阅读说明：本技术 有机纤维增强树脂成型体及其制造方法 (Organic fiber-reinforced resin molded article and method for producing same ) 是由 伊仓幸广 佐武真有 伊藤涼音 中岛康雄 须山健一 金宰庆 田中广树 友松功 于 2020-03-26 设计创作，主要内容包括：一种有机纤维增强树脂成型体及其制造方法,该有机纤维增强树脂成型体是含有树脂和纤维素纤维的树脂成型体,其中,该树脂成型体的密度为0.65g/cm～3以下。(An organic fiber-reinforced resin molded article comprising a resin and cellulose fibers, wherein the resin molded article has a density of 0.65g/cm, and a method for producing the same 3 The following.)

1. An organic fiber-reinforced resin molded article comprising a resin and cellulose fibers, the resin molded article having a density of 0.65g/cm³The following.

2. The organic fiber-reinforced resin molded body according to claim 1, wherein the degree of orientation of the cellulose fibers is 0.40 or more.

3. The organic fiber-reinforced resin molded body according to claim 1 or 2, wherein the linear expansion coefficient of the resin molded body in a temperature range of 60 ℃ to 100 ℃ is 0ppm/K or more and less than 10 ppm/K.

4. The organic fiber-reinforced resin molded body according to any one of claims 1 to 3, wherein the resin comprises a polypropylene resin.

5. The organic fiber-reinforced resin molded body according to any one of claims 1 to 4, wherein the degree of crystal orientation of the resin is more than 0.50 and 1.00 or less.

6. The organic fiber-reinforced resin molding according to any one of claims 1 to 5, wherein a specific strength obtained by dividing a tensile strength of the resin molding by a density of the resin molding is 0.08MJ/kg or more.

7. The organic fiber-reinforced resin molded body according to any one of claims 1 to 6, wherein the storage modulus E at 100 ℃ is₁₀₀Storage modulus E relative to 25 deg.C₂₅Ratio of (A) to (B), i.e., modulus of elasticity maintenance ratio E₁₀₀/E₂₅Is 0.38 or more.

8. The organic fiber-reinforced resin molded body according to any one of claims 1 to 7, wherein the resin molded body is obtained by uniaxially stretching.

9. The organic fiber-reinforced resin molding according to any one of claims 1 to 8, wherein the density is 0.40g/cm³The degree of orientation of the cellulose fibers is 0.40 or more, and the degree of crystal orientation of the resin is 0.65 or more and 1.00 or less.

10. The method for producing an organic fiber-reinforced resin molded body according to any one of claims 1 to 9, which comprises the steps of: an intermediate molded body obtained by melt-kneading a resin and cellulose fibers is stretched at least uniaxially while maintaining the temperature of the intermediate molded body at a temperature not lower than the crystal relaxation temperature of the resin but not higher than the melting point thereof.

Technical Field

The present invention relates to an organic fiber-reinforced resin molded article and a method for producing the same.

Background

In order to improve the mechanical properties of resins, fiber-reinforced resins are known in which reinforcing fibers such as glass fibers and organic fibers are mixed in the resin. Examples of the organic fiber include cellulose fibers such as kraft pulp fiber, wood flour, and jute fiber. It is known that: when organic fibers are used as the reinforcing material, the resulting fiber-reinforced resin is lighter in weight and higher in specific strength (value obtained by dividing mechanical strength by density) than when it is reinforced with glass fibers.

For example, patent document 1 discloses a composite resin composition containing a polypropylene resin and plant fibers having an organic solvent extraction component content of 1 wt% or less.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5762674

Disclosure of Invention

Problems to be solved by the invention

Materials used for transportation equipment materials and the like are required to be lightweight (low density) and to exhibit high mechanical strength, that is, to have high specific strength. In recent years, this demand has been further increasing. Further, it is also required to maintain mechanical properties even when used under severe conditions such as a high-temperature environment.

As a result of studies on conventional organic fiber-reinforced resin molded articles, such as molded articles obtained from the composite resin composition described in patent document 1, the present inventors have found that these organic fiber-reinforced resin molded articles do not have sufficient specific strength to meet the above-mentioned requirements.

The invention aims to provide an organic fiber reinforced resin molded body which has excellent specific strength and is difficult to reduce mechanical properties even in a high-temperature environment.

Means for solving the problems

That is, the above object of the present invention is achieved by the following means.

[1]

An organic fiber-reinforced resin molded article comprising a resin and cellulose fibers, the resin molded article having a density of 0.65g/cm³The following.

[2]

The organic fiber-reinforced resin molded article according to [1], wherein the degree of orientation of the cellulose fibers is 0.40 or more.

[3]

The organic fiber-reinforced resin molded article according to [1] or [2], wherein the resin molded article has a linear expansion coefficient of 0ppm/K or more and less than 10ppm/K in a temperature range of 60 ℃ to 100 ℃.

[4]

The organic fiber-reinforced resin molded article according to any one of [1] to [3], wherein the resin contains a polypropylene resin.

[5]

The organic fiber-reinforced resin molded article according to any one of [1] to [4], wherein the degree of crystal orientation of the resin is more than 0.50 and 1.00 or less.

[6]

The organic fiber-reinforced resin molded body according to any one of [1] to [5], wherein a specific strength obtained by dividing a tensile strength of the resin molded body by a density of the resin molded body is 0.08MJ/kg or more.

[7]

Such as [1]]～[6]The organic fiber-reinforced resin molded body according to any one of the above, wherein the storage modulus E at 100 ℃ is₁₀₀Storage modulus E relative to 25 deg.C₂₅Ratio of (A) to (B), i.e., modulus of elasticity maintenance ratio E₁₀₀/E₂₅Is 0.38 or more.

[8]

The organic fiber-reinforced resin molded article according to any one of [1] to [7], wherein the resin molded article is stretched in a single direction.

[9]

Such as [1]]～[8]The organic fiber-reinforced resin molded body according to any one of the above items, wherein the density is 0.40g/cm³The degree of orientation of the cellulose fibers is 0.40 or more, and the degree of crystal orientation of the resin is 0.65 or more and 1.00 or less.

[10]

[1] The method for producing an organic fiber-reinforced resin molded article according to any one of [1] to [9], comprising the steps of: an intermediate molded body obtained by melt-kneading a resin and cellulose fibers is stretched at least uniaxially while maintaining the temperature of the intermediate molded body at a temperature not lower than the crystal relaxation temperature of the resin but not higher than the melting point thereof.

In the description of the present invention, "-" is used to include numerical values recited before and after the term "through" as the lower limit value and the upper limit value.

ADVANTAGEOUS EFFECTS OF INVENTION

The organic fiber-reinforced resin molded article of the present invention exhibits excellent specific strength and is less likely to suffer from a reduction in mechanical properties even in a high-temperature environment.

Drawings

FIG. 1 is a one-dimensional diffraction pattern measured by wide-angle X-ray diffraction of a molded article of cellulose fiber-reinforced polypropylene resin obtained in example 1. At a scattering vector s of 1.60nm^-1The diffraction peak observed at the position (2) is a diffraction peak derived from the alpha crystal (040) plane of polypropylene, and is 1.92nm in the scattering vector s^-1The diffraction peak observed at the position (2) is a diffraction peak derived from the α crystal (110) plane of polypropylene. Note that the scattering vector s is 2.10nm^-1The diffraction peak observed at the position (2) is a diffraction peak derived from the α -crystal (130) plane of polypropylene.

FIG. 2 is a one-dimensional diffraction pattern measured by wide-angle X-ray diffraction of the molded article of cellulose fiber-reinforced polypropylene resin of example 1. At a scattering vector s of 3.87nm^-1The position of (A) observed diffraction peak is fromDiffraction peak of (004) plane of cellulose fiber.

Detailed Description

[ resin molded article ]

The organic fiber-reinforced resin molded article (hereinafter also simply referred to as "resin molded article") of the present invention contains a resin and cellulose fibers, and the density of the resin molded article is 0.65g/cm³The following. The resin molded article is excellent in specific strength, and is less likely to have a reduced elastic modulus even in a high-temperature environment.

The resin preferably contains a thermoplastic resin, more preferably contains a polyolefin resin (a resin obtained by polymerizing or copolymerizing an ethylenically unsaturated compound, as described in detail later, for example, a polyethylene resin, a polypropylene resin, or the like), and still more preferably contains a polypropylene resin. Details of the resin usable in the present invention are described later.

