JP2023152040A - Polyamide resin composition and production method for polyamide resin composition - Google Patents

Abstract

To provide: a polyamide resin composition which has few black spot foreign materials and is sufficiently improved in mechanical properties such as the flexural modulus, the tensile modulus and the linear expansion coefficient; and a method for producing the same.SOLUTION: A polyamide resin composition contains 0.01-200 pts.mass of cellulose fibers per 100 pts.mass of a polyamide resin. The number of pellets containing black spot foreign materials per 100 pellets comprising the polyamide resin composition is 10 or less. The polyamide resin contains as a monomer component a monomer that is in a liquid state at a polymerization temperature.SELECTED DRAWING: None

Description

The present invention relates to a polyamide resin composition and a method for producing the polyamide resin composition. Specifically, the present invention is directed to a polyamide resin composition that is made of cellulose fibers and a polyamide resin, has few black spots, has improved mechanical properties, is particularly excellent in both tensile elastic modulus and linear expansion coefficient, and has good dispensing properties. The present invention also relates to a method for producing the polyamide resin composition, in which cellulose fibers are uniformly dispersed in the resin even if the cellulose fiber content is large.

Resin compositions in which polyamide resin is reinforced with inorganic fillers such as glass fibers, carbon fibers, talc, and clay are widely known. However, when using reinforcing materials such as these inorganic fillers, there are problems in that mechanical properties and heat resistance cannot be improved unless a large amount of inorganic fillers are blended, and the weight of the resulting resin composition is low due to its high specific gravity. The problem is that it becomes large.

In recent years, the use of cellulose as a reinforcing material for resin materials has been considered. Cellulose includes those obtained from trees, those obtained from non-wood resources such as rice, cotton, kenaf, bagasse, abaca, and hemp, and bacterial cellulose produced by microorganisms. These exist in extremely large quantities on earth. Cellulose has excellent mechanical properties, and its inclusion in a resin is expected to have the effect of improving the properties of the resin composition. Furthermore, since cellulose has a smaller specific gravity than the inorganic filler, there is no problem that the mass of the resin composition obtained by incorporating cellulose into the resin increases.

For example, Patent Document 1 discloses that a polyamide resin composition with improved mechanical properties and heat resistance can be obtained by mixing an aqueous dispersion of cellulose fibers and monomers constituting a polyamide resin and melt polymerizing the mixture. is disclosed.

For example, Patent Document 2 discloses that by increasing the molecular weight of a polyamide resin composition with a specific relative viscosity through solid phase polymerization, it has high strength, good color tone, and payout properties. It is disclosed that a cellulose-containing polyamide resin composition having good properties can be obtained.

For example, Patent Document 3 discloses that while the temperature of the inner wall of the reaction vessel is kept lower than the polymerization temperature of the powdered raw material, the raw material is heated by stirring heat, and the temperature of the inner wall of the reaction vessel is heated to a temperature higher than the temperature of the inner wall of the reaction vessel. A technique of solid state polymerization is described as the polymerization temperature.
Further, for example, Patent Document 4 describes a technique of performing solid phase polymerization using a polyamide low-order condensate.
Further, for example, Patent Document 5 describes a technique for solid phase polymerization of polyamide.
Further, for example, Patent Documents 6 and 7 describe that a reinforcing effect can be obtained by blending cellulose.

International publication 2011/126038 pamphlet International publication 2016/140240 pamphlet International publication 2017/208857 pamphlet Japanese Patent Application Publication No. 2000-159885 JP2006-290978A Japanese Patent Application Publication No. 2014-148629 US Patent Publication No. 2019/0092909

However, in the conventional method, in the process of compositing polyamide resin and cellulose fiber, heat-discolored cellulose, thermally decomposed products of cellulose, and discolored and decomposed products of other components such as hemicellulose and lignin in cellulose are mixed into polyamide. Black spots were sometimes mixed into the resin composition. When a polyamide resin composition containing such black spot foreign matter was used, a molded article having a good appearance could not be obtained. Moreover, by conventional methods, it has not been possible to obtain a polyamide resin composition that is sufficiently excellent in all of the flexural modulus, tensile modulus, and linear expansion coefficient. Furthermore, conventional polyamide resin compositions may not have sufficiently excellent heat resistance.

Details are as follows.
In the method described in Patent Document 1, the polymerization temperature is raised to a temperature higher than the melting point of the polyamide resin during melt polymerization of the polyamide resin composition, so cellulose discolored by heat, thermal decomposition products, etc. may be mixed in as black spot foreign matter. . Moreover, the tensile modulus of the polyamide resin composition cannot be sufficiently improved. Furthermore, the method described in Patent Document 1 may not be able to sufficiently improve the linear expansion coefficient and heat resistance of the polyamide resin composition.
Further, in the method described in Patent Document 2, although a polyamide resin composition having a good color tone can be obtained, black spot foreign matter may be mixed in. Further, although the flexural modulus of the polyamide resin composition is improved, the tensile modulus and linear expansion coefficient cannot be sufficiently improved. Furthermore, the method described in Patent Document 2 may not be able to sufficiently improve the heat resistance of the polyamide resin composition.

In addition, in both the methods of Patent Documents 1 and 2, when the content of cellulose fiber is large (for example, when the content of cellulose fiber exceeds 50 parts by mass with respect to 100 parts by mass of polyamide resin), cellulose is There are problems such as separation, making it difficult to incorporate cellulose fibers into the resin composition, and coloring of the resulting resin composition.

In addition, in both the methods of Patent Documents 1 and 2, the polymer must be kept in a molten state during the production of the resin composition, and as the polymerization progresses, the melt viscosity increases, making it difficult to dispense. There is also the problem that the yield becomes worse.

Furthermore, since the technologies of Patent Documents 3 to 5 perform solid phase polymerization, even if the cellulose fiber blending technology described in Patent Documents 6 and 7 is applied to such technologies, the polyamide resin composition It is not possible to sufficiently improve the mechanical properties (especially tensile modulus and coefficient of linear expansion) and heat resistance of objects.

In view of these points, the present invention provides a polyamide that has few black spots and has sufficiently improved mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (particularly both tensile modulus and linear expansion coefficient). The present invention aims to provide a resin composition and a method for producing the same.

The present invention also has few black spots, sufficiently improved mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (particularly both tensile modulus and linear expansion coefficient), and good dispensing properties. An object of the present invention is to provide a polyamide resin composition having properties and a method for producing the same.

The present invention also has few black spots, sufficiently improved mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (particularly both tensile modulus and linear expansion coefficient), and good dispensing properties. A polyamide resin composition which uniformly contains cellulose fibers even if the content of cellulose fibers is relatively large (for example, 50 parts by mass or more per 100 parts by mass of polyamide resin), and its production. The purpose is to provide a method.

The present invention also provides a polyamide resin that has few black spots and has sufficiently improved mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (especially both tensile modulus and linear expansion coefficient) and heat resistance. The present invention aims to provide a composition and a method for producing the same.

The present invention also has few black spots, sufficiently improved mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (especially both tensile modulus and linear expansion coefficient), and heat resistance. It is an object of the present invention to provide a polyamide resin composition having good dispensing properties and a method for producing the same.

The present invention also has few black spots, sufficiently improved mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (especially both tensile modulus and linear expansion coefficient), and heat resistance. A polyamide resin composition that has good dispensing properties and uniformly contains cellulose fibers even if the content of cellulose fibers is relatively large (for example, 50 parts by mass or more per 100 parts by mass of the polyamide resin); The purpose is to provide a method for producing the same.

The present inventors have conducted extensive research in order to solve such problems. As a result, the present inventors have discovered that the above object can be achieved by obtaining a polyamide resin composition containing cellulose fibers by polymerizing at a temperature below the melting point of the polyamide resin composition, and have developed the present invention. Reached.

The gist of the invention is as follows.
<1> A polyamide resin composition containing 0.01 to 200 parts by mass of cellulose fibers per 100 parts by mass of the polyamide resin, wherein the number of pellets containing black spots per 100 pellets made of the polyamide resin composition is A polyamide resin composition having 10 or less particles.
<2> The polyamide resin composition according to <1>, wherein the polyamide resin contains a monomer that is in a liquid state at a polymerization temperature as a monomer component.
<3> The polyamide resin composition according to <1> or <2>, which is produced using water.
<4> The polyamide resin composition according to any one of <1> to <3>, wherein a molded article obtained from the polyamide resin composition has a tensile modulus exceeding 3.0 GPa.
<5> The polyamide resin composition according to any one of <1> to <4>, wherein the molded body has a linear expansion coefficient of 40×10 ⁻⁶ (1/° C.) or less.
<6> The linear expansion coefficient of the molded body exhibits a reduction rate of 30% or more based on the linear expansion coefficient of a molded body obtained from a polyamide resin composition produced by a melt polymerization method. polyamide resin composition.
<7> The polyamide resin composition according to any one of <1> to <6>, wherein the content of the cellulose fiber is 4 to 100 parts by mass based on 100 parts by mass of the polyamide resin.
<8> The content of the cellulose fiber is 8 to 100 parts by mass based on 100 parts by mass of the polyamide resin,
The polyamide resin composition according to any one of <1> to <7>, wherein the polyamide resin contains a monomer that is in a liquid state at a polymerization temperature as a monomer component.
<9> The content of the cellulose fiber is 22 to 100 parts by mass based on 100 parts by mass of the polyamide resin,
The polyamide resin composition according to any one of <1> to <8>, wherein the polyamide resin is polyamide 6 containing a monomer that is in a liquid state at a polymerization temperature as a monomer component.
<10> The polyamide resin composition according to any one of <1> to <9>, wherein the cellulose fiber (B) has an average fiber diameter of 10 μm or less.
<11> The method for producing a polyamide resin composition according to any one of <1> to <10>, wherein the polymerization reaction is carried out at a temperature below the melting point of the polyamide resin.
<12> The method for producing a polyamide resin composition according to <11>, using a monomer and water in a liquid state at a polymerization temperature.
<13> The method for producing a polyamide resin composition according to <11> or <12>, wherein the polymerization temperature is equal to or higher than the melting point of the polyamide resin -75 (° C.) and lower than the melting point of the polyamide resin.
<14> A method for producing a polyamide resin composition according to any one of <11> to <13>, which comprises producing a polyamide resin composition according to any one of <1> to <10>.
<15> A polyamide resin composition produced by the method for producing a polyamide resin composition according to any one of <11> to <14>.
<16> A molded article obtained by molding the polyamide resin composition according to any one of <1> to <10> or the polyamide resin composition according to <15>.
<17> A recycled material obtained by crushing and/or re-pelletizing the molded article described in <16>.
<18> A mixture of the polyamide resin composition according to any one of <1> to <10> or the polyamide resin composition according to <15> and the recycled material according to <17>.
<19> A molded article obtained by molding the mixture according to <18>.

The polyamide resin composition of the present invention can produce a molded article with fewer black spots and a good appearance.
The polyamide resin composition of the present invention also has sufficiently improved mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (especially both tensile modulus and linear expansion coefficient).
The polyamide resin composition of the present invention also has good dispensing properties. The polyamide resin composition of the present invention further contains cellulose fibers relatively uniformly even if the content of cellulose fibers is relatively large (for example, 50 parts by mass or more based on 100 parts by mass of the polyamide resin). As a result, it is considered that mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (particularly both tensile modulus and linear expansion coefficient) are sufficiently improved.
The polyamide resin composition of the present invention also has sufficiently improved heat resistance.
The polyamide resin composition of the present invention also has good recyclability.

[Polyamide resin composition]
The polyamide resin composition of the present invention contains a polyamide resin and cellulose fibers dispersed in the polyamide resin.

