JP2019157014A - Resin composition - Google Patents

Abstract

To provide a composite resin molding having high elastic modulus and excellent coatability.SOLUTION: There is provided a composite resin composition used as a raw material for a molded article molded by a molding machine, which contains a main agent resin 1 and a fibrous filler 2. The contact angle of the molded article to a solvent contained in a coating composition capable of coating a molded article molded with a resin composition is smaller than the contact angle to the solvent for a main agent resin constituting a resin composition. The fibrous filler 2 partially projects to the surface of a composite resin molding. The end portion in the fiber length direction of the fibrous filler 2 is fibrillated.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a resin composition, and more particularly to a resin composition for molding a molded article having paintability.

  So-called “general-purpose plastics” such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC) are not only very inexpensive, but also easy to mold, and can be used for metals and ceramics. Compared to its weight, it is a fraction of the weight. Therefore, general-purpose plastics are often used as materials for various daily necessities such as bags, various types of packaging, various types of containers and sheets, as industrial parts such as automobile parts and electrical parts, and as materials for daily necessities and miscellaneous goods. It's being used.

  However, general-purpose plastics have drawbacks such as insufficient mechanical strength. Therefore, general-purpose plastics do not have sufficient characteristics required for materials used in machine products for automobiles, various industrial products such as electrical, electronic and information products. The current scope is limited.

  On the other hand, so-called “engineering plastics” such as polycarbonate, fluororesin, acrylic resin, and polyamide are excellent in mechanical properties, and are used in machine products such as automobiles and various industrial products such as electrical, electronic, and information products. Widely used. However, engineering plastics are expensive, have a problem that monomer recycling is difficult, and environmental impact is high.

  Therefore, there is a demand for greatly improving the material properties (such as mechanical strength) of general-purpose plastics. For the purpose of strengthening general-purpose plastics, a technology for improving the mechanical strength of general-purpose plastics by dispersing fiber fillers such as natural fibers, glass fibers, and carbon fibers in general-purpose plastic resins is known. . Among them, organic fibrous fillers such as cellulose are attracting attention as reinforcing fibers because they are inexpensive and have excellent environmental properties at the time of disposal.

  When using fiber reinforced resin as an exterior member for machine products such as automobiles and various industrial products such as electrical, electronic and information products, in order to make the surface property uniform, such as unevenness due to fibers Paint or paste a film. In order to utilize the fiber reinforced resin as an exterior member, strong adhesion to a coating film or film is required as a surface property of the fiber reinforced resin.

  In order to improve the paintability of molded products using fiber reinforced resin, each company is studying. For example, in Patent Document 1, in order to improve paintability, the material and composition of the base coat layer are adjusted by adding a chlorinated polyolefin resin and a hydroxyl group-containing vinyl copolymer to the base coat, so that the base coat layer adheres to the molded body. Increases sex.

JP 2000-518 A

In Patent Document 1, the base coat is used as described above in order to improve the adhesion between the polyolefin molded body and the paint. However, since the base coat has low rigidity, there is a problem that the rigidity of the entire molded body including the base coat is lowered. Further, the technique of Patent Document 1 has a problem that the number of materials and the number of processes are large, which increases the cost.
The present invention solves the above-described conventional problems, and an object thereof is to realize a composite resin molded body having high paintability while maintaining high rigidity, that is, high elastic modulus.

  In order to achieve the above object, the resin composition containing the main resin and the fibrous filler according to the present invention is a solvent contained in a paint capable of coating a molded body molded from the resin composition. The contact angle of the molded body is smaller than the contact angle of the main resin constituting the resin composition with respect to the solvent.

  The resin composition of this invention can implement | achieve a molded object provided with high coating property, maintaining a high elasticity modulus by containing a fibrous filler.

It is a schematic diagram of the composite resin molding by which the coating in embodiment of this invention was given. It is a schematic diagram of the fibrous filler in embodiment of this invention. It is a flowchart of the manufacturing process of the composite resin molding by which the coating in embodiment of this invention was given.