The resin preferably has a crystal structure in at least a part of the resin molded body. For example, when a polypropylene resin is contained as the resin, at least a part of the polypropylene resin preferably forms a crystal structure, and preferably has an α -type crystal (hereinafter also referred to as an α -crystal).

In the resin molded body, the cellulose fibers are preferably oriented. In addition, in the resin molded body, the resin is also preferably oriented. The degree of orientation of the cellulose fibers and the degree of orientation of the resin are as described below.

The resin molded body is preferably a resin molded body stretched in one direction. The stretching method is described later.

The components of the resin molded article of the present invention will be described below.

(cellulose fiber)

The cellulose fiber used in the present invention is fibrous cellulose.

The cellulose fibers contained in the resin molded article of the present invention may be 1 kind or 2 or more kinds.

The source of the cellulose fiber is not particularly limited, and examples thereof include cellulose fibers obtained from wood, bamboo, hemp, jute, kenaf, agricultural product residual waste (for example, straw of wheat, rice, or the like, stalk of corn, cotton, or the like, sugar cane), cloth, recycled pulp, waste paper, and the like. Pulp is a substance as a raw material of paper, and has tracheids extracted from plants as a main component. From a chemical point of view, polysaccharides are the main component, and cellulose is the main component. As the cellulose fiber used in the present invention, a cellulose fiber derived from wood is particularly preferable.

The cellulose fiber is not particularly limited, and a cellulose fiber obtained by any production method can be used. Examples of the cellulose fibers include those obtained by mechanical treatment in which pulverization is performed by physical force, chemical treatment such as sulfate pulp method, sulfide pulp method, and alkali pulp method, and a combination of these treatments. In the chemical treatment, lignin, hemicellulose, and the like are removed from a plant material such as wood by using a chemical such as sodium hydroxide, and a nearly pure cellulose fiber can be taken out. The cellulose fibers thus obtained are also referred to as pulp fibers.

The cellulose fiber used in the present invention is preferably a cellulose fiber produced by chemical treatment, and more preferably a cellulose fiber produced by a kraft pulp method, from the viewpoint of improving mechanical properties such as specific strength and elastic modulus in a high-temperature environment. In particular, when a polypropylene resin is used as the resin, a chemically treated cellulose fiber is preferably used. In the case of the cellulose fiber subjected to the chemical treatment, lignin and the like do not remain in the cellulose fiber, and therefore, the mechanical properties of the resin molded product are improved. One of the reasons for this is that the interaction between the polypropylene resin and the cellulose fiber at the interface therebetween is not inhibited by lignin.

The diameter of the cellulose fiber used in the present invention is preferably 1 to 30 μm, more preferably 1 to 25 μm, and still more preferably 5 to 20 μm. The length (fiber length) is preferably 10 to 2200 μm, more preferably 50 to 1000 μm.

The diameter of the cellulose fiber contained in the resin molded product of the present invention can be measured by a Scanning Electron Microscope (SEM) or a fiber analyzer. The fiber length of the cellulose fiber can be measured by SEM observation. In the measurement of the fiber length by SEM observation, the resin (for example, polypropylene resin) in the resin molded product of the present invention is eluted with hot xylene, and the obtained residue is placed on a stage and subjected to treatment such as vapor deposition, and then the fiber length can be measured by SEM observation.

The aspect ratio (fiber length L/fiber diameter D) of the cellulose fiber is preferably 5 to 100, and more preferably 10 to 50, from the viewpoint of improving mechanical strength.

The content of the cellulose fiber in the resin molded product of the present invention is preferably 1 to 40 parts by mass, and particularly preferably 5 to 30 parts by mass, based on 100 parts by mass of the total amount of the resin and the cellulose fiber.

(resin)

The resin used in the present invention is preferably a thermoplastic resin.

Examples of the thermoplastic resin include, in addition to polyolefin resins, thermoplastic resins such AS polyvinyl chloride resins, acrylonitrile-butadiene-styrene copolymer resins (ABS resins), acrylonitrile-styrene copolymer resins (AS resins), polyethylene terephthalate resins, polybutylene terephthalate resins, polystyrene resins, and polyamide resins.

The thermoplastic resin may include an unmodified resin, as well as a modified resin. For example, a resin modified with an unsaturated carboxylic acid or a derivative thereof (acid-modified resin) is also preferably contained.

The polyolefin resin is not particularly limited as long as it is a resin composed of a polymer obtained by polymerizing or copolymerizing a compound having an ethylenically unsaturated bond (usually, an olefin).

Examples of the polyolefin resin include a polyethylene resin, a polypropylene resin, an ethylene- α -olefin copolymer resin, and a polyolefin copolymer resin having an acid copolymerization component or an acid ester copolymerization component.

The thermoplastic resin preferably contains a polyolefin resin, and more preferably a polyolefin resin. Among them, the thermoplastic resin preferably contains a polypropylene resin, and more preferably a polypropylene resin, from the viewpoint of heat resistance and strength of the molded article. The polypropylene resin may be unmodified or modified, and preferably contains an unmodified polypropylene resin. The polypropylene resin also preferably contains an unmodified polypropylene resin and an acid-modified polypropylene resin.

The content of the resin in the resin molded product of the present invention is preferably 40 to 95 parts by mass in 100 parts by mass of the total amount of the resin and the cellulose fiber, and particularly when the resin contains a polypropylene resin, the polypropylene resin is preferably contained in an amount of 50 to 100% by mass, more preferably 60 to 90% by mass, based on 100% by mass of the resin.

In the present invention, a resin molded article using a polypropylene resin as a resin is sometimes referred to as a cellulose fiber-reinforced polypropylene resin molded article.

Polypropylene resin-

The polypropylene resin is not particularly limited, and for example, any of homopolypropylene, polypropylene block copolymer, and polypropylene random copolymer can be used.

Examples of the polypropylene resin include a propylene homopolymer, a propylene-ethylene random copolymer, a propylene- α -olefin random copolymer, a propylene-ethylene- α -olefin copolymer, a propylene block copolymer (a copolymer composed of a propylene homopolymer component or a copolymer component mainly composed of propylene, and a copolymer component obtained by copolymerizing propylene with at least one monomer selected from ethylene and α -olefin), and the like. These polypropylenes may be used alone or in combination of two or more.

The α -olefin used in the polypropylene resin is preferably 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, or 1-decene, and more preferably 1-butene, 1-hexene, or 1-octene.

Examples of the propylene- α -olefin random copolymer include a propylene-1-butene random copolymer, a propylene-1-hexene random copolymer, and a propylene-1-octene random copolymer.

Examples of the propylene-ethylene- α -olefin copolymer include a propylene-ethylene-1-butene copolymer, a propylene-ethylene-1-hexene copolymer, and a propylene-ethylene-1-octene copolymer.

Examples of the propylene block copolymer include (propylene) - (propylene-ethylene) copolymer, (propylene) - (propylene-ethylene-1-butene) copolymer, (propylene) - (propylene-ethylene-1-hexene) copolymer, (propylene) - (propylene-1-butene) copolymer, (propylene) - (propylene-1-hexene) copolymer, (propylene-ethylene) - (propylene-ethylene-1-butene) copolymer, (propylene-ethylene) - (propylene-ethylene-1-hexene) copolymer, (propylene-ethylene) - (propylene-1-butene) copolymer, propylene-ethylene-propylene-1-butene copolymer, propylene-, (propylene-ethylene) - (propylene-1-hexene) copolymers, (propylene-1-butene) - (propylene-ethylene-1-butene) copolymers, (propylene-1-butene) - (propylene-ethylene-1-hexene) copolymers, (propylene-1-butene) - (propylene-1-butene) copolymers, (propylene-1-butene) - (propylene-1-hexene) copolymers, and the like.

Among these polypropylene resins, homopolypropylene, propylene-ethylene-1-octene copolymer, and polypropylene block copolymer are preferable from the viewpoint of tensile strength and impact resistance.

The flowability of the polypropylene resin is not limited, and a polypropylene resin having an appropriate flowability may be used in consideration of the thickness, volume, and the like of the molded article.

One kind of the polypropylene resin may be used alone, or two or more kinds may be used in combination.

The content of the polypropylene resin in the resin molded article of the present invention is preferably 60 to 99 parts by mass, more preferably 70 to 95 parts by mass, and particularly preferably 75 to 85 parts by mass, based on 100 parts by mass of the total amount of the polypropylene resin and the cellulose fiber.

The polypropylene resin contained in the resin molded article of the present invention is preferably a polypropylene resin a part of which is acid-modified (hereinafter also referred to as "acid-modified polypropylene resin").