The polyamide resin in the present invention refers to a polymer having an amide bond formed by an aminocarboxylic acid, a lactam, or a diamine and a dicarboxylic acid.

Examples of the aminocarboxylic acid include 6-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, and para-aminomethylbenzoic acid.

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, 5 -Methylnonamethylenediamine, 2,4-dimethyloctamethylenediamine, metaxylylenediamine, paraxylylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1-amino-3-aminomethyl-3,5,5 -Trimethylcyclohexane, 3,8-bis(aminomethyl)tricyclodecane, bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl) Examples include propane and bis(aminopropyl)piperazine.

Examples of dicarboxylic acids include adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, and 5-methylisophthalic acid. , 5-sodium sulfoisophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, and diglycolic acid.

Specific examples of polyamide resins include polycaproamide (polyamide 6), polytetramethylene adipamide (polyamide 46), polyhexamethylene adipamide (polyamide 66), polyhexamethylene sebacamide (polyamide 610), Polyhexamethylene dodecamide (polyamide 612), polyundecamethylene adipamide (polyamide 116), polyundecaneamide (polyamide 11), polydodecanamide (polyamide 12), polytrimethylhexamethylene terephthalamide (polyamide TMHT), polyamide Hexamethylene terephthalamide (polyamide 6T), polyhexamethylene isophthalamide (polyamide 6I), polyhexamethylene terephthalamide/isophthalamide (polyamide 6T/6I), polybis(4-aminocyclohexyl)methandodecamide (polyamide PACM12), polybis( 3-Methyl-4-aminocyclohexyl)methandodecamide (polyamide dimethyl PACM12), polymethaxylylene adipamide (polyamide MXD6), polynonamethylene terephthalamide (polyamide 9T), polydecamethylene terephthalamide (polyamide 10T), Examples include undecamethylene terephthalamide (polyamide 11T) and polyundecamethylene hexahydroterephthalamide (polyamide 11T(H)), and copolymers and mixtures thereof may be used. Among them, polyamide 6, polyamide 66, and polyamide 11 are used from the viewpoint of further suppressing black spot foreign substances and further improving mechanical properties (especially tensile modulus and coefficient of linear expansion), heat resistance, payout performance, and cellulose fiber dispersion uniformity. , polyamide 12, or copolymers or mixtures thereof. From the same viewpoint as above, polyamide 6, polyamide 66, or polyamide 12 is more preferable, polyamide 6 or polyamide 12 is even more preferable, and polyamide 6 is particularly preferable. In this specification, mechanical properties are used as a concept including flexural modulus, tensile modulus, and linear expansion coefficient (particularly tensile modulus and linear expansion coefficient).

Examples of cellulose fibers in the present invention include those derived from wood, rice, cotton, kenaf, bagasse, abaca, hemp, and the like. Other examples include biologically derived cellulose, such as bacterial cellulose, valonia cellulose, and ascidian cellulose. Also included are regenerated cellulose and cellulose derivatives. From the viewpoint of further suppressing black spot foreign matter and further improving mechanical properties (especially tensile modulus and coefficient of linear expansion), heat resistance, payout performance, and cellulose fiber dispersion uniformity, cellulose fibers are cellulose fibers derived from wood. It is preferable that there be.

The polyamide resin composition of the present invention can improve mechanical properties by uniformly containing cellulose fibers. In order to improve the mechanical properties more fully, it is preferable to disperse the cellulose fibers more uniformly in the resin without agglomerating them. The more hydroxyl groups the cellulose fiber has on the surface of the cellulose fiber in contact with the polyamide resin, the easier it is to disperse, so it is preferable that the overall surface area of the cellulose fiber is large. For this reason, it is preferable that the cellulose fibers be as fine as possible. The cellulose fibers to be used are not particularly limited, and may be chemically unmodified or chemically modified, as long as they can be uniformly dispersed in the resin composition.

Therefore, the cellulose fibers in the resin composition of the present invention can further suppress black spot foreign substances, and further improve mechanical properties (especially tensile modulus and linear expansion coefficient), heat resistance, payout properties, and cellulose fiber dispersion uniformity. Therefore, the average fiber diameter is preferably 10 μm or less, more preferably 500 nm or less, even more preferably 200 nm or less, particularly preferably 150 nm or less, and most preferably 120 nm or less. . On the other hand, the lower limit of the average fiber diameter is not particularly limited, but in consideration of the productivity of cellulose fibers, it is preferably 4 nm.

The aspect ratio (average fiber length/average fiber diameter) of the cellulose fibers in the resin composition of the present invention is preferably 10 or more, more preferably 30 or more, even more preferably 40 or more, and 50 or more. It is particularly preferably at least 100, most preferably at least 100. When the aspect ratio is 10 or more, the mechanical properties of the polyamide resin composition are further improved.

In the present invention, the average fiber diameter and average fiber length of cellulose fibers in a resin composition refer to the average fiber diameter and average fiber length, respectively, in a molded article obtained using the resin composition. Specifically, the average fiber diameter and Average fiber length is used. The detailed molding conditions at this time are as follows. When the polyamide resin was polyamide 6, the injection molding conditions were a resin temperature of 250°C, a mold temperature of 70°C, an injection time of 12 seconds, and a cooling time of 20 seconds. When the polyamide resin was polyamide 66, the injection molding conditions were a resin temperature of 290°C, a mold temperature of 80°C, an injection time of 12 seconds, and a cooling time of 20 seconds. When the polyamide resin was polyamide 12, the injection molding conditions were a resin temperature of 200°C, a mold temperature of 80°C, an injection time of 12 seconds, and a cooling time of 20 seconds. Note that the average fiber diameter and average fiber length of the cellulose fibers in the resin composition are almost the same as the average fiber diameter and average fiber length in the molded article obtained using the resin composition.

In order to make the average fiber diameter of the cellulose fibers 10 μm or less, it is preferable to use cellulose fibers with an average fiber diameter of 10 μm or less as the cellulose fibers to be blended with the polyamide resin. Cellulose fibers having an average fiber diameter of 10 μm or less can be obtained by tearing cellulose fibers and microfibrillating them. Examples of means for microfibrillation include various pulverizing devices such as a ball mill, a stone mill, a high-pressure homogenizer, and a mixer. A commercially available aqueous dispersion of microfibrillated cellulose fibers includes, for example, "Selish" manufactured by Daicel Finechem.

Further, as the cellulose fiber, an aggregate of cellulose fibers produced as waste yarn in the manufacturing process of textile products using cellulose fibers can also be used. The manufacturing process of textile products includes spinning, weaving, non-woven fabric manufacturing, and other textile processing. These aggregates of cellulose fibers are waste fibers that have been turned into waste threads after the cellulose fibers have gone through these steps, so they are finely divided cellulose fibers.

Further, as the cellulose fiber, bacterial cellulose produced by bacteria can also be mentioned. Examples of bacterial cellulose include those produced using acetic acid bacteria of the genus Acetobacter as producing bacteria. Plant cellulose is a convergence of cellulose molecular chains, made up of bundles of very thin microfibrils. On the other hand, cellulose produced by acetic acid bacteria originally has a ribbon shape with a width of 20 to 50 nm, forming an extremely thin mesh compared to cellulose from plants. Bacterial cellulose may coexist with acetic acid because bacteria produce acetic acid together with the cellulose. In that case, it is preferable to replace the solvent with water.

Moreover, micronized cellulose can also be mentioned as a cellulose fiber. Finely divided cellulose can be produced, for example, by oxidizing cellulose fibers in an aqueous solution containing an N-oxyl compound, a co-oxidizing agent, and an alkali metal bromide, followed by washing with water and fibrillation. Examples of the N-oxyl compound include 2,2,6,6-Tetramethylpiperidine-1-oxylradical and the like. Examples of the co-oxidizing agent include sodium hypochlorite and sodium chlorite.
The oxidation reaction of cellulose fibers is carried out after adjusting the pH to around 10 by adding an alkaline compound such as an aqueous sodium hydroxide solution until no change in pH is observed. The reaction temperature is preferably room temperature. After the reaction, it is preferable to remove the N - oxyl compound, co-oxidant, and alkali metal bromide remaining in the system. Examples of washing methods include filtration and centrifugation. Examples of the defibration method include methods using various types of pulverizing equipment as exemplified as the equipment for microfibrillation described above.

Furthermore, the cellulose fibers may be unmodified cellulose fibers in which the cellulose-derived hydroxyl groups have not been modified with any substituent, or cellulose-derived hydroxyl groups (particularly a part thereof) may have been modified (or substituted). It may also be a modified cellulose fiber. The substituents introduced into the cellulose-derived hydroxyl groups are not particularly limited, and include, for example, hydrophilic substituents and hydrophobic substituents. In the modified cellulose fiber, the hydroxyl groups modified (or substituted) with substituents are some of the hydroxyl groups derived from cellulose, and the degree of substitution is preferably 0.05 to 2.0, and preferably 0.05 to 2.0. It is more preferably from 1 to 1.0, and even more preferably from 0.1 to 0.8. Note that the degree of substitution refers to the number of substituents introduced per unit structure (glucopyranose ring) constituting cellulose. That is, it is defined as "the value obtained by dividing the number of moles of the introduced substituent by the total number of moles of glucopyranose rings." Since pure cellulose has three substitutable hydroxyl groups per unit structure (glucopyranose ring), the theoretical maximum value of the degree of substitution of the cellulose fiber of the present invention is 3, and the theoretical minimum value is 0. Examples of the hydrophilic substituent include a carboxyl group, a carboxymethyl group, and a phosphate ester group. Examples of the hydrophobic substituent include a silyl ether group, an alkyl ether group, and an alkyl ester group.

The content of cellulose fiber in the polyamide resin composition of the present invention is required to be 0.01 to 200 parts by mass based on 100 parts by mass of the polyamide resin, and it is necessary to further suppress black spot foreign substances and improve mechanical properties ( In particular, the amount is preferably 1 to 100 parts by mass, and more preferably 4 to 100 parts by mass, from the viewpoint of further improving the tensile modulus of elasticity and coefficient of linear expansion), heat resistance, payout performance, and uniformity of dispersion of cellulose fibers. , more preferably from 8 to 100 parts by weight, even more preferably from 18 to 100 parts by weight, particularly preferably from 22 to 100 parts by weight, and most preferably from 22 to 80 parts by weight. . When the content of cellulose fibers is less than 0.01 parts by mass based on 100 parts by mass of the polyamide resin, there is no effect of improving mechanical properties and heat resistance. On the other hand, if the content of cellulose fiber exceeds 200 parts by mass based on 100 parts by mass of the polyamide resin, it may be difficult to incorporate the cellulose fiber into the resin composition, or the resulting resin composition may be colored. It may occur.

By obtaining the polyamide resin composition of the present invention by the production method of the present invention as described below, even if the content of cellulose fibers is small, it can be uniformly dispersed in the polyamide resin. The composition has the effect of sufficiently improving mechanical properties and heat resistance. In other words, even if the content of cellulose fiber is 0.01 to 10 parts by mass based on 100 parts by mass of polyamide resin, the polyamide resin composition has improved mechanical properties, especially tensile modulus and coefficient of linear expansion. It will be excellent at both.

Furthermore, by obtaining the polyamide resin composition of the present invention by the production method of the present invention as described below, even if the content of cellulose fibers is large, the cellulose fibers are not separated and are uniformly contained in the polyamide resin. Since it can be dispersed in a large amount of water, it is possible to obtain the effect of further improving mechanical properties. That is, the content of cellulose fiber is 22 to 100 parts by mass, preferably 30 to 100 parts by mass, more preferably 50 to 100 parts by mass, and even more preferably 50 to 80 parts by mass, based on 100 parts by mass of the polyamide resin. Also, the mechanical properties and heat resistance of the polyamide resin composition are improved, and the tensile modulus and linear expansion coefficient are particularly excellent.

