JP6351574B2 - Foam molding - Google Patents

Description

  The present invention relates to a foamed molded article comprising a resin composition using a polyamide resin, having a good surface appearance and excellent impact resistance.

  Polyamide resins are excellent in properties such as mechanical properties, chemical resistance, heat resistance, and moldability, and the molded products have been widely used for automobile parts, electronic parts, and the like.

In addition, many molded articles are molded using a resin composition reinforced by blending polyamide resin with an inorganic filler such as glass fiber, carbon fiber, talc, or clay. However, these reinforcing materials have a problem that the mechanical properties and thermal properties of the molded body cannot be improved unless they are blended in a large amount, and the mass of the resulting molded body increases due to its high specific gravity. It was.
Further, when glass fiber, carbon fiber or the like is used as the reinforcing material, the obtained molded product has a problem that warpage becomes large. In addition, when talc, clay, etc. are used as reinforcing materials, when the obtained molded product is discarded, these reinforcing materials remain as incineration residues, so they are buried in the soil and semi-permanently in the ground. There was a problem of remaining.

  In recent years, cellulose has been used as a reinforcing material for resin materials. Cellulose includes those obtained from trees, those obtained from non-wood resources such as rice, cotton, kenaf and hemp, and bacterial cellulose produced by microorganisms. Cellulose is present in large quantities on the earth. . Cellulose is excellent in mechanical properties. By containing this in the resin, an effect of improving the properties of the resin composition, that is, the properties of the molded product is expected.

  On the other hand, a foamed molded article obtained by foaming by adding a foaming agent to a polyamide resin has been proposed as a molded article that is reduced in weight while utilizing the characteristics of the polyamide resin as described above.

For example, Patent Document 1 discloses a thermoplastic resin molded article having a foam structure, which is made of a thermoplastic resin composition containing a thermoplastic resin and cellulose fibers, and also describes a polyamide resin as the thermoplastic resin. Yes. In this invention, in order to mix a thermoplastic resin and a cellulose fiber, the biaxial high kneading type | mold extruder is used.
As a method of incorporating cellulose into the thermoplastic resin, a method of melt-mixing the resin and cellulose fiber is common. However, in this method, since the cellulose fibers are mixed in the resin in an aggregated state, they are not uniformly dispersed, and the average fiber diameter of the cellulose fibers is large.
Patent Document 1 is intended to obtain a molded article having a touch similar to that of a wooden surface, and in order to achieve this object, a large amount of cellulose fibers are contained to increase the surface roughness of the molded article. It is said.
Therefore, the foam molded article described in Patent Document 1 does not have a large amount of foam cells that are uniform in size and fine, and therefore the foam molded article is inferior in surface appearance and has low impact resistance. It was.

JP 2007-84698 A

  The present invention solves the above problems, and is a foamed molded article comprising a resin composition containing a polyamide resin and cellulose fibers, and has a large amount of foam cells that are uniform in size and fine, An object of the present invention is to provide a foam molded article having a good surface appearance and excellent impact resistance.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems.
That is, the gist of the present invention is as follows.
(1) A resin composition comprising 0.1 to 10 parts by mass of cellulose fibers having an average fiber diameter of 10 μm or less and 0.01 to 15 parts by mass of a foam nucleating agent with respect to 100 parts by mass of a polyamide resin, A foamed molded article having a foamed cell.
(2) The foamed molded article according to (1), wherein the foamed molded article comprises a core layer and a skin layer, and the core layer has foamed cells.
(3) The foamed molded article according to (1) or (2), wherein the foamed cell has a maximum cell diameter of 2 mm or less.
(4) The polyamide resin and the cellulose fiber constituting the resin composition are obtained by performing a polymerization reaction of the monomer constituting the polyamide resin in the presence of the cellulose fiber containing water. The foamed molded product according to any one of (1) to (3).
(5) The foam molded article according to any one of (1) to (4), wherein the resin composition is molded by a core back injection molding method.

The foamed molded article of the present invention is obtained by foaming a resin composition containing a specific amount of cellulose fibers having a small average fiber diameter and a foam nucleating agent. It will have a large amount. For this reason, the foamed molded article of the present invention has excellent surface appearance and excellent impact resistance.
In addition, by using a resin composition containing a specific amount of cellulose fibers having a small average fiber diameter and a foam nucleating agent, molding processing can be performed by a core back injection molding method, and foam having a core layer and a skin layer. It can be set as a molded body. And such a foaming molding of the present invention includes swirl marks (foam marks generated on the surface of the molding), silver streaks (silver marks generated along the flow direction of the resin on the molding surface), sink marks ( It is excellent in surface appearance without causing a dent or the like on the surface of the molded body.

Hereinafter, the present invention will be described in detail.
The foamed molded article of the present invention comprises a resin composition containing a polyamide resin, cellulose fibers having an average fiber diameter of 10 μm or less, and a foam nucleating agent, and has foam cells.

<Polyamide resin>
The polyamide resin used in the present invention refers to a polymer having an amide bond formed from an amino acid, lactam or diamine and a dicarboxylic acid.

Examples of monomers that form such a polyamide resin include 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, paraaminomethylbenzoic acid, and the like.
Examples of the lactam include ε-caprolactam and ω-laurolactam.

Examples of diamines include tetramethylene diamine, hexamethylene diamine, nonamethylene diamine, decamethylene diamine, undecamethylene diamine, dodecamethylene diamine, 2,2,4- / 2,4,4-trimethylhexamethylene diamine, and 5-methyl. Nonamethylenediamine, 2,4-dimethyloctamethylenediamine, metaxylylenediamine, paraxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1-amino-3-aminomethyl-3,5,5-trimethyl Cyclohexane, 3,8-bis (aminomethyl) tricyclodecane, bis (4-aminocyclohexyl) methane, bis (3-methyl-4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, Bis (aminopropyl) pipette Jin, and an amino ethyl piperazine.
Dicarboxylic acids include adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 5- Examples include sodium sulfoisophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, and diglycolic acid.

  More specifically, the polyamide resin used in the present invention includes polycaproamide (nylon 6), polytetramethylene adipamide (nylon 46), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebaca. Mido (nylon 610), polyhexamethylene dodecane (nylon 612), polyundecane methylene adipamide (nylon 116), polyundecanamide (nylon 11), polydodecanamide (nylon 12), polytrimethylhexamethylene terephthalamide (Nylon TMHT), polyhexamethylene terephthalamide (nylon 6T), polyhexamethylene isophthalamide (nylon 6I), polyhexamethylene terephthalamide / isophthalamide (nylon 6T / 6I), polybis (4-aminocyclohexane) Syl) methane dodecamide (nylon PACM12), polybis (3-methyl-4-aminocyclohexyl) methane dodecamide (nylon dimethyl PACM12), polymetaxylylene adipamide (nylon MXD6), polynonamethylene terephthalamide (nylon 9T) , Polydecamethylene terephthalamide (nylon 10T), polyundecamethylene terephthalamide (nylon 11T), polyundecamethylene hexahydroterephthalamide (nylon 11T (H)), and these copolymers and mixtures. May be. Among them, particularly preferred polyamide resins are nylon 6, nylon 66, nylon 11, nylon 12, and copolymers and mixtures thereof.

  The polyamide resin is produced by a polymerization method described later, or by further using a solid phase polymerization method.