When the resin molded article of the present invention contains the acid-modified polypropylene resin as a part of the polypropylene resin, the effect of the acid-modified polypropylene resin and the effect of improving the adhesion between the polypropylene resin which has not been acid-modified and the cellulose fibers can be obtained, and the degree of orientation of the cellulose fibers can be effectively improved.

Examples of the acid-modified polypropylene resin include those obtained by modifying the polypropylene resin with an unsaturated carboxylic acid or a derivative thereof. Examples of the unsaturated carboxylic acid include maleic acid, fumaric acid, itaconic acid, acrylic acid, and methacrylic acid, and examples of the unsaturated carboxylic acid derivative include maleic anhydride, itaconic anhydride, methyl acrylate, ethyl acrylate, butyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, glycidyl methacrylate, monoethyl maleate, diethyl maleate, monomethyl fumarate, and dimethyl fumarate.

As the acid-modified polypropylene resin, maleic acid-modified polypropylene and/or maleic anhydride-modified polypropylene is preferably contained.

When the resin molded article of the present invention contains an acid-modified polypropylene resin, the content of the acid-modified polypropylene resin in the resin molded article of the present invention is preferably 0.3 to 20 parts by mass, preferably 1 to 15 parts by mass, and more preferably 3 to 7 parts by mass, based on 100 parts by mass of the total amount of the polypropylene resin (the sum of the polypropylene resin that is not acid-modified and the acid-modified polypropylene resin) and the cellulose fiber. When the content of the acid-modified polypropylene resin is within the above range, the resin molded article of the present invention can be oriented to mechanical properties such as a high elastic modulus at high temperatures.

(other Components)

The resin molded article of the present invention may be composed of the resin and cellulose fibers, and may be combined with rubber, elastomer, or the like. For example, an elastomer such as a hydrogenated styrene elastomer, a styrene-ethylene-butadiene-styrene copolymer (SEBS), a styrene-ethylene butylene-olefin crystalline block copolymer (SEBC), or an ethylene- α -olefin copolymer may be further compounded to modify the physical properties of the resin molded product. Additives such as antioxidants, light stabilizers, radical scavengers, ultraviolet absorbers, colorants (dyes, organic pigments, inorganic pigments), fillers, lubricants, plasticizers, processing aids such as acrylic processing aids, foaming agents, lubricants such as paraffin wax, surface treatment agents, crystal nucleating agents, mold release agents, hydrolysis inhibitors, anti-blocking agents, antistatic agents, antifogging agents, mildewproofing agents, ion traps, flame retardants, and flame retardant aids may be appropriately contained within a range not to impair the effects of the present invention.

(Crystal Structure of resin and degree of orientation thereof)

In the resin molded body, at least a part of the resin preferably forms a crystal structure. When the resin molded body contains two or more kinds of resins, it is preferable that any one of the two or more kinds of resins forms a crystal structure.

Further, the crystal structure of the resin is preferably oriented. When the resin molded article contains two or more kinds of resins, the crystal structure of any one of the two or more kinds of resins may be oriented.

The orientation degree (crystal orientation degree) of the crystal structure of the resin is preferably more than 0.50 and 1.00 or less. When the degree of crystal orientation of the resin is in the above range, the specific strength can be further improved, and the mechanical properties such as the elastic modulus can be further improved even in a high-temperature environment.

In the resin molded article of the present invention, for example, by stretching in a predetermined temperature range as described later, it is considered that the crystal structure of the resin is easily oriented in the stretching direction, and the resin molded article can exhibit a high degree of crystal orientation.

In contrast, in the conventional foamed low-density cellulose fiber-reinforced resin molded product, the resin orientation is low, and the degree of orientation is usually 0.50 or less, and there is a limit to improvement of mechanical properties such as specific strength and elastic modulus in a high-temperature environment.

In view of improvement of mechanical properties of the resin in the crystal orientation direction, the degree of crystal orientation of the resin is more preferably 0.60 to 0.98, and still more preferably 0.90 to 0.98.

The crystal structure of the resin and the degree of orientation thereof can be confirmed by X-ray diffraction measurement.

Hereinafter, a preferred degree of crystal orientation and a method for measuring the degree of crystal orientation in the case where the resin is a polypropylene resin will be described.

(Crystal Structure of Polypropylene)

It is known that polypropylene mainly adopts a crystal structure such as alpha crystal. The alpha crystal is monoclinic.

In a preferred embodiment of the resin molded article of the present invention, the scattering vector s is 1.61. + -. 0.1nm in a wide-angle X-ray diffraction measurement^-1And 1.92. + -. 0.1nm^-1Diffraction peaks were observed at the positions of (1). That is, in a preferred embodiment of the resin molded article of the present invention, at least a part of the polypropylene has a crystal structure, and at least a part of the polypropylene has α -crystals. The crystal structure other than the α crystal existing in the crystal structure of polypropylene is not particularly limited, and for example, β crystal is preferable.

Method for confirming alpha crystal of polypropylene

In order to confirm the presence of α -crystal, X-ray diffraction measurement can be used. Preferably using wide angle X-ray diffraction measurements. In the case of a general stretch molded product, a strength distribution may occur in an orientation angle direction derived from resin orientation. Therefore, the intensity distribution from the orientation may not be accurately obtained by a one-dimensional scintillation counter, and therefore a two-dimensional detector is preferably used as the detector. The X-ray source preferably uses CuK alpha rays, and the shape preferably uses a pinhole. The beam diameter of the X-ray is preferably 5 to 1500 μm, more preferably 7 to 1000 μm. When the beam diameter is made larger than 1500 μm, sufficient position resolution cannot be obtained, and it is sometimes not suitable for detailed analysis; when the diameter is less than 5 μm, the beam diameter is small, and therefore, the irradiation intensity is insufficient, the measurement time is extremely long, and the measurement efficiency may be deteriorated.

Specifically, the method described in the examples can be used.

The presence of the polypropylene α crystal can also be confirmed as follows. For example, when a resin molded body containing cellulose fibers and a polypropylene resin and having alpha-crystals of the polypropylene resin is measured by wide-angle X-ray diffraction, diffraction peaks are observed at positions having diffraction angles 2 θ of 14.3 ± 0.2 °, 17.1 ± 0.2 °, and 34.6 ± 0.2 °. Since the diffraction peak at the position where the diffraction angle 2 θ is 14.3 ± 0.2 ° and 17.1 ± 0.2 ° is a diffraction peak from the (040) plane of the α -type crystal of polypropylene, it can be judged that the α -crystal is formed when any of these diffraction peaks is observed.

(degree of Crystal orientation of Polypropylene resin)

As crystals of a polypropylene resin (1.92. + -. 0.1nm in scattering vector s)^-1The position of (b) has a diffraction peak), and is preferably 0.60 or more. By setting the degree of orientation of the polypropylene crystal to 0.60 or more, mechanical properties such as specific strength and elastic modulus in a high-temperature environment can be further improved. In the resin molded article of the present invention, for example, by stretching in a predetermined temperature range as described later, the polypropylene crystals are easily oriented in the stretching direction, and it is considered that the resin molded article can exhibit a high degree of crystal orientation.

In view of the improvement of the mechanical properties in the direction along the arrangement (orientation direction) of the polypropylene crystals, the degree of orientation of the polypropylene crystals is more preferably 0.60 to 1.00, still more preferably 0.65 to 0.97, and particularly preferably 0.90 to 0.95.

Method for measuring degree of crystal (alpha-crystal) orientation of polypropylene resin

Regarding the degree of crystal orientation of the polypropylene resin, a two-dimensional diffraction image of X-rays was obtained based on the above-described method for confirming alpha crystals of polypropylene, and the (040) plane (at a scattering vector of 1.92. + -. 0.1 nm) derived from polypropylene was analyzed based on the two-dimensional diffraction image of X-rays^-1Diffraction) was measured, and the degree of crystal orientation of the polypropylene resin was obtained from the profile of the orientation angle direction of the diffraction intensity. Examples of the analysis method include: a method of analyzing the half width of the diffraction peak in the orientation angle direction, a method of obtaining the orientation function, and the like. To confirm the degree of orientation of the polypropylene crystals, samples were cut and a good diffraction image was sought. More specifically, there may be mentioned: in order to adjust the absorption of X-rays by the sample, the sample is cut at an arbitrary position so as to have a thickness of about 0.2mm to 1 mm.