The polyamide resin composition of the present invention containing the polyamide resin and cellulose fibers as described above has a number average molecular weight of 10,000 to 10, from the viewpoint of further improving mechanical properties and heat resistance, and improving moldability. Preferably, it is 10,000. The number average molecular weight is a value determined in terms of PMMA at 40° C. using a gel permeation chromatography (GPC) device equipped with a differential refractive index detector and using hexafluoroisopropanol as an eluent.

The molecular weight of the polyamide resin composition of the present invention can also be controlled by adjusting the terminal group concentration of the polyamide. A method for adjusting the terminal group concentration includes adding a known terminal blocking agent. Examples of the terminal blocking agent include monoamines and monocarboxylic acids. Examples of monoamines include stearylamine, octylamine, cyclohexylamine, and aniline. Examples of monocarboxylic acids include acetic acid, lauric acid, stearic acid, and benzoic acid.

The polyamide resin composition of the present invention may contain pigments, heat stabilizers, antioxidants, weathering agents, plasticizers, lubricants, mold release agents, antistatic agents, impact-resistant agents, and flame retardants, as long as their properties are not significantly impaired. , may contain additives such as a compatibilizer.

Furthermore, the polyamide resin composition of the present invention may contain other polymers than the polyamide resin as long as the properties thereof are not significantly impaired. Examples of other polymers include polyolefin, polyester, polycarbonate, polystyrene, polymethyl (meth)acrylate, poly(acrylonitrile-butadiene-styrene) copolymer, liquid crystal polymer, polyacetal, and elastomer.

[Method for manufacturing polyamide resin composition]
The polyamide resin composition of the present invention can be produced, for example, by adding cellulose fibers during polymerization of the polyamide resin and performing the polymerization reaction at a temperature below the "melting point of the polyamide resin." Specifically, the polyamide resin composition of the present invention is produced by heating a mixed dispersion obtained by uniformly mixing monomers constituting the polyamide resin and an aqueous dispersion of cellulose fibers to a temperature below the "melting point of the polyamide resin". It can be produced by a polymerization reaction. That is, the polyamide resin composition of the present invention is manufactured using a monomer and water, and more specifically, it can be manufactured by performing a polymerization reaction using a monomer and water at a temperature below the "melting point of the polyamide resin." In the present invention, water is typically the medium for the aqueous dispersion of cellulose fibers. In the present invention, by performing a polymerization reaction using a monomer and water at a temperature below the "melting point of the polyamide resin," it is possible to sufficiently suppress the deterioration of the cellulose fibers and to sufficiently uniformly disperse the cellulose fibers. can. As a result, the generation of sunspot foreign matter is sufficiently suppressed, and mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (especially both tensile modulus and linear expansion coefficient) and heat resistance are sufficiently improved. do. At this time, water in the aqueous dispersion of cellulose fibers can be discharged by gradually discharging water vapor while heating the dispersion. In addition, the polymerization reaction may be carried out while standing still or may be carried out with stirring, but it is possible to further suppress black spot foreign substances, improve mechanical properties (especially tensile modulus and coefficient of linear expansion), heat resistance, dispensing properties, From the viewpoint of further improving the uniformity of dispersion of cellulose fibers, it is preferable to leave the process still. The time of polymerization of a polyamide resin includes not only the time of polymerization using a monomer constituting the polyamide resin, but also the time of polymerization using a monomer salt or prepolymer that can constitute the polyamide resin. Thus, the monomers to be polymerized may be monomer salts or prepolymers. A monomer salt is a salt of a diamine and a dicarboxylic acid that can constitute a polyamide resin. A prepolymer is an intermediate product during the polymerization of monomers. When polyamide resin is not produced by a polymerization reaction using monomers and water, that is, when polyamide resin is produced without using cellulose fibers in the form of an aqueous dispersion, black spots occur because the cellulose fibers cannot be uniformly dispersed. Foreign matter may be generated, and/or mechanical properties (eg, tensile modulus and/or coefficient of linear expansion) may be reduced, and/or heat resistance may be reduced.

In the production method of the present invention, the polymerization temperature is lower than the "melting point of the polyamide resin." "The melting point of the polyamide resin" refers to the "melting point of the target polyamide resin," and more specifically, the monomer (which may be a monomer salt or a prepolymer) of the polyamide resin constituting the polyamide resin composition of the present invention. This is the melting point of a polyamide resin obtained by sufficiently polymerizing the polyamide resin using a melt polymerization method. The melt polymerization method is a method of sufficiently polymerizing by heating without using a solvent to obtain a polyamide resin in a molten state. Therefore, the polymerization temperature in the melt polymerization method is higher than the melting point of the resulting polyamide resin (ie, the "target polyamide resin"). The polymerization temperature in such a melt polymerization method is, for example, 230 to 250 °C (especially 240 °C) for polyamide 6, and 250 to 290 °C (especially 280 °C) for polyamide 66, For example, in the case of polyamide 12, the temperature is 220 to 240°C (particularly 230°C). The polymerization time in the melt polymerization method may generally be 0.5 to 2 hours, particularly 1 hour. If the polymerization temperature is higher than the melting point of the polyamide resin (especially higher than the melting point of the polyamide resin), the cellulose fibers will deteriorate, resulting in black spots and/or mechanical properties ( For example, the tensile modulus and/or coefficient of linear expansion may decrease, and/or the heat resistance may decrease.

Therefore, when producing the polyamide resin composition of the present invention, first, sufficient polymerization is carried out by the above-mentioned melt polymerization method using only the monomer (which may be a monomer salt or a prepolymer) as a raw material. to obtain a polyamide resin (specifically, "target polyamide resin"). Next, the melting point of the obtained polyamide resin is measured. For example, when the "target polyamide resin" is polyamide 6, the "melting point of the target polyamide resin" is usually 220°C. For example, when the "target polyamide resin" is polyamide 66, the "melting point of the target polyamide resin" is usually 270°C. For example, when the "target polyamide resin" is polyamide 12, the "melting point of the target polyamide resin" is usually 175°C. The method for measuring the melting point is not particularly limited, and for example, the melting point can be measured using a differential scanning calorimeter. Thereafter, the mixed dispersion containing the monomer (which may be a monomer salt or a prepolymer) and the cellulose fiber aqueous dispersion is subjected to a polymerization reaction at a temperature below the "melting point", thereby producing the polyamide resin composition of the present invention. can be manufactured.

In the method for producing a polyamide resin composition of the present invention, as described above, the polymerization is performed at a lower temperature than the conventional melt polymerization method, so such polymerization can be referred to as "low-temperature polymerization." The polyamide resin composition of the present invention obtained by low-temperature polymerization is obtained in a solid state (or solid phase state).

An aqueous dispersion of cellulose fibers can be obtained by stirring purified water and cellulose fibers with a mixer or the like. The content of cellulose fibers in the aqueous dispersion is preferably 0.01 to 50% by weight, particularly 1 to 30% by weight.

During low-temperature polymerization to obtain the polyamide resin composition of the present invention, a polymerization catalyst may be added as necessary. The polymerization catalyst is not particularly limited as long as it is commonly used for melt polymerization of polyamide. Among these, phosphorus compounds are preferred, and phosphorous acid or sodium hypophosphite is preferably used.

During low-temperature polymerization to obtain the polyamide resin composition of the present invention, the polymerization temperature is, in detail, Mp-75 (°C) or higher, Mp It is preferably less than Mp-55 (°C) and less than Mp-15 (°C), and more preferably less than Mp-45 (°C) and less than Mp-15 (°C). It is preferably Mp-45 (°C) or more and Mp-25 (°C) or less, more preferably Mp-35 (°C) or more and Mp-25 (°C) or less. If the polymerization temperature is less than Mp-75 (°C), the reaction rate will be slow and it will take a long time to reach a practically required degree of polymerization. On the other hand, if the polymerization temperature is higher than Mp, the produced polymer will melt, and the resulting increase in viscosity may reduce operability or cause discoloration. Furthermore, since thermal deterioration of the cellulose fibers occurs, black spot foreign matter may be mixed in and/or the mechanical properties of the obtained polyamide resin composition may not be sufficiently improved.

During low-temperature polymerization to obtain the polyamide resin composition of the present invention, the polymerization time is usually the time during which the polyamide resin constituting the polyamide resin composition has the "melting point of the target polyamide resin", for example. , 2 hours or more (especially 2 to 24 hours), preferably 6 to 20 hours, more preferably 6 to 14 hours.

Low-temperature polymerization may be carried out under an inert gas flow, or may be carried out in an air atmosphere without passing an inert gas, or may be carried out under increased pressure or reduced pressure. It is preferable to carry out the process under inert gas flow from the viewpoint of further suppressing black spot foreign substances and further improving mechanical properties (especially tensile modulus and coefficient of linear expansion), heat resistance, payout performance, and cellulose fiber dispersion uniformity. . If the monomers constituting the polyamide resin have a cyclic structure and are difficult to initiate polymerization, it is preferable to temporarily or continuously pressurize the system during low-temperature polymerization.

The monomer to be polymerized should be in a liquid state at the polymerization temperature from the viewpoint of further suppressing black spot foreign substances and further improving mechanical properties (especially tensile modulus and coefficient of linear expansion), heat resistance, payout performance, and cellulose fiber dispersion uniformity. Preferably, certain monomers are included. That is, the polyamide resin contained in the polyamide resin composition of the present invention preferably contains a monomer that is in a liquid state at the polymerization temperature as a monomer component. A monomer that is in a liquid state at a polymerization temperature is a monomer that is in a molten state at a polymerization temperature (specifically, a monomer that has a melting point below the polymerization temperature). The polymerization temperature refers to the polymerization temperature during low-temperature polymerization to obtain the polyamide resin composition of the present invention. The monomer component refers to a raw material component used as a raw material (that is, a raw material component or compound used in polymerization). Therefore, in the present invention, the polyamide resin contains a monomer that is in a liquid state at the polymerization temperature as a raw material component. In the present invention, by performing low-temperature polymerization and using a monomer that is in a liquid state at the polymerization temperature as a raw material component, it is possible to more uniformly disperse the cellulose fibers while more fully suppressing the deterioration of the cellulose fibers. can. As a result, the generation of sunspot foreign matter is sufficiently suppressed, and mechanical properties such as flexural modulus, tensile modulus, and linear expansion coefficient (especially both tensile modulus and linear expansion coefficient) and heat resistance are further improved. Improve sufficiently.

In the present invention, not all monomers have to be monomers that are in a liquid state at the polymerization temperature, but it is preferred that at least one monomer used is a monomer that is in a liquid state at the polymerization temperature. Specifically, the monomers constituting the polyamide resin of the present invention preferably contain at least one monomer that is in a liquid state at the polymerization temperature. The polyamide resin of the present invention preferably contains monomers that are in a liquid state at the polymerization temperature in an amount of 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more, based on all the monomers constituting the polyamide resin. , particularly preferably in an amount of 80% by mass or more. The content of monomers that are in a liquid state at the polymerization temperature with respect to all the monomers constituting the polyamide resin of the present invention is usually 100% by mass or less, and particularly may be 90% by mass or less.