<Cellulose fiber>
Next, the cellulose fibers used in the present invention include those derived from wood, rice, cotton, hemp, kenaf and the like, as well as those derived from organisms such as bacterial cellulose, valonia cellulose and squirt cellulose. Also included are regenerated cellulose, cellulose derivatives and the like.

  In the present invention, in order to obtain a foamed molded product having a large amount of foam cells that are uniform in size and fine, it is necessary to uniformly disperse the cellulose fibers in the resin without aggregating them. For that purpose, the dispersibility of the cellulose fiber to the polyamide resin and the affinity between the polyamide resin and the cellulose fiber are important. Further, in order to make the cellulose fiber have properties such as hydroxyl groups as much as possible, it is important to increase the surface area of the cellulose fiber. For this reason, it is necessary to use as fine a cellulose fiber as possible.

Therefore, the cellulose fiber contained in the resin composition in the present invention needs to have an average fiber diameter of 10 μm or less, and the average fiber diameter is preferably 1 μm or less, and preferably 500 nm or less. More preferably, it is preferably 300 nm or less, and most preferably 40 to 100 nm.
When the average fiber diameter of the cellulose fibers contained in the resin composition exceeds 10 μm, the surface area of the cellulose fibers cannot be increased, and it becomes difficult to improve the dispersibility and affinity for the polyamide resin. For this reason, the foamed molded article obtained does not have uniform foam cell size, the foam cell becomes large, and the cellulose fibers are visually confirmed, resulting in poor surface appearance and impact resistance. .

  In order to make the average fiber diameter of the cellulose fibers in the resin composition 10 μm or less, it is necessary to use cellulose fibers having an average fiber diameter of 10 μm or less. As such a cellulose fiber, what was microfibrillated by tearing a cellulose fiber is preferable. Various pulverizing apparatuses such as a ball mill, a stone mill, a high-pressure homogenizer, and a mixer can be used as means for microfibrillation. Moreover, as a cellulose fiber, what is marketed can use "Serish" by Daicel FineChem, for example.

  Moreover, the aggregate of the cellulose fiber taken out as a waste thread can also be used in the manufacturing process of the fiber product which uses a cellulose fiber as an average fiber diameter of 10 micrometers or less. The production process of the textile product includes spinning, woven fabric, nonwoven fabric production, and other textile product processing. Since these cellulose fiber aggregates are scrap fibers after the cellulose fibers have undergone these steps, the cellulose fibers are refined.

  In addition, bacterial cellulose produced by bacteria can be used as the cellulose fiber, and for example, those produced using an Acetobacter acetic acid bacterium as a producing bacterium can be used. Plant cellulose is the one in which molecular chains of cellulose converge and is formed by bundling very thin microfibrils, whereas cellulose produced from acetic acid bacteria originally has a width of 20 to 50 nm. It is in the form of a ribbon, and forms an extremely fine network compared to plant cellulose.

Moreover, you may use the refined cellulose fiber obtained by passing through a water washing and a physical fibrillation process after oxidizing a cellulose fiber in presence of an N-oxyl compound as a cellulose fiber.
There are various types of N-oxyl compounds, such as 2,2,6,6-tetramethylpiperidine-1-oxyl radical (hereinafter referred to as TEMPO) as described in Cellulose (1998) 5,153-164. preferable. Such a compound is added to the reaction aqueous solution in a catalytic amount range.
To this aqueous solution, sodium hypochlorite or sodium chlorite is added as a co-oxidant, and the reaction is allowed to proceed by adding an alkali metal bromide. An alkaline compound such as an aqueous sodium hydroxide solution is added to maintain the pH at around 10, and the reaction is continued until no change in pH is observed. The reaction temperature may be room temperature. After the reaction, it is preferable to remove the N-oxyl compound remaining in the system. Various methods such as filtration and centrifugation can be employed for washing.
Then, using various pulverizers as described above, it is possible to obtain refined cellulose fibers through a physical defibrating process.

  The cellulose fiber in the resin composition in the present invention preferably has an aspect ratio (average fiber length / average fiber diameter) which is a ratio of an average fiber diameter to an average fiber length of 10 or more, and more preferably 50 or more. It is preferable that it is 100 or more. When the aspect ratio is 10 or more, the mechanical properties of the obtained foamed molded product are easily improved.

And the content of the cellulose fiber in the resin composition which comprises the foaming molding of this invention needs to be 0.1-10 mass parts with respect to 100 mass parts of polyamide resins, Especially, it is 0. The amount is preferably 5 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass.
When the cellulose fiber content is less than 0.1 parts by mass with respect to 100 parts by mass of the polyamide resin, foaming is difficult to foam in foam molding, so foam molding having a large amount of uniform and fine foam cells. A body cannot be obtained, the surface appearance is inferior, and the foaming ratio is lower than the set expansion ratio.
On the other hand, when the content of the cellulose fiber exceeds 10 parts by mass with respect to 100 parts by mass of the polyamide resin, it becomes difficult to contain the cellulose fiber (A) in the resin composition, or the obtained foamed molded article is A foam cell having a large cell diameter is likely to be generated, the size of the foam cell is not uniform, and the surface appearance and impact resistance are poor.

  Among them, by obtaining the resin composition in the present invention by a production method as described later, even if the cellulose fiber content is small, it becomes a resin composition uniformly dispersed in the polyamide resin. In foam molding, it is possible to obtain a foam molded article that is sufficiently foamed, has a uniform size, and has a large amount of fine foam cells. Furthermore, the impact resistance of the obtained foamed molded product can be increased.

Cellulose fibers have a very high affinity with water, and the smaller the average fiber diameter, the better the dispersion state with respect to water. Further, when water is lost, cellulose fibers are strongly aggregated by hydrogen bonding, and once aggregated, it becomes difficult to achieve a dispersion state similar to that before aggregation. In particular, this tendency becomes more prominent as the average fiber diameter of the cellulose fibers decreases.
Therefore, the cellulose fiber is preferably combined with the polyamide resin in a state containing water.
Therefore, in the present invention, a polyamide resin composition containing cellulose fibers is obtained by performing a polymerization reaction of monomers constituting the polyamide resin in the presence of cellulose fibers containing water during the polymerization of the polyamide resin. It is preferable to take the method of obtaining. Such a production method makes it possible to uniformly disperse the cellulose fibers in the polyamide resin without aggregating them. Details of this manufacturing method will be described below.

<Polyamide resin composition containing cellulose fibers (resin composition A)>
In producing the resin composition in the present invention, it is preferable to prepare a polyamide resin composition (resin composition A) containing cellulose fibers in advance. That is, a polyamide resin having an average fiber diameter of 10 μm or less is obtained by conducting a polymerization reaction of monomers constituting the polyamide resin in the presence of water-containing cellulose fibers to obtain a polyamide resin. It is preferable to prepare a resin composition (resin composition A). For example, the monomer which comprises a polyamide resin and the aqueous dispersion of the cellulose fiber whose average fiber diameter is 10 micrometers or less are mixed, and a polymerization reaction is performed.