  Hereinafter, a composite resin composition and a molded body using the composition according to an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

  The composite resin composition in the embodiment of the present invention is formed of a melt-kneaded material containing a main resin and a fibrous filler, and optionally containing a dispersant. In the composite resin composition, as shown in a schematic diagram including a cross section in FIG. 1, fibrous fillers 2 are dispersed in the main resin 1. And the coating is given to the surface of the molded object 5 shape | molded with this resin composition, and the coating film 3 is formed.

  The main resin 1 is preferably a thermoplastic resin in order to ensure good moldability. Thermoplastic resins include olefin resins (including cyclic olefin resins), styrene resins, (meth) acrylic resins, organic acid vinyl ester resins or derivatives thereof, vinyl ether resins, halogen-containing resins, polycarbonate resins. Polyester resins, polyamide resins, thermoplastic polyurethane resins, polysulfone resins (polyethersulfone, polysulfone, etc.), polyphenylene ether resins (2,6-xylenol polymer, etc.), cellulose derivatives (cellulose esters, cellulose Carbamates, cellulose ethers, etc.), silicone resins (polydimethylsiloxane, polymethylphenylsiloxane, etc.), rubbers or elastomers (polybutadiene, polyisoprene and other diene rubbers, styrene Diene copolymers, acrylonitrile - butadiene copolymer, acrylic rubber, urethane rubber, silicone rubber, etc.) and the like. Said resin may be used independently or may be used in combination of 2 or more types. The main resin 1 is not limited to the above materials as long as it has thermoplasticity.

  The main resin 1 is preferably an olefin resin having a relatively low melting point among these thermoplastic resins. Olefin resins include olefin monomer homopolymers, olefin monomer copolymers, and copolymers of olefin monomers and other copolymerizable monomers. It is. Examples of olefinic monomers include chain olefins (such as α-C2-20 olefins such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 4-methyl-1-pentene, and 1-octene). And cyclic olefins. These olefinic monomers may be used alone or in combination of two or more. Of the olefin monomers, chain olefins such as ethylene and propylene are preferable. Other copolymerizable monomers include, for example, fatty acid vinyl esters such as vinyl acetate and vinyl propionate; (meth) acrylic monomers such as (meth) acrylic acid, alkyl (meth) acrylate, and glycidyl (meth) acrylate. An unsaturated dicarboxylic acid or anhydride thereof, such as maleic acid, fumaric acid, maleic anhydride; vinyl ester of carboxylic acid (eg, vinyl acetate, vinyl propionate, etc.); cyclic olefin such as norbornene, cyclopentadiene; Examples include dienes such as butadiene and isoprene. These copolymerizable monomers may be used alone or in combination of two or more. Specific examples of the olefin resin include ternary copolymer such as polyethylene (low density, medium density, high density or linear low density polyethylene, etc.), polypropylene, ethylene-propylene copolymer, ethylene-propylene-butene-1. Examples thereof include copolymers of chain olefins (particularly α-C2-4 olefins) such as coalescence.

  The fibrous filler 2 will be described. The fibrous filler 2 (hereinafter sometimes simply referred to as “fiber”) contained in the composite resin composition in the present embodiment has mechanical properties in a resin molded body molded using the composite resin composition. The main purpose is to improve or improve the dimensional stability by reducing the linear expansion coefficient. For this purpose, the fibrous filler 2 preferably has a higher elastic modulus than the main resin 1. As such fibrous filler 2, specifically, carbon fiber (carbon fiber); carbon nanotube; pulp; cellulose; cellulose nanofiber; lignocellulose; lignocellulose nanofiber; basic magnesium sulfate fiber (magnesium oxysulfate fiber) ); Potassium titanate fiber; aluminum borate fiber; calcium silicate fiber; calcium carbonate fiber; silicon carbide fiber; wollastonite; zonotlite; various metal fibers; Recycled fibers such as rayon or cupra; Semi-synthetic fibers such as acetate and promix; Synthetic fibers such as polyester, polyacrylonitrile, polyamide, aramid, and polyolefin; Such as the modified fibers. Further, among these, carbons and celluloses are particularly preferable from the viewpoints of availability, high elastic modulus, and low linear expansion coefficient. Furthermore, natural fibers of celluloses are preferable from the viewpoint of environmental properties.