When the polymerization temperature is expressed as α (°C), the melting point β (°C) of a monomer that is in a liquid state at the polymerization temperature is determined by the ability to further suppress black spot foreign substances, mechanical properties (especially tensile modulus and coefficient of linear expansion), and heat resistance. From the viewpoint of further improving the properties, payout properties, and cellulose fiber dispersion uniformity, it is preferable that the following relational expression (x1) is satisfied, it is more preferable that the following relational expression (x2) is satisfied, and the following relational expression (x3 ), it is even more preferable that the following relational expression (x4) is satisfied, it is particularly preferable that the following relational expression (x5) is satisfied, and it is most preferable that the following relational expression (x6) is satisfied. :

α-160≦β≦α (x1)
α-150≦β≦α-2 (x2)
α-140≦β≦α-4 (x3)
α-130≦β≦α-6 (x4)
α-130≦β≦α-50 (x5)
α-130≦β≦α-100 (x6)

The monomer that is in a liquid state at the polymerization temperature cannot be unconditionally defined because it depends on the polymerization temperature (especially the composition of the polyamide resin to be obtained).
For example, in the case of polyamide 6, monomers that can be in a liquid state at the polymerization temperature include ε-caprolactam (melting point about 69° C.).
For example, in the case of polyamide 66, the monomers that can be in a liquid state at the polymerization temperature include adipic acid (melting point: about 152°C), hexamethylene diamine (melting point: about 42°C), and equimolar salts of hexamethylene diamine-adipic acid (melting point: about 42°C). (approximately 200°C). Note that since the equimolar salt of hexamethylene diamine-adipic acid as a raw material for polyamide 66 has a melting point of about 200° C., it may not be in a liquid state at the polymerization temperature.
Further, for example, in the case of polyamide 12, a monomer that can be in a liquid state at the polymerization temperature includes ω-laurolactam (melting point: about 153° C.).

According to the method for producing a polyamide resin composition of the present invention, since polymerization is performed at a temperature below Mp, the produced polyamide does not melt and may proceed to solid phase polymerization. Note that, if necessary, after crushing and/or scouring the produced polyamide resin composition, the molecular weight may be further increased by solid phase polymerization. The polyamide resin composition produced herein also includes intermediate products during the polymerization of monomers, ie, oligomers and low polymers.

Therefore, according to the production method of the present invention, since it is not necessary to maintain the polymer in a molten state, the increase in melt viscosity that occurs during melt polymerization and the accompanying decrease in dispensing properties are improved.

Solid-phase polymerization, which may be performed after low-temperature polymerization, is performed by subjecting the polyamide resin composition obtained by the production method of the present invention, or the polyamide resin composition after crushing and/or scouring as necessary, to an inert gas. It is preferably carried out by heating for 30 minutes or more at a temperature below the "melting point of the polyamide resin composition" under flow or reduced pressure, and preferably by heating for 1 hour or more (for example, 1 to 10 hours).

The "melting point of the polyamide resin composition" can be measured by the same method as the method for measuring the melting point described above, except that the polyamide resin composition is used. The "melting point of the polyamide resin composition" may be the same temperature as the above-mentioned "melting point of the polyamide resin."

The heating temperature during solid phase polymerization is usually Mp'-75 (°C) or more and less than Mp', where Mp' (°C) is the "melting point of the polyamide resin composition", and Mp'-55 (°C). The above is preferably Mp'-15 (°C) or less, more preferably Mp'-45 (°C) or more and Mp'-25 (°C) or less, Mp'-35 (°C) or more, Mp It is more preferable that the temperature is −25 (° C.) or less. If the heating temperature is less than Mp'-75 (°C), the reaction rate may become slow. On the other hand, if the heating temperature is higher than Mp', the polymer (ie, polyamide) constituting the polyamide resin composition may fuse or become colored.

The polyamide resin composition obtained by the production method of the present invention can be collected in its original form at the time of dispensing. Moreover, the polyamide resin composition can be made into a powder shape (or flake shape) by crushing it. Alternatively, the polyamide resin composition may be fed into an extruder and made into pellets using a strand cutter. When pelletizing, it is preferable to have a diameter of 2 to 5 mm and a length of 3 to 6 mm from the viewpoint of handling and efficiency during the scouring described below.

The polyamide resin composition obtained by the production method of the present invention may be classified as necessary. Particularly when the polyamide resin composition is in powder form (or flake form), only the polyamide resin composition of a predetermined size can be collected by classification.

The polyamide resin composition obtained by the production method of the present invention is preferably scoured by immersing it in water at 90 to 100° C. in order to remove unreacted monomers and oligomers.

When the polyamide resin composition of the present invention contains the above-described additives and/or other polymers, the additives and other polymers may be mixed into the mixed dispersion before low-temperature polymerization. Further, the additive and other polymers may be blended into the polyamide resin composition after low-temperature polymerization by melt-kneading or the like.

The polyamide resin composition of the present invention may be obtained as a masterbatch. For example, the polyamide resin composition of the present invention having a relatively high content of cellulose fibers may be used as a masterbatch. By melt-kneading the polyamide resin composition of the present invention (ie, masterbatch) with a polyamide resin that does not contain cellulose fibers for the purpose of dilution, the content of cellulose fibers can be adjusted to a desired value. Moreover, two or more types of polyamide resin compositions of the present invention having different contents of cellulose fibers may be mixed and melt-kneaded with each other.

In the method for producing a polyamide resin composition of the present invention, since low-temperature polymerization is performed as described above, discoloration and decomposition of cellulose due to heat can be sufficiently suppressed. Therefore, it is possible to sufficiently suppress the contamination of black spot foreign matter, and to obtain a molded article having a good appearance.

Furthermore, in the method for producing a polyamide resin composition of the present invention, since low-temperature polymerization is performed as described above, thermal deterioration of cellulose fibers is sufficiently suppressed. Therefore, in the polyamide resin composition of the present invention, not only the cellulose fibers are more uniformly dispersed, but also the thermal deterioration of the cellulose fibers is more fully suppressed. As a result of these, the polyamide resin compositions of the present invention have higher mechanical properties and heat resistance. For example, the polyamide resin compositions of the present invention have at least a higher tensile modulus. In a more preferred embodiment, the polyamide resin composition of the present invention has a higher tensile modulus and a lower coefficient of linear expansion.

In the polyamide resin composition of the present invention, the number of pellets containing black spot foreign matter (black spot foreign matter-containing pellets) per 100 pellets must be 10 or less, and preferably 5 or less. , more preferably one or less, and even more preferably zero. If there are 11 or more black dots, the appearance of the molded product may be impaired or the mechanical properties may deteriorate.

The polyamide resin composition of the present invention needs to have a tensile modulus of more than 3.0 GPa, preferably 3.8 GPa or more, and more preferably 4.7 GPa or more. The upper limit of the tensile modulus is not particularly limited, and is usually 10 GPa, particularly 8 GPa.

The polyamide resin composition of the present invention also preferably has a flexural modulus of 4.0 GPa or more, more preferably 6.0 GPa or more, and even more preferably 8.0 GPa or more. The upper limit of the flexural modulus is not particularly limited, and is usually 20 GPa, particularly 12 GPa.

The polyamide resin composition of the present invention also preferably has a linear expansion coefficient of 40×10 ⁻⁶ /°C or less, more preferably 15×10 ⁻⁶ /°C or less, and 7×10 ⁻⁶ /°C or less. It is more preferable that it is the following. The lower limit of the coefficient of linear expansion is not particularly limited, and is usually 1×10 ⁻⁶ /°C, particularly 2×10 ⁻⁶ /°C.

The tensile elastic modulus, flexural elastic modulus, and linear expansion coefficient of the polyamide resin composition of the present invention refer to the tensile elastic modulus, flexural elastic modulus, and linear expansion coefficient of a molded article obtained using the resin composition, respectively. In addition, the molded object for measuring these characteristic values is the same molded object as the molded object for measuring the above-mentioned average fiber diameter.

For the tensile modulus and flexural modulus, values measured in accordance with ISO527 and ISO178 are used, respectively.

The linear expansion coefficient is the linear expansion coefficient in the injection direction (that is, the flow direction of the resin during injection molding, also referred to as the MD direction) during production of the molded article, and was measured based on JIS K7197. The average value in the range of 20 to 150°C is used.

In particular, the linear expansion coefficient of the polyamide resin composition of the present invention is 30% or more, preferably 60% or more, based on the linear expansion coefficient of a molded article obtained from a polyamide resin composition produced by a melt polymerization method. Preferably, the reduction rate is 65% or more. The upper limit of the rate of decrease is not particularly limited, and is usually 90%, particularly 80%. The polyamide resin composition manufactured by the melt polymerization method is a polyamide resin composition similar to the polyamide resin composition of the present invention except that it is manufactured by adopting the melt polymerization method. It has the same composition and composition ratio as the polyamide resin composition. Therefore, the polyamide resin composition of the present invention has a significant reduction effect on the coefficient of linear expansion compared to a polyamide resin composition produced by melt polymerization having the same composition and composition ratio as the polyamide resin composition. There is. The melt polymerization method is a method similar to the above-mentioned melt polymerization method, and is a method in which polymerization is sufficiently performed by heating without using a solvent to obtain a polyamide resin in a molten state. By the melt polymerization method, a polyamide resin composition containing a polyamide resin in a molten state is obtained. In addition, in the melt polymerization method, water in the aqueous dispersion of cellulose fibers is removed during polymerization, so it is not classified as a solvent.

The rate of decrease in the coefficient of linear expansion is expressed as {(Y- It is a ratio expressed as X)/Y}×100(%).

The rate of decrease in linear expansion coefficient is a characteristic value based on a comparison between the polyamide resin composition of the present invention and a polyamide resin composition prepared by melt polymerization, which has the same content of cellulose fibers. This is one characteristic value that well suggests uniform dispersibility. The larger the reduction rate is, the better the uniform dispersibility of cellulose fibers is.

The polyamide resin composition of the present invention also has excellent heat resistance. Heat distortion temperature is an indicator of heat resistance. Heat resistance includes the property that the heat distortion temperature of the polyamide resin composition at a load of 1.8 MPa is within the range described below, and the property that the heat distortion temperature at a load of 0.45 MPa is within the range described below.

The heat distortion temperature of the polyamide resin composition of the present invention at a load of 1.8 MPa is preferably 50°C or higher, more preferably 60°C or higher, even more preferably 70°C or higher, and even more preferably 130°C. The temperature is particularly preferably at least 170°C, fully preferably at least 170°C, and most preferably at least 188°C. If the heat distortion temperature at a load of 1.8 MPa is less than 50°C, it will not have sufficient heat resistance and will be difficult to use for various purposes.

Further, the polyamide resin composition of the present invention preferably has a heat distortion temperature of 150°C or higher at a load of 0.45 MPa, more preferably 170°C or higher, even more preferably 180°C or higher, The temperature is particularly preferably 200°C or higher, sufficiently preferably 207°C or higher, and most preferably 217°C or higher. If the heat distortion temperature at a load of 0.45 MPa is less than 150°C, it will not have sufficient heat resistance and will be difficult to use for various purposes.

The heat distortion temperature of the polyamide resin composition of the present invention refers to the heat distortion temperature of a molded article obtained using the resin composition. In addition, the molded object for measuring this characteristic value is the same molded object as the molded object for measuring the above-mentioned average fiber diameter.

The heat distortion temperature uses a value measured in accordance with ISO 75.

The polyamide resin composition of the present invention also has excellent recyclability. Recyclability refers to the property that the initial values of physical properties such as tensile modulus and flexural modulus of a molded product obtained using a polyamide resin composition are sufficiently maintained even after repeated crushing and molding. It is about. An indicator of such recyclability is the retention of physical properties during recycling (for example, the retention of flexural modulus and tensile modulus). The polyamide resin composition of the present invention preferably has a physical property retention rate of 85% or more upon recycling, more preferably 90% or more, and even more preferably 95% or more. If the retention rate of physical properties during recycling is less than 85%, the physical properties will deteriorate due to recycling, so that it will not have sufficient recyclability and will be difficult to recycle (ie, reuse).