The aqueous dispersion of cellulose fibers in this preparation method is obtained by dispersing cellulose fibers having an average fiber diameter of 10 μm or less in water, and the content of cellulose fibers in the aqueous dispersion is 0.01 to 50% by mass. It is preferable to do. The aqueous dispersion of cellulose fibers can be obtained by stirring purified water and cellulose fibers with a mixer or the like.
And the aqueous dispersion of a cellulose fiber and the monomer which comprises a polyamide resin are mixed, and it is set as a uniform dispersion by stirring with a mixer etc. Thereafter, the dispersion is heated, and the temperature is raised to 150 to 270 ° C., followed by a polymerization reaction by stirring. At this time, water in the aqueous dispersion of cellulose fibers can be discharged by gradually discharging water vapor when the dispersion is heated. In the polyamide polymerization, a catalyst such as phosphoric acid or phosphorous acid may be added as necessary. Further, a foam nucleating agent may be added during the polyamide polymerization. And after completion | finish of a polymerization reaction, after paying out the obtained resin composition, it is preferable to cut | disconnect and pelletize.

  Further, when bacterial cellulose is used as the cellulose fiber, a cellulose fiber aqueous dispersion obtained by immersing bacterial cellulose in purified water and replacing the solvent may be used. When using a solvent-substituted bacterial cellulose, it is preferable to adjust the solvent concentration to a predetermined concentration and then mix with the monomer constituting the polyamide resin and proceed the polymerization reaction in the same manner as described above.

  In such a preparation method, cellulose fibers having an average fiber diameter of 10 μm or less are used, and the cellulose fibers are subjected to a polymerization reaction in an aqueous dispersion, thereby being subjected to a polymerization reaction with good dispersibility. Become. Furthermore, the cellulose fibers subjected to the polymerization reaction are improved in dispersibility by agitation with the monomer and water during the polymerization reaction and by stirring at the above temperature conditions, and the fibers aggregate. It is possible to obtain a resin composition A in which cellulose fibers having a small average fiber diameter are well dispersed. Thus, according to this preparation method, since the dispersibility of the cellulose fibers is improved, the cellulose fibers contained in the mixture after the completion of the polymerization reaction are more than the average fiber diameter of the cellulose fibers added before the polymerization reaction. However, the average fiber diameter and fiber length may be smaller.

  In addition, in this preparation method, the step of drying the cellulose fibers is not necessary, and the production can be performed without the step of causing the scattering of fine cellulose fibers, so that the resin composition A can be obtained with good operability. Become. Moreover, since it is not necessary to replace water with an organic solvent for the purpose of uniformly dispersing the monomer and cellulose, the handling is excellent and the discharge of chemical substances can be suppressed during the production process.

  Here, as described above, the resin composition A in the present invention is obtained by performing a polymerization reaction of monomers constituting the polyamide resin in the presence of cellulose fibers containing water. . However, when an additive that can be added to the resin composition described later is added at the time of this polymerization reaction, the resin composition A means one that also contains the additive.

  The relative viscosity of the resin composition A prepared by the above method is not particularly limited, but is preferably 1.5 to 5.0, and more preferably 1.7 to 4.0. When the relative viscosity is less than 1.5, it is difficult to form uniform foam cells, foam moldability is lowered, and mechanical properties are also lowered. On the other hand, when the relative viscosity exceeds 5.0, the fluidity of the resin composition A is lowered, and the foam moldability is lowered. In addition, although the measuring method of relative viscosity is mentioned later, 96% sulfuric acid was used as a solvent, and the temperature was 25 ° C. and the concentration was 1 g / 100 ml.

The elongation viscosity of the resin composition A is preferably 8.00 × 10 ^{3 to} 6.00 × 10 ⁵ Pa · s, and more preferably 1.00 × 10 ^{4 to} 9.50 × 10 ⁴ Pa · s. It is preferable that When the extensional viscosity is within the above range, it has a viscosity suitable for foaming, the foam cell size is uniform, and a large number of foam cells of appropriate size are formed. Excellent in properties.
Among these, the resin composition A having an elongation viscosity of 1.00 × 10 ^{4 to} 9.50 × 10 ⁴ Pa · s, which is a preferable range, is the most preferable as described above for the average fiber diameter of the cellulose fibers in the resin composition. It can be prepared by adjusting the content of the cellulose fiber to the range of 40 to 100 nm and the content of the cellulose fiber to the most preferable range of 0.5 to 5 parts by mass.
Even if the average fiber diameter of the cellulose fibers in the resin composition A exceeds the most preferable range of 40 to 100 nm, the elongation viscosity of the resin composition A is 1.00 × 10 ^{4 to} 9.50 ×. Although it may be in the range of 10 ⁴ Pa · s, when the average fiber diameter of the cellulose fibers exceeds 100 nm, the resulting foamed molded product has foam cells having a large cell diameter and tends to be somewhat inferior in uniformity.
Therefore, in the present invention, the resin composition A has an average fiber diameter of 40 to 100 nm and an elongational viscosity of 1.00 × 10 ^{4 to} 9.50 × 10 ⁴ Pa · s. Most preferred.

<Foaming nucleating agent>
The resin composition in the present invention contains a foam nucleating agent in addition to the above-described polyamide resin and cellulose fiber (resin composition A). Examples of the foam nucleating agent used in the present invention include titanium oxide, talc, kaolin, clay, calcium silicate, silica, sodium citrate, calcium carbonate, diatomaceous earth, calcined perlite, zeolite, bentonite, glass, limestone, calcium sulfate, aluminum oxide. , Titanium oxide, magnesium carbonate, sodium carbonate, ferric carbonate, polytetrafluoroethylene powder, and the like.

  The content of the foam nucleating agent in the resin composition needs to be 0.01 to 15 parts by mass, preferably 0.1 to 12 parts by mass, with respect to 100 parts by mass of the polyamide resin. Furthermore, it is preferable that it is 0.2-8 mass parts, More preferably, it is 0.2-5 mass parts. When the content of the foam nucleating agent is less than 0.01 parts by mass, the resulting foamed molded product does not have the effect of adding the foam nucleating agent, and the bubbles are coarse and foaming tends to be insufficient. The apparent overall density is large, and the surface appearance is inferior. On the other hand, when the content of the foam nucleating agent exceeds 15 parts by mass, the number of bubbles becomes excessive and bubble breakage is likely to occur, and the foamed molded article is inferior in surface appearance.

<Resin composition>
The resin composition in this invention can be manufactured by mixing a foaming nucleating agent with the resin composition A which consists of the polyamide resin and cellulose fiber obtained by the said preparation method. Examples of the mixing method include mixing during melt kneading and mixing by addition during polymerization.

  The resin composition in the present invention may contain other polymers as long as the characteristics are not significantly impaired. Examples of such polymers include polybutadiene, butadiene-styrene copolymer, acrylic rubber, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, natural rubber, chlorinated butyl rubber, elastomers such as chlorinated polyethylene, And acid-modified products thereof such as maleic anhydride, styrene-maleic anhydride copolymer, styrene-phenylmaleimide copolymer, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyvinylidene fluoride, polysulfone, polyphenylene sulfide , Polyethersulfone, phenoxy resin, polyphenylene ether, polymethyl methacrylate, polyether ketone, polyarylate, polycarbonate, polytetrafluoroethylene, etc. It is below.

  Furthermore, the resin composition in the present invention has layered silicates such as swellable mica, non-swellable mica, and synthetic smectite, glass fiber, carbon fiber, talc, clay, mica, wax, and the like, as long as the characteristics are not significantly impaired. Contains reinforcements such as lastite, calcium carbonate, barium sulfate, heat stabilizers, antioxidants, pigments, anti-coloring agents, weathering agents, flame retardants, plasticizers, crystal nucleating agents, mold release stabilizers, etc. Also good. Examples of the pigment include nigrosine, carbon black, titanium dioxide, zinc white, zinc sulfide, lithopone, lead white, antimony white, calcium carbonate, alumina white, and metal powder pigment.