  The shape of the fibrous filler 2 will be described with reference to FIG. 2 is the length of the fibrous filler 2 (hereinafter sometimes referred to as “fiber length”), and the symbol d is the width of the fibrous filler 2 (hereinafter “fiber”). It may be referred to as “diameter”). When the aspect ratio (L / d) of the fibrous filler 2 is high, the fibrous filler is easily oriented in the flow direction at the time of injection molding, and the strength in the orientation direction of the fibrous filler is strong, but the strength in the direction perpendicular thereto is weak. As a result, impact strength due to a drop test or the like decreases. Therefore, it is preferable that the aspect ratio (L / d) is small for the fibrous filler as a whole, that is, the fiber diameter d is large.

  On the other hand, from the viewpoint of mechanical properties, the larger the area of the bonding interface between the fiber and the resin, the better the elastic modulus. Therefore, it is preferable that the specific surface area of the fiber is high, that is, the fiber diameter d is small. In order to achieve the two purposes of having a small aspect ratio and a large specific surface area, as shown in FIG. 2, the end in the fiber length direction is partially defibrated within one fiber. The structure is most preferred. The code | symbol 4 has shown the fibrillation site | part. The optimum fiber shape is calculated as follows from experiments and simulation results. That is, the length of the defibrating site 4 is preferably 5% or more and 50% or less of the fiber length L of the entire fibrous filler 2. When the spread site 4 is formed at both one end and the other end of the fiber 2, the total of both is defined as “length of the defibration site 4”. If the length of the defibrating part 4 is less than 5% of the total fiber length L, the specific surface area is small, so that the elastic modulus is hardly improved, and if it exceeds 50%, the defibrating part having a large aspect ratio. Since 4 becomes dominant, it becomes easy to orient at the time of injection molding, and impact strength tends to decrease.

  Also from the viewpoint of the paintability of the molded body composed of the resin composition, a structure in which the end in the fiber length direction is partially defibrated within one fiber as shown in FIG. 2 is most preferable. This is because, by this structure, the surface area of the fibers existing in the vicinity of the surface of the molded body is increased, the wettability of the paint is improved, and the paintability is improved.

  The paintability is further improved by exposing the defibrating portion 4 of the fiber in which the end in the fiber length direction is partially defibrated to the surface of the molded body. By controlling the molding conditions at the time of molding, the above structure can be produced. The length exposed on the surface is preferably 0.1% or more and less than 50% of the defibrated portion 4, that is, the defibrated fiber portion. If it is less than 0.1%, the fibers are not sufficiently exposed and the paintability tends to deteriorate. On the other hand, if the fibers are exposed by 50% or more, the tactile sensation is deteriorated and it is difficult to use as a product.

  The above-described structure in which the fiber defibrating site 4 is exposed on the surface of the molded body is more exposed at the end than at the center of the molded body, thereby improving coating adhesion. This is because, when used as a product, the coating is easily peeled off from the end. By making many fibers exist at the end portion, the coating adhesion at the end portion can be improved, and coating peeling can be suppressed. It is possible to agglomerate many fibers from the central part to the end part by controlling the molding conditions.

  The characteristics required for the fibrous filler 2 will be described. The types of the main resin 1 and the fibrous filler 2 are as described above. If the fibrous filler 2 is too soft with respect to the main resin 1, that is, if the elastic modulus is too small, the composite resin composition as a whole The elastic modulus is reduced, resulting in a decrease in strength. On the other hand, if the fibrous filler 2 is too hard with respect to the main resin 1, that is, if the elastic modulus is too large, a shock wave generated at the time of impact is not propagated and is absorbed at the interface between the main resin 1 and the fibrous filler 2. Therefore, cracks and crazes are likely to occur near the interface, resulting in a drop in impact strength. Therefore, the relationship between the elastic modulus of the main resin 1 and the fibrous filler 2 is preferably higher in the elastic modulus of the fibrous filler 2, and the difference is preferably as small as possible. The optimum relationship is calculated from the simulation results, and the difference in elastic modulus between the main resin 1 and the fibrous filler 2 is preferably within 20 GPa.