The physical property retention rate of the polyamide resin composition of the present invention upon recycling is determined for the physical properties (e.g., flexural modulus and tensile modulus) of a molded article obtained using the resin composition after three times of recycling (i.e., pulverization). It refers to the retention rate after repeating (and molding). In addition, the molded object for measuring this characteristic value is the same molded object as the molded object for measuring the above-mentioned average fiber diameter. The pulverization is performed until the average maximum diameter of any 100 pulverized particles becomes 1 to 5 mm. Flexural modulus and tensile modulus can be measured by methods similar to those described above.

[Molded object]
The polyamide resin composition of the present invention can be made into a molded article by a known molding method. Known molding methods include, for example, injection molding, blow molding, extrusion molding, inflation molding, vacuum forming after sheet processing, pressure forming, and vacuum pressure forming. For example, pellets formed by extrusion molding, molded objects formed by injection molding, films or sheets formed by extrusion molding (hereinafter referred to as "films, etc."), and these films, using the polyamide resin composition of the present invention. Molded bodies formed by processing these or stretched films, etc., hollow bodies formed by blow molding, molded bodies formed by processing these hollow bodies, filaments (fibers) obtained by melt spinning, and It is possible to obtain a shaped body obtained by drawing a filament using a 3D printer, or a shaped body obtained by using a 3D printer to produce a pellet or a pulverized product.

Among the methods described above, injection molding is preferred as the molding method. The injection molding machine used for injection molding is not particularly limited, and examples thereof include a screw in-line injection molding machine and a plunger type injection molding machine. The polyamide resin composition heated and melted in the cylinder of an injection molding machine is measured for each shot, injected into a mold in a molten state, cooled and solidified in a predetermined shape, and then released from the mold as a molded product. taken out. The resin temperature during injection molding is preferably higher than the melting point of the polyamide resin composition, and preferably lower than (melting point + 100°C). It is preferable that the polyamide resin composition to be subjected to injection molding is sufficiently dry. A polyamide resin composition with a high moisture content may foam within the cylinder of an injection molding machine, making it difficult to obtain an optimal molded product. Therefore, the moisture content of the polyamide resin composition to be subjected to injection molding is preferably less than 0.3% by mass, more preferably less than 0.1% by mass.

The polyamide resin composition of the present invention has excellent mechanical properties, particularly both tensile modulus and linear expansion coefficient. Therefore, the polyamide resin composition of the present invention can be suitably used for automobiles, electrical and electronic equipment, agriculture/fisheries, medical equipment, miscellaneous goods, and the like.

The molded product obtained from the polyamide resin composition of the present invention can be made into a recycled material by pulverizing and/or re-pelletizing the molded product. That is, crushed materials such as off-cuts such as sprues and runners, non-standard molded bodies, and used molded bodies, which are generated when the polyamide resin composition of the present invention is used in molding processes such as injection molding, or crushed materials such as A mixture of the re-pelletized product using an extruder or the like and another polyamide resin composition (for example, the polyamide resin composition of the present invention and/or another polyamide resin different from the polyamide resin composition) is molded again. It can be used for. Re-pelletization means to obtain pellets again by pulverizing, melting and kneading a molded body or offcuts. When the recycled material and another polyamide resin composition are mixed and used again for molding, the mixing ratio of the recycled material is not particularly limited, but the recycled material ratio is preferably 5% by mass or more, more preferably 10% by mass or more, More preferably, it is 30% by mass or more, particularly preferably 50% by mass or more. Alternatively, the recycled material alone may be used again for molding. Since the polyamide resin composition of the present invention sufficiently suppresses the generation of black spot foreign matter, it is possible to obtain a molded article having a good appearance even when used as a recycled material. Furthermore, since the polyamide resin composition of the present invention has good adhesion between the polyamide resin and cellulose fibers, deterioration in mechanical properties and heat resistance is suppressed even when used as a recycled material.

As described above, after the polyamide resin composition of the present invention is used as a recycled material, the process of using the recycled material (or a mixture of the recycled material and another polyamide resin composition) again for molding may be repeated. That is, a molded body obtained from a recycled material (or a mixture of a recycled material and another polyamide resin composition) can be made into a recycled material by crushing and/or re-pelletizing the molded body.

Examples of automotive applications include bodies such as bumpers, instrument panels, console boxes, garnishes, door trims, ceilings, floors, lamp reflectors, brush holders, fuel pump module parts, distributors, seat reed valves, wiper motor gears, and speedometers. Meter frame, solenoid ignition coil, alternator, switch, sensor parts, tie rod end stabilizer, ECU cable, exhaust gas control valve, connector, exhaust brake solenoid valve, engine valve, radiator fan, starter, injector, panels around the engine, engine cover , motor covers, door glass holders, sunroof rails, and bearings.

Examples of electrical and electronic equipment applications include personal computers, mobile phones, music players, car navigation systems, SMT connectors, IC card connectors, optical fiber connectors, microswitches, capacitors, chip carriers, coil seals, transistor seals, IC sockets, and switches. , relay parts, capacitor housings, thermistors, various coil bobbins, FDD main chassis, tape coder head mounts, stepping motors, bearings, shaver blade stands, lamp housings for LCD projection TVs, microwave oven parts, coil bases for induction cookers, hair dryers. Nozzles, steam dryer parts, steam iron parts, DVD pickup bases, commutator bases, circuit boards, magazine racks for boards, board holders, ICs, liquid crystal jigs, food cutters, DAT cylinder bases, copy machine gears, printer fixing units Parts, LCD panel light guide plates, communication equipment (antennas), semiconductor sealing materials, power modules, fuse holders, water pump impellers, semiconductor manufacturing equipment pipes, game console connectors, air conditioner drain pans, garbage disposal equipment internal containers , vacuum cleaner motor fan guide, microwave oven roller stay ring, capstan motor bearing, street light, submersible pump, motor insulator, motor brush holder, breaker parts, vacuum cleaner housing, self-propelled vacuum cleaner housing, Examples include computer casings, mobile phone casings, OA equipment casing parts, and gas meters.

Examples of agricultural and fishery uses include containers, cultivation containers, and floats.

Examples of medical device applications include syringes and drip containers.

Examples of miscellaneous goods include plates, cups, spoons, flowerpots, cooler boxes, fans, toys, ballpoint pens, rulers, clips, drain materials, fences, storage boxes, construction switchboards, water heater pump casings, impellers, joints, valves, Examples include faucet equipment and fasteners.

The polyamide resin composition of the present invention can be formed into a film or sheet by a known film forming method such as T-die extrusion or inflation molding. A film or sheet formed by molding the polyamide resin composition of the present invention can be used, for example, as a film capacitor, a release film for FPD, or an insulating film for an in-vehicle motor.

The polyamide resin composition of the present invention can be molded into a foam by a method using a chemical foaming agent or a method using a supercritical gas or an inert gas. A foam formed by molding the polyamide resin composition of the present invention can be used in the electrical/electronic equipment field and the automobile field.

The polyamide resin composition of the present invention can be formed into various fibers and various nonwoven fabrics by known spinning methods such as melt spinning, flash spinning, electrospinning, and melt blowing. Fibers and nonwoven fabrics formed from the polyamide resin composition of the present invention can be used as bag filters for electrostatic precipitators, motor binding threads, core materials for clothing, dry nonwoven fabrics, and felts.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Evaluation of the polyamide resin composition was performed by the following method.
(1) Average fiber diameter and average fiber length of cellulose fibers in polyamide resin composition A sufficiently dried resin composition was injection molded using an injection molding machine (NEX110-12E, manufactured by Nissei Plastics Co., Ltd.), and ISO A dumbbell test piece (test section 80 mm x 10 mm x 4 mm) as described in Standard 3167 was prepared. When the polyamide resin was polyamide 6, the injection molding conditions were a resin temperature of 250°C, a mold temperature of 70°C, an injection time of 12 seconds, and a cooling time of 20 seconds. When the polyamide resin was polyamide 66, the injection molding conditions were a resin temperature of 290°C, a mold temperature of 80°C, an injection time of 12 seconds, and a cooling time of 20 seconds. When the polyamide resin was polyamide 12, the injection molding conditions were a resin temperature of 200°C, a mold temperature of 80°C, an injection time of 12 seconds, and a cooling time of 20 seconds.
A 100 nm thick section was taken from the injection molded piece using a freezing ultramicrotome, and the section was stained and then observed using a transmission electron microscope (JEM-1230, manufactured by JEOL Ltd.). The length in the direction perpendicular to the longitudinal direction and the length in the longitudinal direction of the cellulose fiber (single fiber) were measured from the electron microscope image. At this time, the maximum length in the vertical direction was defined as the fiber diameter, and the length in the longitudinal direction was defined as the fiber length. The fiber diameter and fiber length of 10 cellulose fibers (single fibers) were measured in the same manner, and the average values of the 10 fibers were calculated and defined as the average fiber diameter and average fiber length.
In addition, for cellulose fibers with large fiber diameters exceeding 1 μm in the above average fiber diameter measurement, sections with a thickness of 10 μm were cut out using a microtome and measured using a stereomicroscope (SZ-40 manufactured by OLYMPUS). Observation was performed, and the fiber diameter was measured from the obtained image in the same manner as above to determine the average fiber diameter.

(2) Number of pellets containing black spot foreign matter The sufficiently dried resin composition was supplied to the main hopper of a twin screw extruder (TEM26SS manufactured by Shibaura Kikai Co., Ltd., screw diameter 26 m). The mixture was thoroughly kneaded at 260° C., paid out into strands, and cut to obtain pellets with a diameter of 3 mm and a length of 3 mm. 100 pellets were visually observed, and the number of pellets containing black spot foreign matter was evaluated according to the following criteria.
◎: 0 to 1 (best)
○: 2 to 5 pieces (good);
△: 6 to 10 pieces (no practical problem);
×: 11 or more (practical problems).

(3) Bending elastic modulus The bending elastic modulus of the test piece obtained in (1) was calculated using the ISO178 compliant three-point support bending method (distance between fulcrums: 64 mm, test speed: 2 mm/min, test atmosphere: 23°C, 50° C. %RH, absolute dry state). Flexural modulus was evaluated according to the following criteria.
◎: 8.0GPa≦flexural modulus (best);
○: 6.0GPa≦flexural modulus<8.0GPa (good);
△: 4.0GPa≦flexural modulus<6.0GPa (no practical problem);
×: Flexural modulus <4.0 GPa (practical problem).

(4) Tensile Modulus The tensile modulus of the test piece obtained in (1) was measured based on ISO527. Measurement conditions = distance between fulcrums: 115 mm, test speed: 5 mm/min, test atmosphere: 23° C., 50% RH, bone dry. Tensile modulus was evaluated according to the following criteria.
◎: 4.7GPa≦tensile modulus (best);
○: 3.8GPa≦tensile modulus<4.7GPa (good);
△: 3.0GPa<tensile modulus<3.8GPa (no practical problem);
×: Tensile modulus≦3.0GPa (practical problem).

(5) Coefficient of Linear Expansion The test piece obtained in (1) was cut into a size of 10 mm x 4 mm x 4 mm so that the resin flow direction (MD direction) during injection molding was the longitudinal direction. The linear expansion coefficient of the sample in the MD direction was measured based on JIS K7197, and the average value in the range of 20 to 150°C was calculated. The coefficient of linear expansion was evaluated according to the following criteria.
◎: Linear expansion coefficient ≦7.0×10 ^-6 (1/℃) (best);
○: 7.0×10 ^-6 (1/°C) < linear expansion coefficient ≦15.0×10 ^-6 (1/°C) (good);
△: 15.0×10 ^-6 (1/°C) < linear expansion coefficient ≦40.0×10 ^-6 (1/°C) (no problem in practice);
×: 40.0×10 ^-6 (1/°C) < linear expansion coefficient (practical problem).