<Foamed molded product>
The foamed molded product of the present invention is composed of the above resin composition and has foamed cells.
As described above, since the resin composition contains a specific amount of cellulose fibers having a small average fiber diameter and a foam nucleating agent, by foaming this resin composition, a large amount of foam cells that are uniform in size and fine are produced. A foamed molded product containing is obtained. Formation of such a foam-molded product has a structure in which the polyamide resin is cross-linked by containing an appropriate amount of fine cellulose fibers in the polyamide resin, and the elongation viscosity of the polyamide resin composition containing cellulose is increased. Furthermore, it is considered that this is due to containing an appropriate amount of a foam nucleating agent in such a polyamide resin.

Although the foaming molding of this invention has a foam cell, it is comprised especially from a core layer and a skin layer, and it is preferable that a core layer has a foam cell. Among them, a foamed molded article having a core layer and a skin layer, which is molded by a core back injection molding method, is preferable.
The core back injection molding method is a molding method in which the crystallization of the resin composition is promoted to some extent during the formation of the skin layer, and then the core portion is retracted. When a resin composition having a high crystallization speed is molded by this method, the skin layer is crystallized and at the same time, the resin composition of the core layer portion is crystallized. Can't get.
However, since the resin composition constituting the foamed molded article of the present invention has a small average fiber diameter of cellulose fibers contained therein, the crystallization speed of the polyamide resin is not increased, and it has moderate crystallinity. By performing core back injection molding, a foamed molded article having a core layer and a skin layer can be obtained.
The foamed molded product of the present invention having such a core layer and skin layer is excellent in surface appearance and surface smoothness without causing swirl marks, silver streaks, sink marks and the like in the skin layer. And it can be set as the foaming molding excellent also in impact resistance by having a skin layer.
The ratio of the thickness of the core layer to the skin layer (core layer / skin layer) in the foamed molded article of the present invention is preferably 1/5 to 5/1. When the thickness of the skin layer is larger than this range, the number of foamed cells is reduced, the apparent overall density is increased, and tends to exceed 1.1 g / cm ³ . On the other hand, when the thickness of the skin layer is smaller than this range, it is difficult to obtain the excellent surface appearance and surface smoothness as described above, and the impact resistance tends to be inferior.

  The foam cell which the foaming molding of this invention has can be made into a fine thing. The maximum cell diameter of the foamed cell is preferably 2 mm or less, more preferably 1.5 mm or less, and most preferably 0.9 mm or less. When the maximum cell diameter exceeds 2 mm, the foamed molded article is inferior in surface appearance, does not have impact resistance, and tends to vary due to mechanical properties.

  Moreover, the foam cell which the foaming molding of this invention has can make a magnitude | size uniform. In the present invention, the uniformity was evaluated by the difference between the maximum cell diameter and the average cell diameter of the foamed cells (maximum cell diameter−average cell diameter). That is, if this difference is small, the foamed cells are assumed to be uniform. The difference between the maximum cell diameter and the average cell diameter is preferably 1.3 mm or less, more preferably 1.1 mm or less, and most preferably 0.6 mm or less. If this difference exceeds 1.3 mm, the foamed cells have poor uniformity, and the foamed molded product is likely to break starting from the foamed cells when pressure is applied, such as impact resistance. The mechanical properties may be lowered, and the mechanical properties are likely to vary.

The foamed molded article of the present invention is measured according to JIS K 7222, and the calculated apparent total density is preferably 1.1 g / cm ³ or less, more preferably 0.9 g / cm ³ or less. Most preferably, it is 0.7 g / cm ³ or less. If the foamed molded body has an apparent total density exceeding 1.1 g / cm ³ , the effect of reducing the weight becomes insufficient. In addition, when the apparent overall density is less than 0.2 g / cm ³ , the amount of the foamed cell is excessively increased, and the impact resistance tends to be low.

In addition, the foam molded body of the present invention can be obtained by forming a core layer and a skin layer by a core back injection molding method using, for example, a mold having a mirror finish by polishing the mold surface with an abrasive. Can be mirror-finished. Such a mirror-finished foam molded article is preferably colored black, and is preferably molded using a resin composition containing a black pigment.
Examples of the black pigment in the present invention include black pigments and black dyes. Specific examples include carbon black, nigrosine, titanium-iron composite oxide, and aniline black. Two or more types of black pigments may be mixed and used.
The content of the black pigment in the foamed molded article of the present invention is preferably 0.1 to 5.0 parts by mass and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the polyamide resin. preferable.
In addition, it is preferable to mix a black pigment | dye into the resin composition A containing a polyamide resin and a cellulose fiber, and the mixing method includes the mixing at the time of melt-kneading and the addition by the polymerization.
Further, the foamed molded article of the present invention can be obtained by applying a textured surface by forming a core layer and a skin layer by a core back injection molding method using a textured finish mold.

The foamed molded product of the present invention is excellent in impact resistance as described above. The impact resistance was evaluated using notched Charpy impact strength according to JIS K 7111-1, using a test piece obtained by cutting a foamed molded product. Charpy impact strength was performed in expanded molded article is preferably at 28kJ / ^{m 2} or more, more preferably 30 kJ / ^{m 2} or more. If the foamed molded article has a Charpy impact strength of less than 28 kJ / m ² , it has no impact resistance and is not practical.

<Method for producing foamed molded article>
Next, the manufacturing method of the foaming molding of this invention is demonstrated.
The foamed molded product of the present invention is obtained by foam-molding the above resin composition, and as a foaming agent that can be used for foam molding, as a pyrolytic foaming agent, azo, N-nitroso, heterocyclic nitrogen Examples thereof include organic compounds containing and decomposable groups such as sulfonyl hydrazide groups, and inorganic compounds such as ammonium carbonate and sodium hydrogen carbonate. Specific examples thereof include azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, diazoaminobenzene, dinitrosopentamethylenetetramine, N, N'-dimethyl-N, N'-dinitrosotephthalamide, benzenesulfonyl Hydrazide, 4,4'-oxy-bis (benzenesulfonyl) hydrazide, diphenylsulfone-3,3'-disulfonylhydrazide, 4-toluenesulfonyl hydrazide, 4,4'-oxy-bis (benzenesulfonyl) semicarbazide, 4- Toluenesulfonyl semicarbazide, barium azodicarboxylate, 5-phenyltetrazole, trihydrazinotriazine, 4-toluenesulfonyl azide, 4,4'-diphenyldisulfonyl azide and the like can be mentioned.
In addition, as the foaming agent, liquids such as liquid fluorocarbons and pentanes that are liquid at room temperature, and gaseous fluorocarbons, nitrogen, carbon dioxide, air, helium, argon, and the like that are gaseous or liquefied can be used.

  The blending amount of the foaming agent in the resin composition is preferably 0.05 to 2 parts by mass and more preferably 0.1 to 1 part by mass with respect to 100 parts by mass of the polyamide resin. When the blending amount of the foaming agent is less than 0.05 parts by mass, the amount of gas to be foamed is small, the expansion ratio is not increased, the apparent overall density of the resulting foamed molded article is large, and the mass reduction effect cannot be obtained. There is. On the other hand, if the blending amount exceeds 2 parts by mass, the mechanical strength of the obtained foamed molded product may be lowered, or the surface appearance such as generation of silver streak or swirl mark may be impaired.