Detailed calculation method of the degree of crystal orientation of polypropylene resin-

In order to determine the degree of crystal orientation of the polypropylene resin, the X-ray diffraction pattern of the (040) plane derived from the α -type crystal of the polypropylene crystal was used. And (4) according to the two-dimensional diffraction pattern of the polypropylene crystal, one-dimensionally forming data of orientation angle VS intensity. In order to maintain the two-dimensional data in one dimension, the polypropylene α -type crystal (040) plane of the polypropylene α -type crystal was maintained in one dimension in the range of ± 0.5 ° around the diffraction angle of 17.1 °. Since a diffraction peak derived from the amorphous state of the polypropylene resin is present in the vicinity, in order to eliminate the influence thereof, the polypropylene resin may be one-dimensionally transformed in a range of ± 0.5 ° with 16.1 ° as the center, and subtracted from the one-dimensional diffraction intensity of the polypropylene α -type crystal. The orientation degree is determined from the data of the corrected diffraction intensity of the orientation angle of the α -type crystal of the polypropylene, and any one of a half-width method using a half-width calculation and an orientation function method using an orientation function may be used for determining the orientation degree. In order to obtain the orientation function or the half-width, noise of data obtained by a method such as peak separation of diffraction intensity in the orientation angle direction can be reduced, and analysis can be performed using the function obtained by the peak separation. The above-described operation such as the intensity correction may be performed in addition to this operation. The function used in peak separation and fitting is preferably a gaussian function or a lorentzian function, more preferably a lorentzian function.

(method of confirming the presence or absence of cellulose-containing fibers)

Cellulose of cellulose fibers is known to have various crystal structures such as type I and type II. The natural cellulose has I_αForm (triclinic) or I_βType (monoclinic) crystal structure, plant-derived celluloses usually contain a large amount of I_βForm crystal.

The resin molded body of the present invention has a scattering vector s of 3.86. + -. 0.1nm in a wide-angle X-ray diffraction measurement^-1Has a diffraction peak at the position of (2). The diffraction peak is derived from the I of cellulose_βThe (004) plane of the form crystal. That is, in the resin molded article of the present invention, at least a part of the cellulose fiber has a crystal structure, and at least a part thereof is I_βForm crystal. For fiberI present in the crystal structure of elements_βThe crystal structure other than the form crystal is not particularly limited. Hereinafter, the cellulose fiber may be referred to as "having a scattering vector s of 3.86. + -. 0.1nm^-1Has a diffraction peak component at the position of (a) ".

The cellulose fiber can be confirmed by various methods. For example, the identification can be confirmed by observing a diffraction peak from cellulose crystals in cellulose fibers with X-rays. Note that the diffraction peak position differs depending on the wavelength of the X-ray used, but when CuK α rays (λ 0.15418nm) are used, the scattering vector s is 3.86nm^-1I derived from cellulose can be observed in the vicinity of (2 θ: 34.6 °)_βDiffraction peak of (004) plane of form crystal. In order to obtain diffraction of the (004) plane, it is necessary to rotate the sample at an angle θ and inject X-rays. That is, when CuK α rays are used, the sample stage is rotated by θ of 17.3 °. As a diffraction peak derived from the cellulose crystal, another diffraction peak can be observed inside the (004) plane, but in the case where the polypropylene resin is contained in the resin component, the diffraction position overlaps with a diffraction peak derived from the polypropylene, and a clear diffraction peak may not be determined. Thus, in the present specification, I of cellulose is used_βThe presence or absence of cellulose fibers was judged by the diffraction peak of the (004) plane of the crystalline form.

(degree of orientation of cellulose fiber)

As a cellulose fiber (scattering vector s of 3.86. + -. 0.1 nm)^-1The position of (b) has a diffraction peak), preferably 0.40 or more. By setting the degree of orientation of the cellulose fibers to 0.40 or more, mechanical properties such as specific strength and elastic modulus in a high-temperature environment can be further improved.

In addition, as a preferred embodiment of the present invention, in an embodiment in which a polypropylene resin is used as the resin and at least a part of the polypropylene resin forms α -crystals, it is considered that mechanical properties such as specific strength and elastic modulus in a high-temperature environment can be further improved as described below.

That is, this resin molded article has a diffraction peak derived from an α -type crystal of polypropylene and I derived from cellulose_βDiffraction peak of form crystalThe degree of crystal orientation of the polypropylene resin and the degree of crystal orientation of the cellulose fiber are both improved. Therefore, it is considered that the effect of improving the interaction between the cellulose fibers and the interaction at the interface between the polypropylene resin and the cellulose fibers is obtained, and the mechanical properties such as tensile strength are effectively improved. Further, since the resin molded product of the present invention has a low density, excellent specific strength can be obtained. The resin molded article of the present invention can be effectively improved in the degree of crystal orientation of the polypropylene resin by, for example, drawing at a predetermined temperature range as described later, and can be sufficiently improved in the I content of the cellulose fiber_βThe degree of orientation of the cellulose fibers caused by the orientation of the type crystals.

In contrast, in the conventional foamed low-density cellulose fiber-reinforced resin molded product, the orientation of the cellulose fibers is low, the degree of orientation is usually less than 0.40, and there is a limit to improvement of mechanical properties such as specific strength and elastic modulus in a high-temperature environment. On the other hand, in the case of a resin molded product by injection molding, if a stretching treatment or the like is not performed after injection molding, the degree of orientation of the cellulose fibers is usually less than 0.40, and there is a limit to improvement of mechanical properties such as specific strength and elastic modulus in a high-temperature environment.

In consideration of the improvement of the mechanical properties in the direction along the arrangement (orientation direction) of the cellulose fibers, the degree of orientation of the cellulose fibers is more preferably 0.40 to 1.00, and still more preferably 0.50 to 0.95.

Method for determining the degree of orientation of cellulose fibres

The degree of orientation of the cellulose fibers can be obtained by obtaining a two-dimensional diffraction image of X-rays based on the method for confirming the cellulose-containing fibers, and analyzing a profile in the orientation angle direction of the diffraction intensity from the (004) plane of the cellulose based on the two-dimensional diffraction image of X-rays. Examples of the analysis method include: a method of analyzing the half width of the diffraction peak in the orientation angle direction, a method of obtaining the orientation function, and the like. To confirm the degree of orientation of the cellulose fibers, samples were cut and a good diffraction image was sought. More specifically, there may be mentioned: in order to adjust the absorption of X-rays by the sample, the sample is cut at an arbitrary position so as to have a thickness of about 0.2mm to 1 mm.

Detailed calculation method of the degree of orientation of cellulose fibres-

For determining the degree of orientation of the cellulose fibres, I of the cellulose from the cellulose fibres mentioned above is used_βX-ray diffraction pattern of (004) plane of form crystal. I of cellulose based on cellulose fibers_βThe two-dimensional diffraction pattern of the (004) plane of the form crystal was normalized to data of orientation angle VS intensity. For the one-dimensional formation of the two-dimensional data, the I of the cellulose fibres is used_βThe (004) plane of the crystal was one-dimensional in the range of. + -. 0.5 ℃ around 34.6 ℃. Since diffraction peaks derived from polypropylene resin exist in the vicinity, in order to eliminate the influence thereof, the cellulose fibers may be one-dimensionally converted to within a range of. + -. 0.5 ℃ around 33.6 ℃ and 35.6 ℃ to obtain cellulose I derived from the cellulose fibers_βThe average value of the two is subtracted from the one-dimensional diffraction intensity of the form crystal. I of cellulose of corrected cellulose fiber_βThe orientation degree is determined from the data of the diffraction intensity of the orientation angle of the crystalline, and any one of a half-width method using a half-width calculation and an orientation function method using an orientation function may be used for determining the orientation degree. In order to obtain the orientation function or the half-width, noise of data obtained by a method such as peak separation of diffraction intensity in the orientation angle direction can be reduced, and analysis can be performed using the function obtained by the peak separation. The above-described operation such as the intensity correction may be performed in addition to this operation. The function used in peak separation and fitting is preferably a gaussian function or a lorentzian function, more preferably a lorentzian function.

(specific Strength)

The specific strength as an index of the tensile strength of the resin molded product of the present invention cannot be set generally depending on the type, content, and the like of the resin and the cellulose fiber to be used, and is preferably 0.08MJ/kg or more, more preferably 0.16MJ/kg or more, and still more preferably 0.17MJ/kg or more. The specific strength can be determined from the tensile strength [ MPa ] measured by the method described later]And density [ g/cm ]³]The calculation is performed as follows.