The linear expansion coefficients (X) of Examples 1 to 4, 6 to 15 and 18 are respectively compared to Comparative Examples 5, 7, 9, 11, 15, 17, 19, 21, 23, 25, 27, 29, 11, 31. and the rate of decrease from the linear expansion coefficient (Y) of 33 [={(Y-X)/Y}×100(%)]. Note that the rate of decrease in linear expansion coefficient is a significant characteristic value when comparing polyamide resin compositions having the same content of cellulose fibers.
◎: 65%≦reduction rate (best);
○: 60%≦reduction rate<65% (good);
Δ: 30%≦reduction rate<60% (no problem in practice).

(6) Heat resistance (heat distortion temperature)
The heat distortion temperature of the test piece obtained in (1) was measured based on ISO 75. At this time, the load was measured at 1.8 MPa and 0.45 MPa. The heat distortion temperature was evaluated according to the following criteria.
・Heat distortion temperature (load 1.8MPa)
◎: 188℃≦heat distortion temperature (best);
○: 170°C≦heat distortion temperature<188°C (good);
△: 130°C≦<heat distortion temperature<170°C (no practical problem);
×: Heat deformation temperature <130°C (practical problem).
・Heat distortion temperature (load 0.45MPa)
◎: 217℃≦heat distortion temperature (best);
○: 207°C≦heat distortion temperature<217°C (good);
△: 200°C≦<heat distortion temperature<207°C (no practical problem);
×: Heat deformation temperature <200°C (practical problem).

(7) Number average molecular weight A sample solution was prepared by adding and dissolving 2 mL of hexafluoroisopropanol containing 10 mM sodium trifluoroacetate to 5 mg of polyamide, and filtering the resulting solution with a filter. This sample solution was analyzed using a gel permeation chromatography device (GPC, manufactured by Tosoh Corporation) equipped with a differential refractive index detector. Hexafluoroisopropanol containing 10 mM sodium trifluoroacetate was used as the eluent. The analysis conditions were a flow rate of 0.4 mL/min and a temperature of 40°C. The number average molecular weight was determined using a calibration curve prepared using polymethyl methacrylate as a standard sample.

(8) Physical property retention rate during recycling (retention rate regarding flexural modulus and tensile modulus)
A pulverized product obtained by pulverizing the test piece obtained in (1) was injection molded using an injection molding machine to obtain a dumbbell test piece. The flexural modulus and tensile modulus of the obtained dumbbell test piece were measured in the same manner as in the measurement methods (3) and (4) above (first recycling). The flexural modulus and tensile modulus of the test specimens obtained by repeating this recycling molding (pulverization of the specimen and injection molding) two more times were measured in the same manner as in (3) and (4) above. Measured (third recycling).
Regarding the bending elastic modulus and the tensile elastic modulus, the physical property retention rate was calculated using the following formula using the initial physical property value (initial value) and the physical property value (recycle value) of the test piece after being recycled three times.
Physical property retention rate (%) = {(recycle value)/(initial value)} x 100
The retention of physical properties after three times of recycling was evaluated according to the following criteria.
◎: 95%≦physical property retention rate (best);
○: 90%≦physical property retention rate<95% (good);
△: 85≦physical property retention rate<90% (no practical problem);
×: Physical property retention rate <85% (practical problem).

Raw material (1) Polyamide resin monomer component ε-caprolactam 6-aminocaproic acid Polyamide 66 salt (salt of the raw material monomer constituting polyamide 66, specifically equimolar salt of hexamethylene diamine-adipic acid)
・ω-laurolactam ・12-aminododecanoic acid

(2) Cellulose fiber A-1: KY110N (Selish KY110N manufactured by Daicel FineChem, containing 15% by mass of cellulose fibers with an average fiber diameter of 125 nm. (Unmodified).
- A-2: KY100G (Selish KY100G manufactured by Daicel FineChem, containing 10% by mass of cellulose fibers with an average fiber diameter of 125 nm. (Unmodified).
- A-3: KY100S (Selish KY100S manufactured by Daicel FineChem, containing 25% by mass of cellulose fibers with an average fiber diameter of 140 nm. (Unmodified).

・A-4: Bacterial cellulose fiber (undenatured):
Dispense 50 mL of a medium with a composition of 0.5 mass % glucose, 0.5 mass % polypeptone, 0.5 mass % yeast extract, and 0.1 mass % magnesium sulfate heptahydrate into a 200 mL Erlenmeyer flask, Steam sterilization was performed in an autoclave at 120°C for 20 minutes. One platinum loop of Gluconacetobacter xylinus (NBRC 16670) grown on a test tube slanted agar medium was inoculated into this, and the mixture was statically cultured at 30°C for 7 days. After 7 days, white gel-like bacterial cellulose fibers were formed in the upper layer of the culture solution.
After crushing the obtained bacterial cellulose fibers with a mixer, water replacement was performed by repeatedly soaking and washing with water, and an aqueous dispersion containing 4.1% by mass of bacterial cellulose fibers with an average fiber diameter of 60 nm was prepared. did.

・A-5: Waste thread (undenatured):
Purified water is added to an aggregate of cellulose fibers taken out as waste yarn in the nonwoven fabric manufacturing process and stirred with a mixer to prepare an aqueous dispersion containing 3% by mass of unmodified cellulose fibers with an average fiber diameter of 120 nm. did.

・A-6: TEMPO catalyzed oxidized cellulose fiber (cellulose fiber in which some of the hydroxyl groups derived from cellulose are modified with hydrophilic substituents):
After bleaching, 500 g (absolutely dry) of unbeaten kraft pulp derived from coniferous trees (whiteness 85%) was added to 500 mL of an aqueous solution in which 780 mg of TEMPO and 75.5 g of sodium bromide were dissolved, and the mixture was stirred until the pulp was uniformly dispersed. . An oxidation reaction was started by adding an aqueous solution of sodium hypochlorite to the solution at a concentration of 6.0 mmol/g. Since the pH within the system decreased during the reaction, a 3M aqueous sodium hydroxide solution was successively added to adjust the pH to 10. The reaction was terminated when the sodium hypochlorite was consumed and the pH within the system stopped changing. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was thoroughly washed with water to obtain an oxidized pulp. The oxidized pulp obtained in the above process was adjusted to 1.0% (w/v) with water and treated with an ultra-high pressure homogenizer (20°C, 150 MPa) three times to produce TEMPO catalytic oxidation with an average fiber diameter of 10 nm. An aqueous dispersion containing 1.0% by mass of cellulose fibers was prepared.
In addition, when the TEMPO-catalyzed oxidized cellulose fiber was analyzed by ¹ H-NMR, ¹³ C-NMR, FT-IR, and neutralization titration, it was confirmed that some of the hydroxyl groups derived from cellulose were substituted with carboxyl groups.

・A-7: Ether-modified cellulose fiber (cellulose fiber in which some of the hydroxyl groups derived from cellulose are modified with hydrophobic substituents):
19.94 kg of water was added to 600 g of softwood bleached kraft pulp (manufactured by Oji Paper Co., Ltd., solid content 25%) to prepare an aqueous suspension having a solid content concentration of 0.75% by mass. The resulting slurry was mechanically defibrated using a bead mill (NVM-2 manufactured by Imex) to obtain cellulose fibers (zirconia beads diameter 1 mm, bead filling amount 70%, rotation speed 2000 rpm, number of treatments 2). times). 100 g of the obtained cellulose fiber aqueous dispersion was put into each centrifuge tube, centrifuged (7000 rpm, 20 minutes), the supernatant liquid was removed, and the precipitate was taken out. 100 g of acetone was added to each centrifuge tube, stirred well, and dispersed in acetone. Centrifugation was performed, the supernatant liquid was removed, and the precipitate was taken out. The above operation was repeated two more times to obtain a cellulose fiber acetone slurry with a solid content of 5% by mass.
The obtained cellulose fiber acetone slurry was put into a four-necked 1 L flask equipped with a stirring blade so that the solid content of cellulose fibers was 5 g. 500 mL of N-methyl-2-pyrrolidone (NMP) and 250 mL of toluene were added, and the cellulose fibers were dispersed in NMP/toluene with stirring. A cooler was attached, and the dispersion was heated to 150° C. under a nitrogen atmosphere, and acetone and water contained in the dispersion were distilled off together with toluene. Thereafter, the dispersion was cooled to 40° C., 15 mL of pyridine and 25 g of hexamethyldisilazane (silyl etherification agent) were added, and the mixture was reacted for 90 minutes under a nitrogen atmosphere to prepare an NMP dispersion of ether-modified cellulose fibers.
The resulting NMP dispersion of ether-modified cellulose fibers was centrifuged to precipitate the cellulose fibers and then replaced with water. This was repeated three times to prepare an aqueous dispersion containing 1.0% by mass of ether-modified cellulose fibers with an average fiber diameter of 100 nm.
Incidentally, when the ether-modified cellulose fiber was analyzed by ¹ H-NMR, ¹³ C-NMR, and FT-IR, it was confirmed that some of the hydroxyl groups derived from cellulose were substituted with hydrophobic silyl ether groups.

Example 1 (Polymerization method A: low temperature polymerization)
As an aqueous dispersion of cellulose fibers, Selish KY110N (manufactured by Daicel FineChem, containing 15% by mass of cellulose fibers with an average fiber diameter of 125 nm) was used. 13.3 parts by mass of this aqueous dispersion of cellulose fibers, 83 parts by mass of ε-caprolactam, and 17 parts by mass of 6-aminocaproic acid were stirred and mixed with a mixer until a uniform dispersion was obtained, and a paste-like mixed dispersion was obtained. Obtained. This mixed dispersion was gradually heated under a nitrogen stream, the temperature was raised to 190°C while expelling water vapor during heating, and the polymerization reaction was carried out by standing at 190°C for 12 hours ( low temperature polymerization). At this time, stirring was not performed. At the polymerization temperature (ie, 190°C), ε-caprolactam was in the liquid state (ie, molten state) and 6-aminocaproic acid was in the solid state. The obtained polymerization reaction product was pulverized to obtain a flaky resin composition. The resulting flaky resin composition was scoured with hot water at 95°C and then dried.

Examples 2 to 13 (Polymerization method A: low temperature polymerization)
A polyamide resin composition was obtained in the same manner as in Example 1, except that the type of cellulose fiber and the content of cellulose fiber were changed as shown in Table 1.

Example 14 (Polymerization method A: low temperature polymerization)
As an aqueous dispersion of cellulose fibers, Selish KY110N (manufactured by Daicel FineChem, containing 15% by mass of cellulose fibers with an average fiber diameter of 125 nm) was used. 167 parts by mass of this aqueous dispersion of cellulose fibers and 100 parts by mass of ε-caprolactam were stirred and mixed with a mixer until a uniform dispersion was obtained, to obtain a paste-like mixed dispersion. This mixed dispersion was heated to 190° C. while stirring, and the pressure was increased to 0.7 MPa while gradually releasing steam. Thereafter, the pressure was released to atmospheric pressure, and polymerization was carried out at 190°C for 8 hours. At the polymerization temperature (ie 190°C) the ε-caprolactam was in a liquid state (ie molten state). The obtained polymerization reaction product was pulverized to obtain a flaky resin composition. The resulting flaky resin composition was scoured with hot water at 95°C and then dried.

