin.

  However, it is difficult to prevent the occurrence of MFC aggregation. Since most of the resins do not have the same polarity as MFC, when MFC and resin are simply mixed to remove moisture, MFCs aggregate. For example, FIG. 4A schematically shows a state immediately after mixing MFC 1 and resin 3, and moisture represented by reference numeral 2 coexists in MFC 1. When the moisture 2 is removed from this state, the MFCs 1 condense in the resin 3 as shown in FIG. If MFC1 is present in an aggregated state in resin 3, the high aspect ratio of MFC1 cannot be utilized, and a high reinforcing effect cannot be expected.

  The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide a resin composite material that can be thermally recycled and has excellent mechanical strength.

  The present invention is characterized by the following in order to solve the above problems.

  First, the resin composite material of the present invention is a resin composite material containing microfibrillated cellulose (MFC) surface-treated as a reinforcing material in the resin material, and the surface-treated MFC is a resin composite material. The surface is coated with an emulsion of the base material resin of the material.

  Second, in the method for producing a resin composite material of the present invention, MFC and an emulsion of a base resin are mixed and dehydrated, and then the base resin is added and kneaded.

  Third, the dehydration process in the second invention is to dry the mixture of MFC and base resin emulsion to obtain a dried product.

  Fourth, the resin composite material molded product of the present invention is formed by molding the resin composite material of the first invention.

  According to the first aspect, since the surface-treated MFC is used as the reinforcing material, it is possible to perform thermal recycling in which thermal energy is recovered by the combustion treatment at the time of disposal of the resin composite material. In addition, it is possible to obtain a resin composite material in which MFC is effectively dispersed in the base material resin and a high reinforcing effect utilizing the high aspect ratio of MFC is obtained. Furthermore, since the bondability at the interface between the MFC and the base resin is good, the mechanical strength, particularly the impact resistance, can be improved.

  According to the second aspect of the present invention, it is possible to easily obtain a resin composite material that can be thermally recycled and has excellent mechanical strength.

  According to the third aspect of the invention, in addition to the effect of the second aspect of the invention, a resin composite material that is further excellent in mechanical strength can be obtained effectively.

  According to the fourth aspect of the invention, the above excellent effect can be realized as a resin composite material molded article.

  The resin composite material of the present invention contains microfibrillated cellulose (MFC) surface-treated as a reinforcing material in the resin material. As the surface-treated MFC, the base material resin of the resin composite material is used. The emulsion contains the MFC surface coated.

  The base resin of the resin composite material in the present invention is not limited as long as it can produce an emulsion resin for surface treatment of MFC, such as unsaturated polyester resin, epoxy resin, phenol resin, melanin resin, etc. Thermosetting resins, thermoplastic resins such as polyethylene resins, polypropylene resins, polystyrene resins, polylactic acid and polyglycolic acid, polysaccharides such as starches and alginic acid, and the like can be used. Of these, the use of plant-derived resins such as polylactic acid and starches is preferable in consideration of environmental aspects.

  In the present invention, a surface-treated MFC is used. As described above, MFC may be a conventionally known one, and the raw material is derived from plants such as wood, bamboo, hemp, jute, kenaf, or animals such as sea squirts. Can be mentioned. It is preferable to use a plant-derived material from the viewpoints of environment, cost, availability and the like. This MFC generally has a diameter of about 10 to 800 nm, and the aspect ratio largely depends on the degree of fiber cutting in the defibrating process of the raw material, but for example in the range of 50 to 500,000, particularly 50 to 5000. A range of things can be considered. As described above, MFC is generated in the form of coexisting with a large amount of moisture in the manufacturing process.

  MFC is contained, for example, in the resin composite material at a ratio of 1 to 99% by weight, and the content is appropriately set according to the strength of the required resin composite material. When the resin composite material is kneaded by a kneader, it is generally considered that it is contained in a proportion of 1 to 70% in consideration of the load on the screw, rotor, etc., but preferably a proportion of 10 to 20% It is.