  The foam-molded article of the present invention is foam-molded by a conventional method using the above resin composition and a foaming agent. For example, when the foaming agent is solid, the obtained resin composition is pelletized or powdered, mixed with the foaming agent, and then the mixture is fed into a molding machine, melted, and injection molded. A foamed molded product can be obtained. The foaming agent may be added directly, or may be added using a master batch pellet obtained by melt-kneading a thermoplastic resin and a foaming agent in advance. Moreover, you may use the masterbatch pellet which pressed the foaming nucleating agent, the binder, etc. with the foaming agent using the disk pelleter. When the foaming agent is a gas or liquid, as represented by mucell foaming, the foaming agent is directly added to the molten resin composition and uniformly dispersed, and foamed at the time of molding to obtain a foamed molded article.

In order to improve the surface appearance and mechanical strength of the foamed molded article, it is preferable that the core layer in which the foamed cells exist is covered with a skin layer in which the foamed cells do not exist.
Such a foamed molded article is, for example, in an injection molding machine, when a molten foamable resin composition is injected into a mold cavity, and when the molten resin reaches the vicinity of the flow end, it is 0.2 to 1.0 seconds. An injection core back type injection molding method in which a holding pressure of 20 to 100 MPa is applied, and then a mold core portion adjacent to the mold cavity is retracted at a speed of 10 to 100 mm / sec in a direction in which the thickness of the middle mold cavity expands. Can be obtained at

In the core back type injection molding method, the set foaming ratio (X) is obtained by the following formula from the retreat distance of the die plate and the initial depth of the mold cavity.
Set foaming ratio (X) = (initial depth + retract distance of die plate) / (initial depth)
Further, the actual expansion ratio (Y) of foaming at this time can be calculated as a ratio (ρ ₀ / ρ ₁ ) between the density of the unfoamed body (ρ ₀ ) and the density of the foamed molded body (ρ ₁ ).
The actual magnification of foaming is preferably 1.15 to 3.00, and more preferably 1.25 to 2.60. When the actual magnification ratio of foaming is less than 1.15, the effect of reducing the weight of the foam molded article is insufficient, and when it exceeds 3.00, the foam cell of the core layer becomes coarse in the foam molded article, A skin layer may become thin and the mechanical strength of a foaming molding will fall.
The foaming efficiency (Y / X) calculated from the set foaming ratio (X) and the actual foaming ratio (Y) is an index of surface smoothness, preferably 85% or more, and preferably 90% or more. It is more preferable that When the foaming efficiency (Y / X) is 85% or more, the foamed molded body that foams in the mold increases the adhesion to the mold, and the surface smoothness of the foamed molded body is improved.

  Since the foamed molded article of the present invention has a good surface appearance and excellent impact resistance, it can be suitably used for applications in the electrical / electronic equipment field, the automobile field, or the machine field.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
Measurement methods and evaluation methods for various characteristics in the examples of the present invention are as follows.
(1) Average fiber diameter of cellulose fiber (1.1) Average fiber diameter of cellulose fiber before polymerization reaction Cellulose fibers freeze-dried as necessary were subjected to a field emission scanning electron microscope (S-4000 manufactured by Hitachi, Ltd.). ). The length in the direction perpendicular to the longitudinal direction of the cellulose fiber (single fiber) was measured from an electron microscope (SEM) image. At this time, the maximum of the lengths in the vertical direction was taken as the fiber diameter. Similarly, the fiber diameter of 10 cellulose fibers (single fibers) was measured, and the average value of 10 fibers was calculated as the average fiber diameter.
(1.2) Average Fiber Diameter of Cellulose Fiber in Resin Composition Constructing Foam Molded Body From the obtained mirror-finished foam molded body, a 100 nm-thick slice was collected using a frozen ultramicrotome, and OsO ₄ ( After performing section staining with osmium tetroxide, observation was performed using a transmission electron microscope (JEM-1230 manufactured by JEOL Ltd.). The length in the direction perpendicular to the longitudinal direction of the cellulose fiber (single fiber) was measured from the electron microscope image. At this time, the maximum of the lengths in the vertical direction was taken as the fiber diameter. Similarly, the fiber diameter of 10 cellulose fibers (single fibers) was measured, and the average value of 10 fibers was calculated as the average fiber diameter.
In addition, about the thing with a large fiber diameter of a cellulose fiber, it observed by using a stereomicroscope (OLYMPUS SZ-40) in the state which cut out the 10 micrometers section | slice with the microtome, or a foaming molding as it is, and obtained. The fiber diameter was measured in the same manner as described above from the obtained image, and the average fiber diameter was determined.

(2) Content of cellulose fiber in resin composition Measurement was performed under the following conditions using a TG / DTA 7200 apparatus manufactured by SII Nano Technology.
Fully dried cellulose and resin are weighed in a dedicated pan so that each has a known concentration, and a calibration curve is created using the weight loss from 290 ° C to 320 ° C as the amount of cellulose in the resin. Using, the cellulose fiber content in the obtained mirror-finished foamed molded article was calculated.
At this time, the mirror-finished foamed molded product was freeze-ground and used, and a sample amount of 10 mg was weighed with a precision balance and measured for temperature rise in a nitrogen atmosphere. The temperature was raised from 30 ° C. to 285 ° C. at 5 ° C./min, from 285 ° C. to 320 ° C. at 0.63 ° C./min, and again from 320 ° C. to 350 ° C. at 5 ° C./min. Finally, the temperature was raised from 350 ° C. to 550 ° C. at 10 ° C./min.

(3) Relative viscosity of the polyamide resin composition (resin composition A) containing cellulose fibers The obtained resin composition A pellets (treated with hot water at 95 ° C., scoured and dried) The relative viscosity was measured using 96% sulfuric acid at a temperature of 25 ° C. and a concentration of 1 g / 100 ml.

(4) Elongation Viscosity of Polyamide Resin Composition (Resin Composition A) Containing Cellulose Fiber The obtained resin composition A pellets (treated with hot water at 95 ° C., scoured and dried) The elongation viscosity was calculated from the results of measurement using a die 1 (die diameter 1 mm, die length 0.25 mm) and die 2 (die diameter 1 mm, die length 15 mm) using a Shimadzu flow tester CF-500 apparatus. . In addition, it carried out on 250 degreeC temperature conditions. Further, the extensional viscosity was calculated according to the calculation formulas in paragraphs [0020] to [0040] of JP 2013-525622 A.
In Comparative Example 1, the measurement was performed using polyamide resin pellets, in Comparative Example 3 using melt-kneaded pellets, and in Comparative Example 7 using resin composition B pellets.

(5) Maximum cell diameter (a) of foamed cell, average cell diameter (b)
The cell diameter of the foam cell which the obtained mirror surface processing foaming molding has was measured and calculated by the following method.
The skin layer surface of the mirror-finished foamed product was cut in the thickness direction along the diagonal line, and the cut surface (hereinafter referred to as a measurement surface) was observed with a magnifier or a microscope. And about the foam cell which appeared on the measurement surface, the line segment of the maximum length is calculated | required among the line segments which connect two points which exist on the outer periphery of a foam cell, The length is set to P, Moreover, the line segment The cell length in a direction passing through the midpoint and perpendicular to the line segment was determined, the length was defined as Q, and (P + Q) / 2 was defined as the cell diameter.
Among the foamed cells that appeared on the measurement surface, the cell diameter was measured for the foamed cell considered to be the maximum, and this was taken as the maximum cell diameter.
Further, the measurement surface was divided into 6 equal parts by 5 line segments parallel to the thickness direction, and the cell diameter was measured for 10 foam cells existing near the midpoint of each line segment, for a total of 50 cells. The average value of the cell diameter was calculated and used as the average cell diameter (b).