Example 15 (Polymerization method A: low temperature polymerization)
In the same manner as in Example 1, 33 parts by mass of an aqueous dispersion of cellulose fibers and 100 parts by mass of polyamide 66 salt were stirred and mixed with a mixer until a uniform dispersion was obtained, thereby obtaining a paste-like mixed dispersion. This mixed dispersion was gradually heated under a nitrogen stream, the temperature was raised to 240°C while expelling water vapor during the heating, and the polymerization reaction was carried out by standing at 240°C for 12 hours ( low temperature polymerization). At this time, stirring was not performed. At the polymerization temperature (ie 240°C) the polyamide 66 salt was in a liquid state (ie molten state). The obtained polymerization reaction product was pulverized to obtain a flaky resin composition. The resulting flaky resin composition was scoured with hot water at 95°C and then dried.

Examples 16 and 17 (Polymerization method A: low temperature polymerization)
A polyamide resin composition was obtained in the same manner as in Example 15, except that the content of cellulose fibers and the polymerization temperature were changed as shown in Table 1.
In Example 16, the polyamide 66 salt was in a liquid state (i.e., molten state) at the polymerization temperature (i.e., 240° C.).
In Example 17, the polyamide 66 salt was in a solid state at the polymerization temperature (ie, 195° C.).

Example 18 (Polymerization method A: low temperature polymerization)
In the same manner as in Example 1, 33 parts by mass of an aqueous dispersion of cellulose fibers, 83 parts by mass of ω-laurolactam, and 17 parts by mass of 12-aminododecanoic acid were stirred and mixed with a mixer until a uniform dispersion was obtained, and a paste was prepared. A mixed dispersion liquid was obtained. This mixed dispersion was gradually heated under a nitrogen stream, the temperature was raised to 160°C while expelling water vapor during heating, and the polymerization reaction was carried out by standing at 160°C for 12 hours ( low temperature polymerization). At this time, stirring was not performed. At the polymerization temperature (ie, 160° C.), ω-laurolactam was in the liquid state (ie, molten state) and 12-aminododecanoic acid was in the solid state. The obtained polymerization reaction product was pulverized to obtain a flaky resin composition. The resulting flaky resin composition was scoured with hot water at 95°C and then dried.

Example 19 (Polymerization method A: low temperature polymerization)
A polyamide resin composition was obtained in the same manner as in Example 18, except that the content of cellulose fibers was changed as shown in Table 1.

Example 20
By adjusting the polymerization time in Comparative Example 1, a polyamide 6 resin (number average molecular weight: 20,100, molecular weight distribution: 2.8) was obtained. 50 parts by mass of this polyamide 6 resin and 50 parts by mass of the resin composition obtained in Example 6 were dry-blended and supplied to the main hopper of a twin-screw extruder (TEM26SS manufactured by Shibaura Kikai Co., Ltd., screw diameter 26 mm). The mixture was thoroughly melted and kneaded at 260°C, paid out into strands, and cut to obtain pellets of the resin composition.

Example 21
By adjusting the polymerization time in Comparative Example 1, a polyamide 6 resin (number average molecular weight 21,000, molecular weight distribution 3.6) was obtained. 50 parts by mass of this polyamide 6 resin and 50 parts by mass of the resin composition obtained in Example 6 were dry-blended and supplied to the main hopper of a twin-screw extruder (the same twin-screw extruder as in Example 20). The mixture was thoroughly melted and kneaded at 260°C, paid out into strands, and cut to obtain pellets of the resin composition.

Example 22
By adjusting the polymerization time in Comparative Example 1, a polyamide 6 resin (number average molecular weight 24,200, molecular weight distribution 3.7) was obtained. 50 parts by mass of this polyamide 6 resin and 50 parts by mass of the resin composition obtained in Example 6 were dry-blended and supplied to the main hopper of a twin-screw extruder (the same twin-screw extruder as in Example 20). The mixture was thoroughly melted and kneaded at 260°C, paid out into strands, and cut to obtain pellets of the resin composition.

Example 23
The resin composition obtained in Example 4 was injection molded using an injection molding machine (manufactured by Nissei Jushi Kogyo Co., Ltd.: NEX110-12E), and a dumbbell test piece (test section 80 mm x 10 mm x 4 mm) was prepared according to ISO standard 3167. ) was created. The injection molding conditions were a resin temperature of 250°C, a mold temperature of 70°C, an injection time of 12 seconds, and a cooling time of 20 seconds. The test piece was crushed, and the resulting crushed material was used as a recycled material.
10 parts by mass of the obtained recycled material and 90 parts by mass of the resin composition obtained in Example 4 were dry-blended and supplied to the main hopper of a twin-screw extruder (TEM26SS manufactured by Shibaura Kikai Co., Ltd., screw diameter 26 mm). The mixture was sufficiently melted and kneaded at 260° C., paid out into strands, and cut to obtain pellets of the resin composition.

Example 24
The resin composition obtained in Example 4 was injection molded using an injection molding machine (NEX110-12E, manufactured by Nissei Jushi Kogyo Co., Ltd.) to obtain a dumbbell test piece (test section 80 mm x 10 mm x 4 mm) as described in ISO standard 3167. was created. The injection molding conditions were a resin temperature of 250°C, a mold temperature of 70°C, an injection time of 12 seconds, and a cooling time of 20 seconds. The test piece was crushed and re-pelletized using a twin-screw extruder (TEM26SS manufactured by Shibaura Kikai Co., Ltd., screw diameter 26 mm), and the obtained pellets were used as recycled material.
10 parts by mass of the obtained recycled material and 90 parts by mass of the resin composition obtained in Example 4 were dry-blended and supplied to the main hopper of a twin-screw extruder (TEM26SS manufactured by Shibaura Kikai Co., Ltd., screw diameter 26 mm). The mixture was sufficiently melted and kneaded at 260° C., paid out into strands, and cut to obtain pellets of the resin composition.

Examples 25 and 26
Pellets of the resin composition were obtained by carrying out the same operation as in Example 24, except that the mixing ratio of the recycled material obtained by carrying out the same operation as in Example 24 was changed as described in Table 5. .

Comparative Example 1 (Polymerization method A: low temperature polymerization)
A polyamide resin composition was obtained in the same manner as in Example 1 except that the aqueous dispersion of cellulose fibers was not added.

Comparative Example 2 (Polymerization method A: low temperature polymerization)
A polyamide resin composition was obtained in the same manner as in Example 15 except that the aqueous dispersion of cellulose fibers was not added.

Comparative Example 3 (Polymerization method A: low temperature polymerization)
A polyamide resin composition was obtained in the same manner as in Example 18 except that the aqueous dispersion of cellulose fibers was not added.

Comparative Example 4 (Polymerization method B: melt polymerization + solid phase polymerization)
As an aqueous dispersion of cellulose fibers, Selish KY110N (manufactured by Daicel FineChem, containing 15% by mass of cellulose fibers with an average fiber diameter of 125 nm) was used. By adding purified water to this aqueous dispersion and stirring it with a mixer, an aqueous dispersion having a cellulose fiber content of 3% by mass was prepared. 70 parts by mass of this 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. This mixed dispersion was heated to 240° C. while stirring, and the pressure was increased to 0.7 MPa while gradually releasing steam. Thereafter, the pressure was released to atmospheric pressure, and melt polymerization was performed at 240° C. for 1 hour. The resin composition (pellet) obtained at the time of dispensing was scoured with hot water at 95° C. and then dried. The dried pellets were subjected to solid phase polymerization at 170° C. for 15 hours under a nitrogen stream.

Comparative Example 5 (Polymerization method C: melt polymerization)
A mixed dispersion of 70 parts by mass of cellulose fiber aqueous dispersion and 100 parts by mass of ε-caprolactam, prepared in the same manner as in Comparative Example 4, was heated to 240°C while stirring, and while gradually releasing water vapor, the mixture was heated to 0. The pressure was increased to 7 MPa. Thereafter, the pressure was released to atmospheric pressure, and melt polymerization was performed at 240° C. for 1 hour. The obtained resin composition (pellets) was scoured with hot water at 95°C and then dried.

Comparative Examples 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, and 28 (Polymerization method B: melt polymerization + solid phase polymerization)
A polyamide resin composition was obtained in the same manner as Comparative Example 4, except that the type of cellulose fiber, the content of cellulose fiber, and the polymerization method were changed as shown in Table 2 or Table 3.

Comparative Examples 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27 and 29 (Polymerization method C: melt polymerization)
A polyamide resin composition was obtained in the same manner as Comparative Example 5, except that the type of cellulose fiber, the content of cellulose fiber, and the polymerization method were changed as shown in Table 2 or Table 3.

Comparative Example 30 (Polymerization method B: melt polymerization + solid phase polymerization)
167 parts by mass of an aqueous cellulose fiber dispersion prepared in the same manner as in Comparative Example 4 and 100 parts by mass of polyamide 66 salt were further stirred and mixed with a mixer until a uniform dispersion was obtained. This mixed dispersion was heated at 230° C. while stirring until the internal pressure became 1.5 MPa. After reaching that pressure, heating was continued to maintain that pressure while gradually releasing water vapor. When the temperature reached 280°C, the pressure was released to normal pressure and melt polymerization was carried out for 1 hour. The resin composition (pellet) obtained at the time of dispensing was scoured with hot water at 95° C. and then dried. The dried pellets were subjected to solid phase polymerization at 220° C. for 15 hours under a nitrogen stream.

Comparative Example 31 (Polymerization method C: melt polymerization)
167 parts by mass of an aqueous cellulose fiber dispersion prepared in the same manner as in Comparative Example 4 and 100 parts by mass of polyamide 66 salt were further stirred and mixed with a mixer until a uniform dispersion was obtained. This mixed dispersion was heated at 230° C. while stirring until the internal pressure became 1.5 MPa. After reaching that pressure, heating was continued to maintain that pressure while gradually releasing water vapor. When the temperature reached 280°C, the pressure was released to normal pressure and melt polymerization was carried out for 1 hour. The resin composition (pellet) obtained at the time of dispensing was scoured with hot water at 95° C. and then dried.

Comparative Example 32 (Polymerization method B: melt polymerization + solid phase polymerization)
167 parts by mass of an aqueous cellulose fiber dispersion prepared in the same manner as in Comparative Example 4, 83 parts by mass of ω-laurolactam, and 17 parts by mass of 12-aminododecanoic acid were further stirred and mixed with a mixer until a uniform dispersion was obtained. . This mixed dispersion was gradually heated under a nitrogen stream, the temperature was raised to 200° C. while expelling water vapor during heating, and the mixture was stirred at 230° C. for 1 hour to carry out a polymerization reaction. The resin composition (pellet) obtained at the time of dispensing was scoured with hot water at 95° C. and then dried. The dried pellets were subjected to solid phase polymerization at 150° C. for 15 hours under a nitrogen stream.

Comparative Example 33 (Polymerization method C: melt polymerization)
167 parts by mass of an aqueous cellulose fiber dispersion prepared in the same manner as in Comparative Example 4, 83 parts by mass of ω-laurolactam, and 17 parts by mass of 12-aminododecanoic acid were further stirred and mixed with a mixer until a uniform dispersion was obtained. . This mixed dispersion was gradually heated under a nitrogen stream, the temperature was raised to 200° C. while expelling water vapor during heating, and the mixture was stirred at 230° C. for 1 hour to carry out a polymerization reaction. The resin composition (pellet) obtained at the time of dispensing was scoured with hot water at 95° C. and then dried.

Reference example 1 (Polymerization method C: melt polymerization)
A polyamide resin (PA6) was obtained in the same manner as in Comparative Example 5 except that the aqueous dispersion of cellulose fibers was not added. This operation was repeated 10 times to obtain 10 types of polyamide resins (PA6). The melting points of 10 types of polyamide resins (PA6) were measured using a differential scanning calorimeter, and the average value of these measured values was used as the melting point of the polyamide resin (PA6). The melting point of the polyamide resin (PA6) was 220°C.