  The surface-treated MFC is one in which part or all of the surface of the MFC is coated with the above matrix resin emulsion. This emulsion is generally obtained by finely pulverizing a matrix resin pellet to form fine particles, which are dispersed with a surfactant, for example, having a solid content concentration of 10 to 60 wt%. Can be used. In the MFC coated with the matrix resin emulsion, when water in the emulsion is volatilized on the surface, the fine particles approach and contact each other, forming a continuous resin layer and forming a matrix resin coating (adhesion) Is completed). Above the glass transition temperature of the resin, the fine particles melt together to form a coating.

  The surface treatment of MFC will be described later. For example, the surface of MFC can be coated by adding MFC to an emulsion of a base resin, mixing and stirring. It is considered that the coated matrix resin emulsion at this time is 20 to 70% by weight with respect to MFC (total dryness). Less than 20% is not preferable because aggregation between MFCs may not be sufficiently suppressed. If it exceeds 70%, the surfactant in the emulsion of the base material resin acts in the direction of making the resin component brittle, which is not preferable because the strength of the resulting resin composite material may be reduced.

  The advantage of using the emulsion of the base resin is that the raw material of the resin composite material is mainly limited to two types of MFC and base resin. The small number of types of materials constituting the resin composite material facilitates the material design when other additives are used in order to give the material characteristics that cannot be imparted by MFC and the base resin alone. . Furthermore, it is advantageous in terms of raw material procurement.

  Such a surface-treated MFC has a film formed on the surface of the MFC even if a dehydration treatment is performed to remove moisture coexisting in the MFC when a resin composite material is produced using the MFC. MFCs do not aggregate together. In addition, since the coating formed on the surface of the MFC is made of the same type of resin as the base material resin of the resin composite material, the surface-treated MFC has good compatibility with the base material resin. For this reason, the resin composite material obtained by mixing the surface-treated MFC and the base material resin can have MFC effectively and uniformly dispersed in the base material resin. The interface has good bondability. Therefore, the molded product obtained by molding the resin composite material can have a high reinforcing effect and excellent mechanical strength.

  Next, the manufacturing method of the resin composite material of this invention is demonstrated.

  In the present invention, first, MFC and a matrix resin emulsion are mixed and dehydrated. By this mixing, the base resin emulsion is coated on the surface of the MFC. In the dehydration process, for example, by heating and drying, moisture present in the MFC can be removed without causing the MFCs to aggregate. After the dehydration treatment, a base resin constituting the resin composite material is further added, and these are kneaded to obtain a resin composite material. For the kneading, those generally used as a kneading machine for resin composite materials can be used. For example, various kneading machines such as a roll, a Banbury mixer, a kneader, and a twin-screw kneading extruder can be used. Among these, it is preferable to use a twin-screw kneading extruder because the MFC surface can be efficiently coated with the base resin emulsion, dehydrated, and then kneaded with the base resin. The screw rotation direction in the twin-screw kneading extruder may be either different or the same direction, and there are various types of screw engagement, such as complete engagement type, incomplete engagement type, and non-engagement type. But it is not particularly limited. The rotational speed of the screw can be, for example, in the range of 50 to 400 rpm, and the kneading temperature is generally considered to be in the range of 120 to 200 ° C.

  In FIG. 1-No. FIG. 1B is a side view schematically showing a biaxial kneading and extruding machine composed of 8 and FIG. 1B schematically showing a mixed state of MFC in the resin material of the obtained resin composite material. A method for producing a resin composite material using a biaxial kneading extruder will be described with reference to FIG.

  Segment number of twin-screw kneading extruder At the position 1, the MFC 1 and the emulsion 4 of the base resin are charged, and both are kneaded by rotating the screw. By this kneading, the surface of MFC 1 is coated with the emulsion 4 of the base material resin. In the kneading process up to 6, the water present in the MFC evaporates. And segment no. Resin composite in which the base material resin 31 and the MFC 1 formed with the coating 41 composed of the same kind of resin as the base material resin are combined by charging the base material resin at the position 6 and kneading. The material is obtained (FIG. 1 (b)). By molding the obtained resin composite material by injection molding, extrusion molding, compression molding or the like, a resin composite material molded product having a predetermined shape can be manufactured.