  These fibrous fillers 2 are almost all hydrophilic except for petroleum-derived artificial fibers. In particular, the cellulose fibers described above have many hydroxyl groups in the molecule and are hydrophilic. These hydrophilic fillers are generally hydrophobized when combined with a resin because the resin is hydrophobic. However, in the present invention, for the purpose of improving the paintability, it is preferable that the hydrophobicity is not performed in advance. By not performing hydrophobization in advance, the hydrophilic group of the fiber is likely to remain, and the presence of the fiber in the vicinity of the surface of the molded body improves the paintability.

  The fibrous filler 2 is a titanate coupling agent; a silane coupling agent; an unsaturated carboxylic acid, a maleic acid, for the purpose of improving the adhesiveness with the main resin 1 or the dispersibility in the composite resin composition. A modified polyolefin grafted with maleic anhydride or the same anhydride; a fatty acid; a fatty acid metal salt; a fatty acid ester or a partially surface-treated one may be used. Alternatively, there may be no problem even if the surface is partially treated with a thermosetting or thermoplastic polymer component. When hydrophobizing, it is preferable that the hydrophobized portion is only the outer surface of the fiber. In the present invention, the fibers are defibrated in the composite resin, but since the inside of the defibrated fibers is hydrophilic, in the final molded product, the defibrated ends of the fibers in the molded product The hydrophilicity becomes higher, and the defibrated end portion is exposed on the surface of the molded body, thereby further improving the paintability. At the same time, the hydrophobic group at the center of the fiber has good dispersibility with the resin, and high rigidity can be realized. By leaving a portion that is not hydrophobized as described above, it is possible to achieve both compatibility with the resin and compatibility with the paint.

  By using fibers that have not been hydrophobized in advance as described above, the amount of hydroxyl groups present on the surface of the molded body is greater than the amount of hydroxyl groups in the main resin 1. Thereby, the contact angle of the molded body with respect to the solvent contained in the paint used for coating is lower than the contact angle of the main resin 1 that does not contain fibers with respect to the solvent, so that the paint can easily penetrate. Since the fibers are present so as to have roots inside the molded body, the coating adhesion is good and the coating film is difficult to peel off. Even in the case of partially hydrophobized fibers, as described above, the defibrating portion 4 at the tip is highly hydrophilic and easily exposed to the surface, so that a hydrophilic paint can easily permeate and exhibits excellent paintability. To do. Therefore, in the molded article of the present invention, even a hydrophilic paint that is not easily compatible with the main resin 1 can reduce the contact angle with the paint, increase the wettability, and improve the paintability.

  In general, the surface of the composite resin molded body is roughened to improve paintability. The roughened surface is an aggregate of a plurality of fine uneven portions, but in the present invention, the amount of hydroxyl groups in the concave portions of the uneven portions is larger than that of the convex portions. This is because more fibers existing near the surface of the molded body are exposed on the surface of the recess. With this structure, in the recess, the affinity with the surface layer for protecting and decorating the paint is increased, and the adhesion area between the paint and the composite resin is increased, so that the paintability is further improved.

  The dispersant will be described. The resin composition having a composite structure in the present invention contains a dispersant for the purpose of improving the adhesiveness between the fibrous filler 2 and the main resin 1 or the dispersibility of the fibrous filler 2 in the main resin 1. be able to. Dispersants include various titanate coupling agents; silane coupling agents; modified polyolefins grafted with unsaturated carboxylic acid, maleic acid, maleic anhydride, or the same anhydrides; fatty acids; fatty acid metal salts; fatty acid esters, etc. Can be mentioned. The silane coupling agent is preferably an unsaturated hydrocarbon or epoxy type. There is no problem even if the surface of the dispersant is modified with a thermosetting or thermoplastic polymer component. When the dispersant is contained in the resin composition of the present embodiment, the content thereof is preferably 0.01% by mass or more and 20% by mass or less, and is 0.1% by mass or more and 10% by mass or less. More preferably, it is more preferably 0.5% by mass or more and 5% by mass or less. When the content of the dispersant is less than 0.01% by mass, poor dispersion is likely to occur. On the other hand, when the content of the dispersant exceeds 20% by mass, a composite resin molded by the resin composition is formed. Body strength tends to decrease. The dispersant is appropriately selected depending on the combination of the main resin 1 and the fibrous filler 2 and may not be added in the case of a combination that does not require a dispersant.