(6) Uniformity of foamed cell The difference between the maximum cell diameter (a) and the average cell diameter (b) of the foamed cell obtained by the method (5) was determined, and this was used as the evaluation of uniformity.

(7) Apparent whole density It measured and calculated according to JISK7222 using the obtained mirror surface processing foaming molding.

(8) Actual foaming ratio Ratio (ρ ₁ ) of the density (ρ ₁ ) of the mirror-finished foamed molding obtained by core back and the density (ρ ₀ ) of the mirror-finished foam obtained without core back (ρ ₀ ) ₀ / ρ ₁ ).

(9) Appearance evaluation of mirror-finished portion The surface of the mirror-finished foamed product obtained was measured and evaluated by the following method.
The L values at three arbitrary points on the surface of the mirror-finished portion were measured with a color difference meter SE-6000 manufactured by Nippon Denshoku Co., Ltd., and the appearance of the mirror-finished portion was evaluated with the average value of the L values. If there is silver streak or swirl mark, the foamed molded product becomes whitish and the L value becomes large. The L value is preferably 12 or less, and more preferably 10 or less.

(10) Appearance evaluation of the textured portion The surface of the textured foamed molded product was observed, and the molded product surface was visually observed for silver streaks, swirl marks, and sink marks.
○: No silver streak, swirl mark, or sink mark on the surface.
X: Silver streak, swirl mark, or sink mark is present on the surface.

(11) Charpy impact test Using a specimen obtained by cutting the obtained mirror-finished foamed molded article, a Charpy impact test was conducted without a notch in accordance with JIS K 7111-1, and the impact resistance of the foamed molded article was evaluated. In addition, let the surface which destroys be the surface which has the skin layer (mirror surface process part) which is not cut out by cutting.

Example 1
As an aqueous dispersion of cellulose fibers, serisch KY100G (manufactured by Daicel Finechem Co., Ltd .: containing 10% by mass of cellulose fibers having an average fiber diameter of 125 nm) was added to this, and purified water was added thereto, followed by stirring with a mixer. An aqueous dispersion having a fiber content of 3% by mass was prepared.
70 parts by mass of the aqueous dispersion of cellulose fibers and 100 parts by mass of ε-caprolactam were further stirred and mixed with a mixer until a uniform dispersion was obtained. Subsequently, the mixed dispersion was heated to 240 ° C. with stirring, and the pressure was increased from 0 MPa to 0.7 MPa while gradually releasing water vapor. Thereafter, the pressure was released to atmospheric pressure, and a polymerization reaction was carried out at 240 ° C. for 1 hour to obtain a resin composition A containing a polyamide resin and cellulose fibers. When the polymerization was completed, the resin composition A was discharged, cut into pellets, treated with hot water at 95 ° C., scoured, and dried.
The obtained pellets of resin composition A (relative viscosity ηR = 2.52) and the amount of talc shown in Table 1 as a foam nucleating agent (MICRO ACE K-1, manufactured by Nippon Talc Co., Ltd., average particle size: 7.4 μm) ), Azodicarbonamide as a blowing agent (Binihol AC # 3 manufactured by Eiwa Kasei Kogyo Co., Ltd.), carbon black having an amount of 0.3 parts by mass with respect to 100 parts by mass of polyamide resin, and nigrosine having 0.4 parts by mass. The resin composition was manufactured by dry blending with the black pigment mixture.
Core back injection molding was performed using the obtained resin composition. That is, the resin composition is put into an injection molding machine (S-2000i manufactured by FANUC) equipped with a shut-off nozzle, and a mold having a mirror-finished finish under conditions of a cylinder temperature of 260 ° C. and a mold temperature of 80 ° C. Injection molded. In the injection molding, the test piece was filled in 0.2 seconds to the flow end and then subjected to a pressure holding process at 75 MPa for 0.5 seconds. Immediately thereafter, the die plate of the injection molding machine was set at 60 mm / second. It was made to recede so as to be 5 times to obtain a mirror-finished foamed molded article composed of a core layer and a skin layer.
In addition, except that a textured finish mold was used, injection molding was performed under the same conditions as above to obtain a textured foamed molded article.

Production Example 1: Production of bacterial cellulose 50 ml of a medium composed of 0.5 mass% glucose, 0.5 mass% polypeptone, 0.5 mass% yeast extract and 0.1 mass% magnesium sulfate heptahydrate was added to 200 ml. The solution was dispensed into a conical flask and steam sterilized at 120 ° C. for 20 minutes in an autoclave. One platinum ear of Gluconacetobacter xylinus (NBRC 16670) grown on a test tube slant agar medium was inoculated, and left to stand at 30 ° C. for 7 days. Seven days later, a white gel film-like bacterial cellulose was formed in the upper layer of the culture solution.

Example 2
The bacterial cellulose obtained in Production Example 1 was used as the cellulose fiber. Bacterial cellulose was crushed with a mixer, and then water substitution was performed by repeating immersion and washing with water. 35 parts by mass of an aqueous dispersion of bacterial cellulose after water substitution (containing 6.5% by mass of bacterial cellulose having an average fiber diameter of 60 nm), 194 parts by mass of ε-caprolactam, 40 parts by mass of aminocaproic acid, 90 parts by mass of purified water was stirred and mixed with a mixer until a uniform dispersion was obtained. Subsequently, the mixed dispersion is gradually heated, and the temperature is raised to 240 ° C. while discharging steam during the heating, and the mixture is stirred at 240 ° C. for 1 hour to perform a polymerization reaction. The resin composition A containing this was obtained. When the polymerization was completed, the resin composition A was discharged, cut into pellets, treated with hot water at 95 ° C., scoured, and dried.
A resin composition was produced in the same manner as in Example 1 except that the pellets (relative viscosity ηR = 2.51) of the obtained resin composition A were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

Example 3
Purified water was added to the aggregate of cellulose fibers produced as waste yarn in the nonwoven fabric manufacturing process, and the mixture was stirred with a mixer to prepare an aqueous dispersion containing 3% by mass of cellulose fibers having an average fiber diameter of 120 nm.
170 parts by mass of this aqueous dispersion of cellulose fibers, 216 parts by mass of ε-caprolactam, and 44 parts by mass of aminocaproic acid were stirred and mixed with a mixer until a uniform dispersion was obtained. Subsequently, the mixed dispersion is gradually heated, and the temperature is raised to 240 ° C. while discharging steam during the heating, and the mixture is stirred at 240 ° C. for 1 hour to perform a polymerization reaction. The resin composition A containing this was obtained. When the polymerization was completed, the resin composition A was discharged, cut into pellets, treated with hot water at 95 ° C., scoured, and dried.
A resin composition was produced in the same manner as in Example 1 except that the obtained pellets of resin composition A (relative viscosity ηR = 2.39) were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

Example 4
Except having changed the amount of the aqueous dispersion of cellulose fibers from 70 parts by mass to 105 parts by mass, a polymerization reaction was performed in the same manner as in Example 1 to obtain pellets of the resin composition A, and hot water at 95 ° C. , Scouring and drying.
Except that the pellets of the resin composition A obtained (relative viscosity ηR = 2.50) were used, and the addition amounts of the foam nucleating agent and the foaming agent were changed to the amounts shown in Table 1, in the same manner as in Example 1, A resin composition was produced, and then injection molded under the same conditions as in Example 1 to obtain a foam molded article.