  In the mixing and dehydration treatment of the MFC and the base resin emulsion, for example, as shown in FIG. 2, the MFC and base resin emulsion may be added to water and stirred. Thereby, the surface of MFC1 is reliably coat | covered with the emulsion 4 of base material resin. And by drying this, MFC1 in which the film 41 composed of the same kind of resin as the base resin is formed on the surface thereof can be obtained with certainty. In addition, since water removal is effectively performed, the finally obtained resin composite material molded article has a further improved mechanical strength. When the MFC and matrix resin emulsion is added to water, it is preferable to set the MFC concentration in the aqueous solution low. As a result, the dispersion of the MFC and the base resin particles in the emulsion is promoted, and the MFC and the base resin emulsion can be uniformly mixed.

  FIG. 3 shows a method for producing a resin composite material by a twin-screw kneading extruder using MFC coated with this matrix resin emulsion. As shown in FIG. Inject at position 1 and knead these. Thereby, a resin composite material in which the MFC and the base material resin are combined can be obtained.

  Examples of the present invention are shown below, but the present invention is not limited thereto.

<Example 1>
400 g of MFC (Daicel Chemical Industries, Ltd., Celish KY-100G, solid content: 10 wt%) and an emulsion of polylactic acid that is a plant-derived resin (Miyoshi Oil & Fats Co., Ltd., Randy PL-1000, solid content: 40 wt%) ) 500 g is segment No. shown in FIG. It was loaded at position 1. Moisture coexisting with MFC is segment No. Removed with 3, 4 and 5 (as water vapor), segment no. At position 6, 1400 g of polylactic acid pellets (manufactured by Mitsui Chemicals, LACEA H-100), which is a plant-derived resin, was added as a base material resin and kneaded.

  The kneading conditions were a kneading temperature of 180 ° C., a feed rate of 3.2 kg / hr, and a screw rotation speed of 80 rpm.

  The compound after the kneading treatment was cut with a pelletizer to prepare a pellet having a length of 5 mm. The obtained pellets were dried in a 105 ° C. oven (Espec Corp., PV-220) until reaching a constant weight.

The pellets obtained above were placed in a stainless steel frame and compression molded. Using a compression molding machine (ASFV-25, Kamito Metal Industry Co., Ltd.), molding was performed under vacuum. A compound 1.1 times the amount of sample required to fill the mold was compression molded. Two types of molded products having different dimensions were prepared for evaluation of bending performance and impact resistance, and a predetermined number of specimens having predetermined dimensions were cut out from the respective molded products.
Table 1 shows the molding conditions, the dimensions of the molded article, the dimensions and number of the specimens, and the standards for evaluation.

<Example 2>
A 3-L beaker with 1985 g of water and 200 g of MFC (manufactured by Daicel Chemical Industries, Ltd., serish KY-100G, solid content: 10 wt%) and a polylactic acid that is a plant-derived resin (Miyoshi Oil & Fats Co., Ltd., Randy PL-) 1000, solid content: 40 wt%) was added, and the mixture was stirred for 3 hours with a stirrer (TK homodisper, f-Model manufactured by Tokushu Kika Kogyo Co., Ltd.). The number of revolutions was 1000 rpm, and the liquid temperature was normal temperature throughout.

  The mixed solution was poured into a vat and dried in a 105 ° C. oven (Espec Corp., PV-220) until reaching a constant weight. As a result, a film-like MFC / polylactic acid emulsion mixture was obtained. The obtained mixture was cut into a size of about 10 mm square and subjected to the next step.

  The obtained mixture was pulverized by a pulverizer (Magnum Blender, MB-911) so that there was no compound of 3 mm square or more.