  A method for producing the above composite resin composition will be described. FIG. 3 is a flowchart illustrating the manufacturing process of the composite resin composition in the present embodiment. First, a main resin, a fibrous filler, and, if necessary, a dispersant are charged into a melt-kneading apparatus, and melt-kneaded in the apparatus. Thereby, the main resin is melted, and the fibrous filler and the dispersant are dispersed in the molten main resin. At the same time, due to the shearing action of the apparatus, the fibrillation of the fibrous filler is promoted, and the fibrous filler can be finely dispersed in the main resin.

  Conventionally, as the fibrous filler, a fiber that has been defibrated in advance by a pretreatment such as wet dispersion has been used. However, if the fibrous filler is defibrated in advance in the solvent used in the wet dispersion, it is easier to defibrate than if it is defibrated in the molten main resin, so that it is difficult to defibrate only the end part. The whole filler will be in a defibrated state. In addition, there is a problem that the number of processes increases and productivity deteriorates by combining pretreatment.

  On the other hand, in the manufacturing process of the composite resin composition in the present embodiment, the fibrous filler is the main agent without performing the fiber filler defibrating treatment and the pretreatment by wet dispersion for the purpose of modification treatment. A melt-kneading process (fully dry method) is performed together with a resin and a dispersant. In this construction method, the fibrous filler can be partially defibrated only at the end portion as described above by not performing the wet dispersion treatment of the fibrous filler, and the number of steps is small and productivity is improved. Can do.

  In order to produce the composite resin composition of the present invention by the all-dry method, it is preferable to apply a high shear stress during kneading. Specific examples of the kneader for that purpose include a single-screw kneader, a twin-screw kneader, a roll kneader, and a Banbury mixer. From the viewpoint of easily applying high shear stress and high mass productivity, a continuous biaxial kneader and a continuous roll kneader are particularly preferable. A kneading apparatus other than the above may be used as long as it can apply a high shear stress.

  The composite resin composition extruded from the melt-kneading apparatus is produced into a pellet shape through a cutting process using a pelletizer or the like. As a method of pelletizing, there are an air hot cut method, an underwater hot cut method, a strand cut method and the like as a method performed immediately after the resin is melted. Alternatively, there is a pulverization method in which a molded body or sheet is once molded and then pulverized and cut.

  By injection-molding this pellet, an injection-molded product as a composite resin molded product can be produced. As described above, the fibrous filler in the pellets has been previously unhydrophobized and only its ends are partially defibrated, and the fibers are exposed on the surface of the molded body, thereby improving the paintability. An injection molded product can be obtained.

  Examples of the present invention and comparative examples will be described below.

Example 1
A pulp-dispersed polypropylene composite resin molded article was produced by the following production method.

  Polypropylene (PP) (product name: J108M manufactured by Prime Polymer Co., Ltd.) as the main resin, cotton-like softwood pulp (product name: NBKP Celgar) manufactured by Mitsubishi Paper Industries, and maleic anhydride (Sanyo) as the dispersant Kasei Kogyo Co., Ltd. product name: Yumex) was weighed to a mass ratio of 85: 15: 5 and dry blended. The hydrophobic treatment of the cotton-like softwood pulp as the fibrous filler was not performed in advance, and the resin was kneaded with the compatibilizer in the resin. Thereafter, it was melt-kneaded with a twin-screw kneader (KRC kneader manufactured by Kurimoto Iron Works Co., Ltd.) to disperse each component. The shearing force can be changed by changing the screw configuration of the twin-screw kneader. The resin melt was hot cut to produce pulp-dispersed polypropylene pellets.

  Using the produced pulp-dispersed polypropylene pellets, a test piece as a composite resin molded article was produced by an injection molding machine (180AD manufactured by Nippon Steel Works). The test piece was prepared under the conditions of a resin temperature of 190 ° C., a mold temperature of 60 ° C., an injection speed of 60 mm / s, and a holding pressure of 80 Pa. The pellets were bitten into the screw of the molding machine through the hopper, and the penetration property at that time was measured by the amount of decrease in the pellets per hour, and it was confirmed that the pellets were constant. The shape of the test piece was changed according to the evaluation items described below. Specifically, a size 1 dumbbell was prepared for measuring the elastic modulus, and a 60 mm square and 1.2 mm thick flat plate was prepared for the coating film adhesion test. Using the test piece of the obtained pulp-dispersed polypropylene composite resin molded article, evaluation was performed by the following method. The following evaluation methods were applied to other examples and comparative examples.