Specific strength [ MJ/kg]Not (tensile strength [ MPa ]]Density [ g/cm ]³])/10³

The upper limit of the specific strength is not particularly limited, but is actually 0.50MJ/kg or less.

When the specific strength of the resin molded article of the present invention is in the above range, the resin molded article is light in weight and exhibits high tensile strength, and can be suitably used as a material for transportation equipment, which will be described later.

(tensile Strength)

The tensile strength of the resin molded article of the present invention cannot be generally set depending on the kind, content, and the like of the resin and cellulose fiber used, and is preferably 50MPa to 1000MPa, and more preferably 70MPa to 1000 MPa. The tensile strength can be measured by the method and conditions described in examples according to JIS K7161. In addition, in the case where the sample is small, the sample width or the inter-jig length can be appropriately adjusted.

The tensile strength of the fiber-reinforced resin molded product generally has different values depending on the measured direction. Therefore, in the present invention, the tensile strength and the specific strength refer to a measured value of the tensile strength in the direction in which the resin molded product exhibits the maximum tensile strength and a specific strength using the measured value.

(Density)

The density of the resin molded article of the present invention is 0.65g/cm³The following. The density can be measured according to method a (underwater substitution method) of JIS K7112 by the methods and conditions described in the examples.

The density of the resin molded article of the present invention is 0.65g/cm³The resin and/or cellulose fibers are not particularly limited, and may be those having a high degree of orientation, and may be those having a high tensile strength. The density of the resin molded article is preferably 0.60g/cm³The following.

The lower limit of the density is not particularly limited, but is actually 0.20g/cm³Above, preferably 0.40g/cm³Above, more preferably 0.55g/cm³The above.

(coefficient of linear expansion)

The linear expansion coefficient of the resin molded article at 60 ℃ to 100 ℃ (hereinafter simply referred to as linear expansion coefficient) is not generally set depending on the kind, content and the like of the resin and cellulose fiber used, and is preferably 0ppm/K (kelvin) or more and less than 10ppm/K, more preferably 0ppm/K or more and less than 5 ppm/K. The resin molded body exhibiting the linear expansion coefficient is preferable in terms of suppressing the unidirectional dimensional change in the high temperature region.

The linear expansion coefficient is an average linear expansion coefficient, and can be measured by Thermomechanical Analysis (TMA), specifically, by the method described in examples.

The linear expansion coefficient of the resin molded body generally has a different value depending on the measurement direction. Therefore, in the present invention, the linear expansion coefficient is a measured value of the linear expansion coefficient in a direction in which the resin molded body exhibits the smallest linear expansion coefficient. The direction exhibiting the smallest linear expansion coefficient generally coincides with the orientation direction or the stretching direction of the cellulose fibers.

(measurement of dynamic viscoelasticity)

The dynamic viscoelasticity can be measured according to the method and conditions described in examples in JIS K7244.

(maintenance ratio of modulus of elasticity)

The elastic modulus maintenance ratio can be determined as follows: using the curve obtained from the dynamic viscoelasticity measurement described above, the storage modulus E at 25 ℃ was read₂₅And a storage modulus E at 100 ℃₁₀₀A 1 is mixing E₁₀₀Divided by E₂₅(E₁₀₀/E₂₅) This can be determined.

The lower limit value of the elastic modulus retention rate is preferably 0.38 or more, more preferably 0.40 or more, and still more preferably 0.45 or more. If the elastic modulus is not less than the above-described preferable lower limit, the elastic modulus can be maintained even in a high-temperature environment, and as a result, the resin molded article of the present invention is less likely to be deformed even in a high-temperature environment, and deformation of the resin molded article in use can be suppressed.

The upper limit value of the elastic modulus retention rate is preferably 0.90 or less, more preferably 0.80 or less, and still more preferably 0.70 or less. If the amount is equal to or less than the above-described preferable upper limit, the resin molded article of the present invention can be deformed appropriately by heating, and when the resin molded article of the present invention is heat-molded, the occurrence of cracks during secondary processing can be suppressed, and sufficient workability can be exhibited.

From the viewpoint of suppressing the decrease in the elastic modulus in a high-temperature environment, it is preferable to increase the degree of orientation of the cellulose fibers and the degree of crystal orientation of the resin to be within the respective ranges described above.

When a polypropylene resin is used as the resin, it is preferable that the density is 0.40g/cm³The degree of orientation of the cellulose fibers is 0.40 or more, and the degree of crystal orientation of the resin is 0.65 or more and 1.00 or less. The resin molded body satisfying these conditions has a high elastic modulus retention rate of 0.38 or more while improving the specific strength to 0.08MJ/kg or more. The linear expansion coefficient may be as low as 0ppm/K or more and less than 10 ppm/K.

[ production of resin molded article ]

The method of producing a resin molded product of the present invention preferably includes at least a step of stretching an intermediate molded product obtained by melt-kneading a resin and cellulose fibers in a predetermined temperature range.

The intermediate molded article is a molded article obtained by forming the above melt kneaded product into a rod, a fiber, a film (sheet), or the like. The intermediate molded article is preferably a sheet obtained by melt kneading (hereinafter, also simply referred to as "sheet"). The conditions for melt kneading for obtaining the intermediate molded article are as described below.

The temperature range in which stretching is performed is a temperature range of not less than the crystal relaxation temperature of the resin but not more than the melting point thereof.

That is, a preferred embodiment of the method for producing a resin molded body is a production method having the steps of: an intermediate molded body obtained by melt-kneading a resin and cellulose fibers is stretched at least uniaxially while maintaining the temperature of the intermediate molded body at a temperature not lower than the crystal relaxation temperature of the resin but not higher than the melting point thereof. The crystal relaxation temperature of the resin can be determined from a curve (vertical axis: Tan. delta. and horizontal axis: temperature) obtained by dynamic viscoelasticity measurement. Specifically, in the above-described curve, the temperature at which the shoulder-shaped peak of Tan δ rises above the glass transition temperature is defined as the crystal relaxation temperature.

The temperature range for the above-mentioned stretching is preferably [ melting point-50 ℃ C ] or more and not more than the melting point, more preferably [ melting point-30 ℃ C ] or more and not more than the melting point, still more preferably [ melting point-20 ℃ C ] or more and not more than the melting point, still more preferably [ melting point-15 ℃ C ] or more and not more than the melting point, and particularly preferably [ melting point-10 ℃ C ] or more and not more than the melting point. By applying such a temperature, as will be described later, the degree of orientation of the cellulose fibers and the degree of crystal orientation of the resin can be sufficiently increased at a high draw ratio.

In the stretching step, the cellulose fibers are peeled off from the interface with the resin, and further stretched to form pores, whereby a porous resin molded product can be obtained. That is, the cellulose fibers in the resin molded product of the present invention have not only a function as reinforcing fibers in the resin molded product but also a function of forming the resin molded product of the present invention into a porous body to form a resin molded product having a predetermined low density. In addition, with the above stretching, the crystals of the resin (for example, in the case of using a polypropylene resin as the resin, the α -type crystals of the polypropylene resin) and the I of the cellulose fiber can be made_βThe form crystals are efficiently oriented in the drawing direction. As a result, in the resin molded article of the present invention, the effect of improving the interaction between the oriented cellulose fibers and the resin is combined and sufficiently exerted, and not only the specific strength can be improved, but also the mechanical properties such as the elastic modulus in a high-temperature environment can be sufficiently improved. In addition, the linear expansion coefficient of the obtained resin molded article can be significantly reduced, and the dimensional stability is also excellent.

Conventionally, when a composite material in which a fibrous filler and a resin are combined is stretched at a high stretch ratio in a uniaxial direction, the fibrous filler becomes a starting point of fracture of the resin to be stretched, and it is difficult to achieve desired physical properties and appearance. As a result of the studies by the present inventors, it has been found that the above-described problems tend to be solved when the above-described preferable stretching temperature is adopted. In particular, when a polypropylene resin is used and the above-described preferable stretching temperature is used, it is possible to achieve stretching at a high stretching ratio (for example, 5 times or more) which has been difficult in the past, and it is possible to significantly improve the degree of orientation of the cellulose fibers and the degree of crystal orientation of the resin. As a result, the specific strength, the elastic modulus in a high-temperature environment, and the like can be further improved, and the linear expansion coefficient can be significantly reduced.

In addition, when the above-described preferable stretching temperature is adopted, even if the cellulose fiber having a relatively high major axis is used, the stretching at the above-described high stretching ratio can be performed.