  The above operation was repeated to obtain a total of 300 g of an MFC / polylactic acid emulsion mixture.

  700 g of the above-mentioned MFC / polylactic acid emulsion mixture and 700 g of polylactic acid pellets (manufactured by Mitsui Chemical Co., Ltd., LACEA H-100) as a base material resin were introduced into a small twin-screw kneading extruder and kneaded.

  The kneading conditions were a kneading temperature of 180 ° C., a feed rate of 3.2 kg / hr, and a screw rotation speed of 80 rpm.

  The compound after the kneading treatment was cut with a pelletizer to prepare a pellet having a length of 5 mm.

A test body for evaluating bending performance and impact resistance was prepared from the obtained pellets in the same manner as in Example 1.
<Comparative Example 1>
A test specimen for evaluating bending performance and impact resistance was prepared in the same manner as in Example 1 using only polylactic acid pellets (LACEA H-100, manufactured by Mitsui Chemicals, Inc.).
<Comparative example 2>
400 g of MFC (Daicel Chemical Industry Co., Ltd., Celish KY-100G, solid content: 10 wt%) and 1600 g of polylactic acid pellets (made by Mitsui Chemicals, LACEA H-100) which is a plant-derived resin as a base material resin Segment No. 1 shown in FIG. The mixture was introduced at position 1 and kneaded. The water No. coexisting with MFC is regarded as water vapor and the segment No. 3 and 4 removed.

  The kneading conditions were a kneading temperature of 180 ° C., a feed rate of 3.2 kg / hr, and a screw rotation speed of 80 rpm.

  The compound after the kneading treatment was cut with a pelletizer to prepare a pellet having a length of 5 mm. The obtained pellets were dried in a 105 ° C. oven (Espec Corp., PV-220) until reaching a constant weight.

  A test body for evaluating bending performance and impact resistance was prepared from the obtained pellets in the same manner as in Example 1.

  About the test body created in Examples 1-2 and Comparative Examples 1-2, bending performance and impact resistance were evaluated. Table 2 shows the evaluation results of bending performance and impact resistance, together with the contents of MFC, polylactic acid emulsion and polylactic acid pellets in the test specimen. The thermal deformation temperature was evaluated at a load stress of 0.45 MPa.

  From the results of Table 2, the test specimens obtained by mixing the emulsions of MFC and polylactic acid (Examples 1 and 2) have no flexural modulus, flexural strength, and Izod impact value. It was confirmed that it was higher than that of Example 1) and the test sample not mixed with the polylactic acid emulsion (Comparative Example 2). In particular, it was confirmed that the flexural modulus, flexural strength, and Izod impact value were further improved by mixing the emulsion of MFC and base resin in an aqueous solution.

(A) is the side view which represented the biaxial kneading extruder typically, and is a figure for demonstrating the manufacturing method of a resin composite material. (B) is the figure which showed typically the mixed state of MFC in the resin material. It is a figure for demonstrating the manufacturing method of MFC by which the surface was coat | covered with the emulsion of base material resin. It is a side view of the biaxial kneading extruder which showed another embodiment for demonstrating the manufacturing method of a resin composite material. (A) has shown typically the state immediately after mixing MFC and resin, and (b) is a figure which shows the state after removing a water | moisture content.

Explanation of symbols

1 Microfibrillated cellulose (MFC)
3 Resin 4 Emulsion of base resin

Claims (4)

A resin composite material containing microfibrillated cellulose (MFC) surface-treated as a reinforcing material in a resin material, and the surface-treated MFC is coated with an emulsion of a base resin of the resin composite material Resin composite material characterized by being made. A method for producing a resin composite material, comprising mixing an MFC and an emulsion of a base resin, dehydrating, and then adding and kneading the base resin. 3. The method for producing a resin composite material according to claim 2, wherein the dehydration treatment is performed by drying a mixture of the MFC and the emulsion of the base resin to obtain a dried product. A resin composite material molded article obtained by molding the resin composite material according to claim 1.

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