[Presence / absence of fiber exposure, rate of exposure, in-plane uniformity of exposed area]
By observing the obtained pulp-dispersed polypropylene composite resin molded body with SEM, the form of fibers exposed on the surface was observed. In the SEM, since the plane is observed, the exposure ratio in the depth direction is observed by polishing several μm at a time, and the fiber state is observed three-dimensionally.

  In Example 1, as a result of measuring about 10 representative fibers, there was fiber exposure on the surface, and the exposure ratio, that is, the length of the exposed portion was about 0.5 to 10% with respect to the fiber length, and the exposed portion. The in-plane uniformity was “central uniformity <end uniformity”.

[Length ratio of fiber defibrating part]
The obtained composite resin molding was immersed in a xylene solvent to dissolve polypropylene, and the remaining pulp fiber was observed for the form of the fiber by SEM.

  In Example 1, a defibrated site was observed at the end in the fiber length direction, and the length of the defibrated site was about 20-30% of the total fiber length.

[Contact angle to main resin]
Using the solvent for the paint, the contact angle of the obtained composite resin molding was measured. The contact angle was measured by a liquid suitability method for measuring the angle between the droplet and the surface of the compact when it was suitable for contact with the surface of the compact.

  In Example 1, assuming a coating with a synthetic resin paint, the contact angle was measured using toluene which is a solvent contained in the paint. At that time, the contact angle of polypropylene alone, which is the main resin of the composite resin molded body, was also measured and compared. As a result, the contact angle of the composite resin molded body was smaller than the contact angle of the main resin.

[Hydroxyl amount of composite resin molding relative to main resin]
By measuring microscopic FT-IR for the obtained composite resin molding, the amount of hydroxyl groups in the main resin and the amount of hydroxyl groups in the concavo-convex portions were measured.

  In Example 1, the amount of hydroxyl groups in the obtained composite resin molding was greater than the amount of hydroxyl groups relative to the main resin.

[Elastic modulus of composite resin molding]
A tensile test was performed using the obtained No. 1 dumbbell-shaped test piece. Here, as a method for evaluating the elastic modulus, those having a numerical value of less than 1.8 GPa were determined to be defective, and those having a value of 2.0 GPa or more were determined to be non-defective.

  In Example 1, the elastic modulus of the test piece was 2.2 GPa, and the evaluation was “good”.

[Sense of touch]
Sensory evaluation of the touch was performed using the obtained flat plate-shaped test piece. The case where there was no problem was rated as ◯, the case where there was a slight roughness, and the case where the roughness was large and there was a great sense of discomfort.

  The feel of the composite resin molded body of Example 1 was evaluated as “◯”.

[Coating film adhesion]
The obtained composite resin molded body was coated and evaluated by a cross-cut peel test (JIS K 5600). As a result, the case where the coating film was not peeled was evaluated as ○, the case where the area ratio was 30% or less, Δ, and the case where the area ratio was 50% or more was evaluated as x.

  In Example 1, using a synthetic resin paint containing toluene as a solvent, painting was performed with a brush. As a result, the obtained coated composite resin molded article did not peel off the coating film, and the evaluation was “◯”.

(Example 2)
Compared to Example 1, the screw configuration of the twin-screw kneader was changed to a low shear type. Other material conditions and process conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets and a coated molded body were produced and evaluated.

(Example 3)
Compared to Example 1, the screw configuration of the twin-screw kneader was changed to a high shear type. Other material conditions and process conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets and a coated molded body were produced and evaluated.

Example 4
Pulp-dispersed polypropylene pellets and molded bodies were produced under the same material conditions and process conditions as in Example 1. Further, only a small amount of the resin on the surface was removed by etching with xylene as a solvent, and then painting was performed. And the obtained coating molded object was evaluated.

(Example 5)
Compared to Example 1, the screw configuration of the twin-screw kneader was changed to a conveying screw that is substantially free of shear. Other material conditions and process conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets and coated molded bodies were produced and evaluated.