(stretching)

The stretching temperature in the stretching step is preferably a temperature equal to or higher than the crystal relaxation temperature of the resin and equal to or lower than the melting point thereof.

As described above, the stretching temperature in the stretching step is preferably set to the upper limit of the melting point of the resin. Therefore, when a polypropylene resin is used as the resin, the upper limit of the stretching temperature is preferably 170 ℃ or less, more preferably 165 ℃ or less, and still more preferably 162 ℃ or less. By setting the stretching temperature to the above-described preferable upper limit or less, stretching can be performed without melting the crystals of the resin itself. Further, by allowing the resin to exhibit appropriate orientation relaxation, a high stretch ratio is achieved, and a decrease in mechanical properties such as elastic modulus is unlikely to occur even in a high-temperature environment.

The stretching temperature is preferably set to have a lower limit of the crystal relaxation temperature of the resin. For example, when a polypropylene resin is used as the resin, the lower limit of the stretching temperature is preferably 50 ℃ or more, more preferably 80 ℃ or more, further preferably 100 ℃ or more, further preferably 130 ℃ or more, further preferably 140 ℃ or more, further preferably 150 ℃ or more, and particularly preferably 155 ℃ or more. When the stretching temperature is not lower than the above-described preferable lower limit, a desired stretching ratio can be achieved, and a resin molded product having excellent tensile strength, elastic modulus in a high-temperature environment, and the like, and a low linear expansion coefficient can be obtained. In particular, if the stretching is performed at a temperature lower than the crystal relaxation temperature of the resin (for example, less than 50 ℃ in the case of a polypropylene resin), the resin may be brittle and broken.

In the case of using a polypropylene resin as the resin, the stretching temperature is preferably 100 ℃ to 165 ℃, more preferably 130 ℃ to 162 ℃, further preferably 140 ℃ to 162 ℃, further preferably 150 ℃ to 162 ℃, and further preferably 155 ℃ to 162 ℃ from the viewpoint of increasing both the degree of orientation of the cellulose fibers and the degree of crystal orientation of the polypropylene resin.

The stretching speed may be appropriately set depending on the types of the resin and the cellulose fiber, the shape of the intermediate molded body, the stretching temperature, and the like. For example, the drawing speed when a polypropylene resin is used as the resin and formed into a sheet shape may be set to 0.4mm/min to 200 mm/min.

The apparatus used for the stretching is not particularly limited as long as it can stretch the intermediate molded body, and for example, a stretching machine or a tensile testing machine can be used. In addition, from the viewpoint of performing the stretching at the stretching temperature, a centrifuge or a tensile tester provided with a thermostatic bath is preferably used.

Examples of the stretching at the stretching temperature include: the intermediate molded body is set in a centrifuge or a tensile testing machine equipped with a thermostatic bath, preheated in the thermostatic bath, and then stretched at a desired stretching temperature.

The stretch ratio based on the above stretching can be appropriately adjusted. Examples thereof include: the intermediate molded product is stretched 5 to 20 times, preferably 6 to 20 times, and more preferably 11 to 15 times before stretching. The stretching ratio is an arithmetic average of the stretching ratios calculated by the method described in detail in examples.

The stretching may be multiaxial stretching or uniaxial stretching as long as a predetermined degree of orientation of the cellulose fibers and/or a predetermined degree of crystal orientation of the resin can be achieved. Uniaxial stretching is preferable from the viewpoint of suppressing the averaging of the orientation by stretching in different directions and improving the degree of orientation of the cellulose fibers and/or the degree of crystal orientation of the resin.

After the intermediate molded body is stretched, it is cooled to room temperature (about 25 ℃ C.), thereby obtaining the resin molded body of the present invention.

The cooling conditions are not particularly limited, and the cooling may be performed by any method such as natural cooling or air cooling. For example, cooling at 1 to 500 ℃/min is given.

The method for producing the intermediate molded body used in the method for producing a resin molded body of the present invention is not particularly limited. For example, a method including a step of molding a melt-kneaded product of a resin and cellulose fibers into a desired shape can be mentioned.

(melt kneading)

The melt-kneaded product is not particularly limited as long as it includes a melt-kneading step of a resin and cellulose fibers, and can be produced by a usual method.

The melt-kneading temperature in the melt-kneading step is not particularly limited as long as it is a temperature equal to or higher than the melting point of the resin, and for example, when a polypropylene resin is used as the resin, it is preferably 160 to 230 ℃, more preferably 170 to 210 ℃.

More preferably, the upper limit of the melt kneading temperature is preferably 250 ℃ or less, more preferably 230 ℃ or less, and still more preferably 200 ℃ or less, from the viewpoint of reducing the thermal decomposition of the cellulose fiber.

When the melt-kneading step or the stretching step is performed at a high temperature, additives such as an antioxidant may be added to the resin and the cellulose fiber for the purpose of suppressing thermal deterioration or oxidative deterioration, and the like.

The melt-kneading time is not particularly limited and may be appropriately set.

The apparatus used for the melt-kneading is not particularly limited as long as it can perform melt-kneading at a temperature equal to or higher than the melting point of the resin, and examples thereof include a stirrer, a kneader, a mixing roll, a banbury mixer, a single-screw or twin-screw extruder, and the like, and a twin-screw extruder is preferable.

The obtained melt-kneaded product is preferably processed into a pellet form from the viewpoint of workability in the subsequent molding step (hereinafter, the obtained pellet is also referred to simply as "pellet"). The conditions for processing the pellets are not particularly limited, and the processing may be carried out according to a conventional method. For example, a method of water-cooling the melt-kneaded product and then processing the melt-kneaded product into a pellet form by a strand cutter or the like is exemplified.

The respective components may be dry-blended (premixed) before melt-kneading. The dry blending is not particularly limited and may be carried out according to a conventional method.

(Molding)

The method of obtaining the intermediate molded body by molding the melt-kneaded product is not particularly limited, and examples thereof include a method of melt-compression molding the pellets and a method of injection molding the melt-kneaded product. Among these, a method of melt-compression molding pellets is preferred.

In the melt compression molding, the melt compression temperature is not particularly limited as long as it is a temperature equal to or higher than the melting point of the resin, and when a polypropylene resin is used as the resin, it is preferably 160 to 230 ℃, more preferably 170 to 210 ℃.

More preferably, the upper limit of the melt compression temperature is 250 ℃ or less, more preferably 230 ℃ or less, and still more preferably 200 ℃ or less, from the viewpoint of reducing the thermal decomposition of the cellulose fiber.

The conditions such as the preheating time, the pressing time, and the pressure in the above melt compression molding can be appropriately adjusted.

The apparatus used for the melt compression molding is not particularly limited, and examples thereof include a press. In addition, a pellet mill using an extruder for pellet molding may be used.

The shape of the sheet is not particularly limited, and may be, for example, a dumbbell shape. Further, the width, length, thickness, and the like of the above-described drawing can be appropriately adjusted to facilitate the drawing. For example, the thickness of the sheet is preferably 2mm or less, more preferably 1mm or less.

[ use ]

The resin molded article of the present invention can be suitably used as a material for products, parts, members, and the like, which require excellent properties in specific strength and elastic modulus in a high-temperature environment, as described below. Examples thereof include transportation equipment (automobiles, two-wheeled vehicles, trains, airplanes, etc.), structural members of robot arms, robot parts for amusement, prosthetic members, home electric appliances, OA equipment housings, information processing equipment, mobile terminals, building materials, house films, drainage equipment, toilet materials, various tanks, containers, sheets, packaging materials, toys, sporting goods, and the like.

As the material for transportation equipment, a material for vehicles can be cited. Examples of the material for vehicles include interior parts such as instrument panel garnishes, door garnishes, pillar garnishes, instrument panels, instrument cases, glove boxes, package trays, roof liners, consoles, instrument panels, armrests, seats, backrests, trunk lids, door panels, pillars, spare tire covers, door handles, lamp covers, rear trays, bumpers, engine covers, spoilers, radiator grilles, fenders, fender liners, rocker panels, side pedals, door outer panels, side doors, rear doors, roofs, roof supports, wheel covers, rear mirror covers, and bottom covers, exterior parts such as battery cases, engine hoods, fuel tanks, filler boxes, intake ducts, air cleaner cases, air conditioner cases, coolant storage tanks, radiator storage tanks, windshield washer fluid tanks, intake manifolds, rotating parts such as fans and pulleys, and the like, A member such as a harness protector, a connection box or a connector, and an integrally molded member such as a front end module or a front end plate.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

In the following examples and comparative examples, "part" means "part by mass" unless otherwise specified.