Example 5
The cellulose fiber content is the same as in Example 1 except that serisch KY110N (manufactured by Daicel Finechem Co., Ltd .: cellulose fiber having an average fiber diameter of 150 nm) is used as the aqueous dispersion of cellulose fibers. A cellulose aqueous dispersion was prepared so as to be 3% by mass.
70 parts by mass of the aqueous dispersion of cellulose fibers and 200 parts by mass of ε-caprolactam were further stirred and mixed with a mixer until a uniform dispersion was obtained. Subsequently, the mixed dispersion was heated to 240 ° C. with stirring, and the pressure was increased from 0 MPa to 0.7 MPa while gradually releasing water vapor. Thereafter, the pressure was released to atmospheric pressure, and a polymerization reaction was carried out at 240 ° C. for 3 hours to obtain a resin composition A containing a polyamide resin and cellulose fibers. When the polymerization was completed, the resin composition A was discharged, cut into pellets, treated with hot water at 95 ° C., scoured, and dried.
Except that the pellets (relative viscosity ηR = 3.01) of the obtained resin composition A were used and the addition amount of the foam nucleating agent and the foaming agent was changed to the amounts shown in Table 1, the same as in Example 1, A resin composition was produced, and then injection molded under the same conditions as in Example 1 to obtain a foam molded article.

Example 6
Except that the polymerization reaction time at 240 ° C. was changed from 3 hours to 1 hour, the polymerization reaction was performed in the same manner as in Example 5 to obtain pellets of the resin composition A, which were treated with hot water at 95 ° C. Scouring and drying.
Except having changed the addition amount of a foam nucleating agent and a foaming agent into the quantity shown in Table 1 using the pellet (relative viscosity (eta) R = 2.47) of the obtained resin composition A, it carried out similarly to Example 1, A resin composition was produced, and then injection molded under the same conditions as in Example 1 to obtain a foam molded article.

Example 7
Except that the amount of ε-caprolactam was changed from 200 parts by mass to 100 parts by mass, and the polymerization reaction time at 240 ° C. was changed from 3 hours to 1 hour, the polymerization reaction was carried out in the same manner as in Example 5, A pellet of resin composition A was obtained, treated with hot water at 95 ° C., scoured, and dried.
A resin composition was produced in the same manner as in Example 1 except that the pellets (relative viscosity ηR = 2.52) of the obtained resin composition A were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

Example 8
As an aqueous dispersion of cellulose fiber, 160 parts by mass of cellulose fiber content changed from 3% by mass to 5% by mass was used, and the polymerization reaction time at 240 ° C. was changed from 3 hours to 1 hour. In the same manner as in Example 5, a polymerization reaction was performed to obtain a resin composition A, which was treated with hot water at 95 ° C., scoured, and dried.
A resin composition was produced in the same manner as in Example 1 except that the pellets (relative viscosity ηR = 2.45) of the obtained resin composition A were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

Example 9
The cellulose fiber content is the same as in Example 1 except that serisch KY100S (manufactured by Daicel Finechem: 25% by mass of cellulose fibers having an average fiber diameter of 180 nm) is used as the aqueous dispersion of cellulose fibers. A cellulose aqueous dispersion was prepared so as to be 3% by mass, and polymerization was performed in the same manner as in Example 1 to obtain pellets of the resin composition A.
A resin composition was produced in the same manner as in Example 1 except that the pellets (relative viscosity ηR = 2.47) of the obtained resin composition A were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

Example 10
Celish KY100S was used as an aqueous dispersion of cellulose fibers. 49 parts by mass of this cellulose fiber aqueous dispersion, 216 parts by mass of ε-caprolactam, 44 parts by mass of aminocaproic acid, and 157 parts by mass of purified water were stirred and mixed with a mixer until a uniform dispersion was obtained. Subsequently, the mixed dispersion is gradually heated, and the temperature is raised to 240 ° C. while discharging steam during the heating, and the mixture is stirred at 240 ° C. for 1 hour to perform a polymerization reaction. The resin composition A containing this was obtained. When the polymerization was completed, the resin composition A was discharged, cut into pellets, treated with hot water at 95 ° C., scoured, and dried.
A resin composition was produced in the same manner as in Example 1 except that the pellets (relative viscosity ηR = 2.43) of the obtained resin composition A were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

Examples 11 and 12
Except that the pellet of the resin composition A obtained in Example 1 (relative viscosity ηR = 2.52) was used and the content of the foam nucleating agent was changed to the amount shown in Table 1, the same procedure as in Example 1 was performed. Then, a resin composition was produced, and then injection molded under the same conditions as in Example 1 to obtain a foam molded article.

Example 13
As an aqueous dispersion of cellulose fiber, purified water was added to SERISH KY100G and stirred with a mixer to prepare a cellulose fiber content of 3% by mass.
170 parts by mass of an aqueous dispersion of this cellulose fiber, 254 parts by mass of ε-caprolactam, 2.5 parts by mass of swellable fluoromica as a layered silicate (manufactured by Corp Chemical Chemical Co., Ltd .: ME-100), phosphorous acid 0.25 parts by mass (0.14 mol% based on ε-caprolactam) was stirred and mixed with a mixer until a uniform dispersion was obtained. Subsequently, the mixed solution was heated to 240 ° C. with stirring, and the pressure was increased from 0 MPa to 0.7 MPa while gradually releasing water vapor. Thereafter, the pressure was released to atmospheric pressure, and a polymerization reaction was performed at 240 ° C. for 1 hour to obtain a resin composition A containing a polyamide resin, cellulose fibers, and a layered silicate. When the polymerization was completed, the resin composition A was discharged, cut into pellets, treated with hot water at 95 ° C., scoured, and dried.
A resin composition was produced in the same manner as in Example 1 except that the pellets (relative viscosity ηR = 2.52) of the obtained resin composition A were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

Comparative Example 1
A polyamide resin pellet was obtained in the same manner as in Example 1 except that the aqueous dispersion of cellulose fiber was not added.
A resin composition was produced in the same manner as in Example 1 except that the obtained pellets (relative viscosity ηR = 2.51) were used, and then injection molded under the same conditions as in Example 1, followed by foam molding. Got the body.

Comparative Example 2
Except having used the cotton short fiber (average fiber diameter of 16 micrometers) as a cellulose fiber, it carried out similarly to Example 1, and obtained the pellet of the resin composition A containing a polyamide resin and a cellulose fiber.
A resin composition was produced in the same manner as in Example 1 except that the pellets of the obtained resin composition A (relative viscosity ηR = 2.54) were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

Comparative Example 3
As cellulose fiber, serisch KY100S was freeze-dried and then pulverized to prepare a powder.
A twin screw extruder having a screw diameter of 30 mm and an average groove depth of 2.5 mm is blended with 100 parts by mass of nylon 6 (BRL number average molecular weight 17000 manufactured by Unitika Ltd.) and 2 parts by mass of the obtained powdery cellulose. (PCM-30 manufactured by Ikegai Co., Ltd.) and melt kneaded at a barrel temperature of 240 ° C., a screw rotation speed of 120 rpm, and a residence time of 2.7 minutes. The melt-kneaded product was discharged, cut into pellets, and the resulting pellets were dried.
A resin composition was produced in the same manner as in Example 1 except that the obtained melt-kneaded pellets (relative viscosity ηR = 2.48) were used, and then injection-molded under the same conditions as in Example 1. As a result, a foamed molded product was obtained.