(Example 6)
Compared with Example 1, the pulp fiber was defibrated with a refiner in advance, and the screw configuration of the biaxial kneader was changed to a high shear type. Other material conditions and process conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets and coated molded bodies were produced and evaluated.

(Example 7)
Compared with Example 1, the mold temperature at the time of molding was changed to 20 ° C. or less by water cooling, and the point that a resin skin layer was formed on the surface of the molded body was changed. Other material conditions and process conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets and coated molded bodies were produced and evaluated.

(Example 8)
Compared with Example 4, the etching time was considerably increased and the fiber exposure rate was increased. Otherwise, the evaluation was carried out in the same manner as in Example 4.

Example 9
Compared with Example 1, only the side surface of the molding die was water-cooled, the mold temperature was set to 20 ° C. or less, and a resin skin layer was formed on the surface of the end portion of the molded body. Other material conditions and process conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets and coated molded bodies were produced and evaluated.

(Comparative Example 1)
Compared with Example 1, the point which performed the hydrophobic process to the pulp fiber previously with the silane coupling agent was changed. Other material conditions and process conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets and coated molded bodies were produced and evaluated.

(Comparative Example 2)
Compared to Example 1, the main resin was changed to hydrophilic polypropylene (hydrophilic PP). Other material conditions and process conditions were the same as in Example 1, and pulp-dispersed polypropylene pellets and coated molded bodies were produced and evaluated.

  Table 1 shows molding conditions and evaluation results of Examples 1 to 9 and Comparative Examples 1 and 2.

  As is clear from Table 1, Example 1 obtained excellent evaluation results. In Example 2 in which the screw configuration was changed to the low shear type, the fibers were not defibrated much in the molten resin, and the length ratio of the defibrated portion was 5 to 10%. On the contrary, in Example 3 in which the screw configuration was changed to the high shear type, the fibers were well defibrated in the molten resin, and the length ratio of the defibrated portion was 40 to 50%. In Example 4 in which the surface of the molded body was etched, only the resin on the surface was eluted, and the exposure ratio of the fibers on the surface of the molded body to the fiber length was 20 to 45%. Example 2, Example 3, and Example 4 had no problem in elastic modulus and paintability as in Example 1. Furthermore, if the length ratio of the defibrated portion is 5 to 50%, there is fiber exposure on the surface of the molded body, and the exposure ratio is in the range of 0.1 to 50%, the elastic modulus is lowered. It was confirmed that the paintability can be improved.

  In Example 5 where the screw was changed to a conveying screw that was not sheared so that the fibers were not defibrated in the molten resin, the length ratio of the defibrated portion was 0 to 4%. As a result, the specific surface area of the fiber in the molded body was low and the elastic modulus was slightly reduced to 1.9 GPa, but there was no problem with the paintability.

  In Example 6 in which pulp fibers were defibrated in advance with a refiner and the screw configuration during kneading was changed to a high shear type, the length ratio of the defibrated portion was 80 to 100%. As a result, the number of thin and short fibers increased, and the paint hardly penetrated into the molded product. About 20% was peeled off in the adhesion evaluation by the cross-cut test, and the paintability was slightly lowered.

  In Example 7 in which the mold temperature during molding was set to 20 ° C. or less by water cooling and a resin skin layer was formed on the surface of the molded body, there was no fiber exposure on the surface of the molded body. As a result, the paint hardly wets the molded body, and about 20% peeled off in the adhesion evaluation by the cross-cut test, resulting in a slight decrease in paintability.

  In Example 8 in which the surface of the molded body was etched for a long time, only the resin on the surface was eluted, and the exposure ratio of the fibers on the surface of the molded body to the fiber length was 55 to 70%. When coating was performed on the coating, the adhesion of the coating film was good, but some fibers were exposed on the surface of the coated molded body, resulting in a slightly poor touch feeling.

  In Example 9 in which only the side surface of the mold at the time of molding was set to 20 ° C. or less by water cooling so that a resin skin layer was formed on the surface of the end portion of the molded body, The fiber exposure degree was smaller than the fiber exposure degree at the center. Thereby, the coating adhesiveness of the edge part deteriorated. Since the coating is easy to peel off from the edge, if the edge is weak, it is easy to peel off the entire coating film, and about 20% is peeled off in the adhesion evaluation by the cross-cut test, resulting in a slight decrease in paintability. .