In the following examples, for a polypropylene resin which is not acid-modified, it is referred to simply as "polypropylene resin" for convenience, and is distinguished from an acid-modified polypropylene resin.

Use of materials

The materials used are shown below.

(cellulose fiber)

ARBOCEL B400: trade name, product of sodium hydroxide treatment manufactured by RETTENMAIER

Aspect ratio (L/D): 45

(Polypropylene resin)

Prime Polypro J106 MG: trade name, manufactured by PRIME POLYMER

Crystal relaxation temperature: 70 ℃ and a melting point of 165 DEG C

(acid-modified Polypropylene resin)

Rikeeido MG 250P: trade name, maleic anhydride-modified Polypropylene, manufactured by RIKEN VITAMIN K.K

Rikeeido MG 400P: trade name, maleic anhydride-modified Polypropylene, manufactured by RIKEN VITAMIN K.K

(example 1)

To 80 parts by mass of a polypropylene resin, 20 parts by mass of a cellulose fiber was added, dry-blended, and fed to a 15mm twin-screw extruder (manufactured by Technovel). The resin discharged from the extrusion die after melt-kneading was water-cooled and then processed into pellets by a strand cutter.

The pellets obtained above were sufficiently dried, and then fed to a press (trade name: manufactured by Toyo Seiki Seisaku-Sho, MP-WCH) set at 190 ℃ for a preheating time: 5 minutes, pressing time: 5 minutes, pressure: a polypropylene resin sheet (hereinafter referred to as "compressed sheet") having a thickness of 120 mm. times.120 mm. times.1 mm was obtained as an intermediate molded body under 20 MPa.

The above-mentioned pressed sheet was punched out by a JIS1 dumbbell-shaped test piece punching blade (according to JIS K6251) to prepare a dumbbell test piece.

The dumbbell test piece thus obtained was stretched under the following conditions using an Autograph precision universal tester (product name: TCR2A-200T +125-XSP, Shimadzu corporation) equipped with a thermostatic bath (product name: TCR2A-200T +125-XSP, Inc.).

(Condition)

Preheating time of dumbbell test piece in constant temperature bath of 160 ℃: 5 minutes

Stretching speed: 50mm/min

Length between the clamps: 40mm

After stretching at the draw ratios shown in Table 1, the stretched dumbbell test pieces were removed from the portions held by the tensile test jigs, and only the stretched portions were removed by scissors, thereby obtaining porous cellulose fiber-reinforced polypropylene resin molded articles having a thickness of 0.4mm to 0.6 mm.

The stretching ratios between the respective marks before and after stretching were determined by plotting marks on the dumbbell test piece before stretching with an oil pen at 5mm intervals along the stretching direction, measuring the distance between the marks after stretching with a vernier caliper, and dividing by 5 mm. The "stretch ratio" in table 1 below is an arithmetic average of the stretch ratios between the respective marking points on the test piece. The stretching ratio was determined in consideration of the variation in stretching ratio due to the position in the test piece.

(example 2)

A porous cellulose fiber-reinforced polypropylene resin molded article having a thickness of 0.4mm to 0.6mm was obtained in the same manner as in example 1 except that the blending amount of the polypropylene resin in example 1 was changed from 80 parts by mass to 75 parts by mass, and 5 parts by mass of Rikeeido MG250P was further blended, and the test piece was stretched at the stretch ratio shown in table 1.

(example 3)

A porous cellulose fiber-reinforced polypropylene resin molded article having a thickness of 0.4mm to 0.6mm was obtained in the same manner as in example 1 except that the blending amount of the polypropylene resin in example 1 was changed from 80 parts by mass to 75 parts by mass, and 5 parts by mass of Rikeeido MG400P was further blended, and the test piece was stretched at the stretch ratio shown in table 1.

(example 4)

A porous cellulose fiber-reinforced polypropylene resin molded article having a thickness of 0.4mm to 0.6mm was obtained in the same manner as in example 1 except that the blending amount of the polypropylene resin in example 1 was changed from 80 parts by mass to 77 parts by mass, and 3 parts by mass of Rikeeido MG400P was further blended, and the test piece was stretched at the stretch ratio shown in table 1.

(example 5)

A porous cellulose fiber-reinforced polypropylene resin molded article having a thickness of 0.5mm to 0.7mm was obtained in the same manner as in example 1 except that in example 1, the temperature of the thermostatic bath was set to 100 ℃ and the test piece was stretched at the stretch ratios shown in Table 1.

(reference example 1)

A polypropylene resin molded article having a thickness of 0.4mm to 0.6mm was obtained in the same manner as in example 1 except that the blending amount of the polypropylene resin in example 1 was changed from 80 parts by mass to 100 parts by mass, and the test piece was stretched at the stretch ratio shown in table 1 without adding the cellulose fiber.

(reference example 2)

The compressed tablet before stretching in reference example 1 was obtained as the polypropylene resin molded body of reference example 2. In the following evaluation, a dumbbell test piece obtained by punching the resin molded product was used in accordance with JIS1 dumbbell.

Comparative example 1

The compressed tablet before stretching in example 1 was obtained as the cellulose fiber-reinforced polypropylene resin molded body of comparative example 1. In the following evaluation, a dumbbell test piece obtained by punching the resin molded product was used in accordance with JIS1 dumbbell.

Comparative example 2

The compressed tablet before stretching in example 2 was obtained as the cellulose fiber-reinforced polypropylene resin molded body of comparative example 2. In the following evaluation, a dumbbell test piece obtained by punching the resin molded product was used in accordance with JIS1 dumbbell.

Comparative example 3

Pellets obtained by melt-kneading the pellets in example 1 by a twin-screw extruder were molded at an injection resin temperature of 190 ℃ and a mold temperature of 40 ℃ by an injection molding machine (ROBOTSHOT. alpha. -S30iA (trade name), manufactured by FANUC corporation) to obtain a dumbbell-shaped molded article of a cellulose fiber-reinforced polypropylene resin according to JIS 5.

The following evaluations were carried out on the cellulose fiber-reinforced polypropylene resin molded articles obtained in examples 1 to 5 and comparative examples 1 to 3 and the polypropylene resin molded articles obtained in reference examples 1 and 2. The results obtained are shown in table 1.

(measurement of Density)

From each of the obtained resin molded articles, a density measurement sample having a length of 2mm × a width of 30mm was cut, and the density was measured by the method A (underwater substitution method) according to JIS K7112 using the measurement sample.

(measurement of tensile Strength)

The tensile strength of each of the obtained resin molded articles was measured using an Autograph precision universal tester (manufactured by shimadzu corporation). The stretching conditions were set as follows: 50mm/min, measurement temperature: 25 ℃ and length between clamps: 40 mm. The tensile strength in the tensile direction at which the tensile strength exhibited the maximum was measured for the resin molded bodies (examples 1 to 5 and reference example 1) subjected to the stretching. In reference example 2, comparative examples 1 and 2 among the resin molded articles which were not stretched, since the tensile strength did not show directionality, the tensile strength in the longitudinal direction of the resin molded article was measured. For comparative example 3 of the resin molded article not subjected to stretching, the tensile strength in the flow direction at the time of injection molding showing the maximum value of the tensile strength was measured.

(calculation of specific Strength)

The specific strength was calculated by dividing the tensile strength measured above by the density measured above, as shown in the following formula.

Specific strength [ MJ/kg]Not (tensile strength [ MPa ]]Density [ g/cm ]³])/10³

(measurement of Linear expansion coefficient)

The obtained resin molded body was subjected to measurement of a linear expansion coefficient by a thermomechanical analyzer TMA (manufactured by Mettler Toredo). The inside of the apparatus was kept in a nitrogen atmosphere, and the temperature rise/fall rate was set at 10 ℃/min. The temperature pattern is a pattern of decreasing the temperature from 25 ℃ to-60 ℃, then increasing the temperature to 100 ℃, decreasing the temperature to-60 ℃ after increasing the temperature, and further increasing the temperature to 160 ℃, and a TMA curve is obtained in the second temperature increasing process. The average linear expansion coefficient of the obtained TMA curve in a temperature range of 60 ℃ to 100 ℃ was determined. For the stretched resin molded bodies (examples 1 to 5 and reference example 1), the linear expansion coefficient in the stretching direction was measured, which showed the minimum linear expansion coefficient. In reference example 2, comparative examples 1 and 2 among the resin molded articles not subjected to stretching, since the linear expansion coefficient did not show directionality, the linear expansion coefficient in the longitudinal direction of the resin molded article was measured. For comparative example 3 of the resin molded article not subjected to stretching, the linear expansion coefficient in the flow direction at the time of injection molding showing the minimum linear expansion coefficient was measured.