Comparative Example 4
Resin composition A pellets were obtained in the same manner as in Example 10 except that the polymerization reaction was carried out so that the cellulose fiber content was as shown in Table 1.
A resin composition was produced in the same manner as in Example 1 except that the pellets (relative viscosity ηR = 2.47) of the obtained resin composition A were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

Comparative Example 5
A resin composition was produced in the same manner as in Example 1 except that no foaming nucleating agent was added to the pellets of resin composition A obtained in Example 1 (relative viscosity ηR = 2.52). Injection molding was performed under the same conditions as in Example 1 to obtain a foam molded article.

Comparative Example 6
Except that the pellet of the resin composition A obtained in Example 1 (relative viscosity ηR = 2.52) was used and the content of the foam nucleating agent was changed to the amount shown in Table 1, the same procedure as in Example 1 was performed. Then, a resin composition was produced, and then injection molded under the same conditions as in Example 1 to obtain a foam molded article.

Comparative Example 7
254 parts by mass of ε-caprolactam, 10.2 parts by mass of layered silicate (swelling fluorinated mica) and 0.25 parts by mass of phosphorous acid (0.14 mol% with respect to ε-caprolactam) at 80 ° C. The mixture was stirred and mixed with a homogenizer until a uniform solution was obtained while heating. Subsequently, the mixed solution was heated to 240 ° C. with stirring, and the pressure was increased from 0 MPa to 0.7 MPa while gradually releasing water vapor. Thereafter, the pressure was released to atmospheric pressure, and a polymerization reaction was performed at 240 ° C. for 1 hour to obtain a resin composition B containing a polyamide resin and a layered silicate. When the polymerization was completed, the resin composition B was discharged, cut into pellets, treated with hot water at 95 ° C., scoured, and dried.
A resin composition was produced in the same manner as in Example 1 except that the pellets (relative viscosity ηR = 2.51) of the obtained resin composition B were used, and then injected under the same conditions as in Example 1. Molded to obtain a foamed molded product.

  Table 1 shows the results of measuring the characteristic values of the foam molded articles obtained in Examples 1 to 13 and Comparative Examples 1 to 7. In the measurement of the characteristic value of the foam, a mirror-finished foam was used except for the appearance evaluation.

  In Examples 1 to 13, as described above, by mixing an aqueous dispersion of cellulose fibers having an average fiber diameter of 10 μm or less and a monomer constituting the polyamide resin, and performing a polymerization reaction of the monomer, A fine cellulose fiber was uniformly dispersed without agglomeration, and a resin composition obtained by adding a foam nucleating agent thereto was injection molded by the core back method to obtain a foam molded article. For this reason, the foam molded articles obtained in Examples 1 to 13 are composed of a core layer and a skin layer, and the core layer has foam cells. It had a large amount of uniform and fine foamed cells, had a good surface appearance with no silver streaks, swirl marks, sink marks, etc., and was excellent in impact resistance. Especially in Examples 4-9, since the average fiber diameter and content of the cellulose fiber in a resin composition were the thing of the most preferable range, the value of the extensional viscosity became the thing of the most preferable range. For this reason, the obtained foamed molded article has a maximum cell diameter of 0.8 mm or less, a uniformity of 0.5 mm or less, a particularly large size and a large amount of fine foam cells, and a surface appearance. The impact resistance was very good.

On the other hand, in Comparative Example 1, since the resin composition did not contain cellulose fibers, the foaming ratio was low and it was difficult to foam, and the obtained foamed molded article had large foam cells and was not uniform. there were.
In Comparative Example 2, since the resin composition contained cellulose fibers having an average fiber diameter exceeding 10 μm, the obtained foamed molded article was foam-molded in Example 1 in which the content of cellulose fibers was the same. Compared with the body, the foam cells are large and uneven, cellulose aggregates are observed, silver streaks, swirl marks, sink marks, etc. are confirmed, the surface appearance is inferior, and the impact resistance is also inferior. It was.
In Comparative Example 3, since the polyamide resin and the cellulose fiber were melt-kneaded, the dispersibility of the cellulose fiber was low, and the resin composition was able to visually confirm the aggregation of the cellulose fiber, and contained a cellulose fiber having a large average fiber diameter. It was a thing. The foamed molded product obtained from this resin composition has a large and non-uniform foamed cell as compared with the foamed molded product of Example 9 in which the type and content of cellulose fibers are the same, and the surface appearance is inferior. It was also inferior in impact resistance.
In Comparative Example 4, since the resin composition contained excessive cellulose fibers, the obtained foamed molded article had a small number of foam cells and a small average cell diameter. Large foam cells were also formed, and the uniformity was poor. For this reason, silver streaks, swirl marks, sink marks, etc. were confirmed, the surface appearance was inferior, and the impact resistance was also inferior.
In Comparative Example 5, since the resin composition did not contain a foam nucleating agent, the obtained foamed molded product was foamed as compared with the foamed molded product of Example 1 in which the content of cellulose fibers was the same. The cells were large and uneven, and the foaming was insufficient, so that the apparent overall density was large. Furthermore, the surface appearance was inferior and the impact resistance was also inferior.
In Comparative Example 6, since the resin composition contained excessive foam nucleating agent, the obtained foamed molded product was compared with the foamed molded product of Example 1 having the same cellulose fiber content. Although the foamed cell was small, the number of bubbles became excessive and bubble breakage was likely to occur, and a foamed cell having a large cell diameter was also produced, resulting in poor uniformity. For this reason, silver streaks, swirl marks, sink marks and the like were confirmed, and the surface appearance was inferior.
In Comparative Example 7, since the resin composition did not contain cellulose fibers and contained layered silicate, the obtained foamed molded article had many small foam cells and a small average cell diameter. However, foamed cells having a large cell diameter were also produced, and the uniformity was poor. For this reason, silver streaks, swirl marks, sink marks, etc. were confirmed, the surface appearance was inferior, and the impact resistance was also inferior.

Claims (5)

  It is composed of a resin composition containing 0.1 to 10 parts by mass of cellulose fibers having an average fiber diameter of 10 μm or less and 0.01 to 15 parts by mass of a foam nucleating agent with respect to 100 parts by mass of the polyamide resin. A foam-molded article comprising:   The foam molded article according to claim 1, wherein the foam molded article comprises a core layer and a skin layer, and the core layer has foam cells.   The foamed molded article according to claim 1 or 2, wherein the foamed cell has a maximum cell diameter of 2 mm or less.   The polyamide resin and cellulose fiber constituting the resin composition are obtained by performing a polymerization reaction of a monomer constituting the polyamide resin in the presence of cellulose fiber containing water. The foam-molded article according to any one of claims 1 to 3. The foamed molded article according to any one of claims 1 to 4, wherein the resin composition is molded by a core back injection molding method.