  In Comparative Example 1 in which the pulp fiber was previously subjected to a hydrophobic treatment with a silane coupling agent, the contact angle of the molded body with respect to the solvent contained in the paint used for coating the molded body was the contact angle of the main resin with respect to the solvent. It was almost the same. Furthermore, the amount of hydroxyl groups in the composite resin molded product and the amount of hydroxyl groups in the main resin were almost the same. As a result, about 50% peeled off in the adhesion evaluation by the cross cut test, resulting in poor paintability.

  In Comparative Example 2 in which the resin was changed to hydrophilic PP, the contact angle of the molded body with respect to the solvent contained in the paint used for coating the molded body was larger than the contact angle of the main resin with respect to the solvent. In addition, the amount of hydroxyl groups in the composite resin molding was less than the amount of hydroxyl groups in the main resin. For this reason, the composite resin molded body is likely to contain moisture, bubbles enter the coating film, and about 50% peeled off in the adhesion evaluation by the cross cut test, and the paintability was poor.

  From the above evaluation, it is possible to achieve a high elastic modulus by producing a molded body using a resin material in which only the fiber ends are defibrated, and against the solvent contained in the paint used for coating the molded body. Since the contact angle of the molded body is smaller than the contact angle of the main resin with respect to the same solvent, it was possible to provide a composite resin coated molded body that has good paintability and can achieve a high elastic modulus without using a primer layer. . Similarly, the composite resin molded body has a higher hydroxyl content than the base resin, and the fiber is exposed on the surface of the molded body. We were able to provide a composite resin-coated molded product that can achieve a high elastic modulus.

  The composite resin composition according to the present invention can provide a molded article having better coating film adhesion and superior mechanical strength than conventional general-purpose resins. Since the resin composition in the present invention can improve the properties of the main resin, it can be used as a substitute for engineering plastics or a substitute for metal materials. Therefore, it is possible to drastically reduce the manufacturing cost required for various industrial products made of engineering plastics or metals, or daily necessities. For this reason, the utilization to a household appliance housing, a building material, and a motor vehicle member is possible.

DESCRIPTION OF SYMBOLS 1 Main ingredient resin 2 Fibrous filler 3 Coating film 4 Defibrillation part 5 Molded object

Claims (11)

  A resin composition containing a main resin and a fibrous filler, the contact angle of the molded body with respect to a solvent contained in a paint capable of coating the molded body molded with the resin composition, The resin composition characterized by being smaller than the contact angle with respect to the said solvent of the said main ingredient resin which comprises the said resin composition.   2. The resin composition according to claim 1, wherein the fibrous filler is defibrated only at the ends of the fibers.   The resin composition according to claim 1 or 2, wherein the fibrous filler is a natural fiber such as cellulose.   The resin composition according to any one of claims 1 to 3, wherein the main resin is an olefin resin.   A molded body, which is molded from the resin composition according to any one of claims 1 to 4.   6. The molded body according to claim 5, wherein the fibrous filler is defibrated at an end thereof, and the defibrated portion protrudes from the surface of the molded body.   The length of the defibrating portion of the fibrous filler protruding from the surface of the composite resin molded body is 0.1% or more and less than 50% of the total length of the fibrous filler. Molded body.   The fibrillation site of the fibrous filler protruding from the surface of the molded body has a distribution in the abundance on the surface of the molded body, and the abundance is greater in the center than in the end of the molded body. Item 8. The molded article according to Item 6 or 7.   The molded body according to any one of claims 5 to 8, wherein the amount of hydroxyl groups on the surface of the molded body is greater than the amount of hydroxyl groups in the main resin of the molded body.   The base material in the resin composition which is the coating material containing a solvent with respect to the molded object of any one of Claim 5-9, Comprising: The contact angle of the said molded object with respect to the said solvent forms the said molded object A molded article provided with a coating, characterized in that a coating with a paint smaller than a contact angle of a resin to the solvent is applied.   A method for producing the resin composition according to any one of claims 1 to 4, wherein the hydrophilic fibrous filler is used without being hydrophobized in advance. Manufacturing method.

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