(Wide-angle X-ray diffraction measurement)

Method for confirming alpha crystal of polypropylene

It was confirmed by wide-angle X-ray diffraction measurement using D8 DISCOVER (manufactured by Bruker AXS). For each resin molded body placed, the CuK alpha rays are shrunk toThe pinhole collimator of (1) was irradiated, and the obtained diffraction was detected by a two-dimensional detector VANTEC500 (manufactured by Bruker AXS) set at a camera length of 10cm, to obtain a two-dimensional diffraction image. The obtained two-dimensional diffraction image has a scattering vector s of 0-2.91 nm^-1The range of (1) is subjected to integral averaging processing in an orientation angle direction of 0-360 degrees to obtain one-dimensional data. The one-dimensional data is corrected by subtracting air scattering from the transmittance of X-rays, and then curve fitting is performed using a gaussian function to separate the components into a diffraction component derived from polypropylene crystals and a diffraction component derived from an amorphous state. At a scattering vector s of 1.61 + -0.1 nm^-1And 1.92. + -. 0.1nm^-1When a diffraction peak is observed at the position of (2), it is judged that alpha crystal exists. This is because the diffraction peak of the alpha crystal (110) plane of polypropylene appears at a scattering vector s of 1.61. + -. 0.1nm^-1The diffraction peak of the (040) plane appears at a scattering vector s of 1.92. + -. 0.1nm^-1The position of (a).

Each of the resin molded bodies used for the measurement is appropriately cut as needed.

In the test piece of example 1, as shown in FIG. 1, the scattering vector s was 1.61. + -. 0.1nm^-1And 1.92. + -. 0.1nm^-1Diffraction peaks were observed at the positions of (1). In addition, in the test pieces of examples 2 to 5, comparative examples 1 and 2, and reference examples 1 and 2, the scattering vector s was 1.61. + -. 0.1nm in the same manner^-1And 1.92. + -. 0.1nm^-1Diffraction peaks were observed at the positions of (1).

Method for confirming the degree of orientation of polypropylene alpha crystals

The orientation degree is determined by using data in the range of 0 to 90 DEG in the orientation angle direction of the two-dimensional diffraction image derived from the polypropylene alpha crystal obtained by the method for confirming the polypropylene alpha crystal. The determination of the degree of orientation uses an orientation function of the orientation angle direction. The degree of orientation was determined as the average value of the results obtained by measuring 3 arbitrary points of a test piece cut out from each resin molded article adjusted to a thickness of 0.2mm to 1 mm.

Method for confirming the presence of cellulose fibers

It was confirmed by wide-angle X-ray diffraction measurement using D8 DISCOVER (manufactured by Bruker AXS). The test piece placed with the stage tilted at θ of 17.3 ° was shrunk by CuK α raysThe pinhole collimator of (1) was irradiated, and the obtained diffraction was detected by a two-dimensional detector VANTEC500 (manufactured by Bruker AXS) set at a camera length of 10cm, to obtain a two-dimensional diffraction image. For the obtained two-dimensional diffraction image, the scattering vector s was 1.13nm^-1～4.44nm^-1The range of (1) is subjected to integral averaging processing in an orientation angle direction of 0-90 degrees to obtain one-dimensional data. The one-dimensional data was corrected by subtracting the air scattering from the transmittance of X-rays, and curve-fitted with a gaussian function to separate the diffraction components from polypropylene crystals and from cellulose fibers, and the scattering vector s was 3.86 ± 0.1nm^-1When a diffraction peak is observed at the position of (2), it is judged that cellulose fibers are present in the molded article. This is because a diffraction peak from the (004) plane of the cellulose fiber usually appearsThe scattering vector s is 3.86 +/-0.1 nm^-1The position of (a).

In the test piece of example 1, as shown in FIG. 2, the scattering vector s was 3.86. + -. 0.1nm^-1The diffraction peak was confirmed at the position of (2). In addition, in each of the test pieces of examples 2 to 5 and comparative examples 1 to 3, the scattering vector s was 3.86. + -. 0.1nm in the same manner^-1The diffraction peak was confirmed at the position of (2). In each of the test pieces of reference examples 1 and 2, the scattering vector s was 3.86. + -. 0.1nm^-1No diffraction peak was observed at the position (2).

Method for confirming the degree of orientation of cellulose fibers

The orientation degree is determined by using data in the range of 0-90 DEG in the orientation angle direction of the two-dimensional diffraction image from the cellulose fiber obtained by the method for confirming the existence of the cellulose fiber. The determination of the degree of orientation uses an orientation function of the orientation angle direction. As a baseline of diffraction, data of 33.6 ° ± 0.5 ° and 35.6 ° ± 0.5 ° close to the diffraction peak position of cellulose were used for correction. The degree of orientation was determined as the average value of the results obtained by measuring 3 arbitrary points of a test piece cut out from a test piece adjusted to a thickness of 0.5mm to 1.5 mm.

(measurement of storage modulus and calculation of elastic modulus maintenance Rate)

A test piece for measuring elastic modulus having a width of about 2mm, a thickness of about 0.5mm and a length of 40mm was cut out from the obtained resin molded article with the stretching direction as the longitudinal direction, and subjected to a dynamic viscoelasticity test. The dynamic viscoelasticity test was carried out according to JIS K7244 using RSA-G2 (trade name, manufactured by TA Instruments) as a measuring apparatus under the following conditions.

(Condition)

Measurement temperature range: -90 ℃ to 150 DEG C

Temperature rise rate: 5 ℃/min

Measuring frequency: 1Hz

The length between the clamps is as follows: 20mm

Strain: 0.05 percent

The storage modulus in the stretching direction was measured for the stretched resin molded bodies (examples 1 to 5 and reference example 1). For reference example 2 and comparative examples 1 and 2 of the resin molded body which was not stretched, the storage modulus in the longitudinal direction of the test piece was measured. For comparative example 3 of the resin molded body not subjected to stretching, the storage modulus in the flow direction at the time of injection molding was measured.

The storage modulus E at 25 ℃ was read from the curve obtained by the above test (graph of storage modulus with respect to the horizontal axis: vertical axis of measurement temperature)₂₅And a storage modulus E at 100 ℃₁₀₀。

In addition, E is₁₀₀Divided by E₂₅From this, the elastic modulus maintenance ratio (E) was calculated₁₀₀/E₂₅)。

[ TABLE 1-1 ]

TABLE 1

[ TABLE 1-2 ]

Table 1

The following is evident from the results in Table 1.

The density of the molded articles of the cellulose fiber-reinforced polypropylene resins of comparative examples 1 to 3 was 1.03g/cm³The specification of the present invention is not satisfied. The molded articles of the cellulose fiber-reinforced polypropylene resins of comparative examples 1 and 2 had low specific strength and low retention of elastic modulus, and were inferior.

On the other hand, the cellulose fiber-reinforced polypropylene resin moldings of examples 1 to 5 had a scattering vector s of 1.61. + -. 0.1nm^-1、1.92±0.1nm^-1And 3.86. + -. 0.1nm^-1Has a diffraction peak at a density of 0.65g/cm³The following. The molded articles of the cellulose fiber-reinforced polypropylene resins of examples 1 to 5 were excellent in specific strength and elastic modulus retention rate. Further, the linear expansion coefficient is suppressed to less than 10 ppm/K. Wherein, the particle size is within 3.86 +/-0.1 nm^-1Taking out cellulose crystals having diffraction peaks at the positionsIn the molded articles of the cellulose fiber-reinforced polypropylene resins of examples 1 to 4 in which the degrees of orientation were as high as 0.50 or more, the specific strengths were as high as 0.16MJ/kg or more, and the specific strengths were excellent, and the elastic modulus retention ratios were as high as 0.40 or more, and the mechanical property deterioration in a high-temperature environment was excellent. The specific strength and the retention rate of elastic modulus of the cellulose fiber-reinforced polypropylene resin molded articles of examples 1 to 4 were higher and more excellent than those of the polypropylene resin molded articles of reference examples 1 and 2 containing no cellulose fiber.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

The present application claims priority of japanese patent application 2019-060606, which was filed in japan as a patent on 3, 27, 2019, which is hereby incorporated by reference and the contents of which are incorporated as part of the description of the present specification.