Reference example 2 (polymerization method C: melt polymerization)
A polyamide resin (PA66) was obtained in the same manner as Comparative Example 31 except that the aqueous dispersion of cellulose fibers was not added. This operation was repeated 10 times to obtain 10 types of polyamide resins (PA66). The melting points of 10 types of polyamide resins (PA66) were measured using a differential scanning calorimeter, and the average value of these measured values was used as the melting point of the polyamide resin (PA66). The melting point of the polyamide resin (PA66) was 270°C.

Reference example 3 (polymerization method C: melt polymerization)
A polyamide resin (PA12) was obtained in the same manner as Comparative Example 33 except that the aqueous dispersion of cellulose fibers was not added. This operation was repeated 10 times to obtain 10 types of polyamide resins (PA12). The melting points of 10 types of polyamide resins (PA12) were measured using a differential scanning calorimeter, and the average value of these measured values was used as the melting point of the polyamide resin (PA12). The melting point of the polyamide resin (PA12) was 175°C.

Reference example 4
100 parts by mass of the polyamide resin obtained in Comparative Example 1 was supplied to the main hopper of a twin-screw extruder, and 43 parts by mass of glass fiber was supplied from a side feeder midway. The mixture was thoroughly melted and kneaded at 260°C, paid out into strands, and cut to obtain pellets of the resin composition.

Tables 1 to 5 show the results of measuring the characteristic values of the polyamide resin compositions obtained in Examples 1 to 26, Comparative Examples 1 to 33, and Reference Examples 1 to 4.

Special notes in Tables 1 to 5 are as follows.
Polymerization method A: low temperature polymerization;
Polymerization method B: melt polymerization + subsequent solid phase polymerization;
Polymerization method C: Melt polymerization.
The polymerization temperature of polymerization method B is the temperature during melt polymerization.
(1) The reduction rates of linear expansion coefficients of Examples 1 to 4, 6 to 15, and 18 are respectively Comparative Examples 5, 7, 9, 11, 15, 17, 19, 21, 23, 25, 27, 29, 11, 31 and 33 are shown.
Melting point of the polyamide obtained in Reference Example 1 = 220°C.
Melting point of the polyamide obtained in Reference Example 2 = 270°C.
Melting point of the polyamide obtained in Reference Example 3 = 175°C.

In all of the polyamide resin compositions of Examples 1 to 26, the number of pellets containing black spot foreign matter was 10 or less per 100 pellets.

The polyamide resin compositions of Examples 1 to 26 all have a tensile modulus of 3.2 GPa or more, preferably 3.8 GPa or more, more preferably 4.7 GPa or more, and a linear expansion coefficient in the MD direction of 40× It was 10 ^-6 (1/°C) or less, preferably 15.0x10 ^-6 (1/°C) or less, more preferably 7.0x10 ^-6 (1/°C) or less.

In particular, the linear expansion coefficients of Examples in which low-temperature polymerization was adopted (specifically, Examples 1 to 4, 6 to 15, and 18) were different from each other, except that melt polymerization was adopted instead of low-temperature polymerization. 30% or more based on the linear expansion coefficient of similar comparative examples (comparative examples 5, 7, 9, 11, 15, 17, 19, 21, 23, 25, 27, 29, 11, 31 and 33, respectively). The rate of decline was shown.
In addition, comparative examples employing a combination of melt polymerization method and solid phase polymerization method (in detail, comparative examples 4, 6, 8, 10, 14, 16, 18, 20, 22, 24, 26, 28, 30 and 32) ) were the same as those of the comparative examples (comparative examples 5, 7, 9, 11, 15, 17, 19, 21, 23, 25, 27, respectively) except that only the melt polymerization method was adopted. , 29, 31 and 33).

Since the polyamide resin compositions of Comparative Examples 1 to 3 did not use cellulose fibers, they had lower tensile modulus and higher coefficient of linear expansion.

In all of the polyamide resin compositions of Comparative Examples 4 to 11 and 14 to 33, the polymerization temperature was higher than the melting point of the polyamide resin, so the number of black spot foreign material-containing pellets per 100 pellets was 11 or more, and mechanical Properties, especially tensile modulus, were not sufficiently improved. None of the polyamide resin compositions of Comparative Examples 4 to 11 and 14 to 33 had a sufficiently low coefficient of linear expansion.

In both Comparative Examples 12 and 13, melt polymerization was attempted, but since the content of cellulose fibers was large, cellulose separated and a polymer containing cellulose could not be obtained.

In Examples 1 to 19, it is not necessary to maintain the obtained polyamide resin composition in a molten state during production of the polyamide resin composition, so handling of the polyamide resin composition is extremely easy, and the yield is 99% by mass. That was it. The yields in Examples 1 to 19 are determined by subtracting from 100% by mass the proportion of polymerization reactants that adhere to the reaction vessel and are difficult to recover when the polymerization reactants are taken out of the reaction vessel for scouring after low-temperature polymerization. This is the value.
In Comparative Examples 4 to 33, during the production of the polyamide resin composition, the polyamide resin composition had to be kept in a molten state, and as the polymerization progressed, the melt viscosity increased, making it difficult to dispense, and the yield was low. It was 70% by mass or less. The yields in Comparative Examples 4 to 33 are determined by subtracting from 100% by mass the proportion of polymerization reactants that adhere to the reaction vessel and are difficult to recover when the polymerization reactants are taken out of the reaction vessel for scouring after melt polymerization. This is the value.

In all of Examples 1 to 26, the physical property retention rate (retention rate of flexural modulus and tensile modulus) after three times of recycling was 95% or more. On the other hand, in Reference Example 4, the physical property retention rate after recycling three times was low. In Reference Example 4, this is thought to be because the glass fiber used as a reinforcing material for the resin material was broken during recycling.

The gist of the invention is as follows.
<1> A polyamide resin composition containing 0.01 to 200 parts by mass of cellulose fibers per 100 parts by mass of polyamide resin,
When the polyamide resin composition is made into pellets with a diameter of 3 mm and a length of 3 mm, the number of black spot foreign matter-containing pellets per 100 pellets is 10 or less,
A polyamide resin composition in which a molded article obtained from the polyamide resin composition has a tensile modulus exceeding 3.0 GPa .
<2> The polyamide resin composition according to <1>, wherein the polyamide resin contains a monomer that is in a liquid state at a polymerization temperature as a monomer component.
<3> The polyamide resin composition according to <1> or <2> , wherein a molded article obtained from the polyamide resin composition has a linear expansion coefficient of 40×10 ⁻⁶ (1/° C.) or less.
<4> The linear expansion coefficient of the molded body exhibits a reduction rate of 30% or more based on the linear expansion coefficient of a molded body obtained from a polyamide resin composition produced by a melt polymerization method. polyamide resin composition.
<5> The polyamide resin composition according to <1> or <2> , wherein the content of the cellulose fiber is 4 to 100 parts by mass based on 100 parts by mass of the polyamide resin.
<6><1> or <2> , wherein the content of the cellulose fiber is 8 to 100 parts by mass based on 100 parts by mass of the polyamide resin, and the polyamide resin contains a monomer in a liquid state at the polymerization temperature as a monomer component. The polyamide resin composition described in .
<7> The content of the cellulose fiber is 22 to 100 parts by mass based on 100 parts by mass of the polyamide resin, and the polyamide resin is polyamide 6 containing a monomer in a liquid state at the polymerization temperature as a raw material component, <1> Or the polyamide resin composition according to <2> .
<8> The polyamide resin composition according to <1> or <2> , wherein the cellulose fiber (B) has an average fiber diameter of 10 μm or less.
<9> The method for producing a polyamide resin composition according to claim 1 or 2, wherein the polymerization reaction is carried out at a polymerization temperature lower than the melting point of the polyamide resin.
<10> The method for producing a polyamide resin composition according to <9> , wherein the polyamide resin contains a monomer in a liquid state at a polymerization temperature as a raw material component .
<11> The method for producing a polyamide resin composition according to <9>, wherein a polymerization reaction is performed using water.
<12> The method for producing a polyamide resin composition according to <9> , wherein the polymerization temperature is equal to or higher than the melting point of the polyamide resin -75 (° C.) and lower than the melting point of the polyamide resin.
<13> A molded article obtained by molding the polyamide resin composition according to <1> or <2> .
<14> A recycled material obtained by crushing and/or re-pelletizing the molded article described in <13> .
<15> A mixture of the polyamide resin composition according to <1> or <2> and the recycled material according to claim 14 .
<16> A molded article obtained by molding the mixture according to <15> .

Claims (19)

A polyamide resin composition containing 0.01 to 200 parts by mass of cellulose fibers per 100 parts by mass of the polyamide resin, wherein the number of pellets containing black spot foreign matter is 10 or less per 100 pellets made of the polyamide resin composition. A polyamide resin composition. The polyamide resin composition according to claim 1, wherein the polyamide resin contains a monomer that is in a liquid state at a polymerization temperature as a monomer component. The polyamide resin composition according to claim 1 or 2, which is produced using water. The polyamide resin composition according to any one of claims 1 to 3, wherein a molded article obtained from the polyamide resin composition has a tensile modulus of more than 3.0 GPa. The polyamide resin composition according to any one of claims 1 to 4, wherein the molded body has a linear expansion coefficient of 40 × 10 ^-6 (1/°C) or less. The polyamide resin according to claim 5, wherein the linear expansion coefficient of the molded body exhibits a reduction rate of 30% or more based on the linear expansion coefficient of a molded body obtained from a polyamide resin composition produced by a melt polymerization method. Composition. The polyamide resin composition according to any one of claims 1 to 6, wherein the content of the cellulose fiber is 4 to 100 parts by mass based on 100 parts by mass of the polyamide resin. The content of the cellulose fiber is 8 to 100 parts by mass based on 100 parts by mass of the polyamide resin,
The polyamide resin composition according to any one of claims 1 to 7, wherein the polyamide resin contains a monomer that is in a liquid state at a polymerization temperature as a monomer component. The content of the cellulose fiber is 22 to 100 parts by mass based on 100 parts by mass of the polyamide resin,
The polyamide resin composition according to any one of claims 1 to 8, wherein the polyamide resin is polyamide 6 containing as a monomer component a monomer in a liquid state at a polymerization temperature. The polyamide resin composition according to any one of claims 1 to 9, wherein the cellulose fiber (B) has an average fiber diameter of 10 μm or less. The method for producing a polyamide resin composition according to any one of claims 1 to 10, wherein the polymerization reaction is carried out at a temperature below the melting point of the polyamide resin. 12. The method for producing a polyamide resin composition according to claim 11, which uses monomers and water that are in a liquid state at the polymerization temperature. The method for producing a polyamide resin composition according to claim 11 or 12, wherein the polymerization temperature is equal to or higher than the melting point of the polyamide resin -75 (° C.) and lower than the melting point of the polyamide resin. A method for producing a polyamide resin composition according to any one of claims 11 to 13, which comprises producing a polyamide resin composition according to any one of claims 1 to 10. A polyamide resin composition produced by the method for producing a polyamide resin composition according to any one of claims 11 to 14. A molded article obtained by molding the polyamide resin composition according to any one of claims 1 to 10 or the polyamide resin composition according to claim 15. A recycled material obtained by crushing and/or repelletizing the molded article according to claim 16. A mixture of the polyamide resin composition according to any one of claims 1 to 10 or the polyamide resin composition according to claim 15 and the recycled material according to claim 17. A molded article obtained by molding the mixture according to claim 18.